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Sample records for ratio cement content

  1. Determining the water-cement ratio, cement content, water content and degree of hydration of hardened cement paste: Method development and validation on paste samples

    International Nuclear Information System (INIS)

    Wong, H.S.; Buenfeld, N.R.

    2009-01-01

    We propose a new method to estimate the initial cement content, water content and free water/cement ratio (w/c) of hardened cement-based materials made with Portland cements that have unknown mixture proportions and degree of hydration. This method first quantifies the composition of the hardened cement paste, i.e. the volumetric fractions of capillary pores, hydration products and unreacted cement, using high-resolution field emission scanning electron microscopy (FE-SEM) in the backscattered electron (BSE) mode and image analysis. From the obtained data and the volumetric increase of solids during cement hydration, we compute the initial free water content and cement content, hence the free w/c ratio. The same method can also be used to calculate the degree of hydration. The proposed method has the advantage that it is quantitative and does not require comparison with calibration graphs or reference samples made with the same materials and cured to the same degree of hydration as the tested sample. This paper reports the development, assumptions and limitations of the proposed method, and preliminary results from Portland cement pastes with a range of w/c ratios (0.25-0.50) and curing ages (3-90 days). We also discuss the extension of the technique to mortars and concretes, and samples made with blended cements.

  2. Portland cement concrete air content study.

    Science.gov (United States)

    1987-04-20

    This study took the analysis of Portland cement concrete air content. Based on the information gathered, this study hold the results were : 1) air-entrained concrete was more durable than non-air entrained concrete all other factors being equal; 2) A...

  3. Changes of strength characteristics of pervious concrete due to variations in water to cement ratio

    Science.gov (United States)

    Kovac, M.; Sicakova, A.

    2017-10-01

    Pervious concrete is considered to be a sustainable pavement material due to high water permeability. The experiment presented in this paper was aimed at study the influence of water to cement ratio on both the compressive and splitting tensile strength of pervious concrete. Typically, less water content in concrete mixture leads to less porosity of cement paste and thus it provides desirable mechanical properties. In case of conventional dense concrete, the lower is the water to cement ratio, the higher or better is the strength, density and durability of concrete. This behaviour is not quite clear in case of pervious concrete because of low amount of cement paste present. Results of compressive and splitting tensile strength of pervious concrete are discussed in the paper while taking into account values measured after 2 and 28 days of hardening and variations in water to cement ratio. The results showed that changes of water to cement ratio from 0.25 to 0.35 caused only slight differences in strength characteristics, and this applied to both types of tested strength.

  4. The Effect of Water Cement Ratio on Cement Brick Containing High Density Polyethylene (HDPE as Sand Replacement

    Directory of Open Access Journals (Sweden)

    Ali Noorwirdawati

    2018-01-01

    Full Text Available Waste disposal can contribute to the problem of environmental pollution. Most of the waste material is plastic based, because the nature of difficult of plastic degradable by itself. In order to overcome the problem, many study has been conducted on the reuse of plastic material into various field such as civil engineering and construction. In this study, municipal solid waste (MSW in the form of High Density Polyethylene (HDPE plastic was used to replace sand in cement sand brick production. The HDPE used in this study was obtained from a recycle factory at Nilai, Negeri Sembilan. 3% of HDPE replacement was applied in this study, with the cement-sand mix design of 1:6 and water-cement ratio 0.35, 0.40, 0.45 and 0.50 respectively. All specimens were tested for compressive strength and water absorption at 7 and 28 days. The density of the bricks was also recorded. The finding show that brick with 3% HDPE content and 0.45 of water-cement ratio at 28 days of age curing show the highest compressive strength, which is 19.5N/mm2 compared to the control specimen of 14.4 N/mm2.

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

    Science.gov (United States)

    Li, Dongliang; Liu, Xinrong; Liu, Xianshan

    2015-07-02

    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 ( C v ) on the physical and mechanical properties of the artificial cemented sand were analyzed and the Mohr-Coulomb strength theory was modified by using C v . The research reveals that when C v is high (e.g., C v = 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 C v increases, both the peak strength and residual strength of the samples show a significant increase. When C v is low (e.g., C v = 0.01), the stress-strain curves of the samples indicate strain hardening behavior. From the test data, a function of C v (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.

  6. 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.

  7. Optimal fluorite/gypsum mineralizer ratio in Portland cement clinkering

    Directory of Open Access Journals (Sweden)

    Tobón, J. I.

    2016-06-01

    Full Text Available This paper presents an analysis of the joint effect of fluorite and gypsum as mineralizers in the manufacture of Portland cement. A laboratory- scale Box-Behnken statistical design was used to quantify the effects of the explanatory variables fluorite content (0.00, 0.25, 0.50, and 0.75%, fluorite/gypsum ratio (2/15, 1/3 and 8/15, and clinkering temperature (1250, 1300, and 1350 °C on the response variable free CaO content in the clinker produced. The clinker was characterized by the ethylene method, XRD, DSC and optical microscopy. Free CaO decreases of 81% and 56% were found in the mineralized clinker, compared to the same clinker without mineralizers, at 1300 °C and 1250 °C, respectively. Petrographic analysis showed that at lower temperatures, the amount of alite in the mineralized clinker was higher than the amount of alite in the clinker without mineralizers. The best condition was found for the fluorite/gypsum ratio of 2/15.Este artículo presenta el efecto combinado de la fluorita y el yeso como mineralizadores. Se usó el diseño experimental estadístico Box-Behnken, a escala de laboratorio, para cuantificar el efecto de la fluorita en porcentajes de 0.00, 0.25, 0.50 y 0.75%; relaciones fluorita/yeso de 2/15, 1/3 y 8/15; con temperaturas de clinkerización de 1250, 1300 y 1350 °C y la cal libre como variable de respuesta. El clínker producido fue caracterizado midiendo el contenido de cal libre por el método de etileno, DRX, DSC y microscopía óptica. Se encontró un descenso de la cal libre del 81 y 56% en el clinker mineralizado en comparación con el clinker sin mineralizadores a 1300 y 1250 °C respectivamente. El análisis petrográfico mostró que la cantidad de alita en el clinker mineralizado a bajas temperaturas es más alta que en el clinker sin mineralizadores. La mejor condición se encontró para la relación fluorita/yeso de 2/15.

  8. 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

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

    International Nuclear Information System (INIS)

    Torkittikul, Pincha; Chaipanich, Arnon

    2012-01-01

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

  10. 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...

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

    Science.gov (United States)

    López-Uceda, Antonio; Ayuso, Jesús; López, Martin; Jimenez, José Ramón; Agrela, Francisco; Sierra, María José

    2016-01-26

    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.

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

    Science.gov (United States)

    López-Uceda, Antonio; Ayuso, Jesús; López, Martin; Jimenez, José Ramón; Agrela, Francisco; Sierra, María José

    2016-01-01

    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. PMID:28787874

  13. 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.

  14. Revealing the influence of water-cement ratio on the pore size distribution in hydrated cement paste by using cyclohexane

    Science.gov (United States)

    Bede, Andrea; Ardelean, Ioan

    2017-12-01

    Varying the amount of water in a concrete mix will influence its final properties considerably due to the changes in the capillary porosity. That is why a non-destructive technique is necessary for revealing the capillary pore distribution inside hydrated cement based materials and linking the capillary porosity with the macroscopic properties of these materials. In the present work, we demonstrate a simple approach for revealing the differences in capillary pore size distributions introduced by the preparation of cement paste with different water-to-cement ratios. The approach relies on monitoring the nuclear magnetic resonance transverse relaxation distribution of cyclohexane molecules confined inside the cement paste pores. The technique reveals the whole spectrum of pores inside the hydrated cement pastes, allowing a qualitative and quantitative analysis of different pore sizes. The cement pastes with higher water-to-cement ratios show an increase in capillary porosity, while for all the samples the intra-C-S-H and inter-C-S-H pores (also known as gel pores) remain unchanged. The technique can be applied to various porous materials with internal mineral surfaces.

  15. modified water-cement ratio law for compressive strength of rice

    African Journals Online (AJOL)

    user

    solid agricultural waste (rice husk) and also produce more sustainable cheaper concrete products. To this end, studies on the development of modified water- cement ratio law for concrete incorporating RHA is timely and justifiable. The relationship between the compressive strength and the cement-water ratio is ...

  16. Influence of Solids-to-liquid and Activator Ratios on Calcined Kaolin Cement Powder

    Science.gov (United States)

    Liew, Y. M.; Kamarudin, H.; Bakri, A. M. Mustafa Al; Binhussain, M.; Luqman, M.; Nizar, I. Khairul; Ruzaidi, C. M.; Heah, C. Y.

    This paper summarizes the effect of activator ratio on the processing of cement powder. Geopolymer slurry was produced via alkaline activation of calcined kaolin. Once the geopolymer slurry solidified, it was crushed and ground to obtain cement powder. Ultilizing the concept of "just adding water", hardened cement paste could be produced from cement powder. This paper concluded that solids-to-liquid and sodium silicate-to-sodium hydroxide ratios have a significant effect on compressive strength of hardened cement paste. The optimum solids-to-liquid and sodium silicate-to-sodium hydroxide ratios were 0.80 and 0.20, respectively. SEM micrographs showed that a processing route to produce cement powder by "just adding water" was possible, and the structure became denser and fewer unreacted particles were observed.

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

    International Nuclear Information System (INIS)

    Tan Hongbin; Li Yuxiang

    2005-01-01

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

  18. Influence of packing and dispersion of particles on the cement content of concretes

    Directory of Open Access Journals (Sweden)

    B. L. DAMINELI

    Full Text Available Abstract Due to environmental issues, the concrete chain seeks to reduce CO2 emissions. However, growing demand from developing countries causes the increase of CO2 emissions in production to exceed decreases generated by industrial actions, such as improving kilns and clinker replacement. New strategies are important. Changes in the concrete formulation, making it more efficient, can help if these changes produce concrete with the same performance and lower cement consumption. In this regard, the improvement of packing and dispersion of particles increases this efficiency. The better the packing, the lower the volume of voids between particles, thereby requiring lower fluid content (water to permit flow. The dispersion of the particles also decreases the water content for the same fluidity. The less the water content, the smaller the water/cement (w/c ratio, and the greater the resistance. Thus, both strategies increase the efficiency by uncoupling obtaining fluidity from the water content. This study investigated the influence of packing and dispersion on the efficiency of cement use in concrete. The increase of packing and the complete dispersion of fine particles has been shown to improve efficiency, as measured by the ratio between binder consumption and compressive strength (the performance parameter used in most practical applications.

  19. Modified water-cement ratio law for compressive strength of rice ...

    African Journals Online (AJOL)

    This work examines the modification of age long water – cement ratio law of Ordinary Portland Cement (OPC) concrete to cater for concrete with Rice Husk Ash (RHA). Chemical analysis of RHA produced under controlled temperature of 600°C was carried out. A total of one hundred and fifty (150) RHA concrete cubes at ...

  20. Reducing cement content in concrete mixtures : [research brief].

    Science.gov (United States)

    2011-12-01

    Concrete mixtures contain crushed rock or gravel, and sand, bound together by Portland cement in combination with supplemental cementitious materials (SCMs), which harden through a chemical reaction with water. Portland cement is the most costly comp...

  1. Effects of chemical and mineral additives and the water/cement ratio on the thermal resistance of Portland cement concrete

    International Nuclear Information System (INIS)

    Cesar, Leandro Cesar Dias; Morelli, Arnaldo C.; Baldo, Joao Baptista

    1998-01-01

    The exposure of Portland concrete to high temperatures (>250 deg C) can damage drastically the microstructural integrity of the material. Since the water/cement ratio as well as the inclusion of superplasticizers and mineral additives (silica fume) can alter constitutively and micro structurally the material, in this work it was investigated per effect of these additions on the damage resistance of portland concrete after exposure to high temperatures. (author)

  2. 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

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

    Science.gov (United States)

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

    2012-09-01

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

  4. The Combined Effect of the Initial Cure and the Type of Cement on the Natural Carbonation, the Portlandite Content, and Nonevaporable Water in Blended Cement

    Directory of Open Access Journals (Sweden)

    Saida Boualleg

    2017-01-01

    Full Text Available The aim of this work is to better understand the physical and chemical phenomena involved in hydrated mix (clinker + addition during the natural carbonation process, to characterize cement with supplementary cementitious materials (SCMs under various curing environment. The prepared cement pastes were characterized by thermogravimetric analysis. The results showed a considerable influence of the environment on the properties of mortars and cement and a perfect correlation between compressive strength, natural carbonation, nonevaporable water, and portlandite content. It was observed that the reduction of the curing period makes the mortars more sensitive. The kinetics of process was evaluated from Ca(OH2 content and nonevaporable water contained in mortars. These two parameters reflect the hydration progress of the water/cement ratio studied. The weight loss due to Ca(OH2 decomposition, calculated by DTA/TG analysis, shows the effect of the pozzolanic reaction and the natural carbonation. The supplementary cementitious materials (SCMs play a considerable role in the slowing down of the aggression environment.

  5. Research on influence of water-cement ratio on workability and mechanical properties of geopolymer grouting material

    Science.gov (United States)

    Wang, X. Q.; Wen, P. H.; Gao, Z. W.; Wang, C. H.

    2018-01-01

    To investigate the influence of water-cement ratio on the fluidity and mechanical strength of geopolymer grouting materials, the change of fluidity, compressive strength and flexural strength of road geopolymer grouting material with different water-cement ratio were tested. The results showed that the fluidity of geopolymer grouting material was enhanced while the compressive and flexural strength decreased with the increase of water - cement ratio. The optimum value of water-cement ratio was in range (0.39-0.42). The road geopolymer grouting material had the better fluidity and the strength requirement of reinforcement if the main constituent materials was not changed.

  6. 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.

  7. Arsenic content in Portland cement: a literature review.

    Science.gov (United States)

    Tenório de Franca, Talita Ribeiro; da Silva, Raphaela Juvenal; Sedycias de Queiroz, Michellini; Aguiar, Carlos Menezes

    2010-01-01

    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.

  8. Radionuclide content of local and imported cements used in Egypt

    International Nuclear Information System (INIS)

    Mahmoud, K R

    2007-01-01

    The activity concentrations of natural and artificial gamma-ray emitting radionuclides in local and imported cement have been investigated during the period from 2000 to 2003 using a 50% HPGe γ-spectroscopy system. The total numbers of local and imported samples were 29 and 8, respectively. The results showed a low activity concentration of 137 Cs in both the local and imported samples. The only exception was found in one imported Portland cement (2.8 ± 0.2 Bq kg -1 ) and one local blast furnace slag cement (1.9 ± 0.3 Bq kg -1 ). The average activity concentrations of 226 Ra, 232 Th and 40 K in local cement were 33 ± 17, 14 ± 2.4 and 45 ± 26 Bq kg -1 , respectively, whereas those in imported cement were 27 ± 7, 8 ± 7 and 134 ± 22 Bq kg -1 , respectively. The results showed that blast furnace slag cement contains the highest level of natural radioactivity, whereas white cement contains the lowest levels. The measured activity concentrations of the detected radionuclides were compared with other measurements carried out in Egypt and elsewhere. Radium-equivalent activities were also calculated to assess the radiation hazards arising from using such material in the construction of dwellings. Generally, the radium-equivalents of the analysed samples were smaller than the guideline limit of 370 Bq kg -1

  9. The effect of varied mix proportion and water-cement ratio on the compressive strength of medium grade concretepoduced from Bama gravel

    Directory of Open Access Journals (Sweden)

    L. O. Omundi

    2001-10-01

    Full Text Available Concrete cubes produced from Bama gravel (Category B using varied mix proportions and water-cement ratios were subjected to compressive strength and density tests at the curing ages 7, 14 and 28 days. The results indicated that the strength of 28.00Nmm-2 was recorded from the mix proportion of 1:1/2:4 and water-cement ratio of 0.55, which corresponds to a density of 2495 kgm-3. A careful inspection of the results obtained generally shows that the strenfths are inversely proportional to the fine aggregate content and water-cement ratios. It is recommended that great care should be taken while mixing the aggregate proportions of the Bama gravel in order to obtain high quality medium grade concrete for construction purposes.

  10. Time-domain reflectometry of water content in portland cement concrete

    Science.gov (United States)

    1997-11-01

    Time-domain reflectometry is useful for measuring the moisture content of solids. However, little information exists on its use with portland cement concrete. By monitoring the response from TDR sensors embedded in concrete as the concrete dried, the...

  11. The stability of clay using Portland cement and calsium carbide residue with California bearing ratio (cbr) value

    Science.gov (United States)

    Puji Hastuty, Ika; Roesyanto; Novia Sari, Intan; Simanjuntak, Oberlyn

    2018-03-01

    Clay is a type of soil which is often used for stabilization. This is caused by its properties which are very hard in dry conditions and plastic in the medium content of water. However, at a higher level of water, clay will be cohesive and very lenient causing a large volume change due to the influence of water and also causing the soil to expand and shrink for a short period of time. These are the reasons why stabilization is needed in order to increase bearing capacity value of the clay. Stabilization is one of the ways to the conditon of soil that has the poor index properties, for example by adding chemical material to the soil. One of the chemical materials than can be added to the soil is calsium carbide residue. The purpose of this research is to know the fixation of index properties as the effect of adding 2% PC and calsium carbide residue to the clay, and to know the bearing capacity value of CBR (California Bearing Ratio) as the effect of adding the stabilization agent and to know the optimum content of adding calsium carbide residue. The result of the research shows that the usage of 2% cement in the soil that has CBR value 5,76%, and adding 2% cement and 9% calsium carbide residue with a period of curing 14 days has the lagerst of CBR value that is 9,95%. The unsoaked CBR value shows the increase of CBR value upto the mixture content of calsium carbide residue 9% and, decreases at the mixture content of calsium carbide residue 10% and 11%.

  12. 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.

  13. The Wedge Splitting Test: Influence of Aggregate Size and Water-to-Cement Ratio

    DEFF Research Database (Denmark)

    Pease, Bradley Justin; Skocek, Jan; Geiker, Mette Rica

    2007-01-01

    by the elastic modulus, tensile strength, fracture energy, and the assumed softening behavior. The stress-crack width relation can be implemented in finite element models for computing the cracking behavior of cementitious systems. While inverse analysis provides information about the material properties...... enables the stress-crack width response to be determined simultaneously from multiple experimental tests. The effect of water-to-cement ratio and aggregate size are discussed. A comparison of epoxy-impregnated cracked WST specimen and material properties indicate a relationship between fracture properties...

  14. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash.

    Science.gov (United States)

    Wu, Mengxue; Li, Chen; Yao, Wu

    2017-01-11

    In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the "gel/space ratio" descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system) by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM) replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD). The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel ( G C to G S C M ratio) is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities.

  15. Performance of composite sand cement brick containing recycle concrete aggregate and waste polyethylene terephthalate with different mix design ratio

    Science.gov (United States)

    Azmi, N. B.; Khalid, F. S.; Irwan, J. M.; Mazenan, P. N.; Zahir, Z.; Shahidan, S.

    2018-04-01

    This study is focuses to the performance of composite sand cement brick containing recycle concrete aggregate and waste polyethylene terephthalate. The objective is to determine the mechanical properties such as compressive strength and water absorption of composite brick containing recycled concrete aggregate and polyethylene terephthalate waste and to determine the optimum mix ratio of bricks containing recycled concrete aggregate and polyethylene terephthalate waste. The bricks specimens were prepared by using 100% natural sand, they were then replaced by RCA at 25%, 50% and 75% with proportions of PET consists of 1.0%, 1.5%, 2.0% and 2.5% by weight of natural sand. Based on the results of compressive strength, it indicates that the replacement of RCA shows an increasing strength as the strength starts to increase from 25% to 50% for both mix design ratio. The strength for RCA 75% volume of replacement started to decrease as the volume of PET increase. However, the result of water absorption with 50% RCA and 1.0% PET show less permeable compared to control brick at both mix design ratio. Thus, one would expect the density of brick decrease and the water absorption to increase as the RCA and PET content is increased.

  16. Determination of transmission factors of concretes with different water/cement ratio, curing condition, and dosage of cement and air entraining agent

    International Nuclear Information System (INIS)

    Sahin, Remzi; Polat, Recep; Icelli, Orhan; Celik, Cafer

    2011-01-01

    Highlights: → We determined transmission factors of parameters affecting properties of concrete. → The most important parameter is W/C ratio for attenuation of radiation of concrete. → Taguchi Method provides an appropriate methodology for parameter reduction. - Abstract: This study focuses on determination of transmission factors of main parameters affecting the properties of both normal- and heavy-weight concrete in order to increase knowledge and understanding of radiation attenuation in concrete at a later age. Water/cement (W/C) ratio, curing condition, cement quantity and air entraining agent (AEA) were selected as the main parameters. Eight energy values have been selected within the energy interval of 30.85-383.85 keV to be used in the radiation source. The Taguchi Method was used as the method of optimization. It was determined in the study that the most important parameter affecting the attenuation of the radiation of the concrete is the W/C ratio and the concretes produced with the lowest level of W/C ratio absorb more radiation. However, it was also determined that there was a combined effect between the W/C ratio and the cement dosage.

  17. Evaluation of portland cement concrete pavement with high slag content cement.

    Science.gov (United States)

    2013-10-01

    The performance of a section of concrete pavement built with 30 percent Ground Granulated Blast Furnace Slag (GGBFS) is compared to a control section of concrete pavement built with 25 percent GGBFS to determine if the higher slag content pavement is...

  18. Natural radioactivity levels and danger ratio in cements, concretes and mortars used in construction

    International Nuclear Information System (INIS)

    Meneses, J.; Pacheco, C.; Avila, J. M.; Miro, C.

    2010-01-01

    We have determined the natural radiation level in three types of adhesive cements, five types of concrete and two types of mortars of different strength normally used in the construction field. Of these materials, both concrete and mortars were prepared in our laboratories, cements the contrary were of a commercial nature.

  19. Experimental characterization of the concrete behaviour under high confinement: influence of the saturation ratio and of the water/cement ratio

    International Nuclear Information System (INIS)

    Vu, X.H.

    2007-08-01

    The objective of this thesis is to experimentally characterize the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour under high confinement. This thesis lies within a more general scope of the understanding of concrete behaviour under severe loading situations (near field detonation or ballistic impacts). A near field detonation or an impact on a concrete structure generate very high levels of stress associated with complex loading paths in the concrete material. To validate concrete behaviour models, experimental results are required. The work presented in this thesis concerns tests conducted using a static triaxial press that allows to obtain stress levels of the order of the giga Pascal. The porous character of concrete and the high confinement required on the one hand, a development of a specimen protection device, and on the other hand, a development of an instrumentation with strain gauges, which is unprecedented for such high confinements. Hydrostatic and triaxial tests, conducted on the one hand on model materials and on the other hand on concrete, allowed to validate the developed experimental procedures as well as the technique of strain and stress measurements. The studies concerning the influence of the saturation ratio and of the water/cement ratio of concrete on its behaviour required the formulation of a plain baseline concrete and of two modified concretes with different water/cement ratios. The analysis of triaxial tests performed on the baseline concrete shows that the saturation ratio of concrete has a major influence on its static behaviour under high confinement. This influence is particularly marked for the concrete loading capacity and for the shape of limit state curves for saturation ratios greater than 50%. The concrete loading capacity increases with the confinement pressure for tests on dry concrete whereas beyond a given confinement pressure, it remains limited for wet or saturated concrete

  20. 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.

  1. Variations in powder/liquid ratio of a restorative and luting glass ionomer cement in dental clinics.

    Science.gov (United States)

    Iqbal, Kefi; Islam, Sana Adeba; Ahmad, Iqbal; Asmat, Maria; Aminuddin, Mohammad

    2009-07-01

    A survey was conducted to ascertain the variations practiced in powder/liquid (P/L) ratio of Glass Ionomer Cement (GIC) used as restorative and luting material in dental clinics of Karachi. It has been observed that in the use of GIC brands, 33% (Fuji 2) and 36% (Gold Label 2) of the dentists, did not follow the recommended P/L ratios for restorative purposes. Similarly, 67% (Fuji 1) and 29% (Gold Label 1) did not follow the recommended ratios for luting purposes. The wide variations practiced in P/L mixing ratios against the recommended ratio for restorative purpose (approximately 1:2) and that for luting purpose (~1:1 to 2:1) may affect the performance characteristics of the material.

  2. INFLUENCE OF WATER-TO-CEMENT RATIO ON AIR ENTRAILMENT IN PRODUCTION OF NON-AUTOCLAVED FOAM CONCRETE USING TURBULENCE CAVITATION TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    Gorshkov Pavel Vladimirovich

    2012-10-01

    Full Text Available Non-autoclaved foam concrete is an advanced thermal insulation material. Until recently, foam concrete production has been based on separate preparation of foam and solution, followed by their blending in a mixer. The situation changed when high-quality synthetic foaming agents and turbulence cavitation technology appeared on the market. Every model provides a dependence between the foam concrete strength and the water-to-cement ratio. According to the water-cement ratio we can distinguish strong concrete mixtures (with the water-to-cement ratio equal to 0.3…0.4 and ductile ones (with the water-to-cement ratio equal to 0.5…0.7. Strong concrete mixtures are more durable. The lower the water-to-cement ratio, the higher the foam concrete strength. However super-plastic substances cannot be mixed by ordinary turbulent mixers. Foam concrete produced using the turbulence cavitation technology needs air-entraining, its intensity being dependent on several factors. One of the main factors is the amount of free water, if it is insufficient, the mixture will not be porous enough. A researcher needs to identify the optimal water-to-cement ratio based on the water consumption rate. Practical production of prefabricated concrete products and structures has proven that the reduction of the water-to-cement ratio improves the strength of the product. The task is to find the water-to-cement ratio for the foam concrete mixture to be plastic enough for air entraining. An increase in the ratio causes loss in the strength. The ratio shall vary within one hundredth points. Super-plasticizers are an alternative solution.

  3. Relative permeability of fractured wellbore cement: an experimental investigation using electrical resistivity monitoring for moisture content

    Science.gov (United States)

    Um, W.; Rod, K. A.; Strickland, C. E.

    2016-12-01

    Permeability is a critical parameter needed to understand flow in subsurface environments; it is particularly important in deep subsurface reservoirs where multiphase fluid flow is common, such as carbon sequestration and geothermal reservoirs. Cement is used in the annulus of wellbores due to its low permeable properties to seal aquifers, reducing leaks to adjacent strata. Extreme subsurface environments of CO2 storage and geothermal production conditions will eventually reduce the cement integrity, propagating fracture networks and increasing the permeability for air and/or water. To date, there have been no reproducible experimental investigations of relative permeability in fractured wellbore cement published. To address this gap, we conducted a series of experiments using fractured Portland cement monoliths with increasing fracture networks. The monolith cylinder sides were jacketed with heavy-duty moisture-seal heat-shrink tubing, then fractured using shear force applied via a hydraulic press. Fractures were generated with different severity for each of three monoliths. Stainless steel endcaps were fixed to the monoliths using the same shrink-wrapped jacket. Fracture characteristics were determined using X-ray microtomography and image analysis. Flow controllers were used to control flow of water and air to supply continuous water or water plus air, both of which were delivered through the influent end cap. Effluent air flow was monitored using a flow meter, and water flow was measured gravimetrically. To monitor the effective saturation of the fractures, a RCON2 concrete bulk electrical resistivity test device was attached across both endcaps and a 0.1M NaNO3 brine was used as the transport fluid to improve resistivity measurements. Water content correlated to resistivity measurements with a r2 > 0.96. Data from the experiments was evaluated using two relative permeability models, the Corey-curve, often used for modeling relative permeability in porous media

  4. Application of Factor Analysis on the Financial Ratios of Indian Cement Industry and Validation of the Results by Cluster Analysis

    Science.gov (United States)

    De, Anupam; Bandyopadhyay, Gautam; Chakraborty, B. N.

    2010-10-01

    Financial ratio analysis is an important and commonly used tool in analyzing financial health of a firm. Quite a large number of financial ratios, which can be categorized in different groups, are used for this analysis. However, to reduce number of ratios to be used for financial analysis and regrouping them into different groups on basis of empirical evidence, Factor Analysis technique is being used successfully by different researches during the last three decades. In this study Factor Analysis has been applied over audited financial data of Indian cement companies for a period of 10 years. The sample companies are listed on the Stock Exchange India (BSE and NSE). Factor Analysis, conducted over 44 variables (financial ratios) grouped in 7 categories, resulted in 11 underlying categories (factors). Each factor is named in an appropriate manner considering the factor loads and constituent variables (ratios). Representative ratios are identified for each such factor. To validate the results of Factor Analysis and to reach final conclusion regarding the representative ratios, Cluster Analysis had been performed.

  5. INFLUENCES OF SUPERPLASTICIZER, MIXING TIME, MIXING TEMPERATURE AND CEMENT CONTENT ON HIGH-VOLUME FLY ASH CONCRETE

    OpenAIRE

    Nobuhiro, KAWAGUCHI; Kiyoshi, KOHNO; Masakazu, MITA; Department of Civil Engineering, Faculty of Engineering, The University of Tokushima; Department of Civil Engineering, Faculty of Engineering, The University of Tokushima; Department of Civil Engineering, Faculty of Engineering, The University of Tokushima

    1996-01-01

    The influences of superplasticizers, mixing time, mixing temperature and cement content on high-volume fly ash concrete were investigated in order to use the industrial by-product, fly ash from coal thermal power plant, more actively for concrete. The slump, air content, compressive strength and tensile strength of high-volume fly ash concrete were investigated using different mixtures. The results of these investigations indicate that the properties of fly ash concrete are influenced by the ...

  6. An Experimental Study of Portland Cement and Superfine Cement Slurry Grouting in Loose Sand and Sandy Soil

    Directory of Open Access Journals (Sweden)

    Weijing Yao

    2018-04-01

    Full Text Available Grouting technology is widely applied in the fields of geotechnical engineering in infrastructure. Loose sand and sandy soil are common poor soils in tunnel and foundation treatments. It is necessary to use superfine cement slurry grouting in the micro-cracks of soil. The different effectiveness of Portland cement slurry and superfine cement slurry in sandy soil by the laboratory grouting experiment method were presented in this paper. The grouting situations of superfine cement slurry injected into sand and sandy soil were explored. The investigated parameters were the dry density, wet density, moisture content, internal friction angle, and cohesion force. The results show that the consolidation effect of superfine cement is better than that of Portland cement due to the small size of superfine cement particles. The superfine cement can diffuse into the sand by infiltration, extrusion, and splitting. When the water–cement ratio of superfine cement slurry is less than 2:1 grouting into loose sand, the dry and wet density decrease with the increase in the water–cement ratio, while the moisture content and cohesive force gradually increase. When the water–cement ratio of superfine cement slurry is 1:1 grouting into loose sand and sandy soil, the dry density, wet density, and cohesive force of loose sand are larger than those of sandy soil. The results of the experiment may be relevant for engineering applications.

  7. Influence of HEMA content on the mechanical and bonding properties of experimental HEMA-added glass ionomer cements

    Directory of Open Access Journals (Sweden)

    Ho-Nam Lim

    2009-08-01

    Full Text Available The purpose of this study was to determine the influence of incrementally added uncured HEMA in experimental HEMA-added glass ionomer cement (HAGICs on the mechanical and shear bond strength (SBS of these materials. Increasing contents of uncured HEMA (10-50 wt.% were added to a commercial glass ionomer cement liquid (Fuji II, GC, Japan, and the compressive and diametral tensile strengths of the resulting HAGICs were measured. The SBS to non-precious alloy, precious alloy, enamel and dentin was also determined after these surfaces were subjected to either airborne-particle abrasion (Aa or SiC abrasive paper grinding (Sp. Both strength properties of the HAGICs first increased and then decreased as the HEMA content increased, with a maximum value obtained when the HEMA content was 20% for the compressive strength and 40% for the tensile strength. The SBS was influenced by the HEMA content, the surface treatment, and the type of bonding surface (p<0.05. These results suggest that addition of an appropriate amount of HEMA to glass ionomer cement would increase diametral tensile strength as well as bond strength to alloys and teeth. These results also confirm that the optimal HEMA content ranged from 20 to 40% within the limitations of this experimental condition.

  8. The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

    Science.gov (United States)

    Atapour, Hadi; Mortazavi, Ali

    2018-04-01

    The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

  9. Catechin content and consumption ratio of the collared lemming

    DEFF Research Database (Denmark)

    Berg, Thomas B.

    2003-01-01

    catechin content. Dicrostonyx species are known to have specialised on shrubs, especially Dryas spp. and Salix spp., rather than graminoids like other related microtines. Bioassays were conducted using food material from Dryas spp., Salix arctica, Vaccinium uliginosum, Kobresia myosuroides and Poa glauca...

  10. The effect of aggregate aspect ratio and temperature on the fracture toughness of a low cement refractory concrete

    Directory of Open Access Journals (Sweden)

    Laura Brum Prata

    2003-12-01

    Full Text Available This work investigated the influence of the aggregate's aspect ratio on the fracture behavior of a low cement aluminum silicate refractory castable treated at two different temperatures (110 °C and 1000 °C. The aggregates were cylindrical pellets with an aspect ratio of 1, 2, 3 and 4, produced by extruding a mixture of clay and calcined alumina fired at 1600 °C for 4 h to yield mullite (3Al2O3.2SiO2. The behavior of the R-Curve and other relevant fracture parameters were evaluated based on the "Two Parameter Fracture Model" in a three-point flexure test of single-edge straight through notched specimens. The two temperature treatments produced different degrees of matrix-aggregate adhesion. The larger aspect ratio aggregates were found to promote toughening only in the dried condition, at 110 °C, while the specimens fired at 1000 °C for 4 h, regardless of their aggregate aspect ratio, displayed no significant toughening. The best results for fired samples, however, were obtained from specimens containing conventional angular aggregates.

  11. Preparation and Cutting Performance of Boron-Doped Diamond Coating on Cemented Carbide Cutting Tools with High Cobalt Content

    OpenAIRE

    Zhaozhi Liu; Feng Xu; Junhua Xu; Xiaolong Tang; Ying Liu; Dunwen Zuo

    2015-01-01

    Chemical vapor deposition (CVD) diamond coated cutting tool has excellent cutting performance, it is the most ideal tool for the processing of nonferrous metals and alloys, composites, nonmetallic materials and other difficult-to-machine materials efficiently and accurately. Depositing CVD diamond coating on the cemented carbide with high cobalt content can improve its toughness and strength, therefore, it is very important to research on the preparation technology and cu...

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

    Science.gov (United States)

    Chen, Irvin Allen

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

  13. Analysis of metal contents in Portland Type V and MTA-based cements.

    Science.gov (United States)

    Dorileo, Maura Cristiane Gonçales Orçati; Bandeca, Matheus Coelho; Pedro, Fábio Luis Miranda; Volpato, Luiz Evaristo Ricci; Guedes, Orlando Aguirre; Dalla Villa, Ricardo; Tonetto, Mateus Rodrigues; Borges, Alvaro Henrique

    2014-01-01

    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 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. 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.

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

    Science.gov (United States)

    Dorileo, Maura Cristiane Gonçales Orçati; Bandeca, Matheus Coelho; Pedro, Fábio Luis Miranda; Volpato, Luiz Evaristo Ricci; Guedes, Orlando Aguirre; Villa, Ricardo Dalla; Tonetto, Mateus Rodrigues; Borges, Alvaro Henrique

    2014-01-01

    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. PMID:25436238

  16. The differential dieaway technique applied to the measurement of the fissile content of drums of cement encapsulated waste

    International Nuclear Information System (INIS)

    Swinhoe, M.T.

    1986-01-01

    This report describes calculations of the differential dieaway technique as applied to cement encapsulated waste. The main difference from previous applications of the technique are that only one detector position is used (diametrically opposite the neutron source) and the chamber walls are made of concrete. The results show that by rotating the drum the response to fissile material across the central plane of the drum can be made relatively uniform. The absolute size of the response is about 0.4. counts per minute per gram fissile for a neutron source of 10 8 neutrons per second. Problems of neutron and gamma background and water content are considered. (author)

  17. Early-age Performance of Cement Combination Concrete

    Directory of Open Access Journals (Sweden)

    Samuel Olufemi Folagbade

    2017-03-01

    Full Text Available Heat of hydration up to 72 hours and compressive strength up to 7 days of Portland cement and 17 binary and ternary cements containing fly ash, silica fume, and metakaolin, at a water/cement ratio of 0.50 and addition contents of 20%, 35%, and 55%, were used to examine the early-age performance of concrete. Results revealed that early-age performance depends on the fineness, heat of hydration, and dilution effect of cement combinations. Fly ash, due to dilution effect, reduces the heat of hydration and compressive strength. Using silica fume and metakaolin with increasing content of up to 10% as binary and ternary cement components, due to their fineness and increased heat of hydration, supports the strength development. Most of the cement combinations met the standard of strength requirements for ordinary early-age performance of concrete, while only half of it satisfied the standard for high early-age performance.

  18. Strontium content and strontium-calcium ratio in timothy (Phleum pratense L.) and soil in Finland

    International Nuclear Information System (INIS)

    Paasikallio, Arja

    1979-01-01

    Strontium and calcium contents were determined about 2 000 sample pairs of timothy and soil. An investigation into these element contents was made with reference to parishes and latitudinal zones. The effect of some soil factors on the Sr content of timothy in Carex peat soil was also studied. The Sr content of timothy was highest in northern Finland, while the highest contents of soluble Sr and Ca were generally found in the soils of southern Finland. The Ca content of timothy also tended to rise from the southern to the northern regions but to a lesser extent than Sr. The Sr/Ca ratio both in timothy and soil was generally highest between latitudes 64 deg and 66 deg N. The highest Sr content of timothy in the north was suggested to be due to at least some of the following factors: regional differences in the distribution of soil types, the occurrence of nutritionally poorer soils in the northern regions, climatological factors and plant competition. The present material did not contain any exceptionally high Sr contents in timothy or soil. In Carex peat, the Sr content of timothy increased with decreasing volume weight and pH of the soil. In these soils, the variation in the low Sr content of timothy was explained significantly by soluble Sr in the soil and the straw height; plant Sr increased with increasing soluble Sr and decreasing plant height. In higher Sr contents, plant Sr increased with decreasing soluble Ca. (author)

  19. Optimization of solid content, carbon/nitrogen ratio and food/inoculum ratio for biogas production from food waste.

    Science.gov (United States)

    Dadaser-Celik, Filiz; Azgin, Sukru Taner; Yildiz, Yalcin Sevki

    2016-12-01

    Biogas production from food waste has been used as an efficient waste treatment option for years. The methane yields from decomposition of waste are, however, highly variable under different operating conditions. In this study, a statistical experimental design method (Taguchi OA 9 ) was implemented to investigate the effects of simultaneous variations of three parameters on methane production. The parameters investigated were solid content (SC), carbon/nitrogen ratio (C/N) and food/inoculum ratio (F/I). Two sets of experiments were conducted with nine anaerobic reactors operating under different conditions. Optimum conditions were determined using statistical analysis, such as analysis of variance (ANOVA). A confirmation experiment was carried out at optimum conditions to investigate the validity of the results. Statistical analysis showed that SC was the most important parameter for methane production with a 45% contribution, followed by F/I ratio with a 35% contribution. The optimum methane yield of 151 l kg -1 volatile solids (VS) was achieved after 24 days of digestion when SC was 4%, C/N was 28 and F/I were 0.3. The confirmation experiment provided a methane yield of 167 l kg -1 VS after 24 days. The analysis showed biogas production from food waste may be increased by optimization of operating conditions. © The Author(s) 2016.

  20. 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.

  1. The content and ratio of type I and III collagen in skin differ with age ...

    African Journals Online (AJOL)

    Results obtained showed that the mean content of type I and III and type I/III ratio in normal skin differed significantly among age groups (P0.05), with the lowest levels of type I, III, and the highest ratio of type I/III observed in the elderly age group. Differences between normal uninjured skin and hypertrophic scar tissue were ...

  2. INORGANIC CEMENT CONCRETE

    Directory of Open Access Journals (Sweden)

    Alisson Clay Rios Silva

    2014-07-01

    Full Text Available In this work, a Geopolymeric Cement Concrete (GCC was developed through adequate portions of geopolymer components. Its characteristics were compared with Portland Cement Concrete (PCC, through of the establishment of some parameters of design, as consumption of binders, water/aggregates ratio and mortar content. The concrete mechanical performance was evaluated with emphasis to the fatigue behavior. Were tested the effects of different tensile strength maximum (increasing and decreasing. The results of fatigue tests had shown that GCC presents a better performance when compared to PCC. Its fatigue strength was 15% higher than that of PCC, when 70% of rupture tension of the concrete in static bending (SR, was applied. Tensions of about 80% SR resulted in 96% of increase, when compared to GCC. The SEM microstructural analysis showed that the GCC has a matrix/aggregate bonding very strong, when compared to PCC, probably due to the massive nature of the geopolymeric matrix.

  3. Influence of setting liquid composition and liquid-to-powder ratio on properties of a Mg-substituted calcium phosphate cement.

    Science.gov (United States)

    Pina, S; Olhero, S M; Gheduzzi, S; Miles, A W; Ferreira, J M F

    2009-05-01

    The influence of four variables on various properties of a Mg-substituted calcium phosphate cement (CPC) was investigated. The variables were the heat treatment temperature of the precipitated powders, the composition of the setting liquid, the liquid-to-powder ratio (LPR), and the time over which hardened specimens were cured in air. The properties analysed were the phase composition of the starting powder, the initial setting time, the evolution of the storage shear modulus (G') and the loss shear modulus (G'') with the cement paste curing time (t), and the compressive strength. The presence of alpha-TCP in CPC facilitated the setting and hardening properties due to its progressive dissolution and the formation of brushite crystals. As far as the liquid composition is concerned, in cases where citric acid was used, adding a rheology modifier (10 wt.% polyethylene glycol or 0.5 wt.% hydroxyl propylmethylcellulose) to the acid led to an increase in the initial setting time, while an increase in the acid concentration led to a decrease in the initial setting time. The initial setting time showed to be very sensitive towards the LPR. The evolution of G' and G'' with curing time reflected the internal structural changes of cement pastes during the setting process. The compressive strength of the wet-hardened cement specimens with and without Mg increased with curing time increasing, being slightly higher in the case of Mg-substituted CPC. The results suggest that Mg-substituted CPC holds a promise for uses in orthopaedic and trauma surgery such as for filling bone defects.

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

    Directory of Open Access Journals (Sweden)

    Velazco, G.

    2014-09-01

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

  5. CHH Cement Composite

    Science.gov (United States)

    Cwirzen, A.; Habermehl-Cwirzen, K.; Nasibulina, L. I.; Shandakov, S. D.; Nasibulin, A. G.; Kauppinen, E. I.; Mudimela, P. R.; Penttala, V.

    The compressive strength and electrical resistivity for hardened pastes produced from nanomodified Portland SR cement (CHH- Carbon Hedge Hog cement) were studied. The nanomodification included growing of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) on the cement particles. Pastes having water to binder ratio of 0.5 were produced. The obtained hardened material was characterized by increased compressive strength in comparison with the reference specimens made from pristine SR cement, which was attributed to reinforcing action of the CNTs and CNFs. The electrical resistivity of CHH composite was lower by one order of magnitude in comparison with reference Portland cement paste.

  6. 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

  7. Stable isotope methods: The effect of gut contents on isotopic ratios of zooplankton

    Science.gov (United States)

    Hill, J. M.; McQuaid, C. D.

    2011-05-01

    In the past decade there has been an increased awareness of the potential for methodological bias resulting from multiple pre-analytical procedures in foodweb interpretations based on stable isotope techniques. In the case of small organisms, this includes the effect of gut contents on whole body signatures. Although gut contents may not reflect actual assimilation, their carbon and nitrogen values will be isotopically lighter than after the same material has been assimilated. The potential skewing of isotopic ratios in whole organism samples is especially important for aquatic environments as many studies involve trophic relationships among small zooplankton. This is particularly important in pelagic waters, where herbivorous zooplankton comprise small taxa. Hence this study investigated the effect of gut contents on the δ13C and δ15N ratios of three size classes of zooplankton (1.0-2.0, 2.0-4.0 and >4.0 mm) collected using bongo net tows in the tropical waters of the south-west Indian Ocean. Animals were collected at night, when they were likely to be feeding, sieved into size classes and separated into genera. We focused on Euphausia spp which dominated zooplankton biomass. Three treatment types were processed: bulk animals, bulk animals without guts and tail muscle from each size class at 10 bongo stations. The δ15N ratios were influenced by zooplankton size class, presumably reflecting ontogenetic changes in diet. ANOVA post hoc results and correlations in δ15N signatures among treatments suggest that gut contents may not affect overall nitrogen signatures of Euphausia spp., but that δ13C signatures may be significantly altered by their presence. Carbon interpretations however, were complicated by potential effects of variation in chitin, lipids and metabolism among tissues and the possibility of opportunistic omnivory. Consequently we advocate gut evacuation before sacrifice in euphausiids if specific tissue dissection is impractical and recommend

  8. Silver contents and Cu/Ag ratios in Martian meteorites and the implications for planetary differentiation

    Science.gov (United States)

    Wang, Zaicong; Becker, Harry

    2017-11-01

    Silver and Cu show very similar partitioning behavior in sulfide melt-silicate melt and metal-silicate systems at low and high pressure-temperature (P-T) experimental conditions, implying that mantle melting, fractional crystallization and core-mantle differentiation have at most modest (within a factor of 3) effects on Cu/Ag ratios. For this reason, it is likely that Cu/Ag ratios in mantle-derived magmatic products of planetary bodies reflect that of the mantle and, in some circumstances, also the bulk planet composition. To test this hypothesis, new Ag mass fractions and Cu/Ag ratios in different groups of Martian meteorites are presented and compared with data from chondrites and samples from the Earth's mantle. Silver contents in lherzolitic, olivine-phyric and basaltic shergottites and nakhlites range between 1.9 and 12.3 ng/g. The data display a negative trend with MgO content and correlate positively with Cu contents. In spite of displaying variable initial Ɛ143Nd values and representing a diverse spectrum of magmatic evolution and physiochemical conditions, shergottites and nakhlites display limited variations of Cu/Ag ratios (1080 ± 320, 1 s, n = 14). The relatively constant Cu/Ag suggests limited fractionation of Ag from Cu during the formation and evolution of the parent magmas, irrespectively of whether sulfide saturation was attained or not. The mean Cu/Ag ratio of Martian meteorites thus reflects that of the Martian mantle and constrains its Ag content to 1.9 ± 0.7 ng/g (1 s). Carbonaceous and enstatite chondrites display a limited range of Cu/Ag ratios of mostly 500-2400. Ordinary chondrites show a larger scatter of Cu/Ag up to 4500, which may have been caused by Ag redistribution during parent body metamorphism. The majority of chondrites have Cu/Ag ratios indistinguishable from the Martian mantle value, indicating that Martian core formation strongly depleted Cu and Ag contents, but probably did not significantly change the Cu/Ag ratio of the

  9. Hydration characteristics and structure formation of cement pastes containing metakaolin

    Directory of Open Access Journals (Sweden)

    Dvorkin Leonid

    2018-01-01

    Full Text Available Metakaolin (MK is one of the most effective mineral admixtures for cement-based composites. The deposits of kaolin clays are wide-spread in the world. Metakaolin is comparable to silica fume as an active mineral admixture for cement-based composites. In this paper, the rheological and mechanical properties of cement paste containing metakaolin are investigated. The effect of MK is more evident at “tight” hydration conditions within mixtures with low water-cement ratio, provided by application of superplasticizers. The cement is replaced with 0 to 15% metakaolin, and superplasticizer content ranged from 0 to 1.5% by weight of cementitious materials (i.e. cement and metakaolin. An equation is derived to describe the relationship between the metakaolin and superplasticizer content and consistency of pastes. There is a linear dependence between metakalolin content and water demand. Second-degree polynomial describe the influence of superplasticizer content. The application of SP and MK may produce cement-water suspensions with water-retaining capacity at 50-70% higher than control suspensions. The investigation of initial structure forming of cement pastes with SP-MK composite admixture indicates the extension of coagulation structure forming phase comparing to the pastes without additives. Crystallization stage was characterized by more intensive strengthening of the paste with SP-MK admixture comparing to the paste without admixtures and paste with SP. Results on the porosity parameters for hardened cement paste indicate a decrease in the average diameter of pores and refinement of pore structure in the presence of metakaolin. A finer pore structure associated with an increase in strength. X-ray analysis data reveal a growing number of small-crystalline low-alkaline calcium hydrosilicates and reducing portlandite content, when MK dosage increases. Scanning electron microscopy (SEM data confirm, that hardened cement paste containing MK has

  10. 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.

  11. Analysis of heavy metal contents in gray and white MTA and 2 kinds of Portland cement: a preliminary study.

    Science.gov (United States)

    Chang, Seok Woo; Shon, Won Jun; Lee, WooCheol; Kum, Kee Yeon; Baek, Seung Ho; Bae, Kwang Shik

    2010-04-01

    The levels of 10 heavy metals (arsenic, bismuth, cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc) in gray Portland cement (GPC), white Portland cement (WPC), gray MTA (GMTA), and white MTA (WMTA) were analyzed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). One gram of each material was digested with 80 degrees C "aqua-regia" (7 mL of 60% HNO3 and 21 mL of 35% HCl), filtered, and analyzed by ICP-AES. The analysis was performed 6 times and the data were analyzed statistically. Arsenic and lead concentrations were the highest in GPC (P cements (P Portland cement versus MTA, the differences in purity may be considered. Copyright 2010 Mosby, Inc. All rights reserved.

  12. U and Th background contents in the Crimea rocks, Th/U ratio interpretation

    International Nuclear Information System (INIS)

    Gerasimov, Yu.G.; Voronova, M.A.; AN Ukrainskoj SSR, Kiev. Inst. Geologicheskikh Nauk)

    1981-01-01

    Radiogeochemical sampling of rocks in the Crimea is carried out. Analyses for U are made by luminescence method, while for Th by X-ray one. About 1000 samples, characterizing the whole stratigraphical cross section except Pz of crystalline rocks, have been analyzed. Low background values for U and Th are established; U content of 1.3-2.3 g/kg and Th content of 7.0-9.0 g/kg are predominant, that is lower than the clark of the earth crust. The distribution of radioelements in stepper and submontane Crimea is gradual, while in mountain part - the mosaic one. Results of Th/U ratios interpretation are presented [ru

  13. Ratio

    Science.gov (United States)

    Webster, Nathan A. S.; Pownceby, Mark I.; Madsen, Ian C.; Studer, Andrew J.; Manuel, James R.; Kimpton, Justin A.

    2014-12-01

    Effects of basicity, B (CaO:SiO2 ratio) on the thermal range, concentration, and formation mechanisms of silico-ferrite of calcium and aluminum (SFCA) and SFCA-I iron ore sinter bonding phases have been investigated using an in situ synchrotron X-ray diffraction-based methodology with subsequent Rietveld refinement-based quantitative phase analysis. SFCA and SFCA-I phases are the key bonding materials in iron ore sinter, and improved understanding of the effects of processing parameters such as basicity on their formation and decomposition may assist in improving efficiency of industrial iron ore sintering operations. Increasing basicity significantly increased the thermal range of SFCA-I, from 1363 K to 1533 K (1090 °C to 1260 °C) for a mixture with B = 2.48, to ~1339 K to 1535 K (1066 °C to 1262 °C) for a mixture with B = 3.96, and to ~1323 K to 1593 K (1050 °C to 1320 °C) at B = 4.94. Increasing basicity also increased the amount of SFCA-I formed, from 18 wt pct for the mixture with B = 2.48 to 25 wt pct for the B = 4.94 mixture. Higher basicity of the starting sinter mixture will, therefore, increase the amount of SFCA-I, considered to be more desirable of the two phases. Basicity did not appear to significantly influence the formation mechanism of SFCA-I. It did, however, affect the formation mechanism of SFCA, with the decomposition of SFCA-I coinciding with the formation of a significant amount of additional SFCA in the B = 2.48 and 3.96 mixtures but only a minor amount in the highest basicity mixture. In situ neutron diffraction enabled characterization of the behavior of magnetite after melting of SFCA produced a magnetite plus melt phase assemblage.

  14. Center for Cement Composite Materials

    Science.gov (United States)

    1990-01-31

    DSP cement pastes were prepared using white Portland cement (PC), amorphous silica fume, and a superplasticizer . The fume/cement ratios varied from... superplasticized PC pastes without silica fume. This is due to a reduction in the amount and size of porosity formed in DSP. Specific: surface areas measured

  15. 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.

  16. 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

  17. Assessment of Physical and Mechanical Properties of Cement Panel Influenced by Treated and Untreated Coconut Fiber Addition

    Science.gov (United States)

    Abdullah, Alida; Jamaludin, Shamsul Baharin; Anwar, Mohamed Iylia; Noor, Mazlee Mohd; Hussin, Kamarudin

    This project was conducted to produce a cement panel with the addition of treated and untreated coconut fiber in cement panel. Coconut fiber was added to replace coarse aggregate (sand) in this cement panel. In this project, the ratios used to design the mixture were 1:1:0, 1:0.97:0.03, 1:0.94:0.06, 1:0.91:0.09 (cement: sand: coconut fiber). The water cement ratio was constant at 0.55. The sizes of sample tested were, 160 mm x 40 mm x 40 mm for compression test, and 100 mm x 100 mm x 40 mm for density, moisture content and water absorption tests. After curing samples for 28 days, it was found that the addition of coconut fiber, further increase in compressive strength of cement panel with untreated coconut fiber. Moisture content of cement panel with treated coconut fiber increased with increasing content of coconut fiber whereas water absorption of cement panel with untreated coconut fiber increased with increasing content of coconut fiber. The density of cement panel decreased with the addition of untreated and treated coconut fiber.

  18. Binding of chloride and alkalis in Portland cement systems

    International Nuclear Information System (INIS)

    Nielsen, Erik P.; Herfort, Duncan; Geiker, Mette R.

    2005-01-01

    A thermodynamic model for describing the binding of chloride and alkalis in hydrated Portland cement pastes has been developed. The model is based on the phase rule, which for cement pastes in aggressive marine environment predicts multivariant conditions, even at constant temperature and pressure. The effect of the chloride and alkalis has been quantified by experiments on cement pastes prepared from white Portland cements containing 4% and 12% C 3 A, and a grey Portland cement containing 7% C 3 A. One weight percent calcite was added to all cements. The pastes prepared at w/s ratio of 0.70 were stored in solutions of different Cl (CaCl 2 ) and Na (NaOH) concentrations. When equilibrium was reached, the mineralogy of the pastes was investigated by EDS analysis on the SEM. A well-defined distribution of chloride was found between the pore solution, the C-S-H phase, and an AFm solid solution phase consisting of Friedel's salt and monocarbonate. Partition coefficients varied as a function of iron and alkali contents. The lower content of alkalis in WPC results in higher chloride contents in the C-S-H phase. High alkali contents result in higher chloride concentrations in the pore solution

  19. Optimizing cementious content in concrete mixtures for required performance.

    Science.gov (United States)

    2012-01-01

    "This research investigated the effects of changing the cementitious content required at a given water-to-cement ratio (w/c) on workability, strength, and durability of a concrete mixture. : An experimental program was conducted in which 64 concrete ...

  20. Effect of Slag Content and Hardening Accelerator Dosage on the Physico Mechanical Properties of Cement and Concrete

    International Nuclear Information System (INIS)

    Derabla, R.; Mokrani, I.; Benmalek, M.L.

    2011-01-01

    Our contribution consists at the study of the effect of (0 %, 0.2 % and 0.34 %) dosage of an hardening accelerating plasticizer (Plastocrete 160, produced by Sika Aldjazair) on the properties of normal mortar and concretes prepared with portland cement artificial of Hadjar Soud cement factory (Skikda - Algeria) with addition of (10 % and 20 %) of granulated blast furnace slag finely crushed of the El Hadjar blast furnace (Annaba - Algeria). The tests are focused to the physical and mechanical characteristics of elaborated materials to knowing: setting time, porosity, water absorption capacity and the test of compressive strength at 2, 7 and 28 days. The results obtained show clearly the reliability of the additive used to accelerate the hardening and to obtain high strengths at early age, which increase by increasing of the additive dosage. For the slag, its low hydraulic capacity does not make it profitable than at the long term (beyond 28 days). (author)

  1. The influence of particle size and fluorine content of aluminosilicate glass on the glass ionomer cement properties.

    Science.gov (United States)

    De Caluwé, T; Vercruysse, C W J; Fraeyman, S; Verbeeck, R M H

    2014-09-01

    Glass ionomer cements (GIC) are clinically accepted dental restorative materials mainly due to their direct chemical adhesion to both enamel and dentin and their ability to release fluoride. However, their mechanical properties are inferior compared to those of amalgam and composite. The aim of this study is to investigate if combinations of nano- and macrogranular glass with different compositions in a glass ionomer cement can improve the mechanical and physical properties. Glasses with the composition 4.5 SiO2-3 Al2O3-1.5 P2O5-(5-x) CaO-x CaF2 (x=0 and x=2) were prepared. Of each type of glass, particles with a median size of about 0.73 μm and 6.02 μm were made. The results show that the setting time of GIC decreases when macrogranular glass particles are replaced by nanogranular glass particles, whereas the compressive strength and Young's modulus, measured after 24 h setting, increase. The effects are more pronounced when the nanogranular glass particles contain fluoride. After thermocycling, compressive strength decreases for nearly all formulations, the effect being most pronounced for cements containing nanogranular glass particles. Hence, the strength of the GIC seems mainly determined by the macrogranular glass particles. Cumulative F--release decreases when the macrogranular glass particles with fluoride are replaced by nanogranular glass particles with(out) fluoride. The present study thus shows that replacing macro- by nanogranular glass particles with different compositions can lead to cements with approximately the same physical properties (e.g. setting time, consistency), but with different physicochemical (e.g. F--release, water-uptake) and initial mechanical properties. On the long term, the mechanical properties are mainly determined by the macrogranular glass particles. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  2. Determination of phytate, iron, zinc, calcium contents and their molar ratios in commonly consumed raw and prepared food in malaysia.

    Science.gov (United States)

    Norhaizan, M E; Nor Faizadatul Ain, A W

    2009-09-01

    The inhibitory effect of phytate on the bioavailability of iron, zinc and calcium was determined by measuring their molar ratios. A total of 29 food samples consisting of 12 rice and rice products, 5 wheat and wheat products, 5 grains and cereal based products and 7 different popular varieties of cooked rice and rice products were selected. The phytate content was analysed using anion-exchange chromatography whereas mineral contents were analysed using atomic absorption spectrophotometry(AAS). One-way ANOVA test was used to statistically analyse the mean difference between the phytate and mineral contents between the food group samples. In general, results show that cooked products have lower content of phytate and minerals as compared to raw products. This could be due to the influence of the cooking method on phytate and mineral content in the food. Based on one-way ANOVA test, there were no significant difference in phytate and zinc content between four food groups (p >0.05). Significant differences were found only in iron and calcium content (p 1, 5 food samples had a phytate/zinc molar ratio > 15 and 23 food samples had a phytate/calcium molar ratio of 0.24. These results show that although many of the food samples analysed had high mineral content, the high phytate content may impair the bioavailability of the mineral in the body.

  3. Effect of phase composition of calcium silicate phosphate component on properties of brushite based composite cements

    Energy Technology Data Exchange (ETDEWEB)

    Sopcak, T., E-mail: tsopcak@imr.saske.sk [Institute of Materials Research of SAS, Watsonova 47, 04001 Kosice (Slovakia); Medvecky, L.; Giretova, M.; Stulajterova, R.; Durisin, J. [Institute of Materials Research of SAS, Watsonova 47, 04001 Kosice (Slovakia); Girman, V. [Institute of Physics, Faculty of Science, P. J. Šafárik University, Park Angelinum 9, 04001 Kosice (Slovakia); Faberova, M. [Institute of Materials Research of SAS, Watsonova 47, 04001 Kosice (Slovakia)

    2016-07-15

    The composite cement mixtures were prepared by mixing brushite (B) with, the amorphous hydrated calcium silicate phosphate (CSPH) or annealed calcium silicate phosphate (CSP composed of Si-saturated hydroxyapatite, wollastonite and silica) phases and water as liquid component. The contents of the silicate-phosphate phase in composites were 10.30 and 50 wt%. The significant effect of both the Ca/P ratio and different solubility of calcium silicate phosphate component in starting cement systems on setting time and phase composition of the final composite cements was demonstrated. The compressive strength of the set cements increased with the filler addition and the highest value (~ 48 MPa) exhibited the 50CSP/B cement composite. The final setting times of the composite cements decreased with the CSPH addition from about 25 to 17 min in 50CSHP/B and setting time of CSP/B composites was around 30 min. The higher content of silica in cements caused the precipitation of fine hydroxyapatite particles in the form of nanoneedles or thin plates perpendicularly oriented to sample surface. The analysis of in vitro cement cytotoxicity demonstrated the strong reduction in cytotoxicity of 10CSPH/B composite with time of cultivation (a low cytotoxicity after 9 days of culture) contrary to cements with higher calcium silicate-phosphate content. These results were attributed to the different surface topography of composite substrates and possible stimulation of cell proliferation by the slow continuously release of ions from 10CSPH/B cement. - Highlights: • Ca/P ratio and solubility of calcium silicate-phosphate components affect the self-setting properties of cements. • Strong relationship between the composite in vitro cytotoxicity and surface microtopography was demonstrated. • Plate-like morphology of coarser particles allowed cells to better adhere and proliferate as compared with nanoneedles.

  4. Specific leaf mass, fresh: dry weight ratio, sugar and protein contents in species of Lamiaceae from different light environments.

    Science.gov (United States)

    Castrillo, M; Vizcaino, D; Moreno, E; Latorraca, Z

    2005-01-01

    Samples from eleven species of Lamiaceae were collected from different light environments in Venezuela for laboratory analysis. The studied species were: Plectranthus scutellarioides (Ps), Scutellaria purpurascens (Sp), Hyptis pectinata (Hp)), H. sinuata (Hs). Leonorus japonicus (Lj), Plecthranthus amboinicus (Pa) Ocimum hasilicum (Ocb), O. campechianum (Occ) Origanum majorana (Orm), Rosmarinus officinali, (Ro) and Salvia officinalis (So). Protein and soluble sugar contents per unit of area were measured, Specific Leaf Mass (SLM) and fresh:dry weight (FW/DW) ratios were calculated. The higher values for soluble sugars contents were present in sun species: Lj, Pa, Ocb, Occ, Orm, Ro and So; the lower values were obtained in low light species: Ps, Sp, Hp, Hs. The values of protein content do not show any clear trend or difference between sun and shade environments. The lowest values for the fresh weight: dry weight ratio are observed in sun species with the exception of Lj and Pa, while the highest value is observed in Pa, a succulent plant. The higher values of specific leaf mass (SLM) (Kg DMm(-2)) are observed in sun plants. The two way ANOVA revealed that there were significant differences among species and between sun and low light environments for sugar content and FW:DW ratio. while SLM was significant for environments but no significant for species, and not significant for protein for both species and environments. The soluble sugar content, FW:DW ratio and SLM values obtained in this work, show a clear separation between sun and shade plants. The sugar content and FW:DW ratio are distinctive within the species, and the light environment affected sugar content. FW:DW ratio and SLM. These species may he shade-tolerant and able to survive in sunny environments. Perhaps these species originated in shaded environments and have been adapting to sunny habitats.

  5. 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.

  6. Influence of zeolite and cement additions on mechanical behavior of sandy soil

    Directory of Open Access Journals (Sweden)

    Hossein Mola-Abasi

    2016-10-01

    Full Text Available It is well known that the cemented sand is one of economic and environmental topics in soil stabilization. In this instance, a blend of sand, cement and other materials such as fiber, glass, nanoparticle and zeolite can be commercially available and effectively used in soil stabilization in road construction. However, the influence and effectiveness of zeolite on the properties of cemented sand systems have not been completely explored. In this study, based on an experimental program, the effects of zeolite on the characteristics of cemented sands are investigated. Stabilizing agent includes Portland cement of type II and zeolite. Results show the improvements of unconfined compressive strength (UCS and failure properties of cemented sand when the cement is replaced by zeolite at an optimum proportion of 30% after 28 days. The rate of strength improvement is approximately between 20% and 78%. The efficiency of using zeolite increases with the increases in cement amount and porosity. Finally, a power function of void-cement ratio and zeolite content is demonstrated to be an appropriate method to assess UCS of zeolite-cemented mixtures.

  7. Carbon content and C:N ratio of transparent exopolymeric particles (TEP) produced by bubbling exudates of diatoms

    DEFF Research Database (Denmark)

    Mari, Xavier

    1999-01-01

    The carbon content of transparent exopolymeric particles (TEP) was measured in the laboratory in particles produced by bubbling exudates of the diatom Thalassiosira weissflogii, grown under nitrogen non-limited conditions (N:P = 7). The carbon content of these particles (TEP-C) appears to vary...... for dissolved organic carbon in coastal seas. The carbon to nitrogen ratio of TEP was measured from particles formed by bubbling exudates of the diatoms T. weissflogii, Skeletonema costatum, Chaetoceros neogracile and C. affinis. Each of these diatom species was grown under various N:P ratios, from N......-non-limited to N-limited conditions. While the C:N ratio of the diatom cells grown under N-limited conditions was high (C:N >= 14), the TEP aggregates formed by coagulation of the extracellular release produced by these cells exhibited a C:N ratio relatively constant (C:N = 7.3 ± 2.6) and apparently independent...

  8. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid...

  9. Cement improved highly weathered phyllite for highway subgrades: A case study in Shaanxi province

    Directory of Open Access Journals (Sweden)

    Xuesong Mao

    2017-08-01

    Full Text Available In a cost-saving move, the soft rocks composed of highly-weathered phyllites available on-site were used to fill the subgrade in the eastern Ankang section of the expressway of Shiyan to Tianshui, China. Cement admixture was used to improve the performance of the weathered phyllites. In order to determine the best mix ratio, values corresponding to compaction performance, unconfined compressive strength, and the California bearing ratio (CBR were analyzed for variable cement content weight percentages (3%, 4%, 5%, and 6% using test subgrade plots in the field. Field measurements of resilience modulus and deflection confirmed that the strength of the subgrade increased as the cement ratio increased. In order to further evaluate the cement/phyllite mixture, the performance of the 3% cement ratio sample was evaluated under saturated conditions (with various levels of moisture addition and soaking time using both the wetting deformation and resilient modulus values. Results suggest that moisture added and soaking time are key factors that affect the seepage depth, water content, and resilient modulus. The recommend values for the cement addition and for the water content are given out. This study can aid in prevention of highway damage by improving the foundation capacity and lengthening the lifecycle of the highway in phyllite distributed region at home and abroad.

  10. Uranium contents and 234U/238U activity ratios of modern and fossil marine bivalle molluscan shells

    International Nuclear Information System (INIS)

    Mitsuda, Hiroshi

    1984-01-01

    Uranium contents and 234 U/ 238 U activity ratios in modern and fossil marine bivalle molluscan shells were measured by alpha-spectrometry. Uranium contents and 234 U/ 238 U activity ratios in modern shells were averaged to be 0.266 (dpm/g), and 1.18, respectively and those in fossil shells were averaged to be 0.747 (dpm/g), and 1.19, respectivily. Uranium contents in fossil shells were obviously higher than those in modern shells. It can be explained by the addition of uranium to shell during the deposition. In fossil shells, 234 U/ 238 U activity ratio decreases as 238 U content increases the same tendency is not found in modern shells. The author proposed a mechanism of selective loss of 238 U from the fossil shells for the explanation of this tendency. The height activity ratio of 234 U/ 238 U measured on the fossil shells than that measured on the modern shells, also support the selective loss of 238 U from the fossil shells. (author)

  11. Influence of feed/inoculum ratios and waste cooking oil content on the mesophilic anaerobic digestion of food waste.

    Science.gov (United States)

    Li, Yangyang; Jin, Yiying; Borrion, Aiduan; Li, Jinhui

    2018-03-01

    Information on the anaerobic digestion (AD) of food waste (FW) with different waste cooking oil contents is limited in terms of the effect of the initial substrate concentrations. In this work, batch tests were performed to evaluate the combined effects of waste cooking oil content (33-53%) and feed/inoculum (F/I) ratios (0.5-1.2) on biogas/methane yield, process stability parameters and organics reduction during the FW AD. Both waste cooking oil and the inoculation ratios were found to affect digestion parameters during the AD process start-up and the F/I ratio was the predominant factor affecting AD after the start-up phase. The possible inhibition due to acidification caused by volatile fatty acids accumulation, low pH values and long-chain fatty acids was reversible. The characteristics of the final digestate indicated a stable anaerobic system, whereas samples with F/I ratios ranging from 0.8 to 1.2 display higher propionic and valeric acid contents and high amounts of total ammonia nitrogen and free ammonia nitrogen. Overall, F/I ratios higher than 0.70 caused inhibition and resulted in low biogas/methane yields from the FW. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Cui, Hongzhi; Liao, Wenyu; Memon, Shazim Ali; Dong, Biqin; Tang, Waiching

    2014-12-16

    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.

  13. 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.

  14. Feasibility of backfilling mines using cement kiln dust, fly ash, and cement blends

    Directory of Open Access Journals (Sweden)

    Beltagui H.

    2018-01-01

    Full Text Available Cement kiln dust (CKD is an industrial by-product of the cement manufacturing process, the composition of which can vary widely. Recent years of using alternative fuels have resulted in higher chloride and alkali contents within CKDs; as such, this limits the applications in which CKDs can be utilised. Using a CKD containing a high free lime content of 29.5%, it is shown that this CKD is capable of activating pulverized fuel ash (PFA due to its high alkalinity, which can be utilised in low strength un-reinforced applications. One potential application involves the backfill of mines, reducing the need for continuous maintenance of the mine. This study focuses on the compressive strength achieved by various blends of CKD, PFA, and cement. Samples were hand mixed and compacted in 100 mm x 50 mm diameter cylinders, and unconfined compressive strength measurements taken at 28 and 56 days. The hydration products were assessed through the use of x-ray diffraction and thermogravimetric analysis. Aiming to maximise the use of CKD at a water to binder (w/b ratio of 0.2, it was found that the maximum CKD content possible to achieve the required strength was 90% CKD blended with 10% cement.

  15. Phytate, calcium, iron, and zinc contents and their molar ratios in foods commonly consumed in China

    NARCIS (Netherlands)

    Ma, Guansheng; Jin, Ying; Piao, Jianhua; Kok, F.J.; Bonnema, A.B.; Jacobsen, E.

    2005-01-01

    A total of 60 food samples commonly consumed in China were analyzed for phytate using the anion-exchange method and for calcium, iron, and zinc using atomic absorption spectrophotometry. The foods analyzed included those based on cereal grains and soybean. Phytate contents expressed on a wet weight

  16. Standardized Ultrasound Hepatic/Renal Ratio and Hepatic Attenuation Rate to Quantify Liver Fat Content: An Improvement Method

    Science.gov (United States)

    Xia, Ming-Feng; Yan, Hong-Mei; He, Wan-Yuan; Li, Xiao-Ming; Li, Chao-Lun; Yao, Xiu-Zhong; Li, Ruo-Kun; Zeng, Meng-Su; Gao, Xin

    2012-01-01

    Accurate measures of liver fat content are essential for investigating the role of hepatic steatosis in the pathophysiology of multiple metabolic disorders. No traditional imaging methods can accurately quantify liver fat content. [1H]-magnetic resonance spectroscopy (MRS) is restricted in large-scale studies because of the practical and technological issues. Previous attempts on computer-aided ultrasound quantification of liver fat content varied in method, and the ultrasound quantitative parameters measured from different ultrasound machines were hardly comparable. We aimed to establish and validate a simple and propagable method for quantitative assessment of liver fat content based on the combination of standardized ultrasound quantitative parameters, using [1H]-MRS as gold standard. Totally 127 participants were examined with both ultrasonography (US) and [1H]-MRS. Ultrasound hepatic/renal echo-intensity ratio (H/R) and ultrasound hepatic echo-intensity attenuation rate (HA) were obtained from ordinary ultrasound images using computer program. Both parameters were standardized using a tissue-mimicking phantom before analysis. Standardized ultrasound H/R and HA were positively correlated with the liver fat content by [1H]-MRS (r = 0.884, P liver fat (adjusted explained variance 78.0%, P liver fat contents between different ultrasound machines and operators was reasonably well. Thus, computer-aided US is a valid method to estimate liver fat content and can be applied extensively after standardization of ultrasound quantitative parameters. PMID:22016092

  17. Porosity and ion diffusivity of latex-modified cement

    International Nuclear Information System (INIS)

    Nishi, Takashi; Kuriyama, Osamu; Matsuda, Masami; Chino, Koichi; Kikuchi, Makoto

    1990-01-01

    Latex-modified portland cement, which would be expected to have low permeability and ion diffusivity, was studied for possible application as a solidification agent for radioactive wastes generated from nuclear power plants. In order to predict the leaching ratio of radionuclides from the cementitious waste forms, the effect of water and latex content in the fresh cement paste on total porosity and ion diffusivity of hardened paste was quantitatively estimated. Total porosity of hardened cement paste decreased with the reduction of water content in the fresh paste and it was also reduced by latex addition. This latter effect could be attributed to the latex emulsion forming a water-proof film and filling the capillary pores. Also Cs ions diffusivity, which is the ratio of the diffusion coefficient in pore water to that in bulk water, showed an exponential correlation with total porosity for both cement materials. An empirical equation, expressing ion diffusivity as a function of total porosity, was derived from the consideration that the water constrictivity in this porous medium could cause an increase of the apparent viscosity of pore water. These results suggested a possibility that the transport behavior of radionuclides through the cementitious matrix could be estimated from the mixing parameters of the original cement pastes

  18. Geo-environmental application of municipal solid waste incinerator ash stabilized with cement

    Directory of Open Access Journals (Sweden)

    Davinder Singh

    2017-04-01

    Full Text Available The behavior of soluble salts contained in the municipal solid waste incinerator (MSWI ash significantly affects the strength development and hardening reaction when stabilized with cement. The present study focuses on the compaction and strength behavior of mixed specimens of cement and MSWI ash. A series of indices such as unconfined compressive strength, split tensile strength, California bearing ratio (CBR and pH value was examined. Prior to this, the specimens were cured for 7 d, 14 d, and 28 d. The test results depict that the maximum dry density (MDD decreases and the optimum moisture content (OMC increases with the addition of cement. The test results also reveal that the cement increases the strength of the mixed specimens. Thus, the combination of MSWI ash and cement can be used as a lightweight filling material in different structures like embankment and road construction.

  19. The effects of calcium to magnesium ratio on the increments of dry weight and protein content in tomatoes

    Directory of Open Access Journals (Sweden)

    J. Buczek

    2015-01-01

    Full Text Available A change in the ratio of Ca: Mg ions in the medium or soil from optimum (3:1 to disfavourable values (3:30 causes dwarfing of tomatoes, a decrease of dry weight increment and of protein content. Total-N and protein-N also decrease, whereas the amount of soluble-N increases. It is suggested that the low ratio of Ca:Mg in the medium or soil affects nitrogen metabolism causing a restriction of protein synthesis.

  20. Early postnatal myelin content estimate of white matter via T1w/T2w ratio

    Science.gov (United States)

    Lee, Kevin; Cherel, Marie; Budin, Francois; Gilmore, John; Zaldarriaga Consing, Kirsten; Rasmussen, Jerod; Wadhwa, Pathik D.; Entringer, Sonja; Glasser, Matthew F.; Van Essen, David C.; Buss, Claudia; Styner, Martin

    2015-03-01

    To develop and evaluate a novel processing framework for the relative quantification of myelin content in cerebral white matter (WM) regions from brain MRI data via a computed ratio of T1 to T2 weighted intensity values. We employed high resolution (1mm3 isotropic) T1 and T2 weighted MRI from 46 (28 male, 18 female) neonate subjects (typically developing controls) scanned on a Siemens Tim Trio 3T at UC Irvine. We developed a novel, yet relatively straightforward image processing framework for WM myelin content estimation based on earlier work by Glasser, et al. We first co-register the structural MRI data to correct for motion. Then, background areas are masked out via a joint T1w and T2 foreground mask computed. Raw T1w/T2w-ratios images are computed next. For purpose of calibration across subjects, we first coarsely segment the fat-rich facial regions via an atlas co-registration. Linear intensity rescaling based on median T1w/T2w-ratio values in those facial regions yields calibrated T1w/T2wratio images. Mean values in lobar regions are evaluated using standard statistical analysis to investigate their interaction with age at scan. Several lobes have strongly positive significant interactions of age at scan with the computed T1w/T2w-ratio. Most regions do not show sex effects. A few regions show no measurable effects of change in myelin content change within the first few weeks of postnatal development, such as cingulate and CC areas, which we attribute to sample size and measurement variability. We developed and evaluated a novel way to estimate white matter myelin content for use in studies of brain white matter development.

  1. The carbon isotopes ratio and trace metals content determinations in some Transylvanian fruit juices

    Science.gov (United States)

    Dehelean, A.; Magdas, D. A.; Cristea, G.

    2012-02-01

    This work presents a preliminary study on the carbon isotope signature and trace metal content investigated on the soil-plant-fruit pulp chain. The samples were collected from two Transylvanian areas namely Alba and Salaj. The average value of the δ13C at the soil surface was around δ13C ≈ -27%° and important differences of the δ13C values between the two studied areas were not observed. Meanwhile, differences between fruit pulp of grape juice and the pulp of pear juice relived a difference of about 1.5%° for δ13C values.

  2. Optimization and characterization of a cemented ultimate-storage product

    Science.gov (United States)

    Brunner, H.

    1981-12-01

    The U- and Pu-containing packaging wastes can be homogeneously cemented after a washing and fragmentation process. Both finely crushed and coarsely fragmented raw wastes yield products with sufficient mechanical stability. The processability limit of the coarsely fragmented raw waste using cement paste or mortar is largely determined by the cellulose content, which is not to exceed 1.3% by weight in the end waste. Of 9 binders studied, the most corrosion-resistant products were obtained with blast-furnace slag cement, whereas poured concrete and Maxit are much less resistant in five-component brine. In the cemented product, hydrolysis of plasticizers (DOP) from plastics (PVC) occurs, leading to release of 2-ethyl-hexanol. This reaction occurs to a much lower degree with blast-furnace slag cement than with all other binders studied. The binder chosen for further tests consists of blast-furnace slag cement, concrete fluidizer and a stabilizer, and is processed at a W/C ratio of 0.43.

  3. Alternatives to isotope ratio mass spectrometry for the measurement of deuterium content of body water

    International Nuclear Information System (INIS)

    Bluck, L.J.C.

    2000-01-01

    The measurement of breast milk intake using the isotope dilution techniques is now well established. The methodology involves the administration of a bolus of tracer followed by observation of the kinetics of its passage though the system. For example in the popular 'dose to the mother' method a dose of labeled water is administered to the mother, and over the following days samples of body fluids are taken and the concentration of tracer determined in order to establish the rate of loss of tracer from her body. Likewise samples are taken from the breast fed infant in order to determine the rates of tracer intake and subsequent loss. Deuterium is the tracer of choice for these experiments since it is non-radioactive, and therefore suitable for use in these vulnerable subject groups, and also because of its relative cheapness. Conventionally isotope ratio mass spectrometry (IRMS) has been used for the determination of the amount of deuterium in the body fluids. However this methodology is expensive (an instrument might typically cost US$ 150,000), and it requires a considerable amount of dedicated technical expertise for its operation. Consequently such instrumentation is not widely available, and this has limited the number and scope of studies using this technique. Recently there have been reports of possible alternative technologies for the determination of deuterium in body water which appear attractive because of the wider general availability of the equipment required. It is the purpose of this report to assess these reported methods for their suitability for breast milk intake measurements

  4. Influence of Cement Particle-Size Distribution on Early Age Autogenous Strains and Stresses in Cement-Based Materials

    DEFF Research Database (Denmark)

    Bentz, Dale P.; Jensen, Ole Mejlhede; Hansen, Kurt Kielsgaard

    2001-01-01

    The influence of cement particle-size distribution on autogenous strains and stresses in cement pastes of identical water-to-cement ratios is examined for cement powders of four different finenesses. Experimental measurements include chemical shrinkage, to quantify degree of hydration; internal r...

  5. Uranium contents and 235U/238U atom ratios in soil and earthworms in western Kosovo after the 1999 war

    International Nuclear Information System (INIS)

    Di Lella, L.A.; Nannoni, F.; Protano, G.; Riccobono, F.

    2005-01-01

    The uranium content and 235 U/ 238 U atom ratio were determined in soils and earthworms of an area of Kosovo (Djakovica garrison), heavily shelled with depleted uranium (DU) ammunition during the 1999 war. The aim of the study was to reconstruct the small-scale distribution of uranium and assess the influence of the DU added to the surface environment. The total uranium concentration and the 235 U/ 238 U ratio of topsoils showed great variability and were inversely correlated. The highest uranium levels (up to 31.47 mg kg -1 ) and lowest 235 U/ 238 U ratios (minimum 0.002147) were measured in topsoils collected inside, or very close to, the clusters of DU penetrator holes. Regarding the fractionation of uranium in the surface soils, the uranium concentrations in the soluble and exchangeable fractions increased as the total uranium concentration of the topsoils increased. High and rather uniform percentage contents of uranium (24-36%) were associated with the poorly crystalline iron oxide phases of soils. In the U-enriched soils the elevated levels of the element were probably due to the presence of very small, unevenly distributed oxidized DU particles. The total uranium concentration in earthworms was in the range 0.142-0.656 mg kg -1 , with the highest concentrations in Lumbricus terrestris. The juveniles of all three studied species seemed to accumulate uranium more than adults, probably due to age-related differences in metabolism. The 235 U/ 238 U ratio in the earthworms was variable (0.005241-0.007266) and independent of both the total uranium contents in soils and the absolute uranium levels in the animals. Bioconcentration was greater at lower U concentrations in soil, probably due to an increasing rate of elimination of uranium by the earthworms as the soil contents of the element increase. The results of this study clearly indicate that DU was added to the soil of the study area. Nevertheless, the phenomenon was very limited spatially and the total

  6. Sodium and potassium content and their ratio in meatballs in tomato sauce produced with lower amounts of sodium

    Science.gov (United States)

    Lilić, S.; Nikolić, D.; Pejkovski, Z.; Velebit, B.; Lakićević, B.; Korićanac, V.; Vranić, D.

    2017-09-01

    The goal of this study was to examine the possibility of partial replacement of sodium chloride with potassium chloride and ammonium chloride, with the target of achieving less sodium content in meatballs and tomato sauce as well as achieving a better Na:K ratio. The trial consisted of five groups. In the control group of meatballs and sauce, only sodium chloride was added. In group 1, half of the sodium chloride was replaced with potassium chloride related to control group while in group 2 one third of the sodium chloride was replaced with potassium chloride. In group 3, one third of the sodium chloride was replaced with ammonium chloride, and in group 4, sodium chloride was reduced to half the amount in the control group, and 1 g (0.25%) of ammonium chloride was also added. All products were acceptable according to sensory analyses. The largest reductions of sodium content were 44.64%, achieved in meatballs from group 1 and 50.62% in tomato sauce from group 4 in relation to meatballs and tomato sauce from control group. The highest Na:K ratio was calculated in meatballs and tomato sauce from control group, 2.88 and 4.39, respectively. The best Na:K ratio was in meatballs and tomato sauce from group 1, 0.60 and 0.92, respectively, in which half of sodium chloride was replaced with potassium chloride. However, in meatballs and tomato sauce from group 4, with only half the amount of sodium chloride related to control group, the Na:K ratio was worse because in these products, potassium chloride was not added.

  7. Effects of Particle Size and Cement Replacement of LCD Glass Powder in Concrete

    Directory of Open Access Journals (Sweden)

    Seong Kyum Kim

    2017-01-01

    Full Text Available The high quality liquid crystal display (LCD processing waste glass (LPWG generated from the manufacturing process of Korea’s LCD industries, having the world’s highest technological level and production, was finely ground into particles smaller than cement particles (higher fineness than OPC to verify their applicability and performance as a replacement for cement. For a concrete mix having a W/B ratio of 0.44, cement was replaced with LPWG glass powder (LGP at ratios of 5, 10, 15, and 20% (LGP12 and 5 and 10% (LGP5 according to the particle size to prepare test cylinder specimens, which were tested with respect to air contents, slump in fresh concrete, and compressive strength and splitting tensile strength of hardened concrete. The microstructure of the concrete specimens was analyzed through Scanning Electron Microscopy (SEM, Energy Dispersive X-ray (EDX, and a Mercury Intrusion Porosimetry (MIP. Replacement of cement with LGP for cement could effectively decrease the quantity of cement used due to the excellent performance of LGP. It may positively contribute to the sustainable development of the cement industry as well as waste recycling and environment conservation on a national scale.

  8. Performance evaluation of cement stabilized fly ash-GBFS mixes as a highway construction material.

    Science.gov (United States)

    Singh, S P; Tripathy, D P; Ranjith, P G

    2008-01-01

    Fly ash and granulated blast furnace slag (GBFS) are major by-products of thermal and steel plants, respectively. These materials often cause disposal problems and environmental pollution. Detailed laboratory investigations were carried out on cement stabilized fly ash-(GBFS) mixes in order to find out its suitability for road embankments, and for base and sub-base courses of highway pavements. Proctor compaction test, unconfined compressive strength (UCS) test and California Bearing Ratio (CBR) test were conducted on cement stabilized fly ash-GBFS mixes as per the Indian Standard Code of Practice. Cement content in the mix was varied from 0% to 8% at 2% intervals, whereas the slag content was varied as 0%, 10%, 20%, 30% and 40%. Test results show that an increase of either cement or GBFS content in the mixture, results in increase of maximum dry density (MDD) and decrease of optimum moisture content (OMC) of the compacted mixture. The MDD of the cement stabilized fly ash-GBFS mixture is comparably lower than that of similarly graded natural inorganic soil of sand to silt size. This is advantageous in constructing lightweight embankments over soft, compressible soils. An increase in percentage of cement in the fly ash-GBFS mix increases enormously the CBR value. Also an increase of the amount of GBFS in the fly ash sample with fixed cement content improves the CBR value of the stabilized mix. In the present study, the maximum CBR value of compacted fly ash-GBFS-cement (52:40:8) mixture obtained was 105%, indicating its suitability for use in base and sub-base courses in highway pavements with proper combinations of raw materials.

  9. The Influence of Uranium Content and PVA/U Ratio on Physical Propertiesof PVA-U Gel and Its Oxide

    International Nuclear Information System (INIS)

    Damunir; W, Bangun; Indra-Suryawan; Endang-Nawangsih

    2000-01-01

    The influence of uranium content and PVA/U ratio on physical propertiesof PVA-U gel and its oxide has been investigated. Fifty milliliters of uranylnitrate solution containing 100 g U/l was neutralized using 1M NH 4 0H. Thesolution was converted into PVA-U sol by adding 9.18 % PVA while mixed andheated at 80 o C for 20 minutes. In order to find spherical gel, the solsolution was dropped into a 5 M NH 4 0H solution at room temperature. Theshape formed of the gels small spherical, shape of the formed gels werefiltered, washed and heated at 120 o C. After that the gels were calcined at800 o C for 4 hours. The formed U 3 O 8 particles. Under a similar method, theinfluence of uranium content from 150-400 g/l and the influence of PVA/Uratio of 6.5-12.5 % in 100 g U/l were studied. Characterization of the resultwas obtained from physical properties of the gel and its oxide in the form ofdensity using pycnometer, surface area using surface areameter with N 2 asabsorbent and particle size/ shape using a loop and optical microscope. Theexperimental results showed that both uranium content and PVA/U ratioaffected the physical properties of the kernel properties. The best resultoccurred at uranium content of 100 g/l and PVA/U 9.18 %. The resulted gelwith solid content of 89.17 %, density of 3.36 g/l and size of 124 μm. Theresulted oxide U 3 0 8 had density of 7.98 g U/l, surface area of specific of0.449 m 2 /g and grain size of 810 μm. (author)

  10. Preparation of calcium phosphate cement and polymethyl methacrylate for biological composite bone cements.

    Science.gov (United States)

    Yang, Jun; Zhang, Kairui; Zhang, Sheng; Fan, Jiping; Guo, Xinhui; Dong, Weiqiang; Wang, Shengnan; Chen, Yirong; Yu, Bin

    2015-04-23

    We studied the biological safety, biomechanics, and tissue compatibility of calcium phosphate cement and Polymethyl Methacrylate composite bone cement mixed in different ratios. CPC and PMMA were mixed in different ratios (3:1, 2:1, 1:1, 1:2, 1:5, 1:10, 1:15, and 1:20). PMMA solvent is a general solvent containing a dissolved preparation of the composite bone cement specific to a given specimen to determine biological safety, biomechanics, and tissue compatibility. The CPC/PMMA (33%) group, CPC/PMMA (50%) group, CPC/PMMA (67%) group, and CPC/PMMA (75%) group were more in line with the composite bone cement without cytotoxicity requirements. The compressive strength of the CPC/PMMA (67%) group and CPC/PMMA (75%) group was 20 Mpa-30 Mpa, while that of the CPC/PMMA (4.8%) group, CPC/PMMA (6.25%) group, CPC/PMMA (9.1%) group, CPC/PMMA (16.7%) group, CPC/PMMA (33%) group, and CPC/PMMA (50%) group was 40 Mpa-70 Mpa. Curing time was longer in the CPC group (more than 11 min) and shorter in the PMMA group (less than 2 min). The results of weight loss rate showed that there were no significant differences between the CPC/PMMA group (4.8%, 6.25%, 9.1%, 16.7%, 33%) and PMMA control group (p>0.05). With the decrease of CPC content, the rate of weight loss gradually decreased. The CPC/PMMA (50%) group, CPC/PMMA (67%) group, and CPC/PMMA (75%) group provide greater variability and selectivity for the composite bone cement in obtaining better application.

  11. Magnetization transfer ratio does not correlate to myelin content in the brain in the MOG-EAE mouse model.

    Science.gov (United States)

    Fjær, Sveinung; Bø, Lars; Myhr, Kjell-Morten; Torkildsen, Øivind; Wergeland, Stig

    2015-01-01

    Magnetization transfer ratio (MTR) is a magnetic resonance imaging (MRI) method which may detect demyelination not detected by conventional MRI in the central nervous system of patients with multiple sclerosis (MS). A decrease in MTR value has previously been shown to correlate to myelin loss in the mouse cuprizone model for demyelination. In this study, we investigated the sensitivity of MTR for demyelination in the myelin oligodendrocyte (MOG) 1-125 induced experimental autoimmune encephalomyelitis (EAE) mouse model. A total of 24 female c57Bl/6 mice were randomized to a control group (N = 6) or EAE (N = 18). MTR images were obtained at a preclinical 7 Tesla Bruker MR-scanner before EAE induction (baseline), 17-19 days (midpoint) and 31-32 days (endpoint) after EAE induction. Mean MTR values were calculated in five regions of the brain and compared to weight, EAE severity score and myelin content assessed by immunostaining for proteolipid protein and luxol fast blue, lymphocyte and monocyte infiltration and iron deposition. Contrary to what was expected, MTR values in the EAE mice were higher than in the control mice at the midpoint and endpoint. No significant difference in myelin content was found according to histo- or immunohistochemistry. Changes in MTR values did not correlate to myelin content, iron content, lymphocyte or monocyte infiltration, weight or EAE severity scores. This suggest that MTR measures of brain tissue can give significant differences between control mice and EAE mice not caused by demyelination, inflammation or iron deposition, and may not be useful surrogate markers for demyelination in the MOG1-125 mouse model. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Specific leaf mass, fresh: dry weight ratio, sugar and protein contents in species of Lamiaceae from different light environments

    Directory of Open Access Journals (Sweden)

    M Castrillo

    2005-06-01

    Full Text Available Samples from eleven species of Lamiaceae were collected from different light environments in Venezuela for laboratory analysis.The studied species were: Plectranthus scutellarioides (Ps, Scutellaria purpurascens (Sp, Hyptis pectinata (Hp, H. sinuata (Hs, Leonorus japonicus (Lj, Plecthranthus amboinicus (Pa Ocimum basilicum (Ocb, O.campechianum (Occ Origanum majorana (Orm, Rosmarinus officinali ,(Ro and Salvia officinalis (So. Protein and soluble sugar contents per unit of area were measured, Specific Leaf Mass (SLMand fresh: dry weight (FW/DW ratios were calculated. The higher values for soluble sugars contents were present in sun species: Lj, Pa, Ocb, Occ, Or. m, Ro and So; the lower values were obtained in low light species: Ps, Sp, Hp, Hs. The values of protein content do not show any clear trend or difference between sun and shade environments. The lowest values for the fresh weight: dry weight ratio are observed in sun species with the exception of Lj and Pa, while the highest value is observed in Pa, a succulent plant. The higher values of specific leaf mass (SLM(Kg DMm-2 are observed in sun plants. The two way ANOVA revealed that there were significant differences among species and between sun and low light environments for sugar content and FW: DW ratio, while SLM was significant for environments but no significant for species, and not significant for protein for both species and environments. The soluble sugar content, FW: DW ratio and SLM values obtained in this work, show a clear separation between sun and shade plants. The sugar content and FW:DW ratio are distinctive within the species,and the light environment affected sugar content, FW:DW ratio and SLM. These species may be shade-tolerant and able to survive in sunny environments. Perhaps these species originated in shaded environments and have been adapting to sunny habitats.Rev.Biol.Trop.53(1-2:23-28.Epub 2005 Jun 24En once especies de la familia Lamiaceae: Plecthranthus

  13. E-modulus evolution and its relation to solids formation of pastes from commercial cements

    International Nuclear Information System (INIS)

    Maia, Lino; Azenha, Miguel; Geiker, Mette; Figueiras, Joaquim

    2012-01-01

    Models for early age E-modulus evolution of cement pastes are available in the literature, but their validation is limited. This paper provides correlated measurements of early age evolution of E-modulus and hydration of pastes from five commercial cements differing in limestone content. A recently developed methodology allowed continuous monitoring of E-modulus from the time of casting. The methodology is a variant of classic resonant frequency methods, which are based on determination of the first resonant frequency of a composite beam containing the material. The hydration kinetics — and thus the rate of formation of solids — was determined using chemical shrinkage measurements. For the cements studied similar relationships between E-modulus and chemical shrinkage were observed for comparable water-to-binder ratio. For commercial cements it is suggested to model the E-modulus evolution based on the amount of binder reacted, instead of the degree of hydration.

  14. Optimal content and ratio of lysine to arginine in the diet of Pacific white shrimp, Litopenaeus vannamei

    Science.gov (United States)

    Feng, Zhengfu; Dong, Chaohua; Wang, Linlin; Hu, Yanjiang; Zhu, Wei

    2013-07-01

    The optimal quantity of dietary lysine (Lys) and arginine (Arg), and the optimal ratio of dietary Lys to Arg for Pacific white shrimp Litopenaeus vannamei were investigated. Coated Lys and Arg were added to a basal diet (37.99% crude protein and 7.28% crude lipid) to provide graded levels of Lys and Arg. The experimental diets contained three Lys levels (2.51%, 2.11%, and 1.70% of total diet), and three Arg levels (1.41%, 1.80%, and 2.21% of total diet) and all combinations of these levels were tested. Pacific white shrimp, with a mean weight of 3.62±0.1 g, were randomly distributed in 36 fiberglass tanks with 30 shrimp per tank and reared on the experimental diets for 50 days. After the feeding trial, the growth performance, survival, feed conversion rate (FCR), body composition and protease and lipase activities in the hepatopancreases of the experimental shrimps were determined. The results show that weight gain (WG), specific growth rate (SGR), FCR, body protein, body Lys and Arg content were significantly affected by dietary Lys and Arg ( P 0.05). Therefore, according to our results, the optimal Lys and Arg quantities in the diet of Pacific white shrimp, L. vannamei, were considered to be 2.11%-2.51% and 1.80%-2.21%, respectively, and the optimal ratio to be 1:0.88-1:1.05.

  15. Manufacture Of Pozzolanic Cement From RFCC Spent Catalyst In Khartoum Refinery

    Directory of Open Access Journals (Sweden)

    Husam E Mustafa

    2015-08-01

    Full Text Available Pozzolana is defined as Siliceous and aluminous material which reacts with calcium hydroxide in presence of water at room temperature to form strong slow-hardening cement. Pozzolana has the advantage of reduction of leachibility of calcium hydroxide liberated during the setting and hydration of cement. In Khartoum Refinery five to ten tons per week of spent catalyst are produced in fine powder this quantity is sent to dumping sites or landfills. In this study pilot experiments were successfully carried out at different ratios to produce cement. The RFCC spent catalyst samples were subjected to chemical analysis to determine the content of Al2O3 SiO3TiO3 CaO and V2O5 ..etc. These were found to be 49.5 41.1 0.32 1.4 and 0.09 percent respectively other compounds are Na2O MgO P2O5SO3 K2O MnOFe2O3Co3O4 and NiO2 with. It is found that the percentages of SiO2 Al2O3 and Fe2O3 amount up to 91.5 that is above the ASTM standard C6182003 which stipulated that the minimum of such compound is 70 . Physical properties of RFCC spent catalyst were also carried out including crystallinity and Pozzolanicity index. The cement produced was tested for compressive strength consistency and setting time .It is concluded that RFCC spent catalyst in Khartoum Refinery is a Pozzolanic material and up to 30 replacement from Portland cement blended cement complies with the Sudanese and European Standards No SSMO 39982011and EN-197-11992 respectively. The study shows that the compressive strength of blended Pozzolanic cements decreases with increasing Pozzolana content. From the foregoing it is recommended to use RFCC spent catalyst with Portland cement as blended cement to produce mortars for construction and concrete.

  16. Experimental investigation of the effect of latex solid/water ratio on latex modified co-matrix mechanical properties

    Directory of Open Access Journals (Sweden)

    Ahmed M. Diab

    2013-03-01

    Full Text Available Numerous researches were performed on latex modified concretes and associated properties, however; some vital factors were not given attention in previous works. This study focus on new factor which significantly affects the properties of latex modified cement paste, mortar or concrete. This factor is termed as ‘latex solid/water ratio’ which is defined herein as the ratio of weight of solid latex to weight of total water content of cement composite including the water in latex itself. The effect of this factor on some properties of cement paste, mortar and concrete were experimentally evaluated. Properties of cement paste include the produced calcium hydroxide and ettringite content during hydration process, while those of cement mortar take account of absorption and effect of temperature on compressive strength. Furthermore, the effect of this factor on the compressive and flexural strengths, modulus of elasticity, water penetration depth and drying shrinkage of concrete were explored. Based on experimental evidences, and spite of using different cement contents, sources of latex, water–cement ratios and slump values, it can be generally concluded that the latex solid/water ratio is a dominant factor affecting different properties of latex modified mortars and concrete.

  17. 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.

  18. 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.

  19. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

    The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted...... for the most significant alternative fuel energy contributors in the German cement industry. Solid alternative fuels are typically high in volatile content and they may differ significantly in physical and chemical properties compared to traditional solid fossil fuels. From the process point of view......, considering a modern kiln system for cement production, the use of alternative fuels mainly influences 1) kiln process stability (may accelerate build up of blockages preventing gas and/or solids flow), 2) cement clinker quality, 3) emissions, and 4) decreased production capacity. Kiln process stability...

  20. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  1. A Logistic Based Mathematical Model to Optimize Duplicate Elimination Ratio in Content Defined Chunking Based Big Data Storage System

    Directory of Open Access Journals (Sweden)

    Longxiang Wang

    2016-07-01

    Full Text Available Deduplication is an efficient data reduction technique, and it is used to mitigate the problem of huge data volume in big data storage systems. Content defined chunking (CDC is the most widely used algorithm in deduplication systems. The expected chunk size is an important parameter of CDC, and it influences the duplicate elimination ratio (DER significantly. We collected two realistic datasets to perform an experiment. The experimental results showed that the current approach of setting the expected chunk size to 4 KB or 8 KB empirically cannot optimize DER. Therefore, we present a logistic based mathematical model to reveal the hidden relationship between the expected chunk size and the DER. This model provides a theoretical basis for optimizing DER by setting the expected chunk size reasonably. We used the collected datasets to verify this model. The experimental results showed that the R2 values, which describe the goodness of fit, are above 0.9, validating the correctness of this mathematic model. Based on the DER model, we discussed how to make DER close to the optimum by setting the expected chunk size reasonably.

  2. Content uniformity and dissolution tests of triplicate mixtures by a double divisor-ratio spectra derivative method.

    Science.gov (United States)

    Markopoulou, Catherine K; Malliou, Eleftheria T; Koundourellis, John E

    2005-09-01

    The use of a UV double divisor-ratio spectra derivative calibration for the simultaneous analysis of synthetic samples and commercial tablet preparations without prior separation is proposed. The method was successfully applied to quantify three ternary mixtures, chlorpheniramine maleate and caffeine combined with paracetamol or acetylsalicylic acid and a mixture of acetylsalicylic acid combined with paracetamol and caffeine, using the information in the absorption spectra of appropriate solutions. Beer's law was obeyed in the concentration range of 0.84-4.21 microg/ml for chlorpheniramine maleate, 1.60-15.96 microg/ml for caffeine, 2.0-20.0 microg/ml for acetylsalicylic acid and 1.58-15.93 microg/ml for paracetamol. The whole procedure was applied to synthetic mixtures of pure drugs as well as to commercial preparations (Algon) by using content uniformity and dissolution tests (USP 24) and was found to be precise and reproducible. According to the dissolution profile test more than 84% of paracetamol and caffeine were dissolved within 20 min. Acetylsalicylic acid dissolved more slowly, taking about 45-60 min to dissolve completely. A chemometric method partial least squares (PLS) and a HPLC method were also employed to evaluate the same mixtures. The results of the proposed method were in excellent agreement with those obtained from PLS and HPLC methods and can be satisfactorily used for routine analysis of multicomponent dosage forms.

  3. Pre-portland cements and geopolymers

    Czech Academy of Sciences Publication Activity Database

    Hanzlíček, Tomáš; Perná, Ivana; Ertl, Z.; Miller, S.M.

    2012-01-01

    Roč. 9, č. 1 (2012), s. 57-62 ISSN 1214-9705 Institutional research plan: CEZ:AV0Z30460519 Keywords : caementum * cement itious * calcareous cement Subject RIV: JN - Civil Engineering Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/materialy/acta_content/2012_01/5_Hanzlicek.pdf

  4. 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.

  5. Assessment of strength properties of cemented paste backfill by ultrasonic pulse velocity test.

    Science.gov (United States)

    Yılmaz, Tekin; Ercikdi, Bayram; Karaman, Kadir; Külekçi, Gökhan

    2014-07-01

    Ultrasonic pulse velocity (UPV) test is one of the most popular non-destructive techniques used in the assessment of the mechanical properties of concrete or rock materials. In this study, the effects of binder type/dosage, water to cement ratio (w/c) and fines content (ultrasonic pulse velocity (UPV) of cemented paste backfill (CPB) samples were investigated and correlated with the corresponding unconfined compressive strength (UCS) data. A total of 96 CPB samples prepared at different mixture properties were subjected to the UPV and UCS tests at 7, 14, 28 and 56-days of curing periods. UPV and UCS of CPB samples of ordinary Portland cement (CEM I 42.5 R) and sulphate resistant cement (SRC 32.5) initially increased rapidly, but, slowed down after 14 days. However, UPV and UCS of CPB samples of the blast furnace slag cement (CEM III/A 42.5 N) steadily increased between 7 and 56 days. Increasing binder dosage or reducing w/c ratio and fines content (estimation of the strength of CPB samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. 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......, is subordinating content to methods as seen in modern didactics, hereby transforming content to a medium for achievement of learning-to-learn skills rather than something valuable in its own right. At the level of general didactics quite few attempts have been made to formulate criteria and categories...... secondary levels. In subject matter didactics, the question of content is more developed, but it is still mostly confined to teaching on lower levels. As for higher education didactics, discussions on selection of content are almost non-existent on the programmatic level. Nevertheless, teachers are forced...

  7. 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.

  8. The Suitability of Lime Rice Husk Ash Cement as Construction ...

    African Journals Online (AJOL)

    However, by gradually increasing the percentage contents of silica, potassium oxide and sodium oxide in the Portland cement to the values found in the rice husk ash a new product, "Artificial Lime Rice Husk Ash" (ALRHA) cement was produced. The new product ALRHA cement compared favourably with the ordinary rice ...

  9. Synthesis and characterization of core-shell nanoparticles and their influence on the mechanical behavior of acrylic bone cements.

    Science.gov (United States)

    Gutiérrez-Mejía, A; Herrera-Kao, W; Duarte-Aranda, S; Loría-Bastarrachea, M I; Canché-Escamilla, G; Moscoso-Sánchez, F J; Cauich-Rodríguez, J V; Cervantes-Uc, J M

    2013-04-01

    Core-shell nanoparticles consisting of polybutyl acrylate (PBA) rubbery core and a polymethyl methacrylate (PMMA) shell, with different core-shell ratios, were synthesized in order to enhance the fracture toughness of the acrylic bone cements prepared with them. It was observed by TEM and SEM that the core-shell nanoparticles exhibited a spherical morphology with ca. 120 nm in diameter and that both modulus and tensile strength decreased by increasing the PBA content; the desired structuring pattern in the synthesized particles was confirmed by DMA. Also, experimental bone cements were prepared with variable amounts (0, 5, 10 and 20 wt.%) of nanoparticles with a core-shell ratio of 30/70 in order to study the influence of these nanostructured particles on the physicochemical, mechanical and fracture properties of bone cements. It was found that the addition of nanostructured particles to bone cements caused a significant reduction in the peak temperature and setting time while the glass transition temperature (Tg) of cements increased with increasing particles content. On the other hand, modulus and strength of bone cements decreased when particles were incorporated but fracture toughness was increased. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. 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...

  11. Immobilisation of ion exchange resins in cement

    International Nuclear Information System (INIS)

    Howard, C.G.; Jolliffe, C.B.; Lee, D.J.

    1990-09-01

    The removal of activity from spent decontaminating solutions eg LOMI can be achieved using organic ion exchange resins. These resins can be successfully immobilised in cement based matrices. The optimum cement system contained 10% ordinary Portland cement 84% gg blast furnace slag, 6% microsilica with a water cement ratio of 0.5 and a dry resin loading of 36% with respect to total weight. This formulation was successfully scaled up to 200 litres giving a product with acceptable compressive strength, dimensional stability and elastic modulus. Storage of samples under water appears to have no detrimental effects on the product's properties. (author)

  12. Cement replacement materials. Properties, durability, sustainability

    International Nuclear Information System (INIS)

    Ramezanianpour, Ali Akbar

    2014-01-01

    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.

  13. Geotechnical properties of clayey soil stabilized with cement ...

    African Journals Online (AJOL)

    The study was conducted to investigate the different effects of cement-sawdust ash and cement on a clayey soil sampled from Mandate Lodge, Landmark University, Omu-Aran, Nigeria. The binder mix of cementsawdust ash (CSDA) was mixed in a ratio of 1:1. The CSDA and cement were added to the soil samples at ...

  14. Natural radioactivity levels and danger ratio in cements, concretes and mortars used in construction; Determinacion de niveles radiactivos naturales e indices de peligrosidad en cementos, hormigones y morteros utilizados en construccion

    Energy Technology Data Exchange (ETDEWEB)

    Meneses, J.; Pacheco, C.; Avila, J. M.; Miro, C.

    2010-07-01

    We have determined the natural radiation level in three types of adhesive cements, five types of concrete and two types of mortars of different strength normally used in the construction field. Of these materials, both concrete and mortars were prepared in our laboratories, cements the contrary were of a commercial nature.

  15. 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)

  16. The Effect of Different C:n and C:p Ratio of Media on the Content of Polyhydroxybutyrate in Biofloc Inoculated with Bacterium Bacillus Cereus

    OpenAIRE

    Supono; Hutabarat, Johannes; Prayitno, Slamet Budi; Darmanto, YS

    2013-01-01

    Biofloc technology has added values in aquaculture management, both in water quality management and feeding management. As an optional feed, biofloc is capable to enhance growth due to high protein content. Bacteria, main component biofloc, can produce polyhydroxybutyrate (PHB) as reserve of energy and growth accelerator for fish. The aim of the research were to study the effect of the different C:N and C:P ratio of media on the content of polyhydroxybutyrate in biofloc and to determine...

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  18. 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.

  19. Polymer--calcium phosphate cement composites for bone substitutes.

    Science.gov (United States)

    Mickiewicz, Rafal A; Mayes, Anne M; Knaack, David

    2002-09-15

    The use of self-setting calcium phosphate cements (CPCs) as bioresorbable bone-replacement implant materials presently is limited to non-load-bearing applications because of their low compressive strength relative to natural bone. The present study investigated the possibility of strengthening a commercially available CPC, alpha-BSM, by incorporating various water-soluble polymers into the cement paste during setting. Several polyelectrolytes, poly(ethylene oxide), and the protein bovine serum albumin (BSA) were added in solution to the cement paste to create calcium phosphate-polymer composites. Composites formulated with the polycations poly(ethylenimine) and poly(allylamine hydrochloride) exhibited compressive strengths up to six times greater than that of pure alpha-BSM material, with a maximum value reached at intermediate polymer content and for the highest molecular weight studied. Composites containing BSA developed compressive strengths twice that of the original cement at protein concentrations of 13-25% by weight. In each case, XRD studies correlate the improvement in compressive strength with reduced crystallite dimensions, as evidenced by a broadening of the (0,0,2) reflection. This suggests that polycation or BSA adsorption inhibits crystal growth and possibly leads to a larger crystal aspect ratio. SEM results indicate a denser, more interdigitated microstructure. The increased strength was attributed to the polymer's capacity to bridge between multiple crystallites (thus forming a more cohesive composite) and to absorb energy through plastic flow. Copyright 2002 Wiley Periodicals, Inc.

  20. 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.

  1. Determination of curie content and 134/137cesium ratios by gamma spectroscopy of high burnup plutonium-aluminum fuel assemblies

    International Nuclear Information System (INIS)

    Haggard, D.L.; Tanner, J.E.

    1997-06-01

    Nondestructive assay (NDA) gamma spectroscopy techniques were used to measure 134/137 Cs ratios on nine PuAl Mark 42 fuel assemblies. The purpose of the ratio measurement was to confirm theoretical burnup calculations. 134/137 Cs ratios were determined from the measured activity based on corrected net peak area counts for the 605 keV peak from 134 Cs and the 662 keV peak from 137 Cs/ 137m Ba. Assembly No. 2 134/137 Cs ratio measured on 4-15-92 was 0.19. The measured 134/137 Cs ratio was decay corrected to be 2.11 on 8-1-84 based on the half lives of 134 Cs and 137 Cs. The measured 134/137 Cs ratio range was 1.90--2.14 for all nine assemblies. These measured values compare to a theoretical ratio of 1.7 on 8-1-84 determined by burnup calculations. Total cesium curie content was also requested and determined using the NDA direct measurements. Gamma spectral data were measured on the nine sectioned Mark 42 fuel assemblies. Measured cesium curie content, decay corrected to 8-1-84, ranged from 18170--24480 curies of 134 Cs and 8620--11646 curies of 137 Cs. Theoretical cesium curie content of 8-1-84 was 15200 curies 134 Cs and 8973 curies 137 Cs. Direct assay cesium ratio is 12% to 26% higher than the predicted ratio of 1.7. The measured 134 Cs data indicate between 20%--61% more activity than that predicted by the burnup code, whereas the measured 137 Cs activity is between 4% less to 30% more than the predicted activity. This information may be used to address issues concerning criticality safety, storage, and shipping of this type of material

  2. Determination of curie content and {sup 134/137}cesium ratios by gamma spectroscopy of high burnup plutonium-aluminum fuel assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Haggard, D.L.; Tanner, J.E.

    1997-06-01

    Nondestructive assay (NDA) gamma spectroscopy techniques were used to measure {sup 134/137}Cs ratios on nine PuAl Mark 42 fuel assemblies. The purpose of the ratio measurement was to confirm theoretical burnup calculations. {sup 134/137}Cs ratios were determined from the measured activity based on corrected net peak area counts for the 605 keV peak from {sup 134}Cs and the 662 keV peak from {sup 137}Cs/{sup 137m}Ba. Assembly No. 2 {sup 134/137}Cs ratio measured on 4-15-92 was 0.19. The measured {sup 134/137}Cs ratio was decay corrected to be 2.11 on 8-1-84 based on the half lives of {sup 134}Cs and {sup 137}Cs. The measured {sup 134/137}Cs ratio range was 1.90--2.14 for all nine assemblies. These measured values compare to a theoretical ratio of 1.7 on 8-1-84 determined by burnup calculations. Total cesium curie content was also requested and determined using the NDA direct measurements. Gamma spectral data were measured on the nine sectioned Mark 42 fuel assemblies. Measured cesium curie content, decay corrected to 8-1-84, ranged from 18170--24480 curies of {sup 134}Cs and 8620--11646 curies of {sup 137}Cs. Theoretical cesium curie content of 8-1-84 was 15200 curies {sup 134}Cs and 8973 curies {sup 137}Cs. Direct assay cesium ratio is 12% to 26% higher than the predicted ratio of 1.7. The measured {sup 134}Cs data indicate between 20%--61% more activity than that predicted by the burnup code, whereas the measured {sup 137}Cs activity is between 4% less to 30% more than the predicted activity. This information may be used to address issues concerning criticality safety, storage, and shipping of this type of material.

  3. Dimensional and ice content changes of hardened concrete at different freezing and thawing temperatures

    DEFF Research Database (Denmark)

    Johannesson, Björn

    2010-01-01

    Samples of concrete at different water-to-cement ratios and air contents subjected to freeze/thaw cycles with the lowest temperature at about -80 degrees C are investigated. By adopting a novel technique, a scanning calorimeter is used to obtain data from which the ice contents at different freeze...

  4. Estimation of carotenoid content at the canopy scale using the carotenoid triangle ratio index from in situ and simulated hyperspectral data

    Science.gov (United States)

    Kong, Weiping; Huang, Wenjiang; Zhou, Xianfeng; Song, Xiaoyu; Casa, Raffaele

    2016-04-01

    Precise estimation of carotenoids (Car) content in plants, from remotely sensed data, is challenging due to their small proportion in the overall total pigment content and to the overlapping of spectral absorption features with chlorophyll (Chl) in the blue region of the spectrum. The use of narrow band vegetation indices (VIs) obtained from hyperspectral data has been considered an effective way to estimate Car content. However, VIs have proved to lack sensitivity to low or high Car content in a number of studies. In this study, the carotenoid triangle ratio index (CTRI), derived from the existing modified triangular vegetation index and a single band reflectance at 531 nm, was proposed and employed to estimate Car canopy content. We tested the potential of three categories of hyperspectral indices earlier proposed for Car, Chl, Car/Chl ratio estimation, and the new CTRI index, for Car canopy content assessment in winter wheat and corn. Spectral reflectance representing plant canopies were simulated using the PROSPECT and SAIL radiative transfer model, with the aim of analyzing saturation effects of these indices, as well as Chl effects on the relationship between spectral indices and Car content. The result showed that the majority of the spectral indices tested, saturated with the increase of Car canopy content above 28 to 64 μg/cm2. Conversely, the CTRI index was more robust and was linearly and highly sensitive to Car content in winter wheat and corn datasets, with coefficients of determination of 0.92 and 0.75, respectively. The corresponding root mean square error of prediction were 6.01 and 9.70 μg/cm2, respectively. Furthermore, the CTRI index did not show a saturation effect and was not greatly influenced by changes of Chl values, outperforming all the other indices tested. Estimation of Car canopy content using the CTRI index provides an insight into diagnosing plant physiological status and environmental stress.

  5. Properties of backfilling material for solidifying miscellaneous waste using recycled cement from waste concrete

    International Nuclear Information System (INIS)

    Matsuda, Atsuo; Yamamoto, Kazuo; Konishi, Masao; Iwamoto, Yoshiaki; Yoshikane, Toru; Koie, Toshio; Nakashima, Yoshio.

    1997-01-01

    A large reduction of total radioactive waste is expected, if recycled cement from the waste concrete of decommissioned nuclear power plants would be able to be used the material for backfilling mortar among the miscellaneous waste. In this paper, we discuss the hydration, strength and consistency of recycled cement compared with normal portland cement. The strength of recycled cement mortar is lower than that of normal portland cement mortar on the same water to cement ratio. It is possible to obtain the required strength to reduce the water to cement ratio by using of high range water-reducing AE agent. According to reducing of water to cement ratio, the P-type funnel time of mortar increase with the increase of its viscosity. However, in new method of self-compactability for backfilling mortar, it became evident that there was no difference between the recycled cement and normal portland cement on the self-compactability. (author)

  6. Assessment of Bagasse Ash Effect on the California Bearing Ratio of ...

    African Journals Online (AJOL)

    Assessment of Bagasse Ash Effect on the California Bearing Ratio of Used Oil Contaminated Lateritic Soils. ... However, the highest CBR value of 62 % recoded at 8 % BA content failed to meet the 80 % CBR value recommended by the Nigerian general specification (1997) for cement stabilization. Oil contamination ...

  7. Utilization of Foaming Technology in Cemented Paste Backfill of High-Mud Superfine Unclassified Tailings

    Directory of Open Access Journals (Sweden)

    Jian-wen Zhao

    2017-01-01

    Full Text Available Due to high-mud content in superfine unclassified tailings (SUT, the viscosity of cemented paste backfill (CPB is high and its pipeline transportation properties are poor. Foaming technology was introduced to prepare a new three-phase flow backfill (TFB using a foaming machine. Then the rheological parameters of TFB with different bubble ratio were measured and their pipeline transportation properties were simulated by Fluent. Besides, the simulation results were further verified by a semi-industrial loop test. The results indicate that the optimum ratio of TFB is a cement-sand ratio of 1 : 8, mass concentration of 70%, and bubble ratio of 20%. Compared with CPB, the decrease of bleeding rate, viscosity, and resistance loss of TFB is 27%, 25%, and 30%, respectively. Therefore, foaming technology is an innovative and feasible solution for high-mud CPB in reducing viscosity, decreasing resistance loss, and improving pipeline transporting efficiency.

  8. Diets Rich in Polyunsaturated Fatty Acids With Different Omega-6/Omega-3 Ratio Decrease Liver Content of Saturated Fatty Acids Across Generations of Wistar Rats

    Directory of Open Access Journals (Sweden)

    Simone Halfen

    Full Text Available Our study evaluated how the consumption of diets with low (LOW group - 0.4/1 or high (CON group - 13.6/1 omega-6/omega-3 ratio across generations (F1 and F2 can modulate liver fatty acid (FA profile and blood biomarkers. Liver content of α-linolenic acid was higher in animals always fed with LOW diet than animals that changed from CON to LOW diet, which by your time was higher than animals always fed with CON diet. Liver saturated FA concentration decreased in both groups from F1 to F2. In conclusion, both diets were efficient in decreasing the saturated FA liver content across generations, the LOW ratio diet was more effective in reducing blood triglycerides and non-esterified fatty acids, and there was a multigenerational effect of the LOW ratio diet, improving the FA profile even when the offspring start receiving the CON diet.

  9. 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

  10. Low pH Cements

    International Nuclear Information System (INIS)

    Savage, David; Benbow, Steven

    2007-05-01

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit ≤ 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio ≤ 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  11. Effect of some prepared superplasticizers (Cyclohexanone Based on compressive strength and physico-chemical properties of oil well cement pastes

    Directory of Open Access Journals (Sweden)

    I. Aiad

    2017-09-01

    Full Text Available Two different superplasticizers particularly cyclohexanone formaldehyde sulfanilate (CFS and cyclohexanone glyoxylic sulfanilate (CGS were prepared; also, their effect on mechanical and physico-chemical properties of oil well cement was assessed. The chemical structures were affirmed by FTIR technique. The designed chemical compounds were predestined as superplasticizers for cement pastes. The pastes were made by superplasticizer (CFS or CGS addition to cement by the ratios of 0, 0.25, 0.50, 0.75, and l.00 as mass% of cement. The water of consistency, setting time, chemically combined water content (Wn, the hydration rate and compressive strength of the admixed hardened pastes were predestined at various time periods. The phase composition was intended by DSC and XRD techniques. The results revealed that as the admixture dose rate increases the demand cement paste water of consistency decreases. Also, as the admixture addition rate increases the chemically combined water content decreases, so the rate of hydration decreases; meanwhile compressive strength magnitudes increase accounting for the low water/cement (initial porosity of the sample.

  12. Use of Cemented Super-Fine Unclassified Tailings Backfill for Control of Subsidence

    Directory of Open Access Journals (Sweden)

    Lei Yang

    2017-11-01

    Full Text Available Known for its advantages in preventing geological and environmental hazards, cemented paste backfill (CPB has become a topic of interest for scientists and mining engineers in recent decades. This paper presents the results of a study on the use of cemented super-fine tailings backfill (CSUTB in an underground mine for control of surface subsidence. An analytical solution is developed based on the available model to calculate the required strength of backfill when in contact with non-cemented tailings (NCT. The effect of solid contents on the rheological properties of CSUTB is investigated. A reasonable mix proportion (RMP of CSUTB is determined for Zhongguan Iron Mine (ZGIM based on laboratory experiments. The validity of RMP in surface subsidence control is verified by a 3D numerical model. The obtained results show that CSUTB requires higher strength when in contact with NCT than when in contact with orebody. Rheological characteristics, e.g., slump, fluidity, and bleeding rate of fresh CSUTB, decrease with higher solids content, of which values with a certain solids content can be determined by quadratic polynomial regression equations. RMP with a cement to tailings (c/t ratio of 1:10 and a solids content of 70% is recommended for ZGIM, as it shows favorable mechanical and rheological abilities. The deformation parameters (curvature, inclination, and horizontal deformation rate obtained from numerical modeling are acceptable and lower than critical values, meaning CSUTB can feasibly be used with RMP in subsidence control.

  13. The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental?

    Science.gov (United States)

    Takahashi, E; Kaneuji, A; Tsuda, R; Numata, Y; Ichiseki, T; Fukui, K; Kawahara, N

    2017-05-01

    Favourable results for collarless polished tapered stems have been reported, and cement creep due to taper slip may be a contributing factor. However, the ideal cement thickness around polished stems remains unknown. We investigated the influence of cement thickness on stem subsidence and cement creep. We cemented six collarless polished tapered (CPT) stems (two stems each of small, medium and large sizes) into composite femurs that had been reamed with a large CPT rasp to achieve various thicknesses of the cement mantle. Two or three tantalum balls were implanted in the proximal cement in each femur. A cyclic loading test was then performed for each stem. The migration of the balls was measured three-dimensionally, using a micro-computed tomography (CT) scanner, before and after loading. A digital displacement gauge was positioned at the stem shoulder, and stem subsidence was measured continuously by the gauge. Final stem subsidence was measured at the balls at the end of each stem. A strong positive correlation was observed between mean cement thickness and stem subsidence in the CT slices on the balls. In the small stems, the balls moved downward to almost the same extent as the stem. There was a significant negative correlation between cement thickness and the horizontal:downward ratio of ball movement. Collarless polished tapered stems with thicker cement mantles resulted in greater subsidence of both stem and cement. This suggests that excessive thickness of the cement mantle may interfere with effective radial cement creep. Cite this article: E. Takahashi, A. Kaneuji, R. Tsuda, Y. Numata, T. Ichiseki, K. Fukui, N. Kawahara. The influence of cement thickness on stem subsidence and cement creep in a collarless polished tapered stem: When are thick cement mantles detrimental? Bone Joint Res 2017;6:-357. DOI: 10.1302/2046-3758.65.BJR-2017-0028.R1. © 2017 Kaneuji et al.

  14. Polymer-Cement Mortar with Quarry Waste as Sand Replacement

    Directory of Open Access Journals (Sweden)

    D. N. Gómez-Balbuena

    2018-01-01

    Full Text Available The activities of carved Quarry extraction generate problems of landscape pollution such is the case of solid waste discharged into open land dumps in central Mexico. This article presents the technological application of this solid waste in a new polymeric material with properties similar to those of a traditional mortar. It is concluded that the polymeric material uses low amounts of cement with respect to the traditional mortar, and it is elaborated with the recycled quarry as they are presented in its granulometry. The polymer used favored a low water/cement ratio (0.3 which did not allow to decrease resistance due to the fine nature of the materials (residues and cement in addition to maintaining the workability of the material. The quarry residue was classified as silt with low plasticity and was characterized by X-ray diffraction and Fluorescence to identify 76% of SiO2, which is why it was used as a stone aggregate even though the fines content was approximately 93%. The maximum compression resistance obtained at 28 days were 8 Mpa with the polymer/solid ratios of 0.10, water/solids of 0.30, and quarry/solids of 0.67. Linear equations were analyzed for more representative values with R squared adjustment.

  15. Utilization of Foaming Technology in Cemented Paste Backfill of High-Mud Superfine Unclassified Tailings

    OpenAIRE

    Jian-wen Zhao; Xin-min Wang; Kang Peng; Shuai Li

    2017-01-01

    Due to high-mud content in superfine unclassified tailings (SUT), the viscosity of cemented paste backfill (CPB) is high and its pipeline transportation properties are poor. Foaming technology was introduced to prepare a new three-phase flow backfill (TFB) using a foaming machine. Then the rheological parameters of TFB with different bubble ratio were measured and their pipeline transportation properties were simulated by Fluent. Besides, the simulation results were further verified by a semi...

  16. [Study on dental cements. 1. The cored structure of three luting cements obtained by using Cryo-SEM and image analyzer].

    Science.gov (United States)

    Hosoda, H; Yamada, T; Nakajima, M; Perinka, L

    1990-03-01

    The polished surfaces of three set dental cements for luting (zinc phosphate cement, polycarboxylate cement, and glass ionomer cement) were observed by cryo-SEM at a specimen temperature of -160 degrees C to prevent damage of the cement specimens and also the specimens were analyzed by EDX. Furthermore, the SEM composition images of the polished cement surface were transferred to an image analyzer to obtain the core/matrix area ratio of the set cements. 1. The polished surface of set dental cement could be clearly observed by cryo-SEM without damaging the cement specimens. 2. The image analyzer showed that the core/matrix area ratio of the zinc phosphate cement and the glass ionomer cement was approximately 2 to 8, whereas that of the polycarboxylate cement was approximately 3 to 7. 3. The elements detected in the zinc phosphate cement were Ca, Zn, Mg, Al, and P, in the polycarboxylate cement were Ca, Zn, Mg, Si, and Sr, and in the glass ionomer cement were Al and Si.

  17. 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  

  18. Effect of Modified Rubber Particles Mixing Amount on Properties of Cement Mortar

    Directory of Open Access Journals (Sweden)

    Gang Xue

    2017-01-01

    Full Text Available The crumb rubber cement mortar is prepared by the crumb rubber aggregates in 60 mesh which are modified by 1% polyvinyl alcohol (PVA solution. Some mechanical properties of cement mortar with different crumb rubber aggregate amounts are researched including compressive strength, flexural strength, the ratio of compressive strength to flexural strength, impact resistance, and dry contraction percentage. In our tests, we consider six kinds of the rubber contents, 0%, 7.5%, 15%, 19%, 22.5%, and 30%, respectively. The optimal mixing amount of crumb rubber is determined by measuring three indices, the ratio of compressive strength to flexural strength, impact resistance, and dry contraction percentage. It is shown by test that the ratio of compressive strength to flexural strength is the smallest when the mixing amount of rubber is 19%; meanwhile high impact resistance and rational drying shrinkage are observed. The optimal mixing amount of the rubber particles is 19% determined by this test.

  19. Radiopacity of portland cement associated with different radiopacifying agents.

    Science.gov (United States)

    Húngaro Duarte, Marco Antonio; de Oliveira El Kadre, Guâniara D'arc; Vivan, Rodrigo Ricci; Guerreiro Tanomaru, Juliane Maria; Tanomaru Filho, Mário; de Moraes, Ivaldo Gomes

    2009-05-01

    This study evaluated the radiopacity of Portland cement associated with the following radiopacifying agents: bismuth oxide, zinc oxide, lead oxide, bismuth subnitrate, bismuth carbonate, barium sulfate, iodoform, calcium tungstate, and zirconium oxide. A ratio of 20% radiopacifier and 80% white Portland cement by weight was used for analysis. Pure Portland cement and dentin served as controls. Cement/radiopacifier and dentin disc-shaped specimens were fabricated, and radiopacity testing was performed according to the ISO 6876/2001 standard for dental root sealing materials. Using Insight occlusal films, the specimens were radiographed near to a graduated aluminum stepwedge varying from 2 to 16 mm in thickness. The radiographs were digitized and radiopacity compared with the aluminum stepwedge using Digora software (Orion Corporation Soredex, Helsinki, Finland). The radiographic density data were converted into mmAl and analyzed statistically by analysis of variance and Tukey-Kramer test (alpha = 0.05). The radiopacity of pure Portland cement was significantly lower (p cement/radiopacifier mixtures were significantly more radiopaque than dentin and Portland cement alone (p Portland cement/bismuth oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p Portland cement/zinc oxide presented the lowest radiopacity values of all mixtures (p Portland cement as radiopacifying agents. However, the possible interference of the radiopacifiers with the setting chemistry, biocompatibility, and physical properties of the Portland cement should be further investigated before any clinical recommendation can be done.

  20. Phytosterol content and the campesterol:sitosterol ratio influence cotton fiber development: role of phytosterols in cell elongation.

    Science.gov (United States)

    Deng, Shasha; Wei, Ting; Tan, Kunling; Hu, Mingyu; Li, Fang; Zhai, Yunlan; Ye, Shue; Xiao, Yuehua; Hou, Lei; Pei, Yan; Luo, Ming

    2016-02-01

    Phytosterols play an important role in plant growth and development, including cell division, cell elongation, embryogenesis, cellulose biosynthesis, and cell wall formation. Cotton fiber, which undergoes synchronous cell elongation and a large amount of cellulose synthesis, is an ideal model for the study of plant cell elongation and cell wall biogenesis. The role of phytosterols in fiber growth was investigated by treating the fibers with tridemorph, a sterol biosynthetic inhibitor. The inhibition of phytosterol biosynthesis resulted in an apparent suppression of fiber elongation in vitro or in planta. The determination of phytosterol quantity indicated that sitosterol and campesterol were the major phytosterols in cotton fibers; moreover, higher concentrations of these phytosterols were observed during the period of rapid elongation of fibers. Furthermore, the decrease and increase in campesterol:sitosterol ratio was associated with the increase and decease in speed of elongation, respectively, during the elongation stage. The increase in the ratio was associated with the transition from cell elongation to secondary cell wall synthesis. In addition, a number of phytosterol biosynthetic genes were down-regulated in the short fibers of ligon lintless-1 mutant, compared to its near-isogenic wild-type TM-1. These results demonstrated that phytosterols play a crucial role in cotton fiber development, and particularly in fiber elongation.

  1. Electrochemical and structural characterization of nanocomposite Agy:TiNx thin films for dry bioelectrodes: the effect of the N/Ti ratio and Ag content

    International Nuclear Information System (INIS)

    Pedrosa, P.; Machado, D.; Fiedler, P.; Alves, E.; Barradas, N.P.; Haueisen, J.; Vaz, F.; Fonseca, C.

    2015-01-01

    Highlights: • Ag y :TiN x thin films were sputtered with different N/Ti atomic ratios and Ag contents. • The electroactive area increases (1000-fold) with increasing N/Ti atomic ratios. • The films display impedances <10 kΩ at the 1–50 Hz interval (EEG range). • No Ag surface segregation was visible in the under-stoichiometric samples. • The samples with N/Ti atomic ratio = 0.3 (15 at.% Ag) and 0.7 (32 at.% Ag) are the most appropriate for bioelectrode applications. - ABSTRACT: Ag y :TiN x nanocomposite thin films sputtered with different N/Ti atomic ratios and Ag atomic contents were characterized from the structural and morphological points of view. Their electrochemical behaviour was studied in a synthetic sweat solution, aiming at selecting a suitable material for biolectrode applications. An increase of the N/Ti atomic ratio, which is accompanied by an increase of the Ag atomic content, leads to a substantial increase of the roughness and porosity of the samples, especially for N/Ti ratios >0.2. For N/Ti atomic ratios up to 0.3 (15 at.% Ag) no metallic Ag segregation is visible in the TiN x matrix. Hence, the possible formation of TiAg and Ti 2 Ag intermetallics or even a Ag/TiAg/Ti 2 Ag phase mixture, although not demonstrated, should not be disregarded. As for the N/Ti atomic ratio = 0.7 (32 at.% Ag) sample, the Ag phases are predominantly concentrated near the interface with the substrate. The amount of Ag phases at the surface of the films remains somewhat low for all TiN under-stoichiometric films, even for Ag atomic contents up to 32 at.%. When the TiN x matrix reaches the stoichiometric condition (sample with N/Ti atomic ratio = 1 and 20 at.% Ag), Ag segregation occurs and metallic Ag aggregates are visible at the surface of the film, leading to a substantially different electrochemical behaviour. The impedance of the Ag y :TiN x films in synthetic sweat solution is mainly ruled by the roughness/porosity variation, thus the higher the N

  2. Further evidence of important environmental information content in red-to-green ratios as depicted in paintings by great masters

    Science.gov (United States)

    Zerefos, C. S.; Tetsis, P.; Kazantzidis, A.; Amiridis, V.; Zerefos, S. C.; Luterbacher, J.; Eleftheratos, K.; Gerasopoulos, E.; Kazadzis, S.; Papayannis, A.

    2013-12-01

    This work is a follow-up study of a research carried out since 2005 and presents evidence supporting the findings of an earlier paper (Zerefos et al., 2007), which postulated that sunsets painted by famous artists provide independent proxy information on the aerosol optical depth after major volcanic eruptions. The series of these and additional paintings have been revisited and comparisons between coarser digital images with those derived from precision colour protocols, match together confirming the earlier results as discussed in the text. It was also found that aerosol optical depths (AODs) at 550 nm calculated by feeding Red-to-Green (R/G) ratios from a large number of paintings to a radiative transfer model, were well correlated with independent proxies from stratospheric AOD and optical extinction data, the dust veil index and others. AODs calculated from paintings have been grouped into 50 yr intervals from 1500 to 2000. From each 50 yr time period the year of the eruption and the 3 following years have been excluded. The remaining years have been termed "non-volcanic" and they provide additional evidence of a multidecadal increase in the atmospheric optical depths during the industrial "revolution". The increase of AOD at 550 nm calculated from the paintings, is estimated to range from 0.15 in the middle 19th century to about 0.20 by the end of the 20th century. To corroborate our findings, an experiment was designed in which a master painter/colourist painted successive sunsets during and after the passage of Saharan aerosols over the island of Hydra in Greece. Independent solar radiometric measurements confirmed that the master colourist's R/G ratios which were used to model his AODs, matched to the AOD values measured in situ by the co-located sunphotometers at the declining phase of the Sahara aerosol. Our work concludes that regardless of the school, red-to-green ratios from great masters can provide independent proxy AODs that correlate with widely

  3. Cements research progress. 1988

    International Nuclear Information System (INIS)

    Anon.

    1990-01-01

    This book reviews a survey of the literature on the science of cements published during 1988. The book focuses on an aspect of cement utilization of increasing importance, the immobilization of nuclear wastes

  4. Modeling of Hydration, Compressive Strength, and Carbonation of Portland-Limestone Cement (PLC Concrete

    Directory of Open Access Journals (Sweden)

    Xiao-Yong Wang

    2017-01-01

    Full Text Available Limestone is widely used in the construction industry to produce Portland limestone cement (PLC concrete. Systematic evaluations of hydration kinetics, compressive strength development, and carbonation resistance are crucial for the rational use of limestone. This study presents a hydration-based model for evaluating the influences of limestone on the strength and carbonation of concrete. First, the hydration model analyzes the dilution effect and the nucleation effect of limestone during the hydration of cement. The degree of cement hydration is calculated by considering concrete mixing proportions, binder properties, and curing conditions. Second, by using the gel–space ratio, the compressive strength of PLC concrete is evaluated. The interactions among water-to-binder ratio, limestone replacement ratio, and strength development are highlighted. Third, the carbonate material contents and porosity are calculated from the hydration model and are used as input parameters for the carbonation model. By considering concrete microstructures and environmental conditions, the carbon dioxide diffusivity and carbonation depth of PLC concrete are evaluated. The proposed model has been determined to be valid for concrete with various water-to-binder ratios, limestone contents, and curing periods.

  5. 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.

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

    Science.gov (United States)

    Sikora, Pawel; Augustyniak, Adrian; Cendrowski, Krzysztof; Horszczaruk, Elzbieta; Rucinska, Teresa; Nawrotek, Pawel; Mijowska, Ewa

    2016-01-01

    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. PMID:28773823

  7. Sulfur polymer cement concrete

    International Nuclear Information System (INIS)

    Weber, H.H.; McBee, W.C.

    1990-01-01

    Sulfur-based composite materials formulated using sulfur polymer cement (SPC) and mineral aggregates are described and compared with conventional portland cement based materials. Materials characteristics presented include mechanical strength, chemical resistance, impact resistance, moisture permeation, and linear shrinkage during placement and curing. Examples of preparation and placement of sulfur polymer cement concrete (SC) are described using commercial scale equipment. SC applications presented are focused into hostile chemical environments where severe portland cement concrete (PCC) failure has occurred

  8. Cementation and solidification of Rocky Flats Plant incinerator ash

    International Nuclear Information System (INIS)

    Phillips, J.A.; Semones, G.B.

    1994-01-01

    Cementation studies on various aqueous waste streams at Rocky Flats have shown this technology to be effective for immobilizing the RCRA constituents in the waste. Cementation is also being evaluated for encapsulation of incinerator ash. Experiments will initially evaluate a surrogate ash waste using a Taguchi experimental design to optimize the cement formulation and waste loading levels for this application. Variables of waste loading, fly ash additions, water/cement ratio, and cement type will be tested at three levels each during the course of this work. Tests will finally be conducted on actual waste using the optimized cement formulation developed from this testing. This progression of tests will evaluate the effectiveness of cement encapsulation for this waste stream without generating any additional wastes

  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. The suitability of a supersulfated cement for nuclear waste immobilisation

    International Nuclear Information System (INIS)

    Collier, N.C.; Milestone, N.B.; Gordon, L.E.; Ko, S.-C.

    2014-01-01

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste

  11. Calcium carbonate nodules in soils: 18O/16O and 13C/12C ratios and 14C contents

    International Nuclear Information System (INIS)

    Magaritz, M.; Kaufman, A.; Yaalon, D.H.

    1981-01-01

    delta 18 O values, delta 13 C values and 14 C ages were determined in ten CaCO, nodule populations collected from soil and paleosols in the Israeli coastal plain. The selected soils were carbonate-free when formed and the nodules in them represent either reprecipitation of carbonate illuviated from overlying horizons (descending mode) or precipitated from a raised brackish water table (ascending mode). The 14 C ages represent the time of migration (illuviation) or eustatic movement (both climate-related) and the stable isotopic conditions reflect the environmental conditions at such times. In two cases where nodules were soft both turned out to be young (approx. equal to 1000 years) and to have wide ranges in delta 18 O values; the latter are apparently due to continual re-equilibration with new soil solutions. In three cases of the descending mode of nodule formation, 12,000-14,000 year-old hard nodules had very narrow delta 18 O whose means reflect the rainfall value at that time. The period between 12,000-14,000 years B.P. is independently known to be one of higher precipitation/evaporation ratio and of more intensive soil formation. Three ascending-mode populations of hard nodules had narrow ranges in delta 18 O (reflecting a mixture of sea water and rainfall) and all turned out to be 3,000-4,000 years old. At this period the sea reached its highest elevation, resulting in raising the nearcoast water table. (orig./RB)

  12. Hydration rate and strength development of low-heat type portland cement mortar mixed with pozzolanic materials

    International Nuclear Information System (INIS)

    Matsui, Jun

    1998-01-01

    Recently, low-heat type Portland cement was specified in Japan Industrial Standards (JIS). Its hydration proceeds slowly. The results of the research so far obtained indicate that slow hydration of cement and mixing of pozzolanic materials with cement make micro-structure of harded cement paste dense and durable. In this study, a blended cement using low-heat type Portland cement and some of pozzolanic materials has been newly developed and its strength property and hydration ratio were checked. The followings are conclusion. (1) Hydration rate of cement paste varies with the replacement ratio of pozzolanic materials. (2) A good liner relationship between strength and total hydration rate of cement paste was observed. (3) A proper replacement ratio of both base-cement and pozzolanic material for manufacturing a blended cement is 50%. (author)

  13. 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...... (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  14. Evaluation of the Compressive Strength of Cement-Spent Resins Matrix Mixed with Bio char

    International Nuclear Information System (INIS)

    Zalina Laili; Muhamad Samudi Yasir; Zalina Laili; Mohd Abdul Wahab; Nur Azna Mahmud; Nurfazlina Zainal Abidin

    2015-01-01

    The evaluation of compressive strength of cement-spent resins matrix mixed with bio char was investigated. In this study, bio char with different percentage (5 %, 8 %, 11 % 14 % and 18 %) was used as alternative admixture material for cement solidification of spent resins. Some properties of the physical and chemical of spent resins and bio char were also investigated. The performance of cemented spent resins with the addition of bio char was evaluated based on their compressive strength and the water resistance test. The compressive strength was evaluated at three different curing periods of 7, 14 and 28 days, while 4 weeks of immersion in distilled water was chosen for water resistance test. The result indicated that the compressive strength at 7, 14 and 28 days of curing periods were above the minimum criterion for example > 3.45 MPa of acceptable level for cemented waste form. Statistical analysis showed that there was no significant relationship between the compressive strength of the specimen and the percentage of bio char content. Result from the water resistance test showed that only one specimen that contained of 5 % of bio char failed the water resistance test due to the high of spent resins/ bio char ratio. The compressive strength of cement solidified spent resins was found increased after the water resistance test indicating further hydration occurred after immersed in water. The results of this study also suggest that the specimen with 8 %, 11 %, 14 % and 18 % of bio char content were resistance in water and suitable for the leaching study of radionuclides from cement-bio char-spent resins matrix. (author)

  15. A novel method to produce dry geopolymer cement powder

    Directory of Open Access Journals (Sweden)

    H.A. Abdel-Gawwad

    2016-04-01

    Full Text Available Geopolymer cement is the result of reaction of two materials containing aluminosilicate and concentrated alkaline solution to produce an inorganic polymer binder. The alkali solutions are corrosive and often viscous solutions which are not user friendly, and would be difficult to use for bulk production. This work aims to produce one-mix geopolymer mixed water that could be an alternative to Portland cement by blending with dry activator. Sodium hydroxide (SH was dissolved in water and added to calcium carbonate (CC then dried at 80 °C for 8 h followed by pulverization to a fixed particle size to produce the dry activator consisting of calcium hydroxide (CH, sodium carbonate (SC and pirssonite (P. This increases their commercial availability. The dry activator was blended with granulated blast-furnace slag (GBFS to produce geopolymer cement powder and by addition of water; the geopolymerization process is started. The effect of W/C and SH/CC ratio on the physico-mechanical properties of slag pastes was studied. The results showed that the optimum percent of activator and CC content is 4% SH and 5% CC, by the weight of slag, which give the highest physico-mechanical properties of GBFS. The characterization of the activated slag pastes was carried out using TGA, DTG, IR spectroscopy and SEM techniques.

  16. Microstructure characteristics of cement-stabilized sandy soil using nanosilica

    Directory of Open Access Journals (Sweden)

    Asskar Janalizadeh Choobbasti

    2017-10-01

    Full Text Available An experimental program was conducted to explore the impact of nanosilica on the microstructure and mechanical characteristics of cemented sandy soil. Cement agent included Portland cement type II. Cement content was 6% by weight of the sandy soil. Nanosilica was added in percentages of 0%, 4%, 8% and 12% by weight of cement. Cylindrical samples were prepared with relative density of 80% and optimum water content and cured for 7 d, 28 d and 90 d. Microstructure characteristics of cement-nanosilica-sand mixtures after 90 d of curing have been explored using atomic force microscopy (AFM, scanning electron microscopy (SEM and X-ray diffraction (XRD tests. Effects of curing time on microstructure properties of cemented sandy soil samples with 0% and 8% nanosilica have been investigated using SEM test. Unconfined compression test (for all curing times and compaction test were also performed. The SEM and AFM tests results showed that nanosilica contributes to enhancement of cemented sandy soil through yielding denser, more uniform structure. The XRD test demonstrated that the inclusion of nanosilica in the cemented soil increases the intensity of the calcium silicate hydrate (CSH peak and decreases the intensity of the calcium hydroxide (CH peak. The results showed that adding optimum percentages of nanosilica to cement-stabilized sandy soil enhances its mechanical and microstructure properties.

  17. Modification of Wood Fiber for Use in Cement Board

    Science.gov (United States)

    Han, F. Q.; Tan, X.; Zhao, F. Q.

    2017-12-01

    When ordinary Portland cement is used for wood fiber cement (WFC) board, the setting time is too long, even hard to solidify. Three methods can be used for wood fiber modification, i.e., soaking in water, treated with alkali solution and coated with some substances on the fiber surface. The results show that the proper water-cement ratio of WFC paste is 1:1.3 in the case of wood cement ratio being 1:1. The WFC board from modified wood fiber and cement is better than the control samples, in which the combined treatment, i.e. soaking in hot water and then coating with alkali-BFS-EVA slurry, behaves best. It is proved that ordinary Portland cement can be used to produce WFC board, with the modified wood fiber, which can greatly reduce production costs.

  18. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  19. 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.

  20. Strength development in concrete with wood ash blended cement and use of soft computing models to predict strength parameters

    Directory of Open Access Journals (Sweden)

    S. Chowdhury

    2015-11-01

    Full Text Available In this study, Wood Ash (WA prepared from the uncontrolled burning of the saw dust is evaluated for its suitability as partial cement replacement in conventional concrete. The saw dust has been acquired from a wood polishing unit. The physical, chemical and mineralogical characteristics of WA is presented and analyzed. The strength parameters (compressive strength, split tensile strength and flexural strength of concrete with blended WA cement are evaluated and studied. Two different water-to-binder ratio (0.4 and 0.45 and five different replacement percentages of WA (5%, 10%, 15%, 18% and 20% including control specimens for both water-to-cement ratio is considered. Results of compressive strength, split tensile strength and flexural strength showed that the strength properties of concrete mixture decreased marginally with increase in wood ash contents, but strength increased with later age. The XRD test results and chemical analysis of WA showed that it contains amorphous silica and thus can be used as cement replacing material. Through the analysis of results obtained in this study, it was concluded that WA could be blended with cement without adversely affecting the strength properties of concrete. Also using a new statistical theory of the Support Vector Machine (SVM, strength parameters were predicted by developing a suitable model and as a result, the application of soft computing in structural engineering has been successfully presented in this research paper.

  1. Study on the effects of white rice husk ash and fibrous materials additions on some properties of fiber-cement composites.

    Science.gov (United States)

    Hamzeh, Yahya; Ziabari, Kamran Pourhooshyar; Torkaman, Javad; Ashori, Alireza; Jafari, Mohammad

    2013-03-15

    This work assesses the effects of white rice husk ash (WRHA) as pozzolanic material, virgin kraft pulp (VKP), old corrugated container (OCC) and fibers derived from fiberboard (FFB) as reinforcing agents on some properties of blended cement composites. In the sample preparation, composites were manufactured using fiber-to-cement ratio of 25:75 by weight and 5% CaCl(2) as accelerator. Type II Portland cement was replaced by WRHA at 0%, 25% and 50% by weight of binder. A water-to-binder ratio of 0.55 was used for all blended cement paste mixes. For parametric study, compressive strength, water absorption and density of the composite samples were evaluated. Results showed that WRHA can be applied as a pozzolanic material to cement and also improved resistance to water absorption. However, increasing the replacement level of WRHA tends to reduce the compressive strength due to the low binding ability. The optimum replacement level of WRHA in mortar was 25% by weight of binder; this replacement percentage resulted in better compressive strengths and water absorption. OCC fiber is shown to be superior to VKF and FFB fibers in increasing the compressive strength, due to its superior strength properties. As expected, the increase of the WRHA content induced the reduction of bulk density of the cement composites. Statistical analysis showed that the interaction of above-mentioned variable parameters was significant on the mechanical and physical properties at 1% confidence level. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  2. Tissue sterol composition in Atlantic salmon (Salmo salar L.) depends on the dietary cholesterol content and on the dietary phytosterol:cholesterol ratio, but not on the dietary phytosterol content.

    Science.gov (United States)

    Sissener, Nini H; Rosenlund, Grethe; Stubhaug, Ingunn; Liland, Nina S

    2018-03-01

    The aim of the study was to investigate how the dietary sterol composition, including cholesterol, phytosterol:cholesterol ratio and phytosterols, affect the absorption, biliary excretion, retention, tissue storage and distribution of cholesterol and individual phytosterols in Atlantic salmon (Salmo salar L.). A feeding trial was conducted at two different temperatures (6 and 12°C), using nine different diets with varying contents of phytosterols, cholesterol and phytosterol:cholesterol ratio. Cholesterol retention values were clearly dependent on dietary cholesterol, and showed that fish fed cholesterol levels phytosterol:cholesterol ratio, but not on the dietary phytosterol content in itself. Campesterol and brassicasterol appeared to be the phytosterols with the highest intestinal absorption in Atlantic salmon. There was a high biliary excretion of campesterol, but not of brassicasterol, which accumulated in tissues and particularly in adipose tissue, with 2-fold-higher retention at 12°C compared with 6°C. Campesterol had the second highest retention of the phytosterols in the fish, but with no difference between the two temperatures. Other phytosterols had very low retention. Although brassicasterol retention decreased with increasing dietary phytosterols, campesterol retention decreased with increasing dietary cholesterol, indicating differences in the uptake mechanisms for these two sterols.

  3. Cement for Oil Well Cementing Operations in Ghana

    African Journals Online (AJOL)

    Michael

    performance of three locally manufactured cement samples and imported class G cement sample for oil and gas well ... cement. 2 Materials and Methods. 2.1 Materials. Three brands of cement available on the Ghanaian market and commonly used by Ghanaians for construction ..... Cement Slurry using Factorial Design”,.

  4. Calibration and correction of LA-ICP-MS and LA-MC-ICP-MS analyses for element contents and isotopic ratios

    Directory of Open Access Journals (Sweden)

    Jie Lin

    2016-06-01

    Full Text Available LA-ICP-MS and LA-MC-ICP-MS have been the techniques of choice for achieving accurate and precise element content and isotopic ratio, the state-of-the-art technique combines the advantages of low detection limits with high spatial resolution, however, the analysis accuracy and precision are restricted by many factors, such as sensitivity drift, elemental/isotopic fractionation, matrix effects, interferences and the lack of sufficiently matrix-matched reference materials. Thus, rigorous and suitable calibration and correction methods are needed to obtain quantitative data. This review systematically summarized and evaluated the interference correction, quantitative calculation and sensitivity correction strategies in order to provide the analysts with suitable calibration and correction strategies according to the sample types and the analyzed elements. The functions and features of data reduction software ICPMSDataCal were also outlined, which can provide real-time and on-line data reduction of element content and isotopic ratios analyzed by LA-ICP-MS and LA-MC-ICP-MS.

  5. Heat of hydration measurements on cemented radioactive wastes. Part 1: cement-water pastes

    International Nuclear Information System (INIS)

    Lee, D.J.

    1983-12-01

    This report describes the hydration of cement pastes in terms of chemical and kinetic models. A calorimetric technique was used to measure the heat of hydration to develop these models. The effects of temperature, water/cement ratio and cement replacements, ground granulated blast furnace slag (BFS) and pulverised fuel ash (PFA) on the hydration of ordinary Portland cement (OPC) is reported. The incorporation of BFS or PFA has a marked effect on the hydration reaction. The effect of temperature is also important but changing the water/cement ratio has little effect. Results from cement pastes containing only water and cement yield total heats of reaction of 400, 200 and 100 kJ/kg for OPC, BFS and PFA respectively. Using the results from the models which have been developed, the effect of major salts present in radioactive waste streams can be assessed. Values of the total heat of reaction, the time to complete 50 percent reaction, and the energy of activation, can be compared for different waste systems. (U.K.)

  6. The use of Limestone Powder as an Alternative Cement Replacement

    African Journals Online (AJOL)

    user

    cement productivity, reduced production cost and environmental protection with a significant reduction of CO2 and ... The use of limestone filler in combination with. Portland cement is a common practice in many countries in .... in plastic bags with a content of 1350 g. Water. Throughout the investigation, tap water supplied.

  7. Recent and future of cement and concrete industries- a root of our development

    Directory of Open Access Journals (Sweden)

    Ts Erdenebat

    2014-09-01

    Full Text Available This paper considers that cement and concrete industry is contributing to our country development positively, and cement and concrete industry also can be reduced environmental pressure by;- Continuously reducing the CO2 emission from cement production by increased use of biofuels and alternative raw materials as well as introducing modified low energy clinker types and cement with reduced clinker content or geopolymer cement and a new type concrete.- Exploiting the potential of waste bricks, cement and concrete recycling to decrease the emission of CO2.- Exploiting the thermal mass of concrete to create energy optimized solutions for heating and cooling residential and office buildings.

  8. Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Jung, Hun Bok; Martin, Paul F.; McGrail, B. Peter

    2011-11-01

    Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C) for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron

  9. prediction of flexural strength of chikoko pozzolana blended cement

    African Journals Online (AJOL)

    user

    optimize the flexural strength of chikoko pozzolana blended cement concrete using Osadebe's regression function. The results obtained from the ... Keywords: Pozzolanic properties, Osadebe's regression function, flexural strength, desired strength, mix ratios. 1. ... construction materials such as chikoko to replace cement ...

  10. Sorption and bending properties of wood cement panels produced ...

    African Journals Online (AJOL)

    The study was carried out to investigate the influence of water/cement ratio on the moisture response and mechanical properties of wood cement panels fabricated with mixed hardwood species. The experimental boards so produced were subjected to modulus of rupture (MOR), modulus of elasticity (MOE), water ...

  11. 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.

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

    Science.gov (United States)

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

    2018-01-01

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

  13. Hydration kinetics modeling of Portland cement considering the effects of curing temperature and applied pressure

    International Nuclear Information System (INIS)

    Lin Feng; Meyer, Christian

    2009-01-01

    A hydration kinetics model for Portland cement is formulated based on thermodynamics of multiphase porous media. The mechanism of cement hydration is discussed based on literature review. The model is then developed considering the effects of chemical composition and fineness of cement, water-cement ratio, curing temperature and applied pressure. The ultimate degree of hydration of Portland cement is also analyzed and a corresponding formula is established. The model is calibrated against the experimental data for eight different Portland cements. Simple relations between the model parameters and cement composition are obtained and used to predict hydration kinetics. The model is used to reproduce experimental results on hydration kinetics, adiabatic temperature rise, and chemical shrinkage of different cement pastes. The comparisons between the model reproductions and the different experimental results demonstrate the applicability of the proposed model, especially for cement hydration at elevated temperature and high pressure.

  14. Polyethylene glycol improves elution properties of polymethyl methacrylate bone cements.

    Science.gov (United States)

    Handal, John A; Tiedeken, Nathan C; Gershkovich, Grigory E; Kushner, Jeffrey A; Dratch, Benjamin; Samuel, Solomon P

    2015-03-01

    Bone cements are used as adjuncts to fracture fixation methods and can also function as a local drug delivery system. The ability to elute drugs makes bone cement a promising and powerful chemotherapy treatment modality for osseous tumors. However, because of poor elution rates, the clinical application of this drug delivery mode remains challenging. Soluble fillers, such as sugars, salts, or biocompatible polymers, offer a solution to improve elution rates. This study quantified the effect of polyethylene glycol (PEG) on the elution properties of three commercially available bone cements. Two grams of Vertebroplastic, Palacos, and Confidence bone cement powder containing three concentrations (0%, 20%, or 50%) of PEG filler were hand mixed with 10 mg of methotrexate. This powder mixture was then polymerized with 1.0 mL of the cement specific liquid monomer. The cylindrical elution samples were placed in saline solution and methotrexate elution was recorded for 720 h. The cumulative and daily elution rate increased as the concentration of PEG increased for each bone cement. However, the percent of increase depended on the bone cement used. Cumulative methotrexate elution increased by 40%-54% in case of the highest PEG filler concentration when compared with controls. PEG soluble filler offers a promising method for improving methotrexate drug elution in bone cement. Future studies need to optimize the PEG and bone cement ratio that produces the greatest drug elution profile without sacrificing the biomechanical properties of bone cement. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Alkali-slag cements for the immobilization of radioactive wastes

    International Nuclear Information System (INIS)

    Shi, C.; Day, R.L.

    1996-01-01

    Alkali-slag cements consist of glassy slag and an alkaline activator and can show both higher early and later strengths than Type III Portland cement, if a proper alkaline activator is used. An examination of microstructure of hardened alkali-slag cement pastes with the help of XRD and SEM with EDAX shows that the main hydration product is C-S-H (B) with low C/S ratio and no crystalline substances exist such as Ca(OH) 2 , Al (OH) 3 and sulphoaluminates. Mercury intrusion tests indicate that hardened alkali-slag cement pastes have a lower porosity than ordinary Portland cement, and contain mainly gel pores. The fine pore structure of hardened alkali-slag cement pastes will restrict the ingress of deleterious substances and the leaching of harmful species such as radionuclides. The leachability of Cs + from hardened alkali-slag cement pastes is only half of that from hardened Portland cement. From all these aspects, it is concluded that alkali-slag cements are a better solidification matrix than Portland cement for radioactive wastes

  16. Experimental study of chloride diffusivity in unsaturated ordinary Portland cement mortar

    NARCIS (Netherlands)

    Zhang, Y.; Ye, G.; Santhanam, M.

    2017-01-01

    Experiments are carried out to investigate the chloride diffusivity in partially saturated ordinary Portland cement mortars with water-to-cement (w/c) ratios of 0.4, 0.5 and 0.6. Based on resistivity measurement and Nernst-Einstein equation, the chloride diffusivities of cement mortars at various

  17. Quantitative characterization of the microstructure of fresh cement paste via random packing of polydispersed Platonic cement particles

    International Nuclear Information System (INIS)

    Xu, W X; Chen, H S

    2012-01-01

    On a microscopic scale, fresh cement paste is composed of random packing of irregular cement particles, and their initial packing behavior plays an important role in microstructural evolution. The preponderance of previous works has focused on the microstructure model by random packing of three-dimensional spheroidal particles, and little is known about non-spheroidal particles. In this paper, a modified cement particle size distribution function is used to facilitate the particle size distribution of convex polyhedral cement particles. Based on an overlapping detection algorithm, the microstructure model of fresh cement paste is simulated by the random sequential packing of Platonic cement particles of various sizes. Applying stereological tools and the serial sectioning analysis technique, the modeling microstructure composed of polydispersed Platonic cement particles is characterized and compared with that of ellipsoidal cement particles with various aspect ratios. The statistical results are investigated to evaluate the influence of cement particle shape on the microstructure of fresh cement paste. Finally, with the derived experimental and numerical results of microstructural parameters, the reliability of the statistical results is verified. (paper)

  18. Retention of crowns cemented on implant abutments with temporary cements.

    Science.gov (United States)

    Nagasawa, Yuko; Hibino, Yasushi; Nakajima, Hiroshi

    2014-01-01

    This study was to examine the retentive force of crowns to implant abutments with commercial temporary cements. Six different temporary cements were investigated. Cast crowns were cemented to the abutments using each cement and their retentive forces to abutments were determined 7 or 28 days after cementing (n=10). The retentive force of the cements to abutments varied widely among the products [27-109 N (7-day), 18-80 N (28-days)]. The retentive force of all the cements was not reduced as the time elapsed, except for two products tested. The polycarboxylate cements and paste-mixing type eugenol-free cements revealed comparable retentive force after 28 days of storage. The powder-liquid type cements showed a positive correlation (pcement between the retentive force and compressive strength. Mechanical strength of temporary cements could not be a prominent predicting factor for retention of the crowns on the abutments.

  19. Experimental study with domestic bone cement in the percutaneous vertebroplasty

    International Nuclear Information System (INIS)

    Ni Caifang; Liu Xisheng; Chen Long; Yang Huilin; Tang Tiansi; Ding Yi

    2004-01-01

    Objective: To study the feasibility of injecting domestic bone cement in the process of the percutaneous vertebroplasty. Methods: (1) Various types cement were disposed with domestic PMMA. The concretionary phases of cement were observed according to the stages and holding time. Then the most ideal ratio of the mixed cement was selected and ten cement columns were made with this ratio, which was taken as the trial group. The other ten referring to was taken as the contrast one. The biological mechanics was measured with a load and the data of the results were compared. (2) Twenty thoracic and lumbar adjacent bodies were removed intact from five human corpses. These bodies were divided into two groups, in one group PMMA were injected, the other was severed as the contrast one. Then in these twenty vertebral bodies the biological mechanics was measured and the treatment effect was evaluated. (3) In 12 healthy dogs PVP in lumber was tried so as to observe the operational difficulty during the process of injected this bone cement and CT was used to evaluate the result of PMMA, diffusion and the complications caused by it. Results: The most ideal ratio was 4:2.6:1 (g, ml, ml) between powder, monome and contrast. After injecting this kind of cement, the loading strength of these vertebral bodies was increased remarkably (P<0.01). Conclusion: Injecting domestic bone cement provides the theoretical foundations for the clinical application of PVP. (author)

  20. Characteristics of Portland blast-furnace slag cement containing cement kiln dust and active silica

    Directory of Open Access Journals (Sweden)

    A. Abdel Rahman

    2016-09-01

    Full Text Available This investigation dealt with the effect of active silica, silica fume (SF or rice husk ash (RHA, on the mechanical and physico-chemical characteristics of the hardened blended cement pastes made of Portland blast-furnace slag cement (PSC containing cement kiln dust (CKD cured under normal conditions. Two blends made of PSC and CKD, improved by SF and two blends made of PSC and CKD improved by RHA were investigated. Hardened blended cement pastes were prepared from each cement blend by using water/cement ratio (W/C of 0.30 by weight and hydrated for various curing ages of 1, 3, 7, 28 and 90 days at the normal curing conditions under tap water at room temperature. Each cement paste was tested for its physico-chemical and mechanical characteristics; these characteristics include: compressive strength and kinetics of hydration. The phase composition of the formed hydration products was identified using X-ray diffraction (XRD and differential thermal analysis (DTA. It was found that the partial substitution of PSC by 10% and 15% of CKD is associated with an increase in the rate of hydration and a subsequent improvement of compressive strength of hardened PSC–CKD pastes. In addition, the replacement of PSC, in PSC–CKD blends, by 5% active silica was accompanied by further improvement of the physico-mechanical characteristics of the hardened PSC–CKD pastes.

  1. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    TECS

    are available all over the world. The cement is affected by excessive exposure to moisture, particularly at high temperatures. Use of various additives has been suggested to enhance the durability of this cement. (Bludnov et al 1974; Paul 1975; Mingfen and Wei 1989;. Misra and Mathur 1993; Chandrawat and Yadav 2000).

  2. Advanced cementation concepts

    International Nuclear Information System (INIS)

    Howard, C.G.

    1989-10-01

    The purpose of this programme of work was to investigate whether improvements could be made to existing formulations for cement suitable for the immobilization of intermediate level radioactive waste. Two additives were selected, microsilica and limestone flour. Improvements to the cement were only slight. (author)

  3. Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

    Science.gov (United States)

    López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

    2016-01-01

    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. PMID:28787892

  4. Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete.

    Science.gov (United States)

    López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

    2016-02-02

    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.

  5. 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.

  6. 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.

  7. BEHAVIOR OF DELAYED ADDITION TIME OF SNF SUPERPLASTICIZER ON MICROSILICA-SULPHATE RESISTING CEMENTS

    Directory of Open Access Journals (Sweden)

    El-Didamony H.

    2013-09-01

    Full Text Available Most concrete produced today includes either chemical additions or chemical admixtures added to concrete, or both. These additives alter the properties of cementitious systems, including fluidity, hydration kinetics, microstructure and strength. Therefore, the development and use of the most suitable type, optimum dosage and delayed addition time (DAT of superplasticiser in concrete technology have been of increasing importance. The present investigation aimed to evaluate the influence of DAT of sulfonated naphthalene formaldehyde (SNF condensate on the hydration kinetics of sulfate resisting cement (SRC pastes incorporating 10 mass % silica fume (SF. Superplasticized cement pastes were prepared using the required water of standard consistency with different dosages and DAT of SNF. The pastes were hydrated for 90 days under normal curing conditions. The results revealed that, the fluidity of cement pastes increases with SNF content and DAT up to 7.5 minutes, due to the electrostatic repulsion between cement particles and the decrease of anhydrous C3A content that is minimized with hydration time. Also, the chemical and physico-mechanical characteristics improve with superplasticizer dosage up to 1.0 mass % and DAT up to 7.5 minutes, due to the improvement of superplasticizing effect, leading to increase the hydration of silicate phases (C3S and β-C2S and formation of more CSH, CAH and CASH. These hydrates increase the gel/space ratio, modify the microstructure and consequently enhance the strength of cement paste. FTIR spectra are in a good agreement with those of chemical and physico–mechanical characteristics.

  8. Mercury release from fly ashes and hydrated fly ash cement pastes

    Science.gov (United States)

    Du, Wen; Zhang, Chao-yang; Kong, Xiang-ming; Zhuo, Yu-qun; Zhu, Zhen-wu

    2018-04-01

    The large-scale usage of fly ash in cement and concrete introduces mercury (Hg) into concrete structures and a risk of secondary emission of Hg from the structures during long-term service was evaluated. Three fly ashes were collected from coal-fired power plants and three blend cements were prepared by mixing Ordinary Portland cement (OPC) with the same amount of fly ash. The releasing behaviors of Hg0 from the fly ash and the powdered hydrated cement pastes (HCP) were measured by a self-developed Hg measurement system, where an air-blowing part and Hg collection part were involved. The Hg release of fly ashes at room temperature varied from 25.84 to 39.69 ng/g fly ash during 90-days period of air-blowing experiment. In contrast, the Hg release of the HCPs were in a range of 8.51-18.48 ng/g HCP. It is found that the Hg release ratios of HCPs were almost the same as those of the pure fly ashes, suggesting that the hydration products of the HCP have little immobilization effect on Hg0. Increasing temperature and moisture content markedly promote the Hg release.

  9. Geometric models for lateritic soil stabilized with cement and ...

    African Journals Online (AJOL)

    . Thus this study attempted to investigate into the effects of bagasse ash on compaction and strength characteristics of cement-stabilized lateritic soil and also to develop geometric models. The compaction, California bearing ratio, unconfined ...

  10. Cementation of the solid radioactive waste with polymer-cement solutions using the method of impregnation

    International Nuclear Information System (INIS)

    Gorbunova, O.

    2015-01-01

    Cementation of solid radioactive waste (SRW), i.e. inclusion of solid radioactive waste into cement matrix without cavities - is one of the main technological processes used for conditioning low and intermediate level radioactive waste. At FSUE 'Radon' the industrialized method of impregnation has been developed and since 2003 has been using for cementation of solid radioactive waste. The technology is that the polymer-cement solution, having high penetrating properties, is supplied under pressure through a tube to the bottom of the container in which solid radioactive waste has preliminarily been placed. The polymer-cement solution is evenly moving upwards through the channels between the particles of solid radioactive waste, fills the voids in the bulk volume of the waste and hardens, forming a cement compound, the amount of which is equal to the original volume. The aim of the investigation was a selection of a cement solution suitable for SRW impregnation (including fine particles) without solution depletion and bottom layers stuffing. It has been chosen a polymer: PHMG (polyhexamethylene-guanidine), which is a stabilizing and water-retaining component of the cement solution. The experiments confirm that the polymer increases the permeability of the cement solution by a 2-2.5 factor, the viscosity by a 1.2 factor, the stability of the consistency by a 1.5-1.7 factor, and extends the operating range of the W/C ratio to 0.5-1.1. So it is possible to penetrate a volume of SRW bigger by a 1.5-2.0 factor. It has been proved, that PHMG polymer increases strength and frost-resistance of the final compounds by a 1.8-2.7 factor, and contributes to fast strength development at the beginning of hardening and it decreases Cs-137 leashing rate by a 1.5-2 factor

  11. Effect of olive waste (Husk on behavior of cement paste

    Directory of Open Access Journals (Sweden)

    Sharaf Alkheder

    2016-12-01

    Full Text Available Jordan is a famous country in terms of olive trees agriculture that resulted in a mass production of olive oil products. The huge amounts of olive waste (husk that resulted from olives processing to produce olive oil represent an environmental challenge in the country. The idea in this paper comes to use olive waste as a partial replacement for Portland cement in cement paste to conserve the environment, reduce cement consumption and increase cost efficiency. The wastes were burned properly in an oven and maintained for 6 h until it was fully transformed into ashes. Then, the oven was turned off and ashes were allowed to cool. After cooling, the material passed sieve #200 were used. The sieved ashes were used in the cement mix as a partial cement replacement for making the mortar and cement paste. Normal consistency and setting time were determined as well as soundness, compressive strength. Results indicated that normal consistency of the cement pastes containing different percentage of olive waste is somehow lower than that of the ordinary cement paste and slightly decreases with increasing the percentage. The results also indicated that the compressive strength of hardened blended cement paste containing different percentages of olive waste slightly decrease with olive waste content at 3, 7, and 28 days.

  12. 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.

  13. Personal exposure to inhalable cement dust among construction workers.

    Science.gov (United States)

    Peters, Susan; Thomassen, Yngvar; Fechter-Rink, Edeltraud; Kromhout, Hans

    2009-01-01

    Objective- A case study was carried out to assess cement dust exposure and its determinants among construction workers and for comparison among workers in cement and concrete production.Methods- Full-shift personal exposure measurements were performed and samples were analysed for inhalable dust and its cement content. Exposure variability was modelled with linear mixed models.Results- Inhalable dust concentrations at the construction site ranged from 0.05 to 34 mg/m(3), with a mean of 1.0 mg/m(3). Average concentration for inhalable cement dust was 0.3 mg/m(3) (GM; range 0.02-17 mg/m(3)). Levels in the ready-mix and pre-cast concrete plants were on average 0.5 mg/m(3) (GM) for inhalable dust and 0.2 mg/m(3) (GM) for inhalable cement dust. Highest concentrations were measured in cement production, particularly during cleaning tasks (inhalable dust GM = 55 mg/m(3); inhalable cement dust GM = 33 mg/m(3)) at which point the workers wore personal protective equipment. Elemental measurements showed highest but very variable cement percentages in the cement plant and very low percentages during reinforcement work and pouring. Most likely other sources were contributing to dust concentrations, particularly at the construction site. Within job groups, temporal variability in exposure concentrations generally outweighed differences in average concentrations between workers. 'Using a broom', 'outdoor wind speed' and 'presence of rain' were overall the most influential factors affecting inhalable (cement) dust exposure.Conclusion- Job type appeared to be the main predictor of exposure to inhalable (cement) dust at the construction site. Inhalable dust concentrations in cement production plants, especially during cleaning tasks, are usually considerably higher than at the construction site.

  14. Notes on hydrated cement fractals investigated by SANS

    International Nuclear Information System (INIS)

    Ficker, T; Len, A; Nemec, P

    2007-01-01

    Hydrated cement pastes with different water-to-cement ratios have been investigated by the small-angle scattering neutron technique. Special attention has been paid to the fractal nanostructure of the calcium silicate hydrate (C-S-H solid gel) and its basic building particles, i.e. nanometric globules. The inner stability of these particles has been tested and shown to be sufficiently persistent to withstand all spatial regroupings of the overall nanostructure caused by variations of w/c ratios

  15. Comparative study on liquefaction of creosote and chromated copper arsenate (CCA)-treated wood and untreated southern pine wood: effects of acid catalyst content, liquefaction time, temperature, and phenol to wood ratio

    Science.gov (United States)

    Hui Pan; Chung-Yun Hse; Todd F. Shupe

    2009-01-01

    Creosote- and chromated copper arsenate (CCA)-treated wood waste and untreated southern pine wood were liquefied with phenol and sulfuric acid. The effects of sulfuric acid content, liquefaction time, liquefaction temperature, and phenol to wood ratio on liquefaction rate (i.e., wood residue content) were investigated and analyzed by analysis of variance (...

  16. The large-scale blast score ratio (LS-BSR) pipeline: a method to rapidly compare genetic content between bacterial genomes.

    Science.gov (United States)

    Sahl, Jason W; Caporaso, J Gregory; Rasko, David A; Keim, Paul

    2014-01-01

    Background. As whole genome sequence data from bacterial isolates becomes cheaper to generate, computational methods are needed to correlate sequence data with biological observations. Here we present the large-scale BLAST score ratio (LS-BSR) pipeline, which rapidly compares the genetic content of hundreds to thousands of bacterial genomes, and returns a matrix that describes the relatedness of all coding sequences (CDSs) in all genomes surveyed. This matrix can be easily parsed in order to identify genetic relationships between bacterial genomes. Although pipelines have been published that group peptides by sequence similarity, no other software performs the rapid, large-scale, full-genome comparative analyses carried out by LS-BSR. Results. To demonstrate the utility of the method, the LS-BSR pipeline was tested on 96 Escherichia coli and Shigella genomes; the pipeline ran in 163 min using 16 processors, which is a greater than 7-fold speedup compared to using a single processor. The BSR values for each CDS, which indicate a relative level of relatedness, were then mapped to each genome on an independent core genome single nucleotide polymorphism (SNP) based phylogeny. Comparisons were then used to identify clade specific CDS markers and validate the LS-BSR pipeline based on molecular markers that delineate between classical E. coli pathogenic variant (pathovar) designations. Scalability tests demonstrated that the LS-BSR pipeline can process 1,000 E. coli genomes in 27-57 h, depending upon the alignment method, using 16 processors. Conclusions. LS-BSR is an open-source, parallel implementation of the BSR algorithm, enabling rapid comparison of the genetic content of large numbers of genomes. The results of the pipeline can be used to identify specific markers between user-defined phylogenetic groups, and to identify the loss and/or acquisition of genetic information between bacterial isolates. Taxa-specific genetic markers can then be translated into clinical

  17. 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

  18. Quality control of cemented waste forms

    International Nuclear Information System (INIS)

    Slate, L.J.; Wacks, M.E.; Cornellissen, H.A.W.

    1994-01-01

    Seven day and 28 day compressive strength from radwaste cementation can be predicted during the mixing and early curing stages by at least three methods: maturity, rheology, and impedance. Best results were obtained via the impedance method, where the water-to-cement ratio was seen to be the primary factor. The rheology method produced physically consistent results, but may be to cumbersome to be practical. The results of the maturity method were shown to be limited in its accuracy for determining compressive strength

  19. Cement composite delivery system.

    Science.gov (United States)

    Convery, F R; Devine, S D; Hollis, J M; Woo, S L

    1986-09-01

    Several new and innovative techniques have recently been introduced that purport to increase the strength of polymethyl methacrylate bone cement. One of these concepts is the use of carbon and polymer fibers to form a cement composite. Bone cement composites usually 1% fiber, are very difficult to use clinically. The composite is very sticky and viscous, which precludes effective hand packing or the use of conventional delivery systems. A new delivery system for very viscous materials is presented and examples of in vitro application are shown.

  20. Characteristics and properties of oil-well cements auditioned with blast furnace slag

    International Nuclear Information System (INIS)

    Sanchez, R.; Palacios, M.; Puertas, F.

    2011-01-01

    The present paper addresses the alkali activation of Portland cements containing blast furnace slag (20 and 30% by cement weight) with a view to the possible use of these materials in oil well construction. The hydration studies conducted showed that in cement/slag blends, the sodium silicate activator partially inhibited the dissolution of the silicate phases in the Portland cement, retarding cement hydration and reducing the precipitation of reaction products. Due to such partial inhibition, the cement/slag blends had significantly lower mechanical strength than Portland cements hydrated with water. 2 9Si and 2 7Al MAS NMR and BSE/EDX studies, in turn, showed that the CSH gel forming in the alkali-activated cement/slag pastes contained Al in tetrahedral positions and low Ca/Si ratios. (Author) 29 refs.

  1. Use of petroleum code as fuel in the cement industry

    International Nuclear Information System (INIS)

    Nawaz, S.

    2006-01-01

    The Cement industry is a very energy intensive industry. Each ton of cement produced requires 60 to 130 kilograms of fuel oil or an equivalent fuelling amount also requires an average 110 kWh of electricity as well over 40% of total production cost is the energy requirements in the cement industry (i.2). Normally oil, gas or coal is fired in cement kilns as traditional fuels. However use of waste, both as alternative fuels and raw materials is now common practice in many cement companies. Many different types of wastes are burnt today in cement kilns like used tyres, rubber, paper waste, waste oils, waste wood, paper sludge, sewage, animal meal and animal remains (i,4). The choice of fuel for the purpose is normally based on price and availability considering different properties of the fuel as energy contents, ash contents, moisture and volatiles contents. Petcoke is not yet produced in any petroleum refinery in Pakistan but it is abundantly available in the market worldwide as it is obtained as a waste product during the refining processes. The purpose of the current research is to figure out the suitability of petroleum coke as a fuel for cement industry both on technical and economic basis. (author)

  2. Immobilisation of strontium, nickel and iodide by a sulphate-resisting Portland cement

    International Nuclear Information System (INIS)

    Wieland, E.; Tits, J.; Spieler, P.; Dobler, J.-P.

    1998-01-01

    The interaction of Sr(II), Ni(II) and I(-I) with sulphate-resisting Portland cement was investigated under highly alkaline conditions. Batch-sorption studies were performed by contacting HTS cement (haute teneur en silice, sulphate-resisting Portland cement, Lafarge, France) with artificial cement pore water (ACW). The composition of ACW was 0.18 M KOH, 0.114 M NaOH and 1.2 mM Ca(OH) 2 . 85 Sr, 63 Ni and 125 I were used as tracers. In the experiments with Sr(II) and Ni(II), isosaccharinic acid (ISA) was added to ACW at 10 -5 M to 10 -2 M in order to study the effect of complexing ligands on radionuclide retention. The stability of the tracer solutions and the cement suspensions were first assessed. Moreover, the inventory of the stable elements were determined in cement and cement pore water. We then studied the kinetics of the radionuclide-cement interaction process and measured the dependence of the distribution ratio (R d ) on the concentration of ISA and on the concentration of cement particles (S:L ratio). In the case of 63 Ni and 125 I a strong decrease in the distribution ratio (R d ) with increasing S:L ratio was observed. There is strong indication that the inventory of the stable fraction of an element present in cement pore water accounts for the retention of the radioisotope fraction. The results further indicate that phase transformations may occur in non-pre-equilibrated cement systems (non-equilibrium conditions) which affect 63 Ni uptake by HTS cement. The distribution ratios measured on HTS cement were compared with values obtained from measurements on important cement components (portlandite, CSH/C(A)SH-phases)

  3. Hybrid Alkaline Cements: Bentonite-Opc Binders

    Directory of Open Access Journals (Sweden)

    Ines Garcia-Lodeiro

    2018-03-01

    Full Text Available Moderately alkaline activators can be used to formulate cementitious binders with a high Supplemetary Cementitious Materials (SCMs and a low portland cement content (hybrid alkaline cements. This study aimed to prepare hybrid alkaline cements containing large percentages of dehydroxylated bentonite (BT and small Portland cement (OPC fractions, with 5% Na2SO4 as a solid alkaline activator. The hydration kinetics of the pastes hydrated in water in the presence and absence of the solid activator were assessed by isothermal conduction calorimetry, whilst the reaction products were characterised with X-Ray Powder Diffraction (XRD and Fourier-transform Infrared Spectroscopy (FTIR. The presence of the alkaline activator hastened OPC and BT/OPC hydration: more heat of hydration was released, favouring greater initial bentonite reactivity. The portlandite forming during cement hydration reacted readily with the Na2SO4, raising medium alkalinity and enhancing bentonite dissolution and with it reaction product precipitation (primarily (N,C-A-S-H-like gels that co-exist with C-S-H- or C-A-S-H-like gels. The presence of sulfate ions favoured the formation of AFm-like phases. Preceding aspects accelerated the hydration reactions, with the formation of more reaction product and matrix densification. As a result, the 28 days Na2SO4 activated systems developed greater mechanical strength than the water-hydrated systems, with the 60% BT/40% OPC blends exhibiting higher compressive strength than the 100% OPC pastes.

  4. Use of alternative fuels in the Polish cement industry

    Energy Technology Data Exchange (ETDEWEB)

    Mokrzycki, Eugeniusz; Uliasz-Bochenczyk, Alicja [Polish Academy of Sciences, Mineral and Energy Economy Research Inst., Krakow (Poland); Sarna, Mieczyslaw [Lafarge Cement Polska S.A., Malogoszcz (Poland)

    2003-02-01

    Alternative fuels are made up of mixtures of different wastes, such as industrial, municipal and hazardous wastes. These fuels need to have an appropriate chemical energy content which depends on the type of components and their organic content. An industry that is particularly well suited to the employment of alternative fuels is the cement industry. There are a number of factors that promote the use of alternative fuels in cement kilns. Of these factors, the most notable are: the high temperatures developed, the appropriate kiln length, the long period of time the fuel stays inside the kiln and the alkaline environment inside the kiln. There are a number of countries that use their own alternative fuels in cement plants. These fuels have different trade names and they differ in the amounts and the quality of the selected municipal and industrial waste fractions used. The fuels used should fall within the extreme values of parameters such as: minimum heating value, maximum humidity content, and maximum content of heavy and toxic metals. Cement plants in Poland also use alternative fuels. Within the Lafarge Group, the cement plants owned by Lafarge Poland Ltd. have initiated activities directed at promoting the wider use of alternative fuels. There are a number of wastes that can be incinerated as fuel in cement plants. Some that can be mentioned are: selected combustible fractions of municipal wastes, liquid crude-oil derived wastes, car tyres, waste products derived from paint and varnish production, expired medicines from the pharmaceutical industry and others. The experience gained by the cement plants of Lafarge Cement Poland Ltd confirms that such activities are economically and ecologically beneficial. The incineration of alternative fuels in cement plants is a safe method for the utilisation of waste that is ecologically friendly and profitable for the industrial plants and society alike. (Author)

  5. Portland cement hydration and early setting of cement stone intended for efficient paving materials

    Science.gov (United States)

    Grishina, A.

    2017-10-01

    Due to the growth of load on automotive roads, modern transportation engineering is in need of efficient paving materials. Runways and most advanced highways require Portland cement concretes. This makes important the studies directed to improvement of binders for such concretes. In the present work some peculiarities of the process of Portland cement hydration and early setting of cement stone with barium hydrosilicate sol were examined. It was found that the admixture of said sol leads to a shift in the induction period to later times without significant change in its duration. The admixture of a modifier with nanoscale barium hydrosilicates increases the degree of hydration of the cement clinker minerals and changes the phase composition of the hydration products; in particular, the content of portlandite and tricalcium silicate decreases, while the amount of ettringite increases. Changes in the hydration processes of Portland cement and early setting of cement stone that are caused by the nanoscale barium hydrosilicates, allow to forecast positive technological effects both at the stage of manufacturing and at the stage of operation. In particular, the formwork age can be reduced, turnover of molds can be increased, formation of secondary ettringite and corrosion of the first type can be eliminated.

  6. 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.

  7. Plug cementing: Horizontal to vertical conditions

    Energy Technology Data Exchange (ETDEWEB)

    Calvert, D.G.; Heathman, J.F.; Griffith, J.E.

    1995-12-31

    This paper presents an in-depth study of cement plug placement that was conducted with large-scale models for the improvement of plug cementing practices and plug integrity. Common hole and workstring geometries were examined with various rheology and density ratios between the drilling fluid and cement. The critical conditions dictating the difference between success and failure for various wellbore angles and conditions were explored, and the mechanisms controlling slurry movement before and after placement are now better understood. An understanding of these mechanisms allows the engineer to better tailor a design to specific hole conditions. Controversial concepts regarding plug-setting practices have been examined and resolved. The cumulative effects of density, rheology, and hole angle are major factors affecting plug success. While the Boycott effect and an extrusion effect were observed to be predominant in inclined wellbores, a spiraling or {open_quotes}roping{close_quotes} effect controls slurry movement in vertical wellbores. Ultimate success of a cement plug can be obtained if allowances are made for these effects in the job design, provided all other previously published recommended placement practices are followed. Results of this work can be applied to many sidetracking and plug-to-abandon operations. Additionally, the understanding of the fluid movement (creep) mechanisms holds potential for use in primary and remedial cementing work, and in controlling the placement of noncementitious fluids in the wellbore.

  8. Prediction of chloride ingress and binding in cement paste

    DEFF Research Database (Denmark)

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

    2007-01-01

    This paper summarizes recent work on an analytical model for predicting the ingress rate of chlorides in cement-based materials. An integral part of this is a thermodynamic model for predicting the phase equilibria in hydrated Portland cement. The model’s ability to predict chloride binding...... 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...... 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...

  9. Integrin binding and MAPK signal pathways in primary cell responses to surface chemistry of calcium silicate cements.

    Science.gov (United States)

    Shie, Ming-You; Ding, Shinn-Jyh

    2013-09-01

    Cell attachment, proliferation and differentiation on different materials depend largely on the surface properties of the materials. This study sheds light on the mechanism by which the modulation of the chemical composition of calcium silicate cements with different Si/Ca molar ratios could produce different cell responses. Two primary cell types (human mesenchymal stem cells (hMSCs) and human dental pulp cells (hDPCs)) were used to elicit the changes in total DNA content, integrin subunit levels, phosphor-focal adhesion kinase (pFAK) levels, and mitogen-activated protein kinase (MAPK) signaling pathway activity at the cell attachment stage. The effect of small interfering RNA (siRNA) transfection targeting collagen type I (COL I) and fibronectin (FN) was also evaluated. The results indicated that increased total DNA content, pFAK and total integrin levels were observed upon an increase in cement Si content. Cements with different Si/Ca ratios did not cause the variations of interleukin 1β (IL-1β), epidermal growth factor (EGF) and tumor necrosis factor-α (TNF-α) ligands. The Si-rich cement facilitated COL I and α2β1 subintegrin expression, while Ca-rich cement promoted FN and αvβ3 subintegrin expression. Si component of the calcium silicates stimulated cell adhesion via activation of MAPK/extracellular signal-regulated kinase (ERK) and p38 signaling pathways more effectively than did by Ca component, but it did not affect c-Jun NH2-terminal kinase (JNK) activity. Inhibition of MAPK/ERK and MAPK/p38 signaling pathways in hMSCs and hDPCs significantly attenuated adhesion, proliferation and differentiation as assessed according to total DNA content and alkaline phosphatase activity. hMSCs and hDPCs from the three different donors exhibited a similar preference for cell behaviors. The results of the current study suggest that calcium silicate cements with a higher Si content have the potential to serve as excellent supports for primary cells. Unraveling the

  10. Effect of Limestone Powder on Acid Attack Characteristics of Cement Pastes

    Directory of Open Access Journals (Sweden)

    Shuhua LIU

    2014-12-01

    Full Text Available The acid resistance of cement pastes containing limestone powder with two different water-binder (w/b ratios exposed to acetic (pH = 4 and sulfuric acid (pH = 2 solutions respectively were investigated in this paper. Limestone powder, fly ash and silica fume were also added to the cement paste mixture at different proportions. Static and flowing aqueous environments were set in this experiment. Strength and microstructure of the pastes after acid attack were investigated by using strength test, X-ray diffractometer (XRD and scanning electron microscopy (SEM. The experimental results show that the erosion degree depends not only on pH value of the solution and w/b ratio of the pastes, but also on the content of limestone powder. Acetic acid reacts with calcium hydroxide and carbonate thus dissolving the pastes, while sulfuric acid consumed calcium hydroxide, and generated gypsum and ettringite. The consumption of calcium hydroxide in the flowing solution group is higher than that in the static solution because the flowing sulfuric acid solution has negative effect upon the gypsum crystallization. Fly ash and silica fume are beneficial to limestone cement paste because of the less calcium hydroxide formation, which is among the hydrates vulnerable to acid erosion. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6231

  11. Characterization of polymer-modified cement as a solidification agent for the radwaste

    International Nuclear Information System (INIS)

    Ji, Young-Yong; Kwak, Kyung-Kil; Hong, Dae-Seok; Ryu, Woo-Seog

    2012-01-01

    Highlights: ► Polymer-modified cement (PMC) by modification with water-based resins. ► Determination of the optimized polymer content. ► Evaluation of the improved chemical resistance of the PMC. ► Decrease of the amount of ions released into the demineralized water. ► Highly improved property for the nuclide diffusivity at the Co-60. - Abstract: Polymer-modified cement can be produced by partially replacing cement hydrate binders in ordinary Portland cement with polymeric compounds. It is known that the addition of the polymer to the cement paste leads to improved quality, which would be expected to have a high chemical resistance. In order to investigate the application as a solidification agent for the radwaste, polymer-modified cement specimens, by modification with water-based resins, were prepared according to the polymer content from 0% to 30%. The optimized polymer content in the cement pastes was then determined through the compressive strength and the porosity test. Finally, the improved chemical resistance of the polymer-modified cement with the optimized polymer content was evaluated by the thermal cycling, the immersion, and the leaching tests. From the test results, the amount of ions released into the water showed lower values of about 20% at the polymer-modified cement. Especially, a highly improved nuclide diffusivity of Co-60 was observed in the polymer-modified cement.

  12. Study on Microstructural Evolution and Strength Growth and Fracture Mechanism of Cemented Paste Backfill

    OpenAIRE

    Fu, Jian-Xin; Song, Wei-Dong; Tan, Yu-Ye

    2016-01-01

    The relations among the uniaxial compressive strength of cemented paste backfill (CPB) with solid phase mass fraction, cement sand ratio, and curing age were studied. The UCS of CPB samples increased exponentially with the increase of solid phase mass fraction and curing age but increased linearly with the increase of cement sand ratio. The results of X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that the strength was determined by the amount of ettringite and C-S-H ge...

  13. The large-scale blast score ratio (LS-BSR pipeline: a method to rapidly compare genetic content between bacterial genomes

    Directory of Open Access Journals (Sweden)

    Jason W. Sahl

    2014-04-01

    Full Text Available Background. As whole genome sequence data from bacterial isolates becomes cheaper to generate, computational methods are needed to correlate sequence data with biological observations. Here we present the large-scale BLAST score ratio (LS-BSR pipeline, which rapidly compares the genetic content of hundreds to thousands of bacterial genomes, and returns a matrix that describes the relatedness of all coding sequences (CDSs in all genomes surveyed. This matrix can be easily parsed in order to identify genetic relationships between bacterial genomes. Although pipelines have been published that group peptides by sequence similarity, no other software performs the rapid, large-scale, full-genome comparative analyses carried out by LS-BSR.Results. To demonstrate the utility of the method, the LS-BSR pipeline was tested on 96 Escherichia coli and Shigella genomes; the pipeline ran in 163 min using 16 processors, which is a greater than 7-fold speedup compared to using a single processor. The BSR values for each CDS, which indicate a relative level of relatedness, were then mapped to each genome on an independent core genome single nucleotide polymorphism (SNP based phylogeny. Comparisons were then used to identify clade specific CDS markers and validate the LS-BSR pipeline based on molecular markers that delineate between classical E. coli pathogenic variant (pathovar designations. Scalability tests demonstrated that the LS-BSR pipeline can process 1,000 E. coli genomes in 27–57 h, depending upon the alignment method, using 16 processors.Conclusions. LS-BSR is an open-source, parallel implementation of the BSR algorithm, enabling rapid comparison of the genetic content of large numbers of genomes. The results of the pipeline can be used to identify specific markers between user-defined phylogenetic groups, and to identify the loss and/or acquisition of genetic information between bacterial isolates. Taxa-specific genetic markers can then be translated

  14. TECHNOLOGY AND EFFICIENCY OF PEAT ASH USAGE IN CEMENT CONCRETE

    Directory of Open Access Journals (Sweden)

    G. D. Liakhevich

    2015-01-01

    Full Text Available One of the main ways to improve physical and mechanical properties of cement concrete is an introduction of ash obtained due to burning of fossil fuels into concrete mix. The concrete mixes with ash are characterized by high cohesion, less water gain and disintegration. At the same time the concrete has high strength, density, water resistance, resistance to sulfate corrosion. The aim of this paper is to explore the possibility to use peat ash and slag of peat enterprises of the Republic of Belarus in the concrete for improvement of its physical and mechanical properties and characteristics of peat ash, slag, micro-silica, cement, superplasticizing agent. Compositions and technology for preparation of concrete mixes have been developed and concrete samples have been have been fabricated and tested in the paper. It has been shown that the concrete containing ash, slag obtained due to burning of peat in the industrial installations of the Usiazhsky and Lidsky Peat Briquette Plants and also MK-85-grade micro-silica NSPKSAUsF-1-grade superplasticizing agent have concrete tensile strength within 78–134 MPa under axial compression and 53 MPa – for the control composition. This index is 1.5–2.5 times more than for the sample containing no additives.The usage of peat ash, slag together with MK-85-grade micro-silica and NSPKSAUsF-1-grade superplasticizing agent for fabrication of concrete and reinforced bridge and tunnel structures will provide the following advantages: reduction of cross-sectional area of structures while maintaining their bearing capacity due to higher value of tensile strength in case of axial compression; higher density, waterand gas tightness due to low water cement ratio; high resistance to aggressive environment due to lower content of capillary pores that ensures bridge structure longevity; achievement of environmental and social impacts.

  15. Experimental evaluation of cement materials for solidifying sodium nitrate

    International Nuclear Information System (INIS)

    Sasaki, Tadashi; Numata, Mamoru; Suzuki, Yasuhiro; Kubo, Yoshikazu

    2003-03-01

    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)

  16. Evidences for high gas content beneath the Gorely volcano in Kamchatka (Russia) based on very low Vp/Vs ratio revealed from local earthquake tomography

    Science.gov (United States)

    Koulakov, Ivan; Kuznetsov, Pavel; Ilyich Gordeev, Evgeny; Nikolaevich Chebrov, Viktor

    2015-04-01

    The Gorely volcano, which is located at distance of 70 km from Petropavlovsk-Kamchatsky, is one of the most active volcanoes in Kamchatka. Nowadays, a large fumarole inside the volcano crater ejects approximately 11,000 tons of gases daily. During the last thousands years, eruptions in Gorely were mostly basaltic that determined the shield type of the volcano. However, a large caldera of ~20 km diameter dated at approximately 30,000 years indicates that the volcano has high explosive potential. To identify the feeding mechanisms and to assess the possibility of future large eruptions, scientists from IPGG, Novosibirsk, have deployed the first temporary seismic network on the Gorely volcano. This network consisted of 21 uniformly distributed seismic stations that operated for one year from August 2013 to July 2014. Most of the time during the observation period, dozens to hundreds events per day and frequent tremors were recorded which indicated significant activity inside the volcano. As a result of preliminary processing, almost 300 events were identified during only several weeks of recording. The available distributions of events and stations enables fairly high resolution in the derived seismic velocity models, as demonstrated by a number of synthetic tests. A striking feature of the tomographic inversion is an average ratio of Vp/Vs=1.53, which is an exceptionally low compared to other volcanic areas. We propose that this low Vp/Vs ratio is a signature of high content of gases beneath the volcano. Higher values of Vp/Vs beneath the crater below ~2 km depth might indicate some presence of liquid water, which comes from deeper sources and is transformed to the steam at shallower levels due to the decompression. It appears that Gorely is a kind of a huge steam boiler covered with a solid cover consisting of previously erupted basaltic layers. The fumarole inside the crater plays the role of safety valve which prevents the accumulation of excessive pressure inside

  17. Formulation of geopolymer cement using mixture of slag and class f fly ash for oil well cementing

    Science.gov (United States)

    Kanesan, Dinesh; Ridha, Syahrir; Rao, Prasath

    2017-05-01

    The increase in greenhouse gas emissions has been a factor for the increase in global temperature. Geopolymer cement has been intensively studied to replace conventional ordinary Portland cement, however the focus is limited to civil purposes under atmospheric conditions. This research focuses on the formulation of geopolymer cement to be used in oil well cementing application by taking account the effect of sodium hydroxide (NaoH) molarity, ratio of alkali binder and fly ash, amount of dispersant for oilwell operation under temperature ranging of 80°C and 90C° and pressure of 1000 and 3000psi. The formulated composition is tested for fluid loss where the standard has been from 60 to 80 ml. The cement slurry is cured in a 50mm x 50mm x 50mm mold for period of 24 hours. Four manipulating variables were set in formulating the cement slurry namely, the ratio between fly ash and slag to alkali binder, ratio of sodium hydroxide (NaoH) to sodium silicate, molarity of NaoH and amount of dispersant added. After running a set of 16 experiment, sample (12) was found to possess the best rheological properties and fluid loss according to API RP10B. It was found that as the curing temperature and pressure increase, the compressive strength of the formulated geopolymer cement also increased.

  18. Radiolytic gas generation from cement-based waste hosts for DOE low-level radioactive wastes

    International Nuclear Information System (INIS)

    Dole, L.R.; Friedman, H.A.

    1986-01-01

    Using cement-based immobilization binders with simulated radioactive waste containing sulfate, nitrate, nitrite, phosphate, and fluoride anions, the gamma- and alpha-radiolytic gas generation factors (G/sub t/, molecules/100 eV) and gas compositions were measured on specimens of cured grouts. These tests studied the effects of; (1) waste composition; (2) the sample surface-to-volume ratio; (3) the waste slurry particle size; and (4) the water content of the waste host formula. The radiolysis test vessels were designed to minimize the ''dead'' volume and to simulate the configuration of waste packages

  19. Investigations on cement/polymer Waste packages containing intermediate level waste and organic exchange resins

    International Nuclear Information System (INIS)

    ELsourougy, M.R.; Zaki, A.A.; Aly, H.F.; Khalil, M.Y.

    1995-01-01

    Polymers can be added to cements to improve its nuclear waste immobilization properties. This trend in cementation processes is attracting attention and requiring through investigations. In this work, polymers of different kinds were added to ordinary portland cement for the purpose of solidifying intermediate level liquid wastes and organic ion exchange resins. Epoxy polymer such as Kemapoxy-150 reduced the leaching rate of cesium compared to cement alone. Latex to cement ratio less than 4% caused an increase in leaching rate of cesium. When cesium was absorbed to an organic resin its leachability was improved. 5 figs., 4 tabs

  20. 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.

  1. 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.

  2. Small Scale Variations in Carbon Oxygen Ratio

    International Nuclear Information System (INIS)

    Valkovic, Vladivoj; Sudac, Davorin; Nad, Karlo; Obhodas, Jasmina

    2013-06-01

    The aim of the research reported here is the development of a methodology for the measurement of small scale variations in chemical elements concentrations, in particular of carbon - oxygen ratio. Knowledge of the C/O ratio is of importance to many problems in various fields. Here we single out the application in obtaining important information about the oil fields. The most fundamental reservoir parameters - oil, gas and water content - are critical factors in determining how each oil field should be developed. It is well established that carbon to oxygen ratio log yields accurate and repeatable data that can be used to identify and monitor reserves depletion. Recent improvements in neutron generator and gamma detector technologies resulted in small devices which allowed through-tubing measurements. Although the ratio of carbon and oxygen yields is a measure of the amount of oil around the tool it should be realized that a carbon signal can originate from several sources including the borehole, the cement behind the casing, the formation rock and the formation fluid. In order to evaluate these contributions individually we are proposing the modification of the neutron generator by insertion of segmented associated alpha particle detector. From the measurement of time of flight spectra (alpha particle detector - start signal; gamma ray detector - stop signal) it would be possible to determine the location of gamma ray producing voxel and in such a way to determine radial variations in several chemical elements concentrations, in particular of carbon to oxygen ratio. (authors)

  3. 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.

  4. 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.

  5. Corrosion rate of rebars from linear polarization resistance and destructive analysis in blended cement concrete after chloride loading

    NARCIS (Netherlands)

    Polder, R.B.; Peelen, W.H.A.; Bertolini, L.; Guerriere, M.

    2002-01-01

    Concrete specimens with various binders including Portland cement, fly ash, blast furnace slag and composite cement and three water-to-cement ratios were subjected to cyclic wetting with salt solution and drying. Specimens contained six mild steel bars at two cover depths and two activated titanium

  6. Viability of Eggshells Ash Affecting the Setting Time of Cement

    OpenAIRE

    Fazeera Ujin; Kamran Shavarebi Ali; Zarina Yasmin Hanur Harith

    2016-01-01

    This research paper reports on the feasibility and viability of eggshells ash and its effects on the water content and setting time of cement. An experiment was carried out to determine the quantity of water required in order to follow standard cement paste of normal consistency in accordance with MS EN 196-3:2007. The eggshells ash passing the 90µm sieve was used in the investigation. Eggshells ash with percentage of 0%, 0.1%, 0.5%, 1.0%, 1.5% and 2.0% were constituted to replace the cement....

  7. Mechanical Properties and Durability of CNT Cement Composites

    Directory of Open Access Journals (Sweden)

    María del Carmen Camacho

    2014-02-01

    Full Text Available In the present paper, changes in mechanical properties of Portland cement-based mortars due to the addition of carbon nanotubes (CNT and corrosion of embedded steel rebars in CNT cement pastes are reported. Bending strength, compression strength, porosity and density of mortars were determined and related to the CNT dosages. CNT cement paste specimens were exposed to carbonation and chloride attacks, and results on steel corrosion rate tests were related to CNT dosages. The increase in CNT content implies no significant variations of mechanical properties but higher steel corrosion intensities were observed.

  8. Microstructure of hydrated cement pastes as determined by SANS

    International Nuclear Information System (INIS)

    Sabine, T.; Bertram, W.; Aldridge, L.

    1999-01-01

    Full text: Technologists have known how to make concrete for over 2000 years but despite painstaking research no one has been able to show how and why concrete sets. Part of the problem is that the calcium silicate hydrate (the gel produced by hydrating cement) is amorphous and cannot be characterised by x-ray crystallographic techniques. Small angle neutron scattering on instrument V12a at BENSC was used to characterise the hydration reactions and show the growth of the calcium silicate hydrates during initial hydration and the substantial differences in the rate of growth and structure as different additives are used. SANS spectra were measured as a function of the hydration from three different types of cement paste: 1) Ordinary Portland Cement made with a water to cement ratio of about 0.4; 2) A blend of Ordinary Portland Cement(25%) and Ground Granulated Blast Furnace Slag (75%) with a water to cement ration of about 0.4; 3) A dense paste made from silica fume(24%), Ordinary Portland Cement (76%) at a water to powder ratio of 0.18. The differences in the spectra are interpreted in terms of differences between the microstructure of the pastes

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

    Science.gov (United States)

    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 OCA, with specimens of formulation. PMID:24825796

  10. Thermophysical properties of blends from Portland and sulfoaluminate-belite cements

    International Nuclear Information System (INIS)

    Mojumdar, S.C.; Janotka, I.

    2002-01-01

    The behavior of mortars with blends consisting of sulfoaluminate-belite cements and ordinary Portland cement made with cement to sand ratio of 1:3 by weight and w/c = 0.5 maintained for 90 days at 20 0 C either at 60% relative humidity - dry air or 100% relative humidity - wet air. The results show insufficient character of hydraulic activity of sulfoaluminate-belite cements. Their quality has been improved. The replacement of 15 wt % of sulfoaluminate-belite cement by ordinary Portland cement influences strength positively and elasticity modulus values as well as hydrated phases and pore structure development of sulfoaluminate-belite/ordinary Portland cement blends relative to pure sulfoaluminate-belite cement systems. The above statements confirm the possible making technologies, when improvements in sulfoaluminate-belite cements quality will be achieved. One would then anticipate the competition in usages between sulfoaluminate-belite/ordinary Portland cement and blast furnace-slag Portland cement systems in the practice. It is important to consider because sulfoaluminate-belite cements are of great advantage from the viewpoint of energy savings and quantity of CO 2 released during their production. Thermal characteristics of the samples were studied by thermogravimetry and differential thermal analysis from room temperature to 1000 0 C in air atmosphere. Generally, four significant temperature regions on thermogravimetry curves with the respective differential thermal analysis peak temperature for all types of samples are observed (Authors)

  11. 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.

  12. Technical difficulties in the cementing of horizontal shale gas wells in Weiyuan block and the countermeasures

    Directory of Open Access Journals (Sweden)

    Jinping Yuan

    2016-05-01

    Full Text Available When well cementing is conducted in horizontal shale gas wells in Weiyuan block of the Weiyuan–Changning State Shale Demonstration Area, Sichuan Basin, the oil-based drilling fluid is not compatible with cement slurry, is difficult to be displaced because of its high density, and cement sheath tends to be broken in the situations of large-scale stimulated reservoir volume fracturing. In view of these problems, a series of studies were carried out specifically on the theoretical basis of cement sheath sealing mechanical parameters, oil-displacement preflush improving the interface cementation quality, toughness set cement satisfying large-scale fracturing requirements and cementing technology conducive to the wellbore integrity. The following achievements were made. First, the theoretical model of cement sheath mechanical integrity taking into account the plastic characteristics and interface cementation strength of cement sheath is instructive to the mechanical design of set cement for horizontal shale gas wells, avoiding the micro-annulus as much as possible. Second, oil-displacement preflush is developed and it is well compatible with oil-based drilling fluids and cement slurry with the flushing efficiency on oil-based drilling fluids higher than 90%. Third, the tough set cement which is developed based on the theoretical model of cement sheath sealing integrity not only guarantees higher compressive strength, but decreases Young's modulus by 30%. Forth, it is confirmed that water displacement cementing technology suitable for shale gas wells is conducive to improving the wellbore seal integrity. These research findings were applied in 12 horizontal wells. It is indicated that the quality cementing ratio of horizontal segment reaches 92% and the post fracturing effect is very good, which guarantees the sealing integrity of wellbores and provides a technical support for the highly efficient development of shale gas reservoirs.

  13. Solidification of ion exchange resin wastes in hydraulic cement

    International Nuclear Information System (INIS)

    Neilson, R.M. Jr.; Kalb, P.; Fuhrmann, M.; Colombo, P.

    1982-01-01

    Work has been conducted to investigate the solidification of ion exchange resin wastes with portland cements. These efforts have been directed toward the development of acceptable formulations for the solidification of ion exchange resin wastes and the characterization of the resultant waste forms. This paper describes formulation development work and defines acceptable formulations in terms of ternary phase compositional diagrams. The effects of cement type, resin type, resin loading, waste/cement ratio and water/cement ratio are described. The leachability of unsolidified and solidified resin waste forms and its relationship to full-scale waste form behavior is discussed. Gamma irradiation was found to improve waste form integrity, apparently as a result of increased resin crosslinking. Modifications to improve waste form integrity are described. 3 tables

  14. Bone tissue aging affects mineralization of cement lines.

    Science.gov (United States)

    Milovanovic, Petar; Vom Scheidt, Annika; Mletzko, Kathrin; Sarau, George; Püschel, Klaus; Djuric, Marija; Amling, Michael; Christiansen, Silke; Busse, Björn

    2018-02-07

    Cement lines are known as thin peripheral boundaries of the osteons. With a thickness below 5 μm their composition of inorganic and organic compounds has been a matter of debate. Here, we hypothesized that cement lines become hypermineralized and their degree of mineralization is not constant but related to the tissue age of the osteon. Therefore, we analyzed the calcium content of osteons and their corresponding cement lines in a range of different tissue ages reflected by osteonal mineralization levels in femoral cortical bone of both postmenopausal women with osteoporosis and bisphosphonate-treated cases. Quantitative backscattered electron imaging (qBEI) showed that cement lines are hypermineralized entities with consistently higher calcium content than their corresponding osteons (mean calcium content: 29.46 ± 0.80 vs. 26.62 ± 1.11 wt%; p lines compared to the osteonal bone (8.78 ± 0.66 vs. 6.33 ± 0.58, p lines. A clear positive correlation of cement line mineralization and the mineralization of the osteon was observed (r = 0.839, p = 0.003). However, the magnitude of the difference between cement line and osteonal calcium content decreased with increased osteonal calcium content (r = -0.709, p line calcium content (p lines may represent another tissue-age related phenomenon, given that it strongly relates to the osteonal mineralization level. Understanding of the cement lines' mineralization and their changes in aging and disease states is important for predicting crack propagation pathways and fracture resistance mechanisms in human cortical bone. Copyright © 2018 Elsevier Inc. All rights reserved.

  15. COMPARATIVE ASSESSMENT OF RICE HUSK ASH, POWDERED GLASS AND CEMENT AS LATERITIC SOIL STABILIZERS

    Directory of Open Access Journals (Sweden)

    Adebisi Ridwan

    2016-10-01

    Full Text Available This paper compares the stabilizing effects of three different materials, namely: rice husk ash, powdered glass, and cement on the properties of lateritic soil. The basic properties of the lateritic soil were first obtained through colour, moisture content determination, specific gravity, particle size distribution and Atterberg limits tests. Each of the stabilizing materials was then mixed with the lateritic soil in varying percentages of 2.5%, 5%, 7.5%, 10%, 12.5% and 15% by weight of the soil. Thereafter, compaction and California bearing ratio (CBR tests were carried out on the sample mixes to determine the effects of the materials on the lateritic soil. Chemical tests were also carried out on the samples to determine their percentage oxides composition. The compaction test showed that the highest maximum dry densities (MDD obtained for the mixed samples were 2.32 g/cm3 (at 2.5% cement addition, 2.28g/cm3 (at 5% powdered glass (PG addition and 2.18 g/cm3 (at 5% rice husk ash (RHA addition with corresponding optimum moisture contents (OMC of 10.06%, 14.3% and 12.31% respectively. The CBR tests showed that the CBR values increased in all cases as the materials were added with those of the cement and powdered glass giving the highest values and showing close semblance under unsoaked conditions. The chemical test showed that the significant oxides present in the cement, powdered glass and rice husk ash were CaO (53.60%, SiO2 (68.45% and SiO2 (89.84% respectively.

  16. Optimization of properties of cement-bonded particleboard manufactured from cotton stalk and sawdust containing calcium chloride CaCl2 as an additive

    Directory of Open Access Journals (Sweden)

    morteza nazerian

    2016-06-01

    Full Text Available The aim of this study was investigation of hydration behavior and mechanical properties of cement-bonded particleboard manufactured from different ratio of cotton stalk to poplar wood particle, sawdust content and CaCl2 as additive at different weight ratios. At the first, curing time of cement paste containing different amount of additive (CaCl2 and wood and cotton fines was determined. Besides, the effect of additive (CaCl2 content, weight ratio of cotton to poplar wood particles and percentage of sawdust on modulus of rupture (MOR, modulus of elasticity (MOE and internal bonding (IB of cement-bonded particleboard was evaluated by response surface methodology (RSM. In order to optimize the properties of panels, a mathematical model equation (second order plan was done by a computer simulation program. According to results, there is a good coincidence between predicted values and actual values (R2 for MOR, MOE and IB was 0.93, 0.90 and 0.95, respectively. This study showed that the response surface methodology (RSM can be effectively used for modeling of panel properties. Results showed that using weight ratio of cotton to poplar particle 43:57 the MOR, MOE and IB of panels can be reached to maximum values (12.5, 2545 and 0.35 MPa, respectively. Simultaneously, application of 4.5% additive and 9% sawdust at had a positive effect on the properties of the panels.

  17. Concrete Durability Properties and Microstructural Analysis of Cement Pastes with Nopal Cactus Mucilage as a Natural Additive

    OpenAIRE

    Ramírez-Arellanes, S.; Cano-Barrita, P. F. de J.; Julián-Caballero, F.; Gómez-Yañez, C.

    2012-01-01

    The present study evaluated the addition of a 3% nopal cactus mucilage solution to cement pastes, in its effects on setting times, flow, hydration, and microstructure, as well as on capillary water absorption and chloride diffusion in concrete. Hydration was characterized through XRD and microstructure was characterized with SEM. The mucilage solution/cement and water/cement ratios tested were 0.30, 0.45, and 0.60. The results in cement pastes indicate that the addition of mucilage increases ...

  18. Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement

    Directory of Open Access Journals (Sweden)

    Juan García Olmo

    2013-06-01

    Full Text Available Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC, high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected.

  19. Research, Calculation for Designing the Technological Equipment Line of Cementation with 3,000 Tonnes of Solid Waste/Year Capacity for ZOC Plan

    International Nuclear Information System (INIS)

    Tran Van Hoa; Ngo Van Tuyen; Nguyen Ba Tien; Le Ba Thuan; Phung Quoc Khanh; Mai Duc Lanh; Vuong Huu Anh; Luu Cao Nguyen; Duong Dinh Tho; Phung Vu Phong; Nguyen An Thai; Pham Quang Minh

    2013-01-01

    Technological process and equipment line for cementation with 3,000 tons of solid wastes/year capacity for ZOC plant was studied according to the quantity, the composition and the property of solid wastes from ZOC plant. The influence of several parameters with cementation process such as cement mixing ratio, size, moisture and NaCl content in residue, which affected to mechanical and chemical strength of waste block after cementation was evaluated. The calculation and designing for cementation equipment line were thus conducted and total investment cost of construction and installation as well as operation of this equipment line was also estimated. Radiation safety and environmental protection for waste treatment facility was calculated and the design on radiation safety and environmental protection for equipment line was proposed. Technological process and design document of this production line seemed to be reasonable because it is consistent with properties of wastes as well as it has been commonly used in the world to stabilize solid residues in nuclear industry. The advantages of this propose were simple structure of the devices, locally made, easy operation, locally available and inexpensive materials resulting in low cost of investment and operation. (author)

  20. Reference materials for ratio of moisture content and bulk density of blast furnace coke for neutron moisture and density meters: development and use experience

    Directory of Open Access Journals (Sweden)

    V. D. Savelov

    2016-01-01

    Full Text Available The article deals with reference materials for moisture and bulk density of blast furnace coke for graduation of neutron moisture and density meters. Reference materials are produced from substances and materials which element content is identical to coke elemental content coke.

  1. Studies on Soil Cements : 2 — Physicochemical Properties of the Hardened Soil Cement Pastes.

    OpenAIRE

    Abo El Enein, A. [صلاح عبد الغني ابو العينين; Abdel-Moez, M.S.; Mikhail, R. Sh.; Hekal, E.E.

    1982-01-01

    Various hardened soil-cement pastes were prepared from dry mixtures of montmorillonite clay and portland cement clinker by using different W/C ratios of 0.20, 40, 0.60 and 0.80 and cured in air for various ages. Compressive strength tests were done on the hardened fresh pastes, while the nitrogen adsorption studies were carried out on the D-dried specimens. The variations in compressive strength could be related to the physicochemical properties and the pore structure of the hardened pastes. ...

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

    Directory of Open Access Journals (Sweden)

    Qiang He

    Full Text Available 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.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.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 defect.Our findings suggested a new bioactive

  3. Microstructure and mechanical properties of microwave-assisted heating of pozzolan-Portland cement paste at a very early stage

    Directory of Open Access Journals (Sweden)

    Natt Makul

    2013-12-01

    Full Text Available Portland-pozzolan cement pastes at a very early stage subjecting to microwave heating were investigated. Microwave with a 2.45 GHz and multimode cavity was used for the experiments. The pastes containing pozzolan materials (pulverized fuel ash, metakaolin and silica fume were proportioned with a 0.38 water/solid mass ratio and a 20% by weight replacement of total solid content. It was observed that the temperature increased continuously during microwave heating. Some ettringite rods and amorphous C-S-H fibers appear at 4 hrs. The metakaolin-cement paste exhibited little difference between the watercured and microwave-cured pastes. For the silica fume-cement paste the SF particles under microwave curing had dispersed more than with the 4 hr–cement paste. The produced phases included calcium silicate hydrate, calcium hydroxide and xenotile. The pastes can be developed in compressive strength quite rapidly and also consumed more Ca(OH2 in the pozzolan reaction to produce more C-S-H.

  4. 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.

  5. Sidoarjo Mud: A Potential Cement Replacement Material

    OpenAIRE

    Biyanto T.R.; Masilamani M.B.; Bayuaji R.; Nuruddin M.F.

    2010-01-01

    This paper presents an experimental and analytical research conducted to study the properties of mortar when treated Sidoarjo mud was added into the mix replacing partially the cement content. The replacements were done at 0, 5, 10, 15, and 20%. Compression, tensile, porosity and Ultrasonic Pulse Velocity (UPV) tests were conducted to evaluate the effect of Sidoarjo mud in mortar. Analyses on the mud were also conducted through X-ray diffraction (XRD), X-ray Fluorescence (XRF), and scanning e...

  6. The role of chemical admixtures in the formation of the structure of cement stone

    Directory of Open Access Journals (Sweden)

    Sopov Viktor

    2017-01-01

    Full Text Available The influence of sulfates and carbonates of potassium and sodium on the character of the formation of the microstructure of cement stone was studied. The role of cations in the structure formation of cement stone is shown. The efficiency of chemical additives, hardening accelerators, was estimated from the ratio of the volumes of gel and capillary micropores. The ratio of gel and capillary pores allows to determine the efficiency coefficient of the action of chemical additives. It is shown that the potassium carbonate for Portland cement is the most effective additive for hardening in terms of microstructure modification, and potassium sulfate for slag Portland cement.

  7. Cementation of liquid radioactive waste

    International Nuclear Information System (INIS)

    Efremenkov, V.

    2004-01-01

    The cementation methods for immobilisation of radioactive wastes are discussed in terms of methodology, chemistry and properties of the different types of cements as well as the worldwide experience in this field. Two facilities for cementation - DEWA and MOWA - are described in details

  8. 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.

  9. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

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

  10. EFFECTS OF FLY ASH TRANSITION METAL CONTENT AND FLUE GAS HCL/SO2 RATIO ON MERCURY SPECIATION IN WASTE COMBUSTION

    Science.gov (United States)

    The paper presents results of research on the effect of sulfur dioxide (SO2):HCI ratio on heterogeneous Hg0 oxidation. The addition of SO2 to moist flue gas at high SO2:HCI ratios (4:1 to 10:1) caused a decrease in oxidation of Hg0 relative to flur gas without SO2. This is attrib...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

    2017-03-14

    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.

  13. 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.

  14. Thermal behavior of asphalt cements

    International Nuclear Information System (INIS)

    Claudy, P.M.; Letoffe, J.M.; Martin, D.; Planche, J.P.

    1998-01-01

    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 C n H 2n+2 in an asphalt, as seen by DSC, should be a single peak. For 20 g 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.)

  15. Peat Soil Stabilization using Lime and Cement

    Science.gov (United States)

    Zambri, Nadhirah Mohd; Ghazaly, Zuhayr Md.

    2018-03-01

    This paper presents a study of the comparison between two additive Lime and Cement for treating peat soil in term of stabilization. Peat and organic soils are commonly known for their high compressibility, extremely soft, and low strength. The aim of this paper is to determine the drained shear strength of treated peat soil from Perlis for comparison purposes. Direct Shear Box Test was conducted to obtain the shear strength for all the disturbed peat soil samples. The quick lime and cement was mixed with peat soil in proportions of 10% and 20% of the dry weight peat soil. The experiment results showed that the addition of additives had improved the strength characteristics of peat soil by 14% increment in shear strength. In addition, the mixture of lime with peat soil yield higher result in shear strength compared to cement by 14.07% and 13.5% respectively. These findings indicate that the lime and cement is a good stabilizer for peat soil, which often experienced high amount of moisture content.

  16. Retention, marginal leakage, and cement solubility of provisional crowns cemented with temporary cement containing stannous fluoride.

    Science.gov (United States)

    Lewinstein, Israel; Fuhrer, Nitzan; Gelfand, Katerina; Cardash, Harold; Pilo, Raphael

    2003-01-01

    This in vitro study investigated the (1) retention and microleakage of provisional crowns cemented with temporary cements to which stannous fluoride (SnF2) was added, and (2) solubility of these cements. Provisional crowns were constructed of acrylic resin with shoulder preparations for 12 molars. The crowns were luted with Tempbond, Tempbond NE, and Freegenol temporary cements, and also with SnF2 added to these cements. Specimens were thermocycled 100 times, stored for 6 days, and immersed in 0.5% basic fuschin. Seven days after cementation, crown removal (retention) tests were conducted. Marginal leakage was assessed using a five-level scale to score dye penetration. Solubility in water of the cements with and without SnF2 was assessed using cement disks. Freegenol was more retentive than the other cements. The incorporation of SnF2 significantly increased the retention capacity of Freegenol and Tempbond NE but had no effect on Tempbond. Tempbond showed significantly higher dye penetration than Freegenol. The addition of SnF2 did not alter the dye penetration of the cements. There were no significant differences in the solubility of the cements. However, the incorporation of SnF2 increased the solubility of Freegenol and Tempbond NE (P crowns cemented with Tempbond NE and Freegenol but did not affect the retention of those cemented with Tempbond. The marginal leakage of crowns cemented with the tested temporary cements with and without the incorporation of SnF2 was similar. However, the addition of SnF2 increased the solubility of the cements.

  17. 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.

  18. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    TECS

    ting. It is used in industrial floorings, ship decks, railway passenger coach floorings, hospital floors, ammunition factory floors, missile silos and underground armament factories and bunkers. Recently, concrete of high compres- sive and tensile strength prepared with magnesium oxy- chloride cement and recycled rubber ...

  19. 1D Compressibility of DMS Treated With Cement-GGBS Blend

    Directory of Open Access Journals (Sweden)

    Kaliannan Suaathi

    2017-01-01

    Full Text Available Great quantities of dredged marine soils (DMS have been produced from the maintenance of channels, anchorages and for harbour development. DMS have the potential to pose ecological and human health risks and it is also considered as a geowaste. Malaysia is moving towards the sustainability approach and one of the key factors to achieve it is to reduce waste. Thus, this geowaste should be generated as a new resource to substitute soil for civil works such as for land reclamation and backfilling. This shows the improved settlement of consolidation in treated DMS. DMS is referred to as a cohesive soil which includes clayey silt, sandy clay, silty clay and organic clay. This type of soil has low strength and high compressibility. The objectives were achieved through literature review analysis and also laboratory test which was one dimensional oedometer test. On the other hand, treated DMS with more ground granulated blast furnace slag (GGBS gives a lower settlement compared to specimen with higher percentage of cement in a treated soil. Thus this shows that cement content can be reduced in soil solidification when GGBS is added. The optimum binder ratio found was 3:7 where 3 is cement and 7 is GGBS.

  20. Foamed Cement Interactions with CO2

    Energy Technology Data Exchange (ETDEWEB)

    Verba, Circe [National Energy Technology Lab. (NETL), Albany, OR (United States); Montross, Scott [National Energy Technology Lab. (NETL), Albany, OR (United States). Oak Ridge Inst. for Science and Education (ORISE); Spaulding, Richard [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Dalton, Laura [National Energy Technology Lab. (NETL), Albany, OR (United States). Oak Ridge Inst. for Science and Education (ORISE); National Energy Technology Lab. (NETL), Morgantown, WV (United States); Crandall, Dustin [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Moore, Jonathan [National Energy Technology Lab. (NETL), Morgantown, WV (United States); Glosser, Deborah [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Huerta, Nicolas [National Energy Technology Lab. (NETL), Albany, OR (United States); Kutchko, Barbara [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2017-01-23

    Geologic carbon storage (GCS) is a potentially viable strategy to reduce greenhouse emissions. Understanding the risks to engineered and geologic structures associated with GCS is an important first step towards developing practices for safe and effective storage. The widespread utilization of foamed cement in wells may mean that carbon dioxide (CO2)/brine/foamed cement reactions may occur within these GCS sites. Characterizing the difference in alteration rates as well as the physical and mechanical impact of CO2/brine/foamed cement is an important preliminary step to ensuring offshore and onshore GCS is a prudent anthropogenic CO2 mitigation choice. In a typical oil and gas well, cement is placed in the annulus between the steel casing and formation rock for both zonal isolation and casing support. The cement must have sufficient strength to secure the casing in the hole and withstand the stress of drilling, perforating, and fracturing (e.g. API, 1997, 2010 Worldwide Cementing Practices). As such, measuring the mechanical and properties of cement is an important step in predicting cement behavior under applied downhole stresses (Nelson, 2006). Zonal isolation is the prevention of fluids migrating to different zones outside of the casing and is strongly impacted by the permeability of the wellbore cement (Nelson, 2006). Zonal isolation depends on both the mechanical behavior and permeability (a physical property) of the cement (Mueller and Eid, 2006; Nelson, 2006). Long-term integrity of cement depends on the mechanical properties of the cement sheath, such as Young’s Modulus (Griffith et al., 2004). The cement sheath’s ability to withstand the stresses from changes in pressure and temperature is predominantly determined by the mechanical properties, including Young’s modulus, Poisson’s ratio, and tensile strength. Any geochemical alteration may impact both the mechanical and physical properties of the cement, thus

  1. 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.

  2. Use of Factory-Waste Shingles and Cement Kiln Dust to Enhance the Performance of Soil Used in Road Works

    Directory of Open Access Journals (Sweden)

    Aly Ahmed

    2009-01-01

    Full Text Available An experimental work was conducted to study the use of factory-waste roof shingles to enhance the properties of fine-grained soil used in road works. Cement kiln dust (CKD, a cogenerated product of Portland cement manufacturing, was used as a stabilizing agent while the processed shingles were added to enhance the soil tensile strength. The effects of shingles on strength and stability were evaluated using the unconfined compressive strength, splitting tensile strength, and California Bearing Ratio (CBR tests. The results showed that the use of CKD alone resulted in a considerable increase in the unconfined compressive strength but had a small effect on the tensile strength. The addition of shingles substantially improved the tensile strength of the stabilized soil. A significant reduction in the capillary rise and a slight decrease in the permeability were obtained as a result of shingle addition. An optimal shingle content of 10% is recommended to stabilize the soil.

  3. Persistent hyperlactatemia-high central venous-arterial carbon dioxide to arterial-venous oxygen content ratio is associated with poor outcomes in early resuscitation of septic shock.

    Science.gov (United States)

    Zhou, Juandi; Song, Jia; Gong, Shijin; Li, Li; Zhang, Haixiang; Wang, Minjia

    2017-08-01

    Several studies reported Pv-aCO 2 /Ca-vO 2 ratio as a surrogate of VCO 2 /VO 2 to detect global tissue hypoxia. The present study aimed to evaluate the prognostic value of Pv-aCO 2 /Ca-vO 2 ratio combined with lactate levels during the early phases of resuscitation in septic shock. A retrospective study was conducted in 144 septic shock patients in a 30-bed mixed ICU. A Pv-aCO 2 /Ca-vO 2 ratio>1.4 was considered abnormal. Patients were classified into four predefined groups according to lactate levels and Pv-aCO 2 /Ca-vO 2 ratio after the first 6h of resuscitation. Sequential Organ Failure Assessment (SOFA) score at day 3 was assessed. A Kaplan-Meier curve showed the survival probabilities at day 28 using a log-rank test to evaluate the differences between groups. A receiver operating characteristics (ROC) curve evaluated the ability of lactate, Pv-aCO 2 /Ca-vO 2 ratio and Pv-aCO 2 /Ca-vO 2 ratio combined with lactate to predict mortality at day 28. Combination of hyperlactatemia and high Pv-aCO 2 /Ca-vO 2 ratio was associated with poor SOFA scores and low survival rates at day 28 (Pseptic shock can better predict the prognosis of patients. The Pv-aCO 2 /Ca-vO 2 ratio may become a useful parameter supplementary to lactate in the resuscitation of septic shock. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Utilization of mine tailings as partial cement replacement

    DEFF Research Database (Denmark)

    Sigvardsen, Nina Marie; Nielsen, M.R.; Ottosen, Lisbeth M.

    2017-01-01

    Depositing mine tailings entail major economic costs and negative environmental impacts. Thus finding an alternative to depositing is of interest. This study focused on the use of mine tailings as partial cement replacement, thereby preventing depositing the mine tailings. At the same time......, such use would reduce the CO2 emission related to the production of cement. Mine tailings from two different mines Zinkgruvan (Sweden) and Nalunaq (Greenland) were both tested as 5 and 10 % cement replacement. All mortar specimens with mine tailings had lower compressive strength compared to a reference...... compared to a specimen containing a 10 % replacement of cement with coal fly ash, commonly used in Denmark. The compressive strength of specimens containing mine tailings exceeded the compressive strength of the specimen containing coal fly ash, indicating further the amorphous content of volcanic decent...

  5. Content-aware video quality assessment: predicting human perception of quality using peak signal to noise ratio and spatial/temporal activity

    Science.gov (United States)

    Ortiz-Jaramillo, B.; Niño-Castañeda, J.; Platiša, L.; Philips, W.

    2015-03-01

    Since the end-user of video-based systems is often a human observer, prediction of human perception of quality (HPoQ) is an important task for increasing the user satisfaction. Despite the large variety of objective video quality measures, one problem is the lack of generalizability. This is mainly due to the strong dependency between HPoQ and video content. Although this problem is well-known, few existing methods directly account for the influence of video content on HPoQ. This paper propose a new method to predict HPoQ by using simple distortion measures and introducing video content features in their computation. Our methodology is based on analyzing the level of spatio-temporal activity and combining HPoQ content related parameters with simple distortion measures. Our results show that even very simple distortion measures such as PSNR and simple spatio-temporal activity measures lead to good results. Results over four different public video quality databases show that the proposed methodology, while faster and simpler, is competitive with current state-of-the-art methods, i.e., correlations between objective and subjective assessment higher than 80% and it is only two times slower than PSNR.

  6. Encapsulation of ILW raffinate in the Dounreay cementation plant

    International Nuclear Information System (INIS)

    Sinclair, G.F.

    1998-01-01

    The Dounreay Cementation Plant has been designed and constructed to encapsulate the first cycle liquid raffinate arising from the reprocessing of irradiated Research Reactor fuel into a cementitious matrix. The acidic liquid waste is conditioned with sodium hydroxide prior to mixing with the cement powders (a 9:1 ratio of Blast Furnace Slag / Ordinary Portland Cement with 5% Lime). The complete cement mixing process is performed within the 500-liter drum, which provides the waste package primary containment. The plant has recently been commissioned and has commenced routine operation, processing stocks of existing raffinate that has been stored at Dounreay for up to 30 years. The waste loading per drum has been optimised within the constraints of the chemical composition of the raffinate, with an expected plant throughput of 2.5 m 3 /week. (author)

  7. Preterm delivery among people living around Portland cement plants

    International Nuclear Information System (INIS)

    Yang, C.-Y.; Chang, C.-C.; Tsai, S.-S.; Huang, H.-Y.; Ho, C.-K.; Wu, T.-N.; Sung, F.-C.

    2003-01-01

    The Portland cement industry is the main source of particulate air pollution in Kaohsiung city. Data in this study concern outdoor air pollution and the health of individuals living in communities in close proximity to Portland cement plants. The prevalence of delivery of preterm birth infants as significantly higher in mothers living within 0-2 km of a Portland cement plant than in mothers living within 2-4 km. After controlling for several possible confounders (including maternal age, season, marital status, maternal education, and infant sex), the adjusted odds ratio was 1.30 (95% I=1.09-1.54) for the delivery of preterm infants for mothers living close to he Portland cement plants, chosen at the start to be from 0 to 2 km. These data provide further support for the hypothesis that air pollution can affect he outcome of pregnancy

  8. Cementation of Nuclear Graphite Using Geopolymers

    International Nuclear Information System (INIS)

    Girke, N.A.; Steinmetz, H-J.; Bukaemsky, A.; Bosbach, D.; Hermann, E.; Griebel, I.

    2016-01-01

    Geopolymers are solid aluminosilicate materials usually formed by alkali hydroxide or alkali silicate activation of solid precursors such as coal fly ash, calcined clay and/or metallurgical slag. Today the primary application of geopolymer technology is in the development of alternatives to Portland-based cements. Variations in the ratio of aluminium to silicon, and alkali to silicon or addition of structure support, produce geopolymers with different physical and mechanical properties. These materials have an amorphous three-dimensional structure that gives geopolymers certain properties, such as fire and acid resistance, low leach rate, which make them an ideal substitute for ordinary Portland cement (OPC) in a wide range of applications especially in conditioning and storage of radioactive waste. Therefore investigations have been initiated on how and to which amount graphite as a hydrophobic material can be mixed with cement or concrete to form stable waste products and which concretes fulfil the necessary specifications best. As a result, geopolymers have been identified as a promising matrix for graphite containing nuclear wastes. With geopolymers, both favourable properties in the cementation process and a high long time structural stability of the products can be achieved. Investigations include: • direct mixing of graphite with geopolymers with or without sand as a mechanically stabilizing medium; • production of cement-graphite granulates as intermediate products and embedding of these granulates in geopolymer; • coating of formed graphite pieces with geopolymer.The report shows that carbon in the form of graphite can both be integrated with different grain size spectra as well as shaped in the hydraulic binder geopolymer and meets the requirements for a stable long-term immobilisation. (author)

  9. Evaluation of pozzolime mixtures as a sustainable binder to replace portland cement in structural concrete

    Directory of Open Access Journals (Sweden)

    Kadum Nahida

    2017-01-01

    Full Text Available This study aimed to evaluate the properties of concrete mixes produced mainly of hydrated lime and different types of Pozzolan. This mixture, which is nominated as PozzoLime, is presented as an alternative sustainable binder to replace Portland cement in concrete. The study tends to optimize the Pozzolan to lime proportions with respect to workability and strength of concrete. The investigated parameters are; water to binder ratio, aggregate to binder ratio and type of Pozzolan. The effects of these parameters on properties of the mixture in fresh and hardened states are studied. The included tests were; temperature profile, slump, fresh and oven-dry density, compressive, splitting tensile and flexural strength and dynamic modulus of elasticity. Silicafume, Fly ash and Metakaolin were the used Pozzolan in this study .The temperature profile through hydration (coffee cup test shows that all PozzoLime mixtures have significantly less environmental impacts (evolved heat than Portland cement. The results also show that structural concrete with more than 28 MPa compressive strength at 28 days age can be produced by a binder consisted of 1:1 by weight ratio of Silicafume to hydrated lime, , and with a total binder content of 333 kg/m3.

  10. Cementing of low pressure formations

    Energy Technology Data Exchange (ETDEWEB)

    Brownlie, D. [Trican Well Service Ltd., Calgary, AB (Canada); Coupland, M. [Baytex Energy Ltd., Calgary, AB (Canada)

    2001-07-01

    This paper proposed a solution to the notorious problem of squeeze cementing low pressure formations. It is a well known fact within the petroleum industry that it is difficult to squeeze cement low pressure formations in certain areas. Short of fracturing, most geological formations will not allow cement to penetrate the actual rock. In standard cement squeezing, cement slurries are placed across perforations and then pressure is applied to force the cement into perforation tunnels against the formation causing partial dehydration of the slurry. The cement left in the perforation tunnels makes a seal between the formation and the wellbore that has high compressive strength and low permeability. However, experience has shown that some wells are not capable of holding the hydrostatic pressure of a water column. This paper presented case studies that examined formations with modified geology, a highly unconsolidated sandstone where large volumes of sand were extracted during the production process. In particular, the paper refers to a low pressure field in Western Canada, the remedial cementing in Lloydminster. Within a 3 year period 18 zones were cement squeezed and drilled out. Nine of the zones were cement squeezed using a retainer with thixotropic cement followed by a 0:1:0 Class G cement. Only 11 per cent of the 9 zones was successful on the first attempt. The other 9 zones were cement squeezed using the bullhead technique in which a fluid is shot into the well casing before the downhole equipment. This latter technique proved to be more successful on the first attempt. 2 refs.

  11. Effect of Different Inclusion Level of Condensed Distillers Solubles Ratios and Oil Content on Amino Acid Digestibility of Corn Distillers Dried Grains with Solubles in Growing Pigs

    Directory of Open Access Journals (Sweden)

    P. Li

    2015-01-01

    Full Text Available The purpose of this experiment was to determine and compare the digestibility of crude protein (CP and amino acids (AA in full-oil (no oil extracted and de-oiled (oil extracted corn distillers dried grains with solubles (DDGS with different condensed distillers solubles (CDS ratios. Six barrows (29.6±2.3 kg fitted with ileal T-cannula were allotted into a 6×6 Latin square design. Each period was comprised of a 5-d adaption period followed by a 2-d collection of ileal digesta. The five test diets contained 62% DDGS as the sole source of AA. A nitrogen-free diet was used to measure the basal endogenous losses of CP and AA. Chromic oxide (0.3% was used as an index in each diet. The results showed that CP and AA were very similar in 5 DDGS, but the standardized ileal digestibility (SID of lysine (from 56.16% to 71.15% and tryptophan (from 54.90% to 68.38% had the lowest values and largest variation within the essential AA, which suggests reduced availability of AA and different levels of Maillard reactions in the five DDGS. The apparent ileal digestibility and SID of CP and most of AA in full-oil DDGS (sources 1 and 2 were greater (p0.05 than full-oil with high CDS ratio DDGS (source 2; however, the SID of most AA of de-oiled with low CDS ratios DDGS (source 3 were non-significantly lower (p>0.05 than de-oiled with high CDS ratio DDGS (source 4; and the de-oiled DDGS with middle CDS ratio (source 5 but with different drying processing had the lowest SID AA values. In conclusion, de-oiled DDGS had lower SID of CP and AA than full-oil DDGS; a higher CDS ratio tended to decrease the SID of AA in full-oil DDGS but not in de-oiled DDGS; and compared with CDS ratio, processing, especially drying, may have more of an effect on AA digestibility of DDGS.

  12. Glass recycling in cement production--an innovative approach.

    Science.gov (United States)

    Chen, Guohua; Lee, Harry; Young, King Lun; Yue, Po Lock; Wong, Adolf; Tao, Thomas; Choi, Ka Keung

    2002-01-01

    An innovative approach of using waste glass in cement production was proposed and tested in a laboratory and cement production plant. The laboratory characterization of 32 types of glass show that the chemical composition of glass does not vary significantly with its color or origin but depends on its application. The alkali content of glass, a major concern for cement production varies from 0 to 22%. For the glass bottles mainly found in Hong Kong waste glasses, the alkali content (Na2O) ranges from 10 to 19% with an average around 15%. There is no significant change of the SO2 content in the gas exhaust of the rotary kiln when about 1.8 t/h of glass bottles were loaded along with the 280-290 t/h raw materials. The content of NOx, mainly depends on the temperature of the kiln, does not show significant change either. The SO3 content of the clinker is comparable with that obtained without the loading of glass. The alkaline content shows a slight increase but still within three times the standard deviation obtained from the statistical data of the past year. The detailed analysis of the quality of the cement product shows that there is not any significant impact of glass for the feeding rate tested.

  13. Sidoarjo Mud: A Potential Cement Replacement Material

    Directory of Open Access Journals (Sweden)

    Biyanto T.R.

    2010-01-01

    Full Text Available This paper presents an experimental and analytical research conducted to study the properties of mortar when treated Sidoarjo mud was added into the mix replacing partially the cement content. The replacements were done at 0, 5, 10, 15, and 20%. Compression, tensile, porosity and Ultrasonic Pulse Velocity (UPV tests were conducted to evaluate the effect of Sidoarjo mud in mortar. Analyses on the mud were also conducted through X-ray diffraction (XRD, X-ray Fluorescence (XRF, and scanning electron microscope with an energy dispersive X-ray analysis system (SEM-EDX. The results showed that the mud could be used as a cementitious material with optimum ordinary Portland cement (OPC replacement at 10%.

  14. 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.

  15. 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

  16. Changes in Organic, Inorganic contents, Carbon Nitrogen ratio in decomposing Avicennia marina and Rhizophora mucronata leaves on tidal mudf lats in Hajambro creek, Indus delta, Pakistan

    Directory of Open Access Journals (Sweden)

    Zafar Farooqui

    2014-01-01

    Full Text Available Leaf decomposition of Avicennia marina (Forskal Vierh in Denkschr and Rhizophora mucronata (Poiret was studied in situ using litterbag s in Hajambro creek, Indus delta. A single exponential model was presented, which best described the rate of decomposition for both the species. The rate of decomposition was species specific, A. marina leaves decomposed slower than the R. mucronata (p<0.001. The time in days required for 50% loss of the initial dry mass (t1/2 was 49.55 days for the A. marina and 44.43 days in case of R. mucronata. The organic content in the leaves was high initially but decresed gradually during decomposition, which is negatively correlated with inorganic contents. This study will help in the management and conservation of mangrove ecosystem of Hajambro creek, Indus delta, Pakistan.

  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. DESIGN OF CEMENT COMPOSITES WITH INCREASED IMPERMEABILITY

    Directory of Open Access Journals (Sweden)

    Fedyuk Roman Sergeevich

    2016-05-01

    Full Text Available The paper deals with the development of composite binders for producing concrete with improved characteristics of gas, water and vapor permeability. The authors investigate the processes of composite materials formation in order of decreasing scale levels from macro to nanostructures. The criteria for optimization of the volume of dispersed additives in concrete are offered. The authors theoretically studied the technological features of the formation of hydrated cement stone structure. A positive effect of nanodispersed additives on the structure and physico-mechanical properties of cement composite materials are predicted. Thanks to its improved features, such as good ratio of strength and body density, high density and lifetime, the modified concrete may be used when solving various practical tasks of the construction branch.

  19. An alternative approach to estimate the W/C ratio of hardened concrete using image analysis

    NARCIS (Netherlands)

    Valcke, S.; Nijland, T.G.; Larbi, J.A.

    2009-01-01

    The water cement (w/c) ratio is a typical quality parameter for concrete. The NT Build 361 Nordtest method is a standard for estimating the w/c ratio in hardened concrete and is based on the relationship between the ilc ratio and the capillary porosity in the cement paste. The latter can be

  20. The Optimation of Crude Fiber Content of Diet for Fattening Madura Beef Cattle to Achieve Good A:P Ratio and Low Methane Production

    Science.gov (United States)

    Luthfi, N.; Restitrisnani, V.; Umar, M.

    2018-02-01

    Abtract. Methane (CH4) is one of the major greenhouse gases being reducted. This study was carried out to determine the optimum of crude fiber needed for fattening Madura beef cattle to achieve low methane production. Twenty-four male madura beef cattles with an average body weight of 206.89 ± 7.82 kg were used in this study. Cattle were fed contained 47.65 - 70.23 % Total Digestible Nutrients (TDN), 9.22 - 13.20% Crude Protein (CP), and 10.25 - 28.53% Crude Fiber (CF). Correlation analysis was used to describe the correlations among crude fiber,Methane, and Acetate:Propionate acid ratio. The result showed that crude fiber (%) had medium possitive correlation with methane and the equation was y = 0.0936x + 5.4853 with determination as much as 33.98%. The Acetate: propionate acid had positive correlation withmethane and the equation was y = 1.1121x + 3.581 with determination as much as 61.64%. Crude fiber (%) had low possitive correlation with A/P ratio and the equation was y = 0.039x + 2.4437 with determination as much as 9.56%. According to the results, it can be concluded that the optimum ofcrude fiberof diet for Madura beef cattle should be 15.38% to obtain A:P ratio of 3 or less and methane production of 6.91 MJ/d.

  1. Rheology of acrylic bone cements.

    Science.gov (United States)

    Ferracane, J L; Greener, E H

    1981-01-01

    The rheological properties of setting acrylic bone cements were examined with a rotational cone and plate viscometer. The cements were tested over two orders of magnitude of shear rate to determine the nature of any non-Newtonian flow behavior. All three cements behaved with moderate pseudoplasticity (i.e., shear thinning) during setting, suggesting the use of higher pressures during administration for better flow and penetration. The low viscosity brand was found to be nearly one-half as viscous as the conventional cements during the working time (i.e., 2-5 minutes). A series of sieving experiments were performed to determine the particle size distributions of the powder components. Statistical analysis (chi square) showed the cements to have different distributions, with the low viscosity brand containing a larger proportion of smaller polymer particles. This difference is thought to contribute to the lower viscosity of this cement.

  2. Production of portland cement using Moroccan oil shale and comparative study between conventional cement plant and cement plant using oil shale

    International Nuclear Information System (INIS)

    Doumbouya, M.; Kacemi, K.E.; Kitane, S.

    2012-01-01

    Like the use of coal ash from power plants as an addition to cement, oil shale are used for cement production on an industrial scale in Estonia, China, USA and Germany. Oil shale can be utilized in manufacturing the cement. In addition to the utilization of these by-products after combustion, it can also reduce the required temperature for the clinkering reactions during the production of Portland clinker. We performed a study on the Moroccan oil shale to maximize the use of oil shale ash in the manufacturing of Portland cement. We found that Moroccan oil shale ash can be used up to 30% with 70% Portland clinker without altering its principle properties. The corresponding temperature required to generate the required liquid for the clinkering reactions as well as the essential ingredients for clinker was found to be around 850 to 1000 deg. C. The operating temperatures for this optimized blend ratio were found to 1000 deg. C. The resulting Portland clinker from this ratio will need further testing in accordance with international standards for Portland cement to examine properties like strength and setting time. (author)

  3. 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.

  4. Structure investigations on Portland cement paste by small angle neutron scattering

    International Nuclear Information System (INIS)

    Dragolici, C.A.; Lin, A.

    2004-01-01

    Hydrated Portland cement is a very complex material. Cement paste consists of many crystalline and non-crystalline phases in various ranges of sizes (μm and nm scale). The crystalline phases are embedded in amorphous phases of hydration products. We investigated the structural changes of hydrating phases in a time interval up to 18 days, at Budapest Neutron Center's SANS spectrometer. The small angle neutron scattering of Portland cements prepared with a various water-to-cement ratios, gave us information about the microstructure changes in the material. Fractals were a suitable way for structure modelling. Some comments regarding the opportunity of using the most common models are pointed out. (authors)

  5. Modeling and Optimization of Cement Raw Materials Blending Process

    Directory of Open Access Journals (Sweden)

    Xianhong Li

    2012-01-01

    Full Text Available This paper focuses on modelling and solving the ingredient ratio optimization problem in cement raw material blending process. A general nonlinear time-varying (G-NLTV model is established for cement raw material blending process via considering chemical composition, feed flow fluctuation, and various craft and production constraints. Different objective functions are presented to acquire optimal ingredient ratios under various production requirements. The ingredient ratio optimization problem is transformed into discrete-time single objective or multiple objectives rolling nonlinear constraint optimization problem. A framework of grid interior point method is presented to solve the rolling nonlinear constraint optimization problem. Based on MATLAB-GUI platform, the corresponding ingredient ratio software is devised to obtain optimal ingredient ratio. Finally, several numerical examples are presented to study and solve ingredient ratio optimization problems.

  6. Simultaneous enhancement of methane production and methane content in biogas from waste activated sludge and perennial ryegrass anaerobic co-digestion: The effects of pH and C/N ratio.

    Science.gov (United States)

    Dai, Xiaohu; Li, Xiaoshuai; Zhang, Dong; Chen, Yinguang; Dai, Lingling

    2016-09-01

    It is necessary to find an appropriate strategy to simultaneously enhance the methane production and methane content in biogas from waste activated sludge (WAS) and grass co-digestion. In this study an efficient strategy, i.e., adjusting the initial pH 12 and C/N ratio 17/1, for simultaneous enhancement of methane production and methane content in biogas from WAS and perennial ryegrass co-digestion was reported. Experimental results indicated that the maximal methane production was 310mL/gVSadd at the optimum conditions after 30-d anaerobic digestion, which was, respectively, about 1.5- and 3.8-fold of the sole WAS and sole perennial ryegrass anaerobic digestion. Meanwhile, the methane content in biogas was about 74%, which was much higher than that of sole WAS (64%) or sole perennial ryegrass (54%) anaerobic digestion. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Study of a hydraulic calcium phosphate cement for dental applications.

    Science.gov (United States)

    Serraj, Siham; Michaïlesco, Pierre; Margerit, Jacques; Bernard, Bruce; Boudeville, Philippe

    2002-01-01

    Calcium phosphate-based cements (CPCs) have attracted much interest because of their good osteoconductivity for bone reconstruction. We obtained CPCs by mixing calcium bis-dihydrogenophosphate monohydrate (MCPM) and calcium oxide with water or sodium phosphate buffers (NaP) as liquid phase. Cement samples with different calcium-to-phosphate ratios (Ca/P), liquid-to-powder ratios (L/P) and liquid phases were analyzed by X-rays diffraction (XRD), pH-metry, extensometry and calorimetry. Antibacterial activity on two bacterial strains (Streptococcus mutans, Lactobacillus acidophilus) and a polycontaminated bacterial inoculum was also studied using the agar diffusion method. The best mechanical properties (approximately 25 MPa) corresponded to Ca/P ratios between 1.67 and 2.5, a 1 M sodium phosphate buffer pH 7, as liquid phase and a L/P ratio of 0.6ml g(-1). The final setting time increased with the Ca/P ratio. The setting expansion, around 1-2%, depended on the Ca/P and L/P ratios. The inner temperature of the cements rose to 45 degrees during setting then decreased rapidly. The injectability was 100% up to 3.5 min and then decreased. It increased with increasing the L/P ratio but to the detriment of the compressive strength and setting time. XRD analysis indicated that the setting reaction led to a mixture of calcium hydroxide and calcium-deficient hydroxyapatite even for a Ca/P ratio of 1.67. Consequently, the pH of the surrounding fluids rose to 11.5-12 during their dissolution. Bacterial growth inhibition was only clearly observed for Ca/P>or=2. This bioactive calcium phosphate cement can potentially be employed for pulp capping and cavity lining as classical calcium hydroxide-based cements, but it is not usable, in the present formulation, for root canal filling because of its short setting time.

  8. Immobilization in cement of ion exchange resins from Spanish nuclear reactors

    International Nuclear Information System (INIS)

    Huebra, A.G. de la; Murillo, R.; Ortiz, S.J.

    1990-01-01

    Ion exchange materials used at nuclear power plants can be immobilized in cements less expensive than polymer matrices. Cement solidification of spent ion exchange resins shows swelling and cracking troubles (during setting time, or of storage). The objective of this study was to select the types of cement that produce the best quality on immobilization of three kinds of resins and to set up cement formulations containing the maximum possible loading of resin. Four cements were selected to carried out the study. After a study of hydration-dehydration phenomena of ion exchange resins, a systematic work has been carried out on immobilization. Tests were performed to study compressive strength and underwater stability by changing water/cement ratio and resin/cement ratio. Mixtures made with water, cement and resin only were loaded with 10% by weight dry resin. Mixtures with higher loadings show poor workability. Tests were carried out by adding organic plasticizers and silica products to improve waste loading. Plasticizers reduced water demand and silica products permit the use of more water. Leaching tests have been performed at 40 O C. In conclusion Blast Furnace Slag is the best cement for immobilization of ion exchange resin both bead and powdered form for mechanical strength, stability and leaching

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

    Directory of Open Access Journals (Sweden)

    Jie Zhang

    2015-06-01

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

  10. Mass fractions of 52 trace elements and zinc/trace element content ratios in intact human prostates investigated by inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Zaichick, Sofia; Zaichick, Vladimir; Nosenko, Sergey; Moskvina, Irina

    2012-11-01

    Contents of 52 trace elements in intact prostate of 64 apparently healthy 13-60-year-old men (mean age 36.5 years) were investigated by inductively coupled plasma mass spectrometry. Mean values (M ± SΕΜ) for mass fraction (in milligrams per kilogram, on dry-weight basis) of trace elements were as follows: Ag 0.041 ± 0.005, Al 36 ± 4, Au 0.0039 ± 0.0007, B 0.97 ± 0.13, Be 0.00099 ± 0.00006, Bi 0.021 ± 0.008, Br 29 ± 3, Cd 0.78 ± 0.09, Ce 0.028 ± 0.004, Co 0.035 ± 0.003, Cs 0.034 ± 0.003, Dy 0.0031 ± 0.0005, Er 0.0018 ± 0.0004, Gd 0.0030 ± 0.0005, Hg 0.046 ± 0.006, Ho 0.00056 ± 0.00008, La 0.074 ± 0.015, Li 0.040 ± 0.004, Mn 1.53 ± 0.09, Mo 0.30 ± 0.03, Nb 0.0051 ± 0.0009, Nd 0.013 ± 0.002, Ni 4.3 ± 0.7, Pb 1.8 ± 0.4, Pr 0.0033 ± 0.0004, Rb 15.9 ± 0.6, Sb 0.040 ± 0.005, Se 0.73 ± 0.03, Sm 0.0027 ± 0.0004, Sn 0.25 ± 0.05, Tb 0.00043 ± 0.00009, Th 0.0024 ± 0.0005, Tl 0.0014 ± 0.0001, Tm 0.00030 ± 0.00006, U 0.0049 ± 0.0014, Y 0.019 ± 0.003, Yb 0.0015 ± 0.0002, Zn 782 ± 97, and Zr 0.044 ± 0.009, respectively. The upper limit of mean contents of As, Cr, Eu, Ga, Hf, Ir, Lu, Pd, Pt, Re, Ta, and Ti were the following: As ≤ 0.018, Cr ≤ 0.64, Eu ≤ 0.0006, Ga ≤ 0.08, Hf ≤ 0.02, Ir ≤ 0.0004, Lu ≤ 0.00028, Pd ≤ 0.007, Pt ≤ 0.0009, Re ≤ 0.0015, Ta ≤ 0.005, and Ti ≤ 2.6. In all prostate samples, the content of Te was under detection limit (element contents as well as correlations between Zn and trace elements were calculated. Our data indicate that the human prostate accumulates such trace elements as Al, Au, B, Br, Cd, Cr, Ga, Li, Mn, Ni, Pb, U, and Zn. No special relationship between Zn and other trace elements was found.

  11. Properties of cement based composites modified using diatomaceous earth

    Science.gov (United States)

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

    2017-07-01

    Diatomite belongs among natural materials rich on amorphous silica (a-SiO2). When finely milled, it can potentially substitute part of cement binder and positively support formation of more dense composite structure. In this connection, two types of diatomaceous earth applied as a partial substitution of 5, 10, 15, and 20 mass% of Portland cement in the composition of cement paste were studied. In the tested mixtures with cement blends, the amount of batch water remained same, with water/binder ratio 0.5. For fresh paste mixtures, initial and final setting times were measured. First, hardened pastes cured 28 days in water were characterized by their physical properties such as bulk density, matrix density and open porosity. Then, their mechanical and thermophysical parameters were assessed. Obtained results gave clear evidence of setting time shortening for pastes with diatomite what brought negative effect with respect to the impaired workability of fresh mixtures. On the other hand, there was observed strength improvement for mixtures containing diatomite with higher amount of SiO2. Here, the increase in mechanical resistivity was distinct up to 15 mass% of cement replacement. Higher cement substitution by diatomite resulted in an increase in porosity and thus improvement of thermal insulation properties.

  12. 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

  13. Study of incorporation of casting wastes in soil-cement blocks

    International Nuclear Information System (INIS)

    Folmann, R.; Malkowski, W.; Valentina, L.V.D.; Folgureras, M.V.

    2011-01-01

    Soil-cement bricks are an ecological alternative to conventional ones because they don't need to be burned to gain strength. This study examines the technical possibility of reuse of foundry sand as fine aggregate in soil-cement. The raw materials were characterized by X-ray diffraction, thermal analysis and particle size. The foundry sand wastes were mixed at different levels to soil and cement. Compaction tests were performed to define the mixtures at optimum moisture content corresponding to the maximum density. Isothermal Conduction Calorimeter was performed to study the influence of waste in the cement hydration reaction. The results indicate that the addition of foundry sand waste decreases the optimum moisture content and increases the maximum density without significantly affecting the cement set. (author)

  14. Cemented Backfilling Technology of Paste-Like Based on Aeolian Sand and Tailings

    Directory of Open Access Journals (Sweden)

    Qinli Zhang

    2016-12-01

    Full Text Available Aeolian sand, tailings, and #32.5 Portland cement were used to produce backfilling aggregate, and physicochemical evaluations and proportioning tests were conducted. It is revealed that a mixture of aeolian sand and tailings can be used as a backfilling aggregate for the complementarities of their physicochemical properties; e.g., high Al2O3 content in the aeolian sand and CaO content in the tailings, coarse particles of aeolian sand and fine particles of tailings, etc. In addition, the optimal backfilling aggregate was shown to have a mass fraction of 72%–74%, a cement–sand ratio of 1:8, and an aeolian sand proportion of 25%. Furthermore, viscometer tests were used to analyze the rheological characteristics, and the slurry in these optimized proportions exhibited shear thinning phenomena with an initial yield stress, which belongs to paste-like—a cemented backfilling slurry with a higher mass fraction than a two-phase flow and better flowability than a paste slurry. Finally, the application of this backfilling technology shows that it can not only realize safe mining, but also bring huge economic benefits, and has some constructive guidance for environmental protection.

  15. Research on stress distribution regularity of cement sheaths of radial well based on ABAQUS

    Science.gov (United States)

    Shi, Jihui; Cheng, Yuanfang; Li, Xiaolong; Xiao, Wen; Li, Menglai

    2017-12-01

    To ensure desirable outcome of hydraulic fracturing based on ultra-short radius radial systems, it is required to investigate the stress distribution regularity and stability of the cement sheath. On the basis of the theoretical model of the cement sheath stress distribution, a reservoir mechanical model was built using the finite element software, ABAQUS, according to the physical property of a certain oil reservoir of the Shengli oilfield. The stress distribution of the casing-cement-sheath-formation system under the practical condition was simulated, based on which analyses were conducted from multiple points of view. Results show that the stress on the internal interface of the cement sheath exceeds that on the external interface, and fluctuates with higher amplitudes, which means that the internal interface is the most failure-prone. The unevenness of the cement sheath stress distribution grows with the increasing horizontal principal stress ratio, and so does the variation magnitude. This indicates that higher horizontal principal stress ratios are unfavourable for the structural stability of the cement sheath. Both the wellbore quantity of the URRS and the physical property of the material can affect the cement sheath distribution. It is suggested to optimize the quantity of the radial wellbore and use cement with a lower elastic modulus and higher Poisson’s ratio. At last, the impact level of the above factor was analysed, with the help of the grey correlation analysis.

  16. 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.

  17. Novel Injectable Calcium Phosphate Bone Cement from Wet Chemical Precipitation Method

    Science.gov (United States)

    Hablee, S.; Sopyan, I.; Mel, M.; Salleh, H. M.; Rahman, M. M.; Singh, R.

    2017-06-01

    Calcium phosphate cement has been prepared via chemical precipitation method for injectable bone filling materials. Calcium hydroxide, Ca(OH)2, and diammonium hydrogen phosphate, (NH4)2HPO4, were used as calcium and phosphorus precursors respectively. The synthesized powder was mixed with water at different powder-to-liquid (P/L) ratios, which was adjusted at 0.8, 0.9, 1.0, 1.1 and 1.2. The influence of P/L ratio on the injectability, setting time and mechanical strength of calcium phosphate cement paste has been evaluated. The synthesized powder appeared as purely hydroxyapatite with nanosized and agglomerated spherical particles. All cement pastes show excellent injectability except for the paste with P/L ratio 1.2. Calcium phosphate cement with P/L ratio 1.1 shows the ideal cement for bone filler application with good injectability, the initial and final setting times of 30 min and 160 min, and the compression strength of 2.47 MPa. The result indicated that the newly developed calcium phosphate cement is physically suitable for bone filler application. This paper presents our investigation on the effect of P/L ratio on the handling and mechanical properties of calcium phosphate cement prepared via wet chemical precipitation method.

  18. Optimization of superplasticizer in portland pozzolana cement mortar and concrete

    Science.gov (United States)

    Sathyan, Dhanya; Anand, K. B.; Mini, K. M.; Aparna, S.

    2018-02-01

    Chemical Admixtures are added to concrete at the time of mixing of its constituents to impart workability. The requirement of right workability is the essence of good concrete. It has been found that the use of optimum use of admixtures is very important since low dosage may result in loss of fluidity and over dosage could lead to segregation, bleeding, excessive air entrainment etc in concrete. Hence it is essential to find optimum dosage of superplasticizer for getting good strength and workability. But large number of trial tests are required in the field to find the saturation dosage of superplasticizer in concrete which requires more materials and consume more time. The paper deals with developing a co-relation between the quantity requirements of superplasticiser in mortar to that of cement concrete to get good workability. In this work for preparing mortar and concrete 4 brands of locally available Portland pozzolana cement (PPC) and superplasticizer (SP) belonging to 4 different families namely Polycarboxylate Ether (PCE), Lignosulphate (LS), Sulfonated Naphthalene Formaldehyde (SNF) and Sulfonated Melamine Formaldehyde (SMF) are used. Two different brands of SP’s are taken from each family. Workability study on the superplasticized mortar with cement to sand ratio 1:1.5 and water cement ratio of 0.4 was performed using marsh cone and flow table test and workability study on the concrete with same cement/sand ratio and water cement ratio was done using slump cone and flow table test. Saturation dosage of superplasticizer in mortar and concrete determined experimentally was compared to study the correlation between two. Compressive strength study on concrete cubes were done on concrete mixes with a superplasticizer dosage corresponding to the saturation dosage and a comparative study were done to analyse the improvement in the compressive strength with addition of superplasticizer from different family.

  19. A sorption model for alkalis in cement-based materials - Correlations with solubility and electrokinetic properties

    Science.gov (United States)

    Henocq, Pierre

    2017-06-01

    In cement-based materials, radionuclide uptake is mainly controlled by calcium silicate hydrates (C-S-H). This work presents an approach for defining a unique set of parameters of a surface complexation model describing the sorption behavior of alkali ions on the C-S-H surface. Alkali sorption processes are modeled using the CD-MUSIC function integrated in the Phreeqc V.3.0.6 geochemical code. Parameterization of the model was performed based on (1) retention, (2) zeta potential, and (3) solubility experimental data from the literature. This paper shows an application of this model to sodium ions. It was shown that retention, i.e. surface interactions, and solubility are closely related, and a consistent sorption model for radionuclides in cement-based materials requires a coupled surface interaction/chemical equilibrium model. In case of C-S-H with low calcium-to-silicon ratios, sorption of sodium ions on the C-S-H surface strongly influences the chemical equilibrium of the C-S-H + NaCl system by significantly increasing the aqueous calcium concentration. The close relationship between sorption and chemical equilibrium was successfully illustrated by modeling the effect of the solid-to-liquid ratio on the calcium content in solution in the case of C-S-H + NaCl systems.

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

    Directory of Open Access Journals (Sweden)

    MAHSHAD YAZDANIPOUR

    2011-03-01

    Full Text Available 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 binder ratio of 0.30 exhibits the highest 28-day compressive strength, i.e. 36 MPa. Mixes containing 5 wt.% of ground granulated blast furnace slag showed the least efflorescence or best soundness. Laboratory techniques of X-ray diffractometry (XRD, fourier transform infrared spectroscopy (FTIR, and scanning electron microscopy (SEM were utilized for characterizing a number of mixes and studying their molecular and micro-structure. Investigations done by scanning electron microscopy confirm that smaller blast-furnace slag particles react totally while the larger ones react partially with alkaline activators and contribute to the formation of a composite microstructure.

  1. Health hazards of cement dust

    International Nuclear Information System (INIS)

    Meo, Sultan A.

    2004-01-01

    ven in the 21st century, millions of people are working daily in a dusty environment. They are exposed to different types of health hazards such as fume, gases and dust, which are risk factors in developing occupational disease. Cement industry is involved in the development of structure of this advanced and modern world but generates dust during its production. Cement dust causes lung function impairment, chronic obstructive lung disease, restrictive lung disease, pneumoconiosis and carcinoma of the lungs, stomach and colon. Other studies have shown that cement dust may enter into the systemic circulation and thereby reach the essentially all the organs of body and affects the different tissues including heart, liver, spleen, bone, muscles and hairs and ultimately affecting their micro-structure and physiological performance. Most of the studies have been previously attempted to evaluate the effects of cement dust exposure on the basis of spirometry or radiology, or both. However, collective effort describing the general effects of cement dust on different organ and systems in humans or animals, or both has not been published. Therefore, the aim of this review is to gather the potential toxic effects of cement dust and to minimize the health risks in cement mill workers by providing them with information regarding the hazards of cement dust. (author)

  2. Leaf gas exchange, fv/fm ratio, ion content and growth conditions of the two moringa species under magnetic water treatment

    International Nuclear Information System (INIS)

    Hasan, M.M.; Alharby, H.F.; Hajar, A.; Hakeem, K.R.

    2017-01-01

    The current greenhouse experiment investigates the role of magnetic water on the two Moringa species (Moringa oleifera and Moringa peregrina). Both species were exposed to the magnetic field (30 mT). The magnetic water increased the plant height, leaf number, leaflet number, and internode distances in both the species, respectively. Relative water content (RWC) and leaf area in both the species showed changes under magnetic water treatment. The results showed in magnetic water treatment, the leaf gas exchange parameters such as assimilation (A), stomatal conductance (gs), transpiration rate (E), and vapor pressure deficit (VPD) were increased. Similarly, Photosynthetic pigments (Chl a, Chl b, Chl (a+b), Carotenoids), photosynthetic water use efficiency (WUE) were also increased significantly. Magnetized water had also significant effects on the maximal efficiency of PSII photochemistry (Fv/Fm). Our study suggested that magnetic water treatment could be used as an environment-friendly technology for improving the growth and physiology of Moringa species. In addition, this technology could be further incorporated into the traditional methods of agriculture for the improvement of crop plants, particularly in the arid and sub-arid areas of the world. (author)

  3. Strength and sorption properties of cement-bonded composites ...

    African Journals Online (AJOL)

    Boards produced with less than 30% wood content exhibited superior strength and dimensional stability properties that can be exploited in ceiling applications where sound absorption is important. Keywords: Eucalyptus, Veneer waste, Cement composite, Strength, dimensional stability. Journal of Applied Science, ...

  4. Contribution of fibre-cement building material to environmental ...

    African Journals Online (AJOL)

    In this work, the natural radionuclide contents of some fibre-cement building material widely used in Nigeria were measured by means of gamma-ray spectrometry using an HPGe detector. A total of 20 samples obtained from five batches of the product were analysed. The mean values of 226Ra, 232Th and 40K ...

  5. Possibility of Using Wood Pulp in the Preparation of Cement Composites

    Science.gov (United States)

    Kidalova, Lucia; Stevulova, Nadezda; Geffert, Anton

    2014-06-01

    Sustainable building materials are based on the use of renewable materials instead of non-renewable. Large group of renewable materials composes of plant fibres having high tensile strength are used as fillers into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic fillers, such as wood pulp. Wood pulp cellulose is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. Varying the producing technology (wood pulp and cement ratio in mixture) it is possible to obtain composites with density from 940 to 1260 kgm-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. Based on the experimental results, cement composites with using unbleached wood pulp reach higher values than composites based on bleached wood pulp. Volume ratio of unbleached wood pulp in composites influences water absorbability of cement composites

  6. Possibility of Using Wood Pulp in the Preparation of Cement Composites

    Directory of Open Access Journals (Sweden)

    Kidalova Lucia

    2014-06-01

    Full Text Available Sustainable building materials are based on the use of renewable materials instead of non-renewable. Large group of renewable materials composes of plant fibres having high tensile strength are used as fillers into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic fillers, such as wood pulp. Wood pulp cellulose is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. Varying the producing technology (wood pulp and cement ratio in mixture it is possible to obtain composites with density from 940 to 1260 kgm-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. Based on the experimental results, cement composites with using unbleached wood pulp reach higher values than composites based on bleached wood pulp. Volume ratio of unbleached wood pulp in composites influences water absorbability of cement composites

  7. Scavenging ratios

    International Nuclear Information System (INIS)

    Krey, P.W.; Toonkel, L.E.

    1977-01-01

    Total 90 Sr fallout is adjusted for dry deposition, and scavenging ratios are calculated at Seattle, New York, and Fayetteville, Ark. Stable-lead scavenging ratios are also presented for New York. These ratios show large scatter, but average values are generally inversely proportional to precipitation. Stable-lead ratios decrease more rapidly with precipitation than do those of 90 Sr, a decrease reflecting a lesser availability of lead to the scavenging processes

  8. Golden Ratio

    Indian Academy of Sciences (India)

    Our attraction to another body increases if the body is symmetricaland in proportion. If a face or a structure is in proportion,we are more likely to notice it and find it beautiful.The universal ratio of beauty is the 'Golden Ratio', found inmany structures. This ratio comes from Fibonacci numbers.In this article, we explore this ...

  9. Hydraulic activity of belite cement from class C coal fly ash. Effect of curing and admixtures

    OpenAIRE

    Goñi, S., Guerrero, A.

    2006-01-01

    [EN] The effect of curing method and a water-reducing additive on the hydraulic activity of high lime content (ASTM type C) fly ash belite cement (FABC-2-W) is reported. A class C fly ash was subjected to hydrothermal treatment and subsequent calcination to synthesize FABC. Hydraulic activity was evaluated in the cement paste over 180 days from the physically bound water content as determined by thermogravimetric analysis and the degree of hydration, in turn found with...

  10. Reaction Mechanisms of Magnesium Potassium Phosphate Cement and its Application

    Science.gov (United States)

    Qiao, Fei

    magnesia. With the increase of magnesium ions in the solution, MgHPO4·7H2O is the first product precipitated, and its crystallization is accompanied with the increase of both pH and temperature. Beyond pH of 7, MgHPO4·7H 2O is transformed to Mg2KH(PO4)2·15H 2O, leading to a slight decrease of pH. The following dramatic increase of pH may be due to the formation of Mg2KH(PO4) 2·15H2O. Finally, Mg2KH(PO4) 2·15H2O gradually transforms to MgKPO4·6H 2O and leads to the second decrease of pH. Both increasing molar ratio of magnesium to phosphate (M/P) and decreasing the weight ratio of liquid to solid can speed up the reaction rate while addition of small amount of boron compounds can prolong the process even though the products are not changed. The retarding mechanism of boron compounds is related to their buffering effect on the pH of the solution, i.e. decreasing pH development rate, leads to delaying the formation of reaction products. The performance of MKPC based cementitious materials can be significantly influenced by M/P molar ratio, addition of setting retarder, water content, fly ash replacement of magnesia and aggregate usage. Therefore, the formulation of MKPC based materials is optimized in terms of workability, compressive strength, and cost consideration. With optimized formulation, MKPC mortars show high early compressive and flexural strength, superior bond strength to ordinary Portland cement mortar/concrete substrate, and low drying shrinkage. Undoubtedly, the mechanical properties of this cement is closely related to its inner composition and microstructure. The microstructure examination shows that the phase assemblage and the morphology characteristics of MKPC paste vary with the different formulae. In the formulation with lower M/P ratio of 2, KH2PO4 residues can be found in a flat, smooth, and bulky mass form. The reaction product MgKPO4·6H2O, can be observed as acicular crystal habit with large aspect ratio of 30. With the increase of M/P ratio

  11. Isotopic ratios and elemental contents as indicators of seagrass C processing and sewage influence in a tropical macrotidal ecosystem (Madagascar, Mozambique Channel

    Directory of Open Access Journals (Sweden)

    Gilles Lepoint

    2008-03-01

    Full Text Available Isotopic ratios and elemental concentrations of carbon and nitrogen were measured in seven seagrass species colonising different tidal flats near Toliara (SW Madagascar in order to determine the potential use of these parameters for assessing C processing and sewage use by tropical seagrasses. Nitrogen concentrations measured in upper intertidal seagrasses near Toliara were almost twice those measured on the tidal flat near a healthy mangrove situated 20 km away from Toliara town. At Toliara Beach, δ15N values were correlated with the N concentrations of Halodule sp., one of the dominant species on the tidal flat. This correlation did not exist for Halophila ovalis, the other dominant species. An increase in N concentrations and δ15N values demonstrates the influence of sewage coming directly onto Toliara Beach on the N cycles of intertidal seagrasses. Nevertheless, this influence seems restricted to the upper littoral zone and was not the main cause of seagrass die-off. On the other hand, at the mangrove site, δ15N values were not correlated with the N concentrations of Halodule sp. or Thalassia hemprichii, showing that natural δ15N variability is driven by other factors than the δ15N of N sources. Moreover, inter-individual variability of δ15N values was greater than inter-specific or inter-site variability, making the δ15N difficult to interpret in the context of human-disturbance influence on the N cycle of tropical seagrasses. δ13C values were close to -9‰, indicating the use of HCO3- inorganic carbon source by the seven investigated species. Contrary to our hypothesis, variation between sites and location on the tidal flat was limited, suggesting limited impact on δ13C values of sewage, emersion duration and mechanisms for HCO3- incorporation.

  12. Utility of Urinary Protein-Creatinine Ratio and Protein Content in a 24-Hour Urine Collection in Systemic Lupus Erythematosus: A Systematic Review and Meta-Analysis.

    Science.gov (United States)

    Medina-Rosas, Jorge; Yap, Kristy S; Anderson, Melanie; Su, Jiandong; Touma, Zahi

    2016-09-01

    To systematically review literature on the utility of spot urinary protein-creatinine ratio (PCR) as a screening test for proteinuria and its ability to accurately measure proteinuria compared with 24-hour urine collection (24H-P) in patients with systemic lupus erythematosus (SLE). We conducted a literature search (1900-2015) for articles comparing PCR and 24H-P in SLE patients in the databases Medline, Web of Science, and Embase. Included studies and their results were critically appraised and analyzed. Thirteen studies (1,001 patients; 84.01% women) were included. Ten studies reported on Pearson's correlation (range 0.67-0.94), and 3 studies reported on Spearman's correlation (range 0.78-1.00). The meta-analysis of studies with Pearson's correlation showed a high overall correlation of 0.80 between 24H-P and PCR, yet with high heterogeneity (I(2)  = 97.2%). Correlation analysis is not sufficient to evaluate the utility of a new test against the gold standard test, and analysis on agreement is required. Seven studies reported on agreement: 3 studies analyzed concordance correlation coefficient (0.48-0.94), 3 analyzed intraclass correlation coefficient (0.66-0.95), and 1 analyzed kappa coefficient (0.58). These results confirmed that the agreement between 24H-P and PCR was inappropriate. Three studies included Bland-Altman plots, and the results also demonstrated poor agreement between both tests. The PCR has a utility as a screening test for proteinuria in SLE patients. The studies' results of 24H-P and PCR showed poor agreement between both tests, signifying that PCR should not be a substitute for the gold standard test (24H-P) to accurately measure proteinuria. © 2016, American College of Rheumatology.

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

    African Journals Online (AJOL)

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

  14. Comparative Response of Four Pedogenic Soil Materials to Cement ...

    African Journals Online (AJOL)

    A comparative response of four Pedogenic soil materials to cement stabilization was investigated. The studies focused on the compaction characteristics, the unconfined sompressive strength and the California bearing ratio of the samples. The results obtained show that soil materials from Maiduguri responded favorably to ...

  15. Adaptation of magnesian cements to underground storage of nuclear wastes

    International Nuclear Information System (INIS)

    Dufournet, F.

    1987-01-01

    The aim of this thesis is the experimental study of magnesium oxychloride cements as filling materials for underground granitic cavities containing high level radioactive wastes. After a bibliographic study, mechanical properties are examined before and after setting, in function of the ratio MgO/MgCl 2 . Then behavior with water is investigated: swelling, cracking and leaching [fr

  16. Immobilization of technetium and nitrate in cement-based materials

    International Nuclear Information System (INIS)

    Tallent, O.K.; McDaniel, E.W.; Del Cul, G.D.; Dodson, K.E.; Trotter, D.R.

    1987-01-01

    The leachabilities of technetium and nitrate wastes immobilized in cement-based grouts have been investigated. Factors found to affect the leachabilities include grout mix ratio, grout fluid density, dry solid blend composition, and waste concentration. 10 refs., 7 figs., 3 tabs

  17. Radon exhalation study from cement, cement slabs and concrete slabs with variation in fly ash

    International Nuclear Information System (INIS)

    Sharma, Nisha; Singh, Jaspal

    2012-01-01

    Fly ash is a waste product from coal-fired power plants. Fly ash has become a subject of world-wide interest in recent years because of its diverse uses, e.g. in the manufacture of concrete for building purposes, for the filling of underground cavities, or as a component of building material. The fly ash may contain enhanced levels of the natural radionuclides in the uranium and thorium series and by using the fly ash in building materials, the radiation levels in houses may thus be technologically enhanced. Because of its relatively high radionuclide contents (including 226 Ra), fly ash may, however, present a potential hazard to the population through its radon emanation, which would be highly undesirable. Since fly ash is frequently used as a building material, the idea of the experiment was to mix fly ash in different proportions in the cement in the powder form, cemented slabs and concrete slabs to study the combined behaviors. Alpha sensitive LR-115 type II plastic track detector, commonly known as Solid State Nuclear Track Detectors (SSNTDs), were used to measure the radon concentration. The alpha particles emitted from the radon causes the radiation damaged tracks. The chemical etching in NaOH at 60°C for about 90 minutes was done to reveal these latent tracks, which were then scanned and counted by an optical microscope of suitable magnification. By calculating the track density of registered tracks, the radon concentrations were determined. In case of cement in the powder form and in cemented slab, starting from the pure cement, fly ash was added up to 70% by weight. In this case the radon exhalation rate has increased by addition of fly ash in the cement and in case of concrete slabs by the addition of fly ash in the cement the radon exhalation increases up to 60% and then decreases. Therefore, on the basis of our investigations we concluded that in general radon exhalation rate increases with the addition of fly ash. (author)

  18. The behavior of biogenic silica-rich rocks and volcanic tuffs as pozzolanic additives in cement

    Science.gov (United States)

    Fragoulis, Dimitris; Stamatakis, Michael; Anastasatou, Marianthi

    2015-04-01

    Cements currently produced, include a variety of pozzolanic materials, aiming for lower clinker addition and utilization of vast deposits of certain raw materials and/or mining wastes and byproducts. The major naturally occurring pozzolanic materials include glassy tuffs, zeolitic tuffs, diatomites and volcanic lavas rich in glassy phase, such as perlites. Therefore, based on the available raw materials in different locations, the cement composition might vary according to the accessibility of efficient pozzolanic materials. In the present investigation, the behavior of pozzolanic cements produced with representative samples of the aforementioned materials was studied, following the characterization of the implemented pozzolanas with respect to their chemical and mineralogical characteristics. Laboratory cements were produced by co-grinding 75% clinker, 5% gypsum and 20% pozzolana, for the same period of time (45 min). Regarding pozzolanic materials, four different types of pozzolanas were utilized namely, diatomite, perlite, zeolite tuff and glassy tuff. More specifically, two diatomite samples originated from Australia and Greece, with high and low reactive silica content respectively, two perlite samples originated from Turkey and from Milos Island, Greece, with different reactive silica contents, a zeolite tuff sample originated from Turkey and a glassy tuff sample originated from Milos Island, Greece. The above pozzolana samples, which were ground in the laboratory ball mill for cement production performed differently during grinding and that was reflected upon the specific surface area (cm2/gr) values. The perlites and the glassy tuff were the hardest to grind, whereas, the zeolite tuff and the Australian diatomite were the easiest ones. However, the exceedingly high specific surface area of the Australian diatomite renders cement difficult to transport and tricky to use for concrete manufacturing, due to the high water demand of the cement mixture. Regarding

  19. Characterization of antibacterial and adhesion properties of chitosan-modified glass ionomer cement.

    Science.gov (United States)

    Ibrahim, Marrwa A; Neo, Jennifer; Esguerra, Roxanna J; Fawzy, Amr S

    2015-10-01

    The aim is to investigate the effect of modifying the liquid phase of a conventional glass ionomer restorative material with different chitosan volume contents on the antibacterial properties and adhesion to dentin. The liquids of commercially available restorative glass ionomer cements (GIC) were modified with chitosan (CH) solutions at different volume contents (5%, 10%, 25%, and 50%). The GIC powders were mixed with the unmodified and the CH-modified liquids at the desired powder/liquid (P/L) ratio. For the characterization of the antibacterial properties, Streptococcus mutans biofilms were formed on GIC discs and characterized by scanning electron microscope (SEM), confocal microscopy, colony forming unit (CFU) count, and cell viability assay (MTS). The unmodified and CH-modified GICs were bonded to dentin surfaces and the micro-tensile bond strength (µTBs) was evaluated and the interface was investigated by SEM. Modification with CH solutions enhanced the antibacterial properties against S. mutans in terms of resistance to biofilm formation, CFU count, and MTS assay. Generally, significant improvement in the antibacterial properties was found with the increase in the CH volume content. Modification with 25% and 50% CH adversely affected the µTBs with predominant cohesive failure in the GIC. However, no difference was found between the control and the 5% and 10% CH-modified specimens. Incorporation of acidic solutions of chitosan in the polyacrylic acid liquid of GIC at v/v ratios of 5-10% improved the antibacterial properties of conventional glass ionomer cement against S. mutans without adversely affecting its bonding to dentin surface. © The Author(s) 2015.

  20. Premixed calcium silicate cement for endodontic applications: injectability, setting time and radiopacity.

    Science.gov (United States)

    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 amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications.

  1. Characterization of cement from a well at Teapot Dome Oil Field: Implications for geological sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, George W. [Princeton Univ., NJ (United States); Kutchko, Barbara [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Thaulow, Niels [RJ Lee Group Inc. Monroeville, PA (United States); Duguid, Andrew [Princeton Univ., NJ (United States); Mook, Bryant [Rocky Mountain Oilfield Testing Center (RMOTC), Casper, WY (United States)

    2011-01-01

    Wellbores represent the weakest link in terms of CO2 storage permanence. As a result, special attention to the numerous existing wells that perforate storage formations is needed. The pre-injection condition of the cement can influence the rate (and type) of alteration by the injected CO2 plume. The condition of the existing well cement depends on a variety of factors including wellbore/formation and wellbore/brine interactions as well as the composition and type of cement placed in the well (i.e. type of admixtures used, water/solids ratio, sulfate resistant mixes, etc.). In this paper, the details of recovering wellbore cement from an older well to determine pre-injection seal integrity are described. Petrographical and chemical analyses are presented for samples of cement that were retrieved from a 19-year-old well at Teapot Dome in Wyoming. Examination revealed that the retrieved cement had altered as a result of original slurry composition and with respect to the local downhole wellbore environment. Although samples were obtained from a single well, significant differences were observed in their alteration and condition. Sulfate attack resulted in abundant ettringite formation in a cement sample taken adjacent to the Wall Creek sandstone (3060 ft), while cement taken adjacent to the Tensleep formation (5478 ft) was decalcified and enriched in magnesium, owing to reaction of calcium hydroxide in the cement with the dolomitic formation.

  2. Shrinkage-reducing admixtures and early-age desiccation in cement pastes and mortars

    DEFF Research Database (Denmark)

    Bentz, D. P.; Geiker, Mette Rica; Hansen, Kurt Kielsgaard

    2001-01-01

    to map the drying profile, internal relative humidity (RH), and autogenous deformation. Interestingly, although the SRA accelerates the drying of bulk solutions, in cement paste with a water-to-cement (w/c) ratio of 0.35, it actually reduces the measured drying rate. Based on the accompanying X...... to low w/c ratio concretes undergoing self-desiccation, in addition to their normal usage to reduce drying shrinkage....

  3. Effect of Fly Ash and Silica Fume on the Mechanical Properties of Cement Paste at Different Stages of Hydration

    Science.gov (United States)

    2015-08-10

    hardening, temperature rise, and shrinkage which can lead to cracking . Similarly, the degradation resistance of cement is a property that is less...buildings, bridges, pavements , precast structures, etc. Type 2: Moderate sulfate resistance cement with low C3A content below 8%. Usually used for...cement cracking when subjected to sulfate attack. The belite hydrates to form calcium silicate hydrates and heat. The calcium silicate hydrates

  4. 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) into...

  5. Comparison of the fixation effects of heavy metals by cement rotary kiln co-processing and cement based solidification/stabilization.

    Science.gov (United States)

    Zhang, Junli; Liu, Jianguo; Li, Cheng; Jin, Yiying; Nie, Yongfeng; Li, Jinhui

    2009-06-15

    Cement rotary kiln co-processing of hazardous wastes and cement based solidification/stabilization could both immobilize heavy metals. The different retention mechanisms of the two technologies lead to different fixation effects of heavy metals. The same amount of heavy metal compounds were treated by the two types of fixation technologies. Long-term leaching test (160 days), the maximum availability leaching test (NEN 7341) and a modified three-step sequential extraction procedure, proposed by the Commission of the European Communities Bureau of Reference (BCR) were employed to compare the fixation effects of the two fixation technologies. The leaching concentrations in NEN 7341 and long-term leaching tests were compared with identification standard for hazardous wastes (GB5085.3-1996) and drinking water standard (GB5749-2005). The results indicate that the leaching concentrations of the long-term leaching test and NEN 7341 test were lower than the regulatory limits and the leached ratios were small. Both cement based solidification/stabilization and cement rotary kiln co-processing could effectively fix heavy metals. Calcination in a cement rotary kiln and the following hydration that follows during cement application could fix As, Cd, Pb and Zn more effectively and decrease the release to the environment. Cement solidification/stabilization technology has better effect in immobilizing Cr and Ni. Cr wastes are more fitful to be treated by cement solidification/stabilization.

  6. 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

  7. Crown and bridge cements: clinical applications.

    Science.gov (United States)

    Bunek, Sabiha S; Powers, John M

    2012-12-01

    Cement selection can be confusing because factors such as substrate, the type of restoration, and patient needs must be considered. Some substrates require additional treatment before cementation. This article describes the most commonly used traditional crown and bridge cements (GI and RMGI) used for metal and metal-ceramic restorations, and resin cements used for all-ceramic restorations. Advantages, disadvantages, indications, and contraindications of cements have been reviewed. Recommended uses of cements for metal, ceramic, and laboratory composite restorations have been presented. General guidelines for surface treatment ot silica- and zirconia-based restorations when using resin cements have been discussed.

  8. Improvement of Shear Strength of Sandy Soil by Cement Grout with Fly Ash

    Directory of Open Access Journals (Sweden)

    Haifaa Abdulrasool Ali

    2018-12-01

    Full Text Available The effects of the permeation cement grout with fly ash on the sandy soil skeleton were studied in the present work in two phase; first phase the shear strength parameters, and the second phase effect of these grouted materials on volume grouted zone by injection (51 cm³ of slurry in sandy soil placed in steel cylinder model with dimension 15 cm in diameter and 30 cm in height. The soil sample was obtained from Karbala city and it is classified as poorly graded sand (SP according to USCS. The soil samples were improved by cement grout with three percentages weight of water cement ratio (w:c; (0.1w:0.9c, 0.8w:0.2c, and 0.7w:0.3c, while the soil samples were dehydrated for one day curing time. Fly ash class (F was used with cement grout as filler material; it was added to the mixture as a replacement material for cement in weight percentages; 10%, 25% and 40%. According to the results of tests, both shear strength and approximate volume of the effective grouted zone for treated samples soil with cement grout was increased when the water cement ratio decreased. Fly ash with cement grout needs to increase the water demand for the grout mixing to give best results in both shear strength and filling the soil voids.

  9. Adsorption of iodine and cesium onto some cement materials

    Energy Technology Data Exchange (ETDEWEB)

    Mine, Tatsuya [Mitsui Shipbuilding and Engineering Co. Ltd., Tokyo (Japan); Mihara, Morihiro; Ito, Masaru [Power Reactor and Nuclear Fuel Development Corp., Tokai, Ibaraki (Japan). Tokai Works; Kato, Hiroshige [IDC, Tokai, Ibaraki (Japan)

    1997-06-01

    Cement materials, being expected to be used in structural materials in underground disposals of radioactive wastes, may adsorb nuclides resulting in retardation of their migration in environment. In this report adsorption behaviors of cement pastes toward iodine (as anion) and cesium (as cation) were studied. Adsorption of iodine was remarkable for OPC and MHP pastes that are known to have high molar ratio CaO/SiO{sub 2}, partition coefficient being 100 ml/g for initial tracer concentration of 10{sup -5} mol/l. Partition coefficient for cesium for PFA paste was found to be 5 ml/g on average. (S. Ohno)

  10. Cements in Radioactive Waste Disposal

    International Nuclear Information System (INIS)

    Glasser, F.P.

    2013-01-01

    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

  11. Cement/slag chemistry studies

    International Nuclear Information System (INIS)

    Glasser, F.P.; Macphee, D.; Atkins, M.; Beckley, N.; Carson, S.O.; Wilding, C.R.; McHugh, G.

    1988-01-01

    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 IO 3 - species, but these differ sharply in sorption characteristics. The effect of ionizing radiation of the pH and E h of cement matrices is reported. (author)

  12. Characteristics and properties of oil-well cements auditioned with blast furnace slag; Cementos petroleros con adicion de escoria de horno alto. Caracteristicas y propiedades

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, R.; Palacios, M.; Puertas, F.

    2011-07-01

    The present paper addresses the alkali activation of Portland cements containing blast furnace slag (20 and 30% by cement weight) with a view to the possible use of these materials in oil well construction. The hydration studies conducted showed that in cement/slag blends, the sodium silicate activator partially inhibited the dissolution of the silicate phases in the Portland cement, retarding cement hydration and reducing the precipitation of reaction products. Due to such partial inhibition, the cement/slag blends had significantly lower mechanical strength than Portland cements hydrated with water. {sup 2}9Si and {sup 2}7Al MAS NMR and BSE/EDX studies, in turn, showed that the CSH gel forming in the alkali-activated cement/slag pastes contained Al in tetrahedral positions and low Ca/Si ratios. (Author) 29 refs.

  13. Modified tricalcium silicate cement formulations with added zirconium oxide.

    Science.gov (United States)

    Li, Xin; Yoshihara, Kumiko; De Munck, Jan; Cokic, Stevan; Pongprueksa, Pong; Putzeys, Eveline; Pedano, Mariano; Chen, Zhi; Van Landuyt, Kirsten; Van Meerbeek, Bart

    2017-04-01

    This study aims to investigate the effect of modifying tricalcium silicate (TCS) cements on three key properties by adding ZrO 2 . TCS powders were prepared by adding ZrO 2 at six different concentrations. The powders were mixed with 1 M CaCl 2 solution at a 3:1 weight ratio. Biodentine (contains 5 wt.% ZrO 2 ) served as control. To evaluate the potential effect on mechanical properties, the mini-fracture toughness (mini-FT) was measured. Regarding bioactivity, Ca release was assessed using ICP-AES. The component distribution within the cement matrix was evaluated by Feg-SEM/EPMA. Cytotoxicity was assessed using an XTT assay. Adding ZrO 2 to TCS did not alter the mini-FT (p = 0.52), which remained in range of that of Biodentine (p = 0.31). Ca release from TSC cements was slightly lower than that from Biodentine at 1 day (p > 0.05). After 1 week, Ca release from TCS 30 and TCS 50 increased to a level that was significantly higher than that from Biodentine (p  0.05). EPMA revealed a more even distribution of ZrO 2 within the TCS cements. Particles with an un-reacted core were surrounded by a hydration zone. The 24-, 48-, and 72-h extracts of TCS 50 were the least cytotoxic. ZrO 2 can be added to TCS without affecting the mini-FT; Ca release was reduced initially, to reach a prolonged release thereafter; adding ZrO 2 made TCS cements more biocompatible. TCS 50 is a promising cement formulation to serve as a biocompatible hydraulic calcium silicate cement.

  14. Compacted artificially cemented soil-acid leachate contaminant interactions: breakthrough curves and transport parameters.

    Science.gov (United States)

    Knop, Alexandre; VanGulck, Jamie; Heineck, Karla Salvagni; Consoli, Nilo Cesar

    2008-06-30

    The transport of contaminants through compacted artificially cemented soil subjected to acid leachate contaminant percolation was analyzed by means of laboratory column tests. The effect of cement content, degree of acidity and hydraulic gradient were evaluated after permeation of several pore volumes of acid leachate contaminant flow through the soil. The pH, electric conductivity and solute breakthrough curves were considered throughout the study. The results showed that the increase of cement content increases the solute pore volumes needed before breakthrough occurred. An increase of the degree of acidity of the percolate and of the hydraulic gradient cause a reduction in the pore volumes needed before breakthrough occurred. The larger the soil cement content, the longer the time required to reach maximum effluent solute concentration. The hydraulic conductivity slightly increased due to cement addition and reduced with increasing degree of acidity of the percolate. Finally, it is possible to state that cement addition to the soil was responsible for increasing retardation coefficient (R) and distribution coefficient (kd) values, meaning that the artificially cemented soils have higher capability to retard the propagation of the contamination and amplified affinity with dissolved acid contaminant.

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

    Science.gov (United States)

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

    2017-04-01

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

  16. Sliding wear of cemented carbides

    International Nuclear Information System (INIS)

    Engqvist, H.; Ederyd, S.; Uhrenius, B.; Hogmark, S.

    2001-01-01

    Cemented carbides are known to be very hard and wear resistant and are therefor often used in applications involving surface damage and wear. The wear rate of cemented carbides is often measured in abrasion. In such tests it has been shown that the wear rate is inversely dependent on the material hardness. The sliding wear is even more of a surface phenomenon than a abrasion, making it difficult to predict friction and wear from bulk properties. This paper concentrates on the sliding wear of cemented carbides and elucidates some wear mechanisms. It is especially shown that a fragmenting wear mechanism of WC is very important for the description of wear of cemented carbides. (author)

  17. Elaboration and characterization of an iodate-substituted hydroxyapatite cement

    International Nuclear Information System (INIS)

    Coulon, A.; Campayo, L.; Laurencin, D.; Grandjean, A.; Cau Dit Coumes, C.; Rossignol, S.

    2015-01-01

    In the last decades, robust host matrices have been developed to guarantee a durable confinement of some of the most mobile radionuclides. In this work, we describe a novel method for iodine incorporation into an iodate-substituted hydroxyapatite by means of a cementation route. Such a material is obtained from a stoichiometric mixture of tetra-calcium-phosphate (TTCP)/tricalcium-phosphate (αTCP)/sodium iodate with a molar ratio 1/2/0.5. This material corresponds to an iodine incorporation content ∼6.5 wt.%. The evolution of this system during the early age (followed by calorimetric and conductimetric measurements) was compared to the same cementitious system without iodate. Results show that sodium iodate acts as a retarder that can be appropriate to control setting for an industrial application. The delay is due to the precipitation of non-cohesive intermediate phases like calcium iodate that are then totally consumed when the crystallization of hydroxyapatite occurs. At later age, a porous bulk material consisting of traces of TTCP and αTCP particles covered by needles is obtained. The composition of these needles is in agreement with that of the desired iodate-containing apatite. (authors)

  18. Blasted copper slag as fine aggregate in Portland cement concrete.

    Science.gov (United States)

    Dos Anjos, M A G; Sales, A T C; Andrade, N

    2017-07-01

    The present work focuses on assessing the viability of applying blasted copper slag, produced during abrasive blasting, as fine aggregate for Portland cement concrete manufacturing, resulting in an alternative and safe disposal method. Leaching assays showed no toxicity for this material. Concrete mixtures were produced, with high aggregate replacement ratios, varying from 0% to 100%. Axial compressive strength, diametrical compressive strength, elastic modulus, physical indexes and durability were evaluated. Assays showed a significant improvement in workability, with the increase in substitution of fine aggregate. With 80% of replacement, the concrete presented lower levels of water absorption capacity. Axial compressive strength and diametrical compressive strength decreased, with the increase of residue replacement content. The greatest reductions of compressive strength were found when the replacement was over 40%. For tensile strength by diametrical compression, the greatest reduction occurred for the concrete with 80% of replacement. After the accelerated aging, results of mechanic properties showed a small reduction of the concrete with blasted copper slag performance, when compared with the reference mixture. Results indicated that the blasted copper slag is a technically viable material for application as fine aggregate for concrete mixtures. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Dynamic and static mechanical analysis of resin luting cements.

    Science.gov (United States)

    Tolidis, K; Papadogiannis, D; Papadogiannis, Y; Gerasimou, P

    2012-02-01

    Various types of indirect restorations are available for dental treatment and resin cements are commonly used as a luting medium. The aim of this study was to evaluate the mechanical properties of contemporary resin luting agents under different testing conditions and temperatures. The materials tested were Choice 2 (CH), Clearfil Esthetic Cement (EC), Resicem (RC) and RelyX Unicem (RX). Each material was examined after 24 h of storage at 21 °C dry and wet at 21, 37 and 50 °C under dynamic and static testing and parameters such as shear and flexural modulus, loss tangent, dynamic viscosity and Poisson's ratio were calculated. The resin cements were also subjected to creep testing under different constant loads for 3 h and a recovery time of 50 h. The material with the highest modulus was CH, while RX had the lowest. All resin cements were affected by the presence of water with RX being the least affected and by the increase of temperature, with RC being the least susceptible. None of the materials exhibited full recovery after creep testing and permanent deformation ranged from 0.43% to 5.53%. The resin cements tested in this study showed no major transitions under the different testing conditions. Their behavior was satisfactory for restorations that do not require increased mechanical properties. However, in the case of stress-bearing restorations the conditions in the oral cavity may affect the performance of these materials. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Imaging of Flames in Cement Kilns To Study the Influence of Different Fuel Types

    DEFF Research Database (Denmark)

    Pedersen, Morten Nedergaard; Nielsen, Mads; Clausen, Sønnik

    2017-01-01

    in the three cement kilns and assess the effect of alternative fuels on the flame. It was found that cofiring with solid recovered fuel (SRF) would delay the ignition point by about 2 m and lower the intensity and temperature of the kiln flame compared to a fossil fuel flame. This is related to a larger...... particle size and moisture content of the alternative fuels, which lowers the conversion rate compared to fossil fuels. The consequences can be a lower kiln temperature and cement quality. The longer conversion time may also lead to the possibility of localized reducing conditions in the cement kiln, which......The cement industry aims to use an increased amount of alternative fuels to reduce production costs and CO2 emissions. In this study three cement plants firing different kinds and percentages of alternative fuel were studied. A specially developed camera setup was used to monitor the flames...

  1. Hydration states of AFm cement phases

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-15

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

  2. Mechanical properties of Self-Consolidating Concrete incorporating Cement Kiln Dust

    Directory of Open Access Journals (Sweden)

    Mostafa Abd El-Mohsen

    2015-04-01

    Full Text Available Self-Consolidating Concrete (SCC has been widely used in both practical and laboratory applications. Selection of its components and their ratios depends, mainly, on the target mechanical and physical properties recommended by the project consultant. Partial replacement of cement in SCC with cheap available industrial by-product could produce environmentally durable concrete with similar properties of normal concrete. In the current research, SCC was produced by blending Cement Kiln Dust (CKD with cement in different ratios. Four mixes incorporating cement kiln dust with partial cement replacement of 10%, 20%, 30%, and 40% were produced and compared with a control mix of Normally Vibrated Concrete (NVC. Superplasticizer was used to increase the flow-ability of SCC mixes. The fresh and hardened mechanical properties of all mixes were determined and evaluated. Moreover, time-dependent behavior was investigated for all mixes in terms of drying shrinkage test. The shrinkage strain was measured for all specimens for a period of 120 days. Based on the experimental results, it was found that SCC mixture containing 20% cement replacement of CKD exhibited the highest mechanical strength compared to other SCC mixes and NVC mix as well. It was observed that the volumetric changes of specimens were directly proportional to the increase of the cement replacement ratio.

  3. Rheological measurements on cement grouts

    International Nuclear Information System (INIS)

    Dalton, M.J.

    1986-06-01

    This report describes the techniques which have been developed at Winfrith for assessing the rheological properties of cement grouts. A discussion of the theory of rheology and its application to cement is given and the methodology for calibrating a special paddle measuring system for a commercial viscometer is described. The use of the system for determining flow curves, equilibrium viscosity, viscosity as a function of shearing time and structure changes is also discussed. (author)

  4. Study of Experiment on Rock-like Material Consist of fly-ash, Cement and Mortar

    Science.gov (United States)

    Nan, Qin; Hongwei, Wang; Yongyan, Wang

    2018-03-01

    Study the uniaxial compression test of rock-like material consist of coal ash, cement and mortar by changing the sand cement ratio, replace of fine coal, grain diameter, water-binder ratio and height-diameter ratio. We get the law of four factors above to rock-like material’s uniaxial compression characteristics and the quantitative relation. The effect law can be sum up as below: sample’s uniaxial compressive strength and elasticity modulus tend to decrease with the increase of sand cement ratio, replace of fine coal and water-binder ratio, and it satisfies with power function relation. With high ratio increases gradually, the uniaxial compressive strength and elastic modulus is lower, and presents the inverse function curve; Specimen tensile strength decreases gradually with the increase of fly ash. By contrast, uniaxial compression failure phenomenon is consistent with the real rock common failure pattern.

  5. Influence Of Cement Kiln Dust As Partial Replacement On Some Properties Of Ordinary And White Portland Cement

    Directory of Open Access Journals (Sweden)

    Salah Sharif

    2013-04-01

    Full Text Available Cement Kiln Dust (CKD is produced as a solid waste with large quantities during manufacturing of Portland cement clinker. The possibility of utilizing CKD as partial replacement for Ordinary Portland Cement (OPC and White Portland Cement (WPC produced in factories of the Iraqi cement state company has been examined in this study to fulfil the environmental and economical aims. Different percentages of CKD were blended with OPC and WPC mixes. The results show that the amount of water for normal consistency were increased with about 39 % and 31 % for OPC and WPC blended with 25 % CKD. The setting time (initial and final decreases with increasing percent of CKD added. Compressive strength decreases slightly with increasing CKD content up to 10 %. For 7- day curing time, it decreases 7 % and 9 % for OPC and WPC mixes, respectively. As percent of added CKD increases to more than 10 %, the compressive strength and other parameters where affected significantly. Overall results proved that OPC and WPC blended with up to 10 % CKD are admissible for passing relevant specification requirements.

  6. A review in geopolymer binder with dry mixing method (geopolymer cement)

    Science.gov (United States)

    Bayuaji, Ridho; Yasin, Abdul Karim; Susanto, Tri Eddy; Darmawan, M. Sigit

    2017-09-01

    This paper reviews and explains the potential of more applicable geopolymer binder for use. This method is called: "Dry Mixing Method of Geopolymer Binder-Cement Geopolymer". The mean is that the geopolymer binder is presented in a dry form (like cement powder), which is contains some solid alkali activator and pozzolan materials. How to use it exactly the same as mixing portland cement in general. Through this dry mixing method, it is expected to create a new industry that produces geopolymer cement. With the presence of geopolymer cement, people no longer need to calculate the composition of molarity ratio of the chemicals in the form of the activator alkali solution and pozzolan materials commonly used (wet method of geopolymer binder). In this paper the author will briefly explain the concept in calculating the composition of dry mixing method of geopolymer binder

  7. Effect of water curing duration on strength behaviour of portland composite cement (PCC) mortar

    Science.gov (United States)

    Caronge, M. A.; Tjaronge, M. W.; Hamada, H.; Irmawaty, R.

    2017-11-01

    Cement manufacturing of Indonesia has been introduced Portland Composite Cement (PCC) to minimize the rising production cost of cement which contains 80% clinker and 20% mineral admixture. A proper curing is very important when the cement contains mineral admixture materials. This paper reports the results of an experimental study conducted to evaluate the effect of water curing duration on strength behaviour of PCC mortar. Mortar specimens with water to cement ratio of (W/C) 0.5 were casted. Compressive strength, flexural strength and concrete resistance were tested at 7, 28 and 91 days cured water. The results indicated that water curing duration is essential to continue the pozzolanic reaction in mortar which contributes to the development of strength of mortar made with PCC.

  8. Preliminary evaluation of the in vitro cytotoxicity of PMMA-co-EHA bone cement

    International Nuclear Information System (INIS)

    Almeida, T.; Leite Ferreira, B.J.M.; Loureiro, J.; Correia, R.N.; Santos, C.

    2011-01-01

    This work reports a preliminary in vitro cytotoxicity assessment of new poly (methyl methacrylate)-co-ethyl hexylacrylate (PMMA-co-EHA) bone cement by evaluating the effect of its leachables on the viability of human osteoblast-like cells (MG63 line) and their progression through the cell cycle. MG63 cells were exposed to 72 h-extract dilutions of PMMA-co-EHA and their viability was tested using the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay. Also, putative changes in the progression of cells through the cell cycle were monitored using flow cytometry. For that the relative nuclear DNA content and the ratio of cells at G 1 :S:G 2 stages of the cell cycle were measured after three exposure periods (24, 48 and 72 h). The obtained results revealed a dose-dependent influence of the cement extract in MG63 cell metabolism when compared to cells cultivated in a culture medium only. The MTT assay showed that a moderate number of cells died after exposure to the most concentrated extract. The cell cycle analysis revealed that leachables of PMMA-co-EHA led to significant changes in cellular proliferation, with cells exposed for 48 h to the most concentrated extract being arrested in the S phase of the cell cycle. However, despite the initial period of cytotoxicity, the obtained results suggest that after 72 h of exposure, the surviving cells are able to recover from this arresting condition and continue to proliferate. Therefore, this preliminary study indicates that, at the biological level, PMMA-co-EHA may have potential of being used as a bone cement matrix. However, a more detailed research work is needed to fully understand the factors responsible for the initial cytotoxicity observed.

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

    Science.gov (United States)

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

    2015-02-01

    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 OCA, with specimens of formulation. © 2014 Wiley Periodicals, Inc.

  10. Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets.

    Science.gov (United States)

    Lu, Liulei; Ouyang, Dong

    2017-07-20

    In this work, the effect of graphene oxide nanosheet (GONS) additives on the properties of cement mortar and ultra-high strength concrete (UHSC) is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0-0.03% by weight of cement). Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study.

  11. Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets

    Directory of Open Access Journals (Sweden)

    Liulei Lu

    2017-07-01

    Full Text Available In this work, the effect of graphene oxide nanosheet (GONS additives on the properties of cement mortar and ultra-high strength concrete (UHSC is reported. The resulting GONS-cement composites were easy to prepare and exhibited excellent mechanical properties. However, their fluidity decreased with increasing GONS content. The UHSC specimens were prepared with various amounts of GONSs (0–0.03% by weight of cement. Results indicated that using 0.01% by weight of cement GONSs caused a 7.82% in compressive strength after 28 days of curing. Moreover, adding GONSs improved the flexural strength and deformation ability, with the increase in flexural strength more than that of compressive strength. Furthermore, field-emission scanning electron microscopy (FE-SEM was used to observe the morphology of the hardened cement paste and UHSC samples. FE-SEM observations showed that the GONSs were well dispersed in the matrix and the bonding of the GONSs and the surrounding cement matrix was strong. Furthermore, FE-SEM observation indicated that the GONSs probably affected the shape of the cement hydration products. However, the growth space for hydrates also had an important effect on the morphology of hydrates. The true hydration mechanism of cement composites with GONSs needs further study.

  12. 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.

  13. Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures.

    Science.gov (United States)

    Glinicki, Michał A; Jóźwiak-Niedźwiedzka, Daria; Gibas, Karolina; Dąbrowski, Mariusz

    2016-01-02

    The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement-ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

  14. Modern methods for evaluating the workability of cement used as a binder for the stabilization and solidification of toxic wastes

    Energy Technology Data Exchange (ETDEWEB)

    De Angelis, Giorgio [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Ambiente

    1997-10-01

    The workability of cement pastes has a great influence on the final properties of the solidified products, like mechanical strength, stability density and durability. This is quite relevant in the field of stabilization / solidification of toxic and hazardous wastes. Hence considerable importance attaches to having reliable control over the fresh concrete properties, especially its early stiffening behaviour. This paper discussers measuring methods of the stiffening of two different types of cement pastes, prepared with different water / cement ratios, and examines the possible consequences of the early stiffening of cement pastes on their set times and bleeding.

  15. Solidification of metallic aluminum on magnesium phosphate cements

    International Nuclear Information System (INIS)

    Lahalle, Hugo

    2016-01-01

    This work deals with the stabilization/solidification of radioactive waste using cement. More particularly, it aims at assessing the chemical compatibility between metallic aluminum and mortars based on magnesium phosphate cement. The physical and chemical processes leading to setting and hardening of the cement are first investigated. X-ray diffraction (XRD), thermogravimetry (TGA) and nuclear magnetic resonance spectroscopy ( 31 P and 11 B MAS-NMR) are first used to characterize the solid phases formed during hydration, while inductively coupled plasma atomic emission spectroscopy analysis (ICP-AES), electrical conductometry and pH measurements provide information on the pore solution composition. Then, the corrosion of metallic aluminum in magnesium phosphate mortars is studied by monitoring the equilibrium potential and by electrochemical impedance spectroscopy (EIS). Magnesium phosphate cement is prepared from a mix of magnesium oxide (MgO) and potassium dihydrogen orthophosphate (KH 2 PO 4 ). In the presence of water, hydration occurs according to a dissolution - precipitation process. The main hydrate is K-struvite (MgKPO 4 .6H 2 O). Its precipitation is preceded by that of two transient phases: phosphorrosslerite (MgHPO 4 .7H 2 O) and Mg 2 KH(PO 4 ) 2 .15H 2 O. Boric acid retards cement hydration by delaying the formation of cement hydrates. Two processes may be involved in this retardation: the initial precipitation of amorphous or poorly crystallized minerals containing boron and phosphorus atoms, and/or the stabilization of cations (Mg 2+ , K + ) in solution. As compared with a Portland cement-based matrix, corrosion of aluminum is strongly limited in magnesium phosphate mortar. The pore solution pH is close to neutrality and falls within the passivation domain of aluminum. Corrosion depends on several parameters: it is promoted by a water-to-cement ratio (w/c) significantly higher than the chemical water demand of cement (w/c = 0.51), and by the

  16. Preliminary observations of water movement in cement pastes during curing using X-ray absorption

    DEFF Research Database (Denmark)

    Bentz, D. P.; Hansen, Kurt Kielsgaard

    2000-01-01

    X-ray absorption and concurrent mass measurements are used in quantifying water movement in 4 to 5 mm thick cement paste specimens with their top surface exposed to drying. Experimental variables examined in this preliminary study include water-to-cement (wic) ratio and open vs. capped samples....... Layered specimens (e.g., 0.3 w/c ratio paste over 0.45 wic ratio paste) are also examined to monitor the preferential water movement from less dense (higher wic ratio) paste to denser paste due to capillary forces. For the open samples examined in this study, the initial drying is observed to occur...

  17. Polymer-cement interactions towards improved wellbore cement fracture sealants

    Science.gov (United States)

    Beckingham, B. S.; Iloejesi, C.; Minkler, M. J.; Schindler, A. K.; Beckingham, L. E.

    2017-12-01

    Carbon capture, utilization, and storage (CCUS) in deep geologic formations is a promising means of reducing point source emissions of CO2. In these systems, CO2 is captured at the source and then injected to be utilized (eg. in enhanced oil recovery or as a working fluid in enhanced geothermal energy plants) or stored in geologic formations such as depleted oil and gas reservoirs or saline aquifers. While CCUS in subsurface systems could aid in reducing atmospheric CO2 emissions, the potential for CO2 leakage from these systems to overlying formations remains a major limitation and poses a significant risk to the security of injected CO2. Thus, improved materials for both initial wellbore isolation and repairing leakage pathways that develop over time are sought. One approach for the repair of cement fractures in wellbore (and other) systems is the injection of polymer materials into the fracture with a subsequent environmentally dependent (temperature, pressure, pH, etc.) densification or solidification. Here, we aim to investigate novel polymer materials for use to repair leaking wellbores in the context of CCUS. We synthesize and fully characterize a series of novel polymer materials and utilize a suite of analysis techniques to examine polymer-cement interactions at a range of conditions (namely temperature, pressure and pH). Initial findings will be leveraged to design novel polymer materials for further evaluation in polymer-cement composite cores, cement fracture healing, and the aging behavior of healed cements.

  18. Biphasic products of dicalcium phosphate-rich cement with injectability and nondispersibility

    International Nuclear Information System (INIS)

    Ko, Chia-Ling; Chen, Jian-Chih; Hung, Chun-Cheng; Wang, Jen-Chyan; Tien, Yin-Chun; Chen, Wen-Cheng

    2014-01-01

    In this study, a calcium phosphate cement was developed using tetracalcium phosphate and surface-modified dicalcium phosphate anhydrous (DCPA). This developed injectable bone graft substitute can be molded to the shape of the bone cavity and set in situ through the piping system that has an adequate mechanical strength, non-dispersibility, and biocompatibility. The materials were based on the modified DCPA compositions of calcium phosphate cement (CPC), where the phase ratio of the surface-modified DCPA is higher than that of the conventional CPC for forming dicalcium phosphate (DCP)-rich cement. The composition and morphology of several calcium phosphate cement specimens during setting were analyzed via X-ray diffractometry and transmission electron microscopy coupled with an energy dispersive spectroscopy system. The compressive strength of DCP-rich CPCs was greater than 30 MPa after 24 h of immersion in vitro. The reaction of the CPCs produced steady final biphasic products of DCPs with apatite. The composites of calcium phosphate cements derived from tetracalcium phosphate mixed with surface-modified DCPA exhibited excellent mechanical properties, injectability, and interlocking forces between particles, and they also featured nondispersive behavior when immersed in a physiological solution. - Highlights: • Bone cement precursor with nanocrystals is characterized. • DCP-rich CPCs with nanocrystals exhibited biphasic product phases. • Nanocrystals in cement significantly affected the interlocking ability. • Nanocrystals in cement exhibited higher strength and anti-dispersion. • DCP-rich CPCs increase the potential of bioresorption after reaction

  19. Biphasic products of dicalcium phosphate-rich cement with injectability and nondispersibility

    Energy Technology Data Exchange (ETDEWEB)

    Ko, Chia-Ling [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, Feng Chia University, Taichung, 407, Taiwan (China); Dental Medical Devices and Materials Research Center, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Hung, Chun-Cheng; Wang, Jen-Chyan [Dental Medical Devices and Materials Research Center, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Department of Dentistry, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Department of Orthopaedics, College of Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng, E-mail: wencchen@fcu.edu.tw [Advanced Medical Devices and Composites Laboratory, Department of Fiber and Composite Materials, Feng Chia University, Taichung, 407, Taiwan (China)

    2014-06-01

    In this study, a calcium phosphate cement was developed using tetracalcium phosphate and surface-modified dicalcium phosphate anhydrous (DCPA). This developed injectable bone graft substitute can be molded to the shape of the bone cavity and set in situ through the piping system that has an adequate mechanical strength, non-dispersibility, and biocompatibility. The materials were based on the modified DCPA compositions of calcium phosphate cement (CPC), where the phase ratio of the surface-modified DCPA is higher than that of the conventional CPC for forming dicalcium phosphate (DCP)-rich cement. The composition and morphology of several calcium phosphate cement specimens during setting were analyzed via X-ray diffractometry and transmission electron microscopy coupled with an energy dispersive spectroscopy system. The compressive strength of DCP-rich CPCs was greater than 30 MPa after 24 h of immersion in vitro. The reaction of the CPCs produced steady final biphasic products of DCPs with apatite. The composites of calcium phosphate cements derived from tetracalcium phosphate mixed with surface-modified DCPA exhibited excellent mechanical properties, injectability, and interlocking forces between particles, and they also featured nondispersive behavior when immersed in a physiological solution. - Highlights: • Bone cement precursor with nanocrystals is characterized. • DCP-rich CPCs with nanocrystals exhibited biphasic product phases. • Nanocrystals in cement significantly affected the interlocking ability. • Nanocrystals in cement exhibited higher strength and anti-dispersion. • DCP-rich CPCs increase the potential of bioresorption after reaction.

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

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  1. Potential Mixture of POFA and SCBA as Cement Replacement in Concrete – A Review

    Directory of Open Access Journals (Sweden)

    Ali Noorwirdawati

    2017-01-01

    Full Text Available Concrete is an important material used in all kind of building construction and ordinary Portland cement (OPC is one of an important element in the production of concrete. However, the production of cement causes a problem because of high CO2 emission to atmosphere. The manufacture of 1 tonnes of cement would produce approximately released 1 tonnes of CO2. So, the need to search another material that can replace a cement with same properties and environmental friendly are crucial. The suitable material to replace cement has to be a pozzolanic materials. This is because pozzolanic materials has cementitious properties and high silica content. Palm oil fuel ash (POFA and sugarcane bagasse ash (SCBA are the material that suitable to replace cement because of high silica content. The use of POFA and SCBA in concrete has been studied by many researcher and it has been proved to improve the mechanical strength of the concrete either in normal concrete, high strength concrete or lightweight concrete. This paper would discuss the overview of the previous study on the cement replacement by POFA and SCBA and the potential of the both materials to be mix together to improve its properties. The chemical element which will be the focus point is SiO4, MgO, CaO and SO3, while the physical and mechanical properties such as workability, specific gravity, compressive strength and tensile strength will also be reviewed.

  2. Surface modification of cured cement pastes by silane coupling agents.

    Science.gov (United States)

    Stewart, Andrew; Schlosser, Brett; Douglas, Elliot P

    2013-02-01

    X-ray photoelectron spectroscopy (XPS) and static contact angle measurements were used to study the interaction between silane coupling agents and cured cement paste. Three different silane coupling agents were investigated: aminopropyltriethoxy silane (APTES), 3-glycidyloxypropyltrimethoxy silane (GPTMS), and methoxy-terminated polydimethxyl siloxane (PDMS). These silanes have different end groups, so the change in surface energy after undergoing a successful reaction between the silane and hydroxyls on the surface of the cement paste was demonstrated by a change in contact angle. Relative to untreated samples, APTES samples decreased the contact angle, PDMS samples increased the contact angle, and GPTMS did not show a significant change in contact angle. Samples with a water-to-cement ratio (w/c) of 0.5 showed a larger change in contact angle than 0.4 w/c ratio samples, because of a greater number of hydroxyl groups at the surface. Deconvolution of the O 1s and Si 2p XPS peaks were performed to determine contributions from bridging and nonbridging atoms. An increase in bridging silicon and oxygen atoms relative to untreated samples indicated successful silane condensation and that a covalent bond was formed between the cement paste and silanes.

  3. Technological, economic and financial prospects of carbon dioxide capture in the cement industry

    International Nuclear Information System (INIS)

    Li, Jia; Tharakan, Pradeep; Macdonald, Douglas; Liang, Xi

    2013-01-01

    Cement is the second largest anthropogenic emission source, contributing approximately 7% of global CO 2 emissions. Carbon dioxide capture and storage (CCS) technology is considered by the International Energy Agency (IEA) as an essential technology capable of reducing CO 2 emissions in the cement sector by 56% by 2050. The study compares CO 2 capture technologies for the cement manufacturing process and analyses the economic and financial issues in deploying CO 2 capture in the cement industry. Post-combustion capture with chemical absorption is regarded as a proven technology to capture CO 2 from the calcination process. Oxyfuel is less mature but Oxyfuel partial capture—which only recycles O 2 /CO 2 gas in the precalciner—is estimated to be more economic than post-combustion capture. Carbonate looping technologies are not yet commercial, but they have theoretical advantages in terms of energy consumption. In contrast with coal-fired power plants, CO 2 capture in the cement industry benefits from a higher concentration of CO 2 in the flue gas, but the benefit is offset by higher SO x and NO x levels and the smaller scale of emissions from each plant. Concerning the prospects for financing cement plant CO 2 capture, large cement manufacturers on average have a higher ROE (return on equity) and lower debt ratio, thus a higher discount rate should be considered for the cost analysis than in power plants. IEA estimates that the incremental cost for deploying CCS to decarbonise the global cement sector is in the range US$350–840 billion. The cost estimates for deploying state-of-the art post-combustion CO 2 capture technologies in cement plants are above $60 to avoid each tonne of CO 2 emissions. However, the expectation is that the current market can only provide a minority of financial support for CO 2 capture in cement plants. Public financial support and/or CO 2 utilisation will be essential to trigger large-scale CCS demonstration projects in the cement

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

    Directory of Open Access Journals (Sweden)

    Wuman Zhang

    2017-01-01

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

  5. EFFECT OF DELAYING ADDITION TIME OF SMF SUPERPLASTICIZER ON HYDRATION CHARACTERISTICS OF BLENDED CEMENT PASTES

    Directory of Open Access Journals (Sweden)

    H. EL-DIDAMONY

    2012-09-01

    Full Text Available This paper aims to study the effect of delaying addition time of sulphonate melamine formaldehyde superplasticizer (SMF on the rheology and hydration characteristic of blended cement pastes up to 90 days. The optimum dosage of superplasticizer was chosen as 1.0 mass %, this dosage gives the higher compressive strength and bulk density as well as lower total porosity. The optimum delaying time of superplasticizer was 7.5 min which gives the highest fluidity, bulk density, compressive strength and chemically combined water contents of cement pastes, whereas, the delaying addition time of 15.0 min shows the lower values of bulk density, compressive strength and combined water contents. This is attributed to the reduction of hydration rate of cement, due to the formation of a polymer film around the cement particles and/or hydrated products. The superplasticizing effect improved with a delayed sulphonate melamine formaldehyde superplasticizer addition time.

  6. Effect of borate concentration on solidification of radioactive wastes by different cements

    International Nuclear Information System (INIS)

    Sun Qina; Li Junfeng; Wang Jianlong

    2011-01-01

    Highlights: → The effect of borate on cementation of radioactive borate evaporator concentrates by sulfoaluminate cement (SAC) and Portland cement (PC) was compared. → The X-ray diffraction (XRD) revealed that borate did not interfere with the formation of main hydration products of SAC and PC. → Borate, in the form of B(OH) 4- , incorporated in ettringite as solid solution phase. - Abstract: To investigate the effect of borate on the cementation of radioactive evaporator concentrates, and to provide more data for solidification formula optimization, the simulated borate evaporator concentrates with different borate concentrations (as B) and Na/B ratio (molar ratio) were solidified by sulfoaluminate cement (SAC) and Portland cement (PC), with addition of Ca(OH) 2 , zeolite and accelerator or water reducer. The hydration products of solidified matrices were characterized by X-ray diffraction (XRD). The experimental results showed that borate retarded the cement setting for both SAC and PC formulas, and the final setting time prolonged with decrease of Na/B ratio. Borate could enhance the fluidity of the cement mixture. The 28 d compressive strengths of the solidified matrices for both SAC and PC formulas decreased with increase of borate concentration. The XRD patterns suggested that, in the matrices maintained for 28 d, borate did not interfere with the formation of main hydration products of SAC and PC. Borate, in the form of B(OH) 4- , incorporated in ettringite (3CaO.Al 2 O 3 .3CaSO 4 .32H 2 O) as solid solution phase. The formula of SAC and PC developed in this study was effective for cementation of the simulated borate evaporator concentrates. However further optimization was required to reduce retarding effect of higher borate concentrations and to extend the practical feasibility for actual evaporator concentrates.

  7. Measurement of radioactivity in building materials: The case of Portland cement used in Kinshasa

    International Nuclear Information System (INIS)

    Tshiashala, M.D.; Karisa, N.; Solo, K.; Poloto, I.C.; Bashike, K.M.F.

    2005-01-01

    The study deals with the measurement of radioactivity in some cement samples from the national manufacture of cement of the west area of the Democratic Republic of Congo. The geological materials used in the cement manufacture process may contain some naturel radioactive elements such as U, Th and K. To do so, direct gamma spectrometry using HPGe detector has been performed. Detected radioisotopes from the three main radioactive families have been quantitatively determined. The U, Th and K contents are of the same order of magnitude as in terrestrial crust

  8. 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.

  9. Formulation study on immobilization of spent ion exchange resins in polymer cement

    International Nuclear Information System (INIS)

    Xia Lili; Lin Meiqiong; Bao Liangjin; Fan Xianhua

    2006-01-01

    The aim of this study is to develop a formulation of cement-solidified spent radioactive ion exchange resin form. The solidified form consists of a sort of composite cement, epoxide resin emulsion, and spent ion exchange resins. The composite cement is made up of quick-setting sulphoaluminate cement, silica powder, zeolite, and fly ash in the proportion 1:0.05:0.10:0.05. Sixteen combinations of composite cement, epoxide resin emulsion and mixed anion-cation exchange resins are selected according to a three-factors-four-levels normal design table with the compression strength as the evaluation criterion. The resulted formulation is as follows: the mass ratio of polymer emulsion to composite cement is 0.55:1, the loading of mixed anion-cation exchange resins is 0.3, and the anionic-to-cationic exchange resins ratio is 2:1. The polymer cement solidified forms were tested after 28 d curing for Cs + and Sr 2+ leaching rates, pH and conductivity of the leaching water, and radiation-resistant property in addition to their compressive strength. The measurement results indicate that the performance of thus prepared solidified forms can meet the requirements of the National Standard GB14569.1-93 for near earth's surface disposal of low radioactive waste. (authors)

  10. Golden Ratio

    Indian Academy of Sciences (India)

    of mathematical biology. Our attraction to another body increases if the body is sym- metrical and in proportion. If a face or a structure is in pro- ... his practice of oral and maxillofacial surgery, and he developed a mask using the concept of golden ratio. The mask is called the. Marquardt beauty mask (Figure 1) [1]. Keywords.

  11. 3D basin-shape ratio effects on frequency content and spectral amplitudes of basin-generated surface waves and associated spatial ground motion amplification and differential ground motion

    Science.gov (United States)

    Kamal; Narayan, J. P.

    2015-04-01

    This paper presents the effects of basin-shape ratio (BSR) on the frequency content and spectral amplitudes of the basin-generated surface (BGS) waves and the associated spatial variation of ground motion amplification and differential ground motion (DGM) in a 3D semi-spherical (SS) basin. Seismic responses were computed using a recently developed 3D fourth-order spatial accurate time-domain finite-difference (FD) algorithm based on the parsimonious staggered-grid approximation of the 3D viscoelastic wave equations. The simulated results revealed the decrease of both the frequency content and the spectral amplitudes of the BGS waves and the duration of ground motion in the SS basin with the decrease of BSR. An increase of the average spectral amplification (ASA), DGM and the average aggravation factor (AAF) towards the centre of the SS basin was obtained due to the focusing of the surface waves. A decrease of ASA, DGM and AAF with the decrease of BSR was also obtained.

  12. Degradable borate glass polyalkenoate cements.

    Science.gov (United States)

    Shen, L; Coughlan, A; Towler, M; Hall, M

    2014-04-01

    Glass polyalkenoate cements (GPCs) containing aluminum-free borate glasses having the general composition Ag2O-Na2O-CaO-SrO-ZnO-TiO2-B2O3 were evaluated in this work. An initial screening study of sixteen compositions was used to identify regions of glass formation and cement compositions with promising rheological properties. The results of the screening study were used to develop four model borate glass compositions for further study. A second round of rheological experiments was used to identify a preferred GPC formulation for each model glass composition. The model borate glasses containing higher levels of TiO2 (7.5 mol %) tended to have longer working times and shorter setting times. Dissolution behavior of the four model GPC formulations was evaluated by measuring ion release profiles as a function of time. All four GPC formulations showed evidence of incongruent dissolution behavior when considering the relative release profiles of sodium and boron, although the exact dissolution profile of the glass was presumably obscured by the polymeric cement matrix. Compression testing was undertaken to evaluate cement strength over time during immersion in water. The cements containing the borate glass with 7.5 mol % TiO2 had the highest initial compressive strength, ranging between 20 and 30 MPa. No beneficial aging effect was observed-instead, the strength of all four model GPC formulations was found to degrade with time.

  13. Radioactive wastes dispersed in stabilized ash cements

    International Nuclear Information System (INIS)

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

    1997-01-01

    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 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 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 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

  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. Undetected residual cement on standard or individualized all-ceramic abutments with cemented zirconia single crowns - a prospective randomized pilot trial.

    Science.gov (United States)

    Kappel, Stefanie; Eiffler, Constantin; Lorenzo-Bermejo, Justo; Stober, Thomas; Rammelsberg, Peter

    2016-09-01

    To assess the frequency and amount of residual cement after attachment of monolithic zirconia crowns to standard and individualized ceramic abutments. Twenty patients (mean age 58.9 years at inclusion in the study; 30% male) were randomized to receive either a standard or an individualized abutment on a bone-level implant. Monolithic zirconia single crowns were attached to abutments by use of permanent glass-ionomer cement. Crowns were fabricated with an occlusal hole to enable unscrewing of the abutment-crown complex. Immediately after cementation, superstructures were removed and both the peri-implant soft tissue and the abutment-crown complex were photographed in a standardized manner, to detect residual cement. Photographs were analyzed using Corel Photo Paint X7, and residual cement-to-total abutment and residual cement-to-peri-implant soft tissue area ratios were calculated. Residual cement was observed for 9 of 10 (90%) individualized abutments, compared with 4 of 10 (40%) standard abutments (OR = 13.5, P = 0.049). Twenty-seven of 40 (68%) individualized abutment surfaces were affected, compared with 12 of 40 (30%) standard abutment surfaces. The probability of observing residual cement was approximately five times higher for the surfaces of individualized abutments than for those of standard abutments (P = 0.005). The mean amount of sulcus surface covered by cement was 1.17% (SD 2.85) for the individualized abutments and 3.78% (SD 7.40) for the standard abutments. The position of the margin significantly affected the amount of residual cement. Both individualized and standard all-ceramic abutments result in small amounts of subgingival residual cement on abutment and sulcus surfaces. However, use of individualized abutments does not guarantee complete avoidance of undetected cement rests. Undetected residual cement might be avoided by use of all-ceramic abutments with visible abutment shoulders. © 2015 John Wiley & Sons A/S. Published by John Wiley

  16. Radwaste solidification system (cement)

    International Nuclear Information System (INIS)

    1977-04-01

    The radwaste solidification system described herein is designed to package and solidify radioactive waste material produced at nuclear power plants using cement solidification agents, and is referred to as RSS(C). This integrated system consists of all the equipment necessary to store and transfer solidification agents and additives, collect and transfer process waste in the form of solids, liquids, slurries, and sludges, and continuously mix these materials under controlled conditions prior to letdown into a disposable container. As an integrated system, the RSS(C) also includes the process instrumentation necessary to monitor all process conditions throughout the radwaste packaging cycle and provides the operator with the controls necessary to operate the system in a variety of packaging modes. A single process train which is considered adequate for PWR's is described. A dual process train with crossover capability and two separate filling stations is recommended for most BWR applications. A general description of the solidification process by system configuration and subsystem and detailed equipment descriptions including process equipment data sheets are presented. Equipment listings are also presented. A narrative discussion of the operating procedures for processing a variety of radwaste types normally produced in BWR's and PWR's is presented. A safety analysis is presented, and a detailed discussion of system maintenance requirements and the estimated radiation exposure incident to maintenance is presented. The results of laboratory and prototype testing conducted by Hitman Nuclear and Development Corp. (HNDC) to establish the process parameters required to achieve a satisfactory solidified product are given. A summary of the engineering and quality verification requirements implemented through the HNDC Quality Assurance Program is presented

  17. Structure investigations on Portland cement paste by small angle neutron scattering

    International Nuclear Information System (INIS)

    Dragolici, C. A.; Len, A.

    2003-01-01

    Portland cement pastes consist of many crystalline and non-crystalline phases in various ranges of sizes (nm and mm scale). The crystalline phases are embedded in amorphous phases of the hydration products. We investigated the structural changes of hydrating phases in the time interval of 1-30 days at Budapest Neutron Center's SANS diffractometer. The small angle neutron scattering of Portland cements prepared with a water-to-cement ratio from 0,3 to 0,8 gave us information about the microstructure changes in the material. Fractals were a suitable way for structure modelling. The variation of fractals size depending on the preparation-to-measurement time interval and water-to-cement ratio could be observed. (authors)

  18. Full factorial design analysis of carbon nanotube polymer-cement composites

    Directory of Open Access Journals (Sweden)

    Fábio de Paiva Cota

    2012-08-01

    Full Text Available The work described in this paper is related to the effect of adding carbon nanotubes (CNT on the mechanical properties of polymer-cement composites. A full factorial design has been performed on 160 samples to identify the contribution provided by the following factors: polymeric phase addition, CNT weight addition and water/cement ratio. The response parameters of the full factorial design were the bulk density, apparent porosity, compressive strength and elastic modulus of the polymer-cement-based nanocomposites. All the factors considered in this analysis affected significantly the bulk density and apparent porosity of the composites. The compressive strength and elastic modulus were affected primarily by the cross-interactions between polymeric phase and CNT additions, and the water/cement ratio with polymeric phase factors.

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

    Science.gov (United States)

    2011-12-08

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-461 (Third Review)] Gray Portland Cement... duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... the Commission are contained in USITC Publication 4281 (December 2011), entitled Gray Portland Cement...

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    Li, J.

    2013-01-01

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

  3. Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements

    Directory of Open Access Journals (Sweden)

    Yann-Hwang Wu

    2015-02-01

    Full Text Available This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS. The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO3 (48.5%, SiO2 (21.1%, Al2O3 (13.8%, SO3 (10.06%, Fe2O3 (2.25% and others (4.29%. SA fly ash consists of Al2O3 (19.7%, SiO2 (36.3%, Fe2O3 (28.4% and others (15.6%. SB fly ash consists of Al2O3 (15%, SiO2 (25.4%, Zn (20.6%, SO3 (10.9%, Fe2O3 (8.78% and others (19.32%. The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste. The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements.

  4. Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements.

    Science.gov (United States)

    Wu, Yann-Hwang; Huang, Ran; Tsai, Chia-Jung; Lin, Wei-Ting

    2015-02-16

    This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO₃ (48.5%), SiO₂ (21.1%), Al₂O₃ (13.8%), SO₃ (10.06%), Fe₂O₃ (2.25%) and others (4.29%). SA fly ash consists of Al₂O₃ (19.7%), SiO₂ (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al₂O₃ (15%), SiO₂ (25.4%), Zn (20.6%), SO₃ (10.9%), Fe₂O₃ (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7-14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements.

  5. Recycling of Sustainable Co-Firing Fly Ashes as an Alkali Activator for GGBS in Blended Cements

    Science.gov (United States)

    Wu, Yann-Hwang; Huang, Ran; Tsai, Chia-Jung; Lin, Wei-Ting

    2015-01-01

    This study investigates the feasibility of co-firing fly ashes from different boilers, circulating fluidized beds (CFB) or stokers as a sustainable material in alkali activators for ground granulated blast-furnace slag (GGBS). The mixture ratio of GGBS and co-firing fly ashes is 1:1 by weight. The results indicate that only CF fly ash of CFB boilers can effectively stimulate the potential characteristics of GGBS and provide strength as an alkali activator. CF fly ash consists of CaO3 (48.5%), SiO2 (21.1%), Al2O3 (13.8%), SO3 (10.06%), Fe2O3 (2.25%) and others (4.29%). SA fly ash consists of Al2O3 (19.7%), SiO2 (36.3%), Fe2O3 (28.4%) and others (15.6%). SB fly ash consists of Al2O3 (15%), SiO2 (25.4%), Zn (20.6%), SO3 (10.9%), Fe2O3 (8.78%) and others (19.32%). The mixtures of SA fly ash and SB fly ash with GGBS, respectively, were damaged in the compressive strength test during seven days of curing. However, the built up strength of the CF fly ash and GGBS mixture can only be maintained for 7–14 days, and the compressive strength achieves 70% of that of a controlled group (cement in hardening cement paste). The strength of blended CF fly ash and GGBS started to decrease after 28 days, and the phenomenon of ettrigite was investigated due to the high levels of sulfur content. The CaO content in sustainable co-firing fly ashes must be higher than a certain percentage in reacting GGBS to ensure the strength of blended cements. PMID:28787970

  6. Traction test of temporary dental cements

    OpenAIRE

    Román Rodríguez, Juan Luis; Millan Martínez, Diego; Fons Font, Antonio; Agustín Panadero, Rubén; Fernández Estevan, Lucía

    2017-01-01

    Background Classic self-curing temporary cements obstruct the translucence of provisional restorations. New dual-cure esthetic temporary cements need investigation and comparison with classic cements to ensure that they are equally retentive and provide adequate translucence. The objective is to analyze by means of traction testing in a in vitro study the retention of five temporary cements. Material and Methods Ten molars were prepared and ten provisional resin restorations were fabricated u...

  7. Effect of volcanic tuff on the characteristics of cement mortar

    Directory of Open Access Journals (Sweden)

    Jehad Al-Zou'by

    2014-06-01

    Full Text Available This paper examines how Jordanian volcanic tuff aggregates affect the characteristics of cement mortar. Five mortar mixes were prepared by replacing normal aggregate (standard sand with volcanic tuff aggregate in ratios of 0, 25, 50, 75, and 100% (M1 to M5, respectively. Compressive strength, flexural strength, and unit weight were tested at mortar ages of 3, 7, 28, and 56 days. The results revealed improved compressive and flexural strength, which were maximal for the M3 sample. Unit weight decreased as the ratio of volcanic tuff increased. Based on these results, adding Jordanian volcanic tuff in the appropriate ratio will improve these mortar characteristics.

  8. Investigation of the Mechanical Properties and Microstructure of Graphene Nanoplatelet-Cement Composite

    OpenAIRE

    Wang, Baomin; Jiang, Ruishuang; Wu, Zhenlin

    2016-01-01

    In this work, graphene nanoplatelets (GNPs) were dispersed uniformly in aqueous solution using methylcellulose (MC) as a dispersing agent via ultrasonic processing. Homogenous GNP suspensions were incorporated into the cement matrix to investigate the effect of GNPs on the mechanical behavior of cement paste. The optimum concentration ratio of GNPs to MC was confirmed as 1:7 by ultraviolet visible spectroscopy (UV-Vis), and the optical microscope and transmission electron microscopy (TEM) ima...

  9. Evolution of porosity in a Portland cement paste studied through positron annihilation lifetime spectroscopy

    International Nuclear Information System (INIS)

    Consolati, G.; Quasso, F.

    2003-01-01

    Positron annihilation lifetime spectroscopy experiments were carried out in an ordinary Portland cement paste characterized by a water-to-cement ratio w/c=0.8, in order to monitor the porosity of the paste. It was found that ortho-positronium intensity is a suitable quantity to this purpose, being sensitive to the amount of water contained in the pores. The experimental data show good agreement with the porosity calculated according to the Powers' thin filmsodel

  10. A study on the properties of blended regenerated spent catalyst and cement sandcrete blocks

    International Nuclear Information System (INIS)

    Amissah, Emmanuel Kofi

    2016-07-01

    Sandcrete is widely used as building material. Its properties greatly depend on the properties and proportions of its constituents. The main binder material to produce sandcrete is the Portland cement. The uncertainty about future availability of commonly used Portland materials concomitantly with the environmental problems such as greenhouse gases emissions and high cost of clinker consumption are highlighting the need of identifying other materials for the construction industry, which will aid in minimizing the clinker consumption and reduce the greenhouse gas emissions and cost in the production of cement. The purpose of this study is to examine the properties of sandcrete blocks produced with blended Regenerated Spent Catalyst and cement. In this work, two different series of sandcrete mixtures in which cement was partially replaced with Regenerated Spent Catalyst(RSC) within the range of 5% to 20% (by mass) with an increment of 5%. 100% cement sandcrete was also prepared as reference sandcrete. The physical properties studied were compressive strength, water absorption and setting time. Chemical property studied was chloride content. Comparison of data between the control and that of cement with additives were made. The results obtained in this study clearly indicated that substituting Portland cement up to 20wt. % RSC gave sandcrete strengths higher than the 32.5N/mm 2 , which corresponds to that of Portland cement. The replacement of Portland cement with 10 wt. % of RSC gave the highest strength of 34.0 N/mm 2 . Thus, Regenerated Spent Catalyst may be utilized as effective mineral additive for designing durable sandcrete structures. The optimum amount of RSC recommended to be added as an additive to the Portland cement is 10%. (au)

  11. Influence of free water content on the compressive mechanical ...

    Indian Academy of Sciences (India)

    indicates that the similarity exists in the shape of strain–stress curves of cement mor- tars 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 ...

  12. Influence of Molding Water Content on Shear Strength Characteristic ...

    African Journals Online (AJOL)

    A laboratory investigation was carried out to determine the shear strength characteristics of compacted cement kiln dust treated lateritic soils for use in liners and covers with up to 12.5% cement kiln dust by dry weight of soil. Specimens were prepared at molding water contents of -2, 0, +2 and +4% of the optimum moisture ...

  13. Cementation unit for radioactive wastes

    International Nuclear Information System (INIS)

    Dellamano, Jose Claudio; Vicente, Roberto; Lima, Jose Rodrigues de

    2001-01-01

    This communication describes the waste cementation process and facility developed at Instituto de Pesquisas Energeticas e Nucleares - IPEN. The process is based on 200 litres batch operation, in drum mixing, with continuous cement feeding. The equipment is a single recoverable helicoidal mixer and a turning table that allows the drum to rotate during the mixing operation, simulating a planetary mixer. The facility was designed to treat contact handled liquids and wet solid wastes, but can be adapted for shielded equipment and remote operation. (author)

  14. 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

  15. 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 or...

  16. Multicomponent modelling of Portland cement hydration reactions

    NARCIS (Netherlands)

    Ukrainczyk, N.; Koenders, E.A.B.; Van Breugel, K.

    2012-01-01

    The prospect of cement and concrete technologies depends on more in depth understanding of cement hydration reactions. Hydration reaction models simulate the development of the microstructures that can finally be used to estimate the cement based material properties that influence performance and

  17. Rice Husk Ash Cement – An alternative pozzolana cement for ...

    African Journals Online (AJOL)

    The engineering properties of the cement resulting from a mixture of OPC plus RHA and lime plus RHA were satisfactory with addition of up to 50% RHA. The RHA improved greatly the compressive strength of lime. The cost of producing RHA was considered in pricing the resulting binder and it showed that the use of RHA ...

  18. Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures

    Directory of Open Access Journals (Sweden)

    Michał A. Glinicki

    2016-01-01

    Full Text Available The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash.

  19. Influence of Blended Cements with Calcareous Fly Ash on Chloride Ion Migration and Carbonation Resistance of Concrete for Durable Structures

    Science.gov (United States)

    Glinicki, Michał A.; Jóźwiak-Niedźwiedzka, Daria; Gibas, Karolina; Dąbrowski, Mariusz

    2016-01-01

    The objective of this paper is to examine the possible use of new blended cements containing calcareous fly ash in structural concrete, potentially adequate for structural elements of nuclear power plants. The investigation included five new cements made with different contents of non-clinker constituents: calcareous fly ash, siliceous fly ash, ground granulated blastfurnace slag, and a reference cement—ordinary Portland cement. The influence of innovative cements on the resistance of concrete to chloride and carbonation exposure was studied. Additionally, an evaluation of the microstructure was performed using optical microscopy on concrete thin sections. Test results revealed a substantial improvement of the resistance to chloride ion penetration into concrete containing blended cements. The resistance was higher for increased clinker replacement levels and increased with curing time. However, concrete made with blended cements exhibited higher depth of carbonation than the Portland cement concrete, except the Portland-fly ash cement with 14.3% of calcareous fly ash. The thin sections analysis confirmed the values of the carbonation depth obtained from the phenolphthalein test. Test results indicate the possible range of application for new cements containing calcareous fly ash. PMID:28787821

  20. Estimation of the degree of hydration of blended cement pastes by a scanning electron microscope point-counting procedure

    International Nuclear Information System (INIS)

    Feng, X.; Garboczi, E.J.; Bentz, D.P.; Stutzman, P.E.; Mason, T.O.

    2004-01-01

    A scanning electron microscope (SEM) point-counting technique was employed to study the hydration of plain portland and blended cement pastes containing fly ash or slag. For plain portland cement pastes, the results for the degree of cement hydration obtained by the SEM point-counting technique were consistent with the results from the traditional loss-on-ignition (LOI) of nonevaporable water-content measurements; agreement was within ±10%. The standard deviation in the determination of the degree of cement hydration via point counting ranged from ±1.5% to ±1.8% (one operator, one sample). For the blended cement pastes, it is the first time that the degree of hydration of cement in blended systems has been studied directly. The standard deviation for the degree of hydration of cement in the blended cement pastes ranged from ±1.4% to ±2.2%. Additionally, the degrees of reaction of the mineral admixtures (MAs) were also measured. The standard deviation for the degree of fly ash reaction was ±4.6% to ±5.0% and ±3.6% to ±4.3% for slag. All of the analyses suggest that the SEM point-counting technique can be a reliable and effective analysis tool for use in studies of the hydration of blended cement pastes

  1. Ultra small angle neutron scattering and cement hydration

    International Nuclear Information System (INIS)

    Sabine, T.M.

    1999-01-01

    Waste emanating from research and from nuclear medicine is classed as low-level nuclear waste. Cement is widely used internationally to encapsulate this type of waste. These cemented wastes must comply with relevant safety requirements for interim storage, transportation and disposal. During the last 40 years Australia has produced about 3,500 m 3 of this type of waste from the medical, research and industrial use of radionuclides. ANSTO has studied the way in which cement sets, to provide information at a fundamental level on the viability of the concept of storing low-level waste in cement. The object of our current research is the determination of the size, shape and chemical composition of these precipitate particles. The shape of the particles is of primary importance since, on simple thermodynamic grounds, they should be spheres, to minimise the surface to volume ratio. This will, however, minimise the interaction and interlocking between the particles. Investigation of the reason why simple thermodynamic rules do not apply in systems of this type are being actively pursued in Australia. (author)

  2. 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.

  3. 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.

  4. 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.

  5. Polymer reinforcement of cement systems

    International Nuclear Information System (INIS)

    Swamy, R.N.

    1979-01-01

    In the last couple of decades several cement- and concrete-based composites have come into prominence. Of these, cement-polymer composites, like cement-fibre composites, have been recognised as very promising, and considerable research and development on their properties, fabrication methods and application are in progress. Of the three types of concrete materials which incorporate polymers to form composites, polymer impregnated concrete forms a major development in which hardened concrete is impregnated with a liquid monomer which is subsequently polymerized to form a rigid polymer network in the pores of the parent material. In this first part of the extensive review of the polymer reinforcement of cement systems, the process technology of the various monomer impregnation techniques and the properties of the impregnated composite are assessed critically. It is shown that the high durability and superior performance of polymer impregnated concrete can provide an economic and competitive alternative in in situ strengthening, and in other areas where conventional concrete can only at best provide adequate performance. The review includes a section on radiation-induced polymerization. (author)

  6. Electrically conductive Portland cement concrete.

    Science.gov (United States)

    1986-01-01

    There is a need for an effective, simple-to-install secondary anode system for use in the cathodic protection of reinforced concrete bridge decks. In pursuit of such a system, carbon fibers and carbon black were incorporated in portland cement concre...

  7. Rare earth elements as a tool for studying the formation of cemented layers in an area affected by acid mine drainage

    International Nuclear Information System (INIS)

    Grawunder, Anja; Lonschinski, Martin; Merten, Dirk; Büchel, Georg

    2015-01-01

    Highlights: • Spatially resolved analysis of 14 rare earth elements (REE) by LA-ICP-MS. • Positive correlation of Mn contents and (positive) Ce anomalies. • Linkage of the two cemented layer’s formation to soil solution and groundwater. - Abstract: In a profile with two cemented layers sampled in an area affected by acid mine drainage, both have rare earth element (REE) signatures with positive Ce anomalies in the Post Archean Australian Shale-normalised patterns. Both cemented layers have higher contents of environmentally relevant metals (Cd, Co, Cu, Fe, Mn, U, and Zn) than the over- and underlying unconsolidated Quaternary sediments and are depleted of Al, Ca, K, and Mg. The cemented layers are enriched in middle and heavy REE, but only the bulk pattern of the lower cemented layer reveals a positive Ce anomaly. For the upper cemented layer, this positive Ce anomaly was only determined by spatially resolved laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) studies only for segments with a high abundance of Mn, occurring as Mn phases as proven by energy dispersive X-ray spectroscopy. The Mn phases are formed secondarily to the ferric cement and are especially enriched in Ce and Co. The Ce anomaly of the lower cemented layer most probably is inherited from groundwater to the ferric cement, whereas the Ce anomaly of the upper cemented layer is the result of preferential scavenging of Ce onto the Mn phases compared to other REE

  8. 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.

  9. The characterization of cement waste form for final disposal of decommissioning concrete wastes

    International Nuclear Information System (INIS)

    Lee, Yoon-ji; Lee, Ki-Won; Min, Byung-Youn; Hwang, Doo-Seong; Moon, Jei-Kwon

    2015-01-01

    Highlights: • Decommissioning concrete waste recycling and disposal. • Compressive strength of cement waste form. • Characteristic of thermal resistance and leaching of cement waste form. - Abstract: In Korea, the decontamination and decommissioning of KRR-1, 2 at KAERI have been under way. The decommissioning of the KRR-2 was finished completely by 2011, whereas the decommissioning of KRR-1 is currently underway. A large quantity of slightly contaminated concrete waste has been generated from the decommissioning projects. The concrete wastes, 83ea of 200 L drums, and 41ea of 4 m 3 containers, were generated in the decommissioning projects. The conditioning of concrete waste is needed for final disposal. Concrete waste is conditioned as follows: mortar using coarse and fine aggregates is filled with a void space after concrete rubble pre-placement into 200 L drums. Thus, this research developed an optimizing mixing ratio of concrete waste, water, and cement, and evaluated the characteristics of a cement waste form to meet the requirements specified in the disposal site specific waste acceptance criteria. The results obtained from a compressive strength test, leaching test, and thermal cycling test of cement waste forms conclude that the concrete waste, water, and cement have been suggested as an optimized mixing ratio of 75:15:10. In addition, the compressive strength of the cement waste form was satisfied, including a fine powder up to a maximum of 40 wt% in concrete debris waste of about 75%. According to the scale-up test, the mixing ratio of concrete waste, water, and cement is 75:10:15, which meets the satisfied compressive strength because of an increase in the particle size in the waste

  10. The Use of Micro and Nano Particulate Fillers to Modify the Mechanical and Material Properties of Acrylic Bone Cement

    Science.gov (United States)

    Slane, Joshua A.

    Acrylic bone cement (polymethyl methacrylate) is widely used in total joint replacements to provide long-term fixation of implants. In essence, bone cement acts as a grout by filling in the voids left between the implant and the patient's bone, forming a mechanical interlock. While bone cement is considered the `gold standard' for implant fixation, issues such as mechanical failure of the cement mantle (aseptic loosening) and the development of prosthetic joint infection (PJI) still plague joint replacement procedures and often necessitate revision arthroplasty. In an effort to address these failures, various modifications are commonly made to bone cement such as mechanical reinforcement with particles/fibers and the addition of antibiotics to mitigate PJI. Despite these attempts, issues such as poor particle interfacial adhesion, inadequate drug release, and the development of multidrug resistant bacteria limit the effectiveness of bone cement modifications. Therefore, the overall goal of this work was to use micro and nanoparticles to enhance the properties of acrylic bone cement, with particular emphasis placed on improving the mechanical properties, cumulative antibiotic release, and antimicrobial properties. An acrylic bone cement (Palacos R) was modified with three types of particles in various loading ratios: mesoporous silica nanoparticles (for mechanical reinforcement), xylitol microparticles (for increased antibiotic release), and silver nanoparticles (as an antimicrobial agent). These particles were used as sole modifications, not in tandem with one another. The resulting cement composites were characterized using a variety of mechanical (macro to nano, fatigue, fracture, and dynamic), imaging, chemical, thermal, biological, and antimicrobial testing techniques. The primary outcomes of this dissertation demonstrate that: (1) mesoporous silica, as used in this work, is a poor reinforcement phase for acrylic bone cement, (2) xylitol can significantly

  11. Investigation of the Mechanical Properties and Microstructure of Graphene Nanoplatelet-Cement Composite.

    Science.gov (United States)

    Wang, Baomin; Jiang, Ruishuang; Wu, Zhenlin

    2016-11-04

    In this work, graphene nanoplatelets (GNPs) were dispersed uniformly in aqueous solution using methylcellulose (MC) as a dispersing agent via ultrasonic processing. Homogenous GNP suspensions were incorporated into the cement matrix to investigate the effect of GNPs on the mechanical behavior of cement paste. The optimum concentration ratio of GNPs to MC was confirmed as 1:7 by ultraviolet visible spectroscopy (UV-Vis), and the optical microscope and transmission electron microscopy (TEM) images displayed remarkable dispersing performance. The GNP-cement composite exhibited better mechanical properties with the help of surface-modified GNPs. The flexural strength of cement paste increased up to 15%-24% with 0.05 wt % GNPs (by weight of cement). Meanwhile, the compressive strength of the GNP-cement composite increased up to 3%-8%. The X-ray diffraction (XRD) and thermal analysis (TG/DTG) demonstrated that the GNPs could accelerate the degree of hydration and increase the amount of hydration products, especially at an early age. Meanwhile, the lower porosity and finer pore size distribution of GNP-cement composite were detected by mercury intrusion porosimetry (MIP). In addition, scanning electron microscope (SEM) analysis showed the introduction of GNPs could impede the development of cracks and preserve the completeness of the matrix through the plicate morphology and tortuous behavior of GNPs.

  12. The use of glass powder as a partial Portland cement replacement

    Science.gov (United States)

    Pokorný, Jaroslav; Pavlíková, Milena; Tydlitát, Vratislav; Scheinherrová, Lenka; Rovnaníková, Pavla; Pavlík, Zbyšek

    2017-07-01

    Finely grinded waste glass powder can become material having suitable properties from the point of view of particle size and pozzolanic activity. Glass powder incorporation into cement paste and cement-based composites can bring improvement in porous structure resulting in increased mechanical strength and durability characteristics. On this account, two types of recycled glass powder are investigated in the presented paper as a possible partial Portland cement substitutes in cement blends. For raw glass powders, basic physical parameters and chemical composition are measured. The studied glass powders are applied as 5, 10 and 20 mass% of Portland cement replacement in cement paste mix composition, whereas water/binder ratio of 0.3 is used for all studied pastes. Fresh paste mixtures are characterized using initial and final setting time measurement. For hardened pastes cured 28 days in water, bulk density, matrix density, total open porosity and mechanical properties represented by flexural and compressive strength are accessed. Portlandite consumption by the pozzolanic reaction is monitored with TGA. The obtained results show effectiveness of a borosilicate glass powder that acts as a pozzolanic active admixture. This resulted in improvement of mechanical characteristics for cement substitution up to 10 mass%.

  13. Effect of nylon fiber on mechanical properties of cement based mortar

    Science.gov (United States)

    Hanif, I. M.; Syuhaili, M. R. Noor; Hasmori, M. F.; Shahmi, S. M.

    2017-11-01

    An investigation has been carried out to study the effect of nylon fiber on the mechanical properties of cement based mortar after receiving large quantities of nylon waste. Subsequently, this research was conducted to compare the compressive, tensile and flexural strength of normal cement based mortar with nylon fiber cement based mortar. All samples using constant water-cement ratio of 0.63 and three different percentages of nylon fiber were added in the mixture during the samples preparation period which consists of 0.5%, 1.5% and 2.5% by total weight of cement based mortar. The results obtained with different nylon percentage marked an increases in compressive strength (up to 17%), tensile strength (up to 21%) and flexural strength (up to 13%) when compared with control cement based mortar samples. Therefore, the results obtained from this study shows that by using nylon fiber as additive material can improve the mechanical properties of the cement based mortar and at the same time produce a good sustainable product that can protects and conserve the marine environment.

  14. Investigation of the Mechanical Properties and Microstructure of Graphene Nanoplatelet-Cement Composite

    Directory of Open Access Journals (Sweden)

    Baomin Wang

    2016-11-01

    Full Text Available In this work, graphene nanoplatelets (GNPs were dispersed uniformly in aqueous solution using methylcellulose (MC as a dispersing agent via ultrasonic processing. Homogenous GNP suspensions were incorporated into the cement matrix to investigate the effect of GNPs on the mechanical behavior of cement paste. The optimum concentration ratio of GNPs to MC was confirmed as 1:7 by ultraviolet visible spectroscopy (UV-Vis, and the optical microscope and transmission electron microscopy (TEM images displayed remarkable dispersing performance. The GNP–cement composite exhibited better mechanical properties with the help of surface-modified GNPs. The flexural strength of cement paste increased up to 15%–24% with 0.05 wt % GNPs (by weight of cement. Meanwhile, the compressive strength of the GNP–cement composite increased up to 3%–8%. The X-ray diffraction (XRD and thermal analysis (TG/DTG demonstrated that the GNPs could accelerate the degree of hydration and increase the amount of hydration products, especially at an early age. Meanwhile, the lower porosity and finer pore size distribution of GNP–cement composite were detected by mercury intrusion porosimetry (MIP. In addition, scanning electron microscope (SEM analysis showed the introduction of GNPs could impede the development of cracks and preserve the completeness of the matrix through the plicate morphology and tortuous behavior of GNPs.

  15. Colorimetric study of malvidin-3-O-glucoside copigmented by phenolic compounds: The effect of molar ratio, temperature, pH, and ethanol content on color expression of red wine model solutions.

    Science.gov (United States)

    Zhang, Bo; Yang, Xue-Shan; Li, Ning-Ning; Zhu, Xia; Sheng, Wen-Jun; He, Fei; Duan, Chang-Qing; Han, Shun-Yu

    2017-12-01

    In the recent research, the copigmentations of malvidin-3-O-glucoside with eight types of phenolic copigments have been investigated. The influence of the pigment/copigment molar ratio, the reaction temperature, the pH and the ethanol content of solutions has been examined. The results showed that the copigmentation effect was dependent on not only the particular structures of the phenolic compounds but also the factors of the reaction systems. The increase of the copigment concentration can strengthen the copigmentation effect, improve the solution color, and enhance the red-purple features. Different temperatures had different influences on the copigmentation reactions. The destruction of the copigmentation complexes can result in the hypsochromic shift of the reaction solution when the temperature was higher than 20°C. The bathochromic shift of the solution gradually progressed with the increase of the pH value. A significant copigmentation feature was spotted when pH reached 3.0, which demonstrates obvious red-purple characterization. The addition of the ethanol weakened the copigmentation effect. According to measurement through color analysis, it was found that the color differences caused by ethanol in red wine were typically attributed to quantitative changes. Remarkably, all of the above delicate color deviations caused by the structural or environmental factors can be precisely and conveniently depicted via the CIELAB space analysis. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Effect of Graphene Oxide (GO on the Morphology and Microstructure of Cement Hydration Products

    Directory of Open Access Journals (Sweden)

    Liguo Wang

    2017-12-01

    Full Text Available In this study, the effects of graphene oxide (GO on the microstructure of cement mortars were studied using scanning electron microscopy (SEM, thermogravimetric (TG, and X-ray diffraction (XRD techniques. Cement mortar samples with different proportions of GO (0.02, 0.04, 0.06, and 0.08 wt % based on the weight of cement were prepared. The test results showed that GO affected the crystallization of cement hydration products, C–S–H (calcium silicate hydrate is the main hydrate product and CH (calcium hydroxide. The morphology of hydration products changed with the increase of GO content. Furthermore, the results of XRD analyses showed that the diffraction peak intensity and the crystal grain size of CH (001, (100, (101, and (102 for GO samples increased considerably compared with the control sample. Based on the results, it can be understood that GO can modify the crystal surface of CH, leading to the formation of larger crystals.

  17. Effect of fly and bottom ash mixture from combustion of biomass on strength of cement mortar

    Directory of Open Access Journals (Sweden)

    Ulewicz Małgorzata

    2017-01-01

    Full Text Available The preliminary results of fly and bottom ash mixture form combustion od biomass (80% of tree waste and 20% of palm kernel shells for the produce of ceramic mortars has been presented. Currently, bio- ash from fluidized bed are deposited in landfills. Use of this ash to production of cement mortar instead of sand will reduce the consumption of the mineral resources. The chemical composition of this waste materials was determined using X-ray fluorescence (spectrometer ARL Advant ‘XP. Cement mortar were made using CEM I 42.5 R. The ash were added in an amount 20% of cement weight (in different proportions of fly and bottom ash. The results showed, that the compressive strength (after 28 days of cement mortar containing ash is higher regardless of the type of ash mixture used. The highest compressive strength (increased by 7.0% compared to the control sample was found for cement mortars in which the ratio of fly ash to bottom ash was 10/90. This mortars also showed the highest frost resistance (after 150 cycles freezes and unfreeze. The largest decrease the compressive strength (over 18.7% after the frost resistance test. While cement mortars in which the ratio of fly ash to bottom ash was 90/10 showed the highest frost resistance (after 150 cycles freezes and unfreeze.

  18. Cohesive Soil Stabilized Using Sewage Sludge Ash/Cement and Nano Aluminum Oxide

    Directory of Open Access Journals (Sweden)

    Huan-Lin Luo

    2012-03-01

    Full Text Available In order to improve soft soil strength, a mixture of incinerated sewage sludge ash (SSA and cement was applied as a soil stabilizer. The intended mix ratio for SSA and cement was 3:1. A-6 clay was selected as the untreated soil. In this study, 15% of clay soil was replaced by SSA/cement to produce the treated soil specimens. Then, four different volumes, namely 0, 1, 2, and 3%, of nano-Al2O3 were mixed with the treated soil as an additive. Tests such as compaction, pH values, Atterberg limits, unconfined compressive strength (UCS, swell potential, California bearing ratio (CBR, and permeability were performed. The results indicate that both UCSs and CBR values of untreated soil were greatly improved by the use of 15% SSA/cement. Moreover, a 1% addition of nano-Al2O3 enhanced the treated soil in terms of both UCS and CBR values. Furthermore, the swell potential was effectively reduced by the use of 15% SSA/cement as compared with untreated soil and the 1% nano-Al2O3 additive fraction offered the best performance. From this study, we conclude that 15% of SSA/cement replacement could effectively stabilize A-6 clay soil, and 1% of nano-Al2O3 additive may be the optimum amount to add to the soil.

  19. PERFORMANCE OF CEMENT COMPOSITES REINFORCED WITH SURFACE-MODIFIED POLYPROPYLENE MICRO- AND MACRO-FIBERS

    Directory of Open Access Journals (Sweden)

    Jakub Antoš

    2017-11-01

    Full Text Available This paper focuses on the mechanical properties investigation of cement pastes reinforced with surface treated polymer fibers. The cement matrix was composed of Portland cement (CEM I 42.5 R, w/c ratio equal to 0.4. Two polypropylene fiber types (micro- and macro-fibers were used as randomly distributed and oriented reinforcement in volume amount of 2 %. The fibers were modified in the low-pressure inductively coupled cold oxygen plasma in order to enhance their surface interaction with the cement matrix. The investigated composite mechanical properties (load bearing capacity and response during loading were examined indirectly by means of four-point bending mechanical destructive tests. A response of loaded samples containing treated fibers were compared to samples with reference fibers. Moreover, cracking behavior development was monitored using digital image correlation (DIC. This method enabled to record the micro-cracks system evaluation of both fiber reinforced samples.

  20. Sulfur polymer cement, a solidification and stabilization agent for hazardous and radioactive wastes

    International Nuclear Information System (INIS)

    Darnell, G.R.

    1992-01-01

    Hydraulic cements have been the primary radioactive waste stabilization agents in the United States for 50 years. Twelve years ago, Brookhaven National Laboratory was funded by the Department of Energy's Defense Low-Level Waste Management Program to test and develop sulfur polymer cement (SPC). It has stabilized routine wastes as well as some troublesome wastes with high waste-to-agent ratios. The Department of Energy's Hazardous Waste Remedial Action Program joined the effort by providing funding for testing and developing sulfur polymer cement as a hazardous-waste stabilization agent. Sulfur polymer cement has passed all the laboratory scale tests required by the US Environmental Protection Agency and US Nuclear Regulatory Commission. Two decades of tests by the US Bureau of Mines and private concrete contractors indicate this agent is likely to exceed other agents in longevity. This bulletin provides technical data from pertinent tests conducted by these various entities

  1. Research of magnesium phosphosilicate cement

    Science.gov (United States)

    Ding, Zhu

    Magnesium phosphosilicate cement (MPSC) is a novel phosphate bonded cement, which consists mainly of magnesia, phosphate and silicate minerals. The traditional magnesium phosphate cements (MPCs) usually composed by ammonium phosphate, and gaseous ammonia will emit during mixing and in service. There is no noxious ammonia released from MPSC, furthermore, it can recycle a large volume of the non-hazardous waste. The goal of this research is to investigate the composition, reaction products, reaction mechanism, microstructure, properties, durability and applications of the MPSC. MPSC sets rapidly and has high early strength. It reacts better with solid industrial waste when compared to Portland cement. Many solid industrial wastes, such as fly ash, steel slag, coal gangue, red coal gangue, red mud, barium-bearing slag, copper slag, silica fume, and ground granulated blast furnace slag, have been used as the main component (40% by weight) in MPSC. The research has found that these aluminosilicate (or ironsilicate, or calciumsilicate) minerals with an amorphous or glass structure can enhance the performance of MPSC. The disorganized internal structure of amorphous materials may make it possess higher reactivity compared to the crystalline phases. Chemical reaction between phosphate and these minerals may form an amorphous gel, which is favorable to the cementing. Borax, boric acid and sodium tripolyphosphate have been used as retardants in the MPSC system. It is found that boric acid has a higher retarding effect on the setting of cement, than borax does. However, sodium polyphosphate accelerates the reaction of MPSC. The hydration of MPSC is exothermic reaction. The heat evolution may prompt hydrates formation, and shorten the setting process. Modern materials characterization techniques, XRD, DSC, TG-DTA FTIR, XPS, MAS-NMR, SEM, TEM, MIP, etc. were used to analyze the phase composition, micro morphology, and microstructure of hardened MPSC. The main hydration product

  2. Synchrotron Radiation Pair Distribution Function Analysis of Gels in Cements

    Directory of Open Access Journals (Sweden)

    Ana Cuesta

    2017-10-01

    Full Text Available The analysis of atomic ordering in a nanocrystalline phase with small particle sizes, below 5 nm, is intrinsically complicated because of the lack of long-range order. Furthermore, the presence of additional crystalline phase(s may exacerbate the problem, as is the case in cement pastes. Here, we use the synchrotron pair distribution function (PDF chiefly to characterize the local atomic order of the nanocrystalline phases, gels, in cement pastes. We have used a multi r-range analysis approach, where the ~4–7 nm r-range allows determining the crystalline phase contents; the ~1–2.5 nm r-range is used to characterize the atomic ordering in the nanocrystalline component; and the ~0.2–1.0 nm r-range gives insights about additional amorphous components. Specifically, we have prepared four alite pastes with variable water contents, and the analyses showed that a defective tobermorite, Ca11Si9O28(OH2.8.5H2O, gave the best fit. Furthermore, the PDF analyses suggest that the calcium silicate hydrate gel is composed of this tobermorite and amorphous calcium hydroxide. Finally, this approach has been used to study alternative cements. The hydration of monocalcium aluminate and ye’elimite pastes yield aluminum hydroxide gels. PDF analyses show that these gels are constituted of nanocrystalline gibbsite, and the particle size can be as small as 2.5 nm.

  3. Effect of accelerated aging on the color and opacity of resin cements.

    Science.gov (United States)

    Ghavam, Maryam; Amani-Tehran, Mohammad; Saffarpour, Mahshid

    2010-01-01

    The color stability of resin cements plays a major role in the esthetic performance of porcelain laminate veneers. Some dual-polymerizable resin cements used to bond porcelain laminates were shown to undergo color changes during service. Some recently produced cements are described as being color stable, but scientific data are not available. The current study evaluated the effect of accelerated aging on the color and opacity of resin cements. The hypothesis was that the auto-polymerizing cements would show less color and opacity stability. Forty (0.7 x 18 mm) feldspathic porcelain disks were prepared and divided into four equal groups. The resin cements were bonded to the disks by application of an identical load of 2.5 kilograms, and they were polymerized according to the manufacturer's instructions. The groups were: Variolink Veneer (light-polymerizing), Variolink II (light-polymerizing), Variolink II (dual-polymerizing) and Multilink (auto-polymerizing). A spectrophotometer was used to measure the following color parameters in the CIE L*a*b* color space on a black and white background: deltaa*, deltab*, deltaL*, deltaC, deltaH, deltaE and deltaCR (contrast ratio). The measurements were performed before and after aging. Paired t- and one-way ANOVA tests were used to analyze the data (alpha = .05). None of the groups showed significant differences in deltaE before and after aging (p > .05); deltaE remained in the range of clinical acceptance (deltaE aging. The studied cements can ensure color stability when used to cement porcelain laminate veneers, but the change in opacity can affect clinical results. Auto polymerizing cements become more opaque with aging; therefore, porcelain restorations may lose their match with other teeth.

  4. The Immobilisation of Krom and Stronsium Waste Using Natural Fiber Reinforced Cement

    International Nuclear Information System (INIS)

    Susetyo Haria Putero; Nunung Prabaningrum; Widya Rosita

    2007-01-01

    Cementation of hazardous liquid waste is one of the methods to minimize its detrimental effect on the environmental quality and human health. This research purpose was to study the effect of natural fiber composition and temperature on quality of the cement block reinforced by coconut (Cocos nucifera) fiber and bamboo (Bambusa vulgaris) fiber. This research was pursued by adsorbing stronsium waste and krom using zeolite. Thirteen percent volume of zeolite was mixed with 0.3 of water/cement ratio. Composition of natural fiber was varied by 0.00v/o, 0.05v/o, 0.10v/o, 0.25v/o, 0.50v/o, 0.75v/o and 1.00v/o. The cement blocks produced were heated at 0℃, 50℃, 100℃, 150℃, 200℃ and 250℃ for 10 minutes and then determined their compressive strength and leaching rate. The optimum composition of natural fiber causing increasing of mechanical strength has been founded at 0.50% v/o of fiber. On that composition the axial force resistance of fiber is higher than the radial one. The hydration reaction completely works when cement block is heated until certain temperature that results in the increasing of its compressive strength. However, the compressive strength of cement block heated up to 250℃ is still beyond the standard. Based on its compressive strength, the bamboo (Bambusa vulgaris) fiber is more feasible than coconut (Cocos nucifera) fiber for reinforcing cement block. Heating just influences on the physics properties of cement block. But, the ability of block cement to immobilize a matter is affected by properties of matters. (author)

  5. Characterization of some etalon matrices obtained by cement conditioning of the radioactive sludge

    International Nuclear Information System (INIS)

    Nicu, M.; Mihai, F.

    1998-01-01

    The aim of this work was to establish new ways of investigation of some compounds which are important for studying physico-mechanical mechanisms, nature and structure of the intermediate and final products oc curing in reactions of the technological conditioning processes of the radioactive wastes by cementation after their treatment by precipitation or sorption process. Cement conditioning is, presently, the most used technology for the low and intermediate level waste treatment. Besides many advantages it also presents some disadvantages which limit the utilization area depending, firstly, on the chemical composition of the conditioned radioactive waste. In this work, the influence of different iron precipitates on cement structure is studied and assessed by changes in phase composition and mechanical resistance. Using mechanical resistance data, X-rays diffraction spectra and Moessbauer spectroscopy for iron precipitates and cement-iron precipitate samples, we obtained an image concerning chemical reactions and modifications which appear when iron precipitate is included in cement, between major components of cement and the added one. Moessbauer spectroscopy and X-rays diffraction were proved to be very useful to establish composition and structure of iron compounds used in treatment technology by chemical precipitation. Precipitation mechanism may be elucidated only by a thoroughgoing study of intermediate compounds obtained in successive precipitation phases. Depending on precipitation procedure, initial iron cations and order of adding of reactants, it was observed that the structure of finally obtained precipitates is different. Obtained results at compression tests on cement-iron precipitate samples are similarly with those obtained for reference cement matrix. These results demonstrate that iron precipitate in the sample with precipitate/cement ratio of 1/2 does not influence the mechanical resistance of the obtained matrix The presented results are in

  6. Rheological Properties of Cemented Tailing Backfill and the Construction of a Prediction Model

    Directory of Open Access Journals (Sweden)

    Liu Lang

    2015-04-01

    Full Text Available Workability is a key performance criterion for mining cemented tailing backfill, which should be defined in terms of rheological parameters such as yield stress and plastic viscosity. Cemented tailing backfill is basically composed of mill tailings, Portland cement, or blended cement with supplementary cement material (fly ash and blast furnace slag and water, among others, and it is important to characterize relationships between paste components and rheological properties to optimize the workability of cemented tailing backfill. This study proposes a combined model for predicting rheological parameters of cemented tailing backfill based on a principal component analysis (PCA and a back-propagation (BP neural network. By analyzing experimental data on mix proportions and rheological parameters of cemented tailing backfill to determine the nonlinear relationships between rheological parameters (i.e., yield stress and viscosity and mix proportions (i.e., solid concentrations, the tailing/cement ratio, the specific weight, and the slump, the study constructs a prediction model. The advantages of the combined model were as follows: First, through the PCA, original multiple variables were represented by two principal components (PCs, thereby leading to a 50% decrease in input parameters in the BP neural network model, which covered 98.634% of the original data. Second, in comparison to conventional BP neural network models, the proposed model featured a simpler network architecture, a faster training speed, and more satisfactory prediction performance. According to the test results, any error between estimated and expected output values from the combined prediction model based on the PCA and the BP neural network was within 5%, reflecting a remarkable improvement over results for BP neural network models with no PCA.

  7. Rheological Properties of Cemented Tailing Backfill and the Construction of a Prediction Model

    Science.gov (United States)

    Lang, Liu; Song, KI-IL; Lao, Dezheng; Kwon, Tae-Hyuk

    2015-01-01

    Workability is a key performance criterion for mining cemented tailing backfill, which should be defined in terms of rheological parameters such as yield stress and plastic viscosity. Cemented tailing backfill is basically composed of mill tailings, Portland cement, or blended cement with supplementary cement material (fly ash and blast furnace slag) and water, among others, and it is important to characterize relationships between paste components and rheological properties to optimize the workability of cemented tailing backfill. This study proposes a combined model for predicting rheological parameters of cemented tailing backfill based on a principal component analysis (PCA) and a back-propagation (BP) neural network. By analyzing experimental data on mix proportions and rheological parameters of cemented tailing backfill to determine the nonlinear relationships between rheological parameters (i.e., yield stress and viscosity) and mix proportions (i.e., solid concentrations, the tailing/cement ratio, the specific weight, and the slump), the study constructs a prediction model. The advantages of the combined model were as follows: First, through the PCA, original multiple variables were represented by two principal components (PCs), thereby leading to a 50% decrease in input parameters in the BP neural network model, which covered 98.634% of the original data. Second, in comparison to conventional BP neural network models, the proposed model featured a simpler network architecture, a faster training speed, and more satisfactory prediction performance. According to the test results, any error between estimated and expected output values from the combined prediction model based on the PCA and the BP neural network was within 5%, reflecting a remarkable improvement over results for BP neural network models with no PCA.

  8. Predictors of excess cement and tissue response to fixed implant-supported dentures after cementation.

    Science.gov (United States)

    Korsch, Michael; Robra, Bernt-Peter; Walther, Winfried

    2015-01-01

    The cementation of fixed implant-supported restorations involves the risk of excess cement remaining in the peri-implant tissue that may cause a peri-implant tissue response with attachment loss. The aim was to study the peri-implant tissue response after cementation and to detect potential predictors of excess cement. Clinical complications after cementation in several index cases led to a recall of all patients treated with a special methacrylate cement (one hundred five patients with one hundred eighty-eight implants) and systematic reevaluation of 71 patients (68%) with one hundred twenty-six implants (67%). In all cases, suprastructures including abutments were removed, and findings were documented. Implant diameter was significantly associated with the frequency of excess cement. Implant location or system had no significant effect. Excess cement in turn was associated with bleeding on probing, suppuration, and peri-implant attachment loss. In the absence of excess cement 58.8% of implants had no peri-implant attachment loss versus 37.3% when excess cement was present. With increasing retention time of the methacrylate cement, more peri-implant attachment loss was detected. However, the latter association was not significant. Larger diameters are significantly associated with excess cement in peri-implant tissue. Consequences of excess cement may be increased bleeding on probing, suppuration, and possibly peri-implant attachment loss. © 2013 Wiley Periodicals, Inc.

  9. Retention of gold alloy crowns cemented with traditional and resin cements.

    Science.gov (United States)

    Pinzón, Lilliam M; Frey, Gary N; Winkler, Mark M; Tate, William H; Burgess, John O; Powers, John M

    2009-01-01

    The aim of this study was to measure in vitro retention of cast gold crowns cemented with traditional and resin cements. Forty-eight human molars were prepared on a lathe to produce complete crown preparations with a consistent taper and split into six groups, eight crowns in each group. Crowns were cast in a high-gold alloy and then cemented. After 24 hours, the retention force (N) was recorded and mean values were analyzed by one-way analysis of variance and the Fisher post-hoc least significant difference (PLSD) multiple comparisons test (a = .05). Failure sites were examined under 3100 magnification and recorded. Mean values (SD) for each group in increasing order of retention force were: Harvard Cement: 43 N (27), TempoCem: 59 N (16), PermaCem Dual: 130 N (42), RelyX Luting Cement: 279 N (26), Contax and PermaCem Dual: 286 N (38), and TempoCem with Contax and PermaCem Dual: 340 N (14). The Fisher PLSD interval (P = .05) for comparing cements was 29 N. Zinc-phosphate cement and provisional resin cements had the lowest retention forces. Resin cement with a bonding agent and the hybrid-ionomer cement had similar retention forces. Resin cement with a bonding agent applied after use of a provisional resin cement had a significantly higher retention force than the other cements tested.

  10. Retention of provisional crowns cemented with eight temporary cements: comparative study.

    Science.gov (United States)

    Rego, Mariana Ribeiro de Moraes; Santiago, Luiz Carlos

    2004-09-01

    Many temporary cements are commercially available; therefore, it is necessary to indicate them for each clinical requirement with regard to the tensile strength of prosthetic retainers. Thus, the purpose of this study was to compare the retention of provisional crowns cemented with eight temporary cements, over full crown preparations with standardized mechanical principles as height, taper, and length. For that purpose, eighty human first premolars received full crown preparation with standardized height and taper. Provisional crowns were fabricated and luted with eight brands of temporary cements. Twenty four hours after cementation, the restorations were submitted to tensile strength test in a universal testing machine and the data submitted to ANOVA and Bonferroni tests. Mean tensile strength values ranged from 20.1N for Nogenol cement to 67.5N for Hydro C cement. Statistically significant difference (pcrowns cemented with Hydro C cement were more retentive that than those cemented with the other cements, except for Rely X Temp and Temp Bond. The less retentive crowns were those cemented with Nogenol and Freegenol temporary cements.

  11. 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.

  12. Stabilization and solidification of Pb in cement matrices

    International Nuclear Information System (INIS)

    Gollmann, Maria A.C.; Silva, Marcia M. da; Santos, Joao H. Z. dos; Masuero, Angela B.

    2010-01-01

    Pb was incorporated to a series of cement matrices, which were submitted to different cure time and pH. Pb content leached to aqueous solution was monitored by atomic absorption spectroscopy. The block resistance was evaluated by unconfined compressive strength at 7 and 28 ages. Data are discussed in terms of metal mobility along the cement block monitored by X-ray fluorescence (XRF) spectrometry. The Pb incorporated matrices have shown that a long cure time is more suitable for avoiding metal leaching. For a longer cure period the action of the metal is higher and there is a decreasing in the compressive strength. The XRF analyses show that there is a lower Ca concentration in the matrix in which Pb was added. (author)

  13. Evaluation of the Performance of Local Cements with Imported Class

    African Journals Online (AJOL)

    Portland cement is the most commonly used cement in the oil and gas industry and it accounts for about 99% of all primary cementing operations throughout the world. For Portland cement to qualify as oil well cement, the chemical and physical properties must meet the required standards of the American Petroleum Institute ...

  14. Development of methodology for evaluation of long-term safety aspects of organic cement paste components

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, M.; Holgersson, S. (Chalmers University of Technology, Goeteborg (Sweden)); Ervanne, H. (Helsinki Univ. (Finland)) (and others)

    2008-12-15

    Long-term safety aspects of superplasticizers (SP) and other cement paste components were studied in this joint Nagra - NUMO - SKB - Posiva project with aim to develop a methodology for the evaluation of the long-term safety aspects of superplasticizers (SP) and other organic components of cement pastes. The study also evaluated the effects of SPs and other cement paste components that have already been used or that are most likely to be used in the construction of the high-level nuclear waste repositories in Sweden, Switzerland, Finland and Japan. The main long-term safety issue of concern is whether the superplasticizers and/or other organic components of cement pastes might affect the transport properties of radionuclides. A full evaluation of whether the superplasticizers can be used in a high-level nuclear waste repository cannot be answered based on the studies but a classification of the superplasticizers based on their impact on sorption of radionuclides has been done. The basic methodology for testing, leaching and analyzing of leachants and solid samples of different types was developed at CRIEPI. Two different methodologies for studying the impact of SPs on the sorption of Eu on crushed rock were tested and developed by Helsinki University (HU) and Chalmers University of Technology (CTH). Methods for analyzing organics leaching from grouts were successfully tested by CRIEPI and CTH (Chalmers University of Technology). At CRIEPI the total organic content (TOC) of the leachants was analyzed by Infrared absorption spectrometry (IR) followed by Gel Permeation Chromatography (GPC) for the identification of the organic compounds. At CTH several different analytical methods were tested (e.g. IR, UV spectroscopy, NMR, MALDI-TOF), but these methods still require improvement. In addition to SPs, organics are present in several components of cement pastes, for example in cement grinding aid (CGA) and micro silica slurry. The results suggests that the main high

  15. Development of methodology for evaluation of long-term safety aspects of organic cement paste components

    International Nuclear Information System (INIS)

    Andersson, M.; Holgersson, S.; Ervanne, H.

    2008-12-01

    Long-term safety aspects of superplasticizers (SP) and other cement paste components were studied in this joint Nagra - NUMO - SKB - Posiva project with aim to develop a methodology for the evaluation of the long-term safety aspects of superplasticizers (SP) and other organic components of cement pastes. The study also evaluated the effects of SPs and other cement paste components that have already been used or that are most likely to be used in the construction of the high-level nuclear waste repositories in Sweden, Switzerland, Finland and Japan. The main long-term safety issue of concern is whether the superplasticizers and/or other organic components of cement pastes might affect the transport properties of radionuclides. A full evaluation of whether the superplasticizers can be used in a high-level nuclear waste repository cannot be answered based on the studies but a classification of the superplasticizers based on their impact on sorption of radionuclides has been done. The basic methodology for testing, leaching and analyzing of leachants and solid samples of different types was developed at CRIEPI. Two different methodologies for studying the impact of SPs on the sorption of Eu on crushed rock were tested and developed by Helsinki University (HU) and Chalmers University of Technology (CTH). Methods for analyzing organics leaching from grouts were successfully tested by CRIEPI and CTH (Chalmers University of Technology). At CRIEPI the total organic content (TOC) of the leachants was analyzed by Infrared absorption spectrometry (IR) followed by Gel Permeation Chromatography (GPC) for the identification of the organic compounds. At CTH several different analytical methods were tested (e.g. IR, UV spectroscopy, NMR, MALDI-TOF), but these methods still require improvement. In addition to SPs, organics are present in several components of cement pastes, for example in cement grinding aid (CGA) and micro silica slurry. The results suggests that the main high

  16. Use sulfoferritic cements in construction

    Science.gov (United States)

    Samchenko, Svetlana V.; Zorin, Dmitriy A.

    2018-03-01

    Currently, high-rise construction has received increasing attention around the world. In the big cities under construction is less space and one solution is the high-rise construction. However, high-rise buildings use special requirements, such as strength, thermal insulation, wind load and others. When concrete is exposed to continuous loads by wind or to mechanical loads, it undergoes abrasion. Resistance to this process depends on the characteristics of materials that the concrete and finishing seams are made of. Research on increasing impact and abrasion resistance of calcium sulfoferrite-based cement stone from the perspective of formation of cement stone structure will be instrumental in developing durable materials for application in high-rise construction.

  17. 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

  18. 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...

  19. Initial acidity of dental cements.

    Science.gov (United States)

    Brune, D; Evje, D M

    1984-04-01

    The acidity in aqueous solutions following release of acid components from glass ionomer, silicate, zinc phosphate and zinc polycarboxylate cements has been registered by pH measurements. One brand of each type was studied. Initial setting was accomplished at two different temperatures; 23 degrees C and in the interval from 23 degrees C to about 60 degrees C. In the latter case external heat was transferred to the samples by infrared radiation for a period of 2 min. The highest acidity was associated with the silicate specimen, while the lowest acidity was recorded for the zinc polycarboxylate specimen. Exposure to infrared radiation resulted in a reduced acidity for all types of cements. The effect of infrared exposure was most pronounced for the silicate specimens, resulting in a reduction of acid release by a factor of about 10 compared to the nontreated samples. The resistance to acid release was found to be improved by a factor of about 5 for the glass ionomer and about 3 for the zinc phosphate cement treated in a similar way. Clinically, it seems possible considerably to reduce the risk of pulpal injuries associated with the insertion of silicate restorations by using a moderate infrared radiation treatment. Furthermore, the susceptibility of glass ionomer cements to a high initial erosion should be reduced by the use of such a technique. After exposure of the glass ionomer and silicate specimens to infrared radiation at the temperature interval applied, the samples had a more glossy, tooth-like appearance compared to the nonexposed samples, improving the aesthetic properties.

  20. MRI-based liver iron content determination at 3 T in regularly transfused patients by signal intensity ratio using an alternative analysis approach based on R{sub 2}* theory

    Energy Technology Data Exchange (ETDEWEB)

    Wunderlich, A.P. [Universitaetsklinikum Ulm (Germany). Section for Experimental Radiology; Cario, H. [Universitaetsklinik Ulm (Germany). Children' s Hospital; Bommer, M. [Alb-Fils-Clinics, Goeppingen (Germany). Hematology and Oncology Dept.; Beer, M.; Schmidt, S.A. [Universitaetsklinikum Ulm (Germany). Dept. for Diagnostic and Interventional Radiology; Juchems, M.S. [Klinikum Konstanz (Germany). Diagnostic and Interventional Radiology

    2016-09-15

    To evaluate the feasibility of addressing liver iron content (LIC) in regularly transfused patients by MR imaging at 3 T based on the signal intensity ratio (SIR). An innovative data analysis approach was developed for this purpose. 47 consecutive examinations of regularly transfused patients were included. In all cases, we expected high LIC levels. Patients were scanned with MRI at 3 T with multi-echo gradient echo sequences (GRE) at four different flip angles between 20 and 90 with echo times (TE) ranging from 0.9 to 9.8 ms. Spin-echo protocols were acquired to determine the LIC with a reference MRI method working at 1.5 T. 3 T GRE data were analyzed using the liver-to-muscle SIR. Since the method known for 1.5 T was not expected to be applicable for analyzing 3 T data, theoretic dependence of the SIR on the LIC was derived from the equation describing R{sub 2}* signal decay. Obtained SIR values were correlated to reference LIC to get a relation for calculating LIC from SIR quantities. LIC values and their uncertainties were determined from GRE data and correlated to LIC reference values. For two LIC thresholds, the diagnostic accuracy was determined. LIC was reliably determined from SIR in our patient cohort even for large LIC values. Median of LIC uncertainties was 10%, and the diagnostic accuracy was 0.92 and 0.91, respectively. Determination of even high LIC, resulting in small SIR values, is feasible at 3 T using appropriate SIR analysis.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  2. Gamma Spectrometry Analysis of Different Brands of Cement used in Nigeria

    International Nuclear Information System (INIS)

    Olarinoye, I.O.; Baba-Kutigi, A.N.; Sharifat, I.; Kolo, M.T.

    2014-01-01

    The natural radionuclide content of common brands of cement consumed in Nigeria is presented in this work. Samples of 9 brands of grey ordinary Portland cement (OPC) and 5 brands of white cement were collected and analyzed for their radiological content by gamma spectrometry using a 7.6 x 7.6 NaI(TI) detector. The total average content of 226 Ra, 232 Th and 40 k for all the cement brand samples were 38.1, 27.9 and 301.1 Bq/kg respectively and are lower when compared to the world average (50, 50 and 500 Bq/Kg) in building materials. The evaluated radium equivalent activities, external and internal indices were lower than the recommended safe limit and are comparable with result from similar studies concluded in other countries. The evaluation mean gonadal dose of equivalents of two cement brand samples were found to be higher than the world average in soil while others are less than the world average in soil.

  3. 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

  4. Natural cement as the precursor of Portland cement: Methodology for its identification

    International Nuclear Information System (INIS)

    Varas, M.J.; Alvarez de Buergo, M.; Fort, R.

    2005-01-01

    When cements appeared in the 19th century, they took the place of traditional binding materials (lime, gypsum, and hydraulic lime) which had been used until that time. Early cements can be divided into two groups, natural and artificial (Portland) cements. Natural cements were introduced first, but their widespread usage was short-lived as they were quickly replaced by artificial cements (Portland), still the most important and predominant today. The main differences between natural and artificial cements arise during the manufacturing process. The final properties of the cements are greatly influenced by differences in the raw materials and burning temperatures employed. The aim of this paper is to assess the efficiency of traditional analytical techniques (petrographic microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR)) used to differentiate natural and artificial cements

  5. Use of Incineration Solid Waste Bottom Ash as Cement Mixture in Cement Production

    Science.gov (United States)

    Jun, N. H.; Abdullah, M. M. A. B.; Jin, T. S.; Kadir, A. A.; Tugui, C. A.; Sandu, A. V.

    2017-06-01

    Incineration solid waste bottom ash was use to examine the suitability as a substitution in cement production. This study enveloped an innovative technology option for designing new equivalent cement that contains incineration solid waste bottom ash. The compressive strength of the samples was determined at 7, 14, 28 and 90 days. The result was compared to control cement with cement mixture containing incineration waste bottom ash where the result proved that bottom ash cement mixture able achieve its equivalent performance compared to control cement which meeting the requirement of the standards according to EN 196-1. The pozzolanic activity index of bottom ash cement mixture reached 0.92 at 28 days and 0.95 at 90 and this values can be concluded as a pozzolanic material with positive pozzolanic activity. Calcium hydroxide in Portland cement decreasing with the increasing replacement of bottom ash where the reaction occur between Ca(OH)2 and active SiO2.

  6. Geochemical distinctions between igneous carbonate, calcite cements, and limestone xenoliths (Polino carbonatite, Italy): spatially resolved LAICPMS analyses

    Science.gov (United States)

    Rosatelli, G.; Wall, F.; Stoppa, F.; Brilli, M.

    2010-11-01

    Petrography-controlled laser ablation inductively coupled plasma mass spectrometry (LAICPMS) analyses of carbonate in fresh shallow level sub-volcanic Polino monticellite calcio-carbonatite tuffisite have been performed to assess the geochemical differences between fresh igneous, epigenetic carbonates and sedimentary accidental fragments. Igneous calcite has consistently high LREE/HREE ratios (La/Yb N , 15-130) due to high LREE (ΣLREE, 425-1,269 ppm). Secondary calcite cements are characterized by progressively lower and more variable trace element contents, with lower LREE/HREE ratios. A distinguishing geochemical feature is progressively increasing negative Ce anomalies observed through coarse secondary calcite that can be related to the surface environment processes. The limestone accidental fragments in the tuffisite have trace element contents almost two orders of magnitude lower than igneous carbonate and low LREE (ΣLREE < 9.5 ppm) with low LREE/HREE fractionation (La/Yb N ratios < 18). The stable isotope composition of different carbonate types is consistent with their formation in different environments. The tuffisitization processes during diatreme formation under high CO2-OH fugacity conditions may account for the differences noted in the igneous carbonates.

  7. Performance evaluation of cement-stabilized pond ash-rice husk ash-clay mixture as a highway construction material

    Directory of Open Access Journals (Sweden)

    Deepak Gupta

    2017-02-01

    Full Text Available This paper reports the results of an investigation carried out on clay soil stabilized with pond ash (PA, rice husk ash (RHA and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio (CBR tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%–45% and 5%–20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy (SEM and X-ray diffraction (XRD analyses were carried out, respectively. The results obtained indicated a decrease in the maximum dry density (MDD and a simultaneous increase in the optimum moisture content (OMC with the addition of PA and RHA. Multiple linear regression analysis (MLRA showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

  8. From lime to silica and alumina: systematic modeling of cement clinkers using a general force-field.

    Science.gov (United States)

    Freitas, A A; Santos, R L; Colaço, R; Bayão Horta, R; Canongia Lopes, J N

    2015-07-28

    Thirteen different cement-clinker crystalline phases present in the lime-silica-alumina system have been systematically modeled using a simple and general force field. This constitutes a new type of approach towards the study of lime-silica-alumina systems, where the simpler and more transferable Lennard-Jones potential was used instead of the more traditional Buckingham potential. The results were validated using experimental density and structural data. The elastic properties were also considered. Six amorphous phases (corresponding to calcium/silicon ratios corresponding to belite, rankinite, wollastonite and alumina-doped amorphous wollastonite with 5%, 10% and 15% alumina content) were also studied using molecular dynamics simulations. The obtained MD trajectories were used to characterize the different crystalline and amorphous phases in terms of the corresponding radial distribution functions, aggregate analyses and connectivity among silica groups. These studies allowed a direct comparison between the crystalline and amorphous phases and revealed how the structure of the silica network was modified in the amorphous materials or by the inclusion of other structural units such as alumina. The knowledge at an atomistic level of such modifications is paramount for the formulation of new cement-clinker phases.

  9. classical optimization of bagasse ash content in cement-stabilized ...

    African Journals Online (AJOL)

    Optimization of construction materials with laboratory data is a very possible way of minimizing waste of resources (materials and cost). There had been several successful attempts of optimization of construction materials. However, optimization in soil stabilization for road-work has been very rare because of its complexities ...

  10. Modelling porewater chemistry in hydrated Portland cement

    International Nuclear Information System (INIS)

    Berner, U.R.

    1987-01-01

    Extensive employment of concrete is foreseen in radioactive waste repositories. A prerequisite for modelling the interactions between concrete and formation waters is characterization of the concrete system. Available experimental data from high pressure squeezing of cement pore-water indicate that, besides the high pH due to alkali hydroxide dissolution, cement composition itself influences the solubility determining solid phases. A model which simulates the hydration of Portland cement assuming complete hydration of the main clinker minerals is presented. The model also includes parameters describing the reactions between the cement and blending agents. Comparison with measured pore-water data generally gives a consistent picture and, as expected, the model gives correct predictions for pure Portland cements. For blended cements, the required additional parameters can, to some extent, be derived from pore-water analysis. 14 references, 1 figure, 4 tables

  11. 76 FR 50252 - Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review...

    Science.gov (United States)

    2011-08-12

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-461 (Third Review)] Gray Portland Cement... Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United States International... Act) to determine whether revocation of the antidumping duty order on gray portland cement and cement...

  12. Physical and Thermodynamical Properties of Water Phases in Hardening Portland Cement Systems

    DEFF Research Database (Denmark)

    Hansen, T. Bæk

    The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process.......The present study is devoted to the description of water phases in hardening portland cement paste systems containing a significant amount of micro-filler and having a low to moderate water/powder ratio. Emphasis has been placed on the early stages of the hardening process....

  13. The effect of lime-dried sewage sludge on the heat-resistance of eco-cement.

    Science.gov (United States)

    Li, Wen-Quan; Liu, Wei; Cao, Hai-Hua; Xu, Jing-Cheng; Liu, Jia; Li, Guang-Ming; Huang, Juwen

    2016-01-01

    The treatment and disposal of sewage sludge is a growing problem for sewage treatment plants. One method of disposal is to use sewage sludge as partial replacement for raw material in cement manufacture. Although this process has been well researched, little attention has been given to the thermal properties of cement that has had sewage sludge incorporated in the manufacturing process. This study investigated the fire endurance of eco-cement to which lime-dried sludge (LDS) had been added. LDS was added in proportions of 0%, 3%, 6%, 9%, and 12% (by weight) to the raw material. The eco-cement was exposed to 200, 400, or 600 °C for 3 h. The residual strength and the microstructural properties of eco-cement were then studied. Results showed that the eco-cement samples suffered less damage than conventional cement at 600 °C. The microstructural studies showed that LDS incorporation could reduce Ca(OH)(2) content. It was concluded that LDS has the potential to improve the heat resistance of eco-cement products.

  14. Mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells following their exposure to a discoloration-free calcium aluminosilicate cement.

    Science.gov (United States)

    Niu, Li-Na; Pei, Dan-Dan; Morris, Matthew; Jiao, Kai; Huang, Xue-Qing; Primus, Carolyn M; Susin, Lisiane F; Bergeron, Brian E; Pashley, David H; Tay, Franklin R

    2016-10-01

    An experimental discoloration-free calcium aluminosilicate cement has been developed with the intention of maximizing the beneficial attributes of tricalcium silicate cements and calcium aluminate cements. The present study examined the effects of this experimental cement (Quick-Set2) on the mineralogenic characteristics of osteogenic lineage-committed human dental pulp stem cells (hDPSCs), by comparing the cellular responses with a commercially available tricalcium silicate cement (white mineral trioxide aggregate (ProRoot(®) MTA); WMTA). The osteogenic potential of hDPSCs exposed to the cements was examined using qRT-PCR for osteogenic gene expressions, Western blot for osteogenic-related protein expressions, alkaline phosphatase enzyme activity, Alizarin red S staining, Fourier transform infrared spectroscopy and transmission electron microscopy of extracellular calcium deposits. Results of the six assays indicated that osteogenic differentiation of hDPSCs was significantly enhanced after exposure to the tricalcium silicate cement or the experimental calcium aluminosilicate cement, with the former demonstrating better mineralogenic stimulation capacity. The better osteogenic stimulating effect of the tricalcium silicate cement on hDPSCs may be due to its relatively higher silicate content, or higher OH(-) and Ca(2+) release. Further investigations with the use of in vivo animal models are required to validate the potential augmenting osteogenic effects of the experimental discoloration-free calcium aluminosilicate cement. Published by Elsevier Ltd.

  15. 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.

  16. Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions

    International Nuclear Information System (INIS)

    Husillos Rodriguez, N.; Martinez Ramirez, S.; Blanco Varela, M.T.; Guillem, M.; Puig, J.; Larrotcha, E.; Flores, J.

    2010-01-01

    This paper aims to characterize spray-dried DWTP sludge and evaluate its possible use as an addition for the cement industry. It describes the physical, chemical and micro-structural characterization of the sludge as well as the effect of its addition to Portland cements on the hydration, water demand, setting and mechanical strength of standardized mortars. Spray drying DWTP sludge generates a readily handled powdery material whose particle size is similar to those of Portland cement. The atomized sludge contains 12-14% organic matter (mainly fatty acids), while its main mineral constituents are muscovite, quartz, calcite, dolomite and seraphinite (or clinoclor). Its amorphous material content is 35%. The mortars were made with type CEM I Portland cement mixed with 10 to 30% atomized sludge exhibited lower mechanical strength than the control cement and a decline in slump. Setting was also altered in the blended cements with respect to the control.

  17. Properties, sustainability and elevated temperature behavior of concrete containing Portland limestone cement

    Science.gov (United States)

    El-Hawary, Moetaz; Ahmed, Mahmoud

    2017-09-01

    The utilization of some type of cheap filler as partial cement replacement is an effective way of improving concrete sustainability. With the recent trends to reduce water to cement ratio and improve compaction, there is no enough space or water for complete hydration of cement. This means that actually, a portion of mixed cement acts as expensive filler. Replacing this portion with cheaper filler that requires less energy to produce is, therefore, beneficial. Crushed limestone is the most promising filler. This work is to investigate the effect of the amount of limestone fillers on the sustainability and the fresh and mechanical properties of the resulting concrete. A rich mix is designed with a low water/cement ratio of 0.4. Lime is introduced as a replacement percentage of cement. Ratios of 0, 10, 20 and 30% were used. Slump, compressive strength, specific gravity and water absorption are evaluated for every mix. In addition, the effect of the amount of lime on the residual strength of concrete subjected to elevated temperatures is also investigated. Samples are subjected to six different temperature stations of 20, 100, 200, 300, 500 and 700°C for six hours before being cooled and subsequently tested for compressive strength and specific gravity. Sustainability of the tested mixes is evaluated through reductions in the emitted carbon dioxide, energy and reduction in cost. Based on the annual use of concrete in Kuwait, the sustainability benefits resulting from the use of limestone filler in Kuwait are evaluated and assessed. The paper is concluded with the recommendation of the use of 15% limestone filler as partial cement replacement where the properties and the behavior under high temperature of the resulting concrete are almost the same as those of conventional concrete with considerable cost and sustainability benefits.

  18. Stabilization treatment of soft subgrade soil by sewage sludge ash and cement.

    Science.gov (United States)

    Chen, Li; Lin, Deng-Fong

    2009-02-15

    In this study, incinerated sewage sludge ash (ISSA) is mixed with cement in a fixed ratio of 4:1 for use as a stabilizer to improve the strength of soft, cohesive, subgrade soil. Five different ratios (in wt%: 0%, 2%, 4%, 8%, and 16%) of ISSA/cement admixture are mixed with cohesive soil to make soil samples. In order to understand the influences of admixtures on the soil properties, tests of the pH value, Atterberg limits, compaction, California bearing ratio (CBR), unconfined compressive strength, and triaxial compression were performed on those samples. The study shows that the unconfined compressive strength of specimens with the ISSA/cement addition was improved to approximately 3-7 times better than that of the untreated soil; furthermore, the swelling behavior was also effectively reduced as much as 10-60% for those samples. In some samples, the ISSA/cement additive improved the CBR values by up to 30 times that of untreated soil. This suggests that ISSA/cement has many potential applications in the field of geotechnical engineering.

  19. 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.

  20. Evaluation of cement thixotropy for the cement of oil wells in areas ...

    African Journals Online (AJOL)

    ... economical for cementing job operations in wells with loss zones. The results also show that the effect of LHF is positive, since in addition to his contribution to long term performances, especially the durability of hardened concrete, it improves the thixotropy of cement made of plaster. Keywords: cementing; lost circulation; ...

  1. Properties of paving units incorporating slag cement

    Directory of Open Access Journals (Sweden)

    Hanan A. El Nouhy

    2013-04-01

    Full Text Available The aim of this study is to investigate the effect and possibility of using Portland slag cement in the production of interlocking paving units. Paving units consist of two layers. Four mixes were cast. The first mix was the control mix, in which Portland cement was used in the two layers. In the second mix, Portland slag cement was used in the upper layer, Portland cement was used in the backing layer. In the third mix, Portland cement was placed in the upper layer, while Portland slag cement was used in the backing layer. Finally, in the fourth mix, Portland cement was fully replaced by Portland slag cement in both layers. Tests were carried out in order to investigate the properties of the manufactured specimens at ages 28 and 180 days, respectively. Compressive strength and abrasion resistance were conducted according to the American Society for Testing and Materials (ASTM C 140 and ASTM C418. Water absorption, split tensile strength, abrasion resistance, as well as, skid resistance were performed according to both Egyptian Standard Specifications (ESS 4382 and European Standard (EN 1338. The Egyptian standard is identical with the European standard. The results indicate that it is feasible to use Portland slag cement in the manufacture of paving blocks as the conditions of the conducted tests were satisfied at age180 days except for the minimum splitting tensile strength test.

  2. Integer programming of cement distribution by train

    Science.gov (United States)

    Indarsih

    2018-01-01

    Cement industry in Central Java distributes cement by train to meet daily demand in Yogyakarta and Central Java area. There are five destination stations. For each destination station, there is a warehouse to load cements. Decision maker of cement industry have a plan to redesign the infrastructure and transportation system. The aim is to determine how many locomotives, train wagons, and containers and how to arrange train schedules with subject to the delivery time. For this purposes, we consider an integer programming to minimize the total of operational cost. Further, we will discuss a case study and the solution the problem can be calculated by LINGO software.

  3. Immobilisation of radwaste in cement based matrices

    International Nuclear Information System (INIS)

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

    1989-01-01

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

  4. The influence of silanized nano-SiO{sub 2} on the hydration of cement paste: NMR investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bede, A., E-mail: Andrea.Bede@phys.utcluj.ro; Pop, A.; Ardelean, I. [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 400114 Cluj-Napoca (Romania); Moldovan, M. [“Babes-Bolyai” University, “Raluca Ripan” Chemistry Research Institute, Department of Polymer Composites, 400294 Cluj-Napoca (Romania)

    2015-12-23

    It is known that by adding a small amount of nanoparticles to the cement-based materials a strong influence on the workability, strength and durability is obtained. These characteristics of the material are fundamentally determined by the hydration process taking place after mixing the cement grains with water. In the present study the influence introduced by the addition of nano-silica with silanized surfaces on the hydration process was investigated using low-field nuclear magnetic resonance (NMR) relaxometry. The cement samples were prepared using gray cement at a water-to-cement ratio of 0.4 and a 5% addition of nanosilica. The surface of the nanoparticles was modified using a coating of Silane A174. The cement pastes were monitored during their standard curing time of 28 days. It was established that, by using unmodified nanosilica particles, an acceleration of the hydration process takes place as compared with the pure cement paste. On the other side, by adding silanized nanoparticles, the dormancy stage significantly extends and the hydration process is slower. This slowing down process could enhance the mechanical strength of cement based materials as a result of a better compaction of the hydrated samples.

  5. Evaluation of an injectable bioactive borate glass cement to heal bone defects in a rabbit femoral condyle model.

    Science.gov (United States)

    Cui, Xu; Huang, Wenhai; Zhang, Yadong; Huang, Chengcheng; Yu, Zunxiong; Wang, Lei; Liu, Wenlong; Wang, Ting; Zhou, Jie; Wang, Hui; Zhou, Nai; Wang, Deping; Pan, Haobo; Rahaman, Mohamed N

    2017-04-01

    There is a need for synthetic biomaterials to heal bone defects using minimal invasive surgery. In the present study, an injectable cement composed of bioactive borate glass particles and a chitosan bonding solution was developed and evaluated for its capacity to heal bone defects in a rabbit femoral condyle model. The injectability and setting time of the cement in vitro decreased but the compressive strength increased (8±2MPa to 31±2MPa) as the ratio of glass particles to chitosan solution increased (from 1.0gml -1 to 2.5gml -1 ). Upon immersing the cement in phosphate-buffered saline, the glass particles reacted and converted to hydroxyapatite, imparting bioactivity to the cement. Osteoblastic MC3T3-E1 cells showed enhanced proliferation and alkaline phosphatase activity when incubated in media containing the soluble ionic product of the cement. The bioactive glass cement showed a better capacity to stimulate bone formation in rabbit femoral condyle defects at 12weeks postimplantation when compared to a commercial calcium sulfate cement. The injectable bioactive borate glass cement developed in this study could provide a promising biomaterial to heal bone defects by minimal invasive surgery. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. The Performance and Mechanism Analysis of Cement Pastes Added to Aluminum Sulfate-Based Low-Alkali Setting Accelerator

    Directory of Open Access Journals (Sweden)

    Xingdong Lv

    2017-01-01

    Full Text Available We proposed a type of low-alkali liquid state setting accelerator, named HLSA; it was environmentally friendly product. To investigate the temperature adaptation and cement flexibilities of HLSA, the setting time and strength development properties of cement with HLSA were discussed in this paper. The effects of HLSA on hydration process, hydration products, and microstructure were studied by means of X-ray diffraction (XRD, thermogravimetric analysis (TGA, scanning electron microscope (SEM, and mercury intrusion porosimetry (MIP. The results show that four typical 42.5-grade ordinary Portland cement types with 6–8% HLSA could satisfy the first-grade requirements according to JC477-2005 even at a lower temperature (e.g., 10°C. Further, the percentage ratio of 28 d compressive strength of cement with 6–8% HLSA was over 90%; the XRD diffraction peak of AFt integrated area of cement with 7% HLSA was 3818 at 5 min of hydration; SEM observation revealed that AFt crystals were filled in the pore of cement at 28 d of hydration; the temperature adaptation and cement flexibilities of HLSA were excellent; the cement with HLSA coagulating in a short time attributed to promoting the formation of abundant AFt and the hydration of C3S.

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

    Science.gov (United States)

    Kao, Chia-Tze; Huang, Tsui-Hsien; Chen, Yi-Jyun; Hung, Chi-Jr; Lin, Chi-Chang; Shie, Ming-You

    2014-10-01

    β-Tricalcium phosphate (β-TCP) is an osteoconductive material. For this research we have combined it with a low degradation calcium silicate (CS) to enhance its bioactive and osteostimulative properties. To check its effectiveness, a series of β-TCP/CS composites with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Regarding the formation of bone-like apatite, the diametral tensile strength as well as the ion release and weight loss of composites were compared both before and after immersions in simulated body fluid (SBF). In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on β-TCP/CS composites. The results show that the apatite deposition ability of the β-TCP/CS composites improves as the CS content is increased. For composites with more than a 60% CS content, the samples become completely covered by a dense bone-like apatite layer. At the end of the immersion period, weight losses of 24%, 32%, 34%, 38%, 41%, and 45% were observed for the composites containing 0%, 20%, 40%, 80%, 80% and 100% β-TCP cements, respectively. In addition, the antibacterial activity of CS/β-TCP composite improves as the CS-content is increased. In vitro cell experiments show that the CS-rich composites promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the CS quantity in the composite is less than 60%, the quantity of cells and osteogenesis protein of hDPCs is stimulated by Si released from the β-TCP/CS composites. The degradation of β-TCP and the osteogenesis of CS give strong reason to believe that these calcium-based composite cements will prove to be effective bone repair materials. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Lime kiln dust as a potential raw material in portland cement manufacturing

    Science.gov (United States)

    Miller, M. Michael; Callaghan, Robert M.

    2004-01-01

    In the United States, the manufacture of portland cement involves burning in a rotary kiln a finely ground proportional mix of raw materials. The raw material mix provides the required chemical combination of calcium, silicon, aluminum, iron, and small amounts of other ingredients. The majority of calcium is supplied in the form of calcium carbonate usually from limestone. Other sources including waste materials or byproducts from other industries can be used to supply calcium (or lime, CaO), provided they have sufficiently high CaO content, have low magnesia content (less than 5 percent), and are competitive with limestone in terms of cost and adequacy of supply. In the United States, the lime industry produces large amounts of lime kiln dust (LKD), which is collected by dust control systems. This LKD may be a supplemental source of calcium for cement plants, if the lime and cement plants are located near enough to each other to make the arrangement economical.

  9. Low alkaline cement used in the construction of a gallery in the Horonobe Underground Research Laboratory

    International Nuclear Information System (INIS)

    Nakayama, Masashi; Sato, Haruo; Sugita, Yutaka; Ito, Seiji; Minamide, Masashi; Kitagawa, Yoshito

    2011-01-01

    In Japan, any high level radioactive waste (HLW) pos is to be constructed at over 300 m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various admixtures. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly Flyash Contained Silicafume Cement), containing over 60wt% of silica-fume (SF) and fly-ash (FA). HFSC was used experimentally as the shotcrete material in construction of part of the 140m deep gallery in the Horonobe Underground Research Laboratory (URL). The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40 wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC. The total length of tunnel using HFSC shotcrete is about 73 m and about 500 m 3 of HESC was used. The workability of HESC shotcrete was confirmed in this experimental construction. (author)

  10. Influence of time addition of superplasticizers on the rheological properties of fresh cement pastes

    International Nuclear Information System (INIS)

    Aiad, Ismail

    2003-01-01

    It is well known that the fluidity and the fluidity loss of fresh cement pastes are affected by the kind and the time of addition of organic admixtures. The influence of the time addition of two chemical admixtures, namely, melamine formaldehyde sulfonate (MFS) and naphthalene formaldehyde sulfonate (NFS), on the rheological properties of ordinary Portland and sulfate-resisting cement pastes through the first 120 min of hydration was investigated. The admixture addition was delayed by 0, 5, 10, 15, 20, and 25 min. Shear stress and apparent viscosity of the cement pastes were determined at different shear rates (3-146 s -1 ) and hydration times of 30, 60, 90, and 120 min. The concentration of Ca 2+ and the combined water content of the cement pastes were determined after 120 min. Yield stress and plastic viscosity values were also determined by using the Bingham model. The results show that an increase in the addition time of the admixture reduces the shear stress, the yield stress, and the plastic viscosity of the cement pastes at the early ages (15 min) as well as at later early ages (120 min). The optimum delaying time of admixture addition is found to be 10-15 min. This time does not depend on the cement and superplasticizer type

  11. An Experimental Study on Solidifying Municipal Sewage Sludge through Skeleton Building Using Cement and Coal Gangue

    Directory of Open Access Journals (Sweden)

    Jiankang Yang

    2017-01-01

    Full Text Available The municipal sewage sludge typically has very high water content and low shear strength. Conventional methods of lime and cement solidification of municipal sewage sludge often suffer high cost, significant drying shrinkage, frequent cracking, high hydraulic conductivity, and low strength. To overcome these shortcomings, in this paper a skeleton-building method was used to solidify municipal sewage sludge in which coal gangue, cement and clay, and fiber were used as skeleton materials, cementation materials, and filling materials, respectively. Comprehensive laboratory tests including cracking, nitrogen adsorption, triaxial shearing, and permeability tests were performed to determine cracking, pore structure, shear strength, and hydraulic conductivity of municipal sewage sludge solidified with different proportions of coal gangue, cement, fiber, and clay. Based upon the experimental results, the mechanisms of the skeleton building using cement and coal gangue were discussed and factors controlling the mechanical and hydraulic behavior of the solidified soils were analyzed at both microscopic and macroscopic levels. Based upon the test results and analyses, recommendations were made for solidifying municipal sewage sludge through skeleton building using cement and coal gangue. The solidified soils have high soil strength, high resistance to cracking, and low hydraulic conductivity which are sufficient for being used as landfill liner.

  12. A study on provisional cements, cementation techniques, and their effects on bonding of porcelain laminate veneers.

    Science.gov (United States)

    Vinod Kumar, G; Soorya Poduval, T; Bipin Reddy; Shesha Reddy, P

    2014-03-01

    Minimal tooth preparation is required for porcelain laminate veneers, but interim restorations are a must to protect their teeth against thermal insult, chemical irritation, and to provide aesthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and fit and final bonding of the porcelain laminate veneer. This in vitro study examined the tooth surface for remaining debris of cement after removal of a provisional restoration. Determine the presence of cement debris on prepared tooth surface subsequent to the removal of provisional restoration. Determine the cement with the least residue following the cleansing procedures. Determine the effect of smear layer on the amount of residual luting cement. Eighty-four extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with six bonding methods: varnish combined with glass ionomer cement (GIC), varnish combined with resin modified GIC, varnish, spot etching combined with dual-cure luting cement, adhesive combined with GIC, adhesive combined with resin modified GIC, and adhesive, spot etching combined with dual-cure luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with SEM. Traces of cement debris were found on all the prepared teeth surfaces for all six groups which were cemented with different methods. Cement debris was seen on teeth subsequent to the removal of provisional's. Dual-cure cement had the least residue following the cleansing procedures. Presence of smear layer had no statistical significance in comparison with cement residue. With the use of adhesive the cement debris was always found to be more than with the use of varnish. GIC showed maximum residual cement followed by dual-cure.

  13. Effect of Gum Arabic Karroo as a water-reducing admixture in cement mortar

    Directory of Open Access Journals (Sweden)

    Rose Mbugua

    2016-12-01

    Full Text Available The aim of this study was to develop Gum Acacia Karroo (GAK as set retarding-water reducing admixture in cement mortars. Retarding admixtures are used to counter effect the accelerated hydration of cement at elevated temperatures by slowing down the retarding process especially during the day when concreting work is done. However most retarding admixtures available in the market are expensive, thereby making them out of reach for small consumers of concrete in Africa are expensive and not readily available. GAK, which contains soluble sugars, was investigated as a set-retarding water reducing-admixture. Setting time was measured in cement pastes with different dosages of GAK and a commercial retarding agent (Tard CE. Compressive strength, bleeding and flow test were investigated on cement mortars with the control being cement mortar without admixture. GAK was found to increase final setting time by 6 h above control. Compressive strength increased when water cement ratio was reduced from 0.5 to 0.4. Thermogravimetric analysis revealed increased dosage of GAK reduced hydration rate.

  14. Study on temperature and damage sensing capability of Portland cement paste through the thermoelectric measurements

    Science.gov (United States)

    Hou, Tsung-Chin; Tai, Ko-Hung; Su, Yu-Min

    2017-04-01

    This study attempted to investigate the self-sensing capability of Portland cement composites in sensing temperature and detecting damages through the measurements of materials' thermoelectric properties. Specimens were made of Ordinary Portland Cement (OPC) with the water to cement ratio of 0.4. Temperature sensing property was characterized at various ages of the specimens from 28 to 49 days and at dried/moisturized conditions. It was found there exists an approximately linear relationship between temperature differences (ΔT) and the measured thermoelectric potentials, which is known as the Seebeck effect. This linearity was observed to be varied but able to be characterized for cement pastes at different ages and water saturation conditions. Mechanical loading that introduced different types and degrees of damages also translated into the variations of thermoelectric properties. Specifically, different types of compressive loads were tested for comparison. The study results have shown that Seebeck coefficient dropped with introduced damages, and restored with the subsequent re-curing as well as the continued cement hydration. Mild and moderate damages can be partially or fully restored, while severe damages that have resulted in significant drop of the Seebeck coefficients would restrain the self-restoration. Determination of the damage threshold was not yet revealed in this study, while it was shown obviously there existed one. Our investigation results indicated that characterizing the self-sensing capability of Portland cement composites is achievable through the measurements of thermoelectric properties. This study, in particular, has showcased the temperature sensing and damage detection capability.