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Sample records for calcium aluminate cement

  1. Calcium Aluminate Cement Hydration Model

    Directory of Open Access Journals (Sweden)

    Matusinović, T.

    2011-01-01

    Full Text Available Calcium aluminate cement (AC is a very versatile special cement used for specific applications. As the hydration of AC is highly temperature dependent, yielding structurally different hydration products that continuously alter material properties, a good knowledge of thermal properties at early stages of hydration is essential. The kinetics of AC hydration is a complex process and the use of single mechanisms models cannot describe the rate of hydration during the whole stage.This paper examines the influence of temperature (ϑ=5–20 °C and water-to-cement mass ratio (mH /mAC = 0.4; 0.5 and 1.0 on hydration of commercial iron-rich AC ISTRA 40 (producer: Istra Cement, Pula, Croatia, which is a part of CALUCEM group, Figs 1–3. The flow rate of heat generation of cement pastes as a result of the hydration reactions was measured with differential microcalorimeter. Chemically bonded water in the hydrated cement samples was determined by thermo-gravimetry.Far less heat is liberated when cement and water come in contact for the first time, Fig. 1, than in the case for portland cement (PC. Higher water-to-cement ratio increases the heat evolved at later ages (Fig. 3 due to higher quantity of water available for hydration. A significant effect of the water-to-cement ratio on the hydration rate and hydration degree showed the importance of water as being the limiting reactant that slows down the reaction early. A simplified stoichiometric model of early age AC hydration (eq. (8 based on reaction schemes of principal minerals, nominally CA, C12A7 and C4AF (Table 1, was employed. Hydration kinetics after the induction period (ϑ < 20 °C had been successfully described (Fig. 4 and Table 2 by a proposed model (eq. (23 which simultaneously comprised three main mechanisms: nucleation and growth, interaction at phase boundary, and mass transfer. In the proposed kinetic model the nucleation and growth is proportional to the amount of reacted minerals (eq

  2. Density and mechanical properties of calcium aluminate cement

    Science.gov (United States)

    Ahmed, Syed Taqi Uddin; Ahmmad, Shaik Kareem

    2018-04-01

    Calcium aluminate cements are a special type of cements which have their composition mainly dominated by the presence of Monocalcium Aluminates. In the present paper for the first time we have shown theoretical density and elastic constants for various calcium aluminate cements. The density of the present CAS decrease with aluminates presents in the cement. Using the density data, the elastic moduli namely Young's modulus, bulk and shear modulus show strong linear dependence as a function of compositional parameter.

  3. Carbonation of calcium aluminate cement pastes

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    Fernández-Carrasco, L.

    2001-12-01

    Full Text Available This work discusses the results from accelerated tests intended to investigate the ways the different curing methods affect the carbonation of calcium aluminate cements pastes (CAC. The research was focused on the mineralogical composition of hydrated and carbonated samples. The compressive strengths and the porosity of the samples have been determined. Results point out that vaterite and aragonite are formed as a result of carbonation of both cubic and hexagonal calcium aluminate hydrates. The polymorph of calcium carbonate formed does not depend on the curing process. Carbonation rates is higher in hexagonal than in cubic hydrates. Results obtained through this study evidence that, as a consequence of the carbonation process of CAC pastes, in test conditions, an increase of the mechanical strengths occurs.

    En el presente trabajo se discuten los resultados obtenidos en los ensayos acelerados llevados a cabo para investigar los efectos de diferentes métodos de curado sobre la carbonatacion de pastas del cemento de aluminato de calcio (CAC. Se estudió la composición mineralógica de las muestras hidratadas y carbonatadas. Además, se determinaron las resistencias mecánicas a compresión y la porosidad de las probetas. Los resultados indican que la vaterita y el aragonito son las polimorfías del CaCO3 que se forman al carbonatar los aluminatos cálcicos hidratos, tanto los de naturaleza hexagonal como cúbica. El polimorfo del carbonato cálcico formado no depende del proceso de curado. La velocidad de carbonatación de los hidratos hexagonales es mayor que la de los cúbicos. Los resultados obtenidos en el presente trabajo han evidenciado que como consecuencia del proceso de carbonatación sobre pastas de CAC, en las condiciones realizadas, se produce un incremento en las resistencias mecánicas.

  4. Halting of the calcium aluminate cement hydration process

    International Nuclear Information System (INIS)

    Luz, A.P.; Borba, N.Z; Pandolfelli, V.C.

    2011-01-01

    The calcium aluminate cement reactions with water lead to the anhydrous phases dissolution resulting a saturated solution, followed by nucleation and crystal growth of the hydrate compounds. This is a dynamic process, therefore, it is necessary to use suitable methods to halt the hydration in order to study the phase transformations kinetics of such materials. In this work two methods are evaluated: use of acetone and microwave drying, aiming to withdraw the free water and inhibit further reactions. X ray diffraction and thermogravimetric tests were used to quantify the phases generated in the cement samples which were kept at 37 deg C for 1 to 15 days. The advantages and disadvantages of those procedures are presented and discussed. The use of microwave to halt the hydration process seems to be effective to withdraw the cement free water, and it can further be used in researches of the refractory castables area, endodontic cements, etc. (author)

  5. Another look at the deterioration of calcium aluminate cement concrete

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    Jambor, Jaromir

    1996-03-01

    Full Text Available Potential degradation of concrete structures made of calcium aluminate cement (CAC is well known and is caused by transformation (conversion of the thermodynamically metastable into stable calcium aluminate hydrate phases. This recrystallization is influenced by temperature and humidity; the structural degradation of the concrete itself thus its loss of strength, is strongly related to the pore structure of the hydrated cement paste, the critical parameters being the total volume of pores below 15-20 nm and the median micropore radius. This constitutes a novel procedure for evaluation of existing CAC concrete structure.

    La degradación potencial de estructuras de hormigón elaboradas con cemento aluminoso (CA es bien conocida. Este deterioro está causado por la recristalización (conversión de las fases del aluminato cálcico que son termodinámicamente metastables, en fases estables. En esta recristalización influye la temperatura y la humedad. Tanto la degradación del propio hormigón, como su pérdida de resistencias están relacionadas estrechamente con la estructura porosa de la pasta del cemento hidratado, siendo parámetros críticos el volumen total de los poros inferiores a 15-20 nm y el tamaño medio de los radios de los microporos. Esto constituye un nuevo procedimiento para evaluar las estructuras existentes de hormigón de cemento aluminoso (CA.

  6. Evaluation of bioactivity in vitro of endodontic calcium aluminate cement

    International Nuclear Information System (INIS)

    Oliveira, I.R.; Andrade, T.L.; Santos, G.L.; Pandolfelli, V.C.

    2011-01-01

    Bioactivity is referred to as the capacity of a material to develop a stable bond with living tissue via the deposition of hydroxyapatite. Materials which exhibit this property can be used to repair diseased or damaged bone tissue and can be designed to remain in situ indefinitely. An indication of bioactivity can be obtained by the formation of a hydroxyapatite layer on the surface of a substrate in simulated body fluids (SBF) in vitro. Therefore, set samples of calcium aluminate endodontic cement were maintained in contact with SBF solutions (Kokubo and Rigo) and their surfaces were later evaluated by means of SEM, EDX and DRX. Measurements of pH and ionic conductivity were also carried out for SBF solutions in contact with set samples of endodontic cement. The ideal conditions of precipitation were obtained in SBF Rigo been observed a surface layer with spherical morphology characteristic of stoichiometric hydroxyapatite.(author)

  7. Synthesis optimization of calcium aluminate cement phases for biomedical applications

    International Nuclear Information System (INIS)

    Andrade, T.L.; Santos, G.L.; Oliveira, I.R.; Pandolfelli, V.C.

    2011-01-01

    Calcium aluminate cement (CAC) has been studied as a potential material for applications in the areas of health such as, endodontics and bone reconstruction. These studies have been based on commercial products consisting of a mixture of phases. Improvements can be attained by investigating the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance for biomedical applications. Thus, the aim of this work was to study the CAC synthesis routes in the Al 2 O 3 -CaCO 3 and Al 2 O 3 -CaO systems, as well as the phase characterization attained by means of X ray analysis. The Al 2 O 3 -CaO route enabled the production of the target phases (CA, CA 2 , C 3 A and C 12 A 7 ) with a higher purity compared to the Al2O3-CaCO3 one. As a result the particular properties of these phases can be evaluated to define a more suitable composition that results in better properties for an endodontic cement and other applications. (author)

  8. Calcium aluminate cement hydration in a high alkalinity environment

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    Palomo, Á.

    2009-03-01

    Full Text Available The present paper forms part of a broader research project that aims primarily to devise new cementitious products via the alkali activation of silico-aluminous materials. This work addresses the possibility of using small percentages of calcium aluminate cement (CAC as a source of reactive aluminium. For this reason, a preliminary review was needed of the behaviour of CACs in highly alkaline media (2, 8 and 12M NaOH solutions. Two, 28- and 180-day mechanical strength was determined and the reaction products were characterized with XRD and FTIR. The water-hydrated CAC was used as the control.The results obtained showed that CAC hardening took place much more slowly in highly alkaline media than in water. Nonetheless, the 28-day compressive strength obtained, ≥80MPa. As main reaction products, to ambient temperature and from the two days of cured, cubic aluminate C3AH6, and AH3 polymorphs are formed, instead of the usual hexagonal aluminatos (CAH10 and C2AH8 that are formed in the normal hydrate with water.El presente trabajo forma parte de una amplia investigación cuyo objetivo principal es el de elaborar nuevos materiales con propiedades cementantes mediante la activación alcalina de materiales de naturaleza silito-aluminosa. En estos estudios se contempla la posibilidad de utilizar pequeños porcentajes de cemento de aluminato de calcio (CAC como fuente de aluminio reactivo. Por ello inicialmente se ha estudiado el comportamiento de los CAC en medios fuertemente alcalinos (disoluciones de NaOH 2M, 8M y 12M. Se determinaron las resistencias mecánicas a 2, 28 y 180 días y se realizó una caracterización de los productos de reacción formados por DRX, FTIR. Como sistema de referencia se consideró la hidratación del CAC con agua.Los resultados obtenidos muestran que en medios fuertemente alcalinos se retrasan los procesos de rápido endurecimiento de CAC con agua. No obstante a 28 días se obtienen valores de resistencia a compresión

  9. Barium aluminate cement: its application

    International Nuclear Information System (INIS)

    Drozdz, M.; Wolek, W.

    1975-01-01

    The technology of manufacturing barium aluminate cement from barium sulfate and alumina, using a rotary kiln for firing the clinker is described. The method of granulation of the homogenized charge was used. Conditions of using the ''to mud'' method in industry were indicated. The physical and chemical properties of barium aluminate cement are determined and the quality of several batches of cement prepared on a semi-industrial scale and their suitability for making highly refractory concretes are tested. The optimal composition of the concretes is determined as a function of the mixing water and barium aluminate cement contents. Several experimental batches of concretes were used in the linings of furnaces in the steel industry. The suitability of these cements for use in fields other than steelmaking is examined. It is established that calcium aluminate cement has certain limited applications [fr

  10. BLENDED CALCIUM ALUMINATE-CALCIUM SULFATE CEMENT-BASED GROUT FOR P-REACTOR VESSEL IN-SITU DECOMMISSIONING

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C.; Stefanko, D.

    2011-03-10

    The objective of this report is to document laboratory testing of blended calcium aluminate - calcium hemihydrate grouts for P-Reactor vessel in-situ decommissioning. Blended calcium aluminate - calcium hemihydrate cement-based grout was identified as candidate material for filling (physically stabilizing) the 105-P Reactor vessel (RV) because it is less alkaline than portland cement-based grout which has a pH greater than 12.4. In addition, blended calcium aluminate - calcium hemihydrate cement compositions can be formulated such that the primary cementitious phase is a stable crystalline material. A less alkaline material (pH {<=} 10.5) was desired to address a potential materials compatibility issue caused by corrosion of aluminum metal in highly alkaline environments such as that encountered in portland cement grouts [Wiersma, 2009a and b, Wiersma, 2010, and Serrato and Langton, 2010]. Information concerning access points into the P-Reactor vessel and amount of aluminum metal in the vessel is provided elsewhere [Griffin, 2010, Stefanko, 2009 and Wiersma, 2009 and 2010, Bobbitt, 2010, respectively]. Radiolysis calculations are also provided in a separate document [Reyes-Jimenez, 2010].

  11. Study of belite calcium sulfo-aluminate cement potential for zinc conditioning: From hydration to durability

    International Nuclear Information System (INIS)

    Berger, St.

    2009-12-01

    Calcium silicate cements are widely used for low- and intermediate-level radioactive waste conditioning. However, wastes produced by nuclear activities are very diverse and some of their components may chemically react with cement phases. For instance, ashes resulting from the incineration of technological wastes including neoprene and polyvinylchloride may contain substantial amounts of soluble zinc chloride. This compound is known to strongly delay or inhibit Portland cement setting. One approach to limit adverse cement-waste interactions is to select a binder showing a better compatibility with the waste while keeping cement matrix advantages (low cost, simple process, hydration with water provided by the waste...). This work thus investigates the potential of calcium sulfo-aluminate cement for zinc Zn(II) immobilization. Four aspects were considered: hydration (kinetics and products formed), properties of hydrated binders, mechanisms of zinc retention and durability of the cement pastes (based on leaching experiments and modelling). The influence of three main parameters was assessed: the gypsum content of the cement, the concentration of ZnCl 2 and the thermal evolution at early age. It follows that materials based on a calcium sulfo-aluminate cement containing 20% gypsum are interesting candidates for zinc Zn(II) stabilization/solidification: there is no delay in hydration, mineralogy of the hydrated phases is slightly dependent on thermal history, mechanical strength is high, dimensional changes are limited and zinc Zn(II) is well immobilized, even if the cement paste is leached by pure water during a long period (90 d). (author)

  12. Hydration process for calcium-aluminate cement within EVA emulsion by SPring-8 synchrotron radiation x-ray diffraction method

    International Nuclear Information System (INIS)

    Kotera, Masaru; Matsuda, Ikuyo; Miyashita, Keiko; Adachi, Nobuyuki; Tamura, Hisayuki

    2005-01-01

    Polymer-modified mortars which consist of a polymer emulsion and cement materials have been widely developed in the construction materials fields. Forming process of the polymer-modified cement membrane simultaneously involves evaporation of water within the polymer emulsion and hydration of cement. It is important for the polymer-modified cement paste that the hydrate crystal of cement is generating by the hydration during the setting process under existence of the polymer emulsion. In this study, hydration process for calcium-aluminate cement under existence of poly (ethylene-vinyl acetate) (EVA) emulsion (polymer-cement ratio=100%) was investigated by X-ray diffraction method using synchrotron radiation (SPring-8). The diffraction peaks of calcium aluminate (CA) disappeared after the hardening, on the other hand, the peaks of hydrate crystals of calcium-aluminate cement (C 2 AH 8 and C 3 AH 6 ) could be observed. This polymer-modified cement paste hydrated using the water within the polymer emulsion. The hydration of C 2 AH 8 from CA started at around 300 min, and then C 3 AH 6 hydrate crystal increased after 700 min at ambient temperature. This implies that the conversion from C 2 AH 8 to C 3 AH 6 occurred to be more stable phase. The setting temperature affected the reaction rate. In case of hydration at 35degC, the start time of the hydration for calcium-aluminate cement was quicker than that in the ambient temperature four or more times. (author)

  13. Conditioning highly concentrated borate solutions with calcium sulfo-aluminate cement

    International Nuclear Information System (INIS)

    Champenois, J.B.; Cau dit Coumes, C.; Poulesquen, A.; Le Bescop, P.; Damidot, D.

    2012-01-01

    The early age hydration by borate solution of 3 calcium sulfo-aluminate cements (CSA), containing respectively 0%, 10% and 20% of gypsum by weight of cement was studied using isothermal calorimetry and dynamic mode rheo-metry. XRD and TGA analysis were carried out on pastes with increasing hydration degrees (up to 90 days) to specify the mineralogy and to figure out the mechanisms of borate immobilisation. It has been shown that the retarding effect of borate anions is due to the precipitation of the amorphous calcium borate C 2 B 3 H 8 ; borate anions were then incorporated in Aft-type phases. The macroscopic properties of hydrated binders (compressive strength, length change) were also followed during 180 days. It appears that the mechanical strength continuously increases with the hydration degree. Length changes under wet-curing and sealed bag remain moderate and seem to be stabilized after 180 days

  14. Corrosion Resistance of Calcium Aluminate Cement Concrete Exposed to a Chloride Environment.

    Science.gov (United States)

    Ann, Ki Yong; Cho, Chang-Geun

    2014-01-28

    The present study concerns a development of calcium aluminate cement (CAC) concrete to enhance the durability against an externally chemically aggressive environment, in particular, chloride-induced corrosion. To evaluate the inhibition effect and concrete properties, CAC was partially mixed with ordinary Portland cement (OPC), ranging from 5% to 15%, as a binder. As a result, it was found that an increase in the CAC in binder resulted in a dramatic decrease in the setting time of fresh concrete. However, the compressive strength was lower, ranging about 20 MPa, while OPC indicated about 30-35 MPa at an equivalent age. When it comes to chloride transport, there was only marginal variation in the diffusivity of chloride ions. The corrosion resistance of CAC mixture was significantly enhanced: its chloride threshold level for corrosion initiation exceeded 3.0% by weight of binder, whilst OPC and CAC concrete indicated about 0.5%-1.0%.

  15. Evaluation of mechanical strength and hydrate products evolution of calcium aluminate cement, for endodontic applications

    International Nuclear Information System (INIS)

    Luz, A.P.; Borba, N.Z.; Pandolfelli, V.C.

    2011-01-01

    Mineral trioxide aggregate (MTA) is the most used retrograde filling cement in the endodontic area. Nevertheless, although its composition is similar to the conventional Portland cement, its high cost, long setting time and low mechanical strength have led to a continuous search for new alternative materials. Considering these aspects, the mechanical strength and crystalline phase evolution of a calcium aluminate cement (CAC), during its hydration process, have been evaluated in this work aiming to apply such material for endodontic treatments. Secar 71 cement samples were prepared and kept in contact with water or SBF (simulated body fluid) during 15 days at 37 deg C. Compressive strength, apparent porosity, X ray diffraction and thermogravimetric tests were carried out for the samples evaluation after 1, 3, 7 and 15 days. The main identified phases were CAH_1_0, C_2AH_8, C_3AH_6 and AH_3. Moreover, when in the presence of SBF, some changes in the amount of the hydrates in the CAC samples were observed, which affected the mechanical behavior of the cement. (author)

  16. Study of the ultrasonic waves action on the preparation of calcium aluminates cements

    International Nuclear Information System (INIS)

    Lourenco, R.R.; Exposito, C.C.D.; Rodrigues, J.A.

    2009-01-01

    Calcium aluminates cements were prepared through a route that uses the sonochemical process. In this process, calcia and alumina in an aqueous suspension are put under an ultrasonic bath during some time. After that, the water is evaporated and the material is heat treated. In this work, the action of ultrasonic waves were studied on initials molar compositions calcia:alumina of 1:1. It was also verified the influence of the water on the reactivity of initial solids. SEM and X-ray diffraction were used to characterize the obtained materials. In addition, mechanical strength of the products was evaluated through splitting tensile tests. The X-ray diffractograms showed that the presence of the water was enough to form hydrated compounds. However the material subjected to the sonochemical process presented the highest mechanical strength, indicating the potential of this route of synthesis. (author)

  17. X-AFm stabilization as a mechanism of bypassing conversion phenomena in calcium aluminate cements

    International Nuclear Information System (INIS)

    2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); Department of Materials Science and Engineering, University of California, Los Angeles, CA (United States))" data-affiliation=" (Laboratory for the Chemistry of Construction Materials LC2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); Department of Materials Science and Engineering, University of California, Los Angeles, CA (United States))" >Falzone, Gabriel; Balonis, Magdalena; 2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); California Nanosystems Institute (CNSI), University of California, Los Angeles, CA (United States))" data-affiliation=" (Laboratory for the Chemistry of Construction Materials LC2, Department of Civil and Environmental Engineering, University of California, Los Angeles, CA (United States); California Nanosystems Institute (CNSI), University of California, Los Angeles, CA (United States))" >Sant, Gaurav

    2015-01-01

    Phase conversion phenomena are often observed in calcium aluminate cements (CACs), when the water-rich hydrates (e.g., CAH 10 , C 2 AH 8 ) formed at early ages, at temperatures ≤ 30 °C, expel water in time to form more compact, less water-rich structures (C 3 AH 6 ). The phase conversions follow a path regulated by the thermodynamic stabilities (solubilities) of phases. Based on this premise, it is proposed that conversion phenomena in CACs can be bypassed by provoking the precipitation of phases more preferred than those typically encountered along the conversion pathway. Therefore, X-AFm formation (where in this case, X = NO 3 − ) triggered by the sequential addition of calcium nitrate (Ca(NO 3 ) 2 = CN) additives is identified as a new means of bypassing conversion. A multi-method approach comprising X-ray diffraction (XRD), thermal analytics, and evaluations of the compressive strength is applied to correlate phase balances and properties of CAC systems cured at 25 °C and 45 °C. The results highlight the absence of the C 3 AH 6 phase across all systems and the curing conditions considered, with enhanced strengths being noted, when sufficient quantities of CN are added. The experimental outcomes are supported by insights gained from thermodynamic calculations which highlight thermodynamic selectivity as a means of regulating and controlling the evolutions of solid phase balances using inorganic salts in CACs, and more generally in cementing material systems

  18. Synthesis and hydration behavior of calcium zirconium aluminate (Ca7ZrAl6O18) cement

    International Nuclear Information System (INIS)

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-01-01

    Calcium zirconium aluminate (Ca 7 ZrAl 6 O 18 ) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca 7 ZrAl 6 O 18 was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO 3 coexisted with Ca 7 ZrAl 6 O 18 even at higher temperature (1400 °C). Unexpectedly, Ca 7 ZrAl 6 O 18 synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca 7 ZrAl 6 O 18 was similar to that of Ca 3 Al 2 O 6 (C3A), but the hydration products were Ca 3 Al 2 O 6 ·6H 2 O (C3AH6) and several intermediate products. Thus, Zr (or ZrO 2 ) stabilized the intermediate hydration products of C3A

  19. Calcium aluminate cement concrete: durablllty and conversión. A fresh look at an old subject

    Directory of Open Access Journals (Sweden)

    George, C. M.

    1992-12-01

    Full Text Available This paper re-examines the relationship between durability and conversion of calcium aluminate cement concretes, CACC. Conversion is a natural and inevitable process whereby these materials reach a stable mature condition. Numerous structures built more than half a century ago remain serviceable and in service today. Some of these are illustrated. They are the best testament to the durability of converted concrete having survived far longer in the converted than the unconverted condition. The unique rapid hardening characteristics of CACC offer a valuable selfheating capability. Conversión is immediate and this leads to better long term strengths because more cement is hydrated. Moreover, recent work has shown that the thermodynamically stable hydrates of converted CAC are intrinsically more resistant to attack from such aggressive agents as sulphuric acid. This provides an explanation of the excellent long term performance of Fondu concretes, for example in many saewer applications. Our knowledge and understanding today of the durability of calcium alumínate bonded materials has been built on close to 100 years of accumulated experience and laboratory studies. We know how to use these materials and we know what to expect from them. We can be confident that they will serve us well in the century ahead.

    Este trabajo examina de nuevo la relación entre durabilidad y conversión de hormigones de cemento aluminoso, HAC (High Alumina Cement. La conversión es un proceso natural e inevitable a través del cual este material consigue una condición definitiva y estable. Numerosas estructuras que se edificaron hace más de medio siglo siguen utilizables y utilizadas hoy en día. Algunas de estas estructuras vienen ilustradas en este trabajo. Ellas sirven como mejor ejemplo de la durabilidad del hormigón convertido, ya que han sobrevivido mucho más tiempo en el estado convertido que en el no convertido. Las singulares caracter

  20. Effect of the strontium aluminate and hemihydrate contents on the properties of a calcium sulphoaluminate based cement

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    Velazco, G.

    2014-09-01

    Full Text Available The effect of strontium aluminate (SrAl2O4 on the hydration process of a calcium sulphoaluminate (C4A3Ŝ cement was investigated. Cement pastes were prepared by mixing C4A3Ŝ , hemihydrate (CaSO4· ½H2O, CŜH0.5 and 0, 10 or 20wt% of SrAl2O4 (SrA. The amount of CŜH0.5 was 15, 20 or 25wt% based on the C4A3Ŝ quantity. The cement pastes were hydrated using water to cement ratios (w/c of 0.4 and 0.5. Samples were cured from 1 to 28 d. The compressive strength and setting time were evaluated and the hydration products were characterized. It was found that the setting time was delayed up to 42 min for the samples containing SrAl2O4 compared to samples without addition. The samples with 25wt% hemihydrate containing 20wt% SrAl2O4 developed the highest compressive strength (60 MPa after 28 d of curing. The main product after hydration was ettringite (C6AŜ3H32. The morphology of this phase consisted of thin needle-shaped crystals.Se investigó el efecto de la adición de aluminato de estroncio (SrAl2O4 sobre las propiedades de un cemento de sulfoaluminato de calcio (C4A3Ŝ. Se prepararon muestras mezclando C4A3Ŝ, hemihidrato (CaSO4· ½H2O, CŜH0.5 y 0, 10 o 20% e.p de SrAl2O4 (SrA. La cantidad de CŜH0.5 fue de 15, 20 o 25% e.p. basado en la cantidad de C4A3Ŝ. Las relaciones agua/cemento utilizadas fueron 0.4 y 0.5. Las muestras fueron curadas hasta 28 d. Se evaluó el tiempo de fraguado y la resistencia a la compresión. Los productos de hidratación se caracterizaron mediante DRX y MEB. El tiempo de fraguado se retardó hasta 42 minutos con la adición del SrAl2O4 comparado con las muestras sin adiciones. Las muestras con 25% e.p. de yeso y 20% e.p. de SrAl2O4 desarrollaron la mayor resistencia a la compresión alcanzando 60 MPa a 28 d de curado. Los análisis por MEB y DRX muestran como principal producto de hidratación a la etringita (C6AŜ3H32, cuya morfología se observa como cristales aciculares.

  1. Photocatalytic NO{sub x} abatement by calcium aluminate cements modified with TiO{sub 2}: Improved NO{sub 2} conversion

    Energy Technology Data Exchange (ETDEWEB)

    Pérez-Nicolás, M. [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain); Balbuena, J.; Cruz-Yusta, M.; Sánchez, L. [Department of Inorganic Chemistry, School of Sciences, University of Córdoba, Campus de Rabanales, Edificio Marie Curie, 14071 Córdoba (Spain); Navarro-Blasco, I.; Fernández, J.M. [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain); Alvarez, J.I., E-mail: jalvarez@unav.es [MIMED Research Group, Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, c/Irunlarrea, 1, 31008 Pamplona (Spain)

    2015-04-15

    Photocatalytic activity of TiO{sub 2} was studied in two types of calcium aluminate cement (CAC) under two different curing regimes. The effect of the TiO{sub 2} addition on the setting time, consistency and mechanical properties of the CACs was evaluated. The abatement of gaseous pollutants (NO{sub x}) under UV irradiation was also assessed. These cementitious matrices were found to successfully retain NO{sub 2}: more abundant presence of aluminates in white cement (w-CAC, iron-lean) helped to better adsorb NO{sub 2}, thus improving the conversion performance of the catalyst resulting in a larger NO{sub x} removal under UV irradiation. As evidenced by XRD, SEM, EDAX and zeta potential analyses, the presence of ferrite in dark cement (d-CAC, iron-reach) induced a certain chemical interaction with TiO{sub 2}. The experimental findings suggest the formation of new iron titanate phases, namely pseudobrookite. The reduced band-gap energy of these compounds compared with that of TiO{sub 2} accounts for the photocatalytic activity of these samples.

  2. Evaluation of bioactivity in vitro of endodontic calcium aluminate cement; Avaliacao da bioatividade in vitro de cimento endodontico a base de aluminato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, I.R.; Andrade, T.L.; Santos, G.L., E-mail: ivonero@univap.br [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil); Pandolfelli, V.C. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2011-07-01

    Bioactivity is referred to as the capacity of a material to develop a stable bond with living tissue via the deposition of hydroxyapatite. Materials which exhibit this property can be used to repair diseased or damaged bone tissue and can be designed to remain in situ indefinitely. An indication of bioactivity can be obtained by the formation of a hydroxyapatite layer on the surface of a substrate in simulated body fluids (SBF) in vitro. Therefore, set samples of calcium aluminate endodontic cement were maintained in contact with SBF solutions (Kokubo and Rigo) and their surfaces were later evaluated by means of SEM, EDX and DRX. Measurements of pH and ionic conductivity were also carried out for SBF solutions in contact with set samples of endodontic cement. The ideal conditions of precipitation were obtained in SBF Rigo been observed a surface layer with spherical morphology characteristic of stoichiometric hydroxyapatite.(author)

  3. Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F.

    Science.gov (United States)

    Pyatina, Tatiana; Sugama, Toshifumi; Moon, Juhyuk; James, Simon

    2016-05-27

    An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. This work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersive X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm) and greater compressive strength after 300 °C curing. Mechanical properties of the set cements were not compromised by the retarder.

  4. Effect of Tartaric Acid on Hydration of a Sodium-Metasilicate-Activated Blend of Calcium Aluminate Cement and Fly Ash F

    Directory of Open Access Journals (Sweden)

    Tatiana Pyatina

    2016-05-01

    Full Text Available An alkali-activated blend of aluminum cement and class F fly ash is an attractive solution for geothermal wells where cement is exposed to significant thermal shocks and aggressive environments. Set-control additives enable the safe cement placement in a well but may compromise its mechanical properties. This work evaluates the effect of a tartaric-acid set retarder on phase composition, microstructure, and strength development of a sodium-metasilicate-activated calcium aluminate/fly ash class F blend after curing at 85 °C, 200 °C or 300 °C. The hardened materials were characterized with X-ray diffraction, thermogravimetric analysis, X-ray computed tomography, and combined scanning electron microscopy/energy-dispersive X-ray spectroscopy and tested for mechanical strength. With increasing temperature, a higher number of phase transitions in non-retarded specimens was found as a result of fast cement hydration. The differences in the phase compositions were also attributed to tartaric acid interactions with metal ions released by the blend in retarded samples. The retarded samples showed higher total porosity but reduced percentage of large pores (above 500 µm and greater compressive strength after 300 °C curing. Mechanical properties of the set cements were not compromised by the retarder.

  5. Propriedades e bioatividade de um cimento endodôntico à base de aluminato de cálcio Properties and bioactivity of endodontic calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2011-09-01

    Full Text Available Desde sua introdução na endodontia como um material retro-obturador e selador de defeitos da raiz dental, o agregado de trióxido mineral (MTA tem sido considerado como um material endodôntico revolucionário. Apesar disso, este material apresenta algumas propriedades limitantes, necessitando alterações em sua composição bem como desenvolvimento de novos materiais. Assim, o objetivo desse trabalho foi mostrar a influência de aditivos no desenvolvimento de um cimento endodôntico à base de cimento de aluminato de cálcio (ECAC. Além disso, foram avaliadas as propriedades do ECAC em comparação com o MTA, quando em contato com solução de fluido corporal simulado (SBF. Testes de manipulação e medidas de resistência à compressão, porosidade aparente, tempo de endurecimento, pH e condutividade iônica, foram realizados para os materiais MTA puro e ECAC contendo aditivos. Considerando as propriedades apresentadas pelo ECAC, este material alternativo pode ser indicado para múltiplas aplicações em endodontia.The mineral trioxide aggregate (MTA, a material primarily developed as a root-end filling has been extensively investigated as an innovative product for endodontic applications. However, changes in its formulation/composition involving its mineral aggregates and the development of alternatives of materials have been proposed in an attempt to overcome its negative physical-chemical characteristics. In this work, the influence of additives addition on the development of a novel endodontic cement based on calcium aluminate, has been evaluated. In addition, the properties of endodontic calcium aluminate cement (ECAC were compared with the gold standard mineral-trioxide-aggregate in contact with simulated body fluid (SBF. Manipulation tests and measurements of compressive strength, apparent porosity, setting time, pH and ionic conductivity were carried out on plain MTA and calcium aluminate cement with and without various additives

  6. Synthesis optimization of calcium aluminate cement phases for biomedical applications; Avaliacao da sintese das fases de cimento de aluminato de calcio

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, T.L.; Santos, G.L.; Oliveira, I.R. [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil); Pandolfelli, V.C. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2011-07-01

    Calcium aluminate cement (CAC) has been studied as a potential material for applications in the areas of health such as, endodontics and bone reconstruction. These studies have been based on commercial products consisting of a mixture of phases. Improvements can be attained by investigating the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance for biomedical applications. Thus, the aim of this work was to study the CAC synthesis routes in the Al{sub 2}O{sub 3}-CaCO{sub 3} and Al{sub 2}O{sub 3}-CaO systems, as well as the phase characterization attained by means of X ray analysis. The Al{sub 2}O{sub 3}-CaO route enabled the production of the target phases (CA, CA{sub 2}, C{sub 3}A and C{sub 12}A{sub 7}) with a higher purity compared to the Al2O3-CaCO3 one. As a result the particular properties of these phases can be evaluated to define a more suitable composition that results in better properties for an endodontic cement and other applications. (author)

  7. INFLUENCE OF CURING TEMPERATURE ON THE PHYSICO-MECHANICAL, CHARACTERISTICS OF CALCIUM ALUMINATE CEMENT WITH AIR-COOLED SLAG OR WATER-COOLED SLAG

    Directory of Open Access Journals (Sweden)

    M. Heikal

    2004-12-01

    Full Text Available The nature, sequence, crystallinity and microstructure of hydrated phases were analyzed using differential scanning calorimetry (DSC, X-ray diffraction (XRD and scanning electron microscopy (SEM. The results showed that the formation of different hydrated phases was temperature dependence. The physico-mechanical and microstructural characteristics were investigated after curing at 20, 40 and 60° C. The results indicated that for the substitution of calcium aluminate cement (CAC by air-cooled slag (AS or water-cooled slag (WS at 20° C, the compressive strength increases with slag content up to 10 wt.%, then followed by a decrease with further slag substitution up to 25 wt.%; but the values are still higher than those of the neat CAC pastes at different curing ages up to 60 days. After 28 days of hydration at 40-60° C, the compressive strength increases with the slag content. This is attributed to the prevention of the conversion reaction, which was confirmed by XRD, DSC and SEM techniques, and the preferential formation of stratlingite (gehleinte-like phase. The SEM micrographs showed a close texture of hydrated CAC/slag blends made with AS or WS at 40°C due to the formation of C2ASH8 and C-S-H phases.

  8. Influence of lithium and boron ions on calcium sulfo-aluminate cement hydration: application for the conditioning of boron ion exchange resins

    International Nuclear Information System (INIS)

    Dhoury, Melanie

    2015-01-01

    In pressurized water reactors, a solution of boric acid, the pH of which is controlled by the addition of lithium hydroxide, is injected in the primary circuit. Boron acts as a neutron moderator and helps controlling the fission reactions. The primary coolant is purified by flowing through columns of ion exchange resins. These resins are periodically renewed and constitute a low-level radioactive waste. In addition to radionuclides, they mainly contain borate and lithium ions. They are currently encapsulated in an organic matrix before being stored in a near-surface repository. An evolution of the process is considered, involving the replacement of the organic matrix by a mineral one. In this PhD study, the potential of calcium sulfo-aluminate cements (CSAC) to solidify/stabilize borated resins in the presence of lithium is investigated. These binders have the advantage to form hydrates which can incorporate borate ions in their structure, and their hydration is less retarded than that of Portland cement.An analytical approach is adopted, based on a progressive increase in the complexity of the investigated systems. Hydration of ye-elimite-rich CSAC is thus successively investigated in the presence of (i) lithium salts, (ii) lithium hydroxide and sodium borate, and (iii) lithium hydroxide and borated ion exchange resins. The experimental investigation is supplemented by thermodynamic modelling using a database specially developed for the needs of the study. Lithium ions are shown to accelerate CSAC hydration by decreasing the duration of the period of low thermal activity. The postulated mechanism involves the precipitation of lithium-containing aluminum hydroxide. On the contrary, sodium borate retards CSAC hydration by increasing the duration of the period of low thermal activity. Ulexite, a poorly crystallized mineral containing sodium and borates, transiently precipitates at early age. As long as ulexite is present, dissolution of ye-elimite is strongly slowed

  9. Thermal expansion properties of calcium aluminate hydrates

    International Nuclear Information System (INIS)

    Song, Tae Woong

    1986-01-01

    In order to eliminate the effect of impurities and aggregates on the thermomechanical properties of the various calcium aluminate hydrates, and to prepare clinkers in which all calcium aluminates are mixed homogeneously, chemically pure CaO and Al 2 O 3 were weighed, blended and heated in various conditions. After quantitative X-ray diffractometry(QXRD), the synthesized clinker was hydrated and cured under the conditions of 30 deg C, W/C=0.5, relative humidity> 90% respectively during 24 hours. And then differential thermal analysis(DTA), thermogravimetry(TG), micro calorimetry, thermomechanical analysis(TMA) and scanning electron microanalysis(SEM) were applied to examine the thermal properties of samples containing, calcium aluminate hydrates in various quantity. (Author)

  10. Possibilities of using aluminate cements in high-rise construction

    Science.gov (United States)

    Kaddo, Maria

    2018-03-01

    The article describes preferable ways of usage of alternative binders for high-rise construction based on aluminate cements. Possible areas of rational use of aluminate cements with the purpose of increasing the service life of materials and the adequacy of the durability of materials with the required durability of the building are analyzed. The results of the structure, shrinkage and physical and mechanical properties of concrete obtained from dry mixes on the base of aluminate cements for self-leveling floors are presented. To study the shrinkage mechanism of curing binders and to evaluate the role of evaporation of water in the development of shrinkage was undertaken experiment with simple unfilled systems: gypsum binder, portland cement and «corrosion resistant high alumina cement + gypsum». Principle possibility of binder with compensated shrinkage based on aluminate cement, gypsum and modern superplasticizers was defined, as well as cracking resistance and corrosion resistance provide durability of the composition.

  11. Influência de aditivos dispersantes e acelerador na hidratação de cimento e cimento-matriz Influence of dispersant and accelerator additives on hydration of calcium aluminate cement and cement-matrix

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2006-09-01

    Full Text Available A aplicação de concretos refratários, principalmente na siderurgia, é um processo em constante evolução, que apresenta uma forte dependência dos avanços dos conhecimentos sobre os ligantes hidráulicos. Isso se deve a influência exercida por estes ligantes nas propriedades reológicas e desenvolvimento de resistência mecânica de concretos. O processo de hidratação dos ligantes é sensivelmente influenciado pela presença de aditivos, afetando o tempo requerido para efetuar a desmoldagem do corpo conformado. Além disso, a adição de alumina ao cimento também influencia o seu comportamento de hidratação, bem como a extensão do período de indução, a composição das fases e dos produtos de hidratação. Assim, neste trabalho foi estudada a influência da presença de aditivos dispersantes e/ou acelerador no processo de hidratação de cimento e cimento-matriz. Independente do sistema, os aditivos dispersantes atuaram como retardadores do processo de hidratação, principalmente para o caso do ácido cítrico e citrato de diamônio. Tais aditivos apresentaram-se também como os mais eficientes para a combinação com o acelerador Li2CO3, resultando em um tempo de pega intermediário. Isto mostra ser possível controlar a trabalhabilidade reduzindo o tempo para a desmoldagem.A growing demand for refractory castables with specific behaviors has been promoting a continuous technological evolution, in which, one of the most important aspects concerns in a deep knowledge of hydraulic binders. These materials present a great influence on the rheological properties and mechanical strength development of castables, defining their workability periods and demoulding times, respectively. The hydration process of calcium aluminate cement is influenced by the presence of additives, which affects the setting and demoulding time of the shaped body. Besides that, the alumina addition to cement also influences the hydration behaviour, as well

  12. Hydration of Portland cement with additions of calcium sulfoaluminates

    International Nuclear Information System (INIS)

    Le Saoût, Gwenn; Lothenbach, Barbara; Hori, Akihiro; Higuchi, Takayuki; Winnefeld, Frank

    2013-01-01

    The effect of mineral additions based on calcium aluminates on the hydration mechanism of ordinary Portland cement (OPC) was investigated using isothermal calorimetry, thermal analysis, X-ray diffraction, scanning electron microscopy, solid state nuclear magnetic resonance and pore solution analysis. Results show that the addition of a calcium sulfoaluminate cement (CSA) to the OPC does not affect the hydration mechanism of alite but controls the aluminate dissolution. In the second blend investigated, a rapid setting cement, the amorphous calcium aluminate reacts very fast to ettringite. The release of aluminum ions strongly retards the hydration of alite but the C–S–H has a similar composition as in OPC with no additional Al to Si substitution. As in CSA–OPC, the aluminate hydration is controlled by the availability of sulfates. The coupling of thermodynamic modeling with the kinetic equations predicts the amount of hydrates and pore solution compositions as a function of time and validates the model in these systems.

  13. The formation reaction of calcium hexa-aluminate

    International Nuclear Information System (INIS)

    Tuganova, S.Kh.; Sirajiddinov, N.A.

    1990-01-01

    The formation reaction of CaAl 12 O 19 at interaction of calcium oxide and aluminium in solid form has been studied. Some physical-chemical characteristics of calcium hexa-aluminate are given. (author)

  14. Hot corrosion of pack cementation aluminized carbon steel

    International Nuclear Information System (INIS)

    Waheed, A.F.; Mohamed, K.E.; Abd El-Azim, M.E.; Soliman, H.M.

    1998-01-01

    Low carbon steel was aluminized by the pack cementation technique at various aluminizing temperatures and times in or der to have different aluminide coatings. The aluminized specimens were sprayed at the beginning of the hot corrosion experiments with Na C 1+Na 2 SO 4 solution. The hot corrosion tests were carried out by thermal cycling at 850 degree C in air. The results were evaluated by, corrosion kinetics based on weight change measurements, scanning electron microscopy and energy dispersive X-ray analysis. It was found that the maximum corrosion resistance to this corrosive environment is achieved by aluminizing at 900 degree C for 19 h or 950 degree C for >4 h. These aliminizing conditions lead to formation of thick aluminide coatings with sufficient aluminium concentration (>15 wt%) at their outer surface necessary for continuous formation of protective Al 2 O 3 scale. The tested materials are used in protection of some components used in electric power stations (conventional or nuclear)

  15. Hydration kinetics for the alite, belite, and calcium aluminate phase in Portland cements from 27Al and 29Si MAS NMR spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Jensen, Ole Mejlhede; Jakobsen, Hans Jørgen

    1997-01-01

    29Si magic-angle spinning (MAS) NMR spectroscopy is shown to be a valuable tool for obtaining the quantities of alite and belite in hydrated Portland cements. The hydration (1-180 days) of a white Portland cement with 10 wt.% silica fume added is investigated and the degrees of hydration for alite...

  16. Synthesis of calcium aluminates on the big solar furnace

    International Nuclear Information System (INIS)

    Abdurakhmanov, A. A.; Paizullakhanov, M. S.; Akhadov, Zh.

    2012-01-01

    The processes of synthesizing calcium aluminate in the flow of concentrated solar radiation on Large Solar Furnace are studied. It is shown that the synthesis of calcium aluminate takes place through a process of melting of a mixture of aluminum oxides and calcium (Al 2 O 3 + CaO). At values of power of the concentrated flow of 200 W/cm 2 , thermodynamic conditions for melting of the materials studied were implemented. Full fusion penetration is achieved at a power flow of 400 W/cm 2 . The resulting material exhibits high mechanical properties (the modulus of rupture upon bending is 40 MPa). (author)

  17. Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

    Energy Technology Data Exchange (ETDEWEB)

    Chavda, Mehul A.; Bernal, Susan A. [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Apperley, David C. [Solid-State NMR Group, Department of Chemistry, Durham University, Durham DH1 3LE (United Kingdom); Kinoshita, Hajime [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Provis, John L., E-mail: j.provis@sheffield.ac.uk [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2015-04-15

    The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A {sup 31}P/{sup 27}Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.

  18. Calcium aluminates potential for endodontics and orthopedics applications

    International Nuclear Information System (INIS)

    Santos, G.L. dos; Andrade, T.L.; Oliveira, I.R.; Pandolfelli, V.C.

    2011-01-01

    The mostly used material in the areas of endodontics (MTA, mineral trioxide aggregate) and bone reconstruction (PMMA, polymethyl methacrylate) present some limiting properties requiring thus changes in their compositions as well as the development of alternative materials. In this context, a novel biomaterial-based calcium aluminate cement (CAC) has been studied in order to keep the positive properties and clinical applications of MTA and PMMA, overcoming some their disadvantages. Recent studies involving the use of CAC are based on commercial products consisting of a mixture of phases. Improvements can be attained by searching the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance in applications in the areas of health. By the optimization of the CAC phases production, this article aims to present their characterization based on hydration temperature; working time and setting time; pH, ions solubilization and dissolution in contact with water and different solutions of simulated body fluid. The results indicated the CA phase as the most suitable for application in the areas of health. (author)

  19. Cinética de hidratação de ligantes à base de alumina hidratável ou aluminato de cálcio Kinetics of hydration of binders based on hydratable alumina or calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2007-03-01

    Full Text Available O estado de dispersão da matriz de um concreto refratário apresenta uma grande influência no comportamento reológico desse material, determinando as técnicas utilizadas para a sua aplicação. Tais métodos normalmente exigem a preparação de concretos com elevada fluidez, que possam ser bombeados com facilidade e sejam capazes de preencher moldes de formato complexo sem a necessidade de aplicação de vibração. Entretanto, embora tais requisitos favoreçam uma boa trabalhabilidade do concreto, tendem a aumentar o tempo requerido para efetuar a desmoldagem do corpo conformado. Uma vez que o desenvolvimento da resistência mecânica do concreto está intimamente relacionado ao processo de hidratação do ligante hidráulico, este necessita ser controlado quando se busca a redução do tempo para a desmoldagem. Tal controle depende de um profundo conhecimento das variáveis que determinam a cinética das reações. Neste contexto, o objetivo deste trabalho foi o de avaliar a influência do tipo de ligante hidráulico, da temperatura e da presença de finos (matriz ou de aditivos inorgânicos adicionados ao concreto sobre o processo de hidratação por meio de medidas de temperatura e ensaios reológicos oscilatórios em função do tempo.The dispersion of refractory castables matrix presents a great influence on their rheological behavior, which defines the most appropriate methods for placing these materials. The growing demand for automatically transported refractory castables has promoted the use of pumpable castables, usually specified as self flow compositions. Nevertheless, castables with higher fluidity present longer workability, leading to extended demoulding times. Because the strength development is intimately linked to the hydration process of calcium aluminate cement or hydratable alumina, it needs to be controlled in order to reach the minimum time for demoulding, contributing to reducing overall costs. The control of cement

  20. Electrical transport properties of calcium and barium aluminates

    NARCIS (Netherlands)

    Metselaar, R.; Hoefsloot, A.M.

    1987-01-01

    Electrical conductivity and ionic transport numbers have been measured of barium and calcium aluminates with composition CaO·nAl2O3 (n=7/12, 1, 2, 6) and 0.82 BaO·6Al2O3. At room temperatures these compounds are insulators, but at high temperatures mixed conductivity is observed. Ionic transport

  1. Hydration water and microstructure in calcium silicate and aluminate hydrates

    International Nuclear Information System (INIS)

    Fratini, Emiliano; Ridi, Francesca; Chen, Sow-Hsin; Baglioni, Piero

    2006-01-01

    Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and near-infrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm -1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron scattering (USANS) and wide

  2. Characterization and quantitative determination of calcium aluminate clinker phases through reflected light microscopy

    International Nuclear Information System (INIS)

    Marciano Junior, E.; Cunha Munhoz, F.A. da; Splettstoser Junior, J.; Placido, W.F.

    1989-01-01

    The identification and quantitative determination of phases in calcium aluminate clinker is of great importance to the producer, as it enables a better understanding of the cement and concrete properties, specially those concerning setting time and compressive strenght. Polished sections of three electrofused clinkers, one experimental and two industrial, were used to select the most suitable etchings in order to identify by microscopy the main phases (Ca, CA 2 , C 2 AS, C 12 A 7 , α-Al 2 O 3 ). Quantitative phases determinations by reflected light microscopy showed good results when compared to X-ray diffractometry measurements [pt

  3. Calcium Orthophosphate Cements and Concretes

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-03-01

    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  4. Contribution to the study of wastes stabilization by sulfo-aluminate cement

    International Nuclear Information System (INIS)

    Peysson, S.

    2005-02-01

    Calcium sulfo-aluminate cement is mainly composed of yeelimite known to be a precursor of ettringite formation. Ettringite is able to incorporate several heavy metals by isomorphous substitutions without altering its crystalline structure. The design of a binder required for immobilizing heavy metals was undertaken. The hydration study of clinker, and cement containing 4 amounts of gypsum has been carried out by means of XRD, DTA and IR spectrometry. It was pointed out that the addition of gypsum enhances hydration. Two binders were selected: 80/20 and 70/30. The immobilisation of 7 pollutants was very successful. Nevertheless, damages appeared with the binder 70/30 containing sodium chromate and dichromate: sodium caused activation of yeelimite reactivity and important dissolution of gypsum leading to important ettringite production. With a great amount of gypsum (30 %), dissolution led to secondary ettringite formation which damaged the hardened paste. Adding polyol enhances the retention of sodium chromate. On the other hand, the immobilisation of two types of weakly radioactive wastes supplied by CEA has been made. Results obtained in terms of setting time, compressive strength and leaching were excellent. (author)

  5. Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

    International Nuclear Information System (INIS)

    Li, Xuerun; Zhang, Yu; Shen, Xiaodong; Wang, Qianqian; Pan, Zhigang

    2014-01-01

    The formation kinetics of tricalcium aluminate (C 3 A) and calcium sulfate yielding calcium sulfoaluminate (C 4 A 3 $) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C 3 A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca 3 Al 2 O 6 + CaSO 4 → Ca 4 Al 6 O 12 (SO 4 ) + 6CaO was the primary reaction 4 Al 6 O 12 (SO 4 ) + 10CaO → 6Ca 3 Al 2 O 6 + 2SO 2 ↑ + O 2 ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C 4 A 3 $ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C 4 A 3 $ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca 2+ and SO 4 2− were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C 3 A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion

  6. Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete

    Directory of Open Access Journals (Sweden)

    Bikić Farzet H.

    2010-01-01

    Full Text Available The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper, the influence of chemical bonding of chlorides with aluminates during the process of cement hydration on corrosion of steel bars in concrete was investigated. The process of chlorides bonding with aluminates yielding monochloride aluminate is monitored by XRD analyses. It was found that the amount of chlorides bonding with aluminates increases with an increase of temperature, and as a result, reduces the amount of 'free' chlorides in concrete. Potentiodynamic measurements have shown that increase in temperature of the heat treatment of working electrodes by chlorides leads to a reduction of steel bars corrosion as a result of either the increase of the monochloride-aluminate content or the decrease of free chlorides amount. Chlorides bound in chloroaluminate hydrates do not cause activation of steel bars corrosion in concrete. It was also proven that the increase of free chlorides concentration in the concrete leads to intensification of steel bars corrosion. This additionally approves that free chlorides are only the activators of process of steel bars corrosion in the concrete.

  7. Physical and Mechanical Properties of Composites Made with Aluminous Cement and Basalt Fibers Developed for High Temperature Application

    Directory of Open Access Journals (Sweden)

    Pavel Reiterman

    2015-01-01

    Full Text Available Present paper deals with the experimental study of the composition of refractory fiber-reinforced aluminous cement based composites and its response to gradual thermal loading. Basalt fibers were applied in doses of 0.25, 0.5, 1.0, 2.0, and 4.0% in volume. Simultaneously, binder system based on the aluminous cement was modified by fine ground ceramic powder originated from the accurate ceramic blocks production. Ceramic powder was dosed as partial replacement of used cement of 5, 10, 15, 20, and 25%. Influence of composition changes was evaluated by the results of physical and mechanical testing; compressive strength, flexural strength, bulk density, and fracture energy were determined on the different levels of temperature loading. Increased dose of basalt fibers allows reaching expected higher values of fracture energy, but with respect to results of compressive and flexural strength determination as an optimal rate of basalt fibers dose was considered 0.25% in volume. Fine ground ceramic powder application led to extensive increase of residual mechanical parameters just up to replacement of 10%. Higher replacement of aluminous cement reduced final values of bulk density but kept mechanical properties on the level of mixtures without aluminous cement replacement.

  8. Thermoluminescent response of calcium di aluminate intrinsic and doped with Cr3+

    International Nuclear Information System (INIS)

    Ceron R, P. V.; Vallejo H, M. A.; Sosa A, M. A.; Montes R, E.; Diaz G, J. A. I.; Diaz T, L. A.

    2017-10-01

    In numerous studies the thermoluminescent response (Tl) of aluminum oxide has been presented in which various dopants have been incorporated to increase the number of defects and thus modify their dosimetric properties. In related materials such as aluminates have been doped with trivalent ions and their optical characteristics have been determined. Due to this background, the motivation to study the aluminates as possible thermoluminescent dosimeters arises. In this work the synthesis of intrinsic calcium aluminate powders and doped with Cr 3+ is presented by the combustion method, to elaborate pellets and evaluate their Tl response with different radiation sources. The material obtained was characterized by XRD, X-ray fluorescence and UV-Vis; it was found to belong to the monoclinic phase of calcium di aluminate (CaAl 4 O 7 ) with a crystal size of 55 nm, the presence of Cr 3+ in the crystal lattice was also observed. The samples showed a good response Tl for UV radiation, X-rays from a 70 kV source and for Co-60 gammas. The results found show that CaAl 4 O 7 is a good candidate to study its dosimetric properties. (Author)

  9. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use .... or open dumping which have effect on surface and ... Table 1: Chemical Composition of Calcium Carbide Waste and Cement.

  10. Re-examining the prospects of aluminous cements based on alkali-earth and rare-earth oxides

    International Nuclear Information System (INIS)

    Chatterjee, A.K.

    2009-01-01

    In the family of aluminous cements the potential of strontium aluminate, the strontium-barium aluminate and the barium aluminate cements have been sporadically and incoherently studied over several decades in various parts of the world and more particularly in the East European countries without much wide-spread commercial success. Attempts had also been made to extend the exploratory studies to the (Ca, Sr, Ba)O-Al 2 O 3 -ZrO 2 -HfO 2 system to synthesize super-refractory binders. In fact, the above compositions, prima facie, seem to have the potential of arriving at cementitious formulations that, apart from being super-refractory, may as well be highly resistant to seawater, X-rays and gamma radiation. Looking at these potentials, quite a few experimental studies have been carried out under the guidance and supervision of the present author. The present paper is an endeavour to collate the data on some of these systems both from the published literature as well as from the author's findings. The prime motive has been to review and re-assess the prospects of manufacturing a range of new aluminous binders with superior properties.

  11. Calcium aluminates for quick cesium trapping, application for nuclear power plants

    International Nuclear Information System (INIS)

    Capmas, A.; Dubourg, M.; Boch, P.

    1993-01-01

    It has recently been shown that cesium dissolved in water could be trapped in a solid structure by adding cementitious calcium aluminates and fume silica. Calcium aluminates are heat resistant and widely used as refractory products. Extensive studies on the rheological properties has been achieved. It is now possible to obtain flow properties to such an extent as to percolate a slurry through broken structures and give high mechanical strength in a short time. This along with the other properties of thermal shock resistance and cesium trapping makes a solution possible for nuclear building safety as a preventitive or a curative material. For example, at Chernobyl, this material could improve safety by remote casting techniques, construction of a structure which could serve as as ash tray under the coruim. Remotelly controlled equipment needed for this are in operation in more than 50 standardized PWR's. The equipment performs maintenance and inspection tasks with low radiation exposure

  12. Calcium phosphate cement scaffolds with PLGA fibers.

    Science.gov (United States)

    Vasconcellos, Letícia Araújo; dos Santos, Luís Alberto

    2013-04-01

    The use of calcium phosphate-based biomaterials has revolutionized current orthopedics and dentistry in repairing damaged parts of the skeletal system. Among those biomaterials, the cement made of hydraulic grip calcium phosphate has attracted great interest due to its biocompatibility and hardening "in situ". However, these cements have low mechanical strength compared with the bones of the human body. In the present work, we have studied the attainment of calcium phosphate cement powders and their addition to poly (co-glycolide) (PLGA) fibers to increase mechanical properties of those cements. We have used a new method that obtains fibers by dripping different reagents. PLGA fibers were frozen after lyophilized. With this new method, which was patented, it was possible to obtain fibers and reinforcing matrix which furthered the increase of mechanical properties, thus allowing the attainment of more resistant materials. The obtained materials were used in the construction of composites and scaffolds for tissue growth, keeping a higher mechanical integrity. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Pressure induced reactions amongst calcium aluminate hydrate phases

    KAUST Repository

    Moon, Ju-hyuk; Oh, Jae Eun; Balonis, Magdalena; Glasser, Fredrik P.; Clark, Simon M.; Monteiro, Paulo J.M.

    2011-01-01

    The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt

  14. Microstructure of amorphous aluminum hydroxide in belite-calcium sulfoaluminate cement

    Energy Technology Data Exchange (ETDEWEB)

    Song, Fei; Yu, Zhenglei; Yang, Fengling; Lu, Yinong, E-mail: yinonglu@njtech.edu.cn; Liu, Yunfei, E-mail: yfliu@njtech.edu.cn

    2015-05-15

    Belite-calcium sulfoaluminate (BCSA) cement is a promising low-CO{sub 2} alternative to ordinary Portland cement. Herein, aluminum hydroxide (AH{sub 3}), the main amorphous hydration product of BCSA cement, was investigated in detail. The microstructure of AH{sub 3} with various quantities of gypsum was investigated via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The AH{sub 3} with various morphologies were observed and confirmed in the resulting pastes. Particular attention was paid to the fact that AH{sub 3} always contained a small amount of Ca according to the results of EDS analysis. The AH{sub 3} was then characterized via high resolution transmission electron microscopy (HRTEM). The results of HRTEM indicated that Ca arose from nanosized tricalcium aluminate hexahydrate which existed in the AH{sub 3}.

  15. Synthesis of calcium aluminate with silicon addition for application in biomaterials

    International Nuclear Information System (INIS)

    Rodrigues, P.J.; Almeida, L.H.S.; Pappen, F.G.; Ribeiro, A.S.; Cava, S.S.; Veiga, F.C.T.; Jurado, J.

    2016-01-01

    Ceramic materials have biocompatibility have been studied, researched and applied in various treatments such as endodontics and orthopedics. This study aims to carry out the synthesis by the polymeric precursor method for post calcium trialuminato (C3A) and with addition of 1% and 5% silver, them the powders were calcined in de temperature 1000°C, carried out a comparative study between them. The ceramic powders were characterized by X-ray diffraction, having a phase composition, scanning electron microscopy (SEM) associated with EDS observed grain morphology and quantity of the chemical elements. The analysis flow, pH, release of calcium ions (Ca"2"+) and silver ions (Ag"+) were evaluated with the sealer MTA Fillapex result that calcium aluminate addition of silver improved the MTA Fillapex stream with the release of ions Ca"+"2, being a material that allows applications in the field of endodontics. (author)

  16. Pressure induced reactions amongst calcium aluminate hydrate phases

    KAUST Repository

    Moon, Ju-hyuk

    2011-06-01

    The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies. © 2011 Elsevier Ltd. All rights reserved.

  17. Methods of use of calcium hexa aluminate refractory linings and/or chemical barriers in high alkali or alkaline environments

    Science.gov (United States)

    McGowan, Kenneth A; Cullen, Robert M; Keiser, James R; Hemrick, James G; Meisner, Roberta A

    2013-10-22

    A method for improving the insulating character/and or penetration resistance of a liner in contact with at least one of an alkali and/or alkaline environments is provided. The method comprises lining a surface that is subject to wear by an alkali environment and/or an alkaline environment with a refractory composition comprising a refractory aggregate consisting essentially of a calcium hexa aluminate clinker having the formula CA.sub.6, wherein C is equal to calcium oxide, wherein A is equal to aluminum oxide, and wherein the hexa aluminate clinker has from zero to less than about fifty weight percent C.sub.12A.sub.7, and wherein greater than 98 weight percent of the calcium hexa aluminate clinker having a particle size ranging from -20 microns to +3 millimeters, for forming a liner of the surface. This method improves the insulating character/and or penetration resistance of the liner.

  18. Synthesis and test of sorbents based on calcium aluminates for SE-SR

    International Nuclear Information System (INIS)

    Barelli, L.; Bidini, G.; Di Michele, A.; Gallorini, F.; Petrillo, C.; Sacchetti, F.

    2014-01-01

    Highlights: • Synthesis strategy of CaO incorporation into calcium aluminates was approached. • Three innovative sorbents (M1, M2, M3) were synthesized and characterized. • Sorption capacity of developed sorbents was evaluated in multi-cycle processes. • M3 sorbent showed best performance, much higher than conventional CaO ones. • M3 sorbent functionality in SE-SR process was verified. - Abstract: Greenhouse gases emission of power generation plants will be continuously tightened to achieve European targets in terms of CO 2 emissions. In particular, the switching to a sustainable power generation using fossil fuels will be strongly encouraged in the future. In this context, sorption-enhanced steam reforming (SE-SR) is a promising process because it can be implemented as a CCS pre-combustion methodology. The purpose of this study is to develop and test innovative materials in order to overcome main limitations of standard CaO sorbent, usually used in the SE-SR process. The investigated innovative sorbents are based on incorporation of CaO particles into inert materials which significantly reduce the performance degradation. In particular, sorbent materials based on calcium aluminates were considered, investigating different techniques of synthesis. All synthesized materials were packed, together with the catalyst, in a fixed bed reactor and tested in sorption/regeneration cycles. Significant improvements were obtained respect to standard CaO regarding sorption capacity stability exhibited by the sorbent

  19. Calcium aluminates potential for endodontics and orthopedics applications; Aluminatos de calcio e seu potencial para aplicacao em endodontia e ortopedia

    Energy Technology Data Exchange (ETDEWEB)

    Santos, G.L. dos; Andrade, T.L.; Oliveira, I.R., E-mail: ivonero@univap.br [Universidade do Vale do Paraiba (UNIVAP), Sao Jose dos Campos, SP (Brazil); Pandolfelli, V.C. [Universidade Federal de Sao Carlos (DEMa/UFSCar), SP (Brazil)

    2011-07-01

    The mostly used material in the areas of endodontics (MTA, mineral trioxide aggregate) and bone reconstruction (PMMA, polymethyl methacrylate) present some limiting properties requiring thus changes in their compositions as well as the development of alternative materials. In this context, a novel biomaterial-based calcium aluminate cement (CAC) has been studied in order to keep the positive properties and clinical applications of MTA and PMMA, overcoming some their disadvantages. Recent studies involving the use of CAC are based on commercial products consisting of a mixture of phases. Improvements can be attained by searching the synthesis routes of CAC aiming the proper balance between the phases and the control of impurities that may impair its performance in applications in the areas of health. By the optimization of the CAC phases production, this article aims to present their characterization based on hydration temperature; working time and setting time; pH, ions solubilization and dissolution in contact with water and different solutions of simulated body fluid. The results indicated the CA phase as the most suitable for application in the areas of health. (author)

  20. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.; Chae, S. R.; Benmore, C. J.; Wenk, H. R.; Monteiro, P. J. M.

    2010-01-01

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  1. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  2. Synthesis of Portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance

    Science.gov (United States)

    Chen, Irvin Allen

    Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, (1) incorporation of waste materials in portland cement synthesis, and (2) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S--C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate

  3. Substitution of strontium for calcium in glass ionomer cements (Part ...

    African Journals Online (AJOL)

    Substitution of strontium for calcium in glass ionomer cements (Part 1): Glass synthesis and characterisation, and the effects on the cement handling variables and ... acid to form glass ionomer cements, whose properties were investigated at different time points: working and setting times were determined by rheometry; and, ...

  4. Development of a fully injectable calcium phosphate cement

    Indian Academy of Sciences (India)

    Permanent link: https://www.ias.ac.in/article/fulltext/boms/026/04/0415-0422. Keywords. Calcium phosphate cements; hydroxyapatite; bioceramics; bone substitute; orthopedic; dental. Abstract. A study on the development of a fully injectable calcium phosphate cement for orthopedic and dental applications is presented.

  5. Preparation and characterization of bioceramics produced from calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Andriotis, O.; Katsamenis, O.L. [Department of Materials Science, University of Patras, 26504, Patras (Greece); Mouzakis, D.E. [Technological Educational Institute of Larisa, Department of Mechanical Engineering, T.E.I of Larissa, 411 10, Larissa (Greece); Bouropoulos, N. [Foundation for Research and Technology, Hellas, Institute of Chemical Engineering and High Temperature Chemical Processes, FORTH/ICE-HT, P.O. Box 1414, 26504 Rio Patras (Greece)

    2010-03-15

    The present work reports a method for preparing calcium phosphate ceramics by calcination of calcium phosphate cements composed mainly of calcium deficient hydroxyapatite (CDHA). It was found that hardened cements calcinied at temperatures from to 600 to 1300 C were transformed to tricalcium phosphates. Moreover the compressive strength was determined and porosity was estimated as a function of the calcination temperature. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Investigation of barium-calcium aluminate process to manufacture and characterize impregnated thermionic cathode for power microwave devices

    International Nuclear Information System (INIS)

    Higashi, Cristiane

    2006-01-01

    In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pyrolysis atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques - formation temperature is about 1000 deg C in hydrogen atmosphere), whereas it presented the lower formation temperature (800 deg C) in oxidizing atmosphere (O 2 ). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV. (author)

  7. Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

    International Nuclear Information System (INIS)

    Tsipas, Sophia A.; Gordo, Elena

    2016-01-01

    Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgy (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition conditions

  8. Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

    Energy Technology Data Exchange (ETDEWEB)

    Tsipas, Sophia A., E-mail: stsipas@ing.uc3m.es; Gordo, Elena

    2016-08-15

    Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgy (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations. - Highlights: •Simultaneous co-deposition of Mo-Al onto powder metallurgy and wrought Ti alloy •Thermodynamic calculations were used to optimize deposition conditions

  9. Hydrophobic Calcium Carbonate for Cement Surface

    Directory of Open Access Journals (Sweden)

    Shashi B. Atla

    2017-12-01

    Full Text Available This report describes a novel way to generate a highly effective hydrophobic cement surface via a carbonation route using sodium stearate. Carbonation reaction was carried out at different temperatures to investigate the hydrophobicity and morphology of the calcium carbonate formed with this process. With increasing temperatures, the particles changed from irregular shapes to more uniform rod-like structures and then aggregated to form a plate-like formation. The contact angle against water was found to increase with increasing temperature; after 90 °C there was no further increase. The maximum contact angle of 129° was obtained at the temperature of 60 °C. It was also found that carbonation increased the micro hardness of the cement material. The micro hardness was found to be dependent on the morphology of the CaCO3 particles. The rod like structures which caused increased mineral filler produced a material with enhanced strength. The 13C cross polarization magic-angle spinning NMR spectra gave plausible explanation of the interaction of organic-inorganic moieties.

  10. Ternary Blends of High Aluminate Cement, Fly ash and Blast-furnace slag for Sewerage Lining Mortar

    Science.gov (United States)

    Chao, L. C.; Kuo, C. P.

    2018-01-01

    High aluminate cement (HAC), fly ash (FA) and blast-furnace slag (BFS) have been treated sustainable materials for the use of cement products for wastewater infrastructure due to their capabilities of corrosion resistance. The purpose of this study is to optimize a ternary blend of above mentioned materials for a special type of mortar for sewerage lining. By the using of Taguchi method, four control parameters including water/cementitious material ratio, mix water content, fly ash content and blast-furnace slag content were considered in nine trial mix designs in this study. By evaluating target properties including (1) maximization of compressive strength, (2) maximization of electricity resistance and (3) minimization of water absorption rate, the best possible levels for each control parameter were determined and the optimal mix proportions were verified. Through the implementation of the study, a practical and completed idea for designing corrosion resistive mortar comprising HAC, FA and BSF is provided.

  11. The effect of dolomite type and Al2O3 content on the phase composition in aluminous cements containing spinel

    Directory of Open Access Journals (Sweden)

    R. Naghizadeh

    2011-06-01

    Full Text Available In this paper, the effect of dolomite type and Al2O3 content on the phase composition in aluminous cements containing MA spinel is investigated. For this reason, the raw and calcined dolomites are used as raw materials along with calcined alumina in the preparation of the cement. Then, different compositions are prepared at 1350°C using the sintering method and their mineralogical compositions are investigated using the diffractometric technique. Also, their microstructures arre evaluated. The results indicate that raw materials used have great effect on the type and amount of formed phases in cement composition. Independently of the dolomite type used, a mixed phase product consisting of spinel accompanied by CA and CA2 is obtained. The content of CA phase in the cement composition is decreased with increasing of Al2O3 in the raw materials composition. On the other hand, the content of CA2 phase is increased with the addition of Al2O3. In addition, the results show that the formation of C12A7 is favored by use of calcined dolomite.

  12. Characterization and chemical activity of Portland cement and two experimental cements with potential for use in dentistry.

    Science.gov (United States)

    Camilleri, J

    2008-09-01

    To evaluate the chemical activity of Portland cement and two other cement types with similar chemical composition to mineral trioxide aggregate with the aim of developing these cements for further applications in dentistry. The chemical composition of the three cement types namely Portland cement, calcium sulpho-aluminate cement and calcium fluoro-aluminate cement was evaluated by elemental analysis using energy dispersive analysis with X-ray under the scanning electron microscope and by X-ray diffraction analysis (XRD) to determine the phases. The constituents of the hydration reaction by-products were evaluated by XRD analysis of the set cements at 1, 7, 28 and 56 days and by analysis of the leachate by ion chromatography. The pH of both cements and leachate was determined at different time intervals. Cements admixed with micro-silica were also tested to determine the effect of micro-silica on the reaction by-products. All three cement types were composed of tricalcium silicate as the main constituent phase. The hydration reaction of Portland cement produced calcium hydroxide. However, this was not present in the other cements tested at all ages. Admixed micro-silica had little or no effect on the cements with regard to reaction by-products. The pH of all cements tested was alkaline. Both the experimental calcium sulpho-aluminate cement and calcium fluoro-aluminate cement had different hydration reactions to that of Portland cement even though calcium silicate was the major constituent element of both cement types. No calcium hydroxide was produced as a by-product to cement hydration. Micro-silica addition to the cement had no effect on the hydration reaction.

  13. Development of a degradable cement of calcium phosphate and calcium sulfate composite for bone reconstruction

    International Nuclear Information System (INIS)

    Guo, H; Wei, J; Liu, C S

    2006-01-01

    A new type of composite bone cement was prepared and investigated by adding calcium sulfate (CS) to calcium phosphate cement (CPC). This composite cement can be handled as a paste and easily shaped into any contour, which can set within 5-20 min, the setting time largely depending on the liquid-solid (L/S) ratio; adding CS to CPC had little effect on the setting time of the composite cements. No obvious temperature increase and pH change were observed during setting and immersion in simulated body fluid (SBF). The compressive strength of the cement decreased with an increase in the content of CS. The degradation rate of the composite cements increased with time when the CS content was more than 20 wt%. Calcium deficient apatite could form on the surface of the composite cement because the release of calcium into SBF from the dissolution of CS and the apatite of the cement induced the new apatite formation; increasing the content of CS in the composite could improve the bioactivity of the composite cements. The results suggested that composite cement has a reasonable setting time, excellent degradability and suitable mechanical strength and bioactivity, which shows promising prospects for development as a clinical cement

  14. stabilization of ikpayongo laterite with cement and calcium carbide

    African Journals Online (AJOL)

    PROF EKWUEME

    the stabilization of soil will ensure economy in road construction, while providing an effective way of disposing calcium carbide waste. KEYWORDS: Cement, Calcium carbide waste, Stabilization, Ikpayongo laterite, Pavement material. INTRODUCTION. Road building in the developing nations has been a major challenge to ...

  15. Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements.

    Science.gov (United States)

    Combes, C; Miao, Baoji; Bareille, Reine; Rey, Christian

    2006-03-01

    The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cement set and hardened within 2h at 37 degrees C in an atmosphere saturated with water and the final composition of the cement consisted mostly of aragonite. The hardened cement was microporous and showed poor mechanical properties. Cytotoxicity tests revealed excellent cytocompatibility of calcium carbonate cement compositions. Calcium carbonates with a higher solubility than the apatite formed for most of the marketed calcium phosphate cements might be of interest to increase biomedical cement resorption rates and to favour its replacement by bone tissue.

  16. Influence of ferrite phase in alite-calcium sulfoaluminate cements

    Science.gov (United States)

    Duvallet, Tristana Yvonne Francoise

    Since the energy crisis in 1970's, research on low energy cements with low CO2- emissions has been increasing. Numerous solutions have been investigated, and the goal of this original research is to create a viable hybrid cement with the components of both Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC), by forming a material that contains both alite and calcium sulfoaluminate clinker phases. Furthermore, this research focuses on keeping the cost of this material reasonable by reducing aluminum requirements through its substitution with iron. The aim of this work would produce a cement that can use large amounts of red mud, which is a plentiful waste material, in place of bauxite known as an expensive raw material. Modified Bogue equations were established and tested to formulate this novel cement with different amounts of ferrite, from 5% to 45% by weight. This was followed by the production of cement from reagent chemicals, and from industrial by-products as feedstocks (fly ash, red mud and slag). Hydration processes, as well as the mechanical properties, of these clinker compositions were studied, along with the addition of gypsum and the impact of a ferric iron complexing additive triisopropanolamine (TIPA). To summarize this research, the influence of the addition of 5-45% by weight of ferrite phase, was examined with the goal of introducing as much red mud as possible in the process without negatively attenuate the cement properties. Based on this PhD dissertation, the production of high-iron alite-calcium sulfoaluminateferrite cements was proven possible from the two sources of raw materials. The hydration processes and the mechanical properties seemed negatively affected by the addition of ferrite, as this phase was not hydrated entirely, even after 6 months of curing. The usage of TIPA counteracted this decline in strength by improving the ferrite hydration and increasing the optimum amount of gypsum required in each composition

  17. Review for the improvement of low alkaline cement from viewpoint of hydration control

    International Nuclear Information System (INIS)

    Imoto, Harutake; Yamamoto, Takeshi; Hironaga, Michihiko

    2006-01-01

    It is concerns that high pH pore water from cementitious materials will become harmful to barrier system such as bedrock and buffer materials in the radioactive repository. Then sulpho-aluminate type low alkaline cement 'LAC' was developed. But LAC concrete has some problems on its workability and initial crack due to high reactability. It is necessary for LAC to be improved to avoid these problems. In this study, the conventional knowledge on reactability and hardened properties of sulpho-aluminate cement were reviewed from the viewpoint of hydration controlling. From the results, the recipe for the improvement of 'LAC' was investigated. Early hydration of sulpho-aluminate were delayed by the decreasement of calcium hydroxide quantity and increasement of calcium sulphate in cement. Retarder delayed hydration of sulpho-aluminate more than composition of cement. The effect of cement admixture on the early hydration of sulpho-aluminate cement were not reported. Blast furnace slag as cement admixture affect on the long-term hydration and strength development. So, it was guess that sulpho-aluminate type low alkaline cement 'LAC' have good strength development by controlling recipi of additional ratio of blast furnace slag and be-lite content in the sulpho-aluminate cement. (author)

  18. Substitution of strontium for calcium in glass ionomer cements (Part ...

    African Journals Online (AJOL)

    Objectives: To investigate the effects of substituting strontium for calcium in fluoroaluminosilicate glass on the mechanical and ion-releasing properties of high-viscosity glass ionomer cements. Design: An exploratory, laboratory-based study. Setting: Dental biomaterials research laboratory, Dental Physical Sciences Unit, ...

  19. Injectable biphasic calcium phosphate cements as a potential bone substitute

    NARCIS (Netherlands)

    Sariibrahimoglu, K.; Wolke, J.G.C.; Leeuwenburgh, S.C.G.; Yubao, L.; Jansen, J.A.

    2014-01-01

    Apatitic calcium phosphate cements (CPCs) have been widely used as bone grafts due to their excellent osteoconductive properties, but the degradation properties are insufficient to stimulate bone healing in large bone defects. A novel approach to overcome the lack of degradability of apatitic CPC

  20. Stabilization of Ikpayongo laterite with cement and calcium carbide ...

    African Journals Online (AJOL)

    Laterite obtained from Ikpayongo was stabilized with 2-10 % cement and 2-10 % Calcium Carbide waste, for use as pavement material. Atterberg's limits test, California bearing ratio (CBR) and unconfined compressive strength (UCS) tests were conducted on the natural laterite and the treated soil specimens. The plasticity ...

  1. Preparation, physical-chemical characterisation and cytocompatibility of calcium carbonate cements

    OpenAIRE

    Combes, Christèle; Miao, Baoji; Bareille, Reine; Rey, Christian

    2006-01-01

    The feasibility of calcium carbonate cements involving the recrystallisation of metastable calcium carbonate varieties has been demonstrated. Calcium carbonate cement compositions presented in this paper can be prepared straightforwardly by simply mixing water (liquid phase) with two calcium carbonate phases (solid phase) which can be easily obtained by precipitation. An original cement composition was obtained by mixing amorphous calcium carbonate and vaterite with an aqueous medium. The cem...

  2. Calcium phosphate cements with strontium halides as radiopacifiers.

    Science.gov (United States)

    López, Alejandro; Montazerolghaem, Maryam; Engqvist, Håkan; Ott, Marjam Karlsson; Persson, Cecilia

    2014-02-01

    High radiopacity is required to monitor the delivery and positioning of injectable implants. Inorganic nonsoluble radiopacifiers are typically used in nondegradable bone cements; however, their usefulness in resorbable cements is limited due to their low solubility. Strontium halides, except strontium fluoride, are ionic water-soluble compounds that possess potential as radiopacifiers. In this study, we compare the radiopacity, mechanical properties, composition, and cytotoxicity of radiopaque brushite cements prepared with strontium fluoride (SrF2 ), strontium chloride (SrCl2 ·6H2 O), strontium bromide (SrBr2 ), or strontium iodide (SrI2 ). Brushite cements containing 10 wt % SrCl2 ·6H2 O, SrBr2 , or SrI2 exhibited equal to or higher radiopacity than commercial radiopaque cements. Furthermore, the brushite crystal lattice in cements that contained the ionic radiopacifiers was larger than in unmodified cements and in cements that contained SrF2 , indicating strontium substitution. Despite the fact that the strontium halides increased the solubility of the cements and affected their mechanical properties, calcium phosphate cements containing SrCl2 ·6H2 O, SrBr2 , and SrI2 showed no significant differences in Saos-2 cell viability and proliferation with respect to the control. Strontium halides: SrCl2 ·6H2 O, SrBr2 , and SrI2 may be potential candidates as radiopacifiers in resorbable biomaterials although their in vivo biocompatibility, when incorporated into injectable implants, is yet to be assessed. Copyright © 2013 Wiley Periodicals, Inc.

  3. Silver-Doped Calcium Phosphate Bone Cements with Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    J. V. Rau

    2016-04-01

    Full Text Available Calcium phosphate bone cements (CPCs with antibacterial properties are demanded for clinical applications. In this study, we demonstrated the use of a relatively simple processing route based on preparation of silver-doped CPCs (CPCs-Ag through the preparation of solid dispersed active powder phase. Real-time monitoring of structural transformations and kinetics of several CPCs-Ag formulations (Ag = 0 wt %, 0.6 wt % and 1.0 wt % was performed by the Energy Dispersive X-ray Diffraction technique. The partial conversion of β-tricalcium phosphate (TCP phase into the dicalcium phosphate dihydrate (DCPD took place in all the investigated cement systems. In the pristine cement powders, Ag in its metallic form was found, whereas for CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, CaAg(PO33 was detected and Ag (met. was no longer present. The CPC-Ag 0 wt % cement exhibited a compressive strength of 6.5 ± 1.0 MPa, whereas for the doped cements (CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % the reduced values of the compressive strength 4.0 ± 1.0 and 1.5 ± 1.0 MPa, respectively, were detected. Silver-ion release from CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, measured by the Atomic Emission Spectroscopy, corresponds to the average values of 25 µg/L and 43 µg/L, respectively, rising a plateau after 15 days. The results of the antibacterial test proved the inhibitory effect towards pathogenic Escherichia coli for both CPC-Ag 0.6 wt % and CPC-Ag 1.0 wt % cements, better performances being observed for the cement with a higher Ag-content.

  4. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

  5. Brittle and ductile adjustable cement derived from calcium phosphate cement/polyacrylic acid composites.

    Science.gov (United States)

    Chen, Wen-Cheng; Ju, Chien-Ping; Wang, Jen-Chyan; Hung, Chun-Cheng; Chern Lin, Jiin-Huey

    2008-12-01

    Bone filler has been used over the years in dental and biomedical applications. The present work is to characterize a non-dispersive, fast setting, modulus adjustable, high bioresorbable composite bone cement derived from calcium phosphate-based cement combined with polymer and binding agents. This cement, we hope, will not swell in simulated body fluid and keep the osteogenetic properties of the dry bone and avoid its disadvantages of being brittle. We developed a calcium phosphate cement (CPC) of tetracalcium phosphate/dicalcium phosphate anhydrous (TTCP/DCPA)-polyacrylic acid with tartaric acid, calcium fluoride additives and phosphate hardening solution. The results show that while composite, the hard-brittle properties of 25wt% polyacrylic acid are proportional to CPC and mixing with additives is the same as those of the CPC without polyacrylic acid added. With an increase of polyacrylic acid/CPC ratio, the 67wt% samples revealed ductile-tough properties and 100wt% samples kept ductile or elastic properties after 24h of immersion. The modulus range of this development was from 200 to 2600MPa after getting immersed in simulated body fluid for 24h. The TTCP/DCPA-polyacrylic acid based CPC demonstrates adjustable brittle/ductile strength during setting and after immersion, and the final reaction products consist of high bioresorbable monetite/brushite/calcium fluoride composite with polyacrylic acid.

  6. Biocompatibility of calcium phosphate bone cement with optimised mechanical properties: an in vivo study.

    Science.gov (United States)

    Palmer, Iwan; Nelson, John; Schatton, Wolfgang; Dunne, Nicholas J; Buchanan, Fraser; Clarke, Susan A

    2016-12-01

    This work establishes the in vivo performance of modified calcium phosphate bone cements for vertebroplasty of spinal fractures using a lapine model. A non-modified calcium phosphate bone cement and collagen-calcium phosphate bone cements composites with enhanced mechanical properties, utilising either bovine collagen or collagen from a marine sponge, were compared to a commercial poly(methyl methacrylate) cement. Conical cement samples (8 mm height × 4 mm base diameter) were press-fit into distal femoral condyle defects in New Zealand White rabbits and assessed after 5 and 10 weeks. Bone apposition and tartrate-resistant acid phosphatase activity around cements were assessed. All implants were well tolerated, but bone apposition was higher on calcium phosphate bone cements than on poly(methyl methacrylate) cement. Incorporation of collagen showed no evidence of inflammatory or immune reactions. Presence of positive tartrate-resistant acid phosphatase staining within cracks formed in calcium phosphate bone cements suggested active osteoclasts were present within the implants and were actively remodelling within the cements. Bone growth was also observed within these cracks. These findings confirm the biological advantages of calcium phosphate bone cements over poly(methyl methacrylate) and, coupled with previous work on enhancement of mechanical properties through collagen incorporation, suggest collagen-calcium phosphate bone cement composite may offer an alternative to calcium phosphate bone cements in applications where low setting times and higher mechanical stability are important.

  7. Effect of the calcium to phosphorus ratio on the setting properties of calcium phosphate bone cements.

    Science.gov (United States)

    Vlad, M D; Gómez, S; Barracó, M; López, J; Fernández, E

    2012-09-01

    α-Tricalcium phosphate (α-TCP) has become the main reactant of most experimental and commercial ceramic bone cements. It has calcium-to-phosphorus (Ca/P) ratio of 1.50. The present study expands and reports on the microstructures and mechanical properties of calcium phosphate (CP) cements containing sintered monolithic reactants obtained in the interval 1.29 properties as well as on their microstructure and crystal phase evolution. The results showed that: (a) CP-cements made with reactants with Ca/P ratio other than 1.50 have longer setting and lower hardening properties; (b) CP-cements reactivity was clearly affected by the Ca/P ratio of the starting reactant; (c) reactants with Ca/P calcium pyrophosphate and α- and β-TCP. Similarly, reactants with Ca/P > 1.50 were composed of α-TCP, tetracalcium phosphate and hydroxyapatite; (d) only the reactant with Ca/P = 1.50 was monophasic and was made of α-TCP, which transformed during the setting into calcium deficient hydroxyapatite; (e) CP-cements developed different crystal microstructures with specific features depending on the Ca/P ratio of the starting reactant.

  8. High-temperature Corrosion Resistance of Composite Coating Prepared by Micro-arc Oxidation Combined with Pack Cementation Aluminizing

    Directory of Open Access Journals (Sweden)

    HUANG Zu-jiang

    2018-01-01

    Full Text Available Al2O3 ceramic film was obtained by micro-arc oxidation (MAO process on Al/C103 specimen, which was prepared by pack cementation aluminizing technology on C103 niobium alloy. With the aid of XRD and SEM equipped with EDS, chemical compositions and microstructures of the composite coatings before and after high-temperature corrosion were analyzed. The behavior and mechanism of the composite coatings in high-temperature oxidation and hot corrosion were also investigated. The results indicate that oxidation mass gain at 1000℃ for 10h of the Al/C103 specimen is 6.98mg/cm2, and it is 2.89mg/cm2 of the MAO/Al/C103 specimen. However, the mass gain of MAO/Al/C103 specimen (57.52mg/cm2 is higher than that of Al/C103 specimen (28.08mg/cm2 after oxidation 20h. After hot corrosion in 75%Na2SO4 and 25%NaCl at 900℃ for 50h, the mass gain of Al/C103 and MAO/Al/C103 specimens are 70.54mg/cm2 and 55.71mg/cm2 respectively, Al2O3 and perovskite NaNbO3 phases are formed on the surface; the diffusion of molten salt is suppressed, due to part of NaNbO3 accumulated in the MAO micropores. Therefore, MAO/Al/C103 specimen exhibits better hot corrosion resistance.

  9. Prediction of the Setting Properties of Calcium Phosphate Bone Cement

    Directory of Open Access Journals (Sweden)

    Seyed Mahmud Rabiee

    2012-01-01

    Full Text Available Setting properties of bone substitutes are improved using an injectable system. The injectable bone graft substitutes can be molded to the shape of the bone cavity and set in situ when injected. Such system is useful for surgical operation. The powder part of the injectable bone cement is included of β-tricalcium phosphate, calcium carbonate, and dicalcium phosphate and the liquid part contains poly ethylene glycol solution with different concentrations. In this way, prediction of the mechanical properties, setting times, and injectability helps to optimize the calcium phosphate bone cement properties. The objective of this study is development of three different adaptive neurofuzzy inference systems (ANFISs for estimation of compression strength, setting time, and injectability using the data generated based on experimental observations. The input parameters of models are polyethylene glycol percent and liquid/powder ratio. Comparison of the predicted values and measured data indicates that the ANFIS model has an acceptable performance to the estimation of calcium phosphate bone cement properties.

  10. Synthesis of modified calcium aluminate with lanthanum manganite (LSM) for possible use in solid oxide fuel cell (SOFC)

    International Nuclear Information System (INIS)

    Veiga, F.C.T.; Jurado, J.; Sousa, V.C. de

    2016-01-01

    The fuel cells solid oxide (SOFC) is made up of three basic elements: two electrodes, the anode and cathode and a conductive electrolyte ions. The objective of this work consists of calcium aluminate synthesis modified LSM in a 1: 1 by combustion synthesis method with a view to its use as a cathode in SOFC. The characterization of the post was carried out by the methods of XRD, TEM and EIS. After heat treatment at 1200°C/4 hours it was possible to obtain Ca0.5Sr1.5MnO4 and CaMnO2.56 phases. The material showed a semiconductor characteristics because with increasing temperature the electrical resistance value tends to decrease obtaining electrical conductivity greater than 10-6S / cm featuring an extrinsic semiconductor with an activation energy of 0.12. Therefore, with an activation energy value within the range of materials used for a SOFC cathodes. (author)

  11. Effects of fibers on expansive shotcrete mixtures consisting of calcium sulfoaluminate cement, ordinary Portland cement, and calcium sulfate

    Directory of Open Access Journals (Sweden)

    H. Yu

    2018-04-01

    Full Text Available The mining industry often uses shotcrete for ground stabilization. However, cracking within shotcrete is commonly observed, which delays production schedules and increases maintenance costs. A possible crack reduction method is using expansive shotcrete mixture consisting of calcium sulfoaluminate cement (CSA, ordinary Portland cement (OPC, and calcium sulfate (CS to reduce shrinkage. Furthermore, fibers can be added to the mixture to restrain expansion and impede cracking. The objective of this paper is to study the effects of nylon fiber, glass fiber, and steel fiber on an expansive shotcrete mixture that can better resist cracking. In this study, parameters such as density, water absorption, volume of permeable voids, unconfined compressive strength (UCS, splitting tensile strength (STS, and volume change of fiber-added expansive mixtures were determined at different time periods (i.e. the strengths on the 28th day, and the volume changes on the 1st, 7th, 14th, 21st, and 28th days. The results show that addition of fibers can improve mixture durability, in the form of decreased water absorption and reduced permeable pore space content. Moreover, the expansion of the CSA-OPC-CS mixture was restrained up to 50% by glass fiber, up to 43% by nylon fiber, and up to 28% by steel fiber. The results show that the STS was improved by 57% with glass fiber addition, 43% with steel fiber addition, and 38% with nylon fiber addition. The UCS was also increased by 31% after steel fiber addition, 26% after nylon fiber addition, and 16% after glass fiber addition. These results suggest that fiber additions to the expansive shotcrete mixtures can improve durability and strengths while controlling expansion. Keywords: Shotcrete, Restrained expansion, Fibers, Calcium sulfoaluminate cement (CSA, Ordinary Portland cement (OPC, Calcium sulfate (CS

  12. Calcium silicate-based cements: composition, properties, and clinical applications.

    Science.gov (United States)

    Dawood, Alaa E; Parashos, Peter; Wong, Rebecca H K; Reynolds, Eric C; Manton, David J

    2017-05-01

    Mineral trioxide aggregate (MTA) is a calcium silicate-based cement (CSC) commonly used in endodontic procedures involving pulpal regeneration and hard tissue repair, such as pulp capping, pulpotomy, apexogenesis, apexification, perforation repair, and root-end filling. Despite the superior laboratory and clinical performance of MTA in comparison with previous endodontic repair cements, such as Ca(OH) 2 , MTA has poor handling properties and a long setting time. New CSC have been commercially launched and marketed to overcome the limitations of MTA. The aim of the present review was to explore the available literature on new CSC products, and to give evidence-based recommendations for the clinical use of these materials. Within the limitations of the available data in the literature regarding the properties and performance of the new CSC, the newer products could be promising alternatives to MTA; however, further research is required to support this assumption. © 2015 Wiley Publishing Asia Pty Ltd.

  13. Leach characterization of cement encapsulated wastes

    International Nuclear Information System (INIS)

    Roy, D.M.; Scheetz, B.E.; Wakeley, L.D.; Barnes, M.W.

    1982-01-01

    Matrix encapsulation of defense nuclear waste as well as intermediate-level commercial wastes within a low-temperature cementitious composite were investigated. The cements for this study included both as-received and modified calcium silicate and calcium aluminate cements. Specimens were prepared following conventional formulation techniques designed to produce dense monoliths, followed by curing at 60 0 C. An alternative preparation procedure is contrasted in which the specimens were ''warm'' pressed in a uniaxial press at 150 0 C at 50,000 psi for 0.5 h. Specimens of the waste/cement composites were leached in deionized water following three different procedures which span a wide range of temperatures and solution saturation conditions. Aluminate and compositionally adjusted silicate cements exhibited a better retentivity for Cs and Sr than did the as-received silicate cement. 15 refs

  14. Optimization of calcium chloride content on bioactivity and mechanical properties of white Portland cement

    International Nuclear Information System (INIS)

    Torkittikul, Pincha; Chaipanich, Arnon

    2012-01-01

    This research investigates the optimization of calcium chloride content on the bioactivity and mechanical properties of white Portland cement. Calcium chloride was used as an addition of White Portland cement at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% by weight. Calcium chloride was dissolved in sterile distilled water and blended with White Portland cement using a water to cement ratio of 0.5. Analysis of the bioactivity and pH of white Portland cement pastes with calcium chloride added at various amounts was carried out in simulated body fluid. Setting time, density, compressive strength and volume of permeable voids were also investigated. The characteristics of cement pastes were examined by X-ray diffractometer and scanning electron microscope linked to an energy-dispersive X-ray analyzer. The result indicated that the addition of calcium chloride could accelerate the hydration of white Portland cement, resulting in a decrease in setting time and an increase in early strength of the pastes. The compressive strength of all cement pastes with added calcium chloride was higher than that of the pure cement paste, and the addition of calcium chloride at 8 wt.% led to achieving the highest strength. Furthermore, white Portland cement pastes both with and without calcium chloride showed well-established bioactivity with respect to the formation of a hydroxyapatite layer on the material within 7 days following immersion in simulated body fluid; white Portland cement paste with added 3%CaCl 2 exhibited the best bioactivity. - Highlights: ► Optimization CaCl 2 content on the bioactivity and mechanical properties. ► CaCl 2 was used as an addition at 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10% by weight. ► CaCl 2 resulted in a decrease in setting time and an increase in early strength. ► Addition of 3%CaCl 2 exhibited the optimum formation of hydroxyapatite.

  15. Effect of calcium chloride on physical properties of calcium-enriched mixture cement.

    Science.gov (United States)

    Abbaszadegan, Abbas; Sedigh Shams, Mahdi; Jamshidi, Yasin; Parashos, Peter; Bagheri, Rafat

    2015-12-01

    The aim of this study was to evaluate the effect of adding 10% calcium chloride (CaCl2) on the setting time, solubility and the pH of calcium-enriched mixture (CEM) cement. Setting time was assessed in accordance with American Dental Association specification N°57. Solubility was measured at 24 and 72 h, 7 and 14 days in hydrated and dehydrated conditions by calculating weight change. The pH of MiliQ water in which the CEM cement samples were immersed was measured immediately after each time interval with and without the addition of CaCl2. The data were analysed using the Mann-Whitney U-test and the Student's t-test. The initial setting time was significantly decreased after the addition of 10% CaCl2. The pH of water increased immediately when in contact with the cements in both groups. The weight loss of hydrated and dehydrated specimens was more than 3% and was significantly reduced by the addition of 10% CaCl2. © 2015 Australian Society of Endodontology.

  16. Fabrication and characterization of calcium phosphate cement scaffolds

    International Nuclear Information System (INIS)

    Sousa, E. de; Motisuke, M.; Bertran, C.A.

    2011-01-01

    In Tissue Engineering, the need for scaffolds which are capable of guiding the organization, differentiation and growth of cells leading to the formation of new tissues is highly relevant. For the development of new scaffolds focused on bone tissue therapy, calcium phosphate cements (CPC) have great potential, because besides their resorbability, they present morphology and chemical composition similar to the bone mineral phase. Moreover, there are several processing techniques to produce ceramic scaffolds: polymeric sponge replication, incorporation of organic material into the ceramic powder, gelcasting, emulsion, among others. The aim of this work was to obtain CPCs scaffolds by using two techniques, emulsion and gelcasting. The scaffolds were characterized by their physical and mechanical properties and the crystalline phases formed after the setting reaction of cement were determined by X-ray diffraction. The samples obtained by both methods presented porosity between 61-65% and the microstructure consists of nearly spherical pores (d5o = 50-100 μm). The mechanical strength of the samples ranged from 5.5 to 1.5 MPa. The crystalline phases found were monetite (CaHPO 4 ) and brushite (CaHPO 4 2H 2 O). (author)

  17. Hydration studies of calcium sulfoaluminate cements blended with fly ash

    Energy Technology Data Exchange (ETDEWEB)

    García-Maté, M.; De la Torre, A.G. [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain); León-Reina, L. [Servicios Centrales de Apoyo a la Investigación, Universidad de Málaga, 29071 Málaga (Spain); Aranda, M.A.G. [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain); CELLS-Alba synchrotron, Carretera BP 1413, Km. 3.3, E-08290 Cerdanyola, Barcelona (Spain); Santacruz, I., E-mail: isantacruz@uma.es [Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga (Spain)

    2013-12-15

    The main objective of this work is to study the hydration and properties of calcium sulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied parameters were: i) FA content, 0, 15 and 30 wt.%; and ii) water addition, water-to-CSA mass ratio (w/CSA = 0.50 and 0.65), and water-to-binder mass ratio (w/b = 0.50). Finally, compressive strengths after 6 months of 0 and 15 wt.% FA [w/CSA = 0.50] mortars were similar: 73 ± 2 and 72 ± 3 MPa, respectively. This is justified by the filler effect of the FA as no strong evidences of reactivity of FA with CSA were observed. These results support the partial substitution of CSA cements with FA with the economic and environmental benefits.

  18. Effect of calcium carbonate on hardening, physicochemical properties, and in vitro degradation of injectable calcium phosphate cements.

    NARCIS (Netherlands)

    Sariibrahimoglu, K.; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Yubao, L.; Jansen, J.A.

    2012-01-01

    The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO(3)(2)(-)) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study

  19. Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

    Science.gov (United States)

    Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

    2011-05-01

    Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

  20. Effect of calcium/silicon ratio on retention of uranium (VI) in portland cement materials

    International Nuclear Information System (INIS)

    Tan Hongbin; Li Yuxiang

    2005-01-01

    Calcium silicate hydrate (CSH) materials of varied calcium to silicon (Ca/Si) ratios were prepared by hydrothermal synthesis at 80 degree C, with calcium oxide and micro-silicon employed. These products were determined to be of gel phase by XRD. Leaching tests with 1% hydrochloric acid indicated that more Uranium (VI) was detained by CSH with lower Ca/Si ratios. Alkali-activated slag cement (with a lower Ca/Si ratio) was found to have a stronger retention capacity than Portland cement (with a higher Ca/Si ratio), at 25 degree C in 102-days leaching tests with simulated solidified forms containing Uranium (VI). The accumulative leaching fraction of Uranium (VI) for Alkali-activated slag cement solidified forms is 17.6% lower than that for Portland cement. The corresponding difference of diffusion coefficients is 40.6%. This could be correlated with the difference of Ca/Si ratios between cements of two kinds. (authors)

  1. Synthesis of calcium aluminate with silicon addition for application in biomaterials; Sintese de aluminato de calcio com adicao de prata para aplicacao em biomateriais

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, P.J.; Almeida, L.H.S.; Pappen, F.G.; Ribeiro, A.S.; Cava, S.S. [Universidade Federal de Pelotas (UFPel), RS (Brazil); Veiga, F.C.T.; Jurado, J., E-mail: ati_jg@hotmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)

    2016-07-01

    Ceramic materials have biocompatibility have been studied, researched and applied in various treatments such as endodontics and orthopedics. This study aims to carry out the synthesis by the polymeric precursor method for post calcium trialuminato (C3A) and with addition of 1% and 5% silver, them the powders were calcined in de temperature 1000°C, carried out a comparative study between them. The ceramic powders were characterized by X-ray diffraction, having a phase composition, scanning electron microscopy (SEM) associated with EDS observed grain morphology and quantity of the chemical elements. The analysis flow, pH, release of calcium ions (Ca{sup 2+}) and silver ions (Ag{sup +}) were evaluated with the sealer MTA Fillapex result that calcium aluminate addition of silver improved the MTA Fillapex stream with the release of ions Ca{sup +2}, being a material that allows applications in the field of endodontics. (author)

  2. Immobilisation of radwaste in cement based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Macphee, D.; Atkins, M.; Pointer, C.; Cowie, J.; Wilding, C.R.; Mattingley, N.J.; Evans, P.A.

    1989-01-01

    The solubilities and influence on cement pH are reported for calcium aluminate and aluminosulphate hydrates. The solubility of Ca(OH) 2 is reported to 700 bars. Polymerization of C-S-H is investigated by NMR. Specific interactions of U 6+ and iodine (I - , IO 3 - ) with cement components are described. The impact of radiation on cements and the influence of higher temperature are documented. The role of dissolved Ca and CO 2 in groundwaters as dissolution media for cements are reported. (author)

  3. A hazardous waste from secondary aluminium metallurgy as a new raw material for calcium aluminate glasses.

    Science.gov (United States)

    López-Delgado, Aurora; Tayibi, Hanan; Pérez, Carlos; Alguacil, Francisco José; López, Félix Antonio

    2009-06-15

    A solid waste coming from the secondary aluminium industry was successfully vitrified in the ternary CaO-Al(2)O(3)-SiO(2) system at 1500 degrees C. This waste is a complex material which is considered hazardous because of its behaviour in the presence of water or moisture. In these conditions, the dust can generate gases such as H(2), NH(3), CH(4), H(2)S, along with heat and potential aluminothermy. Only silica sand and calcium carbonate were added as external raw materials to complete the glasses formula. Different nominal compositions of glasses, with Al(2)O(3) ranging between 20% and 54%, were studied to determine the glass forming area. The glasses obtained allow the immobilisation of up to 75% of waste in a multicomponent oxide system in which all the components of the waste are incorporated. The microhardness Hv values varied between 6.05 and 6.62GPa and the linear thermal expansion coefficient, alpha, varied between (62 and 139)x10(-7)K(-1). Several glasses showed a high hydrolytic resistance in deionised water at 98 degrees C.

  4. Polyelectrolyte addition effect on the properties of setting hydraulic cements based on calcium phosphate

    International Nuclear Information System (INIS)

    Santos, Luis A. dos; Oliveira, Luci C. de; Rigo, Eliana C.S.; Boschi, Anselmo Ortega; Carrodeguas, Raul Gracia

    1997-01-01

    In the present work the effects of the addition of some poly electrolytes (sodium alginate and poly acrylic acid) on the solubility, crystalline phases, pH and mechanical strength under compression of three calcium phosphate cements were studied. (author)

  5. Cementation of Radioactive Waste from a PWR with Calcium Sulfoaluminate Cement

    International Nuclear Information System (INIS)

    Li, J.

    2013-01-01

    Spent radioactive ion-exchange resin (SIER) and evaporation concentrates are radioactive wastes that are produced at by pressurized water reactor (PWR) nuclear power stations. Borate, which is used as a retardent for cement, is also present as a moderator in a PWR, therefore, borate will be present in both ion-exchange resins and evaporation concentrates. In this study the use of Calcium sulfoaluminate cements (SAC) as encapsulation medium for these waste streams was investigated. The study involved the manufacturing of different cement test samples with different amounts of SAC cement, waste resins (50% water content) and admixtures. In order to reduce hydration heat during 200 L solidification experiments, different admixtures were investigated. Initial results based on compressive strength tests and hydration temperature studies, indicated that zeolite was the best admixture for the current waste form. Experiments indicated that the addition of resin material into the current cement matrix reduces the hydration heat during curing Experimental results indicated that a combination of SAC (35 wt. %), zeolite (7 wt. %) mix with 42 wt. % resins (50% water content) and 16 wt. % of water forms a optimum cured monolith with low hydration heat. The microstructures of hydrated OPC, SAC and SAC with zeolite addition were studied using a Scanning Electron Microscopy (SEM). SEM results indicated that the SAC matrices consist of a needle type structure that changed gradually into a flake type structure with the addition of zeolite. Additionally, the presence of zeolite material inside the SAC matrix reduced the leaching rates of radionuclides significantly. In a final 200 L grouting test, measured results indicated a hydration temperature below 90oC withno thermal cracks after solidified. The influence of radiation on the compressive strength and possible gas generation (due to radiolysis) on cement waste forms containing different concentrations ion exchange resin was

  6. Molecular mechanism of crystallization impacting calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Giocondi, J L; El-Dasher, B S; Nancollas, G H; Orme, C A

    2009-05-31

    In summary, SPM data has shown that (1) Mg inhibits growth on all steps but relatively high Mg/Ca ratios are needed. Extracting the mechanism of interaction requires more modeling of the kinetic data, but step morphology is consistent with incorporation. (2) Citrate has several effects depending on the citrate/Ca ratio. At the lowest concentrations, citrate increases the step free energy without altering the step kinetics; at higher concentrations, the polar step is slowed. (3) Oxalate also slows the polar step but additionally stabilizes a new facet, with a [100]{sub Cc} step. (4) Etidronate has the greatest kinetic impact of the molecules studied. At 7{micro}M concentrations, the polar step slows by 60% and a new polar step appears. However, at the same time the [10-1]{sub Cc} increases by 67%. It should be noted that all of these molecules complex calcium and can effect kinetics by altering the solution supersaturation or the Ca to HPO{sub 4}{sup 2-} ratio. For the SPM data shown, this effect was corrected for to distinguish the effect of the molecule at the crystal surface from the effect of the molecule on the solution speciation. The goal of this paper is to draw connections between fundamental studies of atomic step motion and potential strategies for materials processing. It is not our intent to promote the utility of SPM for investigating processes in cement dynamics. The conditions are spectacularly different in many ways. The data shown in this paper are fairly close to equilibrium (S=1.6) whereas the nucleation of cements is initiated at supersaturation ratios in the thousands to millions. Of course, after the initial nucleation phase, the growth will occur at more modest supersaturations and as the cement evolves towards equilibrium certainly some of the growth will occur in regimes such as shown here. In addition to the difference in supersaturation, cements tend to have lower additive to calcium ratios. As an example, the additive to Ca ratio is

  7. Biocompatibility of calcium phosphate bone cement with optimized mechanical properties.

    Science.gov (United States)

    Palmer, Iwan; Nelson, John; Schatton, Wolfgang; Dunne, Nicholas J; Buchanan, Fraser J; Clarke, Susan A

    2016-02-01

    The broad aim of this work was to investigate and optimize the properties of calcium phosphate bone cements (CPCs) for use in vertebroplasty to achieve effective primary fixation of spinal fractures. The incorporation of collagen, both bovine and from a marine sponge (Chondrosia reniformis), into a CPC was investigated. The biological properties of the CPC and collagen-CPC composites were assessed in vitro through the use of human bone marrow stromal cells. Cytotoxicity, proliferation, and osteoblastic differentiation were evaluated using lactate dehydrogenase, PicoGreen, and alkaline phosphatase activity assays, respectively. The addition of both types of collagen resulted in an increase in cytotoxicity, albeit not to a clinically relevant level. Cellular proliferation after 1, 7, and 14 days was unchanged. The osteogenic potential of the CPC was reduced through the addition of bovine collagen but remained unchanged in the case of the marine collagen. These findings, coupled with previous work showing that incorporation of marine collagen in this way can improve the physical properties of CPCs, suggest that such a composite may offer an alternative to CPCs in applications where low setting times and higher mechanical stability are important. © 2015 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc.

  8. Shear-peel strength comparison of orthodontic band cements including novel calcium silicate

    DEFF Research Database (Denmark)

    Leo, Mariantonietta; Løvschall, Henrik

    calcium silicate with fluoride and fast-setting, Glass ionomer, and Zinc phosphate cement, used for luting of orthodontic bands on molars kept one month in phosphate buffering solution (PBS). Materials and methods: The roots of 35 extracted human molars were embedded in acryl. Three groups were allocated....... An orthodontic band (AO) was fitted on the free crown. Each group of the teeth (n>10) was cemented with novel calcium silicate (Protooth), Glass ionomer (Orthocem), or Zinc phosphate (DeTrey Zinc). The cements were mixed according to the manufacturers instructions. Samples were stored at 37ºC in humid chamber...... Silicate (Protooth) and Zinc phosphate cement (DeTrey Zinc) were significantly higher than Glass ionomer cement (Orthocem) when looking for the force (N, p

  9. Incorporation of bitumen and calcium silicate in cement and lime stabilized soil blocks

    Science.gov (United States)

    Kwan, W. H.; Cheah, C. B.; Ramli, M.; Al-Sakkaf, Y. K.

    2017-04-01

    Providing affordable housing is the most critical problem in many of the developing countries. Using earth materials in building construction is one of the feasible methods to address this issue and it can be a way towards sustainable construction as well. However, the published information on the stabilized soil blocks is limited. Therefore, the present study is conducted to examine the characterization of the soils and engineering properties of the stabilized soil blocks. Four types of stabilizer were used in the study, namely; cement, slaked lime, bitumen emulsion and calcium silicate. Cement and slaked lime were added at different percentages in the range of 5% to 15%, with interval of 2.5%. The percentage was determined based on weight of soil. Meanwhile, bitumen emulsion and calcium silicate were incorporated at various percentages together with 10% of cement. Dosage of bitumen emulsion is in the range of 2% to 10% at interval of 2% while calcium silicate was incorporated at 0.50%, 0.75%, 1.00%, 1.25%, 1.50% and 2.00%. Results show that cement is the most viable stabilizer for the soil block among all stabilizers in this study. The bulk density, optimum moisture content and compressive strengths were increased with the increasing cement content. The most suitable cement content was 10% added at moisture content of 12%. Lime, bitumen and calcium contents were recommended at 5.0%, 6.0% and 1.25%, respectively.

  10. Experimental study and field application of calcium sulfoaluminate cement for rapid repair of concrete pavements

    Institute of Scientific and Technical Information of China (English)

    Yanhua GUAN; Ying GAO; Renjuan SUN; Moon C.WON; Zhi GE

    2017-01-01

    The fast-track repair of deteriorated concrete pavement requires materials that can be placed,cured,and opened to the traffic in a short period.Type Ⅲ cement and Calcium Sulfoaluminate (CSA) cement are the most commonly used fast-setting hydraulic cement (FSHC).In this study,the properties of Type Ⅲ and CSA cement concrete,including compressive strength,coefficient of thermal expansion (CTE) and shrinkage were evaluated.The test results indicate that compressive strength of FSHC concrete increased rapidly at the early age.CSA cement concrete had higher early-age and long term strength.The shrinkage of CSA cement concrete was lower than that of Type Ⅲ cement concrete.Both CSA and Type Ⅲ cement concrete had similar CTE values.Based on the laboratory results,the CSA cement was selected as the partial-depth rapid repair material for a distressed continuously reinforced concrete pavement.The data collected during and after the repair show that the CSA cement concrete had good short-term and long-term performances and,therefore,was suitable for the rapid repair of concrete pavement.

  11. The effects of excess calcium on the handling and mechanical properties of hydrothermal derived calcium phosphate bone cement

    Science.gov (United States)

    Razali, N. N.; Sukardi, M. A.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.

    2018-01-01

    The objective of this study is to determine the effects of excess calcium on the handling and mechanical properties of hydrothermal derived calcium phosphate cement (CPC) for bone filling applications. Hydroxyapatite powder was synthesized via hydrothermal method using calcium oxide, CaO and ammonium dihydrogen phosphate, NH4H2PO4 as the calcium and phosphorus precursors respectively. The effects of calcium excess were evaluated by varying the CaO content at 0, 5 and 15 mole %. The precursors were then refluxed in distilled water at 90-100°C and dried overnight until the calcium phosphate powder was formed. CPC was then produced by mixing the synthesized powder with distilled water at the powder-to-liquid (P/L) ratio of 1.5. The result from the morphological properties of CPC shows the increase in agglomeration and particles size with 5 mole % of calcium excess but decreased with 15 mole % of calcium excess in CPC. This result was in agreement with the compressive strength result where the CPC increased its strength with 5 mole % of calcium excess but reduced with 15 mole % of calcium excess. The excess in calcium precursor also significantly improved the setting time but reduced the injectability of CPC.

  12. Preparation of in situ hardening composite microcarriers: Calcium phosphate cement combined with alginate for bone regeneration

    Science.gov (United States)

    Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C

    2014-01-01

    Novel microcarriers consisting of calcium phosphate cement and alginate were prepared for use as three-dimensional scaffolds for the culture and expansion of cells that are effective for bone tissue engineering. The calcium phosphate cement-alginate composite microcarriers were produced by an emulsification of the composite aqueous solutions mixed at varying ratios (calcium phosphate cement powder/alginate solution = 0.8–1.2) in an oil bath and the subsequent in situ hardening of the compositions during spherodization. Moreover, a porous structure could be easily created in the solid microcarriers by soaking the produced microcarriers in water and a subsequent freeze-drying process. Bone mineral-like apatite nanocrystallites were shown to rapidly develop on the calcium phosphate cement–alginate microcarriers under moist conditions due to the conversion of the α-tricalcium phosphate phase in the calcium phosphate cement into a carbonate–hydroxyapatite. Osteoblastic cells cultured on the microspherical scaffolds were proven to be viable, with an active proliferative potential during 14 days of culture, and their osteogenic differentiation was confirmed by the determination of alkaline phosphatase activity. The in situ hardening calcium phosphate cement–alginate microcarriers developed herein may be used as potential three-dimensional scaffolds for cell delivery and tissue engineering of bone. PMID:23836845

  13. Device for continuous radiometric determination of the calcium and iron content in raw slurry for cement

    International Nuclear Information System (INIS)

    Wasilewska, M.; Ostachowicz, J.; Lankosz, M.; Molodynska, W.

    1975-01-01

    The characteristic iron and calcium-K series were excited using a Cd-109 isotope source. In order to determine the calcium and iron content in dry slurry, the Compton-effect scattered radiation of the Cd-109 source in the sample was used. A numerical process was worked out which allowed the elimination of the influence of changing contents of iron and water on the results of the calcium content determinations, and a device for continuous radiometric determination of calcium and iron in raw slurry was designed and constructed. The device was installed in the cement plant 'Przyjazn' under technical measuring conditions and its applicability was tested. (orig./LH) [de

  14. CALCIUM ORTHOPHOSPHATES HYDRATES: FORMATION, STABILITY AND INFLUENCE ON STANDARD PROPERTIES OF PORTLAND CEMENT

    Directory of Open Access Journals (Sweden)

    Kaziliunas A.

    2013-12-01

    Full Text Available Preparation of phosphogypsum to produce the binders requires a much higher input than preparation of natural gypsum stone. This makes it uncompetitive material. The investigations presented therein are meant to reduce this input by looking for the ways of rendering impurities harmless. Soluble acid orthophosphates are the main harmful impurity of phosphogypsum. The studies show that dry insoluble calcium orthophosphates hydrates (1.09 % and 2.18 % P2O5 in gypsum have little effect on W/C, setting times and soundness of Portland cement pastes. Insoluble calcium orthophosphates hydrates {CaHPO4∙2H2O, Ca8(HPO42(PO44∙5H2O and Ca9(HPO4(PO45(OH∙4H2O} formed in acidic medium (pH = 4.2 - 5.9 have been destroyed in alkaline medium and reduce standard compressive strength of cement up to 28 %. Calcium orthophosphates hydrates of hydroxyapatite group are stable in alcaline medium, while in dry state they reduce the standard compressive strength of cement until 10 %, but their suspensions prolong setting times of Portland cement as soluble orthophosphates – 2 - 3 times. Alkalis in cement increase pH of paste, but do not change the process of formation of calcium orthophosphates hydrates of hydroxyapatite group: it takes place through an intermediate phase - CaHPO4·2H2O, whose transformation into apatite lasts for 2 - 3 months.

  15. Effects of Montmorillonite on the Mineralization and Cementing Properties of Microbiologically Induced Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2017-01-01

    Full Text Available Carbonate mineralization microbe is a microorganism capable of decomposing the substrate in the metabolic process to produce the carbonate, which then forms calcium carbonate with calcium ions. By taking advantage of this process, contaminative uranium tailings can transform to solid cement, where calcium carbonate plays the role of a binder. In this paper, we have studied the morphology of mineralized crystals by controlling the mineralization time and adding different concentrations of montmorillonite (MMT. At the same time, we also studied the effect of carbonate mineralized cementation uranium tailings by controlling the amount of MMT. The results showed that MMT can regulate the crystal morphology of calcium carbonate. What is more, MMT can balance the acidity and ions in the uranium tailings; it also can reduce the toxicity of uranium ions on microorganisms. In addition, MMT filling in the gap between the uranium tailings made the cement body more stable. When the amount of MMT is 6%, the maximum strength of the cement body reached 2.18 MPa, which increased by 47.66% compared with that the sample without MMT. Therefore, it is reasonable and feasible to use the MMT to regulate the biocalcium carbonate cemented uranium tailings.

  16. Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone

    DEFF Research Database (Denmark)

    Moesgaard, M; Poulsen, Søren Lundsted; Herfort, D

    2012-01-01

    M. MOESGAARD, S.L. POULSEN, D. HERFORT, M. STEENBERG, L.F. KIRKEGAARD, J. SKIBSTED, Y. YUE, Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone, Journal of the American Ceramic Society 95, 403 – 409 (2012).......M. MOESGAARD, S.L. POULSEN, D. HERFORT, M. STEENBERG, L.F. KIRKEGAARD, J. SKIBSTED, Y. YUE, Hydration of Blended Portland Cements Containing Calcium-Aluminosilicate Glass Powder and Limestone, Journal of the American Ceramic Society 95, 403 – 409 (2012)....

  17. Impact of fuel selection on the environmental performance of post-combustion calcium looping applied to a cement plant

    NARCIS (Netherlands)

    Schakel, Wouter; Hung, Christine Roxanne; Tokheim, Lars Andre; Strømman, Anders Hammer; Worrell, Ernst; Ramírez, Andrea

    2018-01-01

    Calcium looping CO2 capture is a promising technology to reduce CO2 emissions from cement production. Coal has been seen as a logical choice of fuel to drive the calcium looping process as coal is already the primary fuel used to produce cement. This study assesses the impact of using different

  18. Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Ming-Hsien [Institute of Oral Science, Chung Shan Medical University, Taichung City, Taiwan (China); Shen, Yu-Fang; Hsu, Tuan-Ti [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China); Huang, Tsui-Hsien [School of Dentistry, Chung Shan Medical University, Taichung City, Taiwan (China); Department of Stomatology, Chung Shan Medical University Hospital, Taichung City, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [3D Printing Medical Research Center, China Medical University Hospital, China Medical University, Taichung City, Taiwan (China)

    2016-08-01

    Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0–10 mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. - Highlights: • The hinokitiol-modified CS up-regulation of odontogenic of hDPCs. • Promoted proliferation of hDPCs on hinokitiol-modified CS. • The hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility. • The hinokitiol-modified CS up-regulation of odontogenic of hPDLs.

  19. Physical characteristics, antimicrobial and odontogenesis potentials of calcium silicate cement containing hinokitiol

    International Nuclear Information System (INIS)

    Huang, Ming-Hsien; Shen, Yu-Fang; Hsu, Tuan-Ti; Huang, Tsui-Hsien; Shie, Ming-You

    2016-01-01

    Hinokitiol is a natural material and it has antibacterial and anti-inflammatory effects. The purpose of this study was to evaluate the material characterization, cell viability, antibacterial and anti-inflammatory abilities of the hinokitiol-modified calcium silicate (CS) cement as a root end filling material. The setting times, diametral tensile strength (DTS) values and XRD patterns of CS cements with 0–10 mM hinokitiol were examined. Then, the antibacterial effect and the expression levels of cyclooxygenase 2 (COX-2) and interleukin-1 (IL-1) of the hinokitiol-modified CS cements were evaluated. Furthermore, the cytocompatibility, the expression levels of the markers of odontoblastic differentiation, mineralized nodule formation and calcium deposition of human dental pulp cells (hDPCs) cultured on hinokitiol-modified CS cements were determined. The hinokitiol-modified CS cements had better antibacterial and anti-inflammatory abilities and cytocompatibility than non-modified CS cements. Otherwise, the hinokitiol-modified CS cements had suitable setting times and better odontoblastic potential of hDPCs. Previous report pointed out that the root-end filling materials may induce inflammatory cytokines reaction. In our study, hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility, antimicrobial properties and active ability of odontoblastic differentiation of hDPCs. Therefore, the hinokitiol-modified CS cement may be a potential root end filling material for clinic. - Highlights: • The hinokitiol-modified CS up-regulation of odontogenic of hDPCs. • Promoted proliferation of hDPCs on hinokitiol-modified CS. • The hinokitiol-modified CS cements not only inhibited the expression level of inflammatory cytokines, but also had better cytocompatibility. • The hinokitiol-modified CS up-regulation of odontogenic of hPDLs.

  20. Improvement of in vitro physicochemical properties and osteogenic activity of calcium sulfate cement for bone repair by dicalcium silicate

    International Nuclear Information System (INIS)

    Chen, Chun-Cheng; Wang, Chien-Wen; Hsueh, Nai-Shuo; Ding, Shinn-Jyh

    2014-01-01

    Highlights: • Dicalcium silicate can improve osteogenic activity of calcium sulfate cement. • The higher the calcium sulfate content, the shorter the setting time in the composite cement. • The results were useful for designing calcium-based cement with optimal properties. -- Abstract: An ideal bone graft substitute should have the same speed of degradation as formation of new bone tissue. To improve the properties of calcium sulfate hemihydrate (CSH) featured for its rapid resorption, a low degradation material of dicalcium silicate (DCS) was added to the CSH cement. This study examined the effect of DCS (20, 40, 60 and 80 wt%) on the in vitro physicochemical properties and osteogenic activities of the calcium-based composite cements. The diametral tensile strength, porosity and weight loss of the composite cements were evaluated before and after soaking in a simulated body fluid (SBF). The osteogenic activities, such as proliferation, differentiation and mineralization, of human mesenchymal stem cells (hMSCs) seeded on cement surfaces were also examined. As a result, the greater the DCS amount, the higher the setting time was in the cement. Before soaking in SBF, the diametral tensile strength of the composite cements was decreased due to the introduction of DCS. On 180-day soaking, the composite cements containing 20, 40, 60 and 80 wt% DCS lost 80%, 69%, 61% and 44% in strength, respectively. Regarding in vitro bioactivity, the DCS-rich cements were covered with clusters of apatite spherulites after soaking for 7 days, while there was no formation of apatite spherulites on the CSH-rich cement surfaces. The presence of DCS could reduce the degradation of the CSH cements, as evidenced in the results of weight loss and porosity. More importantly, DCS may promote effectively the cell proliferation, proliferation and mineralization. The combination of osteogenesis of DCS and degradation of CSH made the calcium-based composite cements an attractive choice for

  1. Production and characterization of setting hydraulic cements based on calcium phosphate

    International Nuclear Information System (INIS)

    Oliveira, Luci C. de; Rigo, Eliana C.S.; Santos, Luis A dos; Boschi, Anselmo Ortega; Carrodeguas, Raul G.

    1997-01-01

    Setting hydraulic cements based on calcium phosphate has risen great interest in scientific literature during recent years due to their total bio compatibility and to the fact that they harden 'in situ', providing easy handling and adaptation to the shape and dimensions of the defect which requires correction, differently from the predecessors, the calcium phosphate ceramics (Hydroxy apatite, β-tri calcium phosphate, biphasic, etc) in the shape of dense or porous blocks and grains. In the work, three calcium-phosphate cement compositions were studied. The resulting compositions were characterized according to the following aspects: setting times, pH, mechanical resistance, crystalline phases, microstructure and solubility in SBF (Simulated Body Fluid). The results show a potential use for the compositions. (author)

  2. Apatite formation on bioactive calcium-silicate cements for dentistry affects surface topography and human marrow stromal cells proliferation.

    Science.gov (United States)

    Gandolfi, Maria Giovanna; Ciapetti, Gabriela; Taddei, Paola; Perut, Francesca; Tinti, Anna; Cardoso, Marcio Vivan; Van Meerbeek, Bart; Prati, Carlo

    2010-10-01

    The effect of ageing in phosphate-containing solution of bioactive calcium-silicate cements on the chemistry, morphology and topography of the surface, as well as on in vitro human marrow stromal cells viability and proliferation was investigated. A calcium-silicate cement (wTC) mainly based on dicalcium-silicate and tricalcium-silicate was prepared. Alpha-TCP was added to wTC to obtain wTC-TCP. Bismuth oxide was inserted in wTC to prepare a radiopaque cement (wTC-Bi). A commercial calcium-silicate cement (ProRoot MTA) was tested as control. Cement disks were aged in DPBS for 5 h ('fresh samples'), 14 and 28 days, and analyzed by ESEM/EDX, SEM/EDX, ATR-FTIR, micro-Raman techniques and scanning white-light interferometry. Proliferation, LDH release, ALP activity and collagen production of human marrow stromal cells (MSC) seeded for 1-28 days on the cements were evaluated. Fresh samples exposed a surface mainly composed of calcium-silicate hydrates CSH (from the hydration of belite and alite), calcium hydroxide, calcium carbonate, and ettringite. Apatite nano-spherulites rapidly precipitated on cement surfaces within 5 h. On wTC-TCP the Ca-P deposits appeared thicker than on the other cements. Aged cements showed an irregular porous calcium-phosphate (Ca-P) coating, formed by aggregated apatite spherulites with interspersed calcite crystals. All the experimental cements exerted no acute toxicity in the cell assay system and allowed cell growth. Using biochemical results, the scores were: fresh cements>aged cements for cell proliferation and ALP activity (except for wTC-Bi), whereas fresh cementscements for collagen synthesis. Summarizing (1) non-aged cements showed higher cell proliferation than aged cements, probably favoured by the presence of Si-OH gel and the early formation of apatite nano-spherulites; (2) the alpha-TCP doped cement aged for 28 days displayed the highest bioactivity and cell proliferation; (3) the deleterious effect of bismuth on cell

  3. Physicochemical properties and biocompatibility of chitosan oligosaccharide/gelatin/calcium phosphate hybrid cements

    Energy Technology Data Exchange (ETDEWEB)

    Chiang, Ting-Yi [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan (China); Ho, Chia-Che [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Chen, David Chan-Hen [Institute of Veterinary Microbiology, National Chung-Hsing University, Taichung 402, Taiwan (China); Lai, Meng-Heng [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Ding, Shinn-Jyh, E-mail: sjding@csmu.edu.tw [Institute of Oral Biology and Biomaterials Science, Chung-Shan Medical University, Taichung 402, Taiwan (China); Department of Dentistry, Chung-Shan Medical University Hospital, Taichung 402, Taiwan (China)

    2010-04-15

    A bone substitute material was developed consisting of a chitosan oligosaccharide (COS) solution in a liquid phase and gelatin (GLT) containing calcium phosphate powder in a solid phase. The physicochemical and biocompatible properties of the hybrid cements were evaluated. The addition of COS to cement did not affect the setting time or diametral tensile strength of the hybrid cements, whereas GLT significantly prolonged the setting time and decreased the strength slightly. The setting reaction was inhibited by the addition of GLT to the initial mixture, but not by COS. However, the presence of GLT appreciably improved the anti-washout properties of the hybrid cement compared with COS. COS may promote the cement's biocompatibility as an approximate twofold increase in cell proliferation for 10% COS-containing cements was observed on day 3 as compared with the controls. The combination of GLT and COS was chosen due to the benefits achieved from several synergistic effects and for their clinical applications. Cement with 5% GLT and 10% COS may be a better choice among cements in terms of anti-washout properties and biological activity.

  4. Reduced CSF leak in complete calvarial reconstructions of microvascular decompression craniectomies using calcium phosphate cement.

    Science.gov (United States)

    Eseonu, Chikezie I; Goodwin, C Rory; Zhou, Xin; Theodros, Debebe; Bender, Matthew T; Mathios, Dimitrios; Bettegowda, Chetan; Lim, Michael

    2015-12-01

    Calcium phosphate cement provides a biomaterial that can be used for calvarial reconstruction in a retrosigmoid craniectomy for microvascular decompression (MVD). This study evaluates the outcomes of postoperative CSF leak and wound infection for patients undergoing a complete cranioplasty using calcium phosphate cement versus incomplete cranioplasty using polyethylene titanium mesh following a retrosigmoid craniectomy for MVD. The authors evaluated 211 cases involving patients who underwent first-time retrosigmoid craniectomies performed by a single attending surgeon fortrigeminal neuralgia from October 2008 to June 2014. From this patient population, 111 patients underwent calvarial reconstruction after retrosigmoid craniectomy using polyethylene titanium mesh, and 100 patients had reconstructions using calcium phosphate cement. A Pearson's chi-square test was used to compare postoperative complications of CSF leak and wound infection in these 2 types of cranioplasties. The polyethylene titanium mesh group included 5 patients (4.5%) with postoperative CSF leak or pseudomeningocele and 3 patients (2.7%) with wound infections. In the calcium phosphate cement group, no patients had a CSF leak, and 2 patients (2%) had wound infections. This represented a statistically significant reduction of postoperative CSF leak in patients who underwent calcium phosphate reconstructions of their calvarial defect compared with those who underwent polyethylene titanium mesh reconstructions (p = 0.03). No significant difference was seen between the 2 groups in the number of patients with postoperative wound infections. Calcium phosphate cement provides a viable alternative biomaterial for calvarial reconstruction of retrosigmoid craniectomy defects in patients who have an MVD. The application of this material provides a biocompatible barrier that reduces the incidence of postoperative CSF leaks.

  5. A low temperature aluminizing treatment of hot work tool steel

    Energy Technology Data Exchange (ETDEWEB)

    Matijevic, B., E-mail: bozidar.matijevic@fsb.hr [University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, Zagreb (Croatia)

    2010-07-01

    Conventional aluminizing processes by pack cementation are typically carried out at elevated temperatures. A low temperature powder aluminizing technology was applied to hot tool steel H13. The aluminizing treating temperature was from 550 to 620°C. Effects of temperature and time on the microstructure and phase evolution were investigated. Also, the intermetallic layer thickness was measured in the aluminized layer of a steel substrate. The cross-sectional microstructures, the aluminized layer thickness and the oxide layer were studied. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), glow discharge optical spectroscopy (GDOS) were applied to observe the cross-sections and the distribution of elements. (author)

  6. A low temperature aluminizing treatment of hot work tool steel

    International Nuclear Information System (INIS)

    Matijevic, B.

    2010-01-01

    Conventional aluminizing processes by pack cementation are typically carried out at elevated temperatures. A low temperature powder aluminizing technology was applied to hot tool steel H13. The aluminizing treating temperature was from 550 to 620°C. Effects of temperature and time on the microstructure and phase evolution were investigated. Also, the intermetallic layer thickness was measured in the aluminized layer of a steel substrate. The cross-sectional microstructures, the aluminized layer thickness and the oxide layer were studied. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), glow discharge optical spectroscopy (GDOS) were applied to observe the cross-sections and the distribution of elements. (author)

  7. Compressive strength and magnetic properties of calcium silicate-zirconia-iron (III) oxide composite cements

    Science.gov (United States)

    Ridzwan, Hendrie Johann Muhamad; Shamsudin, Roslinda; Ismail, Hamisah; Yusof, Mohd Reusmaazran; Hamid, Muhammad Azmi Abdul; Awang, Rozidawati Binti

    2018-04-01

    In this study, ZrO2 microparticles and γ-Fe2O3 nanoparticles have been added into calcium silicate based cements. The purpose of this experiment was to investigate the compressive strength and magnetic properties of the prepared composite cement. Calcium silicate (CAS) powder was prepared by hydrothermal method. SiO2 and CaO obtained from rice husk ash and limestone respectively were autoclaved at 135 °C for 8 h and sintered at 950°C to obtain CAS powder. SiO2:CaO ratio was set at 45:55. CAS/ZrO2 sample were prepared with varying ZrO2 microparticles concentrations by 0-40 wt. %. Compressive strength value of CAS/ZrO2 cements range from 1.44 to 2.44 MPa. CAS/ZrO2/γ-Fe2O3 sample with 40 wt. % ZrO2 were prepared with varying γ-Fe2O3 nanoparticles concentrations (1-5 wt. %). The additions of γ-Fe2O3 nanoparticles showed up to twofold increase in the compressive strength of the cement. X-Ray diffraction (XRD) results confirm the formation of mixed phases in the produced composite cements. Vibrating sample magnetometer (VSM) analysis revealed that the ferromagnetic behaviour has been observed in CAS/ZrO2/γ-Fe2O3 composite cements.

  8. Preparation and characterization of a novel injectable strontium-containing calcium phosphate cement with collagen

    Directory of Open Access Journals (Sweden)

    Zhou Ziqiang

    2015-07-01

    Full Text Available Purpose: To develop a novel injectable strontium-containing calcium phosphate cement with collagen. Methods: A novel calcium phosphate bone cement (CPC was prepared with the addition of strontium element, collagenⅠ, and modified starch; the injectability, solidification time, microstructure, phase composition, compressive strength, anti-collapsibility and histological properties of material were evaluated. Results: The results showed that the material could be injected with an excellent performance; the modified starch significantly improved the anti-washout property of cement; with the liquid to solid ratio of 0.3, the largest compressive strength of cement was obtained (48.0 MPa ± 2.3 MPa; histological examination of repair tissue showed that the bone was repaired after 16 weeks; the degradation of cement was consistent with the new bone growth. Conclusion: A novel injectable collagen-strontium-containing CPC with excellent compressive strength and suitable setting time was prepared, with addition of modified starch. The CPC showed a good antiwashout property and the degradation time of the cement met with the new bone growing. This material is supposed to be used in orthopedic and maxillofacial surgery for bone defects.

  9. Analysis of the color alteration and radiopacity promoted by bismuth oxide in calcium silicate cement.

    Science.gov (United States)

    Marciano, Marina Angélica; Estrela, Carlos; Mondelli, Rafael Francisco Lia; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro

    2013-01-01

    The aim of the study was to determine if the increase in radiopacity provided by bismuth oxide is related to the color alteration of calcium silicate-based cement. Calcium silicate cement (CSC) was mixed with 0%, 15%, 20%, 30% and 50% of bismuth oxide (BO), determined by weight. Mineral trioxide aggregate (MTA) was the control group. The radiopacity test was performed according to ISO 6876/2001. The color was evaluated using the CIE system. The assessments were performed after 24 hours, 7 and 30 days of setting time, using a spectrophotometer to obtain the ΔE, Δa, Δb and ΔL values. The statistical analyses were performed using the Kruskal-Wallis/Dunn and ANOVA/Tukey tests (poxide was added showed radiopacity corresponding to the ISO recommendations (>3 mm equivalent of Al). The MTA group was statistically similar to the CSC/30% BO group (p>0.05). In regard to color, the increase of bismuth oxide resulted in a decrease in the ΔE value of the calcium silicate cement. The CSC group presented statistically higher ΔE values than the CSC/50% BO group (poxide has no relation to the color alteration of calcium silicate-based cements.

  10. A theranostic agent to enhance osteogenic and magnetic resonance imaging properties of calcium phosphate cements

    NARCIS (Netherlands)

    Ventura, M.; Sun, Y.; Cremers, S.; Borm, P.; Tahmasebi Birgani, Zeinab; Habibovic, Pamela; Heerschap, A.; van der Kraan, P.M.; Jansen, J.A.; Walboomers, X.F.

    2014-01-01

    With biomimetic biomaterials, like calcium phosphate cements (CPCs), non-invasive assessment of tissue regeneration is challenging. This study describes a theranostic agent (TA) to simultaneously enhance both imaging and osteogenic properties of such a bone substitute material. For this purpose,

  11. Stabilisation of clayey soils with high calcium fly ash and cement

    Energy Technology Data Exchange (ETDEWEB)

    S. Kolias; V. Kasselouri-Rigopoulou; A. Karahalios [National Technical University of Athens, Athens (Greece)

    2005-02-01

    The effectiveness of using high calcium fly ash and cement in stabilising fine-grained clayey soils (CL,CH) was investigated in the laboratory. Strength tests in uniaxial compression, in indirect (splitting) tension and flexure were carried out on samples to which various percentages of fly ash and cement had been added. Modulus of elasticity was determined at 90 days with different types of load application and 90-day soaked CBR values are also reported. Pavement structures incorporating subgrades improved by in situ stabilisation with fly ash and cement were analyzed for construction traffic and for operating traffic. These pavements are compared with conventional flexible pavements without improved subgrades and the results clearly show the technical benefits of stabilising clayey soils with fly ash and cement. In addition TG-SDTA and XRD tests were carried out on certain samples in order to study the hydraulic compounds, which were formed.

  12. The role of calcium ions and lignosulphonate plasticiser in the hydration of cement

    International Nuclear Information System (INIS)

    Grierson, L.H.; Knight, J.C.; Maharaj, R.

    2005-01-01

    Experiments involving equilibrium dialysis, conductivity, X-ray diffraction analysis (XRD), differential thermal analysis (DTA) and isothermal titration calorimetry (ITC) have been carried out to investigate the role of calcium ions and polymeric plasticisers in cement/admixture hydration. Results from a study of lignosulphonic acid, sodium salt, acetate as a plasticiser shows that a plasticiser has dual role; one mainly as a kinetic inhibitor (poison) in cement hydration mechanism and the other as a dispersant. Evidence of a weak Ca 2+ binding to lignosulphonate sulphonic moieties was found at low ionic strengths of 0.1 M using ITC. No evidence of formal Ca 2+ binding to lignosulphonate sulphonic acid moieties was found using equilibrium dialysis at higher ionic strength of 1 M (ionic strengths of 0.4 M are typically found in Portland cement pore solution), as is often suggested in cement/admixture literature

  13. Development of a fully injectable calcium phosphate cement for ...

    Indian Academy of Sciences (India)

    Unknown

    2003-01-27

    Jan 27, 2003 ... excellent alloplastic material for osseous augmentation because of the ... and basic calcium phosphate compounds on wetting with an aqueous ... ment of acute fracture of the radius through percutaneous administration of ...

  14. Evaluation of Calcium Silicate Cement Bond Strength after Using ...

    African Journals Online (AJOL)

    2018-01-24

    Jan 24, 2018 ... (chloroform, Endosolv E, orange oil, and eucalyptol) on the push‑out bond strength of calcium ... rotary files, lasers, heating apparatuses, or ultrasonic instruments. .... essential factor for the success of endodontic treatments.

  15. SEALING ABILITY OF MINERAL TRIOXIDE AGGREGATE, CALCIUM PHOSPHATE CEMENT, AND GLASS IONOMER CEMENT IN THE REPAIR OF FURCATION PERFORATIONS

    Directory of Open Access Journals (Sweden)

    Prabath Singh

    2013-01-01

    Full Text Available Objectives: The purpose of this study was to evaluate the in vitro sealing ability of three repair materials. Mineral trioxide aggregate (MTA; Group A, calcium phosphate cement (CPC; Group B, and light cured glass ionomer cement (GIC; Group C when used to repair the perforation created in the pulpal floor of fifty extracted human permanent molars. Materials and methods: Preparation of access openings and furcation perforations were done, and the teeth divided into five experimental groups (A, B, C including two controls (D, E with ten samples in each group randomly. Following the repair procedure, the pulp chambers and access openings were filled with composite resin and immersed in 2% methylene blue solution for 48 hours. The teeth were sectioned longitudinally and the linear dye penetration measured under a stereo­microscope. Results: The comparison of the linear length of micro-leakage (mm among the experimental groups revealed no significant difference (p = 0.332. On calculating the percentage of depth of leakage to the total length of the perforation, it was observed that the mean leakage was 35.5% in Group A, 53.6% in Group B and the highest, 87.5% in Group C. The mean of leakage percentage was statistically significant by Kruskal-Wallis test (p = 0.003. The results indicated that the dye penetration used as furcation perforation repair material was least with mineral trioxide aggregate. Comparing the depth of penetration of dye, 50% of the Group A samples showed less than 25% of depth penetration. While 40% of Group B cases had more than 50% dye penetration. In our study, all Group C teeth had ≥ 50% dye penetration. Conclusions: The present study indicated that GIC had the greatest dye penetration followed by CPC and MTA. Mineral trioxide aggregate and calcium phosphate cement had comparatively better sealing ability than glass ionomer cement.

  16. The mechanical properties and hydration characteristics of cement pastes containing added-calcium coal gangue

    Energy Technology Data Exchange (ETDEWEB)

    Dongxu Li; Xuyan Song [Nanjing University of Technology, Nanjing (China). College of Material Science and Engineering

    2008-04-15

    The mechanical properties of several kinds of coal gangue calcined with limestone were researched so as to find the optimum way of calcinations with limestone. The microstructure and property of hydration process of cement pastes containing added-calcium coal gangue were analyzed by means of scanning electron microscope (SEM) and the method of mercury in trusion poremeasurement. When the proper amounst of gypsum and fluorite were taken as mineralizers in the course of calcinations of added-calcium coal gangue, the activity of coal gangue can be effectively improved. The results of mechanical property and structural characteristics such as hydration, hydration products and microstructure etc. of cement pastes containing added-calcium coal gangue are consistent.

  17. Early-age hydration and volume change of calcium sulfoaluminate cement-based binders

    Science.gov (United States)

    Chaunsali, Piyush

    Shrinkage cracking is a predominant deterioration mechanism in structures with high surface-to-volume ratio. One way to allay shrinkage-induced stresses is to use calcium sulfoaluminate (CSA) cement whose early-age expansion in restrained condition induces compressive stress that can be utilized to counter the tensile stresses due to shrinkage. In addition to enhancing the resistance against shrinkage cracking, CSA cement also has lower carbon footprint than that of Portland cement. This dissertation aims at improving the understanding of early-age volume change of CSA cement-based binders. For the first time, interaction between mineral admixtures (Class F fly ash, Class C fly ash, and silica fume) and OPC-CSA binder was studied. Various physico-chemical factors such as the hydration of ye'elimite (main component in CSA cement), amount of ettringite (the main phase responsible for expansion in CSA cement), supersaturation with respect to ettringite in cement pore solution, total pore volume, and material stiffness were monitored to examine early-age expansion characteristics. This research validated the crystallization stress theory by showing the presence of higher supersaturation level of ettringite, and therefore, higher crystallization stress in CSA cement-based binders. Supersaturation with respect to ettringite was found to increase with CSA dosage and external supply of gypsum. Mineral admixtures (MA) altered the expansion characteristics in OPC-CSA-MA binders with fixed CSA cement. This study reports that fly ash (FA) behaves differently depending on its phase composition. The Class C FA-based binder (OPC-CSA-CFA) ceased expanding beyond two days unlike other OPC-CSA-MA binders. Three factors were found to govern expansion of CSA cement-based binders: 1) volume fraction of ettringite in given pore volume, 2) saturation level of ettringite, and 3) dynamic modulus. Various models were utilized to estimate the macroscopic tensile stress in CSA cement

  18. Reinforcement of calcium phosphate cement with multi-walled carbon nanotubes and bovine serum albumin for injectable bone substitute applications

    NARCIS (Netherlands)

    Chew, K.K.; Low, K.L.; Zein, S.H.S.; McPhail, D.; Gerhardt, L.C.; Roether, J.A.; Boccaccini, A.R.

    2011-01-01

    This paper presents the development of novel alternative injectable calcium phosphate cement (CPC) composites for orthopaedic applications. The new CPC composites comprise ß-tri-calcium phosphate (ß-TCP) and di-calcium phosphate anhydrous (DCPA) mixed with bovine serum albumin (BSA) and incorporated

  19. Predictive Mechanical Characterization of Macro-Molecular Material Chemistry Structures of Cement Paste at Nano Scale - Two-phase Macro-Molecular Structures of Calcium Silicate Hydrate, Tri-Calcium Silicate, Di-Calcium Silicate and Calcium Hydroxide

    Science.gov (United States)

    Padilla Espinosa, Ingrid Marcela

    Concrete is a hierarchical composite material with a random structure over a wide range of length scales. At submicron length scale the main component of concrete is cement paste, formed by the reaction of Portland cement clinkers and water. Cement paste acts as a binding matrix for the other components and is responsible for the strength of concrete. Cement paste microstructure contains voids, hydrated and unhydrated cement phases. The main crystalline phases of unhydrated cement are tri-calcium silicate (C3S) and di-calcium silicate (C2S), and of hydrated cement are calcium silicate hydrate (CSH) and calcium hydroxide (CH). Although efforts have been made to comprehend the chemical and physical nature of cement paste, studies at molecular level have primarily been focused on individual components. Present research focuses on the development of a method to model, at molecular level, and analysis of the two-phase combination of hydrated and unhydrated phases of cement paste as macromolecular systems. Computational molecular modeling could help in understanding the influence of the phase interactions on the material properties, and mechanical performance of cement paste. Present work also strives to create a framework for molecular level models suitable for potential better comparisons with low length scale experimental methods, in which the sizes of the samples involve the mixture of different hydrated and unhydrated crystalline phases of cement paste. Two approaches based on two-phase cement paste macromolecular structures, one involving admixed molecular phases, and the second involving cluster of two molecular phases are investigated. The mechanical properties of two-phase macromolecular systems of cement paste consisting of key hydrated phase CSH and unhydrated phases C3S or C2S, as well as CSH with the second hydrated phase CH were calculated. It was found that these cement paste two-phase macromolecular systems predicted an isotropic material behavior. Also

  20. In vitro and in vivo study of commercial calcium phosphate cement HydroSet™.

    Science.gov (United States)

    Kent, Niall W; Blunn, Gordon; Karpukhina, Natalia; Davis, Graham; de Godoy, Roberta Ferro; Wilson, Rory M; Coathup, Melanie; Onwordi, Lyris; Quak, Wen Yu; Hill, Robert

    2018-01-01

    The commercial calcium phosphate cement, HydroSet™, was investigated in vitro, studying phase formation, compressive strength and setting time, followed by an ovine in vivo study to measure osseointegration, bone apposition and bone-to-graft contact. The X-ray diffraction and 31 P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) results showed the initial formation of octacalcium phosphate and hydroxyapatite at one hour. Over 7 days the octacalcium phosphate transformed to apatite, which was the only crystalline phase of the cement at 28 days. This apatite phase is thought to be a calcium deficient apatite. In the scanning electron microscopy, histological images of 12-week ovine in vivo results showed a high degree of osseointegration, 92.5%. Compressive strength comparisons between in vitro and in vivo measurements showed a dramatic difference between the in vitro measurements (highest 25.4 MPa) and in vivo (95 MPa), attributed to bone ingrowth into the cement in vivo. To the best of our knowledge this is the first time phase evolution of HydroSet™ and the properties studied in vitro complement the in vivo evaluation of the cement in a publication. The significance of the new finding of initial formation of octacalcium phosphate in this cement is discussed. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 21-30, 2018. © 2016 Wiley Periodicals, Inc.

  1. Characterization of cement calcium phosphate for use dental

    International Nuclear Information System (INIS)

    Barros, C.M.B.; Oliveira, S.V.; Silva, M.C.; Marques, J.B.; Fook, M.V.L.

    2011-01-01

    Calcium phosphates are interesting biological and medical attention due to its occurrence in different animal species and humans. Ceramics based on calcium phosphate in the form of implants or porous particulate materials, have proven to be suitable replacements for bone tissue when they are only subjected to small mechanical stresses. Was obtained research laboratory DEMA/UFCG a calcium phosphate phase. The goal is to characterize the material by X-ray diffraction (XRD) in order to analyze what the phases and infrared spectroscopy (FTIR) to identify the absorption bands of the bonding characteristic. Was identified by XRD phase present in the sample is hydroxyapatite Ca/P 1.67. In infrared spectroscopy has absorption bands characteristic of the phosphate group at 1032 cm1 region. (author)

  2. Cytotoxicity and Bioactivity of Calcium Silicate Cements Combined with Niobium Oxide in Different Cell Lines.

    Science.gov (United States)

    Mestieri, Leticia Boldrin; Gomes-Cornélio, Ana Lívia; Rodrigues, Elisandra Márcia; Faria, Gisele; Guerreiro-Tanomaru, Juliane Maria; Tanomaru-Filho, Mário

    2017-01-01

    The aim of this study was to evaluate the cytotoxicity and bioactivity of calcium silicate-based cements combined with niobium oxide (Nb2O5) micro and nanoparticles, comparing the response in different cell lines. This evaluation used four cell lines: two primary cultures (human dental pulp cells - hDPCs and human dental follicle cells - hDFCs) and two immortalized cultures (human osteoblast-like cells - Saos-2 and mouse periodontal ligament cells - mPDL). The tested materials were: White Portland Cement (PC), mineral trioxide aggregate (MTA), white Portland cement combined with microparticles (PC/Nb2O5µ) or nanoparticles (PC/Nb2O5n) of niobium oxide (Nb2O5). Cytotoxicity was evaluated by the methylthiazolyldiphenyl-tetrazolium bromide (MTT) and trypan blue exclusion assays and bioactivity by alkaline phosphatase (ALP) enzyme activity. Results were analyzed by ANOVA and Tukey test (a=0.05). PC/Nb2O5n presented similar or higher cell viability than PC/Nb2O5µ in all cell lines. Moreover, the materials presented similar or higher cell viability than MTA. Saos-2 exhibited high ALP activity, highlighting PC/Nb2O5µ material at 7 days of exposure. In conclusion, calcium silicate cements combined with micro and nanoparticles of Nb2O5 presented cytocompatibility and bioactivity, demonstrating the potential of Nb2O5 as an alternative radiopacifier agent for these cements. The different cell lines had similar response to cytotoxicity evaluation of calcium silicate cements. However, bioactivity was more accurately detected in human osteoblast-like cell line, Saos-2.

  3. The physical properties and ion release of CPP-ACP-modified calcium silicate-based cements.

    Science.gov (United States)

    Dawood, A E; Manton, D J; Parashos, P; Wong, Rhk; Palamara, Jea; Stanton, D P; Reynolds, E C

    2015-12-01

    This study investigated the physical properties and ion release of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified calcium silicate-based cements (CSCs) and compared the properties of a trial mineral trioxide aggregate (MTA) with two commercially available CSCs, Biodentine(™) and Angelus(®) MTA. The setting time, solubility, compressive strength and Vickers surface microhardness of the three CSCs incorporated with 0%, 0.5%, 1.0%, 2.0% and 3.0% (w/w) CPP-ACP were investigated. Release of calcium (Ca(2+) ), phosphate ions (Pi ) and pH of the test cements were measured after 24, 72, 168 and 336 h of storage. The addition of up to 1.0% CPP-ACP into Biodentine(™) and 0.5% into the other cements did not adversely affect their physical properties except for the setting time. The addition of 0.5% CPP-ACP increased Ca(2+) released from Biodentine(™) (after 168 and 336 h), Angelus(®) MTA (after 168 h) and the trial MTA (after 72 h). The addition of 1.0-3.0% CPP-ACP increased Ca(2+) and Pi released from all the cements. Biodentine(™) released more Ca(2+) particularly in the early stages and showed shorter setting time and higher mechanical properties than the other cements. The mechanical properties of Angelus(®) MTA and the trial MTA were similar. All the cements produced highly alkaline storage solutions. Up to 1.0% CPP-ACP in Biodentine(™) improves Ca(2+) and Pi release and 0.5% CPP-ACP in Angelus(®) MTA and the trial MTA improves Ca(2+) release without altering the mechanical properties and solubility. The addition of CPP-ACP into CSCs prolonged the setting time. © 2015 Australian Dental Association.

  4. A new aluminium-hydrate species in hydrated Portland cements characterized by 27Al and 29Si MAS NMR spectroscopy

    International Nuclear Information System (INIS)

    Andersen, Morten Daugaard; Jakobsen, Hans J.; Skibsted, Jorgen

    2006-01-01

    Recent 27 Al MAS NMR studies of hydrated Portland cements and calcium-silicate-hydrate (C-S-H) phases have shown a resonance from Al in octahedral coordination, which cannot be assigned to the well-known aluminate species in hydrated Portland cements. This resonance, which exhibits the isotropic chemical shift δ iso = 5.0 ppm and the quadrupole product parameter P Q = 1.2 MHz, has been characterized in detail by 27 Al MAS and 27 Al{ 1 H} CP/MAS NMR for different hydrated white Portland cements and C-S-H phases. These experiments demonstrate that the resonance originates from an amorphous or disordered aluminate hydrate which contains Al(OH) 6 3- or O x Al(OH) 6-x (3+x)- units. The formation of the new aluminate hydrate is related to the formation of C-S-H at ambient temperatures, however, it decomposes by thermal treatment at temperatures of 70-90 o C. From the experiments in this work it is proposed that the new aluminate hydrate is either an amorphous/disordered aluminate hydroxide or a calcium aluminate hydrate, produced as a separate phase or as a nanostructured surface precipitate on the C-S-H phase. Finally, the possibilities of Al 3+ for Ca 2+ substitution in the principal layers and interlayers of the C-S-H structure are discussed

  5. Cytotoxicity and genotoxicity of calcium silicate-based cements on an osteoblast lineage

    Directory of Open Access Journals (Sweden)

    Ana Lívia GOMES-CORNÉLIO

    2016-01-01

    Full Text Available Abstract Several calcium silicate-based biomaterials have been developed in recent years, in addition to Mineral Trioxide Aggregate (MTA. The aim of this study was to evaluate the cytotoxicity, genotoxicity and apoptosis/necrosis in human osteoblast cells (SAOS-2 of pure calcium silicate-based cements (CSC and modified formulations: modified calcium silicate-based cements (CSCM and three resin-based calcium silicate cements (CSCR1 (CSCR 2 (CSCR3. The following tests were performed after 24 hours of cement extract exposure: methyl-thiazolyl tetrazolium (MTT, apoptosis/necrosis assay and comet assay. The negative control (CT- was performed with untreated cells, and the positive control (CT+ used hydrogen peroxide. The data for MTT and apoptosis were submitted to analysis of variance and Bonferroni’s posttest (p < 0.05, and the data for the comet assay analysis, to the Kruskal-Wallis and Dunn tests (p < 0.05. The MTT test showed no significant difference among the materials in 2 mg/mL and 10 mg/mL concentrations. CSCR3 showed lower cell viability at 10 mg/mL. Only CSC showed lower cell viability at 50 mg/mL. CSCR1, CSCR2 and CSCR3 showed a higher percentage of initial apoptosis than the control in the apoptosis test, after 24 hours exposure. The same cements showed no genotoxicity in the concentration of 2 mg/mL, with the comet assay. CSC and CSCR2 were also not genotoxic at 10 mg/mL. All experimental materials showed viability with MTT. CSC and CSCR2 presented a better response to apoptosis and genotoxicity evaluation in the 10 mg/mL concentration, and demonstrated a considerable potential for use as reparative materials.

  6. Production of a calcium silicate cement material from alginate impression material.

    Science.gov (United States)

    Washizawa, Norimasa; Narusawa, Hideaki; Tamaki, Yukimichi; Miyazaki, Takashi

    2012-01-01

    The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified investment materials at 1,200°C produced calcium silicates, firing the set alginate impression material did not. However, we succeeded when firing the set blend of pre-fired set alginate impression material and gypsum at 1,200°C. SEM observations of the powder revealed that the featured porous structures of diatomite as an alginate impression material component appeared useful for synthesizing calcium silicates. Experimentally fabricated calcium silicate powder was successfully mixed with phosphoric acid solution and set by depositing the brushite. Therefore, we conclude that the production of calcium silicate cement material is possible from waste alginate impression material.

  7. Studies on sintering additives for hydroxyapatite, and controlled porosity structures of calcium aluminates and polypropylene-tricalcium phosphate for bone graft applications

    Science.gov (United States)

    Kalita, Samar Jyoti

    Tissue engineering has made a significant contribution in developing new biomaterials that can restore the structural features and physiological functions of natural tissues. Various materials, such as metals, ceramics, polymers and composites have been developed for their use in hard tissue engineering applications. Part A of this thesis describes my research on HAp ceramics. HAp, a bioactive ceramic, is known for its osteoconductivity, but shows poor mechanical performance. This program aimed at improving mechanical performance of synthetic HAp by introducing small quantities of various sintering additives. A range of oxide-based sintering additives were selected and prepared. Dense compacts were prepared using a uniaxial press with an average green density of 1.6 g/cc. Results showed that some of these sintering additives improved densification, hardness and compression strength of synthetic HAp compared to the pure composition. A maximum bulk density of 3.06 g/cc was achieved for 2.5 wt% addition of MgO. A Microhardness of 4.9 GPa (505 HV) was measured for 2.5 wt% addition of BaO, and the highest compression strength (220MPa) was reported for 2.5 wt% addition of CaO. Cytotoxicity and cell proliferation studies with a modified human osteoblast (HOB) cell-line (OPC1) proved most of these materials non-toxic and biocompatible. Microscopic observation revealed that bone cells were attached and grew well on most of these ceramic matrices. Part B describes my work on development of controlled porosity polypropylene-tricalcium phosphate composite scaffolds via the fused deposition modeling (FDM) process. Hg-porosimetry was performed to determine pore size and their distribution. Uniaxial compression testing performed on samples with 36 vol% porosity and pore size of 160 mum showed the best compressive strength of 12.7 MPa. Part C includes my research on development of "3-D honeycomb" porous calcium aluminate structures via the indirect FDM process. Samples of 29% and

  8. Calculation of calcium diffusion coefficient of cement hardenings using minute pore data

    International Nuclear Information System (INIS)

    Hitomi, Takashi; Takeda, Nobufumi; Iriya, Keishiro

    2009-01-01

    This report describes the calculations of the diffusion coefficient of the Ca ion of cement hardenings using minute pore data. The observed hardenings were ordinary Portland cement (OPC), low-heat Portland cement with fly ash (LPC+FA) and highly fly ash containing silica fume cement (HFSC). The samples were cured in the standard and artificially leached by accelerated test. Minute pore datas of the cement hardenings were acquired with image processing of internal structural information obtained from high resolution X-ray computed tomography observations. Upon analysis, several voxels are combined into one bigger voxel, the diffusion coefficient of the voxels were determined in proportion to the number of voxels which were included in. The results reveal that the change in the calcium diffusion coefficient of OPC due to leaching was large, but the LPC+FA and HFSC cements exhibited even greater changes than OPC. It is suggested that the diffusion coefficients are proportional to the Ca/Si ratio of the samples. (author)

  9. Anti-inflammation performance of curcumin-loaded mesoporous calcium silicate cement.

    Science.gov (United States)

    Chen, Yuan-Chien; Shie, Ming-You; Wu, Yuan-Haw Andrew; Lee, Kai-Xing Alvin; Wei, Li-Ju; Shen, Yu-Fang

    2017-09-01

    Calcium silicate (CS) cements have excellent bioactivity and can induce the bone-like apatite formation. They are good biomaterials for bone tissue engineering and bone regenerative medicine. However, they have degradability and the dissolved CS can cause the inflammatory response at the early post-implantation stage. The purpose of this study was to design and prepare the curcumin-loaded mesoporous CS (MesoCS/curcumin) cements as a strategy to reduce the inflammatory reaction after implantation. The MesoCS/curcumin cements were designed and prepared. The characteristics of MesoCS/curcumin specimens were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their physical properties, biocompatibility, and anti-inflammatory ability were also evaluated. The MesoCS/curcumin cements displayed excellent biocompatibility and physical properties. Their crystalline characterizations were very similar with MesoCS cements. After soaking in simulated body fluid, the bone-like apatite layer of the MesoCS/curcumin cements could be formed. In addition, it could inhibit the expression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) after inflammation reaction induced by lipopolysaccharides and had good anti-inflammatory ability. Adding curcumin in MesoCS cements can reduce the inflammatory reaction, but does not affect the original biological activity and properties of MesoCS cements. It can provide a good strategy to inhibit the inflammatory reaction after implantation for bone tissue engineering and bone regenerative medicine. Copyright © 2017. Published by Elsevier B.V.

  10. Addition of 1, 2 and 3% in mass of sodium alginate in calcium phosphate cement

    International Nuclear Information System (INIS)

    Coelho, W.T.; Fernandes, J.M.; Vieira, R.S.; Thurmer, M.B.; Santos, L.A.

    2011-01-01

    The calcium phosphate cement (CFC) are bone substitutes with great potential for use in orthopedics, traumatology and dentistry because of their biocompatibility, bioactivity, osteoconductivity and osteotransdutivity, and a paste that can be easily molded and placed into the surgical site. However, CFCs have low mechanical strength, which equals the maximum mechanical strength of trabecular bone. Aiming to evaluate the strength and time to handle a CFC phase composed mainly of alpha were added to sodium alginate (1%, 2% and 3% wt) and an accelerator handle in an aqueous medium. The cement powder was mixed with liquid takes 2 minutes and resigned in specimens and assessed for apparent density and porosity by the Archimedes method, X-ray diffraction and mechanical strength. We noticed a significant increase in mechanical properties of cement added sodium alginate. (author)

  11. Nano clay-enhanced calcium phosphate cements and hydrogels for biomedical applications

    Science.gov (United States)

    Jammalamadaka, Udayabhanu

    Biomaterials are used as templates for drug delivery, scaffolds in tissue engineering, grafts in surgeries, and support for tissue regeneration. Novel biomaterial composites are needed to meet multifaceted requirements of compatibility, ease of fabrication and controlled drug delivery. Currently used biomaterials in orthopedics surgeries suffer limitations in toxicity and preventing infections. Polymethyl methacrylate (PMMA) used as bone cement suffers from limitations of thermal necrosis and monomer toxicity calls for development of better cementing biomaterials. A biodegradable/bioresorbable cement with good mechanical properties is needed to address this short coming. Metal implants used in fixing fractures or total joint replacement needs improvements in preventing biofilm formation and better tissue integration. This research addressed the above mentioned research gaps by formulating novel biomaterial composites. Calcium phosphate cements are the alternative bone cements that are bioresorbable and promote tissue integration. These cements lack sufficient mechanical strengths to be used in load bearing sites. The addition of nanoparticles is hypothesized to improve the mechanical properties without inducing toxicity to the tissue. This hypothesis was tested by evaluating compression and flexural strengths in addition to cytocompatibility tests. Results indicate that addition of nano-clay particles (halloysites nanotubes) improved the compressive strength and osteoinductive properties of calcium phosphate cements. To address the research need of preventing implant failure due to infection and aseptic loosening, novel coatings are needed. Hydrogels are well establish for their ability to mimic in vivo environment, promote cell viability and as drug delivery vehicles. Use of composites of hydrogels and drug-loaded nanoparticles to prevent infection was evaluated. Cytocompatibility results indicate good cell viability. Antibacterial results show sustained release

  12. Calcium phosphate holmium-166 ceramic to addition in bone cement: synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Donanzam, Blanda A.; Campos, Tarcisio P.R., E-mail: campos@nuclear.ufmg.b [Universidade do Federal de Minas Gerais (DEN/UFMG), Belo Horizonte, MG (Brazil). Escola de Engenharia. Dept. de Engenharia Nuclear; Dalmazio, Ilza; Valente, Eduardo S., E-mail: id@cdtn.b, E-mail: valente@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2011-07-01

    Spine metastases are a common and painful complication of cancer. The treatment often consists of bone cement injection (vertebroplasty or kyphoplasty) within vertebral body for vertebrae stabilization, followed by external beam radiation therapy. Recently, researchers introduced the concept of radioactive bone cement for spine tumors therapy. Then, investigations about bioactive and radioactive materials became interesting. In this study, we present the synthesis of calcium phosphate incorporated holmium (CaP-Ho) via sol-gel technique, and its characterization by XRD, FT-IR, NA and SEM. Results showed a multiphasic bioceramic composed mainly of hydroxyapatite, {beta}-tricalcium phosphate, holmium phosphate and traces of calcium pyrophosphate. Furthermore, the nuclide Ho-166 was the major radioisotope produced. Despite that, the radioactive bioceramic CaP-{sup 166}Ho must be investigated in clinical trials to assure its efficacy and safety on spine tumors treatment (author)

  13. Calcium phosphate holmium-166 ceramic to addition in bone cement: synthesis and characterization

    International Nuclear Information System (INIS)

    Donanzam, Blanda A.; Campos, Tarcisio P.R.

    2011-01-01

    Spine metastases are a common and painful complication of cancer. The treatment often consists of bone cement injection (vertebroplasty or kyphoplasty) within vertebral body for vertebrae stabilization, followed by external beam radiation therapy. Recently, researchers introduced the concept of radioactive bone cement for spine tumors therapy. Then, investigations about bioactive and radioactive materials became interesting. In this study, we present the synthesis of calcium phosphate incorporated holmium (CaP-Ho) via sol-gel technique, and its characterization by XRD, FT-IR, NA and SEM. Results showed a multiphasic bioceramic composed mainly of hydroxyapatite, β-tricalcium phosphate, holmium phosphate and traces of calcium pyrophosphate. Furthermore, the nuclide Ho-166 was the major radioisotope produced. Despite that, the radioactive bioceramic CaP- 166 Ho must be investigated in clinical trials to assure its efficacy and safety on spine tumors treatment (author)

  14. Ph-activated nano-amorphous calcium phosphate-based cement to reduce dental enamel demineralization.

    Science.gov (United States)

    Melo, Mary A S; Weir, Michael D; Passos, Vanara F; Powers, Michael; Xu, Hockin H K

    2017-12-01

    Enamel demineralization is destructive, esthetically compromised, and costly complications for orthodontic patients. Nano-sized amorphous calcium phosphate (NACP) has been explored to address this challenge. The 20% NACP-loaded ortho-cement notably exhibited favorable behavior on reducing demineralization of enamel around brackets in a caries model designed to simulate the carious attack. The 20% NACP-loaded ortho-cement markedly promotes higher calcium and phosphate release at a low pH, and the mineral loss was almost two fold lower and carious lesion depth decreased the by 1/3. This novel approach is promising co-adjuvant route for prevention of dental caries dissemination in millions of patients under orthodontic treatment.

  15. Physical-Mechanical Properties and Micromorphology of Calcium Cements Exposed to Polyacrylic and Phosphoric Acids.

    Science.gov (United States)

    de Souza, Gustavo Fernandes; Arrais, Ana Beatriz; Aragão, Cícero Flávio Soares; Ferreira, Isana Alvares; Borges, Boniek Castillo Dutra

    2018-01-01

    To evaluate if physical and mechanical properties of self-curing calcium hydroxide cements were affected by contact with polyacrylic and phosphoric acids. Resin-containing (Life (LF)) and resin-free (Hydro C (HyC)) materials were subjected to polyacrylic acid conditioning and rinsing (POL); phosphoric acid conditioning and rinsing (PHO); rinsing only; and no treatment ( n = 10). Water sorption/solubility, release of hydroxyl ions (pH), roughness (Ra), and impact resistance were evaluated. Additional samples ( n = 1) were prepared for scanning electron microscopy (SEM) analysis of the surface morphology. Data were analyzed by two-way ANOVA and Tukey post hoc test ( P < 0.05). Water sorption was significantly higher for LF when in contact with PHO and lower for POL ( P < 0.05). The mean solubility was higher with POL for both cements ( P < 0.05). PHO increased the mean surface roughness for HyC ( P < 0.01); a significant decrease was noted for LF after contact with both acids ( P < 0.01). PHO promoted lower release of hydroxyl ions on both cements ( P < 0.05). For LF, rinsing, PHO, and POL presented similar morphology, differing from the control group. For HyC, PHO and POL presented similar morphology, differing from the control group. PHO had a negative effect on the physical properties of the cements tested, except for the solubility test. POL affected roughness and solubility of HyC cement. Clinical procedures that require polyacrylic and phosphoric acid conditioning must be done carefully on self-curing calcium hydroxide cements in order to avoid negative impact on their properties.

  16. THE CURRENT STATE OF CALCIUM SILICATE CEMENTS IN RESTORATIVE DENTISTRY: A REVIEW

    OpenAIRE

    Corral-Núñez, Camila; Fernández-Godoy, Eduardo; Casielles, Javier Martín; Estay, Juan; Bersezio-Miranda, Cristian; Cisternas-Pinto, Patricia; Batista-de Oliveira Jr, Osmir

    2016-01-01

    ABSTRACT Calcium silicate cements have been used as dental materials for more than twenty years; however, their use in restorative dentistry is more recent. Better mechanical properties and shorter curing times make them suitable for a variety of applications in which they are used as a substitute of dentin, including direct/indirect pulp capping and as cavity base/liner. These materials may also be used to restore enamel temporarily. This article seeks to review the available scientific evid...

  17. Preparation, Physical-Chemical Characterization, and Cytocompatibility of Polymeric Calcium Phosphate Cements

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2011-01-01

    Full Text Available Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control. Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications.

  18. Brain aluminium accumulation and oxidative stress in the presence of calcium silicate dental cements.

    Science.gov (United States)

    Demirkaya, K; Demirdöğen, B Can; Torun, Z Öncel; Erdem, O; Çırak, E; Tunca, Y M

    2017-10-01

    Mineral trioxide aggregate (MTA) is a calcium silicate dental cement used for various applications in dentistry. This study was undertaken to test whether the presence of three commercial brands of calcium silicate dental cements in the dental extraction socket of rats would affect the brain aluminium (Al) levels and oxidative stress parameters. Right upper incisor was extracted and polyethylene tubes filled with MTA Angelus, MTA Fillapex or Theracal LC, or left empty for the control group, were inserted into the extraction socket. Rats were killed 7, 30 or 60 days after operation. Brain tissues were obtained before killing. Al levels were measured by atomic absorption spectrometry. Thiobarbituric acid reactive substances (TBARS) levels, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were determined using spectrophotometry. A transient peak was observed in brain Al level of MTA Angelus group on day 7, while MTA Fillapex and Theracal LC groups reached highest brain Al level on day 60. Brain TBARS level, CAT, SOD and GPx activities transiently increased on day 7 and then returned to almost normal levels. This in vivo study for the first time indicated that initial washout may have occurred in MTA Angelus, while element leaching after the setting is complete may have taken place for MTA Fillapex and Theracal LC. Moreover, oxidative stress was induced and antioxidant enzymes were transiently upregulated. Further studies to search for oxidative neuronal damage should be done to completely understand the possible toxic effects of calcium silicate cements on the brain.

  19. A New Type of Biphasic Calcium Phosphate Cement as a Gentamicin Carrier for Osteomyelitis

    Directory of Open Access Journals (Sweden)

    Wen-Yu Su

    2013-01-01

    Full Text Available Osteomyelitis therapy is a long-term and inconvenient procedure for a patient. Antibiotic-loaded bone cements are both a complementary and alternative treatment option to intravenous antibiotic therapy for the treatment of osteomyelitis. In the current study, the biphasic calcium phosphate cement (CPC, called α-TCP/HAP (α-tricalcium phosphate/hydroxyapatite biphasic cement, was prepared as an antibiotics carrier for osteomyelitis. The developed biphasic cement with a microstructure of α-TCP surrounding the HAP has a fast setting time which will fulfill the clinical demand. The X-ray diffraction and Fourier transform infrared spectrometry analyses showed the final phase to be HAP, the basic bone mineral, after setting for a period of time. Scanning electron microscopy revealed a porous structure with particle sizes of a few micrometers. The addition of gentamicin in α-TCP/HAP would delay the transition of α-TCP but would not change the final-phase HAP. The gentamicin-loaded α-TCP/HAP supplies high doses of the antibiotic during the initial 24 hours when they are soaked in phosphate buffer solution (PBS. Thereafter, a slower drug release is produced, supplying minimum inhibitory concentration until the end of the experiment (30 days. Studies of growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa in culture indicated that gentamicin released after 30 days from α-TCP/HAP biphasic cement retained antibacterial activity.

  20. Experimental Calcium Silicate-Based Cement with and without Zirconium Oxide Modulates Fibroblasts Viability.

    Science.gov (United States)

    Slompo, Camila; Peres-Buzalaf, Camila; Gasque, Kellen Cristina da Silva; Damante, Carla Andreotti; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro; de Oliveira, Rodrigo Cardoso

    2015-01-01

    The aim of this study was to verify whether the use of zirconium oxide as a radiopacifier of an experimental calcium silicate-based cement (WPCZO) leads to cytotoxicity. Fibroblasts were treated with different concentrations (10 mg/mL, 1 mg/mL, and 0.1 mg/mL) of the cements diluted in Dulbecco's modified Eagle's medium (DMEM) for periods of 12, 24, and 48 h. Groups tested were white Portland cement (WPC), white Portland cement with zirconium oxide (WPCZO), and white mineral trioxide aggregate Angelus (MTA). Control group cells were not treated. The cytotoxicity was evaluated through mitochondrial-activity (MTT) and cell-density (crystal violet) assays. All cements showed low cytotoxicity. In general, at the concentration of 10 mg/mL there was an increase in viability of those groups treated with WPC and WPCZO when compared to the control group (pcement with 20% zirconium oxide as the radiopacifier showed low cytotoxicity as a promising material to be exploited for root-end filling.

  1. Alteration of a borosilicate glass in cemented water: antagonist effects of calcium

    International Nuclear Information System (INIS)

    Frizon, F.; Depierre, S.; Angeli, F.; Gin, S.

    2013-01-01

    In the framework of the storage of radioactive wastes in deep geological layers, vitrified waste may be in contact with an environment saturated with solutions stemming from various stages of cement degradation. A series of experiments has been performed to assess how a basic aqueous calcium-rich solution can impact the mechanisms and kinetics of glass alteration. This study shows that 2 main parameters have an impact on the kinetics of the dissolution of glass: the S/V ratio (the glass surface divided by the volume of solution) and the calcium concentration. The calcium concentration is a key parameter whatever the kinetics of glass degradation. In a diluted medium with a pH over 11, the kinetics of glass alteration slows down along with an increase in calcium concentration. What happens is that the silicon flux being too weak to allow the nucleation of C-S-H phases, calcium can penetrate the alteration layer which leads to a better retention of glass components through specific silicon-calcium reactivity and a slowing down of the glass alteration kinetics. On the contrary in a confined environment, a high concentration in calcium leads to the precipitation of C-S-H and to less C-S-H available to cover glass grains diminishing its passivating effect and consequently the dissolving of glass can keep on at more or less the same pace. (A.C.)

  2. Evaluation of the sealing ability of bone cement as furcation perforation repair material when compared with mineral trioxide aggregate and calcium phosphate cement: An in-vitro study

    Directory of Open Access Journals (Sweden)

    Rashmi Chordiya

    2010-01-01

    Full Text Available Aim: This study was undertaken to compare the sealing ability of bone cement as furcation perforation repair material when compared with mineral trioxide aggregate and calcium phosphate cement. Materials and Methods: A total of 70 sound mandibular molars were selected for this study. The sample teeth were randomly divided into five groups: group I - n=20, perforation repair material used, mineral trioxide aggregate; group II - n=20, perforation repair material used, calcium phosphate cement; group III - n=20, perforation repair material used, bone cement; group IV - positive control, n=5, the furcation were not repaired with any material; group V - negative control, n=5, furcation area intact, no perforation done. The teeth were immersed in silver nitrate solution for 2 hours and then rinsed with photographic developer solution for 6 hours. They were then sectioned in a longitudinal direction and examined under a stereomicroscope. In each section the actual values of dye leakage were calculated from outer margins of perforation to the level of pulpal floor and were then subjected to statistical analysis. Results: An unpaired ′t′ test revealed that different groups exhibited significantly different dye penetrations (P<0.01. Conclusion: Furcation perforation repaired with MTA showed minimum microleakage (mean 54.5%, calcium phosphate cement showed maximum microleakage (100%, and bone cement showed moderate dye leakage (87.8%.

  3. Possibilities of special cements in ceramic applications

    International Nuclear Information System (INIS)

    Capmas, A.; Bier, T.A.

    1993-01-01

    About 25 years ago, the only way to have confinement material for high temperature applications was to prepare a ceramic by sintering or fusion at high temperature. A new technology came, with the production of Low Cement Castables. This new product was obtained by a careful choice of the granulometry of the aggregates, an optimization of the defloculation of fine particles, including the cement (Calcium Aluminate Cement) and the addition of silica fume. Silica fume brought two improvements: a) a fluidifying effect, due partly to the low sensitivity of viscosity to pH, and partly to the geometric effect of the nicely spherical particle, b) a chemical effect, brought by the reaction of silica and Calcium Aluminate Cement to give a coherent zeolithic structure, through which water could escape during the first firing. From a ceramist point of view, it is interesting to understand how this components, nearly colloidal system mixed in water can be heated up to ceramization without any noticeable change in mechanical characteristics and shrinkage. From a more practical point of view, it is also interesting to realize that some characteristics, usually attributed only to ceramics, also apply with low cement castables technology: high compressive strength, flexural strength, corrosion resistance, abrasion resistance, impact resistance. (orig.)

  4. A LOW TEMPERATURE ALUMINIZING TREATMENT OF HOT WORK TOOL STEEL

    OpenAIRE

    Matijević, Božidar

    2013-01-01

    Conventional aluminizing processes by pack cementation are typically carried out at elevated temperatures. A low temperature powder aluminizing technology was applied to the X40CrMoV5-1 hot tool steel. The aluminizing temperature was from 550 °C to 620 °C. Effects of temperature and time on the microstructure and phase evolution were investigated. Also, the intermetallic layer thickness was measured in the aluminized layer of a steel substrate. The cross-sectional microstructures, the alumini...

  5. Effects of Leaching Behavior of Calcium Ions on Compression and Durability of Cement-Based Materials with Mineral Admixtures

    Science.gov (United States)

    Cheng, An; Chao, Sao-Jeng; Lin, Wei-Ting

    2013-01-01

    Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing reinforcing steel corrosion. This study investigates the effects of leaching behavior of calcium ions on the compression and durability of cement-based materials. Since the parameters influencing the leaching behavior of cement-based materials are unclear and diverse, this paper focuses on the influence of added mineral admixtures (fly ash, slag and silica fume) on the leaching behavior of calcium ions regarding compression and durability of cemented-based materials. Ammonium nitrate solution was used to accelerate the leaching process in this study. Scanning electron microscopy, X-ray diffraction analysis, and thermogravimetric analysis were employed to analyze and compare the cement-based material compositions prior to and after calcium ion leaching. The experimental results show that the mineral admixtures reduce calcium hydroxide quantity and refine pore structure through pozzolanic reaction, thus enhancing the compressive strength and durability of cement-based materials. PMID:28809247

  6. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

    Science.gov (United States)

    Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

    2016-01-01

    The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns. PMID:27023532

  7. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Raphael Pilo

    2016-03-01

    Full Text Available The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC or Self Adhesive Resin Cement (SARC. Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa were significantly higher than those for SARC (2.28 ± 0.58 MPa. The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  8. Calcium aluminates hydration in presence of amorphous SiO2 at temperatures below 90 deg. C

    International Nuclear Information System (INIS)

    Rivas Mercury, J.M.; Turrillas, X.; Aza, A.H. de; Pena, P.

    2006-01-01

    The hydration behaviour of Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 with added amorphous silica at 40, 65 and 90 deg. C has been studied for periods ranging from 1 to 31 days. In hydrated samples crystalline phases like katoite (Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x ) and gibbsite, Al(OH) 3 , were identified, likewise amorphous phases like Al(OH) x , calcium silicate hydrates, C-S-H, and calcium aluminosilicate hydrates, C-S-A-H, were identified. The stoichiometry of Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), which was the main crystalline product, was established by Rietveld refinement of X-ray and neutron diffraction data and by transmission electron microscopy. - Graphical abstract: Katoite, Ca 3 Al 2 (SiO 4 ) 3- x (OH) 4 x (0≤3-x≤0.334), was identified besides gibbsite, Al(OH) 3 , as a crystalline stable hydration products in Ca 3 Al 2 O 6 , Ca 12 Al 14 O 33 and CaAl 2 O 4 hydrated with added amorphous silica between 40 and 90 deg. C

  9. Surface Corrosion and Microstructure Degradation of Calcium Sulfoaluminate Cement Subjected to Wet-Dry Cycles in Sulfate Solution

    Directory of Open Access Journals (Sweden)

    Wuman Zhang

    2017-01-01

    Full Text Available The hydration products of calcium sulfoaluminate (CSA cement are different from those of Portland cement. The degradation of CSA cement subjected to wet-dry cycles in sulfate solution was studied in this paper. The surface corrosion was recorded and the microstructures were examined by scanning electron microscopy (SEM. The results show that SO42-, Na+, Mg2+, and Cl− have an effect on the stability of ettringite. In the initial period of sulfate attack, salt crystallization is the main factor leading to the degradation of CSA cement specimens. The decomposition and the carbonation of ettringite will cause long-term degradation of CSA cement specimens under wet-dry cycles in sulfate solution. The surface spalling and microstructure degradation increase significantly with the increase of wet-dry cycles, sulfate concentration, and water to cement ratio. Magnesium sulfate and sodium chloride reduce the degradation when the concentration of sulfate ions is a constant value.

  10. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties

    Directory of Open Access Journals (Sweden)

    Hongfang Sun

    2015-02-01

    Full Text Available Calcium carbide residue (CCR is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP. The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement pastes was also examined through SEM (scanning electron microscope. Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  11. Properties of Chemically Combusted Calcium Carbide Residue and Its Influence on Cement Properties.

    Science.gov (United States)

    Sun, Hongfang; Li, Zishanshan; Bai, Jing; Memon, Shazim Ali; Dong, Biqin; Fang, Yuan; Xu, Weiting; Xing, Feng

    2015-02-13

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)₂, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (RCP). The properties of paste and mortar in fresh and hardened states (setting time, shrinkage, and compressive strength) with 5% cement replacement by RCP were evaluated. The hydration of RCP and OPC (Ordinary Portland Cement) pastes was also examined through SEM (scanning electron microscope). Test results showed that in comparison to control OPC mix, the hydration products for the RCP mix took longer to formulate. The initial and final setting times were prolonged, while the drying shrinkage was significantly reduced. The compressive strength at the age of 45 days for RCP mortar mix was found to be higher than that of OPC mortar and OPC mortar with silica fume mix by 10% and 8%, respectively. Therefore, the synthesized RCP was proved to be a sustainable active cementitious powder for the strength enhanced of building materials, which will result in the diversion of significant quantities of this by-product from landfills.

  12. In Vivo Evaluation of an Injectable Premixed Radiopaque Calcium Phosphate Cement

    Directory of Open Access Journals (Sweden)

    Jonas Åberg

    2011-01-01

    Full Text Available In this work a radiopaque premixed calcium phosphate cement (pCPC has been developed and evaluated in vivo. Radiopacity was obtained by adding 0–40 % zirconia to the cement paste. The effects of zirconia on setting time, strength and radiopacity were evaluated. In the in vivo study a 2 by 3.5 mm cylindrical defect in a rat vertebrae was filled with either the pCPC, PMMA or bone chips. Nano-SPECT CT analysis was used to monitor osteoblast activity during bone regeneration. The study showed that by adding zirconia to the cement the setting time becomes longer and the compressive strength is reduced. All materials evaluated in the in vivo study filled the bone defect and there was a strong osteoblast activity at the injury site. In spite of the osteoblast activity, PMMA blocked bone healing and the bone chips group showed minimal new bone formation. At 12 weeks the pCPC was partially resorbed and replaced by new bone with good bone ingrowth. The radiopaque pCPC may be considered to be used for minimal invasive treatment of vertebral fractures since it has good handling, radiopacity and allows healing of cancellous bone in parallel with the resorption of the cement.

  13. [Endodontics in motion: new concepts, materials and techniques 1. Hydraulic Calcium Silicate Cements].

    Science.gov (United States)

    Moinzadeh, A T; Jongsma, L; de Groot-Kuin, D; Cristescu, R; Neirynck, N; Camilleri, J

    2015-01-01

    Hydraulic Calcium Silicate Cements (HCSCs) constitute a group of materials that have become increasingly popular in endodontics since the introduction of Mineral Trioxide Aggregate (MTA) in the 1990s. MTA is Portland cement to which bismuth oxide has been added to increase its radiopacity. The most important property of MTA is its capacity to set in water or a humid environment. However, MTA also has important limitations, for example, it's difficult to work with and can discolour teeth. Recently, numerous products based on HCSC chemistry, which can be considered as modifications of MTA intended to reduce its limitations, have become available on the market. Despite their potential advantages, all of these materials have their own specific limitations that are currently insufficiently known and investigated.

  14. Intracanal management of a post traumatic perforative invasive cervical root resorption using calcium enriched matrix cement

    Directory of Open Access Journals (Sweden)

    Saeed Asgary

    2013-01-01

    Full Text Available Invasive cervical root resorption (ICR is a consequence of a resorptive soft-tissue penetrating into dentin that starts below the gingival attachment and tends to be asymptomatic unless dental pulp involvement. Prompt diagnosis is the key to retention of the involved tooth. Treatment procedure includes non-surgical elimination of the resorptive soft-tissues and restoration of the cavity. In case of pulp involvement, endodontic treatment is indicated. This is a report of a non-surgical intra canal treatment case in a maxillary central incisor, which involved the pulp and was successfully treated with calcium enriched mixture (CEM cement. Based on favorable long-term treatment outcomes, CEM cement may be a promising biomaterial in treatment of ICR cases.

  15. Modifications on the properties of a calcium phosphate cement by additions of sodium alginate

    International Nuclear Information System (INIS)

    Coelho, W.T.; Fernandes, J.M.; Vieira, R.S.; Thurmer, M.B.; Santos, L.A.

    2012-01-01

    The Calcium Phosphate Cement (CPC) are bone substitutes with great potential for use in orthopedics, traumatology and dentistry due to its biocompatibility, bioactivity and osteoconductivity, and form a paste that can be easily shaped and placed into the surgical site. However, CPCs have low mechanical strength, which equals the maximum mechanical strength of trabecular bone. In order to assess the strength and time to handle a CPC composed primarily of alpha phase, were added sodium alginate (1%, 2% and 3% wt) and an accelerator in an aqueous solution. The cement powder was mixed with liquid of setting, shaped into specimens and evaluated for apparent density and porosity by Archimedes method, X-ray diffraction and compressive strength. A significant increase in compressive strength by adding sodium alginate was verified. (author)

  16. Characterization of a calcium phosphate cement based on alpha-tricalcium phosphate obtained by wet precipitation process

    International Nuclear Information System (INIS)

    Thurmer, M.B.; Diehl, C.E.; Vieira, R.S.; Coelho, W.T.G.; Santos, L.A.

    2012-01-01

    There are several systems of calcium phosphate cements being studied. Those based on alpha-tricalcium phosphate are of particular interest. After setting they produce calcium deficient hydroxyapatite similar to bone like hydroxyapatite. This work aims to obtain alpha-tricalcium phosphate powders by the wet precipitation process, using calcium nitrate and phosphoric acid as reagents. This powder was characterized by infrared spectroscopy, X-ray diffraction and particle size distribution. In order to prepare the calcium phosphate cement, the powder was mixed with an accelerator in an aqueous solution. The mechanical properties of the cement were assessed and it was evaluated by means of apparent density, X-ray diffraction and scanning electron microscopy. The described method produced crystalline alpha-tricalcium phosphate as the major phase. The calcium phosphate cement showed high values of compression strength (50 MPa). The soaking of the cement in a simulated body fluid (SBF) formed a layer of hydroxyapatite like crystals in the surface of the samples. (author)

  17. Study of a hydraulic dicalcium phosphate dihydrate/calcium oxide-based cement for dental applications.

    Science.gov (United States)

    el-Briak, Hasna; Durand, Denis; Nurit, Josiane; Munier, Sylvie; Pauvert, Bernard; Boudeville, Phillipe

    2002-01-01

    By mixing CaHPO(4) x 2H(2)O (DCPD) and CaO with water or sodium phosphate buffers as liquid phase, a calcium phosphate cement was obtained. Its physical and mechanical properties, such as compressive strength, initial and final setting times, cohesion time, dough time, swelling time, dimensional and thermal behavior, and injectability were investigated by varying different parameters such as liquid to powder (L/P) ratio (0.35-0.7 ml g(-1)), molar calcium to phosphate (Ca/P) ratio (1.67-2.5) and the pH (4, 7, and 9) and the concentration (0-1 M) of the sodium phosphate buffer. The best results were obtained with the pH 7 sodium phosphate buffer at the concentration of 0.75 M. With this liquid phase, physical and mechanical properties depended on the Ca/P and L/P ratios, varying from 3 to 11 MPa (compressive strength), 6 to 10 min (initial setting time), 11 to 15 min (final setting time), 15 to 30 min (swelling time), 7 to 20 min (time of 100% injectability). The dough or working time was over 16 min. This cement expanded during its setting (1.2-5 % according to Ca/P and L/P ratios); this would allow a tight filling. Given the mechanical and rheological properties of this new DCPD/CaO-based cement, its use as root canal sealing material can be considered as classical calcium hydroxide or ZnO/eugenol-based pastes, without or with a gutta-percha point. Copyright 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 447-453, 2002

  18. Development of novel strontium containing bioactive glass based calcium phosphate cement.

    Science.gov (United States)

    D'Onofrio, A; Kent, N W; Shahdad, S A; Hill, R G

    2016-06-01

    The aim of this study was to investigate the effect on properties of increasing strontium substitution for calcium in bioactive glasses used as precursors for novel calcium phosphate cements. Glasses were produced by progressively substituting strontium for calcium. Cements were prepared by mixing the glass powder with Ca(H2PO4)2 powder with a 2.5% solution of Na2HPO4. Setting times and compressive strength were measured after 1h, 1 day, 7 days and 28 days immersion in Tris buffer solution. X-ray diffraction (XRD), Fourier transform infrared spectroscopy and radiopacity were measured and crystal morphology was assessed using scanning electron microscopy. A correlation between the phases formed, morphology of the crystallites, setting time and compressive strength were analyzed. Setting time increased proportionally with strontium substitution in the glass up to 25%, whereas for higher substitutions it decreased. Compressive strength showed a maximum value of 12.5MPa and was strongly influenced by the interlocking of the crystals and their morphology. XRD showed that the presence of strontium influenced the crystal phases formed. Octacalcium phosphate (Ca8H2(PO4)6·5H2O, OCP) was the main phase present after 1h and 1 day whereas after 28 days OCP was completely transformed to strontium-containing hydroxyapatite (SrxCa(10-x)(PO4)6(OH)2, SrHA). Radiopacity increased proportionally to strontium substitution in the glass. A novel method to develop a bone substitute forming in vitro SrHA as a final product by using a bioactive glass as a precursor was shown. These novel injectable bioactive glass cements are promising materials for dental and orthopedic applications. Further in vivo characterizations are being conducted. Copyright © 2016 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. Suitability of alumina cements for the cementation of boreholes under corrosive conditions, especially at the press fitting of CO{sub 2}; Eignung von Tonerdezementen fuer die Bohrlochzementierung unter korrosiven Bedingungen, insbesondere bei CO{sub 2}-Einpressung. Literaturstudie

    Energy Technology Data Exchange (ETDEWEB)

    Plank, J.; Sieber, R. (comps.) [Technische Univ. Muenchen (Germany). Lehrstuhl fuer Bauchemie

    2011-07-15

    Calcium aluminate cements, also called aluminate cements, are special cements based on calcium aluminates. In construction (especially in dry-mix mortars), they are valued for their remarkably higher acid and corrosion resistance compared to Portland cement. Their high temperature resistance especially qualifies them for refractory cements which are used e.g. as liners in cement rotary kilns. The worldwide production of calcium aluminate cements adds up to about 3 million tons. In oil well cementing, calcium aluminate cements have first been used at the beginning of the 90ies, in fact initially for geothermal wells. Applications in permafrost soils as well as fire-flooding wells came later. The reason for the use in geothermal wells. Applications in permafrost soils as well as fire-flooding wells came later. The reason for the use in geothermal wells were severe problems with API Portland cements affected by hot, carbonic acid rich formation brines. With support from the companies Unocal and Halliburton, the Brookhaven National Laboratory (USA) developed a special cement based on 60 parts by weight of calcium aluminate cement and 40 parts ASTM class F fly ash. This binder is notably CO{sub 2} resistant when mixed with a 25 wt.% Na-polyphosphate solution. Laboratory tests and field applications conclude that this cement is resistant to CO{sub 2} corrosion at temperatures up to 300 C for over 20 years. In 1997, for the first time numerous geothermal wells have been cemented using this cement. They are intact to this day. When this cement hardens at room temperature, amorphous reaction products are formed and the reaction is incomplete. However, at higher temperatures hydroxyapatite, boehmite, Na-P-zeolite, analcime or katoite are formed as crystalline reaction products. The CO{sub 2} resistance of this cement is due to specific chemical reactions. In contact with hot alkaline carbonate solutions, analcime converts to cancrinite, and CO{sub 2} is incorporated into

  20. Stabilization of ZnCl2-Containing Waste Using Calcium Sulfoaluminate Cement

    International Nuclear Information System (INIS)

    Cau Dit Coumes, C.; Berger, S.; Le Bescop, P.; Damidot, D.

    2013-01-01

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize radwastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl 2 mixing solution was characterized over one year as a function of the gypsum content of the binder and the thermal history of the material. Blending the CSA clinker with 20% gypsum enabled rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrate assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, straetlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the gypsum content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes, or in their leachates after 3 months of leaching by pure water at pH 7. The good retention of zinc by the cement matrix was mainly attributed to the precipitation of a hydrated and well crystallized phase with platelet morphology (which may belong to the layered double hydroxides family) at early age ≤ 1 day), and to chemisorption onto aluminum hydroxide at later age. (author)

  1. Solid-state 27Al and 29Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

    International Nuclear Information System (INIS)

    Pena, P.; Rivas Mercury, J.M.; Aza, A.H. de; Turrillas, X.; Sobrados, I.; Sanz, J.

    2008-01-01

    Partially deuterated Ca 3 Al 2 (SiO 4 ) y (OH) 12-4y -Al(OH) 3 mixtures, prepared by hydration of Ca 3 Al 2 O 6 (C 3 A), Ca 12 Al 14 O 33 (C 12 A 7 ) and CaAl 2 O 4 (CA) phases in the presence of silica fume, have been characterized by 29 Si and 27 Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca 3 Al 2 (OH) 12 and Al(OH) 3 phases were detected. From the quantitative analysis of 27 Al NMR signals, the Al(OH) 3 /Ca 3 Al 2 (OH) 12 ratio was deduced. The incorporation of Si into the katoite structure, Ca 3 Al 2 (SiO 4 ) 3-x (OH) 4x , was followed by 27 Al and 29 Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of 27 Al MAS-NMR components associated with Al(OH) 6 and Al(OSi)(OH) 5 environments. The 29 Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From 29 Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures. - Graphical abstract: Transmission electron micrograph of CaAl 2 O 4 -microsilica mixture hydrated at 90 deg. C for 31 days showing a cubic Ca 3 Al 2.0±0.2 (SiO 4 ) 0.9±0.2 (OH) 1.8 crystal surrounded by unreacted amorphous silica spheres

  2. Effect of a bonding agent on in vitro biochemical activities of remineralizing resin-based calcium phosphate cements.

    Science.gov (United States)

    Dickens, Sabine H; Flaim, Glenn M

    2008-09-01

    To test whether fluoride in a resin-based Ca-PO4 ion releasing cement or coating with an acidic bonding agent for improved adhesion compromised the cement remineralization potential. Cements were formulated without fluoride (Cement A) or with fluoride (Cement B). The treatment groups were A=Cement A; A2=Cement A+bonding agent; B=Cement B; B2=Cement B+bonding agent. The calcium, phosphate, and fluoride ion release in saliva-like solution (SLS) was determined from hardened cement disks without or with a coating of bonding agent. For the remineralization, two cavities were prepared in dentin of extracted human molars and demineralized. One cavity received composite resin (control); the other received treatment A, A2, B or B2. After 6 week incubation in SLS, 180 microm cross-sections were cut. The percentage remineralization was determined by transverse microradiography comparing the dentin mineral density under the cement to that under the control. The percentage of remineralization (mean+/-S.D.) was A (39+/-14)=B (37+/-18), A2 (23+/-13), B2 (14+/-7). Two-way analysis of variance (ANOVA) and Holm-Sidak test showed a significant effect from the presence of bonding agent (p0.05). The ion solution concentrations of all groups showed undersaturation with respect to dicalcium phosphate dihydrate and calcium fluoride and supersaturation for fluorapatite and hydroxyapatite suggesting a positive remineralization potential. Compared to the control all treatments resulted in mineral increase. The remineralization was negatively affected by the presence of the bonding agent.

  3. Mechanical properties of calcium phosphate cements obtained by solution combustion synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Volkmer, Tiago M.; Barreiro, Oscar; Souza, Vania Caldas; Santos, Luis Alberto dos, E-mail: tiagovolkmer@gmail.com, E-mail: oscarbafer@hotmail.com, E-mail: vania.souza@ufrgs.br, E-mail: luis.santos@ufrgs.br [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Laboratorio de Biomateriais

    2009-07-01

    Bioceramics based on calcium phosphates, especially hydroxyapatite and tricalcium phosphates (TCP) are the most used biomaterials as bone substitutes. The objective of this work is to evaluate the mechanical properties of α-tricalcium phosphate (α-TCP) synthesized by the solution combustion method. The solution combustion synthesis (SCS) can be considered as faster and simpler as other methods, furthermore it allows the obtainment of high purity α-TCP. In the calcium phosphates (CPC), α-TCP reacts with water forming needle like HA, which restrain the movement of grains, increasing mechanical resistance. In the present paper the influence of particle size on mechanical properties of α-TCP cements were evaluated. The α-TCP powder were characterized by XRD, TEM, BET and laser diffraction to asses particle size while the CPC bodies by SEM, Arquimedes method and compression tests. Increasing the milling time, the particle size decreases, resulting in samples with less porosity and consequently with higher compression resistance. (author)

  4. Incorporation of casein phosphopeptide-amorphous calcium phosphate into a glass-ionomer cement.

    Science.gov (United States)

    Mazzaoui, S A; Burrow, M F; Tyas, M J; Dashper, S G; Eakins, D; Reynolds, E C

    2003-11-01

    Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and compressive strength (23%) and significantly enhanced the release of calcium, phosphate, and fluoride ions at neutral and acidic pH. MALDI mass spectrometry also showed casein phosphopeptides from the CPP-ACP nanocomplexes to be released. The release of CPP-ACP and fluoride from the CPP-ACP-containing GIC was associated with enhanced protection of the adjacent dentin during acid challenge in vitro.

  5. Improved workability of injectable calcium sulfate bone cement by regulation of self-setting properties

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zonggang, E-mail: chenzg@sdu.edu.cn [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, Huanye [Department of Orthodontics, School of Stomatology, China Medical University, Shenyang 110001 (China); Liu, Xi [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Lian, Xiaojie [College of Mechanics, Taiyuan University of Technology, Taiyuan 030024 (China); Guo, Zhongwu [National Glycoengineering Research Center, Shandong University, Jinan 250100 (China); Jiang, Hong-Jiang [Wendeng Hospital of Traditional Chinese Orthopedics and Traumatology, Shandong 264400 (China); Cui, Fu-Zhai, E-mail: cuifz@mail.tsinghua.edu.cn [Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2013-04-01

    Calcium sulfate hemihydrate (CSH) powder as an injectable bone cement was prepared by hydrothermal synthesis of calcium sulfate dihydrate (CSD). The prepared materials showed X-ray diffraction peaks corresponding to the CSH structure without any secondary phases, implying complete conversion from CSD phase to CSH phase. Thermogravimetric (TG) analyses showed the crystal water content of CSH was about 6.0% (wt.), which is near to the theoretic crystal water value of CSH. From scanning electron microscopy (SEM) micrographs, sheet crystal structure of CSD was observed to transform into rod-like crystal structure of CSH. Most interesting and important of all, CSD as setting accelerator was also introduced into CSH powder to regulate self-setting properties of injectable CSH paste, and thus the self-setting time of CSH paste can be regulated from near 30 min to less than 5 min by adding various amounts of setting accelerator. Because CSD is not only the reactant of preparing CSH but also the final solidified product of CSH, the setting accelerator has no significant effect on the other properties of materials, such as mechanical properties. In vitro biocompatibility and in vivo histology studies have demonstrated that the materials have good biocompatibility and good efficacy in bone regeneration. All these will further improve the workability of CSH in clinic applications. Highlights: ► Calcium sulfate hemihydrate (CSH) can be an injectable bone cement. ► CSH was produced by hydrothermal synthesis of calcium sulfate dihydrate (CSD). ► CSD was introduced into CSH powder to regulate self-setting properties of CSH. ► Setting accelerator has no significant effect on the other properties of materials. ► Injectable CSH has good biocompatibility and good efficacy in bone regeneration.

  6. Improved workability of injectable calcium sulfate bone cement by regulation of self-setting properties

    International Nuclear Information System (INIS)

    Chen, Zonggang; Liu, Huanye; Liu, Xi; Lian, Xiaojie; Guo, Zhongwu; Jiang, Hong-Jiang; Cui, Fu-Zhai

    2013-01-01

    Calcium sulfate hemihydrate (CSH) powder as an injectable bone cement was prepared by hydrothermal synthesis of calcium sulfate dihydrate (CSD). The prepared materials showed X-ray diffraction peaks corresponding to the CSH structure without any secondary phases, implying complete conversion from CSD phase to CSH phase. Thermogravimetric (TG) analyses showed the crystal water content of CSH was about 6.0% (wt.), which is near to the theoretic crystal water value of CSH. From scanning electron microscopy (SEM) micrographs, sheet crystal structure of CSD was observed to transform into rod-like crystal structure of CSH. Most interesting and important of all, CSD as setting accelerator was also introduced into CSH powder to regulate self-setting properties of injectable CSH paste, and thus the self-setting time of CSH paste can be regulated from near 30 min to less than 5 min by adding various amounts of setting accelerator. Because CSD is not only the reactant of preparing CSH but also the final solidified product of CSH, the setting accelerator has no significant effect on the other properties of materials, such as mechanical properties. In vitro biocompatibility and in vivo histology studies have demonstrated that the materials have good biocompatibility and good efficacy in bone regeneration. All these will further improve the workability of CSH in clinic applications. Highlights: ► Calcium sulfate hemihydrate (CSH) can be an injectable bone cement. ► CSH was produced by hydrothermal synthesis of calcium sulfate dihydrate (CSD). ► CSD was introduced into CSH powder to regulate self-setting properties of CSH. ► Setting accelerator has no significant effect on the other properties of materials. ► Injectable CSH has good biocompatibility and good efficacy in bone regeneration

  7. Assessment of bone healing ability of calcium phosphate cements loaded with platelet lysate in rat calvarial defects.

    Science.gov (United States)

    Babo, Pedro S; Carvalho, Pedro P; Santo, Vítor E; Faria, Susana; Gomes, Manuela E; Reis, Rui L

    2016-11-01

    Injectable calcium phosphate cements have been used as a valid alternative to autologous bone grafts for bone augmentation with the additional advantage of enabling minimally invasive implantation procedures and for perfectly fitting the tissue defect. Nevertheless, they have low biodegradability and lack adequate biochemical signaling to promote bone healing and remodeling. In previous in vitro studies, we observed that the incorporation of platelet lysate directly into the cement paste or loaded in hyaluronic acid microspheres allowed to modulate the cement degradation and the in vitro expression of osteogenic markers in seeded human adipose derived stem cells. The present study aimed at investigating the possible effect of this system in new bone formation when implanted in calvarial bilateral defects in rats. Different formulations were assessed, namely plain calcium phosphate cements, calcium phosphate cements loaded with human platelet lysate, hybrid injectable formulations composed of the calcium phosphate cement incorporating hyaluronin acid non-loaded microparticles (20% hyaluronin acid) or with particles loaded with platelet lysate. The degradability and new bone regrowth were evaluated in terms of mineral volume in the defect, measured by micro-computed tomography and histomorphometric analysis upon 4, 8 and 12 weeks of implantation. We observed that the incorporation of hyaluronin acid microspheres induced an overly rapid cement degradation, impairing the osteoconductive properties of the cement composites. Moreover, the incorporation of platelet lysate induced higher bone healing than the materials without platelet lysate, up to four weeks after surgery. Nevertheless, this effect was not found to be significant when compared to the one observed in the sham-treated group. © The Author(s) 2016.

  8. The biocompatibility of modified experimental Portland cements with potential for use in dentistry.

    Science.gov (United States)

    Camilleri, J

    2008-12-01

    To evaluate the biocompatibility of a group of new potential dental materials and their eluants by assessing cell viability. Calcium sulpho-aluminate cement (CSA), calcium fluoro-aluminate cement (CFA) and glass-ionomer cement (GIC; Ketac Molar), used as the control, were tested for biocompatibility. Using a direct test method cell viability was measured quantitatively using alamarBluetrade mark dye, and an indirect test method where cells were grown on material elutions and cell viability was assessed using methyltetrazolium (MTT) assay as recommended by ISO 10 993-Part 5 for in vitro testing. Statistical analysis was performed by analysis of variance and Tukey multi-comparison test method. Elution collected from the prototype cements and the GIC cured for 1 and 7 days allowed high cell activity after 24 h cell exposure, which reduced after 48 h when compared to the nontoxic glass-ionomer control, but increased significantly after 72 h cell contact. Elutions collected after 28 days revealed reduced cell activity at all cell exposure times. Cells placed in direct contact with the prototype materials showed reduced cell activity when compared with the control. Cell growth was poor when seeded in direct contact with the prototype cements. GIC encouraged cell growth after 1 day of contact. The eluted species for all the cements tested exhibited adequate cell viability in the early ages with reduced cell activity at 28 days. Changes in the production of calcium hydroxide as a by-product of cement hydration affect the material biocompatibility adversely.

  9. The influence of calcium lignosulphonate - sodium bicarbonate on the status of ettringite crystallization in fly ash cement paste

    Energy Technology Data Exchange (ETDEWEB)

    Yang, K.; Zhang, C.; Liu, Z. [Hebei Institute of Technology, Tang Shan (China)

    2002-01-01

    Calcium lignosulphonate (CL) - sodium bicarbonate (SB) (a total of 0.7% by weight of cement and CL to SB ratio of 1:1.8) will cause the fluidity of fly ash cement paste to decrease rapidly. It is the variation of the status of ettringite crystallization that causes this phenomenon. Experimental results show that CL-SB affects the liquid-phase composition of fly ash cement paste remarkably. As a result, ettringite crystallizes out in the shape of needles from the solution. These needle-like crystal particles are distributed in the solution at a certain distance from the surface of clinker particles. At the initial hydration stage, the crystallization of ettringite is stronger in fly ash cement with calcined gypsum than in fly ash cement with gypsum. 5 refs., 10 figs., 2 tabs.

  10. Effect of the leaching of calcium hydroxide from cement paste on mechanical and physical properties

    International Nuclear Information System (INIS)

    Carde, C.; Francois, R.

    1997-01-01

    This paper deals with the effect of the leaching process of cement based materials on their mechanical and physical properties. In order to characterize this effect, the authors have performed experiments on cement paste samples. The leaching process was achieved by the use of a 50% concentrate solution of ammonium nitrate. Both compression tests and water porosity tests were conducted on micro-cylinder samples (10, 12, 14 and 20 mm of diameter) because of the slow kinetics of degradation due to the leaching. The deterioration of the cement paste and the mortar exposed to the action of the ammonium nitrate was manifested by a peripheral zone of less resistance. This process induces mainly a total leaching of Ca(OH) 2 and a progressive decalcification of C-S-H which leads to a gradient of C/S ratio in the leaching zone. Both mechanical tests and water porosity tests show that there is a linear variation of the loss of strength and the increase in porosity in relation to the ratio of degraded area over total area of the sample A d /A t . It means that both compressive resistance and water porosity of the leaching zone are constant whatever the size of the degraded zone and then whatever the time of exposure to the chemical attack. So the authors could venture the hypothesis that the dissolution of calcium hydroxide is the essential parameter governing both decrease in strength and increase in porosity

  11. A histological evaluation on osteogenesis and resorption of methotrexate-loaded calcium phosphate cement in vivo

    Energy Technology Data Exchange (ETDEWEB)

    Li Dong; Yang Zhiping; Li Xin; Li Zhenfeng; Li Jianmin [Department of Orthopedics, Qilu Hospital of Shandong University, Shandong (China); Yang Jingyan, E-mail: yangzhiping@medmail.com.c [Department of Pathology, 2nd Affiliated Hospital of Shandong University, Shandong (China)

    2010-04-15

    In this study, we investigated the resorption of in vivo methotrexate-loaded calcium phosphate cement (MTX-CPC) implants and their effect on osteogenesis. MTX-CPC implants containing 1% methotrexate (MTX) (weight/weight) were preset and implanted into the femoral condyle of rabbits. Calcium phosphate cement (CPC) without MTX was used as the control. The femurs were harvested at day 1 and at 1, 3 and 6 months after implantation and radiological examination were performed. Decalcified sections were examined by hematoxylin and eosin (HE) staining, alkaline phosphatase (ALPase) immunohistochemistry and tartrate-resistant acid phosphatase (TRAPase) enzyme histochemistry. Then, we performed histomorphometric analysis, including determination of the percentage of newly formed bone and osteoblast and osteoclast counts. The results indicated that MTX-CPC implants were biocompatible, biodegradable and osteoconducive. However, MTX release from the implantation site inhibited osteogenesis in the initial period; this inhibition weakened with time, and no difference was observed between CPC and MTX-CPC at 6 months after implantation. Hence, MTX-CPC is an excellent material for filling defects and can be used for preparing effective drug delivery systems to achieve local control of invasive bone tumors.

  12. Effects of calcium leaching on diffusion properties of hardened and altered cement pastes

    Science.gov (United States)

    Kurumisawa, Kiyofumi; Haga, Kazuko; Hayashi, Daisuke; Owada, Hitoshi

    2017-06-01

    It is very important to predict alterations in the concrete used for fabricating disposal containers for radioactive waste. Therefore, it is necessary to understand the alteration of cementitious materials caused by calcium leaching when they are in contact with ground water in the long term. To evaluate the long-term transport characteristics of cementitious materials, the microstructural behavior of these materials should be considered. However, many predictive models of transport characteristics focus on the pore structure, while only few such models consider both, the spatial distribution of calcium silicate hydrate (C-S-H), portlandite, and the pore spaces. This study focused on the spatial distribution of these cement phases. The auto-correlation function of each phase of cementitious materials was calculated from two-dimensional backscattered electron imaging, and the three-dimensional spatial image of the cementitious material was produced using these auto-correlation functions. An attempt was made to estimate the diffusion coefficient of chloride from the three-dimensional spatial image. The estimated diffusion coefficient of the altered sample from the three-dimensional spatial image was found to be comparable to the measured value. This demonstrated that it is possible to predict the diffusion coefficient of the altered cement paste by using the proposed model.

  13. Mechanistic study and modeling of radionuclides retention by the hydrated calcium silicates (HCS) of cements

    International Nuclear Information System (INIS)

    Pointeau, I.

    2000-09-01

    This work attempts to investigate the modelling of radioisotopes (Cs + , Pb 2+ , Eu 3+ ) immobilization in cement matrix, in the frame of the design of engineered barrier of a deep radwaste repository. The model development concept consists of three major steps: - surface chemistry modelling of the calcium silicate hydrate CSH, used to simulate hydrated cement behaviour; - solid analysis of the batch sorption experiments: identification of the uptake mechanism; - both previous steps are used, with isotherm data, in the modelling of the radioisotopes immobilization in the CSH matrix. Final results: (all modelling are available for all the range of studied Ca/Si ratios and have been validated with predictive calculations). - A thermodynamic modelling of the CSH surface chemistry has been developed. The labile calcium and proton sorption constants on silanol sites (>SiOH) have been extracted. - Cs + is sorbed on two sites. The silanol site (weak site) has a high site density (10 sites.nm -2 ), which accounts for the CSH unsaturation in high [CS + ]. A strong site is also identified. - Pb 2+ immobilization in CSH matrix is modelled with surface equilibria and solubility equilibrium. - Eu 3+ fixation has been investigated with solid analysis: Site-Selective anti Time-Resolved Luminescence Spectroscopy, XPS and SEM-EDS. Eu 3+ thus does not precipitate in CSH water but is sorbed on the CSH surface (high hydroxylated environment). Europium is also (minority site) inserted in the CSH framework. (author)

  14. Impact of Fuel Selection on Techno-environmental Performance of Post-combustion Calcium Looping Process Applied to a Cement Plant

    NARCIS (Netherlands)

    Schakel, Wouter; Orregioni, Gabriel; Strømman, Anders; Ramirez, Andrea

    Calcium looping CO2 capture is a promising technology to reduce CO2 emissions from cement production. Coal is generally considered the fuel used to drive the calcium looping process as coal is already used as feedstock for cement production. This study assesses the impact of different fuels (coal,

  15. Marginal Gaps between 2 Calcium Silicate and Glass Ionomer Cements and Apical Root Dentin.

    Science.gov (United States)

    Biočanin, Vladimir; Antonijević, Đorđe; Poštić, Srđan; Ilić, Dragan; Vuković, Zorica; Milić, Marija; Fan, Yifang; Li, Zhiyu; Brković, Božidar; Đurić, Marija

    2018-01-12

    The outcome of periapical surgery has been directly improved with the introduction of novel material formulations. The aim of the study was to compare the retrograde obturation quality of the following materials: calcium silicate (Biodentine; Septodont, Saint-Maur-des-Fosses, France), mineral trioxide aggregate (MTA+; Cerkamed Company, Stalowa Wola, Poland), and glass ionomer cement (Fuji IX; GC Corporation, Tokyo, Japan). Materials' wettability was calculated concerning the contact angles of the cements measured using a glycerol drop. Cements' porosity was determined using mercury intrusion porosimetry and micro-computed tomographic (μCT) imaging. Extracted upper human incisors were retrofilled, and μCT analysis was applied to calculate the volume of the gap between the retrograde filling material and root canal dentin. Experiments were performed before and after soaking the materials in simulated body fluid (SBF). No statistically significant differences were found among the contact angles of the studied materials after being soaked in SBF. The material with the lowest nanoporosity (Fuji IX: 2.99% and 4.17% before and after SBF, respectively) showed the highest values of microporosity (4.2% and 3.1% before and after SBF, respectively). Biodentine had the lowest value of microporosity (1.2% and 0.8% before and after SBF, respectively) and the lowest value of microgap to the root canal wall ([10 ± 30] × 10 -3  mm 3 ). Biodentine and MTA possess certain advantages over Fuji IX for hermetic obturation of retrograde root canals. Biodentine shows a tendency toward the lowest marginal gap at the cement-to-dentin interface. Copyright © 2018 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  16. Biocompatibility and setting time of CPM-MTA and white Portland cement clinker with or without calcium sulfate.

    Science.gov (United States)

    Bramante, Clovis Monteiro; Kato, Marcia Magro; Assis, Gerson Francisco de; Duarte, Marco Antonio Hungaro; Bernardineli, Norberti; Moraes, Ivaldo Gomes de; Garcia, Roberto Brandão; Ordinola-Zapata, Ronald; Bramante, Alexandre Silva

    2013-01-01

    To evaluate the biocompatibility and the setting time of Portland cement clinker with or without 2% or 5% calcium sulfate and MTA-CPM. Twenty-four mice (Rattus norvegicus) received subcutaneously polyethylene tubes filled with Portland cement clinker with or without 2% or 5% calcium sulfate and MTA. After 15, 30 and 60 days of implantation, the animals were killed and specimens were prepared for microscopic analysis. For evaluation of the setting time, each material was analyzed using Gilmore needles weighing 113.5 g and 456.5 g, according to the ASTM specification Number C266-08 guideline. Data were analyzed by ANOVA and Tukey's test for setting time and Kruskal-Wallis and Dunn test for biocompatibility at 5% significance level. Histologic observation showed no statistically significant difference of biocompatibility (p>0.05) among the materials in the subcutaneous tissues. For the setting time, clinker without calcium sulfate showed the shortest initial and final setting times (6.18 s/21.48 s), followed by clinker with 2% calcium sulfate (9.22 s/25.33 s), clinker with 5% calcium sulfate (10.06 s/42.46 s) and MTA (15.01 s/42.46 s). All the tested materials showed biocompatibility and the calcium sulfate absence shortened the initial and final setting times of the white Portland cement clinker.

  17. A novel and easy-to-prepare strontium(II) modified calcium phosphate bone cement with enhanced mechanical properties.

    Science.gov (United States)

    Schumacher, M; Henß, A; Rohnke, M; Gelinsky, M

    2013-07-01

    The aim of this study was to evaluate two different approaches to obtaining strontium-modified calcium phosphate bone cements (SrCPCs) without elaborate synthesis of Sr-containing calcium phosphate species as cement precursors that could release biologically effective doses of Sr(2+) and thus could improve the healing of osteoporotic bone defects. Using strontium carbonate as a strontium(II) source, it was introduced into a hydroxyapatite-forming cement either by the addition of SrCO3 to an α-tricalcium phosphate-based cement precursor mixture (A-type) or by substitution of CaCO3 by SrCO3 during precursor composition (S-type). The cements, obtained after setting in a water-saturated atmosphere, contained up to 2.2at.% strontium in different distribution patterns as determined by time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy. The setting time of CPC and A-type cements was in the range of 6.5-7.5min and increased for substitution-type cements (12.5-13.0min). Set cements had an open porosity between 26 and 42%. Compressive strength was found to increase from 29MPa up to 90% in substituted S-type cements (58MPa). SrCPC samples released between 0.45 and 1.53mgg(-1) Sr(2+) within 21days and showed increased radiopacity. Based on these findings, the SrCPC developed in this study could be beneficial for the treatment of defects of systemically impaired (e.g. osteoporotic) bone. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  18. Properties of calcium depleted hydrated cement paste: mineralogical characterization and cesium adsorption

    International Nuclear Information System (INIS)

    Babaahmadi, A.; Tang, L.; Zareen, A.

    2015-01-01

    Understanding the changes in adsorption properties of cementitious barriers and the effect on the release of radio-nuclides to the environment during the service life of the repository is of high importance. A major degradation scenario within safety assessment analysis of nuclear waste repositories is decalcification of cementitious materials due to long-term contact with groundwater. In order to decrease the uncertainty in the simulation of this process due to extrapolating short term data sets based on short term experimental analysis, acceleration methods enhancing the decalcification process can be used. However it is not yet completely proved that how different the properties of the aged samples through accelerated leaching is compared to the samples aged in natural ageing process. In this study the changes in cesium adsorption of the hydrated cement paste due to calcium depletion is taken in to consideration. The aged samples are prepared with application of an accelerating electro-chemical migration method. The mineralogical properties of decalcified specimens are characterized to demonstrate their comparability with naturally leached samples. The gradual effect of migration function on cementitious materials indicates a relatively homogenous leaching in cementitious specimens and a considerable increase in specific surface area due to the leaching of calcium. It is concluded that the aged samples having a larger surface area and less calcium and alkalis ions compared to pristine materials, exhibit a higher binding potential for Cs ions

  19. Sulfoaluminate-belite cement from low-calcium fly ash and sulfur-rich and other industrial by-products

    Energy Technology Data Exchange (ETDEWEB)

    Arjunan, P.; Silsbee, M.R.; Roy, D.M.

    1999-08-01

    The study describes the preparation and characterization of an environmentally friendly cement with performance characteristics similar to those of Portland cement, from a lime kiln bag house dust, a low-calcium fly ash, and a scrubber sludge. Promising preliminary results show the formation of relatively low-temperature phases calcium sulfoaluminate (4CaO{center{underscore}dot}3Al{sub 2}O{sub 3}{center{underscore}dot}SO{sub 3}) and dicalcium silicate (2CaO{center{underscore}dot}SiO{sub 2}) at {approximately} 1,250 C if nodulized raw means used for clinker preparation and at 1,175 C if powdered raw meal is used as compared to the {approximately} 1,500 C sintering temperature required for Portland cement. Phases of the developed cements were predicted using modified Bogue calculations. Isothermal calorimetric measurements indicate the hydration properties of the cements are comparable to ordinary Portland cement. Mechanical properties and microstructural evaluations also were carried out.

  20. Bulk physicochemical, interconnectivity, and mechanical properties of calcium phosphate cements-fibrin glue composites for bone substitute applications

    NARCIS (Netherlands)

    Lopez-Heredia, M.A.; Pattipeilohy, J.; Hsu, S.; Grykien, M.; Weijden, B. van der; Leeuwenburgh, S.C.G.; Salmon, P.; Wolke, J.G.C.; Jansen, J.A.

    2013-01-01

    Calcium phosphate cements (CPCs) and fibrin glue (FG) are used for surgical applications. Their combination is promising to create bone substitutes able to promote cell attachment and bone remodeling. This study proposes a novel approach to create CPC-FG composites by simultaneous CPC setting and FG

  1. A new acoustic method to determine the setting time of calcium sulfate bone cement mixed with antibiotics.

    Science.gov (United States)

    Cooper, J J; Brayford, M J; Laycock, P A

    2014-08-01

    A new method is described which can be used to determine the setting times of small amounts of high value bone cements. The test was developed to measure how the setting times of a commercially available synthetic calcium sulfate cement (Stimulan, Biocomposites, UK) in two forms (standard and Rapid Cure) varies with the addition of clinically relevant antibiotics. The importance of being able to accurately quantify these setting times is discussed. The results demonstrate that this new method, which is shown to correlate to the Vicat needle, gives reliable and repeatable data with additional benefits expressed in the article. The majority of antibiotics mixed were found to retard the setting reaction of the calcium sulfate cement.

  2. A new acoustic method to determine the setting time of calcium sulfate bone cement mixed with antibiotics

    International Nuclear Information System (INIS)

    Cooper, J J; Brayford, M J; Laycock, P A

    2014-01-01

    A new method is described which can be used to determine the setting times of small amounts of high value bone cements. The test was developed to measure how the setting times of a commercially available synthetic calcium sulfate cement (Stimulan, Biocomposites, UK) in two forms (standard and Rapid Cure) varies with the addition of clinically relevant antibiotics. The importance of being able to accurately quantify these setting times is discussed. The results demonstrate that this new method, which is shown to correlate to the Vicat needle, gives reliable and repeatable data with additional benefits expressed in the article. The majority of antibiotics mixed were found to retard the setting reaction of the calcium sulfate cement. (paper)

  3. Calcium phosphate cements properties with polymers addition; Propriedades do cimento de fosfato de calcio com adicao de polimeros

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.M.; Trajano, W.T.; Escobar, C.F.; Santos, L.A., E-mail: julianafernandes2@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRGS), RS (Brazil)

    2012-07-01

    Calcium phosphate cements (CPC) have attracted great interest to use in orthopedics and dentistry as replacements for damaged parts of the skeletal system, showing good biocompatibility and osseointegration, allowing its use as bone graft. Several studies have shown that the addition of polymer additives have a strong influence on the cement properties. The low mechanical strength is the main obstacle to greater use of CPC as an implant material. The objective of this study was to evaluate properties of a cement based on α-tricalcium phosphate (α-TCP), added polymers. PVA (10%, 8%, 6%), sodium alginate (2%) and polyacrylate ammonia (3%), all in weight, were added to the synthesized α-TCP powder. The samples were molded and evaluated for density, porosity in vitro test (Simulated Body Fluid), crystalline phases and mechanical strength. The results show increased the mechanical properties of the cement when added these polymers.

  4. Wollastonite nanofiber–doped self-setting calcium phosphate bioactive cement for bone tissue regeneration

    Directory of Open Access Journals (Sweden)

    Guo H

    2012-07-01

    Full Text Available Han Guo,1,2 Jie Wei,2 Wenhua Song,2 Shan Zhang,2 Yonggang Yan,3 Changsheng Liu,2 Tiqiao Xiao11Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, People's Republic of China; 2Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai, People's Republic of China; 3School of Physical Science and Technology, Sichuan University, Chengdu, People's Republic of ChinaAbstract: The purpose of this study was to synthesize a self-setting bioactive cement by incorporation of wollastonite nanofibers (WNFs into calcium phosphate cement (CPC. The composition, morphology, setting time, compressive strength, hydrophilicity, and degradation of WNF-doped CPC (wnf-CPC were investigated. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy were utilized. Additionally, methyl-thiazolyl-tetrazolium bromide assay, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, and histological evaluation were used to study the cell and tissue responses to wnf-CPC, both in vitro and in vivo. The results confirmed that the addition of WNFs into CPC had no obvious effect on the setting time or the compressive strength of wnf-CPC, provided the WNF amount was not more than 10 wt%. However, the hydrophilicity and degradability of wnf-CPC were significantly improved by the addition of WNFs – this was because of the change of microstructure caused by the WNFs. The preferred dissolution of WNFs caused the formation of microporosity in wnf-CPC when soaked in tris hydrochloride solution. The microporosity enlarged the surface area of the wnf-CPC and so promoted degradation of the wnf-CPC when in contact with liquid. In addition, MG-63 cell attachment and proliferation on the wnf-CPC were superior to that on the CPC, indicating that

  5. Synthesis and mechanical properties of a calcium sulphoaluminate cement made of industrial wastes

    Directory of Open Access Journals (Sweden)

    Gallardo, M.

    2014-09-01

    Full Text Available Environmentally-friendly calcium sulphoaluminate clinkers were obtained from a mixture of aluminium dross, fluorgypsum, fly ash and CaCO₃ at temperatures within the range of 1100 to 1400 °C. After the heat treatments Ca₄Al₆O₁₂SO₄ was the main phase. Three different cements were prepared using the clinkers synthesized at 1250, 1350 and 1400 °C; the clinker powders were mixed with 20 wt% of hemihydrate. Cement pastes were prepared using a water/cement ratio (w/c, 0.4 followed by curing at 20 or 40 °C for periods of time ranging from 1 to 28 days. Most of the samples showed high compression strengths 40–47 MPa after 28 days, which were comparable to the strength of Portland cement. Ettringite was the main hydration product and its morphology consisted of acicular and hexagonal plates, which is typical of this phase.Se fabricaron clinkers de bajo impacto ambiental a base de sulfoaluminato de calcio calcinando mezclas de escoria de aluminio, fluoryeso, ceniza volante y CaCO₃ a diferentes temperaturas dentro de un rango de 1100 a 1400 °C. Se observó la formación de Ca₄Al₆O₁₂SO₄ como fase principal. Para obtener los cementos, los clinkers obtenidos a 1250, 1350 y 1400 °C se mezclaron con 20% en peso de hemihidrato. Se prepararon pastas usando una relación agua/cemento, de 0.4 y se curaron a 20 y 40 °C por diferentes periodos de tiempo desde 1 hasta 28 días. Los valores de resistencia a la compresión a los 28 días de curado de la mayoría de las muestras estuvieron entre 40–47 MPa, equiparables a los de referencia de pastas de cemento Portland. La etringita fue el principal producto de hidratación y su morfología consistió de placas hexagonales y aciculares, típicas de esta fase.

  6. Nanostructural Deformation Analysis of Calcium Silicate Hydrate in Portland Cement Paste by Atomic Pair Distribution Function

    Directory of Open Access Journals (Sweden)

    Hiroshi Suzuki

    2016-01-01

    Full Text Available The deformation of nanostructure of calcium silicate hydrate (C-S-H in Portland cement (PC paste under compression was characterized by the atomic pair distribution function (PDF, measured using synchrotron X-ray diffraction. The PDF of the PC paste exhibited a unique deformation behavior for a short-range order below 2.0 nm, close to the size of the C-S-H globule, while the deformation for a long-range order was similar to that of a calcium hydroxide phase measured by Bragg peak shift. The compressive deformation of the C-S-H nanostructure was comprised of three stages with different interactions between globules. This behavior would originate from the granular nature of C-S-H, which deforms with increasing packing density by slipping the interfaces between globules, rearranging the overall C-S-H nanostructure. This new approach will lead to increasing applications of the PDF technique to understand the deformation mechanism of C-S-H in PC-based materials.

  7. Orthodontic cement with protein-repellent and antibacterial properties and the release of calcium and phosphate ions.

    Science.gov (United States)

    Zhang, Ning; Weir, Michael D; Chen, Chen; Melo, Mary A S; Bai, Yuxing; Xu, Hockin H K

    2016-07-01

    White spot lesions often occur in orthodontic treatments. The objective of this study was to develop a novel resin-modified glass ionomer cement (RMGI) as an orthodontic cement with protein-repellent, antibacterial and remineralization capabilities. Protein-repellent 2-methacryloyloxyethyl phosphorylcholine (MPC), antibacterial dimethylaminohexadecyl methacrylate (DMAHDM), nanoparticles of silver (NAg), and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into a RMGI. Enamel shear bond strength (SBS) was determined. Calcium (Ca) and phosphate (P) ion releases were measured. Protein adsorption onto specimens was determined by a micro bicinchoninic acid method. A dental plaque microcosm biofilm model was tested. Increasing the NACP filler level increased the Ca and P ion release. Decreasing the solution pH increased the ion release. Incorporating MPC into RMGI reduced protein adsorption, which was an order of magnitude less than that of commercial controls. Adding DMAHDM and NAg into RMGI yielded a strong antibacterial function, greatly reducing biofilm viability and acid production. Biofilm CFU counts on the multifunctional orthodontic cement were 3 orders of magnitude less than that of commercial control (p0.1). A novel multifunctional orthodontic cement was developed with strong antibacterial and protein-repellent capabilities for preventing enamel demineralization. The new cement is promising to prevent white spot lesions in orthodontic treatments. The method of incorporating four bioactive agents may have wide applicability to the development of other bioactive dental materials to inhibit caries. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Cementing Material From Rice Husk-Broken Bricks-Spent Bleaching Earth-Dried Calcium Carbide Residue

    Directory of Open Access Journals (Sweden)

    Muthengia Jackson Washira

    2012-10-01

    Full Text Available A cementious material, coded CSBR (Carbide residue Spent bleaching earth Broken bricks and Rice husks, was made from dried calcium carbide residue (DCCR and an incinerated mix of rice husks (RH, broken bricks (BB and spent bleaching earth (SBE. Another material, coded SBR (Spent bleaching earth Broken bricks and Rice husk ash, was made from mixing separately incinerated RH, SBE and ground BB in the same ash ratio as in CSBR. When CSBR was inter-ground with Ordinary Portland Cement (OPC, it showed a continued decrease in Ca(OH2 in the hydrating cement as a function of curing time and replacement levels of the cement. Up to 45 % replacement of the OPC by CSBR produced a Portland pozzolana cement (PPC material that passed the relevant Kenyan Standard. Incorporation of the CSBR in OPC reduces the resultant calcium hydroxide from hydrating Portland cement. The use of the waste materials in production of cementitious material would rid the environment of wastes and lead to production of low cost cementitious material.

  9. [Experiment of porous calcium phosphate/bone matrix gelatin composite cement for repairing lumbar vertebral bone defect in rabbit].

    Science.gov (United States)

    Wang, Song; Yang, Han; Yang, Jian; Kang, Jianping; Wang, Qing; Song, Yueming

    2017-12-01

    To investigate the effect of a porous calcium phosphate/bone matrix gelatin (BMG) composite cement (hereinafter referred to as the "porous composite cement") for repairing lumbar vertebral bone defect in a rabbit model. BMG was extracted from adult New Zealand rabbits according to the Urist's method. Poly (lactic-co-glycolic) acid (PLGA) microsphere was prepared by W/O/W double emulsion method. The porous composite cement was developed by using calcium phosphate cement (CPC) composited with BMG and PLGA microsphere. The physicochemical characterizations of the porous composite cement were assessed by anti-washout property, porosity, and biomechanical experiment, also compared with the CPC. Thirty 2-month-old New Zealand rabbits were used to construct vertebral bone defect at L 3 in size of 4 mm×3 mm×3 mm. Then, the bone defect was repaired with porous composite cement (experimental group, n =15) or CPC (control group, n =15). At 4, 8, and 12 weeks after implantation, each bone specimen was assessed by X-ray films for bone fusion, micro-CT for bone mineral density (BMD), bone volume fraction (BVF), trabecular thickness (Tb. Th.), trabecular number (Tb.N.), and trabecular spacing (Tb. Sp.), and histological section with toluidine blue staining for new-born bone formation. The study demonstrated well anti-washout property in 2 groups. The porous composite cement has 55.06%±1.18% of porosity and (51.63±6.73) MPa of compressive strength. The CPC has 49.38%±1.75% of porosity and (63.34±3.27) MPa of compressive strength. There were significant differences in porosity and compressive strength between different cements ( t =4.254, P =0.006; t =2.476, P =0.034). X-ray films revealed that the zone between the cement and host bone gradually blurred with the time extending. At 12 weeks after implantation, the zone was disappeared in the experimental group, but clear in the control group. There were significant differences in BMD, BVF, Tb. Th., Tb. N., and Tb. Sp. between

  10. The influence of calcium nitrate on setting and hardening rate of Portland cement concrete at different temperatures

    Science.gov (United States)

    Kičaitė, A.; Pundienė, I.; Skripkiūnas, G.

    2017-10-01

    Calcium nitrate in mortars and concrete is used as a multifunctional additive: as set accelerator, plasticizer, long term strength enhancer and as antifreeze admixture. Used binding material and the amount of calcium nitrate, affect the characteristics of the concrete mixture and strength of hardened concrete. The setting time of the initial and the final binding at different temperatures of hardening (+ 20 °C and + 5 °C) of the pastes made of different cements (Portland cement CEM I 42.5 R and Portland limestone cement CEM II/A-LL 42.5 R) and various amounts of calcium nitrate from 1 % until 3 % were investigated. The effect of calcium nitrate on technological characteristics of concrete mixture (the consistency of the mixture, the density, and the amount of air in the mixture), on early concrete strength after 2 and 7 days, as well as on standard concrete strength after 28 days at different temperatures (at + 20 °C and + 5 °C) were analysed.

  11. Synthesis of modified calcium aluminate with lanthanum manganite (LSM) for possible use in solid oxide fuel cell (SOFC); Sintese de aluminato de calcio modificado com manganita de lantanio (LSM) para possivel utilizacao em celula combustivel de oxido solido (SOFC)

    Energy Technology Data Exchange (ETDEWEB)

    Veiga, F.C.T.; Jurado, J.; Sousa, V.C. de, E-mail: faili.cintia@gmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Escola de Engenharia. Departamento de Materiais; Cava, S.S. [Universidade Federal de Pelotas, RS (Brazil)

    2016-07-01

    The fuel cells solid oxide (SOFC) is made up of three basic elements: two electrodes, the anode and cathode and a conductive electrolyte ions. The objective of this work consists of calcium aluminate synthesis modified LSM in a 1: 1 by combustion synthesis method with a view to its use as a cathode in SOFC. The characterization of the post was carried out by the methods of XRD, TEM and EIS. After heat treatment at 1200°C/4 hours it was possible to obtain Ca0.5Sr1.5MnO4 and CaMnO2.56 phases. The material showed a semiconductor characteristics because with increasing temperature the electrical resistance value tends to decrease obtaining electrical conductivity greater than 10-6S / cm featuring an extrinsic semiconductor with an activation energy of 0.12. Therefore, with an activation energy value within the range of materials used for a SOFC cathodes. (author)

  12. Biphasic calcium sulfate dihydrate/iron-modified alpha-tricalcium phosphate bone cement for spinal applications: in vitro study

    International Nuclear Information System (INIS)

    Vlad, M D; Lopez, J; Torres, R; Barraco, M; Fernandez, E; Valle, L J; Poeata, I

    2010-01-01

    In this study, the cytocompatibility of new 'iron-modified/alpha-tricalcium phosphate (IM/α-TCP) and calcium sulfate dihydrate (CSD)' bone cement (IM/α-TCP/CSD-BC) intended for spinal applications has been approached. The objective was to investigate by direct-contact osteoblast-like cell cultures (from 1 to 14 days) the in vitro cell adhesion, proliferation, morphology and cytoskeleton organization of MG-63 cells seeded onto the new cements. The results were as follows: (a) quantitative MTT-assay and scanning electron microscopy (SEM) showed that cell adhesion, proliferation and viability were not affected with time by the presence of iron in the cements; (b) double immunofluorescent labeling of F-actin and α-tubulin showed a dynamic interaction between the cell and its porous substrates sustaining the locomotion phenomenon on the cements' surface, which favored the colonization, and confirming the biocompatibility of the experimental cements; (c) SEM-cell morphology and cytoskeleton observations also evidenced that MG-63 cells were able to adhere, to spread and to attain normal morphology on the new IM/α-TCP/CSD-BC which offered favorable substratum properties for osteoblast-like cells proliferation and differentiation in vitro. The results showed that these new iron-modified cement-like biomaterials have cytocompatible features of interest not only as possible spinal cancellous bone replacement biomaterial but also as bone tissue engineering scaffolds.

  13. Investigation of barium-calcium aluminate process to manufacture and characterize impregnated thermionic cathode for power microwave devices; Investigacao do processo de obtencao de aluminatos de bario e calcio para construcao e caracterizacao de catodos termionicos impregnados para aplicacao em dispositivos de microondas de potencia

    Energy Technology Data Exchange (ETDEWEB)

    Higashi, Cristiane

    2006-07-01

    In the present work it is described the barium calcium aluminate manufacture processes employed to produce impregnated cathodes to be used in a traveling-wave tube (TWT). The cathodes were developed using a tungsten body impregnated with barium and calcium aluminate with a 5:3:2 proportion (molar). Three different processes were investigated to obtain this material: solid-state reaction, precipitation and crystallization. Thermal analysis, thermogravimetry specifically, supported to determine an adequate preparation procedure (taking into account temperature, time and pyrolysis atmosphere). It was verified that the crystallization showed a better result when compared to those investigated (solid-state reaction and precipitation techniques - formation temperature is about 1000 deg C in hydrogen atmosphere), whereas it presented the lower formation temperature (800 deg C) in oxidizing atmosphere (O{sub 2}). It was used the practical work function distribution theory (PWFD) of Miram to characterize thermionic impregnated cathode. The PWFD curves were used to characterize the barium-calcium aluminate cathode. PWFD curves shown that the aluminate cathode work function is about 2,00 eV. (author)

  14. Development of an Improved Cement for Geothermal Wells

    Energy Technology Data Exchange (ETDEWEB)

    Trabits, George [Trabits Group, LLC, Wasilla, AK (United States)

    2015-04-20

    After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s and early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.

  15. Calcium phosphate cement as a "barrier-graft" for the treatment of human periodontal intraosseous defects

    Directory of Open Access Journals (Sweden)

    Rajesh J

    2009-01-01

    Full Text Available Background : Calcium phosphate cements (CPC are apparently good candidates for periodontal treatment by virtue of their biocompatibility, mouldability and osteoconductivity. However, the clinical efficacy in this regard has not been established. This study is aimed at the evaluation of the efficacy of a formulation of CPC in healing human periodontal intraosseous defects in comparison with hydroxyapatite ceramic granules. Materials and Methods : In this clinical study, 60 patients with periodontal defects were divided into 2 test groups and 1 control group. The defect sites in the test groups were repaired with CPC and hydroxyapatite ceramic granules (HAG. Debridement alone was given in the control group. The progress was assessed at 3, 6, 9 and 12 months observation intervals through soft tissue parameters (probing depth, attachment level and gingival recession. Results: CPC showed significantly better outcome. Probing depth reduction values of CPC, HAG and Control at 6 months were 5.40 ± 1.43, 3.75 ± 1.71 and 2.90 ± 1.48, and those at 12 months were 6.20 ± 1.80, 4.5 ± 1.91 and 2.95 ± 1.73. Clinical attachment gain values of CPC, HAG and Control at 6 months were 5.15 ± 1.50, 3.45 ± 1.96 and 2.25 ± 1.52, and those at 12 months were 5.80 ± 2.02, 3.55 ± 2.06 and 2.30 ± 1.78, In both cases the P value was < 0.001 showing high significance. The gingival recession over 12 months, for the CPC group is lesser than that in the HAG group and the value for the control group is marginally higher than both. Soft-tissue measurements were appended by postoperative radiographs and surgical re-entry in selected cases. Conclusions: Calcium phosphate cement is found to be significantly better than hydroxyapatite ceramic granules. The material could be considered as a "barrier-graft".

  16. Effect of Poly(Vinyl Alcohol) Addition on the Properties of Hydrothermal Derived Calcium Phosphate Cement for Bone Filling Materials

    Science.gov (United States)

    Razali, N. N.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.; Singh, R.

    2017-06-01

    The effect of addition of poly(vinyl alcohol) on hydrothermal derived calcium phosphate cement has been studied. The precursors used to prepare the cement were calcium oxide (CaO) and ammonium dihydrogen phosphate (NH4H2PO4); the reaction was conducted in water at 80-100°C. To improve properties of CPC, poly(vinyl alcohol) (PVA) of 1wt% and 2wt% was added to the liquid phase of CPC and the results were compared to CPC without PVA addition. The addition of PVA was proved to bring remarkable effects on cohesion, setting time and mechanical strength of CPC which make it suitable physically for injectable bone filler applications.

  17. Leaching of both calcium hydroxide and C-S-H from cement paste: Modeling the mechanical behavior

    International Nuclear Information System (INIS)

    Carde, C.; Torrenti, J.M.; Francois, R.

    1996-01-01

    This paper deals with the effect of the leaching process of cement based materials on their mechanical properties. This process induces mainly a total leaching of Ca(OH) 2 and a progressive decalcification of C-S-H which leads to a gradient of C/S ratio in the leaching zone. In a previous work, the authors venture the hypothesis that the dissolution of calcium hydroxide was the essential parameter governing both decrease in strength and increase in porosity in the case of a paste sample made with an OPC cement which leads to a 20% content of calcium. In order to quantify the effect of the decrease of C/S ratio in C-S-H, the authors have performed experiments on paste samples with the admixture of silica fume to reduce the content of calcium hydroxide and thus emphasize the effect of C/S ratio decrease of the C-S-H. The leaching process was achieved by the use of a 50% concentrate solution of ammonium nitrate. Compression tests were conducted on micro-cylinder samples (10, 12, 14, 20 and 30 mm of diameter) because of the slow kinetics of degradation due to the leaching. The deterioration of the cement paste and the mortar exposed to the action of the ammonium nitrate was indicated by a peripheral zone of less resistance. The experimental results allow the modeling of the mechanical behavior of cement pastes in relation to the ratio of degraded area over total area of the sample A d /A t . The model thus defined allows separation of the effect of calcium hydroxide leaching and C-S-H leaching, and shows the importance of the first one. The current research program tries to characterize the deterioration of the mechanical properties of the concrete surrounding radioactive wastes, due to the water flow during storage

  18. Effect of polydopamine on the biomimetic mineralization of mussel-inspired calcium phosphate cement in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zongguang [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Qu, Shuxin, E-mail: qushuxin@swjtu.edu.cn [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Zheng, Xiaotong; Xiong, Xiong [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Fu, Rong; Tang, Kuangyun; Zhong, Zhendong [Department of Plastic Surgery, Academy of Medical Sciences and Sichuan Provincial People' s Hospital, Chengdu 610041 (China); Weng, Jie [Key Lab of Advanced Technologies of Materials, Ministry of Education, School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2014-11-01

    Inspired by the excellent adhesive property of mussel adhesive protein, we added polydopamine (PDA) to calcium phosphate cement (PDA–CPC) to enhance its compressive strength previously. The mineralization and mechanism on PDA–CPC were investigated by soaking it in simulated body fluid in this study. The results indicated that PDA promoted the conversion of dicalcium phosphate dihydrate and α-tricalcium phosphate to hydroxyapatite (HA) in the early stage but inhibited this conversion subsequently. PDA promoted the rapid mineralization on PDA–CPC to form a layer of nanoscale calcium phosphate (CaP) whereas there was no CaP formation on the control-CPC after 1 d of soaking. This layer of nanoscale CaP was similar to that of natural bone, which was always observed during soaking. X-ray photoelectron spectroscopy showed that the peak of C=O of PDA existed in the newly formed CaP on PDA–CPC, indicating the co-precipitation of CaP with PDA. Furthermore, the newly formed CaP on PDA–CPC was HA confirmed by transmission electron microscopy, which the newly formed HA was in association with PDA. Therefore, PDA increased the capacity of mineralization of CPC and induced the formation of nanoscale bone-like apatite on PDA–CPC. Thus, this provides the feasible route for surface modification on CPC. - Highlights: • Effect of polydopamine (PDA) on the in vitro mineralization of PDA-CPC was studied. • PDA promoted the rapid mineralization on PDA-CPC to form a nanoscale HA layer. • The precipitation of the nanoscale HA layer on PDA-CPC accompanied with PDA. • Polydopamine induced mineralization is feasible for surface modification of CaP.

  19. Observation on the role of osteoporotic vertebra augmented with calcium sulfate cement in vivo

    International Nuclear Information System (INIS)

    Zhu Xuesong; Shi Qin; Zhang Zhiming; Geng Dechun; Mao Haiqing; Chen Chunmao; Wang Genlin; Yang Huilin

    2010-01-01

    Objective: To observe the biomechanical and histological performance of calcium sulfate cement (CSC) in osteoporotic vertebral bodies. Methods: Bone voids were created in L 2 ∼ L 5 vertebras of twelve female osteoporotic mature sheep. CSC and polymethylmethacrylate (PMMA) were injected into one bone voids randomly, L 1 and L 6 vertebrae served as the normal control. Six sheep were sacrificed at the 2nd week and the 24th week after operation respectively. Overall observation,biomechanical test and undecalcified bone histology analyses were performed. Results: Biomechanical analysis showed that the vertebrae could be augmented by CSC and PMMA. The biomechanical properties of the vertebrae augmented with CSC were weakened more than that in the PMMA and normal group at the 2nd week, increased significantly at the 24th week. Histological observation showed that CSC was mostly absorbed at the 24th week, mature bone trabecula was seen in the defect area. Conclusion: The osteoporotic vertebrae can be augmented instantly by CSC. As time goes on, CSC can promote bone remodeling, and enhance the vertebrae. It is an alternation for vertebroplasty and kyphoplasty. (authors)

  20. Lithium doped calcium phosphate cement maintains physical mechanical properties and promotes osteoblast proliferation and differentiation.

    Science.gov (United States)

    Li, Li; Wang, Renchong; Li, Baichuan; Liang, Wei; Pan, Haobo; Cui, Xu; Tang, Jingli; Li, Bing

    2017-07-01

    Calcium phosphate cement (CPC) has been widely used in bone tissue repairing due to its physical mechanical properties and biocompatibility. Addition of trace element to CPC has shown promising evidence to improve the physical properties and biological activities of CPC. Lithium (Li) has effect on osteoblast proliferation and differentiation. In this study, we incorporated Li to CPC and examined the physical properties of Li/CPC and its effect on osteoblast proliferation and differentiation. We found that Li doped CPC maintained similar setting time, pore size distribution, compressive strength, composition, and morphology as CPC without Li. Additionally, Li doped CPC improved osteoblast proliferation and differentiation significantly compared to CPC without Li. To our knowledge, our results, for the first time, show that Li doped CPC has beneficial effect on osteoblast in cell culture while keeps the excellent physical-mechanical properties of CPC. This study will lead to potential application of Li doped CPC in bone tissue engineering. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 944-952, 2017. © 2016 Wiley Periodicals, Inc.

  1. Gold nanoparticles in injectable calcium phosphate cement enhance osteogenic differentiation of human dental pulp stem cells.

    Science.gov (United States)

    Xia, Yang; Chen, Huimin; Zhang, Feimin; Bao, Chongyun; Weir, Michael D; Reynolds, Mark A; Ma, Junqing; Gu, Ning; Xu, Hockin H K

    2018-01-01

    In this study, a novel calcium phosphate cement containing gold nanoparticles (GNP-CPC) was developed. Its osteogenic induction ability on human dental pulp stem cells (hDPSCs) was investigated for the first time. The incorporation of GNPs improved hDPSCs behavior on CPC, including better cell adhesion (about 2-fold increase in cell spreading) and proliferation, and enhanced osteogenic differentiation (about 2-3-fold increase at 14 days). GNPs endow CPC with micro-nano-structure, thus improving surface properties for cell adhesion and subsequent behaviors. In addition, GNPs released from GNP-CPC were internalized by hDPSCs, as verified by transmission electron microscopy (TEM), thus enhancing cell functions. The culture media containing GNPs enhanced the cellular activities of hDPSCs. This result was consistent with and supported the osteogenic induction results of GNP-CPC. In conclusion, GNP-CPC significantly enhanced the osteogenic functions of hDPSCs. GNPs are promising to modify CPC with nanotopography and work as bioactive additives thus enhance bone regeneration. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. Microstructure and oxidation behaviour of aluminized coating of inconel 625

    International Nuclear Information System (INIS)

    Khalid, F.A.; Hussain, N.; Shahid, K.A.; Rehman, S.; Qureshi, A.H.; Khan, I.H.

    1999-01-01

    Microstructural and oxidation characteristics of aluminized coated Inconel 625 have been examined using scanning electron microscopy (SEM) and fine-probe spot and linescan EDS microanalysis techniques. The formation of slowly growing adherent metallic coatings is essential for protection against the severe environments. Aluminising of the superalloy samples was carried out by pack cementation process at 900 deg. C. in an argon atmosphere. The samples were subsequently oxidized in air at various temperatures to examine performance of the pack aluminized coated alloy. The microstructural changes that occurred in the aluminized layer at various exposure temperature and time were examined to study the oxidation behavior and formation of different phases in the aluminized coating deposited on Inconel 625. (author)

  3. CT volumetry of intravertebral cement after kyphoplasty. Comparison of polymethylmethacrylate and calcium phosphate in a 12-month follow-up

    International Nuclear Information System (INIS)

    Libicher, M.; Noeldge, G.; Kauffmann, G.W.; Vetter, M.; Wolf, I.; Meinzer, H.P.; Kasperk, C.; Grafe, I.; Fonseca, K.D.; Meeder, P.J.; Hillmeier, J.

    2005-01-01

    This study was intended to measure the volume of intravertebral cement after balloon kyphoplasty with high resolution computed tomography (CT) and dedicated software. Volume changes of biocompatible calcium phosphate cement (CPC) were detected during a follow-up of 12 months. Measurements were compared with a control group of patients treated with polymethylmethacrylate (PMMA). Twenty-three vertebrae (14 CPC, 9 PMMA) of 12 patients were examined with CT using an identical imaging protocol. Dedicated software was used to quantify intravertebral cement volume in subvoxel resolution by analyzing each cement implant with a density-weighted algorithm. The mean volume reduction of CPC was 0.08 ml after 12 months, which corresponds to an absorption rate of 2 vol%. However, the difference did not reach significance level (P>0.05). The mean error estimate was 0.005 ml, indicating excellent precision of the method. CT volumetry appears a precise tool for measurement of intravertebral cement volume. CT volumetry offers the possibility of in vivo measurement of CPC resorption. (orig.)

  4. Tooth Discoloration Induced by Different Calcium Silicate-based Cements: A Systematic Review of In Vitro Studies.

    Science.gov (United States)

    Możyńska, Joanna; Metlerski, Marcin; Lipski, Mariusz; Nowicka, Alicja

    2017-10-01

    On the basis of many clinical observations, some calcium silicate-based cements have a high potential for staining tooth tissue. This feature greatly limits the use of those cements, particularly for anterior teeth. This review aimed to provide a systematic evaluation of published in vitro studies to determine the effect of different calcium silicate-based cements on dental tissue discoloration. This literature review was developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The literature search was based on all publications without a year limit. The last search was performed on October 22, 2016. An electronic search was performed on MEDLINE (PubMed), Cochrane, and Scopus. The articles were selected to address the following research question: Which materials based on calcium silicate-based cements have hard tissue staining potential? The necessary information was extracted by 2 authors independently using a standardized form. The search resulted in 390 titles from all databases. Twenty-three studies met the inclusion criteria. Most of the studies exhibited a moderate risk of bias. The results indicated that some materials showed a strong potential for staining, including gray and white MTA Angelus (Londrina, PR, Brazil), gray and white ProRoot MTA (Dentsply, Tulsa, OK), and Ortho MTA (BioMTA, Seoul, Korea). Individual study results showed that Biodentine (Septodont, Saint Maur des Fosses, France), Retro MTA (BioMTA), Portland cement, EndoSequence Root Repair Material (Brasseler USA, Savannah, GA), Odontocem (Australian Dental Manufacturing, Brisbane, Australia), MM-MTA (Micro Mega, Besancon Cedex, France), and MTA Ledermix (Riemser Pharma GmbH, Greiswald-Insel Riems, Germany) were materials with the smallest staining potential. This review clearly showed that some calcium silicate-based cements have a high potential for staining hard tissue. On the other hand, some showed only a small change in color, which was

  5. SYNTHESIS OF EXPANDER TO PREVENT CONTRACTION OF CEMENT STONE

    Directory of Open Access Journals (Sweden)

    Elenova Aurika Almazovna

    2017-03-01

    Full Text Available This article contains the results of studies of the use of additives containing crystallization components significantly affecting the curing of cement, improving the structure of cement stone and concrete. The crystalline component is obtained using the rotary-pulse unit, which provides not only the grinding of agents, but their interaction with each other as well in order to accelerate the hydration and structure formation in cement stone. The degree, and kinetics of hydration, the composition of hydrated phases, the structure of the additives and cement stone was studied using the following methods: x-ray diffraction (XRD, differential thermal analysis (DTA, scanning electron microscope (SEM. Mechanical properties of cement were determined by standard methods and techniques. The expander produced by means of hydrodynamic activation of the sulfoaluminate clinker (SAC consists of ettringite and hydrated calcium silicates, which are characterized by high dispersion rate (less than 10 µm and reactivity as the seed for the crystallization of hydrated compounds. The introduction of the ultrafine additives of the crystalline SAC (within 1-5% was discovered to cause expansion of the cement stone. Implementation of the additives increases cement hydration and contributes to the formation of active centers of crystallization that lead to the fast formation of ettringite, hydrated calcium aluminates and calcium silicates. The activated crystalline additive provides for significant reduction of porosity, initial curing, and high strength of cement stone. In addition, the additive is an expansive component, forming needle-like crystals of ettringite during hydration. These microcrystals grow in the capillaries of cement stone, filling them, and create conditions for improving the crack resistance of cement concrete.

  6. THERMOCHEMISTRY OF INTERACTION REACTIONS FOR SODIUM AND ALUMINUM SULPHATES WITH COMPONENTS OF HYDRATING PORTLAND CEMENT

    Directory of Open Access Journals (Sweden)

    P. I. Yukhnevskiy

    2018-01-01

    Full Text Available Chemical additives are widely used in the technology of concrete with the purpose to solve various problems and sulphate-containing additives-electrolytes are also used as accelerators for setting and hardening of cement. Action mechanism of additive accelerators for setting and hardening of cement is rather complicated and can not be considered as well-established. An influence of sulfate-containing additives such as sodium sulfate is reduced to acceleration of cement silicate phase hydration by increasing ionic strength of the solution. In addition to it, exchange reactions of anion additive with portlandite phase (Ca(OH2 and aluminate phases of hardening cement have a significant effect on hardening process that lead to formation of readily soluble hydroxides and hardly soluble calcium salts. The influence of sulfate-containing additives on properties of water cement paste and cement stone is quite diverse and depends on salt concentration and cation type. For example, the action of the aluminum sulphate additive becomes more complicated if the additive is subjected to hydrolysis in water, which is aggravated in an alkaline medium of the water cement paste. Formation of hydrolysis products and their reaction with aluminate phases and cement portlandite lead to a significant acceleration of setting. Thus, despite the similarity of additives ensuring participation of anions in the exchange reactions, the mechanism of their influence on cement setting and hardening varies rather significantly. The present paper considers peculiar features concerning the mechanism of interaction of sodium and aluminum sulfate additives in cement compositions from the viewpoint of thermochemistry. Thermochemical equations for reactions of sulfate-containing additives with phases of hydrated cement clinker have been given in the paper. The paper contains description how to calculate thermal effects of chemical reactions and determine an influence of the formed

  7. Long-term heat storage in calcium sulfoaluminate cement (CSA) based concrete

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, Josef P.; Winnefeld, Frank [Empa Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland). Lab. for Concrete and Construction Chemistry

    2011-07-01

    In general, the selection of materials proposed for solar heat storage is based on one of two principal processes: sensible heat storage or latent heat storage. Sensible heat storage utilizes the specific heat capacity of a material, while latent heat storage is based on the change in enthalpy (heat content) associated with a phase change of the material. Long time sensible heat storage requires excellent thermal insulation whereas latent heat storage allows permanent (seasonal) storage without significant energy losses and any special insulation. Ettringite, one of the cement hydration products, exhibits a high dehydration enthalpy. Calcium sulfoaluminate cement based concrete containing a high amount of ettringite is henceproposed as an efficient latent heat storage material. Compared to conventional heat storage materials this innovative concrete mixture has a high loss-free storage energy density (> 100-150 kWh/m{sup 3}) which is much higher than the one of paraffin or the (loss-sensitive) sensible heat of water. Like common concrete the CSA-concrete is stable and even may carry loads. The dehydration of the CSA-concrete is achieved at temperatures below 100 C. The rehydration process occurs as soon as water (liquid or vapor) is added. In contrast to paraffin, the phase change temperature is not fixed and the latent heat may be recovered at any desired temperature. Furthermore the heat conductivity of this material is high, so that the energy transfer from/to an exchange medium is easy. Additionally CSA-concrete is not flammable and absolutely safe regarding any health aspects. The cost of such CSA-concrete isin the order of normal concrete. The main application is seen in house heating systems. Solar heat, mostly generated during the summer period by means of roof collectors, can be stored in CSA-concrete until the winter. A part or even the whole annual heatingenergy may be produced and saved locally by the householder himself. Additional applications may be

  8. Solidification of low-level radioactive wastes in masonry cement

    International Nuclear Information System (INIS)

    Zhou, H.; Colombo, P.

    1987-03-01

    Portland cements are widely used as solidification agents for low-level radioactive wastes. However, it is known that boric acid wastes, as generated at pressurized water reactors (PWR's) are difficult to solidify using ordinary portland cements. Waste containing as little as 5 wt % boric acid inhibits the curing of the cement. For this purpose, the suitability of masonry cement was investigated. Masonry cement, in the US consists of 50 wt % slaked lime (CaOH 2 ) and 50 wt % of portland type I cement. Addition of boric acid in molar concentrations equal to or less than the molar concentration of the alkali in the cement eliminates any inhibiting effects. Accordingly, 15 wt % boric acid can be satisfactorily incorporated into masonry cement. The suitability of masonry cement for the solidification of sodium sulfate wastes produced at boiling water reactors (BWR's) was also investigated. It was observed that although sodium sulfate - masonry cement waste forms containing as much as 40 wt % Na 2 SO 4 can be prepared, waste forms with more than 7 wt % sodium sulfate undergo catastrophic failure when exposed to an aqueous environment. It was determined by x-ray diffraction that in the presence of water, the sulfate reacts with hydrated calcium aluminate to form calcium aluminum sulfate hydrate (ettringite). This reaction involves a volume increase resulting in failure of the waste form. Formulation data were identified to maximize volumetric efficiency for the solidification of boric acid and sodium sulfate wastes. Measurement of some of the waste form properties relevant to evaluating the potential for the release of radionuclides to the environment included leachability, compression strengths and chemical interactions between the waste components and masonry cement. 15 refs., 19 figs., 9 tabs

  9. Addition of Wollastonite Fibers to Calcium Phosphate Cement Increases Cell Viability and Stimulates Differentiation of Osteoblast-Like Cells

    Directory of Open Access Journals (Sweden)

    Juliana Almeida Domingues

    2017-01-01

    Full Text Available Calcium phosphate cement (CPC that is based on α-tricalcium phosphate (α-TCP is considered desirable for bone tissue engineering because of its relatively rapid degradation properties. However, such cement is relatively weak, restricting its use to areas of low mechanical stress. Wollastonite fibers (WF have been used to improve the mechanical strength of biomaterials. However, the biological properties of WF remain poorly understood. Here, we tested the response of osteoblast-like cells to being cultured on CPC reinforced with 5% of WF (CPC-WF. We found that both types of cement studied achieved an ion balance for calcium and phosphate after 3 days of immersion in culture medium and this allowed subsequent long-term cell culture. CPC-WF increased cell viability and stimulated cell differentiation, compared to nonreinforced CPC. We hypothesize that late silicon release by CPC-WF induces increased cell proliferation and differentiation. Based on our findings, we propose that CPC-WF is a promising material for bone tissue engineering applications.

  10. A randomized clinical trial on the use of medical Portland cement, MTA and calcium hydroxide in indirect pulp treatment.

    Science.gov (United States)

    Petrou, Marina Agathi; Alhamoui, Fadi Alhaddad; Welk, Alexander; Altarabulsi, Mohammed Basel; Alkilzy, Mohammed; H Splieth, Christian

    2014-01-01

    Studies on indirect pulp treatment (IPT) show varying success rates of 73 to 97 %. The necessity of re-opening the cavity and the question of the optimal capping material is still under debate. The aim of this prospective in vivo study was to compare the clinical and microbiological outcomes of mineral trioxide aggregate (MTA), medical Portland cement, and calcium hydroxide on the dentin-pulp complex of permanent and primary teeth treated with two-step IPT. In 86 regular patients (51 % men; 49 % women; age 17.2 years ±13.8), one deep carious lesion each was treated with incomplete caries removal, randomly selected capping with either calcium hydroxide (n = 31), medical Portland cement (29) or white MTA (26), and re-entry (6.3 months ±1.0). Clinical (color, humidity, and consistency of dentin) and microbiological (Lactobacilli/Mutans Strep. counts) parameters were recorded at the first and second treatment. The IPT had a high success rate of 90.3 % regardless of the material used (p = 0.72). The arrested lesions showed consistently darker, dry, and therefore, sclerotic dentine (p Portland cement. The findings of this study could promote the improvement of the IPT as a one-step treatment of deep carious lesions when the remaining demineralized dentin would be sealed with durable restorations.

  11. Incorporation of phosphorus guest ions in the calcium silicate phases of Portland cement from 31P MAS NMR spectroscopy.

    Science.gov (United States)

    Poulsen, Søren L; Jakobsen, Hans J; Skibsted, Jørgen

    2010-06-21

    Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P(2)O(5)), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first (31)P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO(4))(3-) guest ions in the main clinker phases and hydration products. The observed (31)P chemical shifts (10 to -2 ppm), the (31)P chemical shift anisotropy, and the resemblance of the lineshapes in the (31)P and (29)Si MAS NMR spectra strongly suggest that (PO(4))(3-) units are incorporated in the calcium silicate phases, alite (Ca(3)SiO(5)) and belite (Ca(2)SiO(4)), by substitution for (SiO(4))(4-) tetrahedra. This assignment is further supported by a determination of the spin-lattice relaxation times for (31)P in alite and belite, which exhibit the same ratio as observed for the corresponding (29)Si relaxation times. From simulations of the intensities, observed in inversion-recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca(2+) is replaced by Fe(3+) ions, which may account for the interaction of the (31)P spins with paramagnetic Fe(3+) ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca(3)(PO(4))(2), as indicated by the observation of a narrow resonance at delta((31)P) = 3.0 ppm for two of the studied cements. (31)P{(1)H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO(4))(3-) incorporated in alite. This similarity and the absence of a large (31)P chemical shift ansitropy indicate that the hydrous (PO(4

  12. The biological performance of injectable calcium phosphate/PLGA cement in osteoporotic rats

    International Nuclear Information System (INIS)

    Van de Watering, Floor C J; Cuijpers, Vincent M; Jansen, John A; Van den Beucken, Jeroen J J P; Laverman, Peter; Gotthardt, Martin; Boerman, Otto C; Bronkhorst, Ewald M

    2013-01-01

    Calcium phosphate cements (CPCs) including poly(D,L-lactic-co-glycolic) acid (PLGA) microparticles are promising candidates for bone regenerative applications. Previous studies with CPC/PLGA demonstrated that the material is non-toxic, biocompatible and osteoconductive. However, the outcome of these studies was based on healthy individuals and consequently does not provide information on bone substitute material performance in a compromised situation, such as osteoporosis. Therefore, this study comparatively evaluated the performance of injectable CPC/PLGA in healthy (SHAM) and osteoporotic rats (OVX) using a rat femoral condyle defect with implantation periods of 4 and 12 weeks. It was hypothesized that in OVX rats the degradation of CPC/PLGA would increase due to a higher osteoclastic activity present in osteoporotic animals and that the obtained space would be rapidly filled with newly formed bone. The results revealed an accelerated degradation of the used CPC/PLGA in osteoporotic animals, but bone formation was less compared to that in healthy animals at 4 and 12 weeks after implantation. In addition, after 4 weeks, the amount of newly formed bone under osteoporotic conditions was less in the femoral condyle defect compared to that present in a non-defect, osteoporotic control femoral condyle, but equal after 12 weeks. On the other hand, in healthy animals, the amount of newly formed bone in the femoral condyle defect was equal to that present in a non-defect control femoral condyle at 4 weeks, while higher after 12 weeks. This indicates that bone regeneration at a defect site under osteoporotic conditions is slower, but can reach native amounts after longer time periods. Consequently, bone regenerative treatments under osteoporotic conditions seem to require additional empowerment of bone substitute materials. (paper)

  13. An i.r. investigation on some calcium aluminate hydrates, Ca2Al(OH)6+X-.yH2O (= 3CaO.Al2O3.CaX2.nH2O, X- = univalent anion)

    NARCIS (Netherlands)

    Houtepen, C.J.M.; Stein, H.N.

    1976-01-01

    The i.r. spectra of some hydrated and dehydrated calcium aluminate hydrates of the type Ca2Al(OH)6+X-·yH2O with X- = Cl-, Br-, J-, ClO3-, NO3-, ClO4- (y = 2) and X- = BrO3-, JO3- (2

  14. Current perspectives of bio-ceramic technology in endodontics: calcium enriched mixture cement - review of its composition, properties and applications

    Science.gov (United States)

    Nawal, Ruchika Roongta; Talwar, Sangeeta; Verma, Mahesh

    2015-01-01

    Advancements in bio-ceramic technology has revolutionised endodontic material science by enhancing the treatment outcome for patients. This class of dental materials conciliates excellent biocompatibility with high osseoconductivity that render them ideal for endodontic care. Few recently introduced bio-ceramic materials have shown considerable clinical success over their early generations in terms of good handling characteristics. Calcium enriched mixture (CEM) cement, Endosequence sealer, and root repair materials, Biodentine and BioAggregate are the new classes of bio-ceramic materials. The aim of this literature review is to present investigations regarding properties and applications of CEM cement in endodontics. A review of the existing literature was performed by using electronic and hand searching methods for CEM cement from January 2006 to December 2013. CEM cement has a different chemical composition from that of mineral trioxide aggregate (MTA) but has similar clinical applications. It combines the biocompatibility of MTA with more efficient characteristics, such as significantly shorter setting time, good handling characteristics, no staining of tooth and effective seal against bacterial leakage. PMID:25671207

  15. Sustainable Nanopozzolan Modified Cement: Characterizations and Morphology of Calcium Silicate Hydrate during Hydration

    Directory of Open Access Journals (Sweden)

    N. Mohamed Sutan

    2015-01-01

    Full Text Available There are environmental and sustainable benefits of partially replacing cement with industrial by-products or synthetic materials in cement based products. Since microstructural behaviours of cement based products are the crucial parameters that govern their sustainability and durability, this study investigates the microstructural comparison between two different types of cement replacements as nanopozzolan modified cement (NPMC in cement based product by focusing on the evidence of pozzolanic reactivity in corroboration with physical and mechanical properties. Characterization and morphology techniques using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, energy-dispersive X-ray spectroscopy (EDS, and scanning electron microscopy (SEM were carried out to assess the pozzolanic reactivity of cement paste modified with the combination of nano- and micro silica as NPMC in comparison to unmodified cement paste (UCP of 0.5 water to cement ratio (w/c. Results were then substantiated with compressive strength (CS results as mechanical property. Results of this study showed clear evidence of pozzolanicity for all samples with varying reactivity with NPMC being the most reactive.

  16. Protective or damage promoting effect of calcium carbonate layers on the surface of cement based materials in aqueous environments

    International Nuclear Information System (INIS)

    Schwotzer, M.; Scherer, T.; Gerdes, A.

    2010-01-01

    Cement based materials permanently exposed to aggressive aqueous environments are subject to chemical changes affecting their durability. However, this holds also for tap water that is considered to be not aggressive to cementitious materials, although in that case a formation of covering layers of CaCO 3 on the alkaline surfaces is commonly supposed to provide protection against reactive transport processes. Thus, investigations of the structural and chemical properties of the material/water interface were carried out in laboratory experiments and case studies to elucidate the consequences of surface reactions for the durability of cement based materials exposed to tap water. Focused Ion Beam investigations revealed that a protective effect of a CaCO 3 covering layer depends on its structural properties, which are in turn affected by the hydro-chemical conditions during crystallization. Surface precipitation of CaCO 3 can trigger further chemical degradation, if the required calcium is supplied by the pore solution of the material.

  17. Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pyatina, T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-11-14

    This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na2O-Al2O3-SiO2-H2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS was crystalline analcime.

  18. Inorganic Corrosion-Inhibitive Pigments for High-Temperature Alkali-activated Well Casing Foam Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pyatina, T. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2014-11-01

    This study evaluates inorganic pigments for improving carbon steel (CS) brine-corrosion protection by the sodium metasilicate-activated calcium aluminate cement/Fly Ash blend at 300°C. Calcium borosilicate (CBS) and zinc phosphate, significantly improved CS corrosion-protection by decreasing cement’s permeability for corrosive ions and inhibiting anodic corrosion. An amorphous Na2O-Al2O3-SiO2-H2O phase tightly attached to CS surface formed at 300oC in CBS-modified cement pore solution. The corrosion rate of the CS covered with this phase was nearly 4-fold lower than in the case of nonmodified cement pore solution where the major phase formed on the surface of CS was crystalline analcime.

  19. Calcium hydroxide poisoning

    Science.gov (United States)

    Hydrate - calcium; Lime milk; Slaked lime ... Calcium hydroxide ... These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement ...

  20. Duplex aluminized coatings

    Science.gov (United States)

    Gedwill, M. A.; Grisaffe, S. J. (Inventor)

    1975-01-01

    The surface of a metallic base system is initially coated with a metallic alloy layer that is ductile and oxidation resistant. An aluminide coating is then applied to the metallic alloy layer. The chemistry of the metallic alloy layer is such that the oxidation resistance of the subsequently aluminized outermost layer is not seriously degraded.

  1. Natural cement and stone restoration of Bourges Cathedral (France

    Directory of Open Access Journals (Sweden)

    C. Gosselin

    2008-01-01

    Full Text Available Natural cement, also called "Roman cement", was invented at the end of the 18th Century and played an important role in the development of civil engineering works until the 1860s. More surprisingly, it was also used to restore historic buildings, such as gothic cathedrals. This paper deals with the mineralogy and the durability of natural cement, in the particular case of the Bourges Cathedral in France. This study illustrates the interest of this material particularly adapted in stone repair or substitution. Contrary to traditional mortars, the present samples are made of neat cement paste, revealed by the absence of mineral additions as quartz or carbonate sand. Several combined techniques (SEM-EDS, TGA, XRD were carried out to determine the composition of the hydraulic binder rich in calcium aluminate hydrates. The raw marl at the origin of the cement production contains oxidized pyrites which consist in a potential source of sulphate pollution of the surrounding limestone. The exposition of the cement in urban environment leads to some weathering features as atmospheric sulphation. Finally a petrophysical approach, based on water porosity, capillary sorption and compressive strength, has been performed to demonstrate the durability and the compatibility of roman cement applied as a restoration mortar of historical building.

  2. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

    Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness

  3. Swelling behavior of ion exchange resins incorporated in tri-calcium silicate cement matrix: I. Chemical analysis

    International Nuclear Information System (INIS)

    Neji, M.; Bary, B.; Le Bescop, P.; Burlion, N.

    2015-01-01

    This paper presents the first part of a theoretical and experimental work aiming at modeling the chemo-mechanical behavior of composites made up of ion exchange resins (IER) solidified in a tri-calcium silicate cement paste (C_3S). Because of ion exchange processes, the volume change of the IER may cause internal pressures leading to the degradation of the material. In this study, a predictive modeling is developed for describing the chemical behavior of such material. It is based on thermodynamic equilibria to determine the evolution of the ion exchange processes, and the potential precipitation of portlandite in the composite. In parallel, a phenomenological study has been set up to understand chemical phenomena related to the swelling mechanisms. The model created has been finally implemented in a finite elements software; the simulation of a laboratory test has been performed and the results compared to experimental data. - Highlights: • Ion exchange theory to model the swelling behavior of Ion exchange resin. • Experimental phenomenon analysis about Chemo-mechanical interaction between IER and cement paste matrix. • Chemo-Transport modeling on a composite material made with IER embedded into cement paste matrix.

  4. Swelling behavior of ion exchange resins incorporated in tri-calcium silicate cement matrix: II. Mechanical analysis

    International Nuclear Information System (INIS)

    Neji, M.; Bary, B.; Le Bescop, P.; Burlion, N.

    2015-01-01

    This paper presents the second part of a study aiming at modelling the mechanical behavior of composites made up of ion exchange resins (IER) solidified in a tri-calcium silicate cement paste (C_3S). Such composites may be subjected to internal pressures due to ion exchange processes between ionic species which are in IER and interstitial solution of the cement paste. The reactive transport model developed in the companion paper is coupled in this study to a multi-scale approach describing the mechanical behavior of the material. It is based on an analogy with thermomechanics for taking in account the IER internal pressures, and on Eshelby-based homogenization techniques to estimate both mechanical and coupling parameters. A laboratory test has been set up to measure the macroscopic strain caused by the swelling phenomenon. The model has been finally implemented in a finite elements software. The simulation of the laboratory tests has been performed and the results have been analyzed and compared to experimental data. - Highlights: • Experimental analysis about mechanical behavior of a composite material. • Chemo-Mechanical-Transport modeling on a composite material made up with IER embedded into cement paste matrix. • Multi-scale modeling.

  5. Production and characterization of setting hydraulic cements based on calcium phosphate; Obtencao e caracterizacao de cimentos de fosfato de calcio de pega hidraulica

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Luci C. de; Rigo, Eliana C.S.; Santos, Luis A dos; Boschi, Anselmo Ortega [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais; Carrodeguas, Raul G. [Universidad de La Habana, Habana (Cuba). Centro de Biomateriales

    1997-12-31

    Setting hydraulic cements based on calcium phosphate has risen great interest in scientific literature during recent years due to their total bio compatibility and to the fact that they harden `in situ`, providing easy handling and adaptation to the shape and dimensions of the defect which requires correction, differently from the predecessors, the calcium phosphate ceramics (Hydroxy apatite, {beta}-tri calcium phosphate, biphasic, etc) in the shape of dense or porous blocks and grains. In the work, three calcium-phosphate cement compositions were studied. The resulting compositions were characterized according to the following aspects: setting times, pH, mechanical resistance, crystalline phases, microstructure and solubility in SBF (Simulated Body Fluid). The results show a potential use for the compositions. (author) 6 figs., 4 tabs.

  6. Interaction of calcium silicate hydrates (C-S-H), the main components of cement, with alkaline chlorides, analogy with clays

    International Nuclear Information System (INIS)

    Viallis-Terrisse, H.

    2000-01-01

    This work, belonging to a more general study on the structure and reactivity of cement, deals with the experimental and theoretical analysis of the interaction of alkaline chlorides with calcium silicate hydrates (C-S-H), the main components of cement paste. The interaction of alkaline cations with C-S-H is interfacial, involving both electrostatic and surface complexation mechanisms. The C-S-H surface is constituted of silanol sites, partially dissociated due to the high pH of the interstitial solution. The calcium ions, present in large amounts in the equilibrium solution of C-S-H, constitute potential determining ions for the C-S-H surface. The alkaline ions seem to compete with calcium for the same surface sites. The adsorption isotherms show that caesium presents a better affinity than sodium and lithium for the C-S-H surface. Moreover, solid-state NMR suggests that caesium forms with the surface sites inner-sphere complexes, whereas sodium seems to keep its hydration sphere. These results are in agreement with zeta potential measurements, which let suppose a specific adsorption of caesium ions, and an indifferent behaviour of both other alkaline ions. A model for the C-S-H surface was proposed, from the electric double layer model, and mass action laws expressing the complexation of the different ionic species with the silanol sites. The whole study relies on a structural analogy with smectites, some clays presenting well-known cationic adsorption properties. The structural similarity between both minerals is enhanced by some similarities of reactivity, though significant behaviour differences could also be noted. (author)

  7. Cu2+, Co2+ and Cr3+ doping of a calcium phosphate cement influences materials properties and response of human mesenchymal stromal cells.

    Science.gov (United States)

    Schamel, Martha; Bernhardt, Anne; Quade, Mandy; Würkner, Claudia; Gbureck, Uwe; Moseke, Claus; Gelinsky, Michael; Lode, Anja

    2017-04-01

    The application of biologically active metal ions to stimulate cellular reactions is a promising strategy to accelerate bone defect healing. Brushite-forming calcium phosphate cements were modified with low doses of Cu 2+ , Co 2+ and Cr 3+ . The modified cements released the metal ions in vitro in concentrations which were shown to be non-toxic for cells. The release kinetics correlated with the solubility of the respective metal phosphates: 17-45 wt.-% of Co 2+ and Cu 2+ , but calcium and phosphate ions with cell culture medium. In case of cements modified with 50mmol Cr 3+ /mol β-tricalcium phosphate (β-TCP), XRD and SEM analyses revealed a significant amount of monetite and a changed morphology of the cement matrix. Cell culture experiments with human mesenchymal stromal cells indicated that the observed cell response is not only influenced by the released metal ions but also by changed cement properties. A positive effect of modifications with 50mmol Cr 3+ or 10mmol Cu 2+ per mol β-TCP on cell behaviour was observed in indirect and direct culture. Modification with Co 2+ resulted in a clear suppression of cell proliferation and osteogenic differentiation. In conclusion, metal ion doping of the cement influences cellular activities in addition to the effect of released metal ions by changing properties of the ceramic matrix. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. The AFm phase in Portland cement

    International Nuclear Information System (INIS)

    Matschei, T.; Lothenbach, B.; Glasser, F.P.

    2007-01-01

    The AFm phase of Portland cements refers to a family of hydrated calcium aluminates based on the hydrocalumite-like structure of 4CaO.Al 2 O 3 .13-19 H 2 O. However OH - may be replaced by SO 4 2- and CO 3 2- . Except for limited replacement (50 mol%, maximum) of sulfate by hydroxide, these compositions do not form solid solutions and, from the mineralogical standpoint, behave as separate phases. Therefore many hydrated cements will contain mixtures of AFm phases. AFm phases have been made from precursors and experimentally-determined phase relationships are depicted at 25 deg. C. Solubility data are reported and thermodynamic data are derived. The 25 deg. C stability of AFm phases is much affected by the nature of the anion: carbonate stabilises AFm and displaces OH and SO 4 at species activities commonly encountered in cement systems. However in the presence of portlandite, and as carbonate displaces sulfate in AFm, the reaction results in changes in the amount of both portlandite and ettringite: specimen calculations are presented to quantify these changes. The scheme of phase balances enables calculation of the mineralogical balances of a hydrated cement paste with greater accuracy than hitherto practicable

  9. Effect of curing conditions on the dimensional and thermal stability of calcium phosphate cement for elevated temperature applications

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Johan [Vrije Universiteit Brussel, Department of Mechanics of Materials and Constructions, Pleinlaan 2, Brussels 1050 (Belgium); Rahier, Hubert [Vrije Universiteit Brussel, Research Group of Physical Chemistry and Polymer Sciences, Pleinlaan 2, Brussels 1050 (Belgium); Wastiels, Jan, E-mail: Jan.Wastiels@vub.ac.be [Vrije Universiteit Brussel, Department of Mechanics of Materials and Constructions, Pleinlaan 2, Brussels 1050 (Belgium)

    2014-12-15

    Calcium phosphate cements (CPCs) are attractive materials for elevated temperature applications, like moulds to process thermoplastics up to 300 °C. The CPC resulting from the reaction of wollastonite with phosphoric acid cured at room temperature however contains hydrated phases like brushite, and is thus not stable when exposed to temperatures above 200 °C. A non-contact method based on digital image correlation demonstrated that isothermal curing at 60 °C reduces the thermal shrinkage up to 300 °C by 25%. This curing method results in the direct formation of the more stable monetite in a shorter curing time. The correlated results of TGA, pH of the filtration water, and DSC analysis on partially cured material indicate this. XRD diffractograms and SEM images in combination with EDX show the evolution of the transformation of wollastonite into monetite, and the structure and morphology of the formed material.

  10. Bone regeneration in experimental animals using calcium phosphate cement combined with platelet growth factors and human growth hormone.

    Science.gov (United States)

    Emilov-Velev, K; Clemente-de-Arriba, C; Alobera-García, M Á; Moreno-Sansalvador, E M; Campo-Loarte, J

    2015-01-01

    Many substances (growth factors and hormones) have osteoinduction properties and when added to some osteoconduction biomaterial they accelerate bone neoformation properties. The materials included 15 New Zealand rabbits, calcium phosphate cement (Calcibon(®)), human growth hormone (GH), and plasma rich in platelets (PRP). Each animal was operated on in both proximal tibias and a critical size bone defect of 6mm of diameter was made. The animals were separated into the following study groups: Control (regeneration only by Calcibon®), PRP (regeneration by Calcibon® and PRP), GH (regeneration by Calcibon® and GH). All the animals were sacrificed at 28 days. An evaluation was made of the appearance of the proximal extreme of rabbit tibiae in all the animals, and to check the filling of the critical size defect. A histological assessment was made of the tissue response, the presence of new bone formation, and the appearance of the biomaterial. Morphometry was performed using the MIP 45 image analyser. ANOVA statistical analysis was performed using the Statgraphics software application. The macroscopic appearance of the critical defect was better in the PRP and the GH group than in the control group. Histologically greater new bone formation was found in the PRP and GH groups. No statistically significant differences were detected in the morphometric study between bone formation observed in the PRP group and the control group. Significant differences in increased bone formation were found in the GH group (p=0.03) compared to the other two groups. GH facilitates bone regeneration in critical defects filled with calcium phosphate cement in the time period studied in New Zealand rabbits. Copyright © 2014 SECOT. Published by Elsevier Espana. All rights reserved.

  11. Effects of Pore Size on the Osteoconductivity and Mechanical Properties of Calcium Phosphate Cement in a Rabbit Model.

    Science.gov (United States)

    Zhao, Yi-Nan; Fan, Jun-Jun; Li, Zhi-Quan; Liu, Yan-Wu; Wu, Yao-Ping; Liu, Jian

    2017-02-01

    Calcium phosphate cement (CPC) porous scaffold is widely used as a suitable bone substitute to repair bone defect, but the optimal pore size is unclear yet. The current study aimed to evaluate the effect of different pore sizes on the processing of bone formation in repairing segmental bone defect of rabbits using CPC porous scaffolds. Three kinds of CPC porous scaffolds with 5 mm diameters and 12 mm length were prepared with the same porosity but different pore sizes (Group A: 200-300 µm, Group B: 300-450 µm, Group C: 450-600 µm, respectively). Twelve millimeter segmental bone defects were created in the middle of the radius bone and filled with different kinds of CPC cylindrical scaffolds. After 4, 12, and 24 weeks, alkaline phosphatase (ALP), histological assessment, and mechanical properties evaluation were performed in all three groups. After 4 weeks, ALP activity increased in all groups but was highest in Group A with smallest pore size. The new bone formation within the scaffolds was not obvious in all groups. After 12 weeks, the new bone formation within the scaffolds was obvious in each group and highest in Group A. At 24 weeks, no significant difference in new bone formation was observed among different groups. Besides the osteoconductive effect, Group A with smallest pore size also had the best mechanical properties in vivo at 12 weeks. We demonstrate that pore size has a significant effect on the osteoconductivity and mechanical properties of calcium phosphate cement porous scaffold in vivo. Small pore size favors the bone formation in the early stage and may be more suitable for repairing segmental bone defect in vivo. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  12. Cements in Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    Glasser, F.P.

    2013-01-01

    burden of proof because with few exceptions, much less is known about their ability chemically to immobilise waste species and their long- term durability relative to Portland cement in a range of natural environments. It is concluded that the most robust of these alternative formulations are based on calcium aluminate and sulfoaluminate cements, on magnesium phosphate and on geopolymers. (author)

  13. Cements in Radioactive Waste Disposal

    Energy Technology Data Exchange (ETDEWEB)

    Glasser, F. P. [University of Aberdeen, Scotland (United Kingdom)

    2013-09-15

    burden of proof because with few exceptions, much less is known about their ability chemically to immobilise waste species and their long- term durability relative to Portland cement in a range of natural environments. It is concluded that the most robust of these alternative formulations are based on calcium aluminate and sulfoaluminate cements, on magnesium phosphate and on geopolymers. (author)

  14. Hydrothermal hardened high-temperature thermal insulation material CALUTHERM {sup registered} from hibonite and alumina cement. Pt. 1; Hydrothermal erhaerteter Hochtemperaturwaermedaemmstoff CALUTHERM {sup registered} aus Hibonit und Tonerdezement. T. 1

    Energy Technology Data Exchange (ETDEWEB)

    Hoelscher, Tobias; Schneider, Hans-Juergen [Calsitherm Silikatbaustoffe GmbH, Bad Lippspringe (Germany); Schlegel, Ernst

    2013-07-01

    The first part features an overview to the properties of all calcium aluminates followed by a presentation of CALUTHERM {sup registered}, a high temperature-thermal insulating material. CALUTHERM is produced on the bases of SLA-92, a calcium hexaaluminat aggregate, and calcium aluminate cement CA-14 W as binder. The comprehensive studies focus on properties and changes of these raw materials during the technological stages of the CALUTHERM's production. The second part will present CALUTHERM's properties and its variants throughout the production process. A possible correlation between the properties of raw materials and thermal insulation material is researched and finally application examples are presented. CALUTHERM is suited for thermal insulation up to 1600 C and has a remarkable low thermal conductivity near 0.4 W/m . K at these high temperatures. For that reason CALUTHERM is a top high-temperature thermal insulating material. (orig.)

  15. The application of thermal analysis to the hydration and conversión Reactions of calcium alumínate Cements

    Directory of Open Access Journals (Sweden)

    Bushnell-Watson, S. M.

    1992-12-01

    Full Text Available The hydration of calcium aluminates cements is dominated by that of CA, CaAl2O4, which is a major constituent of all of them. At ambient temperatures, CAH10 and an amorphous phase are formed initially, but these are metastable and slowly (or more rapidly if exposed to higher temperatures transform into C3AH6 and gíbbsite. This conversion reaction is accompanied by and increase ín porosity, which can lead to a loss in strength and vulnerability to chemical attack. Various methods of thermal analysis have been applied as a routine test to determine the degree of conversion, and the results from these methods are critically evaluated. Thermal analysis is a useful technique for identification of the various hydrates that can form in these systems, especially at early stages of hydration when poorly crystalline phases are present. Differential thermal analysis curves showing peaks attributable to all these hydrates are presented and it is shown that overlap frequently occurs, leading to difficulties in interpretation, which can sometimes be minimized by use of a complementary technique such as X-ray diffraction.

    La hidratación de cementos aluminosos está regida por la de CA, CaAl2O4, que es el componente principal. A temperatura ambiente inicialmente se forman CAH10 y una fase amorfa, pero son metaestables y se transforman lentamente (o más rápidamente si se exponen a temperaturas más altas en C3AH6 y gibsita. Esta reacción de conversión está acompañada de un aumento de porosidad, lo que lleva a la pérdida de resistencia y a la vulnerabilidad al ataque químico. Se han aplicado distintos métodos de análisis térmico como una prueba rutinaria para determinar el grado de conversión y se ofrece una evaluación crítica de los resultados de estos métodos. Análisis térmico es una técnica útil para identificar los

  16. Radiological impact of cement, concrete and admixtures in Spain

    International Nuclear Information System (INIS)

    Chinchon-Paya, S.; Piedecausa, B.; Hurtado, S.; Sanjuan, M.A.; Chinchon, S.

    2011-01-01

    It has been analyzed samples of portland cement (PC) with and without admixtures, samples of calcium aluminate cement (CAC) with different content of Al 2 O 3 and specimens of concrete made with PC and CAC using High Resolution Gamma Spectrometry. The activity concentration index (I) is much less than 0.5 mSv y -1 for all the concrete specimens according to the Radiation protection document 112 of the European Commission. The PC without admixtures (CEM I 52,5 R) and the PC with addition of limestone (CEM II/BL 32,5 N) also have an I value much lower than 0.5 and the PC with the addition of fly ash and blast furnace slag (CEM IV/B (V) 32,5 N and III/A 42.5 N/SR) have an I value close to 0.6. The I value of the CAC used in the manufacture of structural precast concrete is of the order of 1 mSv y -1 . Some of the CAC used in refractory concrete reaches a value close to 2 mSv y -1 . - Highlights: → The activity values (I) of spanish portland cement and admixtures studied are similar to those described by other authors. → For the first time in scientific publications we have shown results of several calcium aluminate cements (CAC). → CAC used in structural concrete has an approximate I value = 1 (similar to blast furnace slag and fly ash). → One type of CAC with Al 2 O 3 content of 51% used in refractory concretes has a value of I = 2.

  17. Effect of addition of nano-hydroxyapatite on physico-chemical and antibiofilm properties of calcium silicate cements

    Directory of Open Access Journals (Sweden)

    Juliane Maria GUERREIRO-TANOMARU

    Full Text Available ABSTRACT Objective Mineral Trioxide Aggregate (MTA is a calcium silicate cement composed of Portland cement (PC and bismuth oxide. Hydroxyapatite has been incorporated to enhance mechanical and biological properties of dental materials. This study evaluated physicochemical and mechanical properties and antibiofilm activity of MTA and PC associated with zirconium oxide (ZrO2 and hydroxyapatite nanoparticles (HAn. Material and Methods White MTA (Angelus, Brazil; PC (70%+ZrO2 (30%; PC (60%+ZrO2 (30%+HAn (10%; PC (50%+ZrO2 (30%+HAn (20% were evaluated. The pH was assessed by a digital pH-meter and solubility by mass loss. Setting time was evaluated by using Gilmore needles. Compressive strength was analyzed by mechanical test. Samples were radiographed alongside an aluminum step wedge to evaluate radiopacity. For the antibiofilm evaluation, materials were placed in direct contact with E. faecalis biofilm induced on dentine blocks. The number of colony-forming units (CFU mL-1 in the remaining biolfilm was evaluated. The results were submitted to ANOVA and the Tukey test, with 5% significance. Results There was no difference in pH levels of PC+ZrO2, PC+ZrO2+HAn (10% and PC+ZrO2+HAn (20% (p>0.05 and these cements presented higher pH levels than MTA (p<0.05. The highest solubility was observed in PC+ZrO2+HAn (10% and PC+ZrO2+HAn (20% (p<0.05. MTA had the shortest initial setting time (p<0.05. All the materials showed radiopacity higher than 3 mmAl. PC+ZrO2 and MTA had the highest compressive strength (p<0.05. Materials did not completely neutralize the bacterial biofilm, but the association with HAn provided greater bacterial reduction than MTA and PC+ZrO2 (p<0.05 after the post-manipulation period of 2 days. Conclusions The addition of HAn to PC associated with ZrO2 harmed the compressive strength and solubility. On the other hand, HAn did not change the pH and the initial setting time, but improved the radiopacity (HAn 10%, the final setting time and

  18. A novel sol-gel-derived calcium silicate cement with short setting time for application in endodontic repair of perforations.

    Science.gov (United States)

    Lee, Bor-Shiunn; Lin, Hong-Ping; Chan, Jerry Chun-Chung; Wang, Wei-Chuan; Hung, Ping-Hsuan; Tsai, Yu-Hsin; Lee, Yuan-Ling

    2018-01-01

    Mineral trioxide aggregate (MTA) is the most frequently used repair material in endodontics, but the long setting time and reduced mechanical strength in acidic environments are major shortcomings. In this study, a novel sol-gel-derived calcium silicate cement (sCSC) was developed using an initial Ca/Si molar ratio of 3, with the most effective mixing orders of reactants and optimal HNO 3 catalyst volumes. A Fourier transform infrared spectrometer, scanning electron microscope with energy-dispersive X-ray spectroscopy, and X-ray powder diffractometer were used for material characterization. The setting time, compressive strength, and microhardness of sCSC after hydration in neutral and pH 5 environments were compared with that of MTA. Results showed that sCSC demonstrated porous microstructures with a setting time of ~30 min, and the major components of sCSC were tricalcium silicate, dicalcium silicate, and calcium oxide. The optimal formula of sCSC was sn200, which exhibited significantly higher compressive strength and microhardness than MTA, irrespective of neutral or pH 5 environments. In addition, both sn200 and MTA demonstrated good biocompatibility because cell viability was similar to that of the control. These findings suggest that sn200 merits further clinical study for potential application in endodontic repair of perforations.

  19. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

    Baquerizo, Luis G., E-mail: luis.baquerizoibarra@holcim.com [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Matschei, Thomas [Innovation, Holcim Technology Ltd., CH-5113 Holderbank (Switzerland); Scrivener, Karen L. [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland); Saeidpour, Mahsa; Wadsö, Lars [Building Materials, Lund University, Box 124, 221 000 Lund (Sweden)

    2015-07-15

    The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water content) depending on the relative humidity (RH), temperature and anion type, which might be linked to volume changes (swelling and shrinkage). Unfortunately the stability conditions of these phases are insufficiently reported. This paper presents novel experimental results on the different hydration states of the most important AFm phases: monocarboaluminate, hemicarboaluminate, strätlingite, hydroxy-AFm and monosulfoaluminate, and the thermodynamic properties associated with changes in their water content during absorption/desorption. This data opens the possibility to model the response of cementitious systems during drying and wetting and to engineer systems more resistant to harsh external conditions.

  20. Kinetics of apatite formation on a calcium-silicate cement for root-end filling during ageing in physiological-like phosphate solutions.

    Science.gov (United States)

    Gandolfi, Maria Giovanna; Taddei, Paola; Tinti, Anna; De Stefano Dorigo, Elettra; Rossi, Piermaria Luigi; Prati, Carlo

    2010-12-01

    The bioactivity of calcium silicate mineral trioxide aggregate (MTA) cements has been attributed to their ability to produce apatite in presence of phosphate-containing fluids. This study evaluated surface morphology and chemical transformations of an experimental accelerated calcium-silicate cement as a function of soaking time in different phosphate-containing solutions. Cement discs were immersed in Dulbecco's phosphate-buffered saline (DPBS) or Hank's balanced salt solution (HBSS) for different times (1-180 days) and analysed by scanning electron microscopy connected with an energy dispersive X-ray analysis (SEM-EDX) and micro-Raman spectroscopy. SEM-EDX revealed Ca and P peaks after 14 days in DPBS. A thin Ca- and P-rich crystalline coating layer was detected after 60 days. A thicker multilayered coating was observed after 180 days. Micro-Raman disclosed the 965-cm(-1) phosphate band at 7 days only on samples stored in DPBS and later the 590- and 435-cm(-1) phosphate bands. After 60-180 days, a layer approximately 200-900 μm thick formed displaying the bands of carbonated apatite (at 1,077, 965, 590, 435 cm(-1)) and calcite (at 1,088, 713, 280 cm(-1)). On HBSS-soaked, only calcite bands were observed until 90 days, and just after 180 days, a thin apatite-calcite layer appeared. Micro-Raman and SEM-EDX demonstrated the mineralization induction capacity of calcium-silicate cements (MTAs and Portland cements) with the formation of apatite after 7 days in DPBS. Longer time is necessary to observe bioactivity when cements are immersed in HBSS.

  1. Development of the foremost light-curable calcium-silicate MTA cement as root-end in oral surgery. Chemical-physical properties, bioactivity and biological behavior.

    Science.gov (United States)

    Gandolfi, Maria Giovanna; Taddei, Paola; Siboni, Francesco; Modena, Enrico; Ciapetti, Gabriela; Prati, Carlo

    2011-07-01

    An innovative light-curable calcium-silicate cement containing a HEMA-TEGDMA-based resin (lc-MTA) was designed to obtain a bioactive fast setting root-end filling and root repair material. lc-MTA was tested for setting time, solubility, water absorption, calcium release, alkalinizing activity (pH of soaking water), bioactivity (apatite-forming ability) and cell growth-proliferation. The apatite-forming ability was investigated by micro-Raman, ATR-FTIR and ESEM/EDX after immersion at 37°C for 1-28 days in DPBS or DMEM+FBS. The marginal adaptation of cement in root-end cavities of extracted teeth was assessed by ESEM/EDX, and the viability of Saos-2 cell on cements was evaluated. lc-MTA demonstrated a rapid setting time (2min), low solubility, high calcium release (150-200ppm) and alkalinizing power (pH 10-12). lc-MTA proved the formation of bone-like apatite spherulites just after 1 day. Apatite precipitates completely filled the interface porosities and created a perfect marginal adaptation. lc-MTA allowed Saos-2 cell viability and growth and no compromising toxicity was exerted. HEMA-TEGDMA creates a polymeric network able to stabilize the outer surface of the cement and a hydrophilic matrix permeable enough to allow water absorption. SiO(-)/Si-OH groups from the mineral particles induce heterogeneous nucleation of apatite by sorption of calcium and phosphate ions. Oxygen-containing groups from poly-HEMA-TEGDMA provide additional apatite nucleating sites through the formation of calcium chelates. The strong novelty was that the combination of a hydraulic calcium-silicate powder and a poly-HEMA-TEGDMA hydrophilic resin creates the conditions (calcium release and functional groups able to chelate Ca ions) for a bioactive fast setting light-curable material for clinical applications in dental and maxillofacial surgery. The first and unique/exclusive light-curable calcium-silicate MTA cement for endodontics and root-end application was created, with a potential

  2. Pore solution in alkali-activated slag cement pastes. Relation to the composition and structure of calcium silicate hydrate

    International Nuclear Information System (INIS)

    Puertas, F.; Fernandez-Jimenez, A.; Blanco-Varela, M.T.

    2004-01-01

    In this work, the relationship between the composition of pore solution in alkali-activated slag cement (AAS) pastes activated with different alkaline activator, and the composition and structure of the main reaction products, has been studied. Pore solution was extracted from hardened AAS pastes. The analysis of the liquids was performed through different techniques: Na, Mg and Al by atomic absorption (AA), Ca ions by ionic chromatography (IC) and Si by colorimetry; pH was also determined. The solid phases were analysed by XRD, FTIR, solid-state 29 Si and 27 Al NMR and BSE/EDX. The most significant changes in the ionic composition of the pore solution of the AAS pastes activated with waterglass take place between 3 and 24 h of reaction. These changes are due to the decrease of the Na content and mainly to the Si content. Results of 29 Si MAS NMR and FTIR confirm that the activation process takes place with more intensity after 3 h (although at this age, Q 2 units already exist). The pore solution of the AAS pastes activated with NaOH shows a different evolution to this of pastes activated with waterglass. The decrease of Na and Si contents progresses with time. The nature of the alkaline activator influences the structure and composition of the calcium silicate hydrate formed as a consequence of the alkaline activation of the slag. The characteristic of calcium silicate hydrate in AAS pastes activated with waterglass is characterised by a low structural order with a low Ca/Si ratio. Besides, in this paste, Q 3 units are detected. The calcium silicate hydrate formed in the pastes activated with NaOH has a higher structural order (higher crystallinity) and contains more Al in its structure and a higher Ca/Si ratio than those obtained with waterglass

  3. The Bone Building Blues: Self-hardening copper-doped calcium phosphate cement and its in vitro assessment against mammalian cells and bacteria.

    Science.gov (United States)

    Rau, Julietta V; Wu, Victoria M; Graziani, Valerio; Fadeeva, Inna V; Fomin, Alexander S; Fosca, Marco; Uskoković, Vuk

    2017-10-01

    A blue calcium phosphate cement with optimal self-hardening properties was synthesized by doping whitlockite (β-TCP) with copper ions. The mechanism and the kinetics of the cement solidification process were studied using energy dispersive X-ray diffraction and it was found out that hardening was accompanied by the phase transition from TCP to brushite. Reduced lattice parameters in all crystallographic directions resulting from the rather low (1:180) substitution rate of copper for calcium was consistent with the higher ionic radius of the latter. The lower cationic hydration resulting from the partial Ca→Cu substitution facilitated the release of constitutive hydroxyls and lowered the energy of formation of TCP from the apatite precursor at elevated temperatures. Addition of copper thus effectively inhibited the formation of apatite as the secondary phase. The copper-doped cement exhibited an antibacterial effect, though exclusively against Gram-negative bacteria, including E. coli, P. aeruginosa and S. enteritidis. This antibacterial effect was due to copper ions, as demonstrated by an almost negligible antibacterial effect of the pure, copper-free cement. Also, the antibacterial activity of the copper-containing cement was significantly higher than that of its precursor powder. Since there was no significant difference between the kinetics of the release of copper from the precursor TCP powder and from the final, brushite phase of the hardened cement, this has suggested that the antibacterial effect was not solely due to copper ions, but due to the synergy between cationic copper and a particular phase and aggregation state of calcium phosphate. Though inhibitory to bacteria, the copper-doped cement increased the viability of human glial E297 cells, murine osteoblastic K7M2 cells and especially human primary lung fibroblasts. That this effect was also due to copper ions was evidenced by the null effect on viability increase exhibited by the copper

  4. Cementing Efficiency of Low Calcium Fly Ash in Fly Ash Concretes

    OpenAIRE

    T. D. Gunneswara Rao; Mudimby Andal

    2014-01-01

    Research on the utilization of fly ash will no longer refer the fly ash as a waste material of thermal power plants. Use of fly ash in concrete making, makes the concrete economical as well as durable. The fly ash is being added to the concrete in three ways namely, as partial replacement to cement, as partial replacement to fine aggregates and as admixture. Addition of fly ash to the concrete in any one of the form mentioned above, makes the concrete more workable and durable than the conven...

  5. ToF-SIMS images and spectra of biomimetic calcium silicate-based cements after storage in solutions simulating the effects of human biological fluids

    Science.gov (United States)

    Torrisi, A.; Torrisi, V.; Tuccitto, N.; Gandolfi, M. G.; Prati, C.; Licciardello, A.

    2010-01-01

    ToF-SIMS images were obtained from a section of a tooth, obturated by means of a new calcium-silicate based cement (wTCF) after storage for 1 month in a saline solutions (DPBS), in order to simulate the body fluid effects on the obturation. Afterwards, ToF-SIMS spectra were obtained from model samples, prepared by using the same cement paste, after storage for 1 month and 8 months in two different saline solutions (DPBS and HBSS). ToF-SIMS spectra were also obtained from fluorine-free cement (wTC) samples after storage in HBSS for 1 month and 8 months and used for comparison. It was found that the composition of both the saline solution and the cement influenced the composition of the surface of disks and that longer is the storage greater are the differences. Segregation phenomena occur both on the cement obturation of the tooth and on the surface of the disks prepared by using the same cement. Indirect evidences of formation of new crystalline phases are supplied.

  6. Effect of saliva and blood contamination on the bi-axial flexural strength and setting time of two calcium-silicate based cements: Portland cement and biodentine.

    Science.gov (United States)

    Alhodiry, W; Lyons, M F; Chadwick, R G

    2014-03-01

    This study evaluated the effect of contamination with saliva and blood on the bi-axial flexural strength and setting time of pure gray Portland cement and Biodentine (Septodont, Allington, UK). A one-way ANOVA showed that contamination caused no significant difference between the cements in bi-axial flexural strength (P> 0.05). However there was a significant difference in setting time (PPortland cement taking longer than Biodentine, regardless of the contaminant, and contamination with blood increased the setting time of both materials. Biodentine was similar in strength to Portland cement, but had a shorter setting time for both contaminated and non-contaminated samples.

  7. The mechanical and biological studies of calcium phosphate cement-fibrin glue for bone reconstruction of rabbit femoral defects

    Directory of Open Access Journals (Sweden)

    Dong J

    2013-03-01

    Full Text Available Jingjing Dong,1,* Geng Cui,2,* Long Bi,1,* Jie Li,3 Wei Lei11Institute of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi’an, Shaanxi, People’s Republic of China; 2Institute of Orthopedics, General Hospital of PLA, Beijing, People’s Republic of China; 3Institute of Gynecology and Obstetrics, General Hospital of PLA, Beijing, People’s Republic of China*These authors contributed equally to this workAbstract: In order to improve the mechanical and biological properties of calcium phosphate cement (CPC, nanometer-biomaterial for bone reconstruction in the rabbit femoral defect model, fibrin glue (FG, the natural product, purified from the blood was introduced at three different ratios. The CPC powder and the FG solution were mixed, respectively, at the powder/liquid (P/L ratios (g/mL of 1:1, 3:1, and 5:1 (g/mL, and pure CPC was used as a control. After being implanted into the femoral defect in rabbit, the healing process was evaluated by micro-computed tomography scan, biomechanical testing, and histological examination. By micro-computed tomography analysis, the P/L ratio of 1:1 (g/mL group indicated the largest quantity of new bone formation at 4 weeks, 8 weeks, and 12 weeks after implantation, respectively. Bone volume per trabecular volume of the 1:1 group was highest in the four groups, which was 1.45% ± 0.42%, 7.35% ± 1.45%, and 29.10% ± 1.67% at 4 weeks, 8 weeks, and 12 weeks after the operation, respectively. In the biomechanical tests, the compressive strength and the elastic modulus of the three CPC–FG groups were much higher than those of the pure CPC group at the determined time point (P < 0.05. The histological evaluation also showed the best osseointegration in the 1:1 group at 4 weeks, 8 weeks, and 12 weeks after the operation, respectively. In the 1:1 group, the bone grew into the pore of the cement in the laminar arrangement and connected with the cement tightly at the 12th week after the operation

  8. Calcium phosphate composite cements based on simple mixture of brushite and apatite phases

    Science.gov (United States)

    Egorov, A. A.; Fedotov, A. Yu; Pereloma, I. S.; Teterina, A. Yu; Sergeeva, N. S.; Sviridova, I. K.; Kirsanova, V. A.; Akhmedova, S. A.; Nesterova, A. V.; Reshetov, I. V.; Barinov, S. M.; Komlev, V. S.

    2018-04-01

    The composite cements based on simple mixtures brishite and apatite with ratio 70/30, 50/50, 30/70 were developed. The processes of phase formation, microstructure and mechanical properties were studied. The kinetics of degradation in simulated body fluid depending on the microstructure and the materials phase composition was carried out. The biological test in vitro were performed using the MTT-test on the human fibroblast immortalized (hFB) cell line and the human osteosarcoma cell line MG-63. The materials didn’t have acute cytoxicity and possessed surface matrix properties. It was determined that the both line of cells actively proliferated, with viable cells values higher 20-60 % then control at all observation periods.

  9. Effects of added antibiotics on the basic properties of anti-washout-type fast-setting calcium phosphate cement.

    Science.gov (United States)

    Takechi, M; Miyamoto, Y; Ishikawa, K; Nagayama, M; Kon, M; Asaoka, K; Suzuki, K

    1998-02-01

    The effect of added antibiotics on the basic properties of anti-washout-type fast-setting calcium phosphate cement (aw-FSCPC) was investigated in a preliminary evaluation of aw-FSCPC containing drugs. Flomoxef sodium was employed as the antibiotic and was incorporated into the powder-phase aw-FSCPC at up to 10%. The setting time, consistency, wet diametral tensile strength (DTS) value, and porosity were measured for aw-FSCPC containing various amounts of flomoxef sodium. X-ray diffraction (XRD) analysis was also conducted for the identification of products. To evaluate the drug-release profile, set aw-FSCPC was immersed in saline and the released flomoxef sodium was determined at regular intervals. The spread area of the cement paste as an index of consistency of the cement increased progressively with the addition of flomoxef sodium, and it doubled when the aw-FSCPC contained 8% flomoxef sodium. In contrast, the wet DTS value decreased with increase in flomoxef sodium content. Bulk density measurement and scanning electron microscopic observation revealed that the set mass was more porous with the amount of flomoxef sodium contained in the aw-FSCPC. The XRD analysis revealed that formation of hydroxyapatite (HAP) from aw-FSCPC was reduced even after 24 h, when the aw-FSCPC contained flomoxef sodium at > or = 6%. Therefore, the decrease of wet DTS value was thought to be partly the result of the increased porosity and inhibition of HAP formation in aw-FSCPC containing large amounts of flomoxef sodium. The flomoxef sodium release from aw-FSCPC showed the typical profile observed in a skeleton-type drug delivery system (DDS). The rate of drug release from aw-FSCPC can be controlled by changing the concentration of sodium alginate. Although flomoxef sodium addition has certain disadvantageous effects on the basic properties of aw-FSCPC, we conclude that aw-FSCPC is a good candidate for potential use as a DDS carrier that may be useful in surgical operations.

  10. Using calcium silicate to regulate the physicochemical and biological properties when using β-tricalcium phosphate as bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Kao, Chia-Tze; Huang, Tsui-Hsien [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Chen, Yi-Jyun [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Dental Department, Taichung Hospital, Ministry of Health and Welfare, Taichung City, Taiwan (China); Hung, Chi-Jr [School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Department of Dentistry, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Lin, Chi-Chang, E-mail: chichang31@gmail.com [Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan (China)

    2014-10-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Regarding the formation of bone-like apatite, the diametral tensile strength as well as the ion release and weight loss of composites were compared both before and after immersions in simulated body fluid (SBF). In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on β-TCP/CS composites. The results show that the apatite deposition ability of the β-TCP/CS composites improves as the CS content is increased. For composites with more than a 60% CS content, the samples become completely covered by a dense bone-like apatite layer. At the end of the immersion period, weight losses of 24%, 32%, 34%, 38%, 41%, and 45% were observed for the composites containing 0%, 20%, 40%, 80%, 80% and 100% β-TCP cements, respectively. In addition, the antibacterial activity of CS/β-TCP composite improves as the CS-content is increased. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 60%, the quantity of cells and osteogenesis protein of hDPCs is stimulated by Si released from the β-TCP/CS composites. The degradation of β-TCP and the osteogenesis of CS give strong reason to believe that these calcium-based composite cements will prove to be effective bone repair materials. - Highlights: • CS improved the physicochemical properties and osteogenic activity of β-TCP. • Higher CS in the composite, the shorter setting time and the higher DTS was found. • With a CS more than 40%, the osteogenesis and angiogenesis proteins were promoted by

  11. EFFECT OF MgO ON THE COMPOSITION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT IN THE PRESENCE OF Na2O AND K2O

    Directory of Open Access Journals (Sweden)

    Jie Zhang

    2015-06-01

    Full Text Available The purpose of this study is to explore the effect of MgO (1 - 9 wt. % on the composition and properties of belite-barium calcium sulphoaluminate cement with additions of Na2O and K2O. The results show that 1 - 5 wt. % content of MgO can stabilize crystal types of M3-C3S, R-C3S and β-C2S. Moreover, MgO can promote the formation of C3S and C4AF, but has little effect on the formation of C2.75B1.25A3$ and C3A. The C3A/C4AF ratio is reduced by 22 % at 5 wt. % MgO, which indicates that appropriate MgO can decrease the liquid viscosity. In the presence of Na2O and K2O, the highest limit of incorporated amount of MgO is about 3 wt. %, which is higher than that in Portland cement clinker of 2 wt. %. Besides, MgO favors the formation of small C3S crystals in size of 4 - 20 μm. MgO enhances the hydration rate and mechanical property of cement at an optimal dosage (1 - 5 wt. %, beyond which an adverse effect could be resulted. At a MgO dosage of 5 wt. %, the compressive strengths of the cement at 1, 3, 7 and 28 days are 15.8, 39.3, 68.6 and 97.3 MPa, which increases by 116 %, 17 %, 10 % and 6 % respectively compared to the cement without MgO dopant. This study could lead to the effective use of magnesia-rich limestone in industrial production of belite-barium calcium sulphoaluminate cement.

  12. Umbilical cord stem cells released from alginate-fibrin microbeads inside macroporous and biofunctionalized calcium phosphate cement for bone regeneration

    Science.gov (United States)

    Chen, Wenchuan; Zhou, Hongzhi; Weir, Michael D.; Bao, Chongyun; Xu, Hockin H.K.

    2012-01-01

    The need for bone repair has increased as the population ages. The objectives of this study were to (1) develop a novel biofunctionalized and macroporous calcium phosphate cement (CPC) containing alginate-fibrin microbeads encapsulating human umbilical cord mesenchymal stem cells (hUCMSCs); and (2) investigate hUCMSC proliferation and osteogenic differentiation inside CPC for the first time. Macroporous CPC was developed using calcium phosphate powders, chitosan, and gas-foaming porogen. Five types of CPCs were fabricated: CPC control, CPC + 0.05% fibronectin (Fn), CPC + 0.1% Fn, CPC + 0.1% Arg-Gly-Asp (RGD), and CPC + 0.1% Fn + 0.1% RGD. Alginate-fibrin microbeads containing 106 hUCMSCs/mL were encapsulated in the CPC paste. After CPC had set, the degradable microbeads released hUCMSCs inside CPC. hUCMScs proliferated inside CPC, with cell density at 21 d being 4-fold that at 1 d. CPC + 0.1% RGD had the highest cell density, which was 4-fold that of CPC control. The released cells differentiated into the osteogenic lineage and synthesized bone minerals. hUCMSCs inside the CPC + 0.1% RGD construct had gene expressions of alkaline phosphatase (ALP), osteocalcin (OC) and collagen I, which were twice those of CPC control. Mineral synthesis by hUCMSCs inside the CPC + 0.1% RGD construct was 2-fold that in CPC control. RGD and Fn incorporation in CPC did not compromise the strength of CPC, which matched the reported strength of cancellous bone. In conclusion, degradable microbeads released the hUCMSCs which proliferated, differentiated and synthesized minerals inside the macroporous CPC for the first time. CPC with RGD greatly enhanced cell functions. The novel biofunctionalized and macroporous CPC-microbead-hUCMSC construct is promising for bone tissue engineering applications. PMID:22391411

  13. Thermoluminescence and sintering of ultra-pure {alpha} alumina doped with zirconium, thorium, calcium or cerium; Thermoluminescence et frittage de l'alumine {alpha} ultra-pure dopee par le zirconium, le thorium, le calcium, ou le cerium

    Energy Technology Data Exchange (ETDEWEB)

    Ferey, F

    2002-01-01

    Thermoluminescence is a technique of identification of the point defects that appear in a solid consecutively to its fabrication. The synthesis parameters of {alpha}-alumina that will be taken into account here are the atmosphere during thermal treatment (oxidising or reducing), and the effect of the dopants: zirconium, thorium, calcium or cerium. The aim of this work is to correlate the point defects to the reactivity of the powder, especially its sintering. The TL mechanisms of the dosimetric peak of {alpha}-alumina, around 200 deg C, were clarified: the trap is an aggregate of 2 point defects (V{sub al}-V{sub O}), and the recombination centre is Cr{sup 3+}. The sensibilizing effect observed for thorium, or for cerium under reducing atmosphere, is attributed to the presence of a large emission band in the blue-green domain. Chromium is the main impurity at the origin of the E' peak (360 deg C) of {alpha}-alumina. It is acting as trap and also as recombination centre. A mechanism of transfer of energy between Cr{sup 3+} and Ti{sup 4+} is also presented in order to explain the increase of the TL intensity of the E' peak when doping by a tetravalent cation. In the case of doping by calcium, TL allows the revelation of the phase CaAl{sub 12}O{sub 19}. A quenching was observed for {alpha}Al{sub 2}O{sub 3}:Ca and {alpha}Al{sub 2}O{sub 3}:Ce under reducing atmosphere. It is attributed to oxygen vacancies for the doping by calcium, and to the presence of Ce{sup 3+} for the doping by cerium. The alumina prepared under reducing conditions exhibit a perturbation of kinetics during sintering, and also abnormal grain growth in doped samples. This unusual kinetic is explained by a decrease in the concentration of aluminium vacancies under reducing atmosphere, conducting indirectly to a greater segregation of Si{sup 4+} at the grain boundaries, and to the formation of a liquid phase at the surface of grains. This phenomenon is amplified in the case of doping by

  14. Enhanced healing of rabbit segmental radius defects with surface-coated calcium phosphate cement/bone morphogenetic protein-2 scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yi; Hou, Juan; Yin, ManLi [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Wang, Jing, E-mail: biomatwj@163.com [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Liu, ChangSheng, E-mail: csliu@sh163.net [Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); The State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China); Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China)

    2014-11-01

    Large osseous defects remain a difficult clinical problem in orthopedic surgery owing to the limited effective therapeutic options, and bone morphogenetic protein-2 (BMP-2) is useful for its potent osteoinductive properties in bone regeneration. Here we build a strategy to achieve prolonged duration time and help inducting new bone formation by using water-soluble polymers as a protective film. In this study, calcium phosphate cement (CPC) scaffolds were prepared as the matrix and combined with sodium carboxymethyl cellulose (CMC-Na), hydroxypropylmethyl cellulose (HPMC), and polyvinyl alcohol (PVA) respectively to protect from the digestion of rhBMP-2. After being implanted in the mouse thigh muscles, the surface-modified composite scaffolds evidently induced ectopic bone formation. In addition, we further evaluated the in vivo effects of surface-modified scaffolds in a rabbit radius critical defect by radiography, three dimensional micro-computed tomographic (μCT) imaging, synchrotron radiation-based micro-computed tomographic (SRμCT) imaging, histological analysis, and biomechanical measurement. The HPMC-modified CPC scaffold was regarded as the best combination for segmental bone regeneration in rabbit radius. - Highlights: • A simple surface-coating method was used to fabricate composite scaffolds. • Growth factor was protected from rapid depletion via superficial coating. • Significant promotion of bone regeneration was achieved. • HPMC-modification displayed optimal effect of bone regeneration.

  15. IMPACT OF INCREASED ALUMINATE CONCENTRATIONS ON PROPERTIES OF SALTSTONE MIXES

    International Nuclear Information System (INIS)

    Harbour, J; Tommy Edwards, T; Erich Hansen, E; Vickie Williams, V

    2007-01-01

    trends observed as the aluminate concentration increased in the salt solution were decreased Bingham Plastic yield stress and plastic viscosity, greater flowability of the grout, and reduced gel times and bleed volume for SWPF based mixes. On the other hand, the set times increased significantly with increasing aluminate concentration in the salt solutions. For the SWPF mixes, the set time increased from 1 to 4 days and for the Tank 11 mixes, the set time increased from 1 to 2 days. Heat of hydration measurements were consistent with the increased set times with extended induction periods (2 to 4 days) as aluminate concentration increased in the salt solution. This extended induction period of heat evolution observed with increasing aluminate concentrations must be addressed for Saltstone operations to avoid exceeding temperature limits. It is anticipated that the induction period will be temperature dependent and should be measured for future projections and included in the thermal modeling. The overall heat generation was greater in the mixes containing higher concentrations of aluminate. In fact, for the total heat release values calculated using curve fitting for longer times, the amount of heat was increased by 33% for SWPF based solutions and by 46% for Tank 11 based solutions. The larger amount of heat from mixes containing higher aluminate concentration must be accounted for in the modeling effort which determines the pour schedule for Saltstone. The increased induction periods were shown to be associated with hydration reactions of the blast furnace slag. The rate of heat generation with high aluminate solutions and Portland cement were only accelerated whereas high aluminate mixes containing blast furnace slag only showed the characteristic increase in induction time that was observed with mixes prepared using the premix blend of cementitious materials. It was shown that fly ash does not react significantly during the first seven days of curing but then

  16. Preparation, characterization and investigation of in vitro and in vivo biological properties of strontium-modified calcium phosphate cement for bone defect repair

    Directory of Open Access Journals (Sweden)

    Reza Masaeli

    2015-12-01

    Full Text Available Background and Aims: The aim of this study was to evaluate the invitro and invivo performance of a 3 wt% of strontium additive hydroxyapatite calcium phosphate cements (CPC. Materials and Methods: The prepared calcium phosphate cement was characterized with XRD, FTIR, setting time, STA and in vitro and in vivo biological analyses. The MTT assay ALP activities as in vitro study and radiological and histological examinations as in vivo study between the three groups of 3 wt% Sr-HA/CPC, CPC and control were performed and compared. Data were analyzed using T-test and One-way ANOVA. Results: XRD analysis demonstrated that by increasing the ratio of Powder/Liquid (P/L, the crystallinity of the prepared cement increased. The substitution of strontium instead of calcium in CPC could also alter the crystal structure, including some structural disorder. However, in the CPC with no strontium hydroxyapatite (Sr-HA, no significant increase in the crystallinity was observed. SEM observations revealed CPC with increasing P/L ratio, the formation of hydroxyapatite crystals arising from the interaction of solid and liquid phase of cement was decreased. Also, the addition of Sr within Ca site culminated in a dramatic increase in crystallinity of hydroxyapatite. In vitro biological properties ascertained that addition of 3 wt. % Sr-HA into CPC enhanced MTT assay and ALP activity, which could be due to the presence of strontium ions. The histological study showed that greater remodeling was seen at 4 weeks after implantation when the 3 wt% Sr-HA/CPC was used. Conclusion: The obtained results cleared that CPC can be a potential candidate as a carrier with strontium additives for bone remodeling and regeneration.

  17. Calcium

    Science.gov (United States)

    ... You can get decent amounts of calcium from baked beans, navy beans, white beans, and others. Canned fish. You're in luck if you like sardines and canned salmon with bones. Almond milk. Working Calcium Into Your ...

  18. Human tooth germ stem cell response to calcium-silicate based endodontic cements

    Directory of Open Access Journals (Sweden)

    Esra Pamukcu Guven

    2013-07-01

    Full Text Available OBJECTIVE: The aim of this study was to compare the cytotoxic effects of endodontic cements on human tooth germ stem cells (hTGSCs. MTA Fillapex, a mineral trioxide aggregate (MTA-based, salicylate resin containing root canal sealer, was compared with iRoot SP, a bioceramic sealer, and AH Plus Jet, an epoxy resin-based root canal sealer. MATERIAL AND METHODS: To evaluate cytotoxicity, all materials were packed into Teflon rings (4 mmµ3 mm and co-cultured with hTGSCs with the aid of 24-well Transwell permeable supports, which had a pore size of 0.4 µm. Coverslips were coated with MTA Fillapex, iRoot SP and AH Plus Jet and each coverslip was placed onto the bottom of one well of a six-well plate for scanning electron microscopy (SEM analysis. Before the cytotoxicity and SEM analysis, all samples were stored at 37ºC and at 95% humidity and 5% CO2 for 24 hours to set. The cellular viability was analyzed using MTS test (3-(4,5-dimethyl-thiazol-2-yl-5-(3-carboxy-methoxy-phenyl-2-(4-sulfo-phenyl-2H-tetrazolium. The cytotoxic effects and SEM visualization of the tested materials were analyzed at 24-hour, 72-hour, one-week and two-week periods. RESULTS: On the 1st day, only MTA Fillapex caused cytotoxicity compared to negative control (NC group (p0.05. After 14 days of incubation with the test materials, MTA Fillapex exhibited significantly higher cytotoxicity compared with iRoot SP, AH Plus Jet and the NC group (P<0.008. In the SEM analysis, the highest levels of cell attachment were observed for iRoot SP and the control group. After 24 hours, MTA Fillapex reduced the number of cells attached to the surface. CONCLUSIONS: Within the limitations of this study, sealers exerted different cytotoxic effects on hTGSCs. Although all materials have exerted cellular toxicity, iRoot SP and AH Plus Jet may promote better attachment to hTGSCs.

  19. Injection laryngoplasty using BIOPEX calcium phosphate cement. The Sanokousei General Hospital experience

    International Nuclear Information System (INIS)

    Okubo, Keisuke; Shinnabe, Akihiro; Saito, Koichiro; Shiotani, Akihiro

    2008-01-01

    The calcium phosphate bone paste BIOPEX is an injectable material developed as a bone replacement that hardens into a hydroxylapatite block after injection. BIOPEX offers many advantages as a material for injection laryngoplasty: it induces little foreign-material reaction, is minimally absorbed, and is easy to prepare in the OR. Between 2004 and 2007, 14 patients, including 13 with vocal fold paralysis and 1 with severe atrophy of the vocal folds, were treated with BIOPEX-injection laryngoplasty at Sanokousei General Hospital. The injection of BIOPEX is usually performed through a direct laryngoscopy under general anesthesia, and no adverse effects were observed in any of the cases. A postoperative three-dimensional CT revealed successful injection of the BIOPEX into the paraglottic space in all cases. BIOPEX is minimally absorbed over long time periods, and this procedure results in a dramatic improvement of glottic function immediately after surgery. We consider this operative technique, which aims at medialization of the vocal fold by injection of a sclerotic agent into the lateral side of the vocal fold, as 'type I thyroplasty from inside the laryngeal framework.' (author)

  20. A Novel Injectable Magnesium/Calcium Sulfate Hemihydrate Composite Cement for Bone Regeneration

    Directory of Open Access Journals (Sweden)

    Shanchuan Zhang

    2015-01-01

    Full Text Available Objective. A novel injectable magnesium/calcium sulfate hemihydrate (Mg/CSH composite with improved properties was reported here. Methods. Composition, setting time, injectability, compressive strength, and bioactivity in simulated body fluid (SBF of the Mg/CSH composite were evaluated. Furthermore, the cellular responses of canine bone marrow stromal cells (cBMSCs and bone formation capacity after the implantation of Mg/CSH in tibia defects of canine were investigated. Results. Mg/CSH possessed a prolonged setting time and markedly improved injectability and mechanical property p<0.05. Mg/CSH samples showed better degradability than CSH in SBF after 21 days of soaking p<0.05. Moreover, the degrees of cell attachment, proliferation, and capability of osteogenic differentiation on the Mg/CSH specimens were higher than those on CSH, without significant cytotoxicity and with the increased proliferation index, ALP activity, and expression levels of integrin β1 and Coll I in cBMSCs p<0.05. Mg/CSH enhanced the efficiency of new bone formation at the tibia defect area, including the significantly elevated bone mineral density, bone area fraction, and Coll I expression level p<0.05. Conclusions. The results implied that this new injectable bone scaffold exhibited promising prospects for bone repair and had a great potential in bone tissue engineering.

  1. Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C–S–H(I)

    KAUST Repository

    Oh, Jae Eun

    2012-05-01

    This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel. © 2012 Elsevier Ltd.

  2. Microstructural and compositional change of NaOH-activated high calcium fly ash by incorporating Na-aluminate and co-existence of geopolymeric gel and C–S–H(I)

    KAUST Repository

    Oh, Jae Eun; Moon, Juhyuk; Oh, Sang-Gyun; Clark, Simon M.; Monteiro, Paulo J.M.

    2012-01-01

    This study explores the reaction products of alkali-activated Class C fly ash-based aluminosilicate samples by means of high-resolution synchrotron X-ray diffraction (HSXRD), scanning electron microscope (SEM), and compressive strength tests to investigate how the readily available aluminum affects the reaction. Class C fly ash-based aluminosilicate raw materials were prepared by incorporating Na-aluminate into the original fly ashes, then alkali-activated by 10 M NaOH solution. Incorporating Na-aluminate reduced the compressive strength of samples, with the reduction magnitude relatively constant regardless of length of curing period. The HSXRD provides evidence of the co-existence of C-S-H with geopolymeric gels and strongly suggests that the C-S-H formed in the current system is C-S-H(I). The back-scattered electron images suggest that the C-S-H(I) phase exists as small grains in a finely intermixed form with geopolymeric gels. Despite providing extra source of aluminum, adding Na-aluminate to the mixes did not decrease the Si/Al ratio of the geopolymeric gel. © 2012 Elsevier Ltd.

  3. Tantalum oxide and barium sulfate as radiopacifiers in injectable calcium phosphate-poly(lactic-co-glycolic acid) cements for monitoring in vivo degradation.

    Science.gov (United States)

    Hoekstra, Jan Willem M; van den Beucken, Jeroen J J P; Leeuwenburgh, Sander C G; Bronkhorst, Ewald M; Meijer, Gert J; Jansen, John A

    2014-01-01

    Monitoring the degradation of calcium phosphate-based bone substitute materials in vivo by means of noninvasive techniques (e.g., radiography) is often a problem due to the chemical resemblance of those substitutes with the mineral phase of bone. In the view of that, the present study aimed at enhancing the radiopacity of calcium phosphate cement enriched with poly(lactic-co-glycolic acid) (CPC-PLGA) microspheres, by adding tantalum oxide (Ta2O5) or the more traditional radiopacifier barium sulfate (BaSO4). The radiopacifying capacity of these radiopacifiers was first evaluated in vitro by microcomputed tomography (μCT). Thereafter, both radiopacifiers were tested in vivo using a distal femoral condyle model in rabbits, with subsequent ex vivo μCT analysis in parallel with histomorphometry. Addition of either one of the radiopacifiers proved to enhance radiopacity of CPC-PLGA in vitro. The in vivo experiment showed that both radiopacifiers did not induce alterations in biological performance compared to plain CPC-PLGA, hence both radiopacifiers can be considered safe and biocompatible. The histomorphometrical assessment of cement degradation and bone formation showed similar values for the three experimental groups. Interestingly, μCT analysis showed that monitoring cement degradation becomes feasible upon incorporation of either type of radiopacifier, albeit that BaSO4 showed more accuracy compared to Ta2O5. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company.

  4. Influences of doping mesoporous magnesium silicate on water absorption, drug release, degradability, apatite-mineralization and primary cells responses to calcium sulfate based bone cements

    International Nuclear Information System (INIS)

    Gu, Zhengrong; Wang, Sicheng; Weng, Weizong; Chen, Xiao; Cao, Liehu; Wei, Jie; Shin, Jung-Woog; Su, Jiacan

    2017-01-01

    In this study, composite cements containing mesoporous magnesium silicate (m-MS) and calcium sulfate (CS) were fabricated. The results revealed that the setting time of the m-MS/CS composite cements (m-MSC) slightly prolonged with the increase of m-MS content while the compressive strength suffered a little loss. The doping of m-MS improved the water absorption, drug release (vancomycin) and degradability of the m-MSC in Tris-HCl solution (pH = 7.4). In addition, addition of m-MS facilitated the apatite-mineralization of m-MSC in simulated body fluid (SBF), indicating good bioactivity. For cell cultural experiments, the results revealed that the m-MSC promoted the cells adhesion and proliferation, and improved the alkaline phosphatase (ALP) activity of MC3T3-E1 cells, revealing good cytocompatibility. It could be suggested that the m-MSC might be promising cements biomaterials for bone tissue regeneration. - Highlights: • The mesoporous magnesium silicate and calcium sulfate composite was fabricated. • The composite possessed good water absorption and drug release of vancomycin. • The bioactive composite could enhance the in vivo apatite formation in SBF. • The composite promoted cell adhesion, proliferation and osteogenic differentiation.

  5. A prospective clinical trial on the influence of a triamcinolone/demeclocycline and a calcium hydroxide based temporary cement on pain perception

    Directory of Open Access Journals (Sweden)

    Willershausen Brita

    2012-03-01

    Full Text Available Abstract Introduction The aim of this clinical trial was to compare the degree of short term post-operative irritation after application of a triamcinolone/demeclocycyline based or a calcium hydroxide based provisional cement. Methods A total of 109 patients (55 female and 54 male; mean age: 51 ± 14 years with primary or secondary dentinal caries were randomly assigned to the two treatment groups of this biomedical clinical trial (phase III. Selection criteria were good systemic health and treated teeth, which were vital and showed no symptoms of pulpitis. Up to three teeth were prepared for indirect metallic restorations, and the provisional restorations were cemented with a triamcinolone/demeclocycyline (Ledermix or a calcium hydroxide (Provicol based material. The intensity of post-operative pain experienced was documented according to the VAS (4, 12, 20, 24, and 82 h and compared to VAS baseline. Results A total of 159 teeth were treated (Ledermix: 83 teeth, Provicol: 76 teeth. The minor irritation of the teeth, experienced prior to treatment, was similar in both groups; however, 4 h after treatment this value was significantly higher in the Provicol group than in the Ledermix group (p Conclusions The patients had no long term post-operative pain experience in both groups. However, within the first hours after cementation the sensation of pain was considerably higher in the Provicol group than in the Ledermix group.

  6. Influences of doping mesoporous magnesium silicate on water absorption, drug release, degradability, apatite-mineralization and primary cells responses to calcium sulfate based bone cements

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Zhengrong [Department of Trauma Orthopaedics, Changhai Hospital, Second Military Medical University, Shanghai 200433 (China); The Department of Orthopaedics, Jing' an District Centre Hospital of Shanghai (Huashan Hospital Fudan University Jing' An Branch), 200040 (China); Wang, Sicheng [Department of Trauma Orthopaedics, Changhai Hospital, Second Military Medical University, Shanghai 200433 (China); Department of Orthopaedics, Zhongye Hospital, Shanghai 200941 (China); Weng, Weizong; Chen, Xiao; Cao, Liehu [Department of Trauma Orthopaedics, Changhai Hospital, Second Military Medical University, Shanghai 200433 (China); Wei, Jie [Key Laboratory for Ultrafine Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237 (China); Shin, Jung-Woog [Department of Biomedical Engineering, Inje University, Gimhae, 621749 (Korea, Republic of); Su, Jiacan, E-mail: jiacansu@sina.com [Department of Trauma Orthopaedics, Changhai Hospital, Second Military Medical University, Shanghai 200433 (China)

    2017-06-01

    In this study, composite cements containing mesoporous magnesium silicate (m-MS) and calcium sulfate (CS) were fabricated. The results revealed that the setting time of the m-MS/CS composite cements (m-MSC) slightly prolonged with the increase of m-MS content while the compressive strength suffered a little loss. The doping of m-MS improved the water absorption, drug release (vancomycin) and degradability of the m-MSC in Tris-HCl solution (pH = 7.4). In addition, addition of m-MS facilitated the apatite-mineralization of m-MSC in simulated body fluid (SBF), indicating good bioactivity. For cell cultural experiments, the results revealed that the m-MSC promoted the cells adhesion and proliferation, and improved the alkaline phosphatase (ALP) activity of MC3T3-E1 cells, revealing good cytocompatibility. It could be suggested that the m-MSC might be promising cements biomaterials for bone tissue regeneration. - Highlights: • The mesoporous magnesium silicate and calcium sulfate composite was fabricated. • The composite possessed good water absorption and drug release of vancomycin. • The bioactive composite could enhance the in vivo apatite formation in SBF. • The composite promoted cell adhesion, proliferation and osteogenic differentiation.

  7. High-level radioactive waste incorporation into (special) cements

    International Nuclear Information System (INIS)

    Roy, D.M.; Gouda, G.R.

    1978-01-01

    A feasibility study has demonstrated that very strong, durable, relatively impermeable cylinders may be prepared by hot pressing combinations of cements with simulated radioactive waste solids. While the properties have not been studied exhaustively, the results suggest an optional method for immobilization and isolation of radioactive waste. Samples prepared with calcium aluminate cements appeared to have properties superior to those with Portland cements. Four simulated radioactive waste compositions having high rare-earth oxide contents, and some containing a large excess of NaNO 3 , were studied. Modest temperatures [423 to 673 K (150 to 400 0 C)] were used for hot pressing at pressures from 178 to 345 MPa. Dense strong very low porosity specimens resulted when mixtures containing from 10 to 50% waste were hot pressed, incorporating also a small percentage of water. In addition, high-strength cement cylinders were prepared with the waste solid (approximately 20 wt% waste) in a separate core and were very resistant to leaching by water near its boiling point. With this configuration, even the NaNO 3 -containing wastes were resistant to leaching by water

  8. Human embryonic stem cell-encapsulation in alginate microbeads in macroporous calcium phosphate cement for bone tissue engineering

    Science.gov (United States)

    Tang, Minghui; Chen, Wenchuan; Weir, Michael D.; Thein-Han, Wahwah; Xu, Hockin H. K.

    2012-01-01

    Human embryonic stem cells (hESCs) are exciting for regenerative medicine applications because of their strong proliferative ability and multilineage differentiation capability. To date there has been no report on hESC seeding with calcium phosphate cement (CPC). The objective of this study was to investigate hESC-derived mesenchymal stem cell (hESCd-MSC) encapsulation in hydrogel microbeads in macroporous CPC for bone tissue engineering. hESCs were cultured to form embryoid bodies (EBs), and the MSCs were then migrated out of the EBs. hESCd-MSCs had surface markers characteristic of MSCs, with positive alkaline phosphatase (ALP) staining when cultured in osteogenic medium. hESCd-MSCs were encapsulated in alginate at a density of 1 million cells/mL, with an average microbead size of 207 µm. CPC contained mannitol porogen to create a porosity of 64% and macropores with size of 218 µm, with 20% absorbable fibers for additional porosity when the fibers degrade. hESCd-MSCs encapsulated in microbeads in CPC had good viability from 1 to 21 d. ALP gene expression at 21 d was 25-fold that at 1 d. Osteocalcin (OC) at 21 d was two orders of magnitude of that at 1 d. ALP activity in colorimetric p-nitrophenyl phosphate assay at 21 d was 5-fold that at 1 d. Mineral synthesis by the encapsulated hESCd-MSCs at 21 d was 7-fold that at 1 d. Potential benefits of the CPC-stem cell paste include injectability, intimate adaptation to complex-shaped bone defects, ease in contouring to achieve esthetics in maxillofacial repairs, and in situ setting ability. In conclusion, hESCd-MSCs were encapsulated in alginate microbeads in macroporous CPC showing good cell viability, osteogenic differentiation and mineral synthesis for the first time. The hESCd-MSC-encapsulating macroporous CPC construct is promising for bone regeneration in a wide range of orthopedic and maxillofacial applications. PMID:22633970

  9. Casein Phosphopeptide-Amorphous Calcium Phosphate Reduces Streptococcus mutans Biofilm Development on Glass Ionomer Cement and Disrupts Established Biofilms.

    Science.gov (United States)

    Dashper, Stuart G; Catmull, Deanne V; Liu, Sze-Wei; Myroforidis, Helen; Zalizniak, Ilya; Palamara, Joseph E A; Huq, N Laila; Reynolds, Eric C

    2016-01-01

    Glass ionomer cements (GIC) are dental restorative materials that are suitable for modification to help prevent dental plaque (biofilm) formation. The aim of this study was to determine the effects of incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into a GIC on the colonisation and establishment of Streptococcus mutans biofilms and the effects of aqueous CPP-ACP on established S mutans biofilms. S. mutans biofilms were either established in flow cells before a single ten min exposure to 1% w/v CPP-ACP treatment or cultured in static wells or flow cells with either GIC or GIC containing 3% w/w CPP-ACP as the substratum. The biofilms were then visualised using confocal laser scanning microscopy after BacLight LIVE/DEAD staining. A significant decrease in biovolume and average thickness of S. mutans biofilms was observed in both static and flow cell assays when 3% CPP-ACP was incorporated into the GIC substratum. A single ten min treatment with aqueous 1% CPP-ACP resulted in a 58% decrease in biofilm biomass and thickness of established S. mutans biofilms grown in a flow cell. The treatment also significantly altered the structure of these biofilms compared with controls. The incorporation of 3% CPP-ACP into GIC significantly reduced S. mutans biofilm development indicating another potential anticariogenic mechanism of this material. Additionally aqueous CPP-ACP disrupted established S. mutans biofilms. The use of CPP-ACP containing GIC combined with regular CPP-ACP treatment may lower S. mutans challenge.

  10. Casein Phosphopeptide-Amorphous Calcium Phosphate Reduces Streptococcus mutans Biofilm Development on Glass Ionomer Cement and Disrupts Established Biofilms.

    Directory of Open Access Journals (Sweden)

    Stuart G Dashper

    Full Text Available Glass ionomer cements (GIC are dental restorative materials that are suitable for modification to help prevent dental plaque (biofilm formation. The aim of this study was to determine the effects of incorporating casein phosphopeptide-amorphous calcium phosphate (CPP-ACP into a GIC on the colonisation and establishment of Streptococcus mutans biofilms and the effects of aqueous CPP-ACP on established S mutans biofilms. S. mutans biofilms were either established in flow cells before a single ten min exposure to 1% w/v CPP-ACP treatment or cultured in static wells or flow cells with either GIC or GIC containing 3% w/w CPP-ACP as the substratum. The biofilms were then visualised using confocal laser scanning microscopy after BacLight LIVE/DEAD staining. A significant decrease in biovolume and average thickness of S. mutans biofilms was observed in both static and flow cell assays when 3% CPP-ACP was incorporated into the GIC substratum. A single ten min treatment with aqueous 1% CPP-ACP resulted in a 58% decrease in biofilm biomass and thickness of established S. mutans biofilms grown in a flow cell. The treatment also significantly altered the structure of these biofilms compared with controls. The incorporation of 3% CPP-ACP into GIC significantly reduced S. mutans biofilm development indicating another potential anticariogenic mechanism of this material. Additionally aqueous CPP-ACP disrupted established S. mutans biofilms. The use of CPP-ACP containing GIC combined with regular CPP-ACP treatment may lower S. mutans challenge.

  11. Deterioration of the mechanical properties of calcium phosphate cements with Poly (γ-glutamic acid) and its strontium salt after in vitro degradation.

    Science.gov (United States)

    Liang, Ting; Gao, Chun-Xia; Yang, Lei; Saijilafu; Yang, Hui-Lin; Luo, Zong-Ping

    2017-11-01

    The mechanical reliability of calcium phosphate cements has restricted their clinical application in load-bearing locations. Although their mechanical strength can be improved using a variety of strategies, their fatigue properties are still unclear, especially after degradation. The evolutions of uniaxial compressive properties and the fatigue behavior of calcium phosphate cements incorporating poly (γ-glutamic acid) and its strontium salt after different in vitro degradation times were investigated in the present study. Compressive strength decreased from the 61.2±5.4MPa of the original specimen, to 51.1±4.4, 42.2±3.8, 36.8±2.4 and 28.9±3.2MPa following degradation for one, two, three and four weeks, respectively. Fatigue life under same loading condition also decreased with increasing degradation time. The original specimens remained intact for one million cycles (run-out) under a maximum stress of 30MPa. After degradation for one to four weeks, the specimens were able to withstand maximum stress of 20, 15, 10 and 10MPa, respectively until run-out. Defect volume fraction within the specimens increased from 0.19±0.021% of the original specimen to 0.60±0.19%, 1.09±0.04%, 2.68±0.64% and 7.18±0.34% at degradation time of one, two, three and four weeks, respectively. Therefore, we can infer that the primary cause of the deterioration of the mechanical properties was an increasing in micro defects induced by degradation, which promoted crack initiation and propagation, accelerating the final mechanical failure of the bone cement. This study provided the data required for enhancing the mechanical reliability of the calcium phosphate cements after different degradation times, which will be significant for the modification of load-bearing biodegradable bone cements to match clinical application. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Mineralogy and microstructure of two Mexican Portland cements for the confinement of radioactive waste

    International Nuclear Information System (INIS)

    Galicia A, E.; Badillo A, V. E.; Ramirez S, J. R.; Nava E, N.

    2014-10-01

    The cementitious materials are involved in the different stages of radioactive waste management because they are used for the waste immobilization in the container, as well as filling in the spaces between containers vaults and also as engineering barrier and construction material in civil construction site. Therefore, is necessary to have a study of commercial cement available nationwide involving solid timely analysis in order to identify which phases are responsible for confinement of radionuclides, if considered the most reactive phase -CSH- or called secondary phases. In this research the hydration products of cement are presented as well as its importance in the nuclear industry. The analysis and observation of the cement clinker and the hydration products on the manufactured pulps with two commercial cements resistant to sulphates was realized using the observation technique of solid X-ray diffraction and nuclear analytic techniques of Moessbauer spectroscopy and X-Ray Fluorescence. The results show the presence of calcium silicate hydrates in the amorphous phase and the presence of ettringite crystals and portlandite sheets is appreciated. The abundant iron phase called tetra calcium ferro aluminate has been identified by Moessbauer spectroscopy. (Author)

  13. Antibiotic-impregnated calcium phosphate cement as part of a comprehensive treatment for patients with established orthopaedic infection.

    Science.gov (United States)

    Niikura, Takahiro; Lee, Sang Yang; Iwakura, Takashi; Sakai, Yoshitada; Kuroda, Ryosuke; Kurosaka, Masahiro

    2016-07-01

    The treatment of established orthopaedic infection is challenging. While the main focus of treatment is wide surgical debridement, systemic and local antibiotic administration are important adjuvant therapies. Several reports have described the clinical use of antibiotic-impregnated calcium phosphate cement (CPC) to provide local antibiotic therapy for bone infections. However, these were all individual case reports, and no case series have been reported. We report a case series treated by a single surgeon using antibiotic-impregnated CPC as part of a comprehensive treatment plan in patients with established orthopaedic infection. We enrolled 13 consecutive patients with osteomyelitis (n = 6) or infected non-union (n = 7). Implantation of antibiotic-impregnated CPC was performed to provide local antibiotic therapy as part of a comprehensive treatment plan that also included wide surgical debridement, systemic antibiotic therapy, and subsequent second-stage reconstruction surgery. We investigated the rate of successful infection eradication and systemic/local complications. The concentration of antibiotics in the surgical drainage fluids, blood, and recovered CPC (via elution into a phosphate-buffered saline bath) were measured. The mean follow-up period after surgery was 50.4 (range, 27-73) months. There were no cases of infection recurrence during follow-up. No systemic toxicity or local complications from the implantation of antibiotic-impregnated CPC were observed. The vancomycin concentration in the fluid from surgical drainage (n = 6) was 527.1 ± 363.9 μg/mL on postoperative day 1 and 224.5 ± 198.4 μg/mL on postoperative day 2. In patients who did not receive systemic vancomycin therapy (n = 3), the maximum serum vancomycin level was antibiotic-impregnated CPC is an option to provide local antibiotic therapy as part of a comprehensive treatment plan. Copyright © 2016 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights

  14. Reliability estimate of unconfined compressive strength of black cotton soil stabilized with cement and quarry dust

    Directory of Open Access Journals (Sweden)

    Dayo Oluwatoyin AKANBI

    2017-06-01

    Full Text Available Reliability estimates of unconfined compressive strength values from laboratory results for specimens compacted at British Standard Light (BSLfor compacted quarry dust treated black cotton soil using cement for road sub – base material was developed by incorporating data obtained from Unconfined compressive strength (UCS test gotten from the laboratory test to produce a predictive model. Data obtained were incorporated into a FORTRAN-based first-order reliability program to obtain reliability index values. Variable factors such as water content relative to optimum (WRO, hydraulic modulus (HM, quarry dust (QD, cement (C, Tri-Calcium silicate (C3S, Di-calcium silicate (C2S, Tri-Calcium Aluminate (C3A, and maximum dry density (MDD produced acceptable safety index value of1.0and they were achieved at coefficient of variation (COV ranges of 10-100%. Observed trends indicate that WRO, C3S, C2S and MDD are greatly influenced by the COV and therefore must be strictly controlled in QD/C treated black cotton soil for use as sub-base material in road pavements. Stochastically, British Standard light (BSL can be used to model the 7 days unconfined compressive strength of compacted quarry dust/cement treated black cotton soil as a sub-base material for road pavement at all coefficient of variation (COV range 10 – 100% because the safety index obtained are higher than the acceptable 1.0 value.

  15. A contribution to the regeneration of ettringite as a donor of aluminous ions

    Directory of Open Access Journals (Sweden)

    Silvie Heviánková

    2005-11-01

    Full Text Available At our institute was developed a technological procedure of mine water desulphation. The metod consists of chemical precipitation by sodium aluminate and calcium hydroxide. By the application of this metod, very interesting results were obtained. The amount of SO42- anions decreased to almost zero-value, using optimal doses of the chemical reagents. The incurred sludge was subjected to the partial dissolving by sulphuric acid with the aim wiev to obtain aluminous ionts in the solution. From this solution, the aluminous ions were separated selectively by two methods. In the first case is added calcium chloride for the precipitation of sulphates. In the second case is added sodium hydroxide for the controled neutralization.

  16. Preparation and corrosion resistance of a nanocomposite plasma electrolytic oxidation coating on Mg-1%Ca alloy formed in aluminate electrolyte containing titania nano-additives

    DEFF Research Database (Denmark)

    Daroonparvar, Mohammadreza; Yajid, M. A. M.; Yusof, N. M.

    2016-01-01

    Titania nanoparticles were utilized as suspension in alkaline aluminate electrolyte to form nanocomposite coatings on magnesium alloy containing 1 wt% calcium by plasma electrolytic oxidation process. Microhardness, wettability, potentiodynamic polarization, wettability, electrochemical impedance...

  17. [An experimental study on a slow-release complex with rifampicin-polylactic-co-glycolic acid-calcium 
phosphate cement].

    Science.gov (United States)

    Wu, Jianhuang; Ding, Zhou; Lei, Qing; Li, Miao; Liang, Yan; Lu, Tao

    2016-09-28

    To prepare the slow-release complex with rifampicin (RFP)-polylactic-co-glycolic acid (PLGA)-calcium phosphate cement (CPC) (RFP-PLGA-CPC complex), and to study its physical and chemical properties and drug release properties in vitro.
 The emulsification-solvent evaporation method was adopted to prepare rifampicin polylactic acid-glycolic acid (RFP-PLGA) slow-release microspheres, which were divided into 3 groups: a calcium phosphate bone cement group (CPC group), a CPC embedded with RFP group (RFP-CPC group), and a PLGA slow-release microspheres carrying RFP and the self-curing CPC group (RFP- PLGA-CPC complex group). The solidification time and porosity of materials were determined. The drug release experiments in vitro were carried out to observe the compressive strength, the change of section morphology before and after drug release. 
 The CPC group showed the shortest solidification time, while the RFP-PLGA-CPC complex group had the longest one. There was statistical difference in the porosity between the CPC group and the RFP-CPC group (Pbehavior of the complex, which was in accordance with zero order kinetics equation F=0.168×t.
 The porosity of RFP-PLGA-CPC complex is significantly higher than that of CPC, and it can keep slow release of the effective anti-tuberculosis drugs and maintain a certain mechanical strength for a long time.

  18. Formulation of calcium dialuminate (CaO·2Al2O3 refractory cement from local bauxite

    Directory of Open Access Journals (Sweden)

    A.B. Tchamba

    2015-06-01

    Full Text Available Three types of bauxites containing aluminum hydroxide of 58.1% gibbsite and 19.3% boehmite for BX3, 95.5% of gibbsite for BX55 and 84.5% of gibbsite for BX8 were used with lime at 95% of CaO through solid state sintering in one stage to prepare a refractory clinker at 1550 °C. The powder obtained after grinding the clinker showed in the XRD curves the presence of CaO·2Al2O3 and CaO·TiO2 phases in the cement samples. The density of cement powder varied between 2.95 and 3.17 g/cm3 and the specific area of powder obtained after grinding was between 0.72 and 0.85 m2/g. The properties of hydrated cement, W/C = 0.33, after stabilization of cement components for 48 h at 105 °C were showed by XRD, DTA, DTG and SEM (C3AH6, AH3, CA2 and CaO·TiO2. The Young's modulus of the cement made varied between 35.5 and 39.4 GPa, and these Young's moduli were compared to conventional CA14M cement.

  19. High-Temperature Self-Healing and Re-Adhering Geothermal Well Cement Composites

    Science.gov (United States)

    Pyatina, T.; Sugama, T.; Boodhan, Y.; Nazarov, L.

    2017-12-01

    Self-healing cementitious materials are particularly attractive for the cases where damaged areas are difficult to locate and reach. High-temperature geothermal wells with aggressive environments impose most difficult conditions on cements that must ensure durable zonal isolation under repeated thermal, chemical and mechanical stresses. The present work evaluates matrix and carbon steel (CS) - cement interface self-healing and re-adhering properties of various inorganic cementitious composites under steam, alkali carbonate or brine environments at 270-300oC applicable to geothermal wells. The composite materials included blends based on Ordinary Portland Cement (OPC) and natural zeolites and alkali or phosphate activated composites of Calcium Aluminate Cement (CAC) with fly ash, class F. Class G cement blend with crystalline silica was used as a baseline. Compressive-strength and bond-strength recoveries were examined to evaluate self-healing and re-adhering properties of the composites after repeated crush tests followed by 5-day healing periods in these environments. The optical and scanning electron microscopes, X-ray diffraction, Fourier Transform infrared, Raman spectroscopy and EDX measurements were used to identify phases participating in the strengths recoveries and cracks filling processes. Amorphous silica-rich- and small-size crystalline phases played an important role in the healing of the tested composites in all environments. Possible ways to enhance self-healing properties of cementitious composites under conditions of geothermal wells were identified.

  20. The influence of calcium chloride on the setting time, solubility, disintegration, and pH of mineral trioxide aggregate and white Portland cement with a radiopacifier.

    Science.gov (United States)

    Bortoluzzi, Eduardo Antunes; Broon, Norberto Juárez; Bramante, Clovis Monteiro; Felippe, Wilson Tadeu; Tanomaru Filho, Mario; Esberard, Roberto Miranda

    2009-04-01

    This study evaluated the influence of addition of 10% calcium chloride (CaCl(2)) on the setting time, solubility, disintegration, and pH of white MTA (WMTA) and white Portland cement (WPC). A test of the setting time was performed following the #57 ADA specifications and a test of the final setting time according to the ASTM. For the solubility tests disintegration and pH, Teflon rings were filled with the cements and weighed after setting. After 24 h in a desiccator, they were once again weighed. Thereafter, they were immersed in MiliQ water for 24 and 72 h and 7, 14, and 28 days, with maintenance in the desiccator and weighing between periods. The pH of water in which the rings were immersed was measured immediately after contact with them and in the other periods. The addition of CaCl(2) provided a significant reduction (50%) in the initial setting time of cements. The final setting time of WMTA was reduced in 35.5% and the final setting time of WPC in 68.5%. The WMTA with CaCl(2) absorbed water and gained weight with time, except for in the 24-h period. The addition of CaCl(2) to the WPC reduced its solubility. The addition of CaCl(2) increased the pH of WMTA in the immediate period and at 24 and 72 h and for WPC in the immediate period and at 24 h. The addition of CaCl(2) to WMTA and WPC reduced the setting times and solubility of both and increased the pH of cements in the initial periods.

  1. Lithium aluminates and tritium production

    International Nuclear Information System (INIS)

    Carrera G, L.M.; Palacios G, O.; Bosch G, P.

    1997-01-01

    In this work it is studied the crystalline structure of lithium aluminates prepared by three different methods, namely: solid state reaction, humid reaction and sol-gel reaction. The analysis methods are the X-ray diffractometry and the scanning and transmission electron microscopy. This study is realized as in original materials as in irradiated materials at the TRIGA Mark reactor, to correlate the synthesis method with response of these materials to the mixed irradiation of nuclear reactor. (Author)

  2. Optimization of a Strontium Aluminate

    Energy Technology Data Exchange (ETDEWEB)

    Bone, Alexandria N. [Maryville College, TN (United States)

    2017-08-01

    Strontium aluminate with Eu2+ and Dy3+ has been at the forefront of emerging applications for storage phosphors since its discovery in 1996. In this study, the emission intensity and luminescence lifetime of SrAl2O4: Eu2+, Dy3+ were enhanced by partial substitution of Ca2+ into Sr2+ sites in the matrix.

  3. Origins of saccharide-dependent hydration at aluminate, silicate, and aluminosilicate surfaces.

    Science.gov (United States)

    Smith, Benjamin J; Rawal, Aditya; Funkhouser, Gary P; Roberts, Lawrence R; Gupta, Vijay; Israelachvili, Jacob N; Chmelka, Bradley F

    2011-05-31

    Sugar molecules adsorbed at hydrated inorganic oxide surfaces occur ubiquitously in nature and in technologically important materials and processes, including marine biomineralization, cement hydration, corrosion inhibition, bioadhesion, and bone resorption. Among these examples, surprisingly diverse hydration behaviors are observed for oxides in the presence of saccharides with closely related compositions and structures. Glucose, sucrose, and maltodextrin, for example, exhibit significant differences in their adsorption selectivities and alkaline reaction properties on hydrating aluminate, silicate, and aluminosilicate surfaces that are shown to be due to the molecular architectures of the saccharides. Solid-state (1)H, (13)C, (29)Si, and (27)Al nuclear magnetic resonance (NMR) spectroscopy measurements, including at very high magnetic fields (19 T), distinguish and quantify the different molecular species, their chemical transformations, and their site-specific adsorption on different aluminate and silicate moieties. Two-dimensional NMR results establish nonselective adsorption of glucose degradation products containing carboxylic acids on both hydrated silicates and aluminates. In contrast, sucrose adsorbs intact at hydrated silicate sites and selectively at anhydrous, but not hydrated, aluminate moieties. Quantitative surface force measurements establish that sucrose adsorbs strongly as multilayers on hydrated aluminosilicate surfaces. The molecular structures and physicochemical properties of the saccharides and their degradation species correlate well with their adsorption behaviors. The results explain the dramatically different effects that small amounts of different types of sugars have on the rates at which aluminate, silicate, and aluminosilicate species hydrate, with important implications for diverse materials and applications.

  4. Parameters of Alumina Cement and Portland Cement with Addition of Chalcedonite Meal

    Science.gov (United States)

    Kotwa, Anna

    2017-10-01

    Aluminous cement is a quick binder with special properties. It is used primarily to make non-standard monolithic components exposed to high temperatures, + 1300°C. It is also a component of adhesives and mortars. It has a very short setting time. It is characterized by rapid increase in mechanical strength and resistance to aggressive sulphates. It can be used in reinforced concrete structures. Laying of concrete, construction mortar made of alumina cement can be carried out even at temperatures of -10°C. This article discusses a comparison of the parameters of hardened mortar made of alumina cement GÓRKAL 40 and Portland cement CEM I 42.5R. The mortars contain an addition of chalcedonite meal with pozzolanic properties, with particle size of less than 0.063μm. The meal was added in amounts of 5% and 20% of cement weight. Chalcedonite meal used in the laboratory research is waste material, resulting from chalcedonite aggregate mining. It has the same properties as the rock from which it originates. We have compared the parameters of hardened mortar i.e. compressive strength, water absorption and capillarity. The addition of 20% chalcedonite meal to mortars made from aluminous cement will decrease durability by 6.1% relative to aluminous cement mortar without addition of meal. Considering the results obtained during the absorbency tests, it can be stated that the addition of chalcedonite meal reduces weight gains in mortars made with cement CEM I 42.5 R and alumina cement. Use of alumina cement without addition of meal in mortars causes an increase of mass by 248% compared to Portland cement mortars without additions, in the absorption tests. The addition of chalcedonite meal did not cause increased weight gain in the capillary action tests. For the alumina cement mortars, a lesser weight gains of 24.7% was reported, compared to the Portland cement mortar after 28 days of maturing.

  5. Polyelectrolyte addition effect on the properties of setting hydraulic cements based on calcium phosphate; Efeito da adicao de polieletrolitos sobre as propriedades de cimentos de fosfato de calcio de pega hidraulica

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Luis A. dos; Oliveira, Luci C. de; Rigo, Eliana C.S.; Boschi, Anselmo Ortega [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais; Carrodeguas, Raul Gracia [Universidad de La Habana, Habana, (Cuba). Centro de Biomateriales

    1997-12-31

    In the present work the effects of the addition of some poly electrolytes (sodium alginate and poly acrylic acid) on the solubility, crystalline phases, pH and mechanical strength under compression of three calcium phosphate cements were studied. (author) 10 refs., 2 figs., 4 tabs.

  6. The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt

    Science.gov (United States)

    Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong

    2018-01-01

    Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl2 deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl2 solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases. PMID:29758008

  7. The Evaluation of Damage Effects on MgO Added Concrete with Slag Cement Exposed to Calcium Chloride Deicing Salt.

    Science.gov (United States)

    Jang, Jae-Kyeong; Kim, Hong-Gi; Kim, Jun-Hyeong; Ryou, Jae-Suk

    2018-05-14

    Concrete systems exposed to deicers are damaged in physical and chemical ways. In mitigating the damage from CaCl₂ deicers, the usage of ground slag cement and MgO are investigated. Ordinary Portland cement (OPC) and slag cement are used in different proportions as the binding material, and MgO in doses of 0%, 5%, 7%, and 10% are added to the systems. After 28 days of water-curing, the specimens are immersed in 30% CaCl₂ solution by mass for 180 days. Compressive strength test, carbonation test, chloride penetration test, chloride content test, XRD analysis, and SEM-EDAX analysis are conducted to evaluate the damage effects of the deicing solution. Up to 28 days, plain specimens with increasing MgO show a decrease in compressive strength, an increase in carbonation resistance, and a decrease in chloride penetration resistance, whereas the S30- and S50- specimens show a slight increase in compressive strength, an increase in carbonation resistance, and a slight increase in chloride penetration resistance. After 180 days of immersion in deicing solution, specimens with MgO retain their compressive strength longer and show improved durability. Furthermore, the addition of MgO to concrete systems with slag cement induces the formation of magnesium silicate hydrate (M-S-H) phases.

  8. Temperature dependence, 0 to 40 deg. C, of the mineralogy of Portland cement paste in the presence of calcium carbonate

    International Nuclear Information System (INIS)

    Matschei, Thomas; Glasser, Fredrik P.

    2010-01-01

    Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH) 2 occur between 0 and 40 deg. C; the changes are affected by added calcite. Hydrogarnet, C 3 AH 6 , is destabilised at low carbonate contents and/or low temperatures 3 -ettringite. A nomenclature scheme is proposed and AFm-AFt phase relations are presented in isothermal sections at 5, 25 and 40 deg. C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO 3 and SO 4 for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance.

  9. Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

    Directory of Open Access Journals (Sweden)

    Moisés Frías

    2018-04-01

    Full Text Available The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12, ettringite and tetracalcium aluminate (C4AH13. The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes.

  10. Boundary conditions for diffusion in the pack-aluminizing of nickel.

    Science.gov (United States)

    Sivakumar, R.; Seigle, L. L.; Menon, N. B.

    1973-01-01

    The surface compositions of nickel specimens coated for various lengths of time in aluminizing packs at 2000 F were studied, in order to obtain information about the kinetics of the pack-cementation process in the formation of aluminide coatings. The results obtained indicate that the surface compositions of the coated nickel specimens are independent of time, at least for time between 0.5 and 20 hrs. Another important observation is that the specimens gained weight during the coating process.

  11. The role of integrin αv in proliferation and differentiation of human dental pulp cell response to calcium silicate cement.

    Science.gov (United States)

    Hung, Chi-Jr; Hsu, Hsin-I; Lin, Chi-Chang; Huang, Tsui-Hsien; Wu, Buor-Chang; Kao, Chia-Tze; Shie, Ming-You

    2014-11-01

    It has been proved that integrin αv activity is related to cell proliferation, differentiation, migration, and organ development. However, the biological functions of integrin αv in human dental pulp cells (hDPCs) cultured on silicate-based materials have not been explored. The aim of this study was to investigate the role of integrin αv in the proliferation and odontogenic differentiation of hDPCs cultured with the effect of calcium silicate (CS) cement and β-tricalcium phosphate (TCP) cement. In this study, hDPCs were cultured on CS and TCP materials, and we evaluated fibronectin (FN) secretion and integrin αv expression during the cell attachment stage. After small interfering RNA transfection targeting integrin αv, the proliferation and odontogenesis differentiation behavior of hDPCs were analyzed. The results indicate that CS releases Si ion-increased FN secretion and adsorption, which promote cell attachment more effectively than TCP. The CS cement facilitates FN and αv subintegrin expression. However, the FN adsorption and integrin expression of TCP are similar to that observed in the control dish. Integrin αv small interfering RNA inhibited odontogenic differentiation of hDPCs with the decreased formation of mineralized nodules on CS. It also down-regulated the protein expression of multiple markers of odontogenesis and the expression of dentin sialophosphoprotein protein. These results establish composition-dependent differences in integrin binding and its effectiveness as a mechanism regulating cellular responses to biomaterial surface. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  12. A simple and effective approach to prepare injectable macroporous calcium phosphate cement for bone repair: Syringe-foaming using a viscous hydrophilic polymeric solution.

    Science.gov (United States)

    Zhang, Jingtao; Liu, Weizhen; Gauthier, Olivier; Sourice, Sophie; Pilet, Paul; Rethore, Gildas; Khairoun, Khalid; Bouler, Jean-Michel; Tancret, Franck; Weiss, Pierre

    2016-02-01

    In this study, we propose a simple and effective strategy to prepare injectable macroporous calcium phosphate cements (CPCs) by syringe-foaming via hydrophilic viscous polymeric solution, such as using silanized-hydroxypropyl methylcellulose (Si-HPMC) as a foaming agent. The Si-HPMC foamed CPCs demonstrate excellent handling properties such as injectability and cohesion. After hardening the foamed CPCs possess hierarchical macropores and their mechanical properties (Young's modulus and compressive strength) are comparable to those of cancellous bone. Moreover, a preliminary in vivo study in the distal femoral sites of rabbits was conducted to evaluate the biofunctionality of this injectable macroporous CPC. The evidence of newly formed bone in the central zone of implantation site indicates the feasibility and effectiveness of this foaming strategy that will have to be optimized by further extensive animal experiments. A major challenge in the design of biomaterial-based injectable bone substitutes is the development of cohesive, macroporous and self-setting calcium phosphate cement (CPC) that enables rapid cell invasion with adequate initial mechanical properties without the use of complex processing and additives. Thus, we propose a simple and effective strategy to prepare injectable macroporous CPCs through syringe-foaming using a hydrophilic viscous polymeric solution (silanized-hydroxypropyl methylcellulose, Si-HPMC) as a foaming agent, that simultaneously meets all the aforementioned aims. Evidence from our in vivo studies shows the existence of newly formed bone within the implantation site, indicating the feasibility and effectiveness of this foaming strategy, which could be used in various CPC systems using other hydrophilic viscous polymeric solutions. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  13. Quantitative phase analysis of alumina/calcium-hexaluminate composites using neutron diffraction data and the Rietveld method

    International Nuclear Information System (INIS)

    Asmi, D.; Low, I.M.; O'Connor, B.H.; Kennedy, S.J.

    2000-01-01

    Full text: The Al 2 O 3 -CaO system is the basis of an important class of high-temperature refractories in the steel industry. It contains a number of stable intermediate compounds which include C 3 A, C 12 A 7 , CA, CA 2 , and CA 6 . These calcium aluminates are also important constituents of high alumina cement and have been used to produce high-strength and high-toughness ceramic-polymer composite materials. More recently, alumina composites containing 30 wt% CA 6 platelets have been developed by An et al which show characteristics of self-reinforcement and enhanced toughening through crack-bridging. In this paper, we describe the use of high-temperature neutron diffraction to monitor the in-situ phase formation and abundances of calcium aluminates (CA, CA 2 , and CA 6 ) in alumina composites containing 5-50 wt % CA 6 .at temperatures in the range 1000 - 1600 deg C. These composites were produced using reaction sintering of alumina and calcium oxide. For comparison purposes, control samples of pure α-alumina and CA 6 were also produced. Determination of relative phase abundances in these materials has been performed using the standardless Rietveld refinement method. Results show that the relative phase abundance of calcium aluminates in the composites increased with temperature and in proportion with the amount of calcium oxide present. The formation temperatures of CA, CA 2 , and CA 6 have been observed to occur at 1000 deg , 1200 deg, and ∼1350 deg C respectively, which agree well with results obtained from x-ray diffraction, synchrotron radiation diffraction and differential thermal analysis

  14. Cu{sup 2+}, Co{sup 2+} and Cr{sup 3+} doping of a calcium phosphate cement influences materials properties and response of human mesenchymal stromal cells

    Energy Technology Data Exchange (ETDEWEB)

    Schamel, Martha [Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, 97070 Würzburg (Germany); Bernhardt, Anne; Quade, Mandy; Würkner, Claudia [Centre for Translational Bone, Joint and Soft Tissue Research, University Hospital Carl Gustav Carus and Faculty of Medicine of Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden (Germany); Gbureck, Uwe; Moseke, Claus [Department for Functional Materials in Medicine and Dentistry, University of Würzburg, Pleicherwall 2, 97070 Würzburg (Germany); Gelinsky, Michael [Centre for Translational Bone, Joint and Soft Tissue Research, University Hospital Carl Gustav Carus and Faculty of Medicine of Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden (Germany); Lode, Anja, E-mail: anja.lode@tu-dresden.de [Centre for Translational Bone, Joint and Soft Tissue Research, University Hospital Carl Gustav Carus and Faculty of Medicine of Technische Universität Dresden, Fetscherstraße 74, 01307 Dresden (Germany)

    2017-04-01

    The application of biologically active metal ions to stimulate cellular reactions is a promising strategy to accelerate bone defect healing. Brushite-forming calcium phosphate cements were modified with low doses of Cu{sup 2+}, Co{sup 2+} and Cr{sup 3+}. The modified cements released the metal ions in vitro in concentrations which were shown to be non-toxic for cells. The release kinetics correlated with the solubility of the respective metal phosphates: 17–45 wt.-% of Co{sup 2+} and Cu{sup 2+}, but < 1 wt.-% of Cr{sup 3+} were released within 28 days. Moreover, metal ion doping led to alterations in the exchange of calcium and phosphate ions with cell culture medium. In case of cements modified with 50 mmol Cr{sup 3+}/mol β-tricalcium phosphate (β-TCP), XRD and SEM analyses revealed a significant amount of monetite and a changed morphology of the cement matrix. Cell culture experiments with human mesenchymal stromal cells indicated that the observed cell response is not only influenced by the released metal ions but also by changed cement properties. A positive effect of modifications with 50 mmol Cr{sup 3+} or 10 mmol Cu{sup 2+} per mol β-TCP on cell behaviour was observed in indirect and direct culture. Modification with Co{sup 2+} resulted in a clear suppression of cell proliferation and osteogenic differentiation. In conclusion, metal ion doping of the cement influences cellular activities in addition to the effect of released metal ions by changing properties of the ceramic matrix. - Highlights: • A brushite-forming calcium phosphate cement was modified by doping with bioactive Cu{sup 2+}, Co{sup 2+} and Cr{sup 3+} ions. • The metal ions were integrated in the cement matrix, setting was not affected. • The modified cements released the metal ions in doses non-toxic for cells. • Modification with Cr{sup 3+} ions enhanced the biocompatibility of the cement.

  15. Regulation of physicochemical properties, osteogenesis activity, and fibroblast growth factor-2 release ability of β-tricalcium phosphate for bone cement by calcium silicate

    International Nuclear Information System (INIS)

    Su, Ching-Chuan; Kao, Chia-Tze; Hung, Chi-Jr; Chen, Yi-Jyun; Huang, Tsui-Hsien; Shie, Ming-You

    2014-01-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of bone-like apatite, the diametral tensile strength, and weight loss of composites were considered before and after immersion in simulated body fluid (SBF). In addition, we also examined the effects of fibroblast growth factor-2 (FGF-2) released from β-TCP/CS composites and in vitro human dental pulp cell (hDPC) and studied its behavior. The results showed that the apatite deposition ability of the β-TCP/CS composites was enhanced as the CS content was increased. For composites with more than 50% CS contents, the samples were completely covered by a dense bone-like apatite layer. At the end of the immersion point, weight losses of 19%, 24%, 33%, 42%, and 51% were observed for the composites containing 0%, 30%, 50%, 70% and 100% β-TCP cements, respectively. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 70%, the amount of cells and osteogenesis protein of hDPCs was stimulated by FGF-2 released from β-TCP/CS composites. The combination of FGF-2 in degradation of β-TCP and osteogenesis of CS gives a strong reason to believe that these calcium-based composite cements may prove to be promising bone repair materials. - Highlights: • CS improved physicochemical properties and osteogenic activity of β-TCP. • The higher the CS in the cement, the shorter the setting time and the higher the DTS. • The cell behavior was stimulated by FGF-2 released from composite containing 50% CS. • β-TCP/CS composite with FGF-2 has optimal properties for

  16. Mechanistic study and modeling of radionuclides retention by the hydrated calcium silicates (HCS) of cements; Etude mecanistique et modelisation de la retention de radionucleides par les silicates de calcium hydrates (CSH) des ciments

    Energy Technology Data Exchange (ETDEWEB)

    Pointeau, I

    2000-09-01

    This work attempts to investigate the modelling of radioisotopes (Cs{sup +}, Pb{sup 2+}, Eu{sup 3+}) immobilization in cement matrix, in the frame of the design of engineered barrier of a deep radwaste repository. The model development concept consists of three major steps: - surface chemistry modelling of the calcium silicate hydrate CSH, used to simulate hydrated cement behaviour; - solid analysis of the batch sorption experiments: identification of the uptake mechanism; - both previous steps are used, with isotherm data, in the modelling of the radioisotopes immobilization in the CSH matrix. Final results: (all modelling are available for all the range of studied Ca/Si ratios and have been validated with predictive calculations). - A thermodynamic modelling of the CSH surface chemistry has been developed. The labile calcium and proton sorption constants on silanol sites (>SiOH) have been extracted. - Cs{sup +} is sorbed on two sites. The silanol site (weak site) has a high site density (10 sites.nm{sup -2}), which accounts for the CSH unsaturation in high [CS{sup +}]. A strong site is also identified. - Pb{sup 2+} immobilization in CSH matrix is modelled with surface equilibria and solubility equilibrium. - Eu{sup 3+} fixation has been investigated with solid analysis: Site-Selective anti Time-Resolved Luminescence Spectroscopy, XPS and SEM-EDS. Eu{sup 3+} thus does not precipitate in CSH water but is sorbed on the CSH surface (high hydroxylated environment). Europium is also (minority site) inserted in the CSH framework. (author)

  17. Calcium Sulfoaluminate Sodalite (Ca 4 Al 6 O 12 SO 4 ) Crystal Structure Evaluation and Bulk Modulus Determination

    KAUST Repository

    Hargis, Craig W.

    2013-12-12

    The predominant phase of calcium sulfoaluminate cement, Ca 4(Al6O12)SO4, was investigated using high-pressure synchrotron X-ray diffraction from ambient pressure to 4.75 GPa. A critical review of the crystal structure of Ca4(Al 6O12)SO4 is presented. Rietveld refinements showed the orthorhombic crystal structure to best match the observed peak intensities and positions for pure Ca4(Al6O 12)SO4. The compressibility of Ca4(Al 6O12)SO4 was studied using cubic, orthorhombic, and tetragonal crystal structures due to the lack of consensus on the actual space group, and all three models provided similar results of 69(6) GPa. With its divalent cage ions, the bulk modulus of Ca4(Al6O 12)SO4 is higher than other sodalites with monovalent cage ions, such as Na8(AlSiO4)6Cl2 or Na8(AlSiO4)6(OH)2·H 2O. Likewise, comparing this study to previous ones shows the lattice compressibility of aluminate sodalites decreases with increasing size of the caged ions. Ca4(Al6O12)SO4 is more compressible than other cement clinker phases such as tricalcium aluminate and less compressible than hydrated cement phases such as ettringite and hemicarboaluminate. © 2013 The American Ceramic Society.

  18. Elastic properties and strain-to-crack-initiation of calcium phosphate bone cements: Revelations of a high-resolution measurement technique.

    Science.gov (United States)

    Ajaxon, Ingrid; Acciaioli, Alice; Lionello, Giacomo; Ginebra, Maria-Pau; Öhman-Mägi, Caroline; Baleani, Massimiliano; Persson, Cecilia

    2017-10-01

    Calcium phosphate cements (CPCs) should ideally have mechanical properties similar to those of the bone tissue the material is used to replace or repair. Usually, the compressive strength of the CPCs is reported and, more rarely, the elastic modulus. Conversely, scarce or no data are available on Poisson's ratio and strain-to-crack-initiation. This is unfortunate, as data on the elastic response is key to, e.g., numerical model accuracy. In this study, the compressive behaviour of brushite, monetite and apatite cements was fully characterised. Measurement of the surface strains was done using a digital image correlation (DIC) technique, and compared to results obtained with the commonly used built-in displacement measurement of the materials testers. The collected data showed that the use of fixed compression platens, as opposed to spherically seated ones, may in some cases underestimate the compressive strength by up to 40%. Also, the built-in measurements may underestimate the elastic modulus by up to 62% as compared to DIC measurements. Using DIC, the brushite cement was found to be much stiffer (24.3 ± 2.3GPa) than the apatite (13.5 ± 1.6GPa) and monetite (7.1 ± 1.0GPa) cements, and elastic moduli were inversely related to the porosity of the materials. Poisson's ratio was determined to be 0.26 ± 0.02 for brushite, 0.21 ± 0.02 for apatite and 0.20 ± 0.03 for monetite. All investigated CPCs showed low strain-to-crack-initiation (0.17-0.19%). In summary, the elastic modulus of CPCs is substantially higher than previously reported and it is concluded that an accurate procedure is a prerequisite in order to properly compare the mechanical properties of different CPC formulations. It is recommended to use spherically seated platens and measuring the strain at a relevant resolution and on the specimen surface. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  19. Comparing the reinforcing effects of a resin modified glassionomer cement, Flowable compomer, and Flowable composite in the restoration of calcium hydroxide-treated immature roots in vitro

    Directory of Open Access Journals (Sweden)

    S Prathibha Rani

    2011-01-01

    Full Text Available One hundred and sixty human permanent central incisors were enlarged to a 120 file size after crown removal procedure to simulate immature teeth. The root canals were filled with calcium hydroxide and stored for 15 days (phase I, 30 days (phase II, 90 days (phase III, and 180 days (Phase IV. At the end of these selected time periods, calcium hydroxide was cleaned off the root canals of forty teeth that were randomly selected and obturated with gutta-percha points in the apical 2 mm of the root canals with a sealer. The specimens were further equally divided into four groups. Unrestored Group I served as control and the root canals of teeth in the other three group specimens were reinforced with resin modified glassionomer cement (RMGIC (Group II, Flowable Compomer (Group III, and Flowable Composite (Group IV, respectively, using a translucent curing post. All specimens were subjected to compressive force using an Instron Testing machine, until fracture occurred. All the materials evaluated substantially reinforced the root specimens compared to the control. At the end of 180 days, Flowable composites showed maximum reinforcement compared to the other groups; however, no significant differences were found between the reinforcement capabilities of Flowable Compomer and RMGIC.

  20. Evolution of cement based materials in a repository for radioactive waste and their chemical barrier function

    International Nuclear Information System (INIS)

    Kienzler, Bernhard; Metz, Volker; Schlieker, Martina; Bohnert, Elke

    2015-01-01

    The use of cementitious materials in nuclear waste management is quite widespread. It covers the solidification of low/intermediate-level liquid as well as solid wastes (e.g. laboratory wastes) and serves as shielding. For both high-level and intermediate-low level activity repositories, cement/concrete likewise plays an important role. It is used as construction material for underground and surface disposals, but more importantly it serves as barrier or sealing material. For the requirements of waste conditioning, special cement mixtures have been developed. These include special mixtures for the solidification of evaporator concentrates, borate binding additives and for spilling solid wastes. In recent years, low-pH cements were strongly discussed especially for repository applications, e.g. (Celine CAU DIT COUMES 2008; Garcia-Sineriz, et al. 2008). Examples for relevant systems are Calcium Silicate Cements (ordinary Portland cement (OPC) based) or Calcium Aluminates Cements (CAC). Low-pH pore solutions are achieved by reduction of the portlandite content by partial substitution of OPC by mineral admixtures with high silica content. The blends follow the pozzolanic reaction consuming Ca(OH) 2 . Potential admixtures are silica fume (SF) and fly ashes (FA). In these mixtures, super plasticizers are required, consisting of polycarboxilate or naphthalene formaldehyde as well as various accelerating admixtures (Garcia-Sineriz, et al. 2008). The pH regime of concrete/cement materials may stabilize radionuclides in solution. Newly formed alteration products retain or release radionuclides. An important degradation product of celluloses in cement is iso-saccharin acid. According to Glaus 2004 (Glaus and van Loon 2004), it reacts with radionuclides forming dissolved complexes. Apart from potentially impacting radionuclide solubility limitations, concrete additives, radionuclides or other strong complexants compete for surface sites for sorbing onto cement phases. In

  1. The effect of chemically adjusting cement compositions on leachabilities of waste ions

    International Nuclear Information System (INIS)

    Barnes, M.W.; Scheetz, B.E.; Roy, D.M.

    1986-01-01

    The chemical composition of both portland and aluminate cements was adjusted by adding amorphous silica. In the case of portland cement, the object was to react with excess portlandite and obtain an overall composition compatible with C-S-H gel or C-S-H gel + silica at low temperatures, and to obtain the tobermorite composition in order to be in equilibrium with this phase at temperatures above normal ambient. In the case of aluminate cement, the object was to be in equilibrium with more silica-rich phases. These silica-adjusted cements were used to make composites with nuclear waste forms. Leach tests showed that the silica-adjusted composites were chemically more stable than those made with as-received cement. Leach rates were lower in the case of the adjusted cements for Rb, Cs, Ca, Sr, Ba, La, Ce, Nd, Gd, Al, and Si. Only Na in the case of both portland and aluminate cements, and Mg and U in the case of aluminate cements, had greater leach rates in adjusted cements. Adjusting the composition of cements with silica is concluded to be beneficial when making composites to encapsulate nuclear waste forms

  2. Effects of Stirring and Fluid Perfusion on the In Vitro Degradation of Calcium Phosphate Cement/PLGA Composites

    NARCIS (Netherlands)

    An, J.; Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Jansen, J.A.

    2015-01-01

    In vitro degradation rates of calcium phosphate bioceramics are investigated using a large variation of soaking protocols that do not all match the dynamic conditions of the perfused physiological environment. Therefore, we studied the effect of stirring and fluid perfusion on the in vitro

  3. The influence of cement type and temperature on chloride binding in cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

    1998-01-01

    This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  4. Characterization of experimental cements with endodontic goal

    International Nuclear Information System (INIS)

    Dantas, A.M.X.; Sousa, W.J.B.; Oliveira, E.D.C.; Carrodeguas, R.G.; Fook, M.V. Lia; Universidade Estadual da Paraiba

    2017-01-01

    The present study aimed to characterize experimental endodontic cements using as comparative parameter MTA cement. Two experimental endodontic cements were assessed: one based on 95% tri-strontium aluminate and 5% gypsum (CE1) and another based on 50% Sr_3Al_2O_6 and 50% non-structural white cement (CE2). Experimental cements were manipulated and characterized by scanning electron microscopy (SEM), coupled to EDS mode, X-ray diffractometer (XRD) and Thermogravimetric (TG) analysis. Data analysis demonstrated that the particles of the materials used presented varied shapes and sizes, with similar elements and crystalline behavior. However, CE1 presented increased mass loss. Experimental cements presents similarities to MTA, nevertheless, further studies are encourage to determinate comparative properties with the commercially material. (author)

  5. Synthesis of pure Portland cement phases

    DEFF Research Database (Denmark)

    Wesselsky, Andreas; Jensen, Ole Mejlhede

    2009-01-01

    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases...... in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the The process of solid state synthesis are is described in general including practical advice on equipment and techniques. Finally In addition, some exemplary mix compositions...

  6. Corrosion of Spiral Rib Aluminized Pipe : [Summary

    Science.gov (United States)

    2012-01-01

    Large diameter, corrugated steel pipes are a common sight in the culverts that run alongside many Florida roads. Spiral-ribbed aluminized pipe (SRAP) has been widely specified by the Florida Department of Transportation (FDOT) for runoff drainage. Th...

  7. Corrosion of Spiral Rib Aluminized Pipe

    Science.gov (United States)

    2012-08-01

    Large diameter, corrugated steel pipes are a common sight in the culverts that run alongside many Florida roads. Spiral-ribbed aluminized pipe (SRAP) has been widely specified by the Florida Department of Transportation (FDOT) for runoff drainage. Th...

  8. Mineralogy and microstructure of two Mexican Portland cements for the confinement of radioactive waste; Mineralogia y microestructura de dos cementos mexicanos Portland para el confinamiento de desechos radiactivos

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E. [Universidad Autonoma del Estado de Mexico, Facultad de Ciencias, Campus El Cerrillo, Piedras Blancas, Carretera Toluca-Ixtlahuaca Km. 15.5, Estado de Mexico (Mexico); Badillo A, V. E.; Ramirez S, J. R. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Nava E, N., E-mail: nasiega_181@hotmail.com [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)

    2014-10-15

    The cementitious materials are involved in the different stages of radioactive waste management because they are used for the waste immobilization in the container, as well as filling in the spaces between containers vaults and also as engineering barrier and construction material in civil construction site. Therefore, is necessary to have a study of commercial cement available nationwide involving solid timely analysis in order to identify which phases are responsible for confinement of radionuclides, if considered the most reactive phase -CSH- or called secondary phases. In this research the hydration products of cement are presented as well as its importance in the nuclear industry. The analysis and observation of the cement clinker and the hydration products on the manufactured pulps with two commercial cements resistant to sulphates was realized using the observation technique of solid X-ray diffraction and nuclear analytic techniques of Moessbauer spectroscopy and X-Ray Fluorescence. The results show the presence of calcium silicate hydrates in the amorphous phase and the presence of ettringite crystals and portlandite sheets is appreciated. The abundant iron phase called tetra calcium ferro aluminate has been identified by Moessbauer spectroscopy. (Author)

  9. Method of producing spherical lithium aluminate particles

    International Nuclear Information System (INIS)

    Yang, L.; Medico, R.R.; Baugh, W.A.

    1983-01-01

    Spherical particles of lithium aluminate are formed by initially producing aluminium hydroxide spheroids, and immersing the spheroids in a lithium ion-containing solution to infuse lithium ions into the spheroids. The lithium-infused spheroids are rinsed to remove excess lithium ion from the surface, and the rinsed spheroids are soaked for a period of time in a liquid medium, dried and sintered to form lithium aluminate spherical particles. (author)

  10. Study of mechanical properties of calcium phosphate cement with addition of sodium alginate and dispersant; Estudo das propriedades mecanicas de cimento de fosfato de calcio com adicao de alginato de sodio e defloculante

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, J.M.; Coelho, W.T.; Thurmer, M.B.; Vieira, P.S.; Santos, L.A., E-mail: julianafernandes2@yahoo.com.br [Universidade Federal do Rio Grande do Sul (UFRS), RS (Brazil)

    2011-07-01

    Several studies in literature have shown that the addition of polymer additives and deflocculant has a strong influence on the mechanical properties of cements in general.The low mechanical strength is the main impediment to wider use of bone cement of calcium phosphate (CFCs) as the implant material, since they have mechanical strength which equals the maximum of trabecular bone.In order to evaluate the strength of a CFC compound alpha-tricalcium phosphate, sodium alginate were added (1%, 2% and 3% by weight) and dispersant ammonium polyacrylate (3%) in aqueous solution.Specimens were made and evaluated for density, porosity, crystalline phases and mechanical strength.The results show the increase of the mechanical properties of cement when added sodium alginate and dispersant. (author)

  11. Physical properties and comparative strength of a bioactive luting cement.

    Science.gov (United States)

    Jefferies, Steven; Lööf, Jesper; Pameijer, Cornelis H; Boston, Daniel; Galbraith, Colin; Hermansson, Leif

    2013-01-01

    New dental cement formulations require testing to determine physical and mechanical laboratory properties. To test an experimental calcium aluminate/glass-ionomer cement, Ceramir C and B (CC and B), regarding compressive strength (CS), film thickness (FT), net setting time (ST) and Vickers hardness. An additional test to evaluate potential dimensional change/expansion properties of this cement was also conducted. CS was measured according to a slightly modified ISO 9917:2003 for the CC and B specimens. The samples were not clamped while being exposed to relative humidity of great than 90 percent at 37 degrees C for 10 minutes before being stored in phosphate-buffered saline at 37 degrees C. For the CS, four groups were tested: Group 1-CC and B; Group 2-RelyX Luting Cement; Group 3-Fuji Plus; and Group 4-RelyX Unicem. Samples from all groups were stored for 24 hours before testing. Only CCandB was tested for ST and FT according to ISO 9917:2003. The FT was tested 2 minutes after mixing. Vickers hardness was evaluated using the CSM Microhardness Indentation Tester using zinc phosphate cement as a comparison material. Expansion testing included evaluating potential cracks in feldspathic porcelain jacket crowns (PJCs). The mean and standard deviation after 24 hours were expressed in MPa: Group 1 equals 160 plus or equal to 27; Group 2 equals 96 plus or equal to 10; Group 3 equals 138 plus or equal to 15; Group 4 equals 157 plus or equal to 10. A single-factor ANOVA demonstrated statistically significant differences between the groups (P less than 0.001). Pair-wise statistical comparison demonstrated a statistically significant difference between Groups 1 and 2. No statistically significant differences were found between other groups. The FT was 16.8 plus or equal to 0.9 and the ST was 4.8 plus or equal to 0.1 min. Vickers hardness for Ceramir C and B was 68.3 plus or equal to 17.2 and was statistically significantly higher (P less than 0.05) than Fleck's Zinc Phosphate

  12. Preparation and physical characterization of calcium sulfate cement/silica-based mesoporous material composites for controlled release of BMP-2

    Directory of Open Access Journals (Sweden)

    Tan H

    2015-07-01

    Full Text Available Honglue Tan,1 Shengbing Yang,2 Pengyi Dai,1 Wuyin Li,1 Bing Yue2 1Luoyang Orthopedics and Traumatology Institution, Luoyang Orthopedic-Traumatological Hospital, Luoyang, 2Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China Abstract: As a commonly used implant material, calcium sulfate cement (CSC, has some shortcomings, including low compressive strength, weak osteoinduction capability, and rapid degradation. In this study, silica-based mesoporous materials such as SBA-15 were synthesized and combined with CSC to prepare CSC/SBA-15 composites. The properties of SBA-15 were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherms. SBA-15 was blended into CSC at 0, 5, 10, and 20 wt%, referred to as CSC, CSC-5S (5% mass ratio, CSC-10S (10% mass ratio, and CSC-20S (20% mass ratio, respectively. Fourier-transform infrared spectroscopy and compression tests were used to determine the structure and mechanical properties of the composites, respectively. The formation of hydroxyapatite on composite surfaces was analyzed using scanning electron microscopy and X-ray diffraction after soaking in simulated body fluid. BMP-2 was loaded into the composites by vacuum freeze-drying, and its release characteristics were detected by Bradford protein assay. The in vitro degradation of the CSC/SBA-15 composite was investigated by measuring weight loss. The results showed that the orderly, nanostructured, mesoporous SBA-15 possessed regular pore size and structure. The compressive strength of CSC/SBA-15 increased with the increase in SBA-15 mass ratio, and CSC-20S demonstrated the maximum strength. Compared to CSC, hydroxyapatite that formed on the surfaces of CSC/SBA-15 was uniform and compact. The degradation rate of CSC/SBA-15 decreased with increasing

  13. Modelling of chemical evolution of low pH cements at long term

    International Nuclear Information System (INIS)

    El Bitouri, Y.; Buffo-Lacarriere, L.; Sellier, A.; Bourbon, X.

    2015-01-01

    In the context of the underground radioactive waste repository, low-pH cements were developed to reduce interactions between concrete and clay barrier. These cements contain high proportions of mineral additions like silica fume, fly ash or blast furnace slag for example. The high ratio of cement replacement by pozzolanic additions allows to reduce the pH by a global reduction of Ca/Si ratio of the hydrates (according to the one observed on CEM I pastes). In order to predict the short term development of the hydration for each component of this cement, a multiphasic hydration model, previously developed, is used. The model predicts the evolution of hydration degree of each anhydrous phase and consequently the quantity of each hydrate in paste (CH, aluminates, CSH with different Ca/Si ratios). However, this model is not suitable to determine the long term mineralogical and chemical evolution of the material, due to the internal change induced by chemical imbalance between initial hydrates. In order to evaluate the chemical characteristics of low pH cement based materials, and thus assess its chemical stability in the context of radioactive waste storage, a complementary model of chemical evolution at long term is proposed. This original model is based on 'solid-solution' principles. It assumes that the microdiffusion of calcium plays a major role to explain how the different Ca/Si ratio of initial C-S-H tends together toward a medium stabilized value. The main mechanisms and full development of the model equations are presented first. Next, a comparison of the model with experimental data issue from EDS (Energy Dispersive X-ray Spectroscopy) analysis on low pH cement allows to test the model. (authors)

  14. [Reconstruction of maxillary sinus superior wall fractures with calcium phosphate cement/recombinant human bonemorphogenetic protein 7 compound implanted material in rabbit].

    Science.gov (United States)

    Zhang, Qunhui; Yu, Feng; Zhang, Haoliang; Gong, Huicheng; Lin, Ying

    2015-11-01

    To evaluate the osteogenetic character and repairing maxillary sinus superior wall fractures capability of calcium phosphate cement (CPC) before and after combined with recombinant human bone morphogenetie protein-7(rhBMP-7). A 10 mmX5 mm bone defect in the maxillary sinus superior wall was induced by surgery in all 24 New Zealand white rabbits. These 24 rabbits were randomly divided into two groups. The defects were repaired with CPC group (n = 12) and CPC/rhBMP-7 group (n = 12). The osteogenesis of bone defect was monitored by gro'ss observation, histological examination, observation under scanning electron microscope and measurement of ALP activity at 6 and 12 weeks after the implantation. In group CPC,new bone was found to form slowly and little by little. In group CPC/rhBMP-7, however, new bone was observed to form early and massively. The ALP activity in group CPC showed significant statistical difference with that of group CPC/rhBMP-7 (P < 0.05). The CPC/rhBMP-7 composite has osteoconductibility and osteoinductibility, comparing the use of CPC/rhBMP-7 with CPC for the repair of orbital fracture, the former show obvious advantage repairing ability in maxillary sinus superior wall defect.

  15. Characterization of the calcium-fluoroaluminosilicate glass prepared by a non-hydrolytic sol-gel route for future dental application as glass ionomer cement

    Directory of Open Access Journals (Sweden)

    Alexandre Cestari

    2009-06-01

    Full Text Available Glass ionomer cements are widely employed in dentistry due to their physical, biological and mainly anti-caries properties. Glass ionomers consist of an aluminosilicate glass matrix modified with other elements, and they contain large quantities of fluorine. In this study, we report on the preparation of calcium-fluoroaluminosilicate glasses by a nonhydrolytic sol-gel route as an alternative approach to obtaining alumina-silica matrices. The glass powders were prepared via the non-hydrolytic sol-gel method, by mixing AlCl3, SiCl4, CaF2, AlF3, NaF, and AlPO4. The powders were studied by thermal analysis (TG/DTA/DSC, photoluminescence (PL, nuclear magnetic resonance (NMR27Al-29Si, and X ray diffraction (XRD. TG/DTA/DSC analyses revealed a constant mass loss due to structural changes during the heating process, which was confirmed by NMR and PL. A stable aluminosilicate matrix with potential future application as a glass ionomer base was obtained.

  16. Strontium doping promotes bioactivity of rhBMP-2 upon calcium phosphate cement via elevated recognition and expression of BMPR-IA.

    Science.gov (United States)

    Huang, Baolin; Tian, Yu; Zhang, Wenjing; Ma, Yifan; Yuan, Yuan; Liu, Changsheng

    2017-11-01

    Preserving and improving osteogenic activity of bone morphogenetic protein-2 (BMP-2) upon implants remains one of the key limitations in bone regeneration. With calcium phosphate cement (CPC) as model, we have developed a series of strontium (Sr)-doped CPC (SCPC) to address this issue. The effects of fixed Sr on the bioactivity of recombinant human BMP-2 (rhBMP-2) as well as the underlying mechanism were investigated. The results suggested that the rhBMP-2-induced osteogenic activity was significantly promoted upon SCPCs, especially with a low amount of fixed Sr (SrCO 3 content IA (BMPR-IA) to rhBMP-2 and an increased expression of BMPR-IA in C2C12 model cells. As a result, the activations of BMP-induced signaling pathways were different in C2C12 cells incubated upon CPC/rhBMP-2 and SCPCs/rhBMP-2. These findings explicitly decipher the mechanism of SCPCs promoting osteogenic bioactivity of rhBMP-2 and signify the promising application of the SCPCs/rhBMP-2 matrix in bone regeneration implants. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Effects of the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on mechanical properties of luting and lining glass ionomer cement

    Science.gov (United States)

    Heravi, Farzin; Bagheri, Hossein; Rangrazi, Abdolrasoul; Mojtaba Zebarjad, Seyed

    2016-07-01

    Recently, the addition of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) into glass ionomer cements (GICs) has attracted interest due to its remineralization of teeth and its antibacterial effects. However, it should be investigated to ensure that the incorporation of CPP-ACP does not have significant adverse effects on its mechanical properties. The purpose of this study was to evaluate the effects of the addition of CPP-ACP on the mechanical properties of luting and lining GIC. The first step was to synthesize the CPP-ACP. Then the CPP-ACP at concentrations of 1%, 1.56% and 2% of CPP-ACP was added into a luting and lining GIC. GIC without CPP-ACP was used as a control group. The results revealed that the incorporation of CPP-ACP up to 1.56%(w/w) increased the flexural strength (29%), diametral tensile strength (36%) and microhardness (18%), followed by a reduction in these mechanical properties at 2%(w/w) CPP-ACP. The wear rate was significantly decreased (23%) in 1.56%(w/w) concentration of CPP-ACP and it was increased in 2%(w/w). Accordingly, the addition of 1.56%(w/w) CPP-ACP into luting and lining GIC had no adverse effect on the mechanical properties of luting and lining GIC and could be used in clinical practice.

  18. Utilization of municipal solid waste incineration (MSWI) fly ash in blended cement

    International Nuclear Information System (INIS)

    Aubert, J.E.; Husson, B.; Sarramone, N.

    2006-01-01

    This paper is the first of a series of two articles dealing with the processes applied to MSWI fly ash with a view to reusing it safely in cement-based materials. Part 1 presents two stabilization processes and Part 2 deals with the use of the two treated fly ashes (TFA) in mortars. Two types of binder were used: an Ordinary Portland Cement (OPC) containing more than 95% clinker (CEM I 52.5R) and a binary blend cement composed of 70% ground granulated blast furnace slag and 30% clinker (CEM III-B 42.5N). In this first part, two stabilization processes are presented: the conventional process, called 'A', based on the washing, phosphation and calcination of the ash, and a modified process, called 'B', intended to eliminate metallic aluminum and sulfate contained in the ash. The physical, chemical and mineralogical characteristics of the two TFA were comparable. The main differences observed were those expected, i.e. TFA-B was free of metallic aluminum and sulfate. The mineralogical characterization of the two TFAs highlighted the presence of large amounts of a calcium aluminosilicate phase taking two forms, a crystalline form (gehlenite) and an amorphous form. Hydration studies on pastes containing mixed TFA and calcium hydroxide showed that this phase reacted with calcium hydroxide to form calcium aluminate hydrates. This formation of hydrates was accompanied by a hardening of the pastes. These results are very encouraging for the reuse of such TFA in cement-based materials because they can be considered as pozzolanic additions and could advantageously replace a part of the cement in cement-based materials. Finally, leaching tests were carried out to evaluate the environmental impact of the two TFAs. The elements which were less efficiently stabilized by process A were zinc, cadmium and antimony but, when the results of the leaching tests were compared with the thresholds of the European landfill directive, TFA-A could nevertheless be accepted at landfills for non

  19. Utilization of municipal solid waste incineration (MSWI) fly ash in blended cement

    Energy Technology Data Exchange (ETDEWEB)

    Aubert, J.E. [Laboratoire Materiaux et Durabilite des Constructions (L.M.D.C.), INSA-UPS, 135 avenue de Rangueil, 31077 Toulouse cedex 4 (France)]. E-mail: aubert@insa-toulouse.fr; Husson, B. [Laboratoire Materiaux et Durabilite des Constructions (L.M.D.C.), INSA-UPS, 135 avenue de Rangueil, 31077 Toulouse cedex 4 (France); Sarramone, N. [Laboratoire Materiaux et Durabilite des Constructions (L.M.D.C.), INSA-UPS, 135 avenue de Rangueil, 31077 Toulouse cedex 4 (France)

    2006-08-25

    This paper is the first of a series of two articles dealing with the processes applied to MSWI fly ash with a view to reusing it safely in cement-based materials. Part 1 presents two stabilization processes and Part 2 deals with the use of the two treated fly ashes (TFA) in mortars. Two types of binder were used: an Ordinary Portland Cement (OPC) containing more than 95% clinker (CEM I 52.5R) and a binary blend cement composed of 70% ground granulated blast furnace slag and 30% clinker (CEM III-B 42.5N). In this first part, two stabilization processes are presented: the conventional process, called 'A', based on the washing, phosphation and calcination of the ash, and a modified process, called 'B', intended to eliminate metallic aluminum and sulfate contained in the ash. The physical, chemical and mineralogical characteristics of the two TFA were comparable. The main differences observed were those expected, i.e. TFA-B was free of metallic aluminum and sulfate. The mineralogical characterization of the two TFAs highlighted the presence of large amounts of a calcium aluminosilicate phase taking two forms, a crystalline form (gehlenite) and an amorphous form. Hydration studies on pastes containing mixed TFA and calcium hydroxide showed that this phase reacted with calcium hydroxide to form calcium aluminate hydrates. This formation of hydrates was accompanied by a hardening of the pastes. These results are very encouraging for the reuse of such TFA in cement-based materials because they can be considered as pozzolanic additions and could advantageously replace a part of the cement in cement-based materials. Finally, leaching tests were carried out to evaluate the environmental impact of the two TFAs. The elements which were less efficiently stabilized by process A were zinc, cadmium and antimony but, when the results of the leaching tests were compared with the thresholds of the European landfill directive, TFA-A could nevertheless be accepted at

  20. The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement.

    Science.gov (United States)

    Coleman, Nichola J; Li, Qiu

    2013-01-01

    Zirconium oxide has been identified as a candidate radiopacifying agent for use in Portland cement-based biomaterials. During this study, the impact of 20 wt.% zirconium oxide on the hydration and setting reactions of white Portland cement (WPC) was monitored by powder X-ray diffraction (XRD), (29)Si and (27)Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), transmission electron microscopy (TEM) and Vicat apparatus. The presence of 20 wt.% zirconium oxide particles in the size-range of 0.2 to 5 μm was found to reduce the initial and final setting times of WPC from 172 to 147 min and 213 to 191 min, respectively. Zirconium oxide did not formally participate in the chemical reactions of the hydrating cement; however, the surface of the zirconium oxide particles presented heterogeneous nucleation sites for the precipitation and growth of the early C-S-H gel products which accelerated the initial setting reactions. The presence of zirconium oxide was found to have little impact on the development of the calcium (sulpho)aluminate hydrate phases. Copyright © 2012 Elsevier B.V. All rights reserved.

  1. X-ray spectra and theoretical elastic properties of crystalline calcium silicate hydrates: comparison with cement hydrated gels

    Directory of Open Access Journals (Sweden)

    Ayuela, A.

    2010-09-01

    Full Text Available For 22 crystalline Calcium Silicates Hydrates, we have calculated their structure and their elastic properties by atomistic force field methods as well as simulate their Xray diffraction patterns. From the computed Young moduli, it can be suggested that the key parameters to determine the elastic properties of crystalline Calcium Silicate Hydrates are densities and water content. We have compared these trends with those of cementitious C-S-H gel and synthetic C-S-H type I as a function of their C/S ratios and nominal water content. Our comparison show that the experimentally suggested values of density and Young moduli for C-S-H gel lie in the range of the calculated CSH crystals. However, we conclude that a detailed correspondence might require investigating structurally within CSH gels the role of water and especially of Ca and Si sites through their C/S ratio.

    En este trabajo se han calculado para 22 Silicatos Cálcicos Hidratados cristalinos, su estructura y sus propiedades elásticas mediante métodos atomísticos “force field”, así como simulado sus espectros de difracción de rayos X. De los módulos de Young calculados se puede deducir, que los parámetros clave que determinan las propiedades elásticas de los Silicatos Cálcicos Hidratados cristalinos son la densidad y el contenido en agua. Nuestros resultados muestran que los valores experimentales de la densidad y de los módulos de Young para el gel C-S-H están dentro del rango de los cristales de CSH calculados. Sin embargo, podemos concluir que para establecer una correlación más directa sería necesario investigar el papel que juegan el agua y sobre todo el Ca y Si, mediante la relación C/S, en la estructura del gel CSH.

  2. Hydration of refractory cements, with spinel phase generated in-situ

    International Nuclear Information System (INIS)

    Lavat, A.E; Grasselli, M.C; Giuliodori Lovecchio, E

    2008-01-01

    High alumina refractory materials with additions of synthetic spinel (MgAl 2 O 4 ) have good thermo mechanical and attack from slag properties, which are useful in many technological applications. The spinel phase generated in-situ, MA, has proven to be a suitable and economic alternative to the use of sintered or electrocast spinels. Prior studies have established synthesis conditions for refractory cements with the spinel phase generated in-situ (CCAMA) starting with alumina mixtures and Buenos Aires dolomites. The binding properties of the aluminous cements depend on the hydrated calcium aluminates that form in the setting and hardening stages of the pastes. To avoid breaks, the refractory material must undergo programmed heating before reaching the serviceable temperature. It should also include the present phases and the transformations that occur at different temperatures. In this context knowledge about the green mineral composition and its response to an increase in temperature is especially important. This work presents studies to define the composition of CCAMA cement mortars at different hydration ages, and to estimate phase proportions and behavior during dehydration. DRX and FTIR techniques are applied in order to follow the structural changes that take place during the hydration process. The evolution of the dehydration is also studied, mostly using FTIR. The mortars were prepared with a water/cement ration of 0.5, recommended for this kind of work. The hydration was carried out at room temperature and samples were analyzed at the following ages: 15 min.; 1 h.; 1, 3, 7, 14, 28, 60 and 90 days. With the results the evolution of the phases as a function of the age of the hydration were studied. The main hydrate that was formed was CAH 10 , with a significantly increased proportion during the first 14 days of hydration. Its carbonation was also observed by the presence of calcium carboaluminates and the formation of gibbsite. The MA phase is also

  3. The synergistic effects of CO2 laser treatment with calcium silicate cement of antibacterial, osteogenesis and cementogenesis efficacy

    International Nuclear Information System (INIS)

    Hsu, T-T; Yang, J-J; Kao, C-T; Huang, T-H; Chen, Y-W; Shie, M-Y

    2015-01-01

    Calcium silicate-based material (CS) has been successfully used in dental clinical applications. Some researches show that the antibacterial effects of CO 2 laser irradiation are highly efficient when bacteria are embedded in biofilm, due to a photo-thermal mechanism. The purpose of this study was to confirm the effects of CO 2 laser irradiation on CS, with regard to both material characterization and human periodontal ligament cell (hPDLs) viability. CS was irradiated with a dental CO 2 laser using directly mounted fiber optics in wound healing mode with a spot area of 0.25 cm 2 , and then stored in an incubator at 100% relative humidity and 37 °C for 1 d to set. The hPDLs cultured on CS were analyzed, along with their proliferation and odontogenic differentiation behaviors. The results indicate that the CO 2 laser irradiation increased the amount of Ca and Si ions released from the CS, and regulated cell behavior. CO 2 laser-irradiated CS promoted cementogenic differentiation of hPDLs, with the increased formation of mineralized nodules on the substrate’s surface. It also up-regulated the protein expression of multiple markers of cementogenic and the expression of cementum attachment protein. The current study provides new and important data about the effects of CO 2 laser irradiation on CS. Taking cell functions into account, the Si concentration released from CS with laser irradiated may be lower than a critical value, and this information could lead to the development of new regenerative therapies for dentin and periodontal tissue. (letter)

  4. The synergistic effects of CO2 laser treatment with calcium silicate cement of antibacterial, osteogenesis and cementogenesis efficacy

    Science.gov (United States)

    Hsu, T.-T.; Kao, C.-T.; Chen, Y.-W.; Huang, T.-H.; Yang, J.-J.; Shie, M.-Y.

    2015-05-01

    Calcium silicate-based material (CS) has been successfully used in dental clinical applications. Some researches show that the antibacterial effects of CO2 laser irradiation are highly efficient when bacteria are embedded in biofilm, due to a photo-thermal mechanism. The purpose of this study was to confirm the effects of CO2 laser irradiation on CS, with regard to both material characterization and human periodontal ligament cell (hPDLs) viability. CS was irradiated with a dental CO2 laser using directly mounted fiber optics in wound healing mode with a spot area of 0.25 cm2, and then stored in an incubator at 100% relative humidity and 37 °C for 1 d to set. The hPDLs cultured on CS were analyzed, along with their proliferation and odontogenic differentiation behaviors. The results indicate that the CO2 laser irradiation increased the amount of Ca and Si ions released from the CS, and regulated cell behavior. CO2 laser-irradiated CS promoted cementogenic differentiation of hPDLs, with the increased formation of mineralized nodules on the substrate’s surface. It also up-regulated the protein expression of multiple markers of cementogenic and the expression of cementum attachment protein. The current study provides new and important data about the effects of CO2 laser irradiation on CS. Taking cell functions into account, the Si concentration released from CS with laser irradiated may be lower than a critical value, and this information could lead to the development of new regenerative therapies for dentin and periodontal tissue.

  5. Casein Aggregates Built Step-by-Step on Charged Polyelectrolyte Film Surfaces Are Calcium Phosphate-cemented*

    Science.gov (United States)

    Nagy, Krisztina; Pilbat, Ana-Maria; Groma, Géza; Szalontai, Balázs; Cuisinier, Frédéric J. G.

    2010-01-01

    The possible mechanism of casein aggregation and micelle buildup was studied in a new approach by letting α-casein adsorb from low concentration (0.1 mg·ml−1) solutions onto the charged surfaces of polyelectrolyte films. It was found that α-casein could adsorb onto both positively and negatively charged surfaces. However, only when its negative phosphoseryl clusters remained free, i.e. when it adsorbed onto a negative surface, could calcium phosphate (CaP) nanoclusters bind to the casein molecules. Once the CaP clusters were in place, step-by-step building of multilayered casein architectures became possible. The presence of CaP was essential; neither Ca2+ nor phosphate could alone facilitate casein aggregation. Thus, it seems that CaP is the organizing motive in the casein micelle formation. Atomic force microscopy revealed that even a single adsorbed casein layer was composed of very small (in the range of tens of nanometers) spherical forms. The stiffness of the adsorbed casein layer largely increased in the presence of CaP. On this basis, we can imagine that casein micelles emerge according to the following scheme. The amphipathic casein monomers aggregate into oligomers via hydrophobic interactions even in the absence of CaP. Full scale, CaP-carrying micelles could materialize by interlocking these casein oligomers with CaP nanoclusters. Such a mechanism would not contradict former experimental results and could offer a synthesis between the submicelle and the block copolymer models of casein micelles. PMID:20921229

  6. The impact of zirconium oxide radiopacifier on the early hydration behaviour of white Portland cement

    International Nuclear Information System (INIS)

    Coleman, Nichola J.; Li, Qiu

    2013-01-01

    Zirconium oxide has been identified as a candidate radiopacifying agent for use in Portland cement-based biomaterials. During this study, the impact of 20 wt.% zirconium oxide on the hydration and setting reactions of white Portland cement (WPC) was monitored by powder X-ray diffraction (XRD), 29 Si and 27 Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), transmission electron microscopy (TEM) and Vicat apparatus. The presence of 20 wt.% zirconium oxide particles in the size-range of 0.2 to 5 μm was found to reduce the initial and final setting times of WPC from 172 to 147 min and 213 to 191 min, respectively. Zirconium oxide did not formally participate in the chemical reactions of the hydrating cement; however, the surface of the zirconium oxide particles presented heterogeneous nucleation sites for the precipitation and growth of the early C-S-H gel products which accelerated the initial setting reactions. The presence of zirconium oxide was found to have little impact on the development of the calcium (sulpho)aluminate hydrate phases. - Highlights: ► This is the first study of Portland cement-based biomaterials by 27 Al and 29 Si NMR. ► 20 wt.% ZrO 2 radiopacifier accelerates the early cement hydration reactions. ► Extent of hydration after 6 h is increased from 5.7% to 15% in the presence of ZrO 2 . ► Initial and final setting times are reduced by 25 and 22 min, respectively. ► ZrO 2 provides nucleation sites for the precipitation of early hydration products.

  7. Structural study and crystallography of the major compound of anhydrous cement: tri-calcium silicate; Etude structurale et cristallographie du compose majoritaire du ciment anhydre: le silicate tricalcique

    Energy Technology Data Exchange (ETDEWEB)

    Noirfontaine, M.N. de

    2000-01-01

    Anhydrous (Portland) cement is mainly composed of a synthetic material, the clinker, whose major compound is tri-calcium silicate (Ca{sub 3}SiO{sub 5}), often referred as C{sub 3}S with the compact oxides notations, C = CaO et S = SiO{sub 2}. The polymorphism of C{sub 3}S, still not well known, is the main subject of the thesis. Various crystal structures (rhombohedral R, monoclinic M1, M2, M3 and triclinic T1, T2, T3) can be found, depending on temperature and impurities. The only known structures are T1, M1 and M3, involving large unit cells with an orientational disorder of silicate tetrahedra. The single crystal studies exhibit no clear relation between the various polymorphs. Starting from known results from literature single crystal experiments, we establish the metric and structural relations between the different structures. Averaged structures for the T1, M1 and M3 polymorphs are proposed, together with all the matrices of transformation between the unit cells. We also introduce new 1-D, 2-D, and 3-D structural units, which make easier the understanding of the structures of C{sub 3}S, with the result of a better description of the orientational disorder. The effects of impurities on the structure are discussed. In industrial clinkers, impurities stabilize mainly M1 and M3 monoclinic forms. We propose a space group (Pc) and two structural models (a superstructure and an approximate averaged structure) for the M1 form. All the models are validated on synthetic compounds (M3, M2, M1 et T1) and industrial clinkers analysed by X-Ray powder diffraction with Rietveld analysis. (author)

  8. Experimental survey on percutaneous injection of calcium phosphate cement in preventing the articular surface collapsing secondary to avascular necrosis of femoral head

    International Nuclear Information System (INIS)

    Hou Changlong; Lv Weifu; Zhang Xuebin; Wang Weiyu; Zhang Xingming

    2007-01-01

    Objective: To study the technical way for animal model of ANFH with TAE (transcatheter arterial embolization)and to observe the image and pathologic changes of percutaneous injection with CPC (Calcium Phosphate Cement)in preventing the articular surface collapsing secondary to ANFH (avascular necrosis of femoral head)in pigs and its feasibility and safety. Methods: Branch arteries of the pig's left femoral head were embolized with woolly threads. Twenty pigs were randomly divided into A and B groups, and after about 1 month changes were assessed by imagings. Group A(n=8)was served as control of model contrast group, with only TAE and then surveyed the avascular necrosis features of femoral head by imaging together with pathologic and histologic examinations. Group B (n=12) was designated as percutaneous injection with CPC for interventional treatment group of ANFH at the stage Ficat II. Results: The animal models of ANFH in early stage were established by embolization of feeding arteries. In Group A, bone collapse occurred in 1.5 months after TAE, with imaging features of femoral head necrosis aggravated gradually. In group B, technical success of percutaneous injection with CPC was high and technical criteria included precise injection time, vigorous percutaneous fixing of bone, suitable proportion of CPC powder to liquid. CT scan of femoral head with injection CPC showed that it diffused well. Volume of bone trabecula (TBV)and percentage of bone lacuna (PBL)at unit area under microscopy were also inspected in two groups. TBV and PBL of two groups were compared in different special times and calculated especially for group B (P<0.05). Conclusion: The percutaneous injection of CPC to femoral head is a quite safe and effective palliative therapy for ANFH in early stage. (authors)

  9. Influence of the mineralogical composition of cement in the diffusion of chemical species

    International Nuclear Information System (INIS)

    Galicia A, E.

    2015-01-01

    , color and others. Portland cements commonly used in the construction industry, they are based primarily on the mineral phases of limestone and silica. In conventional cement admixtures the chemical reactivity depends on the ratio of tricalcium and dicalcium silicate (C 3 S/C 2 S), the tricalcium aluminate (C 3 A) influences in the setting time and tetra calcium ferro aluminate (C 4 AF) gives a different color to the cement. In this research the mineralogical composition of two commercial cements is studied and its influence on the phenomenon of radionuclides retention. For this particular concrete discs were manufactured with water, sand and two commercial cements: Tolteca Extra CPC 30-RRS and Cruz Azul CPC Type II 30-R. The solid observation techniques used for analysis of the cement paste and concrete they are: X-ray Diffraction and Scanning Electron Microscopy, as well as the nuclear analytic techniques of Moessbauer and X-ray Fluorescence. (Author)

  10. Cermet cements.

    Science.gov (United States)

    McLean, J W

    1990-01-01

    Cermet ionomer cements are sintered metal/glass powders, which can be made to react with poly(acids). These new cements are significantly more resistant to abrasion than regular glass ionomer cements and are widely accepted as core build-up materials and lining cements. They can strengthen teeth and provide the clinician with an opportunity to treat early dental caries.

  11. Mise en valeur de l'andalousite dans des betons a haute teneur en alumine

    Science.gov (United States)

    Rebouillat, Lionel

    alumina with silicon carbide, with and without calcium aluminate cement. For a weight amount of 0% or 4% of ultrafine andalusite, with a 25wt% of coarse andalusite grains base, the theoretical mullitization potential is very nearly reached. (Abstract shortened by UMI.)

  12. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Macphee, D.; McCulloch, C.E.; Angus, M.J.

    1985-06-01

    The kinetics of reaction between cement and clinoptilolite are elucidated and rate equations containing temperature dependent constants derived for this reaction. Variations in clinoptilolite particle size and their consequences to reactivity are assessed. The presence of pozzolanic agents more reactive than clinoptilolite provides sacrificial agents which are partially effective in lowering the clinoptilolite reactivity. Blast furnace slag-cements have been evaluated and the background literature summarized. Experimental studies of the pore fluid in matured slag-cements show that they provide significantly more immobilization for Cs than Portland cement. The distribution of Sr in cemented waste forms has been examined, and it is shown that most of the chemical immobilization potential in the short term is likely to be associated with the aluminate phases. The chemical and structural nature of these are described. Carbonation studies on real cements are summarized. (author)

  13. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Macphee, D.; McCulloch, C.E.; Angus, M.J.

    1984-01-01

    Model studies of the behaviour of cement systems have been advanced by considering the nature of the phases formed during hydration and deriving pH-composition models for the CaO-SiO 2 -H 2 O system. Preliminary results of Esub(h) measurements are also reported. Leach tests on Sr from cements are interpreted in terms of Sr retention mechanisms. Present results indicate that the aluminate phases in OPC contribute to the chemical retentivity. Studies on cement-clinoptilolite reactions, made using coarse grained clinoptilolite are reported: ferrierite also reacts chemically with cement. Two critical surveys are presented, together with new data: one on the potential of blended cements, the other on cement durability in CO 2 -containing environments. (author)

  14. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Macphee, D.; Angus, M.J.; Atkins, M.; Dept. of Chemistry)

    1985-01-01

    A solubility model of the system CaO-SiO 2 -H 2 O is developed which takes account of the state of Si polymerization in the solid. Free energies of formations of its bonding hydrogel are tabulated. The internal redox conditions in cements have been measured; in particular, slags lower the Esub(eta) relative to OPC. The fate of Sr and U in cement systems has been determined; Sr is incorporated in the aluminate phases, while U 6+ is precipitated as Ca-U-O-H 2 O phases. Lowering the internal Esub(eta) reduces U solubility. Studies of the carbonation of slag-cement blends are reported. (author)

  15. Lithium aluminate spheroids prepared by emulsion procedure

    International Nuclear Information System (INIS)

    Mateos, A.G.; DiBello, P.M.; Zaleski, A.B.

    1991-01-01

    Lithium aluminate powders were prepared by emulsion evaporation method. The procedure involved preparation of water-in-oil emulsion, with the aqueous phase being a solution of Li and Al nitrates. The mixed salts precursor crystallized to gamma-LiAlO 2 at 700C. Single phase LiAlO 2 occurred as μm spherical particles with average crystallite size of 81 angstrom and surface area of 14 M 2 /g. After prolonged heating at 900C, the aluminate powder crystallite size grew by 5 times with a reduction in particle porosity. The emulsion technique promotes close control of particle size and shape of product and the technique facilitates chemical reaction of constituents and sinterability of resulting product

  16. Nanoscaled Mechanical Properties of Cement Composites Reinforced with Carbon Nanofibers

    OpenAIRE

    Barbhuiya, Salim; Chow, PengLoy

    2017-01-01

    This paper reports the effects of carbon nanofibers (CNFs) on nanoscaled mechanical properties of cement composites. CNFs were added to cement composites at the filler loading of 0.2 wt % (by wt. of cement). Micrographs based on scanning electron microscopy (SEM) show that CNFs are capable of forming strong interfacial bonding with cement matrices. Experimental results using nanoindentation reveal that the addition of CNFs in cement composites increases the proportions of high-density calcium...

  17. Equilibrium leaching of toxic elements from cement stabilized soil.

    Science.gov (United States)

    Voglar, Grega E; Leštan, Domen

    2013-02-15

    The toxicity characteristics leaching procedure (TCLP) is commonly used to assess the efficiency of solidification/stabilization (S/S) of pollutants in wastes, despite recent objections to this method. In this study, formulations of 7, 10, 15 and 20% (w/w) of calcium aluminate cement (CAC) and sulfate resistant Portland cement (SRC) were used for S/S of soil from brownfield contaminated with 43,149, 10,115, 7631, 6130, 90, 82 mg kg(-1) of Zn, Pb, Cu, As, Cd and Ni, respectively. CAC produced S/S soil monoliths of higher mechanical strength (up to 7.65 N mm(-2)). Mass-transfer analysis indicated surface wash-off as a mechanism of toxic elements release, and equilibrium leaching as a crucial parameter of S/S efficiency assessment. In the expected range of field soil pH after S/S (pH 7-9), the TCLP gave markedly different results than the multi-point pH equilibrium leaching method (using nine targeted pH values): up to 2953-, 94-, 483-, 1.3-, 27- and 1.5-times more Zn, Pb, Cu, As, Cd and Ni, respectively, was determined in the TCLP leachate. S/S with CAC reduced leachability of toxic elements more effectively than SRC. Our results indicate that, under given field conditions, the TCLP significantly underrates the efficiency of S/S of contaminated soil with cementitious binders. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

    Science.gov (United States)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

    A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

  19. Magnesium: Origin and role in calcium-treated inclusions

    CSIR Research Space (South Africa)

    Pistorius, CP

    2006-08-01

    Full Text Available Calcium treatment of alumina inclusions, to convert the alumina to molten or partially molten calcium aluminates, is a well-established treatment for steel, to improve the castability of aluminium-killed steel. However, the role of magnesium...

  20. Design of a cement-based formulation for the conditioning of a NaNO3-rich intermediate-level long-lived radioactive effluent using a surrogate

    International Nuclear Information System (INIS)

    Coppens, E.; Antonucci, P.; Cau dit Coumes, C.

    2015-01-01

    Since the immobilization of concentrates in a bituminous matrix has been abandoned in Belgium in the late nineties, CEA and ONDRAF/NIRAS recently started developing an alternative conditioning technique for a historic radioactive effluent, rich in NaNO 3 . Multiple ways of treatment - in the domain of homogeneous cementation - were tested on a non-radioactive simulant of this aqueous waste stream, but due to its very low pH (∼ 0), the solution has to be neutralized to a higher pH in order to make it more compatible with general hydraulic binders. Therefore the research started by looking for a suitable base (i.e. KOH, NaOH or Ca(OH) 2 ) to neutralize the stream. Due to the formation of a viscous gel in different pH-domains, the resulting neutralization curve was separated in multiple areas of interest, i.e. those areas resulting in a highly liquid, water-like product. Only in a next step the research focused on selecting a suitable hydraulic binder (e.g. OPC, blended cement (OPC / blast-furnace slag with high contents of slag), KOH-activated slag, Fondu calcium aluminate cement). In a third step, two final formulations were established taking into account the specifications for grout implementation at industrial scale and further management of the waste packages. (authors)

  1. The Effect of TiO₂ Doped Photocatalytic Nano-Additives on the Hydration and Microstructure of Portland and High Alumina Cements.

    Science.gov (United States)

    Pérez-Nicolás, María; Navarro-Blasco, Íñigo; Fernández, José M; Alvarez, José Ignacio

    2017-10-14

    Mortars with two different binders (Portland cement (PC) and high alumina cement (HAC)) were modified upon the bulk incorporation of nano-structured photocatalytic additives (bare TiO₂, and TiO₂ doped with either iron (Fe-TiO₂) or vanadium (V-TiO₂)). Plastic and hardened state properties of these mortars were assessed in order to study the influence of these nano-additives. Water demand was increased, slightly by bare TiO₂ and Fe-TiO₂, and strongly by V-TiO₂, in agreement with the reduction of the particle size and the tendency to agglomerate. Isothermal calorimetry showed that hydration of the cementitious matrices was accelerated due to additional nucleation sites offered by the nano-additives. TiO₂ and doped TiO₂ did not show pozzolanic reactivity in the binding systems. Changes in the pore size distribution, mainly the filler effect of the nano-additives, accounted for the increase in compressive strengths measured for HAC mortars. A complex microstructure was seen in calcium aluminate cement mortars, strongly dependent on the curing conditions. Fe-TiO₂ was found to be homogeneously distributed whereas the tendency of V-TiO₂ to agglomerate was evidenced by elemental distribution maps. Water absorption capacity was not affected by the nano-additive incorporation in HAC mortars, which is a favourable feature for the application of these mortars.

  2. The Effect of TiO2 Doped Photocatalytic Nano-Additives on the Hydration and Microstructure of Portland and High Alumina Cements

    Directory of Open Access Journals (Sweden)

    María Pérez-Nicolás

    2017-10-01

    Full Text Available Mortars with two different binders (Portland cement (PC and high alumina cement (HAC were modified upon the bulk incorporation of nano-structured photocatalytic additives (bare TiO2, and TiO2 doped with either iron (Fe-TiO2 or vanadium (V-TiO2. Plastic and hardened state properties of these mortars were assessed in order to study the influence of these nano-additives. Water demand was increased, slightly by bare TiO2 and Fe-TiO2, and strongly by V-TiO2, in agreement with the reduction of the particle size and the tendency to agglomerate. Isothermal calorimetry showed that hydration of the cementitious matrices was accelerated due to additional nucleation sites offered by the nano-additives. TiO2 and doped TiO2 did not show pozzolanic reactivity in the binding systems. Changes in the pore size distribution, mainly the filler effect of the nano-additives, accounted for the increase in compressive strengths measured for HAC mortars. A complex microstructure was seen in calcium aluminate cement mortars, strongly dependent on the curing conditions. Fe-TiO2 was found to be homogeneously distributed whereas the tendency of V-TiO2 to agglomerate was evidenced by elemental distribution maps. Water absorption capacity was not affected by the nano-additive incorporation in HAC mortars, which is a favourable feature for the application of these mortars.

  3. THE MECHANISM OF BONDING PARTICLES DISTENSILIMANITA SODIUM ALUMINATE

    Directory of Open Access Journals (Sweden)

    O. S. Komarov

    2016-01-01

    Full Text Available The interaction of the filler (distensillimanit or binder (sodium aluminate after mixing them to form a mold wash, drying the paint and removing water of crystallization. The conclusion of the sodium aluminate suitability as a foundry binder paints.

  4. Subgrade stabilization alternatives to lime and cement.

    Science.gov (United States)

    2010-04-15

    This project involved four distinct research activities, (1) the influence of temperature on lime-stabilized soils, (2) the influence of temperature on cement-stabilized soils (3) temperature modeling of stabilized subgrade and (4) use of calcium chl...

  5. Comparative evaluation of the calcium release from mineral trioxide aggregate and its mixture with glass ionomer cement in different proportions and time intervals – An in vitro study

    Directory of Open Access Journals (Sweden)

    Surbhi Sawhney

    2015-10-01

    Conclusions: Adding GIC to improve the setting time and handling properties of the MTA powder can be detrimental to the calcium-releasing ability of the resultant mixture, depending on the proportion of GIC added. Adding MTA and GIC at a proportion of 2:1 by volume did not impact calcium release from the mixture. These findings should be verified through further clinical studies.

  6. Role of Adsorption Phenomena in Cubic Tricalcium Aluminate Dissolution.

    Science.gov (United States)

    Myers, Rupert J; Geng, Guoqing; Li, Jiaqi; Rodríguez, Erich D; Ha, Juyoung; Kidkhunthod, Pinit; Sposito, Garrison; Lammers, Laura N; Kirchheim, Ana Paula; Monteiro, Paulo J M

    2017-01-10

    The workability of fresh Portland cement (PC) concrete critically depends on the reaction of the cubic tricalcium aluminate (C 3 A) phase in Ca- and S-rich pH >12 aqueous solution, yet its rate-controlling mechanism is poorly understood. In this article, the role of adsorption phenomena in C 3 A dissolution in aqueous Ca-, S-, and polynaphthalene sulfonate (PNS)-containing solutions is analyzed. The zeta potential and pH results are consistent with the isoelectric point of C 3 A occurring at pH ∼12 and do not show an inversion of its electric double layer potential as a function of S or Ca concentration, and PNS adsorbs onto C 3 A, reducing its zeta potential to negative values at pH >12. The S and Ca K-edge X-ray absorption spectroscopy (XAS) data obtained do not indicate the structural incorporation or specific adsorption of SO 4 2- on the partially dissolved C 3 A solids analyzed. Together with supporting X-ray ptychography and scanning electron microscopy results, a model for C 3 A dissolution inhibition in hydrated PC systems is proposed whereby the formation of an Al-rich leached layer and the complexation of Ca-S ion pairs onto this leached layer provide the key inhibiting effect(s). This model reconciles the results obtained here with the existing literature, including the inhibiting action of macromolecules such as PNS and polyphosphonic acids upon C 3 A dissolution. Therefore, this article advances the understanding of the rate-controlling mechanism in hydrated C 3 A and thus PC systems, which is important to better controlling the workability of fresh PC concrete.

  7. Use of Incineration Solid Waste Bottom Ash as Cement Mixture in Cement Production

    Science.gov (United States)

    Jun, N. H.; Abdullah, M. M. A. B.; Jin, T. S.; Kadir, A. A.; Tugui, C. A.; Sandu, A. V.

    2017-06-01

    Incineration solid waste bottom ash was use to examine the suitability as a substitution in cement production. This study enveloped an innovative technology option for designing new equivalent cement that contains incineration solid waste bottom ash. The compressive strength of the samples was determined at 7, 14, 28 and 90 days. The result was compared to control cement with cement mixture containing incineration waste bottom ash where the result proved that bottom ash cement mixture able achieve its equivalent performance compared to control cement which meeting the requirement of the standards according to EN 196-1. The pozzolanic activity index of bottom ash cement mixture reached 0.92 at 28 days and 0.95 at 90 and this values can be concluded as a pozzolanic material with positive pozzolanic activity. Calcium hydroxide in Portland cement decreasing with the increasing replacement of bottom ash where the reaction occur between Ca(OH)2 and active SiO2.

  8. Optimization of properties of cement-bonded particleboard manufactured from cotton stalk and sawdust containing calcium chloride CaCl2 as an additive

    Directory of Open Access Journals (Sweden)

    morteza nazerian

    2016-06-01

    Full Text Available The aim of this study was investigation of hydration behavior and mechanical properties of cement-bonded particleboard manufactured from different ratio of cotton stalk to poplar wood particle, sawdust content and CaCl2 as additive at different weight ratios. At the first, curing time of cement paste containing different amount of additive (CaCl2 and wood and cotton fines was determined. Besides, the effect of additive (CaCl2 content, weight ratio of cotton to poplar wood particles and percentage of sawdust on modulus of rupture (MOR, modulus of elasticity (MOE and internal bonding (IB of cement-bonded particleboard was evaluated by response surface methodology (RSM. In order to optimize the properties of panels, a mathematical model equation (second order plan was done by a computer simulation program. According to results, there is a good coincidence between predicted values and actual values (R2 for MOR, MOE and IB was 0.93, 0.90 and 0.95, respectively. This study showed that the response surface methodology (RSM can be effectively used for modeling of panel properties. Results showed that using weight ratio of cotton to poplar particle 43:57 the MOR, MOE and IB of panels can be reached to maximum values (12.5, 2545 and 0.35 MPa, respectively. Simultaneously, application of 4.5% additive and 9% sawdust at had a positive effect on the properties of the panels.

  9. Acute intraoperative reactions during the injection of calcium sulfate bone cement for the treatment of unicameral bone cysts: a review of four cases.

    Science.gov (United States)

    Nystrom, Lukas; Raw, Robert; Buckwalter, Joseph; Morcuende, Jose A

    2008-01-01

    Unicameral bone cysts can predispose patients to pathologic fracture and deformities of growth. Treatment options vary from continuous decompression with transcortical placement of a cannulated screw to percutaneous aspiration and injection of medical-grade calcium sulfate. From 2005 to 2007, we treated 22 patients with unicameral bone cysts using aspiration and injection of calcium sulfate. Three patients experienced acute laryngospasm and one patient developed tachyarrhythmia, temporarily, associated with injection of calcium sulfate. All reactions occurred in patients under age 18 without predisposing risk factors and resolved spontaneously with supportive care. Although the mechanism is unclear, we hypothesize that these reactions are either due to the nociceptive stimulus of the calcium sulfate injection or a systemic calcium bolus. Clinicians using this product for this indication should be aware that such reactions may occur. We suggest endotracheal intubation and communication to the anesthesiologist about the time of the injection in preparation for these idiopathic responses. Further research is necessary to determine exactly how this reaction occurs and how it can be avoided.

  10. Interaction of calcium silicate hydrates (C-S-H), the main components of cement, with alkaline chlorides, analogy with clays; Interaction des silicates de calcium hydrates, principaux constituants du ciment, avec les chlorures d'alcalins. Analogie avec les argiles

    Energy Technology Data Exchange (ETDEWEB)

    Viallis-Terrisse, H

    2000-10-06

    This work, belonging to a more general study on the structure and reactivity of cement, deals with the experimental and theoretical analysis of the interaction of alkaline chlorides with calcium silicate hydrates (C-S-H), the main components of cement paste. The interaction of alkaline cations with C-S-H is interfacial, involving both electrostatic and surface complexation mechanisms. The C-S-H surface is constituted of silanol sites, partially dissociated due to the high pH of the interstitial solution. The calcium ions, present in large amounts in the equilibrium solution of C-S-H, constitute potential determining ions for the C-S-H surface. The alkaline ions seem to compete with calcium for the same surface sites. The adsorption isotherms show that caesium presents a better affinity than sodium and lithium for the C-S-H surface. Moreover, solid-state NMR suggests that caesium forms with the surface sites inner-sphere complexes, whereas sodium seems to keep its hydration sphere. These results are in agreement with zeta potential measurements, which let suppose a specific adsorption of caesium ions, and an indifferent behaviour of both other alkaline ions. A model for the C-S-H surface was proposed, from the electric double layer model, and mass action laws expressing the complexation of the different ionic species with the silanol sites. The whole study relies on a structural analogy with smectites, some clays presenting well-known cationic adsorption properties. The structural similarity between both minerals is enhanced by some similarities of reactivity, though significant behaviour differences could also be noted. (author)

  11. Influence of the mineralogical composition of cement in the diffusion of chemical species; Influencia de la composicion mineralogica del cemento en la difusion de especies quimicas

    Energy Technology Data Exchange (ETDEWEB)

    Galicia A, E.

    2015-07-01

    , setting time, color and others. Portland cements commonly used in the construction industry, they are based primarily on the mineral phases of limestone and silica. In conventional cement admixtures the chemical reactivity depends on the ratio of tricalcium and dicalcium silicate (C{sub 3}S/C{sub 2}S), the tricalcium aluminate (C{sub 3}A) influences in the setting time and tetra calcium ferro aluminate (C{sub 4}AF) gives a different color to the cement. In this research the mineralogical composition of two commercial cements is studied and its influence on the phenomenon of radionuclides retention. For this particular concrete discs were manufactured with water, sand and two commercial cements: Tolteca Extra CPC 30-RRS and Cruz Azul CPC Type II 30-R. The solid observation techniques used for analysis of the cement paste and concrete they are: X-ray Diffraction and Scanning Electron Microscopy, as well as the nuclear analytic techniques of Moessbauer and X-ray Fluorescence. (Author)

  12. Mortar and concrete based on calcium sulphate binders

    NARCIS (Netherlands)

    Bakker, J.J.F.; Brouwers, H.J.H.; Fischer, H.B

    2006-01-01

    In this study both hemi-hydrate and anhydrite are tested as calcium sulphate binders for structural mortar and concrete. The advantage of using calcium sulphates instead of cement as a binder is the fact that the production of calcium sulphate is more environmental friendly than that of cement. For

  13. Chemical composition influence of cement based mortars on algal biofouling

    Science.gov (United States)

    Estelle, Dalod; Alexandre, Govin; Philippe, Grosseau; Christine, Lors; René, Guyonnet; Denis, Damidot

    2013-04-01

    The main cause of building-facade biodegradation is the growth of microorganisms. This phenomenon depends on several parameters such as the geographical situation, the environmental conditions and the surface state of the substrate. Several researches have been devoted to the study of the effect of porosity and roughness on the biofouling of stones and mortars. However, none of them have addressed the influence of the mortar chemistry on the microorganism growth kinetic. The main objective of this study is to highlight the influence of the mortar chemistry in relationship with its physical properties on biological weathering. Earlier work showed a good resistance of Calcium Aluminate Cements to biodeterioration by acidogenic bacteria (Thiobacillus) and fungi (Alternaria alternata, Aspergillus Niger and Coniosporium uncinatum). In order to characterize the influence of the mortar chemistry on biofouling, two Portland cements and two alumina cements are used. Among micro-organisms able to grow, green algae are most involved in the aesthetic deterioration of facades. Indeed, they can colonize any type of media and can be a source of nutrients for other micro-organisms such as fungi. The green algae Klebsormidium flaccidum is chosen because of its representativeness. It is indeed the species the most frequently identified and isolated from samples taken on sites. The biofouling kinetic is followed on samples exposed outdoor and on samples tested in a laboratory bench which consists in spraying an algae culture on mortar specimens. The results obtained by in situ trials are compared with the results obtained on the laboratory bench. The microorganism growth kinetic is measured by image analysis. To improve the detection of algae on the surface of the cementitious samples, the raw image is converted in the YIQ color space. Y, I and Q correspond respectively to luminance, in-phase, and quadrature. On the Q channel, the areas covered by algae and the areas of clean mortar

  14. Effects of cement organic additives on the adsorption of uranyl ions on calcium silicate hydrate phases: experimental determination and computational molecular modelling

    International Nuclear Information System (INIS)

    Androniuk, Iuliia

    2017-01-01

    Cementitious materials are extensively used in the design and construction of radioactive waste repositories. One of the ways to enhance their performance is to introduce organic admixtures into the cement structure. However, the presence of organics in the pore water may affect the radionuclide mobility: organic molecules can form water-soluble complexes and compete for sorption sites. This work was designed to get detailed understanding of the mechanisms of such interactions on the molecular level. The model system has three components. First, pure C-S-H phases with different Ca/Si ratios were chosen as a cement model. Secondly, gluconate (a simple well-described molecule) is selected as a good starting organic additive model to probe the interaction mechanisms on the molecular scale. A more complex system involving poly-carboxylate super-plasticizer (PCE) was also tested. The third, U(VI), is a representative of the actinide radionuclide series. The development of description of the effects of organics for radioactive waste disposal applications was the primary objective of this work. The study of binary systems provides reference data for the investigation of more complex ternary (C-S-H/organic/U(VI)). The interactions are studied by means of both experimental and computational molecular modelling techniques. Data on sorption and desorption kinetics and isotherms for additives and for U(VI) on C-S-H are acquired in this work. In parallel, atomistic models are developed for the interfaces of interest. Structural, energetic, and dynamic aspects of the sorption processes on surface of cement are quantitatively modeled by molecular dynamics technique. (author)

  15. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid......−liquid reactions are discussed, as are the influences of particles sizes on clinker phase formation. Furthermore, a mechanism for clinker phase formation in an industrial rotary kiln reactor is outlined....

  16. Effect of polycarboxylate admixture structure on cement paste rheology

    Directory of Open Access Journals (Sweden)

    Aranda, M. A. G.

    2007-06-01

    Full Text Available The purpose of the present study was to analyze the effect of the structural differences in four polycarboxylate and polyether admixtures on the rheological properties of cement pastes with different chemical and mineralogical compositions and different active additions (CEM I 42.5 R, CEM I 52.5 R, CEM I 52.5 N/SR, CEM II/AV 42.5R, CEM II/B-L 32.5 R, CEM III/B 32.5R, BL I 52.5R and CAC – European standard EN 197-1:2000. The results of the minislump test concurred with the variations observed in the values of the rheological parameters (shear stress and plastic viscosity. The structural characteristic of the admixtures found to play the most prominent role in their fluidizing effect was the proportion of carboxylate (CG and polyether (EG group components. In cements characteristics such as fineness and the C3A/calcium sulphate and C3S/C3A ratios were also observed to be essential to admixture effectiveness. In this regard, the rheological parameters varied most widely in CEM I 52.5N/SR pastes and least in BL I 52.5R cement pastes. Of the additioned cements, the CEM III/B 32.5R pastes, which contained granulated blast furnace slag, showed the highest rises in flowability. Finally, the fluidizing effect of polycarboxylate superplasticizers was much more intense in calcium aluminate cements, although flowability declined rapidly in this material.El objetivo de este trabajo ha sido estudiar el efecto de las diferencias estructurales de cuatro aditivos basados en policarboxilatos y poliéteres sobre las propiedades reológicas de pastas de cemento con diferente composición química, mineralógica y con distintas adiciones activas (CEM I 42,5 R, CEM I 52,5 R, CEM I 52,5 N/SR, CEM II/AV 42,5R, CEM II/ B-L 32,5 R, CEM III/B 32,5R, BL I 52,5R y CAC - Norma EN 197-1:2000. Los resultados obtenidos sobre la fluidez de la pasta en el ensayo del “Minislump” coinciden con la evolución de los valores de los parámetros reológicos (esfuerzo de

  17. Properties of lithium aluminate for application as an OSL dosimeter

    International Nuclear Information System (INIS)

    Twardak, A.; Bilski, P.; Marczewska, B.; Lee, J.I.; Kim, J.L.; Gieszczyk, W.; Mrozik, A.; Sądel, M.; Wróbel, D.

    2014-01-01

    Several samples of undoped and carbon or copper doped lithium aluminate (LiAlO 2 ) were prepared in an attempt to achieve a material, which can be applicable in optically stimulated luminescence (OSL) dosimetry. All investigated samples are highly sensitive to ionizing radiation and show good reproducibility. The undoped and copper doped samples exhibit sensitivity several times higher than that of Al 2 O 3 :C, while sensitivity of the carbon doped samples is lower. The studied samples exhibit significant fading, but dynamics of signal loss is different for differently doped samples, what indicates a possibility of improving this characteristic by optimizing dopant composition. - Highlights: • OSL properties of lithium aluminate for personal dosimetry. • Doping influence on OSL fading of lithium aluminate. • Application of lithium aluminate in thermal neutron measurements

  18. A drift chamber constructed of aluminized mylar tubes

    International Nuclear Information System (INIS)

    Baringer, P.; Jung, C.; Ogren, H.O.; Rust, D.R.

    1987-01-01

    A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls. (orig.)

  19. A drift chamber constructed of aluminized mylar tubes

    Science.gov (United States)

    Baringer, P.; Jung, C.; Ogren, H. O.; Rust, D. R.

    1987-03-01

    A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls.

  20. Is it cement to be? Downhole cement that uses zeolite additive may offer lightweight alternative

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, J.

    2001-05-01

    C2C Zeolite Corporation produces zeolites from a large deposit near Cache Creek, British Columbia, and processes them for use as an additive in downhole cement well casings. Early research indicates that zeolites can significantly improve the way downhole cement is made in the oil industry. Zeolites are made up mostly of silicates of aluminum and calcium. They have a great ability to absorb water, resulting in a lighter and more fluid cement than is currently available. C2C claims that zeolites will reduce cement weight, column pressure and operator costs. The cost benefits of using lighter cement downhole includes easier moving, processing and handling of the mix. Initial research suggests that zeolites might prove to be viable alternatives to other cement lighteners such as silica fumes or flyash. Zeolite-based cement also performed reasonably well in freeze-thaw tests and showed good adhesion and no evidence of shrinkage in downhole tests. 3 figs.

  1. Comparative evaluation of antimicrobial action of MTA, calcium hydroxide and Portland cement Avaliação comparativa da ação antimicrobiana do MTA, hidróxido de cálcio e cimento Portland

    Directory of Open Access Journals (Sweden)

    Caroline Sousa Ribeiro

    2006-10-01

    Full Text Available The present study aimed to evaluate and compare the antimicrobial effect of MTA Dentsply, MTA Angelus, Calcium Hydroxide and Portland cement. Four reference bacterial strains were used: Pseudomonas aeruginosa, Escherichia coli, Bacteroides fragilis, and Enterococcus faecalis. Plates containing Mueller-Hinton agar supplemented with 5% sheep blood, hemin, and menadione were inoculated with the bacterial suspensions. Subsequently, wells were prepared and immediately filled with materials and incubated at 37ºC for 48 hours under anaerobic conditions, except P. aeruginosa. The diameters of inhibition zones were measured, and data analyzed using ANOVA and the Tukey test with 1% level of significance. MTA Dentsply, MTA Angelus and Portland cement inhibited the growth of P. aeruginosa. Calcium Hydroxide was effective against P. aeruginosa and B. fragillis. Under anaerobic conditions, which may hamper the formation of reactive oxygen species, the materials failed to inhibit E. faecalis, and E. coli.O objetivo do presente trabalho foi avaliar e comparar o efeito antimicrobiano do MTA Dentsply, MTA Angelus, hidróxido de cálcio e cimento Portland sobre quatro cepas bacterianas: Pseudomonas aeruginosa, Escherichia coli, Bacteroides fragilis, e Enterococcus faecalis. Placas contendo agar Muller-Hinton suplementadas com 5% de sangue de carneiro, hemina e menadiona foram inoculadas com as suspensões bacterianas. Poços foram confeccionados com auxílio de perfuradores e imediatamente preenchidos com os materiais, e incubados a 37ºC por 48 horas em atmosfera de anaerobiose, exceto P. aeruginosa. O diâmetro dos halos de inibição foi medido e os dados analisados usando o teste estatístico ANOVA e o de Tukey com nível de significância de 1%. O MTA Dentsply, MTA Angelus e Cimento Portland inibiram o crescimento da P.aeruginosa. O hidróxido de cálcio foi efetivo contra P. aeruginosa e B. fragillis. Sob atmosfera de anaerobiose, condição que pode

  2. Mechanoluminescence of Dy doped strontium aluminate nanophosphors

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Ravi, E-mail: rvsharma65@gmail.com [Department of Physics, Govt. Arts and Commerce Girls College, Raipur, C.G. 492001 (India); Bisen, D.P. [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur, C.G. 492010 (India); Chandra, B.P. [Department of Postgraduate Studies and Research in Physics and Electronics, Rani Durgavati University, Jabalpur 482001 (India)

    2015-12-15

    Nanosized strontium aluminate phosphors activated with Dy{sup 3+} were prepared by a combustion method. Nanophosphor was prepared by this method at reaction temperatures as low as 600 °C. Powder X-ray diffraction (XRD), scanning electron microscope analysis was used to characterize the prepared product. The monoclinic phase was observed in the XRD pattern. The particle size of the samples was calculated around 35 nm. The SEM images show irregular shape of the prepared nanophosphor. Two peaks were found in the mechanoluminescence (ML) response curve plotted between time and ML intensity. The H{sub 3}BO{sub 3} added strontium aluminate phosphors activated with Dy show more bright ML peak as compared to the powders of SrAl{sub 2}O{sub 4}:Dy{sup 3+} without H{sub 3}BO{sub 3.} It was found that the PL and ML intensity increases with increasing concentration of Dy, it becomes maximum for 3% of Dy. The photoluminescence emission shows two intense fluorescence transitions peaks at 498 nm and 583 nm, {sup 4}F{sub 9/2}→{sup 6}H{sub 15/2} in the blue and {sup 4}F{sub 9/2}→{sup 6}H{sub 13/2} in the yellow-orange wavelength region. - Highlights: • Combustion synthesis route is used to prepare the SrAl{sub 2}O{sub 4}: Dy {sup 3+} nanophosphors. • The size of the synthesized sample was found to be in the nano-meter range. • The mechanoluminescence of SrAl{sub 2}O{sub 4}:Dy {sup 3+} nanophosphors is studied. • The photoluminescence of SrAl{sub 2}O{sub 4}: Dy {sup 3+} nanophosphors showed blue-shift as compared to bulk. • Effect of H{sub 3}BO{sub 3} on the mechanoluminescence of SrAl{sub 2}O{sub 4}:Dy{sup 3+} was studied.

  3. X-ray diffractometry of steam cured ordinary Portland and blast-furnace-slag cements

    International Nuclear Information System (INIS)

    Camarini, G.; Djanikian, J.G.

    1994-01-01

    This work studies some aspects of the phases produced by hydration of ordinary and blast-furnace-slag cements, at normal conditions and steam cured (60 and 95 0 C), using an X-ray diffraction technique. The blast-furnace-slag cement was a mixture of 50% of ordinary Portland cement and 50% of blast-furnace-slag (separately grinding). After curing the X-ray diffraction reveals that, in relation to ordinary Portland cement, the main phases in blast-furnace-slag cement are hydrated silicates and aluminates, hydro garnet, etringitte and mono sulphate. After steam curing the hydration of blast-furnace-slag cement proceeds. This is a result of the slag activation by the curing temperature. (author). 8 refs., 3 figs., 1 tab

  4. Characterization of experimental cements with endodontic goal; Caracterizacao de cimentos experimentais com finalidade endodontica

    Energy Technology Data Exchange (ETDEWEB)

    Dantas, A.M.X.; Sousa, W.J.B.; Oliveira, E.D.C.; Carrodeguas, R.G.; Fook, M.V. Lia, E-mail: alana.mxd@hotmail [Universidade Federal de Campina Grande (CCT/UFCG), PB (Brazil). Unidade Academica de Engenharia de Materiais; Universidade Estadual da Paraiba (UEPB), Campina Grande, PB (Brazil). Departamento de Quimica

    2017-10-01

    The present study aimed to characterize experimental endodontic cements using as comparative parameter MTA cement. Two experimental endodontic cements were assessed: one based on 95% tri-strontium aluminate and 5% gypsum (CE1) and another based on 50% Sr{sub 3}Al{sub 2}O{sub 6} and 50% non-structural white cement (CE2). Experimental cements were manipulated and characterized by scanning electron microscopy (SEM), coupled to EDS mode, X-ray diffractometer (XRD) and Thermogravimetric (TG) analysis. Data analysis demonstrated that the particles of the materials used presented varied shapes and sizes, with similar elements and crystalline behavior. However, CE1 presented increased mass loss. Experimental cements presents similarities to MTA, nevertheless, further studies are encourage to determinate comparative properties with the commercially material. (author)

  5. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives

    International Nuclear Information System (INIS)

    Voglar, Grega E.; Lestan, Domen

    2011-01-01

    Highlights: → We assess the feasibility of using soil S/S for industrial land reclamation. → Retarders, accelerators, plasticizers were used in S/S cementitious formulation. → We proposed novel S/S efficiency model for multi-metal contaminated soils. - Abstract: In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085 mg kg -1 of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12 N mm -2 achieved after S/S with CAC + PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively.

  6. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives.

    Science.gov (United States)

    Voglar, Grega E; Leštan, Domen

    2011-08-30

    In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085mg kg(-1) of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12N mm(-2) achieved after S/S with CAC+PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC+Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Effect of endodontic cement on bone mineral density using serial dual-energy x-ray absorptiometry.

    Science.gov (United States)

    Saghiri, Mohammad Ali; Orangi, Jafar; Tanideh, Nader; Janghorban, Kamal; Sheibani, Nader

    2014-05-01

    Materials with new compositions were tested in order to develop dental materials with better properties. Calcium silicate-based cements, including white mineral trioxide aggregate (WMTA), may improve osteopromotion because of their composition. Nano-modified cements may help researchers produce ideal root-end filling materials. Serial dual-energy x-ray absorptiometry measurement was used to evaluate the effects of particle size and the addition of tricalcium aluminate (C3A) to a type of mineral trioxide aggregate-based cement on bone mineral density and the surrounding tissues in the mandible of rabbits. Forty mature male rabbits (N = 40) were anesthetized, and a bone defect measuring 7 × 1 × 1 mm was created on the semimandible. The rabbits were divided into 2 groups, which were subdivided into 5 subgroups with 4 animals each based on the defect filled by the following: Nano-WMTA (patent application #13/211.880), WMTA (as standard), WMTA without C3A, Nano-WMTA + 2% Nano-C3A (Fujindonjnan Industrial Co, Ltd, Fujindonjnan Xiamen, China), and a control group. Twenty and forty days postoperatively, the animals were sacrificed, and the semimandibles were removed for DXA measurement. The Kruskal-Wallis test followed by the Mann-Whitney U test showed significant differences between the groups at a significance level of P density at both intervals and P20 day = .004 and P40 day = .005 for bone mineral content. This study showed that bone regeneration was enhanced by reducing the particle size (nano-modified) and C3A mixture. This may relate to the existence of an external supply of minerals and a larger surface area of nano-modified material, which may lead to faster release rate of Ca(2+), inducing bone formation. Adding Nano-C3A to Nano-WMTA may improve bone regeneration properties. Copyright © 2014 American Association of Endodontists. All rights reserved.

  8. Efficiency modeling of solidification/stabilization of multi-metal contaminated industrial soil using cement and additives

    Energy Technology Data Exchange (ETDEWEB)

    Voglar, Grega E. [RDA - Regional Development Agency Celje, Kidriceva ulica 25, 3000 Celje (Slovenia); Lestan, Domen, E-mail: domen.lestan@bf.uni-lj.si [Agronomy Department, Centre for Soil and Environmental Science, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana (Slovenia)

    2011-08-30

    Highlights: {yields} We assess the feasibility of using soil S/S for industrial land reclamation. {yields} Retarders, accelerators, plasticizers were used in S/S cementitious formulation. {yields} We proposed novel S/S efficiency model for multi-metal contaminated soils. - Abstract: In a laboratory study, formulations of 15% (w/w) of ordinary Portland cement (OPC), calcium aluminate cement (CAC) and pozzolanic cement (PC) and additives: plasticizers cementol delta ekstra (PCDE) and cementol antikorodin (PCA), polypropylene fibers (PPF), polyoxyethylene-sorbitan monooleate (Tween 80) and aqueous acrylic polymer dispersion (Akrimal) were used for solidification/stabilization (S/S) of soils from an industrial brownfield contaminated with up to 157, 32,175, 44,074, 7614, 253 and 7085 mg kg{sup -1} of Cd, Pb, Zn, Cu, Ni and As, respectively. Soils formed solid monoliths with all cementitious formulations tested, with a maximum mechanical strength of 12 N mm{sup -2} achieved after S/S with CAC + PCA. To assess the S/S efficiency of the used formulations for multi-element contaminated soils, we propose an empirical model in which data on equilibrium leaching of toxic elements into deionized water and TCLP (toxicity characteristic leaching procedure) solution and the mass transfer of elements from soil monoliths were weighed against the relative potential hazard of the particular toxic element. Based on the model calculation, the most efficient S/S formulation was CAC + Akrimal, which reduced soil leachability of Cd, Pb, Zn, Cu, Ni and As into deionized water below the limit of quantification and into TCLP solution by up to 55, 185, 8750, 214, 4.7 and 1.2-times, respectively; and the mass transfer of elements from soil monoliths by up to 740, 746, 104,000, 4.7, 343 and 181-times, respectively.

  9. Use of a strontium-enriched calcium phosphate cement in accelerating the healing of soft-tissue tendon graft within the bone tunnel in a rabbit model of anterior cruciate ligament reconstruction.

    Science.gov (United States)

    Kuang, G M; Yau, W P; Lu, W W; Chiu, K Y

    2013-07-01

    We investigated whether strontium-enriched calcium phosphate cement (Sr-CPC)-treated soft-tissue tendon graft results in accelerated healing within the bone tunnel in reconstruction of the anterior cruciate ligament (ACL). A total of 30 single-bundle ACL reconstructions using tendo Achillis allograft were performed in 15 rabbits. The graft on the tested limb was treated with Sr-CPC, whereas that on the contralateral limb was untreated and served as a control. At timepoints three, six, nine, 12 and 24 weeks after surgery, three animals were killed for histological examination. At six weeks, the graft-bone interface in the control group was filled in with fibrovascular tissue. However, the gap in the Sr-CPC group had already been completely filled in with new bone, and there was evidence of the early formation of Sharpey fibres. At 24 weeks, remodelling into a normal ACL-bone-like insertion was found in the Sr-CPC group. Coating of Sr-CPC on soft tissue tendon allograft leads to accelerated graft healing within the bone tunnel in a rabbit model of ACL reconstruction using Achilles tendon allograft.

  10. Incorporation of tv tube glass waste in aluminous porcelain

    Energy Technology Data Exchange (ETDEWEB)

    Holanda, J.N.F.; Santos, T.F.; Paes Junior, H.R. [Universidade Estadual do Norte Fluminense (UENF), Campos dos Goytacazes, RJ (Brazil)

    2016-07-01

    Full test: This work analyzes the reuse of TV tube glass waste as a method to provide alternative raw material for aluminous porcelain, through of replacement of natural sodic feldspar by up to 30 wt.%. Aluminous porcelain formulations containing TV tube glass waste were pressed and fired in air at 1300 deg C using a fast-firing cycle. Ceramic pieces were characterized by X-ray diffraction, scanning electron microscopy, linear shrinkage, apparent density, apparent porosity, water absorption, and electrical resistivity. XRD and SEM results indicated that all aluminous porcelain pieces are composed essentially of mullite, quartz, and ?-alumina embedded in a vitreous matrix. The results also showed that the aluminous porcelain pieces containing TV tube glass waste presented low water absorption values between 0.42 and 0.45 %, apparent density between 2.44 and 2.46 g/cm3, and volume electrical resistivity between 1.91 and 2.93 x 1011 ?.cm. Thus, the TV tube glass waste could be used into aluminous porcelain formulations, in the range up to 30 wt.%, as a replacement for traditional flux material (sodic feldspar). (author)

  11. Synthesis of magnesium aluminate spinel by periclase and alumina chlorination

    International Nuclear Information System (INIS)

    Orosco, Pablo; Barbosa, Lucía; Ruiz, María del Carmen

    2014-01-01

    Highlights: • Use of chlorination for the synthesis of magnesium aluminate spinel. • The reagents used were alumina, periclase and chlorine. • Isothermal and non-isothermal assays were performed in air and Cl 2 –N 2 flows. • The chlorination produced magnesium aluminate spinel at 700 °C. • Selectivity of the chlorination reaction to obtain spinel is very high. - Abstract: A pyrometallurgical route for the synthesis of magnesium aluminate spinel by thermal treatment of a mechanical mixture containing 29 wt% MgO (periclase) and 71 wt% Al 2 O 3 (alumina) in chlorine atmosphere was developed and the results were compared with those obtained by calcining the same mixture of oxides in air atmosphere. Isothermal and non-isothermal assays were performed in an experimental piece of equipment adapted to work in corrosive atmospheres. Both reagents and products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Thermal treatment in Cl 2 atmosphere of the MgO–Al 2 O 3 mixture produces magnesium aluminate spinel at 700 °C, while in air, magnesium spinel is generated at 930 °C. The synthesis reaction of magnesium aluminate spinel was complete at 800 °C

  12. Study of thermocycling effect on the bond strength between an aluminous ceramic and a resin cement Estudo do efeito da ciclagem térmica na resistência da união adesiva entre uma cerâmica aluminizada e um cimento resinoso

    Directory of Open Access Journals (Sweden)

    Osvaldo Daniel Andreatta Filho

    2005-03-01

    Full Text Available This study evaluated the effect of thermocycling on the bond strength between Procera AllCeram (Nobel-Biocare and a resin cement (Panavia F, Kuraray CO. Nine ceramic blocks with dimensions of 5x6x6mm were conditioned at one face with Rocatec System (Espe. After, they were luted with Panavia F to composite resin blocks (Clearfil AP-X, Kuraray CO. The nine groups formed by ceramic, cement and composite resin were split up obtaining 75 samples with dimensions of 12x1x1mm and adhesive surface presenting 1mm²±0.1mm² of area. The samples were divided into 3 groups (n=25: G1 - 14 days in distilled water at 37ºC; G2 - 6,000 cycles in water (5ºC - 55ºC - 30s; G3 - 12,000 cycles in water (5ºC - 55ºC - 30s. The samples were tested in a universal testing machine (EMIC at a crosshead speed of 1mm/min. Data were analyzed by ANOVA and Tukey tests. The results indicated that mean values of rupture tension (MPa of G1 (10.71 ± 3.54 did not differ statistically (p Este trabalho avaliou o efeito da ciclagem térmica sobre a resistência adesiva entre a cerâmica aluminizada (Procera AllCeram, Nobel-Biocare e um cimento resinoso (Panavia F, Kuraray CO. Nove blocos de cerâmica, com dimensões de 5x6x6mm, foram condicionados em uma de suas faces com o Sistema Rocatec (ESPE. A seguir foram cimentados a blocos de resina composta (Clearfil AP-X, Kuraray CO. Os conjuntos cerâmica-cimento-resina foram cortados em 75 corpos-de-prova com formato retangular com dimensões de 12x1x1mm e superfície adesiva apresentando 1mm² ± 0,1mm². Os corpos-de-prova foram divididos em três grupos (n=25: G1 - 14 dias em água destilada a 37ºC, G2 - 6000 ciclos em água (5ºC e 55ºC e G3 - 12000 ciclos em água (5ºC e 55ºC. Os corpos-de-prova foram ensaiados sob velocidade de 1mm/min em máquina de ensaio universal (EMIC. Os dados foram tratados estatisticamente com os testes de Anova e Tukey e indicaram que os valores médios de tensão de rupturas (MPa de G1 (10,71 ± 3

  13. Actinide-Aluminate Speciation in Alkaline Radioactive Waste

    International Nuclear Information System (INIS)

    Clark, David L.; Fedosseev, Alexander M.

    2001-01-01

    Investigation of behavior of actinides in alkaline media containing AL(III) showed that no aluminate complexes of actinides in oxidation states (IIII-VIII) were formed in alkaline solutions. At alkaline precipitation IPH (10-14) of actinides in presence of AL(III) formation of aluminate compounds is not observed. However, in precipitates contained actinides (IIV)<(VI), and to a lesser degree actinides (III), some interference of components takes place that is reflected in change of solid phase properties in comparison with pure components or their mechanical mixture. The interference decreases with rise of precipitation PH and at PH 14 is exhibited very feebly. In the case of NP(VII) the individual compound with AL(III) is obtained, however it is not aluminate of neptunium(VII), but neptunate of aluminium(III) similar to neptunates of other metals obtained earlier

  14. Oxidation behavior and compositional analysis of aluminized superalloy

    International Nuclear Information System (INIS)

    Khalid, F.A.; Nawaz, F.

    2003-01-01

    The high temperature oxidation behavior of superalloy specimens used for the manufacture of turbine blades has been examined using scanning electron microscopy (SEM) and fine-probe spot and line scan EDS microanalysis techniques. The performance of aluminized coating applied to the specimens has also been examined. It was observed that complex oxides are formed in both coated and uncoated specimens. However the coated specimens revealed a greater stability of gamma phase and integrity of aluminized coating as compared with uncoated specimens. The microchemical and microstructural changes that occurred during oxidation have been analyzed to examine characteristics of oxide layers. (author)

  15. Effect of aluminizing on hardenability of steel (S45C)

    Science.gov (United States)

    Prayitno, D.; Sugiarto, R.

    2018-01-01

    The objective of research is to know the effect of aluminizing on hardenability of steel (S45C). The research methodologies were as follows. The Steels (S45C) were machined into the Jominy test samples. Next the samples were preheating at 700 ° C for 30 minutes and then the samples were dipped into the molten of aluminium for 3 minutes as a hot dip aluminizng method. The aluminium molten was 700 ° C. Then the samples were cooled into room temperatures. Finally the samples were into the jominy tested. The results show that the aluminizing (include the preheating process) increases the hardenability of steel (S45C).

  16. Granuloma debridement and the use of an injectable calcium phosphate bone cement in the treatment of osteolysis in an uncemented total knee replacement

    Directory of Open Access Journals (Sweden)

    Ranawat Vijai S

    2010-04-01

    Full Text Available Abstract Polyethylene particulate debris-induced periprosthetic osteolysis is a known complication of knee arthroplasty surgery, and may result in the need for revision surgery. The management of these bony defects can be surgically challenging, and full revisions of well-fixed total knee components can lead to substantial bone loss. We present the case of a 71 year old man who developed knee pain and osteolysis around an uncemented total knee replacement. Due to significant medical comorbidies he was treated by percutaneous cyst granuloma debridement and grafting using an injectable calcium phosphate bone substitute. There were no wound complications, and the patient was allowed to fully weight-bear post-operatively. Histopathology and microbiology of the cyst material confirmed polyethylene granulomata without any evidence of infection. At 6 weeks post-operatively the patient's previous knee pain had resolved, he was able to comfortably fully weight-bear. Preoperative scores (Knee Society Score (KSS 41, WOMAC score 46.2, and Oxford Knee Score 39 had all improved at the 12-month post-operative review KSS 76, WOMAC 81.7 and Oxford Knee score 21. This is a safe and effective technique with minimal morbidity and may be an appropriate treatment modality when more extensive revision surgery is not possible. The case is discussed with reference to the literature.

  17. Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

    Directory of Open Access Journals (Sweden)

    Yufei Yang

    2013-01-01

    Full Text Available To improve the understanding of the immobilization mechanism and the leaching risk of Arsenic (As in the cement product from coprocessing wastes using cement kiln, distribution and species of As in cement product were determined by microscale investigation methods, including electron probe microanalysis (EPMA and X-ray absorption spectroscopy. In this study, sodium arsenate crystals (Na3AsO412H2O were mixed with cement production raw materials and calcined to produce cement clinker. Then, clinker was mixed water to prepare cement paste. EPMA results showed that As was generally distributed throughout the cement paste. As content in calcium silicate hydrates gel (C-S-H was in low level, but higher than that in other cement mineral phases. This means that most of As is expected to form some compounds that disperse on the surfaces of cement mineral phases. Linear combination fitting (LCF of the X-ray absorption near edge structure spectra revealed that As in the cement paste was predominantly As(V and mainly existed as Mg3(AsO42, Ca3(AsO42, and Na2HAsO4.

  18. Development of hydroxyapatite bone cement for controlled drug ...

    Indian Academy of Sciences (India)

    The purpose of this work was to study the preparation and characterization of drug–hydroxyapatite cement. The hydroxyapatite (HA) cement has been synthesized by using tricalcium phosphate, calcium carbonate and dicalcium phosphate anhydrous with sodium hydrogen phosphate as liquid phase. The effect of added ...

  19. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  20. Function of magnesium aluminate hydrate and magnesium nitrate ...

    Indian Academy of Sciences (India)

    MgO was added both as spinel (MgAl2O4) forming precursor i.e. magnesium aluminate hydrate, and magnesium nitrate. Sintering investigations were conducted in the temperature range 1500–1600°C with 2 h soaking. Structural study of sintered pellets was carried out by extensive XRD analysis. Scanning electron mode ...

  1. Gas sensing behaviour of cerium oxide and magnesium aluminate

    Indian Academy of Sciences (India)

    Gas sensing behaviour of cerium oxide and magnesium aluminate composites ... A lone pairof the electron state was identified from the electro paramagnetic ... carbon monoxide (CO) (at 0.5, 1.0 and 1.5 bar) and ethanol (at 50 and 100 ppm) was ... The magnitude of the temperature varied linearly regardless of the gas ...

  2. On structural, optical and dielectric properties of zinc aluminate ...

    Indian Academy of Sciences (India)

    reports on the dielectric properties of this material is very rarely found in literature. ... C placed on a heating man- ... and dielectric loss of the material using the equation ε = ε tan δ, ..... ble mechanism of a.c. conduction in zinc aluminate particles.

  3. Investigation of tritium release and retention in lithium aluminate

    International Nuclear Information System (INIS)

    Kopasz, J.P.; Tistchenko, S.; Botter, F.

    1991-01-01

    Tritium release from lithium aluminate, although previously investigated by both in-reactor and ex-reactor experiments, remains poorly understood. Agreement between experiments is lacking, and the mechanisms responsible for tritium release from lithium aluminate are under debate. In an effort to improve our understanding of the mechanisms of tritium release from lithium ceramics, we have investigated tritium release from pure lithium aluminate and lithium aluminate doped with impurities. The results of these experiments on large grain size material indicate that after anneals at low temperature, a large fraction of the tritium present before the anneal remains in the sample. We have modeled this behavior based on first-order release from three types of sites. At the lowest temperature, the release is dominated by one site, while the tritium in the other sites is retained in the solid. Adding magnesium dopant to the ceramic appears to alter the distribution of tritium between the sites. This addition decreases the fraction of tritium released at 777 degree C, while increasing the fractions released at 538 and 950 degree C. 11 refs., 8 figs., 1 tab

  4. BoneSource hydroxyapatite cement: a novel biomaterial for craniofacial skeletal tissue engineering and reconstruction.

    Science.gov (United States)

    Friedman, C D; Costantino, P D; Takagi, S; Chow, L C

    1998-01-01

    BoneSource-hydroxyapatite cement is a new self-setting calcium phosphate cement biomaterial. Its unique and innovative physical chemistry coupled with enhanced biocompatibility make it useful for craniofacial skeletal reconstruction. The general properties and clinical use guidelines are reviewed. The biomaterial and surgical applications offer insight into improved outcomes and potential new uses for hydroxyapatite cement systems.

  5. Ecologically safe process for sulfo-aluminizing of steel parts

    Directory of Open Access Journals (Sweden)

    Plyatsuk L. D.

    2018-06-01

    Full Text Available The present technical solution refers to the field of electrophysical and electrochemical processing of parts, in particular, to the electroerosion alloying (EEA of the surfaces of steel parts with aluminum (aluminizing and sulfur (sulfidizing, and it can be used to treat the surfaces of heat-treated steel parts in order to increase their hardness, wear resistance, to prevent frictional seizure and improve the resistance to atmospheric corrosion. When aluminizing steel parts with the use of the method of electroerosion alloying (EEA by aluminum electrode at discharge energy Wp = 0.52–6.8 J and productivity of 1.0–3.0 cm2 / min, before the EEA process by an aluminum electrode, to the surface of the part to be aluminized, there is applied a consistency substance containing sulfur and aluminum powder, and thereafter, not having waited for drying of the consistency substance, the process of aluminizing by the EEL method with an aluminum electrode is carried out, and the consistency substance should have the aluminum powder content of not more than 56 %. There have been carried out metallographic and durametric analyses of the features of the surface layers made of carbon steels after simultaneous aluminizing and sulfidizing them by the EEA method. It is shown that the structure of the layer consists of three portions, namely, a “white” layer, a diffusion zone and a base metal. Such qualitative surface layer parameters as thickness, “white” layer and transition zone microhardness values, and also roughness increase with increasing discharge energy. The “white” layer continuity for all the investigated discharge energies of Wp = 0.52, 2.60 and 6.80 J is 100 %.

  6. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  7. The C-S-H gel of Portland cement mortars: Part I. The interpretation of energy-dispersive X-ray microanalyses from scanning electron microscopy, with some observations on C-S-H, AFm and AFt phase compositions

    International Nuclear Information System (INIS)

    Famy, C.; Brough, A.R.; Taylor, H.F.W.

    2003-01-01

    Scanning electron microscopy (SEM) microanalyses of the calcium-silicate-hydrate (C-S-H) gel in Portland cement pastes rarely represent single phases. Essential experimental requirements are summarised and new procedures for interpreting the data are described. These include, notably, plots of Si/Ca against other atom ratios, 3D plots to allow three such ratios to be correlated and solution of linear simultaneous equations to test and quantify hypotheses regarding the phases contributing to individual microanalyses. Application of these methods to the C-S-H gel of a 1-day-old mortar identified a phase with Al/Ca=0.67 and S/Ca=0.33, which we consider to be a highly substituted ettringite of probable composition C 6 A 2 S-bar 2 H 34 or {Ca 6 [Al(OH) 6 ] 2 ·24H 2 O}(SO 4 ) 2 [Al(OH) 4 ] 2 . If this is true for Portland cements in general, it might explain observed discrepancies between observed and calculated aluminate concentrations in the pore solution. The C-S-H gel of a similar mortar aged 600 days contained unsubstituted ettringite and an AFm phase with S/Ca=0.125

  8. Facial skeletal augmentation using hydroxyapatite cement.

    Science.gov (United States)

    Shindo, M L; Costantino, P D; Friedman, C D; Chow, L C

    1993-02-01

    This study investigates the use of a new calcium phosphate cement, which sets to solid, microporous hydroxyapatite, for facial bone augmentation. In six dogs, the supraorbital ridges were augmented bilaterally with this hydroxyapatite cement. On one side, the hydroxyapatite cement was placed directly onto the bone within a subperiosteal pocket. On the opposite side, the cement was contained within a collagen membrane tubule and then inserted into a subperiosteal pocket. The use of collagen tubules facilitated easy, precise placement of the cement. All implants maintained their original augmented height throughout the duration of the study. They were well tolerated without extrusion or migration, and there was no significant sustained inflammatory response. Histologic studies, performed at 3, 6, and 9 months revealed that when the cement was placed directly onto bone, progressive replacement of the implant by bone (osseointegration of the hydroxyapatite with the underlying bone) without a loss of volume was observed. In contrast, when the cement-collagen tubule combination was inserted, primarily a fibrous union was noted. Despite such fibrous union, the hydroxyapatite-collagen implant solidly bonded to the underlying bone, and no implant resorption was observed. Hydroxyapatite cement can be used successfully for the experimental augmentation of the craniofacial skeleton and may be applicable for such uses in humans.

  9. Effect of conditioning methods on the microtensile bond strength of phosphate monomer-based cement on zirconia ceramic in dry and aged conditions

    NARCIS (Netherlands)

    Amaral, Regina; Ozcan, Mutlu; Valandro, Luiz Felipe; Balducci, Ivan; Bottino, Marco Antonio

    The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 X 5 X 4 mm 3) of a glass-in filtrated zirconia-alumina ceramic (inCeram Zirconia Classic) were randomly

  10. Radiopacity of portland cement associated with different radiopacifying agents.

    Science.gov (United States)

    Húngaro Duarte, Marco Antonio; de Oliveira El Kadre, Guâniara D'arc; Vivan, Rodrigo Ricci; Guerreiro Tanomaru, Juliane Maria; Tanomaru Filho, Mário; de Moraes, Ivaldo Gomes

    2009-05-01

    This study evaluated the radiopacity of Portland cement associated with the following radiopacifying agents: bismuth oxide, zinc oxide, lead oxide, bismuth subnitrate, bismuth carbonate, barium sulfate, iodoform, calcium tungstate, and zirconium oxide. A ratio of 20% radiopacifier and 80% white Portland cement by weight was used for analysis. Pure Portland cement and dentin served as controls. Cement/radiopacifier and dentin disc-shaped specimens were fabricated, and radiopacity testing was performed according to the ISO 6876/2001 standard for dental root sealing materials. Using Insight occlusal films, the specimens were radiographed near to a graduated aluminum stepwedge varying from 2 to 16 mm in thickness. The radiographs were digitized and radiopacity compared with the aluminum stepwedge using Digora software (Orion Corporation Soredex, Helsinki, Finland). The radiographic density data were converted into mmAl and analyzed statistically by analysis of variance and Tukey-Kramer test (alpha = 0.05). The radiopacity of pure Portland cement was significantly lower (p cement/radiopacifier mixtures were significantly more radiopaque than dentin and Portland cement alone (p cement/bismuth oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p cement/zinc oxide presented the lowest radiopacity values of all mixtures (p cement as radiopacifying agents. However, the possible interference of the radiopacifiers with the setting chemistry, biocompatibility, and physical properties of the Portland cement should be further investigated before any clinical recommendation can be done.

  11. Synthesis and physical and chemical properties of poly-hydro-aluminates and poly-halogen-aluminates metals of II A group

    International Nuclear Information System (INIS)

    Khudoydodov, B.O.

    1990-01-01

    The purpose of the present work is investigation of conditions and mechanism of passing of formation reactions of aluminum hydrides, poly-hydride-aluminates and poly-halogen-aluminates of alkaline-earth metals and magnesium and studying of their physical and chemical properties

  12. Characterization of films formed by the aluminizing of T91 steel

    Science.gov (United States)

    Sanabria Cala, J. A.; Conde Rodríguez, G. R.; Y Peña Ballesteros, D.; Laverde Cataño, D.; Quintero Rangel, L. S.

    2017-12-01

    The aluminizing of a T91 martensitic ferritic steel was carried out by a novel modification to the traditional technique of packed cementation, with the objective of producing a diffusion coating of aluminum in a shorter time and operating cost, from a technique that allows the reuse of powder packaging and which the coating of metal parts with complex shapes can be secured. As an aluminum source, commercial foil is used to wrap the piece to be coated, while the powder packaging contains aluminum oxide Al2O3 and an activating salt, ammonium chloride NH4Cl. During the deposition process of the coating, the NH4Cl is decomposed by reacting with foil, and thus, aluminum halides can be transferred to the metallic substrate, which deposit aluminum on the T91 steel surface while Al2O3 can be recycled for subsequent processes. The results of the diffractograms and micrographs indicated the strong influence of temperature, exposure time and ammonium chloride concentration in the formation and growth evolution of a stable coating of iron-aluminum and iron-aluminum-nickel on the T91 steel surface, which was effectively deposited at a temperature of 700°C and an exposure period of 9 hours. The coating formed on the T91 steel surface could play a protective role towards the material by acting as a physical barrier between the alloy and other corrosive species in high temperature operated systems.

  13. Microstructure of aluminized coating on a Ni-Cr alloy after annealing treatment

    International Nuclear Information System (INIS)

    Huang, H.-L.; Gan Dershin

    2008-01-01

    The effects of annealing on the microstructure of first stage (high-Al activity pack) aluminized coating on Ni-15Cr alloy prepared by pack cementation method were analyzed by transmission electron microscope. The coating consists of a thin layer of γ'-Ni 3 Al, an interfacial zone of mixed β-NiAl and α-Cr, and a thick outer zone of β-NiAl (A layer) and mixed β-NiAl and α-Cr (B layer). Martensitic transformation was observed in the β-NiAl grains in the interfacial zone. Parallel crystallographic relationship was found at the γ/γ' interface in the substrate and the α/β interface in the interfacial zone. Cr 2 Al was found to precipitate in the β-NiAl and α-Cr grains in the B layer of the outer zone. The formation mechanisms of the coating layers, the precipitates, and the observed crystallographic relationships are discussed

  14. Low pH Cements

    International Nuclear Information System (INIS)

    Savage, David; Benbow, Steven

    2007-05-01

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit ≤ 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio ≤ 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  15. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  16. Phase transformations in lithium aluminates irradiated with neutrons

    International Nuclear Information System (INIS)

    Carrera, L.M.; Delfin L, A.; Urena N, F.; Basurto, R.; Bosch, P.

    2003-01-01

    The lithium aluminate like candidate to be used in the coverings producers of tritium in the fusion nuclear reactors, presents high resistance to the corrosion to the one to be stuck to structural materials as special steels. However, the crystallographic changes that take place in the cover that is continually subjected to irradiation with neutrons, can alter its resistance to the corrosion. In this work the changes of crystalline structure are shown that they present two types of nano structures of lithium aluminates, subjected to an average total dose 7.81 x 10 8 Gy in the fixed irradiation system of capsules of the one TRIGA Mark lll nuclear reactor of the Nuclear Center of Mexico. The studied nano structures presented only phase transformations without formation of amorphous material. (Author)

  17. Age and geochemistry of Alumine's Ignimbrites, Neuquen province, Argentina

    International Nuclear Information System (INIS)

    Lagorio, Silvia; Massaferro, Gabriela

    1998-01-01

    Geochemical and geochronological data from Alumine riolitic welded tuffs are analysed. Minor elements show enrichment in Rb, Th and K and depletion in Nb, Ti, P and Sr. La/Yb ratios are low. The geochemical features are consistent with a volcanic arc genesis. The radiometric data obtained by K/Ar method point out a Paleocene age for these rocks, allowing to correlate them with the Ventana Formation or the equivalent Auca Pan Formation. (author)

  18. Role of calcium-enriched mixture in endodontics

    Directory of Open Access Journals (Sweden)

    Pradeep Kabbinale

    2015-01-01

    Full Text Available Calcium-enriched mixture (CEM has been recently introduced as a hydrophilic tooth-colored cement. The CEM cement powder is composed of calcium oxide, calcium sulfate, phosphorus oxide, and silica as major elements. CEM is alkaline cement (pH~11 that releases calcium hydroxide (CH during and after setting. The physical properties of CEM, such as flow, film thickness, and primary setting time are favorable. This cement is biocompatible and induces formation of cementum, dentin, bone and periodontal tissues. This novel cement has an antibacterial effect comparable to CH and superior to mineral trioxide aggregate (MTA and sealing ability similar to MTA. Its clinical applications include pulp capping, pulpotomy, root-end filling and perforation repair. This review describes the composition, properties and clinical applications of CEM in endodontics.

  19. Tritium extraction from neutron-irradiated lithium aluminate

    International Nuclear Information System (INIS)

    Garcia H, F.

    1995-01-01

    Lithium aluminate is being strongly considered as a breeder material because of its thermophysical, chemical and mechanical stability at high temperatures and its favorable irradiation behavior. Furthermore, it is compatible with other blanket and structural materials. In this work, the effects of calcination temperature during preparation, extraction temperature and sweep gas composition were observed. Lithium aluminate prepared by four different methods, was neutron irradiated for 30 minutes at a flux of 10 12 -10 13 n/cm 2 s in the TRIGA Mark III reactor at Salazar, Mexico; and the tritium extraction rate was measured. Calcination temperature do not affect the tritium extraction rate. However, using high calcination temperature, gamma lithium aluminate was formed. The tritium extraction at 600 Centigrade degrees was lower than at 800 Centigrade degrees and the tritium amount extracted by distillation of the solid sample was higher. The sweep gas composition showed that tritium extraction was less with Ar plus 0.5 % H 2 that with Ar plus 0.1 % H 2 . This result was contrary to expected, where the tritium extraction rate could be higher when hydrogen is added to the sweep gas. Probably this effect could be attributed to the gas purity. (Author)

  20. Morphological and microstructural studies on aluminizing coating of carbon steel

    Energy Technology Data Exchange (ETDEWEB)

    Samsu, Zaifol; Othman, Norinsan Kamil; Daud, Abd Razak; Hussein, Hishammuddin [School of Applied Physics, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor (Malaysia)

    2013-11-27

    Hot dip aluminizing is one of the most effective methods of surface protection for steels and is gradually gaining popularity. The morphology and microstructure of an inter-metallic layer form on the surface of low carbon steel by hot dip aluminization treatment had been studied in detail. This effect has been investigated using optical and scanning electron microscopy, and X-ray diffraction. The result shows that the reaction between the steel and the molten aluminium leads to the formation of Fe–Al inter-metallic compounds on the steel surface. X-ray diffraction and electron microscopic studies showed that a two layer coating was formed consisting of an external Al layer and a (Fe{sub 2}Al{sub 5}) inter metallic on top of the substrate after hot dip aluminizing process. The inter-metallic layer is ‘thick’ and exhibits a finger-like growth into the steel. Microhardness testing shown that the intermetallic layer has high hardness followed by steel substrate and the lowest hardness was Al layer.

  1. Inhibited Aluminization of an ODS FeCr Alloy

    International Nuclear Information System (INIS)

    Vande Put Ep Rouaix, Aurelie; Pint, Bruce A.

    2012-01-01

    Aluminide coatings are of interest for fusion energy applications both for compatibility with liquid Pb-Li and to form an alumina layer that acts as a tritium permeation barrier. Oxide dispersion strengthened (ODS) ferritic steels are a structural material candidate for commercial reactor concepts expected to operate above 600 C. Aluminizing was conducted in a laboratory scale chemical vapor deposition reactor using accepted conditions for coating Fe- and Ni-base alloys. However, the measured mass gains on the current batch of ODS Fe-14Cr were extremely low compared to other conventional and ODS alloys. After aluminizing at two different Al activities at 900 C and at 1100 C, characterization showed that the ODS Fe-14Cr specimens formed a dense, primarily AlN layer that prevented Al uptake. This alloy batch contained a higher (> 5000 ppma) N content than the other alloys coated and this is the most likely reason for the inhibited aluminization. Other factors such as the high O content, small (∼ 140 nm) grain size and Y-Ti oxide nano-clusters in ODS Fe-14Cr also could have contributed to the observed behavior. Examples of typical aluminide coatings formed on conventional and ODS Fe- and Ni-base alloys are shown for comparison.

  2. Dentin-cement Interfacial Interaction

    Science.gov (United States)

    Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.

    2012-01-01

    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

  3. Use sulfoferritic cements in construction

    Science.gov (United States)

    Samchenko, Svetlana V.; Zorin, Dmitriy A.

    2018-03-01

    Currently, high-rise construction has received increasing attention around the world. In the big cities under construction is less space and one solution is the high-rise construction. However, high-rise buildings use special requirements, such as strength, thermal insulation, wind load and others. When concrete is exposed to continuous loads by wind or to mechanical loads, it undergoes abrasion. Resistance to this process depends on the characteristics of materials that the concrete and finishing seams are made of. Research on increasing impact and abrasion resistance of calcium sulfoferrite-based cement stone from the perspective of formation of cement stone structure will be instrumental in developing durable materials for application in high-rise construction.

  4. Development of nanosilica bonded monetite cement from egg shells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: huanzhou@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu (China); Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Division of Dentistry, The University of Toledo, Toledo, OH (United States)

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement.

  5. Development of nanosilica bonded monetite cement from egg shells

    International Nuclear Information System (INIS)

    Zhou, Huan; Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri; Agarwal, Anand K.; Goel, Vijay K.; Bhaduri, Sarit B.

    2015-01-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement

  6. The suitability of a supersulfated cement for nuclear waste immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C., E-mail: nick.collier@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Milestone, N.B. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Callaghan Innovation, 69 Gracefield Road, PO Box 31310, Lower Hutt 5040 (New Zealand); Gordon, L.E. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria 3010 (Australia); Ko, S.-C. [Holcim Technology Ltd, Hagenholzstrasse 85, CH-8050 Zurich (Switzerland)

    2014-09-15

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  7. The suitability of a supersulfated cement for nuclear waste immobilisation

    International Nuclear Information System (INIS)

    Collier, N.C.; Milestone, N.B.; Gordon, L.E.; Ko, S.-C.

    2014-01-01

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste

  8. Tobermorite/jennite- and tobermorite/calcium hydroxide-based models for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate, β-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace slag, metakaolin, or silica fume

    International Nuclear Information System (INIS)

    Richardson, I.G.

    2004-01-01

    The purpose of this article is to discuss the applicability of the tobermorite-jennite (T/J) and tobermorite-'solid-solution' calcium hydroxide (T/CH) viewpoints for the nanostructure of C-S-H present in real cement pastes. The discussion is facilitated by a consideration of the author's 1992 model, which includes formulations for both structural viewpoints; its relationship to other recent models is outlined. The structural details of the model are clearly illustrated with a number of schematic diagrams. Experimental observations on the nature of C-S-H present in a diverse range of cementitious systems are considered. In some systems, the data can only be accounted for on the T/CH structural viewpoint, whilst in others, both the T/CH and T/J viewpoints could apply. New data from transmission electron microscopy (TEM) are presented. The 'inner product' (Ip) C-S-H in relatively large grains of C 3 S or alite appears to consist of small globular particles, which are ∼4-8 nm in size in pastes hydrated at 20 deg. C but smaller at elevated temperatures, ∼3-4 nm. Fibrils of 'outer product' (Op) C-S-H in C 3 S or β-C 2 S pastes appear to consist of aggregations of long thin particles that are about 3 nm in their smallest dimension and of variable length, ranging from a few nanometers to many tens of nanometers. The small size of these particles of C-S-H is likely to result in significant edge effects, which would seem to offer a reasonable explanation for the persistence of Q 0 (H) species. This would also explain why there is more Q 0 (H) at elevated temperatures, where the particles seem to be smaller, and apparently less in KOH-activated pastes, where the C-S-H has foil-like morphology. In blended cements, a reduction in the mean Ca/Si ratio of the C-S-H results in a change from fibrillar to a crumpled-foil morphology, which suggests strongly that as the Ca/Si ratio is reduced, a transition occurs from essentially one-dimensional growth of the C-S-H particles to

  9. Solidification and performance of cement doped with phenol

    International Nuclear Information System (INIS)

    Vipulanandan, C.; Krishnan, S.

    1991-01-01

    Treating mixed hazardous wastes using the solidification/stabilization technology is becoming a critical element in waste management planning. The effect of phenol, a primary constituent in many hazardous wastes, on the setting and solidification process of Type I Portland cement was evaluated. The leachability of phenol from solidified cement matrix (TCLP test) and changes in mechanical properties were studied after curing times up to 28 days. The changes in cement hydration products due to phenol were studied using the X-ray diffraction (XRD) powder technique. Results show that phenol interferes with initial cement hydration by reducing the formation of calcium hydroxide and also reduces the compressive strength of cement. A simple model has been proposed to quantify the phenol leached from the cement matrix during the leachate test

  10. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Glasser, F.P.; Rahman, A.A.; Crawford, R.W.; McCulloch, C.E.; Angus, M.J.

    1984-01-01

    Tobermorite and xonotlite, two synthetic calcium silicate hydrates, improve the Cs retention of cement matrices for Cs, when incorporated at the 6 to 10% level. A kinetic and mechanistic scheme is presented for the reaction of fine grained, Cs-loaded clinoptilolite with cement. The Magnox waste form reacts quickly with cement, leading to an exchange of carbonate between waste form and cement components. Carbonation of cements leads to a marked improvement in their physical properties of Cs retentivity. Diffusion models are presented for cement systems whose variable parameters can readily be derived from experimental measurements. Predictions about scaled-up behaviour of large immobilized masses are applied to extrapolation of laboratory scale results to full-size masses. (author)

  11. Cement-Based Materials for Nuclear Waste Storage

    CERN Document Server

    Cau-di-Coumes, Céline; Frizon, Fabien; Lorente, Sylvie

    2013-01-01

    As the re-emergence of nuclear power as an acceptable energy source on an international basis continues, the need for safe and reliable ways to dispose of radioactive waste becomes ever more critical. The ultimate goal for designing a predisposal waste-management system depends on producing waste containers suitable for storage, transportation and permanent disposal. Cement-Based Materials for Nuclear-Waste Storage provides a roadmap for the use of cementation as an applied technique for the treatment of low- and intermediate-level radioactive wastes.Coverage includes, but is not limited to, a comparison of cementation with other solidification techniques, advantages of calcium-silicate cements over other materials and a discussion of the long-term suitability and safety of waste packages as well as cement barriers. This book also: Discusses the formulation and production of cement waste forms for storing radioactive material Assesses the potential of emerging binders to improve the conditioning of problemati...

  12. Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

    Science.gov (United States)

    Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

    2015-03-01

    Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

  13. Prompt gamma analysis of fly ash, silica fume and Superpozz blended cement concrete specimen

    Energy Technology Data Exchange (ETDEWEB)

    Naqvi, A.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)], E-mail: aanaqvi@kfupm.edu.sa; Garwan, M.A. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Maslehuddin, M. [Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Nagadi, M.M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Amoudi, O.S.B. [Department of Civil Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Khateeb-ur-Rehman; Raashid, M. [Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2009-09-15

    Preventive measures against corrosion of reinforcing steel require making the concrete dense by adding pozzolanic materials, such as fly ash, silica fume, Superpozz, blast furnace slag, etc. to Portland cement. In order to obtain the desired strength and durability of concrete, it is desirable to monitor the concentration of the pozzolan in the blended cement concrete. Addition of pozzolan to blended cement changes the overall concentration of calcium and silicon in the blended cement concrete. The resulting variation in calcium and silicon gamma-ray yield ratio from blended cement concrete has found to have an inverse correlation with concentration of fly ash, silica fume, Superpozz, blast furnace slag in the blended cement concrete. For experimental verification of the correlation, intensities of calcium and silicon prompt gamma-ray due to capture of thermal neutrons in blended cement concrete samples containing 5-80% (by weight of cement) silica fume, fly ash and Superpozz were measured. The gamma-ray intensity ratio was measured from 6.42 MeV gamma-rays from calcium and 4.94 MeV gamma-ray from silicon. The experimentally measured values of calcium to silicon gamma-ray yield ratio in the fly ash, silica fume and Superpozz cement concrete specimens agree very well with the results of the Monte Carlo simulations.

  14. Prompt gamma analysis of fly ash, silica fume and Superpozz blended cement concrete specimen

    International Nuclear Information System (INIS)

    Naqvi, A.A.; Garwan, M.A.; Maslehuddin, M.; Nagadi, M.M.; Al-Amoudi, O.S.B.; Khateeb-ur-Rehman,; Raashid, M.

    2009-01-01

    Preventive measures against corrosion of reinforcing steel require making the concrete dense by adding pozzolanic materials, such as fly ash, silica fume, Superpozz, blast furnace slag, etc. to Portland cement. In order to obtain the desired strength and durability of concrete, it is desirable to monitor the concentration of the pozzolan in the blended cement concrete. Addition of pozzolan to blended cement changes the overall concentration of calcium and silicon in the blended cement concrete. The resulting variation in calcium and silicon gamma-ray yield ratio from blended cement concrete has found to have an inverse correlation with concentration of fly ash, silica fume, Superpozz, blast furnace slag in the blended cement concrete. For experimental verification of the correlation, intensities of calcium and silicon prompt gamma-ray due to capture of thermal neutrons in blended cement concrete samples containing 5-80% (by weight of cement) silica fume, fly ash and Superpozz were measured. The gamma-ray intensity ratio was measured from 6.42 MeV gamma-rays from calcium and 4.94 MeV gamma-ray from silicon. The experimentally measured values of calcium to silicon gamma-ray yield ratio in the fly ash, silica fume and Superpozz cement concrete specimens agree very well with the results of the Monte Carlo simulations.

  15. Synthesis of a Cementitious Material Nanocement Using Bottom-Up Nanotechnology Concept: An Alternative Approach to Avoid CO2 Emission during Production of Cement

    Directory of Open Access Journals (Sweden)

    Byung Wan Jo

    2014-01-01

    Full Text Available The world’s increasing need is to develop smart and sustainable construction material, which will generate minimal climate changing gas during their production. The bottom-up nanotechnology has established itself as a promising alternative technique for the production of the cementitious material. The present investigation deals with the chemical synthesis of cementitious material using nanosilica, sodium aluminate, sodium hydroxide, and calcium nitrate as reacting phases. The characteristic properties of the chemically synthesized nanocement were verified by the chemical composition analysis, setting time measurement, particle size distribution, fineness analysis, and SEM and XRD analyses. Finally, the performance of the nanocement was ensured by the fabrication and characterization of the nanocement based mortar. Comparing the results with the commercially available cement product, it is demonstrated that the chemically synthesized nanocement not only shows better physical and mechanical performance, but also brings several encouraging impacts to the society, including the reduction of CO2 emission and the development of sustainable construction material. A plausible reaction scheme has been proposed to explain the synthesis and the overall performances of the nanocement.

  16. THE IMPACT OF DISSOLVED SALTS ON PASTES CONTAINING FLY ASH, CEMENT AND SLAG

    Energy Technology Data Exchange (ETDEWEB)

    Harbour, J.; Edwards, T.; Williams, V.

    2009-09-21

    The degree of hydration of a mixture of cementitious materials (Class F fly ash, blast furnace slag and portland cement) in highly concentrated alkaline salt solutions is enhanced by the addition of aluminate to the salt solution. This increase in the degree of hydration, as monitored with isothermal calorimetry, leads to higher values of dynamic Young's modulus and compressive strength and lower values of total porosity. This enhancement in performance properties of these cementitious waste forms by increased hydration is beneficial to the retention of the radionuclides that are also present in the salt solution. The aluminate ions in the solution act first to retard the set time of the mix but then enhance the hydration reactions following the induction period. In fact, the aluminate ions increase the degree of hydration by {approx}35% over the degree of hydration for the same mix with a lower aluminate concentration. An increase in the blast furnace slag concentration and a decrease in the water to cementitious materials ratio produced mixes with higher values of Young's modulus and lower values of total porosity. Therefore, these operational factors can be fine tuned to enhance performance properties of cementitious waste form. Empirical models for Young modulus, heat of hydration and total porosity were developed to predict the values of these properties. These linear models used only statistically significant compositional and operational factors and provided insight into those factors that control these properties.

  17. Personal exposure to inhalable cement dust among construction workers

    International Nuclear Information System (INIS)

    Peters, Susan; Kromhout, Hans; Thomassen, Yngvar; Fechter-Rink, Edeltraud

    2009-01-01

    A case study was carried out in 2006-2007 to assess the actual cement dust exposure among construction workers involved in a full-scale construction project and as a comparison among workers involved in various stages of cement and concrete production. Full-shift personal exposure measurements were performed for several job types. Inhalable dust and cement dust (based on analysis of elemental calcium) concentrations were determined. Inhalable dust exposures at the construction site ranged from 0.05 to 34 mg/m3, with a mean concentration of 1.0 mg/m3. For inhalable cement dust mean exposure was 0.3 mg/m3 (range 0.02-17 mg/m3). Reinforcement and pouring workers had the lowest average concentrations. Inhalable dust levels in the ready-mix and pre-cast concrete plants were, on average, below 0.5 mg/m3 for inhalable dust and below 0.2 mg/m3 for inhalable cement dust. Highest dust concentrations were measured in cement production, particularly during cleaning tasks (inhalable dust GM=55 mg/m3; inhalable cement dust GM=33 mg/m3) at which point the workers wore personal protective equipment. Elemental measurements showed highest but very variable cement percentages in the cement plant and very low percentages of cement during reinforcement work and pouring.

  18. Development of fluorapatite cement for dental enamel defects repair.

    Science.gov (United States)

    Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

  19. Producing cement

    Energy Technology Data Exchange (ETDEWEB)

    Stone, E G

    1923-09-12

    A process and apparatus are described for producing Portland cement in which pulverized shale is successively heated in a series of inclined rotary retorts having internal stirrers and oil gas outlets, which are connected to condensers. The partially treated shale is removed from the lowermost retort by a conveyor, then fed separately or conjointly into pipes and thence into a number of vertically disposed retorts. Each of these retorts may be fitted interiorly with vertical arranged conveyors which elevate the shale and discharge it over a lip, from whence it falls to the bottom of the retorts. The lower end of each casing is furnished with an adjustable discharge door through which the spent shale is fed to a hopper, thence into separate trucks. The oil gases generated in the retorts are exhausted through pipes to condensers. The spent shale is conveyed to a bin and mixed while hot with ground limestone. The admixed materials are then ground and fed to a rotary kiln which is fired by the incondensible gases derived from the oil gases obtained in the previous retorting of the shale. The calcined materials are then delivered from the rotary kiln to rotary coolers. The waste gases from the kiln are utilized for heating the retorts in which the ground shale is heated for the purpose of extracting therefrom the contained hydrocarbon oils and gases.

  20. Study of damages by neutron irradiation in lithium aluminates

    International Nuclear Information System (INIS)

    Palacios G, O.

    1999-01-01

    Lithium aluminates proposed to the production of tritium in fusion nuclear reactors, due to the thermal stability that they present as well as the behavior of the aluminium to the irradiation. As a neutron flux with profile (≅ 14 Mev) of a fusion reactor is not available. A irradiation experiment was designed in order to know the micro and nano structure damages produced by fast and thermal neutrons in two irradiation positions of the fusion nuclear reactor Triga Mark III: CT (Thermal Column) and SIFCA (System of Irradiation Fixed of Capsules). In this work samples of lithium aluminate were characterized by XRD (X-Ray Diffraction), TEM (Transmission Electron Microscopy) and SEM (Scanning Electron Microscopy). Two samples were prepared by two methods: a) coalition method and b) peroxide method. This characterization comprised original and irradiated samples. The irradiated sample amounted to 4 in total: one for each preparation method and one for each irradiation position. The object of this analysis was to correlate with the received neutron dose the damages suffered by the samples with the neutron irradiation during long periods (440 H), in their micro and nano structure aspects; in order to understand the changes as a function of the irradiation zone (with thermal and fast neutron flux) and the preparation methods of the samples and having as an antecedent the irradiation in SIFCA position by short times (2h). The obtained results are referred to the stability of γ -aluminate phase, under given conditions of irradiation and defined nano structure arrangement. They also refer to the proposals of growth mechanism and nucleation of new phases. The error associated with the measurement of neutron dose is also discussed. (Author)

  1. A influência do tipo de cimento no desempenho de concretos avançados formulados a partir do método de dosagem computacional The influence of cement type on the performance of advanced concretes designed by computing mix proportion technique

    Directory of Open Access Journals (Sweden)

    A. L. de Castro

    2011-03-01

    . Thus, variations on cement characteristics influence the properties of a concrete, being observed different behaviors for mixtures produced with distinct cements. The present paper aims to evaluate the influence of cement type on the performance of special concretes designed using computing techniques. The fresh properties were evaluated measuring the fluidity index and the rheological behavior of the material. In the hardened condition, the mechanical strength were evaluated by the compressive, splitting tensile and 3 point bending tests, whereas the Young's modulus was measured by the static and dynamic methods. By comparing all the measured properties, the concretes produced with Portland cement showed better performance than that containing calcium aluminate cement, being the high early strength Portland cement more efficient than the slag-modified Portland cement for the production of high performance mixtures and until the age of 28 days.

  2. In-situ Mechanical Manipulation of Wellbore Cements as a Solution to Leaky Wells

    Science.gov (United States)

    Kupresan, D.; Radonjic, M.; Heathman, J.

    2013-12-01

    Wellbore cement provides casing support, zonal isolation, and casing protection from corrosive fluids, which are essential for wellbore integrity. Cements can undergo one or more forms of failure such as debonding at cement/formation and cement/casing interface, fracturing and defects within cement matrix. Failures and defects within cement will ultimately lead to fluids migration, resulting in inter-zonal fluid migration and premature well abandonment. There are over 27,000 abandoned oil and gas wells only in The Gulf of Mexico (some of them dating from the late 1940s) with no gas leakage monitoring. Cement degradation linked with carbon sequestration can potentially lead to contamination of fresh water aquifers with CO2. Gas leaks can particularly be observed in deviated wells used for hydraulic fracking (60% leakage rate as they age) as high pressure fracturing increases the potential for migration pathways. Experimental method utilized in this study enables formation of impermeable seals at interfaces present in a wellbore by mechanically manipulating wellbore cement. Preliminary measurements obtained in bench scale experiments demonstrate that an impermeable cement/formation and cement/casing interface can be obtained. In post-modified cement, nitrogen gas flow-through experiments showed complete zonal isolation and no permeability in samples with pre-engineered microannulus. Material characterization experiments of modified cement revealed altered microstructural properties of cement as well as changes in mineralogical composition. Calcium-silicate-hydrate (CSH), the dominant mineral in hydrated cement which provides low permeability of cement, was modified as a result of cement pore water displacement, resulting in more dense structures. Calcium hydroxide (CH), which is associated with low resistance of cement to acidic fluids and therefore detrimental in most wellbore cements, was almost completely displaced and/or integrated in CSH as a result of

  3. Aluminized film, seam sealing tests and observations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1994-06-16

    The purpose of this work was to investigate various seam sealing techniques, reinforcing methods, fitting installations, seam tolerances and geometric configurations pertinent to an aluminized plastic laminate. The program seeks a successful fabricating method for producing low-diffusion, cylindrical, spar liners to contain pressurized GH{sub 2} and GO{sub 2}. The test plan included: (1) seaming techniques on metallized Mylar film; (2) ``double patches`` for end fittings; (3) stainless steel bulkhead fitting assembly with seals; (4) minimum run tolerance on linear shear seam; (5) peel seam vs. inverted seal seam fabrication.

  4. System and process for aluminization of metal-containing substrates

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Yeong-Shyung; Stevenson, Jeffry W.

    2017-12-12

    A system and method are detailed for aluminizing surfaces of metallic substrates, parts, and components with a protective alumina layer in-situ. Aluminum (Al) foil sandwiched between the metallic components and a refractory material when heated in an oxidizing gas under a compression load at a selected temperature forms the protective alumina coating on the surface of the metallic components. The alumina coating minimizes evaporation of volatile metals from the metallic substrates, parts, and components in assembled devices that can degrade performance during operation at high temperature.

  5. System and process for aluminization of metal-containing substrates

    Science.gov (United States)

    Chou, Yeong-Shyung; Stevenson, Jeffry W

    2015-11-03

    A system and method are detailed for aluminizing surfaces of metallic substrates, parts, and components with a protective alumina layer in-situ. Aluminum (Al) foil sandwiched between the metallic components and a refractory material when heated in an oxidizing gas under a compression load at a selected temperature forms the protective alumina coating on the surface of the metallic components. The alumina coating minimizes evaporation of volatile metals from the metallic substrates, parts, and components in assembled devices during operation at high temperature that can degrade performance.

  6. The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

    Science.gov (United States)

    Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

    2016-04-01

    Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

  7. Effects of Na4EDTA and EDTA on seeded precipitation of sodium aluminate solution

    Institute of Scientific and Technical Information of China (English)

    吕保林; 陈启元; 尹周澜; 胡慧萍

    2010-01-01

    Na4EDTA and EDTA were adopted as new additives to intensify the seeded precipitation process of sodium aluminate solution. The effects of the two additives at certain concentrations on the seeded precipitation rate of sodium aluminate solution, particle size distribution (PSD) and morphology of precipitated gibbsite were investigated using titration method, particle size analyzer and scanning electron microscope (SEM), respectively. The results show that the two additives can accelerate the seeded precipitation rate of sodium aluminate solution. At relatively high concentration, the facilitative effect of EDTA on sodium aluminate solution is more obvious than that of Na4EDTA. EDTA makes gibbsite particles thinner than Na4EDTA. The Na+ and H+ result in the different effects on the seeded precipitation rate of sodium aluminate solution in spite of the same EDTA anion in the two additives.

  8. Calcium supplements

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007477.htm Calcium supplements To use the sharing features on this page, please enable JavaScript. WHO SHOULD TAKE CALCIUM SUPPLEMENTS? Calcium is an important mineral for the ...

  9. Asphalt cement poisoning

    Science.gov (United States)

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

  10. Radioactivity of bone cement

    International Nuclear Information System (INIS)

    Scherer, M.A.; Winkler, R.; Ascherl, R.; Lenz, E.

    1993-01-01

    A total of 14 samples of different types of bone cement from five different manufacturers were examined for their radioactivity. Each of the investigated bone cements showed a low radioactivity level, i.e. between [de

  11. Ultrafine portland cement performance

    Directory of Open Access Journals (Sweden)

    C. Argiz

    2018-04-01

    Full Text Available By mixing several binder materials and additions with different degrees of fineness, the packing density of the final product may be improved. In this work, ultrafine cement and silica fume mixes were studied to optimize the properties of cement-based materials. This research was performed in mortars made of two types of cement (ultrafine Portland cement and common Portland cement and two types of silica fume with different particle-size distributions. Two Portland cement replacement ratios of 4% and 10% of silica fume were selected and added by means of a mechanical blending method. The results revealed that the effect of the finer silica fume mixed with the coarse cement enhances the mechanical properties and pore structure refinement at a later age. This improvement is somewhat lower in the case of ultrafine cement with silica fume.

  12. Preparation of iron-modified portland cement adsorbent and the investigation of its decolorization performance

    Science.gov (United States)

    Jiang, Bo; Wang, Huifeng; Li, Yang; Li, Zhen

    2018-02-01

    The ordinary portland cement was modified by ferric salt impregnation method. Through the technologies of x-ray diffraction, scanning electron microscope and energy dispersive spectroscopy, the physicochemical properties of modified cement were detected and analyzed. It was found that after the modification, the main constituents of raw cement, tricalcium silicate and dicalcium silicate had been depleted, and the new crystal mineral of antarcticite replaced them. The iron precipitates and cement hydration products calcium silicate hydrate gel mainly existed in the form of amorphous on modified cement. The results of BET specific surface determination showed that the modified cement particles had mesoporous distribution. The results of adsorption experiment revealed modified cement exhibited excellent adsorption performance on reactive brilliant blue KNR. The combination mechanism between modified cement and adsorbate was mainly electrostatic interaction. The adsorption process satisfied with the pseudo-second order kinetics model, and the adsorption reaction was a spontaneous endothermic process.

  13. R7T7 glass alteration in the presence of mortar: effect of the cement grade

    International Nuclear Information System (INIS)

    Andriambololona, Z.; Godon, N.; Vernaz, E.

    1991-01-01

    R7T7 glass alteration was investigated in the presence of four mortars prepared from four different cement grades: 'CPA' Portland cement (mortar M1), CPA with pozzolana additive (M2), CPA with amorphous silica additive (M3) and 'CLK' blast furnace slag cement (M4). Glass specimens were also altered in Volvic mineral water and in a cement effluent. Glass corrosion in the cement media was greater than in Volvic water, but well below what could be expected from the high pH (approx 12.5). The relatively low alteration was probably related to the protective action of the calcium-enriched gel layer that formed at the glass surface. The glass corrosion rate was 2 to 3 times lower with cement containing pozzolana or silica gel additives or with CLK cement than with CPA cement alone. 8 refs., 8 figs

  14. Dielectric behavior and ac electrical conductivity of nanocrystalline nickel aluminate

    International Nuclear Information System (INIS)

    Kurien, Siby; Mathew, Jose; Sebastian, Shajo; Potty, S.N.; George, K.C.

    2006-01-01

    Nanocrystalline nickel aluminate was prepared by chemical co-precipitation, and nanoparticles having different particle size were obtained by annealing the precursor at different temperatures. The TG/DTA measurements showed thermal decomposition was a three-step process with crystallisation of the spinel phase started at a temperature 420 deg. C. The X-ray diffraction analysis confirmed that the specimen began to crystallise on annealing above 420 deg. C and became almost crystalline at about 900 deg. C. The particle sizes were calculated from XRD. Dielectric properties of nickel aluminate were studied as a function of the frequency of the applied ac signal at different temperatures. It was seen the real dielectric constant ε', and dielectric loss tan δ decreased with frequency of applied field while the ac conductivity increased as the frequency of the applied field increased. The dielectric relaxation mechanism is explained by considering nanostructured NiAl 2 O 4 as a carrier-dominated dielectric with high density of hopping charge carriers. The variation of ε' with different particle size depends on several interfacial region parameters, which change with the average particle size

  15. Sulfur polymer cement concrete

    International Nuclear Information System (INIS)

    Weber, H.H.; McBee, W.C.

    1990-01-01

    Sulfur-based composite materials formulated using sulfur polymer cement (SPC) and mineral aggregates are described and compared with conventional portland cement based materials. Materials characteristics presented include mechanical strength, chemical resistance, impact resistance, moisture permeation, and linear shrinkage during placement and curing. Examples of preparation and placement of sulfur polymer cement concrete (SC) are described using commercial scale equipment. SC applications presented are focused into hostile chemical environments where severe portland cement concrete (PCC) failure has occurred

  16. Application of Carbonate Looping to Cement Industry

    DEFF Research Database (Denmark)

    Lin, Weigang; Illerup, Jytte Boll; Dam-Johansen, Kim

    2012-01-01

    In the present work, cycle experiments of different types of limestone, cement raw meal and a mixture of limestone and clay were carried out in laboratory scale setups at more realistic conditions (i.e. calcination temperature is 950°C and CO2 concentration is 80%) to simulate the performance...... with an increase in the CO2 partial pressure during calcination, indicating enhancement of sintering by the presence of CO2. As sorbents, cement raw meal and the mixture of limestone and clay show a similar trend as limestone with respect to the decay of the CO2 carrying capacity and this capacity is lower than...... that of limestone at the same conditions in most cases. SEM and XRD analyses indicate that a combination of severe sintering and formation of calcium silicates attributes to the poor performance of the cement raw meal....

  17. Hydrate Phase Assemblages in Calcium Sulfoaluminate - Metakaolin - Limestone Blends

    DEFF Research Database (Denmark)

    Pedersen, Malene Thostrup; Lothenbach, Barbara; Winnefeld, Frank

    2017-01-01

    The combination of a commercial calcium sulfoaluminate (CSA) cement with metakaolin (MK) and limestone (LS) as supplementary cementitious materials (SCMs) is investigated for a CSA replacement level of 20 wt%. In addition to a pure CSA cement, paste samples have been prepared for three blends wit...

  18. Calcium absorption

    International Nuclear Information System (INIS)

    Carlmark, B.; Reizenstein, P.; Dudley, R.A.

    1976-01-01

    The methods most commonly used to measure the absorption and retention of orally administered calcium are reviewed. Nearly all make use of calcium radioisotopes. The magnitude of calcium absorption and retention depends upon the chemical form and amount of calcium administered, and the clinical and nutritional status of the subject; these influences are briefly surveyed. (author)

  19. Influence of chloride admixtures on cement matrix durability

    International Nuclear Information System (INIS)

    Sheikh, I.A.; Zamorani, E.; Serrini, G.

    1989-01-01

    The influence of various inorganic salts, as chloride admixtures to Portland cement, on the mechanical properties and the durability of the matrix has been studied. The salts used in this study are chromium, nickel and cadmium chlorides. Improved compressive strength values are obtained which have been correlated to the stable metal hydroxide formation in high pH environment. Under static water conditions at 50 0 C, hydrolyzed chloride ions exhibit adverse effects on the matrix durability through rapid release of calcium as calcium chloride in the initial period of leaching. On the contrary, enhanced matrix durability is obtained on long term leaching in the case of cement containing chromium chloride

  20. Microstructure of hydrated cement pastes as determined by SANS

    International Nuclear Information System (INIS)

    Sabine, T.; Bertram, W.; Aldridge, L.

    1999-01-01

    Full text: Technologists have known how to make concrete for over 2000 years but despite painstaking research no one has been able to show how and why concrete sets. Part of the problem is that the calcium silicate hydrate (the gel produced by hydrating cement) is amorphous and cannot be characterised by x-ray crystallographic techniques. Small angle neutron scattering on instrument V12a at BENSC was used to characterise the hydration reactions and show the growth of the calcium silicate hydrates during initial hydration and the substantial differences in the rate of growth and structure as different additives are used. SANS spectra were measured as a function of the hydration from three different types of cement paste: 1) Ordinary Portland Cement made with a water to cement ratio of about 0.4; 2) A blend of Ordinary Portland Cement(25%) and Ground Granulated Blast Furnace Slag (75%) with a water to cement ration of about 0.4; 3) A dense paste made from silica fume(24%), Ordinary Portland Cement (76%) at a water to powder ratio of 0.18. The differences in the spectra are interpreted in terms of differences between the microstructure of the pastes

  1. Effect of provisional cements on shear bond strength of porcelain laminate veneers.

    Science.gov (United States)

    Altintas, Subutay Han; Tak, Onjen; Secilmis, Asli; Usumez, Aslihan

    2011-08-01

    The purpose of this study was to evaluate the effect of three provisional cements and two cleaning techniques on the final bond strength of porcelain laminate veneers. The occlusal third of the crowns of forty molar teeth were sectioned and embedded in autopolymerizing acrylic resin. Dentin surfaces were polished and specimens were randomly divided into four groups (n=10). Provisional restorations were fabricated and two provisional restorations were cemented onto each tooth. Restorations were fixed with one of three different provisional cements: eugenol-free provisional cement (Cavex), calcium hydroxide (Dycal), and light-cured provisional cement (Tempond Clear). Provisional restorations were removed with either a dental explorer and air-water spray, or a cleaning bur (Opticlean). In the control group, provisional restorations were not used on the surfaces of specimens. IPS Empress 2 ceramic discs were luted with a dual-cured resin cement (Panavia F). Shear bond strength was measured using a universal testing machine. Data were statistically analyzed by ANOVA, Tukey's HSD and Dunnett tests. Surfaces were examined by scanning electronic microscopy. Significant differences were found between the control group and both the light-cured provisional cement groups and the eugenol-free provisional cement-cleaning bur group (Pprovisional cement showed the lowest bond strength values. Selection of the provisional cement is an important factor in the ultimate bond strength of the final restoration. Calcium hydroxide provisional cement and cleaning with a dental explorer are advisable.

  2. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    Fred Sabins

    2001-01-01

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter

  3. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    Fred Sabins

    2001-01-01

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job

  4. Electrical properties and thermal expansion of strontium aluminates

    Energy Technology Data Exchange (ETDEWEB)

    Zakharchuk, K.V. [Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Yaremchenko, A.A., E-mail: ayaremchenko@ua.pt [Department of Materials and Ceramic Engineering, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Fagg, D.P. [TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro (Portugal)

    2014-11-15

    Highlights: • Sr{sub 3}Al{sub 2}O{sub 6}, SrAl{sub 2}O{sub 4} and Sr{sub 4}Al{sub 14}O{sub 25} ceramics are semiconductors. • Electrical conductivity is as low as 10{sup −6}−4×10{sup −5} S/cm at 1273 K in dry air. • SrAl{sub 2}O{sub 4} is a mixed conductor with predominant ionic conductivity. • Sr{sub 3}Al{sub 2}O{sub 6} shows significant contribution of protonic transport in wet atmospheres. • Average TECs vary in the range (8.5–11.1)×10{sup −6} K{sup −1} and are p(O{sub 2})-independent. - Abstract: Strontium aluminate ceramics, including Sr{sub 3}Al{sub 2}O{sub 6}, SrAl{sub 2}O{sub 4} and Sr{sub 4}Al{sub 14}O{sub 25}, synthesized by glycine–nitrate combustion and sintered at 1773 K in air, were characterized by thermal analysis, dilatometry and electrical measurements in controlled atmospheres. All studied strontium aluminates are semiconductors with electrical conductivities as low as 10{sup −6}−4×10{sup −5} S/cm at 1273 K in dry air. Electrical measurements in controlled atmospheres in combination with ion transference number determination demonstrated that SrAl{sub 2}O{sub 4} is a mixed conductor with predominant ionic conductivity and increasing n-type and p-type electronic contributions under highly reducing and oxidizing conditions, respectively. While the behavior of electrical conductivity of Sr{sub 3}Al{sub 2}O{sub 6} in dry atmospheres was qualitatively similar to that of SrAl{sub 2}O{sub 4}, a significant increase of conductivity in wet atmospheres was attributed to a protonic contribution to electrical conduction, in correlation with thermogravimetric data and the tendency of this material to form a hydrogarnet at low temperatures. The average thermal expansion coefficients of strontium aluminates, (8.5–11.1)×10{sup −6} K{sup −1} at 333–1373 K, increase with increasing strontium content in the sequence Sr{sub 4}Al{sub 14}O{sub 25} < SrAl{sub 2}O{sub 4} < Sr{sub 3}Al{sub 2}O{sub 6} and are essentially

  5. Solubilities of sodium nitrate, sodium nitrite, and sodium aluminate in simulated nuclear waste

    International Nuclear Information System (INIS)

    Reynolds, D.A.; Herting, D.L.

    1984-09-01

    Solubilities were determined for sodium nitrate, sodium nitrite, and sodium aluminate in synthetic nuclear waste liquor. Solubilities were determined as a function of temperature and solution composition (concentrations of sodium hydroxide, sodium nitrate, sodium nitrite, and sodium aluminate). Temperature had the greatest effect on the solubilities of sodium nitrate and sodium nitrite and a somewhat lesser effect on sodium aluminate solubility. Hydroxide had a great effect on the solubilities of all three salts. Other solution components had minor effects. 2 references, 8 figures, 11 tables

  6. Antagonist effects of calcium on borosilicate glass alteration

    Energy Technology Data Exchange (ETDEWEB)

    Mercado-Depierre, S. [CEA Marcoule, DTCD SPDE LCLT, 30207 Bagnols sur Cèze (France); Angeli, F., E-mail: frederic.angeli@cea.fr [CEA Marcoule, DTCD SPDE LCLT, 30207 Bagnols sur Cèze (France); Frizon, F. [CEA Marcoule, DTCD SECM LP2C, 30207 Bagnols sur Cèze (France); Gin, S. [CEA Marcoule, DTCD SPDE LCLT, 30207 Bagnols sur Cèze (France)

    2013-10-15

    Graphical abstract: Display Omitted -- Highlights: •Kinetic study of glass alteration is investigated in calcium-enriched solutions. •New insights into silicon–calcium interactions in glass/cement systems are proposed. •Glass alteration is controlled by pH, Ca concentration and reaction progress. •Evidence of antagonist effects according to the importance of these parameters. -- Abstract: Numerous studies have been conducted on glass and cement durability in contact with water, but very little work to date has focused directly on interactions between the two materials. These interactions are mostly controlled by silicon–calcium reactivity. However, the physical and chemical processes involved remain insufficiently understood to predict the evolution of coupled glass–cement systems used in several industrial applications. Results are reported from borosilicate glass alteration in calcium-rich solutions. Our data show that four distinct behaviors can be expected according to the relative importance of three key parameters: the pH, the reaction progress (short- or long-term alteration) and the calcium concentration. Glass alteration is thus controlled by specific mechanisms depending on the solution chemistry: calcium complexation at the glass surface, precipitation of calcium silicate hydrates (C–S–H) or calcium incorporation in the altered layer. These findings highlight the impact of silicon–calcium interactions on glass durability and open the way for a better understanding of glass–cement mixing in civil engineering applications as well as in nuclear waste storage.

  7. Antagonist effects of calcium on borosilicate glass alteration

    International Nuclear Information System (INIS)

    Mercado-Depierre, S.; Angeli, F.; Frizon, F.; Gin, S.

    2013-01-01

    Graphical abstract: Display Omitted -- Highlights: •Kinetic study of glass alteration is investigated in calcium-enriched solutions. •New insights into silicon–calcium interactions in glass/cement systems are proposed. •Glass alteration is controlled by pH, Ca concentration and reaction progress. •Evidence of antagonist effects according to the importance of these parameters. -- Abstract: Numerous studies have been conducted on glass and cement durability in contact with water, but very little work to date has focused directly on interactions between the two materials. These interactions are mostly controlled by silicon–calcium reactivity. However, the physical and chemical processes involved remain insufficiently understood to predict the evolution of coupled glass–cement systems used in several industrial applications. Results are reported from borosilicate glass alteration in calcium-rich solutions. Our data show that four distinct behaviors can be expected according to the relative importance of three key parameters: the pH, the reaction progress (short- or long-term alteration) and the calcium concentration. Glass alteration is thus controlled by specific mechanisms depending on the solution chemistry: calcium complexation at the glass surface, precipitation of calcium silicate hydrates (C–S–H) or calcium incorporation in the altered layer. These findings highlight the impact of silicon–calcium interactions on glass durability and open the way for a better understanding of glass–cement mixing in civil engineering applications as well as in nuclear waste storage

  8. Model of Inclusion Evolution During Calcium Treatment in the Ladle Furnace

    Science.gov (United States)

    Tabatabaei, Yousef; Coley, Kenneth S.; Irons, Gordon A.; Sun, Stanley

    2018-04-01

    Calcium treatment of steel is typically employed to modify alumina inclusions to liquid calcium aluminates. However, injected calcium also reacts with the dissolved sulfur to form calcium sulfide. The current work aims to develop a kinetic model for the evolution of oxide and sulfide inclusions in Al-killed alloyed steel during Ca treatment in the ladle refining process. The model considers dissolution of the calcium from the calcium bubbles into the steel and reduction of calcium oxide in the slag to dissolved calcium. A steel-inclusion kinetic model is used for mass transfer to the inclusion interface and diffusion within the calcium aluminate phases formed on the inclusion. The inclusion-steel kinetic model is then coupled with a previously developed steel-slag kinetic model. The coupled inclusion-steel-slag kinetic model is applied to the chemical composition changes in molten steel, slag, and evolution of inclusions in the ladle. The result of calculations is found to agree well with an industrial heat for species in the steel as well as inclusions during Ca treatment.

  9. Biphasic products of dicalcium phosphate-rich cement with injectability and nondispersibility

    International Nuclear Information System (INIS)

    Ko, Chia-Ling; Chen, Jian-Chih; Hung, Chun-Cheng; Wang, Jen-Chyan; Tien, Yin-Chun; Chen, Wen-Cheng

    2014-01-01

    In this study, a calcium phosphate cement was developed using tetracalcium phosphate and surface-modified dicalcium phosphate anhydrous (DCPA). This developed injectable bone graft substitute can be molded to the shape of the bone cavity and set in situ through the piping system that has an adequate mechanical strength, non-dispersibility, and biocompatibility. The materials were based on the modified DCPA compositions of calcium phosphate cement (CPC), where the phase ratio of the surface-modified DCPA is higher than that of the conventional CPC for forming dicalcium phosphate (DCP)-rich cement. The composition and morphology of several calcium phosphate cement specimens during setting were analyzed via X-ray diffractometry and transmission electron microscopy coupled with an energy dispersive spectroscopy system. The compressive strength of DCP-rich CPCs was greater than 30 MPa after 24 h of immersion in vitro. The reaction of the CPCs produced steady final biphasic products of DCPs with apatite. The composites of calcium phosphate cements derived from tetracalcium phosphate mixed with surface-modified DCPA exhibited excellent mechanical properties, injectability, and interlocking forces between particles, and they also featured nondispersive behavior when immersed in a physiological solution. - Highlights: • Bone cement precursor with nanocrystals is characterized. • DCP-rich CPCs with nanocrystals exhibited biphasic product phases. • Nanocrystals in cement significantly affected the interlocking ability. • Nanocrystals in cement exhibited higher strength and anti-dispersion. • DCP-rich CPCs increase the potential of bioresorption after reaction

  10. Creep-rupture Behaviors of a Diffusionally Aluminized Alloy 617

    Energy Technology Data Exchange (ETDEWEB)

    Sah, Injin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, Sung Hwan; Jang, Chang Heui [KAIST, Daejeon (Korea, Republic of)

    2015-05-15

    In light of the surface reaction, a sufficient Cr content in the matrix leads to an external chromia (Cr{sub 2}O{sub 3}) layer on the surface with the occurrence of internal oxides (Al{sub 2}O{sub 3}) into the matrix. It is well known that the internal oxides will reduce the effective cross-sectional area and/or be a notch under the loading condition. Thus, there have been extensive efforts to improve the oxidation resistance by imposing an aluminized layer (βNiAl or γ-Ni{sub 3}Al) for Ni-Cr alloys. In particular, the extensively formed carbide free zone below the affected substrate will reduce the creep-rupture strengths because the inter-granular carbides present along the grain boundaries effectively impede the grain boundary sliding under high-temperature tensile loading conditions.

  11. X-ray diffractometry of steam cured ordinary Portland and blast-furnace-slag cements; Difratometria de raios X de pastas de cimento Portland comum e de alto-forno submetidas a cura termica

    Energy Technology Data Exchange (ETDEWEB)

    Camarini, G [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia; Djanikian, J G [Sao Paulo Univ., SP (Brazil). Escola Politecnica

    1994-12-31

    This work studies some aspects of the phases produced by hydration of ordinary and blast-furnace-slag cements, at normal conditions and steam cured (60 and 95{sup 0} C), using an X-ray diffraction technique. The blast-furnace-slag cement was a mixture of 50% of ordinary Portland cement and 50% of blast-furnace-slag (separately grinding). After curing the X-ray diffraction reveals that, in relation to ordinary Portland cement, the main phases in blast-furnace-slag cement are hydrated silicates and aluminates, hydro garnet, etringitte and mono sulphate. After steam curing the hydration of blast-furnace-slag cement proceeds. This is a result of the slag activation by the curing temperature. (author). 8 refs., 3 figs., 1 tab.

  12. Reactions between rocks and the hydroxides of calcium, sodium and potassium: progress report no. 1

    International Nuclear Information System (INIS)

    Van Aardt, J.H.P.; Visser, S.

    1982-01-01

    The reaction between the hydroxides of calcium, sodium and potassium, and clay minerals, feldspars, and some rocks (aggregates for use in concrete) was investigated. The reaction products were examined by means of x-ray diffraction and chemical analysis. The solid reaction products identified were hydrated calcium silicates,hydrated calcium aluminates, and hydrated calcium alumina silicates. It was found that, in the presence of water, calcium hydroxide liberated alkali into solution if the rocks and minerals contained alkali metals in their structure. Two crystalline hydrated sodium calcium silicates (12A and 16A) were prepared in the system Na 2 O-CaO-SiO 2 -H 2 O at 80 degrees Celsius. The one compound (12A) was also observed when sodium hydroxide plus calcium hydroxide and water reacted with silica- or silicate-containing rocks

  13. Lime kiln dust as a potential raw material in portland cement manufacturing

    Science.gov (United States)

    Miller, M. Michael; Callaghan, Robert M.

    2004-01-01

    In the United States, the manufacture of portland cement involves burning in a rotary kiln a finely ground proportional mix of raw materials. The raw material mix provides the required chemical combination of calcium, silicon, aluminum, iron, and small amounts of other ingredients. The majority of calcium is supplied in the form of calcium carbonate usually from limestone. Other sources including waste materials or byproducts from other industries can be used to supply calcium (or lime, CaO), provided they have sufficiently high CaO content, have low magnesia content (less than 5 percent), and are competitive with limestone in terms of cost and adequacy of supply. In the United States, the lime industry produces large amounts of lime kiln dust (LKD), which is collected by dust control systems. This LKD may be a supplemental source of calcium for cement plants, if the lime and