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Sample records for cement content

  1. Cements with low Clinker Content

    Science.gov (United States)

    García-Lodeiro, I.; Fernández-Jiménez, A.; Palomo, A.

    2015-11-01

    Hybrid alkaline cements are multi-component systems containing a high percentage of mineral additions (fly ash, blast furnace slag), low proportions (alkaline activators. The substantially lower amount of clinker needed to manufacture these binders in comparison to ordinary Portland cement is both economically and ecologically beneficial. Their enormous versatility in terms of the raw materials used has made them the object of considerable interest. The present study explored the mechanical strength of binary blends mixes; B1= 20% clinker (CK) + 80% fly ash (FA) and B2=20% clinker + 80% blast furnace slag (BFS), both hydrated in the presence and absence of an alkaline activator specifically designed for this purpose. The use of the activator enhanced the development of early age strength considerably. All the hydrated matrices were characterised with XRD, SEM/EDX and (29Si and 27Al) NMR. The use of the alkaline activator generated reaction products consisting primarily of a mix of gels ((N,C)-A-S-H and C-A-S-H) whose respective proportions were found to depend upon system composition and initial reactivity.

  2. Serviceability and Reinforcement of Low Content Whisker in Portland Cement

    Institute of Scientific and Technical Information of China (English)

    CAO Mingli; WEI Jianqiang; WANG Lijiu

    2011-01-01

    In order to explore the serviceability and reinforcement of CaCO3 whisker in portland cement matrix,the durability of CaCO3 whisker and effect of low whisker content(0%-4.0%)on the working performance and mechanical properties of portland cement were investigated.The experimental results show that CaCO3 whiskers have a good stability and serviceability in cement,and should not significantly alter the rheological properties of the cement paste.The flexural and compressive strength of portland cement reinforced by CaCO3 whiskers was increased by 33.3% and 12.83%,respectively.

  3. Experimental Study on Artificial Cemented Sand Prepared with Ordinary Portland Cement with Different Contents

    Directory of Open Access Journals (Sweden)

    Dongliang Li

    2015-07-01

    Full Text Available Artificial cemented sand test samples were prepared by using ordinary Portland cement (OPC as the cementing agent. Through uniaxial compression tests and consolidated drained triaxial compression tests, the stress-strain curves of the artificial cemented sand with different cementing agent contents (0.01, 0.03, 0.05 and 0.08 under various confining pressures (0.00 MPa, 0.25 MPa, 0.50 MPa and 1.00 MPa were obtained. Based on the test results, the effect of the cementing agent content (Cv on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using Cv. The research reveals that when Cv is high (e.g., Cv = 0.03, 0.05 or 0.08, the stress-strain curves of the samples indicate a strain softening behavior; under the same confining pressure, as Cv increases, both the peak strength and residual strength of the samples show a significant increase. When Cv is low (e.g., Cv = 0.01, the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of Cv (the cementing agent content with c′ (the cohesion force of the sample and Δϕ′ (the increment of the angle of shearing resistance is obtained. Furthermore, through modification of the Mohr-Coulomb strength theory, the effect of cementing agent content on the strength of the cemented sand is demonstrated.

  4. Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement

    DEFF Research Database (Denmark)

    Fullerton, A; Gammelgaard, Bente; Avnstorp, C;

    1993-01-01

    The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used....... The cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate...... and unexposed skin was observed, despite a more permeable skin barrier at the alkaline pH of the cement suspensions, i.e., pH 12.5. Increased chromium levels in epidermis and dermis were seen when ordinary Portland cement was applied as a suspension with added sodium sulphate (20%) on the skin surface for 96 h...

  5. Cement content influence in rebar corrosion in carbonated mortars

    Directory of Open Access Journals (Sweden)

    Américo, P. O.

    2003-12-01

    Full Text Available The cement hydration products protect the concrete rebars of the reinforced concrete due to the production of Ca(OH2, NaOH, and KOH that, upon dissolving in the concrete s aqueous phase, generate a pH above 12.5. However, reinforced concrete structures are exposed to pollutant gases, such as, CO2 which upon penetrating the concrete, reacts with the alkaline components, consequently reducing the pH of the aqueous phase causing the loss of passivity by the rebar and as a consequence its corrosion when there is the presence of humidity and oxygen. The objective of the current paper is the analysis of the alkaline reserve influence, measured by the cement content, in the corrosion of rebars employing the polarization resistance technique for determining the corrosion intensity. Results for corrosion intensity of rebars embedded in prismatic mortar test specimens are produced with three cement content levels, with equal water/cement ratio. Cylindrical test specimens were also used for verification of the capillary absorption and the porosity by means of mercury porosymetry The results show that the initiation period is shorter and the corrosion intensity of the rebars is higher when the cement content is lower However, there is also an alteration in the microstructure upon altering the cement content, and far this reason one cannot conclude that the alkaline reserve alone is responsible for these results.

    Los productos de hidratación del cemento protegen las armaduras embebidas en el hormigón debido a la gran cantidad de Ca(OH2, NaOH y KOH disueltos en la fase acuosa del hormigón que proporcionan un pH mayor que 12,5. Sin embargo, las estructuras de hormigón armado están expuestas a los gases contaminantes como el CO2, que al penetrar en el hormigón reacciona con los compuestos alcalinos, se reduce el pH de la fase acuosa y provocan la despasivación de la armadura. Posteriormente, si hay

  6. STUDY ON HIGH CONTENT OF BLENDS IN CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The technology of activation by a]dding few activators(<1%) to increase the amount of blends in cement was investigated.The results show that outer activation has a remarkable effect on improving the physical properties of slag cement,flyash cement and volcanic cement.For example,the compressive strength was increased by 5-10 MPa.Morever,the application of activation is beneficial to grind-aiding,early strength and water-reducing etc.

  7. Optimization of the Content of Tricalcium Silicate of High Cementing Clinker

    Institute of Scientific and Technical Information of China (English)

    CHEN Lin; SHEN Xiaodong; MA Suhua; HUANG Yeping; ZHONG Baiqian

    2011-01-01

    Optimization of the content of tricalcium silicate (C3S) of high cementing clinker was investigated. The content of free-CaO(f-CaO), mineral composite, the content of C3S in the clinker and the hydration product were analyzed by chemical analysis and X-ray diffraction (XRD). "K Value" method of QXRD was selected as a quantitative analysis way to measure the content of C3S, and the strength of cement paste was determined. The results show that at a water cement ratio of 0.29, the strength of cement paste with 73% C3S can be up to 97.5 MPa at 28 days age. The strength at 28 d of cement with 73% C3S is 16% higher than that with 78% C3S at water requirement for normal consistency. The relationship between the strength of high cementing Portland cement and the content of C3S in the clinker is nonlinear. According to the strength of cement paste, the optimal content of C3S in cement clinker is around 73% in this paper.

  8. Influence of particle packing density on the rheology of low cement content concrete

    NARCIS (Netherlands)

    Fennis-Huijben, S.A.A.M.; Grunewald, S.; Walraven, J.C.; Den Uijl, J.A.

    2012-01-01

    Optimizing concrete mixtures with regard to cement content is one of the most important solutions in sustainable concrete design. Workability o f these low cement content or ecological mixtures is very important. Eleven mortar mixtures are presented, which show how a higher packing density can be us

  9. Using SP and SF to Lower Cement Content

    Directory of Open Access Journals (Sweden)

    Yassen A. Saleh

    2013-05-01

    Full Text Available In the present research, using different percents of superplasticizer (SP and silica fume (SF to improve the characteristics of concrete is performed. SP and SF are added to two types of  normal concrete, the first is of mixing ratio (1:2:4 and the second is of mixing ratio (1:1.5:3.28The results show that adding SF lead to increase compressive strength for first mix by about 45.3% and 47.7% while adding SP lead to increase the compressive strength by about 43% and 41%  compared to reference mix at 7 and 28 day respectively. The corresponding values for second mix are 46.7% , 49%, 44% and 43% respectively.The maximum compressive strength when SP and SF used together can be attained when the percents of SF and SP are 5% and 3% respectively. The increase in compressive strength is about 49.3% and 48.4%  for first mix, while the corresponding values for second mix are 52.4% and 51.2% as they compared to reference mix at 7 and 28 day respectively.For Tensile strength, adding SP lead to increase it by about 29.2% and 31.6% for first and second mix respectively, while the corresponding values when adding SF are 38.1% and 40.3%. The effect of using SP and SF together on increase tensile strength is more than the effect of using each one separately. The maximum tensile strength can be attained when the percents of SF and SP are 5% and 3% respectively as they increase the tensile strength by about 38.9% and 40.7% for first and second mix.The effect of using admixtures on cement content can be noted clearly as the maximum reduction percents are about 8.7% and 9.35% for first and second mix respectively when the percent of SP is 3%. The corresponding values are 9.4% and 11.26% when the percent of SF is 5%. Using SP and SF together at percents 3% and 5% respectively lead to reduce cement content by about 10.15% and 13.54% for first and second mix respectively.

  10. Arsenic content in Portland cement: A literature review

    Directory of Open Access Journals (Sweden)

    Tenorio de Franca Talita

    2010-01-01

    Full Text Available Portland cement (PC is a hydraulic binding material widely used in the building industry. The main interest in its use in dentistry is focused on a possible alternative to mineral trioxide aggregate (MTA because PC is less expensive and is widely available. In dentistry, PC has been used in dental procedures such as pulpotomy, pulp capping, repair of root perforation and root-end filling. The purpose of this article is review the dental literature about the PC, its composition with special attention to arsenic content, properties, and application in dentistry. A bibliographic research was performed in Bireme, PubMed, LILACS and Scopus data bases looking for national and international studies about the PC composition, properties and clinical use. It was observed that PC has favorable biological properties very similar to those of MTA. The PC has shown good cell proliferation induction with formation of a monolayer cell, satisfactory inflammatory response, inhibitory effect of prostaglandin and antimicrobial effect. Studies have shown that PC is not cytotoxic, stimulates the apposition of reparative dentin and permits cellular attachment and growth. Regarding arsenic presence, its levels and release are low. PC has physical, chemical and biological properties similar to MTA. Arsenic levels and release are low, therefore, unable to cause toxic effects.

  11. Clay content of argillites: Influence on cement based mortars

    OpenAIRE

    Habert, Guillaume; CHOUPAY, Nathalie; Escadeillas, Gilles; MONTEL, Jean Marc; Guillaume, D

    2009-01-01

    The pozzolanic activity of four heated powders containing different clays has been tested. Mineral transformations during calcination from 20 to 900 °C have been followed by X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). Compressive strength tests were performed at 1, 7 and 28 days on cement-clay mortars using 30% of pozzolanic material as a replacement by mass for cement. Calcination temperatures corresponded to the stages of potentially high reactivity identified by XR...

  12. Influence of CG With High Content of Metallic Particles as a Cement Admixture on Cement Strength

    Institute of Scientific and Technical Information of China (English)

    WAN Hui-wen; LIN Zong-shou; ZHAO Qian; HUANG Yun

    2003-01-01

    Copper gangue (CG), containing a large amount of water with grain sizes of 0.037 to 0.10mm,is an inactive industrial waste generated from copper refineries. When it is dried and used as a cement admixture, the influence of the presence of finely dispersed metallic particles in CG on the microstructure and compressive strength of cement paste has been studied.The results show that the higher the replacement of CG is,the lower the compressive strength of cement mortar is.However,the long-term strength of the specimens with 10% CG,especially after being cured for 3 months,approached to that of the plain mortar.Its mechanism was studied by an electron probe X-ray microanalyzer (EPXMA).The results indicate that a small quantity of Fe(OH)3·nH2O slowly formed from Fe2O3 in the presence of Ca(OH)2, free CaO and MgO of the clinker also slowly hydrated and formed Ca(OH)2 and Mg(OH)2 respectively,so the hardened cement paste became more compact.

  13. Quantification of Water Content Across a Cement-clay Interface Using High Resolution Neutron Radiography

    Science.gov (United States)

    Shafizadeh, A.; Gimmi, T.; Van Loon, L.; Kaestner, A.; Lehmann, E.; Maeder, U. K.; Churakov, S. V.

    In many designs for radioactive waste repositories, cement and clay will come into direct contact. The geochemical contrast between cement and clay will lead to mass fluxes across the interface, which consequently results in alteration of structural and transport properties of both materials that may affect the performance of the multi-barrier system. We present an experimental approach to study cement-clay interactions with a cell to accommodate small samples of cement and clay. The cell design allows both in situ measurement of water content across the sample using neutron radiography and measurement of transport parameters using through-diffusion tracer experiments. The aim of the high-resolution neutron radiography experiments was to monitor changes in water content (porosity) and their spatial extent. Neutron radiographs of several evolving cement-clay interfaces delivered quantitative data which allow resolving local water contents within the sample domain. In the present work we explored the uncertainties of the derived water contents with regard to various input parameters and with regard to the applied image correction procedures. Temporal variation of measurement conditions created absolute uncertainty of the water content in the order of ±0.1 (m3/m3), which could not be fully accounted for by correction procedures. Smaller relative changes in water content between two images can be derived by specific calibrations to two sample regions with different, invariant water contents.

  14. Cement content influence in rebar corrosion in carbonated mortars

    OpenAIRE

    Américo, P. O.; A.A. Nepomuceno

    2003-01-01

    The cement hydration products protect the concrete rebars of the reinforced concrete due to the production of Ca(OH)2, NaOH, and KOH that, upon dissolving in the concrete s aqueous phase, generate a pH above 12.5. However, reinforced concrete structures are exposed to pollutant gases, such as, CO2 which upon penetrating the concrete, reacts with the alkaline components, consequently reducing the pH of the aqueous phase causing the loss of passivit...

  15. LONG – TERM PROPERTIES OF CEMENT COMPOSITES WITH VARIOUS METAKAOLINITE CONTENT

    Directory of Open Access Journals (Sweden)

    ĽUDOVÍT KRAJČI

    2013-03-01

    Full Text Available The optimal temperature transformation of kaolin sand to metakaolin sand (MKS resulting in complete conversion of kaolinite to pozzolanic active metakaolinite (MK is 650°C in the time of 1 hour. To obtain information on mechanism of pozzolanic reaction in studied binary system, the cement pastes with two MKS at substitution level of Ordinary Portland cement (OPC with MKS by 10, 20 and 40 wt. % corresponding to 3.6 - 16.0 % MK content in pastes, were tested. Pozzolanic reaction of MK with hydrating OPC was clearly confirmed mainly by XRD and thermal analyses. This process accompanied with gradual reduction of Ca(OH2 content was the most intense in pastes with the highest MK contents (14.4 and 16.0 %. The decrease of micropore and total pore volume until MK content in paste of 7.2 % is measure of pore structure improvement specified as pore structure refinement. Until MK content of 8.0 % in paste, micropores portion with pore radius less than 10 nm rises and pore radius in the range between 10 and 100 nm declines. Resulted compressive strengths of related cement pastes with various MK content were comparable with strengths of pastes without MK. The obtained results confirmed that MKS can be used as promising additive in OPC to form prospective blended cements.

  16. Study of elastic-plastic damage model of cement consolidated soil with high organic content

    Institute of Scientific and Technical Information of China (English)

    CHEN Huie; WANG Qing; CAI Keyi

    2009-01-01

    On the basis of elastic-plastic damage model of cement consolidated soil, the authors took organic contents into reasonable damage variable evolution equation in order to seek relation between the organic contents and parameters in the equation, and established the elastic-plastic damage model of cement consolidated soil considering organic contents. The results show that the parameters change correspondingly with difference of the organic contents. The higher the organic contents are, the less the valves of the parameters such as elastic modulus (E), material parameters (K, n) and damage evolution parameter (ε) become, but the larger strain damage threshold value (εd) of the sample is. Meanwhile, the calculation results obtained from established model are compared with the test data in the condition of common indoors test, which is testified with reliability.

  17. Properties of Non-Structural Concrete Made with Mixed Recycled Aggregates and Low Cement Content

    Directory of Open Access Journals (Sweden)

    Antonio López-Uceda

    2016-01-01

    Full Text Available In spite of not being legally accepted in most countries, mixed recycled aggregates (MRA could be a suitable raw material for concrete manufacturing. The aims of this research were as follows: (i to analyze the effect of the replacement ratio of natural coarse aggregates with MRA, the amount of ceramic particles in MRA, and the amount of cement, on the mechanical and physical properties of a non-structural concrete made with a low cement content; and (ii to verify if it is possible to achieve a low-strength concrete that replaces a greater amount of natural aggregate with MRA and that has a low cement content. Two series of concrete mixes were manufactured using 180 and 200 kg/m3 of CEM II/A-V 42.5 R type Portland cement. Each series included seven concrete mixes: one with natural aggregates; two MRA with different ceramic particle contents; and one for each coarse aggregate replacement ratio (20%, 40%, and 100%. To study their properties, compressive and splitting tensile strength, modulus of elasticity, density, porosity, water penetration, and sorptivity, tests were performed. The results confirmed that the main factors affecting the properties analyzed in this research are the amount of cement and the replacement ratio; the two MRAs used in this work presented a similar influence on the properties. A non-structural, low-strength concrete (15 MPa with an MRA replacement ratio of up to 100% for 200 kg/m3 of cement was obtained. This type of concrete could be applied in the construction of ditches, sidewalks, and other similar civil works.

  18. Indirect measurement of the ice content curve of partially frozen cement based materials

    OpenAIRE

    Fabbri, Antonin; FEN CHONG, Teddy

    2013-01-01

    The goal of this paper is to investigate the validity of indirectly built ice content curves from porous network characterization tests to predict the behavior of a freezing cement based material. To do so, the results obtained by the two classical methods, namely the mercury intrusion porosimetry (MIP) and the gravimetric water desorption (WD) tests, are compared with the direct measurement of the ice content with a dielectric capacitive apparatus. A corrective approach, based on an interfac...

  19. Electrical resistance stability of high content carbon fiber reinforced cement composite

    Institute of Scientific and Technical Information of China (English)

    YANG Zai-fu; TANG Zu-quan; LI Zhuo-qiu; QIAN Jue-shi

    2005-01-01

    The influences of curing time, the content of free evaporable water in cement paste, environmental temperature, and alternative heating and cooling on the electrical resistance of high content carbon fiber reinforced cement (CFRC) paste are studied by experiments with specimens of Portland cement 42.5 with 10 mm PAN-based carbon fiber and methylcellulose. Experimental results indicate that the electrical resistance of CFRC increases relatively by 24% within a hydration time of 90 d and almost keeps constant after 14 d, changes hardly with the mass loss of free evaporable water in the concrete dried at 50℃C, increases relatively by 4% when ambient temperature decreases from 15℃ to-20℃, and decreases relatively by 13% with temperature increasing by 88℃. It is suggested that the electric resistance of the CFRC is stable, which is testified by the stable power output obtained by electrifying the CFRC slab with a given voltage. This implies that such kind of high content carbon fiber reinforced cement composite is potentially a desirable electrothermal material for airfield runways and road surfaces deicing.

  20. PORE STRUCTURE MODEL OF CEMENT HYDRATES CONSIDERING PORE WATER CONTENT AND REACTION PROCESS UNDER ARBITRARY HUMIDITY

    Science.gov (United States)

    Fujikura, Yusuke; Oshita, Hideki

    A simulation model to estimate the pore structure of cement hydrates by curing in arbitrary relative humidity is presented. This paper describes procedures for predicting phase compositions based on the classical hydration model of Portland cement, calculating the particle size distribution of constituent phases and evaluating the pore size distribution by stereological and statistical considerations. And to estimate the water content in pore structure under any relative humidity, we proposed the simulation model of adsorption isotherm model based on the pore structure. To evaluate the effectiveness of this model, simulation results were compared with experimental results of the pore size distribution measured by mercury porosimetry. As a result, it was found that the experimental and simulated results were in close agreement, and the simulated results indicated characterization of the po re structure of cement hydrates.

  1. ASR mitigation by the use of supplementary cementing materials : evaluation of the available alkali content

    Energy Technology Data Exchange (ETDEWEB)

    Duchesne, J. [Laval Univ., Quebec City, PQ (Canada). Dept. of Geology and Geological Engineering

    2006-07-01

    Cement companies in Canada are involved in the global initiative to voluntarily implement strategies to address global warming, enhance occupational health and safety, reduce emissions, and use fuels and raw materials in a sustainable manner. This paper reported on a study in which the behaviour of common supplementary cementing materials (SCMs) were compared with an industrial by-product from the aluminium industry (ABP). The alkali content in SCMs is particularly critical in terms of its ability to prevent excessive expansion due to alkali-silica reactivity (ASR). The 6 common SCMs with various total alkali contents were: 2 condensed silica fumes, 3 pulverized fly ashes and 1 ground granulated blast furnace slag. The ABP was also investigated as a suitable candidate to replace Portland cement. The testing program involved measuring the expansion and alkali content. The methods used to evaluate the amount of available alkalies were ASTM C114; ASTM C311; modified ASTM C311; pore fluid expression; and, the accelerated mortar bar method. The main objectives of this study were to determine the best procedure for evaluating the amount of available alkalies from SCMs and to discuss the relationship between concrete expansion and alkali content. The recommended methods to evaluate the performance of non usual SCM as suitable candidates to replace Portland cement in the presence of potentially reactive aggregates were accelerated mortar bar method CSA A23.2-25A as well as the available alkalies from cement-SCM paste samples measured by the pore solution expression method. 10 refs., 2 tabs., 2 figs.

  2. Effect of Coal Gangue with Different Kaolin Contents on Compressive Strength and Pore Size of Blended Cement Paste

    Institute of Scientific and Technical Information of China (English)

    CHEN Yimin; ZHOU Shuangxi; ZHANG Wensheng

    2008-01-01

    The effects of activated coal gangue on compressive strength,porosity and pore size distribution of hardened cement pastes were investigated.Activated coal gangue with two different kaolin contents,one higher and one lower,were used to partially replace Portland cement at 0%,10%,and 30% by weight.The water to binder ratio(w/b)of 0.5 was used for all the blended cement paste mixes.Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content.The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.

  3. Hypoplastic model for simulation of compressibility characteristics of cement-admixed Bangkok soft clay at high water content

    Science.gov (United States)

    Chattonjai, Piyachat

    2016-06-01

    The developed hypoplastic model for simulation of compressibility characteristics of cement-admixed Bangkok soft clay at high water content was proposed in this paper. By using unique equation, the model is able to predict the relationship between void ratio and vertical effective stress of different water and cement content of soil cement. For practically convenient utilization and understanding, the parameters of Q1 which represented to initial cement bonding of soil (the initial value of structure tensor at time = 0) and C2 which effected to the model stiffness on isotropic consolidation direction, at 45° for loading and 225° for unloading of stress response envelope, were proposed as the function of cement and water content by comparing with dry weight of soil. By numerical integration that satisfied one-dimensional settlement, the simulation results were directly compared with fifteen experimental results to verify the accuracy of the proposed model.

  4. Study of elemental content in cement raw meal using D-D neutron generator

    International Nuclear Information System (INIS)

    Content of main elements, Si, Al, Fe and Ca, and their oxides in cement raw meal were detected by prompt γ rays neutron activation analysis(PGNAA) while D-D neutron generator was employed as neutron source. γ rays were emitted when the elements were irradiated by neutron. Qualitative and quantitative analysis of cement raw meal could be carried out by measuring the energy and the intensity of the γ rays. The results, which were of good repeatability, were consistent with the results tested by chemical methods. And the standard deviation was in the allowable range. Compared with chemical methods, the PGNAA method could meet the demand of industrial production because of its short testing time, high accuracy, high precision and the ability to measure many elements simultaneously. (authors)

  5. Influence of inorganic filler content on the radiopacity of dental resin cements.

    Science.gov (United States)

    Furtos, Gabriel; Baldea, Bogdan; Silaghi-Dumitrescu, Laura; Moldovan, Marioara; Prejmerean, Cristina; Nica, Luminita

    2012-01-01

    Digital radiography was used to measure the radiopacity of 18 resin cements to determine the influence of inorganic filler content on radiopacity. Four disk specimens (n=4) of each light-curing cement were digitally radiographed alongside an aluminum step wedge using an intraoral sensor (XIOS Plus, Sirona, Germany), and their mean gray value measured. Percentage of filler by weight was determined using an analytical combustion furnace. Data were statistically analyzed using one-way ANOVA and Tukey's test (α=0.05). All materials were more radiopaque than dentin and 12 materials were more radiopaque than enamel. Filler percentage ranged between 17.36 to 53.56 vol% and radiopacity between 1.02 to 3.40 mm Al. There were no statistically significant differences in inorganic filler percentage and radiopacity among the different shades of the same material (p>0.05), but the highest radiopacity was measured for the material which contained a higher percentage of filler.

  6. Preparation of Super Composite Cement with a Lower Clinker Content and a Larger Amount of Industrial Wastes

    Institute of Scientific and Technical Information of China (English)

    HE Zhen; LIANG Wen-quan; LI Bei-xing; LI Xiang-guo

    2002-01-01

    The effects of the grinding mode,fineness, gypsum kinds and dosage, mix proportions on properties of the composite cements consisting of slag,fly ash, limestone and a lower content clinker were investigated,respectively. The results show that when the proportions among slag, fly ash and limestone are appropriate, the grinding technology and system are reasonable, the optimized gypsums and additives are effective, the 52.5 R grade cement (52.5 R grade cement means a higher strength than 52.5 at early age ) can be prepared by clinker dosage of 50% in weight, the 42.5R or 42.5,32.5 grade composite cement containing 40% and 30% clinker also may be made, respectively. Moreover, the high performance concrete prepared from the above composite cements was studied experimentally.

  7. Non destructive determination of the free chloride content in cement based materials

    Energy Technology Data Exchange (ETDEWEB)

    Elsener, B. [Department of Inorganic and Analytical Chemistry, University of Cagliari, I-09128 Cagliari (Italy); Institute of Materials Chemistry and Corrosion, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zuerich (Switzerland); Zimmermann, L.; Boehni, H. [Institute of Materials Chemistry and Corrosion, Swiss Federal Institute of Technology, ETH Hoenggerberg, CH-8093 Zuerich (Switzerland)

    2003-06-01

    A non-destructive chloride sensitive sensor element for use in cement based porous materials is presented. The sensor element determines the activity of the free chloride ions in solutions and in porous cement based materials such as cement paste, mortar or concrete. The calibration in synthetic pore solution showed a response according to Nernst law over three decades of chloride concentration. The sensor element has shown excellent reproducibility and long term stability. The sensor element has been used to monitor the chloride uptake into mortar specimens. The results show a good agreement between the free chloride content determined by the sensor and by pore water expression. Applications in monitoring of reinforced concrete structures and their limitations are discussed. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] In der vorliegenden Arbeit wird ein Chloridsensor zur zerstoerungsfreien Erfassung des Chloridgehalts in zementoesen Materialien beschrieben. Der Sensor bestimmt die Aktivitaet der freien Chloridionen in Loesungen und in Zementstein, Moertel oder Beton. Die Kalibrierungskurve in synthetischer Betonporenloesung zeigt das erwartete Nernst'sche Verhalten ueber mehr als drei Konzentrationsdekaden. Der Sensor weist eine sehr hohe Reproduzierbarkeit und Langzeitstabilitaet auf. Der Chloridsensor wurde eingesetzt, um das Eindringen der Chloridionen in Moertelpruefkoerpern zu untersuchen. Ein Vergleich der Chloridkonzentration bestimmt durch Auspressen der Porenloesung am Ende der Versuche mit den von Sensoren bestimmten Chloridkonzentration zeigt eine sehr gute Uebereinstimmung. Praktische Anwendungen und die Einsatzgrenzen des Sensors werden diskutiert. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  8. High Water Content Material Based on Ba-Bearing Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    CHANG Jun; CHENG Xin; LU Lingchao; HUANG Shifeng; YE Zhengmao

    2005-01-01

    A new type of high water content material which is made up of two pastes is prepared, one is made from lime and gypsum, and another is based on Ba-bearing stdphoaluminate cement. It has excellent properties such as slow single paste solidifing,fast double pastes solidifing,fast coagulating and hardening, high early strength, good suspension property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD , DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.

  9. Quantification of water content across a cement-clay interface using high resolution neutron radiography

    OpenAIRE

    Shafizadeh, A; Gimmi, Thomas; Van Loon, L.; Kaestner, A.; Lehmann, E; Mäder, Urs; Churakov, Sergey

    2015-01-01

    In many designs for radioactive waste repositories, cement and clay will come into direct contact. The geochemical contrast between cement and clay will lead to mass fluxes across the interface, which consequently results in alteration of structural and transport properties of both materials that may affect the performance of the multi-barrier system. We present an experimental approach to study cement-clay interactions with a cell to accommodate small samples of cement and clay. The cell des...

  10. Measurement of Monochromatic Emissivity of Cement Clinker with Various Fe2O3 Content at High Temperature

    Institute of Scientific and Technical Information of China (English)

    Z.J.Ye; C.F.Ma; 等

    1996-01-01

    An applicatiopn of the optical pyrometer is studied for measuring monochromatic emissivities of cement clinker with various Fe2O3 contnet.The idsa of using “brightness temperature” is introduced into the eimssivity measurement.In this method,there is no need for measuring an actual temperature of sample surfaces,only with determining both brightness temperatures of a sample and a blackbody can the required emissivity be evaluated according to Wien's radiation law.In practice,the cement clinker is regarded as a greybody,the monochromatic emissivity is approximately equal to the total emissivity,so a single-colour optical pyrometer is applied for this purpose,Test measurements are carried out on 10 kinds of cement clinkers,Experimental data are treated by the least square method.As a result ,the emissivity variation with temperature at a certain Fe2O3 content is quite well represented by εn=a+bT.Furthermore,this work first reported that the eimissivities of cement clinker change consierably with Fe2O3 contents.In multiple cement production this conclusion is very important.

  11. Influence of free water content on the compressive mechanical behaviour of cement mortar under high strain rate

    Indian Academy of Sciences (India)

    Jikai Zhou; Xudong Chen; Longqiang Wu; Xiaowei Kan

    2011-06-01

    The effect of free water content upon the compressive mechanical behaviour of cement mortar under high loading rate was studied. The uniaxial rapid compressive loading testing of a total of 30 specimens, nominally 37 mm in diameter and 18.5 mm in height, with five different saturations (0%, 25%, 50%, 75% and 100%, respectively) were executed in this paper. The technique ‘Split Hopkinson pressure bar’ (SHPB) was used. The impact velocity was 10 m/s with the corresponding strain rate as 102/s. Water-cement ratio of 0.5 was used. The compressive behaviour of the materials was measured in terms of the maximum stress, Young’s modulus, critical strain at maximum stress and ultimate strain at failure. The data obtained from test indicates that the similarity exists in the shape of strain–stress curves of cement mortars with different water content, the upward section of the stress–strain curve shows bilinear characteristics, while the descending stage (softening state) is almost linear. The dynamic compressive strength of cement mortar increased with the decreasing of water content, the dynamic compressive strength of the saturated specimens was 23% lower than that of the totally dry specimens. With an increase in water content, the Young’s modulus first increases and then decreases, the Young’s modulus of the saturated specimens was 23% lower than that of the totally dry specimens. No significant changes occurred in the critical and ultimate strain value as the water content is changed.

  12. The Influence of Free Water Content on Dielectric Properties of Alkali Active Slag Cement Paste

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The dielectric performance of alkali activated slag (AAS) cement paste was investigated in the frequency range of 1 to 1000 MHz. The experimental results showed the unstable dielectric properties of harden paste were mostly influenced by the fraction of free water in paste or absorbed water from ambient, but not including hydration water and microstructure. The free water was completely eliminated by heat treatment at 105 ℃ about 4 hours, and then its dielectric loss was depressed; but with the exposure time in air increasing,the free water adsorption in ambient air made the dielectric property of harden cement paste to be bad. The temperature and relative humidity of environment was the key factors of free water adsorption; hence, if the influence of free water on dielectric constant was measured or eliminated, the cement-based materials may be applied in humidity sensitive materials or dielectric materials domains.

  13. Analysis of Metal Contents in Portland Type V and MTA-Based Cements

    Directory of Open Access Journals (Sweden)

    Maura Cristiane Gonçales Orçati Dorileo

    2014-01-01

    Full Text Available The aim of this study was to determine, by Atomic Absorption Spectrometry (AAS, the concentration levels of 11 metals in Type V gray and structural white PC, ProRoot MTA, and MTA Bio. Samples, containing one gram of each tested cement, were prepared and transferred to a 100 mL Teflon tube with a mixture of 7.0 mL of nitric acid and 21 mL of hydrochloric acid. After the reaction, the mixture was filtered and then volumed to 50 mL of distilled water. For each metal, specific patterns were determined from universal standards. Arsenic quantification was performed by hydride generator. The analysis was performed five times and the data were statistically analyzed at 5% level of significance. Only the cadmium presented concentration levels of values lower than the quantification limit of the device. The AAS analysis showed increased levels of calcium, nickel, and zinc in structural white PC. Type V PC presented the greatest concentration levels of arsenic, chromium, copper, iron, lead, and manganese (P<0.05. Bismuth was found in all cements, and the lowest concentration levels were observed in Portland cements, while the highest were observed in ProRoot MTA. Both PC and MTA-based cements showed evidence of metals inclusion.

  14. Resin content in cement liquids of resin-modified glass ionomers.

    Science.gov (United States)

    Ikeda, K; Fujishima, A; Suzuki, M; Inoue, M; Sasa, R; Miyazaki, T

    1999-09-01

    Qualitative and quantitative analyses were conducted on four kinds of resin-modified glass ionomer (RMGI) cement liquids, LC, LC II, LC III (hereinafter referred to as LCs) and VM, using HPLC and laser Raman spectroscopic methods. HPLC revealed that among the RMGI liquids LCs contain 31-32% HEMA (2-Hydroxyethyl methacrylate), and VM contains 18% of the same. The composition of RMGI cement liquids varied significantly between manufacturers. In Raman spectroscopic analyses, the spectra of liquids of various ratios of polyacrylic acid and HEMA were measured, and calculations were made on the peak intensity ratios of C=C stretch vibration to C=O stretch vibration, common in both HEMA and polyacrylic acid. The composition ratio of polycarboxylic acid to HEMA of commercial glass ionomer cements was assessed by the regression curve generated by a combination of peak intensity ratios and composition ratios. In addition, Raman spectroscopy was able to identity the differences in form of the methacryloyloxy group. PMID:10786135

  15. Determination of the Elemental Contents in Soils Around Diamond Cement Factory, Aflao

    Directory of Open Access Journals (Sweden)

    Hyacinthe Ahiamadjie

    2011-01-01

    Full Text Available This research is to assess the impact of the dusts particles given out by a cement factory on the physicochemical characteristics of the soil at the vicinity of the cement factory. Total concentration of five trace metals (Ca, Cu, Mn, Pb and V was measured in soils from within and surrounding areas of the Diamond Cement Factory, Aflao. Thirty four (34 surface soils (0-20 cm were collected during the month of November, 2009. The soil samples were air dried and sieved to appropriate sizes for analysis. The samples were subsequently pelletized and analyzed using XRF at the physics Department, Ghana Atomic Energy Commission. The results of the analysis showed the following range of concentration for the selected metals Ca (532.83-143880.3 ppm, Cu (65.46-212.65 ppm, Mn (1006.88-11099.87 ppm, Pb (0.33-1.9 ppm and V (100.57-199.95 ppm. In addition, calculation of Enrichment Factors (Efs, Pollution Index (PIs and Geoaccumulation Index (Igeos was done. The calculated results of Igeo and EF of heavy metals revealed the order of are Mn>Cu>Pb>Ca>V. EF of Mn and Cu record higher percentage values indicating that there is considerable Mn and Cu pollution, which mainly originate from activities of the factory.

  16. PRODUCTION OF WOOD-CEMENT BONDED PARTICLEBOARDS WITH DIFFERENT CONTENTS OF BARK AND MICROSILICA

    Directory of Open Access Journals (Sweden)

    Gilmar Correia Silva

    2010-08-01

    Full Text Available This work’s objective was to evaluate the effect of three percentages of addition of microsilica (0, 20 and 30% on the physical and mechanical properties of wood-cement bonded particleboards of Eucalyptus urophylla composed by three wood:bark ratios (100:0, 95:5 and 90:10. Results showed that the most significant effect of the additive on the produced panels was in those containing bark, and that of 20% of additive was more efficient on the physical and mechanical properties.

  17. The characterisation, improvement and modelling aspects of Frost Salt Scaling of Cement-Based Materials with a High Slag Content

    NARCIS (Netherlands)

    Copuroglu, O.

    2006-01-01

    Blast furnace slag cement concrete is used extensively in a number of countries. In comparison with OPC, it is particularly well known for its excellent performance in marine environments. One dis-advantage of slag cement is its vulnerability to scaling under the combined load of freezing-thawing an

  18. Reactivity and burnability of cement raw materials witt high manganese content

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    1988-06-01

    Full Text Available It has been verified that high manganese content in raw mixes causes alters the mineralogical composition of clinkers. New phases like 2 CaO.Mn02 and Ca2AIMnO5 are developed and C3A formation can be inhibited. Manganese is a flux similar to iron in the traditional raw mixes. The presence of manganese will modify the expressions of the lime saturation factor (LSF, silica modulus (Ms and aluminum modulus (Mf. This has as consequence an increase of the proportion of interstitial phase in the obtained clinkers.

    Se ha comprobado que contenidos elevados de manganeso en el crudo provoca una modificación significativa en la composición mineralógica del clinker. Se desarrollan las fases no tradicionales 2 CaO.Mn02 y Ca2AIMnO5 , y se puede llegar, incluso, a inhibir la formación de alumínate tricálcico. El manganeso tiene un comportamiento fundente muy similar al jugado por el hierro en los crudos tradicionales, por lo que la incorporación de óxidos de manganeso al crudo produce una alteración significativa en los módulos tradicionales (LSF, Ms y Mf. Esto tiene como consecuencia inmediata un gran incremento en la proporción de fase intersticial en los clínkeres producidos.

  19. Density and water content corrections in the gamma count rate of a PGNAA system for cement raw material analysis using the MCNP Code

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Carlos; Salgado, Jose [Nuclear and Technological Institute, Sacavem (Portugal); Leitao, Francisco [Technical Centre, Cimpor, Lisbon (Portugal)

    1998-05-11

    A MCNP simulation study for a prompt gamma neutron activation analysis system for on-line characterisation of cement raw materials has been carried out. A neutron source is located below a conveyor belt. Two detector banks were used: a lower bank positioned symmetrically around the source to detect {gamma}-rays emitted downwards; an upper bank detects the radiation emitted upwards. The count rate of both detector banks for a given composition depends on the bulk density and water content. This paper reports a few corrections which linearise the dependence of the corrected count rate on the mass content.

  20. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  1. Influence of cement properties in the reaction rate and mechanical behavior of concrete with high fl y ash content

    OpenAIRE

    Molina Bas, Omar I.; Moragues Terrades, Amparo; Gálvez Ruíz, Jaime; Guerrero Bustos, Ana

    2011-01-01

    The use of fly ash (FA) as an admixture to concrete is broadly extended for two main reasons: the reduction of costs that supposes the substitution of cement and the micro structural changes motivated by the mineral admixture. Regarding this second point, there is a consensus that considers that the ash generates a more compact concrete and a reduction in the size of the pore. However, the measure in which this contributes to the pozzolanic activity or as filler is not well defined. Ther...

  2. 含砂量对水泥砂浆强度与孔结构的影响%Effect of Sand Content on Strength and Pore Structure of Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    周继凯; 金龙; 丁宁

    2013-01-01

    Results of a study conducted to evaluate the effect of four sand content on the compressive,flexural and splitting-tensile strength of cement mortar are report.An experimental investigation in the pore structure of cement mortar brought about by changing the sand content and water/cement ratio is also reportsed.The changes in the pore structure were quantified by measuring the porosity,and pore size distribution obtained using mercury intrusion porosimetry technique.Test results show that the strengths of cement mortar increase with increasing sand content.Sand content is an important parameter influencing the pore structure of cement mortar.Moreover,there is a good relationship between pore structure and strength of cement mortar.A quantative expression is given between strength and pore parameters.%探讨四种不同含砂量对水泥砂浆抗压、弯拉和劈拉强度的影响.通过试验研究了随着含砂量和水灰比的变化水泥砂浆孔结构的不同.通过测量孔隙率及压汞法测量孔径分布来描述水泥砂浆的孔结构.试验结果表明水泥砂浆的强度(弯拉,劈拉和抗压)随含砂量的增加而提高.含砂量对水泥砂浆的孔结构也有十分重要的影响,水泥砂浆强度与其孔结构间有一定的相关性,给出相对应孔结构参数(孔径分布与孔隙率)与强度的定量关系表达式.

  3. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    OpenAIRE

    Nediljka Gaurina-Međimurec; Davorin Matanović; Gracijan Krklec

    1994-01-01

    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...

  4. Manufacture and properties of fluoride cement

    Science.gov (United States)

    Malata-Chirwa, Charles David

    process. It was observed in the laboratory simulated production of fluoride cement, that the clinkering temperature is much lower (around 1 170 °C) compared to that for the production of ordinary Portland cement. The other observed differences were attributed to the different mineralogical composition as a result of fluoride incorporation into the cement. While fluorine content is very minimal in fluoride cement, not more than 2 %, the resulting cementitious products are altered significantly as was observed from the study. Part of the experimental results has been used as reference material in the preparation of a draft Malawi Standard on fluoride cement. This draft standard will be submitted to the Malawi Bureau of Standards for further processing before it can be officially endorsed as a Malawi Standard.

  5. 水泥砂孔隙特征对抗冻性影响的研究%Research of cement mortar air content on the effects of pore characterstics and frost resistance

    Institute of Scientific and Technical Information of China (English)

    陈松; 李建新; 王起才; 李伟龙

    2015-01-01

    Through the frost resistance test,mercury intrusion test,hole spacing coefficient test to determine the cement mortar pore structure characteristics and the frost resistance under different air content,study the relationship between frost resistance and cement mortar pore structure characteristics,in addition,also analyzed the compressive strength of cement mortar under different air content. Ex-perimental results show that the as increase of air content the pore porosity of cement mortar,total pore volume,total hole area,average pore diameter are all increased,hole spacing coefficient decreases,and improved pore structure internal of cement mortar ,and pore size distribution more uniform and reasonable,although the strength decreases a bit,but the frost resistance was improved greatly.%通过抗冻性试验、压汞试验、孔间距系数试验测定了不同含气量下水泥砂的浆孔结构特征及其抗冻性,研究了抗冻性与孔结构之间的关系,此外,还分析了不同含气量水泥砂浆的抗压强度。试验结果表明:含气量的增加使水泥砂浆孔隙率、总孔体积、总孔面积、平均孔径均增加,孔间距系数减小,改善了其内部孔结构,孔径分布也比较均匀合理,虽然其强度有所降低,但大大提高了抗冻性。

  6. Rietveld quantitative phase analysis of Yeelimite-containing cements

    OpenAIRE

    Álvarez-Pinazo, Gema; Cuesta, Ana; García-Maté, Marta; Santacruz, Isabel; Losilla, Enrique R.; De la Torre, Ángeles G.; León-Reina, Laura; Aranda, Miguel A. G.

    2012-01-01

    Yeelimite-containing cements are attracting attention for their tailored properties. Calcium sulfoaluminate, CSA, cements have high contents of Yeelimite and they are used for special applications. Belite calcium sulfoaluminate, BCSA or sulfobelite, cements have high contents of belite and intermediate contents of Yeelimite, and they may become an alternative to OPC. Here, we report Rietveld quantitative phase analyses for three commercially available CSA clinkers, one CSA cement,...

  7. 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......−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....

  8. Composite cements containing natural pozzolan and granulated blast furnace slag

    OpenAIRE

    Irassar, E. F.; Rahhal, V. F.; Donza, H. A.; Menéndez, G.; Bonavetti, V. L.

    2006-01-01

    For reasons of market demand and Portland cement production,the manufacture of cements with two or more separately ground additions to produce customized cements is becoming common practice.When pozzolan or slag content in this type of cements is high, however, the initial strength of the resulting product may be adversely impacted. This problem can be minimized by activating one or both of the replacement materials. The present study analyzes the effect of Portland cement additions such as p...

  9. Toward accelerated bone regeneration by altering poly(D,L-lactic-co-glycolic) acid porogen content in calcium phosphate cement.

    Science.gov (United States)

    van Houdt, C I A; Preethanath, R S; van Oirschot, B A J A; Zwarts, P H W; Ulrich, D J O; Anil, S; Jansen, J A; van den Beucken, J J J P

    2016-02-01

    This work aimed to compare in vitro degradation of dense PLGA microspheres and milled PLGA particles as porogens within CPC, considering that the manufacturing of milled PLGA is more cost-effective when compared with PLGA microspheres. Additionally, we aimed to examine the effect of porogen amount within CPC/PLGA on degradation and bone formation. Our in vitro results showed no differences between both forms of PLGA particles (as porogens in CPC; spherical for microspheres, irregular for milled) regarding morphology, porosity, and degradation. Using milled PLGA as porogens within CPC/PLGA, we evaluated the effect of porogen amount on degradation and bone forming capacity in vivo. Titanium landmarks surrounded by CPC/PLGA with 30 and 50 wt % PLGA, were implanted in forty femoral bone defects of twenty male Wistar rats. Histomorphometrical results showed a significant temporal decrease in the amount of CPC, for both formulas, and confirmed that 50 wt % PLGA degrades faster than 30 wt%, and allows for a 1.5-fold higher amount of newly formed bone. Taken together, this study demonstrated that (i) milled PLGA particles perform equal to PLGA microspheres, and (ii) tuning of the PLGA content in CPC/PLGA is a feasible approach to leverage material degradation and bone formation.

  10. Natural Radionuclide Contents in Raw Materials and the Aggregate Finished Product from Dangote Cement Plc, Obajana, Kogi State, North Central Nigeria

    Directory of Open Access Journals (Sweden)

    J.O. Ajayi

    2012-11-01

    Full Text Available Assessment of gamma ray activity in raw materials and the end product in Dangote Cement from Dangote Cement Plc, Obajana and Kogi State has been investigated in this study. Gamma ray spectrometry that possesses scintillation detector was used to analyze the samples collected from the company. Samples collected as raw materials are limestone, clay, gypsum and laterite and cement as finished product. The 40K, 238U, 232Th activity concentration were detected. The concentration of 40K range from 4649±366 to 0±65 Bq/Kg with highest value in limestone and lowest in laterite. The 238U concentration is highest in gypsum range from 696±233 to 41±27 Bq/Kg in laterite. 232Th activity is below detectable limit in all the raw materials but it has activity concentration of 40±26 Bq/Kg in the finished product which may be traceable to the fact that some finished additives are present which are not in the basic raw materials of this cement under investigation. It is concluded that the natural radionuclide measured for 40K, 238U and 232Th has mean activities of 2189.75±219.5, 331.25±132.25 and 0±31 Bq/Kg respectively, while its corresponding mean absorbed dose rate in air at 1 m above the ground was calculated to be 235.61 nGy/h or 2.064 mSv/y and the aggregate finished product (cement has absorbed dose rate of 342.22 nGy/h and an effective dose equivalent of 2.998 mSv/y. The calculated absorbed doses in nGy/h and mSv/y shows that Dangote cement under consideration has higher activities of the isotopes than the permissible level suggested by ICRP (80 nGy/h or 0.7 mSv/y

  11. The effects of micron WC contents on the microstructure and mechanical properties of ultrafine WC–(micron WC–Co) cemented carbides

    International Nuclear Information System (INIS)

    Highlights: • The ultrafine WC–(micron WC–Co) cemented carbides were fabricated. • The addition of micron-sized WC particles can generate the deflection of crack in the extension process. • The addition of micron-sized WC particles can improve the fracture toughness obviously. - Abstract: In this work, the effects of micron grained WC additions on the microstructure and properties of ultrafine WC–(micron WC–Co) cemented carbides produced through low pressure sintering processes were investigated by scanning electron microscope and mechanical properties tests. The results show that the obvious crack deflection and transgranular fracture phenomenon could be observed with the addition of micron WC, which can resist the crack propagation and improve the toughness of cemented carbides. The sintered ultrafine WC–(micron WC–Co) hardmetals demonstrate excellent hardness and fracture toughness values (HV30: 1700 kg/mm2, KIC: 13.82 MPa m1/2). These inhomogeneous ultrafine WC–(micron WC–Co) cemented carbides have considerable potential for use in structural applications

  12. The effects of micron WC contents on the microstructure and mechanical properties of ultrafine WC–(micron WC–Co) cemented carbides

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chao; Lin, Nan, E-mail: linnan@csu.edu.cn; He, Yuehui; Wu, Chonghu; Jiang, Yao

    2014-05-01

    Highlights: • The ultrafine WC–(micron WC–Co) cemented carbides were fabricated. • The addition of micron-sized WC particles can generate the deflection of crack in the extension process. • The addition of micron-sized WC particles can improve the fracture toughness obviously. - Abstract: In this work, the effects of micron grained WC additions on the microstructure and properties of ultrafine WC–(micron WC–Co) cemented carbides produced through low pressure sintering processes were investigated by scanning electron microscope and mechanical properties tests. The results show that the obvious crack deflection and transgranular fracture phenomenon could be observed with the addition of micron WC, which can resist the crack propagation and improve the toughness of cemented carbides. The sintered ultrafine WC–(micron WC–Co) hardmetals demonstrate excellent hardness and fracture toughness values (HV{sub 30}: 1700 kg/mm{sup 2}, K{sub IC}: 13.82 MPa m{sup 1/2}). These inhomogeneous ultrafine WC–(micron WC–Co) cemented carbides have considerable potential for use in structural applications.

  13. A Blended Cement Containing Blast Furnace Slag and Phosphorous Slag

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Blended cement containing blast furnace slag(BFS) and phosphorous slag(PS) is a new kind of cement.The total content of blended materials could increase if two additives were used. Using the same admixtures, the properties of the blended cement with 70% additives could reach the standard of 525-grade slag cement according to GB.The strength of cement with 80% additives could reach the standard of 425-grade slag cement.The tests of strength, pore structure,hydration products,inhibiting alkali-aggregate reaction, resistance to sulfate corrosion of BFS-PSC were performed.

  14. Shrinkage Properties of Cement Stabilized Gravel

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard

    2014-01-01

    Cement stabilized gravel is an attractive material in road construction because its strength prop-erties are accommodating the increasingly higher requirements to the bearing capacity of a base course. However, reflection cracking of cement stabilized gravel is a major concern. In this pa......-per the shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...

  15. ASSESSMENT OF DEFORMATION AND STRENGTH OF SOILS STRENGTHENED BY CEMENTING

    Directory of Open Access Journals (Sweden)

    Sainov Mihail Petrovich

    2014-09-01

    Full Text Available Currently there are few studies of deformation and strength properties of loose soils strengthened by cementing. Based on the data of already arranged grout curtains it was determined that in cemented gravel-pebble soil there are 7...9 % of cement, which is less than in concrete. To assess deformation and strength of such soils it is possible to use the data of tests conducted by other authors, where the effect of cement contents on sand-cement mix properties was studied. Analysis of experimental data showed that cemented soil may be identified with concrete only with high content of cement (more than 10 %. At cement content 7...9 % in soil the strength deformation of cemented soil varies to a small extent. Its deformation becomes 2-3 times less. It greatly depends on compression stresses. The formulae are proposed which permit assessing the effect of compression and cement content on deformation of cemented soil. It is shown that strength of cemented soil is less than that even of the weakest concrete. It has a sufficiently high cohesion, but the friction angle is approximately the same as that of the initial soil.

  16. Cement replacement materials. Properties, durability, sustainability

    Energy Technology Data Exchange (ETDEWEB)

    Ramezanianpour, Ali Akbar [Amirkabir Univ. of Technology, Tehran (Iran, Islamic Republic of). Concrete Technology Center

    2014-04-01

    The aim of this book is to present the latest findings in the properties and application of Supplementary Cementing Materials and blended cements currently used in the world in concrete. Sustainability is an important issue all over the world. Carbon dioxide emission has been a serious problem in the world due to the greenhouse effect. Today many countries agreed to reduce the emission of CO2. Many phases of cement and concrete technology can affect sustainability. Cement and concrete industry is responsible for the production of 7% carbon dioxide of the total world CO2 emission. The use of supplementary cementing materials (SCM), design of concrete mixtures with optimum content of cement and enhancement of concrete durability are the main issues towards sustainability in concrete industry.

  17. Content

    DEFF Research Database (Denmark)

    Keiding, Tina Bering

    Aim, content and methods are fundamental categories of both theoretical and practical general didactics. A quick glance in recent pedagogical literature on higher education, however, reveals a strong preoccupation with methods, i.e. how teaching should be organized socially (Biggs & Tang, 2007...... a theoretical approach, which takes complexity as fundamental premise for modern society (Luhmann, 1985, 2002). In educational situations conditionally valuable content generally will exceed what can actually be taught within the frames of an education. In pedagogy this situation is often referred...... to as ‘abundance of material’, and in many cases it is not obvious, how the line between actually chosen and conditionally relevant content can be draw. Difficulties in drawing the line between actual educational content and conditionally relevant content can be handled in different way. One way, quite efficient...

  18. INFLUENCE OF WINE ACID ON RHEOLOGICAL PROPERTIES OF WELL BORE CEMENT SLURRIES AND HARDENED CEMENT PROPERTIES

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1989-12-01

    Full Text Available Adaptation of commercial types of domestic cements for use in cementing the deep wells is a process by which Yugoslav oil industry tends to solve problems of completion of those wells independently. In order to design a domestic, cheep and effective retarder, tests of applicability of wine acid on cement slurries have been carried out. Besides examining the necessary wine acid content to achieve desirable Theological properties, the influence of this additive on properties of hardened cement samples has been tested too (the paper is published in Croatian.

  19. Cementation of Loose Sand Particles based on Bio-cement

    Institute of Scientific and Technical Information of China (English)

    RONG Hui; QIAN Chunxiang

    2014-01-01

    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  20. Ni含量对粗晶WC-Co-Ni硬质合金组织和性能的影响%Effect of Ni Content on the Microstructure and Properties of WC-Co-Ni Cemented Carbide

    Institute of Scientific and Technical Information of China (English)

    饶承毅; 龙坚战; 袁红梅

    2012-01-01

    In this paper the effect of the Ni content in Co-Ni binder on the microstructure and properties of WC-Co-Ni cemented carbide processed by conventional powder metallurgy was studied. The results show that, with the increase of the nickel content in Co-Ni binder, the distribution of binder phase becomes inhomogenous and the size and roundness of the WC grain in alloy increases. The transverse flexural strength of the alloy appears maximum value in WC-(60wt%Co-40wt%Ni ) cemented carbide. Meanwhile, with the increase of Ni content, the hardness decreases, the density is almost the same, the cobalt magnetism drops and the coercive force first grows and then reduces.%以WC-10%(Co+Ni)硬质合金为研究对象,在相同含量的Co+Ni粘结相中采用不同的钴镍比来研究Ni含量对WC-Co-Ni硬质合金组织和性能的影响.结果表明随Co+Ni粘结相中的镍含量的增加,合金中显微组织结构中的粘结相的分布均匀性变差;WC晶粒的尺寸和圆度增大.合金的强度性能结果表明WC-(Co+Ni)硬质合金在粘结相质量分数为60%Co-40%Ni时抗弯强度出现最大值;随Ni含量的增加,WC-(Co+Ni)硬质合金的硬度值相差不大,但呈下降趋势;合金的密度几乎没有变化;合金的钴磁降低,磁力呈现先增后降.

  1. The effect of microsilica and refractory cement content on the properties of andalusite based Low Cement Castables used in aluminum casthouse O efeito do teor de microsílica e de cimento refratário nas propriedades de LCCs usados em moldagem de alumínio

    Directory of Open Access Journals (Sweden)

    E. A. Firoozjaei

    2010-12-01

    Full Text Available The bonding system in low cement castables is achieved by the use of calcium aluminate cement, microsilica and reactive alumina. The lime/silica ratio critically impacts the liquid phase formation at high temperatures and subsequently the corrosion resistance and the mechanical and physical properties of the refractory. In the current study, the effects of microsilica and cement contents on the corrosion resistance and the physical and mechanical properties of Andalusite Low Cement Castables (LCCs refractories were investigated. Alcoa Cup test was used to evaluate the corrosion resistance of the castables at 850 ºC and 1160 ºC. The study showed that an increase in the microsilica/cement ratio improves the physical and mechanical properties of the castable, but at the expense of the corrosion resistance. When a fixed amount of BaSO4 was added to the base refractory material, barium celsian along with glassy phase formation was observed to increase with the increase in the microsilica/cement ratio in the refractory. The presence of the glassy phases was noted to lower the positive effect of Ba-celsian formation on improving the corrosion resistance of the refractory. The observed results were validated using thermodynamic calculations which indicated that Ba-celsian phase was more resistant than Ca-anorthite for applications involving contact with molten aluminum.O sistema de ligantes em concretos de baixo cimento é produzido com o uso de cimento de aluminato de cálcio, microsílica e alumina reativa. A razão cálcia/sílica tem importância crucial na formação de fase líquida a altas temperaturas e posteriormente na resistência a corrosão e nas propriedades mecânicas e físicas do refratário. Neste trabalho foram investigados os efeitos do teor de microsílica e de cimento na resistência à corrosão e nas propriedades mecânicas e físicas de refratários de baixo teor de cimento Andalusita (LCC. O teste da Alcoa foi usado para

  2. Neutron Scattering Studies of Cement

    Science.gov (United States)

    Allen, Andrew

    2010-03-01

    Despite more than a century of research, basic questions remain regarding both the internal structure and the role of water in Ordinary Portland cement (OPC) concrete, the world's most widely used manufactured material. Most such questions concern the primary hydration product and strength-building phase of OPC paste, the calcium silicate hydrate (C-S-H) gel. When cement and water are mixed, this phase precipitates as clusters of nanoscale (nearly amorphous) colloidal particles with an associated water-filled inter-particle pore system. Most attempts to characterize the C-S-H gel and the behavior of the associated water involve drying or other processes that, themselves, change the bound water content within and around the gel. Neutron scattering methods do not suffer from this disadvantage. Furthermore, the neutron isotope effect and the neutron's sensitivity to molecular motion have enabled considerable progress to be made in recent years by: (i) determining the C-S-H composition, density and gel structure in small-angle neutron scattering (SANS) H/D contrast variation studies; (ii) elucidating the changing state of water within cement as hydration progresses using quasielastic neutron scattering (QENS); and (iii) measuring the production and consumption of nanoscale calcium hydroxide (CH), a by-product of cement hydration that co-exists with the C-S-H gel, using inelastic neutron scattering (INS). These experiments have provided new insights into the physics and chemistry of cement hydration, and have implications for the design of new concretes with pozzolanic cement additions that are intended to address environmental concerns and sustainability issues.

  3. Improvement of Cement Strength by Induction Method

    Institute of Scientific and Technical Information of China (English)

    YANG Li-yuan; LIN Zong-shou

    2004-01-01

    The induction method of improving the strength of Portland cement by adding fine slag powder,high aluminate component and hydrated paste was investigated through determining the physical properties,hydration heat and pore size distribution,and its mechanism was discussed.The experimental results reveal that a certain content of high aluminate component,fine slag powder and hydrated paste can improve remarkably the strength of Portland cement.

  4. 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.

  5. Cement with silica fume and granulated blast-furnace slag: strength behavior and hydration

    OpenAIRE

    Bonavetti, V. L.; Castellano, C.; Donza, H.; Rahhal, V. F.; Irassar, E. F.

    2014-01-01

    This paper analyses the influence of portland cement replacement by silica fume (up to 10%) and/or granulated blast furnace slag (up to 70%) on the hydration cement (XRD, heat of hydration, non evaporable water content and calcium hydroxide content) curing under sealed conditions and their effect on the mechanical strength. The obtained results indicate that binary cements containing silica fume and ternary cements there was a significant increase of hydration rate at early age. At later a...

  6. CONTENTS

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    The Development and Evolution of the Idea of the Mandate of Heaven in the Zhou Dynasty The changes in the idea of Mandate of Heaven during the Shang and Zhou dynasties are of great significance in the course of the development of traditional Chinese culture. The quickening and awakening of the humanistic spirit was not the entire content of the Zhou idea of Mandate of Heaven. In the process of annihilating the Shang dynasty and setting up their state, the Zhou propagated the idea of the Mandate of Heaven out of practical needs. Their idea of the Mandate of Heaven was not very different from that of the Shang. From the Western Zhou on, the Zhou idea of Mandate of Heaven by no means developed in a linear way along a rational track. The intermingling of rationality and irrationality and of awakening and non-awakening remained the overall state of the Zhou intellectual superstructure after their "spiritual awakening".

  7. Absorption Characteristics of Cement Combination Concrete Containing Portland Cement, fly ash, and Metakaolin

    Directory of Open Access Journals (Sweden)

    Folagbade S.O.

    2016-03-01

    Full Text Available The resistance to water penetration of cement combination concretes containing Portland cement (PC, fly ash (FA, and metakaolin (MK have been investigated at different water/cement (w/c ratios, 28-day strengths, and depths of water penetration using their material costs and embodied carbon-dioxide (eCO2 contents. Results revealed that, at equal w/c ratio, eCO2 content reduced with increasing content of FA and MK. MK contributed to the 28-day strengths more than FA. Compared with PC, FA reduced cost and increased the depth of water penetration, MK increased cost and reduced the depth of water penetration, and their ternary combinations become beneficial. At equal strengths and levels of resistance to water penetration, most of the cement combination concretes are more environmentally compatible and costlier than PC concrete. Only MK binary cement concretes with 10%MK content or more and ternary cement concretes at a total replacement level of 55% with 10%MK content or more have higher resistance to water penetration than PC concrete.

  8. 不同含气量水泥砂浆孔体积分形维数研究%Study on Pore Volume Fractal Dimension for Cement Mortar with Different Air Contents

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    The pore structure parameters of cement mortar with different air contents are measured by mercury porosimeter and pore structure analyzer. Fractal model based on thermodynamic method is used in calculation of different scales' pore structure fractal dimensions of cement mortar. The relationships between fractal dimension and porosity, average pore diameter, pore specific surface area, pore spacing coefficient, total pore volume of cement mortar are analyzed. The result shows that ( 1 ) the fractal dimension of pore structures with different scales calculated by the fractal model based on thermodynamics presents multiplicity, it can represent the complexity of cement mortar pore structure very well; ( 2 ) the increase of air content makes the fractal dimension of the pore whose diameter is more than the range of 102 nm has increase trend, while the fractal dimension of the pore whose diameter is under the range of 102 nm shows a trend of decrease; (3) the increase of age makes the fractal dimension of the pore whose diameter is in the range of 103 nm to 104 nm shows a trend of decrease, the others shows a trend of increase; (4) among the pore structure parameters, the pore volume fractal dimension has good correlation with porosity, average pore diameter and total pore volume, and has poor correlation with pore specific surface area in the range of 103 -104 nm and 102 -103 nm pore diameters. Considering the pores whose diameters in the range of 102 -103 nm have a high proportion in the total pore, it can be as a unified fractal dimension to signify the change of pore structure parameters.%采用压汞仪、气孔结构分析仪测定了不同含气量水泥砂浆的孔结构参数,通过热力学关系的分形模型计算得到了水泥砂浆不同尺度孔结构分形维数,并分析了水泥砂浆不同尺度孔结构孔体积分形维数与孔隙率、平均孔径、孔比表面积、孔间距系数、孔总体积关系.结果表明:基于热力学关系的分

  9. 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.

  10. Effect of Cement Replacement with Carbide Waste on the Strength of Stabilized Clay Subgrade

    Directory of Open Access Journals (Sweden)

    Muntohar A.S.

    2016-03-01

    Full Text Available Cement is commonly used for soil stabilization and many other ground improvement techniques. Cement is believed to be very good to improve the compressive and split-tensile strength of clay subgrades. In some application cement could be partly or fully replaced with carbide waste. This research is to study the effectiveness of the cement replacement and to find the maximum carbide waste content to be allowed for a clay subgrade. The quantities of cement replaced with the carbide waste were 30, 50, 70, 90, and 100% by its mass. The results show that replacing the cement with carbide waste decreased both the compressive and split tensile strength. Replacing cement content with carbide waste reduced its ability for stabilization. The carbide waste content should be less than 70% of the cement to provide a sufficient stabilizing effect on a clay subgrade.

  11. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    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

  12. Contents

    Directory of Open Access Journals (Sweden)

    Editor IJRED

    2012-11-01

    Full Text Available International Journal of Renewable Energy Development www.ijred.com Volume 1             Number 3            October 2012                ISSN 2252- 4940   CONTENTS OF ARTICLES page Design and Economic Analysis of a Photovoltaic System: A Case Study 65-73 C.O.C. Oko , E.O. Diemuodeke, N.F. Omunakwe, and E. Nnamdi     Development of Formaldehyde Adsorption using Modified Activated Carbon – A Review 75-80 W.D.P Rengga , M. Sudibandriyo and M. Nasikin     Process Optimization for Ethyl Ester Production in Fixed Bed Reactor Using Calcium Oxide Impregnated Palm Shell Activated Carbon (CaO/PSAC 81-86 A. Buasri , B. Ksapabutr, M. Panapoy and N. Chaiyut     Wind Resource Assessment in Abadan Airport in Iran 87-97 Mojtaba Nedaei       The Energy Processing by Power Electronics and its Impact on Power Quality 99-105 J. E. Rocha and B. W. D. C. Sanchez       First Aspect of Conventional Power System Assessment for High Wind Power Plants Penetration 107-113 A. Merzic , M. Music, and M. Rascic   Experimental Study on the Production of Karanja Oil Methyl Ester and Its Effect on Diesel Engine 115-122 N. Shrivastava,  , S.N. Varma and M. Pandey  

  13. The Setting Chemistry of Glass Ionomer Cement

    Institute of Scientific and Technical Information of China (English)

    CHENG Hanting; LIU Hanxing; ZHANG Guoqing

    2005-01-01

    The setting chemistry of glass ionomer cement was investigated by using mechanical determination of compressive strength at predetermined intervals, and measurement of structure changes of corresponding fracture sample by means of IR spectra and differential scanning calorimetry ( DSC). Zinc polycarboxylate cement was used as a comparison sample. The compressive strength of glass ionomer cement (GIC) increases with aging. IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied, however, no significant changes occur in the zinc polycarxyolate cement. Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging. The structure changes include the crosslink density, the ratio of complex form to ionic form, the content ratio of Al-PAA to Ca-PAA, the forming and mauring process of the interface layer comprising of silica gel.

  14. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    The objective of this project is to develop an improved ultra-lightweigh cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems, Task 2: Review Russian Ultra-Lightweight Cement Literature, and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary surface pipe and intermediate casing cementing conditions historically encountered in the US and establishment of average design conditions for ULHS cements. Russian literature concerning development and use of ultra-lightweight cements employing either nitrogen or ULHS was reviewed, and a summary is presented. Quality control testing of materials used to formulate ULHS cements in the laboratory was conducted to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS. This protocol is presented and discussed. finally, results of initial testing of ULHS cements is presented along with analysis to establish cement performance design criteria to be used during the remainder of the project

  15. Reinforcement of osteosynthesis screws with brushite cement.

    Science.gov (United States)

    Van Landuyt, P; Peter, B; Beluze, L; Lemaître, J

    1999-08-01

    The fixation of osteosynthesis screws remains a severe problem for fracture repair among osteoporotic patients. Polymethyl-methacrylate (PMMA) is routinely used to improve screw fixation, but this material has well-known drawbacks such as monomer toxicity, exothermic polymerization, and nonresorbability. Calcium phosphate cements have been developed for several years. Among these new bone substitution materials, brushite cements have the advantage of being injectable and resorbable. The aim of this study is to assess the reinforcement of osteosynthesis screws with brushite cement. Polyurethane foams, whose density is close to that of cancellous bone, were used as bone model. A hole was tapped in a foam sample, then brushite cement was injected. Trabecular osteosynthesis screws were inserted. After 24 h of aging in water, the stripping force was measured by a pull-out test. Screws (4.0 and 6.5 mm diameter) and two foam densities (0.14 and 0.28 g/cm3) were compared. Cements with varying solid/liquid ratios and xanthan contents were used in order to obtain the best screw reinforcement. During the pull-out test, the stripping force first increases to a maximum, then drops to a steady-state value until complete screw extraction. Both maximum force and plateau value increase drastically in the presence of cement. The highest stripping force is observed for 6.5-mm screws reinforced with cement in low-density foams. In this case, the stripping force is multiplied by 3.3 in the presence of cement. In a second experiment, cements with solid/liquid ratio ranging from 2.0 to 3.5 g/mL were used with 6.5-mm diameter screws. In some compositions, xanthan was added to improve injectability. The best results were obtained with 2.5 g/mL cement containing xanthan and with 3.0 g/mL cements without xanthan. A 0.9-kN maximal stripping force was observed with nonreinforced screws, while 1.9 kN was reached with reinforced screws. These first results are very promising regarding screw

  16. Multiscale Lattice Boltzmann-Finite Element Modelling of Transport Properties in Cement-based Materials

    NARCIS (Netherlands)

    Zhang, M.

    2013-01-01

    Cement-based materials are the most widely used man-made materials in the world. The durability of cement-based materials has been a major concern due to the premature failure and serviceability issues of many reinforced concrete structures. Durability of cement-based materials is to a large content

  17. Experimental study on the electrical resistivity of soil cement admixtures

    Science.gov (United States)

    Liu, Song Yu; Du, Yan Jun; Han, L. H.; Gu, M. F.

    2008-05-01

    Recently in China, soil cement is widely used to improve the soft ground in the highway construction engineering. Literature studies are mainly investigating the mechanical properties of the soil cement, while its properties of the electrical resistivity are not well addressed. In this paper, the properties of the electrical resistivity of the reconstituted soil-cement and the in situ soil cement columns are investigated. The test results show that the electrical resistivity of the soil cement increases with the increase in the cement-mixing ratio and curing time, whereas it decreases with the increase in the water content, degree of saturation and water cement ratio. A simple equation is proposed to predict the electrical resistivity of soil cement under the condition of the specified curing time and water cement ratio. It is found that the electrical resistivity has a good relationship with the unconfined compression strength and blow count of SPT. It is expected that the electrical resistivity method can be widely used for checking/controlling the quality of soil cement in practice.

  18. Injectable Premixed Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new type of injectable premixed bone cement consisting of nano-hydroxyapatite (n-HA) and polyamide 66(PA66) composite is investigated. This cement can be handled as paste and easily shaped, which can set in air, in physiological saline solution and in blood. The setting time, injectability and compressive strength of the cement largely depend on the ratio of liquid to powder (L/P). Moreover, the content of n-HA in composite also affects the compressive strength and injectability of the cement. The premixed composite cement can remain stable in the package for a long period and harden only after delivery to the defects site. The results suggest that injectable premixed cement has a reasonable setting time, reasonable viscosity for injecting, excellent washout resistance and high mechanical strength, which can be developed for root canal filling, sealing and various bone defects augmentation.

  19. Chemical and physical properties of bone cement for vertebroplasty

    Directory of Open Access Journals (Sweden)

    Po-Liang Lai

    2013-08-01

    Full Text Available Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.

  20. Coupled effect of cement hydration and temperature on hydraulic behavior of cemented tailings backfill

    Institute of Scientific and Technical Information of China (English)

    WU Di; CAI Si-jing

    2015-01-01

    Cemented tailings backfill (CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process can release significant amount of heat to raise the temperature of CTB and in turn increase the rate of cement hydration. Meanwhile, the progress of cement hydration consumes water and produces hydration products to change the pore structures within CTB, which further influences the hydraulic behavior of CTB. In order to understand the hydraulic behavior of CTB, a numerical model was developed by coupling the hydraulic, thermal and hydration equations. This model was then implemented into COMSOL Multiphysics to simulate the evolutions of temperature and water seepage flow within CTB versus curing time. The predicted outcomes were compared with correspondent experimental results, proving the validity and availability of this model. By taking advantage of the validated model, effects of various initial CTB and curing temperatures, cement content, and CTB's geometric shapes on the hydraulic behavior of CTB were demonstrated numerically. The presented conclusions can contribute to preparing more environmentally friendly CTB structures.

  1. Frost Resistance and Permeability of Cement Stabilized Gravel used as Filling Material for Pearl-Chain Bridges

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard; Hertz, Kristian Dahl

    2014-01-01

    The Pearl-Chain Bridge Technology introduces a new innovative arch bridge solution which com-bines the statical advantages of an arch bridge with a minimum of traffic disturbance. The arch-shaped substructure is stabilized by a filling material, e.g. cement stabilized gravel, which should meet...... several requirements on its moisture properties. In this paper the frost resistance, the liquid water permeability and the water vapour permeability of cement stabilized gravel are examined for two different cement contents. It is found that a small increase in cement content from 4% to 5% increases...... the 28-days compressive strength from 6.2 MPa to 12.3 MPa. The frost resistance of cement stabilized gravel with 5% cement content is better than for cement stabilized gravel with 4% cement content. The liquid water permeability coefficient and the water vapour permeability coefficient are significantly...

  2. Tympanoplasty with ionomeric cement

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy...

  3. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  4. Pack cementation coatings for alloys

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  5. Analytical method to estimate resin cement diffusion into dentin

    Science.gov (United States)

    de Oliveira Ferraz, Larissa Cristina; Ubaldini, Adriana Lemos Mori; de Oliveira, Bruna Medeiros Bertol; Neto, Antonio Medina; Sato, Fracielle; Baesso, Mauro Luciano; Pascotto, Renata Corrêa

    2016-05-01

    This study analyzed the diffusion of two resin luting agents (resin cements) into dentin, with the aim of presenting an analytical method for estimating the thickness of the diffusion zone. Class V cavities were prepared in the buccal and lingual surfaces of molars (n=9). Indirect composite inlays were luted into the cavities with either a self-adhesive or a self-etch resin cement. The teeth were sectioned bucco-lingually and the cement-dentin interface was analyzed by using micro-Raman spectroscopy (MRS) and scanning electron microscopy. Evolution of peak intensities of the Raman bands, collected from the functional groups corresponding to the resin monomer (C–O–C, 1113 cm-1) present in the cements, and the mineral content (P–O, 961 cm-1) in dentin were sigmoid shaped functions. A Boltzmann function (BF) was then fitted to the peaks encountered at 1113 cm-1 to estimate the resin cement diffusion into dentin. The BF identified a resin cement-dentin diffusion zone of 1.8±0.4 μm for the self-adhesive cement and 2.5±0.3 μm for the self-etch cement. This analysis allowed the authors to estimate the diffusion of the resin cements into the dentin. Fitting the MRS data to the BF contributed to and is relevant for future studies of the adhesive interface.

  6. Triaxial shear behavior of a cement-treated sandegravel mixture

    Institute of Scientific and Technical Information of China (English)

    Younes Amini; Amir Hamidi

    2014-01-01

    A number of parameters, e.g. cement content, cement type, relative density, and grain size distribution, can influence the mechanical behaviors of cemented soils. In the present study, a series of conventional triaxial compression tests were conducted on a cemented poorly graded sandegravel mixture containing 30%gravel and 70%sand in both consolidated drained and undrained conditions. Portland cement used as the cementing agent was added to the soil at 0%, 1%, 2%, and 3%(dry weight) of sandegravel mixture. Samples were prepared at 70%relative density and tested at confining pressures of 50 kPa, 100 kPa, and 150 kPa. Comparison of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded samples. Undrained failure envelopes determined using zero Skempton’s pore pressure coefficient ðA ¼ 0Þ criterion were consistent with the drained ones. Energy absorption potential was higher in drained condition than undrained condition, suggesting that more energy was required to induce deformation in cemented soil under drained state. Energy ab-sorption increased with increase in cement content under both drained and undrained conditions.

  7. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2003-01-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. DOE joined the Materials Management Service (MMS)-sponsored joint industry project ''Long-Term Integrity of Deepwater Cement under Stress/Compaction Conditions.'' Results of the project contained in two progress reports are also presented in this report.

  8. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Kaplan, Hasan; Hanifi BİNİCİ

    1995-01-01

    Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, ce...

  9. Utilizing wood wastes as reinforcement in wood cement composite bricks

    Directory of Open Access Journals (Sweden)

    Nusirat Aderinsola Sadiku

    2015-07-01

    Full Text Available This paper presents the research work undertaken to study the properties of Wood Cement Composite Bricks (WCCB from different wood wastes and cement / wood content. The WCBBs with nominal density of 1200 kg m-3 were produced from three tropical wood species and at varying cement and wood content of 2:1, 2.5:1 and 3:1 on a weight to weight basis. The properties evaluated were compressive strength, Ultra Pulse Velocity (UPV, water absorption (WA and thickness swelling (TS. The Compressive strength values ranged from 0.25 to 1.13 N mm-2 and UPV values ranged from 18753 to 49992 m s-1. The mean values of WA after 672 hours (28 days of water soaking of the WCCBs ranged from 9.50% to 47.13% where there were no noticeable change in the TS of the bricks. The observed density (OD ranged from 627 to 1159 kg m-3. A. zygia from the three wood/cement content were more dimensionally stable and better in compressive strength than the other two species where T. scleroxylon had the best performance in terms of UPV. All the properties improved with increasing cement content. WCCBs at 3.0:1 cement/wood content are suitable for structural application such as panelling, ceiling and partitioning

  10. Experimental evaluation of cement materials for solidifying sodium nitrate

    International Nuclear Information System (INIS)

    Low-level liquid waste containing sodium nitrate is planned to be transformed to salt block by evaporation with sodium borate in the Low-level Waste Treatment Facility (LWTF), then salt block will be stored temporally. It should be important to investigate the method how to treat these liquid waste suitable to final disposal criteria that will be settled in future. Cement solidification is one of promising candidates because it has been achieved as the solidification material for the shallow land disposal. The research was conducted to evaluate applicability of various cement materials to solidification of sodium nitrate. The following cements were tested. Ordinary Portland Cement (OPC). Portland Blast-furnace Slag Cement; C type (PBFSC). Alkali Activated Slag Cement (AASC, supplied by JGC). The test results are as follows; (1) AASC is characterized by a high sodium nitrate loading (-70 wt%) compared with other types of cement material. High fluidity of the cement paste, high strength after solidification, and minimization of free water on the cement paste are achieved under all test conditions. (2) OOPC and PBFSC produced free water on the cement paste in the early days and delayed the hardening period. 3 or more days are required to harden evan with 30 wt% content of sodium nitrate. (3) Though PBFSC contains blast furnace slag similar to AASC, there is no advantage prior to OPC. To design an ideal cement conditioning system for sodium nitrate liquid waste in the LWTF, the further studies are necessary such as the simulated waste test, Kd test, pilot test, and layout design. (author)

  11. A New Kind of Eco-Cement Made of Cement Kiln Dust and Granular Blast Furnace Slag

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A research project was conducted to manufacture eco-cement for sustainable development using cement kiln dust( CKD ) and granular blast furnace slag( GBFS ).In the project, the burning process and mineral compositions of CKD clinker were investigated.Dife rent mineralizers such as CaSO4 and CaF2 , sulfur and alkali content were considered.The strength of CKD and GBFS eco-cement were evaluated.The results indicate the CKD clinker can not only form ordinary cement clinker minerals such as C3 S, C2 S and C4 AF, but also form strength to the Portland cement grade 32.5 when blend proportion is properly applied.

  12. Influence of the activators’ type and content on the properties of no cement mortars%激发剂种类及掺量对无水泥砂浆性能的影响

    Institute of Scientific and Technical Information of China (English)

    张海龙; 裴长春

    2015-01-01

    为了优化工业垃圾粉煤灰、高炉矿渣及生石灰作为胶凝材料的无水泥砂浆配合比设计,提高无水泥砂浆的基础性能,试验通过改变碱性激发剂的种类及掺量,研究了无水泥砂浆的表观密度及力学性能,得出了一些有价值的结论。%In order to optimize the mix design of no cement mortars with fly ash, blast furnace slag and lime as cementitious materials and to im-prove the performance of no cement mortars, the test studied the apparent density and mechanical properties of no cement mortars by changing the type and dosage of alkaline activator, some valuable conclusions are obtained.

  13. Pollution and Prevention of Pb during Cement Calcination

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Emission pollution and prevention measures of Pb during cement calcination were discussed. The content of Pb and the variation of composition were explored by means of atomic absorption spectroscopy (AAS) and X-ray diffraction. The results show that a number of Pb emits during cement calcination, F and C1 promote the emission of Pb, and Pb is enriched in kiln dust. The smaller the particle of kiln dust, the higher the content of Pb. When utilizing the raw materials with a high content of Pb, a more efficient dust collector should be used and the kiln dust should be used as the addition of cement. Pb in clinker is enriched in the intermediate phase. The reduction of silica modulus is useful to increase the solidification content of Pb in clinker. The solidification content of Pb in calcium sulphoaluminate mineral is higher than that in calcium aluminate mineral.

  14. Biocompatibility of alendronate-loaded acrylic cement for vertebroplasty

    Directory of Open Access Journals (Sweden)

    T Calvo-Fernández

    2010-10-01

    Full Text Available This paper reports a biological evaluation of a non-resorbable acrylic cement loaded with alendronate for the treatment of osteoporotic vertebral compression fractures. The cement formulation was based on polymethyl methacrylate and acrylic monomers; one of these had covalently linked vitamin E residues. The same cement in the absence of alendronate was used as a control. The setting of the charged cement presented a maximum polymerization temperature of 44ºC, a setting time of 24 min, a residual monomer content lower than 3 wt.%, a compressive strength of 99±10 MPa and an elastic modulus of 1.2±0.2 GPa. Cytotoxicity studies using human osteoblast cultures revealed that the leachable substances of the alendronate loaded cement collected between 1 and 7 days decreased cell viability to values lower than 80%. However, morphological changes and cellular damage in cells produced by the extracts decreased with the leak time. Cell adhesion and growth on charged cement was significantly lower than on the control. Implantation of the cement paste in the intra-femoral cavity of rabbits showed that initially the osteogenic activity was evident for the cement charged with alendronate, and the osteosynthesis process took place mainly in the trabeculae and was manifested by the presence of a non-mineralised osseous spicule. The interface between material and adjacent bone tissue was initially characterized by a variable fibrous response that in many cases it appeared reduced to thin connective tissue after a 24-week-period.

  15. Preparation and mechanical properties of graphene oxide: cement nanocomposites.

    Science.gov (United States)

    Babak, Fakhim; Abolfazl, Hassani; Alimorad, Rashidi; Parviz, Ghodousi

    2014-01-01

    We investigate the performance of graphene oxide (GO) in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1-2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM) used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H) gels in GO cement mortar compared with the normal cement mortar.

  16. Preparation and Mechanical Properties of Graphene Oxide: Cement Nanocomposites

    Directory of Open Access Journals (Sweden)

    Fakhim Babak

    2014-01-01

    Full Text Available We investigate the performance of graphene oxide (GO in improving mechanical properties of cement composites. A polycarboxylate superplasticizer was used to improve the dispersion of GO flakes in the cement. The mechanical strength of graphene-cement nanocomposites containing 0.1–2 wt% GO and 0.5 wt% superplasticizer was measured and compared with that of cement prepared without GO. We found that the tensile strength of the cement mortar increased with GO content, reaching 1.5%, a 48% increase in tensile strength. Ultra high-resolution field emission scanning electron microscopy (FE-SEM used to observe the fracture surface of samples containing 1.5 wt% GO indicated that the nano-GO flakes were well dispersed in the matrix, and no aggregates were observed. FE-SEM observation also revealed good bonding between the GO surfaces and the surrounding cement matrix. In addition, XRD diffraction data showed growth of the calcium silicate hydrates (C-S-H gels in GO cement mortar compared with the normal cement mortar.

  17. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    DEFF Research Database (Denmark)

    Pietro, Lura; Ye, Guang; van Breugel, Klaas

    2004-01-01

    In this paper, measurements of non-evaporable water content, chemical shrinkage, autogenous deformation, internal relative humidity (RH), pore solution composition, and early-age elastic modulus are presented and discussed. All experiments were performed on Portland cement and blast-furnace slag ...

  18. 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.

  19. Properties of Cement Mortar Produced from Mixed Waste Materials with Pozzolanic Characteristics.

    Science.gov (United States)

    Yen, Chi-Liang; Tseng, Dyi-Hwa; Wu, Yue-Ze

    2012-07-01

    Waste materials with pozzolanic characteristics, such as sewage sludge ash (SSA), coal combustion fly ash (FA), and granulated blast furnace slag (GBS), were reused as partial cement replacements for making cement mortar in this study. Experimental results revealed that with dual replacement of cement by SSA and GBS and triple replacement by SSA, FA, and GBS at 50% of total cement replacement, the compressive strength (Sc) of the blended cement mortars at 56 days was 93.7% and 92.9% of the control cement mortar, respectively. GBS had the highest strength activity index value and could produce large amounts of CaO to enhance the pozzolanic activity of SSA/FA and form calcium silicate hydrate gels to fill the capillary pores of the cement mortar. Consequently, the Sc development of cement mortar with GBS replacement was better than that without GBS, and the total pore volume of blended cement mortars with GBS/SSA replacement was less than that with FA/SSA replacement. In the cement mortar with modified SSA and GBS at 70% of total cement replacement, the Sc at 56 days was 92.4% of the control mortar. Modifying the content of calcium in SSA also increased its pozzolanic reaction. CaCl(2) accelerated the pozzolanic activity of SSA better than lime did. Moreover, blending cement mortars with GBS/SSA replacement could generate more monosulfoaluminate to fill capillary pores.

  20. Properties of Cement Mortar Produced from Mixed Waste Materials with Pozzolanic Characteristics

    Science.gov (United States)

    Yen, Chi-Liang; Tseng, Dyi-Hwa; Wu, Yue-Ze

    2012-01-01

    Abstract Waste materials with pozzolanic characteristics, such as sewage sludge ash (SSA), coal combustion fly ash (FA), and granulated blast furnace slag (GBS), were reused as partial cement replacements for making cement mortar in this study. Experimental results revealed that with dual replacement of cement by SSA and GBS and triple replacement by SSA, FA, and GBS at 50% of total cement replacement, the compressive strength (Sc) of the blended cement mortars at 56 days was 93.7% and 92.9% of the control cement mortar, respectively. GBS had the highest strength activity index value and could produce large amounts of CaO to enhance the pozzolanic activity of SSA/FA and form calcium silicate hydrate gels to fill the capillary pores of the cement mortar. Consequently, the Sc development of cement mortar with GBS replacement was better than that without GBS, and the total pore volume of blended cement mortars with GBS/SSA replacement was less than that with FA/SSA replacement. In the cement mortar with modified SSA and GBS at 70% of total cement replacement, the Sc at 56 days was 92.4% of the control mortar. Modifying the content of calcium in SSA also increased its pozzolanic reaction. CaCl2 accelerated the pozzolanic activity of SSA better than lime did. Moreover, blending cement mortars with GBS/SSA replacement could generate more monosulfoaluminate to fill capillary pores. PMID:22783062

  1. Extended fatigue life of a catalyst-free self-healing acrylic bone cement using microencapsulated 2-octyl cyanoacrylate

    OpenAIRE

    Brochu, Alice B. W.; Matthys, Oriane B.; Craig, Stephen L.; Reichert, William M.

    2014-01-01

    The tissue adhesive 2-octyl cyanoacrylate (OCA) was encapsulated in polyurethane microshells and incorporated into bone cement to form a catalyst free, self-healing bone cement comprised of all clinically approved components. The bending strength, modulus, and fatigue lifetime were investigated in accordance with ASTM and ISO standards for the testing of PMMA bone cement. The bending strength of bone cement specimens decreased with increasing wt% capsules content for capsules without or with ...

  2. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; 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; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  3. Rheological and hydration characterization of calcium sulfoaluminate cement pastes

    OpenAIRE

    García-Maté, Marta; Santacruz, Isabel; de la Torre, Ángeles G.; León-Reina, Laura; Aranda, Miguel A. G.

    2012-01-01

    Calcium sulfoaluminate (CSA) cements are currently receiving a lot of attention because their manufacture produces less CO2 than ordinary Portland cement (OPC). However, it is essential to understand all parameters which may affect the hydration processes. This work deals with the study of the effect of several parameters, such as superplasticizer (SP), gypsum contents (10, 20 and 30 wt%) and w/c ratio (0.4 and 0.5), on the properties of CSA pastes during early hydration. This characteriza...

  4. 过硫磷石膏矿渣水泥混凝土中 PSC 浆磷石膏含量测定方法研究%Study of the Determination Methods of the PSC Pulp Phosphogypsum Content in the Excess-sulfate Phosphogypsum Slag Cement Concrete

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    通过分离过硫磷石膏矿渣水泥混凝土中的过硫磷石膏矿渣水泥浆,并测定各原料的 SO 3含量,然后根据各原料 SO 3的平衡关系,计算出了过硫磷石膏矿渣水泥混凝土中的过硫磷石膏矿渣水泥浆的磷石膏含量。经实验反复验证,显示磷石膏含量的测定误差均可在1.0%范围之内,可作为过硫磷石膏矿渣水泥混凝土生产过程中磷石膏配合比的日常控制和测定方法。%Through the separation of the Excess-Sulfate Phosphogypsum Slag pulp from the Excess-Sulfate Phosph-ogypsum Slag Cement Concrete,and the determination of the SO 3 content in each material,this study calculated the Phosphogypsum Content in the Excess-Sulfate Phosphogypsum Slag pulp of the Excess-Sulfate Phosphogypsum Slag Cement Concrete according to the equilibrium relationship of SO 3 in each material.Through repeated verification,it showed that the measurement deviation of the Phosphogypsum Content is within 1.0% range,so this method can be used to daily control and determine the mix proportion of the Phosphogypsum during the production of the Excess-Sul-fate Phosphogypsum Slag Cement Concrete.

  5. Correlation Between Initial Calcium Oxide Content of Slag Blended Cement and Mortar Leaching Mass Loss%矿渣混合水泥中初始氧化钙含量与砂浆溶蚀质量损失的关系

    Institute of Scientific and Technical Information of China (English)

    王培铭; 庞敏; 刘贤萍

    2016-01-01

    In the accelerated corrosion 142 d, the leaching mass loss behavior of Portland cement and slag blended cement of three different slag contents (50%, 70% and 90%, in mass fraction) mortar with two different pre-cured ages (28 and 180 d) was investigated. The initial CaO content, calcium hydroxide (CH) content and total hydration degree were analyzed. Based on the relation between CH content and initial CaO content in cement as well as mass loss, the correlation between the initial CaO content and mass loss, and the effect of total hydration degree on mass loss were studied. The results show that the mass loss of all the specimens of two different pre-cured age increase with the increase of leaching time (after 84 d increased slowly), decrease with the increase of addition of slag in blended cement. That is slag can improve the corrosion resistance performance, the fundamental cause of above improvement lies in slag reduced the CH content and hydration degree of blended cement paste. The mass loss with leaching time of 84 d and CH content (0 except) in cement paste, as well as the hydration degree (only slag blended cement) has the following linear relationship respectively. The former is y=0.207 5x–0.015 7, the latter is y=0.029 6x–0.125 4. The mass loss with leaching time of 84 d and initial CaO content in cement has a logarithmic relationship. Pre-cured 28 d, the regression equation is y=6.059ln(x)–22.164. Pre-cured 180 d, the regression equation is y=7.612 3ln(x)–27.656. Based on the logarithmic relationship, cement mortar corrosion resistance can be preliminary judged.%研究了2个预养护龄期(28和180 d)的硅酸盐水泥和3个矿渣粉掺量(50%、70%和90%)的混合水泥砂浆在加速溶蚀142 d 内的溶蚀质量损失规律,分析了硅酸盐水泥和混合水泥初始 CaO 含量、浆体中氢氧化钙(CH)含量和水化程度,基于浆体中 CH 含量与水泥初始 CaO 含量,以及溶蚀质量损失之间的

  6. Effects of aggregate volume content on sulfate resistance properties of cement based materials with supplementary cementitious materials%集料含量对掺矿物掺合料水泥基材料抗硫酸盐侵蚀性能的影响

    Institute of Scientific and Technical Information of China (English)

    吴凯; 徐玲琳; 施惠生; 高云

    2016-01-01

    The degradation of cement-based materials with different aggregate volume contents and ad-ditions, was analyzed when they were exposed to 5 and 50 g/L Na2 SO4 at 20℃.The microstructures of the corresponding cement-based materials was determined by mercury intrusion porosimetry (MIP), scanning electron microscopy backscattered electron ( SEM-BSE) image, and energy dispersive spec-trum ( EDS) analysis.The influence mechanism of the mineral addition and the aggregate volume con-tent on the sulfate resistance properties of cement-based materials was investigated.Results show that the addition of limestone powder ( LP) causes an increase in the porosity of hardened paste, exerting an adverse effect on the sulfate-resistance ability of cement-based materials.The incorporation of high amount of slag increases the total porosity, but refines the slurry pore structure from coarse pore to fi-ner one (>10 nm) .Moreover, the addition of slag strengthens the sulfate-resistance ability of ce-ment-based materials significantly.After corrosion by Na2 SO4 , the degradation of cement-based mate-rials prepared with pure Portland cement or Portland cement-limestone powder binary binders is more severe as the aggregate volume content increases.However, this negative effect caused by the aggre-gate is less remarkable in case of the slag blended system.From the BSE image and EDS analysis, the preferable deposition of gypsum in the region close to the aggregate is the main reason for the expand-ed degradation of specimens with a relative high amount of aggregate.%对不同集料体积掺量及掺合料配制的水泥基材料在室温、Na2 SO4溶液浓度为5和50 g/L时的损伤破坏过程进行分析,并采用压汞法、扫描电镜背散射电子图像分析和能谱扫描等方法得到相应水泥基材料的微观结构,研究了矿物掺合料和集料含量对水泥基材料抗硫酸盐侵蚀性能的影响机理。结果表明:单掺石灰石粉造成的硬化浆体

  7. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  8. Porous surface modified bioactive bone cement for enhanced bone bonding.

    Directory of Open Access Journals (Sweden)

    Qiang He

    Full Text Available BACKGROUND: Polymethylmethacrylate bone cement cannot provide an adhesive chemical bonding to form a stable cement-bone interface. Bioactive bone cements show bone bonding ability, but their clinical application is limited because bone resorption is observed after implantation. Porous polymethylmethacrylate can be achieved with the addition of carboxymethylcellulose, alginate and gelatin microparticles to promote bone ingrowth, but the mechanical properties are too low to be used in orthopedic applications. Bone ingrowth into cement could decrease the possibility of bone resorption and promote the formation of a stable interface. However, scarce literature is reported on bioactive bone cements that allow bone ingrowth. In this paper, we reported a porous surface modified bioactive bone cement with desired mechanical properties, which could allow for bone ingrowth. MATERIALS AND METHODS: The porous surface modified bioactive bone cement was evaluated to determine its handling characteristics, mechanical properties and behavior in a simulated body fluid. The in vitro cellular responses of the samples were also investigated in terms of cell attachment, proliferation, and osteoblastic differentiation. Furthermore, bone ingrowth was examined in a rabbit femoral condyle defect model by using micro-CT imaging and histological analysis. The strength of the implant-bone interface was also investigated by push-out tests. RESULTS: The modified bone cement with a low content of bioactive fillers resulted in proper handling characteristics and adequate mechanical properties, but slightly affected its bioactivity. Moreover, the degree of attachment, proliferation and osteogenic differentiation of preosteoblast cells was also increased. The results of the push-out test revealed that higher interfacial bonding strength was achieved with the modified bone cement because of the formation of the apatite layer and the osseointegration after implantation in the bony

  9. Reducing cement's CO2 footprint

    Science.gov (United States)

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  10. Cement Mason's Curriculum. Instructional Units.

    Science.gov (United States)

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  11. Cement og politik

    DEFF Research Database (Denmark)

    Lund, Joachim

    2012-01-01

    as well as in the public sphere. Most of the extensive job creating measures he carried out as a minister for public works necessarily involved the use of great amounts of cement – the primary produce of F.L. Smidth & Co. Gunnar Larsen thus became an easy target for Communist propaganda, picturing him...... of the Soviet Union (including an F.L. Smidth & Co. cement plant in former Estonia). He spent the last 15 months of the occupation in Sweden and was arrested after having returned to Copenhagen in May, 1945. Although a Copenhagen city court prison sentence for economic collaboration was reversed, he had...

  12. Technology Roadmaps: Cement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    To support its roadmap work focusing on key technologies for emissions reductions, the International Energy Agency (IEA) also investigated one particular industry: cement. Cement production includes technologies that are both specific to this industry and those that are shared with other industries (e.g., grinding, fuel preparation, combustion, crushing, transport). An industry specific roadmap provides an effective mechanism to bring together several technology options. It outlines the potential for technological advancement for emissions reductions in one industry, as well as potential cross-industry collaboration.

  13. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    .17, H/S ratio of 2.5 and N/S ratio of 0.18. In the second phase of this research, theoretical models are built using a modified version of an existing cement hydration modelling code, "CEMHYD3D", to simulate the chemical reaction of the activated glass powder hydration and glass powder in cement. The modified model, which is referred to as the "MOD-model" is further used to predict the types, compositions and quantities of reaction products. Furthermore, the glass powder hydration data, which is obtained experimentally, is incorporated into the MOD-model to determine the effect of adding glass powder to the paste on the process of cement hydration and resulting paste properties. Comparisons between theoretical and experimental results are made to evaluate the developed models. The MOD-model predictions have been validated using the experimental results, and were further used to investigate various properties of the hydrated glass powder cement paste. These properties include, for example, CH content of the paste, porosity, hydration degree of the glass powder and conventional C-S-H and GP CS-H contents. The results show that the MOD-model is capable of accurately simulating the hydration process of glass powder-blended cement paste and can be used to predict various properties of the hydrating paste.

  14. Cementing a wellbore using cementing material encapsulated in a shell

    Science.gov (United States)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  15. The mechanical effect of the existing cement mantle on the in-cement femoral revision.

    LENUS (Irish Health Repository)

    Keeling, Parnell

    2012-08-01

    Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

  16. Thermal behavior of asphalt cements

    International Nuclear Information System (INIS)

    Asphalt cements are highly complex mixtures of hydrocarbon molecules whose thermal behavior is of prime importance for petroleum and road industry. From DSC, the determination of several thermal properties of asphalts is given, e.g. glass-transition temperature and crystallized fraction content.The dissolution of a pure n-paraffin CnH2n+2 in an asphalt, as seen by DSC, should be a single peak. For 20g of these glasses change with time and temperature. The formation of the crystallized phases is superposed to the enthalpic relaxation of the glasses, making a kinetic study very difficult. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  17. Superplasticized Portland cement: Production and compressive strength of mortars and concrete

    Energy Technology Data Exchange (ETDEWEB)

    Bouzoubaa, N.; Zhang, M.H.; Malhotra, V.M. [Natural Resources Canada, Ottawa, Ontario (Canada)

    1998-12-01

    This paper deals with the effect of intergrinding different percentages of a naphthalene-based superplasticizer with Portland cement clinker and gypsum on the fineness of the product, and on the water requirement and the compressive strength of the mortars made with the superplasticized cement. The properties of the fresh and hardened concrete made with the superplasticized cements were also investigated. The results showed that the intergrinding of a given amount of a naphthalene-based superplasticizer with Portland clinker and gypsum reduced the grinding time required for obtaining the same Blaine fineness as that of the control Portland cement without the superplasticizer. The water requirement of the mortars made with the superplasticized cements was similar to that of the mortars made with the control Portland cements when the same amount of the superplasticizer was added at the mortar mixer; for a given grinding time and a Blaine fineness of {approximately}4500 cm{sup 2}/g, the mortars made with the superplasticized cement had higher compressive strength than those made with the control Portland cement. For a given grinding time or Blaine fineness of cement {ge}5000 cm{sup 2}/g, the slump loss, air content stability, bleeding, autogenous temperature rise, setting times, and compressive strength of the concrete made with the superplasticized cements were generally comparable to those of the concrete made with the control Portland cements when the superplasticizer was added at the concrete mixer.

  18. EVALUATION OF CHEMICALS INCORPORATED WOOD FIBRE CEMENT MATRIX PROPERTIES

    Directory of Open Access Journals (Sweden)

    MST. SADIA MAHZABIN

    2013-08-01

    Full Text Available Wood fibre cement (WFC boards are well established commercially and widely used in many developed countries. The combination of the properties of two important materials, i.e., cement, and previously treated fibrous materials like wood or agricultural residues; which made up the board, contributed in the performance of the board as building material. In this work, the WFC matrix (WFCM samples are produced to determine the physical properties of WFCM such as the density and water absorption. The wood fibres are incorporated/treated with three different chemical additives; calcium formate (Ca(HCOO2, sodium silicate (Na2.SiO3 and magnesium chloride (MgCl2 prior to mixing with cement. The mechanical properties of the WFCM, with or without chemicals treatment of fibres, such as the compressive strength and flexural strength are evaluated. Three wood/cement ratios (50:50, 40:60, 30:70 are used and the percentages of water and accelerator were 80% and 3% based on the cement weight, respectively. Three moisture-conditioned samples; accelerated aging, dry and wet conditions are used for flexural test. The results reveal that the wood/cement ratio, chemical additives and moisture content had a marked influence on the physical and mechanical properties of the matrix. Finally, it has been shown that the 40:60 wood/cement ratio samples with prior chemicals treatment of the fibres that undergo accelerated aging conditioning achieve higher strength then dry and wet-conditioned boards.

  19. PURIFIED WASTE FCC CATALYST AS A CEMENT REPLACEMENT MATERIAL

    Directory of Open Access Journals (Sweden)

    Danute Vaiciukyniene

    2015-06-01

    Full Text Available Zeolites are commonly used in the fluid catalytic cracking process. Zeolite polluted with oil products and became waste after some time used. The quantity of this waste inevitably rises by expanding rapidly oil industry. The composition of these catalysts depends on the manufacturer and on the process that is going to be used. The main factors retarding hydration process of cement systems and modifying them strength are organic compounds impurities in the waste FCC catalyst. The present paper shows the results of using purified waste FCC catalyst (pFCC from Lithuania oil refinery, as Portland cement replacement material. For this purpose, the purification of waste FCC catalyst (FCC samples was treated with hydrogen peroxide. Hydrogen peroxide (H2O2 is one of the most powerful oxidizers known. By acting of waste with H2O2 it can eliminate the aforementioned waste deficiency, and the obtained product becomes one of the most promising ingredients, in new advanced building materials. Hardened cement paste samples with FCC or pFCC were formed. It was observed that the pFCC blended cements developed higher strength, after 28 days, compared to the samples with FCC or reference samples. Typical content of Portland cement substituting does not exceed 30 % of mass of Portland cement in samples. Reducing the consumption of Portland cement with utilizing waste materials is preferred for reasons of environmental protection.

  20. 聚丙烯纤维添加量对发泡水泥性能影响研究∗%Study on Effect of Polypropylene Fiber Content to Foamed Cement Performance

    Institute of Scientific and Technical Information of China (English)

    孙楠

    2016-01-01

    Polypropylene fibers was added to foam cement, the effect of different addition of polypropylene fibers to mechanical properties, insulation properties and the cell structures of foam cement was studied. The result showed that adding polypropylene fibers improved the cell structures. When added 0. 55 g polypropylene fiber, after 28 d, the optimum performance foam cement bending strength was 1. 7 MPa. When added 0. 55 g polypropylene fiber, after 28 d, the optimum performance foam cement compressive strength was 1. 18 MPa. When added 0. 55 g, polypropylene fiber thermal conductivity coefficient was 1. 124 W/( m·K) .%研究了聚丙烯纤维添加量对发泡水泥力学性能、保温性能及泡孔结构的影响。结果表明聚丙烯纤维的添加改善发泡水泥的泡孔结构。在聚丙烯纤维添加量为0.55 g,养护28 d时试样抗折强度最大为1.7 MPa。当聚丙烯纤维添加量为0.55 g,养护28 d时发泡水泥的抗压强度最大1.18 MPa。当聚丙烯纤维添加量为0.5 g时发泡水泥导热系数最小为1.124 W/( m·K),保温性能最好。

  1. Produktie van cement

    NARCIS (Netherlands)

    Smit JRK; Coenen PWHG; Matthijsen AJCM; LAE; TAUW

    1995-01-01

    This document on cement production has been published within the SPIN project. In this project information has been collected on industrial plants or industrial processes to afford support to governmental policy on emission reduction. This document contains information on the processes, emission sou

  2. Osteotransductive bone cements.

    Science.gov (United States)

    Driessens, F C; Planell, J A; Boltong, M G; Khairoun, I; Ginebra, M P

    1998-01-01

    Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA approximately CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CHDA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).

  3. Pulmonary bone cement embolism: CT angiographic evaluation with material decomposition using gemstone special imaging

    Energy Technology Data Exchange (ETDEWEB)

    Huh, Sun; Lee, Heon [Dept. of Radiology, Soonchunhyang University Hospital Bucheon, Bucheon (Korea, Republic of)

    2014-08-15

    We report a case of pulmonary bone cement embolism in a female who presented with dyspnea following multiple sessions of vertebroplasty. She underwent spectral CT pulmonary angiography and the diagnosis was made based on enhanced visualization of radiopaque cement material in the pulmonary arteries and a corresponding decrease in the parenchymal iodine content. Here, we describe the CT angiography findings of bone cement embolism with special emphasis on the potential benefits of spectral imaging, providing additional information on the material composition.

  4. Prediction of chloride ingress and binding in cement paste

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Nielsen, Erik Pram; Herforth, Duncan

    2007-01-01

    Finite Difference Model for the ingress of chlorides into concrete which takes into account its multi-component nature. The “composite theory” was then used to predict the diffusivity of each ion based on the phase assemblage present in the hydrated Portland cement paste. Agreement was found between...... in Portland cement pastes at any content of chloride, alkalis, sulfates and carbonate was verified experimentally and found to be equally valid when applied to other data in the literature. The thermodynamic model for predicting the phase equilibria in hydrated Portland cement was introduced into an existing...... profiles for the Cl/Ca ratio predicted by the model and those determined experimentally on 0.45 water/powder ratio Portland cement pastes exposed to 650 mM NaCl for 70 days. This confirms the assumption of essentially instantaneous binding where quasi-equilibrium is established locally. This does not imply...

  5. Rheological Influence of Synthetic Zeolite on Cement Pastes

    Science.gov (United States)

    Baldino, N.; Gabriele, D.; Frontera, P.; Crea, F.; de Cindio, B.

    2008-07-01

    Self Compacting Concrete (SCC) is characterized by specific and particular mechanical properties, often due to the addition of components, able to modify the paste rheology. Concrete properties are strongly affected by characteristics of the fresh cement paste that is the continuous phase dispersing larger aggregates. Therefore, aiming to characterize mechanical properties of final concrete is relevant to know rheological properties of the base cement paste. In this work cement pastes for SCC were prepared by using, as additive, synthetic zeolite 5A in different amounts and they were analyzed by small amplitude oscillations. Experimental results have shown a relationship between dynamic moduli and zeolite content, identifying a proper level of zeolite addition. Moreover samples containing traditional fine additives, such as silica fume and limestone, were prepared and experimental data were compared to those obtained by using zeolite. It was found that zeolite seems to give better properties to cement paste than other additives can do.

  6. Characteristics of Bamboo Leaf Ash Blended Cement Paste and Mortar

    Directory of Open Access Journals (Sweden)

    Umoh A.A.

    2015-01-01

    Full Text Available The use of bamboo leaf ash as cement supplement can contribute to reduction in cost and environmental hazard associated with cement production as well as waste pollution caused by the littered bamboo leaves. Therefore, the characteristics of cement paste and mortar incorporating bamboo leaf ash were investigated. The results of the physical properties of the pastes were within the requirements stipulated by relevant standards while that of the mortar cubes indicated that the compressive strength generally increased with curing age, and that the mix containing 15% Bamboo Leaf Ash (BLA by mass competes favorably with that of the reference mix at 28days and above. The water absorption and apparent porosity were observed to increase with increase in BLA content, while the bulk density decreases as the percentage of BLA increases from 5% to 25% by mass. The study concluded that 15% BLA replacing cement is adequate for the production of masonry mortar.

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

    Science.gov (United States)

    Rau, J. V.; Fosca, M.; Graziani, V.; Egorov, A. A.; Zobkov, Yu. V.; Fedotov, A. Yu.; Ortenzi, M.; Caminiti, R.; Baranchikov, A. E.; Komlev, V. S.

    2016-01-01

    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(PO3)3 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. PMID:27096874

  8. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect th

  9. Effect of Lime on Mechanical and Durability Properties of Blended Cement Based Concrete

    Science.gov (United States)

    Acharya, Prasanna Kumar; Patro, Sanjaya Kumar; Moharana, Narayana C.

    2016-06-01

    This work presents the results of experimental investigations performed to evaluate the effect of lime on mechanical and durability properties of concrete mixtures made with blended cement like Portland Slag Cement (PSC) and Portland Pozzolana Cement (PPC) with lime content of 0, 5, 7 and 10 %. Test result indicated that inclusion of hydraulic lime on replacement of cement up to 7 % increases compressive strength of concrete made with both PSC and PPC. Flexural strength increased with lime content. Highest flexural strength is reported at 7 % lime content for both PSC and PPC. Workability is observed to decrease with lime addition which could be compensated with introduction of super plasticizer. Acid and sulphate resistance increase slightly up to 7 % of lime addition and is found to decrease with further addition of lime. Lime addition up to 10 % does not affect the soundness of blended cements like PSC and PPC.

  10. POZZOLAN AND CEMENTS WITH POZZOLAN

    Directory of Open Access Journals (Sweden)

    Hasan KAPLAN

    1995-02-01

    Full Text Available Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, cement with pozzolan is produced by adding the pozzolan, which has a large reservoir in the country, in cement in sertain amount. However this type of cement is consumed in the construction sector, sortage of scientific investigation and speculative news on the subject.are worried the users and producers. In this paper, prior to an experimental study on the cements having pozzolan additive, historical development of pozzolan, reservoir of Turkiye, and comparison with portland cement is carried out. Advantages and disadvantages of pozzolan are also discussed in some points.

  11. Mineral resource of the month: hydraulic cement

    Science.gov (United States)

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  12. Effects of using pozzolan and Portland cement in the treatment of dispersive clay.

    Science.gov (United States)

    Vakili, A H; Selamat, M R; Moayedi, H

    2013-01-01

    Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone.

  13. Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay

    Directory of Open Access Journals (Sweden)

    A. H. Vakili

    2013-01-01

    Full Text Available Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone.

  14. Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay

    Science.gov (United States)

    Vakili, A. H.; Selamat, M. R.; Moayedi, H.

    2013-01-01

    Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable of reducing dispersion potential to almost zero percent in only 7 days; and a 2% cement content was capable of achieving similar result in 14 days. However, treatment by cement alone is costly and could jeopardize the long term performance. Thus, a combined 5% pozzolan and 1.5% cement content was found capable of reducing dispersion potential from 100% to zero percent in 14 days. The results indicate that although simultaneous treatment with pozzolan and cement would extend the required curing time in comparison to treatment by cement alone of a higher content, the task could still be carried out in a reasonable period of curing time while avoiding the drawbacks of using either pozzolan or cement alone. PMID:23864828

  15. US cement industry

    Energy Technology Data Exchange (ETDEWEB)

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  16. Feedback experience from a 30 years old concrete using cement with a high content of blast furnace slag; Retour d'experience sur un beton age de 30 ans contenant un ciment riche en laitier

    Energy Technology Data Exchange (ETDEWEB)

    Charron, Ch. [Holcim, Obourg (Belgium); Lion, M.; Jeanpierre, A. [Electricite de France (EDF), Ceidre-TEGG, 13 - Aix en Provence (France); Ammouche, A. [LERM, 13 - Arles (France)

    2009-08-15

    In this study, we analyze the aspect of a slag cement concrete used in the seventies for the construction of the walls of a structure located close to the channel sea. From different characterization tests (chemical, physical, and micro structural), it can be conclude that the concrete is not showing any pathology and any important attack, due to the marine environment. After being exposed during 30 years, the chlorides ions have not reach the steel metal bar reinforcement and the carbonation depth is still low. This study details the results of chloride diffusion coefficient and carbonation depth measurements, sulfates and chloride quantification, XRD analysis, and SEM examination. (authors)

  17. Performance of Cement Containing Laterite as Supplementary Cementing Material

    Directory of Open Access Journals (Sweden)

    Abbas Bukhari, Z. S.

    2013-03-01

    Full Text Available The utilization of different industrial waste, by-products or other materials such as ground granulated blast furnace slag, silica fume, fly ash, limestone, and kiln dust, etc. as supplemen- tary cementing materials has received considerable attention in recent years. A study has been conducted to look into the performance of laterite as Supplementary Cementing Materials (SCM. The study focuses on compressive strength performance of blended cement containing different percentage of laterite. The cement is replaced accordingly with percentage of 2 %, 5 %, 7 % and 10 % by weight. In addition, the effect of use of three chemically different laterites have been studied on physical performance of cement as in setting time, Le-Chatlier expansion, loss on ignition, insoluble residue, free lime and specifically compressive strength of cement cubes tested at the age of 3, 7, and 28 days. The results show that the strength of cement blended with laterite as SCM is enhanced. Key words: Portland cement, supplementary cementing materials (SCM, laterite, compressive strength KUI – 6/2013 Received January 4, 2012 Accepted February 11, 2013

  18. Tympanoplasty with ionomeric cement.

    Science.gov (United States)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    Patients with isolated erosion of the long incus process suffer from severe hearing loss caused by lack of continuity of the ossicular chain. This study is a retrospective evaluation of the hearing results using two different surgical procedures. Since January 1993, 12 consecutive patients with isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those in a group of 20 historical controls who underwent surgery in 1991 and 1992 using incus autograft interposition. Among the 12 index patients, 7 (58%) achieved improvement in PTA of > 10 dB, in 3 there was no difference and in 2 a slight decline. Among the 20 controls, 14 (70%) achieved improvement in PTA of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy to perform, presents less risk of damage to the stapes and cochlea, requires less extensive surgery and does not exclude other surgical methods in cases of reoperation. PMID:10909000

  19. Mechanism of cement-stabilized soil polluted by magnesium sulfate

    Institute of Scientific and Technical Information of China (English)

    HAN Peng-ju; WANG Shuai; Frank Y. Chen; BAI Xiao-hong

    2015-01-01

    In order to simulate and study the mechanism of cement stabilized soils polluted by different contents of magnesium sulfate (MS), a series of tests were conducted on the cemented soil samples, including unconfined compression strength (UCS) tests of blocks, X-ray diffraction (XRD) phase analysis of powder samples, microstructure by scanning electronic microscopy (SEM), element composition by energy dispersive spectrometry (EDS), and pore distribution analysis by Image Processed Plus 6.0 (IPP 6.0) software. The UCS test results show that UCS of cemented soils reaches the peak value when the MS content is 4.5 g/kg. While, the UCS for Sample MS4 having the MS content of 18.0 g/kg is the lowest among all tested samples. Based on the EDS analysis results, Sample MS4 has the greater contents for the three elements, oxygen (O), magnesium (Mg) and sulfur (S), than Sample MS1. From the XRD phase analysis, C-A-S-H (3CaO·Al2O3·3CaSO4·32H2O and 3CaO·Al2O3·CaSO4·18H2O), M-A-H (MgO·Al2O3·H2O), M-S-H (MgO·SiO2·H2O), Mg(OH)2 and CaSO4phase diffraction peaks are obviously intense due to the chemical action associated with the MS. The pore distribution analysis shows that the hydrated products change the distribution of cemented soil pores and the pores with average diameter (AD) of 2-50μm play a key role in terms of the whole structure of cemented soil. The microscopic structure of the cemented soil with MS exhibits the intertwined and embedded characteristics between the cement and granular soils from the SEM images of cemented soils. The microstructure analysis shows that the magnesium sulfate acts as the additive, which is beneficial to the soil strength when the MS content is low (i.e., Sample MS2). However, higher MS amount involving a chemical action makes samples crystallize and expand, which is adverse to the UCS of cemented soils (i.e., Sample MS4).

  20. Fresh-water cementation of a 1,000-year-old oolite

    Science.gov (United States)

    Halley, R. B.; Harris, P. M.

    1979-01-01

    Calcite cementation of aragonite ooid sand is producing oolite on Joulters Cays, Bahamas. During the last 1,000 years, calcite cement has formed at an average rate of between 27 and 55 cm3 /m3 /yr and is derived from dissolution of ooid aragonite in fresh water. The dissolution-reprecipitation of carbonate minerals in the aquifer results in ground waters of unusually high Sr content. Sea water and mixtures of fresh and sea water appear to inhibit cementation. A pronounced cement fabric change occurs across the water table and has produced an obvious petrographic record of fresh-water diagenesis. Above the water table, cement is typically near grain contact positions, where water is held by capillarity; below the water table, cement is more randomly distributed around grains. At the water table a transition zone, 1 meter thick, marks the boundary between cement textures. No porosity reduction is associated with cementation; calcite cement precipitation is apparently compensated by an equal or greater amount of aragonite dissolution in the interval undergoing cementation. Permeability is more variable above the water table than below it, reflecting early channelling of flow patterns in the vadose zone. Effective permeability below the water table is one to two orders of magnitude higher than above the water table because of entrained gas in the vadose zone. This permeability difference promotes preservation of unstable minerals above the water table and continued diagenetic alteration below the water table.

  1. [Haemotoxicity of dental luting cements].

    Science.gov (United States)

    Anders, A; Welker, D

    1989-06-01

    A glass ionomer luting cement (AquaCem) shows a relatively low haemolytic activity in comparison with two zinc phosphate cements. Especially the initial irritation by this cement is smaller. Although it is possible that AquaCem particularly, in unfavourable cases, may damage the pulpa dentin system; this is due to the slowly decrease of the haemolytic activity with increasing of the probes. We found that Adhesor showed in dependence of the batches a varying quality. PMID:2626769

  2. Cement penetration after patella venting.

    Science.gov (United States)

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R

    2009-01-01

    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement. PMID:19010682

  3. Effect of Heavy Metal Present in Cement Dust on Soil and Plants of Nokha (Bikaner

    Directory of Open Access Journals (Sweden)

    Dr.(Mrs.Suruchi Gupta

    2013-08-01

    Full Text Available In Nokha(Bikaner cement industries emittes cement dust in nearby farmers fields. In these industries cement dust emitted contains traces of hexavalent chromium and lead well above permissible limit in area under investigation. However, cadmium and nickel were found below limits prescribed. To analyse heavy metals viz, Cr+6, lead, Cadmium and nickel one hundred and twenty samples were collected from four directions on surface and 20 cm depth, and analyzed on atomic absorption spectrophotometer. From the above study it is clear that in case of Sarvottam cement works only lead content was higher in all directions and depths than other two plants. At tiger and Nokha cement works contamination of lead was more over limited in the first 1 km except in east direction. Mobility of lead was relatively more on top soil than 20cm depth. Hexavalent chromium content in south western direction was more for Nokha cement. Whereas, it was more in east direction in case of tiger cement. This indicated influence of prevailing direction of wind on distribution of heavy metals present in cement dust.Heavy metal toxicity results in reduction in plant height, burning of leaf margins and tip, slow leaf growth and over all wilting of Prosopis cineraria, Pearlmillet and clusterbean plants, when this metal deposits in Human body results in genetic disorders. Electrostatic precipitator can be installed to reduce the cement dust emission.

  4. Isotropic Compression Behaviour of Fibre Reinforced Cemented Sand

    Directory of Open Access Journals (Sweden)

    Salahuddin

    2013-07-01

    Full Text Available Fibre-reinforced cemented sands have many applications in improving the response of soils. In this paper, an experimental investigation for the analysis of fiber-reinforced cemented sand in the framework of isotropic compression is presented. The experimental investigations were carried out using a high pressure triaxial apparatus having the capacity of 64 MPa of confining pressure. Tests have been conducted on Portaway sand specimens reinforced with randomly oriented discrete polypropylene fibers with different percentages of fiber and cement contents. Results are presented in the form of e-logp` curves as well as SEM (Scanning Electron Microscopy micrographs. The effects of the addition of fibre in sand and cemented sand for different initial void ratios were investigated. The results demonstrate that the influence of fibre is not significant in both cemented and uncemented sand during the isotropic compression stage. Moreover, from the SEM micrographs it could be seen that there is breakage of sand particles and cement bonds. The fiber threads were seen pinched and found rarely broken in the specimen exhumed after isotropic compression.

  5. Respiratory Health among Cement Workers in Ethiopia

    OpenAIRE

    Zeleke, Zeyede K.

    2011-01-01

    Background: Little is known on dust exposure and respiratory health among cement cleaners. There are only a few follow-up studies on respiratory health among cement factory workers and also studies on acute effects of cement dust exposure are limited in numbers. Objective: This study aimed at assessing cement dust exposure and adverse respiratory health effects among Ethiopian cement production workers, with particular focus on cement cleaners. Method: The first paper was...

  6. A new radionuclide sorption database for benchmark cement accounting for geochemical evolution of cement

    International Nuclear Information System (INIS)

    This paper presents the data selection strategy and the selected sorption values on cement for twenty-five elements (Ag, Am, Be, C, Ca, Cl, Cs, H, I, Mo, Nb, Ni, Np, Pa, Pb, Pd, Pu, Ra, Sr, Se, Sn, Tc, Th, U, Zr) that need to be considered in safety assessment calculations for the future near-surface disposal facility at Dessel, Belgium. Mainly on the basis of literature data, best estimate sorption values in addition to upper and lower bound values were determined for a so-called benchmark cement - the unperturbed cement without effects of organics, high chloride content or other chemical components that might adversely impact radionuclide sorption. Effects of perturbing components are discussed separately. The geochemical evolution of the cementitious engineered barriers was also addressed to clarify the conditions under which sorption values are applicable. A substantial part of the scientific basis supporting the data selection was established at several meetings of an International Panel of Experts who reviewed and endorsed the data selection. To this end, the sorption data were checked for: reliability, appropriateness for the conditions expected for the Dessel disposal facility, data quality, time frames (i.e. states of cement degradation), heterogeneity (presence of components in conditioned wastes that could affect sorption) and completeness (in terms of mechanisms explaining the sorption processes). (authors)

  7. Dust Exposure and Respiratory Health Effects in Cement Production

    Directory of Open Access Journals (Sweden)

    Golamreza Pouryaghoub

    2012-02-01

    Full Text Available Dust can be produced by almost all production processes in Portland cement factory. Dust exposure potentially can affect respiratory function. But evidence for respiratory effect of cement dust exposure has not been conclusive. In this study we assessed effect of cement dust exposure on respiratory function in a cement production factory. A respiratory symptoms questionnaire was completed and pulmonary function tests were carried out on 94 exposed and 54 non exposed workers at a cement factory in the east of Iran. Additionally, respirable dust level was determined by the gravimetric method. X-ray fluorescence (XRF technique was performed to determine the silica phases and the SiO2 contents of the bulk samples. The arithmetic means (AM of personal respirable dust were 30.18 mg/m3 in the crushing, 27 mg/m3 in the packing, 5.4 mg/m3 in the cement mill, 5.9 mg/m3 in the kiln and 5.48 mg/m3 in the maintenance that were higher than threshold limit value (TLV of the American Conference of Governmental Industrial Hygienists (ACGIH which is 5 mg/m3. This value in the unexposed group was 0.93 mg/m3. In this study cough, sputum, wheezing and dyspnea were more prevalent among exposed subjects. Exposed workers compared to the unexposed group showed significant reduction in Forced Expiratory Volume in one second (FEV1, Forced Vital Capacity (FVC, and Forced Expiratory Flow between 25% and 75% of the FVC (FEF25-75% (P<0.05. It can be concluded that in our study there was close and direct association between cement dust exposure and functional impairment among the cement factory workers.

  8. Thermal Shock-resistant Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  9. Effect of PCs superplasticizers on the rheological properties and hydration process of slag-blended cement pastes

    OpenAIRE

    Palacios, M.; Puertas, F.; Bowen, P.; Houst, Y. F.

    2009-01-01

    The effect of polycarboxylate (PC) superplasticizers with different structure on the rheological properties and hydration process of slag-blended cement pastes with a slag content between 0 and 75% has been studied. Fluidizing properties of PCs admixtures are significantly higher in slag-blended cement with respect to non-blended Portland cement. Also, it has been observed that the rise of the fluidity induced by the PCs on the cement pastes increases with the slag content. This effect is mainl...

  10. Strength and Deformability of Fiber Reinforced Cement Paste on the Basis of Basalt Fiber

    Directory of Open Access Journals (Sweden)

    Yury Barabanshchikov

    2016-01-01

    Full Text Available The research object of the paper is cement paste with the particulate reinforcement of basalt fiber. Regardless of fibers’ length at the same fiber cement mix workability and cement consumption equality compressive solidity of the specimens is reduced with increasing fiber content. This is due to the necessity to increase the water-cement ratio to obtain a given workability. The flexural stability of the specimens with increasing fiber content increments in the same conditions. There is an optimum value of the fibers’ dosage. That is why stability has a maximum when crooking. The basaltic fiber particulate reinforcement usage can abruptly increase the cement paste level limiting extensibility, which is extremely important in terms of crack resistance.

  11. Effects of Carbon Content and B Class Porosity on Bending Strength of WC-8% Co Cemented Carbide%碳量及B类孔隙对WC-8%Co硬质合金抗弯强度的影响

    Institute of Scientific and Technical Information of China (English)

    闵召宇; 廖军; 时凯华; 蒋阳

    2013-01-01

    采用粉末冶金方法制备了WC-8%Co硬质合金试样,经氢气烧结后,利用钴磁测试仪、强度测试仪、电子显微镜和金相显微镜分别对试样的钴磁和抗弯强度进行测定、对试样断口和金相缺陷进行观察.研究了WC-8%Co硬质合金抗弯强度与碳量(相对磁饱和)、金相缺陷(B类孔隙)之间的关系.结果表明:将试样碳含量及孔隙度控制在一定的范围内,可以使试样抗弯强度保持在较高的水平,当试样相对磁饱和为88%~92%,B类孔隙为B00时,合金显微组织中WC晶粒较为均匀,无异常长大情况,WC-8%Co硬质合金抗弯强度可达3 286 N/mm2;同时,抗弯强度值的大小随孔隙度的增多而下降.另外,氢气烧结后经HIP处理可以有效消除WC-8%Co硬质合金中的孔隙缺陷,从而提高合金抗弯强度,经HIP处理的试样的强度比正常样的强度高出2.3%.%WC-8%Co cemented carbide specimens were prepared by powder metallurgy method. The cobalt magnetism and bending strength of the specimens were tested. The fracture surface and the defects in the microstructure were observed. Furthermore the effects of the carbon content (relative magnetic saturation) and the defects (B class pores) on the bending strength of the cemented carbide were studied. The results show that by means of controlling the carbon content and the porosity in the certain ranges, the bending strength of the WC-8%Co cemented carbide remains at a high level. When the relative magnetic saturation is in the range of 88%~92% and the metallographic B class porosity is BOO, the WC grain size of WC-8% Co is more uniform and the bending strength of the cemented carbide reaches its highest values at 3 286 N/mm2. Meanwhile, the bending strength value decreases with the increasing of porosity. In addition, HIP treatment after hydrogen sintering can effectively eliminate pore defects in the WC-8%Co cemented carbide, thus the bending strength is enhanced up to 2.3%.

  12. Laboratory evaluation of cement treated aggregate containing crushed clay brick

    Directory of Open Access Journals (Sweden)

    Liqun Hu

    2014-10-01

    Full Text Available The waste clay bricks from debris of buildings were evaluated through lab tests as environmental friendly materials for pavement sub-base in the research. Five sets of coarse aggregates which contained 0, 25%, 50%, 75% and 100% crushed bricks, respectively, were blended with sand and treated by 5% cement. The test results indicated that cement treated aggregate which contains crushed clay brick aggregate had a lower maximum dry density (MDD and a higher optimum moisture content (OMC. Moreover, the unconfined compressive strength (UCS, resilience modulus, splitting strength, and frost resistance performance of the specimens decreased with increase of the amount of crushed clay brick aggregate. On the other hand, it can be observed that the use of crushed clay brick in the mixture decreased the dry shrinkage strain of the specimens. Compared with the asphalt pavement design specifications of China, the results imply that the substitution rate of natural aggregate with crushed clay brick aggregate in the cement treated aggregate sub-base material should be less than 50% (5% cement content in the mixture. Furthermore, it needs to be noted that the cement treated aggregate which contains crushed clay bricks should be cautiously used in the cold region due to its insufficient frost resistance performance.

  13. Applicability of the Waste Fibres in Cement Paste

    Directory of Open Access Journals (Sweden)

    Regina KALPOKAITĖ DIČKUVIENĖ

    2013-09-01

    Full Text Available Fibres produced from waste catalyst together with commercially available polypropylene fibres were incorporated into ordinary Portland cement paste. The effects of fibre content as well as a mix of different type of fibres on mechanical and physical properties of wet and dry samples were investigated. The results showed that presence of fibres reduced compressive strength of the plain cement in wet and dry state. Contrary, when the combination of 1.5 wt% waste and 1.5 wt% polypropylene fibres was used flexural strength of cement mixture increased by up to 9 % at the age of 28 days. It was observed that addition of 1.5 wt% of only waste fibres improved flexural strength after long hydration period as well. However, the lowest mechanical strength results showed samples with 3 wt% of waste fibres. It was also observed that higher content of waste fibres reduced porosity of the cement mixture and consequently, decreased water absorption capacity. Presence of fibres reduced drying shrinkage of samples and they were lower than plain cement after 28 days of hydration. DOI: http://dx.doi.org/10.5755/j01.ms.19.3.1992

  14. Specific Examples of Hybrid Alkaline Cement

    OpenAIRE

    Fernández-Jiménez Ana; García-Lodeiro Inés; Donatello Shane; Maltseva Olga; Palomo Ángel

    2014-01-01

    Hybrid alkaline cements are obtained by alkali-activating cementitious blends in the Na2O-CaO-SiO2-Al2O3-H2O system. The present paper discusses the results of activating different cementitious blends containing a low OPC clinker content ( 15MPa a 2 days) different alkaline activators were used (liquid and solid). The reaction products obtained were also characterised by XRD, SEM/EDX and 27Al and 29Si NMRMAS. The results showed that the main reaction product was a mix of cementitious gels C-A...

  15. The Effect of Cement Dust on the Lung Function in a Cement Factory, Iran

    Directory of Open Access Journals (Sweden)

    Farhad Ferasati

    2010-07-01

    Full Text Available The present study aimed at assessing cement dust exposure and its relationship to lung function at a Portland cement factory in Ilam, Iran. Lung function tests were carried out on 112 workers at the cement factory in 2008-09. Simultaneously 85 non exposed workers were used as control. Lung function tests were performed for all subjects. Additionally, total dust level was determined by the gravimetric method. Moreover, X-ray diffraction (XRD technique was performed to determine the SiO2 contents of the bulk samples. The arithmetic means (AM of personal total dust were higher in the crusher (27.49 mg/m3, packing (16.90 mg/m3, kiln (15.60 mg/m3, cement mill (13.07 mg/m3, raw mill (10.31 mg /m3 than in the maintenance (3.14 mg /m3, and administration (1.55 mg/m3. The geometrical mean (GM concentration was 12.12 mg/m3, which were considerably higher than occupational exposure limit (OEL of the American Conference of Governmental Industrial Hygienists (ACGIH, which is 10 mg/m3. Based on the results, the probability of the long-term mean exposure exceeding to the OEL of 10 mg/m3 for total dust were higher in the kiln (100%, packing (100%, cement mill (90%, crusher (73%, raw mill (60% than in the maintenance (0%, and administration (2.3%. Ventiliatory function evaluation, as measured by the function parameters, showed that 35.7% of the exposed workers had abnormality in lung function compared with 5.7% of those unexposed. Statistical analysis of the data indicated that exposed workers compared to the unexposed groups showed significant reductions in Forced Expiratory Volume in one second percent (FEV1, Forced Vital Capacity (FVC, and FEV1/FVC (p< 0.05.

  16. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    A K Misra; Renu Mathur

    2007-06-01

    The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, -values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

  17. Thermophysical and Mechanical Properties of Hardened Cement Paste with Microencapsulated Phase Change Materials for Energy Storage

    Directory of Open Access Journals (Sweden)

    Hongzhi Cui

    2014-12-01

    Full Text Available In this research, structural-functional integrated cement-based materials were prepared by employing cement paste and a microencapsulated phase change material (MPCM manufactured using urea-formaldehyde resin as the shell and paraffin as the core material. The encapsulation ratio of the MPCM could reach up to 91.21 wt%. Thermal energy storage cement pastes (TESCPs incorporated with different MPCM contents (5%, 10%, 15%, 20% and 25% by weight of cement were developed, and their thermal and mechanical properties were studied. The results showed that the total energy storage capacity of the hardened cement specimens with MPCM increased by up to 3.9-times compared with that of the control cement paste. The thermal conductivity at different temperature levels (35–36 °C, 55–56 °C and 72–74 °C decreased with the increase of MPCM content, and the decrease was the highest when the temperature level was 55–56 °C. Moreover, the compressive strength, flexural strength and density of hardened cement paste decreased with the increase in MPCM content linearly. Among the evaluated properties, the compressive strength of TESCPs had a larger and faster degradation with the increase of MPCM content.

  18. Utilization of municipal sewage sludge as additives for the production of eco-cement

    International Nuclear Information System (INIS)

    Highlights: ► The results of X-ray diffraction (XRD) pattern and scanning electron micrograph (SEM) indicated that the major components in the eco-cement clinkers were similar to those in ordinary Portland cement. ► Though the C2S phase formation increased with the increase of sewage sludge contents. ► All the eco-cement pastes had a longer initial setting time and final setting time than those of plain cement paste, which increased as the sewage sludge contents in raw meal increased. ► All the eco-cement pastes had lower early flexural strengths and it increased with the increase of sewage sludge contents increased, while the compressive strengths decreased slightly. ► However, it had no significant effect on all the strengths at later ages. - Abstract: The effects of using dried sewage sludge as additive on cement property in the process of clinker burning were investigated in this paper. The eco-cement samples were prepared by adding 0.50–15.0% of dried sewage sludge to unit raw meal, and then the mixtures were burned at 1450 °C for 2 h. The results indicated that the major components in the eco-cement clinkers were similar to those in ordinary Portland cement. Although the C2S phase formation increased with the increase of sewage sludge content, it was also found that the microstructure of the mixture containing 15.0% sewage sludge in raw meal was significantly different and that a larger amount of pores were distributed in the clinker. Moreover, all the eco-cement pastes had a longer initial setting time and final setting time than those of plain cement paste, which increased as the sewage sludge content in the raw meal increased. All the eco-cement pastes had lower early flexural strengths, which increased as the sewage sludge content increased, while the compressive strengths decreased slightly. However, this had no significant effect on all the strengths at later stages. Furthermore, the leaching concentrations of all the types of eco-cement

  19. Development of the Use of Alternative Cements for the Treatment of Intermediate Level Waste

    International Nuclear Information System (INIS)

    This paper describes initial development studies undertaken to investigate the potential use of alternative, non ordinary Portland cement (OPC) based encapsulation matrices to treat historic legacy wastes within the UK's Intermediate Level Waste (ILW) inventory. Currently these wastes are encapsulated in composite OPC cement systems based on high replacement with blast furnace slag of pulverised fuel ash. However, the high alkalinity of these cements can lead to high corrosion rates with reactive metals found in some wastes releasing hydrogen and forming expansive corrosion products. This paper therefore details preliminary results from studies on two commercial products, calcium sulfo-aluminate (CSA) and magnesium phosphate (MP) cement which react with a different hydration chemistry, and which may allow wastes containing these metals to be encapsulated with lower reactivity. The results indicate that grouts can be formulated from both cements over a range of water contents and reactant ratios that have significantly improved fluidity in comparison to typical OPC cements. All designed mixes set in 24 hours with zero bleed and the pH values in the plastic state were in the range 10-11 for CSA and 5-7 for MP cements. In addition, a marked reduction in aluminium corrosion rate has been observed in both types of cements compared to a composite OPC system. These results therefore provide encouragement that both cement types can provide a possible alternative to OPC in the immobilisation of reactive wastes, however further investigation is needed. (authors)

  20. Cement pastes alteration by liquid manure organic acids: chemical and mineralogical characterization

    International Nuclear Information System (INIS)

    Liquid manure, stored in silos often made of concrete, contains volatile fatty acids (VFAs) that are chemically very aggressive for the cementitious matrix. Among common cements, blast-furnace slag cements are classically resistant to aggressive environments and particularly to acidic media. However, some standards impose the use of low C3A content cements when constructing the liquid manure silos. Previous studies showed the poor performance of low-C3A ordinary Portland cement (OPC). This article aims at clarifying this ambiguity by analyzing mechanisms of organic acid attack on cementitious materials and identifying the cement composition parameters influencing the durability of agricultural concrete. This study concentrated on three types of hardened cement pastes made with OPC, low-C3A OPC and slag cement, which were immersed in a mixture of several organic acids simulating liquid manure. The chemical and mineralogical modifications were analyzed by electronic microprobe, XRD and BSE mode SEM observations. The attack by the organic acids on liquid manure may be compared with that of strong acids. The alteration translates into a lixiviation, and the organic acid anions have no specific effect since the calcium salts produced are soluble in water. The results show the better durability of slag cement paste and the necessity to limit the amount of CaO, to increase the amount of SiO2 (i.e., reduction of the Ca/Si ratio of C-S-H is not sufficient) and to favor the presence of secondary elements in cement

  1. Triaxial shear behavior of a cement-treated sand–gravel mixture

    Directory of Open Access Journals (Sweden)

    Younes Amini

    2014-10-01

    Full Text Available A number of parameters, e.g. cement content, cement type, relative density, and grain size distribution, can influence the mechanical behaviors of cemented soils. In the present study, a series of conventional triaxial compression tests were conducted on a cemented poorly graded sand–gravel mixture containing 30% gravel and 70% sand in both consolidated drained and undrained conditions. Portland cement used as the cementing agent was added to the soil at 0%, 1%, 2%, and 3% (dry weight of sand–gravel mixture. Samples were prepared at 70% relative density and tested at confining pressures of 50 kPa, 100 kPa, and 150 kPa. Comparison of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded samples. Undrained failure envelopes determined using zero Skempton's pore pressure coefficient (A¯=0 criterion were consistent with the drained ones. Energy absorption potential was higher in drained condition than undrained condition, suggesting that more energy was required to induce deformation in cemented soil under drained state. Energy absorption increased with increase in cement content under both drained and undrained conditions.

  2. The Cement Solidification of Municipal Solid Waste Incineration Fly Ash

    Institute of Scientific and Technical Information of China (English)

    HOU Haobo; HE Xinghua; ZHU Shujing; ZHANG Dajie

    2006-01-01

    The chemical composition, the content and the leachability of heavy metals in municipal solid waste incineration ( MSWI) fly ash were tested and analyzed. It is shown that the leachability of Pb and Cr exceeds the leaching toxicity standard, and so the MSWI fly ash is considered as hazardous waste and must be solidifled. The effect of solidifying the MSWI fly ash by cement was studied, and it is indicated that the heavy metals can be well immobilized if the mass fraction of the fly ash is appropriate. The heavy metals were immobilized within cement hydration products through either physical fixation, substitution, deposition or adsorption mechanisms.

  3. 21 CFR 888.4200 - Cement dispenser.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  4. Durability of Cement Composites Reinforced with Sisal Fiber

    Science.gov (United States)

    Wei, Jianqiang

    This dissertation focuses mainly on investigating the aging mechanisms and degradation kinetics of sisal fiber, as well as the approaches to mitigate its degradation in the matrix of cement composites. In contrast to previous works reported in the literature, a novel approach is proposed in this study to directly determine the fiber's degradation rate by separately studying the composition changes, mechanical and physical properties of the embedded sisal fibers. Cement hydration is presented to be a crucial factor in understanding fiber degradation behavior. The degradation mechanisms of natural fiber consist of mineralization of cell walls, alkali hydrolysis of lignin and hemicellulose, as well as the cellulose decomposition which includes stripping of cellulose microfibrils and alkaline hydrolysis of amorphous regions in cellulose chains. Two mineralization mechanisms, CH-mineralization and self-mineralization, are proposed. The degradation kinetics of sisal fiber in the cement matrix are also analyzed and a model to predict the degradation rate of cellulose for natural fiber embedded in cement is outlined. The results indicate that the time needed to completely degrade the cellulose in the matrix with cement replacement by 30wt.% metakaolin is 13 times longer than that in pure cement. A novel and scientific method is presented to determine accelerated aging conditions, and to evaluating sisal fiber's degradation rate and durability of natural fiber-reinforced cement composites. Among the static aggressive environments, the most effective approach for accelerating the degradation of natural fiber in cement composites is to soak the samples or change the humidity at 70 °C and higher temperature. However, the dynamic wetting and drying cycling treatment has a more accelerating effect on the alkali hydrolysis of fiber's amorphous components evidenced by the highest crystallinity indices, minimum content of holocellulose, and lowest tensile strength. Based on the

  5. Cements in Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    The use of cement and concrete to immobilise radioactive waste is complicated by the wide- ranging nature of inorganic cementing agents available as well as the range of service environments in which cement is used and the different functions expected of cement. For example, Portland cement based concretes are widely used as structural materials for construction of vaults and tunnels. These constructions may experience a long pre-closure performance lifetime during which they are required to protect against collapse and ingress of water: strength and impermeability are key desirable characteristics. On the other hand, cement and concrete may be used to form backfills, ranging in permeability. Permeable formulations allow gas readily to escape, while impermeable barriers retard radionuclide transport and reduce access of ground water to the waste. A key feature of cements is that, while fresh, they pass through a fluid phase and can be formed into any shape desired or used to infiltrate other materials thereby enclosing them into a sealed matrix. Thereafter, setting and hardening is automatic and irreversible. Where concrete is used to form structural elements, it is also natural to use cement in other applications as it minimises potential for materials incompatibility. Thus cement- mainly Portland cement- has been widely used as an encapsulant for storage, transport and as a radiation shield for active wastes. Also, to form and stabilise structures such as vaults and silos. Relative to other potential matrices, cement also has a chemical immobilisation potential, reacting with and binding with many radionuclides. The chemical potential of cements is essentially sacrificial, thus limiting their performance lifetime. However performance may also be required in the civil engineering sense, where strength is important, so many factors, including a geochemical description of service conditions, may require to be assessed in order to predict performance lifetime. The

  6. Cement/slag chemistry studies

    International Nuclear Information System (INIS)

    The performance of cement-based matrices intended for radwaste immobilization is assessed. The long-term performance of the matrix is characterized by thermodynamic evaluation of experimental data. The results are presented in a general form, amenable to a range of specific formulations. The interaction of specific radwaste components with cements has been studied, using Iodine as an example. It occurs as both I- and IO3- species, but these differ sharply in sorption characteristics. The effect of ionizing radiation of the pH and Eh of cement matrices is reported. (author)

  7. Dust exposure and respiratory health effects in cement production.

    Science.gov (United States)

    Kakooei, Hossein; Gholami, Abdollah; Ghasemkhani, Mehdi; Hosseini, Mostapha; Panahi, Davoud; Pouryaghoub, Golamreza

    2012-01-01

    Dust can be produced by almost all production processes in Portland cement factory. Dust exposure potentially can affect respiratory function. But evidence for respiratory effect of cement dust exposure has not been conclusive. In this study we assessed effect of cement dust exposure on respiratory function in a cement production factory. A respiratory symptoms questionnaire was completed and pulmonary function tests were carried out on 94 exposed and 54 non exposed workers at a cement factory in the east of Iran. Additionally, respirable dust level was determined by the gravimetric method. X-ray fluorescence (XRF) technique was performed to determine the silica phases and the SiO(2) contents of the bulk samples. The arithmetic means (AM) of personal respirable dust were 30.18 mg/m(3) in the crushing, 27 mg/m(3) in the packing, 5.4 mg/m(3) in the cement mill, 5.9 mg/m(3) in the kiln and 5.48 mg/m(3) in the maintenance that were higher than threshold limit value (TLV) of the American Conference of Governmental Industrial Hygienists (ACGIH) which is 5 mg/m(3). This value in the unexposed group was 0.93 mg/m(3). In this study cough, sputum, wheezing and dyspnea were more prevalent among exposed subjects. Exposed workers compared to the unexposed group showed significant reduction in Forced Expiratory Volume in one second (FEV(1)), Forced Vital Capacity (FVC), and Forced Expiratory Flow between 25% and 75% of the FVC (FEF(25-75%)) (Pexposure and functional impairment among the cement factory workers. PMID:22359082

  8. Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

    Energy Technology Data Exchange (ETDEWEB)

    Champenois, Jean-Baptiste; Dhoury, Mélanie [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Cau Dit Coumes, Céline, E-mail: celine.cau-dit-coumes@cea.fr [CEA, DEN, DTCD, SPDE, F-30207 Bagnols-sur-Cèze Cedex (France); Mercier, Cyrille [LMCPA, Université de Valenciennes et du Hainaut Cambrésis, 59600 Maubeuge (France); Revel, Bertrand [Centre Commun de Mesure RMN, Université Lille1 Sciences Technologies, Cité Scientifique, 59655 Villeneuve d' Ascq Cedex (France); Le Bescop, Patrick [CEA, DEN, DPC, SECR, F-91192 Gif-sur-Yvette (France); Damidot, Denis [Ecole des Mines de Douai, LGCgE-GCE, 59508 Douai (France)

    2015-04-15

    Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorly crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay.

  9. Influence of sodium borate on the early age hydration of calcium sulfoaluminate cement

    International Nuclear Information System (INIS)

    Calcium sulfoaluminate (CSA) cements are potential candidates for the conditioning of radioactive wastes with high sodium borate concentrations. This work thus investigates early age hydration of two CSA cements with different gypsum contents (0 to 20%) as a function of the mixing solution composition (borate and NaOH concentrations). Gypsum plays a key role in controlling the reactivity of cement. When the mixing solution is pure water, increasing the gypsum concentration accelerates cement hydration. However, the reverse is observed when the mixing solution contains sodium borate. Until gypsum exhaustion, the pore solution pH remains constant at ~ 10.8, and a poorly crystallized borate compound (ulexite) precipitates. A correlation is established between this transient precipitation and the hydration delay. Decreasing the gypsum content in the binder, or increasing the sodium content in the mixing solution, are two ways of reducing the stability of ulexite, thus decreasing the hydration delay

  10. Effects of moisture on ultrasound propagation in cement mortar

    Science.gov (United States)

    Ju, Taeho; Li, Shuaili; Achenbach, Jan; Qu, Jianmin

    2015-03-01

    In concrete structures, moisture is often a major cause of chemically related degradations such as alkaline-silica reaction. To develop ultrasonic nondestructive evaluation techniques for monitoring such chemical degradations, it is necessary to understand how moisture affects the propagation of ultrasound in concrete. To this end, the objective of this paper is to experimentally determine the correlation between the moisture content in cement mortar and ultrasonic wave propagation. Specifically, effects of moisture on the ultrasonic phase velocity and attenuation are examined. It is found that, for the cement mortar samples considered in this study, moisture has negligible effect on the ultrasonic phase velocity. However, moisture can significantly increase the attenuation of ultrasound in cement mortar even in the sub-MHz frequency range.

  11. Cementing porcelain-fused-to-metal crowns.

    Science.gov (United States)

    Vadachkoria, D

    2009-12-01

    The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/micro flora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper cement. Popular use of cements for PFM crowns has shifted from zinc phosphate and glass ionomer cements to resin-reinforced glass ionomer, or RRGI, cements. This change has been rapid and profound. Dental cements have always been less than ideal materials, but this is shift to the relatively new RRGI category justified. Resin-reinforced glass ionomer (RRGI) cements appear to be better than zinc phosphate and glass ionomer cements when placing porcelain-to-metal crowns. RRGI cements, such as RelyX Luting, Fuji Plus and Vitremer Luting Cement, satisfy more of the ideal characteristics of PFM cementation than any other previous cement. Expansion of all three cements has not caused any apparent problems with the cements when used with PFM or metal crowns, but these cements, however, should be avoided when cementing all-ceramic crowns. PMID:20090144

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

    International Nuclear Information System (INIS)

    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

  13. A rapid cyclic voltammetric method for studying cement factors affecting the corrosion of reinforced concrete

    Energy Technology Data Exchange (ETDEWEB)

    Foulkes, F.R.; McGrath, P. (Univ. of Toronto, Ontario (Canada))

    1999-06-01

    A rapid cyclic voltammetric method for studying the influence of cement factors on the corrosion of embedded iron and steel in hardened cement paste is described. The technique employs a cement electrode'' consisting of an iron or steel wire embedded in a miniature cylinder of hardened cement paste. The rapid cyclic voltammetric method is fast, reproducible, and provides information on the corrosiveness of the pore solution environment surrounding the embedded metal. The usefulness of the method is demonstrated by showing how it can be used to evaluate the threshold chloride content of hardened ordinary portland cement paste at which corrosion begins and by using it to evaluate the relative efficacy of several admixed corrosion inhibitors.

  14. Analyses of microstructural properties of VA/VeoVA copolymer modified cement pastes

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo M. Gomes

    2005-07-01

    Full Text Available Recently, modern techniques have been applied for analysis of the influence of polymers on microstructural properties of Portland cement, such as Thermogravimetric Analyses (TG, Scanning Electronic Microscopy (SEM, Fourier Transform Infrared Spectroscopy (FT-IR and Mercury Intrusion Porosimetry (MIP. In this study, thermogravimetric analyses were used to study the influence of vinyl acetate-versatic vinylester copolymer (VA/VeoVA in seven pastes of 28-day old Portland cement, in which distinct polymer contents and water/cement ratios were employed. In addition, analyses of FT-IR and MIP on Portland cement pastes modified by the copolymer were employed. The results showed that the addition of polymer interferes significantly in the reduction of Portlandite formation and increases the porosity of the matrices. A possible chemical interaction between the copolymer and hydrated products of Portland cement was also observed.

  15. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    OpenAIRE

    Adriana Eštoková; Lenka Palaščáková

    2013-01-01

    The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices) of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in t...

  16. Assessment of the compatibility of wood and plastic with cement for their recycling in cement composites

    OpenAIRE

    Andrade, André De; Caldeira, Fernando

    2010-01-01

    The compatibility between maritime pine wood and cement, and between plastic (LDPE) and cement, was assessed for the recycling of wood and plastic in cement composites. Temperature vs. time profiles of cement setting were registered and compatibility indices were calculated. Results indicate that recycling of plastics in plastic-cement composites does not pose any questions regarding chemical compatibility. However, maritime pine hinders cement setting in some extent. So, in or...

  17. Specific Examples of Hybrid Alkaline Cement

    Directory of Open Access Journals (Sweden)

    Fernández-Jiménez Ana

    2014-04-01

    Full Text Available Hybrid alkaline cements are obtained by alkali-activating cementitious blends in the Na2O-CaO-SiO2-Al2O3-H2O system. The present paper discusses the results of activating different cementitious blends containing a low OPC clinker content ( 15MPa a 2 days different alkaline activators were used (liquid and solid. The reaction products obtained were also characterised by XRD, SEM/EDX and 27Al and 29Si NMRMAS. The results showed that the main reaction product was a mix of cementitious gels C-A-S-H and (N,C-A-S-H, and that their relative proportions were strongly influenced by the calcium content in the initial binder

  18. 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

  19. CO2 REDUCTION OPTIONS IN CEMENT INDUSTRY - THE NOVI POPOVAC CASE

    Directory of Open Access Journals (Sweden)

    Gordana M Stefanović

    2010-01-01

    Full Text Available The cement industry contributes about 5% to global anthropogenic CO2 emissions, and is thus an important sector in CO2-emission mitigation strategies. Carbon dioxide is emitted from the calcination process of limestone, from combustion of fuels in the kiln, and from the coal combustion during power generation. Strategies to reduce these CO2 emissions include energy efficiency improvement, new processes, shift to low carbon fuels or waste fuels in cement production, increased use of additives in cement production, alternative cements, and CO2 removal from flue gases in clinker kilns. Increased use of fly ash as an additive to cement and concrete has a number of advantages, the primary being reduction of costs of fly ash disposal, resource conservation, and cost reduction of the product. Since the production of cement requires a large amount of energy (about 2.9-3.2 GJt-1, the substitution of cement by fly ash saves not only energy but also reduces the associated greenhouse gas emissions. The paper evaluates the reduction of CO2 emissions that can be achieved by these mitigation strategies, as well as by partial substitution of cement by fly ash. The latter is important because the quality of the produced concrete depends on the physical-chemical properties of the fly ash and thus partial substitution as well as the type of fly ash (e.g., the content of CaO has an effect not only on energy consumption and emissions, but also on the produced concrete quality.

  20. Hydration Characteristics and Immobilization of Cr (VI) in Slag Cement-CKD Pastes under Hydrothermal Treatment

    Institute of Scientific and Technical Information of China (English)

    M R Shatat; Gomaa A M Ali; M A Tantawy

    2015-01-01

    The effect of hydrothermal curing regimes on the hydration characteristics of slag cement containing different ratios of cement kiln dust has been studied. The samples for this study were combination of slag cement and cement kiln dust (5%-25%) without and with immobilization of 5% Cr (VI) by mass. Pastes were hydrothermally treated at 180℃ for different periods (2-24 h) in well closed stainless steel capsule. The hydration characteristics of these pastes were studied by measuring the compressive strength, bulk density, total porosity and combined water content. The findings were further supported by XRD and SEM analysis. The results indicated that the hydration characteristics of slag cement paste containing cement kiln dust 10% by mass were enhanced, especially at later ages (24 h) of hydration. That is due to the hydrothermal curing regimes of immobilized pastes accelerating hydration reactions and precipitation of CaCrO4, indicating that Cr (VI) can be solidiifed in the cement paste. This precipitation leads to pore formation in hydrated slag cement pastes.

  1. Hydration of blended cement pastes containing waste ceramic powder as a function of age

    Science.gov (United States)

    Scheinherrová, Lenka; Trník, Anton; Kulovaná, Tereza; Pavlík, Zbyšek; Rahhal, Viviana; Irassar, Edgardo F.; Černý, Robert

    2016-07-01

    The production of a cement binder generates a high amount of CO2 and has high energy consumption, resulting in a very adverse impact on the environment. Therefore, use of pozzolana active materials in the concrete production leads to a decrease of the consumption of cement binder and costs, especially when some type of industrial waste is used. In this paper, the hydration of blended cement pastes containing waste ceramic powder from the Czech Republic and Portland cement produced in Argentina is studied. A cement binder is partially replaced by 8 and 40 mass% of a ceramic powder. These materials are compared with an ordinary cement paste. All mixtures are prepared with a water/cement ratio of 0.5. Thermal characterization of the hydrated blended pastes is carried out in the time period from 2 to 360 days. Simultaneous DSC/TG analysis is performed in the temperature range from 25 °C to 1000 °C in an argon atmosphere. Using this thermal analysis, we identify the temperature, enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates gels dehydration, portlandite, vaterite and calcite decomposition and their changes during the curing time. Based on thermogravimetry results, we found out that the portlandite content slightly decreases with time for all blended cement pastes.

  2. Alkali Aggregate Reaction in Alkali Slag Cement Mortars

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By means of "Mortar Bar Method",the ratio of cement to aggregate was kept as a constant 1∶2.25,the water-cement ratio of the mixture was 0.40,and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2℃ and RH≥95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement(ASC) mortars due to alkali aggregate reaction(AAR) were studied. According to atomic absorption spectrometry,the amount of free alkali was measured in ASC mortars at 90d.The results show above factors affect AAR remarkably,but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O).Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously.Moreover,slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.

  3. Peach leaf responses to soil and cement dust pollution.

    Science.gov (United States)

    Maletsika, Persefoni A; Nanos, George D; Stavroulakis, George G

    2015-10-01

    Dust pollution can negatively affect plant productivity in hot, dry and with high irradiance areas during summer. Soil or cement dust were applied on peach trees growing in a Mediterranean area with the above climatic characteristics. Soil and cement dust accumulation onto the leaves decreased the photosynthetically active radiation (PAR) available to the leaves without causing any shade effect. Soil and mainly cement dust deposition onto the leaves decreased stomatal conductance, photosynthetic and transpiration rates, and water use efficiency due possibly to stomatal blockage and other leaf cellular effects. In early autumn, rain events removed soil dust and leaf functions partly recovered, while cement dust created a crust partially remaining onto the leaves and causing more permanent stress. Leaf characteristics were differentially affected by the two dusts studied due to their different hydraulic properties. Leaf total chlorophyll decreased and total phenol content increased with dust accumulation late in the summer compared to control leaves due to intense oxidative stress. The two dusts did not cause serious metal imbalances to the leaves, except of lower leaf K content.

  4. Behavior of multi-walled carbon nanotubes on the porosity and microstructure of cement-based materials

    Science.gov (United States)

    Nochaiya, Thanongsak; Chaipanich, Arnon

    2011-01-01

    The porosity and microstructure of a Portland cement-multi-walled carbon nanotube composite were investigated. Multi-walled carbon nanotubes (CNTs), up to 1 wt.% of cement, synthesized by infusion chemical vapor deposition, and Portland cement type I (PC) were used to produce pastes with a water to cement ratio of 0.5. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to characterize Portland cement-CNTs systems. MIP analysis of the results indicates that total porosity of the mixes with CNTs was found to decrease with increasing CNTs content. Moreover, an important effect of additional CNTs was a reduction in the number of mesopores, while SEM technique showed dispersion of CNTs between the hydration phases of Portland cement pastes.

  5. Lack of inhibiting effect of oil emplacement on quartz cementation: Evidence from Cambrian reservoir sandstones, Paleozoic Baltic Basin

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; Cyziene, Jolanta; Sliaupa, Saulius;

    2008-01-01

    Currently, the question of whether or not the presence of oil in sandstone inhibits quartz cementation and preserves porosity is still debated. Data from a number of Cambrian sandstone oil fields and dry fields have been studied to determine the effects of oil emplacement on quartz cementation...... cementation is derived from internal sources. Rather, in spite of large variation in porosity and quartz cement content, a regular pattern of porosity decrease is related to increasing temperature or depth. The observed heterogeneity is due to local factors that influence the precipitation of quartz cement......, including sandstone architecture, i.e., distribution of shales within the sandstone bodies, and sandstone thickness. Heterogeneity is inherent to sandstone architecture and to the fact that silica for quartz cementation is derived from heterogeneously distributed local pressure solution. Models predicting...

  6. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.”...

  7. Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: cement hydration, strength development and volume stability.

    Science.gov (United States)

    Berger, Stéphane; Cau Dit Coumes, Céline; Le Bescop, Patrick; Damidot, Denis

    2011-10-30

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes 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 its 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 hydrates 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, strätlingite, 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. PMID:21889260

  8. Characterization and utilization of cement kiln dusts (CKDs) as partial replacements of Portland cement

    Science.gov (United States)

    Khanna, Om Shervan

    mineralogical phases within CKDs. It was found that CKDs can contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or flyash (calcium langbeinite (chloride ions. The second objective was to utilize the material characterization analysis to determine the relationships among the composition properties of CKD-PC blends and their effects on fresh and hardened properties. The study found that CKDs from preheater/precalciner kilns have different effects on workability and heat evolution than CKDs from wet and long-dry kilns due to the presence of very reactive and high free lime contents (>20%). The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other CKD-PC blends and control cements. The hardened properties of CKD as a partial substitute of PC appear to be governed by the sulfate content of the CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should be less than ˜0.40% above the optimum sulfate content of the PC. It was also found that the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of gypsum during the grinding process to control the early hydration of C3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of limestone filler in PC.

  9. CONTRIBUTION TO THE STATISTICAL INTERPRETATION OF RAW MATERIALS FOR THE CEMENT INDUSTRY OF SPLIT

    OpenAIRE

    Miroslav Matijaca; Slavko Vujec

    1990-01-01

    Up to the last two decades cement was produced from mari called »tupina« (with about 76% CaCOj) which is an ideal mixture for cement production. Due to the quantity decrease of this raw material, cement production went on using the mixture of other members of the flysch series: limestones, marls, clay, loess, sandstones a.o. By the analysis of natural materials the CaCO^ content has mostly been proved. Therefore, knowing the correlation of oxides in mineral raw material is of special signific...

  10. Portland cement hydration in the presence of admixtures: black gram pulse and superplasticizer

    Directory of Open Access Journals (Sweden)

    Viveka Nand Dwivedi

    2008-12-01

    Full Text Available Effect of admixtures such as black gram pulse (BGP and sulfonated naphthalene based superplasticizer (SP on the hydration of Portland cement has been studied. The hydration characteristics of OPC in the presence of BGP and SP were studied with the help of non evaporable water content determinations, calorimetric method, Mössbauer spectroscopic and atomic force microscopic techniques. Results have shown that both BGP and SP get adsorbed at the surface of cement and its hydration products. The hydration of Portland cement is retarded in the presence of both the admixtures and nanosize hydration products are formed.

  11. Damping Property of a Cement-Based Material Containing Carbon Nanotube

    OpenAIRE

    Wei-Wen Li; Wei-Ming Ji; Yi Liu; Feng Xing; Yu-Kai Liu

    2015-01-01

    This study aimed to explore the damping property of a cement-based material with carbon nanotube (CNT). In the study, the cement composites with different contents of CNT (0 wt%, 0.033 wt%, 0.066 wt%, and 0.1 wt%) were investigated. Logarithmic Decrement method and Dynamic Mechanical Analysis (DMA) method were utilized to study the damping property of CNT/cement composite. The influences of CNT on pore size distribution and microstructure of composite were analyzed by Mercury Intrusion Porosi...

  12. 温度对大掺量粉煤灰水泥水化C-S-H聚合度的影响%Effect of Temperature on Aggregate States of Hydration Products C-S-H Gel of Cement with High Content of Fly Ash

    Institute of Scientific and Technical Information of China (English)

    于文金; 罗永传; 弓子成; 丁庆军

    2011-01-01

    Effect of curing temperature and temperature variation on silicon-oxy tetrahedron aggregate states of hydra-tion products C-S-H gel of cement with high content of fly ash materials by high-resolution solid "Si NMR,XRD and FT-IR testing techniques. The results show that silicon-oxy tetrahedron aggregate states C-S-H gel and contents of alumi-num-oxy tetrahedron increased and then stabilized with the increase of curing temperature. Curing at normal temperature was good for increasing silicon-oxy tetrahedron aggregate states of CSH gels and contents of aluminum-oxy tetrahedron at the periods from 7 d to 28 d.%采用固体29Si核磁共振、FTIR、XRD测试方法研究了养护温度、温度变化对大掺量粉煤灰水泥基材料水化C-S-H凝胶硅氧四面体聚合程度的影响规律.结果表明:粉煤灰掺量为50%时,C-S-H凝胶硅氧四面体的聚合程度和C-S-H凝胶中铝氧四面体的比例随着养护温度的升高而呈现先增加后稳定的趋势.在7d至28 d龄期阶段,常温养护更加有利于C-S-H凝胶硅氧四面体聚合程度的增加,也更有利于Al原子取代Si原子.

  13. Radioactive wastes dispersed in stabilized ash cements

    International Nuclear Information System (INIS)

    One of the most widely-used methods for the solidification/stabilization of low-level radwaste is by incorporation into Type-I/II ordinary portland cement (OPC). Treating of OPC with supercritical fluid carbon dioxide (SCCO2) has been shown to significantly increase the density, while simultaneously decreasing porosity. In addition, the process significantly reduces the hydrogenous content, reducing the likelihood of radiolytic decomposition reactions. This, in turn, permits increased actinide loadings with a concomitant reduction in disposable waste volume. In this article, the authors discuss the combined use of fly-ash-modified OPC and its treatment with SCCO2 to further enhance immobilization properties. They begin with a brief summary of current cement immobilization technology in order to delineate the areas of concern. Next, supercritical fluids are described, as they relate to these areas of concern. In the subsequent section, they present an outline of results on the application of SCCO2 to OPC, and its effectiveness in addressing these problem areas. Lastly, in the final section, they proffer their thoughts on why they believe, based on the OPC results, that the incorporation of fly ash into OPC, followed by supercritical fluid treatment, can produce highly efficient wasteforms

  14. Radioactive wastes dispersed in stabilized ash cements

    Energy Technology Data Exchange (ETDEWEB)

    Rubin, J.B.; Taylor, C.M.V.; Sivils, L.D.; Carey, J.W.

    1997-12-31

    One of the most widely-used methods for the solidification/stabilization of low-level radwaste is by incorporation into Type-I/II ordinary portland cement (OPC). Treating of OPC with supercritical fluid carbon dioxide (SCCO{sub 2}) has been shown to significantly increase the density, while simultaneously decreasing porosity. In addition, the process significantly reduces the hydrogenous content, reducing the likelihood of radiolytic decomposition reactions. This, in turn, permits increased actinide loadings with a concomitant reduction in disposable waste volume. In this article, the authors discuss the combined use of fly-ash-modified OPC and its treatment with SCCO{sub 2} to further enhance immobilization properties. They begin with a brief summary of current cement immobilization technology in order to delineate the areas of concern. Next, supercritical fluids are described, as they relate to these areas of concern. In the subsequent section, they present an outline of results on the application of SCCO{sub 2} to OPC, and its effectiveness in addressing these problem areas. Lastly, in the final section, they proffer their thoughts on why they believe, based on the OPC results, that the incorporation of fly ash into OPC, followed by supercritical fluid treatment, can produce highly efficient wasteforms.

  15. Effects of Using Pozzolan and Portland Cement in the Treatment of Dispersive Clay

    OpenAIRE

    Vakili, A. H.; Selamat, M. R.; H. Moayedi

    2013-01-01

    Use of dispersive clay as construction material requires treatment such as by chemical addition. Treatments to dispersive clay using pozzolan and Portland cement, singly and simultaneously, were carried out in this study. When used alone, the optimum amount of pozzolan required to treat a fully dispersive clay sample was 5%, but the curing time to reduce dispersion potential, from 100% to 30% or less, was 3 month long. On the other hand, also when used alone, a 3% cement content was capable o...

  16. The study of the basic mechanical properties of polyvinyl alcohol fiber cement stabilized macadam

    Directory of Open Access Journals (Sweden)

    Wang Shipeng

    2015-06-01

    Full Text Available As a new material in the construction field,polyvinyl alcohol fiber cement stabilized macadam pavement has a very broad application prospects. The study of the basic mechanical properties of polyvinyl alcohol fiber cement stabilized macadam is also a hot spot today. This paper studies the flexural strength of polyvinyl alcohol fiber content is at 0.9Kg / m3 ,and the affect between the splitting tensile strength and the polyvinyl alcohol fiber.

  17. A modified PMMA cement (Sub-cement) for accelerated fatigue testing of cemented implant constructs using cadaveric bone.

    Science.gov (United States)

    Race, Amos; Miller, Mark A; Mann, Kenneth A

    2008-10-20

    Pre-clinical screening of cemented implant systems could be improved by modeling the longer-term response of the implant/cement/bone construct to cyclic loading. We formulated bone cement with degraded fatigue fracture properties (Sub-cement) such that long-term fatigue could be simulated in short-term cadaver tests. Sub-cement was made by adding a chain-transfer agent to standard polymethylmethacrylate (PMMA) cement. This reduced the molecular weight of the inter-bead matrix without changing reaction-rate or handling characteristics. Static mechanical properties were approximately equivalent to normal cement. Over a physiologically reasonable range of stress-intensity factor, fatigue crack propagation rates for Sub-cement were higher by a factor of 25+/-19. When tested in a simplified 2 1/2-D physical model of a stem-cement-bone system, crack growth from the stem was accelerated by a factor of 100. Sub-cement accelerated both crack initiation and growth rate. Sub-cement is now being evaluated in full stem/cement/femur models. PMID:18774136

  18. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    LENUS (Irish Health Repository)

    Addison, Owen

    2010-09-01

    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  19. The Effects of Eggshell Ash on Strength Properties of Cement-stabilized Lateritic

    Directory of Open Access Journals (Sweden)

    Okonkwo U. N

    2012-04-01

    Full Text Available Eggshell ash obtained by incinerating Fowls’ eggshells to ash has been established to be a good accelerator for cement-bound materials and this would be useful for road construction work at the peak of rainy seasons for reducing setting time of stabilized road pavements. However this should be achieved not at the expense of other vital properties of the stabilized matrix. This is part of the effort in adding value to agricultural materials which probably cause disposal problems. Thus this study aimed at determining the effect of eggshell ash on the strength properties of cement-stabilized lateritic soil. The lateritic soil was classified to be A-6(2 in AASHTO rating system and reddish-brown clayey sand (SC in the Unified Classification System. Constant cement contents of 6% and 8% were added to the lateritic soil with variations in eggshell ash content of 0% to 10% at 2% intervals. All proportions of cement and eggshell ash contents were measured in percentages by weight of the dry soil. The Compaction test, California Bearing Ratio test, Unconfined Compressive Strength test and Durability test were carried out on the soil-cement eggshell ash mixtures. The increase in eggshell ash content increased the Optimum Moisture Content but reduced the Maximum Dry Density of the soil-cement eggshell ash mixtures. Also the increase in eggshell ash content considerably increased the strength properties of the soil-cement eggshell ash mixtures up to 35% in the average but fell short of the strength requirements except the durability requirement was satisfied.

  20. Direct shear tests on cemented paste backfill–rock wall and cemented paste backfill–backfill interfaces

    Directory of Open Access Journals (Sweden)

    Nabassé J.F. Koupouli

    2016-08-01

    Full Text Available This paper presents the results of the shear strength (frictional strength of cemented paste backfill-cemented paste backfill (CPB-CPB and cemented paste backfill–rock wall (CPB-rock interfaces. The frictional behaviors of these interfaces were assessed for the short-term curing times (3 d and 7 d using a direct shear apparatus RDS-200 from GCTS (Geotechnical Consulting & Testing Systems. The shear (friction tests were performed at three different constant normal stress levels on flat and smooth interfaces. These tests aimed at understanding the mobilized shear strength at the CPB-rock and CPB-CPB interfaces during and/or after open stope filling (no exposed face. The applied normal stress levels were varied in a range corresponding to the usually measured in-situ horizontal pressures (longitudinal or transverse developed within paste-filled stopes (uniaxial compressive strength, σc ≤ 150 kPa. Results show that the mobilized shear strength is higher at the CPB-CPB interface than that at the CPB-rock interface. Also, the perfect elastoplastic behaviors observed for the CPB-rock interfaces were not observed for the CPB-CPB interfaces with low cement content which exhibits a strain-hardening behavior. These results are useful to estimate or validate numerical model for pressures determination in cemented backfill stope at short term. The tests were performed on real backfill and granite. The results may help understanding the mechanical behavior of the cemented paste backfill in general and, in particular, analyzing the shear strength at backfill–backfill and backfill-rock interfaces.

  1. Resistance Responses of Carbon Fiber Cement to Cycled Compressive Stresses

    Institute of Scientific and Technical Information of China (English)

    SHUI Zhonghe; LI Chao; LIAO Weidong

    2005-01-01

    The stress-resistance relationship of carbon fiber cement was studicd. Attention has been paid to explore the improvement of the stress-resistance sensitivity under cycled stress restriction. The prismy carbon fiber cement sensors were pre-fabricated. The factors such as contents of carbon fibers, silica fume, dispersant and the w/ c were taken into account. The electrical resistance variations with the dynamic and static loads were simulated using a strain-controlled test machine. The test results show that there is an optimal fiber content, with which the compression-sensitivity achieves a high level. The addition of silica fume can improve the sensitivity. Urder the optimal test conditions, the measured resistances can greatly correspond with the changes of the load.

  2. Cement radwaste solidification studies third annual report

    International Nuclear Information System (INIS)

    This report summarises cement radwaste studies carried out at AEE Winfrith during 1981 on the encapsulation of medium and low active waste in cement. During the year more emphasis has been placed on the work which is directly related to the solidification of SGHWR active sludge. Information has been obtained on the properties of 220 dm3 drums of cemented waste. The use of cement grouts for the encapsulation of solid items has also been investigated during 1981. (U.K.)

  3. Coagulated silica - a-SiO2 admixture in cement paste

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Záleská, Martina; Rovnaníková, Pavla; Pavlík, Zbyšek

    2016-07-01

    Amorphous silica (a-SiO2) in fine-grained form possesses a high pozzolanic activity which makes it a valuable component of blended binders in concrete production. The origin of a-SiO2 applied in cement-based composites is very diverse. SiO2 in amorphous form is present in various amounts in quite a few supplementary cementing materials (SCMs) being used as partial replacement of Portland cement. In this work, the applicability of a commercially produced coagulated silica powder as a partial replacement of Portland cement in cement paste mix design is investigated. Portland cement CEM I 42.5R produced according to the EU standard EN 197-1 is used as a reference binder. Coagulated silica is applied in dosages of 5 and 10 % by mass of cement. The water/binder ratio is kept constant in all the studied pastes. For the applied silica, specific surface area, density, loss on ignition, pozzolanic activity, chemical composition, and SiO2 amorphous phase content are determined. For the developed pastes on the basis of cement-silica blended binder, basic physical properties as bulk density, matrix density, and total open porosity are accessed. Pore size distribution is determined using MIP analysis. Initial and final setting times of fresh mixtures are measured by automatic Vicat apparatus. Effect of silica admixture on mechanical resistivity is evaluated using compressive strength, bending strength, and dynamic Young's modulus measurement. The obtained data gives evidence of a decreased workability of paste mixtures with silica, whereas the setting process is accelerated. On the other hand, reaction activity of silica with Portland cement minerals results in a slight decrease of porosity and improvement of mechanical resistivity of cement pastes containing a-SiO2.

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

    International Nuclear Information System (INIS)

    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 ZnCl2 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)

  5. UNIFORMITY ASSESSMENT OF CARBON FIBRES DISPERSION IN CEMENT PASTE BY IMPEDANCE MEASUREMENTS

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    An alternating current was applied to measure the impedance of a hardened cement paste with various contents of carbon fibres.When the free water content in the hardened cement paste is 90%-98%,and the measuring frequency 500Hz,an approximate linear relationship was found between fibre content and impedance of the composite.Based on this relationship,a new attempt was made to evaluate the dispersion uniformity of carbon fibres in cement paste by impedance measurement.The standard deviation S and the coefficient of vriation S/(X-)i of impedance of the fibre-cement specimens randomly taken locating in different points were used as main parameters for the uniformity assessment.As a case,four different mixing processes were designed for dispersing carbon fibres into the cement paste.The results demonstrate that the relative longer mixing time increases the dispersion uniformity of carbon fibres in cement paste,and the addition of the water reducer dramatically improves the uniformity due to the change of the fluidity of the paste.The ground fly ash can increase the uniformity to a certain extent.

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

    Science.gov (United States)

    Chaunsali, Piyush

    -based binders without taking into account the viscoelastic effects. For the first time, model based on poromechanics was used to calculate the macroscopic tensile stress that develops in CSA cement-based binders due to crystallization of ettringite. The models enabled a reasonable prediction of tensile stress due to crystallization of ettringite including the failure of an OPC-CSA binder which had high CSA cement content. Elastic strain based on crystallization stress was calculated and compared with the observed strain. A mismatch between observed and calculated elastic strain indicated the presence of early-age creep. Lastly, the application of CSA cement in concretes is discussed to link the paste and concrete behavior.

  7. PERFORMANCE OF PULVERIZED SLAG-SUBSTITUTED CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Portland cement is equivalently substituted by slag micropowders with various specific areas. The workability,activity and acid-corrosion resistance of the slag-substituted cements are investigated,the activation of gypsum is discussed,also the porosity and pore distribution of mortars of the slag micropowders cement are determined by mercury intrusion porosimetry.

  8. 21 CFR 872.3275 - Dental cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns...

  9. ADVANCED CEMENTS FOR GEOTHERMAL WELLS

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2007-01-01

    Using the conventional well cements consisting of the calcium silicate hydrates (CaO-SiO{sub 2}-H{sub 2}O system) and calcium aluminum silicate hydrates (CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O system) for the integrity of geothermal wells, the serious concern confronting the cementing industries was their poor performance in mechanically supporting the metallic well casing pipes and in mitigating the pipe's corrosion in very harsh geothermal reservoirs. These difficulties are particularly acute in two geological regions: One is the deep hot downhole area ({approx} 1700 m depth at temperatures of {approx} 320 C) that contains hyper saline water with high concentrations of CO{sub 2} (> 40,000 ppm) in conjunction with {approx} 100 ppm H{sub 2}S at a mild acid of pH {approx} 5.0; the other is the upper well region between the well's surface and {approx} 1000 m depth at temperatures up to 200 C. The specific environment of the latter region is characterized by highly concentrated H{sub 2}SO{sub 4} (pH < 1.5) brine containing at least 5000 ppm CO{sub 2}. When these conventional cements are emplaced in these harsh environments, their major shortcoming is their susceptibility to reactions with hot CO{sub 2} and H{sub 2}SO4, thereby causing their deterioration brought about by CO{sub 2}-catalyzed carbonation and acid-initiated erosion. Such degradation not only reduced rapidly the strength of cements, lowering the mechanical support of casing pipes, but also increased the extent of permeability of the brine through the cement layer, promoting the rate of the pipe's corrosion. Severely carbonated and acid eroded cements often impaired the integrity of a well in less than one year; in the worst cases, casings have collapsed within three months, leading to the need for costly and time-consuming repairs or redrilling operations. These were the reasons why the geothermal well drilling and cementing industries were concerned about using conventional well

  10. Evolution of the hydration in cements with additions

    OpenAIRE

    Bonavetti, V. L.; Rahhal, V. F.; Irassar, E. F.

    2002-01-01

    In this paper, the hydration mechanism of portland cement pastes with limestone, quartz and natural pozzolan (80/20 weight) was analized. The techniques used were nonevaporable water content, pozzolanic activity and X-ray diffraction. Results show that filler effect increases initially the amount of hydration products in all pastes. For limestone pastes, the dilution effect is significant at long time, for quartz and pozzolan pastes the dilution effect was lower due to the contribution of the...

  11. Sealing of cracks in cement using microencapsulated sodium silicate

    OpenAIRE

    Giannaros, Petros; Kanellopoulos, Antonios; Al-Tabbaa, Abir

    2016-01-01

    Cement-based materials possess inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been expl...

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

    OpenAIRE

    Garcia-Maté, Marta; De la Torre, Angeles G; León-Reina, Laura; Aranda, Miguel A. G.; Santacruz, Isabel

    2013-01-01

    The main objective of this work is to study the hydration and properties of calciumsulfoaluminate 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 paramet...

  13. Effect of Microwave Processing on Aluminate Cement Clinkering

    Institute of Scientific and Technical Information of China (English)

    DONG Jianmiao; LONG Shizong

    2005-01-01

    When raw materials were preheated to 1000-1300 ℃ by electricity and microwave was inputted for 1 min 5 s-4 mins, then alunminate clinkers were obtained. The f-CaO contents,XRD patterns and lithofacies analysis show that the microwave processing accelerates the clinkering reaction,and Fe2O3 is contributed to the aluminate cement clinkering. The appearance of liquid phase in process of microwave heating increases the microwave absorbability of materials greatly.

  14. Microscale Investigation of Arsenic Distribution and Species in Cement Product from Cement Kiln Coprocessing Wastes

    OpenAIRE

    Yufei Yang; Jingchuan Xue; Qifei Huang

    2013-01-01

    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, ...

  15. The comparison between sulfate salt weathering of portland cement paste and calcium sulfoaluminate cement paste

    OpenAIRE

    Liu, Zanqun; Deng, Dehua; De Schutter, Geert

    2015-01-01

    In this paper, the damage performances of sulfate salt weathering of Portland cement paste and calcium sulfoaluminate (CSA) cement paste were compared according to authors' previous studies. It was found that the evaporation zone of speciments partially immersed in 10% Na2SO4 solution were both severely deteriorated for Portland cement and CSA cement. However, the differences were more significant: (1) the CSA cement paste were damaged just after 7 days exposure compared to the 5 months expos...

  16. Influence of Geosta Addition on Cement-stabilised Chicoco Mud of the Niger Delta

    Directory of Open Access Journals (Sweden)

    Olujide Omotosho

    2005-01-01

    Full Text Available Chicoco is a very soft and extremely compressible organic marine mud found extensively and to considerable depths within the saline tidal flat or mangrove swamp of the Niger delta in southern Nigeria. Natural chicoco is highly undesirable, barely able to support a human of average weight but air-dried chicoco has been used successfully by the indigeneous people for shore protection, etc. especially if placed above water. Plain cement stabilization of most organic soils (including chicoco is known to be ineffective. In this study, geosta, a chemical stabiliser relatively newly developed for organic soils was combined with ordinary Portland cement to stabilise chicoco. It was observed that neutralisation of acidic "air-dried" chicoco by basic geosta inhibited the expected ion-exchange reaction and its attendant improvement on mechanical properties. As a result and as geosta content increases, maximum dry density (MDD was found to be only marginally improved but better for higher cement contents while optimum moisture content (OMC decreases but with higher values for lower cement contents. Unsoaked CBR (but with samples wax-cured for 3 days on the other hand was found to maximise at low geosta content and thereafter decreases continually - a major cost advantage in earthworks. In fact, the most effective influence was obtained at 4.0% cement plus about 1.5% geosta. This stabilization was also found to produce optimum road sub-base materials.

  17. Leachability and strength of kaolin stabilized with cement and rubber

    Directory of Open Access Journals (Sweden)

    Meei-Hoan Ho

    2011-07-01

    Full Text Available Yearly, the disposal of used tyres is a major environmental problem for countries all over the world. This causes environmental hazards such as uncontrolled fire, consume landfill space, breeding ground for mosquitoes and contaminating the soil and vegetation. Hence, urgent steps were identified to produce new methods of recycling the waste tyres to solve this hazard. This study reviews the feasibility of using waste tyres in the form of rubber chips with cement to stabilize soft clay and the effect to the environment. The focus of this study was mainly the strength and leachability characteristics of kaolin as base clay, admixed with cement as the binder and rubber chips as an additive. Leaching test is used to evaluate the performance of cementitious materials for stabilization and solidification (S & S of hazardous materials such as waste or contaminated soil. In this study, cylindrical stabilized clay specimens were prepared with various rubber chips contents and cement, and then aged for 28 days. Cylindrical specimens were then subjected to unconfined compressive strength test (using Geocomp LoadTrac II and the specimens were later dried in oven at 105° before tested for leaching tests. These leaching methods are Acid Neutralization Capacity Test (ANC and Synthetic Precipitation Leaching Procedure (SPLP. The solidified samples were checked on six different heavy metals, namely copper, chromium, cadmium, arsenic, zinc and plumbum. Analysis was carried out by relating the effects of 0, 2 or 4 % cement as well as 0, 5, 10 and 15 % rubber chips addition to the base clay and its leachability. As observed, the curing of specimen for 28 days was in a range of 66.24 to 249.4 kPa. Specimen with 4 % cement is able to produce ANC9 of about 0.13 meq HNO3/g specimen. However specimen with 0 % and 2 % cement for different rubberchips content shows that the specimen do not have the capacity to neutralize acid at pH 9. Therefore, more cement (> 4 % is

  18. Using of borosilicate glass waste as a cement additive

    Science.gov (United States)

    Han, Weiwei; Sun, Tao; Li, Xinping; Sun, Mian; Lu, Yani

    2016-08-01

    Borosilicate glass waste is investigated as a cement additive in this paper to improve the properties of cement and concrete, such as setting time, compressive strength and radiation shielding. The results demonstrate that borosilicate glass is an effective additive, which not only improves the radiation shielding properties of cement paste, but also shows the irradiation effect on the mechanical and optical properties: borosilicate glass can increase the compressive strength and at the same time it makes a minor impact on the setting time and main mineralogical compositions of hydrated cement mixtures; and when the natural river sand in the mortar is replaced by borosilicate glass sand (in amounts from 0% to 22.2%), the compressive strength and the linear attenuation coefficient firstly increase and then decrease. When the glass waste content is 14.8%, the compressive strength is 43.2 MPa after 28 d and the linear attenuation coefficient is 0.2457 cm-1 after 28 d, which is beneficial for the preparation of radiation shielding concrete with high performances.

  19. Assessment of radioactivity and radon exhalation rate in Egyptian cement.

    Science.gov (United States)

    El-Bahi, S M

    2004-05-01

    The cement industry is considered as one of the basic industries that plays an important role in the national economy of developing countries. Activity concentration of 238U, 232Th, and 40K in local cement types from different Egyptian factories has been measured using a shielded HPGe detector. The average values obtained for 238U, 232Th, and 40K activity concentrations in different types of cement are lower than the corresponding global values reported in UNSCEAR publications. On the basis of the hazard index and the radium equivalent concentration, it can be shown that the natural radioactivity of cement samples is not greater than the values permitted in the established standards in other countries. A solid-state nuclear track detector SSNTD (Cr-39) was used to measure the radon concentration as well as exhalation rate for these samples. The effective radium content and the exhalation rate are found to vary from 12.75 to 38.52 Bq kg(-1) and 61.19 to 181.39 Bq m(-2) d(-1), respectively.

  20. Osteogenesis and angiogenesis properties of dental pulp cell on novel injectable tricalcium phosphate cement by silica doped.

    Science.gov (United States)

    Su, Ying-Fang; Lin, Chi-Chang; Huang, Tsui-Hsien; Chou, Ming-Yung; Yang, Jaw-Ji; Shie, Ming-You

    2014-09-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material in clinical. In this study, we have doped silica (Si) into β-TCP and enhanced its bioactive and osteostimulative properties. To check its effectiveness, a series of Si-doped with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of the diametral tensile strength, ions released and weight loss of cements was considered after immersion. In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on Si-doped β-TCP cements. The results showed that setting time and injectability of the Si-doped β-TCP cements were decreased as the Si content was increased. At the end of the immersion point, weight losses of 30.1%, 36.9%, 48.1%, and 55.3% were observed for the cement doping 0%, 10%, 20%, and 30% Si into β-TCP cements, respectively. In vitro cell experiments show that the Si-rich cements promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the Si-doped in the cement is more than 20%, the amount of cells and osteogenesis protein of hDPCs was stimulated by Si released from Si-doped β-TCP cements. The degradation of β-TCP and osteogenesis of Si gives a strong reason to believe that these Si-doped β-TCP cements may prove to be promising bone repair materials.

  1. Thoughts on the Current Cement Industry Development

    Institute of Scientific and Technical Information of China (English)

    Gan Zhihe

    2003-01-01

    According to the analysis of cement capacity andits relations with macro economy running index, the mainreasons for the present rapid development of cement capacityare the rapid development of economy and the shot up ofwhole society fixed asset investment. According to the presentspeed of economy development, cement still enjoys a po-tential increase, So here has not been an overall excessivepopularity of cement industry. The best way to prevent lowlevel repeated construction is to promote the development ofnew dry- process cement as well as try to get rid of blindness.

  2. Effect of temporary cements on the shear bond strength of luting cements

    Directory of Open Access Journals (Sweden)

    Marco Fiori-Júnior

    2010-02-01

    Full Text Available OBJECTIVE: The purpose of this study was to evaluate, by shear bond strength (SBS testing, the influence of different types of temporary cements on the final cementation using conventional and self-etching resin-based luting cements. Material and Methods: Forty human teeth divided in two halves were assigned to 8 groups (n=10: I and V (no temporary cementation; II and VI: Ca(OH2-based cement; III and VII: zinc oxide (ZO-based cement; IV and VIII: ZO-eugenol (ZOE-based cement. Final cementation was done with RelyX ARC cement (groups I to IV and RelyX Unicem cement (groups V to VIII. Data were analyzed statistically by ANOVA and Tukey's test at 5% significance level. RESULTS: Means were (MPa: I - 3.80 (±1.481; II - 5.24 (±2.297; III - 6.98 (±1.885; IV - 6.54 (±1.459; V - 5.22 (±2.465; VI - 4.48 (±1.705; VII - 6.29 (±2.280; VIII - 2.47 (±2.076. Comparison of the groups that had the same temporary cementation (Groups II and VI; III and VII; IV and VIII showed statistically significant difference (p0.05 for the different luting cements (RelyX TM ARC and RelyX TM Unicem. The groups that had no temporary cementation (Groups I and V did not differ significantly from each other either (p>0.05. CONCLUSION: When temporary cementation was done with ZO- or ZOE-based cements and final cementation was done with RelyX ARC, there was an increase in the SBS compared to the control. In the groups cemented with RelyX Unicem, however, the use of a ZOE-based temporary cement affected negatively the SBS of the luting agent used for final cementation.

  3. Prediction of calcite Cement Distribution in Shallow Marine Sandstone Reservoirs using Seismic Data

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, N.E.

    1996-12-31

    This doctoral thesis investigates how calcite cemented layers can be detected by reflection seismic data and how seismic data combined with other methods can be used to predict lateral variation in calcite cementation in shallow marine sandstone reservoirs. Focus is on the geophysical aspects. Sequence stratigraphy and stochastic modelling aspects are only covered superficially. Possible sources of calcite in shallow marine sandstone are grouped into internal and external sources depending on their location relative to the presently cemented rock. Well data and seismic data from the Troll Field in the Norwegian North Sea have been analysed. Tuning amplitudes from stacks of thin calcite cemented layers are analysed. Tuning effects are constructive or destructive interference of pulses resulting from two or more closely spaced reflectors. The zero-offset tuning amplitude is shown to depend on calcite content in the stack and vertical stack size. The relationship is found by regression analysis based on extensive seismic modelling. The results are used to predict calcite distribution in a synthetic and a real data example. It is found that describing calcite cemented beds in shallow marine sandstone reservoirs is not a deterministic problem. Hence seismic inversion and sequence stratigraphy interpretation of well data have been combined in a probabilistic approach to produce models of calcite cemented barriers constrained by a maximum amount of information. It is concluded that seismic data can provide valuable information on distribution of calcite cemented beds in reservoirs where the background sandstones are relatively homogeneous. 63 refs., 78 figs., 10 tabs.

  4. Damping Property of a Cement-Based Material Containing Carbon Nanotube

    Directory of Open Access Journals (Sweden)

    Wei-Wen Li

    2015-01-01

    Full Text Available This study aimed to explore the damping property of a cement-based material with carbon nanotube (CNT. In the study, the cement composites with different contents of CNT (0 wt%, 0.033 wt%, 0.066 wt%, and 0.1 wt% were investigated. Logarithmic Decrement method and Dynamic Mechanical Analysis (DMA method were utilized to study the damping property of CNT/cement composite. The influences of CNT on pore size distribution and microstructure of composite were analyzed by Mercury Intrusion Porosimetry (MIP and Scanning Electron Microscopy (SEM, respectively. The experimental results showed that CNT/cement composite presented higher flexural strength index than that of a pure cement paste. Additional CNT could improve the vibration-reduction capacity of cement paste. Furthermore, the experiments proved that CNT could bridge adjacent hydration products and support load transfer within cement matrix, which contributed to the energy dissipation during the loading process.

  5. An assessment of Mercury immobilisation in alkali activated fly ash (AAFA) cements.

    Science.gov (United States)

    Donatello, Shane; Fernández-Jiménez, Ana; Palomo, Angel

    2012-04-30

    This paper presents total and soluble Mercury contents for three coal fly ashes and alkali-activated fly ash (AAFA) cements consisting of 100% fly ash as starting material. To evaluate the potential of the AAFA cement matrix to immobilise Hg from an external source, another batch of cements, doped with 5000 mg/kg Hg as highly soluble HgCl(2), was prepared. The ashes and control AAFA cements complied with Mercury leaching criteria for non-hazardous wastes according to both TCLP and EN 12457 tests. Fly ash activated cements doped with 5000 mg/kg Hg and aged for 2 days immobilised 98.8-99.6% and 97.3-98.8% of Hg according to TCLP and EN 12457 tests respectively. Evidence from SEM-EDX suggests that Hg was immobilised by precipitation as highly insoluble HgS or Hg(2)S, although partial precipitation as less insoluble HgO or Hg silicates could not be entirely ruled out based on data presented. The results for Hg-doped cements contribute to the growing body of evidence that shows AAFA cement as a useful material for immobilizing elevated concentrations of toxic and hazardous elements. PMID:22341491

  6. Setting temperature evolution of nitrate radwaste immobilized in ordinary portland cement

    International Nuclear Information System (INIS)

    Materials based on hydraulic cements such as ordinary Portland cement (OPC) have many applications in the radioactive waste disposal field. Cement hydration process is an exothermic reaction and can cause a considerable temperature rise in the cemented waste form. Specially when large blocks of waste forms are produced it is necessary to have some information about the temperature build up which occurs inside the mass, because this effect may have some influences on the ultimate properties of the hardened cement paste. This temperature rise cause expansion while the cement paste is hardening. When the cooling process takes place, to the surrounding temperature, crackings and contractions may then occur. Whether cracking arise it depends both on the magnitude of the temperature induced stress and on the capacity of the mixture to accommodate the strain. This paper compares the temperature growth in pastes into two different geometries: one uses a waste container with 3.8 dm3 (one US gallon) capacity placed inside a 0.21 m3 (55 gallons) concrete lined drum, which acts as a radiation shielding, and the other the same container placed in ambient at room temperature. Correlations between the time of temperature occurrence, maximum temperature, the water to cement ratio and salt content were observed

  7. Laboratory Test on Long-Term Deterioration of Cement Soil in Seawater Environment

    Institute of Scientific and Technical Information of China (English)

    杨俊杰; 闫楠; 刘强; 张玥宸

    2016-01-01

    Laboratory tests were conducted to study the effects of curing time, cement ratio and seawater pressure on cement soil deterioration formed at simulative marine soft clay sites. Deterioration depth was determined on the basis of characteristics of penetration resistance and penetration depth curves, and the deterioration depth of cement soil with the cement ratio of 7%, reached 31.8 mm after 720 d. Results of research indicated that deterioration ex-tended quickly under seawater environment and the deterioration depth increased with the prolonging curing time. In addition, the water pressure could speed up deterioration. With the increase of cement content, the strength of cement soil increased obviously. At the same time, the deterioration depth decreased significantly. The concentra-tion of calcium ion in the cement stabilized soil increased with the increase of depth, while that of magnesium ion gradually decreased. The variations were consistent with energy dispersive spectrometer(EDS)analysis results, and the calcium concentration with depth was in a good consistency with strength distribution at long term. The results showed that the deterioration became more serious with the curing time, and it was related to calcium leaching.

  8. False set in aireated cements

    Directory of Open Access Journals (Sweden)

    Vázquez, T.

    1986-06-01

    Full Text Available The influence of aireation on the appearance or elimination of the false setting in industrial portland cements is studied by means of infrared spectroscopy.

    Se estudia por medio de la espectroscopia infrarroja la influencia de la aireación sobre la aparición o eliminación del fraguado, en cemento portland industriales.

  9. Influence of various amount of diatomaceous earth used as cement substitute on mechanical properties of cement paste

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Medved, Igor; Pavlík, Zbyšek; Zahálková, Jana; Rovnaníková, Pavla; Černý, Robert

    2016-06-01

    Active silica containing materials in the sub-micrometer size range are commonly used for modification of strength parameters and durability of cement based composites. In addition, these materials also assist to accelerate cement hydration. In this paper, two types of diatomaceous earths are used as partial cement replacement in composition of cement paste mixtures. For raw binders, basic physical and chemical properties are studied. The chemical composition of tested materials is determined using classical chemical analysis combined with XRD method that allowed assessment of SiO2 amorphous phase content. For all tested mixtures, initial and final setting times are measured. Basic physical and mechanical properties are measured on hardened paste samples cured 28 days in water. Here, bulk density, matrix density, total open porosity, compressive and flexural strength, are measured. Relationship between compressive strength and total open porosity is studied using several empirical models. The obtained results give evidence of high pozzolanic activity of tested diatomite earths. Their application leads to the increase of both initial and final setting times, decrease of compressive strength, and increase of flexural strength.

  10. Pressurization of bioactive bone cement in vitro.

    Science.gov (United States)

    Fujita, H; Iida, H; Kawanabe, K; Okada, Y; Oka, M; Masuda, T; Kitamura, Y; Nakamura, T

    1999-01-01

    We have developed a bioactive bone cement consisting of MgO-CaO-SiO2-P2O5-CaF2 glass-ceramic powder (AW glass-ceramic powder), silica glass powder as an inorganic filler, and bisphenol-a-glycidyl methacrylate (bis-GMA) based resin as an organic matrix. The efficacy of this bioactive bone cement was investigated by evaluating its pressurization in a 5-mm hole and small pores using a simulated acetabular cavity. Two types of acetabular components were used (flanged and unflanged sockets) and a commercially available polymethylmethacrylate (PMMA) bone cement (CMW 1 Radiopaque Bone Cement) was selected as a comparative control. Bioactive bone cement exerted greater intrusion volume in 5-mm holes than PMMA bone cement in both the flanged and unflanged sockets 10 minutes after pressurization (p anchor holes than PMMA bone cement.

  11. Leaching of tritium from a cement composite

    International Nuclear Information System (INIS)

    Leaching of tritium from cement composites into an aqueous phase has been studied to evaluate the safety of incorporation of the tritiated liquid waste into cement. Leaching tests were performed by the method recommended by the International Atomic Energy Agency. The Leaching fraction was measured as functions of waste-cement ratio (Wa/C), temperature of leachant and curing time. The tritium leachability of cement in the long term test follows the order: alumina cement portland cement slag cement. The fraction of tritium leached increases with increasing Wa/C and temperature and decreasing curing period. A deionized water as a leachant gives a slightly higher leachability than synthetic sea water. The amount leached of tritium from a 200 l drum size specimen was estimated on the basis of the above results. (author)

  12. Understanding cement mechanical behavior in SAGD wells

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J.; Zahacy, T. A. [C-FER Technologies (Canada)

    2011-07-01

    In the heavy oil industry, the steam assisted gravity drainage process is often used to enhance oil recovery but it can cause cracks in the cement sheath. These cracks are the result of high steam temperatures and thermal expansion. In order to mitigate this risk, improved well designs are required. The aim of this paper is to present the mechanical behavior of the cement sheath during the heating phase. An analysis of the impact of design and operating parameters was conducted through thermal hydraulic and thermal mechanical analyses to assess cement integrity. These analyses were then performed on an example of an SAGD project in the southern part of the Athabasca oilsands region to assess the performance of the cement sheath. Results showed that potential damage to the cement can be reduced by slow heating and a lower Young's modulus cement blend. This paper makes recommendations for optimizing cement design in thermal recovery wells.

  13. Mesoscale texture of cement hydrates.

    Science.gov (United States)

    Ioannidou, Katerina; Krakowiak, Konrad J; Bauchy, Mathieu; Hoover, Christian G; Masoero, Enrico; Yip, Sidney; Ulm, Franz-Josef; Levitz, Pierre; Pellenq, Roland J-M; Del Gado, Emanuela

    2016-02-23

    Strength and other mechanical properties of cement and concrete rely upon the formation of calcium-silicate-hydrates (C-S-H) during cement hydration. Controlling structure and properties of the C-S-H phase is a challenge, due to the complexity of this hydration product and of the mechanisms that drive its precipitation from the ionic solution upon dissolution of cement grains in water. Departing from traditional models mostly focused on length scales above the micrometer, recent research addressed the molecular structure of C-S-H. However, small-angle neutron scattering, electron-microscopy imaging, and nanoindentation experiments suggest that its mesoscale organization, extending over hundreds of nanometers, may be more important. Here we unveil the C-S-H mesoscale texture, a crucial step to connect the fundamental scales to the macroscale of engineering properties. We use simulations that combine information of the nanoscale building units of C-S-H and their effective interactions, obtained from atomistic simulations and experiments, into a statistical physics framework for aggregating nanoparticles. We compute small-angle scattering intensities, pore size distributions, specific surface area, local densities, indentation modulus, and hardness of the material, providing quantitative understanding of different experimental investigations. Our results provide insight into how the heterogeneities developed during the early stages of hydration persist in the structure of C-S-H and impact the mechanical performance of the hardened cement paste. Unraveling such links in cement hydrates can be groundbreaking and controlling them can be the key to smarter mix designs of cementitious materials. PMID:26858450

  14. Prediction of zeolite-cement-sand unconfined compressive strength using polynomial neural network

    Science.gov (United States)

    MolaAbasi, H.; Shooshpasha, I.

    2016-04-01

    The improvement of local soils with cement and zeolite can provide great benefits, including strengthening slopes in slope stability problems, stabilizing problematic soils and preventing soil liquefaction. Recently, dosage methodologies are being developed for improved soils based on a rational criterion as it exists in concrete technology. There are numerous earlier studies showing the possibility of relating Unconfined Compressive Strength (UCS) and Cemented sand (CS) parameters (voids/cement ratio) as a power function fits. Taking into account the fact that the existing equations are incapable of estimating UCS for zeolite cemented sand mixture (ZCS) well, artificial intelligence methods are used for forecasting them. Polynomial-type neural network is applied to estimate the UCS from more simply determined index properties such as zeolite and cement content, porosity as well as curing time. In order to assess the merits of the proposed approach, a total number of 216 unconfined compressive tests have been done. A comparison is carried out between the experimentally measured UCS with the predictions in order to evaluate the performance of the current method. The results demonstrate that generalized polynomial-type neural network has a great ability for prediction of the UCS. At the end sensitivity analysis of the polynomial model is applied to study the influence of input parameters on model output. The sensitivity analysis reveals that cement and zeolite content have significant influence on predicting UCS.

  15. Cement with silica fume and granulated blast-furnace slag: strength behavior and hydration

    Directory of Open Access Journals (Sweden)

    Bonavetti, V. L.

    2014-09-01

    Full Text Available This paper analyses the influence of portland cement replacement by silica fume (up to 10% and/or granulated blast furnace slag (up to 70% on the hydration cement (XRD, heat of hydration, non evaporable water content and calcium hydroxide content curing under sealed conditions and their effect on the mechanical strength. The obtained results indicate that binary cements containing silica fume and ternary cements there was a significant increase of hydration rate at early age. At later ages, most of studied cements have an equivalent or greater strength that those obtained in the plain portland cement.En este trabajo se analiza la influencia de la incorporación al cemento portland de humo de sílice (hasta 10% y/o escoria granulada de alto horno (hasta 70% sobre la hidratación (DRX, calor de hidratación, contenido de agua no evaporable y de hidróxido de calcio, bajo condiciones de curado sellado y su incidencia sobre la resistencia mecánica. Los resultados obtenidos indican que en los cementos binarios con humo de sílice y en los cementos ternarios se produce un importante aumento de la velocidad de hidratación en las primeras edades, mientras que a edades más avanzadas la mayor parte del dominio estudiado alcanza o supera la resistencia obtenida por el cemento portland sin adición.

  16. Effect of Palmyra Palm Leaf Ash on Cement Stabilization of Makurdi Shale

    Directory of Open Access Journals (Sweden)

    Amos Yala IORLIAM

    2012-08-01

    Full Text Available Makurdi Shale was treated with palmyra palm leaf ash (PPLA and cement to assess its suitability as a material in construction of flexible pavement. Classification, Compaction, Consistency, California bearing ratio (CBR and Unconfined compressive strength (UCS tests, were conducted on the shale specimen treated with, cement and PPLA in a combined incremental order of 2% up to 10% of cement and 2% up to 14% of PPLA of dry weight of soil sample respectively. Results of tests showed that Makurdi shale is an A-7-6, high plasticity (CH and high swell potential soil by the American Association of State Highway and Transportation Officials (AASHTO, Unified Soil Classification System (USCS and Nigerian Building and Road Research Institute (NBRRI classification systems respectively. The plasticity index (PI reduced from 30.5% for untreated Makurdi shale to 4% at 10% cement +14% PPLA contents. The maximum soaked CBR and 7 day UCS values of 92% and 1041 kN/m2 were obtained at 10% cement+14 % PPLA contents respectively. From the results, Makurdi shale treated with a combination of 10%cement+14% PPFA with a soaked CBR value of 92 %, 7 day UCS value of 1041 kN/m2 and 82 % value of resistance to loss in strength, satisfied the requirement for sub-base specification. It is therefore recommended for use as sub-base materials in flexible pavement.

  17. Strength of Limestone-based Non-calcined Cement and its Properties

    Institute of Scientific and Technical Information of China (English)

    LIN Zongshou; ZHAO Qian

    2009-01-01

    A new type of cement was prepared with ground limestone powder,blastfurnace slag,steel slag and gypsum without calcination.The fraction of ground limestone powder in the cement was as high as 40 wt%-60 wt%without Portland clinker.All of its physical properties can meet the requirements of masonry cement standards.The impact of limestone content on physical properties of the cement and determined its impact on law was investigated.The steel slag can excit the aquation activity of this cement effectively,and the influence of its quantity on the strength of the materials was studied,which shows that the optimum quantity of mixing is 10%.By way of changing the different content of the lime stone by quartzy sample,the law of the compression strength and the PH value was determined,confirming that the lime stone can promote the early aquation of the slag and improve the early strength.The main hydration product of this cement is calcium aluminate hydrate, ettringite and calcium silicate hydrate,as indicated by XRD and SEM analysis.

  18. Advanced technologies of production of cemented carbides and composite materials based on them

    International Nuclear Information System (INIS)

    The paper presents new technological processes of production of W, WC and (Ti, W)C powders, cemented carbides having a controlled carbon content, high-strength nonmagnetic nickel-bonded cemented carbides, cemented carbide-based composites having a wear-resistant antifriction working layer as well as processes of regeneration of cemented carbide waste. It is shown that these technological processes permit radical changes in the production of carbide powders and products of VK, TK, VN and KKhN cemented carbides. The processes of cemented carbide production become ecologically acceptable and free of carbon black, the use of cumbersome mixers is excluded, the power expenditure is reduced and the efficiency of labor increases. It becomes possible to control precisely the carbon content within a two-phase region -carbide-metal. A high wear resistance of parts of friction couples which are lubricated with water, benzine, kerosene, diesel fuel and other low-viscosity liquids, is ensured with increased strength and shock resistance. (author)

  19. Compound soil-tyre chips modified by cement as a road construction material

    Directory of Open Access Journals (Sweden)

    Panu Promputthangkoon

    2013-10-01

    Full Text Available This research attempts to overcome the two problems of low-quality soil and a growing number of discarded tyres bymixing low-CBR soil with recycled tyre chips. The compound soil-tyre chips was then stabilised by Portland cement with theaim of using them as a new material in road construction in order to reduce the occurrence of shrinkage cracks. To achievethe purposes of this research three standard geotechnical testing programmes were employed: (1 modified compaction tests,(2 California Bearing Ratio tests (CBR, and (3 unconfined compression tests. The modified compaction test results provedthat for the mixtures having very low tyre chips and cement content, the behaviour is very complex. It was also observed thatthe greater the percentage of rubber added the lower the global density. However, this is predictable as the specific gravityof the rubber is much lower than that of the soil. For the relationship between the optimum moisture content (OMC and thecement content, it was observed that there is no clear pattern.For the specimens having no cement added, the CBR for unsoaked specimens was observed to be greater than that forsoaked specimens. However, when the cement was introduced the CBR test showed that the resistance to penetration for thesoaked specimens was significantly greater, indicating the effects of cement added on the strength. In addition, it was foundthat the CBR values for both soaked and unsoaked specimens gradually increased with the increase of cement content.Lastly, the unconfined compressive strength progressively increased with the increased percentage of cement.

  20. Physical and geotechnical properties of cement-treated clayey soil using silica nanoparticles: An experimental study

    Science.gov (United States)

    Ghasabkolaei, N.; Janalizadeh, A.; Jahanshahi, M.; Roshan, N.; Ghasemi, Seiyed E.

    2016-05-01

    This study investigates the use of nanosilica to improve geotechnical characteristics of cement-treated clayey soil from the coastal area of the eastern Caspian Sea in the Golestan province, Iran. Atterberg limits, unconfined compressive strength, and California bearing ratio (CBR) tests were performed to investigate the soil plastic and strength parameters. The specimens were prepared by mixing soil with 9% cement and various contents of nanosilica. An ultrasonic bath device was used to disperse nanosilica in water. The addition of nanosilica enhanced the strength parameters of the clayey soil. Moreover, a nanosilica percentage of 1.5% by weight of cement improved the compressive strength of the cement-treated clay up to 38%, at age of 28 days. A scanning electron microscope (SEM) and an atomic force microscope (AFM) were used to evaluate specimen morphology. SEM and AFM results confirm the experimental ones. Therefore, nanosilica can be employed for soil improvement in geotechnical engineering.

  1. Utilization of washed MSWI fly ash as partial cement substitute with the addition of dithiocarbamic chelate.

    Science.gov (United States)

    Gao, Xingbao; Wang, Wei; Ye, Tunmin; Wang, Feng; Lan, Yuxin

    2008-07-01

    The management of the big amount of fly ash as hazardous waste from the municipal solid waste incinerator (MSWI) has encountered many problems in China. In this study, a feasibility research on MSWI fly ash utilization as partial cement substitute in cement mortars was therefore carried out. MSWI fly ash was subjected to washing process to reduce its chlorine content (from 10.16% to 1.28%). Consequently, it was used in cement mortars. Ten percent and 20% replacement of cement by washed ash showed acceptable strength properties. In TCLP and 180-day monolithic tests, the mortars with washed ash presented a little stronger heavy metal leachability, but this fell to the blank level (mortar without washed ash) with the addition of 0.25% chelate. Therefore, this method is proposed as an environment-friendly technology to achieve a satisfactory solution for MSWI fly ash management.

  2. Performance of Periwinkle Shell Ash Blended Cement Concrete Exposed to Magnesium Sulphate

    Directory of Open Access Journals (Sweden)

    Umoh A.A.

    2013-01-01

    Full Text Available The study examined the compressive strength of periwinkle shell ash (PSA blended cement concrete in magnesium sulphate medium. Specimens were prepared from designed characteristics strength of 25 MPa. The cement replacement with PSA ranged between 0 and 40% by volume. A total of 180 cube specimens were cast and cured in water. At 28 days curing, 45 specimens each were transferred into magnesium sulphate of 1%, 3%, and 5% solution, while others were continuously cured in water and tested at 62, 92, and 152 days. The results revealed a higher loss in compressive strength with the control mix, and that it increases with increased in MgSO4 concentration and exposure period, whereas, the attack on the PSA blended cement concrete was less and the least value recorded by 10% PSA content. Therefore, the study concluded that the optimum percentage replacement of cement with 10% PSA could mitigate magnesium sulphate attack.

  3. Preparation and Properties of a New Composite of Epoxy Emulsion(EEM)Modified Cement

    Institute of Scientific and Technical Information of China (English)

    XIAO Liguang; JIN Yujie; GU Lixia

    2009-01-01

    High performance cement based composite materials was prepared by adding epoxy emulsion.The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory.This epoxy emulsion has advantages over other emulsion,such as dehydrated slightly,and well film formation abilities.The mechanical properties, corruptness resistance and structure of ep-oxy emulsion modified cement mortars were studied.Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength.The corruptness resistance of all modified mortars is better than the unmodified mortar.The polymer film forms the bridge phases between the matrix and the aggregate regions,and forms a three-dimension structure in the cement hydration system,which improves the mechanical properties of modified mortars.

  4. Utilization of Industrial Borax Wastes (BW) for Portland Cement Production

    OpenAIRE

    ELBEYLİ, İffet YAKAR

    2004-01-01

    Industrial borax wastes (BWs) are formed as solid waste during the production of borax from tincal [Na2B4O5(OH)4.8H2O] in Bandırma, Turkey. These wastes cause different environmental problems and lead to economic losses because of high boron oxide (B2O3) content. The primary aim of this study is the removal of B2O3 from BWs and the second aim is the usage of BWs with low boron content in cement as an additive material. For this purpose, the BW was treated with water for removal of b...

  5. Sealing of cracks in cement using microencapsulated sodium silicate

    Science.gov (United States)

    Giannaros, P.; Kanellopoulos, A.; Al-Tabbaa, A.

    2016-08-01

    Cement-based materials possess an inherent autogenous self-healing capability allowing them to seal, and potentially heal, microcracks. This can be improved through the addition of microencapsulated healing agents for autonomic self-healing. The fundamental principle of this self-healing mechanism is that when cracks propagate in the cementitious matrix, they rupture the dispersed capsules and their content (cargo material) is released into the crack volume. Various healing agents have been explored in the literature for their efficacy to recover mechanical and durability properties in cementitious materials. In these materials, the healing agents are most commonly encapsulated in macrocontainers (e.g. glass tubes or capsules) and placed into the material. In this work, microencapsulated sodium silicate in both liquid and solid form was added to cement specimens. Sodium silicate reacts with the calcium hydroxide in hydrated cement paste to form calcium-silicate-hydrate gel that fills cracks. The effect of microcapsule addition on rheological and mechanical properties of cement is reported. It is observed that the microcapsule addition inhibits compressive strength development in cement and this is observed through a plateau in strength between 28 and 56 days. The improvement in crack-sealing for microcapsule-containing specimens is quantified through sorptivity measurements over a 28 day healing period. After just seven days, the addition of 4% microcapsules resulted in a reduction in sorptivity of up to 45% when compared to specimens without any microcapsule addition. A qualitative description of the reaction between the cargo material and the cementitious matrix is also provided using x-ray diffraction analysis.

  6. Characterization of vapor phase mercury released from concrete processing with baghouse filter dust added cement.

    Science.gov (United States)

    Wang, Jun; Hayes, Josh; Wu, Chang-Yu; Townsend, Timothy; Schert, John; Vinson, Tim; Deliz, Katherine; Bonzongo, Jean-Claude

    2014-02-18

    The fate of mercury (Hg) in cement processing and products has drawn intense attention due to its contribution to the ambient emission inventory. Feeding Hg-loaded coal fly ash to the cement kiln introduces additional Hg into the kiln's baghouse filter dust (BFD), and the practice of replacing 5% of cement with the Hg-loaded BFD by cement plants has recently raised environmental and occupational health concerns. The objective of this study was to determine Hg concentration and speciation in BFD as well as to investigate the release of vapor phase Hg from storing and processing BFD-added cement. The results showed that Hg content in the BFD from different seasons ranged from 0.91-1.44 mg/kg (ppm), with 62-73% as soluble inorganic Hg, while Hg in the other concrete constituents were 1-3 orders of magnitude lower than the BFD. Up to 21% of Hg loss was observed in the time-series study while storing the BFD in the open environment by the end of the seventh day. Real-time monitoring in the bench system indicated that high temperature and moisture can facilitate Hg release at the early stage. Ontario Hydro (OH) traps showed that total Hg emission from BFD is dictated by the air exchange surface area. In the bench simulation of concrete processing, only 0.4-0.5% of Hg escaped from mixing and curing BFD-added cement. A follow-up headspace study did not detect Hg release in the following 7 days. In summary, replacing 5% of cement with the BFD investigated in this study has minimal occupational health concerns for concrete workers, and proper storing and mixing of BFD with cement can minimize Hg emission burden for the cement plant. PMID:24444016

  7. The cement recycling of the earthquake disaster debris by Hachinohe Cement Co., Ltd

    International Nuclear Information System (INIS)

    A tremendous quantity of earthquake disaster debris and tsunami sediment was resulted by the Great East Japan Earthquake on March 11, 2011. Hachinohe Cement Co., Ltd., a Sumitomo Osaka Cement subsidiary, was the first cement industry company to receive and process such waste materials outside of their usual prefecture area, while the company is performing their treatment and recycling services locally in Hachinohe City and Aomori Prefecture. This report provides an explanation about the recycling mechanism of waste materials and by-products in cement manufacturing process, and introduces an example of actual achievements for the disaster debris treatment by utilizing the cement recycling technologies at the Hachinohe Cement Plant. (author)

  8. Utilization of Red Mud as Raw Material in the Production of Field Road Cement

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao; LUO Zhongtao; ZHANG Lei; RONG Hui; YANG Jiujun

    2016-01-01

    The total utilization amount of red mud is limited due to its high content of alkali, heavy metals and naturally occurring radioactive element. In order to rationalize the use of red mud, a typical ifeld road cement using dealkalized red mud (content of alkali lower than 1%) as raw material was ifrstly prepared in this paper. Then, a preliminary research on the radioactivity of the red mud based ifeld road cement has been carried out. For that reason, two samples of raw materials were prepared. One was with ordinary raw materials, as the control group (CG), the other was with 23w % red mud, as the experimental group (EG). The clinkers were acquired by sintering the above two raw materials at 1 400℃. Subsequently, the two types of cement prepared by the above two kinds of clinkers were tested by measuring the normal consistency, setting time, mechanical strength and drying shrinkage. Meanwhile, the hydration products of the two types of cement were examined by XRD analysis at the curing age of 6 hours, 1, 3, 7, and 28 days, respectively. The radioactivity of the two kinds of cement clinkers was then measured by gamma-ray spectrometry. The experimental results indicate that the main mineralogical phases components in the EG ifeld road cement clinkers are C3S, C2S, and C4AF, the 28 days lfexural and compressive strength of the EG ifeld road cement mortars could be up to 8.45 and 53.2 MPa, respectively. The radioactive measuring results of the EG field road cement show that the value of radium equivalent activity index (Raeq) is 254.8 Bq/Kg-1, which is lower than the upper limit.

  9. The detection method of anti-carbonation property of cement based on the quantitative analysis of carbonate content%基于碳酸盐定量分析的水泥石抗碳化性能测试方法

    Institute of Scientific and Technical Information of China (English)

    陈璐圆; 钱春香

    2011-01-01

    针对目前各种碳化深度测量方法的弊端,结合所发明的检测装置,形成了一套新型抗碳化性能测试方法一碳酸盐含量法.试验结果表明,这是一种更加精确的碳化测试方法,不仅能划分完全碳化区和碳化进行区,还不会因受到其它水泥石中性化因素的干扰而影响测量结果.基于试验结果,对比酚酞喷涂法,说明该方法更具有优势,不但原理简单,而且可以测得试件碳化部分全部的碳化产物含量.%Thinking of the disadvantages of all the present testing methods for carbonization depth, the author combined with their invention of the detection devices,and then formed a new anti-carbonation property detection method--method of carbonate content. This is a much more accurater determination of carbonation. For it can not only distinguish the area of carbonation out of carbonation reaction zone, but also won't be affected by other factors which lead to cement neutral. Based on the experiment, we concluded that this method is indeed much better than phenolphthalein spray method. It is simple in principle and easy for operation. What's more,it can measure all of the carbons derived from carbonized parts of the sample.

  10. Drying effect on cement paste porosity at early age observed by NMR methods

    OpenAIRE

    FAURE, Paméla; CARE, Sabine; Magat, Julie; Chaussadent, Thierry

    2012-01-01

    Nuclear Magnetic Resonance (NMR) methods (imaging and relaxation time) allow studying water content and porous network in cementitious materials. Hydration of cement pastes with two water to cement ratios (W/C of 0.4 and 0.45) has been studied under two conditions (with drying or without drying) at early age. The objectives of this study were, firstly to determine the water content and the drying mechanisms with Magnetic Resonance Imaging (MRI) and to validate this result with oven-drying met...

  11. The properties of polymerizable luting cements.

    Science.gov (United States)

    Nicholson, J W; McKenzie, M A

    1999-10-01

    The properties of a polyacid-modified composite resin and two resin-modified luting cements have been studied. The polyacid-modified composite resin had the slowest setting reaction and, in this respect, it did not conform to the current international standard for luting cements. The compressive strength of all of the materials was studied after varying periods of storage from 24 h to 1 year. The polyacid-modified composite resin showed a distinct dip in strength at 1 month in all of the storage media, but otherwise it showed no significant variation with either age or storage medium. The resin-modified glass-ionomers showed variation at 24 h with storage medium (deionized water, 0.9% NaCl or 20 mmol dm(-3) lactic acid), but thereafter they showed little variation, until 1 year, when Vitremer luting showed a significant decline in strength in pure water. However, at 24 h and when stored in water, all of the materials had strengths that easily exceeded the minimum requirement of the current standard (70 MPa). They all took up water on storage, with diffusion coefficients ranging from 1.32 to 17. 19x10(-7) cm2 s(-1). These values were found to depend on whether the specimens were stored in pure water or in physiological saline. However, equilibrium water contents varied only slightly between water and saline. The polyacid-modified composite resin, Dyract-Cem, took up the least water, as well as showing the smallest variation in strength with age. By contrast, it was more difficult to mix than the other materials and the high viscosity of the paste led to the formation of voids and other imperfections in the specimens. PMID:10564431

  12. Effect of graphene on mechanical properties of cement mortars

    Institute of Scientific and Technical Information of China (English)

    曹明莉; 张会霞; 张聪

    2016-01-01

    Functionalized graphene nano-sheets (FGN) of 0.01%−0.05% (mass fraction) were added to produce FGN-cement composites in the form of mortars. Flow properties, mechanical properties and microstructure of the cementitious material were then investigated. The results indicate that the addition of FGN decreases the fluidity slightly and improves mechanical properties of cement-based composites significantly. The highest strength is obtained with FGN content of 0.02% where the flexural strength and compressive strength at 28 days are 12.917 MPa and 52.42 MPa, respectively. Besides, scanning electron micrographs show that FGN can regulate formation of massive compact cross-linking structures and thermo gravimetric analysis indicates that FGN can accelerate the hydration reaction to increase the function of the composite effectively.

  13. Cement mixtures containing copper tailings as an additive: durability properties

    Directory of Open Access Journals (Sweden)

    Obinna Onuaguluchi

    2012-12-01

    Full Text Available The effects of copper tailings as an additive, on some durability properties of cement mixtures were investigated. In each mixture, copper tailings addition levels by mass were 0%, 5% and 10%. Compared to the control samples, copper tailings blended pastes showed superior performance against autoclave expansion while insignificant decreases in sulfate resistance of mortars were observed. Copper tailings increased the water absorption and total permeable voids of concretes slightly. However, the compressive and flexural strengths of blended concretes were higher than those of the control samples. Similarly, improved resistance to acid attack and chloride penetration as the copper tailings content of concretes increased were also observed. Results further showed that the ASTM C 1202 rapid chloride permeability test may not be a valid indicator of chloride migration in mixtures containing conductive copper tailings. These results suggest that copper tailings can potentially enhance the durability properties of cement based materials.

  14. Sulfur Release during Alternative fuels Combustion in Cement Rotary Kilns

    DEFF Research Database (Denmark)

    Cortada Mut, Maria del Mar

    Cement production is an energy-intensive process, whic h has traditionally been dependent on fossil fuels. However, the usage of selected waste, biomass, and by-products with recoverable calorific value, defined as alternative fuels, is increasing and their combustion is mo re challenging compared...... to fossil fuels, due to the lack of experience in handling the different and va rying combustion characteristics caused by different chemical and physical properties, e.g. higher moisture content and larger particle sizes. When full combustion of alternative fuels in the calcin er and/or main burner...... in order to separate the influence of the simultaneous phenomena occurring in the experimental set-up, such as mixing th e fuel with the bed material, heating up of a particle, 5 iii Abstract Cement production is an energy-intensive process, whic h has traditionally been dependent on fossil fuels. However...

  15. Use of alternative fuels in cement manufacture. Effect on clinker and cement characteristics and properties

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    2004-06-01

    Full Text Available This paper compares industrial clinker and cement produced using conventional and alternative fuels (animal meal, tyres or a mixture of the two. The results show no relevant differences in terms of mineralogical composition between the clinker manufactured with alternative fuels and the product obtained using conventional fuel. Clinker produced with alternative fuels at any one factory have a very similar or even lower content in heavy metals than the product manufactured with conventional fuel in the same plant (with the sole exception of Zn when the alternative fuel used is shredded tyres. Mineralogical and morphological analyses reveal no significant differences between the two types of products that can be attributed to the type of fuel used in their manufacture. All six types of cement studied are compliant with the existing legislation as regards both physical and chemical properties. Cement compressive strength is found to be to legal standards regardless of the type of fuel used. Finally, the rheological properties of the cement paste are observed to be unaffected by the type of fuel.

    Se han estudiado clínkeres y cementos obtenidos en procesos industriales que han utilizado combustibles convencionales y combustibles alternativos (harinas cárnicas, neumáticos usados y mezclas de ambos. Los resultados obtenidos han demostrado que los clínkeres fabricados con los combustibles alternativos no presentan diferencias significativas en la composición mineralógica respecto a los obtenidos con combustibles convencionales. Los contenidos de metales pesados en los clínkeres procedentes de la misma fábrica (a excepción de los contenidos en Zn en aquéllos que utilizan neumáticos son muy similares o incluso inferiores a los fabricados con combustibles convencionales. Los análisis mineralógico y morfológico de los clínkeres no evidencian diferencias asignables al tipo de combustible utilizado. Todos los cementos estudiados cumplen

  16. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    OpenAIRE

    Y.C.P RAMANA BABU; B.SAI DOONDI; N. M .V .VAMSI KRISHNA; K.Prasanthi

    2013-01-01

    India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO) and carbon dioxide (CO2) are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green hous...

  17. ROTARY SCREW SYSTEMS IN CEMENT

    OpenAIRE

    Taratuta V. D.; Belokur K. A.; Serga G. V.

    2016-01-01

    The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometr...

  18. Modifications induced by adding natural zeolitic pozzolans to cement paste

    Directory of Open Access Journals (Sweden)

    Blanco-Varela, M. T.

    2005-12-01

    Full Text Available Volcanic pozzolans owe their pozzolanic activity chiefly to the presence of vitreous or zeolitic material rich in SiO2, and Al20y compounds that react with the portlandite produced during cement hydration to generate amorphous gels with cementitious properties. The present study analyzes the modifications taking place in the composition, structure and micro structure of the hydra ted cement paste when 20% of the cement by weight is replaced by two finely ground zeolitic rocks from Cuban deposits. Hydrated cement pastes were prepared with a CEM I35 cement, as well as with mixes of the cement and two Cuban zeolitic rocks (20% by weight. After eight months of hydration, the pastes were characterized -mineralogically, chemically and microstructurally- with XRD, FTIR, 29Si and 27Al MAS NMR, DTA/TG, back scattered electron microscopy and mercury porosimetry techniques. The replacement of 20% by weight of the cement with two finely ground zeolitic rocks significantly modified the composition, structure, quantity and microstructure of the hydrated cement paste reaction product. The C-S-H gel formed in these pastes differed in quantity, which was larger, and composition from the original cement gel. Moreover, the gel formed in addition-free cement had a higher Ca and a lower Al content and shorter silicate chains than the C-S-H product formed in the pastes made with zeolitic rocks. Finally, the pastes with pozzolan additions had fewer and smaller pores.

    La actividad de las puzolanas de origen volcánico procede fundamentalmente de la presencia de material vitreo o zeolítico rico en SiO2 y Al2Oy que son los que reaccionan con la portlandita producida en la hidratación del cemento generando geles amorfos con propiedades cementantes. El objetivo del presente trabajo es estudiar las modificaciones que produce la sustitución del 20% en peso de cemento por dos

  19. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    Y.C.P RAMANA BABU

    2013-04-01

    Full Text Available India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO and carbon dioxide (CO2 are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green house gases (i.e., CO and CO2 and also saves lot of money in the long run process. A small amount of these gases in environment can cause major problems over time. Use of white cement in composite pavement design where there is heavy traffic loads are acting as well as number of vehicles are more such as junctions, bus stops, check posts etc., can perform better and acts asenvironment friendly. Its light colour reflects more than bituminous pavement so that it can be easily identified and avoid accidents to some extent. White cement helps to lower the average bus stop, junction temperature providing comfort to the people because it has high solar reflectance there by reducing “urban heat island” effect. In addition to this it has some more advantages which increase the sustainability, durability and workability of the pavements.

  20. Effect of Selected Alternative Fuels and Raw Materials on the Cement Clinker Quality

    Directory of Open Access Journals (Sweden)

    Strigáč Július

    2015-11-01

    Full Text Available The article deals with the study of the effects of alternative fuels and raw materials on the cement clinker quality. The clinker quality was expressed by the content of two principal minerals alite C3S and belite C2S. The additions of alternative fuels ashes and raw materials, in principle, always increased the belite content and conversely reduced the amount of alite. The alternative fuels with high ash content were used such as the meat-bone meal, sewage sludge from sewage treatment plants and paper sludge and the used alternative raw materials were metallurgical slags - granulated blastfurnace slag, air cooled blastfurnace slag and demetallized steel slag, fluidized bed combustion fly ash and waste glass. Meat-bone meal, sewage sludge from sewage treatment plants and paper sludge were evaluated as moderately suitable alternative fuels which can be added in the amounts of 2.8 wt. % addition of meat-bone meals ash, 3.64 wt. % addition of sewage sludge ash and 3.8 wt. % addition of paper sludge ash to the cement raw mixture. Demetallised steel slag is suitable for production of special sulphate resistant cement clinker for CEM I –SR cement with addition up to 5 wt. %. Granulated blastfurnace slag is a suitable alternative raw material with addition 4 wt. %. Air cooled blastfurnace slag is a suitable alternative raw material with addition 4.2 wt. %. Waste glass is not very appropriate alternative raw material with addition only 1.16 wt. %. Fluidized bed combustion fly ash appears not to be equally appropriate alternative raw material for cement clinker burning with less potential utilization in the cement industry and with addition 3.41 wt. %, which forms undesired anhydrite CaSO4 in the cement clinker.

  1. Permeability Changes on Wellbore Cement Fractures Modified by Geochemical and Geomechanical Processes

    Science.gov (United States)

    Rod, K. A.; Um, W.

    2015-12-01

    Experimental studies were conducted using batch reactors, X-ray microtomography (XMT), and computational fluid dynamics (CFD) modeling to determine changes in cement fracture surfaces, fluid flow pathways and permeability, and cement fracture propagation with geochemical and geomechanical processes. Portland cement-basalt interface sample with artificial fractures was prepared to study the geochemical and geomechanical effects on the integrity of wellbores containing defects caused by subsurface activities. Cement-basalt interface sample was subjected to mechanical stress at 2.7 MPa before the chemical reaction. CFD modeling was performed to simulate flow of supercritical CO2 within the fractures before and after the application of mechanical stress. The model results highlighted the complex flow characteristics within the fracture and also changes in flow patterns due to application of geomechanical stress. The CFD model predicted ~45% increase in permeability after the application of geomechanical force, which increases the fracture aperture. The same sample was reacted with CO2-saturated groundwater with impurity H2S (1 wt.%) at 50°C and 10 MPa for 3 to 3.5 months under static conditions. XMT provided three-dimensional (3-D) visualization of the opening and interconnection of cement fractures due to mechanical stress. Even after a 3.5-month reaction with CO2-H2S-saturated groundwater at 50°C and 10 MPa, CaCO3 (s) precipitation occurred more extensively within the cement fracture rather than along the cement-basalt interfaces. Micro X-ray diffraction analysis also showed that major cement carbonation products of CO2-saturated groundwater reacting with impurity H2S were calcite, aragonite, and vaterite, consistent with cement carbonation by pure CO2-saturated groundwater, while pyrite was not identified due to low H2S content. The experimental results imply that the wellbore cement with fractures is likely to be healed during exposure to CO2-saturated

  2. Scanning electron microscopy analysis of dental cements

    Directory of Open Access Journals (Sweden)

    Radosavljević Radivoje D.

    2009-01-01

    Full Text Available The aim of this study was to compare in vitro the characteristics of different types of luting cements (zinc phosphate, glass-ionomer and resin based composite cement using scanning electron microscopy (SEM analysis and microleakage for the quality range of materials. Dental cements were mixed in accordance with the manufacturer's instructions and formed with posts in dental root canals of extracted teeth. The quality of cement was determined by SEM observation on horizontal sectioned roots with fixed posts according to specific pore and marginal gap diameter. The microleakage was measured on specimens immersed in Lofler (methylene blue solution. The mean values of the maximal diameter of pores, marginal gaps and microleakage of conventional cements are remarkably larger in comparison with composite luting agents. In conclusion, the quality and efficiency of composite luting agents in comparison with conventional cements are more successful in protecting the interior of tooth from penetration of oral fluids, bacteria and bacterial toxins into unprotected dentine.

  3. Detailed characterization of current North American portland cements and clinkers and the implications for the durability of modern concrete

    Science.gov (United States)

    Arjunan, P.

    The current study has been undertaken with a view to rationalize the relation between the cement characteristics and concrete properties with the fresh set of data collected from the North American portland cements. The important chemical and physical characteristics of the cement discussed are (a) chemical analysis, (b) phase calculations, (c) various particle characterizations and (d) rheological properties. The important concrete properties discussed are (a) alkali silica reactivity, (b) sulfate attack, (c) delayed ettringite formation (d) chloride ion permeability and (e) compressive strength. Relationship between the cement characteristics and concrete durability was determined using regression methods. The heat of hydration was mainly influenced by the variation in C 3A, SO3, equivalent Na2O contents, and fineness of portland cements. When there was no variation in C3A, SO 3, and fineness, the hydration kinetics of the cement was mainly controlled by the silicate phase hydration. The 7-day hydration was negatively correlated to C2S or C4AF content. As the C2S or C 4AF content increased, the 7-day heat of hydration decreased. C 3S content showed a positive correlation to 1 and 7-day heats of hydration, but significant negative correlation to 14 and 28-day hydration. Equivalent alkalis showed a strong positive correlation to ASR at 2 weeks. SO3 content of portland cement also showed a positive correlation to ASR expansion. A strong negative correlation was observed between C4AF content of portland cement and sulfate attack expansion at 4 and 6 months of exposure. The correlation to sulfate attack was stronger when the ratios of C3A/C4AF were taken into account. C3A content exhibited a negative correlation to chloride ion permeability. This correlation decreased as the curing period increased. SO 3 content also exhibited a negative correlation to the chloride ion permeability. Only alkalis showed a strong negative correlation to the compressive strength after 3

  4. Effect of W/C Ratio on Durability and Porosity in Cement Mortar with Constant Cement Amount

    Directory of Open Access Journals (Sweden)

    Yun-Yong Kim

    2014-01-01

    Full Text Available Water is often added to concrete placing for easy workability and finishability in construction site. The additional mixing water can help easy mixing and workability but causes increased porosity, which yields degradation of durability and structural performances. In this paper, cement mortar samples with 0.45 of W/C (water to cement ratio are prepared for control case and durability performances are evaluated with additional water from 0.45 to 0.60 of W/C. Several durability tests including strength, chloride diffusion, air permeability, saturation, and moisture diffusion are performed, and they are analyzed with changed porosity. The changing ratios and patterns of durability performance are evaluated considering pore size distribution, total porosity, and additional water content.

  5. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    OpenAIRE

    Konstantin Sobolev

    2003-01-01

    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecologi...

  6. Global Cement Industry: Competitive and Institutional Dimensions

    OpenAIRE

    Selim, Tarek; Salem, Ahmed

    2010-01-01

    The cement industry is a capital intensive, energy consuming, and vital industry for sustaining infrastructure of nations. The international cement market –while constituting a small share of world industry output—has been growing at an increasing rate relative to local production in recent years. Attempts to protect the environment in developed countries –especially Europe—have caused cement production plants to shift to countries with less stringent environmental regulations. Along with con...

  7. Characterization of cement composites with mineral additives

    OpenAIRE

    Korat, Lidija

    2015-01-01

    Doctoral dissertation is aimed at characterizing cement composites with mineral additives representing the industrial waste material (fly ash, granulated blast furnace slag and biomass fly ash). Their usage can replace high cement shares in individual cases and is, however, favourable due to the production costs reduction and environment burden decrease, including the decreased emission of greenhouse gases as well as lower energy use. Cement composites (in fresh or hardened state)...

  8. Premixed calcium silicate cement for endodontic applications

    OpenAIRE

    Persson, Cecilia; Engqvist, Håkan

    2011-01-01

    Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and am...

  9. Water dynamics in glass ionomer cements

    Science.gov (United States)

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.

    2016-07-01

    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  10. 铝酸三钙的含量对含石灰石粉水泥浆体碳硫硅酸钙形成的影响%Effect of Tricalcium Aluminate Content on Thaumasite Formation of Cement-limestone Powder Pastes

    Institute of Scientific and Technical Information of China (English)

    李相国; 何超; 罗忠涛; 马保国; 田振; 谭洪波

    2013-01-01

    通过X 射线衍射分析、扫描电子显微镜、Fourier变换红外光谱分析及激光Raman光谱分析等技术,研究了C3A和C3S的比例对掺30%石灰石粉水泥浆体经5% MgSO4溶液侵蚀后碳硫硅酸钙形成的影响及机理。结果表明:C3A的存在及相对含量并不是碳硫硅酸钙形成的必备条件,硫酸盐、碳酸盐会与水泥水化产物CSH凝胶直接发生反应,导致水泥水化产物CSH凝胶解体,生成无任何胶结性的碳硫硅酸钙,无需或者只需少许铝相参与反应,而且掺少量或不掺铝相的腐蚀试样中主要含有碳硫硅酸钙、钙矾石和石膏。%The effect of aluminum-bearing phase content on the thaumasite formation of cement pastes containing limestone powder was investigated. The specimens were the mixture of different ratios of tricalcium aluminate to tricalcium silicate with limestone powder of 30% and cured in 5% MgSO4 solution. The formation of thaumasite was analyzed by X-ray diffraction, scanning electron microscopy, laser-Raman spectroscopy and Fourier transform infrared spectroscopy, respectively. The results show that the C3A con-tent is not one of the necessary conditions for the thaumasite formation. The thaumasite formation is the direct result from calcium silicate hydrate reacting with appropriate carbonate, sulfate, Ca2+ ions and excess water. Moreover, the deteriorated products in specimen with a little or no aluminum mainly contain thaumasite, ettringite and gypsum.

  11. Beneficial use of a cell coupling rheometry, conductimetry, and calorimetry to investigate the early age hydration of calcium sulfo-aluminate cement

    International Nuclear Information System (INIS)

    A specific cell was designed to monitor simultaneously the evolution of the viscoelastic properties, electrical conductivity, and temperature of a cement paste with ongoing hydration. Hydration of calcium sulfo-aluminate cement by demineralized water or by a borated solution was then investigated as an example. Borate anions acted as set retarders but to a smaller extent than with ordinary Portland cement. The delay in cement hydration resulted from the precipitation of an amorphous or poorly crystallized calcium borate, which also caused a rapid stiffening (and thus a loss of workability) of the paste after mixing. The gypsum content of the CSA cement was shown to play a key role in the control of the cement reactivity. (authors)

  12. Effect of gypsum content on sulfoaluminate mortars stability

    OpenAIRE

    DESBOIS, Tiffany; Le Roy, Robert; PAVOINE, Alexandre; PLATRET, Gérard; FERAILLE-FRESNET, Adélaïde; ALAOUI, Amina

    2010-01-01

    Calcium sulfoaluminate clinker is one of the most promising cements that would lower the greenhouse gas effect accompanying cement production. This article examines the effect of gypsum content on the dimensional stability of sulfoaluminate mortars. Mechanical properties as chemical evolution are studied. Our results show that the mortar with the greatest gypsum content expands without a decrease of its mechanical properties when it is cured in water. Two hypotheses about the mortars hydratio...

  13. Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment.

    Science.gov (United States)

    Sahafi, A; Benetti, A R; Flury, S; Peutzfeldt, A

    2015-01-01

    The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc] and a self-etch adhesive resin cement [Panavia F2.0]) were used. After removal of the crowns of 360 extracted premolars, canines, or incisors, the root canals were prepared with a parallel-sided drill system to three different final diameters. Half the posts did not receive any pretreatment. The other half received tribochemical silicate coating according to the manufacturer's instructions. Posts were then luted in the prepared root canals (n=30 per group). Following water storage at 37°C for seven days, retention of the posts was determined by the pull-out method. Irrespective of the luting cement, pretreatment with tribochemical silicate coating significantly increased retention of the posts. Increased cement film thickness resulted in decreased retention of untreated posts and of pretreated posts luted with zinc phosphate cement. Increased cement film thickness had no influence on retention of pretreated posts luted with resin cement. Thus, retention of the posts was influenced by the type of luting cement, by the cement film thickness, and by the post pretreatment. PMID:25764045

  14. The mechanical effects of different levels of cement penetration at the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The mechanical effects of varying the depth of cement penetration in the cement-bone interface were investigated using finite element analysis (FEA) and validated using companion experimental data. Two FEA models of the cement-bone interface were created from micro-computed tomography data and the p

  15. The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements

    Directory of Open Access Journals (Sweden)

    Atiyeh Feiz

    2013-01-01

    Conclusion: Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia and the self-etch self-adhesive (Maxcem Elite resin cements.

  16. Case Study of the California Cement Industry

    OpenAIRE

    Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn; Friedmann, Rafael

    2005-01-01

    California is the largest cement producing state in the U.S., accounting for between 10 percent and 15 percent of U.S. cement production and cement industry employment. The cement industry in California consists of 31 sites that consume large amounts of energy, annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3 million tons of coal, 0.25 tons of coke, and smaller amounts of waste materials, including tires. The case study summarized in this paper focused on providi...

  17. Immobilisation of radwaste in cement based matrices

    International Nuclear Information System (INIS)

    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 U6+ and iodine (I-, IO3-) 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 CO2 in groundwaters as dissolution media for cements are reported. (author)

  18. Acoustic evaluation of cementing quality using obliquely incident ultrasonic signals

    Institute of Scientific and Technical Information of China (English)

    Duan Wen-Xing; Qiao Wen-Xiao; Che Xiao-Hua; Xie Hui

    2014-01-01

    Ultrasonic cement bond logging is a widely used method for evaluating cementing quality. Conventional ultrasonic cement bond logging uses vertical incidence and cannot accurately evaluate lightweight cement bonding. Oblique incidence is a new technology for evaluating cement quality with improved accuracy for lightweight cements. In this study, we simulated models of acoustic impedance of cement and cementing quality using ultrasonic oblique incidence, and we obtained the relation between cementing quality, acoustic impedance of cement, and the acoustic attenuation coeffi cient of the A0-mode and S0-mode Lamb waves. Then, we simulated models of different cement thickness and we obtained the relation between cement thickness and the time difference of the arrival between the A0 and A0′ modes.

  19. Fiber reinforced cement boards made from recycled newsprint paper

    International Nuclear Information System (INIS)

    Highlights: → Recycled newsprint paper (RNP) fibers had significant effects on the physicomechanical properties of the boards. → Addition of 5% CaCl2 had the most significant positive effects on all properties of the boards. → Increase in RNP content had adverse effect on the samples and resulted in lower than expected strength properties. → The optimum condition was obtained when the RNP and CaCl2 contents were 10% and 5% by weight, respectively. - Abstract: In this study, the reinforcing effect of recycled newsprint paper (RNP) in cement boards has been investigated. The experimental design consisted of two variable factors namely RNP and calcium chloride (CaCl2). In the sample preparation, boards with density of 0.7 kg/m3 were manufactured using fiber/cement ratios of 10:90, 15:85 and 20:80 by weight and 3% and 5% CaCl2 as accelerator. At least four boards (replications) were fabricated for each treatment, and the mechanical and physical properties of the boards were evaluated. The statistical analysis showed that the differences between the mean values of the RNP and CaCl2 contents among each of the groups (treatments) compared were significant. Test results showed that addition of CaCl2 tends to enhance both the mechanical and physical properties of the boards. All properties of the boards were improved when the CaCl2 content was increased from 3% to 5%. The rupture and elasticity moduli of the boards decreased with an increase in the RNP content, and the maximum values were obtained at RNP loading of 10%. The results also showed that as the fiber content was increased, significant increased in water absorption and thickness swelling occurred. Increasing RNP fiber content from 10% to 20% reduced both the mechanical and physical properties considerably. The optimum condition was obtained when the RNP and CaCl2 contents were 10% and 5%, respectively.

  20. Effects of Carbon Nanotubes on Mechanical and 2D-3D Microstructure Properties of Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    LIU Qiaoling; SUN Wei; JIANG Hao; WANG Caihui

    2014-01-01

    To study the influence of multi-wall carbon nanotubes (MWCNTs) on the mechanical and microstructural properties of cementitious composites, 0.00, 0.02, 0.08, 0.10, and 0.20 wt% of multi-wall carbon nanotubes were added into cement mortar, in which the cement-sand ratio was 1:1.5. The flexural and compressive strengths of cement mortar at the age of 3, 7, 28 and 90 d and the fracture performance at the age of 28 d were determined, its 2D micrograph was tested by means of SEM, and the 3D defects distribution was firstly determined with or without CNTs by means of XCT (X-ray computerized tomography). The results showed that 0.08 wt% of CNTs improved the compressive strength and flexural strength by 18% and 19%, respectively, and a significant improvement of its fracture property was observed. Moreover lower addition of carbon nanotubes to cement mortars can improve its microstructure and decrease the defects significantly compared to the cement mortar without CNTs. With the increase of the content of CNTs, the mechanical properties of cement mortars presented to be declined largely due to the agglomeration of CNTs.

  1. DSC and TG Analysis of a Blended Binder Based on Waste Ceramic Powder and Portland Cement

    Science.gov (United States)

    Pavlík, Zbyšek; Trník, Anton; Kulovaná, Tereza; Scheinherrová, Lenka; Rahhal, Viviana; Irassar, Edgardo; Černý, Robert

    2016-03-01

    Cement industry belongs to the business sectors characteristic by high energy consumption and high {CO}2 generation. Therefore, any replacement of cement in concrete by waste materials can lead to immediate environmental benefits. In this paper, a possible use of waste ceramic powder in blended binders is studied. At first, the chemical composition of Portland cement and ceramic powder is analyzed using the X-ray fluorescence method. Then, thermal and mechanical characterization of hydrated blended binders containing up to 24 % ceramic is carried out within the time period of 2 days to 28 days. The differential scanning calorimetry and thermogravimetry measurements are performed in the temperature range of 25°C to 1000°C in an argon atmosphere. The measurement of compressive strength is done according to the European standards for cement mortars. The thermal analysis results in the identification of temperature and quantification of enthalpy and mass changes related to the liberation of physically bound water, calcium-silicate-hydrates dehydration and portlandite, vaterite and calcite decomposition. The portlandite content is found to decrease with time for all blends which provides the evidence of the pozzolanic activity of ceramic powder even within the limited monitoring time of 28 days. Taking into account the favorable results obtained in the measurement of compressive strength, it can be concluded that the applied waste ceramic powder can be successfully used as a supplementary cementing material to Portland cement in an amount of up to 24 mass%.

  2. Immobilization of Co (Ⅱ) Ions in Cement Pastes and Their Effects on the Hydration Characteristics

    Institute of Scientific and Technical Information of China (English)

    Eisa Hekal; Essam Kishar; Wafaa Hegazi; Maha Mohamed

    2011-01-01

    The immobilization of Co (Ⅱ) in various cement matrices was investigated by using the solidification/stabilization (S/S) technique. The different cement pastes used in this study were ordinary Portland cement in absence and presence of water reducing- and water repelling-admixtures as well as blended cement with kaolin. Two ratios of Co (Ⅱ) were used (0.5% and 1.0% by weight of the solid binder). The hydration characteristics of the used cement pastes were tested uia the determination of the combined water content, phase composition and compressive strength at different time intervals up to 180 d. The degree of immobilization of the added heavy metal ions was evaluated by determining the leached ion concentration after time intervals extended up to 180 d. The leachability experiments were carried out by using two modes: the static and the semi-dynamic leaching processes. It was noticed that the concentration of the leached Co2+ ions in the static mode of leachability was lower than the solubility of its hydroxide in all the investigated cement pastes.

  3. Applied technique of the cemented fill with fly ash and fine-sands

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Traditional stabilization of backfilling material is done by using Portland cement. However, the high price of cement forced mining engineers to seek cheaper binding materials. Fly ash, which is the industrial waste from thermal power plant, possess the potential activity of jellification, and can be used in cemented fill as a partial substitute for cement to reduce the fill cost. Tests were done during the past few years in Xinqiao Pyrite Mine and Phoenix Copper Mine to determine the technology parameters and the suitable content of fly ash. Specimens with different cement/fly/ash tailings (sands) ratios were tested to obtain the strength values of the fill mass based on the analyses of both the chemical composition and physical and mechanical properties of fly ash. The compressive strength of specimens with a ratio of 1: 2: 8 (cement to fly ash to tailings)can reach 2 MPa after 90 d curing, totally meeting the requirement of artificial pillar and reducing the fill cost by 20%-30%.

  4. Design and manufacture of Portland cement Application of statistical analysis

    OpenAIRE

    Svinning, Ketil

    2011-01-01

    The purpose of the work is to enable design and manufacture of cement with emphasis on the quality and the properties of cement. Data used in the design and manufacture were collected from predictions of properties and characteristics of cement. The properties of cement were predicted from its characteristics and from the production conditions in cement kiln and mill. The cement characteristics were in some investigations predicted from the production conditions. The design was based on sensi...

  5. Biocompatibility and other properties of acrylic bone cements prepared with antiseptic activators.

    Science.gov (United States)

    de la Torre, B; Fernández, M; Vázquez, B; Collía, F; de Pedro, J A; López-Bravo, A; San Román, J

    2003-08-15

    Acrylic bone cements prepared with activators of reduced toxicity have been formulated with the aim of improving the biocompatibility of the final material. The activators used were N,N-dimethylaminobenzyl alcohol (DMOH) and 4,4'-dimethylamino benzydrol (BZN). The toxicity, cytotoxicity, and antiseptic action of these activators were first studied. DMOH and BZN presented LD50 values 3-4 times higher than DMT, were less cytotoxic against polymorphonuclear leucocytes, and possessed an antimicrobial character, with a high activity against the most representative microorganisms involved in postoperative infections. The properties of the acrylic bone cements formulated with DMOH and BZN were evaluated to determine the influence of these activators on the curing process and the physicochemical characteristics of the cements. A decrease of the peak temperature was observed for the curing with DMOH or BZN with respect to that of one commercially available formulation (CMW 3). However, residual monomer content and mechanical properties in tension and compression were comparable to those of CMW 3. The biocompatibility of acrylic bone cements containing DMOH or BZN was studied and compared with CMW 3. To that end, intramuscular and intraosseous implantation procedures were carried out and the results were obtained from the histological analysis of the surrounding tissues at different periods of time. Implantation of rods of cement into the dorsal muscle of rats showed the presence of a membrane of connective tissue, which increased in collagen fibers with time of implantation, for all formulations. The intraosseous implantation of the cements in the dough state in the femur of rabbits, revealed a higher and early osseous neoformation, with the presence of osteoid material surrounding the rest of the cured material, for the cement prepared with the activator BZN in comparison with that obtained following the implantation of the cement cured with DMOH or DMT (CMW 3).

  6. The effects of utilizing silica fume in Portland Cement Pervious Concrete

    Science.gov (United States)

    Mann, Daniel Allen

    Silica fume has long been used as a supplementary cementing material to provide a high density, high strength, and durable building material. Silica fume has a particle size a fraction of any conventional cement, which allows it to increase concrete strength by decreasing the porosity especially near the aggregates surface. Because Portland Cement Pervious Concrete (PCPC) has a smaller bond area between aggregate and paste, silica fume has significant impacts on the properties of the PCPC. The research in this paper studies the workability of a cement paste containing silica fume in addition to analyzing the results of testing on Portland Cement Pervious Concrete mixtures that also contained silica fume. Testing conducted included a study of the effects of silica fume on cement's rheological properties at various dosage rates ranging from zero to ten percent by mass. It was determined that silica fume has negligible effects on the viscosity of cement paste until a dosage rate of five percent, at which point the viscosity increases rapidly. In addition to the rheological testing of the cement paste, trials were also conducted on the pervious concrete samples. Sample groups included mixes with river gravel and chipped limestone as aggregate, washed and unwashed, and two different void contents. Workability tests showed that mixtures containing a silica fume dosage rate of 5 percent or less had comparable or slightly improved workability when compared to control groups. Workability was found to decrease at a 7 percent dosage rate. Samples were tested for compressive strength at 7 and 28 days and splitting tensile strength at 28 days. It was found in most sample groups, strength increased with dosage rates of 3 to 5 percent but often decreased when the dosage reached 7 percent. Abrasion testing showed that both samples containing washed aggregate and samples containing silica fume exhibited a reduced mass loss.

  7. THE USE OF SISAL FIBRE AS REINFORCEMENT IN CEMENT BASED COMPOSITES

    Directory of Open Access Journals (Sweden)

    Romildo Dias Tolêdo Filho

    1999-08-01

    Full Text Available ABSTRACT The inclusion of fibre reinforcement in concrete, mortar and cement paste can enhance many of the engineering properties of the basic materials, such as fracture toughness, flexural strength and resistance to fatigue, impact, thermal shock and spalling. In recent years, a great deal of interest has been created worldwide on the potential applications of natural fibre reinforced, cement based composites. Investigations have been carried out in many countries on various mechanical properties, physical performance and durability of cement based matrices reinforced with naturally occurring fibres including sisal, coconut, jute, bamboo and wood fibres. These fibres have always been considered promising as reinforcement of cement based matrices because of their availability, low cost and low consumption of energy. In this review, the general properties of the composites are described in relation to fibre content, length, strength and stiffness. A chronological development of sisal fibre reinforced, cement based matrices is reported and experimental data are provided to illustrate the performance of sisal fibre reinforced cement composites. A brief description on the use of these composite materials as building products has been included. The influence of sisal fibres on the development of plastic shrinkage in the pre-hardened state, on tensile, compressive and bending strength in the hardened state of mortar mixes is discussed. Creep and drying shrinkage of the composites and the durability of natural fibres in cement based matrices are of particular interest and are also highlighted. The results show that the composites reinforced with sisal fibres are reliable materials to be used in practice for the production of structural elements to be used in rural and civil construction. This material could be a substitute asbestos-cement composite, which is a serious hazard to human and animal health and is prohibited in industrialized countries. The

  8. Antibacterial activity of selected glass ionomer cements

    Directory of Open Access Journals (Sweden)

    Elżbieta Łuczaj-Cepowicz

    2014-01-01

    Full Text Available Introduction: The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus. Material and methods: Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC, Fuji IX (GC, Ketac Molar (3M Espe and Ketac Silver (3M Espe. Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Results: Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Discussion: Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  9. Microscopic evaluation regarding time behavior of orthodontic cements used for disjunctor cementing

    Directory of Open Access Journals (Sweden)

    Ruxandra Bartok

    2015-11-01

    Full Text Available In order to fulfill their function, orthodontic devices must be cemented on teeth using orthodontic rings. The retention of the orthodontic ring is influenced mainly by the type of dental-ring adhesion. This study was initiated to determine possible microleakage events while using zinc phosphate cement Adhesor (Spofa Dental, conventional glass ionomer Ketac Cem (3M ESPE and Fuji Ortho (GC and a compomer Transbond Plus (3M Unitek. The results of the study are consistent with those reported in the literature reference, the compomer is the preferred adhesive material for cementing the orthodontic rings, compared to conventional glass ionomer cements and zinc-phosphate cement.

  10. Consolidation behavior of cement-and lime/cement-mixed column foundations

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 徐长节

    2002-01-01

    The consolidation behavior of mixed in place cement- and lime/cement-mixed column was studied. Consolidation of the composite foundation was modeled as a three-dimensional axi-symmetric problem. The authors used the finite difference method to obtain the pore pressure variation with time at any location below the surface. A computer program developed by the authors was used to draw some interesting conclusions about the consolidation behaviors of cement- and lime/cement-mixed pile foundation. Finally, a combined model including the permeability coefficients of cement-mixed piles and soil, was studied and its feasibility was evaluated.

  11. Composite cements containing natural pozzolan and granulated blast furnace slag

    Directory of Open Access Journals (Sweden)

    Irassar, E. F.

    2006-09-01

    Full Text Available For reasons of market demand and Portland cement production,the manufacture of cements with two or more separately ground additions to produce customized cements is becoming common practice.When pozzolan or slag content in this type of cements is high, however, the initial strength of the resulting product may be adversely impacted. This problem can be minimized by activating one or both of the replacement materials. The present study analyzes the effect of Portland cement additions such as physically activated natural pozzolan(up to 20% and/or granulated blast furnace slag (up to 35% on mortar flexural and compressive strength. The results show that higher strength is attained in ternary than binary cements. Initially (2 and 7 days, the highest compressive strengths are reached by mortars with up to 13% natural pozzolan and 5% slag, whereas at later ages mortars with larger proportions of additions are found to perform best.Debido a las exigencias del mercado y de la producción de cemento Portland, es cada vez más frecuente la elaboración de cementos con dos o más adiciones a partir de la molienda separada de sus constituyentes, dando origen a la formulación de los cementos a medida.Cuando el contenido de adiciones es alto, la utilización de puzolana y escoria en este tipo de cementos presenta la peculiaridad de disminuir la resistencia inicial del cemento resultante. Sin embargo, si algunas o ambas adiciones se activan, este problema puede minimizarse. En este trabajo se analiza la influencia de la incorporación al cemento Portland de puzolana natural (hasta 20% activada físicamente y/o escoria granulada de alto horno (hasta 35% sobre la resistencia a flexión y a compresión de morteros. Los resultados indican que los cementos ternarios presentan un mejor comportamiento resistente que los cementos binarios. Las máximas resistencias a compresión en las primeras edades (2 y 7 díasse alcanzan con hasta 13% de puzolana natural y 5% de

  12. Radon exhalation of cementitious materials made with coal fly ash: Part 1 - scientific background and testing of the cement and fly ash emanation

    International Nuclear Information System (INIS)

    Increased interest in measuring radionuclides and radon concentrations in fly ash, cement and other components of building products is due to the concern of health hazards of naturally occurring radioactive materials (NORM). The current work focuses on studying the influence of fly ash (FA) on radon-exhalation rate (radon flux) from cementitious materials. The tests were carried out on cement paste specimens with different FA contents. The first part of the paper presents the scientific background and describes the experiments, which we designed for testing the radon emanation of the raw materials used in the preparation of the cement-FA pastes. It is found that despite the higher 226Ra content in FA (more than 3 times, compared with Portland cement) the radon emanation is significantly lower in FA (7.65% for cement vs. 0.52% only for FA)

  13. Partial Replacement of Cement with Marble Dust Powder

    Directory of Open Access Journals (Sweden)

    Mr. Ranjan Kumar

    2015-08-01

    Full Text Available The waste generated from the industries cause environmental problems. Hence the reuse of this waste material can be emphasized. MarbleDust Powder (MDP is a developing composite materialthatwillallow the concrèteindustry to optimisemateriel use, generateeconomicbenefits and build structures thatwillstrong, durable and sensitive to environnement. MDP is by-product obtained during the quarrying process from the parent marble rock; which contains high calcium oxide content of more than 50%. The potential use of MDP can be an ideal choice for substituting in a cementitious binder as the reactivity efficiency increases due to the presence of lime. In this research work, the waste MDP passing through 90 microns,has used for investigating of hardened concrete properties. Furthermore, the effect of different percentage replacement of MDP on the compressive strength, splitting tensile strength (indirect tensile strength&flexural strength has been observed. Inthis experimental study, the effect of MDP in concrete on strength ispresented. Five concrete mixtures containing 0%, 5%, 10%, and 20% MDP as cement replacement by weightbasis has been prepared. Water/cement ratio (0.43 was kept constant, in all the concretemixes. Compressive strength, split tensile strength & flexural strength of the concrete mixtures has been obtainedat 7 and 28 days. The results of the laboratory work showed thatreplacement of cement with MDP increase, upto 10% for compressive strength,&upto 15% for split tensilestrength &flexural strength of concrete.

  14. Microbial analysis of biofilms on cement surfaces: An investigation in cement-associated peri-implantitis.

    Science.gov (United States)

    Korsch, Michael; Walther, Winfried; Marten, Silke-Mareike; Obst, Ursula

    2014-09-05

    The cementation of implant-supported restorations always poses the risk of excess cement retained in the peri-implant sulcus despite careful clinical control. Excess cement can become the basis of colonization by oral microorganisms. As a result of the biofilm formation peri-mucositis or peri-implantitis may develop. Complications were observed in the routine prosthetic restoration of implants when a methacrylate-based cement was used. These developed a few weeks after cementation of the suprastructure and caused bleeding on probing as well as suppuration from the peri-implant tissue. In the revision therapy, excess cement in the peri-implant sulcus was found in many cases. This excess cement was sampled from ten patients and investigated for biofilm formation. For this purpose, the cement samples were collected and analyzed for bacterial in situ colonization by 16S rDNA-based methods. In laboratory experiments, the methacrylate-based cement and two other dental cements were then investigated for their proneness to form biofilm. The results of the in situ and in vitro investigations revealed a strong tendency towards bacterial invasion of the methacrylate-based cement by opportunistic species and pathogens.

  15. 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

    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......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...... 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....

  16. Copper Slag Blended Cement: An Environmental Sustainable Approach for Cement Industry in India

    Directory of Open Access Journals (Sweden)

    Jagmeet Singh

    2016-04-01

    Full Text Available Indian cement industry is facing environmental issue of emission of carbon dioxide (CO2, a greenhouse gas. Blended cements including supplementary cementitious materials are substitute of Portland cement to reduce CO2 emission. The present paper investigates theappropriateness of copper slag (CS as supplementary cementitious material. Strength properties and hydration of mixes were determined at different replacement levels of CS with cement. Compressive, flexural and tensile strength of each mix was found out at different curing periods. The hydration of cement was investigated through X-ray diffraction (XRD. The strength test results showed that substitution of up to 20% of CS can significantly replace Portland cement.XRD test results were corresponding to strength test results. The present study encourages the utilization of CS as supplementary cementitious material to make economical and environmentally sustainable blended cement

  17. Cements in radioactive waste management. Characterization requirements of cement products for acceptance and quality assurance purposes

    International Nuclear Information System (INIS)

    Cementitious materials are used as immobilizing matrices for low (LLW) and medium-level wastes (MLW) and are also components of the construction materials in the secondary barriers and the repositories. This report has concerned itself with a critical assessment of the quality assurance aspects of the immobilization and disposal of MLW and LLW cemented wastes. This report has collated the existing knowledge of the use and potential of cementitious materials in radioactive waste immobilization and highlighted the physico-chemical parameters. Subject areas include an assessment of immobilization objectives and cement as a durable material, waste stream and matrix characterization, quality assurance concepts, nature of cement-based systems, chemistry and modelling of cement hydration, role and effect of blending agents, radwaste-cement interaction, assessment of durability, degradative and radiolytic processes in cements and the behaviour of cement-based matrices and their near-field interactions with the environment and the repository conditions

  18. Evolution of cement based materials in a repository for radioactive waste and their chemical barrier function

    Energy Technology Data Exchange (ETDEWEB)

    Kienzler, Bernhard; Metz, Volker; Schlieker, Martina; Bohnert, Elke [Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany). Inst. fuer Nukleare Entsorgung (INE)

    2015-07-01

    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){sub 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

  19. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

    in particular is influenced by insufficient carbon burnout in the calciner system, which results in reducing conditions in the material inlet of the rotary kiln and consequently an increased tendency to form deposits induced by sticky eutectic melts. Clinker quality is mainly affected by minor components from...... a decisive influence on the fuel carbon burnout in cement kiln systems. The oxidation kinetics of a char from TDF was investigated experimentally and by mathematical modelling. Experiments were performed in a fixed bed reactor under well - iii - defined conditions, where small particles (102-212μm) of TDF...

  20. Smart cement modified with iron oxide nanoparticles to enhance the piezoresistive behavior and compressive strength for oil well applications

    Science.gov (United States)

    Vipulanandan, C.; Mohammed, A.

    2015-12-01

    In this study, smart cement with a 0.38 water-to-cement ratio was modified with iron oxide nanoparticles (NanoFe2O3) to have better sensing properties, so that the behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated the piezoresistive smart cement behavior with and without NanoFe2O3 in order to identify the most reliable sensing properties that can also be relatively easily monitored. Tests were performed on the smart cement from the time of mixing to a hardened state behavior. When oil well cement (Class H) was modified with 0.1% of conductive filler, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the setting properties of the cement. During the initial setting the electrical resistivity changed with time based on the amount of NanoFe2O3 used to modify the smart oil well cement. A new quantification concept has been developed to characterize the smart cement curing based on electrical resistivity changes in the first 24 h of curing. Addition of 1% NanoFe2O3 increased the compressive strength of the smart cement by 26% and 40% after 1 day and 28 days of curing respectively. The modulus of elasticity of the smart cement increased with the addition of 1% NanoFe2O3 by 29% and 28% after 1 day and 28 days of curing respectively. A nonlinear curing model was used to predict the changes in electrical resistivity with curing time. The piezoresistivity of smart cement with NanoFe2O3 was over 750 times higher than the unmodified cement depending on the curing time and nanoparticle content. Also the nonlinear stress-strain and stress-change in resistivity relationships predicated the experimental results very well. Effects of curing time and NanoFe2O3 content on the model parameters have been quantified using a nonlinear model.

  1. Physico-mechanical properties of solid cement bricks containing recycled aggregates

    Directory of Open Access Journals (Sweden)

    Dina M. Sadek

    2012-07-01

    Full Text Available Recycling and reuse of solid wastes as alternative building materials present interesting possibilities for economy on waste disposal sites and conservation of natural resources. This paper investigates the physical and mechanical properties of solid cement bricks manufactured with crushed clay bricks as recycled aggregates. Four series of mixtures with cement content 100, 150, 200 and 300 kg/m3 were prepared. In each series, either natural fine aggregate, coarse aggregate or both were replaced with crushed brick aggregates (CBA at 0%, 50% and 100% by volume. Compressive strength, unit weight and water absorption were determined and compared with the relevant national and international standards for load bearing and non-load bearing units, respectively. The experimental results showed that as the replacement level of natural aggregates increased, the unit weight and compressive strength of solid cement bricks decreased and the water absorption increased regardless of cement content. Furthermore, it is possible to manufacture different grades of solid cement bricks with CBA to be used as load bearing and non-load bearing units depending on the size of the crushed bricks and the replacement percentage of natural aggregates.

  2. A note on cement in asteroids

    Science.gov (United States)

    Bilalbegović, G.

    2016-09-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 μm were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 μm.

  3. Basic Chemistry for the Cement Industry.

    Science.gov (United States)

    Turner, Mason

    This combined student workbook and instructor's guide contains nine units for inplant classes on basic chemistry for employees in the cement industry. The nine units cover the following topics: chemical basics; measurement; history of cement; atoms; bonding and chemical formulas; solids, liquids, and gases; chemistry of Portland cement…

  4. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  5. A note on cement in asteroids

    CERN Document Server

    Bilalbegovic, G

    2016-01-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 microns were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 microns.

  6. Chloride ingress in cement paste and mortar

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Coats, Alison M.;

    1999-01-01

    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature), The measurements...

  7. A Pause for China's Cement Industry

    Institute of Scientific and Technical Information of China (English)

    Li Zhen

    2009-01-01

    @@ Cement industry suffers excess productionWith the advent of global financial crisis,the Chinese government has laid out a stimulus package on infrastructure construction.Driven by the investment spree,China's cement makers are flocking to expand output capacity,which is now leading the industry into a much-higher-thanneeded state.

  8. Osteogenesis and angiogenesis properties of dental pulp cell on novel injectable tricalcium phosphate cement by silica doped

    Energy Technology Data Exchange (ETDEWEB)

    Su, Ying-Fang [Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan (China); Department of Stomatology, Chung Shan Medical University Hospital, Taichung, Taiwan (China); School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Lin, Chi-Chang, E-mail: chichang31@gmail.com [Department of Anatomy, Chung Shan Medical University, Taichung City, Taiwan (China); Huang, Tsui-Hsien; Chou, Ming-Yung [Department of Stomatology, Chung Shan Medical University Hospital, Taichung, Taiwan (China); School of Dentistry, Chung Shan Medical University, Taichung, Taiwan (China); Yang, Jaw-Ji, E-mail: jjyang@csmu.edu.tw [Department of Chemical and Materials Engineering, Tunghai University, Taichung, Taiwan (China); Shie, Ming-You, E-mail: eviltacasi@gmail.com [Department of Anatomy, Chung Shan Medical University, Taichung City, Taiwan (China)

    2014-09-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material in clinical. In this study, we have doped silica (Si) into β-TCP and enhanced its bioactive and osteostimulative properties. To check its effectiveness, a series of Si-doped with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of the diametral tensile strength, ions released and weight loss of cements was considered after immersion. In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on Si-doped β-TCP cements. The results showed that setting time and injectability of the Si-doped β-TCP cements were decreased as the Si content was increased. At the end of the immersion point, weight losses of 30.1%, 36.9%, 48.1%, and 55.3% were observed for the cement doping 0%, 10%, 20%, and 30% Si into β-TCP cements, respectively. In vitro cell experiments show that the Si-rich cements promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the Si-doped in the cement is more than 20%, the amount of cells and osteogenesis protein of hDPCs was stimulated by Si released from Si-doped β-TCP cements. The degradation of β-TCP and osteogenesis of Si gives a strong reason to believe that these Si-doped β-TCP cements may prove to be promising bone repair materials. - Highlights: • The higher the Si in the cement, the shorter the setting time and the higher the DTS. • Si20-doped in TCP improved cell adhesion, proliferation and differentiation. • The Si ion stimulated collagen secreted from cells. • The Si released from substrate can promote osteogenic and angiogenic.

  9. Compressive Strength and Static Modulus of Elasticity of Periwinkle Shell Ash Blended Cement Concrete

    Directory of Open Access Journals (Sweden)

    Akaninyene Afangide Umoh

    2012-12-01

    Full Text Available The study examined the effect of periwinkle shell ash as supplementary cementitious material on the compressive strength and static modulus of elasticity of concrete with a view to comparing it’s established relation with an existing model. The shells were calcined at a temperature of 800oC. Specimens were prepared from a mix of designed strength 25N/mm2. The replacement of cement with periwinkle shell ash (PSA was at five levels of 0, 10, 20, 30 and 40% by volume. A total of 90 cubical and cylindrical specimens each were cast and tested at 7, 14, 28, 90, 120 and 180 days. The results revealed that the PSA met the minimum chemical and physical requirements for class C Pozzolans. The compressive strength of the PSA blended cement concrete increased with increase in curing age up to 180 days but decreased as the PSA content increased. The design strength was attained with 10%PSA content at the standard age of 28 days. The static modulus of elasticity of PSA blended cement concrete was observed to increase with increased in curing age and decreases with PSA content. In all the curing ages 0%PSA content recorded higher value than the blended cement concrete. The statistical analysis indicated that the percentage PSA replacement and the curing age have significant effect on the properties of the concrete at 95% confidence level. The relation between compressive strength and static modulus of elasticity fitted into existing model for normal-weight concrete.

  10. Energetically Modified Cement (EMC) - Performance Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement

    2003-03-01

    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  11. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll;

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone....... The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in N2...

  12. Conditioning of radioactive waste solutions by cementation

    International Nuclear Information System (INIS)

    For the cementation of the low and intermediate level evaporator concentrates resulting from the reprocessing of spent fuel numerous experiments were performed to optimize the waste form composition and to characterize the final waste form. Concerning the cementation process, properties of the waste/cement suspension were investigated. These investigations include the dependence of viscosity, bleeding, setting time and hydration heat from the waste cement slurry composition. For the characterization of the waste forms, the mechanical, thermal and chemical stability were determined. For special cases detailed investigations were performed to determine the activity release from waste packages under defined mechanical and thermal stresses. The investigations of the interaction of the waste forms with aqueous solutions include the determination of the Cs/Sr release, the corrosion resistance and the release of actinides. The Cs/Sr release was determined in dependence of the cement type, additives, setting time and sample size. (orig./DG)

  13. Application of Neutron imaging in pore structure of hydrated wellbore cement: comparison of hydration of H20 with D2O based Portland cements

    Science.gov (United States)

    Dussenova, D.; Bilheux, H.; Radonjic, M.

    2012-12-01

    storage of the hydrogen atom. In such case, neutron tomography does not give information of the pore structure as neutrons will strongly scatter of H and the data have low count and low statistics or low neutron transmission. Hence, as the comparison and the possible tuning technique, neutron tomography measurements are performed on a Deuterium Oxide (D2O) or heavy water samples the same dimensions, cement composition, cement/liquid content and hydration time as the H2O samples. The advantage of using heavy water is that the total neutron cross-section for Deuterium is approximately four times smaller than Hydrogen's and, thus, permits better neutron transmission, i.e. better statistics. D2O does not alter cement properties or its chemical composition; therefore, the samples are almost identical. Comparison of the measurements using water and heavy water samples and the preparation of the measurement cement samples are discussed in this

  14. Performance Comparison between EAFD and Conventional Supplementary Cementing Materials

    Directory of Open Access Journals (Sweden)

    Amir Fauzi Hasbi

    2016-02-01

    Full Text Available Sustainability of concrete construction necessitates exploring potential renewable resource, especially from industrial waste products.  Electric arc furnace dust (EAFD, a by-product of the modern electric arc furnace (EAF process from the steel manufacturing industry has an adverse impact on the environment. Utilizing EAFD in concrete production as a cement replacement material together with silica fume (SF and fly ash (FA has raised the interest of many researchers.  This study investigates the use optimum 5% EAFD content refers to both 15% SF and 20% FA in water binder ratio of 0.5 and sand to cement ratio of 2. The aim of this study is to obtain the percentage replacement levels of EAFD that are equivalent to the SF and FA regarding workability, setting time, compressive strength and resistance to rapid chloride permeability. The compressive strength results showed that replacement of 5% SF and 15% FA are the equivalent replacement levels to 3% EAFD. Similarly, results from resistance to rapid chloride permeability showed that the optimum EAFD content performed better than the replacement levels of FA.  However, SF replacement levels showed the best resistance to rapid chloride permeability. Therefore, 3% replacement of EAFD provided an intermediate performance between the optimum SF and FA contents and exceeded that of the control.

  15. ROTARY SCREW SYSTEMS IN CEMENT

    Directory of Open Access Journals (Sweden)

    Taratuta V. D.

    2016-01-01

    Full Text Available The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometrical shapes with form inside the screw breaks or smooth edges, screw surfaces and screw grooves. It is shown that the housing of the rotary kiln is expedient to produce helical surfaces whose centers of curvature are located within the housing. Using the proposed constructions rotary kiln during the firing when preparing cement wedge can increase the speed of rotation of the housing, furnaces 5-10 times due to changes in the rotary-screw systems increase efficiency and reduce the size of furnaces

  16. Lead, mercury, cadmium, chromium, nickel, copper, zinc, calcium, iron, manganese and chromium (VI) levels in Nigeria and United States of America cement dust.

    Science.gov (United States)

    Ogunbileje, J O; Sadagoparamanujam, V-M; Anetor, J I; Farombi, E O; Akinosun, O M; Okorodudu, A O

    2013-03-01

    This study was aimed at investigating the relative abundance of heavy metals in cement dust from different cement dust factories in order to predict their possible roles in the severity of cement dust toxicity. The concentrations of total mercury (Hg), copper (Cu), chromium (Cr), cadmium (Cd), nickel (Ni), manganese (Mn), lead (Pb), iron (Fe) and chromium (VI) (Cr (VI)) levels in cement dust and clinker samples from Nigeria and cement dust sample from the United States of America (USA) were determined using graphite furnace atomic absorption (GFAAS), while Zn and Ca were measured by flame atomic absorption spectrophotometry (FAAS), and Cr (VI) by colorimetric method. Total Cu, Ni and Mn were significantly higher in cement dust sample from USA (pcement dust compared with Nigeria cement dust or clinker (pcement dust and clinker (pMercury was more in both Nigeria cement dust and clinker (pcement dust contain mixture of metals that are known human carcinogens and also have been implicated in other debilitating health conditions. Additionally, it revealed that metal content concentrations are factory dependent. This study appears to indicate the need for additional human studies relating the toxicity of these metals and their health impacts on cement factory workers. PMID:23261125

  17. Reuse of sewage sludge ashes (SSA) in cement mixtures: the effect of SSA on the workability of cement mortars.

    Science.gov (United States)

    Monzó, J; Payá, J; Borrachero, M V; Girbés, I

    2003-01-01

    The influence of sewage sludge ash (SSA) on workability of cement mortars has been studied. The irregular morphology of SSA particles produced a decrease of mortar workability. A nonlinear reduction of workability in mortars containing SSA was observed, but when SSA content in mortars was increased the workability reduction was less significant. A superplasticizer is used in order to compensate the decrease of workability produced by SSA. When SSA sized fractions were used, only significant differences in workability for mortars prepared with high water volumes or with the presence of superplasticizer were observed.

  18. Experimental research on the strength of cemented backfilling body of waste rocks%废石尾砂胶结充填体强度试验研究

    Institute of Scientific and Technical Information of China (English)

    罗根平; 乔登攀

    2015-01-01

    Experimental study is systematically conducted on cemented backfilling with waste rocks.The paper states the applicability and mechanism of waste rock cemented filling process and focuses on the influencing factors on the strength of cemented filling body of waste rocks,namely the water-cement ratio,cement-sand ratio,cement content, the grading and proportioning of the particle size of waste rocks.The research results show that the lager the water-ce-ment ratio and cement-sand ratio are,the less the strength of cemented backfilling body becomes,contrary to that rela-tion between cement content and the backfilling body's strength.With constant strength,cemented filling with waste rocks consumes less cement per unit volume and cost less than other filling methods.%对废石尾砂胶结充填进行了系统的试验研究。阐述了废石尾砂胶结充填工艺的工业性及原理,着重研究了废石尾砂胶结充填体强度的影响因素:水灰比、灰砂比、水泥含量、废石尾砂的粒径级配及配比。研究结果表明,废石尾砂胶结充填体强度随水灰比、灰砂比的减小而增大,随水泥含量的增加而增加。在强度一定的条件下,废石尾砂胶结充填比其他充填方式,单位体积内水泥耗量少,成本低。

  19. Characteristics of glass ionomer cements composed of glass powders in CaO-SrO-ZnO-SiO₂ system prepared by two different synthetic routes.

    Science.gov (United States)

    Kim, Ill Yong; Ohtsuki, Chikara; Coughlan, Aisling; Placek, Lana; Wren, Anthony W; Towler, Mark R

    2013-12-01

    Glass ionomer cements (GICs) are composed of an acid degradable glass, polyacrylic acid and water. Sol-gel processing to prepare the glass phase has certain advantages, such as the ability to employ lower synthesis temperatures than melt quenching and glasses that are reported to have higher purity. A previous study reported the effects of glass synthesis route on GIC fabrication. However, in that study, the sol-gel derived glass exhibited a reduced concentration of cations. This study investigates increasing the cation content of a sol-gel derived glass, 12CaO.4SrO.36ZnO.48SiO2 (molar ratio) by heating before aging to reduce dissolution of cations. This glass was prepared by both sol-gel and melt-quenched routes. GICs were subsequently prepared using both glasses. The resultant cement based on the sol-gel derived glass had a shorter working time than the cement based on the melt-quenched one. Contrary to this, setting time was considerably longer for the cement based on the sol-gel derived glass than for the cement based on the melt-quenched one. The cements based on the sol-gel derived glass were stronger in both compression and biaxial flexure than the cements prepared from the melt-quenched glass. The differences in setting and mechanical properties were associated with both cation content in the glass phase and the different surface area of the resultant cements.

  20. Solidification of Municipal Solid Waste Incineration Fly Ash with Cement and Its Leaching Behaviors of Heavy Metals

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The solidifying effect of cement addition on municipal solid waste incineration fly ash (MSWFA for short,collected from the gas exhaust system of MSW incinerator),the interaction of MSWFA with cement and water and the leaching of heavy metals from cement-solidified MSWFA are investigated.The main results show that:(1) when MSWFA is mixed with cement and water,H2 evolution,the formation and volume expansion of AFt will take place,the volume expansion can be reduced by ground rice husk ash addition;(2) heavy metals do leach from cement-solidified MSWFA and at lower pH more leaching will occur;(3) compared with cement-solidified fly ash,the leachate of solidified MSWFA is with higher heavy metal contents;(4) with the increment of cement addition leached heavy metals are decreased;and (5) concentrations of Zn,Mn,Cu and Cd in all the leachates can meet the relevant Standards of Japan,but as the regulations for soil and groundwater protection of Japan are concerned,precautions against the leaching of Pb,Cl- and Cr6+ and so on are needed.

  1. Extraoral Cementation Technique to Minimize Cement-Associated Peri-implant Marginal Bone Loss: Can a Thin Layer of Zinc Oxide Cement Provide Sufficient Retention?

    Science.gov (United States)

    Frisch, Eberhard; Ratka-Krüger, Petra; Weigl, Paul; Woelber, Johan

    2016-01-01

    This report describes the use of laboratory-fabricated crown intaglio replicas for extraorally prepared cementation of fixed restorations to implants. This technique minimizes excess cement and may therefore reduce the risk of cement-related marginal peri-implant bone loss. It is unclear whether the remaining thin layer of luting agent provides sufficient retention if low-adhesive zinc oxide (ZnO) cement is used. In 85 consecutive patients, 113 single crowns were cemented to implants using extraoral cementation technique (ECT) and ZnO cement. All patients were followed for 6 months and investigated for decementation. Seven events of decementation (incidence: 6.19%) were found in 7 patients (8.24%). ECT may represent a viable cementation technique for implant-supported single crowns, even using low-adhesion cements. PMID:27479343

  2. EFFECTS OF BLAST-FURNACE SLAG ON NATURAL POZZOLAN-BASED GEOPOLYMER CEMENT

    OpenAIRE

    MAHSHAD YAZDANIPOUR; EBRAHIM NAJAFI KANI; ALI ALLAHVERDI

    2011-01-01

    A number of geopolymer cement mixes were designed and produced by alkali-activation of a pumice-type natural pozzolan. Effects of blast-furnace slag on basic engineering properties of the mixes were studied. Different engineering properties of the mixes such as setting times and 28-day compressive strength were studied at different amounts of blast-furnace slag, sodium oxide content, and water-to-cement ratio. The mix comprising of 5 wt.% blast-furnace slag and 8 wt.% Na2O with a water-to-dry...

  3. CSER 00-001 Criticality Safety Evaluation Report for Cementation Operations at the PFP

    International Nuclear Information System (INIS)

    Glovebox HA-20MB is located in Room 235B of the 234-5Z Building at the Plutonium Finishing Plant. This enclosure contains mixers, mixer bowls, a crusher unit, an isolated inoperable conveyor unit, plutonium residue feed cans, cemented cans, and a feedwater container. Plutonium residue, not conducive to other forms of stabilization, is prepared for storage and ultimate disposal by cementation. The feed residue material cans can have plutonium contents of only a few grams or up to 200 grams. This evaluation accommodates this wide range of container fissile concentrations

  4. CSER 00-001 Criticality Safety Evaluation Report for Cementation Operations at the PFP

    Energy Technology Data Exchange (ETDEWEB)

    DOBBIN, K.D.

    2000-04-18

    Glovebox HA-20MB is located in Room 235B of the 234-5Z Building at the Plutonium Finishing Plant. This enclosure contains mixers, mixer bowls, a crusher unit, an isolated inoperable conveyor unit, plutonium residue feed cans, cemented cans, and a feedwater container. Plutonium residue, not conducive to other forms of stabilization, is prepared for storage and ultimate disposal by cementation. The feed residue material cans can have plutonium contents of only a few grams or up to 200 grams. This evaluation accommodates this wide range of container fissile concentrations.

  5. Dermatoses in cement workers in southern Taiwan.

    Science.gov (United States)

    Guo, Y L; Wang, B J; Yeh, K C; Wang, J C; Kao, H H; Wang, M T; Shih, H C; Chen, C J

    1999-01-01

    Construction workers are known to have occupational dermatoses. The prevalence of such dermatoses was unknown in Taiwanese construction workers. The objective of this study was to determine the work exposure, prevalence of skin manifestations, and sensitivity to common contact allergens in cement workers of southern Taiwan. A total of 1147 current regular cement workers were telephone-interviewed about skin problems during the past 12 months, work exposure, and personal protection. Among those interviewed, 166 were examined and patch tested with common contact allergens. A high % of cement workers reported skin problems in the past 12 months. More men (13.9%) reported skin problems possibly related to work than women (5.4%). Prevalence was associated with lower use of gloves, duration of work as cement worker, and more time in jobs involving direct manual handling of cement, especially tiling. A high % of dermatitis was noted in the 166 workers examined, which correlated with reported skin problems. On patch testing, construction workers had a high frequency of sensitivity to chromate. Sensitivity to chromate or cobalt was associated with reported skin problems, or dorsal hand dermatitis on examination. These workers' dermatitis was under-diagnosed and inadequately managed. It is concluded that cement workers in southern Taiwan had a high prevalence of skin problems related to cement use. Protective measures, work practice, and physician education should be improved to prevent or manage such problems.

  6. Effect of cements on fracture resistance of monolithic zirconia crowns

    OpenAIRE

    Nakamura, Keisuke; Mouhat, Mathieu; Nergård, John Magnus; Lægreid, Solveig Jenssen; Kanno, Taro; Milleding, Percy; Örtengren, Ulf

    2016-01-01

    Abstract Objectives The present study investigated the effect of cements on fracture resistance of monolithic zirconia crowns in relation to their compressive strength. Materials and methods Four different cements were tested: zinc phosphate cement (ZPC), glass-ionomer cement (GIC), self-adhesive resin-based cement (SRC) and resin-based cement (RC). RC was used in both dual cure mode (RC-D) and chemical cure mode (RC-C). First, the compressive strength of each cement was tested according to a...

  7. Laboratory studies on the longevity of cement grouts

    International Nuclear Information System (INIS)

    This paper describes laboratory studies of the longevity of cement-based grouts being carried out as part of the International Stripa Project Phase III. The longevity properties determined for a reference grout (90% Sulphate Resistant Portland Cement, 10% silica fume, 0.4< water/cement<0.6 and superplasticizer) are compared with those of a slag cement grout. Laboratory tests have been carried out to determine the following: the mechanistic function of superplasticizer in fresh cement pastes; the leachability of the sorbed superplasticizer and its location in the structure of hardened cement paste; and the general leaching properties of selected cement-based grouts

  8. CO2 Sequestraion by Mineral Carbonation of Cement Material

    Science.gov (United States)

    Jo, H.; Jang, Y.

    2010-12-01

    CO2 sequestration by mineral carbonation with cement materials was investigated in this study. Ca extraction and CO2 injection tests were conducted on three different materials (lime, Portland cement, waste concrete) using different extract reagents (NH4Cl, CH3COOH, HCl, and Deionized water) under ambient temperature and pressure conditions. CO2 gas (99.9%) was injected to either supernatant without solids or suspension with solids obtained from extraction tests at 4 ml/min of flow rate. Ca concentrations were measured from filtered solutions before and after CO2 injection. The chemical and mineralogical composition of raw materials and precipitates were determined using X-ray fluorescence and X-ray diffraction, respectively. The morphology and chemical composition of precipitates were analyzed with Field Emission Scanning Electron Microscopy equipped with the Energy Dispersive X-ray analysis. For the extraction tests, Ca concentrations of the extracts were related with the CaO content and type of CaO bearing minerals of the materials, regardless of the extraction solutions. Lime had a higher Ca concentration ranging between 942.7 and 39945.0 mg/L in the extracts than waste concrete (188.4 ~ 2978.1 mg/L) in the extracts due to its higher content of CaO (CaO : 24.5% and waste concrete : 20.3%). In contrast, the Portland cement (6346.0 and 28903.5 mg/L) had lower Ca concentrations than lime (94.27 ~ 39945.0 mg/L), even though the Portland cement (56.3%) had a higher CaO content than lime (24.5%). For a given extraction solution, lime had the highest CO2 carbonation efficiency. In addition, for a given material, the CO2 carbonation efficiency was the highest when NH4Cl solution was used as an extraction solution. Results of material analyses indicate that precipitates from the CO2 injection tests consisted of mostly CaCO3, regardless of types of materials and extraction solutions.

  9. Quartz cementation mechanisms between adjacent sandstone and shale in Middle Cambrian, West Lithuania

    Science.gov (United States)

    Zhou, Lingli; Friis, Henrik

    2013-04-01

    Quartz is an important cementing material in siliciclastic sandstones that can reduce porosity and permeability severely. For efficiently predicting and extrapolating petrophysical properties such as porosity and permeability, the controls on the occurrence and the degree of quartz cementation need to be better understood. Because it is generally difficult to identify specific sources for quartz cement, many models attempting to explain quartz cementation conclude that external sources of silica are needed to explain the observed quantity of quartz cement, such as the mass transfer between sandstone and shale. Cambrian sandstones in Lithuania have abundant quartz cement which has significant effect on reservoir properties. The detrital quartz grains have been dissolved extensively along the shale-quartz contacts zones, making it a natural laboratory to study the influence of mass transfer between sandstone and shale to quartz cementation on petrophysical properties and reservoir quality. Our Cambrian shale samples in west Lithuania are mainly silty shale or siltstone (sample locations vary from 330 to 2090 m of burial depth). They are composed of quartz, clay and traces of feldspars, sericite, calcite, and pyrite. The clay minerals are mainly illite, with variable content of kaolinite and traces of chlorite. In the sandstone lamina, authigenic illite occurs as pore-filling cement which was composed of fibrous illite; pore-filling kaolinite is generally well crystallized and occurs as hexagonal plates arranged in booklets; quartz overgrowth are obvious in these sandstone laminas, especially in the contact zones between sandstone and shale. Dolomite and pyrite cementation are also present in some sandstone laminas but with few quartz overgrowth. Depositional facies and architecture played an important role in the precipitation of silica. Three different possible sources are distinguished for the quartz overgrowths in the intercalated sandstones: 1) Pressure

  10. Superplasticizer function and sorption in high performance cement based grouts

    International Nuclear Information System (INIS)

    This report describes laboratory studies undertaken to determine interactions between the main components of high-performance cement-based grout. These interactions were studied with the grouts in both their unset and hardened states with the specific intention of determining the following: the mechanistic function of superplasticizer; the phase of residence of the superplasticizer in hardened materials; and the permanence of the superplasticizer in hardened grouts. In unset pastes attempts were made to extract superplasticizer by mechanical processes. In hardened grout the superplasticizer was leached from the grouts. A microautoradiographic method was developed to investigate the phases of residence of superplasticizer in hardened grouts and confirm the inferences from the leaching studies. In hardened grout the superplasticizer was located on the hydrated phases formed during the early stages of cement hydration. These include tricalcium aluminate hydrates and tricalcium silicate phases. There is some tendency for the superplasticizer to sorb on ettringite. The presence of superplasticizer did not coincide with the locations of unreacted silica fume and high silica content phases such as C2S-H. The observations explain the findings of the studies of unset pastes which also showed that the sorption of superplasticizer is likely to be enhanced with increased mixing water content and, hence, distribution in and exposure to the hydration reaction surfaces in the grout. Superplasticizer can be leached in very small quantities from the hardened grouts. Rapid release takes place from the unsorbed superplasticizer contained in the accessible pore space. Subsequent release likely occurs with dissolution of the cement phases and the exposure of isolated pores to groundwater. (au) (37 refs.)

  11. Use of Cement-Sand Admixture in Laterite Brick Production for Low Cost Housing

    Directory of Open Access Journals (Sweden)

    Isaac Olufemi AGBEDE

    2008-06-01

    Full Text Available Laterite was modified with 45% sand content by dry weight and stabilized with up to 9% cement content respectively and used in the production of 330 mm × 150 mm × 150 mm bricks through the application of a pressure of 3 N/mm2 with a brick moulding machine. Results showed that laterite used in this study cannot be stabilized for brick production within the economic cement content of 5% specified for use in Nigeria. However, bricks made with laterite admixed with 45% sand and 5% cement attained a compressive strength of 1.80 N/mm2 which is greater than the specified minimum strength value of 1.65 N/mm2. Cost comparison of available walling materials in Makurdi metropolis showed that the use of bricks made from 45% sand and 5% cement resulted in a saving of 30 - 47% when compared with the use of sandcrete blocks while the use of fired clay bricks resulted in a savings of 19% per square meter of wall. The study therefore recommends the use of laterite bricks in Makurdi and other locations because it is more economical and environmental friendly than fired clay bricks.

  12. HYDRATION CHARACTERISTICS OF PROMPT CEMENT IN THE PRESENCE CITRIC ACID AS RETARDER

    Directory of Open Access Journals (Sweden)

    Mohamed Heikal

    2015-03-01

    Full Text Available The aim of the present work is to study the influence of citric acid (CA as retarder on the properties of prompt cement pastes. The dosages of CA were 0.50, and 0.75, 1.00 and 1.25 mass % of prompt cement. The initial and final setting times, bulk density, compressive strength, total porosity, and hydration kinetics such as free lime, combined water contents and XRD for selected sample were investigated. The results obtained in this study showed that the addition of CA elongates the initial and final setting times and decreases the compressive strength and combined water contents, whereas, it increases the total porosity at all ages of hydration. CA retards the liberation of Ca(OH2 of prompt pastes. The free lime contents of prompt cement pastes are slightly increased up to 28 days then sharply increased up to 90 days. Thus, it is suggested that citrate sorbed onto the clinker surface and formed a protective layer around the clinker grains retarding their dissolution. The sharp increase of compressive strength at later ages after 28 days up to 90 days. The presence of 0.75 mass % citric acid achieves the initial and final setting time of the prompt cement according to the ASTM specification.

  13. Piezoresistivity of Carbon Fiber Graphite Cement-based Composites with CCCW

    Institute of Scientific and Technical Information of China (English)

    FAN Xiaoming; FANG Dong; SUN Mingqing; LI Zhuoqiu

    2011-01-01

    The electrical conductivity and piezoresistivity of carbon fiber graphite cement-matrix composites(CFGCC) with carbon fiber content(l% by the weight of cement), graphite powder contents (0%-50% by the weight of cement) and CCCW(cementitious capillary crystalline waterproofing materials, 4% by the weight of cement) were studied. The experimental results showed that the relationship between the resistivity of CFGCC and the concentration of graphite powders had typical features of percolation phenomena. The percolation threshold was about 20%. A clear piezoresistive effect was observed in CFGCC with 1 wt% of carbon fibers, 20wt% or 30wt% of graphite powders under uniaxial compressive tests, indicating that this type of smart composites was a promising candidate for strain sensing. The measured gage factor (defined as the fractional change in resistance per unit strain) of CFGCC with graphite content of 20wt% and 30wt% were 37 and 22, respectively. With the addition of CCCW, the mechanical properties of CFGCC were improved, which benefited CFGCC piezoresistivity of stability.

  14. 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...

  15. Silica Transport and Cementation in Quartz Aggregates

    Science.gov (United States)

    Pebble, C.; Farver, J.; Onasch, C.; Winslow, D.

    2008-12-01

    Silica transport and cementation in quartz aggregates have been experimentally investigated. Starting materials include a natural quartz arenite (Pocono sandstone), sized clasts of synthetic quartz, and sized grains of disaggregated natural sandstones. Experimental charges consisted of amorphous silica powder (~25 mg), AlCl3 powder (~3 mg), 25 wt% NaCl brine solution (~20 mg), and the starting material (~150 mg). The charges were weld-sealed in gold capsules and run in cold-seal pressure vessels at 300°C to 600°C at 150 MPa confining pressure for up to 4 weeks. Detailed calibrations of the furnaces indicate the maximum temperature variation across the length of the sample charges (3-7mm) was vacuum impregnated with epoxy containing a blue dye and sawn in half along the long axis of the sample charge. The nature and amount of silica transport and cementation in the samples was determined by a combination of Cathodoluminescence (CL), Light Microscopy (LM), and Scanning Electron Microscopy (SEM). Photomosaics of the samples were collected and the amount of cement, porosity, and average grain sizes were determined by point-counting. The cement was easily recognized from the quartz grains by the difference in luminescence. The experiments indicate that the presence of amorphous silica results in rapid silica cementation in quartz aggregates (e.g., up to 12% cement by volume in 4 weeks at 450°C). The amount of cementation is a function of substrate type, time, temperature, and ionic strength of the brine. The rate of silica transport through the length of the experimental charge appears to be limited by the silica solubility and its rapid depletion by cementation. Although most of the cement was derived from the amorphous silica, evidence for local dissolution-precipitation was observed. The experiments demonstrate that the mobility of silica, and consequent precipitation of cement, does not require a temperature or pressure gradient as is commonly assumed. Rather

  16. INFLUENCE OF GLASS CULLET IN CEMENT PASTES

    Institute of Scientific and Technical Information of China (English)

    A.Karamberi; E.Chaniotakis; D.Papageorgiou; A.Moutsatsou

    2006-01-01

    The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction.Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

  17. Operating experience with KRAFTWERK UNION cementation line

    International Nuclear Information System (INIS)

    A facility is described designed for fixation in a cement matrix of the radioactive concentrate produced by thickening waste water from the Bohunice nuclear power plant. The cementation line output is 0.6 m3 concentrate/h. The concentrate is put in 200 l drums. The individual operating units, cement management, air conditioning, dosimetric monitoring and the building part are described. The requirements for the operators and the assessment of the quality of raw materials and the product are discussed. (M.D.). 3 figs., 4 refs

  18. Leaf structural traits of tropical woody species resistant to cement dust.

    Science.gov (United States)

    Siqueira-Silva, Advanio Inácio; Pereira, Eduardo Gusmão; Modolo, Luzia Valentina; Paiva, Elder Antonio Sousa

    2016-08-01

    Cement industries located nearby limestone outcrops in Brazil have contributed to the coating of cement dust over native plant species. However, little is known about the extent of the response of tropical woody plants to such environmental pollutant particularly during the first stages of plant development and establishment. This work focused on the investigation of possible alterations in leaf structural and ultrastructural traits of 5-month-old Guazuma ulmifolia Lam. (Malvaceae), 6-month-old Myracrodruon urundeuva Allemão (Anacardiaceae), and 9-month-old Trichilia hirta L. (Meliaceae) challenged superficially with cement dust during new leaf development. Leaf surface of plants, the soil or both (leaf plus soil), were treated (or not) for 60 days, under controlled conditions, with cement dust at 2.5 or 5.0 mg cm(-2). After exposure, no significant structural changes were observed in plant leaves. Also, no plant death was recorded by the end of the experiment. There was also some evidence of localized leaf necrosis in G. ulmifolia and T. hirta, leaf curling in M. urundeuva and T. hirta, and bulges formation on epidermal surface of T. hirta, after cement dust contact with plant shoots. All species studied exhibited stomata obliteration while T. hirta, in particular, presented early leaf abscission, changes in cellular relief, and organization and content of midrib cells. No significant ultrastructural alterations were detected under the experimental conditions studied. Indeed, mesophyll cells presented plastids with intact membrane systems. The high plant survival rates, together with mild morphoanatomic traits alterations in leaves, indicate that G. ulmifolia is more resistant to cement dust pollutant, followed by M. urundeuva and T. hirta. Thus, the three plant species are promising for being used to revegetate areas impacted by cement industries activities. PMID:27146683

  19. Effect of cementing technique and cement type on thermal necrosis in hip resurfacing arthroplasty - a numerical study

    NARCIS (Netherlands)

    Janssen, D.; Srinivasan, P.; Scheerlinck, T.; Verdonschot, N.J.J.

    2012-01-01

    Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly resulting from heat generated by cement polymerization. The amount of heat generated depends on cement mantle volume and type of cement. Using finite element analysis, the effect of cement type and volume

  20. The behavior of the micro-mechanical cement-bone interface affects the cement failure in total hip replacement

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2011-01-01

    In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle were investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically im

  1. Characterization of high-calcium fly ash and its influence on ettringite formation in portland cement pastes

    Science.gov (United States)

    Tishmack, Jody Kathleen

    High-calcium Class C fly ashes derived from Powder River Basin coal are currently used as supplementary cementing materials in portland cement concrete. These fly ashes tend to contain significant amounts of sulfur, calcium, and aluminum, thus they are potential sources of ettringite. Characterization of six high-calcium fly ashes originating from Powder River Basin coal have been carried out. The hydration products formed in pastes made from fly ash and water were investigated. The principal phases produced at room temperature were ettringite, monosulfate, and stratlingite. The relative amounts formed varied with the specific fly ash. Removal of the soluble crystalline sulfur bearing minerals indicated that approximately a third of the sulfur is located in the fly ash glass. Pore solution analyses indicated that sulfur concentrations increased at later ages. Three fly ashes were selected for further study based on their ability to form ettringite. Portland cement-fly ash pastes made with the selected fly ashes were investigated to evaluate ettringite and monosulfate formation. Each of the fly ashes were mixed with four different types of portland cements (Type I, I/II, II, and III) as well as three different Type I cements exhibiting a range of C3A and sulfate contents. The pastes had 25% or 35% fly ash by total weight of solids and a water:cement-fly ash ratio of 0.45. The samples were placed in a curing room (R.H. = 100, 23°C) and were then analyzed at various ages by x-ray diffraction (XRD) and differential scanning calorimetry (DSC) to determine the principal hydration products. The hydration products identified by XRD were portlandite, ettringite (an AFt phase), monosulfate, and generally smaller amounts of hemicarboaluminate and monocarboaluminate (all AFm phases). Although the amount of ettringite formed varied with the individual cement, only a modest correlation with cement sulfate content and no correlation with cement C3A content was observed. DSC

  2. CONTRIBUTION TO THE STATISTICAL INTERPRETATION OF RAW MATERIALS FOR THE CEMENT INDUSTRY OF SPLIT

    Directory of Open Access Journals (Sweden)

    Miroslav Matijaca

    1990-12-01

    Full Text Available Up to the last two decades cement was produced from mari called »tupina« (with about 76% CaCOj which is an ideal mixture for cement production. Due to the quantity decrease of this raw material, cement production went on using the mixture of other members of the flysch series: limestones, marls, clay, loess, sandstones a.o. By the analysis of natural materials the CaCO^ content has mostly been proved. Therefore, knowing the correlation of oxides in mineral raw material is of special significance. The article discusses investigation results of the correlation between CaCO-i and other oxides of the raw material (the paper is published in Croatian.

  3. Corrosion sensor for monitoring the service condition of chloride-contaminated cement mortar.

    Science.gov (United States)

    Lu, Shuang; Ba, Heng-Jing

    2010-01-01

    A corrosion sensor for monitoring the corrosion state of cover mortar was developed. The sensor was tested in cement mortar, with and without the addition of chloride to simulate the adverse effects of chloride-contaminated environmental conditions on concrete structures. In brief, a linear polarization resistance method combined with an embeddable reference electrode was utilized to measure the polarization resistance (Rp) using built-in sensor electrodes. Subsequently, electrochemical impedance spectroscopy in the frequency range of 1 kHz to 50 kHz was used to obtain the cement mortar resistance (Rs). The results show that the polarization resistance is related to the chloride content and Rs; ln (Rp) is linearly related to the Rs values in mortar without added chloride. The relationships observed between the Rp of the steel anodes and the resistance of the surrounding cement mortar measured by the corrosion sensor confirms that Rs can indicate the corrosion state of concrete structures.

  4. The Effect of Cement Stabilized Subgrade on Cost of the Flexible Pavement

    Directory of Open Access Journals (Sweden)

    Baha Vural Kök

    2012-03-01

    Full Text Available The road authorities aim roads that are resistant, with less maintenance, with high traffic security, with long life and economic. It is difficult to have an economic pavement construction on the subgrade with weak bearing capacity. In this study the effect of the cement stabilization on the weak subgrade and pavement costs has been studied. For this purpose the California Bearing Ratio (CBR of a weak subgrade that has been stabilized with 4% - 16% cement have been determined. The effect of the increase in the CBR on the pavement costs has been determined thanks to MATLAB program by considering thousands of alternatives. Consequently, the optimum cement content between the decrease on the pavement costs with increase on subgrade' CBR value and the additional costs spent to increase the CBR value has been determined.

  5. Valorization of electric arc furnace primary steelmaking slags for cement applications.

    Science.gov (United States)

    Kim, Hyung-Seok; Kim, Kee-Seok; Jung, Sung Suk; Hwang, Jin Ill; Choi, Jae-Seok; Sohn, Il

    2015-07-01

    To produce supplementary cementitious materials from electric arc furnace (EAF) slags, FeO was reduced using a two-stage reduction process that included an Al-dross reduction reaction followed by direct carbon reduction. A decrease in FeO was observed on tapping after the first-stage reduction, and further reduction with a stirred carbon rod in the second-stage reduction resulted in final FeO content below 5wt%, which is compatible with cement clinker applications. The reduced electric arc furnace slags (REAFS) mixed with cement at a unit ratio exhibited physical properties comparable to those of commercialized ground granulated blast furnace slags (GGBFS). Confocal laser scanning microscopy (CLSM) was used to obtain fundamental information on the cooling characteristics and conditions required to obtain amorphous REAFS. REAFS can be applied in cement mixtures to achieve the hydraulic properties needed for commercial use.

  6. Magnetic forward models of Cement oil field, Oklahoma, based on rock magnetic, geochemical, and petrologic constraints

    Science.gov (United States)

    Reynolds, R.L.; Webring, M.; Grauch, V.J.S.; Tuttle, M.

    1990-01-01

    Magnetic forward models of the Cement oil field, Oklahoma, were generated to assess the possibility that ferrimagnetic pyrrhotite related to hydrocarbon seepage in the upper 1 km of Permian strata contributes to aeromagnetic anomalies at Cement. Six bodies having different magnetizations were constructed for the magnetic models. Total magnetizations of the bodies of highest pyrrhotite content range from about 3 ?? 10-3 to 56 ?? 10-3 A/m in the present field direction and yield magnetic anomalies (at 120 m altitude) having amplitudes of less than 1 nT to ~6 to 7 nT, respectively. Numerous assumptions were made in the generation of the models, but nevertheless, the results suggest that pyrrhotite, formed via hydrocarbon reactions and within a range of concentrations estimated at Cement, is capable of causing magnetic anomalies. -from Authors

  7. Effect of Fine Steel Slag Powder on the Early Hydration Process of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Hydration heat evolution, non-evaporative water, setting time and SEM tests were performed to investigate the effect of fine steel slag powder on the hydration process of Portland cement and its mechanism.The results show that the effect of fine steel slag powder on the hydration process of Portland cement is closely related to its chemical composition, mineral phases, fineness, etc.Fine steel slag powder retards the hydration of portland cement at early age.The major reason for this phenomenon is the relative high content of MgO , MnO2, P2 O5in steel slag, and MgO solid solved in C3 S contained in steel slag.

  8. Preliminary study using pulsating water jet for bone cement demolition

    OpenAIRE

    S. Hloch; Kloc, J.; Foldyna, J.; Pude, F.; Smolko, I.; M. Zeleňák; Sitek, L. (Libor); Hvizdoš, P.; Monka, P.; Monková, K.; Kozak, D.; A. Stoić; A. Sedmak; Milosevic, M; Lehocká, D.

    2015-01-01

    The paper deals with the study of using the selective property of ultrasonic pulsating water jet for the disintegration of bone cement which creates the interface between femoral stem and trabecular bone tissue. For investigation, commercial bone cements were used. Bone cements were tested by nanoindentation in order to review their mechanical properties. A representative sample Palacos R+G was selected for disintegration of bone cement. Bone cements samples fixed between two plexiglass...

  9. ANALYSIS OF UNCERTAINTIES IN CEMENT INDUSTRY IN TURKEY

    OpenAIRE

    Kemal Yildirim; Omer Arioz

    2013-01-01

    Cement industry having 4,5 billion Dollars revenue and 1 billion Dollar export volume plays very important role in Turkey’s economy. Turkish cement industry is very sensitive to economic crisis and involves many uncertainties. In this study, price uncertainties, technological uncertainties, and price-technological uncertainties in Turkish cement industry were analyzed. The cement demand is mostly affected by demand to ready mixed concrete. Demand to cement is also related to the picture of co...

  10. Effect of Abutment Modification and Cement Type on Retention of Cement-Retained Implant Supported Crowns

    OpenAIRE

    Mitra Farzin; Kianoosh Torabi; Ahmad Hasan Ahangari; Reza Derafshi

    2014-01-01

    Objective: Provisional cements are commonly used to facilitate retrievability of cement-retained fixed implant restorations; but compromised abutment preparation may affect the retention of implant-retained crowns.The purpose of this study was to investigate the effect of abutment design and type of luting agent on the retentive strength of cement-retained implant restorations. Materials and Method: Two prefabricated abutments were attached to their corresponding analogs and embedded in an ac...

  11. Slagment Cement Improve the Cement Resistance Toward Acids Attack During Acidizing Treatment

    Directory of Open Access Journals (Sweden)

    Nik Khairul Irfan Bin Nik Ab. Lah.

    2013-05-01

    Full Text Available Acidizing treatment in past experience shows several zonal isolation problems after the treatment. This study presents the effect of the acid treatment toward class G cement and slagment cement as the improvement method to improve the cement resistance toward the acid. Lab experiments were conducted by immerge the respective cement cubes into 12% HCl/3% HF solution for 40 min before several analysis were conducted. Based on the result, the mass loss and compressive strength loss of the cement cubes decrease as the curing temperature and pressure increase due to more evenly distributed cement chemical composition crystal in high curing condition as shown in Scanning Electron Microscopy (SEM analysis. From X-Ray Diffraction (XRD and X-Ray Fluorescence (XRF analysis, only the first layer of the cement cubes shows chemical component change due to the reaction between the acid. This study found that, replacing class G cement to slagment cement can reduce the mass loss and compressive strength loss up to 72% and 82%, respectively.

  12. Exposure to cement dust at a Portland cement factory and the risk of cancer.

    OpenAIRE

    Vestbo, J; Knudsen, K.M.; Raffn, E; Korsgaard, B; Rasmussen, F V

    1991-01-01

    The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 1...

  13. 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.

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

    International Nuclear Information System (INIS)

    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

  15. Radiographic appearance of commonly used cements in implant dentistry.

    Science.gov (United States)

    Pette, Gregory A; Ganeles, Jeffrey; Norkin, Frederic J

    2013-01-01

    Cement-retained restorations allow for a conventional fixed partial denture approach to restoring dental implants. However, inadequate removal of excess cement at the time of cementation may introduce a severe complication: cement-induced peri-implantitis. Radiopaque cements are more easily detected on radiographs and should improve the recognition of extravasated cement at the time of insertion. The purpose of this study was to evaluate the radiopacity of commercially available cements in vitro. Eighteen different cements commonly used for luting restorations to implants were tested at both 0.5- and 1.0-mm thicknesses. The cements examined were zinc oxide eugenol, zinc oxide, zinc polycarboxylate, zinc phosphate, resin-reinforced glass ionomer, urethane resin, resin, and composite resin. Two samples of each cement thickness underwent standardized radiography next to an aluminum step wedge as a reference. The mean grayscale value of each of the nine 1-mm steps in the step wedge were used as reference values and compared to each of the cement samples. Temp Bond Clear (resin), IMProv (urethane resin), Premier Implant Cement (resin), and Temrex NE (resin) were not radiographically detectable at either sample thickness. Cements containing zinc were the most detectable upon radiographic analysis. There are significant differences in the radiopacity of many commonly used cements. Since cementinduced peri-implantitis can lead to late implant failure, cements that can be visualized radiographically may reduce the incidence of this problem.

  16. Characterization of Mechanical and Bactericidal Properties of Cement Mortars Containing Waste Glass Aggregate and Nanomaterials

    Directory of Open Access Journals (Sweden)

    Pawel Sikora

    2016-08-01

    Full Text Available The recycling of waste glass is a major problem for municipalities worldwide. The problem concerns especially colored waste glass which, due to its low recycling rate as result of high level of impurity, has mostly been dumped into landfills. In recent years, a new use was found for it: instead of creating waste, it can be recycled as an additive in building materials. The aim of the study was to evaluate the possibility of manufacturing sustainable and self-cleaning cement mortars with use of commercially available nanomaterials and brown soda-lime waste glass. Mechanical and bactericidal properties of cement mortars containing brown soda-lime waste glass and commercially available nanomaterials (amorphous nanosilica and cement containing nanocrystalline titanium dioxide were analyzed in terms of waste glass content and the effectiveness of nanomaterials. Quartz sand is replaced with brown waste glass at ratios of 25%, 50%, 75% and 100% by weight. Study has shown that waste glass can act as a successful replacement for sand (up to 100% to produce cement mortars while nanosilica is incorporated. Additionally, a positive effect of waste glass aggregate for bactericidal properties of cement mortars was observed.

  17. Application of Granulated Blast Furnace Slag in Cement Composites Exposed to Biogenic Acid Attack

    Science.gov (United States)

    Kovalcikova, M.; Estokova, A.; Luptakova, A.

    2015-11-01

    The deterioration of cement-based materials used for the civil infrastructure has led to the realization that cement-based materials, such as concrete, must be improved in terms of their properties and durability. 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 corrosion of concrete. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to deterioration by aggressive chemicals. The paper is focused on the investigation of the influence of biogenic acid attack on the cement composites affected by bacteria Acidithiobacillus thiooxidans. The concrete specimens with 65 wt. % addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were studied. The experiments proceeded during 150 days under model laboratory conditions. The pH values and chemical composition of leachates were measured after each 30- day cycle. The calcium and silicon contents in leachates were evaluated using X - ray fluorescence method (XRF). Summarizing the results, the 65% wt. addition of antimicrobial activated granulated blast furnace slag was not confirmed to be more resistant.

  18. USE OF CONSTRUCTION AND DEMOLITION WASTES AS RAW MATERIALS IN CEMENT CLINKER PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    Christos-Triantafyllos Galbenis; Stamatis Tsimas

    2006-01-01

    The aim of the present paper was to investigate the possibility of utilizing Construction and Demolition(C&D) wastes as substitutes of Portland cement raw meal. The C&D wastes that were so used, were the Recycled Concrete Aggregates (RCA) and the Recycled Masonry Aggregates (RMA) derived from demolished buildings in Attica region, Greece. RCA and RMA samples were selected because of their calcareous and siliceous origin respectively,which conformed the composition of the ordinary Portland cement raw meal. For that reason, six samples of cement raw meals were prepared: one with ordinary raw materials, as a reference sample, and five by mixing the reference sample with RCA and RMA in appropriate proportions. The effect on the reactivity of the generated mixtures, was evaluated on the basis of the free lime content (fCaO) in the mixtures sintered at 1350℃, 1400℃ and 1450℃. Test showed that the added recycled aggregates improved the burnability of the cement raw meal without affecting negatively the cement clinker properties. Moreover, the formation of the major components (C3S, C2S, C3A and C4AF) of the produced clinkers(sintered at 1450℃) was corroborated by X-Ray Diffraction (XRD).

  19. Cementation of sand grains based on carbonate precipitation induced by microorganism

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Microbes can produce 2 3 CO32-in an environment conductive to precipitation,so the incompact sands will be consolidated.This technology is environmentally friendly not only because it gives strength to the sand body,but also it allows water to penetrate into the sand body,which is unlike silicate cement that will destroy the ecosystem of the earth.After comparing the activity of three kinds of bacteria,the most suitable one was chosen for the study.However,the activity of this bacterium was still not high enough for the purpose,so it was purified.A suitable program for the consolidation and cementation of sands was also found in the experiment.The compressive strength and the porosity of the cemented sand body were tested to characterize the cementation effectiveness.XRD analysis showed that a new phase of calcite was produced between sand grains.The content of calcite was detected by TG.The study showed that the precipitation program was quite important to obtain a sound cemented sand body in addition to the activity of the bacteria.

  20. Three-point bending fatigue behavior of WC–Co cemented carbides

    International Nuclear Information System (INIS)

    Highlights: ► Mechanical fatigue tests were conducted on a specific designed jig. ► Three-point bending fatigue behavior of WC–Co cemented carbides was studied. ► Fatigue mechanisms of WC–Co cemented carbides with different WC grain sizes and Co binder contents were revealed. -- Abstract: WC–Co cemented carbides with different WC grain sizes and Co binder contents were sintered and fabricated. The three-point bending specimens with a single edge notch were prepared for tests. In the experiments, the mechanical properties of materials were investigated under static and cyclic loads (20 Hz) in air at room temperature. The fatigue behaviors of the materials under the same applied loading conditions are presented and discussed. Optical microscope and scanning electron microscopy were used to investigate the micro-mechanisms of damage during fatigue, and the results were used to correlate with the mechanical fatigue behavior of WC–Co cemented carbides. Experimental results indicated that the fatigue fracture surfaces exhibited more fracture origins and diversification of crack propagation paths than the static strength fracture surfaces. The fatigue fracture typically originates from inhomogeneities or defects such as micropores or aggregates of WC grains near the notch tip. Moreover, due to the diversity and complexity of the fatigue mechanisms, together with the evolution of the crack tip and the ductile deformation zone, the fatigue properties of WC–Co cemented carbides were largely relevant with the combination of transverse rupture strength and fracture toughness, rather than only one of them. Transverse rupture strength dominated the fatigue behavior of carbides with low Co content, whilst the fatigue behavior of carbides with high Co content was determined by fracture toughness.

  1. Influence of using slag cement on the microstructure and durability related properties of cement grouts for micropiles

    OpenAIRE

    Ortega Álvarez, José Marcos; Albaladejo Ruiz, Arturo; Pastor Navarro, José Luis; Sánchez Martín, Isidro; Climent, Miguel-Ángel

    2013-01-01

    Today, the use of micropiles for different applications has become very common. In Spain, the cement grouts for micropiles are prepared using ordinary Portland cement and w:c ratio 0.5, although the micropiles standards do not restrict the cement type to use, provided that it reaches a certain compressive strength. In this study, the influence of using slag cement on the microstructure and durability related properties of cement grouts for micropiles have been studied until 90 hardening days,...

  2. REMOVAL OF SOLUBLE CR(VI IN CEMENTS BY FERROUS SULPHATE MONOHYDRATE, SOLID LIGNIN AND OTHER MATERIALS

    Directory of Open Access Journals (Sweden)

    T. TUNÇ

    2011-03-01

    Full Text Available Various reducing agents such as ferrous sulphate heptahydrate (HH and monohydrate (MH, solid lignin (SL, Na2S2O4, NaHSO3, SnCl2·2H2O, N2H4·H2O and FeS are used to reduce Cr(VI contents of three types of cements under 2 mg/L, as it is requested by European Parliament Standards. Optimum conversion temperature of HH to MH was found as 130°C, for 20 min., by thermal analysis. Minimum amounts of various agents to be used as additives in cements to reduce Cr(VI contents under the standard value were determined. Minimum reducing agent amounts of SL, MH and their mixture of 1:3 mole fractions were found as 0.44 %, 0.14 %, 0.24 % by weight, respectively for Portland cement (CEM I 42.5 R, 0.40 %, 0.26 %, 0.24 % for Portland Pozzolanic cement (CEM II/A-P 42.5 N and 0.16 %, 0.05 %, 0.04 % for Pozzolanic cement (CEM IV/B (P 32.5 N. Minimum amounts of other materials to reduce Cr(VI content of three type cements under the required value, were found as 0.24 %, 0.16 %, 0.0 9 % (N2H4·H2O, 0.10 %, 0.07 %, 0.04 % (Na2S2O4, 0.04 %, 0.025 %, 0.01 % (SnCl2·2H2O and 0.28 %, 0.27 %, 0.12 % (NaHSO3, respectively. It was found that SL, the MH and their mixture of 1:3 mole fractions can be used successfully as additives for reducing Cr(VI contents of cement. There are two advantages of this usage of MH. It converts Cr(VI to Cr(III and extends the shelf-life of cement. On the other hand, SL reduces Cr(VI and increases durability of cements by lowered water/cement ratio.

  3. Calcium phosphate cements properties with polymers addition

    International Nuclear Information System (INIS)

    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. Low-cycle fatigue of surgical cements

    Directory of Open Access Journals (Sweden)

    A. Balin

    2007-01-01

    Full Text Available Purpose: In case when surgical cement is used to fix endoprostheses of joints the fatigue character of mechanicalinterraction in the cement seems to be a significant importance. The paper suggests to adapt the research methodof low cycle fatigue for modelling the loads on surgical cements in an artificial hip joint. Surgical cements havealso been modified in order to improve their functional properties.Design/methodology/approach: Low cycle fatigue tests were conducted on samples made from Palamedcement without an addition and on samples modified with glassy carbon and titanium. The tests were conductedon a servohydraulic fatigue testing machine, MTS-810, with displacement control.Findings: Fatigue tests proved viscoelastic character of all the tested materials. During the fatigue tests, thephenomenon of stress cyclic relaxation was observed.Research limitations/implications: Modelling the loadings of cement in endoprostheses of joints with the lowcycle fatigue method takes into account all high value stresses, while cement is being used for endoprosthesesfor many years in the conditions of random stress and deformation courses. Therefore the obtained stress anddeformation values are bigger than those which would have been obtained in real conditions in the same time.Practical implications: The low cycle fatigue tests carried out showed how important is the factor of timefor the behavior of surgical cement in the conditions of changeable loadings. This fact is essential to assessits usability for endoprosthesoplasty of joints, specially of a hip joint. Post deformation return which is acharacteristic feature for material viscoelasticity enables its regeneration conditioning expected durability ofendoprosthesis of joints.Originality/value: Low cycle fatigue testing method for modelling of loads on surgical cement in artificial hipjoint enables to carry out the tests in a shorter period of time.

  5. Acrylic Bone Cements Modified with Starch

    OpenAIRE

    Krilova, V; Vītiņš, V

    2010-01-01

    The successful result of restorative and replacement surgical operation depends significantly on properties of used bone cement. Acrylic bone cements are usually based on methylmethacrylate polymer, while monomer polymerization begins after mixing of components in mixing device and terminates in living tissue. Polymerization of methylmethacrylate is exothermic process, and temperature increase might cause tissue necrosis with concomitant implant aseptic loosening. Developed non-ionogenic and ...

  6. Radiological changes in asbestos cement workers.

    OpenAIRE

    Jakobsson, K; Strömberg, U; Albin, M; Welinder, H; Hagmar, L

    1995-01-01

    OBJECTIVE--To explore associations between exposure to asbestos cement dust and radiographic findings in lung parenchyma and pleura. METHODS--Radiographs from 174 blue collar workers and 29 white collar workers from an asbestos cement plant formed one part of the study. Progression of small opacities was further studied in those 124 blue collar workers, for whom two radiographs taken after the end of employment were available. The median readings from five readers who used the full ILO 1980 c...

  7. Microstructure Analysis of Heated Portland Cement Paste

    OpenAIRE

    Q. Zhang; Ye, G.

    2011-01-01

    When a concrete structure is exposed to high temperature, the mechanical damage and chemical transformation take place simultaneously, which will change the microstructure of material. On the other hand, the mechanical properties and transport properties depend on the development of microstructure of cement paste. In order to study the microstructure changes at high temperature, in this contribution the cement paste samples were firstly heated to varied temperatures from 100 °C to 1000 °C wit...

  8. Dynamic properties of composite cemented clay

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 梁旭

    2004-01-01

    In this work,the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

  9. Topics in Cement and Concrete Research

    OpenAIRE

    Brouwers, H. J. H.

    2006-01-01

    The present paper addresses several topics in regard to the sustainable design and use of concrete. First, major features concerning the sustainable aspects of the material concrete are summarised. Then the major constituent, from an environmental point of view, cement is discussed in detail, particularly the hydration and application of slag cement. The intelligent combining of mineral oxides, which are found in clinker, slag, fly ashes etc., is designated as mineral oxide engineering. It re...

  10. Estimating the chloride transport in cement paste

    OpenAIRE

    Princigallo, A.

    2012-01-01

    A method was developed to measure the diffusion coefficient of chloride ions in cement paste based on an analytical solution to Fick’s 2nd law in a cylindrical coordinate system. This natural method yielded diffusivity results within as little as a month. Testing time was reduced by exploiting the three-dimensional inward flux in the specimen. In an attempt to determine the saturation concentration, dense portland cement pastes were exposed to a concentrated chloride solution. The method prov...

  11. Performance of the Cement Matrix Composite Material With Rubber Powder

    Institute of Scientific and Technical Information of China (English)

    SONG Shao-min; LIU Juan-hong; ZHANG Xi-qing

    2004-01-01

    The effect of the deferent rubber content substituted for fine aggregate on the mortar performancewas studied. The effects of the rubber coated with the coating materials on the mortar compressive strength, bendingstrength and impact work were discussed. The optimum rubber powder content and the suitable coating materialwere found. Through the electrical probe test- BEI, SEI and calcium ion distribution, and the slight crack and theinterface between the rubber and cement matrix are analyzed. The results show that the rubber powder coated withthe surface treatment materials A, B and C bas the capability of absorbing a large amount of energy under thecompressive and flexural load and the slight cracks of R- C were controlled and restrained.

  12. Case Study of the California Cement Industry

    Energy Technology Data Exchange (ETDEWEB)

    Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn; Friedmann, Rafael

    2005-05-01

    California is the largest cement producing state in theU.S., accounting for between 10 percent and 15 percent of U.S. cementproduction and cement industry employment. The cement industry inCalifornia consists of 31 sites that consume large amounts of energy,annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3million tons of coal, 0.25 tons of coke, and smaller amounts of wastematerials, including tires. The case study summarized in this paperfocused on providing background information, an assessment ofenergy-efficiency opportunities and barriers, and program recommendationsthat can be used by program planners to better target products to thecement industry. The primary approach to this case study involvedwalk-through surveys of customer facilities and in depth interviews withcustomer decision makers and subsequent analysis of collected data. Inaddition, a basic review of the cement production process was developed,and summary cement industry energy and economic data were collected, andanalyzed. The analysis of secondary data provides background informationon the cement industry and identification of potential energy-efficiencyopportunities. The interviews provide some understanding of the customerperspective about implementation of energy-efficiencyprojects.

  13. Alkali-silica reaction resistant concrete using pumice blended cement

    Science.gov (United States)

    Ramasamy, Uma

    Durability of structures is a major challenge for the building industry. One of the many types of concrete deterioration that can affect durability is alkali-silica reaction (ASR). ASR has been found in most types of concrete structures, including dams, bridges, pavements, and other structures that are 20 to 50 years old. The degradation mechanism of ASR produces a gel that significantly expands in the presence of water as supplied from the surrounding environment. This expansion gel product can create high stresses and cracking of the concrete, which can lead to other forms of degradation and expensive structural replacement costs. The four essential factors that produce an expansive ASR gel in concrete are the presence of alkalis, siliceous aggregate, moisture, and free calcium hydroxide (CH). If concrete is starved of any one of these essential components, the expansion can be prevented. Reducing CH through the use of a supplementary cementitious material (SCM) such as natural pozzolan pumice is the focus of this research. By using a pozzolan, the amount of CH is reduced with time based on the effectiveness of the pozzolan. Many pozzolans exist, but one such naturally occurring pozzolanic material is pumice. This research focuses on determining the effect of a finely ground pumice as a SCM in terms of its resistance to ASR expansion, as well as improving resistance to other potential concrete durability mechanisms. In spite of having high alkali contents in the pumice, mixtures containing the SCM pumice more effectively mitigated the ASR expansion reaction than other degradation mechanisms. Depending on the reactivity of the aggregates and fineness of the pumice, 10-15% replacement of cement with the pumice was found to reduce the ASR expansion to the acceptable limits. The amount of CH remaining in the concrete was compared to the ASR expansion in order to improve understanding of the role of CH in the ASR reaction. Thermo-gravimetric analysis (TGA) and X

  14. Secondary raw materials for synthesising new kind of cements

    Directory of Open Access Journals (Sweden)

    Goñi, S.

    2001-12-01

    Full Text Available The present paper is a comparative study of some characteristics of new belite cements obtained from two kind of wastes, which were used as secondary raw materials: fly ash (FA, of low CaO content, from coal combustion, and ash from incineration of municipal solid waste (MSWIA. Cements were synthesised in a range of temperature between 700°C and 900°C from MSWIA and FA, which were previously activated by hydrothermal treatment at 200°C The evolution of cemented phases with the heating temperature was followed by X-ray diffraction (XRD. The results were compared with those obtained from heating the starting FA and MSWIA without the previous hydrothermal treatment. The degree of hydration was quantitatively evaluated by the combined water content, determined from thermogravimetric analyses, during a period of 28 days or 200 days from mixing depending of hydration kinetics of each cement.

    Este trabajo es un estudio comparativo de algunas de las características de nuevos cementos belíticos, obtenidos a partir de dos tipos de residuos, como materia prima secundaria: cenizas volantes (CV de bajo contenido en cal, procedentes de la combustión del carbón y cenizas procedentes de la incineración de residuos sólidos urbanos (CIRSU. Los cementos fueron sintetizados en un rango de temperaturas comprendido entre 700°C y 900°C después de un tratamiento hidrotermal de la CV y CIRSU a 200°C La evolución de las fases cementicias, con la temperatura de calentamiento, fue estudiada por difracción de rayos X (DRX. Los resultados fueron comparados con aquellos obtenidos, directamente, por calentamiento de los residuos, sin un tratamiento hidrotermal previo de los mismos. El grado de hidratación fue cuantitativamente evaluado, por medio del análisis termogravimétrico, a partir del agua combinada de los cementos hidratados durante un período de 28 días o 200 días, dependiendo de la cinética de hidratación de cada cemento.

  15. Use of MRF residue as alternative fuel in cement production.

    Science.gov (United States)

    Fyffe, John R; Breckel, Alex C; Townsend, Aaron K; Webber, Michael E

    2016-01-01

    Single-stream recycling has helped divert millions of metric tons of waste from landfills in the U.S., where recycling rates for municipal solid waste are currently over 30%. However, material recovery facilities (MRFs) that sort the municipal recycled streams do not recover 100% of the incoming material. Consequently, they landfill between 5% and 15% of total processed material as residue. This residue is primarily composed of high-energy-content non-recycled plastics and fiber. One possible end-of-life solution for these energy-dense materials is to process the residue into Solid Recovered Fuel (SRF) that can be used as an alternative energy resource capable of replacing or supplementing fuel resources such as coal, natural gas, petroleum coke, or biomass in many industrial and power production processes. This report addresses the energetic and environmental benefits and trade-offs of converting non-recycled post-consumer plastics and fiber derived from MRF residue streams into SRF for use in a cement kiln. An experimental test burn of 118 Mg of SRF in the precalciner portion of the cement kiln was conducted. The SRF was a blend of 60% MRF residue and 40% post-industrial waste products producing an estimated 60% plastic and 40% fibrous material mixture. The SRF was fed into the kiln at 0.9 Mg/h for 24h and then 1.8 Mg/h for the following 48 h. The emissions data recorded in the experimental test burn were used to perform the life-cycle analysis portion of this study. The analysis included the following steps: transportation, landfill, processing and fuel combustion at the cement kiln. The energy use and emissions at each step is tracked for the two cases: (1) The Reference Case, where MRF residue is disposed of in a landfill and the cement kiln uses coal as its fuel source, and (2) The SRF Case, in which MRF residue is processed into SRF and used to offset some portion of coal use at the cement kiln. The experimental test burn and accompanying analysis indicate

  16. Use of MRF residue as alternative fuel in cement production.

    Science.gov (United States)

    Fyffe, John R; Breckel, Alex C; Townsend, Aaron K; Webber, Michael E

    2016-01-01

    Single-stream recycling has helped divert millions of metric tons of waste from landfills in the U.S., where recycling rates for municipal solid waste are currently over 30%. However, material recovery facilities (MRFs) that sort the municipal recycled streams do not recover 100% of the incoming material. Consequently, they landfill between 5% and 15% of total processed material as residue. This residue is primarily composed of high-energy-content non-recycled plastics and fiber. One possible end-of-life solution for these energy-dense materials is to process the residue into Solid Recovered Fuel (SRF) that can be used as an alternative energy resource capable of replacing or supplementing fuel resources such as coal, natural gas, petroleum coke, or biomass in many industrial and power production processes. This report addresses the energetic and environmental benefits and trade-offs of converting non-recycled post-consumer plastics and fiber derived from MRF residue streams into SRF for use in a cement kiln. An experimental test burn of 118 Mg of SRF in the precalciner portion of the cement kiln was conducted. The SRF was a blend of 60% MRF residue and 40% post-industrial waste products producing an estimated 60% plastic and 40% fibrous material mixture. The SRF was fed into the kiln at 0.9 Mg/h for 24h and then 1.8 Mg/h for the following 48 h. The emissions data recorded in the experimental test burn were used to perform the life-cycle analysis portion of this study. The analysis included the following steps: transportation, landfill, processing and fuel combustion at the cement kiln. The energy use and emissions at each step is tracked for the two cases: (1) The Reference Case, where MRF residue is disposed of in a landfill and the cement kiln uses coal as its fuel source, and (2) The SRF Case, in which MRF residue is processed into SRF and used to offset some portion of coal use at the cement kiln. The experimental test burn and accompanying analysis indicate

  17. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  18. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  19. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

    Science.gov (United States)

    2011-12-08

    ... review. Background The Commission instituted this review on May 2, 2011 (76 FR 24519) and determined on August 5, 2011 that it would conduct an expedited review (76 FR 50252, August 12, 2011). The Commission... COMMISSION Gray Portland Cement and Cement Clinker From Japan Determination On the basis of the record...

  20. Characterization of cement minerals, cements and their reaction products at the atomic and nano scale

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Hall, Christopher

    2008-01-01

    Recent advances and highlights in characterization methods are reviewed for cement minerals, cements and their reaction products. The emphasis is on X-ray and neutron diffraction, and on nuclear magnetic resonance methods, although X-ray absorption and Raman spectroscopies are discussed briefly...

  1. Hydration of alumina cement containing ferrotitanium slag with polycarboxylate-ethers (PCE) additives

    Science.gov (United States)

    Rechkalov, Denis; Chernogorlov, Sergey; Abyzov, Victor

    2016-01-01

    The paper is discussing results of study of alumina binder containing aluminous cement and ferrotitanium slag from aluminothermic process by Kliuchevskoi Ferroalloys corp. with various additives containing polycarboxylate-ethers (PCE). Selecting ferrotitanium slag as additive is based on the fact that its content of alumina and phase composition is closest to the alumina cement. The composition of the ferrotitanium slag is displayed. In order to compensate the decrease in strength caused by addition of ferrotitanium slag having low activity, PCE additives were added. As PCE additives were used Melflux 1641F, Melflux 2651F and Melflux PP200F by BASF. The effect of additives on the hydration of the binder, depending on the amount and time of additives hardening is shown. The composition of the hydration products in the cement was studied by physico-chemical analysis: derivatography and X-ray analysis. It is found that in the early stages of hardening PCE additives have inhibitory effect on hydration processes and promote new phase amorphization. The optimal content of additives was investigated. The basic properties of the binders have been tested. It was observed that the modified binders meet the requirements of Russian National State Standard GOST 969 to the alumina cement.

  2. Monte-Carlo simulation of cement neutron field distribution characteristics in PGNAA

    International Nuclear Information System (INIS)

    The distribution characteristics of the neutron field in cement was simulated using the MCNP code to comply with the requirements of an online Prompt Gamma Neutron Activation Analysis system. Simulation results showed that the neutron relative flux proportion reduced with increasing cement thickness. When the cement thickness remains unchanged, the reduced proportion of thermal neutrons increases to a small extent, but the epithermal, intermediate, and fast neutrons will decrease according to the geometric progression. H element in the cement mainly affects the reduction of fast neutrons and other single-substance elements, e.g., O, Ca, 56Fe, Si, and Al. It also slows down the reduction of the fast neutrons via inelastic scattering. O contributes more than other elements in the reduction of fast neutrons. Changing the H content affects the thermal, epithermal, intermediate, and fast neutrons, while changing the Ca, Fe, and Si contents only influences the thermal, epithermal, and intermediate neutrons; hence, there is little effect on the reduction of fast neutrons. (authors)

  3. Reuse of de-inking sludge from wastepaper recycling in cement mortar products.

    Science.gov (United States)

    Yan, Shiqin; Sagoe-Crentsil, Kwesi; Shapiro, Gretta

    2011-08-01

    This paper presents results of an investigation into the use of de-inking sludge from a paper recycling mill as feedstock material in the manufacture of cement mortar products, including masonry blocks and mortar renders. Both physical and mechanical properties of mortar specimens containing various amounts of de-inking sludge were investigated. It was observed that the addition of de-inking sludge to cement mortar at a fixed water-to-cement ratio significantly reduced flow properties and increased setting time. Water absorption and volume of permeable voids of cement mortar increased with increased dosage of de-inking sludge, with a corresponding reduction of bulk density. The 91-day compressive strength of mortar samples with 2.5 wt% and 20 wt% de-inking sludge loadings retained 83% and 62% respectively of the reference mortar strength. The corresponding drying shrinkage increased by up to 160% compared to reference samples. However, a de-inking sludge loading of up to 2.5 wt% did not significantly alter measured physical and mechanical properties. The results demonstrate that despite the high moisture absorbance of de-inking sludge due to its organic matter and residual cellulose fibre content, it serves as a potential supplementary additive and its cellulosic content proving to be an active set retardant to cementitious masonry products.

  4. Composition Design for High C3S Cement Clinker and Its Mineral Formation

    Institute of Scientific and Technical Information of China (English)

    HOU Guihua; SHEN Xiaodong; XU Zhongzi

    2007-01-01

    A new composition of Portland cement clinker was studied, in which KH, SM and IM was 0.98,2.4 and 2.4 respectively as well as its meal added 1%CuO (in mass). Fired at 1 200 ℃,1 350 ℃,1 400℃ and 1 450 ℃ for 30 min, the resultant mineral phases component and mineral morphology were analyzed.The performances of the cement which was made of clinker burned at 1 450 ℃ and fly ash were determined. By means of QXRD, XRD and optical microscopy, it is shown that the clinker burnt at 1 450 ℃ has the larger size crystals and distinct crystal interface, in which the C3S content is 73.37% and the mineral phases is dominantly C3S, following by minor C2S, C3A and tetracalcium aluminoferrite. The results reveal that a new type of high C3S content clinker can completely be made by traditional temperature-time schedule. The performances of the cement produced from this clinker with addtion of 50% fly ash and 5% gupsum were in agreement with the 32.5 strength grade of Portland fly-ash cement. The results also show that the clinker has a significant effect of saving energy and utilizing waste slag.

  5. A new method to analyze copolymer based superplasticizer traces in cement leachates.

    Science.gov (United States)

    Guérandel, Cyril; Vernex-Loset, Lionel; Krier, Gabriel; De Lanève, Michel; Guillot, Xavier; Pierre, Christian; Muller, Jean François

    2011-03-15

    Enhancing the flowing properties of fresh concrete is a crucial step for cement based materials users. This is done by adding polymeric admixtures. Such additives have enabled to improve final mechanicals properties and the development of new materials like high performance or self compacting concrete. Like this, the superplasticizers are used in almost cement based materials, in particular for concrete structures that can have a potential interaction with drinking water. It is then essential to have suitable detection techniques to assess whether these organic compounds are dissolved in water after a leaching process or not. The main constituent of the last generation superplasticizer is a PolyCarboxylate-Ester copolymer (PCE), in addition this organic admixture contains polyethylene oxide (free PEO) which constitutes a synthesis residue. Numerous analytical methods are available to characterize superplasticizer content. Although these techniques work well, they do not bring suitable detection threshold to analyze superplasticizer traces in solution with high mineral content such as leachates of hardened cement based materials formulated with superplasticizers. Moreover those techniques do not enable to distinguish free PEO from PCE in the superplasticizer. Here we discuss two highly sensitive analytical methods based on mass spectrometry suitable to perform a rapid detection of superplasticizer compounds traces in CEM I cement paste leachates: MALDI-TOF mass spectrometry, is used to determine the free PEO content in the leachate. However, industrial copolymers (such as PCE) are characterized by high molecular weight and polymolecular index. These two parameters lead to limitation concerning analysis of copolymers by MALDI-TOFMS. In this study, we demonstrate how pyrolysis and a Thermally assisted Hydrolysis/Methylation coupled with a triple-quadrupole mass spectrometer, provides good results for the detection of PCE copolymer traces in CEM I cement paste

  6. Alternative Fuel for Portland Cement Processing

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Anton K; Duke, Steve R; Burch, Thomas E; Davis, Edward W; Zee, Ralph H; Bransby, David I; Hopkins, Carla; Thompson, Rutherford L; Duan, Jingran; ; Venkatasubramanian, Vignesh; Stephen, Giles

    2012-06-30

    The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

  7. Alternative Fuel for Portland Cement Processing

    Energy Technology Data Exchange (ETDEWEB)

    Anton K. Schindler; Steve R. Duke; Thomas E. Burch; Edward W. Davis; Ralph H. Zee; David I. Bransby; Carla Hopkins; Rutherford L. Thompson; Jingran Duan; Vignesh Venkatasubramanian; Stephen Giles.

    2012-06-30

    The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

  8. Characterisation of cemented/bituminized LAW and MAW waste products

    International Nuclear Information System (INIS)

    In the context of work for characterising low and medium activity waste products, investigations were carried out to determine the release of radioactivity from binding waste in given accidents, such as mechanical and thermal loading for the operating phase of a final store. The effects of mechanical loads on MAW cement products and the effects of thermal laods on MAW cement and MAW bitumen products were examined. The release of fine dust reaching the lungs, with a particle size of ≤10 μm from a 200 litre roller seam cement binder with a maximum mechanical load of 3x105 Nm covering the accident case is about 1.5 g and therefore corresponds to ≅ 10-4% of the total radio-activity inventory for homogeneous products. With thermal loading (60 minute oil fire, 8000C) ≅ 10-3% of the radioactivity inventory is released via the release of water from the waste binder. The activity release of MAW bitumen products containing NaNO3 (175 litre drum) with thermal load is considerably higher, as due to the NaNO3 content of the products, after an induction period of about 20 minutes there is an exothermal reaction between the bitumen and the NaNO3, which leads to burning of the bitumen with considerable aerosol formation. The Na losses are about 32% and the Pu losses, derived from the results of laboratory experiments with samples containing Eu and Pu and samples containing Eu on the original size, are only 15% maximum, even with complete burn up. It was shown for all the investigations with samples of the original size that the effects of the load cases considered can be reduced or completely avoided by additional packing (concrete shielding). (orig./RB)

  9. Carbonation Resistance of Sulphoaluminate Cement-based High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen

    2009-01-01

    The influences of water/cement ratio and admixtures on carbonation resistance of sulphoaluminate cement-based high performance concrete(HPC)were investigated.The experimental results show that with the decreasing water/cement ratio,the carbonation depth of sulphoaluminate cement-based HPC is decreased remarkably,and the carbonation resistance capability is also improved with the adding admixtures.The morphologies and structure characteristics of sulphoaluminate cement hydration products before and after carbonation were analyzed using SEM and XRD.The analysis results reveal that the main hydration product of sulphoaluminate cement,that is ettringite(AFt),de-composes after carbonation.

  10. [Burns caused by cement mortar (based on expert opinion)].

    Science.gov (United States)

    Kleinhans, D

    1984-01-01

    A 35-year-old farmer with scars on his right arm, following erosion obviously due to wet cement (case of an expert opinion), was examined. Cement water had continuously soaked his shirt while he was planing a freshly applied wet cement ceiling with his right arm upwards. The cement did not contain special additives, so the normal alkalinity of wet cement and occlusion effects caused the erosion. The farmer sued the manufacturer of the cement for damages because of missing warning notices. The court decided in his favor.

  11. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

    Experimental and theoretical studies of hydrated cement systems are described. The behaviour of slag-based cement is described with a view to predicting their long term pH, Esub(n) and mineralogical balance. Modelling studies which enable the prediction at long ages of cement composites are advanced and a base model of the CaO-SiO2-H2O system presented. The behaviour of U and I in cements is explored. The tolerance of cement systems for a wide range of miscellaneous waste stream components and environmental hazards is described. The redox potential in cements is effectively lowered by irradiation. (author)

  12. Quality control of cemented waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Slate, L.J.

    1994-12-31

    To insure that cemented radwaste remains immobilized after disposal, certain standards have been set in Europe by the Commission of the European Communities. One such standard is compressive strength. If the compressive strength can be predicted during the early curing stages, time and money can be saved and the quality of the final waste form guaranteed. It was determined that the 7- and 28-day compressive strength from radwaste cementation can be predicted during the mixing and early curing stages by at least three methods. The three that were studied were maturity, rheology, and impedance. Maturity is a temperature-to-time measurement, rheology is a shear stress-to-shear rate measurement, and impedance is the opposition offered to the flow of alternating current. These three methods were employed on five different cemented radwaste concentrations with three different water-to-cement ratios; thus, a total of 15 different mix designs were considered. The results showed that the impedance was the easiest to employ for an on-line process. The results of the impedance method showed a very good relationship between impedance and water-to-cement ratio; therefore, an accurate prediction of compressive strength of cemented radwaste can be drawn from this method. The results of the theology method were very good. The method showed that concrete conforms to the Bingham plastic rheologic model, and the theology method can be used to predict the compressive strength of cemented radwaste, but may be too cumbersome. The results of the maturity method were shown to be limited in accuracy for determining compressive strength.

  13. Colorectal cancer and non-malignant respiratory disease in asbestos cement and cement workers

    International Nuclear Information System (INIS)

    Radiologically visible parenchymal changes (small opacities >= 1/0;ILO 1980 classification) were present in 20% of a sample of workers (N=174), employed for 20 years (median) in an asbestos cement plant. Exposure-response relationships were found, after controlling for age and smoking habits. In a sample of asbestos cement workers with symptoms and signs suggestive of pulmonary disease (N=33), increased lung density measured by x-ray computed tomography, and reduced static lung volumes and lung compliance was found. In a cohort of asbestos cement workers (N=1.929) with an estimated median exposure of 1.2 fibres/ml, the mortality from non-malignant respiratory disease was increased in comparison to a regional reference cohort (N=1.233). A two-to three-fold increase of non-malignant respiratory mortality was noted among workers employed for more than a decade in the asbestos cement plant, compared to cement workers (N=1.526), who in their turn did not experience and increased risk compared to the general population. In the cohorts of asbestos cement and cement workers, there was a tow-to three-fold increased incidence of cancer in the right part of the colon, compared to the general population as well as to external reference cohorts of other industrial workers (N=3.965) and fishermen (N=8.092). A causal relation with the exposure to mineral dust and fibres was supported by the findings of higher risk estimated in subgroups with high cumulated asbestos doses or longer duration of cement work. The incidence of cancer in the left part of the colon was not increased. Morbidity data, but not mortality data, disclosed the subsite-specific risk pattern. Both asbestos cement workers and cement workers has an increased incidence of rectal cancer, compared with the general population, and with the fishermen. The risk was, however, of the same magnitude among the other industrial workers. 181 refs

  14. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    Directory of Open Access Journals (Sweden)

    Adriana Eštoková

    2013-12-01

    Full Text Available The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

  15. Microstructure and Properties of Cement Foams Prepared by Magnesium Oxychloride Cement

    Institute of Scientific and Technical Information of China (English)

    WANG Fazhou; YANG Lu; GUAN Lingyue; HU Shuguang

    2015-01-01

    Microstructural features including pore size distribution, cell walls and phase compositions of magnesium oxychloride cement foams (MOCF) with various MgO powders and water mixture ratios were studied. Their influences on compressive strength, water absorption and resistance of MOCF were also discussed in detail. The experimental results indicated that moderate and slight excess MgO powders (MgO/MgCl2 molar ratios from 5.1 to 7) were beneficial to the formation of excellent microstructure of MOCF, but increasing water contents (H2O/MgO mass ratios from 0.9 to 1.29) might result in opposite conclusions. The microstructure of MOCF produced with moderate and slight excess MgO powders could enhance the compressive strength, while serious excess MgO powders addition (MgO/MgCl2 molar ratios=9) would destroy the cell wall structures, and therefore decrease the strength of the system. Although MOCF produced with excess MgO powders could decrease the water absorption, its softening coefficient was lower than that of the material produced with moderate MgO powders. This might be due to the instability of phase 5, the volume expansion and cracking of cell walls as immersed the sample into water.

  16. Analysis of system and methods for improved cementing of oil- and gas wells

    OpenAIRE

    Stensrud, Magnus

    2011-01-01

    Cement is a crucial part of well construction. If a good cement bond between the casing and well bore wall cannot be achieved in the primary cementing, expensive remedial cementing jobs or possible loss of the well bore can occur.When cementing casings and liners in deep waters or pressure depleted reservoirs there is often a small pressure margin between pore pressure and fracture pressure, this makes cement operations more complex. New cementing techniques and cements are being developed to...

  17. Glass Polyalkenoate Cements Designed for Cranioplasty Applications: An Evaluation of Their Physical and Mechanical Properties.

    Science.gov (United States)

    Khader, Basel A; Curran, Declan J; Peel, Sean; Towler, Mark R

    2016-01-01

    Glass polyalkenoate cements (GPCs) have potential for skeletal cementation. Unfortunately, commercial GPCs all contain, and subsequently release, aluminum ions, which have been implicated in degenerative brain disease. The purpose of this research was to create a series of aluminum-free GPCs constructed from silicate (SiO₂), calcium (CaO), zinc (ZnO) and sodium (Na₂O)-containing glasses mixed with poly-acrylic acid (PAA) and to evaluate the potential of these cements for cranioplasty applications. Three glasses were formulated based on the SiO₂-CaO-ZnO-Na₂O parent glass (KBT01) with 0.03 mol % (KBT02) and 0.06 mol % (KBT03) germanium (GeO₂) substituted for ZnO. Each glass was then mixed with 50 wt % of a patented SiO₂-CaO-ZnO-strontium (SrO) glass composition and the resultant mixtures were subsequently reacted with aqueous PAA (50 wt % addition) to produce three GPCs. The incorporation of Ge in the glass phase was found to result in decreased working (142 s to 112 s) and setting (807 s to 448 s) times for the cements manufactured from them, likely due to the increase in crosslink formation between the Ge-containing glasses and the PAA. Compressive (σc) and biaxial flexural (σf) strengths of the cements were examined at 1, 7 and 30 days post mixing and were found to increase with both maturation and Ge content. The bonding strength of a titanium cylinder (Ti) attached to bone by the cements increased from 0.2 MPa, when placed, to 0.6 MPa, after 14 days maturation. The results of this research indicate that Germano-Silicate based GPCs have suitable handling and mechanical properties for cranioplasty fixation. PMID:27023623

  18. Characterization of waste products prepared from radioactive contaminated clayey soil cemented according to the GEODUR process

    International Nuclear Information System (INIS)

    Radioactive contaminated soil may arise due to accidents of various types or may be detected during decommisioning of nuclear installations. Ordinary surface soil cannot normally be conditioned using conventional cementation processes since the content of humic materials retards or prevents the solidification. An additive available from the Danish firm Geodur A/S makes it possible to circumvent this difficulty and to produce a monolithic, nondusting waste type using rather small amounts of cement. The report describes work on characterization of such a cemented waste product prepared on basis of clayey top soil from the Risoe area. The claimed advantages of the process was verified, and data for the compression strength (low), hydraulic conductivity (satisfactory) and other pore structure-related properties are given for the obtained products. Unfortunately the behaviour of cesium and strontium, representing two of the most relevant radionuclides, was not too promising. The retention of cesium is satisfactory, but less good than for the untreated soil. Greatly improved cesium retention after drying of the materials was noticed. Good retention of strontium is only obtained after reaction of the material with carbon dioxide from the atmosphere. The behaviour of the two isotopes in other types of cemented waste is somewhat similar, but the decrease in retention compared with untreated soil makes the process less interesting as a possibility for remedial actions after accidents, etc. Some further studies of the cemented soil waste are beeing made within the frame of the Nordic Nuclear Safety Studies. Elements forming low solublity components in the high pH environment in the cemented soil will probably be retained quite efficiently. This was demonstrated in case of Zn. (author) 11 tabs., 22 ills., 8 refs

  19. Estimation of longevity of portland cement grout using chemical modeling techniques

    International Nuclear Information System (INIS)

    Portland cement has been identified as a likely candidate seal material by programs investigating the deep burial of nuclear waste as a disposal mechanism. The longevity of performance of cement grout is currently being investigated, along with bentonite, under the auspices of the Stripa Project. Coordinated laboratory, field, and modeling studies are underway to produce fundamental data, practical experience, and estimates of long-range performance, respectively. Long-term performance of cement grout is of particular concern. Since most of the solid phases of which grout is comprised are metastable, it is likely that grout performance will decrease with time. The question is whether performance will still be acceptable after this decrease. This issue is being addressed with the coupled use of geochemical and permeability modeling. For a simplified cement system, two mechanisms for chemical degradation have been considered: phase change and dissolution. For dissolution, both equilibrium (slow flow) and open (fast flow) systems have been analyzed as bounding scenarios. Granitic terrain groundwaters ranging from fresh to saline have been used in the analyses. To assess the consequences in terms of flow, an empirical relation between cement permeability and porosity has been developed. Performance changes with time have been predicted by making conservative estimates of local hydraulic head conditions for successive periods of repository history. For the granitic rock environments considered, preliminary results indicate that cement grout performance may be acceptable for tens of thousands to millions of years, providing its initial hydraulic conductivity is on the order of 10-12 m/s. Other conditions favoring long-term performance include minimizing the ettringite content of the grout, and emplacement at a site where the groundwater has an elevated TDS, and where the local hydraulic gradient is flat or repository resaturation times are short

  20. Hydraulic activity of cement mixed with slag from vitrified solid waste incinerator fly ash.

    Science.gov (United States)

    Lin, Kae-Long; Wang, Kuen-Sheng; Tzeng, Bor-Yu; Lin, Chung-Yei

    2003-12-01

    This study investigates the effects of the slag composition on the hydraulic activity in slag blended cement pastes that incorporate synthetic slag prepared by melting CaO-modified municipal solid waste incinerator fly ash. Two types of composition-modified slag were prepared for this study. First, fly ash was mixed with the modifier (CaO) at 5% and 15% (by weight) respectively, resulting in two fly ash mixtures. These mixtures were then melted at 1400 degrees C for 30 minutes and milled to produce two types of slag with different modifier contents, designated as C1-slag and C2-slag. These synthetic slags were blended with ordinary Portland cement at various weight ratios ranging from 10% to 40%. The synthetic slags presented sufficient hydraulic activity, and the heavy metal leaching concentrations all met the EPA's regulatory thresholds. The pore size distribution was determined by mercury intrusion porosimetry, and the results correlated with the compressive strength. The results also indicate that the incorporation of the 10% C1-slag tended to enhance the hydration degree of slag blended cement pastes during the early ages (3-28 days). However, at later ages, no significant difference in hydration degree was observed between ordinary Portland cement pastes and 10% C1-slag blended cement pastes. In the 10% C2-slag case, the trend was similar, but with a more limited enhancement during the early ages (3-28 days). Thus vitrified waste incinerator fly ash is a technically useful additive to cement, reducing the disposal needs for the toxic fly ash. PMID:14986718

  1. A cost effective cultivation medium for biocalcification of Bacillus pasteurii KCTC 3558 and its effect on cement cubes properties.

    Science.gov (United States)

    Yoosathaporn, S; Tiangburanatham, P; Bovonsombut, S; Chaipanich, A; Pathom-Aree, W

    2016-01-01

    Application of carbonate precipitation induced by Bacillus pasteurii for improving some properties of cement has been reported. However, it is not yet successful in commercial scale due to the high cost of cultivation medium. This is the first report on the application of effluent from chicken manure bio-gas plant, a high protein content agricultural waste, as an alternative growth medium for carbonate precipitation by B. pasteurii KCTC3558. Urease activity of B. pasteurii KCTC3558 cultured in chicken manure effluent medium and other three standard media were examined using phenate method. The highest urease production was achieved in chicken manure effluent medium (16.756Umg(-1) protein). Cost per liter of chicken manure effluent medium is up to 88.2% lower than other standard media. The most effective cultivation media was selected for carbonate precipitation study in cement cubes. Water absorption, voids, apparent density and compressive strength of cement cubes were measured according to the ASTM standard. The correlation between the increasing density and compressive strength of bacterial added cement cube was evident. The density of bacterial cement cube is 5.1% higher than control while the compressive strength of cement mixed with bacterial cells in chicken manure effluent medium increases up to 30.2% compared with control. SEM and XRD analysis also found the crystalline phase of calcium carbonate within bacterial cement which confirmed that the increasing density and compressive strength were resulted from bacterial carbonate precipitation. This study indicated that the effluent from chicken manure bio-gas plant could be used as an alternative cost effective culture medium for cultivation and biocalcification of B. pasteurii KCTC3558 in cement. PMID:27242150

  2. Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives

    Science.gov (United States)

    Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.

    2008-12-01

    Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the

  3. EFFECT OF NANOMATERIALS IN CEMENT MORTAR CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    WAIL N. AL-RIFAIE

    2016-09-01

    Full Text Available Concrete is considered as brittle materials and widely used due to high compressive strength but unfortunately having and has low tensile strength that has a numerous negative impacts on the lifespan of concrete made structures. Therefore, mechanical properties of cement mortar have been investigated experimentally using different types and ratios of nano material to improve the properties. Since the strength of the concrete is of high importance, different materials have been used to enhance the compressive and the tensile characteristics of the cement mortar compressive and tensile strength. Mainly, this objective has been implemented through using micro cement, micro sand, nano silica, and nano clay in developing a nano-cement mortar which can to improve the concrete for the constructional applications. The samples were prepared and tested under tensile and compressive mode according to ASTM-2011 regulations for concrete. The parameters that are taken consideration during the investigation were micro sand, micro cement, nano silica, developed nano clay, and naphthalene sulphonate as super- plasticizers. In general, it has been observed that the results showed a significant increase in both compressive and tensile strength of the mortar at early stages of hardening, where a maximum increase of 22% in the compressive strength was achieved , whereas 3.7 time increase in the compressive strength was recorded over the tradition levels of the concrete strength.

  4. Pulmonary Artery Cement Embolism after a Vertebroplasty

    Directory of Open Access Journals (Sweden)

    Anas Nooh

    2015-01-01

    Full Text Available Background Context. Vertebroplasty is a minimally invasive procedure most commonly used for the treatment of vertebral compression fractures. Although it is relatively safe, complications have been reported over time. Among those complications, massive cement pulmonary embolism is considered a rare complication. Here we report a case of massive diffuse cement pulmonary embolism following percutaneous vertebroplasty for a vertebral compression fracture. Study Design. Case report. Methods. This is a 70-year-old female who underwent vertebroplasty for T11 and T12 vertebral compression fracture. Results. CT-scan revealed an incidental finding of cement embolism in the pulmonary trunk and both pulmonary arteries. Since the patient was asymptomatic, she was monitored closely and she did not need any intervention. Conclusion. Vertebroplasty is a minimally invasive procedure used for treatment of vertebral compression fracture. Despite the low rate of complications, a pulmonary cement embolism can occur. The consequences of cement embolism range widely from being asymptomatic to embolism that can cause paralysis, radiculopathy, or a fatal pulmonary embolism.

  5. Microbial-influenced cement degradation: Literature review

    International Nuclear Information System (INIS)

    The Nuclear Regulatory Commission stipulates that disposed low-level radioactive waste (LLW) be stabilized. Because of apparent ease of use and normal structural integrity, cement has been widely used as a binder to solidify LLW. However, the resulting waste forms are sometimes susceptible to failure due to the actions of waste constituents, stress, and environment. This report reviews literature which addresses the effect of microbiologically influenced chemical attack on cement-solidified LLW. Groups of microorganisms are identified, which are capable of metabolically converting organic and inorganic substrates into organic and mineral acids. Such acids aggressively react with concrete and can ultimately lead to structural failure. Mechanisms inherent in microbial-influenced degradation of cement-based material are the focus of this report. This report provides sufficient evidence of the potential for microbial-influenced deterioration of cement-solidified LLW to justify the enumeration of the conditions necessary to support the microbiological growth and population expansion, as well as the development of appropriate tests necessary to determine the resistance of cement-solidified LLW to microbiological-induced degradation that could impact the stability of the waste form

  6. Durability of compressed soil-cement bricks

    Directory of Open Access Journals (Sweden)

    Acosta Valle, A.

    2001-06-01

    Full Text Available This papers shows the evaluation process of the durability of compressed soil-cement bricks. A great number of tests were made to determine the behavior of bricks when they are compression loaded and under the influence of moisture. Two different types of soils were used to produce the bricks, a lime-clay soil and a sand one. The sand soil is very resistant. The other one has a limited use. An experimental design was used to test the bricks. It is a rotational and quadratic method with a hexagonal figure which contains replicas at the central point. This method ensures the reliability of test results. Otherwise, it would reduce the amount of specimens necessary for the tests. The optimun moisture content is obtained by using a press machine. It is more rational than the standard Proctor compactation test, because it applies the same type and amount of energy used to produce the bricks. The obtained results show the behavior differences between the two compressed soil-cement bricks subjected to the compression test, water absorption and wetting and drying tests. The durability tests results are very important in the possible use of the bricks produced.

    En el trabajo se evalúa la durabilidad de elementos aglomerados de suelo estabilizado. Se realiza un amplio número de ensayos encaminados a determinar el comportamiento frente a la acción de las cargas y la humedad de dos suelos con características diferentes: uno limo-arcilloso y el otro arenoso. Este último presenta resultados muy favorables en ambas direcciones. El otro, con un posible uso más limitado. Se emplea un método de diseño experimental del tipo rotacional cuadrático en hexágono, con réplicas en el punto central, el que garantiza la confiabilidad de los resultados de los ensayos, a la vez que disminuye la cantidad de especímenes a ensayar. Se determina la humedad óptima a utilizar en las diferentes dosificaciones empleando la máquina compactadora, que resulta m

  7. NEURO-FUZZY MODELLING OF BLENDING PROCESS IN CEMENT PLANT

    Directory of Open Access Journals (Sweden)

    Dauda Olarotimi Araromi

    2015-11-01

    Full Text Available The profitability of a cement plant depends largely on the efficient operation of the blending stage, therefore, there is a need to control the process at the blending stage in order to maintain the chemical composition of the raw mix near or at the desired value with minimum variance despite variation in the raw material composition. In this work, neuro-fuzzy model is developed for a dynamic behaviour of the system to predict the total carbonate content in the raw mix at different clay feed rates. The data used for parameter estimation and model validation was obtained from one of the cement plants in Nigeria. The data was pre-processed to remove outliers and filtered using smoothening technique in order to reveal its dynamic nature. Autoregressive exogenous (ARX model was developed for comparison purpose. ARX model gave high root mean square error (RMSE of 5.408 and 4.0199 for training and validation respectively. Poor fit resulting from ARX model is an indication of nonlinear nature of the process. However, both visual and statistical analyses on neuro-fuzzy (ANFIS model gave a far better result. RMSE of training and validation are 0.28167 and 0.7436 respectively, and the sum of square error (SSE and R-square are 39.6692 and 0.9969 respectively. All these are an indication of good performance of ANFIS model. This model can be used for control design of the process.

  8. The Next Generation Ecological Self Compacting Concrete with Glass Waste Powder as a Cement Component in Concrete and Recycled Concrete Aggregates

    OpenAIRE

    Kara, P

    2013-01-01

    In the present study the performance characteristics (workability, compressive strength, frost resistance, permeability and temperature of hydration) of the ecological self compacting concrete with reduced cement content and with the next generation recycled concrete aggregates which are obtained from crashed concrete specimens with cement substitution at level of 30% with waste glass powder were investigated. Waste glass as powder ground to certain fineness accelerates beneficial chemical re...

  9. Effect ofAuxiliary Cementing Materials on the SulphateAluminium Cement%辅助凝胶材料对硫铝酸盐水泥性能影响研究

    Institute of Scientific and Technical Information of China (English)

    刘文斌

    2013-01-01

      研究普通硅酸盐水泥、石膏及石灰掺入硫铝酸盐水泥中后对其凝结时间和强度的影响。研究表明:普通硅酸盐水泥掺量增大使得硫铝酸盐水泥凝结时间缩短,强度下降;石灰和石膏的掺入对硫铝酸盐水泥水化有一定的促进作用,且适当的比例对硫铝酸盐水泥的后期强度无不利影响。普通硅酸盐水泥、石灰和石膏的混掺对硫铝酸盐水泥的影响大小则与其掺量的多少有关。%The setting time and strength of sulphate aluminium cement admixed with Portland cement, gypsum and lime were studied. The result indicated that the setting time shortened and the strength declined with Portland cement content increasing. Lime and gypsum could promote hydration of sulphate aluminium cement, and they would be not unfavorable to late strength of sulphate aluminium if there was an appropriate proportion. The performance of sulphate aluminium cement was relevant to their mixing content.

  10. The importance of a thick cement mantle depends on stem geometry and stem-cement interfacial bonding.

    Science.gov (United States)

    Caruana, J; Janssen, D; Verdonschot, N; Blunn, G W

    2009-04-01

    The thickness of the cement mantle around the femoral component of total hip replacements is a contributing factor to aseptic loosening and revision. Nevertheless, various designs of stems and surgical tooling lead to cement mantles of different thicknesses. Opinion is divided on whether a thick mantle enhances implant longevity. This study investigates the effect of cement mantle thickness on accumulated damage in the cement, and how this is influenced by the presence or absence of a proximal collar and on whether the stem-cement interface remains bonded. Three-dimensional finite element simulations incorporating creep and non-linear damage accumulation were performed to investigate cracking in the cement mantles around Stanmore Hips under physiologically informed stair-climbing and gait loads. Cement mantle thickness, stem-cement interfacial bonding, and collar design were varied to assess the interactive effects of these parameters. In all cases, damage levels were three to six times higher when the stem-cement interface remained bonded. Cement mantle thickness had little effect on cement damage accumulation around debonded collared stems but was critical in both bonded and collarless cases, where a thicker mantle reduced cement cracking. Damage around a smooth debonded stem with a collar is thus much less sensitive to cement thickness than around bonded or collarless stems. PMID:19405437

  11. Present Situation and Perspective of Chinese Cement Industry

    Institute of Scientific and Technical Information of China (English)

    Gao Changming

    2003-01-01

    @@ Totally, there are 12 types of cement kiln pro-duction lines in China and running with a quite differenttechnical- economical levels. The cement productionof different types product lines in 1997 ~ 2002 is shownin Table 1.

  12. Effect of aluminium phosphate as admixture on oxychloride cement

    Indian Academy of Sciences (India)

    M P S Chandrawat; R N Yadav

    2000-02-01

    The effect of admixing of aluminium phosphate on oxychloride cement in the matrix has been investigated. It is shown that aluminium phosphate retards the setting process of the cement and improves water-tightness.

  13. Migration of ions in cement paste as studied by SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Prince, K.E.; Aldridge, L.P. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); Rougeron, P. [Electricite de France Direction des Etudes et Recherches, Les Renardiers (France)

    1998-06-01

    Cement is often used to condition and encapsulate low level radioactive waste before it is disposed of in a repository. Ground water can attack these waste-forms by transporting aggressive ions into the cement paste and by removing radioactive ions from the paste. The extent of the attack will be governed by the diffusion of the ions in the cement paste. In this study we examine the migration of aggressive carbonate ions and inactive Cs and Sr through cement pastes. The use of SIMS for establishing the penetration depths and diffusion profiles for Cs and Sr in cement will be explored. The penetration profiles of Cs and Sr in a non-zeolite cement paste were examined and compared to those of a paste made with zeolite. The effects of the non-homogeneous nature of the cement was most pronounced in the study of the zeolite rich cement; Cs being preferentially accumulated in the zeolite material. (authors). 4 refs., 2 figs.

  14. Exposure to cement dust at a Portland cement factory and the risk of cancer.

    Science.gov (United States)

    Vestbo, J; Knudsen, K M; Raffn, E; Korsgaard, B; Rasmussen, F V

    1991-01-01

    The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 14 cases of respiratory cancer were observed (observed/expected (O/E) 1.52, 95% confidence interval (95% CI) 0.90-2.57) when compared with all Danish men. Men with 1-20 years exposure had O/E 1.14 (95% CI 0.59-2.19) based on nine cases of cancer. After excluding all men with documented exposure to asbestos during employment in an asbestos cement factory no increased risk of overall cancer or respiratory cancer was found among cement workers compared with white collar workers from the local reference population, using a Cox regression model controlling for age and smoking habits. Relative risks were 0.5 (95% CI 0.1-1.5) and 1.0 (95% CI 0.4-2.6) for men with 1-20 and more than 20 years of exposure to cement dust respectively compared with white collar workers. PMID:1772795

  15. Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

    Science.gov (United States)

    Walling, Sam A; Provis, John L

    2016-04-13

    This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis. PMID:27002788

  16. Pore structure in blended cement pastes

    DEFF Research Database (Denmark)

    Canut, Mariana Moreira Cavalcanti

    Supplementary cementitious materials (SCMs), such as slag and fly ash, are increasingly used as a substitute for Portland cement in the interests of improvement of engineering properties and sustainability of concrete. According to studies improvement of engineering properties can be explained...... supplement each other. Cement pastes (w/b=0.4) with and without slag and fly ash cured at two moisture (sealed and saturated) and temperature (20 and 55ºC) conditions were used to investigate the combined impact of SCMs addition and curing on the pore structure of pastes cured up to two years. Also...... volume and threshold pore size were found when comparing with plain cement paste at the same curing conditions. The porosity methods MIP, LTC and SEM have been shown to be suitable to characterise pore parameters of the pastes. MIP is a simple and fast method which covers a large range of pore sizes...

  17. Immobilisation of ion exchange resins in cement

    International Nuclear Information System (INIS)

    Over the last seven years, Low Oxidation State Metal Ion reagents (LOMI) have been used to decontaminate the 100 MW(e) Steam Generating Heavy Water Ractor (SGHWR) at Winfrith. The use of these reagents has resulted in a dilute ionic solution containing activation products which are produced by corrosion of metallic components in the reactor. It has been demonstrated that the amount of activity in the solution can be reduced using organic ion exchanger resins. These resins consist of a cross linked polystyrene with sulphonic acid or quaternary ammonium function groups and can be successfully immobilised in blended cement systems. The formulation which has been developed is produced from a 9 to 1 blend of ground granulated blast furnace slag (BFS) and ordinary Portland cement (OPC) containing 28% ion exchange resin in the water saturated form. If 6% Microsilica is added to the blended cement the waste loading can be increased to 36 w/o. (author)

  18. Micromotion of cemented and uncemented femoral components.

    Science.gov (United States)

    Burke, D W; O'Connor, D O; Zalenski, E B; Jasty, M; Harris, W H

    1991-01-01

    We evaluated the initial stability of cemented and uncemented femoral components within the femoral canals of cadaver femurs during simulated single limb stance and stair climbing. Both types were very stable in simulated single limb stance (maximum micromotion of 42 microns for cemented and 30 microns for uncemented components). However, in simulated stair climbing, the cemented components were much more stable than the uncemented components (76 microns as against 280 microns). There was also greater variation in the stability of uncemented components in simulated stair climbing, with two of the seven components moving 200 microns or more. Future implant designs should aim to improve the initial stability of cementless femoral components under torsional loads; this should improve the chances of bony ingrowth. PMID:1991771

  19. Experimental techniques for cement hydration studies

    Directory of Open Access Journals (Sweden)

    Andreas Luttge

    2011-10-01

    Full Text Available Cement hydration kinetics is a complex problem of dissolution, nucleation and growth that is still not well understood, particularly in a quantitative way. While cement systems are unique in certain aspects they are also comparable to natural mineral systems. Therefore, geochemistry and particularly the study of mineral dissolution and growth may be able to provide insight and methods that can be utilized in cement hydration research. Here, we review mainly what is not known or what is currently used and applied in a problematic way. Examples are the typical Avrami approach, the application of Transition State Theory (TST to overall reaction kinetics and the problem of reactive surface area. Finally, we suggest an integrated approach that combines vertical scanning interferometry (VSI with other sophisticated analytical techniques such as atomic force microscopy (AFM and theoretical model calculations based on a stochastic treatment.

  20. Applications of Moessbauer spectroscopy in cement studies

    International Nuclear Information System (INIS)

    In the last two decades Moessbauer spectrometer has been employed to investigate cement and its clinker. In this work some of these investigations are exhibited briefly hoping that this would facilitate further investigations. It has already been seen that Moessbauer spectroscopy gives good information about some vague points which were present before using this technique as a tool in cement studies such as clinker formation, iron solubility, the iron states in the different phases of clinker as well as the effect of hydration at different times on the states of iron cement pastes, methods for the quality control of the manufactured clinker, the evaluation of the degree of hydration and the compressive strength have been assessed. A concept about the Moessbauer spectroscopy is presented. (author)

  1. Performance of cemented coal gangue backfill

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qin-li; WANG Xin-min

    2007-01-01

    Possibility of cemented gangue backfill was studied with gangue of Suncun Coal Mine, Xinwen Coal Group, Shandong,and fly ash of nearby thermal power plant, in order to treat enormous coal gangue on a large scale and to recovery safety coal pillars.The results indicate that coal gangue is not an ideal aggregate for pipeline gravity flow backfill, but such disadvantages of gangue as bad fluidity and serious pipe wear can be overcome by addition of fly ash. It is approved that quality indexes such as strength and dewatering ratio and piping feature of slurry can satisfy requirement of cemented backfill if mass ratio of cement to fly ash to gangue higher middle and long term comprehensive strength.

  2. Increasing the compressive strength of portland cement concrete using flat glass powder

    Energy Technology Data Exchange (ETDEWEB)

    Miranda Junior, Edson Jansen Pedrosa de; Bezerra, Helton de Jesus Costa Leite; Politi, Flavio Salgado; Paiva, Antonio Ernandes Macedo, E-mail: edson.jansen@ifma.edu.br [Instituto Federal de Educacao, Ciencia e Tecnologia do Maranha (IFMA), Sao Luis, MA (Brazil). Dept. de Mecanica e Materiais

    2014-08-15

    This paper analyzes the compressive strength of Portland cement concrete in response to the incorporation of 5%, 10% and 20% of flat glass powder in place of sand, at w/c (water/cement) ratios of 0.50, 0.55 and 0.58. A statistical analysis of variance (ANOVA) was performed after 7, 14 and 28 days of curing. The compressive strength test results indicate that the concrete containing a w/c ratio of 0.50 can be used for structural applications, regardless of the waste glass content, as can that with a w/c ratio of 0.55 containing 20% of waste glass. We suggest that the use of flat glass powder in place of sand in the above mentioned percentages is feasible for the production of an environmentally appropriate and structurally applicable concrete. However, the concrete's fluidity and void content must be taken into account. (author)

  3. Radon resistant potential of concrete manufactured using Ordinary Portland Cement blended with rice husk ash

    Science.gov (United States)

    Chauhan, R. P.; Kumar, Amit

    2013-12-01

    The emission of radon from building materials and soil depends upon the radium content, porosity, moisture content and radon diffusion length of materials. Several techniques have been used to reduce the radon emission from the soil using different flooring materials. But the effectiveness of radon shielding depends upon the diffusion of radon through these materials. The present study proposes a method for producing a radon resistant material for decreasing radon diffusion through it. The method involves rice husk ash (RHA) in addition to cement for the preparation of concrete used for flooring and walls. The radon diffusion, exhalation and mechanical property of concrete prepared by rice husk ash blended cement were studied. The addition of RHA caused the reduction in radon diffusion coefficient, exhalation rates, porosity and enhanced the compressive strength of concrete. The bulk radon diffusion coefficient of cementitious concrete was reduced upto 69% by addition of rice husk ash as compare to that of control concrete.

  4. Spatial analysis of cement production and consumption in Turkey

    OpenAIRE

    Beygo, Cem; Cakmak, Goksenin

    1998-01-01

    After 1950?s, the rapid urbanization of Turkey stimulated the production and consumption of cement and the number of cement factories increased since then. In addition, construction of highways, bridges, dams and industrialization also contribute to the consumption of cement. Construction industry became a locomotif of the economy of the country and cement industry is the most element of the construction industry. This study analyzes the growth of population and urbanization according to new ...

  5. Respiratory tract mortality in cement workers: a proportionate mortality study

    OpenAIRE

    Rachiotis George; Drivas Spyros; Kostikas Konstantinos; Makropoulos Vasilios; Hadjichristodoulou Christos

    2012-01-01

    Abstract Background The evidence regarding the association between lung cancer and occupational exposure to cement is controversial. This study investigated causes of deaths from cancer of respiratory tract among cement workers. Methods The deaths of the Greek Cement Workers Compensation Scheme were analyzed covering the period 1969-1998. All respiratory, lung, laryngeal and urinary bladder cancer proportionate mortality were calculated for cement production, maintenance, and office workers i...

  6. A new geopolymeric binder from hydrated-carbonated cement

    OpenAIRE

    Paya Bernabeu, Jorge Juan; Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Soriano Martinez, Lourdes; Mitsuuchi Tashima, Mauro

    2012-01-01

    This paper evaluates the use of hydrated Portland cement as the raw material in the production of geopolymers. The silicon and aluminium oxides needed for the geopolymerization process were produced by the carbonation of hydrated Portland cement, which transforms CSH and CAH (Portland cement hydrates) into silica and alumina gels. Hydrated-carbonated Portland cement was alkali activated with a NaOH/waterglass solution. Pastes and mortars were prepared, and micro-structural and mechanical prop...

  7. Practical clinical considerations of luting cements: A review

    OpenAIRE

    Lad, Pritam P; Kamath, Maya; Tarale, Kavita; Kusugal, Preethi B

    2014-01-01

    The longevity of fixed partial denture depends on the type of luting cement used with tooth preparation. The clinician’s understating of various cements, their advantages and disadvantages is of utmost importance. In recent years, many luting agents cements have been introduced claiming clinically better performance than existing materials due to improved characteristics. Both conventional and contemporary dental luting cements are discussed here. The various agents discussed are: Zinc pho...

  8. Survival in cohorts of asbestos cement workers and controls.

    OpenAIRE

    Albin, M; Horstmann, V; Jakobsson, K; Welinder, H

    1996-01-01

    OBJECTIVES: To measure the impact on survival of being exposed to asbestos cement dust. METHODS: Survival of 866 asbestos cement workers and 755 controls was studied with Cox's proportional hazards regression models with age as the basic time variable. The effect of cumulative exposure up to the age of 40 was investigated in an internal analysis of 635 asbestos cement workers who had dose estimates. RESULTS: The death risk was higher for the asbestos cement workers than for the controls with ...

  9. The aggressiveness of pig slurry to cement mortars

    OpenAIRE

    Massana Guitart, Jordi; Guerrero Bustos, Ana; Antón Fuentes, Rebeca; Garcimartin Molina, Miguel Angel; Sanchez Espinosa, Elvira

    2013-01-01

    The aim was to measure the behaviour of various mortars employed in livestock media in central Spain and to analyse the aggressiveness of pig slurry to cement blended with fly ash mortars. To achieve this, mortar specimens were immersed in ponds storing pig slurry. Mortar specimens, of 40 ? 40 ? 160 mm, were made from four types of cement commonly used and recommended for rural areas. The types were a sulphate-resistant Portland cement and three cements blended in different proportions with ...

  10. Compressibility Behavior of Tropical Peat Reinforced with Cement Columns

    OpenAIRE

    Youventharan Duraisamy; Bujang B.K. Huat; Azlan A. Aziz

    2007-01-01

    This paper presents the compressibility of tropical peat reinforced with cylindrical cement columns. When a cement column is installed vertically in peat, its com-pressibility is reduced because of the hardened skeleton matrix formed by cement parti-cles bonding with adjacent soil particles in the presence of pore water. The effects of the cement column diameter on the compressibility have been investigated in this study. The results indicated that compressibility index Cc and Cα decreas...

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

    International Nuclear Information System (INIS)

    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 ZnCl2 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)

  12. Early and late hydration of supersulphated cements of blast furnace slag with fluorgypsum

    Directory of Open Access Journals (Sweden)

    Bazaldúa-Medellín, M. E.

    2015-03-01

    Full Text Available The hydration, strength development and composition of hydration products of supersulphated cements were characterized from the first 48 hours up to 360 days. Two compositions of 80% Blast furnace slag, 10–15% Fluorgypsum and 10–5% Portland cement were cured in dry and wet conditions. The main hydration products were ettringite and C-S-H since the first hours and up to 360 days as evidenced by X-ray diffraction, thermal analysis and electron microscopy. The strength was favored by higher fluorgypsum contents and lower Portland cement contents. These cements generated heats of hydration of 40–57 KJ/Kg after 28 hours, which are lower than portland cement.Se realizó la caracterización de la hidratación, desarrollo de resistencia y la composición de los productos de hidratación de los cementos supersulfatados durante las primeras 48 horas y hasta 360 días. Se estudiaron dos composiciones de 80% de Escoria de alto horno, 10–15% de Fluoryeso y 10–5% de Cemento portland, se curaron en condiciones secas y húmedas. Los principales productos de hidratación fueron etringita y C-S-H desde las primeras horas y hasta 360 días, como se evidenció por difracción de rayos X, análisis térmico y microscopía electrónica de barrido. La resistencia se favoreció con mayor contenido de fluoryeso y bajos contenidos de cemento portland. Estos cementos generaron calores de hidratación de 40–57 KJ/Kg después de 28 horas, los cuales resultan más bajos que los generados por el cemento portland.

  13. Expansion control for cementation of incinerated ash

    International Nuclear Information System (INIS)

    A method, in which incinerated ash is solidified with a cement material, has been developed to dispose of radioactive incinerated ash waste. A small amount of metallic Al, which was not oxidized in the incineration, existed in the ash. When such ash was mixed with a cement material and water, alkaline components in the ash and the cement were dissolved in the mixing water and then metallic Al reaction with the alkaline compounds resulted in generation of H2. Because the H2 generation began immediately just after the mixing, H2 bubbles pushed up the mixed grout material and an expanded solidified form was obtained. The expansion leads to lowering the strength of the solidified form and making harmful void. In this study, we tried to control H2 generation from the reaction of metallic Al in the cementation by means of following two methods, one was a method to let metallic Al react prior to the cementation and the other was a method to add an expansion inhibitor that made an oxide film on the surface of metallic Al. In the pre-treatment, the ash was soaked in water in order to let metallic Al react with it, and then the ash with the immersion solution was dried at 105 Celsius degrees. The pre-treated ash was mixed with an ordinary portland cement and water. The inhibitor of lithium nitrite, sodium nitrite, phosphoric acid, or potassium dihydrogen phosphate was added at the mixing process. The solidified forms prepared using the pre-treated ash and lithium nitrite were not expanded. Phosphoric acid and sodium nitrite were effective for expansion control, but potassium dihydrogen phosphate did not work. (authors)

  14. Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; LI Zongjin; XIAO Lianzhen; THONG Wangfai

    2006-01-01

    The influence of calcium sulfate state and fineness of cement on hydration of Portland cement was studied using electrical resistivity measurement. The bulk resistivity curve of the paste from the abnormal cement mainly with hemihydrate had a characteristic abnormal peak and rapid increase in early period. The resistivity measurement technique can be used to discriminate abnormal setting. For normal cement with gypsum, the increase in fineness of the Portland cement decreases the minimum resistivity due to a higher ionic concentration and increases the 24 hour resistivity due to a reduction in macroscopic pore size. Thesetting time, compressive strength, pore structure of pastes made from different cements were carried out to compare the influence of water to cement ratio, calcium sulfate state and fineness. It is found that the electrical and mechanical properties are strongly affected by the initial porosity, the presence of hemihydrate or gypsum, and the fineness of cement.

  15. Experimental Investigation of Second Interface Cement Bond Evaluation

    Institute of Scientific and Technical Information of China (English)

    Che Xiaohua; Qiao Wenxiao

    2007-01-01

    Cement bond model wells (1:10 scaled-down) were made with a gradually degrading cement annulus for cement bond evaluation of the first interface (between the casing and the cement annulus) and the second interface (between the cement annulus and the formation).Experimental simulation on cement bond logging was carried out with these model wells.The correlation of acoustic waveforms,casing wave energy and free casing area before and after cement bonding of the second interface was established.The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface,but the amplitude of the casing head wave decreased obviously after the second interface was bonded.So,cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals.Strong cement annulus waves with early arrivals were observed before the second interface was bonded,while obvious "formation waves" instead of cement annulus waves were observed after the second interface was bonded.

  16. 21 CFR 888.4210 - Cement mixer for clinical use.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement mixer for clinical use. 888.4210 Section... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4210 Cement mixer for clinical use. (a) Identification. A cement mixer for clinical use is a device consisting of a container intended for use in...

  17. Research of dynamic mechanical performance of cement rock

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; WANG Tong; WANG Xiang-lin

    2007-01-01

    As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock. Dynamic fracture toughness of cement rock will be changed under the influence of filler. In order to study the damage mechanism of the cement circle during perforation and carry out comprehensive experiments on preventing and resisting connection, a kind of comprehensive experiment equipment used to simulate perforation and multifunctional equipment for testing the dynamic properties of the material are designed. Experimental study of the dynamical mechanical performance of original and some improved cement rock and experiment used to simulate the well cementation and perforation are carried out. Standard for dynamical mechanical performance of the cement rock with fine impact resistance and mechanical properties of some improved cement rock are also given.

  18. 21 CFR 888.4230 - Cement ventilation tube.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted...

  19. 21 CFR 888.4220 - Cement monomer vapor evacuator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement monomer vapor evacuator. 888.4220 Section... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4220 Cement monomer vapor evacuator. (a) Identification. A cement monomer vapor evacuator is a device intended for use during surgery to contain or...

  20. The suitability of a supersulfated cement for nuclear waste immobilisation

    Science.gov (United States)

    Collier, N. C.; Milestone, N. B.; Gordon, L. E.; Ko, S.-C.

    2014-09-01

    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.

  1. Porosity and liquid absorption of cement paste

    DEFF Research Database (Denmark)

    Krus, M.; Hansen, Kurt Kielsgaard; Kunzel, H. M.

    1997-01-01

    be a slowing-down effect which is related to water because the absorption of organic liquids, such as hexane, is quite normal. Measurements of the porosity of hardened cement paste determined by helium pycnometry and water saturation show that water molecules can enter spaces in the microstructure which...... are not accessible to the smaller helium atoms. Considering the results of dilatation tests both before and after water and hexane saturation, it seems possible that a contraction of capillary pores due to moisture-related swelling of the cement gel leads to the non-linear water absorption over the square root...

  2. Structure and mechanical properties of cement and intermetallic compounds via ab-initio simulations

    Science.gov (United States)

    Dharmawardhana, Chamila Chathuranga

    Calcium silicate hydrates comprise a class of minerals formed synthetically during Portland cement hydration or naturally through various geological processes. The importance of these minerals is immense since they are the primary binding phases for Portland cement derived construction materials. Efforts spanning centuries have been devoted to understand the structural aspects of cohesion in these minerals. In recent years, the focus has progressively turned to atomic level comprehension. Structurally these minerals can range from crystalline to highly disordered amorphous phases. This thesis focuses upon unraveling the nature of chemical bonding in a large subset of calcium silicate hydrate (CSH) crystals. Thus their electronic structure was calculated and bonding mechanisms were investigated quantitatively. Results highlight a wide range of contributions from each type of bonding (Si-O, Ca-O, O-H and hydrogen bond) with respect to silicate polymerization, crystal symmetry, water and OH content. Consequently, total bond order density (TBOD) was designated as the overall single criterion for characterizing crystal cohesion. The TBOD categorization indicates that a rarely known orthorhombic phase Suolunite is closest to the ideal composition and structure of cement. Present work finds the relationship of partial bond order density (PBOD) of each bond species, especially HBs to the mechanical properties of CSH crystals. This can be used as a basis to validate existing C-S-H models and to build improved ones. This work goes further and validates the recently proposed models (2014) for C-S-H (I) phase on the same basis of proposed electronic structure parameters. Then the respective Calcium aluminosilicate hydrates C-A-S-H (I) phase models are proposed. Finally, these results lead to improved interpretations and construction of realistic atomistic models of cement hydrates. Ab initio molecular dynamics (AIMD) could be vital to solve critical problems in complex

  3. Water dynamics in hardened ordinary Portland cement paste or concrete: from quasielastic neutron scattering.

    Science.gov (United States)

    Bordallo, Heloisa N; Aldridge, Laurence P; Desmedt, Arnaud

    2006-09-14

    Portland cement reacts with water to form an amorphous paste through a chemical reaction called hydration. In concrete the formation of pastes causes the mix to harden and gain strength to form a rock-like mass. Within this process lies the key to a remarkable peculiarity of concrete: it is plastic and soft when newly mixed, strong and durable when hardened. These qualities explain why one material, concrete, can build skyscrapers, bridges, sidewalks and superhighways, houses, and dams. The character of the concrete is determined by the quality of the paste. Creep and shrinkage of concrete specimens occur during the loss and gain of water from cement paste. To better understand the role of water in mature concrete, a series of quasielastic neutron scattering (QENS) experiments were carried out on cement pastes with water/cement ratio varying between 0.32 and 0.6. The samples were cured for about 28 days in sealed containers so that the initial water content would not change. These experiments were carried out with an actual sample of Portland cement rather than with the components of cement studied by other workers. The QENS spectra differentiated between three different water interactions: water that was chemically bound into the cement paste, the physically bound or "glassy water" that interacted with the surface of the gel pores in the paste, and unbound water molecules that are confined within the larger capillary pores of cement paste. The dynamics of the "glassy" and "unboud" water in an extended time scale, from a hundred picoseconds to a few nanoseconds, could be clearly differentiated from the data. While the observed motions on the picosecond time scale are mainly stochastic reorientations of the water molecules, the dynamics observed on the nanosecond range can be attributed to long-range diffusion. Diffusive motion was characterized by diffusion constants in the range of (0.6-2) 10(-9) m(2)/s, with significant reduction compared to the rate of diffusion

  4. Performance Characteristics of Waste Glass Powder Substituting Portland Cement in Mortar Mixtures

    OpenAIRE

    Kara, P; Csetényi, L; Borosnyói, A

    2014-01-01

    In several countries, waste glass causes environmental concerns as quantities stockpiled exceed recycling in the packaging stream. Being amorphous and having relatively high silicium and calcium contents, glass is pozzolanic or even cementitious, when finely ground. Reducing particle sizes typically to less than 100 µm may give control over the alkali-silica reaction in concrete, therefore making this material a possible substitute to Portland cement. Such use may moderate the problem of dump...

  5. Fracture and fatigue behavior of WC-Co and WC-CoNi cemented carbides

    OpenAIRE

    Tarragó Cifre, Jose María; Roa Rovira, Joan Josep; Valle, Vladimir; Marsahll, J. M.; Llanes Pitarch, Luis Miguel

    2015-01-01

    The fracture and fatigue characteristics of several cemented carbide grades are investigated as a function of their microstructure. In doing so, the influence of binder chemical nature and content (Co and 76 wt.% Co-24 wt.% Ni), as well as carbide grain size on hardness, flexural strength, fracture toughness and fatigue crack growth (FCG) behavior is evaluated. Mechanical testing is combined with a detailed inspection of crack-microstructure interaction, by means of scanning electron microsco...

  6. Improved cement mortars by addition of carbonated fly ash from solid waste incinerators

    OpenAIRE

    López-Zaldívar, O.; Mayor-Lobo, P. L.; Fernández-Martínez, F.; Hernández-Olivares, F.

    2015-01-01

    This article presents the results of a research developing high performance cement mortars with the addition of municipal solid waste incineration fly ash (MSWIFA) stabilized as insoluble carbonates. The encapsulation of hazardous wastes in mortar matrixes has also been achieved. The ashes present high concentrations of chlorides, Zn and Pb. A stabilization process with NaHCO3 has been developed reducing 99% the content of chlorides. Developed mortars replace 10% per weight of the aggregates ...

  7. Mineral fibres, fibrosis, and asbestos bodies in lung tissue from deceased asbestos cement workers.

    OpenAIRE

    Albin, M; L. Johansson; Pooley, F D; Jakobsson, K; Attewell, R; Mitha, R

    1990-01-01

    Lung tissue from 76 deceased asbestos cement workers (seven with mesothelioma) exposed to chrysotile asbestos and small amounts of amphiboles, has been studied by transmission electron microscopy, together with lung tissue from 96 controls. The exposed workers with mesothelioma had a significantly higher total content of asbestos fibre in the lungs than those without mesothelioma, who in turn, had higher concentrations than the controls (medians 189, 50, and 29 x 10(6) fibres/g (f/g]. Chrysot...

  8. Cement Formation:A Success Story in a Black Box: High Temperature Phase Formation of Portland Cement Clinker

    OpenAIRE

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten; Dam-Johansen, Kim

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledgeabout 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 ...

  9. Effect of Minor Elements on Silicate Cement Clinker

    Institute of Scientific and Technical Information of China (English)

    HUANG Congyun; ZHANG Mingfei; ZHANG Meixiang; LONG Shizong; CHEN Yuankui; MA Baoguo

    2005-01-01

    The effect of rare-earth and HX addition agent on the burn-ability of silicate cement clinker was investigated by orthogonal experiment. The result shows, compared with blank sample, f- CaO of the samples added with rare-earth and HX agent drops by 84.95% , its 3d and 28d compressive strength enhances by 24.40%and 16.90%, respectively. It was discovered by means of X-ray diffraction and high temperature microscope analysis that sintering temperature of the sample added with rare-earth and HX addition agent is about 1320℃. At the same time, the burning temperature of tricalcium silicate desends and its crystal growth forming-rate increases.Tricalcium silicate content in burning clinker is higher and its crystal is larger.

  10. Structural evolution of an alkali sulfate activated slag cement

    Science.gov (United States)

    Mobasher, Neda; Bernal, Susan A.; Provis, John L.

    2016-01-01

    In this study, the effect of sodium sulfate content and curing duration (from fresh paste up to 18 months) on the binder structure of sodium sulfate activated slag cements was evaluated. Isothermal calorimetry results showed an induction period spanning the first three days after mixing, followed by an acceleration-deceleration peak corresponding to the formation of bulk reaction products. Ettringite, a calcium aluminium silicate hydrate (C-A-S-H) phase, and a hydrotalcite-like Mg-Al layered double hydroxide have been identified as the main reaction products, independent of the Na2SO4 dose. No changes in the phase assemblage were detected in the samples with curing from 1 month up to 18 months, indicating a stable binder structure. The most significant changes upon curing at advanced ages observed were growth of the AFt phase and an increase in silicate chain length in the C-A-S-H, resulting in higher strength.

  11. Properties of Portland cement concretes containing pozzolanic admixtures

    Science.gov (United States)

    Simmons, D. D.; Pasko, T. J., Jr.; Jones, W. R.

    1981-04-01

    A laboratory comparison was made of the properties of a concrete containing no pozzolan with several mixtures containing pozzolans. Used were a natural pozzolan (Lassenite), two fly ashes of different fineness and low carbon and an amorphous silica fume dust from a metal-producing plant. One cement, one coarse crushed limestone aggregate, and one fine river aggregate were used. Replacing a faster reacting binder with a slower one, produced lower early strengths and adversely affected the properties which are highly dependent on strength. The measures of durability were greatly affected by the air contents and aging or treatment prior to exposure. The amorphous silica fume dust increased the early strengths of a fly ash mixture.

  12. Advanced cement solidification technique for spent resins

    International Nuclear Information System (INIS)

    In the past 40 years, the nuclear facilities of China Institute of Atomic Energy (CIAE) produced an amount of radioactive organic resins, a kind of problematic stream in nuclear industry. As these facilities were stepping into decommissioning, the treatment of the spent organic resins was put on the agenda. The various routes for spent resin treatment such as incineration, advanced oxidation, cement immobilization, etc, were considered. Each method has its advantages and disadvantages when applied in the treatment of spent resins. Since the quantities of the spent organic resins were relatively small and an experience with variety of cementation processes existed in CIAE, predominately for immobilization of the evaporated concentrates, the option of direct encapsulation of the spent organic resins into cementitious materials was adopted in 2003, as a preferred method from the point of view of saving the on the cost of the disposal. In order to realize the end goal, the main work consisted of: the survey of the source terms; cementitious material formula investigation; and the process development. This work, which was undertaken in the following years, is addressed as follows. Source terms of the spent resins in CIAE were to be made clear firstly. The results showed that a total of 24-29 m3 of spent resins was generated and accumulated in the past 40 years. Spent resin arose from two research reactors (heavy water reactor and light water reactor), and from the waste management plant. The amount of the spent resins from the heavy water reactor was 1m3 or so, but its radioactive concentration was high to ∼108-∼109Bq/m3. Two kinds of cements, ASC and OPC cement were selected next, as the solidifying matrix to be investigated. A mixture surface response approach was employed to design experiment and interpret data. In comparison, ASC was superior to OPC cement and it displayed preferable performances to encapsulate spent resins. The optimum formulation is:1) resin

  13. Hydration of portland cement, natural zeolite mortar in water and sulphate solution

    Directory of Open Access Journals (Sweden)

    Janotka, I.

    2003-03-01

    Full Text Available The objective of this paper is to characterise sulphate resistance of mortars made from ordinary Portland cement ( PC and Portland-pozzolan cement with 35 wt.% of zeolite addition (zeolite-blended cement-ZBC . Mortars with two different cement types were tested in water and 5% sodium sulphate solution for 720 days. A favourable effect of zeolite on increased sulphate resistance of the cement is caused by decrease in free Ca(OH2 content of the mortar There is not sufficient of Ca(OH2 available for reacting with the sulphate solution to form voluminous reaction products. A decreased C3A, content due to 35 wt.% replacement of PC by zeolite is the next pronounced factor improving resistance of the mortar with such blended cement.

    El objetivo de este trabajo ha sido estudiar la resistencia a los sulfatos de morteros preparados con cemento portland ordinario (PC y cemento portland puzolánico, con un 35% en peso de zeolita (zeolite-blended cement (ZBC. Ambos tipos de morteros fueron conservados en agua y en una disolución de sulfato sódico al 5% durante 720 días. Se observó una mayor resistencia a los sulfatos en el mortero preparado con el cemento que contenía zeolita debido a su menor contenido en Ca(OH2. No hay cantidad suficiente de Ca(OH2 para que se produzca la reacción de los constituyentes de la pasta con la disolución de sulfato sódico y formar así productos de naturaleza expansiva. La disminución en el contenido de C,3A, debida a la sustitución de un 35% en peso de PC por zeolita, es el factor más determinante en el aumento de la resistencia del mortero en los cementos con adición.

  14. Pozzolanic Activity of Burned Coal Gangue and Its Effects on Structure of Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    ZHANG Changsen

    2006-01-01

    The pozzolanic activity of coal gangue burned at different burning temperatures was investigated. The burned coal gangue was mixed with portland cement in different proportions ( 20%-60% ). The pozzolanic activity of coal gangue burned and the hydration products were examined, the compressive strengths of the pastes of the mixtures were tested, and the mechanism of the reaction was discussed. The experimental results show that the coal gangue burned at 750 ℃ has the optimum pozzolanic activity, and the burned coal gangue with SiO2 and Al2O3 is in an active form. When the coal gangue burned at 750 ℃ is mixed into portland cement, the content of calcium hydroxide in paste is significantly reduced, while the contents of hydrated calcium silicate and hydrated calcium aluminate are increased accordingly, hence resulting in the improvement of the microstructure of mortar. The compressive strength of cement paste decreases with increasing the content of burned coal gangue. The decease in strength is small in the range of 20%- 30% coal gangue substitution and significant in 30%- 60% substitution.

  15. Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

    Directory of Open Access Journals (Sweden)

    Antonio López-Uceda

    2016-02-01

    Full Text Available This research aims to produce non-structural concrete with mixed recycled aggregates (MRA in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%, using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

  16. Possibility of using waste tire rubber and fly ash with Portland cement as construction materials.

    Science.gov (United States)

    Yilmaz, Arin; Degirmenci, Nurhayat

    2009-05-01

    The growing amount of waste rubber produced from used tires has resulted in an environmental problem. Recycling waste tires has been widely studied for the last 20 years in applications such as asphalt pavement, waterproofing systems and membrane liners. The aim of this study is to evaluate the feasibility of utilizing fly ash and rubber waste with Portland cement as a composite material for masonry applications. Class C fly ash and waste automobile tires in three different sizes were used with Portland cement. Compressive and flexural strength, dry unit weight and water absorption tests were performed on the composite specimens containing waste tire rubber. The compressive strength decreased by increasing the rubber content while increased by increasing the fly ash content for all curing periods. This trend is slightly influenced by particle size. For flexural strength, the specimens with waste tire rubber showed higher values than the control mix probably due to the effect of rubber fibers. The dry unit weight of all specimens decreased with increasing rubber content, which can be explained by the low specific gravity of rubber particles. Water absorption decreased slightly with the increase in rubber particles size. These composite materials containing 10% Portland cement, 70% and 60% fly ash and 20% and 30% tire rubber particles have sufficient strength for masonry applications. PMID:19110410

  17. Reactive magnesium oxide cements: geochemical modelling of pH profile and solid phase composition

    International Nuclear Information System (INIS)

    Due to a range of technical and sustainability advantages, reactive magnesium oxide cements (MgO) are a potential alternative to Portland cement (PC) for conditioning intermediate level radioactive waste (ILW). MgO cements consist of a mixture of hydraulic cement and reactive magnesium oxide to which pozzolans such as silica fume (SF) may be added. While favourable, the mechanical and chemical properties of MgO matrices still require further investigation to ensure effective immobilisation of contaminants. In this study a solubility-speciation model was developed using PHREEQC to simulate blends based on low and high contents of MgO, including SF as a supplementary material. Analyses aimed at characterising binding systems focusing on their equilibrium pH with pure water and saturation index (SI) of solid phases. The geochemical model successfully confirmed that the equilibrium pH is inversely proportional to the fraction of MgO and SF present in the hydrated paste. Comparison with data available on literature mostly gave a consistent picture and the model provided reasonable predictions of existent solid phases. (authors)

  18. Increase in the strength characteristics of Portland cement due to introduction of the compound mineral supplements

    Science.gov (United States)

    Il'ina, Liliia; Gichko, Nikolai; Mukhina, Irina

    2016-01-01

    At the initial phase of hardening it is the limestone component that plays a major role in the hardening process, which acts as the substrate for the crystallization of hydrate tumors due to its chemical affinity with the products of Portland cement hydration. After 7 days, the diopside supplement influences the processes more significantly. Diopside has a high modulus of elasticity compared to the cement paste. As a result, stresses are redistributed within the cement paste and the whole composition is hardened. An increase in the quantity of diopside in the compound supplement to more than 66.7% does not provide a substantial increase in the strength of the cement paste. As the hardness of diopside is higher than the hardness of limestone, much more energy is required to grind it down to a usable component. Therefore, a further increase in the quantity of diopside in the compound supplement is not economically feasible. An evaluation of the optimum quantity of input compound mineral supplements can be made based on the ideas of close packing of spherical particles and the Pauling rules. The optimum content of the supplement is 8-8.5% provided that its dispersion and density are close to the dispersion and density of the binder. An increase in the dispersion of the supplement reduces its optimal quantity.

  19. Crystal chemistry of the high temperature product of transformation of cement-asbestos.

    Science.gov (United States)

    Viani, Alberto; Gualtieri, Alessandro F; Pollastri, Simone; Rinaudo, Caterina; Croce, Alessandro; Urso, Giancarlo

    2013-03-15

    In this work, the high-temperature inertization product of a representative batch of samples of cement-asbestos (CA) from different localities in Italy have been characterized with a multidisciplinary approach. All the raw CA samples were heated at 1200°C for 15 min. After firing, they underwent a series of solid state reactions leading to global structural changes of the matrix. Effects of annealing time and temperature on the crystallization kinetics were thoroughly investigated. Both factors acted in favour of equilibrium. Three classes of CA were identified with the aid of phase diagrams and of specific plots relating chemical and mineralogical parameters. This result was considered of importance in view of the potential use of transformed cement-asbestos as a secondary raw material. In principle, the content of CA packages removed from the environment and their corresponding heat-treated products can be classified simply using XRF. This method allows for the selection of appropriate fractions in function of the most suitable recycling solution adopted. Samples belonging to the class called larnite-rich, turned out to be of great interest as possible candidate for substituting a fraction of cement in many building materials and innovative green cement productions. PMID:23380447

  20. Steel foundry electric arc furnace dust management: stabilization by using lime and Portland cement.

    Science.gov (United States)

    Salihoglu, Guray; Pinarli, Vedat

    2008-05-30

    The purpose of this study was to determine an appropriate treatment for steel foundry electric arc furnace dust (EAFD) prior to permanent disposal. Lime and Portland cement (PC)-based stabilization was applied to treat the EAFD that contains lead and zinc above the landfilling limits, and is listed by USEPA as hazardous waste designation K061 and by EU as 10 02 07. Three types of paste samples were prepared with EAFD content varying between 0 and 90%. The first type contained the EAFD and Portland cement, the second contained the EAFD, Portland cement, and lime, and the third contained the EAFD and lime. All the samples were subjected to toxicity characteristics leaching procedure (TCLP) after an air-curing period of 28 days. pH changes were monitored and acid neutralization capacity of the samples were examined. Treatment effectiveness was evaluated in terms of reducing the heavy metal leachability to the levels below the USEPA landfilling criteria. An optimum composition for the EAFD stabilization was formulated as 30% EAFD +35% lime +35% Portland cement to achieve the landfilling criteria. The pH interval, where the solubility of the heavy metals in the EAFD was minimized, was found to be between 8.2 and 9.4.

  1. Antibacterial Properties of Nano Silver-containing Orthodontic Cements in the Rat Caries Disease Model

    Institute of Scientific and Technical Information of China (English)

    LI Fujun; FANG Ming; PENG Yuying; ZHANG Jiayin

    2015-01-01

    The purpose of this study was to evaluate the antibacterial properties of experimental nano silver-containing cements (NSCs) using rat caries disease model. Nano silver base inorganic antibacterial powder was added to the reinforced glass ionomer cement at three different weight ratios to obtain a series of nano silver-containing cements, then two orthodontic cement products and three NSC samples were implanted into rat caries disease model, and their antibacterial properties were evaluated by the scanning electron microscope(SEM). Moreover, the rat caries disease model were established by inoculating cariogenic bacteria S mutans into antibiotics treated rat mouths and feeding with cariogenic diet. The tested materials were bonded on the surface of the buccal half crowns of the upper ifrst premolar, and then ifxed under the rats’front teeth lingual side to acquire enough retention. The SEM results indicated that the growth of streptococcus mutans was very active in group of Transbond XT. One month later, S mutans scattered on the GC Fuji ORTHO LC surface, and then the number signiifcantly increased and arranged in chains after three months. In groups of NSC2, NSC3 and NSC4, the number of S mutans presented the downward trend and tended to disperse individually with the increase of silver nanoparticle content. We may conclude that the incorporation of silver nanoparticle enhanced GC Fuji ORTHO LC the adhesion restrain and killing effect to S mutans.

  2. Action-Dependent Adaptive Critic Design Based Neurocontroller for Cement Precalciner Kiln

    Directory of Open Access Journals (Sweden)

    Baosheng Yang

    2009-10-01

    Full Text Available There are many factors that can affect the calciner process of cement production, such as highly nonlinearity and time-lag, making it very difficult to establish an accurate model of the cement precalciner kiln (PCK system. In order to reduce transport energy consumption and to ensure the quality of cement clinker burning, one needs to explore different control methods from the traditional way. Adaptive Critic Design (ACD integrated neural network, reinforcement learning and dynamic programming techniques, is a new optimal method. As the PCK system parameters change frequently with high real-time property, ADACD (Action-Dependant ACD algorithm is used in PCK system to control the temperature of furnace export and oxygen content of exhaust. ADACD does not depend on the system model, it may use historical data to train a controller offline, and then adapt online. Also the BP network of artificial neural network is used to accomplish the network modeling, and action and critic modules of the algorithm. The results of simulation show that, after the fluctuations in the early control period, the controlled parameters tend to be stabilized guaranteeing the quality of cement clinker calcining.

  3. Microstructure and Mechanical Properties of CaCO3 Whisker-reinforced Cement

    Institute of Scientific and Technical Information of China (English)

    CAO Mingli; WEI Jianqiang

    2011-01-01

    Composite Portland cement (PC) played an important role in various kinds of construction engineering owing to low hydration heat,low-cost,and application of solid industrial waste,but its brittleness and low strength limited its use in stress-bearing locations.The aim of this study is to improve the toughness and fracture resistance by incorporating CaCO3 whisker in cement matrix.Effect of different content of calcium carbonate whiskers on the mechanical properties of PC was investigated.The results showed that the flexural strength,impact strength and split tensile strength were increased by 39.7%,39.25% and 36.34% at maximum,respectively.Microstructure and elements of the whiskers in hardened cement were observed and analyzed by SEM/EDS.The mechanisms of the reinforcement of CaCO3 whisker on cement were also discussed,and the conclusion was that the improvement could be correlated to energy-dissipating processes owing to crack bridging,crack deflection,and whisker pull-out at the crack tips.

  4. 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.

  5. Cytotoxicity evaluation of five different dual-cured resin cements used for fiber posts cementation

    Science.gov (United States)

    Dioguardi, M; Perrone, D; Troiano, G; Laino, L; Ardito, F; Lauritano, F; Cicciù, M; Muzio, L Lo

    2015-01-01

    Custom-cast posts and cores are usually used to treat endodontically treated teeth. However, several researches have underlined how these devices may be a much higher elastic modulus than the supporting dentine and the difference in the modulus could lead to stress concentrating in the cement lute, leading to failure. The role of the cement seems to play a fundamental role in order to transfer the strength during the chewing phases. Aim of this research is to record the rate of cytotoxicity of five different dual-cured resin cements used for fiber posts cementation. We tested the cytotoxicity of this five materials on MG63 osteoblast-like cells through two different methods: MTT ([3-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide succinate) assay which tests for mitochondrial enzyme activity6 and xCELLigence® system. PMID:26309592

  6. The influence of cement mantle thickness and stem geometry on fatigue damage in two different cemented hip femoral prostheses.

    Science.gov (United States)

    Ramos, A; Simões, J A

    2009-11-13

    Experimental models can be used for pre-clinical testing of cemented and other type of hip replacements. Total hip replacement (THR) failure scenarios include, among others, cement damage accumulation and the assessment of accurate stress and strain magnitudes at the cement mantle interfaces (stem-cement and cement-bone) can be used to predict mechanical failure. The aseptic loosening scenario in cemented hip replacements is currently not fully understood, and methods of evaluating medical devices must be developed to improve clinical performance. Different results and conclusions concerning the cement micro-cracking mechanism have been reported. The aim of this study was to verify the in vitro behavior of two cemented femoral stems with respect to fatigue crack formation. Fatigue crack damage was assessed at the medial, lateral, anterior and posterior sides of the Lubinus SPII and Charnley stems. All stems were loaded and tested in stair climbing fatigue loading during one million cycles at 2 Hz. After the experiments each implanted synthetic femur was sectioned and analyzed. We observed more damage (cracks per area) for the Lubinus SPII stem, mainly on the proximal part of the cement mantle. The micro-cracking formation initiated in the stem-cement interface and grew towards the direction of cortical bone of the femur. Overall, the cement-bone interface seems to be crucial for the success of the hip replacement. The Charnley stem provoked more damage on the cement-bone interface. A failure index (maximum length of crack/maximum thickness of cement) considered was higher for the cement-stem interface of the Lubinus SPII stem. For a cement mantle thickness higher than 5 mm, cracking initiated at the cement-bone interface and depended on the opening canal process (reaming procedure and instrumentation). The analysis also showed that fatigue-induced damage on the cement mantle, increasing proximally, and depended on the axial position of the stem. The cement

  7. Design of Fit-for-Purpose Cement to Restore Cement-Caprock Seal Integrity

    Science.gov (United States)

    Provost, R.

    2015-12-01

    This project aims to study critical research needs in the area of rock-cement interfaces, with a special focus on crosscutting applications in the Wellbore Integrity Pillar of the SubTER initiative. This study will focus on design and test fit-for-purpose cement formulations. The goals of this project are as follows: 1) perform preliminary study of dispersing nanomaterial admixtures in Ordinary Portland Cement (OPC) mixes, 2) characterize the cement-rock interface, and 3) identify potential high-performance cement additives that can improve sorption behavior, chemical durability, bond strength, and interfacial fracture toughness, as appropriate to specific subsurface operational needs. The work presented here focuses on a study of cement-shale interfaces to better understand failure mechanisms, with particular attention to measuring bond strength at the cement-shale interface. Both experimental testing and computational modeling were conducted to determine the mechanical behavior at the interface representing the interaction of cement and shale of a typical wellbore environment. Cohesive zone elements are used in the finite element method to computationally simulate the interface of the cement and rock materials with varying properties. Understanding the bond strength and mechanical performance of the cement-formation interface is critical to wellbore applications such as sequestration, oil and gas production and exploration and nuclear waste disposal. Improved shear bond strength is an indication of the capability of the interface to ensure zonal isolation and prevent zonal communication, two crucial goals in preserving wellbore integrity. Understanding shear bond strength development and interface mechanics will provide an idea as to how the cement-formation interface can be altered under environmental changes (temperature, pressure, chemical degradation, etc.) so that the previously described objectives can be achieved. Sandia National Laboratories is a multi

  8. Microscopic evaluation regarding time behavior of orthodontic cements used for disjunctor cementing

    OpenAIRE

    Ruxandra Bartok; Dimitriu B.; Varlan C.; Stanciu R; Sanziana Scarlatescu; Loredana Mitran; Mitran M.; Irina Gheorghiu; Ioana Suciu; Iliescu D.M.

    2015-01-01

    In order to fulfill their function, orthodontic devices must be cemented on teeth using orthodontic rings. The retention of the orthodontic ring is influenced mainly by the type of dental-ring adhesion. This study was initiated to determine possible microleakage events while using zinc phosphate cement Adhesor (Spofa Dental), conventional glass ionomer Ketac Cem (3M ESPE) and Fuji Ortho (GC) and a compomer Transbond Plus (3M Unitek). The results of the study are consistent with those reported...

  9. Development of Clinical Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new type of inorganicorganic biomimetic bone cement consisting of nanohydroxyapatite and polyamide 66 composite was investigated. This cement can be handled as paste and easily shaped into any contour. Nanoapatite and polyamide composite cement has a reasonable setting time, excellent washout resistance, high mechanical strength and bioactivity, and it is easily handled and shaped, which can be developed as a clinical cement. It can be predicted that nanoapatite/polymer composite cement would be a new trend of biomedical material, showing a promising prospect.

  10. Effects of a discoloration-resistant calcium aluminosilicate cement on the viability and proliferation of undifferentiated human dental pulp stem cells.

    Science.gov (United States)

    Niu, Li-na; Watson, Devon; Thames, Kyle; Primus, Carolyn M; Bergeron, Brian E; Jiao, Kai; Bortoluzzi, Eduardo A; Cutler, Christopher W; Chen, Ji-hua; Pashley, David H; Tay, Franklin R

    2015-11-30

    Discoloration-resistant calcium aluminosilicate cement has been formulated to overcome the timely problem of tooth discoloration reported in the clinical application of bismuth oxide-containing hydraulic cements. The present study examined the effects of this experimental cement (Quick-Set2) on the viability and proliferation of human dental pulp stem cells (hDPSCs) by comparing the cellular responses with commercially available calcium silicate cement (white mineral trioxide aggregate; WMTA) after different aging periods. Cell viability and proliferation were examined using assays that examined plasma membrane integrity, leakage of cytosolic enzyme, caspase-3 activity for early apoptosis, oxidative stress, mitochondrial metabolic activity and intracellular DNA content. Results of the six assays indicated that both Quick-Set2 and WMTA were initially cytotoxic to hDPSCs after setting for 24 h, with Quick-Set2 being comparatively less cytotoxic than WMTA at this stage. After two aging cycles, the cytotoxicity profiles of the two hydraulic cements were not significantly different and were much less cytotoxic than the positive control (zinc oxide-eugenol cement). Based on these results, it is envisaged that any potential beneficial effect of the discoloration-resistant calcium aluminosilicate cement on osteogenesis by differentiated hDPSCs is more likely to be revealed after outward diffusion and removal of its cytotoxic components.

  11. Crystallographic characterization of cement pastes hydrated with NaCl; Caracterizacao cristalografica de pastas de cimento hidratadas com NaCl

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Carina Gabriela de Melo e; Martinelli, Antonio Eduardo; Melo, Dulce Maria Araujo; Melo, Marcus Antonio de Freitas; Melo, Vitor Rodrigo de Melo e [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2012-07-01

    One of the major current challenges faced by oil companies is the exploration of pre salt basins. Salt layers deposited upon the evaporation of ocean water and continental separation are mainly formed by NaCl and isolate immense oil reservoirs. The mechanical stability and zonal isolation of oil wells that run through salt layers must be fulfilled by cement sheaths saturated with NaCl to assure chemical compatibility between cement and salt layer. The present study aimed at evaluating the effect of NaCl addition on the hydration of oil well cement slurries as well as identifying the nature of crystalline phases present in the hardened cement. To that end, cement slurries containing NaCl were mixed, hardened and characterized by X-ray diffraction. The results revealed that the presence of NaCl affects the formation of hydration products by the presence of Friedel's salt. The intensity of the corresponding peaks increase as the contents of NaCl in the slurry increase. High concentrations of NaCl in Portland slurries increase the setting time of cement and the presence of Friedel's salt decreases the strength of the hardened cement. (author)

  12. Effects of a discoloration-resistant calcium aluminosilicate cement on the viability and proliferation of undifferentiated human dental pulp stem cells

    Science.gov (United States)

    Niu, Li-na; Watson, Devon; Thames, Kyle; Primus, Carolyn M.; Bergeron, Brian E.; Jiao, Kai; Bortoluzzi, Eduardo A.; Cutler, Christopher W.; Chen, Ji-hua; Pashley, David H.; Tay, Franklin R.

    2015-01-01

    Discoloration-resistant calcium aluminosilicate cement has been formulated to overcome the timely problem of tooth discoloration reported in the clinical application of bismuth oxide-containing hydraulic cements. The present study examined the effects of this experimental cement (Quick-Set2) on the viability and proliferation of human dental pulp stem cells (hDPSCs) by comparing the cellular responses with commercially available calcium silicate cement (white mineral trioxide aggregate; WMTA) after different aging periods. Cell viability and proliferation were examined using assays that examined plasma membrane integrity, leakage of cytosolic enzyme, caspase-3 activity for early apoptosis, oxidative stress, mitochondrial metabolic activity and intracellular DNA content. Results of the six assays indicated that both Quick-Set2 and WMTA were initially cytotoxic to hDPSCs after setting for 24 h, with Quick-Set2 being comparatively less cytotoxic than WMTA at this stage. After two aging cycles, the cytotoxicity profiles of the two hydraulic cements were not significantly different and were much less cytotoxic than the positive control (zinc oxide–eugenol cement). Based on these results, it is envisaged that any potential beneficial effect of the discoloration-resistant calcium aluminosilicate cement on osteogenesis by differentiated hDPSCs is more likely to be revealed after outward diffusion and removal of its cytotoxic components. PMID:26617338

  13. Carbonate cementation as related to the diagenesis of clay in a mixed siliciclastic-carbonate system: Examples from the Centerfield biostrome, east central Pennsylvania

    Energy Technology Data Exchange (ETDEWEB)

    Burns, C.D. (Univ. of North Carolina, Chapel Hill, NC (United States))

    1994-03-01

    The Middle Devonian Mahantango Formation consists of siliciclastic and mixed carbonate-siliciclastic sediment packages that pulse in and out of the stratigraphy. The formation crops out in several places throughout the folded rocks of eastern Pennsylvania and Maryland. The Centerfield Member is one of the mixed siliciclastic-carbonate packages in the Mahantango Fm. This member crops out in east central Pennsylvania. The Centerfield Mbr. has been interpreted as a series of biostromes and contain abundant rugosan corals, crinoids, bryozoans, and brachiopods. The biostromes have undergone a complex diagenetic history. Illite, smectite, chlorite and muscovite have been found with the use of powder x-ray diffraction and petrographic analysis. The smectite and some of the illite are depositional clays, while, the remaining illite, chlorite and muscovite represent recrystallization of the depositional clays. There are six phases of cement in the biostrome. The paragenetic sequence of the cements is as follows: non-ferroan low magnesian calcite (LMC), intermediate ferroan LMC, ferroan LMC, non-ferroan dolomite, ferroan baroque dolomite, and quartz cement in the form of chert and blocky cement. Staining shows that the iron content of the cement changes within individual crystals and between cement phases. Preliminary data suggest that the cements may be directly related to the steady release of ions during the diagenesis of the surrounding clays in the shale.

  14. CEMENT BONDED COMPOSITES – A MECHANICAL REVIEW

    Directory of Open Access Journals (Sweden)

    Stephan Frybort

    2008-05-01

    Full Text Available Over the last years promising cement bonded wood composites for structural purposes have evolved. Durability, toughness, high dimen-sional stability, resistance against environmental influences such as biodegradation or weathering but also availability of the raw material as well as economic factors are features which can make cement-bonded composites superior to conventionally bonded composites. This paper reviews the relationship of diverse parameters, including density and particle size on mechanical and physical properties of cement bonded composites, based on published sources from the last 60 years. For general and recent information about bonding mechanisms, compatibility and setting problems, determination and improvement of compatibility, the used raw materials as well as accelerators are discussed. The main part deals with failure mechanisms in connection with several production parameters. Furthermore, the influence of particle size and geometry, orientation of the particles, cement-wood ratio and the effect of accelerators and treatment of the particles on modulus of elasticity, modulus of rupture as well as thickness swelling are discussed.

  15. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  16. Formulation of an injectable phosphocalcium cement

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, S. [CIRIMAT Equipe de Physico-Chimie des Phosphates ENSCT INP, Toulouse (France); TEKNIMED, Vic en Bigorre (France); Brouchet, A.; Delisle, B. [CHU Rangueil, Toulouse (France). Service d' Anatomie Pathologie; Freche, M.; Lacout, J.L. [CIRIMAT Equipe de Physico-Chimie des Phosphates ENSCT INP, Toulouse (France); Rodriguez, F. [Lab. de Galenique, Chmin des Maraichers, Toulouse (France)

    2001-07-01

    In orthopedic surgery, the loss or the reinforcement of osseous substance often requires filling of the defective part. In order to make the surgical operations easier we sought to make an injectable form. This study examined the effect of silicone and polyglycol on the injectability, setting time and mechanical properties of the cement. The basic solid phase was composed of a mixture of tetracalcium phosphate (Ca{sub 4}(PO{sub 4}){sub 2}O), {alpha}-tricalcium phosphate (Ca{sub 3}(PO{sub 4}){sub 2}) and sodium glycerophosphate. The basic liquid phase was made up of lime, orthophosphoric acid and water. Silicone was previously dissolved in cyclohexane and introduced in the solid phase. Polyglycol is a water-soluble compound so it is introduced in the liquid phase. For the mechanical properties, the strong increase in the percentage of additives decreased the compressive strength. Silicone and polyglycol made it possible to improve viscosity without modifying the basic setting time. The rate of evolution was different with the two different additives. From the data it was possible to optimize the formulation of cements to give predicted properties. Testing the in vivo implantation of the cement has already started. Preliminary results show the perfect osteointegration of the new cements without reactions to the foreign body in spite of the presence of silicone. (orig.)

  17. Kinetics of strength gain of biocidal cements

    Directory of Open Access Journals (Sweden)

    Rodin Aleksandr Ivanovich

    Full Text Available Biocorrosion becomes the determinative durability factor of buildings and constructions. Damages of construction materials caused by bacteria, filamentous fungi, actinomycetes constitute a serious danger to the constructions of a building or a structure and to the health of people. Biodeteriorations are typical both in old and new constructions. A great quantity of destruction factors of industrial and residential buildings under the influence of microorganisms was established in practice. Providing products and constructions based on concretes fungicidal and bactericidal properties is an important direction of modern construction material science. The most efficient way to solve this task is creation of biocidal cements. The article presents the results of experimental studies of kinetic dependences of strength gain by biocidal cements by physico-mechanical and physico-chemical analysis methods. The identical velocity character of initial hydration of the developed compositions of biocidal cements is set, as well as a more calm behavior of hardening processes at later terms. It has been established that the compositions of biocidal cements modified by sodium sulfate and sodium fluoride possess the greatest strength.

  18. Marginal adaptation of ceramic inserts after cementation

    NARCIS (Netherlands)

    Ozcan, M; Pfeiffer, P; Nergiz, [No Value

    2002-01-01

    The advantage of using ceramic inserts is to prevent major drawbacks of composite resins such as polymerization shrinkage, wear and microleakage. This in vitro study evaluated the marginal adaptation of two approximal ceramic insert systems after cementation to the cavities opened with ultrasonic ti

  19. 海排灰的氯盐含量对三灰结合料微观机理影响研究%Study of Influence of Content of Chloride and Salt in Sea-Removed Dust on Microcosmic Mechanism for Binder of Cement-Lime-Fly Ash(3 dusts)

    Institute of Scientific and Technical Information of China (English)

    袁炜; 包龙生; 于玲

    2009-01-01

    Study of microcosmic mechanism of '3 dusts' binder hydrated product, based on sea-removed dust, has revealed influence of chlorid ion on thrength of subbase materials. Study results show that cement and lime have consolidating effect on chloride ion in sea removed dust. Adequate amount of chloride ion in sea removed dust is helpful to subbase.%对基于海排灰的三灰结合料水化产物的微观机理进行研究,揭示氯离子对底基层材料强度形成的影响.研究表明:水泥、石灰材料对海排灰中的氯离子有固化作用,海排灰中适量的氯离子对底基层材料有益.

  20. Retention of overdenture posts cemented with self-adhesive resin cements.

    Science.gov (United States)

    Elsayed, Mohamed Ezzat; El-Mowafy, Omar; Fenton, Aaron

    2009-01-01

    This study investigated the effects of two self-adhesive resin cements on the retention of overdenture anchor posts after 30 days of aging in water. Forty caries-free human canines were randomly assigned to four test groups. Uni-Anchor posts were cemented to specimens in groups A and B with Breeze and Maxcem self-adhesive resin cements, respectively. In groups C and D, Fuji glass-ionomer cement and Fleck's zinc phosphate cement were used, respectively. Specimens were stored in distilled water at 37 degrees C for 30 days. Each specimen was loaded in tension in an Instron universal testing machine. The maximum force required to dislodge each post was recorded. Means and standard deviations (SDs) were calculated and data were statistically analyzed with analysis of variance (ANOVA). Means and SDs were 706.5 +/- 204.6 N for Breeze, 585.1 +/- 213.5 N for Maxcem, 449.2 +/- 181.1 N for Fuji, and 330.4 +/- 120.6 N for Fleck's. ANOVA revealed significant differences among the means (P < .0003). Adhesive failure was observed with all groups except group A, in which eight specimens underwent a cohesive fracture of the dentin. Breeze cement (group A) resulted in the highest retention force and most frequent cohesive failure and thus would be expected to clinically perform in a superior manner.

  1. Reactive-Transport Model of Buffer Cementation

    Energy Technology Data Exchange (ETDEWEB)

    Arthur, Randy; Wei Zhou [Monitor Scientific LLC, Denver, CO (United States)

    2005-10-15

    Thermal gradients during the early, non-isothermal period of near-field evolution in a KBS-3 repository for spent nuclear fuel could alter the mineralogy of the bentonite buffer and cause the constituent clay particles to become cemented together by mineral precipitates. Cementation is a potential concern because it could alter the ductility, mechanical strength and swelling pressure of the buffer, thereby possibly adversely affecting the primary performance function of this key barrier to provide a stable diffusional transport pathway between the canister and rock. The present study uses the TOUGHREACT computer program to simulate reactive-transport processes that are thought to control buffer cementation. TOUGHREACT is generally applicable to problems involving non-isothermal, multiphase reactive transport in variably saturated media. For cementation problems, the modeling approach must account specifically for the temperature dependence of equilibrium and kinetic constraints on dissolution/precipitation reactions involving the primary smectite clays and accessory phases in bentonite, and for diffusive transport of aqueous reactants and products along concentration gradients that are aligned with, or in opposition to, the direction of decreasing temperatures across the near field. The modeling approach was evaluated in two stages. A conceptual model of buffer cementation was first calibrated using observations from field tests carried out at the Stripa mine and Aespoe HRL (LOT pilot experiments). The calibrated model was then used to simulate the geochemical evolution of the KBS-3 buffer during the non-isothermal period of repository evolution. This model accounts for the imbibition of groundwater from a granitic host rock into initially unsaturated buffer materials under capillary and hydraulic pressure gradients, and uses realistic time-temperature constraints on the thermal evolution of the near-field. Preliminary results suggest that the total extent of

  2. Practical clinical considerations of luting cements: A review.

    Science.gov (United States)

    Lad, Pritam P; Kamath, Maya; Tarale, Kavita; Kusugal, Preethi B

    2014-02-01

    The longevity of fixed partial denture depends on the type of luting cement used with tooth preparation. The clinician's understating of various cements, their advantages and disadvantages is of utmost importance. In recent years, many luting agents cements have been introduced claiming clinically better performance than existing materials due to improved characteristics. Both conventional and contemporary dental luting cements are discussed here. The various agents discussed are: Zinc phosphate, Zinc polycarboxylate, Zinc oxide-eugenol, Glass-ionomer, Resin modified GIC, Compomers and Resin cement. The purpose of this article is to provide a discussion that provides a clinical perspective of luting cements currently available to help the general practitioner make smarter and appropriate choices. How to cite the article: Lad PP, Kamath M, Tarale K, Kusugal PB. Practical clinical considerations of luting cements: A review. J Int Oral Health 2014;6(1):116-20. PMID:24653615

  3. Mechanical Properties and Decay Resistance of Hornbeam Cement Bonded Particleboards

    Directory of Open Access Journals (Sweden)

    Antonios N. Papadopoulos

    2008-01-01

    Full Text Available Cement bonded particleboards were manufactured from hornbeam (Carpinus betulus L. wood particles. Hydration tests were carried out to determine the inhibitory index in order to characterise wood-cement compatibility. The results revealed that the mixture of hornbeam-cement can be classified as moderate inhibition. Two wood: cement ratios were applied in this study, namely, 1 : 3 and 1 : 4, for the board manufacture. It was found that an increase of cement-wood ratio resulted in an improvement in all properties examined, except MOR. All properties of the boards made from 1 : 4 wood: cement ratio surpassed the minimum requirements set forth by the building type HZ code. Boards were exposed to brown and white rot fungi, Coniophora puteana, and Trametes versicolor, respectively. Overall, both fungi failed to attack the cement-bonded boards.

  4. Assessment of cement durability in repository environment

    International Nuclear Information System (INIS)

    The present research aimed at investigating the durability of cement paste under nuclear waste repository conditions using accelerated tests. Cement paste samples are examined after being exposed to the environmental conditions that are expected to prevail in the repository environment and the results are compared with those obtained with unexposed specimens or specimens exposed to reference conditions. The following exposure conditions were selected: a) Immersion in salt solution, distilled water, or kept in dry storage; b) Room temperature (20 C. degrees) or high temperature (60 C. degrees); c) Immersion time of 30 days or 60 days (not for dry storage); d) Irradiation to a dose of (400 kGy) or background radiation (0 kGy). After exposure to the stressing conditions, the effects of each factor on the cement paste samples were observed by changes in their characteristics. Compressive strength tests were performed on all samples and some of them were investigated in terms of changes in mineralogy by X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). With the results obtained so far it was possible to point out the following conclusions. First, after a period of immersion in water, cement paste samples further hydrated and presented higher mechanical resistance, as expected. Secondly, dry storage did not allow a complete hydration as a consequence of pore water evaporation. High temperatures intensified this process and led to the ettringite decomposition to meta-ettringite. Thirdly, higher temperature accelerated hydration kinetics and promoted higher mechanical resistance in samples kept under immersion. Fourthly, the irradiation dose applied was unable to change the mineralogy of cement paste samples and fifthly, no statistically significant differences were observed between 30 or 60 days exposure time, for the test conditions

  5. Fundamental properties of industrial hybrid cement: utilization in ready-mixed concretes and shrinkage-reducing applications

    Directory of Open Access Journals (Sweden)

    Martauz, P.

    2016-06-01

    Full Text Available Utility properties of novel hybrid cement (H-Cement are influenced by pozzolanic reaction of fly ash, latent hydraulic reaction of metallurgical slag together with the alkali activation of inorganic geopolymer based on precipitated waste water coming from bauxite residues. Content of Portland cement clinker is at maximum of 20 mass %, the remaining portion consists of inorganic geopolymer. Up to 80% of CO2 emissions are saved by H-Cement manufacture compared to ordinary Portland cement (OPC. No heat treatment or autoclaving is needed at H-Cement production. The field application of H-Cement is performed by the same way than that of common cements listed in EN 197-1, and is also connected with highly efficient recovery and safe disposal of red mud waste. H-Cement is suitable for ready-mixed concretes up to C30/37 strength class and is specified by beneficial shrinkage-reducing property of the concrete kept in long dry-air cure opposite to common cements.Las propiedades de un nuevo cemento híbrido (cemento-H vienen determinadas por la reaccion puzolánica de cenizas volantes, la hidráulica latente de las escorias metalúrgicas y la activación alcalina mediante las aguas residuales generadas por el tratamiento de la bauxita para dar un geopolímero inorgánico. La proporción máxima de clínker de cemento en este nuevo material es del 20%, y por ello, en su fabricación se emite hasta un 80% menos de CO2 que en la producción del cemento portland (OPC. El cemento-H se prepara sin necesidad de tratamiento térmico ni de estancia en autoclave y su aplicación es la misma que los cementos convencionales definidos en la norma EN 197-1. Por otra parte, su fabricación supone la recuperación y la valorización segura de los lodos rojos de bauxita. El cemento-H es apto para la preparación de hormigones premezclados hasta la categoría C30/37, presentando el nuevo material, además, una menor retracción que los cementos convencionales, por lo que su

  6. Incorporation of trace elements in Portland cement clinker: Thresholds limits for Cu, Ni, Sn or Zn

    International Nuclear Information System (INIS)

    This paper aims at defining precisely, the threshold limits for several trace elements (Cu, Ni, Sn or Zn) which correspond to the maximum amount that could be incorporated into a standard clinker whilst reaching the limit of solid solution of its four major phases (C3S, C2S, C3A and C4AF). These threshold limits were investigated through laboratory synthesised clinkers that were mainly studied by X-ray Diffraction and Scanning Electron Microscopy. The reference clinker was close to a typical Portland clinker (65% C3S, 18% C2S, 8% C3A and 8% C4AF). The threshold limits for Cu, Ni, Zn and Sn are quite high with respect to the current contents in clinker and were respectively equal to 0.35, 0.5, 0.7 and 1 wt.%. It appeared that beyond the defined threshold limits, trace elements had different behaviours. Ni was associated with Mg as a magnesium nickel oxide (MgNiO2) and Sn reacted with lime to form a calcium stannate (Ca2SnO4). Cu changed the crystallisation process and affected therefore the formation of C3S. Indeed a high content of Cu in clinker led to the decomposition of C3S into C2S and of free lime. Zn, in turn, affected the formation of C3A. Ca6Zn3Al4O15 was formed whilst a tremendous reduction of C3A content was identified. The reactivity of cements made with the clinkers at the threshold limits was followed by calorimetry and compressive strength measurements on cement paste. The results revealed that the doped cements were at least as reactive as the reference cement.

  7. Calibration curves of a PGNAA system for cement raw material analysis using the MCNP code

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Carlos; Salgado, Jose

    1998-12-01

    In large samples, the {gamma}-ray count rate of a prompt gamma neutron activation analysis system is a multi-variable function of the elemental dry composition, density, water content and thickness of the material. The experimental calibration curves require tremendous laboratory work, using a great number of standards with well-known compositions. Although a Monte Carlo simulation study does not avoid the experimental calibration work, it reduces the number of experimental calibration standards. This paper is part of a feasibility study for a PGNAA system for on-line continuous characterisation of cement raw material conveyed on a belt (Oliveira, C., Salgado, J. and Carvalho, F. G. (1997) Optimisation of PGNAA instrument design for cement raw materials using the MCNP code. J. Radioanal. Nucl. Chem. 216(2), 191-198; Oliveira, C., Salgado, J., Goncalves, I. F., Carvalho, F. G. and Leitao, F. (1997a) A Monte Carlo study of the influence of geometry arrangements and structural materials on a PGNAA system performance for cement raw materials analysis. Appl. Radiat. Isot. (accepted); Oliveira, C., Salgado, J. and Leitao, F. (1997b) Density and water content corrections in the gamma count rate of a PGNAA system for cement raw material analysis using the MCNP code. Appl. Radiat. Isot. (accepted).]. It reports on the influence of the density, mass water content and thickness on the calibration curves of the PGNAA system. The MCNP-4A code, running in a Pentium-PC and in a DEC workstation, was used to simulate the PGNAA configuration system.

  8. Calibration curves of a PGNAA system for cement raw material analysis using the MCNP code

    International Nuclear Information System (INIS)

    In large samples, the γ-ray count rate of a prompt gamma neutron activation analysis system is a multi-variable function of the elemental dry composition, density, water content and thickness of the material. The experimental calibration curves require tremendous laboratory work, using a great number of standards with well-known compositions. Although a Monte Carlo simulation study does not avoid the experimental calibration work, it reduces the number of experimental calibration standards. This paper is part of a feasibility study for a PGNAA system for on-line continuous characterisation of cement raw material conveyed on a belt (Oliveira, C., Salgado, J. and Carvalho, F. G. (1997) Optimisation of PGNAA instrument design for cement raw materials using the MCNP code. J. Radioanal. Nucl. Chem. 216(2), 191-198; Oliveira, C., Salgado, J., Goncalves, I. F., Carvalho, F. G. and Leitao, F. (1997a) A Monte Carlo study of the influence of geometry arrangements and structural materials on a PGNAA system performance for cement raw materials analysis. Appl. Radiat. Isot. (accepted); Oliveira, C., Salgado, J. and Leitao, F. (1997b) Density and water content corrections in the gamma count rate of a PGNAA system for cement raw material analysis using the MCNP code. Appl. Radiat. Isot. (accepted).]. It reports on the influence of the density, mass water content and thickness on the calibration curves of the PGNAA system. The MCNP-4A code, running in a Pentium-PC and in a DEC workstation, was used to simulate the PGNAA configuration system

  9. In vitro tensile strength of luting cements on metallic substrate.

    Science.gov (United States)

    Orsi, Iara A; Varoli, Fernando K; Pieroni, Carlos H P; Ferreira, Marly C C G; Borie, Eduardo

    2014-01-01

    The aim of this study was to determine the tensile strength of crowns cemented on metallic substrate with four different types of luting agents. Twenty human maxillary molars with similar diameters were selected and prepared to receive metallic core castings (Cu-Al). After cementation and preparation the cores were measured and the area of crown's portion was calculated. The teeth were divided into four groups based on the luting agent used to cement the crowns: zinc phosphate cement; glass ionomer cement; resin cement Rely X; and resin cement Panavia F. The teeth with the crowns cemented were subjected to thermocycling and later to the tensile strength test using universal testing machine with a load cell of 200 kgf and a crosshead speed of 0.5 mm/min. The load required to dislodge the crowns was recorded and converted to MPa/mm(2). Data were subjected to Kruskal-Wallis analysis with a significance level of 1%. Panavia F showed significantly higher retention in core casts (3.067 MPa/mm(2)), when compared with the other cements. Rely X showed a mean retention value of 1.877 MPa/mm(2) and the zinc phosphate cement with 1.155 MPa/mm(2). Glass ionomer cement (0.884 MPa/mm(2)) exhibited the lowest tensile strength value. Crowns cemented with Panavia F on cast metallic posts and cores presented higher tensile strength. The glass ionomer cement showed the lowest tensile strength among all the cements studied. PMID:25140718

  10. Stiffness and strength of composite acrylic bone cements

    Directory of Open Access Journals (Sweden)

    I. Knets

    2007-01-01

    Full Text Available Purpose: Different acrylic bone cements based upon PMMA-MMA system are applicable for implant fixation inbone tissue. The aim of present study is the optimisation of the structure of some new bone acrylic cements madeon the basis of PMMA-ethylmethacrylate-triethyleneglycoldimethacrylate and bone cements having additives (HAand radio pacifier, and the finding of the effect of these modifications on the flexural strength and stiffness.Design/methodology/approach: Different new bone cements on the basis of PMMA-EMA-TEGDMA system(ABC were developed experimentally. The stiffness and strength of the samples of these modified cements weredetermined in the special three point bending equipment.Findings: A comparison of the flexural properties of new PMMA-EMA-TEGDMA cements and commercialavailable PMMA-MMA cement showed that commercial bone cement had larger values of ultimate strengthand modulus of elasticity, but the difference is not very important. As concerns the polymerisation peaktemperature, then there is a significant difference between commercial PMMA-MMA cement (~ 800C andPMMA-EMA-TEGDMA modified cements (50 – 600C. The introduction of 10% and 18% of HA into solidphase does not influence essentially strength and modulus of elasticity of the PMMA-EMA-TEGDMA bonecements. The introduction of radio pacifier BaSO4 into bone cement leads to flexural strength diminishing.Low polymerisation peak temperature and appropriate mechanical properties of bone cements developed allowsregarding new 3-D structure acrylic bone cements as promising biomaterials.Research limitations/implications: It is supposed to carry out animal testing to learn more about reaction ofmodified implanted material on the biological environment.Practical implications: The new materials could be efficiently used as bone cements because they will notdamage surrounding biological tissue during curing.Originality/value: Paper is providing the new information about possibilities to

  11. Stimulation of Odontogenesis and Angiogenesis via Bioactive Nanocomposite Calcium Phosphate Cements Through Integrin and VEGF Signaling Pathways.

    Science.gov (United States)

    Lee, Sang-Im; Lee, Eui-Suk; El-Fiqi, Ahmed; Lee, So-Youn; Eun-Cheol Kim; Kim, Hae-Won

    2016-05-01

    Formulating self-setting calcium phosphate cements (CPCs) with secondary phases particularly in the nanoscale order holds great promise to improve biological properties. Here, we focus on the effect that bioactive glass nanoparticles (BGN) incorporated in CPC compositions can have on the proliferation, odontogenic differentiation, and angiogenic stimulation of stem cells derived from human dental pulp (HDPSCs). These odontogenic and angiogenic events are of special importance in the dentin-pulp regeneration processes. In comparison to pure CPCs, nanocomposite cements exhibit a significantly improved proliferation of HDPSCs, and the improvement is more significant as the BGN content increases. The nanocomposite cements substantially enhance the adhesion of cells, and significantly up-regulate odontogenic differentiation, including alkaline phosphatase (ALP) activity and the expressions of odontogenic genes (sialophosphoprotein, dentin matrix protein I, ALP, osteopontin and osteocalcin). Furthermore, the use of nanocomposite cements result in stimulation of angiogenic gene expression (VEGF, FGF-2, VEGFRs, PECAM-1, and VE-cadherin) and protein production (VEGF, VEGFR-1). The angiogenic stimulation by the HDPSCs significantly affects the endothelial cell behaviors, that is, the endothelial cell migration and the tubular network formation are substantially improved when treated with HDPSC-conditioned medium, particularly with the help of nanocomposite cements. The integrin and VEGF signaling pathways are reasoned for the stimulation of the odontogenesis and angiogenesis of cells, where the nanocomposite cements up-regulate the integrin subsets α1, α2, α3, and β1, and activate the integrin downstream signal pathways, such as p-FAK, p-Akt, p-paxillin, JNK, EK, and NF-κB, as well as other nuclear transcriptional factors, including CREB, STAT-3, and ELK-1. The current results indicate that the new formulation of the nanocomposite self-setting cements might provide some

  12. 浅谈水泥土强度的影响因素%Study on the factors affecting the strength of cement-soil

    Institute of Scientific and Technical Information of China (English)

    林云腾

    2011-01-01

    针对水泥土在土体加固中的广泛应用,在综合各种文献的基础上,本文重点探讨了水泥土强度的若干影响因素。主要因素有土的天然含水率、土的物理性质、有机质含量、pH值、水泥掺入比、水灰比、水泥土含水率、龄期、养护条件,明确这些因素,有利于指导水泥土设计和施工从而达到预期目的。%Because of widely using of cement-soil in the soil reinforcement,this paper focuses on a number of factors affecting cement-soil strength in the basis of summarization of the literature.The main factors are the natural soil moisture,soil physical properties,organic matter content,pH value,SO2-4,cement ratio,water-cement ratio,moisture content of soil-cement,age,curing conditions.Definition of these factors is conducive for changing various factors in the design and construction of cement-soil to achieve the intended purpose.

  13. Effect of Nano-TiO2 Addition on the Hydration and Hardening Process of Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; LI Hainan; MEI Junpeng; OUYANG Pei

    2015-01-01

    The influences of nano-TiO2 on the setting time, hydration process, hydration products and morphology of sulphoaluminate cement were studied by Vicat apparatus, isothermal calorimetry, X-ray diffraction (XRD), thermal analysis and scanning electron microscopy (SEM). The experimental results show that the incorporation of nano-TiO2 can obviously promote the setting and hardening process of sulphoaluminate cement, and shorten the interval between the initial and ifnal setting time, the hydration induction period of sulphoaluminate cement is significantly shortened and the acceleration period begins immediately, but the hydration exothermic rate at hydration stationary phase is not obviously impacted. The nano-TiO2 additives have inlfuence on the formation rate and degree of crystallinity, but do not affect the type of hydration process. The structure of hydration products is compact at middle age, but their content and microstructure do not change.

  14. Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

    Science.gov (United States)

    Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

    Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

  15. Performance of RHA Cement Concrete under Marine Environment via Wetting and Drying Cyclic by Rapid Migration Test

    Directory of Open Access Journals (Sweden)

    Ramadhansyah Putra Jaya

    2013-12-01

    Full Text Available In this research, the performance of concrete containing rice husk ash (RHA under marine environment through wetting and drying cycles was investigated. Five levels of cement replacement (0%, 10%, 20%, 30% and 40% by weight were used. The total cementitious content used was 420 kg/m3. A water/binder ratio of 0.49 was used to produce concrete having a target compressive strength of 40MPa at the age of 28 days. The performance of blended cement concrete under marine environment was evaluated using rapid migration test (RMT.  The results clearly showed that RHA can be satisfactorily used as a cement replacement material in order to reduce the chloride penetration depth and hence increases the durability of concrete. Generally, the chloride penetration depth of concrete containing higher RHA replacement is decreased as the RHA replacement increases, resulting in concrete with higher resistance to seawater attack.

  16. Temperature dependence of autogenous shrinkage of silica fume cement pastes with a very low water–binder ratio

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, I., E-mail: ippei@dali.nuac.nagoya-u.ac.jp [Graduate School of Environmental Studies, Nagoya University, ES Building, No. 539, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Teramoto, A. [Graduate School of Environmental Studies, Nagoya University, Faculty of Engineering, ES Building, No. 546, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2013-08-15

    Ultra-high-strength concrete with a large unit cement content undergoes considerable temperature increase inside members due to hydration heat, leading to a higher risk of internal cracking. Hence, the temperature dependence of autogenous shrinkage of cement pastes made with silica fume premixed cement with a water–binder ratio of 0.15 was studied extensively. Development of autogenous shrinkage showed different behaviors before and after the inflection point, and dependence on the temperature after mixing and subsequent temperature histories. The difference in autogenous shrinkage behavior poses problems for winter construction because autogenous shrinkage may increase with decrease in temperature after mixing before the inflection point and with increase in temperature inside concrete members with large cross sections.

  17. A Comparative Study on Compressive and Flexural Strength of Concrete Containing Different Admixtures as Partial Replacement of Cement

    Directory of Open Access Journals (Sweden)

    Apoorv Singh

    2014-09-01

    Full Text Available Concrete is the most widely used material in the world today. This paper is about the comparative study of the flexural strength and compressive strength of concrete when different admixtures are used as partial replacement of cement in the concrete mix. The mineral admixtures that are used here are Silica Fume, Rice Husk Ash and Iron slag as partial replacement of cement. All these materials are industrial waste products and are abundantly available nowadays. These materials have high silica content and pozzolanic properties and can be effectively used as a replacement of cement during the formation of High Performance Concrete. Compressive and Flexural strength are the two most important characteristic of concrete and are calculated for the hardened concrete to analyze the load bearing capacity for design purposes. Thus for the effective judgment of type of mineral admixtures to be used a comparative study is very useful.

  18. An evaluation of the composition of soil cement bricks with construction and demolition waste - doi: 10.4025/actascitechnol.v33i2.9377

    Directory of Open Access Journals (Sweden)

    Antonio Anderson da Silva Segantini

    2011-04-01

    Full Text Available Sustainable development requires the existence of a production network that includes the reuse of construction waste for new materials. Current analysis investigates an optimal soil-cement composition made up of construction and demolition waste for the manufacture of pressed bricks. Soil-cement bricks were manufactured from construction and demolition wastes (CDW, A-4 classified fine sandy soil and cement CP II Z 32. Laboratory tests, comprising test compaction, optimum water content and maximum dry specific weight, consistency limits, grain size distribution and linear shrinkage, were made to characterize the materials researched. Compressive strength and absorption tests were also undertaken in different combinations of composition. Results showed that the application of CDW improved soil-cement qualities and reduced shrinkage of the material used.

  19. Characterisation and use of biomass fly ash in cement-based materials.

    Science.gov (United States)

    Rajamma, Rejini; Ball, Richard J; Tarelho, Luís A C; Allen, Geoff C; Labrincha, João A; Ferreira, Victor M

    2009-12-30

    This paper presents results about the characterisation of the biomass fly ashes sourced from a thermal power plant and from a co-generation power plant located in Portugal, and the study of new cement formulations incorporated with the biomass fly ashes. The study includes a comparative analysis of the phase formation, setting and mechanical behaviour of the new cement-fly ash formulations based on these biomass fly ashes. Techniques such as X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermal gravimetric and differential thermal analysis (TG/DTA), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and environmental scanning electron spectroscopy (ESEM) were used to determine the structure and composition of the formulations. Fly ash F1 from the thermal power plant contained levels of SiO(2), Al(2)O(3) and Fe(2)O(3) indicating the possibility of exhibiting pozzolanic properties. Fly ash F2 from the co-generation plant contained a higher quantity of CaO ( approximately 25%). The fly ashes are similar to class C fly ashes according to EN 450 on the basis of chemical composition. The hydration rate and phase formation are greatly dependant on the samples' alkali content and water to binder (w/b) ratio. In cement based mortar with 10% fly ash the basic strength was maintained, however, when 20% fly ash was added the mechanical strength was around 75% of the reference cement mortar. The fly ashes contained significant levels of chloride and sulphate and it is suggested that the performance of fly ash-cement binders could be improved by the removal or control of these chemical species.

  20. Apatite precipitation on a novel fast-setting calcium silicate cement containing fluoride

    Science.gov (United States)

    Ranjkesh, Bahram; Chevallier, Jacques; Salehi, Hamideh; Cuisinier, Frédéric; Isidor, Flemming; Løvschall, Henrik

    2016-01-01

    Abstract Aim: Calcium silicate cements are widely used in endodontics. Novel fast-setting calcium silicate cement with fluoride (Protooth) has been developed for potential applications in teeth crowns including cavity lining and cementation. Objective: To evaluate the surface apatite-forming ability of Protooth compositions as a function of fluoride content and immersion time in phosphate-buffered saline (PBS). Material and methods: Three cement compositions were tested: Protooth (3.5% fluoride and 10% radiocontrast), ultrafast Protooth (3.5% fluoride and 20% radiocontrast), and high fluoride Protooth (15% fluoride and 25% radiocontrast). Powders were cap-mixed with liquid, filled to the molds and immersed in PBS. Scanning electron microscopy, energy dispersive X-ray analysis, and Raman spectroscopy were used to characterize the precipitations morphology and composition after 1, 7, 28, and 56 days. Apatite/belite Raman peak height indicated the apatite thickness. Results: Spherical calcium phosphate precipitations with acicular crystallites were formed after 1-day immersion in PBS and Raman spectra disclosed the phosphate band at 965 cm−1, supporting the apatite formation over Protooth compositions. The apatite deposition continued and more voluminous precipitations were observed after 56 days over the surface of all cements. Raman bands suggested the formation of β-type carbonated apatite over Protooth compositions. High fluoride Protooth showed the most compact deposition with significantly higher apatite/belite ratio compared to Protooth and ultrafast Protooth after 28 and 56 days. Conclusions: Calcium phosphate precipitations (apatite) were formed over Protooth compositions after immersion in PBS with increasing apatite formation as a function of time. High fluoride Protooth exhibited thicker apatite deposition. PMID:27335901