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Sample records for water cement ratio

  1. Effect of Water-Cement Ratio on Pore Structure and Strength of Foam Concrete

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    Zhongwei Liu

    2016-01-01

    Full Text Available Foam concrete with different dry densities (400, 500, 600, 700, and 800 kg/m3 was prepared from ordinary Portland cement (P.O.42.5R and vegetable protein foaming agent by adjusting the water-cement ratio through the physical foaming method. The performance of the cement paste adopted, as well as the structure and distribution of air pores, was characterized by a rheometer, scanning electron microscope, vacuum water saturation instrument, and image analysis software. Effects of the water-cement ratio on the relative viscosity of the cement paste, as well as pore structure and strength of the hardened foam concrete, were discussed. Results showed that water-cement ratio can influence the size, distribution, and connectivity of pores in foam concrete. The compressive strength of the foam concrete showed an inverted V-shaped variation law with the increase in water-cement ratio.

  2. Effect of strain rate and water-to-cement ratio on compressive mechanical behavior of cement mortar

    Institute of Scientific and Technical Information of China (English)

    周继凯; 葛利梅

    2015-01-01

    Effects of strain rate and water-to-cement ratio on the dynamic compressive mechanical behavior of cement mortar are investigated by split Hopkinson pressure bar (SHPB) tests. 124 specimens are subjected to dynamic uniaxial compressive loadings. Strain rate sensitivity of the materials is measured in terms of failure modes, stress−strain curves, compressive strength, dynamic increase factor (DIF) and critical strain at peak stress. A significant change in the stress−strain response of the materials with each order of magnitude increase in strain rate is clearly seen from test results. The slope of the stress−strain curve after peak value for low water-to-cement ratio is steeper than that of high water-to-cement ratio mortar. The compressive strength increases with increasing strain rate. With increase in strain rate, the dynamic increase factor (DIF) increases. However, this increase in DIF with increase in strain rate does not appear to be a function of the water-to-cement ratio. The critical compressive strain increases with the strain rate.

  3. Effect of Water to Cement Ratio and Age on Portland Composite Cement Mortar Porosity, Strength and Evaporation Rate

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    Enamur R. Latifee

    2016-08-01

    Full Text Available Durability and the compressive strength of concrete are directly related to the porosity. Water to cement ratio is the main parameter behind the nature and amount of pores within the matrix. Porosity is also influenced by the degree of cement hydration and the length of moist-curing. Even after the standard moist curing period, i.e. 28 days the concrete can gain strength and porosity can be reduced under ambient relative humidity and temperature. However, this fact, that is the age effect on porosity reduction of the cement mortar or concrete, kept in air with ambient relative humidity and temperature for long duration could not be found in the literature. Therefore, in this research, different w/c were used with constant amount Portland Composite Cement to find out whether the mortar porosity decreases significantly over time, after 28 days of water curing, while kept in air and if there is any interaction effect between the age of the mortar and different w/c; regarding porosity. It was also intended to find out if water-loss rate variation with different w/c has similar trend as porosity variation with different w/c. It was found that, there is significant decrease in porosity with time for the first six weeks in air and after that it dwindles down gradually, and there is no interaction between age and w/c. Also, after 100 days in air, samples were submerged under water for 24 hours and then kept in air for the evaporation in subsequent days. It has been found that the water evaporation vs. w/c curve, using 11-day evaporation of water from different w/c specimens in ambient condition is almost parallel to porosity vs. w/c curve. Therefore, 11-day evaporation of aged saturated mortar or concrete sample, such as core can also be used as a durability index, which can be used for old structure evaluation.

  4. Behavior of High Water-cement Ratio Concrete under Biaxial Compression after Freeze-thaw Cycles

    Institute of Scientific and Technical Information of China (English)

    SHANG Huaishuai; SONG Yupu; OU Jinping

    2008-01-01

    The high water-cement ratio concrete specimens under biaxial compression that completed in a triaxial testing machine were experimentally studied.Strength and deformations of plain concrete specimens after 0,25,50 cycles of freeze-thaw.Influences of freeze-thaw cycles and stress ratio on the peak stress and deformation of this point were analyzed aecording to the experimental results.Based on the test data,the failure criterion expressed in terms of principal stress after difierent cycles of freeze-thaw,and the failure criterion with consideration of the influence of freeze-thaw cycle and sffess ratio were proposed respectively.

  5. EFFECTS OF VARYING CURING AGE AND WATER/CEMENT RATIO ON THE ELASTIC PROPERTIES OF LATERIZED CONCRETE

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    Ata Olugbenga

    2007-01-01

    Full Text Available This paper reports the results of investigations carried out on the effect of varying curing age and water/cement ratio on the modulus of elasticity and modulus of deformability of laterized concrete. The test specimens were made with sieved samples of selected grain size ranges of laterite used as fine aggregates to replace sand in normal concrete. Batching was by weight. Three mix ratios of (1:1½:3, (1:2:4 and (1:3:6 were used. Water/cement ratio of 0.5, 0.6, 0.7 and 0.75 were used for each of the mix ratios. The specimens were tested at curing ages of seven to 28 days. The results showed that there was a corresponding increase in both modulus of elasticity and modulus of deformability of laterized concrete due to increase in curing ages. The mix proportion, compressive strength and water/cement ratio were found to have significant effects on both modulus of elasticity and modulus of deformability of laterized concrete.

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

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    Sahin, Remzi, E-mail: rsahin@atauni.edu.tr [Dept. of Civil Eng., Faculty of Eng., Atatuerk University, Erzurum (Turkey); Polat, Recep [Dept. of Physics, Faculty of Education, Erzincan University, Erzincan (Turkey); Icelli, Orhan [Dept. of Physics, Faculty of Arts and Science, Yildiz Technical University, Istanbul (Turkey); Celik, Cafer [Dept. of Industrial Eng., Faculty of Eng., Atatuerk University, Erzurum (Turkey)

    2011-07-15

    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.

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

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    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.

  8. Influence of magnesia-to-phosphate molar ratio on microstructures, mechanical properties and thermal conductivity of magnesium potassium phosphate cement paste with large water-to-solid ratio

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Biwan, E-mail: xubiwan@gmail.com [Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Ma, Hongyan, E-mail: mhy1103@gmail.com [Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Li, Zongjin [Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2015-02-15

    This paper describes the influence of the magnesia-to-phosphate (M/P) molar ratios ranging from 4 to 12, on the properties and microstructures of magnesium potassium phosphate cement (MKPC) pastes with a large water-to-solid ratio (w/s) of 0.50. The setting behavior, compressive strength, tensile bonding strength and thermal conductivity of the MKPC pastes, were investigated. The results show that an increase in the M/P ratio can slow down the setting reaction, and clearly degrade the mechanical strengths, but clearly improve the thermal conductivity of MKPC pastes. Furthermore, micro-characterizations including X-ray diffraction, scanning electron microscopy and thermogravimetric analysis, on the MKPC pastes reveal that a lower M/P ratio can facilitate better crystallization of the resultant magnesium potassium phosphate hexahydrate (MKP) and a denser microstructure. Moreover, strong linear correlations are found between the mechanical strengths and the MKP-to-space ratio, and between thermal conductivity and the volume ratio of the unreacted magnesia to the MKP. - Highlights: • Increase of M/P molar ratio causes clear mechanical degradations on MKPC pastes. • Thermal conductivity of MKPC pastes is improved with increase of M/P molar ratio. • Lower M/P ratio leads to better MKP crystallization and denser microstructure. • Strengths of MKPC pastes are linearly correlated to the MKP-to-space ratios. • Thermal conductivity is affected by the volume ratio of unreacted magnesia to MKP.

  9. 水灰比对高抗硫硅酸盐水泥混凝土抗侵蚀性能的影响%Influence of Water-cement Ratio on Resistance to Erosive Ability of High Sulfur Resistant Cement

    Institute of Scientific and Technical Information of China (English)

    胡全; 唐新军; 翟超; 李双喜; 苏建彪; 王文政

    2013-01-01

    The objective of this study was designed to conduct a sulfate erosive experiment on mortar specimen with different water-cement ratio prepared with high sulfur resistant cement.The result showed that the resistance to erosive ability of high sulfur resistant portland cement concrete were affected by water-cement ratio and curing age,which were hard to resist the erosion of higher concentration sulfate solution for a long time under the conditions of higher water-cement ratio and shorter curing age;In the erosive solution of sulfuric acid root ion concentration of less than or equal to 10 000 mg/L,reducing the water-cement ratio of high resistance of sulfur cement concrete sulfate can enhance its ability to resist erosion.However,when the erosive solution of sulfuric acid root ion concentration was more than or equal to 20 250 mg/L,even if cutting down the water-cement ratio can hardly guarantee the long term resistance to sulfate erosive ability; In the case of the same water-cement ratio,the ability of the resistance to erosion of 3 days' maintenance of high corrosive resistance of the specimens are significantly lower than that of 28 days'.%对高抗硫硅酸盐水泥配制的不同水灰比的胶砂试件进行硫酸盐侵蚀实验.结果表明,高抗硫水泥混凝土的抗侵蚀能力受水灰比和养护龄期的影响,在较大水灰比或较短养护龄期情况下,难以长期抵抗较高浓度硫酸盐溶液的侵蚀;在硫酸根离子浓度≤10 000 mg/L的侵蚀溶液中,降低高抗硫水泥混凝土的水灰比,可增强其抗侵蚀能力,但是,当硫酸根离子浓度≥20 250 mg/L时,即使降低水灰比,也难以保证长期抵抗硫酸盐侵蚀的能力;在相同水灰比情况下,养护3d高抗试件的抗蚀能力明显低于养护28 d高抗试件.

  10. Form and Mechanism of Sulfate Attack on Cement-based Material Made of Limestone Powder at Low Water-binder Ratio under Low Temperature Conditions

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    LIU Juanhong; SONG Shaomin; XU Guoqiang; XU Weiguo

    2012-01-01

    The development of strength and the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment were studied.The results indicate that when water-binder ratio is lower than 0.40,the cement-based material with limestone powder has insignificant change in appearance after being soaked in 10% magnesium sulfate solution at low temperature for 120 d,and has significant change in appearance after being soaked at the age of 200 d.Expansion damage and exfoliation occur on the surface of concrete test cube at different levels.When limestone powder accounts for about 28 percent of cementitious material,with the decrease of water-binder ratio,the compressive strength loss has gradually decreased after the material is soaked in the magnesium sulfate solution at low temperature at the age of 200 d.After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200 d,gypsum attack-led destruction is caused to the concrete test cube,without thaumasite sulfate attack.

  11. The participation ratios of cement matrix and latex network in latex cement co-matrix strength

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    Ahmed M. Diab

    2014-06-01

    Full Text Available This investigation aims to determine the participation ratio of cement matrix and latex network in latex cement co-matrix strength. The first stage of this study was carried out to investigate the effect of styrene butadiene rubber (SBR on cement matrix participation ratio by measuring degree of hydration and compressive strength. The second stage in this study shows an attempt to evaluate the latex participation ratio in mortar and concrete strength with different latex chemical bases. Effect of latex particle size on latex network strength was studied. The test results indicated that the latex participation ratio in co-matrix strength is influenced by type of cement matrix, type of curing, latex type, latex solid/water ratio, strength type and age. For modified concrete, when the SBR solid/water ratio increases the latex participation ratio in flexural and pull out bond strength increases. The latex participation ratio in co-matrix strength decreases as latex particle size increases.

  12. Effect of super absorbent polymer on the properties of cement mortar with high water-cement ratio%高吸水树脂对高水灰比水泥砂浆性能的影响

    Institute of Scientific and Technical Information of China (English)

    马先伟; 张艳会; 武双磊

    2015-01-01

    Super absorbent polymer( SAP)is considered as an effective curing agent of high performance concrete,but the researches on the effect of SAP in mortar with high water-cement ratio is less. The effects of SAP on the fluidity,strength,water loss rate,shrinkage rate of cement mortar were analyzed. The results show that increasing the amount of SAP decreases the fluidity and strength,but raise the dry water loss rate and shrinkage. The proper dosage,however,can improve the strength and reduce dry shrinkage.%高吸水树脂被认为高性能混凝土的一种有效的内养护剂,但是在高水灰比的砂浆体系SAP的作用效果如何研究较少。因而,对两种高吸水树脂对水泥砂浆流动度、强度、失水率、收缩率的影响进行了研究,发现随着SAP掺量增加,砂浆的流动度、强度降低,但是干燥失水率和收缩增加。不过,适当的SAP掺量可以提高砂浆强度,降低干燥收缩。

  13. The Hydration of Blended Cement at Low W/B Ratio

    Institute of Scientific and Technical Information of China (English)

    HU Shu-guang; LU Lin-nu; HE Yong-jia; LI Yue; DING Qing-jun

    2003-01-01

    The hydration process, hydration product and hydration heat of blended cement paste mixed with mineral admixture and expansive agent at low W/B ratio are studied by XRD , thermo analysis , and calorimetry instrument, and they were compared with those of pure cement paste. The results show that pure cement and blended cement at low W/B ratio have the same types of hydration products, but their respective amounts of hydration products of various blended cements at same ages and the vatiation law of the amount of same hydration products with ages are different; Tim joint effect of tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore and riff caused by the crystalloid ettringite is the impetus of the volume expansion of cement paste , and the former effect is much greater than the latter one .

  14. 中高水灰比混凝土强度与工作性能的研究%Research on High Water-Cement Ratio of Concrete Strength and Workability

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    王翠英

    2014-01-01

    The water-cement ratio (W/B) decides the performance of concrete. The use of super-soleplate ce-ment can result in a relatively higher strength for high water-cement ratio concrete. During the hydration ultra-sul-fur cement can form a large number of ettringite crystals so as to resist shrinkage of concrete section. Therefore, high water-cement ratio of the concrete guarantees its performance as well as its strength. The main contents of the experiment:(1)Ultra-sulfur cement in different proportions of water requirement of normal consistency, fluidity, setting time.(2)Using different proportions of ultra-sulfur cement concrete of the slump and compressive and flex-ural strength test. It aims to find a good concrete, mix of the strength and workability through experiments.%混凝土依赖水灰比(W/B)获得工作性能,中高水灰比混凝土之所以有较高的强度,是因为使用了超硫酸盐水泥。超硫水泥在水化期间能够形成大量的钙矾石晶体,从而抵抗了部分混凝土的收缩,因此中高水灰比混凝土在工作性得到保证的同时,也具有较高的强度。本研究内容是:(1)超硫水泥在不同配比下的标准稠度需水量、流动度、凝结时间。(2)使用不同配比超硫水泥的混凝土的坍落度、扩展度、含气量及抗压抗折强度实验。通过实验找出强度和工作性能良好的混凝土配合比。

  15. 水灰比对再生混凝土抗压强度影响的研究%Study of Water Cement Ratios on Compressive Strength of Recycled Concrete

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    席鹏

    2014-01-01

    指出了再生混凝土是将废弃混凝土经过清洗、破碎、分级,并按一定比例相互配合后得到的,是将再生骨料作为部分或者全部骨料配置的混凝土。水灰比是影响混凝土的抗压强度的主要因素。不同的水灰比对混凝土的其它方面的性能也有一定的影响。在相同的水灰比下,普通混凝土的性能与再生混凝土的性能又是否存在着差异,是试验研究的问题。试验采用不同的水灰比,将再生混凝土与普通混凝土的强度进行了比较,分析了不同水灰比对再生混凝土强度的影响。%Recycled concrete is made of waste concrete by cleaning ,crushing ,grading and under a certain proportion of mutual cooperation ,and is configured by concrete recycled aggregate as part of or all of the aggregate .The water cement ratio influences the strength of concrete ,and different water cement ratios also influence concrete′s other properties .This test focuses on the problems of whether there are some influences on the recycled concrete performance and whether there are differences between the performance of ordinary concrete and recycled concrete performance in the same water cement ratio .By adopting different water -cement ratios to the recycled concrete and normal concrete strength ,it compares their durability ,carbonation resistance .Finally ,it analyzes the influences of different water cement ratios on the properties of recycled concrete .

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

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    Yun-Yong Kim

    2014-01-01

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

  17. 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.

  18. 掺合料和水胶比对水泥基材料水化产物和力学性能的影响%Influence of admixture and water-cement ratio on hydration products and mechanical properties of cement-based materials

    Institute of Scientific and Technical Information of China (English)

    吴福飞; 侍克斌; 董双快; 陈亮亮; 慈军; 王欣; 张凯

    2016-01-01

    Admixture and water-cement ratio are important factors affecting the development of properties of cement mortar or concrete. In order to study the influence of admixtures and water-cement ratio on the hydration products and the mechanical properties of cement-based materials, the study combined hydration reaction mechanism of pure cement and silicate admixture, derived the formulae of hydration products, theoretical maximum mixing amount and total porosity of composite cement-based materials, and investigated the effects of mixing amount of cement mortar with fly ash, steel slag and lithium slag on total porosity, mechanical properties and hydration products. This paper designed 3 gradients of water-cement ratio (0.50, 0.42 and 0.34), 3 kinds of admixtures (lithium slag, fly ash and steel slag) and 2 contents (20% and 60%); the ratio of cementitious material to sand was 1:2.5, and then, molding specimen accorded with the mix of mortar in the triple mold and the mechanical properties of mortar were tested when specimen was cured to 1, 3, 7, 28 and 90 d. The results showed that, after the same content of fly ash, steel slag and lithium slag incorporation, the contents of hydration products of composite cementitious materials, i.e. calcium hydroxide (CH) and calcium silicate hydrate (CSH), and the total porosity were smaller than those of pure cement; when the water-cement ratio decreased from 0.50 to 0.34, the total porosity of cement mortar decreased from 16.0% to 9.3%, and the contents of CH and CSH increased for the compound cement-based materials with mixing amount of 5%, but the increments were not big; the porosity of fly ash, steel slag and lithium slag cement-based composite materials reduced from 16.6%, 17.2% and 16.0% to 9.9%, 10.9% and 9.3%, respectively. When the admixture amount increased to 10%, the variation of porosity and hydration products of the 3 kinds of mortar was different. The content of hydration products (CH and CSH) of composite

  19. Effects of chemical and mineral additives and the water/cement ratio on the thermal resistance of Portland cement concrete; O efeito de aditivos quimicos e minerais e da relacao agua/cimento na resistencia ao calor do concreto de concreto de cimento Portland

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    Cesar, Leandro Cesar Dias; Morelli, Arnaldo C.; Baldo, Joao Baptista [Sao Carlos Univ., SP (Brazil). Dept. de Engenharia de Materiais

    1998-07-01

    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)

  20. The Effect of Ratio of Water to Binder on the Properties of Magnesium Potassium Phosphate Cement Paste%水灰比对磷酸钾镁水泥性能的影响

    Institute of Scientific and Technical Information of China (English)

    徐选臣; 邵云霞

    2013-01-01

    The effect of ratio of water to binder on the properties of magnesium potassium phosphate cement ( MKPC) paste with composite retarder was investigated through measuring initial setting time f fluidity and hydration temperature of MKPC pastes, and through testing the compressive strength and analyzing micro morphology and phase compositions. The result indicated that, there was an obvious effect of ratio of water to binder on the properties of MKPC There was an optimum range of water to binder of MKPC paste when hardened MKPC pastes had more perfect structure and higher compressive strength.%通过测试不同水灰比的含复合缓凝剂的新型磷酸钾镁水泥(MKPC)浆体的凝结时间、流动性和水化过程温度变化,测试其硬化体的抗压强度、分析硬化体的物相组成和微观结构,研究水灰比对MKPC浆体特性的影响.结果表明:水灰比对MKPC的抗压强度和微观结构有显著影响;存在最佳的水灰比范围(0.10,0.11),使MKPC硬化体的结构较完善和后期抗压强度较高.

  1. The Hydration Characteristics and Expansion Machanism of Expansive Cement at Low W/B Ratio

    Institute of Scientific and Technical Information of China (English)

    LU Lin-nu; HE Yong-jia; LI Yue; DING Qing-jun; HU Shu-guang

    2003-01-01

    The hydration characteristics and expansion impetus of three kinds of cement paste under freeand confined-curing conditions were investigated, which were respectively mixed with three different kinds of expansive agent at low W/ B ratio. The results show that the hydration products of pure cement paste and paste mixed with expansive agent are same, but the amount of hydration products , un-hydrated C3 S and C2 S are obviously different at the same hydration age. At 3 d age, the amount of CH in pure cement paste is less than that of paste mixed with expaasive agent, but it is reverse when at 28d age. The amount of AFt at 3d and 28d age in pure cement paste is less than those of paste mixed with expansive agent. Regardless of under free- or confined-curing condition, the amount of ettringite produced varies little since 3 d age. The joint effect of the tumefaction of gel-ettringite due to water absorption and the expansive pressure on the pore caased by the crystalloid ettringite is the cause of the volume expansion of cement paste, and the former effect is much greater than the latter .

  2. Fluid inclusions in vadose cement with consistent vapor to liquid ratios, Pleistocene Miami Limestone, southeastern Florida

    Science.gov (United States)

    Barker, C.E.; Halley, R.B.

    1988-01-01

    Vadose cements in the Late Pleistocene Miami Limestone contain regions with two-phase aqueous fluid inclusions that have consistent vapor to liquid (V-L) ratios. When heated, these seemingly primary inclusions homogenize to a liquid phase in a range between 75??C and 130??C (mean = 100??C) and have final melting temperatures between -0.3?? and 0.0??C. The original distribution of Th was broadened during measurements because of fluid inclusion reequilibration. The narrow range of Th in these fluid inclusions suggest unusually consistent V-L ratios. They occur with small, obscure, single phase liquid-filled inclusions, which infer a low temperature origin (less than 60??C), and contradict the higher temperature origin implied by the two phase inclusions. The diagenetic environment producing these seemingly primary fluid inclusions can be inferred from the origin of the host calcite enclosing them. The ??18O composition of these cements (-4 to-5.5%., PDB) and the fresh water in the fluid inclusions are consistent with precipitation from low-temperature meteoric water. The carbon-isotope composition of the vadose cements that contain only rare two-phase fluid inclusions are comparable to the host rock matrix (??13C between 0 and +4%., PDB). Cements that contain common two-phase fluid-inclusions have a distinctly lighter carbon isotopic composition of -3 to -5%.. The carbon isotope composition of cements that contain common two-phase inclusions are about 6%. lighter than those of other vadose cements; models of early meteoric diagenesis indicate that this is the result of precipitation from water that has been influenced by soil gas CO2. Our hypothesis is that the primary fluid inclusions, those with consistent V-L ratios and the single-phase liquid inclusions, form at near-surface temperature (25??C) and pressure when consistent proportions of soil gas and meteoric water percolating through the vadose zone are trapped within elongate vacuoles. This study corroborates

  3. Microstructural variation of hardened cement-fly ash pastes leached by soft water

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The microstructural variations of hardened cement-fly ash pastes leached by soft water were investigated by MIP, XRD, TG and SEM. The results show that the mass of hardened cement-fly ash paste reduces and its microstructure deteriorates partly after leaching of soft water. At the leaching duration of 180 days, the hardened paste containing fly ash deteriorated a little more serious than the plain cement paste, but the incorporation of fly ash in a proper ratio was helpful to defer the trend of deterioration of the hardened paste microstructure. The microstructural stability of hardened cement-fly ash paste wasn’t damaged severely during the 180 days leaching duration.

  4. Measurement of water transport from saturated pumice aggregates to hardening cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Bentz, Dale; Lange, David A.;

    2006-01-01

    In internal water curing of High Performance Concrete, it is fundamental to know how and when the water contained in the internal curing agent is released into the hydrating cement paste. In this study, X-ray absorption measurements showed that considerable transport of water from saturated pumice...... stone to hydrating cement paste with water/cement ratio 0.3 took place in the first days after casting and covered a distance of at least 4 mm. As a consequence, the total amount of water released by the lightweight aggregates, rather than the spatial distribution of the aggregates, is in this case...

  5. Microstructure Mechanism Analysis of Cementitious Composites at Low Water-cement Ratio%低水胶比条件下水泥基复合材料的微结构形成机理

    Institute of Scientific and Technical Information of China (English)

    戎志丹; 虞焕新; 林发彬

    2013-01-01

    The hydration process of ultra high performance of cementitious composite(UHPCC) is obviously different from common concrete owing to its low water-cement ratio. The hydration process and microstructure of UHPCC were investigated via different analysis testing methods. The results indicate that the hydration process of UHPCC continues for a long time, the pozzolanic reaction consumes Ca(OH)2 ,the porosity reduced(<4%) and the interface is strengthened as the curing time increased. Nanoindentation results indicate that most hydrated products of UHPCC is UHD C-S-H and unhydrated cement,a few HD C-S-H and no LD C-S-H are observed in UHPCC. The unhydrated cement particles are surrounded by UHD C-S-H which is not influenced the durability of UHPCC. So the UHPCC has excellent mechanical performance and durability.%超高性能水泥基复合材料(UHPCC)由于其水胶比极低,水化进程明显与普通混凝土不同,故采用多种分析测试手段以期揭示其水化过程及微结构形成机理.结果表明,低水胶比条件下的UHPCC材料水化反应一直持续进行,随着养护龄期的延长,火山灰反应消耗了Ca(OH)2,孔隙率得以进一步降低(4%以下),界面得到强化.纳米力学性能测试分析表明,UHPCC材料存在大量未水化的水泥颗粒,且绝大部分水化产物为UHD C-S-H凝胶,未发现类似普通混凝土材料中的LD C-S-H凝胶,存在少量的HD C-S-H凝胶,且未水化水泥颗粒被水化产物UHD C-S-H凝胶紧密包围,不会对后期的耐久性能产生过多影响,因此UHPCC才显示出优异的力学性能和耐久性能.

  6. Effect of the calcium to phosphate ratio of tetracalcium phosphate on the properties of calcium phosphate bone cement.

    Science.gov (United States)

    Burguera, Elena F; Guitian, Francisco; Chow, Laurence C

    2008-06-01

    Six different tetracalcium phosphate (TTCP) products were synthesized by solid state reaction at high temperature by varying the overall calcium to phosphate ratio of the synthesis mixture. The objective was to evaluate the effect of the calcium to phosphate ratio on a TTCP-dicalcium phosphate dihydrate (DCPD) cement. The resulting six TTCP-DCPD cement mixtures were characterized using X-ray diffraction analysis, scanning electron microscopy, and pH measurements. Setting times and compressive strength (CS) were also measured. Using the TTCP product with a Ca/P ratio of 2.0 resulted in low strength values (25.61 MPa) when distilled water was used as the setting liquid, even though conversion to hydroxyapatite was not prevented, as confirmed by X-ray diffraction. The suspected CaO presence in this TTCP may have affected the cohesiveness of the cement mixture but not the cement setting reaction, however no direct evidence of CaO presence was found. Lower Ca/P ratio products yielded cements with CS values ranging from 46.7 MPa for Ca/P ratio of 1.90 to 38.32 MPa for Ca/P ratio of 1.85. When a dilute sodium phosphate solution was used as the setting liquid, CS values were 15.3% lower than those obtained with water as the setting liquid. Setting times ranged from 18 to 22 min when water was the cement liquid and from 7 to 8 min when sodium phosphate solution was used, and the calcium to phosphate ratio did not have a marked effect on this property.

  7. 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....

  8. 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

    uniformly throughout the thickness of the specimen, as opposed to proceeding as a sharp front progressing inward from the surface exposed to the external environment. In the layered specimens, the higher w/c ratio paste layer is seen to "dry out" first regardless of its location within the composite......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...

  9. Temperature influence on water transport in hardened cement pastes

    Energy Technology Data Exchange (ETDEWEB)

    Drouet, Emeline [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Poyet, Stéphane, E-mail: stephane.poyet@cea.fr [CEA, DEN, DPC, SECR, Laboratoire d' Etude du Comportement des Bétons et des Argiles, F-91191 Gif sur Yvette Cedex (France); Torrenti, Jean-Michel [Université Paris-Est, IFSTTAR, Département Matériaux & Structures, 14-52 boulevard Newton, F-77447 Marne la Vallée cedex 2 (France)

    2015-10-15

    Describing water transport in concrete is an important issue for the durability assessment of radioactive waste management reinforced concrete structures. Due to the waste thermal output such structures would be submitted to moderate temperatures (up to 80 °C). We have then studied the influence of temperature on water transport within hardened cement pastes of four different formulations. Using a simplified approach (describing only the permeation of liquid water) we characterized the properties needed to describe water transport (up to 80 °C) using dedicated experiments. For each hardened cement paste the results are presented and discussed.

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

    Science.gov (United States)

    Chattonjai, Piyachat

    2016-06-01

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

  11. 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

  12. Influence of relationship water/cement upon the processing of cements with pozzolana in standard mortar

    Directory of Open Access Journals (Sweden)

    Gener Rizo, M.

    2002-03-01

    Full Text Available The processing of standard mortar is completed following different methods in accordance with the country, but they exist two fundamental tendecies, the ISO and the ASTM. The cuban norm for mechanic-physic tests is based in ISO, and so they use a constant relationship water/cement in the processing of standard mortar a great problem concerning the cement users when they tested those mixed with puzzolanes, because they don't take care of the bigger water needs of those materials. In this work we present an study of the behaviour of Pozzolanic Portland cements (PP-250 elaborates with a fix and changeable relationship water/cement, obtained starting from the fluidity of the pure Portland cement. (P-350 The results obtained shows that the mechanical resistance decreased in cement mortars PP-250 realised with changeable relationship water/cement. So we recommend the adoption of an optional procedure to elaborate a quality mortar with pozzolana cements.

    La elaboración del mortero normalizado se realiza internacionalmente por diferentes métodos, pero existen dos tendencias fundamentales, la enunciada por ISO y por ASTM. La norma cubana de ensayos físico-mecánicos de cemento se basa en la norma ISO, por lo que para la elaboración del mortero normalizado se utiliza una relación agua/cemento constante. Esto ha provocado discrepancias con los usuarios del cemento, especialmente cuando se ensayan los cementos que contienen puzolanas, ya que se plantea que no se tiene en cuenta la mayor demanda de agua de estos materiales. En el presente trabajo se presenta un estudio del comportamiento de cementos Portland Puzolánicos (PP-250 elaborados con una relación agua/ cemento fija y variable, lograda a partir de la fluidez de la pasta de cemento Portland puro (P-350. Los resultados obtenidos indican que se producen disminuciones en la resistencia mecánica en los morteros de cemento PP-250 elaborados con agua/ cemento variable y recomienda la

  13. Water-resisting ability of cemented broken rocks

    Institute of Scientific and Technical Information of China (English)

    Yu Bangyong; Chen Zhanqing; Yu Linli

    2016-01-01

    Using the self-designed testing system, the seepage tests for cemented broken rocks were conducted, and the impact of different factors on water-resisting ability was analyzed. The results show that (1) seepage process of the cemented broken rocks can be divided into two categories:in one category, seepage insta-bility occurs after a period of time, in the other, the permeability decreases slowly and tends to be stable, and seepage instability does not occur;(2) cementing performance of cementing agent and grain size dis-tribution are the decisive factors for water-resisting ability, with the increase of cementing performance and the mass percentage of large grains, the water-resisting ability of the specimen strengthens; (3) aggregate type has little effect on seepage stability, for the specimens with different aggregate types, the permeability and the duration of seepage instability have small difference; (4) initial porosity has a certain effect on the water-resisting ability of the specimen, but has no decisive role. With the increase of the initial porosity, the duration of seepage instability decreases.

  14. WATER QUALITY AND TREATMENT CONSIDERATIONS FOR CEMENT-LINED AND A-C PIPE

    Science.gov (United States)

    Both cement mortar lined (CML) and asbestos-cement pipes (A-C) are widely used in many water systems. Cement linings are also commonly applied in-situ after pipe cleaning, usually to prevent the recurrence of red water or tuberculation problems. Unfortunately, little consideratio...

  15. 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.

  16. Sand/cement ratio evaluation on mortar using neural networks and ultrasonic transmission inspection.

    Science.gov (United States)

    Molero, M; Segura, I; Izquierdo, M A G; Fuente, J V; Anaya, J J

    2009-02-01

    The quality and degradation state of building materials can be determined by nondestructive testing (NDT). These materials are composed of a cementitious matrix and particles or fragments of aggregates. Sand/cement ratio (s/c) provides the final material quality; however, the sand content can mask the matrix properties in a nondestructive measurement. Therefore, s/c ratio estimation is needed in nondestructive characterization of cementitious materials. In this study, a methodology to classify the sand content in mortar is presented. The methodology is based on ultrasonic transmission inspection, data reduction, and features extraction by principal components analysis (PCA), and neural network classification. This evaluation is carried out with several mortar samples, which were made while taking into account different cement types and s/c ratios. The estimated s/c ratio is determined by ultrasonic spectral attenuation with three different broadband transducers (0.5, 1, and 2 MHz). Statistical PCA to reduce the dimension of the captured traces has been applied. Feed-forward neural networks (NNs) are trained using principal components (PCs) and their outputs are used to display the estimated s/c ratios in false color images, showing the s/c ratio distribution of the mortar samples.

  17. Effect of hydrogen sulfide emissions on cement mortar specimens

    Energy Technology Data Exchange (ETDEWEB)

    Idriss, A. F. [Alberta Environment, Science and Technology Branch, Edmonton, AB (Canada); Negi, S. C.; Jofriet, J. C.; Haywoard, G. L. [Guelph Univ., Guelph, ON (Canada)

    2001-07-01

    Six different cement mortar specimens used in animal buildings, where they were exposed to hydrogen sulfide generated from anaerobic fermentation of manure during a period of one year, were investigated. Primary interest was on comparing the corrosion resistance of different cement mortar specimens under long term exposure to hydrogen sulfide. The impressed voltage technique was used to test the specimens in the laboratory. Results revealed that test specimens made with eight per cent silica fume cement replacement performed best and similar Portland cement mortar specimens with a water-cement ratio of 0.55 (PC55) the poorest. All other treatments, (Portland cement with a water to cement ratio of 045, Portland cement Type 50, Portland cement with fibre mesh and Portland cement Type 10 coated with linseed oil) all with water-cement ratios of 0.45, were less effective in preventing corrosion than silica fume replacement.

  18. Study on performance of high strength pumping concrete compounded by fly ash composite powder under low water-cement ratio%低水胶比下粉煤灰复合矿粉配制高强泵送混凝土的性能研究

    Institute of Scientific and Technical Information of China (English)

    龙小明; 吴福飞; 董双快; 侍克斌; 郭江华

    2014-01-01

    In order to investigate the performance of high performance concrete compounded by fly ash composite powder under low water-cement ratio (0.20),the paper discovered through mechanical proper-ty and microstructure analysis that the strength of fly ash concrete is low in early period but high in late period.The strength of slag micro powder concrete can rapidly increase in early phase .The strength of concrete is obvious when two complementary complex mixed .The work performance is better and meets the requirements of pumping concrete when fly ash , slag single blending and composite admixture .The Ca(OH)2 produced by surface-active of SiO2 and Al2O3 of particle and cement can occur volcano ashes reaction and create C-S-H gel that can reduce Ca ( OH) 2 in the concrete interface region .pozzolan cement produced in a slurry , Refinement and reduction of concrete .The unhydrated particles can be filled with concrete and significantly improve the density of concrete , reduce calcium silicon ratio of concrete .%为了探讨低水胶比(0.20)下粉煤灰复合矿粉高性能混凝土的性能,对其力学性能和微观形貌进行了实验分析。结果表明:粉煤灰混凝土早期强度低后期强度高,矿渣微粉混凝土早期强度发展迅速,两者复掺时对混凝土强度的互补较明显;粉煤灰、矿渣单掺和复掺时高性能混凝土拌和物的工作性较好,均满足泵送混凝土对工作性的要求;其颗粒表面活性的Al2O3和SiO2与水泥产生的Ca(OH)2在浆体中发生火山灰反应,生成C-S-H凝胶,细化和减少混凝土界面区域的Ca( OH)2,未水化的颗粒能够填充于混凝土,能够明显地改善混凝土的密实度,降低混凝土的钙硅比。

  19. Using Neutron Radiography to Quantify Water Transport and the Degree of Saturation in Entrained Air Cement Based Mortar

    Science.gov (United States)

    Lucero, Catherine L.; Bentz, Dale P.; Hussey, Daniel S.; Jacobson, David L.; Weiss, W. Jason

    Air entrainment is commonly added to concrete to help in reducing the potential for freeze thaw damage. It is hypothesized that the entrained air voids remain unsaturated or partially saturated long after the smaller pores fill with water. Small gel and capillary pores in the cement matrix fill quickly on exposure to water, but larger pores (entrapped and entrained air voids) require longer times or other methods to achieve saturation. As such, it is important to quantitatively determine the water content and degree of saturation in air entrained cementitious materials. In order to further investigate properties of cement-based mortar, a model based on Beer's Law has been developed to interpret neutron radiographs. This model is a powerful tool for analyzing images acquired from neutron radiography. A mortar with a known volume of aggregate, water to cement ratio and degree of hydration can be imaged and the degree of saturation can be estimated.

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

    Directory of Open Access Journals (Sweden)

    Mengxue Wu

    2017-01-01

    Full Text Available 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.

  1. Effects of cement flue dusts from a Nigerian cement plant on air, water and planktonic quality.

    Science.gov (United States)

    Olaleye, Victor F; Oluyemi, Emmanuel A

    2010-03-01

    Effects of cement flue dust from Ewekoro cement Kilns were monitored at some aquatic receptor locations. High levels of total suspended particulates (TSPs) and atmospheric deposition rates (ADRs) were recorded within the factory compared to ancillary locations outside the factory. The TSP and ADR levels which were location dependent were significantly higher (P cement factory catchment areas.

  2. UTILIZATION OF AGARWOOD DISTILLATION WASTE IN OILWELL CEMENT AND ITS EFFECT ON FREE WATER AND POROSITY

    Directory of Open Access Journals (Sweden)

    Arina Sauki

    2013-10-01

    Full Text Available The intent of this research is to utilize the waste produced by distillation process of Agarwood oil and convert it into a profitable oilwell cement additive. Common problem during oilwell cementing is free wáter separation. This problem could weaken cement at the top, gas migration problem and non uniform density of cement slurry that are even worst in cementing deviated well. Another concern on cementing design is the porosity of the hardened cement. If the cement is too porous, it can lead to gas migration and casing corrosion. All tests were conducted according to API Specification-10B. Free water test was determined at different concentrations of Agarwood Waste Additive (AWA, different inclination angles and different temperatures. Based on the findings, it was observed that zero free water was produced when 2% BWOC of AWA was used at all angles. The findings also revealed that AWA can maintain good thermal stability as it could maintain zero free water at increased temperature up to 60˚C.  The porosity of AWA cement was comparable with standard API neat cement as the porosity did not differ much at 2% BWOC of AWA. Therefore, it can be concluded that the AWA is suitable to  be used as an additive in oil well cement (OWC  with 2% BWOC is taken as the optimum concentration.

  3. Influence of water content on hardening and handling of a premixed calcium phosphate cement.

    Science.gov (United States)

    Engstrand, Johanna; Aberg, Jonas; Engqvist, Håkan

    2013-01-01

    Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring to syringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15) N to 39 (±9) N, the compression strength was almost doubled, and the setting time decreased from 29 (±4) min to 19 (±2) min, while the working time remained 5 to 6h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

  4. Effect of heavy metals and water content on the strength of magnesium phosphate cements.

    Science.gov (United States)

    Buj, Irene; Torras, Josep; Casellas, Daniel; Rovira, Miquel; de Pablo, Joan

    2009-10-15

    In this paper the mechanical properties of magnesium potassium phosphate cements used for the Stabilization/Solidification (S/S) of galvanic wastes were investigated. Surrogate wastes (metal nitrate dissolutions) were employed containing Cd, Cr(III), Cu, Ni, Pb or Zn at a concentration of 25 g dm(-3) and different water-to-solid (W/S) ratios (0.3, 0.4, 0.5 and 0.6 dm(3)kg(-1)) have been employed. Cements were prepared by mixing hard burned magnesia of about 70% purity with potassium dihydrogen phosphate. Compressive strength and tensile strength of specimens were determined. In addition the volume of permeable voids was measured. It was found that when comparing pastes that the volume of permeable voids increases and mechanical strength decreases with the increase of water-to-solid ratio (W/S). Nevertheless pastes with the same material proportions containing different metals show different mechanical strength values. The hydration products were analyzed by XRD. With the increase of water content not previously reported hydration compound was detected: bobierrite.

  5. Influence of chemical admixtures on the dispersion of carbon nanotubes in water and cement pastes

    Science.gov (United States)

    Liu, Hui; Cui, Suping; Wang, Jiachen; Wang, Jianfeng

    2017-03-01

    The influence of ultrasonic and three types of chemical surfactants (including cationic surfactants: CTAB, anionic surfactants: SDS, and nonionic surfactants: TX-405) on the dispersion of CNTs was investigated. The techniques include UV-Vis-NIR spectrophotometer, laser particle size analyser and scanning electrical microscope (SEM). The results show that: 1) Ultrasonic leads to a dispersive effect on CNTs in water, and the optimal ultrasonic time is 120 s; 2) Three types of surfactants have positive effects on the dispersion of CNTs in water, among which cationic surfactant (CATB) leads to the best dispersibility; 3) CNTs with more carboxyl groups show better dispersion in water indicated from UV-vis-NIR spectra and particle size measurement; 4) The optimum concentration of surfactants is 5:1 (the mass ratio of dispersant to CNTs); 5) Three types of surfactants can improve the dispersion of CNTs in cement pastes indicated from SEM images at the optimum dosage.

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

    Institute of Scientific and Technical Information of China (English)

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen

    2009-01-01

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

  7. The effect of water on the mechanical properties of soluble and insoluble ceramic cements.

    Science.gov (United States)

    Koh, Ilsoo; López, Alejandro; Pinar, Ana B; Helgason, Benedikt; Ferguson, Stephen J

    2015-11-01

    Ceramic cements are good candidates for the stabilization of fractured bone due to their potential ease of application and biological advantages. New formulations of ceramic cements have been tested for their mechanical properties, including strength, stiffness, toughness and durability. The changes in the mechanical properties of a soluble cement (calcium sulfate) upon water-saturation (saturation) was reported in our previous study, highlighting the need to test ceramic cements using saturated samples. It is not clear if the changes in the mechanical properties of ceramic cements are exclusive to soluble cements. Therefore the aim of the present study was to observe the changes in the mechanical properties of soluble and insoluble ceramic cements upon saturation. A cement with high solubility (calcium sulfate dihydrate, CSD) and a cement with low solubility (dicalcium phosphate dihydrate, DCPD) were tested. Three-point bending tests were performed on four different groups of: saturated CSD, non-saturated CSD, saturated DCPD, and non-saturated DCPD samples. X-ray diffraction analysis and scanning electron microscopy were also performed on a sample from each group. Flexural strength, effective flexural modulus and flexural strain at maximum stress, lattice volume, and crystal sizes and shape were compared, independently, between saturated and non-saturated groups of CSD and DCPD. Although material dissolution did not occur in all cases, all calculated mechanical properties decreased significantly in both CSD and DCPD upon saturation. The results indicate that the reductions in the mechanical properties of saturated ceramic cements are not dependent on the solubility of a ceramic cement. The outcome raised the importance of testing any implantable ceramic cements in saturated condition to estimate its in vivo mechanical properties.

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

    Institute of Scientific and Technical Information of China (English)

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

    2005-01-01

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

  9. Integrated Environmental Quality Assessments of Surface Water around Obajana Cement Production Area

    Directory of Open Access Journals (Sweden)

    E.G. Ameh

    2014-04-01

    Full Text Available Due to industrialization, there is enormous amount of heavy metals been released from anthropogenic sources into the environment. Heavy metals are considered as one of the main sources of environmental pollution since they have significant effect on the ecological quality and water in particular. These pollutants are hazardous to consumers of water that have significant quantity of these heavy metals. The population most exposed to cement polluted water includes workers in cement factories, families of workers living in Staff houses of factories like in Obajana and other neighborhood habitations. The Obajana cement factory consists of cement kilns/coolers with clinkers. The kilns are equipped with pre-heaters and Electro-Static Precipitators (ESP. The facility has raw mills, crushing operations, cement mills that are potential source of pollutants into the water bodies. Storage silos, conveyors, vehicular travel, and other unquantified fugitive source of water contamination exist in the factory. Monitoring the contamination of water with respect to heavy metals is of interest due to their influence on humans, animals and to some extent plants. A good approach to estimate how much of the water is impacted is by using the heavy metal pollution index and metal index for metal concentrations above the control points in water bodies around Obajana cement.

  10. Rheological Properties of Very High-Strength Portland Cement Pastes: Influence of Very Effective Superplasticizers

    OpenAIRE

    Adriano Papo; Luciano Piani; Riccardo Ricceri

    2010-01-01

    The influence of the addition of very effective superplasticizers, that are commercially available, employed for maximising the solid loading of very high-strength Portland cement pastes, has been investigated. Cement pastes were prepared from deionized water and a commercially manufactured Portland cement (Ultracem 52.5 R). Cement and water were mixed with a vane stirrer according to ASTM Standard C305. The 0.38 to 0.44 water/cement ratio range was investigated. Three commercial superplastic...

  11. Evaluation of the incorporation ratio of ZnO, PbO and CdO into cement clinker.

    Science.gov (United States)

    Barros, A M; Tenório, J A S; Espinosa, D C R

    2004-08-09

    Zinc, lead, and cadmium are minor elements that might be brought by wastes to the cement kilns. This work studies the incorporation ratio of ZnO, PbO, and CdO when they are added to the clinker raw material. The cement raw material used in this work was prepared by mixing pure compounds, this choice was made to avoid the effect of other elements and provide a better understanding of the behavior of these metals during the clinkering process. The samples contained additions of 0.05, 0.10, 0.30, 0.50, 0.80 and 1.00 wt.% of a specific oxide (ZnO, PbO, or CdO) to the clinker raw-meal. The chlorine influence in the ZnO incorporation ratio was also evaluated. A device to simulate the thermal cycle imposed on the charge during the clinker production was used to evaluate the incorporation ratio of these oxides as well as thermogravimetric tests. The products of the tests in the simulator device were submitted to X-ray fluorescence chemical analysis or energy disperse scanning (EDS) microprobe analysis. The results led to the conclusions that the evaporation of Zn in cements kilns is due to the chlorine content and the Pb and Cd incorporation ratio stands around 50 wt.%.

  12. An ongoing investigation on modeling the strength properties of water-entrained cement-based materials

    DEFF Research Database (Denmark)

    Esteves, L.P.

    2012-01-01

    Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...

  13. Changes in constituent equilibrium leaching and pore water characteristics of a Portland cement mortar as a result of carbonation.

    Science.gov (United States)

    Garrabrants, A C; Sanchez, F; Kosson, D S

    2004-01-01

    Two equilibrium-based characterization protocols were applied to ground samples of a cement-based material containing metal oxide powders in both noncarbonated and carbonated states. The effects of carbonation were shown through comparison of (i) material buffering capacity, (ii) constituent equilibrium as a function of leachate pH, and (iii) constituent solubility and release as a function of liquid-to-solid (LS) ratio. As expected, the material alkalinity was significantly neutralized during carbonation. In addition, carbonation of the cement material led to the formation of calcium carbonate and a corresponding increase in arsenic release across the entire pH range. The solubility as a function of pH for lead and copper was lower in the alkaline pH range (pH>9) for carbonated samples compared with the parent material. When solubility and release as a function of LS ratio was compared, carbonation was observed to decrease calcium solubility, sodium and potassium release, and ionic strength. In response to carbonate solid formation, chloride and sulfate release as a function of LS ratio was observed to increase. Trends in constituent concentration as a function of LS ratio were extrapolated to estimate pore water composition at a 0.06 mL/g LS ratio. Significant differences were observed upon comparison of estimated pore water composition to leachate concentrations extracted at LS ratio of 5 mL/g. These differences show that practical laboratory extractions cannot be assumed directly representative of pore water concentrations.

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

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

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

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

    Indian Academy of Sciences (India)

    Jikai Zhou; Xudong Chen; Longqiang Wu; Xiaowei Kan

    2011-06-01

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

  16. Experimental studies on the inventory of cement-derived colloids in the pore water of a cementitious backfill material

    Energy Technology Data Exchange (ETDEWEB)

    Wieland, E

    2001-06-01

    experimental results of the study. Predictions of the colloidal effect on radionuclide mobility were based on the assumption that colloids dispersed in the pore water of the backfill material may reduce radionuclide sorption (R{sub d} values) on cement. This effect was described in terms of a sorption reduction factor. The distribution ratios (R{sub c}) of radionuclides between the cement pore water and the colloidal phase as well as the colloid mass concentration (m{sub c}) are the two important colloidal parameters affecting sorption reduction. No significant sorption reduction is expected for weakly and moderately sorbing radionuclides (R{sub d} {<=} 1 m{sup 3} kg{sup -1}) up to a colloid concentration of 1 ppm. Moreover, no significant sorption reduction is anticipated for strongly sorbing radionuclides (R{sub d} > 1 m{sup 3} kg{sup -1}) below colloid concentrations of 0.1 ppm. This value is considered to be representative for the backfill material. At higher colloid concentrations, however, sorption reduction may occur in case of the strongly sorbing radionuclides. Nevertheless, due to an extremely strong uptake of these elements by cement in the absence of colloids, the effective sorption values in the presence of colloids are predicted to be still high. (author)

  17. Improvement of Water Sensitivity of Macro-defect-free Cement Based Composites with Cross Coupling Agent

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The enhancement of interface bonding between cement and polymer and the structural reticulation of the water-soluble polymer are proposed to minimize the shortening of the mechanical properties of macro-defect-free (MDF) cement based composites at high relative humidity. The MDF composites incorporated with various cross-coupling agents were studied experimentally. The results show that the MDF composites modified with small amounts of cross-coupling agent had raised mechanical properties, but it is more important that the modified MDF composites had a significant increase in water resistance compared to the original one. In the meantime if the water resistant material such as fine powder of α-alumina was used to substitute for the unreacted cement grains in the MDF composites, a more efficient improvement of water resistance would be obtained. The loss in flexural strength of the MDF composites after 90 days of water immersion decreased from 62% before unmodified to 15% after modified.

  18. [The pulsed water jet for selective removal of bone cement during revision arthroplasty].

    Science.gov (United States)

    Honl, Matthias; Schwieger, Karsten; Carrero, Volker; Rentzsch, Reemt; Dierk, Oliver; Dries, Sebastian; Pude, Frank; Bluhm, Andrea; Hille, Ekkehard; Louis, Hartmut; Morlock, Michael

    2003-10-01

    Conventional tools used in prosthetic revision surgery have a limited range of action within the narrow cement mantle. Water jet cutting technology permits tiny and precisely controlled cuts, and may therefore be an alternative method of bone cement removal. Our study compares the cutting performance on bone cement (PMMA) and bone of a pulsed water jet and a continuous water jet. The aim of the study was to establish whether selective removal of PMMA is possible. 55 bone specimens (bovine femora) and 32 specimens of PMMA were cut with a continuous and a pulsed water jet at different pressures (40 MPa, 60 MPa) and pulse frequencies (0Hz, 50Hz, 250Hz). To ensure comparability of the results, the depths of cut were related to the hydraulic power of that part of the jet actually impinging on the material. While for PMMA the power-related depth of cut increased significantly with the pulse frequency, this did not apply to bone. The cuts produced in bone were sharp-edged. Since PMMA is more brittle than bone, the water jet caused cracks that enlarged further until particles of bone broke away. Although selective removal of PMMA without doing damage to the bone was not possible at the investigated settings of the jet parameters, the results do show that a pulsed water jet can cut bone cement much more effectively than bone. This is an important advantage over conventional non-selective tools for the removal of bone cement.

  19. Optimum reaction ratio of coal fly ash to blast furnace cement for effective removal of hydrogen sulfide.

    Science.gov (United States)

    Asaoka, Satoshi; Okamura, Hideo; Kim, Kyunghoi; Hatanaka, Yuzuru; Nakamoto, Kenji; Hino, Kazutoshi; Oikawa, Takahito; Hayakawa, Shinjiro; Okuda, Tetsuji

    2017-02-01

    Reducing hydrogen sulfide concentration in eutrophic marine sediments is crucial to maintaining healthy aquatic ecosystems. Managing fly ash, 750 million tons of which is generated annually throughout the world, is another serious environmental problem. In this study, we develop an approach that addresses both these issues by mixing coal fly ash from coal-fired power plants with blast furnace cement to remediate eutrophic sediments. The purpose of this study is to optimize the mixing ratio of coal fly ash and blast furnace cement to improve the rate of hydrogen sulfide removal based on scientific evidence obtained by removal experiments and XAFS, XRD, BET, and SEM images. In the case of 10 mg-S L(-1) of hydrogen sulfide, the highest removal rate of hydrogen sulfide was observed for 87 wt% of coal fly ash due to decreased competition of adsorption between sulfide and hydroxyl ions. Whereas regarding 100 mg-S L(-1), the hydrogen sulfide removal rate was the highest for 95 wt% of coal fly ash. However, for both concentrations, the removal rate obtained by 87 wt% and 95 wt% were statistically insignificant. The crushing strength of the mixture was over 1.2 N mm(-2) when the coal fly ash mixing ratio was less than 95 wt%. Consequently, the mixing ratio of coal fly ash was optimized at 87 wt% in terms of achieving both high hydrogen sulfide removal rate and sufficient crushing strength.

  20. Effect of Hydration Aging and Water Binder Ratio on Microstructure and Mechanical Properties of Sprayed Concrete

    Institute of Scientific and Technical Information of China (English)

    NIU Ditao; WANG Jiabin; WANG Yan

    2015-01-01

    In order to study the durability of sprayed concrete (shotcrete), effects of different hydration aging and water-binder ratio (w/b) on the microstructure of cement paste and basic mechanical properties of test specimens were investigated. The phase composition, mass percentage of ettringite and portland in hydration production and microstructure were characterized by X-ray diffraction (XRD), thermo gravimetry-differential scanning calorimetry (TG-DSC) and scanning electron microscopy (SEM), respectively. The experimental results showed that changes in phase composition was more signiifcant than those of water-binder ratio. With hydration aging and water-binder ratio increased, the mass percentage of ettringite and portland was decreased from 4.42%, 1.49% to 3.31%, 1.35%, respectively and the microstructure of paste was signiifcantly compacted. Likewise, the mechanical properties including cubic compressive strength and splitting tensile strength were rised obviously.

  1. 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.

  2. An ongoing investigation on modeling the strength properties of water-entrained cement-based materials

    DEFF Research Database (Denmark)

    Esteves, L.P.

    2012-01-01

    -based materials. Beyond the discussion of whether or not the introduction of superabsorbent polymers leads to a strength reduction, this paper uses both experimental and theoretical background to separate the effect of SAP in both pore structure and internal relative humidity and the effect from the active......Water-entrained cement based materials by superabsorbent polymers is a concept that was introduced in the research agenda about a decade ago. However, a recent application in the production of high performance concrete revealed potential weaknesses when the proportioning of this intelligent...... material is not well performed, raising doubts among both academic and industrial society about the usability of superabsorbent polymers in cement-based materials. This work constitutes the baseline tentatively to be used on modeling the compressive strength of SF-modified water-entrained cement...

  3. Influence of fly ash fineness on water requirement and shrinkage of blended cement mortars

    Directory of Open Access Journals (Sweden)

    Vanissorn Vimonsatit

    2015-12-01

    Full Text Available In this paper, the influence of fly ash fineness on water requirement and shrinkage of blended cement mortar was studied. The results indicate that the water requirement and shrinkage characteristic of the blended cement mortar are dependent on fly ash fineness and replacement level. The use of coarse fly ash slightly reduces the water requirement but greatly reduced the drying and the autogenous shrinkage of the blended cement mortars and the reduction is more with an increase in the fly ash replacement level. The finer fly ashes further reduce the water requirement, but increase the drying and the autogenous shrinkages as compared with coarser fly ash. The incorporation of superplasticizer drastically reduces the water requirement, but the effect on the drying and autogenous shrinkages of the normal Portland cement mortar is small. However, for the fly ash mortar, the use of superplasticizer results in a decrease in drying shrinkage and in a substantial increase in the autogenous shrinkage particularly for the fine fly ash at a high replacement level.

  4. 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...

  5. 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.

  6. Grout cement. ; Grout cement to fill ground/grout cement to fill cracks. Chunyuyo cement. ; Jiban chunyuyo cement /hibiware chunyuyo cement

    Energy Technology Data Exchange (ETDEWEB)

    Okaue, H. (Nittetsu Cement Co. Ltd., Hokkaido (Japan))

    1991-09-01

    Ground grout cement is grouted into the ground under high pressure in high water ratio (100 to 1000%) in the form of milk differing from concrete in terms of the water-cement ratio. The grouted milk is governed by characteristics of the cement the milk itself possesses, resulting in variable grouting modes, which are divided in fracture grouting, permeation grouting and boundary grouting. Their applications include cutting off of water in dams, ground reinforcement, prevention of water gushing in tunnel excavation, natural ground reinforcement, improvement of sandy soil and prevention of its collapse, and stabilization of ground for urban civil engineering works such as subway, water supply and sewerage constructions. Grout cement to fill cracks in concrete structures is so grouted into cracks that the slurry fills up contiguous cracks to a certain level and goes upward while pushing out air or water existing in the cracks. The slurry filled into the cracks solidifies and hardens while being absorbed into the concrete, and finally integrates with the concrete. The grout cement is used to rework such concrete structures as dams, tunnels, and bridge bases. 6 figs., 4 tabs.

  7. Mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions

    Institute of Scientific and Technical Information of China (English)

    熊良宵; 虞利军

    2015-01-01

    To investigate the mechanical properties of cement mortar in sodium sulfate and sodium chloride solutions, uniaxial compression test and ultrasonic test were performed. Test results show that the relative dynamic elastic modulus, the mass variation, and the compressive strength of cement mortar increase first, and then decrease with increasing erosion time in sodium sulfate and sodium chloride solutions. The relative dynamic elastic moduli and the compressive strengths of cement mortars with water/cement ratios of 0.55 and 0.65 in sodium sulfate solution are lower than those in sodium chloride solution with the same concentration at the 420th day of immersion. The compressive strength of cement mortar with water/cement ratio of 0.65 is more sensitive to strain rate than that with water/cement ratio of 0.55. In addition, the strain-rate sensitivity of compressive strength of cement mortar will increase under attacks of sodium sulfate or sodium chloride solution.

  8. Development of near-zero water consumption cement materials via the geopolymerization of tektites and its implication for lunar construction

    Science.gov (United States)

    Wang, Kai-Tuo; Tang, Qing; Cui, Xue-Min; He, Yan; Liu, Le-Ping

    2016-07-01

    The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology.

  9. Effect of the crystal/gel ratio of cement hydrates on the flexural strength of cement%水泥水化物晶胶比对水泥抗折性能的影响

    Institute of Scientific and Technical Information of China (English)

    黄新; 龙世宗

    2001-01-01

    Crystalline material was introduced into cement to adjust the crystal/gel ratio of cement hydrates and therefore to improve the flexural strength of cement. Through the evaluation of the mortar strength and fragile parameter with the addition of varying crystalline materials, CA was determined to be suitable for regulating the crystal/gel ratio of cement hydrates. Mortar expansion ratio and strength were also measured with different dosage of CA. The optimum addition of CA was confirmed through the analysis of experiment results.%通过在水泥中引入晶体源调整水化物晶胶比以提高水泥的抗折性能,测试了引入不同晶体源的水泥胶砂强度及脆性系数,确定用 CA调整水泥石的晶胶比较为适宜。测定了不同 CA掺量时水泥砂浆膨胀率及强度,对试验结果进行了分析,得出了 CA的最佳掺量。

  10. Effect of Raw Materials and Their Ratio on Compressive Strength of Magnesium Phosphate Cement%原材料及配比对磷酸镁水泥强度的影响

    Institute of Scientific and Technical Information of China (English)

    齐召庆; 徐哲; 孙运亮; 丁建华; 张时豪; 姜自超

    2015-01-01

    The influence of M/P ratio (mass ratio of MgO and K2HPO4), water/cement ratio (W/C), borax content, MgO specific surface area on the early strength of magnesium phosphate cement was studied. And microstructure of magnesium phosphate cement was analyzed by using scanning electron microscope (SEM). The results show that the compressive strength of magnesium phosphate cement at the age of 1h decreases with the increase of M/P ratio, when hydration age is 3 d and 7 d, M/P ratio is 4:1,magnesium phosphate cement stone has the highest strength, the highest intensity can reach to 74.68 MPa; water-binder ratio has little effect on early strength of magnesium phosphate cement;when hydration age is 7 d, the strength decreases with the increase of water-binder ratio; in the early hydration, with the increasing of borax content, crystal of magnesium phosphate cement hydration products becomes small, the structure becomes loose, the crystal defect increases, so its strength decreases; in the later hydration, the structure becomes compact, the strength after 7 d has little change. Within 7 d, the strength of the magnesium phosphate cement increases with increasing of MgO specific surface area.%研究了 M/P 比值(MgO 与 K2HPO4的质量比),水胶比(W/C),硼砂掺量,MgO 比表面积对磷酸镁水泥早期强度的影响,采用扫描电子显微镜对磷酸镁水泥的微观形貌进行了表征。结果表明:磷酸镁水泥1 h的抗压强度随 M/P 比值的增大而减小,在水化龄期为3 d 和7 d 时,M/P 比值为4:1时磷酸镁水泥石的强度最高,最高强度达到了74.68 MPa,水胶比对磷酸镁水泥石早期强度影响不大,7 d 强度随着水胶比的增大而减小,磷酸镁水泥在水化早期随着硼砂掺量的增加,水化产物晶体变得细小,晶体缺陷增多,结构疏松,其强度随着硼砂掺量增加而降低,后期水化产物连接成一体,结构致密,7 d 的强度几乎

  11. Durability of Alite-calcium Barium Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    LU Lingchao; LU Zeye; LIU Shiquan; WANG Shoude; CHENG Xin

    2009-01-01

    The durability of the cement was mainly studied.Under 1.0 MPa of hydraulic pressure for 8 hours,water could penetrate completely through the sample made by portland cement,but could not penetrate through that by alite-barium sulphoaluminate cement.Under the condition of freezing and thawing cycle,the loss ratio of compressive strength of the cement was only about 17.3%at curing 28 d ages,but the loss of portland cement was as high as 29.5%.Alite-calcium bar-ium sulphoaluminate cement also has an excellent resistance to sulfate attack.The coefficients of resistance to sulfate attack of the cement exceeded 1.0.Meanwhile,the composition and microstructure of the hardened paste of alite-calcium barium sulphoaluminate cement were analyzed by XRD and SEM.

  12. Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

    Science.gov (United States)

    Baronins, J.; Setina, J.; Sahmenko, G.; Lagzdina, S.; Shishkin, A.

    2015-11-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

  13. Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; LI Zongjin; XIAO Lianzhen; THONG Wangfai

    2006-01-01

    The influence of calcium sulfate state and fineness of cement on hydration of Portland cement was studied using electrical resistivity measurement. The bulk resistivity curve of the paste from the abnormal cement mainly with hemihydrate had a characteristic abnormal peak and rapid increase in early period. The resistivity measurement technique can be used to discriminate abnormal setting. For normal cement with gypsum, the increase in fineness of the Portland cement decreases the minimum resistivity due to a higher ionic concentration and increases the 24 hour resistivity due to a reduction in macroscopic pore size. Thesetting time, compressive strength, pore structure of pastes made from different cements were carried out to compare the influence of water to cement ratio, calcium sulfate state and fineness. It is found that the electrical and mechanical properties are strongly affected by the initial porosity, the presence of hemihydrate or gypsum, and the fineness of cement.

  14. The influence of iron on water radiolysis in cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bouniol, P., E-mail: pascal.bouniol@cea.f [CEA, DEN, DPC, SCCME, Laboratoire d' Etude du Comportement des Betons et des Argiles, F-91991 Gif-Sur-Yvette (France)

    2010-08-15

    For the time being, assessing the H{sub 2} source term generated by {gamma} irradiated cement-based materials consists of simulating the radiolysis of the pore liquid on the only elementary reactions relating to the decomposition of alkaline water. Such incomplete description does not take into account the impurities contained in the cement and leads to underestimate the production of H{sub 2}. Systematically present in cement materials, iron is likely to influence radiolysis by the disturbance induced on radical chemistry throughout the irradiation period. The faster reactivity of e{sub aq}{sup -} and OH{sup {center_dot}} radicals on Fe(III) and Fe(II), respectively, than on H{sub 2}O{sub 2} and H{sub 2} is responsible for the lower recycling capability of the 'Allen's chain reaction', allowing for H{sub 2} to be preserved in a closed system. A critical review of reaction data about iron complexes (hydroxo-, peroxo-) is presented in order to build up an 'iron' database. Radiolysis simulations in cement porewater in the presence of Fe(OH){sub 3} (considered as a model phase) show, as expected, an increase in the effective production of radiolytic H{sub 2} and the co-existence of exotic valence Fe(IV) with Fe(II) and (III) during the irradiation period ({gamma}).

  15. Germinant-enhanced decontamination of Bacillus spores adhered to iron and cement-mortar drinking water infrastructures.

    Science.gov (United States)

    Szabo, Jeffrey G; Muhammad, Nur; Heckman, Lee; Rice, Eugene W; Hall, John

    2012-04-01

    Germination was evaluated as an enhancement to decontamination methods for removing Bacillus spores from drinking water infrastructure. Germinating spores before chlorinating cement mortar or flushing corroded iron was more effective than chlorinating or flushing alone.

  16. Mechanism and Preventive Technology of the Thaumasite Form of Sulfate Attack on Cement Mortars

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The deterioration mechanism of thaumasite towards cement or concrete structure and the deterioration pattern of in-situ construction caused by the formation of thaumasite were studied in this paper. To improve the TSA (the thaumasite form of sulfate attack) resistance, the cement type, water to cement ratios, the mineral admixture and the circumstance factors should be taken into consideration.

  17. Resistance of Phosphogypsum Cement Pozzolanic Compositions against the Influence of Water

    Directory of Open Access Journals (Sweden)

    Sergejus GAIDUČIS

    2011-09-01

    Full Text Available The reprocessing of freshly removed extractive hemihydrate phosphogypsum into hydraulic composite phosphogypsum cement pozzolana (PGCP binder using mechanical activation is analyzed in this work. In order to increase the effectiveness of the dealing with phosphogypsum reprocessing problem and to lower the energy consumption required for the production of binding materials from phosphogypsum, physical mechanical and water resistance properties of the PGCP binder with less amount (10 % of cement (PGCP(10 were analyzed and compared with the properties of conventional PGCP binder, where the amount of cement is 20 % (PGCP(20. The PGCP binder with pozzolana additives of two types - carbonate opoka and microsilica are analysed. Fresh wet hemihydrate phosphogypsum, cement and pozzolana additive were mechanically activated together and from resulting mixture the samples were formed by vibrating. Compressive strength of PGCP(10 samples after 28 days was 26 MPa - 29 MPa, after 4 months - 30 MPa - 32 MPa, PGCP(20 - 32 MPa - 35 MPa and 36 MPa - 42 MPa accordingly. It is found, that hardened PGCP(10 are also quite resistant to short-term (2 days impact of water (softening coefficient was 0.91 - 0.94, however, its resistance to long-term impact of water is significantly less than PGCP(20. PGCP with microsilica is more strength and more resistant to impact of water than PGCP with opoka. Both, PGCP with opoka, as well as the ones with microsilica, are resistant to the formation of ettringite. However, the primary ettringite and high amount of carbonates, found in the PGCP with opoka, stimulates the formation of thaumasite at low positive temperature and humidity.http://dx.doi.org/10.5755/j01.ms.17.3.599

  18. Determination of strontium and simultaneous determination of strontium oxide, magnesium oxide and calcium oxide content of Portland cement by derivative ratio spectrophotometry.

    Science.gov (United States)

    Idriss, K A; Sedaira, H; Ahmed, S S

    2009-04-15

    A derivative spectrophotometric method has been developed for the determination of strontium in Portland cement. The method is applied successfully for the simultaneous determination of SrO, MgO and CaO. It is based on the use of Alizarin Complexone (AC) as a complexing agent and measurement of the derivative ratio spectra of the analytes. Interferences of manganese(II) and zinc(II) were eliminated by precipitation. The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The strontium complex formed at pH 9.5 allows precise and accurate determination of strontium over the concentration range of 1.5-18 mg L(-1) of strontium. The MDL (at 95% confidence level) was found to be 25 ng mL(-1) for strontium in National Institute of Standards and Technology (NIST) cement samples using the proposed method.

  19. Hydration of portland cement, natural zeolite mortar in water and sulphate solution

    Directory of Open Access Journals (Sweden)

    Janotka, I.

    2003-03-01

    Full Text Available The objective of this paper is to characterise sulphate resistance of mortars made from ordinary Portland cement ( PC and Portland-pozzolan cement with 35 wt.% of zeolite addition (zeolite-blended cement-ZBC . Mortars with two different cement types were tested in water and 5% sodium sulphate solution for 720 days. A favourable effect of zeolite on increased sulphate resistance of the cement is caused by decrease in free Ca(OH2 content of the mortar There is not sufficient of Ca(OH2 available for reacting with the sulphate solution to form voluminous reaction products. A decreased C3A, content due to 35 wt.% replacement of PC by zeolite is the next pronounced factor improving resistance of the mortar with such blended cement.

    El objetivo de este trabajo ha sido estudiar la resistencia a los sulfatos de morteros preparados con cemento portland ordinario (PC y cemento portland puzolánico, con un 35% en peso de zeolita (zeolite-blended cement (ZBC. Ambos tipos de morteros fueron conservados en agua y en una disolución de sulfato sódico al 5% durante 720 días. Se observó una mayor resistencia a los sulfatos en el mortero preparado con el cemento que contenía zeolita debido a su menor contenido en Ca(OH2. No hay cantidad suficiente de Ca(OH2 para que se produzca la reacción de los constituyentes de la pasta con la disolución de sulfato sódico y formar así productos de naturaleza expansiva. La disminución en el contenido de C,3A, debida a la sustitución de un 35% en peso de PC por zeolita, es el factor más determinante en el aumento de la resistencia del mortero en los cementos con adición.

  20. DURABILITY PERFORMANCE OF RFCC SPENT CATALYSTBLENDED PORTLAND CEMENT PASTE EXPOSED TO SEA WATER ATTACK

    Directory of Open Access Journals (Sweden)

    Allahverdi A.

    2013-12-01

    Full Text Available This paper discusses the performance of the paste of Portland cement blended with spent catalyst from Resid Fluidized Catalytic Cracking (RFCC unit of petroleum refining processes in sea water. 28-day cured paste specimens prepared from binary cement mixes containing different amounts of spent catalyst were exposed to Persian Gulf sea water. Compressive strength, weight, and length changes of the specimens were monitored and considered for evaluating the extent of deterioration. Laboratory techniques of X-ray diffractometry, scanning electron microscopy, and Energy dispersive X-ray spectroscopy were also used to study the deteriorated specimens. The results confirm that at relatively high replacement levels, the pozzolanic property of the spent catalyst and the increased open pore volume of such blended cements may result in contradictory consequences. Specimens of relatively higher replacement levels exhibit higher rates of deterioration in spite of their superior mechanical strength behavior caused by pozzolanic reaction. The results obtained by X-ray diffractometry confirm the presence of higher amounts of chlorine-containing Friedel’s salt in specimens containing RFCC spent catalyst compared to plain reference specimens.

  1. Effects of a new modifier on the water-resistance of magnesite cement tiles

    Science.gov (United States)

    Xu, Kejing; Xi, Jintao; Guo, Yanqing; Dong, Shuhua

    2012-01-01

    The magnesium oxychloride composite is an inorganic cementitious material with high bending and compression strength in air characteristics. However its strength decreases significantly after immersion in water. The preparing process of a new magnesite cement tile using nano rice husk ashes and a complex water-resistance agent as modifiers was described in the paper. The effects of low-temperature rice husk ashes (RHAs) and the complex water-resistance agent constituted with phosphoric acid, calcium superphosphate, wooden calcium and styrene-acrylic emulsion on the water-resistance of magnesite materials were mainly studied. The samples properties were characterized by XRD, SEM, BET, a laser particle size analyzer and bending test. The experiments show that the proportional addition of nano RHAs markedly increases the water-resistance of magnesite materials without reducing the bending strength and promotes the softening coefficient from 0.29 to 0.78, while the softening coefficient reaches up to 0.97 combined with the use of complex water-resistance agent. The new magnesite cement tiles prepared were not scumming, not warping, and not contracting at room temperature for 360 d.

  2. 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 ...

  3. Physicochemical changes of cements by ground water corrosion in radioactive waste storage; Evolucion fisicoquimica de los cementos por corrosion de aguas subterraneas en un almacen de desechos radioactivos

    Energy Technology Data Exchange (ETDEWEB)

    Contreras R, A.; Badillo A, V. E.; Robles P, E. F. [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Nava E, N. [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas No. 152, Col. San Bartolo Atepehuacan, 07730 Mexico D. F. (Mexico)], e-mail: aida.contreras@inin.gob.mx

    2009-10-15

    Knowing that the behavior of cementations materials based on known hydraulic cement binder is determined essentially by the physical and chemical transformation of cement paste (water + cement) that is, the present study is essentially about the cement paste evolution in contact with aqueous solutions since one of principal risks in systems security are the ground and surface waters, which contribute to alteration of various barriers and represent the main route of radionuclides transport. In this research, cements were hydrated with different relations cement-aqueous solution to different times. The pastes were analyzed by different solid observation techniques XRD and Moessbauer with the purpose of identify phases that form when are in contact with aqueous solutions of similar composition to ground water. The results show a definitive influence of chemical nature of aqueous solution as it encourages the formation of new phases like hydrated calcium silicates, which are the main phases responsible of radionuclides retention in a radioactive waste storage. (Author)

  4. Effects of coronal substrates and water storage on the microhardness of a resin cement used for luting ceramic crowns

    Directory of Open Access Journals (Sweden)

    Luana Menezes de MENDONÇA

    2014-07-01

    Full Text Available Composite resin and metallic posts are the materials most employed for reconstruction of teeth presenting partial or total destruction of crowns. Resin-based cements have been widely used for cementation of ceramic crowns. The success of cementation depends on the achievement of adequate cement curing. Objectives: To evaluate the microhardness of Variolink® II (Ivoclar Vivadent, Schaan, Liechtenstein, used for cementing ceramic crowns onto three different coronal substrate preparations (dentin, metal, and composite resin, after 7 days and 3 months of water storage. The evaluation was performed along the cement line in the cervical, medium and occlusal thirds on the buccal and lingual aspects, and on the occlusal surface. Material and Methods: Thirty molars were distributed in three groups (N=10 according to the type of coronal substrate: Group D- the prepared surfaces were kept in dentin; Groups M (metal and R (resin- the crowns were sectioned at the level of the cementoenamel junction and restored with metallic cast posts or resin build-up cores, respectively. The crowns were fabricated in ceramic IPS e.max® Press (Ivoclar Vivadent, Schaan, Liechtenstein and luted with Variolink II. After 7 days of water storage, 5 specimens of each group were sectioned in buccolingual direction for microhardness measurements. The other specimens (N=5 were kept stored in deionized water at 37ºC for three months, followed by sectioning and microhardness measurements. Results: Data were first analyzed by three-way ANOVA that did not reveal significant differences between thirds and occlusal surface (p=0.231. Two-way ANOVA showed significant effect of substrates (p<0.001 and the Tukey test revealed that microhardness was significantly lower when crowns were cemented on resin cores and tested after 7 days of water storage (p=0.007. Conclusion: The type of material employed for coronal reconstruction of preparations for prosthetic purposes may influence the

  5. Experimental study of Ni solubility in sulphidic groundwater and cement water under anoxic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Carlsson, T.; Vuorinen, U.; Kekki, T.; Aalto, H. [VTT Chemical Technology, Espoo (Finland)

    2001-06-01

    The nickel solubility was studied during a 177-day period under anoxic conditions in three types of waters: a synthetic reference groundwater (OL-SR), a natural Olkiluoto groundwater (PVA2), and a cement-conditioned groundwater (C-PVA2). To each water, nickel, ferrous iron and sulphide were added yielding eight combinations of, approximately, the following initial concentrations: nickel: 1.0x10{sup -6} and 1.0x10{sup -3} mol/L, ferrous iron: 1.8 10{sup -6} and 1.8x10{sup -5} mol/L, and sulphide: 3.1x10{sup -6} and 9.4x10{sup -5} mol/L. The concentrations of these elements in the natural groundwater PVA2 as well as in the cement-conditioned water C-PVA2 was insignificant. In the synthetic water, the nickel concentration was unchanged in all samples having a high initial nickel concentration of 1.0x10{sup -3} mol/L. In the samples with an initial low nickel concentration of 1.0x10{sup -6} mol/L, the sulphide content determined the final nickel concentration. Where the initial sulphide concentration was low, the nickel concentration remained at the level of 1.0x10{sup -6} mol/L, but the higher sulphide concentration caused the nickel concentration to drop to below 10{sup -8} mol/L. In the natural groundwater PVA2, the nickel concentration dropped to below 10{sup -4} mol/L in all samples with an initially high nickel concentration, and to values of roughly 10{sup -7} mol/L in samples with an initially low nickel content. In the cement-conditioned water, the nickel concentration reached a value of 3x10{sup -6} mol/L in samples with initial high nickel concentrations, and to a value of 1x10{sup -7} mol/L in samples with a low initial nickel content. The added amounts of iron and sulphide did not have any significant effect on the observed nickel solubility. The solid phases formed in the natural and synthetic groundwater were analyzed by XRD but could not be identified. In the case of cement-conditioned water the XRD analyses showed the presence of Ni(OH){sub 2} as well

  6. Preliminary Examination of the System Fly Ash-Bottom Ash-Flue Gas Desulphurization Gypsum-Portland Cement-Water for Road Construction

    Directory of Open Access Journals (Sweden)

    R. Tokalic

    2013-01-01

    Full Text Available This paper describes an investigation into the use of three power plant wastes: fly ash, flue gas desulphurization gypsum, and bottom ash for subbase layers in road construction. Two kinds of mixtures of these wastes with Portland cement and water were made: first with fly ash consisting of coarser particles (<1.651 mm and second with fly ash consisting of smaller particles (<0.42 mm. The mass ratio of fly ash-Portland cement-flue gas desulphurization gypsum-bottom ash was the same (3 : 1 : 1 : 5 in both mixtures. For both mixtures, the compressive strength, the mineralogical composition, and the leaching characteristics were determined at different times, 7 and 28 days, after preparation. The obtained results showed that both mixtures could find a potential use for subbase layers in road construction.

  7. Stability of cemented dried water hyacinth used for biosorption of radionuclides under various circumstances

    Science.gov (United States)

    Saleh, H. M.

    2014-03-01

    This paper investigates the influence of frost attack and flooding conditions during disposal on the compressive strength, porosity and durability of cemented waste form contained dried and grinded water hyacinth. This plant was used as a phytoremediating agent to treat liquid waste simulate contaminated with radionuclides. The obtained results showed that an increase in the incorporated dry plants decreases the compressive strength and increases the porosity of the solidified waste form. Raising the number of freeze-thaw cycles was accompanied with noticeable increase in the mass-loss of tested specimens and unsteady trend of compressive strength and consequently the mechanical integrity. The presence and increase of immersion duration per turned positively the mass change and affect in different ways on the solidified waste form. Spectroscopic analyses such as infrared and X-ray as well as microscopic investigation were performed to evaluate the solidified waste form exposed to different undesirable climatic conditions during extending disposal durations. The use of Portland cement as a stabilizer for water hyacinth, following the phytoremediation process, achieves the requirements for durability and strength against the freeze-thaw cycles or flooding in different types of water during prolonged disposal.

  8. Stability of cemented dried water hyacinth used for biosorption of radionuclides under various circumstances

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, H.M., E-mail: hosamsaleh70@yahoo.com

    2014-03-15

    This paper investigates the influence of frost attack and flooding conditions during disposal on the compressive strength, porosity and durability of cemented waste form contained dried and grinded water hyacinth. This plant was used as a phytoremediating agent to treat liquid waste simulate contaminated with radionuclides. The obtained results showed that an increase in the incorporated dry plants decreases the compressive strength and increases the porosity of the solidified waste form. Raising the number of freeze–thaw cycles was accompanied with noticeable increase in the mass-loss of tested specimens and unsteady trend of compressive strength and consequently the mechanical integrity. The presence and increase of immersion duration per turned positively the mass change and affect in different ways on the solidified waste form. Spectroscopic analyses such as infrared and X-ray as well as microscopic investigation were performed to evaluate the solidified waste form exposed to different undesirable climatic conditions during extending disposal durations. The use of Portland cement as a stabilizer for water hyacinth, following the phytoremediation process, achieves the requirements for durability and strength against the freeze–thaw cycles or flooding in different types of water during prolonged disposal.

  9. Puzzolanic cements of greater resistance at the attack of selenitic waters than the high sulfate resistance portland cements, and viceverse

    Directory of Open Access Journals (Sweden)

    Talero, Rafael

    1987-09-01

    Full Text Available This work confirms the certainty of the predictions of useful service given by Kaluosek and al. for the sulphate resistant portland cements (type V, USA, subject to severe selenitic attack. Two sulphate resistant portland cements, were tested by means of the Le Chatelier Anstett method. The tarts were destroyed at ages of three years, having detected in them the presence of thaumasite by XRD. Even so, the impossibility and possibility thaumasite formation was confirmed in pozzolanic cements tarts, which either had or did not have adequate amount of pozzolana (diatomite for such purpose.

    Este trabajo confirman las predicciones de vida útil dadas por Kalousek y colaboradores, para los cementos portland de elevada resistencia al ataque de los iones sulfato (tipo V, USA, sometidos a un severo ataque selenitoso. Se ensayaron dos cementos portland de elevada resistencia al ataque del yeso, mediante el ensayo de Le Chatelier-Anstett. Sus tortas correspondientes se destruyeron a la edad de tres años, habiéndose detectado en las mismas la presencia de thaumasita por DRX. Asimismo se confirmó la imposibilidad y posibilidad de formación de thaumasita en tortas de cementos puzolánicos, los cuales tenían, o no, respectivamente, una adecuada cantidad de puzolana (diatomita para tales fines.

  10. Carbonation of low heat portland cement paste procured in water for different time

    Institute of Scientific and Technical Information of China (English)

    Deping Chen; Etsuo Sakai; Masaki Daimon; Yoko Ohba

    2007-01-01

    The carbonation technique was applied to accelerate the hydration of low heat portland cement (LHC). Before carbonation, the demoulded pastes were precured in water for 0, 2, 7, and 21 d, respectively. The results show that procuring time in water strongly influences the carbonation process. The phenolphthalein test indicates that the paste precured in water for a shorter time is more quickly carbonated than that for a longer time. The content of calcium hydroxide increases with increasing the procuring time in water, whereas, the amount of absorbed carbon dioxide changes contrarily. Scanning electron microscope (SEM) observation shows that portlandite always fills up big air bubbles in the paste during precuring in water, and the mercury intrusion porosimetry (MIP) results show that there are less large capillary pores in the paste precured in water for a longer time. It is found that the paste without precuring in water has more carbon dioxide absorption during curing in carbon dioxide atmosphere, and its total pore volume decreases remarkably with an increase in the carbonation time than that precured in water. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area analyses indicate that the carbonate products are vaterite and calcite; CxSHy,, formed from carbonation has low BET surface area in comparison with that of C-S-H formed from curing in water.

  11. Controlled erosion in asbestos-cement pipe used in drinking water distribution systems

    Directory of Open Access Journals (Sweden)

    Mariana Ramos, P.

    1990-06-01

    Full Text Available Samples of asbestos-cement pipe used for drinking water conveyance, were submerged in distilled water, and subjected to two controlled erosive treatments, namely agitation (300 rpm for 60 min and ultrasound (47 kHz for 30 min. SEM was used to observe and compare the morphology of the new pipe with and without erosive treatment, and of samples taken from asbestos-cement pipes used in the distribution system of drinking water in Santiago city for 10 and 40-years of service. TEM was used to determine the concentration of asbestos fibers in the test water: 365 MFL and 1690 MFL (millions of fibers per litre as an agitation and result ultrasound, respectively. The erosive treatments by means of agitation or ultrasound applied to new asbestos-cement pipes used in the drinking water distribution system were evaluated as being equivalent to 4 and 10 years of service, respectively.

    Se sometió a dos tratamientos erosivos controlados uno por agitación (300 rpm, 60 min. y otro por ultrasonido (47 kHz, 30 min. a muestras de tubos de asbesto cemento, sumergidas en agua destilada, usados para el trasporte de agua potable. Con SEM se observó la morfología de muestras de tubos sin uso, con y sin tratamiento erosivo y la de muestras extraídas de tubos de asbesto cemento de la red de distribución de agua potable de ía ciudad de Santiago con 10 y 14 años de servicio. Con TEM se determinó la concentración de fibras de asbesto en el agua de ensayo: 365 MFL y 1690 MFL (millones de fibras por litro en agitación y ultrasonido, respectivamente. Se estimó en 4 y 10 años de servicio equivalente los tratamientos erosivos de agitación y ultrasonido, respectivamente en tubos de asbesto cemento empleados en la red de agua potable.

  12. Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, K.M.; Serne, R.J. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-05-01

    The US Nuclear Regulatory Commission is developing a technical position document that provides guidance regarding the performance assessment of low-level radioactive waste disposal facilities. This guidance considers the effects that the chemistry of the vault disposal system may have on radionuclide release. The geochemistry of pore waters buffered by cementitious materials in the disposal system will be different from the local ground water. Therefore, the cement-buffered environment needs to be considered within the source term calculations if credit is taken for solubility limits and/or sorption of dissolved radionuclides within disposal units. A literature review was conducted on methods to model pore-water compositions resulting from reactions with cement, experimental studies of cement/water systems, natural analogue studies of cement and concrete, and radionuclide solubilities experimentally determined in cement pore waters. Based on this review, geochemical modeling was used to calculate maximum concentrations for americium, neptunium, nickel, plutonium, radium, strontium, thorium, and uranium for pore-water compositions buffered by cement and local ground-water. Another literature review was completed on radionuclide sorption behavior onto fresh cement/concrete where the pore water pH will be greater than or equal 10. Based on this review, a database was developed of preferred minimum distribution coefficient values for these radionuclides in cement/concrete environments.

  13. 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

  14. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample.

    Science.gov (United States)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-30

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  15. Time resolved X-ray Dark-Field Tomography Revealing Water Transport in a Fresh Cement Sample

    Science.gov (United States)

    Prade, Friedrich; Fischer, Kai; Heinz, Detlef; Meyer, Pascal; Mohr, Jürgen; Pfeiffer, Franz

    2016-06-01

    Grating-based X-ray dark-field tomography is a promising technique for biomedical and materials research. Even if the resolution of conventional X-ray tomography does not suffice to resolve relevant structures, the dark-field signal provides valuable information about the sub-pixel microstructural properties of the sample. Here, we report on the potential of X-ray dark-field imaging to be used for time-resolved three-dimensional studies. By repeating consecutive tomography scans on a fresh cement sample, we were able to study the hardening dynamics of the cement paste in three dimensions over time. The hardening of the cement was accompanied by a strong decrease in the dark-field signal pointing to microstructural changes within the cement paste. Furthermore our results hint at the transport of water from certain limestone grains, which were embedded in the sample, to the cement paste during the process of hardening. This is indicated by an increasing scattering signal which was observed for two of the six tested limestone grains. Electron microscopy images revealed a distinct porous structure only for those two grains which supports the following interpretation of our results. When the water filled pores of the limestone grains empty during the experiment the scattering signal of the grains increases.

  16. Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff

    Energy Technology Data Exchange (ETDEWEB)

    South, D.L.; Daemen, J.J.K.

    1986-10-01

    Boreholes near a repository must be sealed to prevent rapid migration of radionuclide-contaminated water to the accessible environment. The objective of this research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals. Performance partially recovers upon resaturation. A skillfully sealed borehole may be as impermeable as the host rock. Analysis of the influence of relative seal-rock permeabilities shows that a plug with permeability one order of magnitude greater than that of the rock results in a flow increase through the hole and surrounding rock of only 1-1/2 times compared to the undisturbed rock. Since a borehole is only a small part of the total rock mass, the total effect is even less pronounced. The simplest and most effective way to decrease flow through a rock-seal system is to increase the seal length, assuming it can be guaranteed that no dominant by-pass flowpath through the rock exists.

  17. A new cement slurry modified with chitosan/alginate interpenetrating networks and hydroxyapatite: structural characteristics after long-term contact with hyper-saline produced water from oil well operations

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Ivory Marcos Gomes dos; Santos, Danilo Oliveira; Cestari, Antonio Reinaldo, E-mail: ivorymarcos@hotmail.com, E-mail: danilo.quimico@yahoo.com.br, E-mail: rcestari@gmail.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Departamento de Ciencia dos Materiais; Ribeiro, Joenesson Filip Santos, E-mail: joenesson.joe@hotmail.com [Universidade Federal de Sergipe (UFS), Sao Cristovao, SE (Brazil). Lab, Materiais e Calorimetria; Alves, Jose do Patrocinio Hora; Ferreira, Angelica Baganha, E-mail: jphalves@uol.com.br, E-mail: angelica.bferreira@itps.se.gov.br [Instituto Tecnologico e de Pesquisas do Estado de Sergipe (ITPS), Aracaju, SE (Brazil)

    2017-01-15

    Oil is an important source of energy, mainly in developing countries. Important research has been conducted to find cementing procedures that guarantee safe and cost-effective oil exploration below pre-salt layers. This work aimed to make a new cement paste with cement, seawater, silica, biopolymers (chitosan and sodium alginate) and hydroxyapatite (HA), found in nature. For comparison purposes, slurry without additives was prepared and characterized. The HA used was extracted from fish scales (Cynoscion acoupa) in optimized condition NaOH concentration, temperature and reaction time. Both slurry were prepared with ratios water/cement (w/c) and silica/cement (s/c) equal to 0.50 and 0.35, respectively. The new cement slurry was obtained with proportions of 5% of each biopolymer and HA with respect to the total weight of the cement. In the immersion tests, specimens were immersed in samples of hyper production of saline water by 35°C for 15 days. Thereafter, they were washed, dried and its surface layers were scraped. Before, the resulting materials were characterized. The values of the ratios Ca/Si of new cement slurry (3.38 ± 0.06) were superior compared to standard (2.58 ± 0.05). The new slurry had high thermal stability and low amounts of small crystallite-type portlandite (35.70 nm). Conversely, a slurry standard formed larger crystals of about 50.3 nm. Significantly, after continuous long-term contact of both slurries with hyper-saline produced water from oil well fields operations, in comparison with standard slurry structural characteristics, the new slurry has practically maintained its pristine chemical structure, as well as has shown crystallite-type particles of NaCl and Friedel’s/Kuzel’s salts with lower proportion. The presence of the biopolymers and HA has driven the improved the self-healing properties observed in the new cement slurry. In this first study, the new slurry has shown adequate characteristics to contribute to cost effective and

  18. Thermodynamic Simulation of Carbonate Cements-Water-Carbon Dioxide Equilibrium in Sandstone for Prediction of Precipitation/Dissolution of Carbonate Cements.

    Science.gov (United States)

    Duan, Yiping; Feng, Mingshi; Zhong, Xinyan; Shang, Ruishu; Huang, Lihong

    2016-01-01

    -2.17 mmol·L-1 and remains negative, indicating it is also a precipitation process at burial depth of 3.9 km where overpressure generated. The method used in this study can be applied in assessing burial precipitation-dissolution processes and predicting possible pores in reservoirs with carbonate cement-water-carbon dioxide.

  19. Translational and rotational dynamics of water contained in aged Portland cement pastes studied by quasi-elastic neutron scattering.

    Science.gov (United States)

    Li, Hua; Zhang, Li-Li; Yi, Zhou; Fratini, Emiliano; Baglioni, Piero; Chen, Sow-Hsin

    2015-08-15

    Cement is a widely used construction material in the world. The quality and durability of aged cement pastes have a strong relationship with the water contained in it. The translational and rotational dynamics of water in ordinary Portland cement (OPC) pastes cured for 7, 14 and 30days were studied by analyzing Quasi-elastic Neutron Scattering (QENS) data. The effect of a new super-plasticizer (SP) additive was also studied by comparing the samples with and without the additive. By fitting the QENS spectra with the Jump-diffusion and Rotation-diffusion Model (JRM), six important parameters including the bound water index (BWI), the self-diffusion coefficient, D(t), the average residence time, τ0, the rotational diffusion constant, D(r), the rotational residence time, τ(r), and the mean squared displacement (MSD), 〈u(2)〉, were obtained. From these parameters, we can quantitatively follow the evolution of the bound water fraction (BWI). We can clearly see the different time ranges for the translational and rotational dynamics of water contained in the OPC pastes by τ0 and τ(r). From the MSD values compared with those of molecular dynamics simulation, we can distinguish between immobile water (mainly bound water) and mobile water, which includes confined water and ultraconfined water. Furthermore, by the fitted parameters' values and their change of slopes with increasing setting time for cement pastes with and without additive SP, it becomes clear that the effect of additive SP is to make the mobile water more confined and induce a more uniform the aging process during the evolution of the OPC pastes.

  20. Effects of Nanosilica on Compressive Strength and Durability Properties of Concrete with Different Water to Binder Ratios

    Directory of Open Access Journals (Sweden)

    Forood Torabian Isfahani

    2016-01-01

    Full Text Available The effects of the addition of different nanosilica dosages (0.5%, 1%, and 1.5% with respect to cement on compressive strength and durability properties of concrete with water/binder ratios 0.65, 0.55, and 0.5 were investigated. Water sorptivity, apparent chloride diffusion coefficient, electrical resistivity, and carbonation coefficient of concrete were measured. The results showed that compressive strength significantly improved in case of water/binder = 0.65, while for water/binder = 0.5 no change was found. Increasing nanosilica content, the water sorptivity decreased only for water/binder = 0.55. The addition of 0.5% nanosilica decreased the apparent chloride diffusion coefficient for water/binder = 0.65 and 0.55; however, higher nanosilica dosages did not decrease it with respect to reference value. The resistivity was elevated by 0.5% nanosilica for all water/binder ratios and by 1.5% nanosilica only for water/binder = 0.5. The carbonation coefficient was not notably affected by increasing nanosilica dosages and even adverse effect was observed for water/binder = 0.65. Further information of microstructure was also provided through characterization techniques such as X-ray diffraction, thermal gravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. The effectiveness of a certain nanosilica dosage addition into lower strength mixes was more noticeable, while, for the higher strength mix, the effectiveness was less.

  1. Surface Roughness and Porosity of Hydrated Cement Pastes

    Directory of Open Access Journals (Sweden)

    T. Ficker

    2011-01-01

    Full Text Available . Seventy-eight graphs were plotted to describe and analyze the dependences of the height and roughness irregularities on the water-to-cement ratio and on the porosity of the cement hydrates. The results showed unambiguously that the water-to-cement ratio or equivalently the porosity of the specimens has a decisive influence on the irregularities of the fracture surfaces of this material. The experimental results indicated the possibility that the porosity or the value of the water-to-cement ratio might be inferred from the height irregularities of the fracture surfaces. It was hypothesized that there may be a similarly strong correlation between porosity and surface irregularity, on the one hand, and some other highly porous solids, on the other, and thus the same possibility to infer porosity from the surfaces of their fracture remnants.

  2. Computation of Water-Stress Ratio in Western Nigeria

    Directory of Open Access Journals (Sweden)

    Philipa Omamhe Idogho

    2012-09-01

    Full Text Available An increasing world population exerts a continually growing demand on usable freshwater resources. Access to water plays a key role in development; it supports human life in direct consumption, agricultural uses and industrial activities. Time and drudgery involved to access safe drinking water resulted to loss of human resources and capital, thus affecting nearly every household life. This paper focuses on the determination of water-stressed ratio using Integrated Water Measurement Tool (IWMT. Structured simple time analysis and Adjusted composite index approaches were employed to compute (IWMT values in all the sampled areas. Variables such as access to safe water coverage, water availability and use of water were considered. IWMT values from the two approaches show that Ese-Odo is the most water-scarce region with least IWMT values of 14.1 (Adjusted composite index: ACI and highest value of 2.6 minsl -1 (Structured simple time analysis: SSA, while Owo, Ondo-West and Ose local government areas experience fair distribution of protected water supply with IWMT values of 1.05 minsl -1 , 20.8; 1.00 minsl -1 , 17.2; and 0.55 minsl -1 , 16.9 respectively. The results obtained indicate that constructive investments in water and sanitation would reduce proportion of household income spent in sourcing for safe drinking water, prevention of water-related diseases and in turn improves productivity. However, this paper concludes that top-down technical approach must be balanced with a bottom-up mechanism in order to derive realistic systems to prevent persistent water scarcity, shortage and to draw realistic adaption measures.

  3. EQUIVALENT MODEL OF EXPANSION OF CEMENT MORTAR UNDER SULPHATE EROSION

    Institute of Scientific and Technical Information of China (English)

    Jue Zhu; Minqiang Jiaug; Jiankang Chen

    2008-01-01

    The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods.First,cement mortars are fabricated with the ratio of water to cement of 0.4,0.6,and 0.8.Secondly,the expansion of specimen immerged in sulphate solution is measured at different times.Thirdly,a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method.In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account.Finally,the numerical calculation is performed.The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

  4. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  5. Some aspects of cellulose ethers influence on water transport and porous structure of cement-based materials

    OpenAIRE

    Pourchez, Jérémie; Ruot, Bertrand; Debayle, Johan; Rouèche-Pourchez, Emilie; Grosseau, Philippe

    2010-01-01

    International audience; This paper evaluates and compares the impact of cellulose ethers (CE) on water transport and porous structure of cement-based materials in both fresh and hardened state. Investigations of the porous network (mercury intrusion porosimetry, apparent density, 2D and 3D observations) emphasize an air-entrained stabilisation depending on CE chemistry. We also highlight that CE chemistry leads to a gradual effect on characteristics of the water transport. The global tendenci...

  6. Soil-water characteristics of sandy soil and soil cement with and without vegetation

    OpenAIRE

    2014-01-01

    The use of soil cement as a growth medium was examined in this study. During the monitoring, green soil cement revealed diverse ecological values. The survival rates of plants in each soil conditions were higher than 80%,which was very promising. Furthermore, the survival rates dropped when the soil density reached95%, which means soil density might influence the survival rate of plant. Plant growth rates in sandy soil were higher than that in soil cement. In particular, low soil density faci...

  7. 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 estimate

  8. Influence of pore structure on compressive strength of cement mortar.

    Science.gov (United States)

    Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

  9. Laboratory Investigation on the Strength Gaining of Brick Aggregate Concrete Using Ordinary Portland Cement and Portland Composite Cement

    Directory of Open Access Journals (Sweden)

    Hoque M H, Numen E H, Islam N., Mohammed

    2014-05-01

    Full Text Available This study focused on the laboratory investigation of strength variation of brick aggregate concrete made with ordinary Portland cement (OPC and Portland composite cement (PCC.The investigation was conducted by testing concrete cylinder specimens at different ages of concrete with concrete mix ratios: 1:1.5:3 and 1:2:4 by volume and with water cement ratios=0.45 and 0.60. The test result reveals that at the early age, concrete composed with OPC attained larger compressive strength than the concrete made of PCC. However, in the later age concrete made with PCC achieved higher strength than OPC.

  10. Effect of Sodium Carboxymethyl Celluloses on Water-catalyzed Self-degradation of 200-degree C-heated Alkali-Activated Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.

    2012-05-01

    We investigated the usefulness of sodium carboxymethyl celluloses (CMC) in promoting self-degradation of 200°C-heated sodium silicate-activated slag/Class C fly ash cementitious material after contact with water. CMC emitted two major volatile compounds, CO2 and acetic acid, creating a porous structure in cement. CMC also reacted with NaOH from sodium silicate to form three water-insensitive solid reaction products, disodium glycolate salt, sodium glucosidic salt, and sodium bicarbonate. Other water-sensitive solid reaction products, such as sodium polysilicate and sodium carbonate, were derived from hydrolysates of sodium silicate. Dissolution of these products upon contact with water generated heat that promoted cement’s self-degradation. Thus, CMC of high molecular weight rendered two important features to the water-catalyzed self-degradation of heated cement: One was the high heat energy generated in exothermic reactions in cement; the other was the introduction of extensive porosity into cement.

  11. 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...... relative humidity development; autogenous deformation; and eigenstress development, using a novel embedded spherical stress sensor. Because the latter three measurements are conducted under sealed conditions, whereas chemical-shrinkage measurements are made under "saturated" conditions, the National...... controls the initial pore-size distribution of the cement paste, which, in turn, regulates the magnitude of the induced autogenous shrinkage stresses produced by the water/air menisci in the air-filled pores formed throughout the hydration process. The experimental results indicate that a small autogenous...

  12. Influence of vinyl acetate-versatic vinylester copolymer on the microstructural characteristics of cement pastes

    OpenAIRE

    Carlos Eduardo Marmorato Gomes; Osny Pellegrino Ferreira; Mauro Roberto Fernandes

    2005-01-01

    To understand the principles of polymer modification and its interference in the formation of some phases of Portland cement composites, several techniques are adopted such as Fourier Transform Infrared Spectroscopy and Thermogravimetric Analysis. In this study, these techniques were adopted to verify the influence of VA/VeoVA copolymer in seven pastes of high-early-strength portland cement twenty-eight days old, being four pastes with different polymer content and the same water/cement ratio...

  13. 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.

  14. The water jet as a new tool for endoprosthesis revision surgery--an in vitro study on human bone and bone cement.

    Science.gov (United States)

    Honl, Matthias; Rentzsch, Reemt; Schwieger, Karsten; Carrero, Volker; Dierk, Oliver; Dries, Sebastian; Louis, Hartmut; Pude, Frank; Bishop, Nick; Hille, Ekkehard; Morlock, Michael

    2003-01-01

    In revision surgeries of endoprostheses, the interface between implant and bone cement or bone must be loosened. Conventional tools have many disadvantages because of their size and limited range. Taking advantage of the selective and athermic cutting process, a plain water jet is already used in order to cut soft tissues. This study investigates the possibilities of both a plain and an abrasive water jet as cutting tools for revision surgery. Samples of the mid-diaphysis of human femora and bone cement (CMW3) were cut with a plain water jet (PWJ) and an abrasive water jet (AWJ) at two different jet-to-surface angles (30 degrees,90 degrees ) and at five different pressure levels (30, 40, 50, 60, 70 MPa). For a PWJ a selective pressure range was identified, where only bone cement was cut. Injecting a bio-compatible abrasive (lactose) to the jet stream resulted in significantly higher cut depths in both materials. Material removal in bone was significantly less at the smaller jet-to-surface angle for both techniques. No clear selectivity between bone and bone cement was observed for application of the AWJ. However, the material removal rate was significantly higher for bone cement than for bone at all pressure levels. The results indicate that an AWJ might be an alternative tool for cement removal. The possibility for localised cutting at interfaces could be an advantage for revision of a non-cemented prosthesis.

  15. How the oxygen isotope ratio of rain water influences the isotope ratio of chicken eggshell carbonate

    Science.gov (United States)

    Price, Gregory; Grimes, Stephen

    2015-04-01

    The stable oxygen isotope ratio of chicken eggshell carbonate was analysed from chicken eggs laid under free range, and organic farming regimes from across the UK. The eggshell carbonate oxygen isotope data shows a clear depletion in delta18O distribution from the southwest to the northeast. Although consistently offset by around 1 permil, the same isotopic distribution as that seen in eggshell carbonate is observed in the delta18O ratio of rainfall and groundwater from across the UK. This distribution is related to the Rayleigh distillation of rainfall driven by westerly winds across the UK landmass. The clear relationship observed between eggshell delta18O values and that of rainwater presumably reflects the nature of free range chickens which must be drinking locally derived rainwater and supplementing their diet and water intake with locally derived food. These results suggest that the oxygen isotope value of chicken eggshells can be used as a forensic tool to identify the locality that free range and organic eggs were laid within the UK. Furthermore, if suitable material is preserved in the archaeological and geological record then such a relationship can potentially be used to establish the oxygen isotope value of rainwater from which ancient and / or ancestral birds lived.

  16. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

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

  17. High-performance binders with reduced autogenous shrinkage on the basis of fine cement

    Energy Technology Data Exchange (ETDEWEB)

    Martschuk, V. [Inst. of the Cement Industry, Dusseldorf (Germany)

    2001-07-01

    A study on the hydration of portland cement was presented. The paper presented special features of the chemical shrinkage of cement paste at high and low water-cement ratios. It also described the effect of silica fume on the deformation behaviour of cement paste, as well as on the behaviour of hardened binder paste at water-binder ratios of 0.40 and 0.25. High performance concrete has a high density and a tendency to chemically shrink because of its low water-cement ratio. The study showed that the autogenous shrinkage increases if silica fume is added. Theoretical calculations were performed and showed that the typical addition of silica fume results in an increase in total porosity, and therefore, to the deterioration of the packing density of the binder mixture. The specific surface area of the dry powder is also increased. It was concluded that replacing cement by optimized fine cements improves the theoretical packing density in binders. The hardened cement paste studies showed that this makes a cement that is denser with less tendency to shrink. 7 refs., 3 tabs., 8 figs.

  18. EVALUATION OF CHEMICALS INCORPORATED WOOD FIBRE CEMENT MATRIX PROPERTIES

    Directory of Open Access Journals (Sweden)

    MST. SADIA MAHZABIN

    2013-08-01

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

  19. Thermodynamic Simulation of Carbonate Cements-Water-Carbon Dioxide Equilibrium in Sandstone for Prediction of Precipitation/Dissolution of Carbonate Cements

    OpenAIRE

    Duan, Yiping; Feng, Mingshi; Zhong, Xinyan; Shang, Ruishu; Huang, Lihong

    2016-01-01

    Carbonate cements, such as calcite, dolomite, ferrocalcite and ankerite, play important roles in the formation of pores in sandstones: precipitation of carbonate cements modifies pores and inhibits compaction, while dissolution creates secondary pores. This work proposed a precipitation-dissolution model for carbonate cements-CO2-H2O system by means of ion equilibrium concentration ([M2+], M = Ca, Mg, Fe or Mn) with different factors, such as temperature, depth, pH, P CO 2 , variable rock com...

  20. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  1. Using cement, lignite fly ash and baghouse filter waste for solidification of chromium electroplating treatment sludge

    Directory of Open Access Journals (Sweden)

    Wantawin, C.

    2004-02-01

    Full Text Available The objective of the study is to use baghouse filter waste as a binder mixed with cement and lignite fly ash to solidify sludge from chromium electroplating wastewater treatment. To save cost of solidification, reducing cement in binder and increasing sludge in the cube were focused on. Minimum percent cement in binder of 20 for solidification of chromium sludge was found when controlling lignite fly ash to baghouse filter waste at the ratio of 30:70, sludge to binder ratio of 0.5, water to mixer ratio of 0.3 and curing time of 7 days. Increase of sludge to binder ratio from 0.5 to 0.75 and 1 resulted in increase in the minimum percent cement in binder up to 30 percent in both ratios. With the minimum percent cement in binder, the calculated cement to sludge ratios for samples with sludge to binder ratios of 0.5, 0.75 and 1 were 0.4, 0.4 and 0.3 respectively. Leaching chromium and compressive strength of the samples with these ratios could achieve the solidified waste standard by the Ministry of Industry. For solidification of chromium sludge at sludge to binder ratio of 1, the lowest cost binder ratio of cement to lignite fly ash and baghouse filter waste in this study was 30:21:49. The cost of binder in this ratio was 718 baht per ton dry sludge.

  2. Immobilization in cement mortar of chromium removed from water using titania nanoparticles.

    Science.gov (United States)

    Husnain, Ahmed; Qazi, Ishtiaq Ahmed; Khaliq, Wasim; Arshad, Muhammad

    2016-05-01

    Because of the high toxicity of chromium, particularly as Cr (VI), it is removed from industrial effluents before their discharge into water bodies by a variety of techniques, including adsorption. Ultimate disposal of the sludge or the adsorbate, however, is a serious problem. While titania, in nanoparticle form, serves as a very good adsorbent for chromium, as an additive, it also helps to increase the compressive strength of mortar and concrete. Combining these two properties of the material, titania nanoparticles were used to adsorb chromium and then added to mortar up to a concentration of 20% by weight. The compressive strength of the resulting mortar specimens that replaced 15% of cement with chromium laden titania showed an improved strength than that without titania, thus confirming that this material had positive effect on the mortar strength. Leachate tests using the Toxicity Characteristics Leaching Procedure (TCLP) confirmed that the mortar sample chromium leachate was well within the permissible limits. The proposed technique thus offers a safe and viable method for the ultimate disposal of toxic metal wastes, in general, and those laden waste chromium, in particular.

  3. Tap water isotope ratios reflect urban water system structure and dynamics across a semiarid metropolitan area

    Science.gov (United States)

    Jameel, Yusuf; Brewer, Simon; Good, Stephen P.; Tipple, Brett J.; Ehleringer, James R.; Bowen, Gabriel J.

    2016-08-01

    Water extraction for anthropogenic use has become a major flux in the hydrological cycle. With increasing demand for water and challenges supplying it in the face of climate change, there is a pressing need to better understand connections between human populations, climate, water extraction, water use, and its impacts. To understand these connections, we collected and analyzed stable isotopic ratios of more than 800 urban tap water samples in a series of semiannual water surveys (spring and fall, 2013-2015) across the Salt Lake Valley (SLV) of northern Utah. Consistent with previous work, we found that mean tap water had a lower 2H and 18O concentration than local precipitation, highlighting the importance of nearby montane winter precipitation as source water for the region. However, we observed strong and structured spatiotemporal variation in tap water isotopic compositions across the region which we attribute to complex distribution systems, varying water management practices and multiple sources used across the valley. Water from different sources was not used uniformly throughout the area and we identified significant correlation between water source and demographic parameters including population and income. Isotopic mass balance indicated significant interannual and intra-annual variability in water losses within the distribution network due to evaporation from surface water resources supplying the SLV. Our results demonstrate the effectiveness of isotopes as an indicator of water management strategies and climate impacts within regional urban water systems, with potential utility for monitoring, regulation, forensic, and a range of water resource research.

  4. [Microbial settlement of paint- and building-materials in the sphere of drinking water. 5. Communication: Macrocolonies on the cement mortar lining in a water main (author's transl)].

    Science.gov (United States)

    Schoenen, D

    1980-09-01

    It is reported a microbial growth in form of macrocolonies on a cement mortar line in a potable water main. Simultaneously an increase of bacterial content in the water could be observed. The bacterial content could be reduced by chlorination, but the microbial growth on the surface of the lining was not suppressed. Macrocolonies could be observed the same as before at the last inspection 6 1/2 years after opening of the main.

  5. 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.

  6. 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

    of various concrete mixtures there are limitations to the current analysis techniques. To date these techniques analyze the result of one WST specimen, thereby providing an estimate of material properties from single result. This paper utilizes a recent improvement to the inverse analysis technique, which......Since the development of the wedge splitting test (WST), techniques have been used to extract material properties that can describe the fracture behavior of the tested materials. Inverse analysis approaches are commonly used to estimate the stress-crack width relationship; which is described...... 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...

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

    African Journals Online (AJOL)

    user

    Chemical analysis of RHA produced under controlled temperature of 600°C was carried out. A ... Test results show that the compressive strength of hardened RHA concrete ..... by [22]. However the loss on ignition (LOI) of 13.33 is lower.

  8. Evaluating the cement stabilization of arsenic-bearing iron wastes from drinking water treatment.

    Science.gov (United States)

    Clancy, Tara M; Snyder, Kathryn V; Reddy, Raghav; Lanzirotti, Antonio; Amrose, Susan E; Raskin, Lutgarde; Hayes, Kim F

    2015-12-30

    Cement stabilization of arsenic-bearing wastes is recommended to limit arsenic release from wastes following disposal. Such stabilization has been demonstrated to reduce the arsenic concentration in the Toxicity Characteristic Leaching Procedure (TCLP), which regulates landfill disposal of arsenic waste. However, few studies have evaluated leaching from actual wastes under conditions similar to ultimate disposal environments. In this study, land disposal in areas where flooding is likely was simulated to test arsenic release from cement stabilized arsenic-bearing iron oxide wastes. After 406 days submersed in chemically simulated rainwater, wastes. Presenting the first characterization of cement stabilized waste using μXRF, these results revealed the majority of arsenic in cement stabilized waste remained associated with iron. This distribution of arsenic differed from previous observations of calcium-arsenic solid phases when arsenic salts were stabilized with cement, illustrating that the initial waste form influences the stabilized form. Overall, cement stabilization is effective for arsenic-bearing wastes when acidic conditions can be avoided.

  9. Effects of Water Reducer on the Properties of High-volume Fly Ash Cement Mortar%减水剂对高掺量粉煤灰砂浆性能的影响

    Institute of Scientific and Technical Information of China (English)

    郑大锋; 邱学青; 欧阳新平; 杨东杰; 楼宏铭

    2006-01-01

    Effects of FDN and Calcium lignosulfonate (LS) on the properties of high-volume fly ash cement mortar were studied. It was found that compared with FDN, the water-reducing ratio of LS was lower and the ability of retaining the fluidity of the cement mortar was better; for the stability of the cement mortar, the effect of LS was almost the same as that of FDN at the dosage of 0.4 %. The adsorption on the cementitious surface, the effect on the zeta potential of cement particle surface and the foaming capacity of FDN and LS were measured. The results showed that, for the reasons of stronger air-entraining capacity of LS and the incomplete adsorption of FDN on the surface of cementitious particles, the water-reducing ratio of LS was close to FDN when the dosage was lower than 0.4 %. The better fluidity retention capacity of LS was attributed to the more stable zeta potential of the cement surface and the retarding effect of mortar setting. The experimental results suggested that for the purpose of utilizing LS better in the high-volume fly ash cement mortar in the grouting, some modification should be conducted to increase its water-reducing ratio.%研究了萘系高效减水剂(FDN)和木质素磺酸钙(LS)对高掺量粉煤灰砂浆性能的影响,测定了减水剂在胶凝颗粒表面的吸附、对水泥颗粒表面zeta电位等方面的影响.结果表明,和FDN相比,LS对砂浆的减水率较低,而对砂浆流动度保持能力较优;当掺量为0.4 wt%时,两者对砂浆稳定性的影响几乎一样.当掺量低于0.4 %时,LS的减水率和FDN接近是因为其具有较强的引气作用和FDN在胶凝颗粒表面吸附不完全;LS保持砂浆流动性能力较好是由于它的缓凝作用以及吸附LS的水泥颗粒表面zeta电位较稳定导致的.为了更好地将LS应用在高掺量粉煤灰砂浆中,可以从提高其减水率方面对其进行改性.

  10. Water isotopic ratios from a continuously melted ice core sample

    Directory of Open Access Journals (Sweden)

    V. Gkinis

    2011-11-01

    Full Text Available A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS purchased from Picarro Inc. and a Continuous Flow Analysis (CFA system. The system offers the possibility to perform simultaneuous water isotopic analysis of δ18O and δD on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub μl amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100% efficiency in a~home made oven at a temperature of 170 °C. A calibration procedure allows for proper reporting of the data on the VSMOW–SLAP scale. We apply the necessary corrections based on the assessed performance of the system regarding instrumental drifts and dependance on the water concentration in the optical cavity. The melt rates are monitored in order to assign a depth scale to the measured isotopic profiles. Application of spectral methods yields the combined uncertainty of the system at below 0.1‰ and 0.5‰ for δ18O and δD, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sample in the transfer lines limits the temporal resolution of the technique. In this work we investigate and assess these dispersion effects. By using an optimal filtering method we show how the measured profiles can be corrected for the smoothing effects resulting from the sample dispersion. Considering the significant advantages the technique offers, i.e. simultaneuous measurement of δ18O and δD, potentially in combination with chemical components that are traditionally measured on CFA systems, notable reduction on analysis time and power consumption, we consider it as an alternative to traditional isotope ratio mass spectrometry with the possibility to

  11. Early age monitoring of cement mortar using embedded piezoelectric sensors

    Science.gov (United States)

    Narayanan, Arun; Subramaniam, Kolluru V. L.

    2016-04-01

    A piezoceramic based sensor consisting of embedded Lead Zirconate Titanate (PZT) patch is developed for assessing the progression of hydration and evolution of properties of cement mortar. A method for continuous assessment of cement mortar with different water to cement ratios after casting is presented. The method relies on monitoring changes in the electromechanical (EM) conductance of a PZT patch embedded in mortar. Changes in conductance are shown to sensitively reflect the changes in the mechanical impedance of the cementitious material as it transforms from fluid to solid state.

  12. Quality control of cemented waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Slate, L.J.

    1994-12-31

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

  13. Water isotopic ratios from a continuously melted ice core sample

    Directory of Open Access Journals (Sweden)

    V. Gkinis

    2011-06-01

    Full Text Available A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We build an interface between an Infra Red Cavity Ring Down Spectrometer (IR-CRDS and a Continuous Flow Analysis (CFA system. The system offers the possibility to perform simultaneuous water isotopic analysis of δ18O and δD on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub μl amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100 % efficiency in a home made oven at a temperature of 170 °C. A calibration procedure allows for proper reporting of the data on the VSMOW scale. We apply the necessary corrections based on the assessed performance of the system regarding instrumental drifts and dependance on humidity levels. The melt rates are monitored in order to assign a depth scale to the measured isotopic profiles. Application of spectral methods yields the combined uncertainty of the system at below 0.1 ‰ and 0.5 ‰ for δ18O and δD, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sample in the transfer lines limits the resolution of the technique. In this work we investigate and assess these dispersion effects. By using an optimal filtering method we show how the measured profiles can be corrected for the smoothing effects resulting from the sample dispersion. Considering the significant advantages the technique offers, i.e. simultaneuous measurement of δ18O and δD, potentially in combination with chemical components that are traditionally measured on CFA systems, notable reduction on analysis time and power consumption, we consider it as an alternative to traditional isotope ratio mass spectrometry with the possibility to be deployed for field ice core studies. We present data acquired in the

  14. Chloride ingress in cement paste and mortar

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, O.M.; Hansen, P.F.; Coats, A.M.; Glasser, F.P.

    1999-09-01

    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 are modelled on Fick's law modified by a term for chloride binding. Inclusion of chloride binding significantly improves the profile shape of the modelled ingress profiles. The presence of fine aggregate and formation of interfacial transition zones at paste-aggregate boundaries does not significantly affect diffusion rates.

  15. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1

  16. Porosity prediction of calcium phosphate cements based on chemical composition.

    Science.gov (United States)

    Öhman, Caroline; Unosson, Johanna; Carlsson, Elin; Ginebra, Maria Pau; Persson, Cecilia; Engqvist, Håkan

    2015-07-01

    The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% β-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37°C and 100% relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 °C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

  17. Final Report on Isotope Ratio Techniques for Light Water Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Gerlach, David C.; Gesh, Christopher J.; Hurley, David E.; Mitchell, Mark R.; Meriwether, George H.; Reid, Bruce D.

    2009-07-01

    The Isotope Ratio Method (IRM) is a technique for estimating the energy or plutonium production in a fission reactor by measuring isotope ratios in non-fuel reactor components. The isotope ratios in these components can then be directly related to the cumulative energy production with standard reactor modeling methods.

  18. Liquid water permeability of partially saturated cement paste assessed by dem-based methodology

    NARCIS (Netherlands)

    Li, K.; Stroeven, P.; Stroeven, M.; Sluys, L.J.

    2015-01-01

    Permeability of virtual cement seems to exceed experimental data by several orders of magnitude. The differences may actually not be that dramatic, since experimental samples are in practice not always fully saturated as generally assumed. This paper demonstrates that this has enormous effects on pe

  19. Leaching due to hygroscopic water uptake in cemented waste containing soluble salts

    DEFF Research Database (Denmark)

    Brodersen, K.

    1992-01-01

    Considerable amounts of easily soluble salts such as sodium nitrate, sulphate, or carbonate are introduced into certain types of cemented waste. When such materials are stored in atmospheres with high relative humidity or disposed or by shallow land burial under unsaturated, but still humid...

  20. 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.

  1. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-01-23

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

  2. A study of the water vapor sorption isotherms of hardened cement pastes: Possible pore structure changes at low relative humidity and the impact of temperature on isotherms

    DEFF Research Database (Denmark)

    Wu, Min; Johannesson, Björn; Geiker, Mette Rica

    2014-01-01

    Using water vapor sorption isotherms measured by the “dynamic vapor sorption” (DVS) method, a resaturation study was conducted to investigate possible pore structure changes of hardened cement paste samples caused by the drying at low relative humidity during desorption measurements. The results...... indicate that either the relatively short term drying does not cause any microstructure changes or the pore structure of the hardened cement paste samples can be restored during the absorption process. Additionally, the temperature dependency of sorption isotherms was investigated using both hardened...... cement paste samples and a model material MCM-41. The pronounced impact of temperature on desorption isotherms of cement based materials as reported in literature was not found in this investigation. The results suggest that the differences between the sorption isotherms measured at different...

  3. Attack of carbonic anhydride and hydrogen sulfide on API class H cement slurries exposed to saline formation waters

    Directory of Open Access Journals (Sweden)

    Márquez, G.

    2011-09-01

    Full Text Available This paper discusses the attack of the major ions (sulfate, chloride, and magnesium and sour gases, present in natural gas (CO2 y SH2, on API class H cement, the type used in gas wells under high pressure and temperature. The effects of these chemical agents on this cement was simulated to study the physicochemical changes due to the action of sour gases and formation water. Cement specimens were immersed in neutral solutions containing fixed concentrations of the major ions inside Parr reactors. These solutions were analysed and XRD analyses were conducted for over two months to identify mineralogical variations from 14 to 60 days. The objective of this research was to determine the effects of the joint attack of major ions and sour gases on cement pastes. The main effects of both gases, jointly or separately, on cement durability were, respectively, the carbonation process and the leaching of some components.

    Se simuló la acción agresiva de los denominados iones fundamentales (sulfato, cloruro y magnesio y los gases agrios presentes en el gas natural (CO2 y H2S sobre un cemento API clase H utilizado en pozos gasíferos a presión y temperatura elevadas, al objeto de observar sus alteraciones fisicoquímicas por la acción combinada de tales gases y las aguas de formación. Se prepararon varias probetas del material cementante para su inmersión en disoluciones neutras, conteniendo los iones fundamentales en concentraciones fijas, dentro de reactores tipo Parr. Se analizaron durante más de dos meses una serie de disoluciones en contacto con el cemento utilizado; así como, mediante DRX, la evolución de la mineralogía de dicho material entre los 14 y los 60 días. Los principales efectos de ambos gases, en conjunto o por separado, sobre la durabilidad del cemento fueron, respectivamente, la formación de carbonato cálcico y la lixiviación de algunos componentes.

  4. Probing the metabolic water contribution to intracellular water using oxygen isotope ratios of PO4

    Science.gov (United States)

    Li, Hui; Yu, Chan; Wang, Fei; Chang, Sae Jung; Yao, Jun; Blake, Ruth E.

    2016-05-01

    Knowledge of the relative contributions of different water sources to intracellular fluids and body water is important for many fields of study, ranging from animal physiology to paleoclimate. The intracellular fluid environment of cells is challenging to study due to the difficulties of accessing and sampling the contents of intact cells. Previous studies of multicelled organisms, mostly mammals, have estimated body water composition—including metabolic water produced as a byproduct of metabolism—based on indirect measurements of fluids averaged over the whole organism (e.g., blood) combined with modeling calculations. In microbial cells and aquatic organisms, metabolic water is not generally considered to be a significant component of intracellular water, due to the assumed unimpeded diffusion of water across cell membranes. Here we show that the 18O/16O ratio of PO4 in intracellular biomolecules (e.g., DNA) directly reflects the O isotopic composition of intracellular water and thus may serve as a probe allowing direct sampling of the intracellular environment. We present two independent lines of evidence showing a significant contribution of metabolic water to the intracellular water of three environmentally diverse strains of bacteria. Our results indicate that ˜30-40% of O in PO4 comprising DNA/biomass in early stationary phase cells is derived from metabolic water, which bolsters previous results and also further suggests a constant metabolic water value for cells grown under similar conditions. These results suggest that previous studies assuming identical isotopic compositions for intracellular/extracellular water may need to be reconsidered.

  5. Decontamination of Bacillus spores adhered to iron and cement-mortar drinking water infrastructure in a model system using disinfectants.

    Science.gov (United States)

    Szabo, Jeffrey G; Meiners, Greg; Heckman, Lee; Rice, Eugene W; Hall, John

    2017-02-01

    Decontamination of Bacillus spores adhered to common drinking water infrastructure surfaces was evaluated using a variety of disinfectants. Corroded iron and cement-mortar lined iron represented the infrastructure surfaces, and were conditioned in a 23 m long, 15 cm diameter (75 ft long, 6 in diameter) pilot-scale drinking water distribution pipe system. Decontamination was evaluated using increased water velocity (flushing) alone at 0.5 m s(-1) (1.7 ft s(-1)), as well as free chlorine (5 and 25 mg L(-1)), monochloramine (25 mg L(-1)), chlorine dioxide (5 and 25 mg L(-1)), ozone (2.0 mg L(-1)), peracetic acid 25 mg L(-1)) and acidified nitrite (0.1 mol L(-1) at pH 2 and 3), all followed by flushing at 0.3 m s(-1) (1 ft s(-1)). Flushing alone reduced the adhered spores by 0.5 and 2.0 log10 from iron and cement-mortar, respectively. Log10 reduction on corroded iron pipe wall coupons ranged from 1.0 to 2.9 at respective chlorine dioxide concentrations of 5 and 25 mg L(-1), although spores were undetectable on the iron surface during disinfection at 25 mg L(-1). Acidified nitrite (pH 2, 0.1 mol L(-1)) yielded no detectable spores on the iron surface during the flushing phase after disinfection. Chlorine dioxide was the best performing disinfectant with >3.0 log10 removal from cement-mortar at 5 and 25 mg L(-1). The data show that free chlorine, monochloramine, ozone and chlorine dioxide followed by flushing can reduce adhered spores by > 3.0 log10 on cement-mortar.

  6. Corrosion of steel bars in cracked concrete made with ordinary portland, slag and fly ash cements

    Energy Technology Data Exchange (ETDEWEB)

    Mohammed, T.U.; Yamaji, T.; Hamada, H. [Port and Harbor Research Inst., Ministry of Land, Infrastructure and Transport (Japan); Aoyama, T. [PS Corp. (Japan)

    2001-07-01

    A study was conducted in which the marine durability of ordinary portland cement, slag and fly ash cement was examined using 15 year old plain and reinforced concrete cylindrical specimens. The performance of these cements was then examined for pre-cracked reinforced concrete prism samples. The process of manufacturing cement emits huge amounts of carbon dioxide into the global atmosphere. Replacing a portion of the cement with by-products from the steel industry and thermal power plants (which are both huge emitters of carbon dioxide) can lower carbon dioxide emissions and also solve the disposal issue of slag and fly ash while increasing the long-term durability of concrete structures. In this study, concrete cylindrical specimens were made of ordinary portland cement, slag and fly ash cements. The specimens were 100 x 100 x 600 mm prisms of different types of cement. Water-to-cement ratios were 0.45 and 0.55. Both tap water and seawater were used as mixing water. The samples were exposed in tidal pools for 15 years to evaluate the compressive strength of the concrete, corrosion of the steel bars, and chloride-ion concentrations in the concrete. It was shown that, with the exception of fly ash cements, the compressive strength of most cements increased after 15 years of exposure compared to its 28 day strength. Type C slag cement demonstrated the best performance against chloride-ion at the surface of concrete made with slag and fly ash. Voids in the steel-concrete interface make it possible for corrosion pits to develop. The use of seawater as mixing water results in earlier strength development at 28 days and does not cause to the strength of the concrete to regress after 15-years of exposure, but it causes more corrosion of steel bars at a lower cover depth. Corrosion of steel bars is not an issue at deeper cover depths. 15 refs., 19 tabs., 13 figs.

  7. Diffusion of Tritiated Water (HTO) and {sup 22}Na{sup +}-Ions through Non-Degraded Hardened Cement Pastes - II. Modelling Results

    Energy Technology Data Exchange (ETDEWEB)

    Jakob, A

    2002-12-01

    In this report, the procedure and the results of an inverse modelling study on the through-diffusion of tritiated water (HTO) and {sup 2}2Na{sup +}-ions are presented using high-porous hardened cement pastes with a water/cement ratio of 1.3 in the first stage of the cement degradation. For the analysis two alternative models were applied: 1) a diffusion model where a possible sorption of the tracer was entirely neglected, and 2) a diffusion model with linear sorption. The analysis of the through-diffusion phase allowed extracting values for the effective diffusion coefficient (D{sub e}) and the rock-capacity factor ({alpha}). Both models could fit the breakthrough curves equally well, and also mass-balance considerations did not allow to clearly preferring one of the two competing models to the other. But blind-predictions for tracer out-diffusion using the best-fit parameter values deduced from analysing the former through-diffusion phase gave a clear indication that linear sorption had to be included in the diffusion model. The extracted K{sub d} values for HTO are in excellent agreement with values from batch sorption experiments and are of the order of 0.8. 10{sup -3} m{sup 3}/kg. Those for {sup 2}2Na{sup +} are of the order of 1.0. 10{sup -3} m{sup 3}/kg and are by a factor of two larger than values from batch sorption experiments. The values for the effective diffusion coefficients for HTO are of the order of (2-3).10{sup -1}0 m{sup 2}/s, and those for sodium are roughly by a factor of two smaller than values for HTO. On the one hand, the observed tracer uptake could only partially be addressed to isotope exchange; the most obvious process which could account for the remaining part of the uptaken tracer mass is diffusion into a second type of porosity, the dead-end pores. On the other hand, the results and conclusions drawn are encouraging for future investigations; therefore no major deficiency concerning the applied equipment and the modelling methodology

  8. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    A K Misra; Renu Mathur

    2007-06-01

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

  9. Cement-based materials' characterization using ultrasonic attenuation

    Science.gov (United States)

    Punurai, Wonsiri

    relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

  10. Visualization and quantification of water movement in porous cement-based materials by real time thermal neutron radiography:Theoretical analysis and experimental study

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Water movement in porous cement-based materials is of great importance when studying their deterioration processes and durability.Many traditional methods based on mass changes,electricity or nuclear magnetic resonances are available for studying water transport in cement-based materials.In this research,an advanced technique i.e.thermal neutron radiography was utilized to achieve visualization and quantification of time dependent water movement including water penetration and moisture vapor in porous cement-based materials through theoretical analysis and experimental study.Because thermal neutrons ex-perience a strong attenuation by hydrogen,neutron radiography exhibits high sensitivity to small amounts of water.A neutron transmission analysis for quantitative evaluation of raw radiographic measurements was developed and optimized based on point scattered functions(PScF).The determinations of the real time and space dependent water penetration into uncracked and cracked mortar samples,as well as the drying process have been presented in this paper.It is illustrated that thermal neutron radiography can be a useful research tool for visualization and quantification of water movement in porous building materials.The obtained results will help us to better understand deteriorating processes of cement-based materials and to find ways to improve their durability.

  11. Development of LiCl-containing calcium aluminate cement for bone repair and remodeling applications.

    Science.gov (United States)

    Acuña-Gutiérrez, I O; Escobedo-Bocardo, J C; Almanza-Robles, J M; Cortés-Hernández, D A; Saldívar-Ramírez, M M G; Reséndiz-Hernández, P J; Zugasti-Cruz, A

    2017-01-01

    The effect of LiCl additions on the in vitro bioactivity, hemolysis, cytotoxicity, compressive strength and setting time of calcium aluminate cements was studied. Calcium aluminate clinker (AC) was obtained via solid state reaction from reagent grade chemicals of CaCO3 and Al2O3. Calcium aluminate cements (CAC) were prepared by mixing the clinker with water or aqueous LiCl solutions (0.01, 0.0125 or 0.015M (M)) using a w/c ratio of 0.4. After 21days of immersion in a simulated body fluid (SBF) at physiological conditions of temperature and pH, a Ca-P rich layer, identified as hydroxyapatite (HA), was formed on the cement without LiCl and on the cement prepared with 0.01M of LiCl solution. This indicates the high bioactivity of these cements. The cements setting times were significantly reduced using LiCl. The measured hemolysis percentages, all of them lower than 5%, indicated that the cements were not hemolytic. The compressive strength of the cements was not negatively affected by the LiCl additions. The obtained cement when a solution of LiCl 0.010M was added, presented high compressive strength, appropriated bioactivity, no cytotoxicity and low setting time, making this material a potentially bone cement.

  12. Cement and concrete

    Science.gov (United States)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  13. 钙磷摩尔比对新型PCCP+DCPA体系骨水泥性能的影响%INFLUENCE OF CALCIUM TO PHOSPHATE MOLAR RATIO ON PERFORMANCE OF A NOVEL CALCIUM PHOSPHATE CEMENT

    Institute of Scientific and Technical Information of China (English)

    王秀鹏; 叶建东; 王迎军

    2007-01-01

    Partially crystallized calcium phosphates (PCCP) with different calcium to phosphate molar ratios (n(Ca)/n(P), the same below) and containing carbonate were synthesized by chemical precipitation method. A novel calcium phosphate cement was prepared by PCCP and dicalcium phosphate anhydrous (DCPA). The effects of n(Ca)/n(P) ratio on the properties of the PCCP-DCPA cement system were studied by X-ray diffraction, scanning electron microscope, porosity measurement, and compressive strength analysis.The results show that with the increase of n(Ca)/n(P) ratio, the compressive strength of the cement samples decreased significantly,whereas the crystallinity, porosity and pore fractions larger than 100 nm in the hydrated cement increased. The properties of the cement were greatly influenced by the n(Ca)/n(P) ratio. The n(Ca)/n(P) ratio must be carefully considered in the preparation of calcium phosphate cement.%用化学沉淀法合成了不同钙/磷摩尔比并含碳酸根的部分结晶磷酸钙(partially crystallized calcium phosphates,PCCP),用PCCP和无水磷酸氢钙(dicalcium phosphate anhydrous ,DCPA)配制了PCCP+DCPA体系磷酸钙骨水泥,用去离子水作为骨水泥的固化液.通过相组成的X射线衍射分析、扫描电子显微镜观察、孔隙率和抗压强度测定,研究了钙磷摩尔[n(Ca)/n(P)]对PCCP+DCPA磷酸钙骨水泥性能的影响.结果表明:随着部分结晶磷酸钙中n(Ca)/n(P)的提高,磷酸钙骨水泥试件的抗压强度明显下降,但磷酸钙骨水泥水化产物羟基磷灰石的结晶度提高,固化体中大于100 nm的孔隙增多、固化体的孔隙率增大,可见,n(Ca)/n(P)对磷酸钙骨水泥的性能有重要影响,在制备磷酸钙骨水泥时应选择适当的n(Ca)/n(P).

  14. 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...

  15. 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

  16. 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

  17. Stable hydrogen and oxygen isotope ratios of bottled waters of the world.

    Science.gov (United States)

    Bowen, Gabriel J; Winter, David A; Spero, Howard J; Zierenberg, Robert A; Reeder, Mathew D; Cerling, Thure E; Ehleringer, James R

    2005-01-01

    Bottled and packaged waters are an increasingly significant component of the human diet. These products are regulated at the regional, national, and international levels, and determining the authenticity of marketing and labeling claims represents a challenge to regulatory agencies. Here, we present a dataset of stable isotope ratios for bottled waters sampled worldwide, and consider potential applications of such data for regulatory, forensic and geochemical standardization applications. The hydrogen and oxygen isotope ratios of 234 samples of bottled water range from -147 per thousand to +15 per thousand and from -19.1 per thousand to +3.0 per thousand, respectively. These values fall within and span most of the normal range for meteoric waters, indicating that these commercially available products represent a source of waters for use as laboratory working standards in applications requiring standardization over a large range of isotope ratios. The measured values of bottled water samples cluster along the global meteoric water line, suggesting that bottled water isotope ratios preserve information about the water sources from which they were derived. Using the dataset, we demonstrate how bottled water isotope ratios provide evidence for substantial evaporative enrichment of water sources prior to bottling and for the marketing of waters derived from mountain and lowland sources under the same name. Comparison of bottled water isotope ratios with natural environmental water isotope ratios demonstrates that on average the isotopic composition of bottled water tends to be similar to the composition of naturally available local water sources, suggesting that in many cases bottled water need not be considered as an isotopically distinct component of the human diet. Our findings suggest that stable isotope ratios of bottled water have the power to distinguish ultimate (e.g., recharge) and proximal (e.g., reservoir) sources of bottled water and constitute a potential

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

    Institute of Scientific and Technical Information of China (English)

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

    2011-01-01

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

  19. Effect of cement sand ratio on industrial waste residue dry-mixed mortar properties%灰砂比对工业废渣干混砂浆性能的影响

    Institute of Scientific and Technical Information of China (English)

    刘秀伟; 杨林; 秦贤顺

    2015-01-01

    研究了高掺量磷渣粉、粉煤灰干混砂浆的灰砂比对砂浆性能的影响及激发剂对砂浆的作用机理。结果表明,在砂浆稠度基本不变的前提下,随着灰砂比减小,砂浆和易性变差,凝结时间延长,抗压强度降低,拉伸黏结强度逐渐减小,28 d干缩逐渐增大,但在灰砂比为1:1~1:6的范围内其性能均能满足GB/T 25181—2010《预拌砂浆》中对应等级标准要求,调整灰砂比可以配制出M5.0~M30不同强度等级的普通干混砂浆。%Study on the mechanism of effect of high content of phosphorus slag powder,fly ash dry mixed mortar cement sand ratio on the properties of mortar and activator on the mortar. The results show that,on the premise of mortar consistency basically unchanged, with the cement sand ratio decreases,mortar workability variation,extended the setting time,compressive strength decreases,the tensile bond strength decreases,28 d shrinking gradually increased,but in the cement sand ratio is in the range of 1:1~1:6 and its performance can meet the GB/T 25181—2010 ready mixed mortar in the corresponding grade standards,adjust the cement sand ratio can be prepared M5.0~M30 of different strength grade of ordinary dry mixed mortar.

  20. A Comparative Study Between the Early Stages Hydration of a High Strength and Sulphate Resistant Portland Cement and the Type II F Portland Cement Through Non Conventional Differential Thermal Analysis and Thermogravimetry

    OpenAIRE

    Neves Junior,Alex; Viana,Marcelo Mendes; Dweck,Jo; Toledo Filho,Romildo Dias

    2015-01-01

    This work presents a study, which compares the early stages of hydration of a High Initial Strength and Sulphate Resistant Portland Cement (HIS SR PC) with those of Type II F Portland Cement (PC II), by Non-Conventional Differential Thermal Analysis (NCDTA) within the first 24 hours of hydration. Water/cement (w/c) ratios equal to 0.5, 0.6 and 0.66 were used to prepare the pastes. The hydration of these two types of cement was monitored on real time by NCDTA curves, through the thermal effect...

  1. A remark on nano-particle stability of cement C-S-H gel

    Science.gov (United States)

    Ficker, Tomáš; Len, Adél; Martišek, Dalibor

    2011-04-01

    Hydrated pastes of ordinary Portland cement prepared with different water-to-cement ratios were investigated by using the small-angle neutron scattering technique in the region of Q ∈ (0.0045, 0.11) Å-1. Samples of cement pastes were subjected to non-standard hydration conditions using a mix with D2O, low RH, and water-to-cement ratios spread over a very wide interval (0.4; 1.4). The investigation was focused on testing the structural stability of nano-metric particles in the cement C-S-H gel. Owing to the high structural stability of these nano-particles, their average diameter might be used as a microscopic parameter characterizing the nano-metric structure of C-S-H gels. The average diameter of the nano-particles of the studied ordinary Portland cement CEMI 42.5 R-SC was found to be close to the value of 4.2 nm and independent of the water-to-cement ratios.

  2. 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.

  3. Long-Term In Vitro Degradation of a High-Strength Brushite Cement in Water, PBS, and Serum Solution

    Directory of Open Access Journals (Sweden)

    Ingrid Ajaxon

    2015-01-01

    Full Text Available Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs. CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material’s physical changes over a relevant time frame.

  4. Long-Term In Vitro Degradation of a High-Strength Brushite Cement in Water, PBS, and Serum Solution.

    Science.gov (United States)

    Ajaxon, Ingrid; Öhman, Caroline; Persson, Cecilia

    2015-01-01

    Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material's physical changes over a relevant time frame.

  5. Influence of mixture ratio and pH to solidification/stabilization process of hospital solid waste incineration ash in Portland cement.

    Science.gov (United States)

    Sobiecka, Elzbieta; Obraniak, Andrzej; Antizar-Ladislao, Blanca

    2014-09-01

    Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. This research explored the influence of pH (3-12) on the immobilization of heavy metals present in five mixtures of hospital solid waste incinerator ash and Portland cement, following two different processes of waste solidification/stabilization (cement hydration and granulation). In general, cement hydration process resulted in more stable products than granulation process. A high ash content in the mixture with Portland cement (60wt%) resulted in the highest immobilization of Pb(2+) and Cu(2+), while a low ash content in the mixture (10wt%) resulted in the lowest leachability of Zn(2+). When ash and Portland cement was mixed in equal proportions (50wt%) the highest encapsulation was observed for Ni(2+), Cd(2+) and Cr(3+). Neutral and weak alkaline pH values within the range pH=7-8 resulted in the lowest leachability of the monitored heavy metals.

  6. Water isotopic ratios from a continuously melted ice core sample

    CERN Document Server

    Gkinis, V; Blunier, T; Bigler, M; Schüpbach, S; Kettner, E; Johnsen, S J

    2014-01-01

    A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS) purchased from Picarro Inc. and a Continuous Flow Analysis (CFA) system. The system offers the possibility to perform simultaneous water isotopic analysis of $\\delta^{18}$O and $\\delta$D on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub ${\\mu}$l amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100% efficiency in a home made oven. A calibration procedure allows for proper reporting of the data on the VSMOW--SLAP scale. Application of spectral methods yields the combined uncertainty of the system at below 0.1 permil and 0.5 permil for $\\delta^{18}$O and $\\delta$D, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sampl...

  7. [Microbial settlement of paint- and building-materials in the sphere of drinking water. 9. Communication: experimental examination of cement mortar for the lining with tiles (author's transl)].

    Science.gov (United States)

    Schoenen, D; Thofern, E

    1981-12-01

    The observation of a microbial growth in form of macrocolonies upon the joints of a tiled drinking water reservoir caused the microbiological testing of different pure mineral and some plastic containing cement mortar. Besides the conditions allowing the growth of macrocolonies on tiled plates with a construction like in a reservoir were examined.

  8. Adhesive luting of all-ceramic restorations--the impact of cementation variables and short-term water storage on the strength of a feldspathic dental ceramic.

    LENUS (Irish Health Repository)

    Addison, Owen

    2008-08-01

    To investigate the impact of resin cement luting variables and short-term water storage on the strength of an adhesively luted all-ceramic restorative material. An understanding of the strengthening mechanisms will result in optimisation of operative techniques and materials selection criteria.

  9. Isosteric Vapor Pressure – Temperature Data for Water Sorption in Hardened Cement Paste: Enthalpy, Entropy and Sorption Isotherms at Different Temperatures

    DEFF Research Database (Denmark)

    Radjy, Fariborz; Sellevold, Erik J.; Hansen, Kurt Kielsgaard

    . The accuracies for pressure, enthalpy and entropy are found to be 0.5% or less. PART II: The TPA-system has been used to generate water vapor pressure – temperature data for room temperature – and steam cured hardened cement pastes as well as porous vycor glass. The moisture contents range from saturated to dry...

  10. [Water jet cutting for bones and bone cement--parameter study of possibilities and limits of a new method].

    Science.gov (United States)

    Honl, M; Rentzsch, R; Lampe, F; Müller, V; Dierk, O; Hille, E; Louis, H; Morlock, M

    2000-09-01

    Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p cutting depth between the two materials was significant (p abrasive, the quality of the cut was better for both materials. The water jet technology--in particular the abrasive technique--can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the "depth control" of the jet.

  11. On the development of an apatitic calcium phosphate bone cement

    Indian Academy of Sciences (India)

    Manoj Komath; H K Varma; R Sivakumar

    2000-04-01

    Development of an apatitic calcium phosphate bone cement is reported. 100 Particles of tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD) were mixed in equimolar ratio to form the cement powder. The wetting medium used was distilled water with Na2HPO4 as accelerator to manipulate the setting time. The cement powder, on wetting with the medium, formed a workable putty. The setting times of the putty were measured using a Vicat type apparatus and the compressive strength was determined with a Universal Testing Machine. The nature of the precipitated cement was analyzed through X-ray diffraction (XRD), fourier transform infrared spectrometry (FTIR) and energy dispersive electron microprobe (EDAX). The results showed the phase to be apatitic with a calcium–to–phosphorous ratio close to that of hydroxyapatite. The microstructure analysis using scanning electron microscopy (SEM) showed hydroxyapatite nanocrystallite growth over particulate matrix surface. The structure has an apparent porosity of ∼ 52%. There were no appreciable dimensional or thermal changes during setting. The cement passed the in vitro toxicological screening (cytotoxicity and haemolysis) tests. Optimization of the cement was done by manipulating the accelerator concentration so that the setting time, hardening time and the compressive strength had clinically relevant values.

  12. Ortho-to-para ratio of interstellar heavy water

    CERN Document Server

    Vastel, C; Caux, E; Coutens, A; Cernicharo, J; Bottinelli, S; Demyk, K; Faure, A; Wiesenfeld, L; Scribano, Y; Bacmann, A; Hily-Blant, P; Maret, S; Walters, A; Bergin, E A; Blake, G A; Castets, A; Crimier, N; Dominik, C; Encrenaz, P; Gérin, M; Hennebelle, P; Kahane, C; Klotz, A; Melnick, G; Pagani, L; Parise, B; Schilke, P; Wakelam, V; Baudry, A; Bell, T; Benedettini, M; Boogert, A; Cabrit, S; Caselli, P; Codella, C; Comito, C; Falgarone, E; Fuente, A; Goldsmith, P F; Helmich, F; Henning, T; Herbst, E; Jacq, T; Kama, M; Langer, W; Lefloch, B; Lis, D; Lord, S; Lorenzani, A; Neufeld, D; Nisini, B; Pacheco, S; Pearson, J; Phillips, T; Salez, M; Saraceno, P; Schuster, K; Tielens, X; van der Tak, F; van der Wiel, M H D; Viti, S; Wyrowski, F; Yorke, H; Cais, P; Krieg, J M; Olberg, M; Ravera, L

    2010-01-01

    Despite the low elemental deuterium abundance in the Galaxy, enhanced molecular D/H ratios have been found in the environments of low-mass star forming regions, and in particular the Class 0 protostar IRAS 16293-2422. The CHESS (Chemical HErschel Surveys of Star forming regions) Key Program aims at studying the molecular complexity of the interstellar medium. The high sensitivity and spectral resolution of the HIFI instrument provide a unique opportunity to observe the fundamental 1,1,1 - 0,0,0 transition of the ortho-D2O molecule, inaccessible from the ground, and to determine the ortho-to-para D2O ratio. We have detected the fundamental transition of the ortho-D2O molecule at 607.35 GHz towards IRAS 16293-2422. The line is seen in absorption with a line opacity of 0.62 +/- 0.11 (1 sigma). From the previous ground-based observations of the fundamental 1,1,0 - 1,0,1 transition of para-D2O seen in absorption at 316.80 GHz we estimate a line opacity of 0.26 +/- 0.05 (1 sigma). We show that the observed absorpti...

  13. Universal One-Parametric Dependence of Dielectric Water and Water Steam Permeability on Density-Temperature Ratio

    OpenAIRE

    Yu. V. Mulev; K. M. Arefiev; O. V. Beliayeva; M. Yu. Mulev; T. A/ Zaiats

    2011-01-01

    Available experimental data on dielectric permeability of water and water steam have been analyzed in the paper. The paper presents an universal one-parametric dependence of dielectric water and water steam permeability in single-phase areas and also on boundary curves on density -temperature ratio.

  14. Universal One-Parametric Dependence of Dielectric Water and Water Steam Permeability on Density-Temperature Ratio

    Directory of Open Access Journals (Sweden)

    Yu. V. Mulev

    2011-01-01

    Full Text Available Available experimental data on dielectric permeability of water and water steam have been analyzed in the paper. The paper presents an universal one-parametric dependence of dielectric water and water steam permeability in single-phase areas and also on boundary curves on density -temperature ratio.

  15. Experimental Study for Improving the Toughness of Harden Cement Using Carbon Fiber%碳纤维改善水泥石韧性实验研究

    Institute of Scientific and Technical Information of China (English)

    步玉环; 程荣超; 王瑞和; 曹祥元

    2005-01-01

    Many measures, such as water injection, acid fracturing, thermal recovery, have been taken in the oilfield development. These can easily induce brittle fracture of set cement. Most of all, there are greater potential for fractures in set cement in slim holes. Therefore, it is necessary to improve the toughness of the cement mantle. Results obtained from experiments show that carbon fiber, with a concentration of 0.12%-0.19% in cement and a length of 700 to 1,400 μm, plays an important role in improving cement quality. Addition of carbon fiber can improve the bending strength of set cement by up to 30%. At the same time, the increase in fiber concentration can lower the elastic modulus and increase the Poisson's ratio of set cement. Thin-section analysis shows that fiber can effectively prevent the propagation of fractures and enhance the plasticity of the matrix and the ability to prevent fracture.

  16. Properties and Mechanism of CFBC Fly Ash-cement based Stabilizers for Lake Sludge

    Institute of Scientific and Technical Information of China (English)

    TANG Hua; LIXiangguo; LI Menglei; SONG Liuqing; WU Zhenjun; XU Haixing

    2012-01-01

    Circulating fluidized bed combustion (CFBC) fly ash was mixed with cement or lime at a different ratio as a stabilizer to stabilize lake sludge.In order to understand the influences of stabilizers on the lake sludge properties,tests unconfined compressive strength,water stability and SEM observation were performed.The experimental results show that with the increase of the curing time,the strength of all the stabilized specimens increase,especially the samples containing cement.The strength of the specimens is decreased with the increasing of the CFBC fly ash/cement ratio,the optimum ratio between CFBC fly ash and cement is 2:3.The water stability of CFBC fly ash-cement based stabilizers is higher than those of cement and lime.Moreover,the lake sludge stabilization mechanism of CFBC fly ash-cement based stabilizers includes gelation and filling of the hydration products,i e,C-S-H gel and the AFt crystal,which act as benders to solidify those particles together and fill in the packing void of the aggregates.

  17. Obtaining and physical mechanical properties of cement composites with the use of fillers and mixing water from the Chechen Republic fields

    Directory of Open Access Journals (Sweden)

    Erofeev Vladimir Trofimovich

    Full Text Available Improving physical mechanical and operational properties of concretes and other composite materials is one of the most important tasks in construction material science. At the present time various methods are applied for that, which includes the use of additives, composite binders, activated mixing water, etc. Composite construction materials based on cement binders with mineral additives are widelu used, because they possess improved physical mechanical and technological properties. Implementation of additives improve placeability and nonsegregation factors of concrete and mortar mixes, lead to compaction of concrete and mortars structure. The additives substantially lower heat generation of concretes, which is of great importance in concrete casting of large structures. The article presents the results of experimental studies of cement composites filled with powders of rocks and mixable with activated water from the deposits of the Chechen Republic. The soundness of cement compositions with the additives of mountain and river limestone, sandstone and quartz sand was established. The results of experimental studies on establishing the effect of fine and coarse aggregate on strength formation of cement composites activated by water mixing were presented.

  18. Effect of Superplasticizers on the Early Age Hydration of Sulfoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    YUAN Xiaohui; CHEN Wei; YANG Mo

    2014-01-01

    The effects of two types of superplasticizers on the properties of CSA cement pastes during early hydration were studied. The influences of two types of superplasticizers on the properties of cement pastes, including the normal consistency, setting time, fluidity, and compressive strength, were investigated by using various methods. The hydration products of the cement pastes cured for 1 day and 3 days were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the PCE type superplasticizer retards the early age hydration while the FDN type superplasticizer accelerates the early age hydration of the CSA cement. Both types of superplasticizers have no influence on the further hydration of CSA cement, confirmed by the calorimeter tests as well. The ultrasonic pulse velocity measurements were used to probe the influence of two types of superplasticizers on the hydration of CSA cement pastes at a high water-cement ratio (0.45). The results show that the PCE type superplasticizer retards the early age hydration of the CSA cement while the FDN type superplasticizer has little influence on the early age hydration of the CSA cement.

  19. Investigation on the potential of waste cooking oil as a grinding aid in Portland cement.

    Science.gov (United States)

    Li, Haoxin; Zhao, Jianfeng; Huang, Yuyan; Jiang, Zhengwu; Yang, Xiaojie; Yang, Zhenghong; Chen, Qing

    2016-12-15

    Although there are several methods for managing waste cooking oil (WCO), a significant result has not been achieved in China. A new method is required for safe WCO management that minimizes the environmental threat. In this context, this work was developed in which cement clinker and gypsum were interground with various WCOs, and their properties, such as grindability, water-cement ratio required to achieve a normal consistency, setting times, compressive strength, contents of calcium hydroxide and ettringite in the hardened paste, microstructure and economic and environmental considerations, were addressed in detail. The results show that, overall, WCO favorably improves cement grinding. WCO prolonged the cement setting times and resulted in longer setting times. Additionally, more remarkable effects were found in cements in which WCO contained more unsaturated fatty acid. WCOs increased the cement strength. However, this enhancement was rated with respect to the WCO contents and components. WCOs decreased the CH and AFt contents in the cement hardened paste. Even the AFt content at later ages was reduced when WCO was used. WCO also densify microstructure of the hardened cement paste. It is economically and environmentally feasible to use WCOs as grinding aids in the cement grinding process. These results contribute to the application of WCOs as grinding aids and to the safe management of WCO. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Association of macroscopic laboratory testing and micromechanics modelling for the evaluation of the poroelastic parameters of a hardened cement paste

    CERN Document Server

    Ghabezloo, Siavash

    2010-01-01

    The results of a macro-scale experimental study performed on a hardened class G cement paste [Ghabezloo et al. (2008) Cem. Con. Res. (38) 1424-1437] are used in association with the micromechanics modelling and homogenization technique for evaluation of the complete set of poroelastic parameters of the material. The experimental study consisted in drained, undrained and unjacketed isotropic compression tests. Analysis of the experimental results revealed that the active porosity of the studied cement paste is smaller than its total porosity. A multi-scale homogenization model, calibrated on the experimental results, is used to extrapolate the poroelastic parameters to cement pastes prepared with different water-to-cement ratio. The notion of cement paste active porosity is discussed and the poroelastic parameters of hardened cement paste for an ideal, perfectly drained condition are evaluated using the homogenization model.

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

    Science.gov (United States)

    Nochaiya, Thanongsak; Chaipanich, Arnon

    2011-01-01

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

  2. Observation and quantification of water penetration into Strain Hardening Cement-based Composites (SHCC) with multiple cracks by means of neutron radiography

    Science.gov (United States)

    Zhang, P.; Wittmann, F. H.; Zhao, T. J.; Lehmann, E. H.; Tian, L.; Vontobel, P.

    2010-08-01

    Durability of reinforced concrete structures has become a crucial issue with respect to economy, ecology and sustainability. One major reason for durability problems of concrete structures is the limited strain capacity of cement-based materials under imposed tensile stress. By adding PVA fibers, a new material named Strain Hardening Cement-based Composites (SHCC) with high strain capacity can be produced. Due to the formation of multiple micro-cracks, wide cracks can be avoided in SHCC under an imposed strain. The high strain capacity, however, is beneficial with respect to durability only if the multi-crack formation in SHCC does not lead to significantly increased water penetration. If water and aggressive chemical compounds such as chlorides and sulfates dissolved in water penetrate into the cement-based matrix and reach the steel reinforcement service-life of reinforced concrete structures will be reduced significantly. In this project, neutron radiography was applied to observe and quantify the process of water penetration into uncracked SHCC and after the multi-crack formation. In addition, water penetration into integral water repellent cracked and uncracked SHCC, which has been produced by adding a silane-based water repellent agent to the fresh SHCC mortar has been investigated. Results will be discussed with respect to durability.

  3. Observation and quantification of water penetration into Strain Hardening Cement-based Composites (SHCC) with multiple cracks by means of neutron radiography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, P. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Wittmann, F.H., E-mail: wittmann@aedificat.d [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Aedificat Institute Freiburg, D-79100 Freiburg (Germany); Zhao, T.J. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Lehmann, E.H. [Department of Spallation Neutron Source (ASQ), Paul Scherrer Institute (PSI), CH-5232 Villigen (Switzerland); Tian, L. [Center for Durability and Sustainability Studies of Shandong Province, Qingdao Technological University, Qingdao 266033 (China); Vontobel, P. [Department of Spallation Neutron Source (ASQ), Paul Scherrer Institute (PSI), CH-5232 Villigen (Switzerland)

    2010-08-21

    Durability of reinforced concrete structures has become a crucial issue with respect to economy, ecology and sustainability. One major reason for durability problems of concrete structures is the limited strain capacity of cement-based materials under imposed tensile stress. By adding PVA fibers, a new material named Strain Hardening Cement-based Composites (SHCC) with high strain capacity can be produced. Due to the formation of multiple micro-cracks, wide cracks can be avoided in SHCC under an imposed strain. The high strain capacity, however, is beneficial with respect to durability only if the multi-crack formation in SHCC does not lead to significantly increased water penetration. If water and aggressive chemical compounds such as chlorides and sulfates dissolved in water penetrate into the cement-based matrix and reach the steel reinforcement service-life of reinforced concrete structures will be reduced significantly. In this project, neutron radiography was applied to observe and quantify the process of water penetration into uncracked SHCC and after the multi-crack formation. In addition, water penetration into integral water repellent cracked and uncracked SHCC, which has been produced by adding a silane-based water repellent agent to the fresh SHCC mortar has been investigated. Results will be discussed with respect to durability.

  4. Studies on termite hill and lime as partial replacement for cement in plastering

    Energy Technology Data Exchange (ETDEWEB)

    Olusola, K.O.; Olanipekun, E.A.; Ata, O.; Olateju, O.T. [Obafemi Awolowo University, Ile-Ife, Osun State (Nigeria). Department of Building

    2006-03-15

    This study investigated the compressive strength and water absorption capacity of 50x50x50mm mortar cubes made from mixes containing lime, termite hill and cement and sand. Two mix ratios (1:4 and 1:6) and varying binder replacements of cement with lime or termite hill amounting to 0%, 10%, 20%, 30%, 40% and 50% were used. Test results showed that the compressive strength of the mortar cubes increases with age and decreases with increasing percentage replacement of cement with lime and termite hill. However, for mix ratio 1:6, up to 20% replacement of cement with either lime or termite hill, all the mortar cubes had the same strength; subsequently, the termite hill exhibited a higher compressive strength. For mix ratio 1:4, mortar cubes made from lime/cement and termite hill/cement mixtures had the same strength at 50% replacement. Generally, water absorption is higher in mixtures containing lime (18.10% and 14.20% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level) than those containing termite hill (16.10% and 13.02% for mix ratios 1:6 and 1:4, respectively, both at 50% replacement level). Termite hills seem to be promising as a suitable, locally available housing material for plastering. (author)

  5. Reuse of cement-solidified municipal incinerator fly ash in cement mortars: physico-mechanical and leaching characteristics.

    Science.gov (United States)

    Cinquepalmi, Maria Anna; Mangialardi, Teresa; Panei, Liliana; Paolini, Antonio Evangelista; Piga, Luigi

    2008-03-01

    The reuse of cement-solidified Municipal Solid Waste Incinerator (MSWI) fly ash (solidified/stabilised (S/S) product) as an artificial aggregate in Portland cement mortars was investigated. The S/S product consisted of a mixture of 48 wt.% washed MSWI fly ash, 20 wt.% Portland cement and 32 wt.% water, aged for 365 days at 20 degrees C and 100% RH. Cement mortars (water/cement weight ratio=0.62) were made with Portland cement, S/S product and natural sand at three replacement levels of sand with S/S product (0%, 10% and 50% by mass). After 28 days of curing at 20 degrees C and 100% RH, the mortar specimens were characterised for their physico-mechanical (porosity, compressive strength) and leaching behaviour. No retardation in strength development, relatively high compressive strengths (up to 36 N/mm2) and low leaching rates of heavy metals (Cr, Cu, Pb and Zn) were always recorded. The leaching data from sequential leach tests on monolithic specimens were successfully elaborated with a pseudo-diffusional model including a chemical retardation factor related to the partial dissolution of contaminant.

  6. 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.

  7. 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

  8. How to build a small ferro-cement water tank: technical guide

    CSIR Research Space (South Africa)

    Sadzik, P

    1988-05-01

    Full Text Available This guide will assist on how to build a small water tank which can be used to store spring water, rainwater or water pumped from a stream or dam. Small water tanks can be constructed from many different materials such as corrugated iron, bricks...

  9. 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.

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

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo M. Gomes

    2005-07-01

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

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

    Science.gov (United States)

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

    2016-07-01

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

  12. Size effect on cubic and prismatic compressive strength of cement paste

    Institute of Scientific and Technical Information of China (English)

    苏捷; 叶缙垚; 方志; 赵明华

    2015-01-01

    A series of compression tests were conducted on 150 groups of cement paste specimens with side lengths ranging from 40 mm to 200 mm. The specimens include cube specimens and prism specimens with height to width ratio of 2. The experiment results show that size effect exists in the cubic compressive strength and prismatic compressive strength of the cement paste, and larger specimens resist less in terms of strength than smaller ones. The cubic compressive strength and the prismatic compressive strength of the specimens with side length of 200 mm are respectively about 91% and 89% of the compressive strength of the specimens with the side length of 40 mm. Water to binder ratio has a significant influence on the size effect of the compressive strengths of the cement paste. With a decrease in the water to binder ratio, the size effect is significantly enhanced. When the water to binder ratio is 0.2, the size effects of the cubic compressive strength and the prismatic compressive strength of the cement paste are 1.6 and 1.4 times stronger than those of a water to binder ratio of 0.6. Furthermore, a series of formulas are proposed to calculate the size effect of the cubic compressive strength and the prismatic compressive strength of cement paste, and the results of the size effect predicted by the formulas are in good agreement with the experiment results.

  13. 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.

  14. A non-equilibrium ortho-to-para ratio of water in the Orion PDR

    NARCIS (Netherlands)

    Choi, Y.; van der Tak, F. F. S.; Bergin, E. A.; Plume, R.

    2014-01-01

    Context. The ortho-to-para ratio (OPR) of H2O is thought to be sensitive to the temperature of water formation. The OPR of H2O is thus useful for studying the formation mechanism of water. Aims: We investigate the OPR of water in the Orion PDR (photon-dominated region), at the Orion Bar and Orion S

  15. Experimental Study of Influencing Factors of Cement Curing Time%水泥候凝时间及其影响因素的试验研究

    Institute of Scientific and Technical Information of China (English)

    朱水英; 李维彦; 章成广; 周继宏

    2001-01-01

    针对温度、水灰比、缓凝剂这些影响水泥候凝时间的主要因素展开了试验研究。试验结果分析得出:①对同一温度同一缓凝剂,水灰比每减少约10%,最佳时间相应减少1~3 h;②对同一水灰比同一缓凝剂,温度每升高10℃,最佳测井时间缩短约2 h;③对同一温度同一水灰比,缓凝剂增加0.2%,最佳测量时间延迟2~3 h;④温度、水灰比、缓凝剂都是单独起作用,相互不受影响。%The key factors such as curing temperature, water-cement ratio and cement retarder, which influence the cement curing time, are studied experimentally. The experimental results demonstrate that:①optimal logging time reduces 1~3 hours when the density of cement slurry increases 0. 1g/cm3 under the conditions of the same temperature and same cement retarder;②optimal logging time reduces about 2 hours when the temperature increases 10C under the conditions of the same water-cement ratio and same cement retarder;③optimal logging time delay 2~3 hours when cement retarder increases 0. 2 % under the same temperature and same water-cement ratio; ④temperature, water-cement ratio and cement retarder act independently.

  16. Degradation of Pore Structure and Microstructures in Hardened Cement Paste Subjected to Flexural Loading and Wet-dry Cycles in Sea Water

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wuman; SUN Wei; ZHANG Yunsheng; CHEN Huisu

    2009-01-01

    Hardened cement paste was subjected to the flexural loading and wet-dry cycles in sea water.The degradation of microstructures was obtained using scanning electron microscope(SEM),and the energy dispersive spectrum(EDS)analysis was carried to analyze the local composition.Mercury intrusion porosimetry(Poremaster GT-60)was used to analyze the degradation of pore structures.The experimental results show that the synergistic action of the flexural loading,wet-dry cycles and sea water leads to significant deterioration of hardened cement paste.The degradation of microstructures in the tensile region is more serious than that in the compressive region.The flexural loading and wet-dry cycles accelerate the chemical attack of sea water.

  17. Experimental evidence of the influence of iron on pore water radiolysis in cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Bouniol, P., E-mail: pascal.bouniol@cea.fr [CEA, DEN, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des Argiles, F-91991 Gif-Sur-Yvette (France); Muzeau, B. [CEA, DEN, DPC, SECR, Laboratoire d’Etude du Comportement des Bétons et des Argiles, F-91991 Gif-Sur-Yvette (France); Dauvois, V. [CEA, DEN, DPC, SECR, Laboratoire de Radiolyse et de la Matière Organique, F-91991 Gif-Sur-Yvette (France)

    2013-06-15

    Hydrated tricalcium silicate based cement pastes or mixes, with the addition or not of amorphous iron oxyhydroxide, were irradiated for 1 year in a closed system (γ radiation) with the aim of provoking radiolysis of the alkaline pore solution (pH > 13). The data collected (on-line monitoring of the total pressure and the H{sub 2} content in 500 cm{sup 3} mini-containers irradiated at 45 °C and 1.07 kGy/h with V{sub gas}/V{sub paste} ≈ 1) enable us to conclude that the addition of 1% of FeOOH{sub am} gives rise to about 26% of additional residual H{sub 2} after 1 year. This result appears to validate the hypothesis of a partial mobilisation of the e{sub aq}{sup -} and O{sup ·−} radicals in a continuous process of Fe(III) ↔ Fe(II) oxidation–reduction, at the expense of their action within the Allen type reaction chain that is responsible for the recycling of H{sub 2}. Despite the complexity of the porous material, the simulation of the experiment with the CHEMSIMUL application leads to a result that is quite close, and stresses the importance of the kinetic coupling between gas transport in the porous material and the reaction system.

  18. Ca-Mg Carbonate Cements in Ophiolite-Hosted Creek Waters of the Del Puerto Ophiolite, CA, and their Potential Significance as a Planetary Biosignature

    Science.gov (United States)

    Blank, J. G.

    2015-12-01

    Serpentinization, the reaction at moderate pressure and temperature of water with olivine and pyroxene that are common in basalts and ultramafic rocks, results in the formation of alkaline fluids and the precipitation of a variety of secondary minerals. Terrestrial localities where active serpentinization is occurring are ideal Mars analogs for examining the characteristics of an environment that possesses two of the key features that we assume necessary to host life: water and an internally generated energy source. This study focuses on a related but different feature present where active serpentinization is occurring - namely, carbonate cements forming under plain air in the vicinity of Adobe Springs, CA. This site is located in the Del Puerto ophiolite about 150 km ESE of San Francisco, in the Coast Range of California. Two alkaline spring water compositions have been described at the site, a Ca-OH water (which is not currently being emitted by the active springs), and a Mg-CO3 water. Abundant dolomitic and calcitic carbonate cements are found in the creek drainages near the springs, associated with a diverse microbial community. We conducted a systematic study of the carbonate cements using SEM, EMP, XRD, TEM, and SIMS, focusing on sub-mm variations in texture, mineral chemistry and stable isotope (COH) composition. We compared our measurements with thermodynamic modeling results constrained by chemical analysis of water chemistry from the site and known partition coefficients and stable isotope fractionation factors. The wide range of carbonate compositions and textures observed at the Adobe Springs site suggests that more than one process is involved in their precipitation, including the possibility of microbially mediated dolomite mineralization. These carbonate cements could be a mineralogic biomarker of serpentinization and microbiological processes on Mars and other rocky planets and, therefore, prime targets for future astrobiological investigations.

  19. Rapid Evaluation of Water-in-Oil (w/o) Emulsion Stability by Turbidity Ratio Measurements.

    Science.gov (United States)

    Song; Jho; Kim; Kim

    2000-10-01

    In this Note, we investigated the turbidity ratio method for the evaluation of water-in-oil emulsion stability. The slope of turbidity ratio of water-in-oil emulsions with time was taken as an index of stability; the higher the slope, the less stable the system. Various factors affecting the stability of emulsion such as HLB of emulsifier, amount of emulsifiers, and water were tested using this technique. The results of the turbidity ratio technique for the evaluation of emulsion stability were well consistent with those obtained by the measurement of phase separation when incubated for 30 days at room temperature. Copyright 2000 Academic Press.

  20. Evaluation of compressive strength and water absorption of soil-cement bricks manufactured with addition of pet (polyethylene terephthalate wastes

    Directory of Open Access Journals (Sweden)

    João Alexandre Paschoalin Filho

    2016-04-01

    Full Text Available This paper presents the evaluation of compressive strength of soil-cement bricks obtained by the inclusion in their mixture of PET flakes through mineral water bottles grinding. The Polyethylene Terephthalate (PET has been characterized by its difficulty of disaggregation in nature, requiring a long period for this. On the other hand, with the increase in civil construction activities the demand for raw material also increases, causing considerable environmental impacts. In this context, the objective of this research is to propose a simple methodology, preventing its dumping and accumulation in irregular areas, and reducing the demand of raw materials by the civil construction industry. The results showed that compressive strengths obtained were lower than recommended by NBR 8491 (Associação Brasileira de Normas Técnicas [ABNT], 2012b at seven days of curing time. However, they may be used as an alternative solution in masonry works in order to not submit themselves to great loads or structural functions. The studied bricks also presented water absorption near to recommended values by NBR 8491 (ABNT, 2012b. Manufacturing costs were also determined for this brick, comparing it with the costs of other brick types. Each brick withdrew from circulation approximately 300 g of PET waste. Thus, for an area of 1 m2 the studied bricks can promote the withdrawal of approximately 180 beverage bottles of 2 L capacity.

  1. 类比法在大型水泥灰岩矿床勘探中的应用——焦作柿园大型水泥灰岩矿床勘探网度的确定%Application of analogy in lager cement limestone deposits exploration——Determination of Jiaozuo Shiyuan large cement limestone deposits exploratory grid ratio

    Institute of Scientific and Technical Information of China (English)

    杨东潮

    2011-01-01

    This paper makes an analogical study by choosing Huitoushan cement limestone deposits as the subject,which is similar to Shiyuan cement limestone deposits.By using the research methods of analogy,pumping dilate and statistical hypothesis and so on,it can define the reasonable exploratory grid ratio in Shiyuan cement limestone deposits,reduce the exploratory costs,shorten the exploratory cycle,and achieve the requirement of accuracy in similar deposits exploration.%选择与柿园水泥灰岩矿床相似的回头山水泥灰岩矿床为类比研究对象,采用类比法、稀空法、统计假设检验等研究方法,确定了柿园水泥灰岩矿床经济合理的勘探网度,降低了勘探成本,缩短了勘探周期,达到了同类矿床勘探的精度要求。

  2. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Ince, C.

    2015-06-01

    Full Text Available The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs on water transport kinetics and mechanical properties of hydrated lime (CL90 and Portland cement (PC mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.El objetivo de este artículo es investigar el papel de los materiales cementantes suplementarios (SCMs en la cinética de transporte del agua y en las propiedades mecánicas de los morteros de cal hidratada (CL90 y cemento Portland. Las propiedades de la cal hidratada son significativamente diferentes a las del cemento y por lo tanto el control de las propiedades de los morteros frescos y endurecidos es fundamental en la optimización mortero/substrato en albañilería. Los parámetros estudiados en este trabajo son a menudo las principales barreras para el uso de la cal hidratada en la práctica de la construcción. Los resultados indican que la absortividad y el tiempo necesario para deshidratar morteros de cal hidratada recién mezclados pueden ser controlados cuando el conglomerante es parcialmente remplazado por SCMs. La resistencia a compresión de los morteros CL90 aumenta sistem

  3. Interactive Effect of Air-Water Ratio and Temperature on the Air ...

    African Journals Online (AJOL)

    Windows User

    KEYWORDS: Interactive effect, air-water ratio, temperature, volatile organic ... VOCs removal from wastewater by increasing the surface ... surface area (m2). ... where α and n are constants, DL is liquid diffusion coefficient .... Packing volume.

  4. Water content - void ratio swell-shrink paths of compacted expansive soils

    National Research Council Canada - National Science Library

    Tripathy S; Rao K.S; Fredlund D.G

    2002-01-01

    .... The void ratio and water content of the specimens at several intermediate stages during swelling until the end of swelling and during shrinkage until the end of shrinkage were determined to trace...

  5. Dielectric study on hierarchical water structures restricted in cement and wood materials

    Science.gov (United States)

    Abe, Fumiya; Nishi, Akihiro; Saito, Hironobu; Asano, Megumi; Watanabe, Seiei; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin; Fukuzaki, Minoru; Sudo, Seiichi; Suzuki, Youki

    2017-04-01

    Dielectric relaxation processes for mortar observed by broadband dielectric spectroscopy were analyzed in the drying and hydration processes for an aging sample in the frequency region from 1 MHz up to 2 MHz. At least two processes for structured water in the kHz frequency region and another mHz relaxation process affected by ionic behaviors were observed. Comparison of the relaxation parameters obtained for the drying and hydration processes suggests an existence of hierarchical water structures in the exchange of water molecules, which are originally exchanged from free water observed at around 20 GHz. The water molecules reflected in the lower frequency process of the two kHz relaxation processes are more restricted and take more homogeneous structures than the higher kHz relaxation process. These structured water usually hidden in large ionic behaviors for wood samples was observed by electrodes covered by a thin Teflon film, and hierarchical water structures were also suggested for wood samples. Dielectric spectroscopy technique is an effective tool to analyze the new concept of hierarchical water structures in complex materials.

  6. Isosteric Vapor Pressure – Temperature Data for Water Sorption in Hardened Cement Paste: Enthalpy, Entropy and Sorption Isotherms at Different Temperatures

    DEFF Research Database (Denmark)

    Radjy, Fariborz; Sellevold, Erik J.; Hansen, Kurt Kielsgaard

    and the temperatures range from 2 to 95 °C, differing for the specimen types. The data has been analyzed to yield differential enthalpy and entropy of adsorption, as well as the dependence of the relative vapor pressure on temperature at various constant moisture contents. The implications for the coefficient......PART I: In order to generate isosteric (constant mass) vapor pressure – temperature data (P-T data) for adsorbed pore water in hydrated cement paste, the Thermo Piestic Analysis system (the TPA system) described herein was developed. The TPA system generates high precision equilibrium isosteric P....... The accuracies for pressure, enthalpy and entropy are found to be 0.5% or less. PART II: The TPA-system has been used to generate water vapor pressure – temperature data for room temperature – and steam cured hardened cement pastes as well as porous vycor glass. The moisture contents range from saturated to dry...

  7. Study of Solid-Liquid Ratio of Fly Ash Geopolymer as Water Absorbent Material

    Directory of Open Access Journals (Sweden)

    Angga Prasetya Fandi

    2017-01-01

    Full Text Available Geopolymer has been synthesized from fly ash to be applicated as water absorbent material. This research conducted to determine the ability of geopolymer to abrsop water by variation of solid – liquid ratio at optimum molarity of NaOH; 3 M. In this research, the synthesis of geopolymer was conducted at the variation of solid-liquid ratio; 60:40, 65:35, 70:30, and 75:25. Result of the treatment were characterized by XRD and SEM to compare the geopolymer structure. Water absorption capacity was measured by immersing the geopolymer specimens in water for 24 hours. Based on the result, solid – liquid ratio with maximum water absorbed was 70:30 with 13,04 wt%.

  8. Effects of Specimen Height on the Acoustic Emission Rate Value ‘a’ for Cement Mortar

    Institute of Scientific and Technical Information of China (English)

    WANG Yan; HU Hongxiang; LU Guijuan; CHEN Shijie; LIU Shaojun; WANG Yao

    2016-01-01

    In order to study the size effect on the AE rate ‘a’ value, three kinds of mix ratios were set up by different particle sizes and water cement ratios, 45 cement mortar specimens with ifve different heights were tested under axial compression. And the whole damage processes were monitored by full-digital acoustic emission acquisition system, followed by an analysis of mechanical behavior and AE activity. The experimental results show that the height of the cement specimen has signiifcant effects on the compressive strength and the acoustic emission rate ‘a’ value, but a slight effect on the accumulated AE hits number, which is analyzed from aspects of failure process of cement mortar specimens.

  9. Physical, mechanical, and durability properties of gypsum-Portland cement-natural pozzolan blends

    National Research Council Canada - National Science Library

    Colak A

    2001-01-01

    This paper deals with the effect of gypsum Portland cement and gypsum Portland cement natural pozzolan ratios on the physical, mechanical, and durability properties of gypsum Portland cement natural pozzolan blends...

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

    Institute of Scientific and Technical Information of China (English)

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

    2015-01-01

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

  11. 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.

  12. Effect of Genetic Strain and Sex on Water Absorption and Water-To-Protein Ratio in Chicken Meat

    Directory of Open Access Journals (Sweden)

    MJGS Ferrari

    Full Text Available ABSTRACT The objectives of the present study were to evaluate the water and protein contents and the water-to-protein ratio of chicken parts before and after the pre-chilling process, to compare these results with the values officially recommended by the Brazilian Ministry of Agriculture, and to evaluate the effect of genetic strain and sex on these parameters. Water (% and protein (% contents, and water-to-protein ratio (WPR of boneless and skinless breast (FILLETS and breast with bone and skin (BREAST were determined before (BPC and after (APC carcass pre-chilling. A total of 585 samples were evaluated: 221 fillets/male, 216 breasts/male, 76 fillets/female, and 72 fillets/female of four different broilers strains were evaluated before (BPC and after (APC samples. Water and protein contents and water-to-protein ratio were determined according to the Brazilian legislation. Results showed that there were no significant differences between genetic strains (p<0.05 neither in samples collected before or after the chiller. There were no statistical differences in the parameters studied among genetic strains. However, a high percentage of male breast samples presented water level and water-to-protein ratio above the official limits already before pre-chilling.

  13. Early Carbonation Behavior of High-volume Dolomite Powder-cement Based Materials

    Institute of Scientific and Technical Information of China (English)

    YANG Huamei; HE zhen; SHAO Yixin

    2015-01-01

    Combined with DTG analysis, X-Ray diffraction analysis (XRD) andfi eld emission scanning electron microscopy analysis (FSEM) affi liated with energy dispersive spectrometer analysis (EDS), the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio (0.15) was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refi nement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation of nanometer CaCO3 skeleton network at early age.

  14. Micromechanics analysis of thermal expansion and thermal pressurization of a hardened cement paste

    CERN Document Server

    Ghabezloo, Siavash

    2011-01-01

    The results of a macro-scale experimental study of the effect of heating on a fluid-saturated hardened cement paste are analysed using a multi-scale homogenization model. The analysis of the experimental results revealed that the thermal expansion coefficient of the cement paste pore fluid is anomalously higher than the one of pure bulk water. The micromechanics model is calibrated using the results of drained and undrained heating tests and permits the extrapolation of the experimentally evaluated thermal expansion and thermal pressurization parameters to cement pastes with different water-to-cement ratios. It permits also to calculate the pore volume thermal expansion coefficient f a which is difficult to evaluate experimentally. The anomalous pore fluid thermal expansion is also analysed using the micromechanics model.

  15. Monte Carlo simulations on the water-to-air stopping power ratio for carbon ion dosimetry.

    Science.gov (United States)

    Henkner, Katrin; Bassler, Niels; Sobolevsky, Nikolai; Jäkel, Oliver

    2009-04-01

    Many papers discussed the I value for water given by the ICRU, concluding that a value of about 80 +/- 2 eV instead of 67.2 eV would reproduce measured ion depth-dose curves. A change in the I value for water would have an effect on the stopping power and, hence, on the water-to-air stopping power ratio, which is important in clinical dosimetry of proton and ion beams. For energies ranging from 50 to 330 MeV/u and for one spread out Bragg peak, the authors compare the impact of the I value on the water-to-air stopping power ratio. The authors calculate ratios from different ICRU stopping power tables and ICRU reports. The stopping power ratio is calculated via track-length dose calculation with SHIELD-HIT07. In the calculations, the stopping power ratio is reduced to a value of 1.119 in the plateau region as compared to the cited value of 1.13 in IAEA TRS-398. At low energies the stopping power ratio increases by up to 6% in the last few tenths of a mm toward the Bragg peak. For a spread out Bragg peak of 13.5 mm width at 130 mm depth, the stopping power ratio increases by about 1% toward the distal end.

  16. Phosphate based oil well cements

    Science.gov (United States)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  17. 矿渣对磷酸镁水泥耐水性能的影响%Influence of Slag on Water Resistance of Magnesia Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    丁耀堃; 王哲; 许四法; 熊壮; 周红利; 许斌; 邵烨

    2016-01-01

    Effect of different curing conditions on the mechanical properties of magnesium phosphate cement (MPC), and the water resistance of MPC was improved by adding slag, the influence of slag on component and microstructure of the hydrated product were studied in this paper. The additive amount of slag was 0% ~ 30% separately in the ratio of total amount of MPC. It indicates that the compressive strength and flexural strength of MPC deceased to 28.63% and 13.22% at 28 d under water, respectively, which indicates that MPC has poor water resistance; the compressive strength and flexural strength increase by about 30%,40% when the amount of slag reaches 10% of phosphate cement, respectively , and the dissolution of some phosphate which has not reacted can be prevented when cured in water for days, it improves the pH value of the solution, so the main hydration product-MgKPO4·6H2O hard to be dissolved under alkaline environment resulting in the decreasing of porosity ,and the decrease of strength would be controlled.%通过掺加矿渣改善磷酸镁水泥(MPC)的力学耐水性能,并对空气养护和水中养护条件下矿渣对MPC水化产物的成分和微观结构的影响进行了分析。其中MPC中的矿渣掺量分别为0%~30%。结果表明在水养的条件下,磷酸镁水泥28 d的抗压强度与抗折强度跟自然养护条件下相比分别倒缩了28.63%,13.22%,磷酸镁水泥的耐水性能较差;当MPC掺加10%矿渣后,耐水性得到加强,其中水养条件下,抗压强度提高了近30%,以及抗折强度提高近40%,并且在水养条件下能防止MPC基体中少量未反应的磷酸盐溶解,使养护水溶液的pH值环境呈碱性,从而克服了水泥主要水化凝胶MgKPO4·6H2O (MKP)溶解的问题,孔隙不在增大,使水泥本身不易受水的侵蚀,可以长期有效地控制强度的回缩。

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

    Institute of Scientific and Technical Information of China (English)

    杨俊杰; 闫楠; 刘强; 张玥宸

    2016-01-01

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

  19. Investigation into the use of cement kiln dust in high density sludge (HDS) treatment of acid mine water.

    Science.gov (United States)

    Mackie, Allison L; Walsh, Margaret E

    2015-11-15

    The purpose of this study was to investigate the potential to replace lime with cement kiln dust (CKD) in high density sludge (HDS) treatment of acid mine drainage (AMD). The bench-scale study used two water samples: AMD sampled from a lead-zinc mine with high concentrations of iron (Fe), zinc (Zn), and arsenic (As) (Fe/Zn-AMD) and a synthetic AMD solution (Syn-AMD) spiked with ferric sulfate (Fe2(SO4)3). Arsenic was found to be significantly reduced with CKD-HDS treatment of Fe/Zn-AMD compared to lime-HDS treatment, to concentrations below the stringent mine effluent discharge regulation of 0.10 mg As/L (i.e., 0.04 ± 0.02 mg/L). Both CKD- and lime-HDS treatment of the two AMD samples resulted in settled water Fe concentrations above the stringent discharge guideline of 0.3 mg Fe/L. CKD addition in the HDS process also resulted in high settled water turbidity, above typical discharge guidelines of 15 mg TSS/L. CKD-HDS treatment was found to result in significantly improved settled solids (i.e., sludge) quality compared to that generated in the lime-HDS process. HDS treatment with CKD resulted in 25-88% lower sludge volume indices, 2 to 9 times higher % wet solids, and 10 to 20 times higher % dry solids compared to lime addition. XRD and XPS testing indicated that CKD-HDS sludge consisted of mainly CaCO3 and SiO2 with Fe(3+) precipitates attached at particle surfaces. XRD and XPS testing of the lime-HDS generated sludge showed that it consisted of non-crystalline Fe oxides typical of sludge formed from precipitates with a high water concentration. Increased sedimentation rates were also found for CKD (1.3 cm/s) compared to lime (0.3 cm/s). The increased solids loading with CKD addition compared to lime addition in the HDS process was suggested to both promote surface complexation of metal precipitates with insoluble CKD particles and increase compression effects during Type IV sedimentation. These mechanisms collectively contributed to the reduced water content of

  20. Sorption of Arsenic from Drinking Water to Mg(OH)2 Sorrel's Cements, and Zirconium Doped Materials

    Energy Technology Data Exchange (ETDEWEB)

    MOORE, ROBERT C.; ZHAO, HONGTING; SANCHEZ, CHARLES ANTHONY; HOLT, KATHLEEN C.; SALAS, FRED; HASAN, AHMED ALI MOHAMED; LUCERO, DANIEL A.

    2002-11-01

    It was discovered that MgO or Mg(OH){sub 2} when it reacts with water is a very strong sorbent for arsenic. Distribution constants, or K{sub d} values, are as high as 1 x 10{sup 6} L/mole. In this work, Mg(OH){sub 2} and other compounds have been investigated as sorbents for arsenic and other contaminants. This work has resulted in several major accomplishments including: (1) design, construction, and testing of a pressure sand filter to remove Mg(OH){sub 2} after it has sorbed arsenic from water, (2) stabilization of Mg(OH){sub 2} as a Sorrel's cement against reaction with carbonate that results in MgCO{sub 3} formation decreasing the efficiency of Mg(OH){sub 2} to sorb arsenic, and (3) the development of a new, very promising sorbent for arsenic based on zirconium. Zirconium is an environmentally benign material found in many common products such as toothpaste. It is currently used in water treatment and is very inexpensive. In this work, zirconium has been bonded to activated carbon, zeolites, sand and montmorillonite. Because of its high charge in ionic form (+6), zirconium is a strong sorbent for many anions including arsenic. In equilibrium experiments arsenic concentrations in water were reduced from 200 ppb to less than 1 ppb in less than 1 minute of contact time. Additionally, analytical methods for detecting arsenic in water have also been investigated. Various analytical techniques including HPLC, AA and ICP-MS are used for quantification of arsenic. Due to large matrix interferences HPLC and AA techniques are not very selective and are time consuming. ICP-MS is highly efficient, requires a low sample volume and has a high tolerance for interferences. All these techniques are costly and require trained staff, and with the exception of ICP-MS, these methods cannot be used at low ppb arsenic concentration without using a pre-concentration step. An alternative to these traditional techniques is to use a colorimetric method based on leucocrystal violet

  1. A Plant-Based Proxy for the Oxygen Isotope Ratio of Atmospheric Water Vapor

    Science.gov (United States)

    Helliker, B.

    2007-12-01

    Atmospheric water vapor is a major component of the global hydrological cycle, but the isotopic balance of vapor is largely unknown. It is shown here that the oxygen isotope ratio of leaf water in the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides (Spanish Moss) is controlled by the oxygen isotope ratio of atmospheric water vapor in both field and lab studies. Assuming that the leaf-water isotopic signature (and hence the atmospheric water vapor signature) is recorded in plant organic material, the atmospheric water vapor oxygen isotope ratios for Miami, Florida (USA) were reconstructed for several years from 1878 to 2005 using contemporary and herbarium specimens. T. usneoides ranges from Virginia, USA southwards through the tropics to Argentina, and the CAM epiphytic lifeform is widespread in other species. Therefore, epiphytes may be used to reconstruct the isotope ratio of atmospheric water for spatial scales that span over 60° of latitude and temporal scales that cover the last century of global temperature increase.

  2. Application of water vapor sorption measurements for porosity characterization of hardened cement pastes

    DEFF Research Database (Denmark)

    Wu, Min; Johannesson, Björn; Geiker, Mette Rica

    2014-01-01

    Water vapor sorption can be used to study important properties of porous materials including specific surface area and pore size distribution (PSD). However, the data analysis is somewhat inconsistent in literature. In this work, the important factors influencing the analyzed results using sorpti...

  3. Effects of Water-bincler Ratio on Strength of Concrete With Iron Ore Tailings%水胶比对铁尾矿混凝土强度的影响

    Institute of Scientific and Technical Information of China (English)

    崔孝炜; 倪文; 吴辉

    2011-01-01

    Ansteel Qidashan iron tailings with slag,natural gypsum and cement clinker are mixed, and produced ce-mentitious materials. And then the cementitious materials are mixed with original tailing,and became high-strength concrete materials by adding water-reducing agent. The effects of water cement ratio on the strength of concrete is researched. And the microstructure of hydration products is analyzed by SEM. The experiments indicate that,with the water-bincler ratio increases,the fluidity of concrete is also increased, but the flexural strength and compressive strength have shown a gradual decreasing trend. With actual production needs, making with Qidashan iron tailings, the suitable concrete water cement ratio is 0.24.%将鞍钢齐大山铁矿尾矿与高炉矿渣、水泥熟料、脱硫石膏进行3级混磨,形成胶凝材料,然后将胶凝材料与作为骨料的原始粒级铁尾矿混合,并加入减水剂制备成无粗骨料的高强混凝土材料.研究了水胶比对混凝土强度的影响,并通过SEM对水化产物及微观结构进行了分析.试验结果表明,随着水胶比的增大,混凝土的流动度也增大,但抗折强度和抗压强度均呈现下降趋势;结合实际生产需要,利用齐大山铁尾矿制备混凝土最合适的水胶比为0.24.

  4. 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%.

  5. Recent measurements of 234U/238U isotope ratio in spring waters from the Hadzici area.

    Science.gov (United States)

    Vidic, Alfred; Ilić, Zorana; Benedik, Ljudmila

    2013-06-01

    The Hadzici area has become interesting for investigation since depleted uranium ammunition had been employed in 1995 during the NATO air strike campaign in Bosnia and Herzegovina. The purpose of this study is to determine uranium concentration and (234)U/(238)U activity ratio in the spring waters of this area and to investigate their relationship, as well as spatial variations. The spring water samples were taken at 18 sites in total. For the determination of uranium radioisotopes, radiochemical separation procedure followed by alpha-particle spectrometry was applied. Uranium concentration in analyzed waters range from 0.15 to 1.12 μg/L. Spring waters from carbonate based sediments have a lower uranium concentration of between 0.15 and 0.43 μg/L, in comparison to waters sampled within sandstone-based sediments ranging from 0.53 to 1.12 μg/L. Dissolved uranium shows significant spatial variability and correlation with bedrock type confirmed by Principal Component Analysis and Hierarchical Cluster Analysis. The majority of the analyzed waters have a (234)U/(238)U activity ratio ranging from 1.02 to 1.90, of which half of the results range between 1.02 and 1.16. No apparent depleted uranium (DU) contamination was observed, as (234)U/(238)U activity ratio is dependent on geochemical conditions in the environment. Even though the tested spring waters demonstrate significant variability in uranium concentration, (234)U/(238)U activity ratio and (234)U excess, waters with similar uranium isotopic signatures are observable within the region. The guidelines on the spatial redistribution of dissolved uranium (corresponding to (238)U mass concentration), along with (234)U/(238)U activity ratios were provided by the Inverse Distance Weighting (IDW) method. Waters having similar isotopic signature have been delineated.

  6. Effects of shock and Martian alteration on Tissint hydrogen isotope ratios and water content

    Science.gov (United States)

    Hallis, L. J.; Huss, G. R.; Nagashima, K.; Taylor, G. J.; Stöffler, D.; Smith, C. L.; Lee, M. R.

    2017-03-01

    The Tissint meteorite, a picritic shergottite, fell to Earth in Morocco on the 18th of July 2011, and is only the fifth Martian meteorite witnessed to fall. Hydrogen isotope ratios and water contents are variable within different minerals in Tissint. Ringwoodite and shock melt pockets contain elevated D/H ratios relative to terrestrial values (δD = 761-4224‰). These high ratios in recrystallized phases indicate significant implantation of hydrogen from the D-rich Martian atmosphere during shock. In contrast, although olivine has detectable water abundances (230-485 ppm), it exhibits much lower D/H ratios (δD = +88 to -150‰), suggesting this water was not implanted from the Martian atmosphere. The minimal terrestrial weathering experienced by Tissint gives confidence that the olivine-hosted water has a Martian origin, but its high concentration indicates direct inheritance from the parental melt is improbable, especially given the low pressure of olivine crystallisation. Incorporation of a low δD crustal fluid, or deuteric alteration during crystallisation, could explain the relatively high water contents and low D/H ratios in Tissint olivine.

  7. Mechanical Properties of Recycled Aggregate Concrete at Low and High Water/Binder Ratios

    Directory of Open Access Journals (Sweden)

    Gai-Fei Peng

    2013-01-01

    Full Text Available This paper presents an experimental research on mechanical properties of recycled aggregate concrete (RAC at low and high water/binder (W/B ratios. Concrete at two W/B ratios (0.255 and 0.586 was broken into recycled concrete aggregates (RCA. A type of thermal treatment was employed to remove mortar attached to RCA. The RAC at a certain (low or high W/B ratio was prepared with RCA made from demolished concrete of the same W/B ratio. Tests were conducted on aggregate to measure water absorption and crushing values and on both RAC and natural aggregate concrete (NAC to measure compressive strength, tensile splitting strength, and fracture energy. The mechanical properties of RAC were lower than those of NAC at an identical mix proportion. Moreover, the heating process caused a decrease in compressive strength and fracture energy in the case of low W/B ratio but caused an increase in those properties in the case of high W/B ratio. The main type of flaw in RCA from concrete at a low W/B ratio should be microcracks in gravel, and the main type of flaw in RCA from concrete at a high W/B ratio should be attached mortar.

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

    Institute of Scientific and Technical Information of China (English)

    CHEN Yimin; ZHOU Shuangxi; ZHANG Wensheng

    2008-01-01

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

  9. Correlation between hydrocarbon distribution and water-hydrocarbon ratio in Fischer-Tropsch synthesis

    Institute of Scientific and Technical Information of China (English)

    Xiaofeng Zhou; Qingling Chen; Yuewu Tao; Huixin Weng

    2011-01-01

    In order to shorten the evaluation cycle of cobalt catalyst before the optimized catalyst is fixed on,a mathematical method is proposed to calculate weight percentage of C5+ hydrocarbons.Based on the carbide polymerization mechanism and the main hydrocarbons being linear alkanes and α-olefins,the correlation between hydrocarbon distribution and the molecular mass ratio of water to hydrocarbons is discussed.The result shows the ratio was within the range of 1.125-1.286 and the lower the ratio,the more gaseous hydrocarbons were obtained.Moreover,a linear equation between the weight percentage of C5+ hydrocarbons and the weight ratio of C5+ hydrocarbons to the total water is established.These results are validated by corresponding experiments.The weight percentage of C5+ hydrocarbons could be immediately calculated by this linear equation without detailed gas chromatography (GC) analysis of them.

  10. Chloride accelerated test: influence of silica fume, water/binder ratio and concrete cover thickness

    Directory of Open Access Journals (Sweden)

    E. Pereira

    Full Text Available In developed countries like the UK, France, Italy and Germany, it is estimated that spending on maintenance and repair is practically the same as investment in new constructions. Therefore, this paper aims to study different ways of interfering in the corrosion kinetic using an accelerated corrosion test - CAIM, that simulates the chloride attack. The three variables are: concrete cover thickness, use of silica fume and the water/binder ratio. It was found, by analysis of variance of the weight loss of the steel bars and chloride content in the concrete cover thickness, there is significant influence of the three variables. Also, the results indicate that the addition of silica fume is the path to improve the corrosion protection of low water/binder ratio concretes (like 0.4 and elevation of the concrete cover thickness is the most effective solution to increase protection of high water/binder ratio concrete (above 0.5.

  11. Monte Carlo Simulations on the water-to-air stopping power ratio for carbon ion dosimetry

    DEFF Research Database (Denmark)

    Henkner, Katrin; Bassler, Niels; Sobolevsky, Nikolai;

    2009-01-01

    Many papers discussed the I value for water given by the ICRU, concluding that a value of about 80±2  eV instead of 67.2  eV would reproduce measured ion depth-dose curves. A change in the I value for water would have an effect on the stopping power and, hence, on the water-to-air stopping power...... ratio, which is important in clinical dosimetry of proton and ion beams. For energies ranging from 50  to  330  MeV/u and for one spread out Bragg peak, the authors compare the impact of the I value on the water-to-air stopping power ratio. The authors calculate ratios from different ICRU stopping power...... tables and ICRU reports. The stopping power ratio is calculated via track-length dose calculation with SHIELD-HIT07. In the calculations, the stopping power ratio is reduced to a value of 1.119 in the plateau region as compared to the cited value of 1.13 in IAEA TRS-398. At low energies the stopping...

  12. Marine durability of 15 year old concrete specimens made with ordinary portland, slag, and fly ash cements

    Energy Technology Data Exchange (ETDEWEB)

    Mohammed, T.U.; Yamaji, T.; Hamada, H. [Port and Harbor Research Inst., Ministry of Land, Infrastructure and Transport (Japan); Aoyama, T. [PS Corp. (Japan)

    2001-07-01

    A study was conducted in which the marine durability of ordinary portland cement, slag and fly ash cement was examined using 15 year old plain and reinforced concrete cylindrical specimens. In addition, the performance of these cements was also examined in another study for pre-cracked reinforced concrete prism samples. The process of manufacturing cement emits huge amounts of carbon dioxide into the global atmosphere. Replacing a portion of the cement with by-products from the steel industry and thermal power plants (which are both huge emitters of carbon dioxide) can lower carbon dioxide emissions and also solve the disposal issue of slag and fly ash while increasing the long-term durability of concrete structures. In this study, concrete cylindrical specimens were made of ordinary portland cement, slag and fly ash cements. Water-to-cement ratios were 0.45 and 0.55 and the compressive strength of the concrete, corrosion of the steel bars, and chloride-ion concentrations in the concrete were evaluated. It was shown that, with the exception of fly ash cements, the compressive strength of most cements increased after 15 years of exposure compared to its 28 day strength. Type C slag cement demonstrated the best performance against chloride-ion at the surface of concrete made with slag and fly ash. Voids in the steel-concrete interface make it possible for corrosion pits to develop. The use of seawater as mixing water results in earlier strength development at 28 days and does not cause to the strength of the concrete to regress after 15-years of exposure, but it causes more corrosion of steel bars at a lower cover depth. Corrosion of steel bars is not an issue at deeper cover depths. 15 refs., 18 tabs., 8 figs.

  13. Alkali Aggregate Reaction in Alkali Slag Cement Mortars

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

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

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

    Science.gov (United States)

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

    2016-07-01

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

  15. Biological Evaluation of α-TCP/TTCP Composite Bone Cement

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    α-tricalcium phosphate(α-TCP)/tetracalcium phosphate(TTCP) composite bone cement had good hydration characteristic.In our system,α-TCP/TTCP powder mixture was mixed with water at a powder/liquid (P/L) ratio of 1.50g*mL-1.The setting time could be adjusted,the maximum compressive strength was 45.36MPa,and the hydration product was hydroxyapatite (HAP).In vitro biological simulated experiments indicate that α-TCP/TTCP bone cement has α certain dissolubility.The hardened product is mainly HAP after soaking in simulated body fluid (SBF) for 10 weeks.The results of in vitro test and animal experiments and SEM analyses show that no local or general toxicity response,no muscle stimulation,no haemolysis,no cruor,no inflammatory reaction and no exclusion response are caused by α-TCP/TTCP cement, which can be contributed to bone tissue spreading and impinging.α-TCP/TTCP cement hydrated and hardened continually in vivo.The materials fused with host bone together with implanting time prolonging.Therefore,it is believed that α-TCP/TTCP composite bone cement has a high biocompatibility and bioactivity,a certain biodegradation and good osteogenesis as well.

  16. Astro & cosmo-chemical consequences of accretion bursts I: the D/H ratio of water

    CERN Document Server

    Owen, James E

    2014-01-01

    The D/H ratio of water in protostellar systems is a result of both inheritance from the parent molecular cloud and isotopic exchange in the disc. A possibly widespread feature of disc evolution, ignored in previous studies, is accretion bursts (or FU Orionis outbursts), which may thermally process a large fraction of the water. One proposed underlying mechanism for FU Orionis outbursts relies on the presence of a magnetically dead zone. Here we examine the evolution of (D/H)$_{\\rm water}$ in 1D simulations of a disc's evolution that include dead zones and infall from an envelope with given D/H ratio in the infalling water ($\\sim 10^{-3}$), and compare the results with similar calculations without dead zones. We find that the accretion bursts result in a significantly lower (D/H)$_{\\rm water}$ ratio and a more extended region (radius up to $\\sim 1-3$ AU) where water is equilibrated with hydrogen gas (D/H=$2\\times 10^{-5}$), when compared to burst-free models. Solar system constraints suggest that our solar neb...

  17. Use of Variamine Blue dye in Spectrophotometric determination of Water Soluble Cr(VI in Portland Cement

    Directory of Open Access Journals (Sweden)

    Devesh K. Sharma

    2015-12-01

    Full Text Available Variamine blue dye as chromogenic reagent was used for Portland cement samples in determination of soluble hexavalent chromium. This method was based on the reaction of Cr(VI with potassium iodide in acidic medium to liberate iodine, which oxidized variamine blue to form a violet colored species having an absorption maximum 556 nm. The extraction of soluble Cr(VI for quantification in cement was done according to European method. The validity of this method was thoroughly examined by comparing with standard DPC method as well as the accuracy of the method was checked using a standard reference material of National Institute of Standards & Technology (NIST, USA.

  18. Changes in Escherichia coli to Cryptosporidium ratios for various fecal pollution sources and drinking water intakes.

    Science.gov (United States)

    Lalancette, Cindy; Papineau, Isabelle; Payment, Pierre; Dorner, Sarah; Servais, Pierre; Barbeau, Benoit; Di Giovanni, George D; Prévost, Michèle

    2014-05-15

    Assessing the presence of human pathogenic Cryptosporidium oocysts in surface water remains a significant water treatment and public health challenge. Most drinking water suppliers rely on fecal indicators, such as the well-established Escherichia coli (E. coli), to avoid costly Cryptosporidium assays. However, the use of E. coli has significant limitations in predicting the concentration, the removal and the transport of Cryptosporidium. This study presents a meta-analysis of E. coli to Cryptosporidium concentration paired ratios to compare their complex relationships in eight municipal wastewater sources, five agricultural fecal pollution sources and at 13 drinking water intakes (DWI) to a risk threshold based on US Environmental Protection Agency (USEPA) regulations. Ratios lower than the USEPA risk threshold suggested higher concentrations of oocysts in relation to E. coli concentrations, revealing an underestimed risk for Cryptosporidium based on E. coli measurements. In raw sewage (RS), high ratios proved E. coli (or fecal coliforms) concentrations were a conservative indicator of Cryptosporidium concentrations, which was also typically true for secondary treated wastewater (TWW). Removals of fecal indicator bacteria (FIB) and parasites were quantified in WWTPs and their differences are put forward as a plausible explanation of the sporadic ratio shift. Ratios measured from agricultural runoff surface water were typically lower than the USEPA risk threshold and within the range of risk misinterpretation. Indeed, heavy precipitation events in the agricultural watershed led to high oocyst concentrations but not to E. coli or enterococci concentrations. More importantly, ratios established in variously impacted DWI from 13 Canadian drinking water plants were found to be related to dominant fecal pollution sources, namely municipal sewage. In most cases, when DWIs were mainly influenced by municipal sewage, E. coli or fecal coliforms concentrations agreed with

  19. Solidification/Stabilization of Fly Ash from a Municipal Solid Waste Incineration Facility Using Portland Cement

    Directory of Open Access Journals (Sweden)

    Qiang Tang

    2016-01-01

    Full Text Available This study investigated the solidification/stabilization of fly ash containing heavy metals using the Portland cement as a binder. It is found that both the cement/fly ash ratio and curing time have significant effects on the mechanical (i.e., compressive strength and leaching behaviors of the stabilized fly ash mixtures. When the cement/fly ash ratio increases from 4 : 6 to 8 : 2, the increase of compressive strength ratio raises from 42.24% to 80.36%; meanwhile, the leaching amount of heavy metals decreases by 2.33% to 85.23%. When the curing time increases from 3 days to 56 days, the compressive strength ratio of mixtures raises from 240.00% to 414.29%; meanwhile, the leaching amount of heavy metals decreases by 16.49% to 88.70%. The decrease of compressive strength with the lower cement/fly ash ratios and less curing time can be attributed to the increase of fly ash loading, which hinders the formation of ettringite and destroys the structure of hydration products, thereby resulting in the pozzolanic reaction and fixation of water molecules. Furthermore, the presence of cement causes the decrease of leaching, which results from the formation of ettringite and the restriction of heavy metal ion migration in many forms, such as C-S-H gel and adsorption.

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

    Institute of Scientific and Technical Information of China (English)

    Eisa Hekal; Essam Kishar; Wafaa Hegazi; Maha Mohamed

    2011-01-01

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

  1. Rheological Properties of Very High-Strength Portland Cement Pastes: Influence of Very Effective Superplasticizers

    Directory of Open Access Journals (Sweden)

    Adriano Papo

    2010-01-01

    Full Text Available The influence of the addition of very effective superplasticizers, that are commercially available, employed for maximising the solid loading of very high-strength Portland cement pastes, has been investigated. Cement pastes were prepared from deionized water and a commercially manufactured Portland cement (Ultracem 52.5 R. Cement and water were mixed with a vane stirrer according to ASTM Standard C305. The 0.38 to 0.44 water/cement ratio range was investigated. Three commercial superplasticizing agents produced by Ruredil S.p.a. were used. They are based on a melamine resin (Fluiment 33 M, on a modified lignosulphonate (Concretan 200 L, and on a modified polyacrylate (Ergomix 1000. Rheological tests were performed at 25°C by using the rate controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-osc., measuring device MV2P with serrated surfaces. The tests were carried out under continuous flow conditions. The results of this study were compared with those obtained in a previous article for an ordinary Portland cement paste.

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

    Science.gov (United States)

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

    2016-05-01

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

  3. Modeling the soil water retention properties of same-textured soils with different initial void ratios

    Science.gov (United States)

    Tan, Fang; Zhou, Wan-Huan; Yuen, Ka-Veng

    2016-11-01

    This study presents a method of predicting the soil water retention curve (SWRC) of a soil using a set of measured SWRC data from a soil with the same texture but different initial void ratio. The relationships of the volumetric water contents and the matric suctions between two samples with different initial void ratios are established. An adjustment parameter (β) is introduced to express the relationships between the matric suctions of two soil samples. The parameter β is a function of the initial void ratio, matric suction or volumetric water content. The function can take different forms, resulting in different predictive models. The optimal predictive models of β are determined for coarse-grained and fine-grained soils using the Bayesian method. The optimal models of β are validated by comparing the estimated matric suction and measured data. The comparisons show that the proposed method produces more accurate SWRCs than do other models for both coarse-grained and fine-grained soils. Furthermore, the influence of the model parameters of β on the predicted matric suction and SWRC is evaluated using Latin Hypercube sampling. An uncertainty analysis shows that the reliability of the predicted SWRC decreases with decreasing water content in fine-grained soils, and the initial void ratio has no apparent influence on the reliability of the predicted SWRCs in coarse-grained and fine-grained soils.

  4. The use of the chrysotile cement waste as the secondary aggregate for the concrete

    Science.gov (United States)

    Semenov, V.; Pligina, A.; Rozovskaya, T.

    2015-01-01

    The article presents the results of research on the effective concrete with secondary chrysotile cement aggregate. One of the important problems of modern science of construction materials is the use of secondary resources for the production of construction materials, and a considerable part of them are the chrysotile cement waste and scrapped chrysotile cement products. The aim of presented research is the development of effective concrete for the production of foundation wall blocks with the use of crushed chrysotile cement products as a secondary aggregate. The main characteristics of the secondary chrysotile cement aggregate have been determined. The concrete with different compositions and with different content of secondary chrysotile cement rubble has been studied. The dependences of the strength and the specific strength of concrete with a constant W/C ratio and constant binder consumption on the consumption of the secondary aggregate have been obtained. It is stated that the introduction of secondary chrysotile cement aggregate does not significantly effect the water resistance and frost resistance of the concrete. It is shown that the variation of the fractions of secondary aggregates and the binder makes it possible to obtain the effective concrete with a wide range of strength values.

  5. Effect of aluminium phosphate as admixture on oxychloride cement

    Indian Academy of Sciences (India)

    M P S Chandrawat; R N Yadav

    2000-02-01

    The effect of admixing of aluminium phosphate on oxychloride cement in the matrix has been investigated. It is shown that aluminium phosphate retards the setting process of the cement and improves water-tightness.

  6. The migration of cesium-137 through cement formulations applicable to radioactive waste management

    Energy Technology Data Exchange (ETDEWEB)

    Rudin, M.J.

    1989-01-01

    Eighteen portland cement formulations containing three levels of cement/fly ash content (100%/0%, 85%/15%, and 60%/40%), two levels of water to cementitious solids ratio (0.33 and 0.43) and three levels of additive (none, silica fume, and latex polymer) were tested. Each formulation was molded into a solid cement specimen containing a centered well space which served as a reservoir for a {sup 137}Cs solution. After a predetermined time period, the {sup 137}Cs solution was removed and a 2-cm long by 1.27-cm diameter cement core was extracted from the monolith well bottom using a diamond core drill. Each cement core was then cut into successive horizontal slices with a diamond saw blade. The net activity of {sup 137}Cs in each slice was determined with a NaI(T1) detector connected to a single-channel analyzer. Analysis of variance (ANOVA) and regression models were used to examine the statistical relationship between different formulations in terms of the {sup 137}Cs activity in the cement slices versus the migration distance as indicated by the respective slice depths. Results indicated that mixes incorporating 5% silica fume at a low w/s ratio are relatively effective in retarding {sup 137}Cs migration when compared to the other formulations tested. Formulations with a w/s ratio of 0.33 consistently demonstrated better containment of the {sup 137}Cs solution compared to those formulations with a w/s ratio of 0.43. However, it was possible to obtain comparable {sup 137}Cs retardation at a higher w/s ratio if large amounts of fly ash were added to 5% EMSAC mixes at w/s = 0.43. The addition of 5% latex polymer did not improve the ability of cements to retard {sup 137}Cs ion migration under the curing conditions used.

  7. Maximum Deformation Ratio of Droplets of Water-Based Paint Impact on a Flat Surface

    Directory of Open Access Journals (Sweden)

    Weiwei Xu

    2017-06-01

    Full Text Available In this research, the maximum deformation ratio of water-based paint droplets impacting and spreading onto a flat solid surface was investigated numerically based on the Navier–Stokes equation coupled with the level set method. The effects of droplet size, impact velocity, and equilibrium contact angle are taken into account. The maximum deformation ratio increases as droplet size and impact velocity increase, and can scale as We1/4, where We is the Weber number, for the case of the effect of the droplet size. Finally, the effect of equilibrium contact angle is investigated, and the result shows that spreading radius decreases with the increase in equilibrium contact angle, whereas the height increases. When the dimensionless time t* < 0.3, there is a linear relationship between the dimensionless spreading radius and the dimensionless time to the 1/2 power. For the case of 80° ≤ θe ≤ 120°, where θe is the equilibrium contact angle, the simulation result of the maximum deformation ratio follows the fitting result. The research on the maximum deformation ratio of water-based paint is useful for water-based paint applications in the automobile industry, as well as in the biomedical industry and the real estate industry. Please check all the part in the whole passage that highlighted in blue whether retains meaning before.

  8. Magnesium substitution in brushite cements.

    Science.gov (United States)

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  9. Compact diode-laser spectrometer ISOWAT for highly sensitive airborne measurements of water-isotope ratios

    Science.gov (United States)

    Dyroff, C.; Fütterer, D.; Zahn, A.

    2010-02-01

    The tunable diode-laser absorption spectrometer ISOWAT for airborne measurements of the water-isotope ratios 18O/16O and D/H is described. The spectrometer uses a distributed feedback (DFB) diode laser to probe fundamental rovibrational water-absorption lines at around 2.66 μm. Very-low-noise system components along with signal averaging allow for a detection limit of 1.2 and 4.5 ‰ for measurements of 18O/16O and D/H, respectively, for a water-vapour mixing ratio of 100 ppmv and an averaging time of 60 s. This corresponds to a minimum detectable absorbance of ˜5×10-6 or ˜6.6×10-10 cm-1 when normalized to pathlength. In addition to its high sensitivity, the spectrometer is highly compact (19-inch rack at a height of 35 cm, excluding pump and calibration unit) and light weight (automated. ISOWAT will be calibrated during flight with known water-isotope ratios using a compact calibration-gas source.

  10. Dependence of Brillouin frequency shift on water absorption ratio in polymer optical fibers

    Science.gov (United States)

    Minakawa, Kazunari; Koike, Kotaro; Hayashi, Neisei; Koike, Yasuhiro; Mizuno, Yosuke; Nakamura, Kentaro

    2016-06-01

    We studied the dependence of the Brillouin frequency shift (BFS) on the water-absorption ratio in poly(methyl methacrylate)-based polymer optical fibers (POFs) to clarify the effect of the humidity on POF-based Brillouin sensors. The BFS, deduced indirectly using an ultrasonic pulse-echo technique, decreased monotonically as the water absorption ratio increased, mainly because of the decrease in the Young's modulus. For the same water absorption ratio, the BFS change was larger at a higher temperature. The maximal BFS changes (absolute values) at 40, 60, and 80 °C were 158, 285, and 510 MHz, respectively (corresponding to the temperature changes of ˜9 °C, ˜16 °C, and ˜30 °C). Thus, some countermeasure against the humidity is indispensable in implementing strain/temperature sensors based on Brillouin scattering in POFs, especially at a higher temperature. On the other hand, Brillouin-based distributed humidity sensors might be developed by exploiting the BFS dependence on water absorption in POFs.

  11. Interactive Effect of Air-Water Ratio and Temperature on the Air Stripping of Benzene

    Directory of Open Access Journals (Sweden)

    M. E. Abdullahi

    2014-06-01

    Full Text Available High cost of pilot scale studies has led engineers to use simulation to study the factors that affect process performance. This study focuses on the interactive effect of air water ratio and temperature on the removal of volatile organic compounds from polluted water using packed column air stripper taking benzene as a case study. The process governing equations developed based on two-film model of mass transfer were solved using MATLAB and a surface response plot was done. The mass transfer coefficient increased from 0.1237x10-5 to 0.1932x10-5 s-1 as the temperature was raised from 293 to 323 K. Also, the Henry’s constant increased from 228.59 to 883.36 K as the temperature was raised from 293 to 323 K. Benzene removal efficiencies of over 99% were obtained for all combinations of temperature and air-water ratio. The result also indicated that air stripping of benzene from wastewater is most dependent on temperature and moderately on air-water ratio.

  12. Detecting shifts in tropical moisture imbalances with satellite-derived isotope ratios in water vapor

    Science.gov (United States)

    Bailey, A.; Blossey, P. N.; Noone, D.; Nusbaumer, J.; Wood, R.

    2017-06-01

    As global temperatures rise, regional differences in evaporation (E) and precipitation (P) are likely to become more disparate, causing the drier E-dominated regions of the tropics to become drier and the wetter P-dominated regions to become wetter. Models suggest that such intensification of the water cycle should already be taking place; however, quantitatively verifying these changes is complicated by inherent difficulties in measuring E and P with sufficient spatial coverage and resolution. This paper presents a new metric for tracking changes in regional moisture imbalances (e.g., E-P) by defining δDq—the isotope ratio normalized to a reference water vapor concentration of 4 mmol mol-1—and evaluates its efficacy using both remote sensing retrievals and climate model simulations in the tropics. By normalizing the isotope ratio with respect to water vapor concentration, δDq isolates the portion of isotopic variability most closely associated with shifts between E- and P-dominated regimes. Composite differences in δDq between cold and warm phases of El Niño-Southern Oscillation (ENSO) verify that δDq effectively tracks changes in the hydrological cycle when large-scale convective reorganization takes place. Simulated δDq also demonstrates sensitivity to shorter-term variability in E-P at most tropical locations. Since the isotopic signal of E-P in free tropospheric water vapor transfers to the isotope ratios of precipitation, multidecadal observations of both water vapor and precipitation isotope ratios should provide key evidence of changes in regional moisture imbalances now and in the future.

  13. S Isotope Ratios of Central Italy Waters to Assess Their Origin

    Science.gov (United States)

    Castorina, Francesca; Masi, Umberto

    2010-05-01

    Sr isotopes have so far applied only occasionally to the study of the waters from central Italy. Therefore, we have analyzed more than 30 water samples from thermal and cold springs, and from the lakes located in the Quaternary K-alkaline volcanic districts of Latium, aimed at providing significant information on the sources of Sr and the hydrologic circulation. The 87Sr/86Sr composition of the waters shows a general correlation with the aquifer rocks, resulting in the waters from older carbonatic rocks having a less radiogenic signature than those from younger K-alkaline volcanic rocks. The Sr-isotope ratios of most thermal waters range narrowly by 0.708, indicating a common source of Sr, likely represented by the Upper Triassic Burano Anhydrites, i.e. the lowermost permeable formation in the study area. Moreover, the positive correlation between Sr and Ca suggests that bulk Ca was also supplied from that source. A minor number of thermal waters as well as all the waters from the lakes and cold springs display a larger Sr isotopic range (0.7085-0.7115), suggesting a relative large spectrum of sources for Sr. In particular, some waters derive their Sr from a singular source, but the most show isotopic signatures suggestive of mixed contributions from different aquifers. As a whole, the results from this study confirm that Sr isotopes are a useful tool contributing to explain the geochemical characteristics of surficial and groundwaters.

  14. 53rd Cement Technical Conference. Expansion and contraction 1; Dai 53 kai semento gijutsu taikai. Bocho, shushuku 1

    Energy Technology Data Exchange (ETDEWEB)

    Shimomura, Takumi [Nagaoka University of Technology, Niigata (Japan)

    1999-08-10

    Mokuzen et al studied the relationship of gas pressure and speed constant while deriving suction speed constant from the results of suction experiments of gas molecule to minute pore wall, and discussed what changes will occur caused by different cement water ratio and ages of the cement. Baba et al reported the experiment results concerning changing of gap pressure and contraction of very initial age cement paste under dry and non-dry conditions. Yamada et al reported the experiment results concerning water motion and contraction properties inside plane plate specimens of super high strength concrete. Imori et al reported the experiment results of shearing resistance of reinforced concrete beams that have cracks pre-introduced in cross section by dry contraction or temperature stress, and discussed its calculation method. Hotta et al studied the experimental method concerning volume changing of cement paste including that before agglutination, and reported the experiment results. (NEDO)

  15. Engineering and sustainability aspect of palm oil shell powder in cement

    Science.gov (United States)

    Karim, Mohammad Razaul; Hossain, Md. Moktar; Yusoff, Sumiani Binti

    2017-06-01

    Palm oil shell (POS) is a waste material which significantly produced in palm oil mills. In current practice, this waste is dumped in open land or landfill sites or is used as fuel to run a steam turbine of a boiler, which leads to environmental pollutions. The characterization, engineering and sustainability aspect of this waste for using in cement-based applications lead to reduce the emission of carbon dioxide and cost, save natural resources for cement production and also sustainable usage of waste material. The characterization was carried out using particle size analyzer, XRF, SEM and total organic carbon analyzer. ASTM standard methods were used to observe the setting time and water for normal consistency. The compressive strength of palm oil shell powder (POSP) blended cement was explored with the water to cement and cement to sand ratio of 0.40 and 0.50, respectively up to 40% replacement levels of OPC. Result found that the setting time and water demand were increased, but compressive strength was decreased to replacement levels. However, the incorporation of POSP in cement was reduced 9.6% of CO2 emission, 25 % of the cost and save natural resource, i.e. limestone, clay, iron ore, silica shale and gypsum of 35.1%, 4.95%, 0.9%, 4.05 % and 1.2 %, respectively at 30% replacement level of OPC. The results of this extensive study on POSP characterization, effect on basic cement properties and sustainability aspect provide the guidance for using the POSP at industrial scale for cement production.

  16. Study on nitrobenzene ratio in water-ice system under different conditions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A series of ice freezing-thawing experiments are performed under different nitro- benzene concentrations of 1.7, 8, 17, 170, and 1700 μg/L. A special flume, made of stainless steel and glass, is built to simulate the flowing water for the experiments. The ice frozen in cold room has similar crystal structure of natural ice, therefore the behaviors of nitrobenzene in the ice frozen in cold room is also believed to be similar to that in natural ice. The results of the experiments reveal that the freezing rate of ice decreases with the increase of nitrobenzene concentration in water, and that the nitrobenzene ratio in water-ice system becomes higher with the increase of freezing rate. In addition, the nitrobenzene in ice does not move and is only re- leased into water after melt.

  17. Study on nitrobenzene ratio in water-ice system under different conditions

    Institute of Scientific and Technical Information of China (English)

    LI ZhiJun; WANG Xin; LI QingShan; XU ShiGuo; XU XiangZhou; BAI Yan

    2008-01-01

    A aeries of ice freezing-thawing experiments are performed under different nitro-benzene concentrations of 1.7, 8, 17, 170, and 1700 μg/L. A special flume, made of stainless steel and glass, is built to simulate the flowing water for the experiments. The ice frozen in cold room has similar crystal structure of natural ice, therefore the behaviors of nitrobenzene in the ice frozen in cold room is also believed to be similar to that in natural ice. The results of the experiments reveal that the freezing rate of ice decreases with the increase of nitrobenzene concentration in water, and that the nitrobenzene ratio in water-ice system becomes higher with the increase of freezing rate. In addition, the nitrobenzene in ice does not move and is only re-leased into water after melt.

  18. The use of water-jetting technology in prostheses revision surgery-first results of parameter studies on bone and bone cement.

    Science.gov (United States)

    Honl, M; Rentzsch, R; Müller, G; Brandt, C; Bluhm, A; Hille, E; Louis, H; Morlock, M

    2000-01-01

    Water-jet cutting techniques have been used in industrial applications for many different materials. Recently these techniques have been developed into a revolutionary cutting tool for soft tissues in visceral surgery. The present study investigates the usage of this cutting technology for the revision surgery of endoprostheses. In the first part of the study, samples of bovine bone and acrylic bone cement (PMMA) were cut using an industrial jet cutting device with pure water. Below 400 bar, only PMMA was cut; above 400 bar, bone was also cut, but only pressures above 800 bar resulted in clinically useful rates of material removal (cut depth 2. 4 mm at 10 mm/min traverse speed). In the second part of the study, the effect of adding biocompatible abrasives to the water in order to reduce the required pressure was investigated, resulting in a significantly higher removal of material. At 600 bar, PMMA was cut 5. 2 mm deep with plain water and 15.2 mm deep with added abrasives. The quality of the cuts was increased by the abrasive. Though there was no clear selectivity between bone and PMMA any more, the rate of material removal at similar pressures was significantly higher for PMMA than for bone (600 bar: 1.6 mm cut depth for bone samples, 15.2 mm for PMMA). The measured cut depths with either method were not influenced by a change of the cutting direction with respect to the main direction of the osteons in the bone. However, a reduction of the jet surface angle (90 degrees to 23 degrees ) resulted for bone in a significantly lower cut depth at 600 bar (plain water: 0.62 mm vs. 0.06 mm; abrasive: 1.61 mm vs. 0.60 mm). The laboratory experiments indicate that abrasive water jets may be suitable for cutting biomaterials like bone and bone cement.

  19. Experimental characterization of mechanical properties of the cement pasteaggregate interface in concrete

    Science.gov (United States)

    Jebli, M.; Jamin, F.; Malachanne, E.; Garcia-Diaz, E.; El Youssoufi, M. S.

    2017-06-01

    Granular materials are extensively used in the field of civil engineering. These materials are either used in their dry state, or mixed with water or with a binder. In the case of concrete, the binder could be cement or mortar. For ordinary concretes, it is generally admitted that there is a thin heterogeneous zone of paste, with a thickness of about 15-60 μm, surrounding the aggregates surface. This zone, commonly named the Interfacial Transition Zone (ITZ), is characterized by a higher porosity than the bulk paste and a high concentration of the portlandite crystals. Some of these crystals react with the aggregates' surface (limestone aggregates), leading to a good adhesion. In this work, the mechanical properties of the cement paste and of the cement-aggregate interface are experimentally analyzed. Experimental tensile and shear tests are performed on parallelipipedic samples. These samples are made by linking limestone aggregates with Portland cement paste using a water / cement ratio of 0.5. The results show that the cement-aggregate interface is the weak zone in the composite.

  20. On-line determination of oxygen isotope ratios of water or ice by mass spectrometry.

    Science.gov (United States)

    Leuenberger, M; Huber, C

    2002-09-15

    Oxygen isotope ratio determination on any of the water phases (water vapor, water, ice) is of great relevance in different research fields such as climate and paleoclimate studies, geological surveys, and hydrological studies. The conventional technique for oxygen isotope measurement involves equilibration with carbon dioxide gas for a given time with a subsequent isotope determination. The equilibration technique is available in different layouts, but all of them are rather time-consuming. Here we report a new on-line technique that processes water samples as well as ice samples. The same principal, CO2 hydration, is used but speeded up by (i) a direct injection and full dissolution of CO2 in the water, (ii) an increased isotope exchange temperature at 50 degrees C, and (iii) a rapid gas extraction by means of an air-permeable membrane into a continuous helium flux supplying the isotope ratio mass spectrometer with the sample gas. The precision is better than 0.1/1000 which is only slightly larger than with the conventional equilibration technique. This on-line technique allows analysis of 1 m of ice with a resolution of 1-3 cm, depending on the meltwater flux, within 1 h. Similarly, continuous and fast analysis can be performed for aqueous samples for hydrological, geological, and perhaps medical applications.

  1. Experiment on Sewage Water Treatment by Cement-Soil%多孔水泥土净化生活污水试验

    Institute of Scientific and Technical Information of China (English)

    蓝俊康; 刘宝剑

    2011-01-01

    Composite cement (ωB = 25% ), red clay (ωB = 75% ) and proper amount of ultra-pure water are mixed together and put into a PVC pipe. After pricking and conservation, short porous cylinders of cement-soil are made. Several cement-soil cylinders appear in a row up and down to form a reaction column and to treat sewage water. The raw sewage is collected from the inflow path of a wastewater treatment plan and mainly consisted of domestic sewage. The experiment monitoring data show that the sewage water can be effectively treated by the cement-soil reaction column. The removal of BOD5 and COD is high and the removal efficiency of TP、 TN、 NH3-N also significant. The treatment effect under 30 ℃ temperature is better than that under 10 t temperature. It is concluded that the mechanism of wastewater purified by cement-soil cylinder is very similar to that of the porous eco-concrete. However, the cost of the former is more lower than the latter. Because it can be easily crushed into cultivated soil, there is no worry about its durability after abandoned. Cement-soil is thought to be beneficial to environment protection than other ordinary eco-concrete.%用复合水泥(wB= 25%)、红粘土(wB= 75%)和适量的蒸馏水拌合后置入PVC管内,经插孔和养护,制成多孔的圆柱形水泥土反应节,再由多个反应节上下串联而成反应柱,以此反应装置处理从某污水处理厂采集的污水,该污水组分以生活污水为主.监测结果显示,此反应器对污水中BOD5、COD的净化效果十分突出,对TP、TN、NH3-N的处理也有一定的效果;30℃条件下各个指标的去除率要明显优于10℃的环境.综合分析后认为,水泥土对污水的净化机理与“生态型多孔混凝土”的基本相同,但是由于水泥土的制作成本更低,废弃后可破碎作耕土,不需考虑其耐久性问题,更利于环保.

  2. Chloride/bromide and chloride/fluoride ratios of domestic sewage effluents and associated contaminated ground water

    Energy Technology Data Exchange (ETDEWEB)

    Vengosh, A.; Pankratov, I. [Hydrological Service, Jerusalem (Israel)

    1998-09-01

    To establish geochemical tools for tracing the origin of ground water contamination, the authors examined the variations of Cl/Br and Cl/F (weight) ratios in (1) domestic waste water from the Dan Region Sewage Reclamation Project and from reservoirs in the central coast of Israel; (2) associated contaminated ground water; and (3) pristine ground water from the Mediterranean coastal aquifer of Israel. The data show that supply water, anthropogenic NaCl and fluoridation control the Cl/Br and Cl/F ratios of domestic waste water, and conventional sewage treatment does not affect the anthropogenic inorganic signals. The Cl/Br ratios of ground water contaminated with sewage effluent reflect conservative mixing proportions of sewage and regional ground water components. Sensitivity tests demonstrate that it is possible to detect and distinguish sewage contamination from marine ratios after a sewage contribution of 5 to 15% is mixed with regional ground water. Mixing with Br-enriched fresh water however, would reduce this sensitivity. Since the high Cl/Br signal of sewage effluents is distinguishable from other anthropogenic sources with low Cl/Br ratios and from natural contamination sources, Cl/Br ratios can therefore be a useful inorganic tracer for identification of the origin of contaminated ground water. The Cl/F ratios of sewage-contaminated ground water were higher than those in the original sewage effluent, which suggests retention of fluoride into the aquifer solid phase.

  3. Asymmetric Transfer Hydrogenation of Imines in Water by Varying the Ratio of Formic Acid to Triethylamine.

    Science.gov (United States)

    Shende, Vaishali S; Deshpande, Sudhindra H; Shingote, Savita K; Joseph, Anu; Kelkar, Ashutosh A

    2015-06-19

    Asymmetric transfer hydrogenation (ATH) of imines has been performed with variation in formic acid (F) and triethylamine (T) molar ratios in water. The F/T ratio is shown to affect both the reduction rate and enantioselectivity, with the optimum ratio being 1.1 in the ATH of imines with the Rh-(1S,2S)-TsDPEN catalyst. Use of methanol as a cosolvent enhanced reduction activity. A variety of imine substrates have been reduced, affording high yields (94-98%) and good to excellent enantioselectivities (89-98%). In comparison with the common azeotropic F-T system, the reduction with 1.1/1 F/T is faster.

  4. 变压式水泥混凝土智能养护研究%The study of intelligent curing cement concrete by changing water pressure

    Institute of Scientific and Technical Information of China (English)

    甘露

    2015-01-01

    为实现施工现场水泥混凝土养护的智能化、自动化,提出了变压式水泥混凝土智能养护,变压式智能混凝土养护机通过检测混凝土路面、桥面或者楼板的温度湿度,并通过ZigBee无线传输将数据传给主机,主机根据相关数据改变出水水压,控制定时器及电磁阀,实现混凝土的定向定距喷灌,对提高养护效率以及养护规范性有重要作用。%To implement the intelligent of the cement concrete auto curing,this paper puts forward pressure type cement concrete intelligent main-tenance,variable pressure type intelligent concrete curing machine through the test of concrete pavement and bridge deck or slab temperature, humidity,and through the ZigBee wireless transmission to transmit the data to host,the host according to the relevant data change of water pres-sure,water control timer and solenoid valve,realize the directional distance of concrete irrigation,to improve the efficiency of maintenance and maintenance normative has vital function.

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

    Science.gov (United States)

    Kleinhans, D

    1984-01-01

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

  6. Linear and Non-linear Modeling of Cement-bonded Moulding Sand System Using Conventional Statistical Regression Analysis

    Science.gov (United States)

    Parappagoudar, Mahesh B.; Pratihar, Dilip K.; Datta, Gouranga L.

    2008-08-01

    A cement-bonded moulding sand system takes a fairly long time to attain the required strength. Hence, the moulds prepared with cement as a bonding material will have to wait a long time for the metal to be poured. In this work, an accelerator was used to accelerate the process of developing the bonding strength. Regression analysis was carried out on the experimental data collected as per statistical design of experiments (DOE) to establish input-output relationships of the process. The experiments were conducted to measure compression strength and hardness (output parameters) by varying the input variables, namely amount of cement, amount of accelerator, water in the form of cement-to-water ratio, and testing time. A two-level full-factorial design was used for linear regression model, whereas a three-level central composite design (CCD) had been utilized to develop non-linear regression model. Surface plots and main effects plots were used to study the effects of amount of cement, amount of accelerator, water and testing time on compression strength, and mould hardness. It was observed from both the linear as well as non-linear models that amount of cement, accelerator, and testing time have some positive contributions, whereas cement-to-water ratio has negative contribution to both the above responses. Compression strength was found to have linear relationship with the amount of cement and accelerator, and non-linear relationship with the remaining process parameters. Mould hardness was seen to vary linearly with testing time and non-linearly with the other parameters. Analysis of variance (ANOVA) was performed to test statistical adequacy of the models. Twenty random test cases were considered to test and compare their performances. Non-linear regression models were found to perform better than the linear models for both the responses. An attempt was also made to express compression strength of the moulding sand system as a function of mould hardness.

  7. SODIUM POLYPHOSPHATE-MODIFIED CLASS C/CLASS F FLY ASH BLEND CEMENTS FOR GEOTHERMAL WELLS.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA, T.; BROTHERS, L.E.; KASPEREIT, D.

    2006-02-01

    The authors investigated the usefulness of the coal combustion by-products, Class C fly ash (C) and Class F fly ash (F), in developing cost-effective acid-resistant phosphate-based cements for geothermal wells. In the temperature range of 20-100 C, sodium polyphosphate (NaP) as the acidic cement-forming solution preferentially reacted with calcium sulfate and lime in the C as the base solid reactant through the exothermic acid-base reaction route, rather than with the tricalcium aluminate in C. This reaction led to the formation of hydroxyapatite (HOAp). In contrast, there was no acid-base reaction between the F as the acidic solid reactant and NaP. After autoclaving the cements at 250 C, a well-crystallized HOAp phase was formed in the NaP-modified C cement that was responsible for densifying the cement's structure, thereby conferring low water permeability and good compressive strength on the cement. however, the HOAp was susceptible to hot CO{sub 2}-laden H{sub 2}SO{sub 4} solution (pH 1.1), allowing some acid erosion of the cement. On the other hand, the mullite in F hydrothermally reacted with the Na from NaP to form the analcime phase. Although this phase played a pivotal role in abating acid erosion, its generation created an undesirable porous structure in the cement. They demonstrated that blending fly ash with a C/F ratio of 70/30 resulted in the most suitable properties for acid-resistant phosphate-based cement systems.

  8. 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.

  9. Long-Term In Vitro Degradation of a High-Strength Brushite Cement in Water, PBS, and Serum Solution

    OpenAIRE

    2015-01-01

    Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for ...

  10. Long-term in vitro degradation of a high-strength brushite cement in water, PBS, and serum solution

    OpenAIRE

    2015-01-01

    Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for ...

  11. Gelatinization and retrogradation phenomena in starch/montmorillonite nanocomposites plasticized with different glycerol/water ratios.

    Science.gov (United States)

    Lara, Sandra Camila; Salcedo, Felipe

    2016-10-20

    This study aims to gain insights into the intermolecular interactions present in thermoplastic starch (TPS)/montmorillonite (MMT) nanocomposites prepared using water and/or glycerol as plasticizers. Specifically, the impact of using different glycerol/water proportions on the nature of gelatinization and retrogradation processes is studied. Nanocomposites were characterized by rheometry, scanning electron microscopy (SEM) and X-rays diffraction (XRD). It is shown that clay tactoids preferentially interact with glycerol molecules rather than starch macromolecules. Consequently, the effects of MMT incorporation strongly depend on the glycerol/water ratio; when a ratio of 0.5 is used minor variations were observed on the starch gelatinization process-although stronger clays-starch interactions were evident-whereas at higher ratios the addition of clays significantly increased the gelatinization temperature, up to values over 100°C. In the gelatinization process of starch in TPS samples having only glycerol as a plasticizer, the leaching of amylose and the melting of amylopectin crystalline domains seem to occur simultaneously. This different gelatinization mechanism produces a TPS having a substantially different morphology, which exhibited reduced retrogradation characteristics.

  12. Hidration kinetics study of tlie mixed cements

    OpenAIRE

    Duque Fernández, Gabriel . L; Díaz Quintanilla, David; Zapata Sierra, Manuel; Rubio Frías, Ester

    1993-01-01

    A study of the hydration process of cements with 10% and 20% addition of a tuff from "Las Carolinas" quarry (Cienfuegos, Cuba) by different methods was done. The results obtained by different methods showed a good agreement. It was proved an increment of the hydration products, an acceleration of alite hydration and a swelling of the fixed water in mixed cements. The resistance of the cement with 10% addition is similar to that of the pure cement for ages of 28 days, whereas with 20% addition...

  13. The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles

    Science.gov (United States)

    Vitali, Victoria; Sutka, Moira; Amodeo, Gabriela; Chara, Osvaldo; Ozu, Marcelo

    2016-01-01

    Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf. We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf/Ps), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements

  14. The water to solute permeability ratio governs the osmotic volume dynamics in beetroot vacuoles

    Directory of Open Access Journals (Sweden)

    Victoria Vitali

    2016-09-01

    Full Text Available Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf. We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modelling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf/Ps, which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons or stems that perform extensive rhythmic

  15. Recycled water technological design of a cement plant in Shanxi Province%山西省某水泥厂中水回用工艺设计

    Institute of Scientific and Technical Information of China (English)

    尤伟静; 邓先涛; 杨亮

    2014-01-01

    The combined process,full automatic purifier+ultra-filtration,has been used for the pretreatment of dis-charged wastewater from a cement plant in Shanxi Province. Then the subsequent reverse osmosis process has been used for realizing recycled water reuse. Its treatment capacity of water is 28 t/h. The quality of the final effluent is favorable. For example,the turbidity drops from 34.1 NTU to 0,and total hardness drops from 3 160 mg/L to 40 mg/L. Therefore,it can directly be reused as make-up water for the excess heat power circulating water in the cement plant. The water yield is 20 t/h,and the rate of reuse up to 75%. It has been proved by practical application that the com-bined process could guarantee that the advanced treatment of discharge wastewater from cement plants is stable and its recycle quality is high.%采用全自动净水器+超滤组合工艺,对山西省某水泥厂排放废水进行预处理,联合后续反渗透工艺以实现中水回用,处理水量为28 t/h。经该工艺处理后,最终出水水质良好,浊度由34.1 NTU降至0,总硬度由3160 mg/L降至40 mg/L,可直接回用于该水泥厂余热发电循环水补充用水,出水量为20 t/h,回用率达75%。工程实践表明,该联合工艺可实现对水泥厂排放废水的深度处理和高质回用。

  16. The D/H Ratio of Water Ice at Low Temperatures

    CERN Document Server

    Lee, Jeong-Eun

    2014-01-01

    We present the modeling results of deuterium fractionation of water ice, H2, and the primary deuterium isotopologues of H3+ adopting physical conditions associated with the star and planet formation process. We calculated the deuterium chemistry for a range of gas temperatures (T_gas ~ 10 - 30 K), molecular hydrogen density (n(H2)~ 10^4 - 10^7), and ortho/para ratio (opr) of H2 based on state-to-state reaction rates and explore the resulting fractionation including the formation of a water ice mantle coating grain surfaces. We find that the deuterium fractionation exhibits the expected temperature dependence of large enrichments at low gas temperature. More significantly the inclusion of water ice formation leads to large D/H ratios in water ice (>= 10^-2 at 10 K) but also alters the overall deuterium chemistry. For T < 20 K the implantation of deuterium into ices lowers the overall abundance of HD which reduces the efficiency of deuterium fractionation at high density. In agreement with an earlier study, ...

  17. An Evaluation of Total Solar Reflectance and Spectral Band Ratioing Techniques for Estimating Soil Water Content

    Science.gov (United States)

    Reginato, R. J.; Vedder, J. F.; Idso, S. B.; Jackson, R. D.; Blanchard, M. B.; Goettelman, R.

    1977-01-01

    For several days in March of 1975, reflected solar radiation measurements were obtained from smooth and rough surfaces of wet, drying, and continually dry Avondale loam at Phoenix, Arizona, with pyranometers located 50 cm above the ground surface and a multispectral scanner flown at a 300-m height. The simple summation of the different band radiances measured by the multispectral scanner proved equally as good as the pyranometer data for estimating surface soil water content if the multispectral scanner data were standardized with respect to the intensity of incoming solar radiation or the reflected radiance from a reference surface, such as the continually dry soil. Without this means of standardization, multispectral scanner data are most useful in a spectral band ratioing context. Our results indicated that, for the bands used, no significant information on soil water content could be obtained by band ratioing. Thus the variability in soil water content should insignificantly affect soil-type discrimination based on identification of type-specific spectral signatures. Therefore remote sensing, conducted in the 0.4- to 1.0-micron wavelength region of the solar spectrum, would seem to be much More suited to identifying crop and soil types than to estimating of soil water content.

  18. Cement paste compressive strength estimation using nondestructive microwave reflectometry

    Science.gov (United States)

    Zoughi, Reza; Gray, S.; Nowak, Paul S.

    1994-09-01

    Microwave reflection properties of four cement paste samples with various water-cement (w/c) ratios were measured daily for 28 days using microwave frequencies of 5, 9, and 13 GHz. The dielectric properties of these samples, and hence their reflection coefficients, were measured daily and shown to decrease as a function of increasing w/c ratio. This is as a direct result of curing (no chemical interaction or hydration). The presence of curing as indicated by this result indicates that microwaves could be used to monitor the amount of curing in a concrete member. The variation in the reflection coefficient of these samples as a function of w/c ratio followed a trend similar to the variation of compressive strength as a function of w/c ratio. Subsequently, a correlation between the measured compressive strength and reflection coefficient of these blocks was obtained. The early results indicated that lower frequencies are more sensitive to compressive strength variations. However, further investigations showed that there may be a frequency around 5 GHz which is the optimum measurement frequency. This result can be used to directly and nondestructively estimate the compressive strength of a cement paste and mortar blocks.

  19. 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.

  20. Hydration of fly ash cement

    Energy Technology Data Exchange (ETDEWEB)

    Etsuo Sakai; Shigeyoshi Miyahara; Shigenari Ohsawa; Seung-Heun Lee; Masaki Daimon [Tokyo Institute of Technology, Tokyo (Japan). Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering

    2005-06-01

    It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO{sub 2} generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.

  1. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2006-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  2. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2007-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  3. Data cleaning methodology for monthly water-to-oil and water-to-gas production ratios in continuous resource assessments

    Science.gov (United States)

    Varela, Brian A.; Haines, Seth S.; Gianoutsos, Nicholas J.

    2017-01-19

    Petroleum production data are usually stored in a format that makes it easy to determine the year and month production started, if there are any breaks, and when production ends. However, in some cases, you may want to compare production runs where the start of production for all wells starts at month one regardless of the year the wells started producing. This report describes the JAVA program the U.S. Geological Survey developed to examine water-to-oil and water-to-gas ratios in the form of month 1, month 2, and so on with the objective of estimating quantities of water and proppant used in low-permeability petroleum production. The text covers the data used by the program, the challenges with production data, the program logic for checking the quality of the production data, and the program logic for checking the completeness of the data.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Moridis, George

    2014-11-01

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

  5. 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.

  6. 氯氧镁水泥耐水性能改善研究%Research on improving the water resistance of magnesium oxychloride cement

    Institute of Scientific and Technical Information of China (English)

    冯扣宝; 王路明; 陈雪霏

    2015-01-01

    On the basis of the research on the modification on magnesium oxychloride cement (MOC) with phos‐phoric acid ,fly ash and calcium stearate respectively ,then phosphoric acid ,fly ash and calcium stearate or phosphoric acid ,fly ash and styrene‐acrylic emulsion were adopted to improve the water resistance of MOC . The results show that ,while adding 1wt% phosphoric acid ,20wt% fly ash and 1wt% calcium stearate or 1wt% styrene‐acrylic emulsion to the cement ,the stability of 5 ・1・8 main phase in water ,the density and water resistance of the cement were improved effectively ,among them ,phosphoric acid ,fly ash and styrene‐acrylic emulsion as compound modifiers are the best .Compressive strength of optimal modified specimen cured 3 and 7 d could reach 63 4. ,75 1. MPa respectively .softening coefficient were up to 0 9. ,when soaked in water 7 d ,compressive strength still can maintain 68 1. MPa ,improving 60 2.% compared with the blank .Compound modification effect is remarkable .%在磷酸、粉煤灰、硬脂酸钙单一改性研究的基础上,采取磷酸、粉煤灰、硬脂酸钙和磷酸、粉煤灰、苯丙乳液两种复合体系分别对氯氧镁水泥进行复合改性。结果表明,同时掺入1%磷酸、20%粉煤灰和1%硬脂钙或1%苯丙乳液均可有效提高5・1・8主晶相在水中的稳定性,提高材料的密实度和耐水性能,其中以磷酸、粉煤灰及苯丙乳液三者复合改性效果最佳;最优改性试样的3及7d强度分别高达634.,751.MPa,软化系数高达0.9,浸水7 d,泡水强度保持在681. M Pa ,较空白样提升了60.2%,复合改性效果显著。

  7. Experimental study of the mechanical stabilization of electric arc furnace dust using fluid cement mortars.

    Science.gov (United States)

    Ledesma, E F; Jiménez, J R; Ayuso, J; Fernández, J M; Brito, J de

    2017-03-15

    This article shows the results of an experimental study carried out in order to determine the maximum amount of electric arc furnace dust (EAFD) that can be incorporated into fluid cement-based mortars to produce mechanically stable monolithic blocks. The leaching performance of all mixes was studied in order to classify them according to the EU Council Decision 2003/33/EC. Two mortars were used as reference and three levels of EAFD incorporation were tested in each of the reference mortars. As the incorporation ratio of EAFD/cement increases, the mechanical strength decreases. This is due to the greater EAFD/cement and water/cement ratios, besides the presence of a double-hydrated hydroxide of Ca and Zn (CaZn2(OH)6·2H2O) instead of the portlandite phase (Ca(OH)2) in the mixes made with EAFD, as well as non-hydrated tricalcium silicate. A mass ratio of 2:1 (EAFD: cement-based mortar) can be added maintaining a stable mechanical strength. The mechanical stabilization process also reduced the leaching of metals, although it was not able to reduce the Pb concentration below the limit for hazardous waste. The high amount of EAFD mechanically stabilized in this experimental study can be useful to reduce the storage volume required in hazardous waste landfills.

  8. STUDY ON HIGH CONTENT OF BLENDS IN CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

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

  9. Dynamic properties of composite cemented clay

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 梁旭

    2004-01-01

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

  10. Herschel/SPIRE observations of water production rates and ortho-to-para ratios in comets★

    Science.gov (United States)

    Wilson, Thomas G.; Rawlings, Jonathan M. C.; Swinyard, Bruce M.

    2017-04-01

    This paper presents Herschel/SPIRE (Spectral and Photometric Imaging Receiver) spectroscopic observations of several fundamental rotational ortho- and para-water transitions seen in three Jupiter-family comets and one Oort-cloud comet. Radiative transfer models that include excitation by collisions with neutrals and electrons, and by solar infrared radiation, were used to produce synthetic emission line profiles originating in the cometary coma. Ortho-to-para ratios (OPRs) were determined and used to derived water production rates for all comets. Comparisons are made with the water production rates derived using an OPR of 3. The OPR of three of the comets in this study is much lower than the statistical equilibrium value of 3; however they agree with observations of comets 1P/Halley and C/2001 A2 (LINEAR), and the protoplanetary disc TW Hydrae. These results provide evidence suggesting that OPR variation is caused by post-sublimation gas-phase nuclear-spin conversion processes. The water production rates of all comets agree with previous work and, in general, decrease with increasing nucleocentric offset. This could be due to a temperature profile, additional water source or OPR variation in the comae, or model inaccuracies.

  11. Mobile lidar system for measurement of water vapor mixing ratio and ozone number density

    Science.gov (United States)

    Whiteman, D.

    1988-01-01

    The Water Vapor Lidar was modified and extended to make differential absorption measurements of ozone. Water vapor measurements make use of a weak molecular scattering process known as Raman scattering. It is characterized by a shift in wavelength of the scattered beam of light relative to the incident one. Some of the energy of the incident photon is converted to vibrational or rotational energy within the molecule leaving the scattered photon shifted to a slightly longer wavelength. When performing water vapor measurements, profiles are acquired of water vapor mixing ratio from near the ground to beyond 7 km every 2 minutes. By forming a color composite image of the individual profiles, the spatial and temporal evolution of water vapor is visible with vertical resolution of 75 to 150m and temporal resolution of 2 minutes. The ozone lidar is intended for use as a cross calibration facility for other stationary ozone lidar systems. The ozone measurement employs the technique known as differential absorption. The backscattered laser radiation from two different wavelengths is measured. Successful measurements of 308 nm returns were made from 80 km with an averaging period of 6 hours. Using these data and a standard atmosphere density curve, an ozone number density profile was made which agrees very well with the standard ozone curve between 20 and 40 km.

  12. Ortho-to-para ratio in interstellar water on the sightline toward Sagittarius B2(N).

    Science.gov (United States)

    Lis, Dariusz C; Bergin, Edwin A; Schilke, Peter; van Dishoeck, Ewine F

    2013-10-03

    The determination of the water ortho-to-para ratio (OPR) is of great interest for studies of the formation and thermal history of water ices in the interstellar medium and protoplanetary disk environments. We present new Herschel observations of the fundamental rotational transitions of ortho- and para-water on the sightline toward Sagittarius B2(N), which allow improved estimates of the measurement uncertainties due to instrumental effects and assumptions about the excitation of water molecules. These new measurements, suggesting a spin temperature of 24-32 K, confirm the earlier findings of an OPR below the high-temperature value on the nearby sightline toward Sagittarius B2(M). The exact implications of the low OPR in the galactic center molecular gas remain unclear and will greatly benefit from future laboratory measurements involving water freeze-out and evaporation processes under low-temperature conditions, similar to those present in the galactic interstellar medium. Given the specific conditions in the central region of the Milky Way, akin to those encountered in active Galactic nuclei, gas-phase processes under the influence of strong X-ray and cosmic ray ionization also have to be carefully considered. We summarize some of the latest laboratory measurements and their implications here.

  13. Bacterial spore heat resistance correlated with water content, wet density, and protoplast/sporoplast volume ratio.

    Science.gov (United States)

    Beaman, T C; Greenamyre, J T; Corner, T R; Pankratz, H S; Gerhardt, P

    1982-05-01

    Five types of dormant Bacillus spores, between and within species, were selected representing a 600-fold range in moist-heat resistance determined as a D100 value. The wet and dry density and the solids and water content of the entire spore and isolated integument of each type were determined directly from gram masses of material, with correction for interstitial water. The ratio between the volume occupied by the protoplast (the structures bounded by the inner pericytoplasm membrane) and the volume occupied by the sporoplast (the structures bounded by the outer pericortex membrane) was calculated from measurements made on electron micrographs of medially thin-sectioned spores. Among the various spore types, an exponential increase in the heat resistance correlated directly with the wet density and inversely with the water content and with the protoplast/sporoplast volume ratio. Altogether with results supported a hypothesis that the extent of heat resistance is based in whole or in part on the extent of dehydration and diminution of the protoplast in the dormant spore, without implications about physiological mechanisms for attaining this state.

  14. Development and Airborne Operation of a Compact Water Isotope Ratio Infrared Spectrometer

    Science.gov (United States)

    Iannone, Rosario Q.; Kassi, Samir; Jost, Hans-Juerg; Chenevier, Marc; Romanini, Daniele; Meijer, Harro A. J.; Dhaniyala, Suresh; Snels, Marcel; Kerstel, Erik R. T.

    2009-01-01

    A sensitive laser spectrometer, named IRIS (water isotope ratio infrared spectrometer), was developed for the in situ detection of the isotopic composition of water vapour in the upper troposphere and the lower stratosphere. Isotope ratio measurements can be used to quantify troposphere stratosphere exchange, and to study the water chemistry in the stratosphere. IRIS is based on the technique of optical feedback cavity-enhanced absorption spectroscopy. It uses a room temperature near-infrared laser, and does not require cryogenic cooling of laser or detectors. The instrument weighs 51 kg including its support structure. Airborne operation was demonstrated during three flights aboard the European M55-Geophysica stratospheric research aircraft, as part of the AMMA/SCOUT-03 (African Monsoon Multidisciplinary Analysis/Stratospheric Climate links with emphasis on the Upper Troposphere and lower stratosphere) campaign in Burkina Faso in August 2006. The data are discussed with reference to a Rayleigh distillation model. As expected, there is no indication of non-mass-dependent fractionation (also known as mass-independent fractionation) in the troposphere. Furthermore, improvements to the thermal management system and a move to a (cryogen-free) longer-wavelength laser source are discussed, which together should result in approximately two orders of magnitude improvement of the sensitivity

  15. Physical and Chemical Aspects of the Nucleation of Cement-Based Materials

    Directory of Open Access Journals (Sweden)

    Pavel Demo

    2012-01-01

    Full Text Available A theoretical model of the nucleation of portlandite is proposed, and the critical size of a portlandite cluster and the energy barrier of nucleation are determined. The steady state nucleation rate and the time lag of the nucleation of portlandite are estimated for a pure solution of Ca(OH2 in water. Possible connections with the corresponding properties for cement paste are discussed. A new method is developed for experimentally determining the concentration of Ca2+ ions during the initial stage of hydration of a cement paste. The time dependence of Ca2+ ions is measured for various water-to-cement ratio values. The results are discussed from the point of view of existing models of the induction period.

  16. Corrosion behavior of steel in concrete made with slag-blended cement

    Energy Technology Data Exchange (ETDEWEB)

    Dehghanian, C. [Univ. of Technology, Isfahan (Iran, Islamic Republic of). Dept. of Chemical Engineering

    1999-03-01

    Concretes formulated with slag as a partial replacement for cement were used to evaluate the corrosion behavior of steel embedded in concrete, resistivity, and the compressive strength of the concrete. Corrosion rates and pitting corrosion of steel in concrete with up to 30% slag and exposed to sodium chloride (NaCl) solutions decreased. Slag-blended cement concrete increased concrete resistivity. A water-to-cement ratio <0.55 and submersion in water for a period of 18 days gave the best chloride (Cl{sup {minus}}) diffusion resistance from the external salt solutions. Compressive strength of the concrete decreased with addition of slag in the early ages of the concrete. After 5 months of age, compressive strength of the concrete increased with addition of slag. This trend continued with up to 30% slag addition.

  17. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  18. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

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

  19. 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

  20. Online stable carbon isotope ratio measurement in formic acid, acetic acid, methanol and ethanol in water by high performance liquid chromatography-isotope ratio mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Tagami, Keiko [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)], E-mail: k_tagami@nirs.go.jp; Uchida, Shigeo [National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba 263-8555 (Japan)

    2008-05-05

    A suitable analysis condition was determined for high performance liquid chromatography-isotope ratio mass spectrometry (HPLC-IRMS) while making sequential measurements of stable carbon isotope ratios of {delta}{sup 13}C in formic acid, acetic acid, methanol and ethanol dissolved in water. For this online column separation method, organic reagents are not applicable due to carbon contamination; thus, water and KH{sub 2}PO{sub 4} at low concentrations were tested as mobile phase in combination with a HyPURITY AQUASTAR{sup TM} column. Formic acid, acetic acid, methanol and ethanol were separated when 2 mM KH{sub 2}PO{sub 4} aqueous solution was used. Under the determined analysis condition for HPLC-IRMS, carbon concentrations could be measured quantitatively as well as carbon isotope ratio when carbon concentration was higher than 0.4 mM L for each chemical.

  1. Determining water sources in the boundary layer from tall tower profiles of water vapor and surface water isotope ratios after a snowstorm in Colorado

    Directory of Open Access Journals (Sweden)

    D. Noone

    2013-02-01

    Full Text Available The D/H isotope ratio is used to attribute boundary layer humidity changes to the set of contributing fluxes for a case following a snowstorm in which a snow pack of about 10 cm vanished. Profiles of H2O and CO2 mixing ratio, D/H isotope ratio, and several thermodynamic properties were measured from the surface to 300 m every 15 min during four winter days near Boulder, Colorado. Coeval analysis of the D/H ratios and CO2 concentrations find these two variables to be complementary with the former being sensitive to daytime surface fluxes and the latter particularly indicative of nocturnal surface sources. Together they capture evidence for strong vertical mixing during the day, weaker mixing by turbulent bursts and low level jets within the nocturnal stable boundary layer during the night, and frost formation in the morning. The profiles are generally not well described with a gradient mixing line analysis because D/H ratios of the end members (i.e., surface fluxes and the free troposphere evolve throughout the day which leads to large uncertainties in the estimate of the D/H ratio of surface water flux. A mass balance model is constructed for the snow pack, and constrained with observations to provide an optimal estimate of the partitioning of the surface water flux into contributions from sublimation, evaporation of melt water in the snow and evaporation from ponds. Results show that while vapor measurements are important in constraining surface fluxes, measurements of the source reservoirs (soil water, snow pack and standing liquid offer stronger constraint on the surface water balance. Measurements of surface water are therefore essential in developing observational programs that seek to use isotopic data for flux attribution.

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

    Science.gov (United States)

    Park, Jung-Hui; Lee, Eun-Jung; Knowles, Jonathan C; Kim, Hae-Won

    2014-03-01

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

  3. Durability Index Performance of High Strength Concretes Made Based on Different Standard Portland Cements

    Directory of Open Access Journals (Sweden)

    Stephen O. Ekolu

    2012-01-01

    Full Text Available A consortium of three durability index test methods consisting of oxygen permeability, sorptivity and chloride conductivity were used to evaluate the potential influence of four (4 common SANS 10197 cements on strength and durability of concrete. Twenty four (24 concrete mixtures of water-cement ratios (w/c's = 0.4, 0.5, 0.65 were cast using the cement types CEM I 42.5N, CEM II/A-M (V-L 42.5N, CEM IV/B 32.5R and CEM II/A-V 52.5N. The concretes investigated fall in the range of normal strength, medium strength and high strength concretes. It was found that the marked differences in oxygen permeability and sorptivity results observed at normal and medium strengths tended to vanish at high concrete strengths. Also, the durability effects attributed to use of different cement types appear to diminish at high strengths. Cements of low strength and/or that contained no extenders (CEM 32.5R, CEM I 42.5N showed greater sensitivity to sorptivity, relative to other cement types. Results also show that while concrete resistance to chlorides generally improves with increase in strength, adequately high chloride resistance may not be achieved based on high strength alone, and appropriate incorporation of extenders may be necessary.

  4. Performance of Laterite-Cement Blocks as Walling Units in Relation to Sandcrete Blocks

    Directory of Open Access Journals (Sweden)

    James Isiwu AGUWA

    2010-12-01

    Full Text Available A study of the performance of laterite-cement blocks as walling materials in relation to those of sandcrete was conducted, for the purpose of establishing a cheaper building material in Minna, Niger state, Nigeria and surrounding towns, in the present ever increasing cost of building material. An A-2-6 laterite according to the AASHTO classification system was stabilized with 0-10% cement content by weight of the soil at a constant interval of 2% to produce 20 blocks of size 100mm × 100mm × 100mm for each mix. One hundred laterite-cement blocks were produced, cured under laboratory conditions and subjected to compressive strength test at 7, 14, 21, and 28-days of age, in five applications for each cement mix ratio. The average compressive strength was determined from five blocks crushed in each mix at every age of curing and the same procedure was repeated using sandcrete blocks. At a common cement content of 6%, the compressive strengths, densities, water absorption and the cost per square metre of wall for both types of blocks were determined. The study recommends the use of laterite-cement blocks as walling materials in Minna and environs because it has better engineering properties and more economical with a saving of 30% per square metre of wall when compared with the use of sandcrete blocks.

  5. CHRONIC ZINC SCREENING WATER EFFECT RATIO FOR THE H-12 OUTFALL, SAVANNAH RIVER SITE

    Energy Technology Data Exchange (ETDEWEB)

    Coughlin, D.; Looney, B.; Millings, M.

    2009-01-13

    In response to proposed Zn limits for the NPDES outfall H-12, a Zn screening Water Effects Ratio (WER) study was conducted to determine if a full site-specific WER is warranted. Using standard assumptions for relating the lab results to the stream, the screening WER data were consistent with the proposed Zn limit and suggest that a full WER would result in a similar limit. Addition of a humate amendment to the outfall water reduced Zn toxicity, but the toxicity reduction was relatively small and unlikely to impact proposed Zn limits. The screening WER data indicated that the time and expense required to perform a full WER for Zn is not warranted.

  6. Chemical stability of seven years aged cement-PET composite waste form containing radioactive borate waste simulates

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, H.M., E-mail: hosamsaleh70@yahoo.com [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt); Tawfik, M.E. [Department of Polymers and Pigments, National Research Center, Dokki (Egypt); Bayoumi, T.A. [Radioisotope Department, Atomic Energy Authority, Dokki (Egypt)

    2011-04-15

    Different samples of radioactive borate waste simulate [originating from pressurized water reactors (PWR)] have been prepared and solidified after mixing with cement-water extended polyester composite (CPC). The polymer-cement composite samples were prepared from recycled poly (ethylene terephthalate) (PET) waste and cement paste (water/cement ratio of 40%). The prepared samples were left to set at room temperature (25 deg. C {+-} 5) under humid conditions. After 28 days curing time the obtained specimens were kept in their molds to age for 7 years under ambient conditions. Cement-polymer composite waste form specimens (CPCW) have been subjected to leach tests for both {sup 137}Cs and {sup 60}Co radionuclides according to the method proposed by the International Atomic Energy Agency (IAEA). Leaching tests were justified under various factors that may exist within the disposal site (e.g. type of leachant, surrounding temperature, leachant behavior, the leachant volume to CPCW surface area...). The obtained data after 260 days of leaching revealed that after 7 years of aging the candidate cement-polymer composite (CPC) containing radioactive borate waste samples are characterized by adequate chemical stability required for the long-term disposal process.

  7. Chemical stability of seven years aged cement-PET composite waste form containing radioactive borate waste simulates

    Science.gov (United States)

    Saleh, H. M.; Tawfik, M. E.; Bayoumi, T. A.

    2011-04-01

    Different samples of radioactive borate waste simulate [originating from pressurized water reactors (PWR)] have been prepared and solidified after mixing with cement-water extended polyester composite (CPC). The polymer-cement composite samples were prepared from recycled poly (ethylene terephthalate) (PET) waste and cement paste (water/cement ratio of 40%). The prepared samples were left to set at room temperature (25 °C ± 5) under humid conditions. After 28 days curing time the obtained specimens were kept in their molds to age for 7 years under ambient conditions. Cement-polymer composite waste form specimens (CPCW) have been subjected to leach tests for both 137Cs and 60Co radionuclides according to the method proposed by the International Atomic Energy Agency (IAEA). Leaching tests were justified under various factors that may exist within the disposal site (e.g. type of leachant, surrounding temperature, leachant behavior, the leachant volume to CPCW surface area…). The obtained data after 260 days of leaching revealed that after 7 years of aging the candidate cement-polymer composite (CPC) containing radioactive borate waste samples are characterized by adequate chemical stability required for the long-term disposal process.

  8. Effect of glass and polyacid preparations on the strength of glass ionomer cements for dental applications

    Directory of Open Access Journals (Sweden)

    Naruporn Monmaturapoj

    2009-08-01

    Full Text Available Glass ionomer cements (GICs, widely used as restorative materials in dentistry, are principally composed of fluoroaluminosilicateglass powder combined with a water-soluble polyacid. The investigation of new glass compositions and polyacid components are very important to improve the mechanical properties of these cements. The objective of this work was to prepare glass ionomers and polyacids for the use as GICs. The effects of spherical bodies, Al2O3:SiO2 ratios, replacing CaO by SrO, and ZrO2 adding in glass powder in combination with the variation of acidic copolymer concentration on the compressive strength were investigated and discussed.

  9. Comparison of Temperature Field Distribution between Cement Preclinkering Technology and Cement Precalcining Technology

    Institute of Scientific and Technical Information of China (English)

    XU Xun; WANG Lan

    2016-01-01

    Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology, we studied the characteristics of temperature ifeld distribution of cement preclinkering technology systems including cyclone preheater, preclinkering furnace, and rotary kiln. We used numerical simulation method to obtain data of temperature ifeld distribution.Some results are found by system study. The ratio of tail coal of cement preclinkering technology is about 70%, and raw meal temperature can reach 1070℃. ShorterL/D kiln type of preclinkering technology can obtain more stable calcining zone temperature. The highest solid temperature of cement preclinkering technology is higher than 80℃, and high temperature region (>1450℃) length is 2 times, which is beneifcial for calcining clinker and higher clinker quality. So cement preclinkering technology can obtain more performance temperature ifled, which improves both the solid-phase reaction and liquid-phase reaction.

  10. 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.

  11. Determination of the products coming from the cellulose hydrolysis by a cement water; Identification et caracterisation des produits d'hydrolyse de la cellulose par une eau cimentaire

    Energy Technology Data Exchange (ETDEWEB)

    Motelier, S.; Charles, Y.; Richet, C.; Ayache, R. [CEA Saclay, Dept. d' Entreposage et de Stockage des Dechets, 91 - Gif-sur-Yvette (France)

    2001-07-01

    Capillary electrophoresis is a useful method to separate the degradation products of cellulose in cement water medium and to quantify their acid-base and complexing properties. The perfected method can be applied to all the cations having relatively soluble hydroxides. (O.M.)

  12. A Moderate D/H Ratio for a Surficial Water Reservoir on Mars

    Science.gov (United States)

    Usui, Tomohiro; Alexander, C. M. O. D.; Wang, J.; Simon, J. I.; Jones, J. H.

    2013-01-01

    Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface and that water played a significant role in the formation of weathered/altered terrains [e.g., 1, 2, 3]. Volatiles exhaled by volcanic activity would have been the dominant greenhouse gases and would have significantly affected the Martian climate. The enrichment of some volatile elements in the atmosphere, which would have dissolved in surface water, could also have influenced water chemistry (e.g., acidity) and played a significant role in weathering and aqueous alteration processes. While much of this picture is qualitative, Martian meteorites contain records of major Martian volatile reservoirs. This study characterizes Martian surficial volatile reservoirs based on in situ ion microprobe analyses of volatile abundances and H-isotopes of glassy phases (groundmass glass [GG] and impact melt [IM]) in Martian basalts (shergottites). Although these meteorites are of igneous origin, some glassy phases underwent impact-induced modification that trapped surficial and atmospheric volatile components [4, 5]; e.g., inert gases contained in IMs from EETA79001 (EETA79) match the relative abundances of modern Martian atmosphere [6]. Analyses of these glassy phases demonstrate that surficial volatile reservoirs have distinct D/H ratios from their magmatic volatiles.

  13. Physical, chemical and mineralogical characterization of water treatment plant waste for use in soil-cement brick; Caracterizacao fisica, quimica e mineralogica de residuo de estacao de tratamento de aguas para aproveitamento em tijolo solo-cimento

    Energy Technology Data Exchange (ETDEWEB)

    Pessin, L.R.; Destefani, A.Z.; Holanda, J.N.F., E-mail: larapessin@hotmail.com [Universidade Estadual do Norte Fluminense Darcy Ribeiro (CCT/PPGECM/UENF), Campos dos Goytacazes, RJ (Brazil)

    2011-07-01

    The water treatment plants (WTP) for human consumption generate huge amounts of waste in the form of sludge (sludge) that have been over the years mostly inadequately prepared in water resources and the environment. Moreover, traditional methods of disposal of waste water treatment plants commonly used are generally costly activities. An alternative method for disposal of this waste abundant is its incorporation in ceramic products. This work is focused on the physical-chemical and mineralogical composition of a sample of waste water treatment plants from the region of Campos dos Goytacazes-RJ to their use in the manufacture of soil-cement brick. Several characterization techniques were used including X-ray diffraction, X-ray fluorescence, scanning electron microscopy, picnometry, particle size analysis and plasticity. The experimental results indicate that the waste water treatment plants have the potential to be used in the manufacture of ecologic soil-cement bricks. (author)

  14. Hydrochemistry and 18O/16O and 2H/1H Ratios of Ugandan Waters

    Science.gov (United States)

    Gebremichael, M. G.; Jasechko, S.

    2013-12-01

    Today, 70% of the 35 million people living in Uganda have access to an improved water source, ranking Uganda 148 out of 179 nations reporting in 2010 (Millennium Development Goals Indicators). 80% of Ugandans rely on groundwater as their primary drinking water source, collecting at springs or from shallow wells. Similarly, 80% of Ugandans rely upon agriculture - usually rain fed - as their primary income source. Despite lack of access to protected water sources faced by 10 million Ugandans, and the importance of the blue economy to Uganda's continued development, a country-wide investigation of the chemistry and the stable oxygen and hydrogen isotope compositions of waters has yet to be completed. Here we present 250 analyses of 18O/16O, 2H/1H and dissolved ion concentrations of Ugandan lakes, rivers, groundwaters and springs collected during July, 2013. We use the new data to characterize regional scale groundwater recharge sources, advection pathways and interactions with surface waters. Large lakes - Albert, Edward and Victoria - show increases in 18O/16O and 2H/1H ratios consistent with open water evaporation, and are shown to be distinct from nearby groundwaters, suggesting minimal recharge from large lakes to the subsurface. Salinities of eastern Ugandan groundwaters are elevated relative to samples collected from the central and western regions, suggesting that longer groundwater residence times and enhanced water-rock interactions characterize these waters. Springs from western Uganda show a shift in 18O/16O to higher values as a result of hydrothermal water-rock exchanges. Dissolved ion and noble gas concentrations show potential for use in assessing geothermal energy resources, perhaps aiding the Ugandan Ministry for Energy, Minerals and Development to meet their goal of increasing renewable energy from 4% (current) to 61% of total use by 2017 (Nyakabwa-Atwoki, 2013). Millennium Development Goals Indicators. mdgs.un.org/unsd/mdg/data.aspx Nyakabwa

  15. The effect of zeolite treatment by acids on sodium adsorption ratio of coal seam gas water.

    Science.gov (United States)

    Wang, Xiaoyu; Ozdemir, Orhan; Hampton, Marc A; Nguyen, Anh V; Do, Duong D

    2012-10-15

    Many coal seam gas (CSG) waters contain a sodium ion concentration which is too high relative to calcium and magnesium ions for environment acceptance. Natural zeolites can be used as a cheap and effective method to control sodium adsorption ratio (SAR, which is a measure of the relative preponderance of sodium to calcium and magnesium) due to its high cation exchange capacity. In this study, a natural zeolite from Queensland was examined for its potential to treat CSG water to remove sodium ions to lower SAR and reduce the pH value. The results demonstrate that acid activated zeolite at 30%wt solid ratio can reduce the sodium content from 563.0 to 182.7 ppm; the pH from 8.74 to 6.95; and SAR from 70.3 to 18.5. Based on the results of the batch experiments, the sodium adsorption capacity of the acid-treated zeolite is three times greater than that of the untreated zeolite. Both the untreated and acid-treated zeolite samples were characterized using zeta potential, surface characterization, DTA/TG and particle size distribution in order to explain their adsorption behaviours.

  16. Migration of ions in cement paste as studied by SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Prince, K.E.; Aldridge, L.P. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); Rougeron, P. [Electricite de France Direction des Etudes et Recherches, Les Renardiers (France)

    1998-06-01

    Cement is often used to condition and encapsulate low level radioactive waste before it is disposed of in a repository. Ground water can attack these waste-forms by transporting aggressive ions into the cement paste and by removing radioactive ions from the paste. The extent of the attack will be governed by the diffusion of the ions in the cement paste. In this study we examine the migration of aggressive carbonate ions and inactive Cs and Sr through cement pastes. The use of SIMS for establishing the penetration depths and diffusion profiles for Cs and Sr in cement will be explored. The penetration profiles of Cs and Sr in a non-zeolite cement paste were examined and compared to those of a paste made with zeolite. The effects of the non-homogeneous nature of the cement was most pronounced in the study of the zeolite rich cement; Cs being preferentially accumulated in the zeolite material. (authors). 4 refs., 2 figs.

  17. A non-destructive test method to monitor corrosion products and corrosion-induced cracking in reinforced cement based materials

    DEFF Research Database (Denmark)

    Michel, Alexander; Pease, Bradley Justin; Peterova, Adela;

    2011-01-01

    ) was conducted to describe the impact of water-to-cement ratio and corrosion current density (i.e., corrosion rate) on the reinforcement corrosion process. Focus was placed, in particular on the determination of the corrosion accommodating region (CAR) and time to corrosion-induced cracking. Experimental results...

  18. A void ratio dependent water retention curve model including hydraulic hysteresis

    Directory of Open Access Journals (Sweden)

    Pasha Amin Y.

    2016-01-01

    Full Text Available Past experimental evidence has shown that Water Retention Curve (WRC evolves with mechanical stress and structural changes in soil matrix. Models currently available in the literature for capturing the volume change dependency of WRC are mainly empirical in nature requiring an extensive experimental programme for parameter identification which renders them unsuitable for practical applications. In this paper, an analytical model for the evaluation of the void ratio dependency of WRC in deformable porous media is presented. The approach proposed enables quantification of the dependency of WRC on void ratio solely based on the form of WRC at the reference void ratio and requires no additional parameters. The effect of hydraulic hysteresis on the evolution process is also incorporated in the model, an aspect rarely addressed in the literature. Expressions are presented for the evolution of main and scanning curves due to loading and change in the hydraulic path from scanning to main wetting/drying and vice versa as well as the WRC parameters such as air entry value, air expulsion value, pore size distribution index and slope of the scanning curve. The model is validated using experimental data on compacted and reconstituted soils subjected to various hydro-mechanical paths. Good agreement is obtained between model predictions and experimental data in all the cases considered.

  19. Monte Carlo based water/medium stopping-power ratios for various ICRP and ICRU tissues.

    Science.gov (United States)

    Fernández-Varea, José M; Carrasco, Pablo; Panettieri, Vanessa; Brualla, Lorenzo

    2007-11-07

    Water/medium stopping-power ratios, s(w,m), have been calculated for several ICRP and ICRU tissues, namely adipose tissue, brain, cortical bone, liver, lung (deflated and inflated) and spongiosa. The considered clinical beams were 6 and 18 MV x-rays and the field size was 10 x 10 cm(2). Fluence distributions were scored at a depth of 10 cm using the Monte Carlo code PENELOPE. The collision stopping powers for the studied tissues were evaluated employing the formalism of ICRU Report 37 (1984 Stopping Powers for Electrons and Positrons (Bethesda, MD: ICRU)). The Bragg-Gray values of s(w,m) calculated with these ingredients range from about 0.98 (adipose tissue) to nearly 1.14 (cortical bone), displaying a rather small variation with beam quality. Excellent agreement, to within 0.1%, is found with stopping-power ratios reported by Siebers et al (2000a Phys. Med. Biol. 45 983-95) for cortical bone, inflated lung and spongiosa. In the case of cortical bone, s(w,m) changes approximately 2% when either ICRP or ICRU compositions are adopted, whereas the stopping-power ratios of lung, brain and adipose tissue are less sensitive to the selected composition. The mass density of lung also influences the calculated values of s(w,m), reducing them by around 1% (6 MV) and 2% (18 MV) when going from deflated to inflated lung.

  20. The HCN-Water Ratio in the Planet Formation Region of Disks

    CERN Document Server

    Najita, Joan R; Pontoppidan, Klaus M; Salyk, Colette; van Dishoeck, Ewine F; Blake, Geoffrey A

    2013-01-01

    We find a trend between the mid-infrared HCN/H2O flux ratio and submillimeter disk mass among T Tauri stars in Taurus. While it may seem puzzling that the molecular emission properties of the inner disk (< few AU) are related to the properties of the outer disk (beyond ~20 AU) probed by the submillimeter continuum, an interesting possible interpretation is that the trend is a result of planetesimal and protoplanet formation. Because objects this large are decoupled from the accretion flow, when they form, they can lock up water (and oxygen) beyond the snow line, thereby enhancing the C/O ratio in the inner disk and altering the molecular abundances there. We discuss the assumptions that underlie this interpretation, a possible alternative explanation, and related open questions that motivate future work. Whatever its origin, understanding the meaning of the relation between the HCN/H2O ratio and disk mass is of interest as trends like this among T Tauri disk properties are relatively rare.

  1. Proportions of convective and stratiform precipitation revealed in water isotope ratios

    Science.gov (United States)

    Aggarwal, Pradeep K.; Romatschke, Ulrike; Araguas-Araguas, Luis; Belachew, Dagnachew; Longstaffe, Frederick J.; Berg, Peter; Schumacher, Courtney; Funk, Aaron

    2016-08-01

    Tropical and midlatitude precipitation is fundamentally of two types, spatially limited and high-intensity convective or widespread and lower-intensity stratiform, owing to differences in vertical air motions and microphysical processes governing rain formation. These processes are difficult to observe or model and precipitation partitioning into rain types is critical for understanding how the water cycle responds to changes in climate. Here, we combine two independent data sets--convective and stratiform precipitation fractions, derived from the Tropical Rainfall Measuring Mission satellite or synoptic cloud observations, and stable isotope and tritium compositions of surface precipitation, derived from a global network--to show that isotope ratios reflect rain type proportions and are negatively correlated with stratiform fractions. Condensation and riming associated with boundary layer moisture produces higher isotope ratios in convective rain, along with higher tritium when riming in deep convection occurs with entrained air at higher altitudes. On the basis of our data, stable isotope ratios can be used to monitor changes in the character of precipitation in response to periodic variability or changes in climate. Our results also provide observational constraints for an improved simulation of convection in climate models and a better understanding of isotope variations in proxy archives, such as speleothems and tropical ice.

  2. Signal to noise ratio in water balance maps with different resolution

    Science.gov (United States)

    Yan, Ziqi; Gottschalk, Lars; Wang, Jianhua

    2016-12-01

    What is the best resolution of annual water balance maps for a correct balance between the basic spatial signal in the observations of precipitation, actual evapotranspiration and runoff across a larger drainage basin and the error in estimates for grid cells in the map to avoid giving a false impression of accuracy? To answer this question an approach based a signal to noise ratio is proposed, which allows finding the optimal resolution maximizing the signal in the map. The approach is demonstrated on gauge data in the Huai River Basin, China. Stochastic interpolation methods were applied to create grid maps of long-term mean values, as well as for estimating variances of the three water balance components in a range of scales from 5 × 5 km to 200 × 200 km2 grid cells. Interpolation algorithms using covariances of long-term means of data with different spatial support were developed. The identified optimal resolutions by the signal to noise ratio appeared to be very different - 10 × 10, 50 × 50, and 30 × 30 km2 for precipitation, actual evapotranspiration, and runoff, respectively. These values are directly linked to the observation network densities. The magnitude of the signal to noise ratio shows similar strong differences with values 34, 3.7, and 5.4, respectively. It gives a direct indication of the reliability of the map, which can be considered as satisfactory only for precipitation for the data available for the present study. The critical factors for this magnitude are parameters characterising the spatial covariance in data and the network density.

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

    Science.gov (United States)

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

    2013-12-01

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

  4. 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.

  5. Microstructural evaluation of oil well cementing slurries using alternative materials

    Energy Technology Data Exchange (ETDEWEB)

    Paiva, Maria D.M.; Melo, Dulce M.A.; Martinelli, Antonio E. [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2004-07-01

    n this work, cementing slurries were prepared with densities between 12.2 and 13.8 lb/gal with addition of clay materials (vermiculite and paligorskite) and pozzolans (metakaolin), comparing with neat reference slurries, from 15.6 to 15.8 lb/gal. The cements employed were the Portland G and ordinary Portland. These mixes were evaluated microstructurally through microhardness testing and acquisition of electronic images by ESEM and X-ray maps by EDS. A semi-quantitative analysis software was developed to identify phase distributions from the X-ray maps. It was found that the addition of metakaolin generated slurries with microhardness comparable to or superior to neat slurries, although a new phase was introduced in the hardened material. On the other hand, clay materials generated slurries with lower microhardness. It was observed in these cases a lower hydration degree, possibly due to water absorption by the clays' grains. One exception was the light slurry with paligorskite, which has an excess of water compared to the others. However, the higher water-cement ratio produced a lower microhardness due to the presence of voids, visible by ESEM. Clay inclusions also decreased the microhardness of the slurries. Based on these results, we can recommend metakaolin as the best performing addition to be further evaluated in the field. (author)

  6. EVALUATION OF CEMENT-BONDED PARTICLE BOARD PRODUCED FROM AFZELIA AFRICANA WOOD RESIDUES

    Directory of Open Access Journals (Sweden)

    OLUFEMI A. SOTANNDE

    2012-12-01

    Full Text Available The study was design to evaluate the physical and mechanical properties of cement-bonded particleboards produced from Afzelia africana wood residues. The production variables investigated were three wood particle types (flakes, flake-sawdust mix and sawdust, three chemical accelerators (CaCl2, MgCl2 and AlCl3 and four wood-cement ratios (1:2.0, 1:2.5, 1:3.0 and 1:3.5. The accelerators were based on 2% by weight of cement used. The boards produced were subjected to physical tests such as density, percentage water absorption and thickness swelling. Mechanical properties evaluated were modulus of rupture, internal bonding strength and compressive strength. The results revealed that the type of particle used, wood-cement ratio and chemical additives had a marked influence on the physical and mechanical properties of the boards (p < 0.05. From quality view point, flake-sawdust composite ranked best while flake boards ranked least. Similarly, CaCl2 had the best influence on the setting of the boards followed by MgCl2 and AlCl3. Finally, it has been shown that particle boards that satisfied the BISON type HZ requirement and ISO 8335 can be produced from Afzelia africana particularly at wood-cement of 1:2.5 and above.

  7. Study on similar model of high pressure water jet impacting coal rock

    Science.gov (United States)

    Liu, Jialiang; Wang, Mengjin; Zhang, Di

    2017-08-01

    Based on the similarity theory and dimensional analysis, the similarity criterion of the coal rock mechanical parameters were deduced. The similar materials were mainly built by the cement, sand, nitrile rubber powder and polystyrene, by controlling the water-cement ratio, cement-sand ratio, curing time and additives volume ratio. The intervals of the factors were obtained by carrying out series of material compression tests. By comparing the basic mechanical parameters such as the bulk density, compressive strength, Poisson ratio and elastic modulus between the coal rock prototype and similar materials, the optimal producing proposal of the coal rock similar materials was generated based on the orthogonal design tests finally.

  8. Detection of water molecules in inert gas based plasma by the ratios of atomic spectral lines

    Science.gov (United States)

    Bernatskiy, A. V.; Ochkin, V. N.

    2017-01-01

    A new approach is considered to detect the water leaks in inert plasma-forming gas present in the reactor chamber. It is made up of the intensity ratio of D α and H α spectral lines in combination with O, Ar and Xe lines intensity. The concentrations of H2O, O, H and D particles have been measured with high sensitivity. At the D2 admixture pressure {{p}{{\\text{D}\\text{2}}}}   =  0.025 mbar, we used the acquisition time of 10 s to measure the rate of water molecules injected from the outside, Γ0  =  1.4 · 10-9 mbar · m3 · s-1, and the incoming water molecules to plasma, Γ  =  5 ·10-11 mbar · m3 · s-1. The scaling proves that at small D2 admixtures (10-4 mbar), the leaks with the rates Γ0  ≈  6 · 10-12 mbar · m3 · s-1 and Γ  ≈  2 · 10-13 mbar · m3 · s-1 can be detected and measured. The difference between Γ0 and Γ values is due to the high degree of H2O dissociation, which can be up to 97-98%.

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

    Directory of Open Access Journals (Sweden)

    Antonio López-Uceda

    2016-01-01

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

  10. 磷酸镁水泥耐水性能改善的研究%Researching on Water Resistance Improvement of Magnesium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    毛敏; 王智; 贾兴文

    2012-01-01

    Magnesium phosphate cement(MPC) is a novel cementing material characterized by Early strength and fast hard. The present researches refer to the chemical composition, hydration mechanism, mechanic and repairing performance of MPC while seldom come to the water resistance. This paper compared the water resistance of MPC with different amount of aluminum salt, ferric salt, coal ash and outer waterproof agent. The results indicated that aluminum salt, ferric salt, coal ash and outer waterproof agent can all improve the water resistance of MPC in some extent. For instance, when the proportion of ferric salt was 0.50%, the strength retention of 90 d of MPC was 88.09%.when the proportion of ferric salt was 0.75%, the strength retention of 90d of MPC was 80.18%. It achieved cheerful effect about the water resistance of MPC. When the proportion of coal ash and increasing of the waterproof agent. It also improved the water resistance of MPC significantly. With the increasing of the waterproof agent, the compression strength of the solid MPC specimen is growing at the same time.%磷酸镁水泥(MPC)是一种早强快硬的新型胶凝材料.研究了不同掺量的铝盐、铁盐、粉煤灰以及外涂不同涂层防水剂对磷酸镁水泥耐水性能的影响.结果表明,90d时,铁盐掺量0.50%,强度保留率为88.09%,铝盐掺量0.75%,强度保留率为80.18%,与磷酸镁水泥基准组强度保留率56.50%相比,分别提高了31.59%和23.68%,说明对磷酸镁水泥耐水性改性效果较好;掺加粉煤灰以及外涂防水剂也能不同程度的改善磷酸镁水泥耐水性,且随着防水剂涂层的增加,MPC试件在水养条件下的抗压强度呈增长趋势.

  11. Durability and compressive strength of blast furnace slag-based cement grout for special geotechnical applications

    Directory of Open Access Journals (Sweden)

    Ortega, J. M.

    2014-03-01

    Full Text Available Special foundations, most prominently micropiles and soil anchors, are frequently used in construction today. In Spain, the grout for these special technical applications is generally prepared with portland cement, although the codes and standards in place stipulate only the minimum compressive strength required, with no mention of cement type. Those texts also establish a range of acceptable water:cement ratios. In the present study, durability and compressive strength in cement grout prepared with blast furnace slag cement at different w/c ratios are characterised and compared to the findings for a reference portland cement grout. The results show that slag grout exhibits greater durability than the portland cement material and complies with the compressive strength requirements laid down in the respective codes.Actualmente es muy frecuente el empleo de cimentaciones especiales, entre las que destacan los micropilotes y los anclajes. En España, las lechadas de cemento para estos trabajos geotécnicos especiales se preparan habitualmente con cemento Portland, aunque las diferentes normativas al respecto no restringen el tipo de cemento a emplear, siempre que se alcance una determinada resistencia a compresión. Respecto a la dosificación de las lechadas, la normativa permite emplear diferentes relaciones agua/cemento dentro de un determinado rango. En vista de ello, en este trabajo se han caracterizado las propiedades de durabilidad y resistencia a compresión de lechadas de cemento preparadas con un cemento con escoria de alto horno y con diferentes relaciones a/c, tomando como referencia de comportamiento lechadas de cemento Portland. El uso de un cemento con escoria conlleva una mejora en la durabilidad de las lechadas, cumpliendo los requisitos de resistencia a compresión establecidos por la normativa.

  12. Control of in vivo mineral bone cement degradation.

    Science.gov (United States)

    Kanter, Britta; Geffers, Martha; Ignatius, Anita; Gbureck, Uwe

    2014-07-01

    The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation.

  13. The preparation of water resistance magnesium oxychloride cement/glass fiber composite materials%耐水氯氧镁水泥/玻璃纤维复合材料的研制

    Institute of Scientific and Technical Information of China (English)

    郑亚林; 刘涛; 刘旭华; 林海燕; 阳勇福; 王玉江

    2013-01-01

    通过添加外加剂,对氯氧镁水泥进行改性,制备耐水氯氧镁水泥/玻璃纤维复合材料,实验结果表明:单一外加剂在氯氧镁水泥中有最佳掺量;磷酸的加入,可以增加氯氧镁水泥/玻璃纤维复合材料的耐水性能;减水剂与FeSO4的交互作用显著,当减水剂用量为0.25%、FeSO4用量为1.5%时复合材料的强度最高,耐水性能良好;通过外加剂的复配,可以制备耐水的氯氧镁水泥/玻璃纤维复合材料.%Magnesium oxychloride cement was modified with additive,and the water resistant magnesium oxychloride cement/glass fiber composite materials were prepared.Test results showed that:a single admixture in magnesium oxychloride cement had the best dosage; the properties of the magnesium oxychloride cement/glass fiber composite material could be increased with phosphoric acid; the interaction of water reducing agent and FeSO4 was significant,when superplasticizer dosage was 0.25% and FeSO4 dosage was 1.5%,the intensity of composite material was the highest,and water resistance was very well.The high strength,water resistance magnesium oxychloride cement/glass fiber composite material the could be prepared with additive compound

  14. Influence of vinyl acetate-versatic vinylester copolymer on the microstructural characteristics of cement pastes

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo Marmorato Gomes

    2005-03-01

    Full Text Available To understand the principles of polymer modification and its interference in the formation of some phases of Portland cement composites, several techniques are adopted such as Fourier Transform Infrared Spectroscopy and Thermogravimetric Analysis. In this study, these techniques were adopted to verify the influence of VA/VeoVA copolymer in seven pastes of high-early-strength portland cement twenty-eight days old, being four pastes with different polymer content and the same water/cement ratio, and the other three with extra water content increased by polymer content. In addition, scanning electronic microscopy was employed to verify the formation of copolymer film. The results showed possible interaction between acetate anion from the partial hydrolysis of copolymer and Ca++ ion from C2S and C3S hydration. Moreover, the magnitude of the decrease of portlandite formation is directly affected by water/cement ratio. By SEM analyses, the formation of two matrices, being one organic and the other inorganic, was also observed.

  15. Effect of Moringa oleifera-alum Ratios on Surface Water Treatment in North East Nigeria

    Directory of Open Access Journals (Sweden)

    N.E. Nwaiwu

    2011-06-01

    Full Text Available The aim of this study is to find out the optimum combination for MO and alum using alum as a coagulant aid in household treatment of natural pond surface water for domestic use. The physico-chemical properties investigated for in the raw, settled and filtered water were Ph, Total Dissolved Solids (tds, turbidity, colour and total suspended solids (tss. The various coagulant combinations with which the raw water from the pond was treated include Moringa oleifera (MO seed powder only (i.e., 100% MO, aluminium sulphate (alum only (i.e., 100% alum, 20% alum and 80% Moringa oleifera seed powder, 40% alum and 60% Moringa oleifera seed powder, 50% alum and 50% Moringa oleifera seed powder; 60% alum and 40% Moringa oleifera seed powder; and 80% alum and 20% Moringa oleifera seed powder. Five of the seven used coagulant combinations gave acceptable turbidity reduction i.e., below 10 NTU. When Moringa oleifera seed powder was used as the sole coagulant, a filter was needed to obtain an acceptable turbidity value of 7.8 NTU but there was no need for pH adjustment or correction. Moringa oleifera seed powder can be used in treating household drinking water either as a sole coagulant or in combination with alum (using the alum as a coagulant aid. The settling time for the MO seed powder is longer than that of the combined coagulants if the same results are to be obtained. The recommended ratio for the combined coagulant dose is 60% MO seed powder and 40% alum.

  16. Chronic lower respiratory diseases among demolition and cement workers

    DEFF Research Database (Denmark)

    Mølgaard, Ellen Fischer; Hannerz, Harald; Tüchsen, Finn

    2013-01-01

    To estimate standardised hospitalisation ratios (SHR) for chronic lower respiratory diseases among demolition and cement workers in Denmark, 1995-2009.......To estimate standardised hospitalisation ratios (SHR) for chronic lower respiratory diseases among demolition and cement workers in Denmark, 1995-2009....

  17. Reduction of water-oil ratio using polyacrylamides in vulgar carbonate reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Legere, R.F.

    1977-01-01

    The use of partially hydrolyzed polyacrylamides to control water production in oil wells has been attempted in various areas of North America over the past 10 yr. This use has met with various amounts of success. It is felt that a careful evaluation of past treatment techniques and materials compared to well response can provide valuable data applicable to future treatment design. The purpose of this study is to review and evaluate past treatments and to show how the information developed has been used to design specific treatments. The results of these treatments, in turn, are evaluated in an attempt to establish guidelines for engineering future treatment designs to achieve a higher success ratio. (58 refs.)

  18. Center for Cement Composite Materials

    Science.gov (United States)

    1990-01-31

    pastes have shown that the matrix is microporous; mesopores are absent unless the material is allowed to dry out. This results in water adsorption at low...only to water. When subsequently dried a portion of3 the porosity is converted to larger mesopores . • Only about one third of the cement reacts in a...Frictional sliding, in this case was characterized by a decreasing slope in the loading curve followed by hysteresis in the unload/reloading curves

  19. The Setting Chemistry of Glass Ionomer Cement

    Institute of Scientific and Technical Information of China (English)

    CHENG Hanting; LIU Hanxing; ZHANG Guoqing

    2005-01-01

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

  20. Effect of Admixtures on the Yield Stresses of Cement Pastes under High Hydrostatic Pressures

    Directory of Open Access Journals (Sweden)

    Hong Jae Yim

    2016-03-01

    Full Text Available When cement-based materials are transported at a construction site, they undergo high pressures during the pumping process. The rheological properties of the materials under such high pressures are unknown, and estimating the workability of the materials after pumping is a complex problem. Among various influential factors on the rheology of concrete, this study investigated the effect of mineral and chemical admixtures on the high-pressure rheology. A rheometer was fabricated that could measure the rheological properties while maintaining a high pressure to simulate the pumping process. The effects of superplasticizer, silica fume, nanoclay, fly ash, or ground granulated blast furnace slag were investigated when mixed with two control cement pastes. The water-to-cement ratios were 0.35 and 0.50.

  1. Properties of Cement-based Composite Materials under Different Storing Environment Temperature

    Science.gov (United States)

    Weng, T. L.; Weng, S. H.; Cho, S. W.

    2017-02-01

    This study reports on the properties of cement-based composite materials (mortars) under different storing environment temperature, as determined using the accelerated chloride migration test (ACMT). Mortars with a water/cement ratio of 0.45 and five fine aggregate volume fractions (0%, 15%, 30%, 50% and 60%) under various environment temperatures (25, 40, 60 and 80°C) were evaluated according to the passage of chloride ions through the specimens using ACMT. Calculate chloride migration coefficients on the steady-state. Cement-based composite materials with 60 % fine aggregate presented a migration coefficient higher than that of other specimens, whereas mortar with 30 % fine aggregate was lower, due to the effects of dilution and tortuosity.

  2. Effect of Admixtures on the Yield Stresses of Cement Pastes under High Hydrostatic Pressures

    Science.gov (United States)

    Yim, Hong Jae; Kim, Jae Hong; Kwon, Seung Hee

    2016-01-01

    When cement-based materials are transported at a construction site, they undergo high pressures during the pumping process. The rheological properties of the materials under such high pressures are unknown, and estimating the workability of the materials after pumping is a complex problem. Among various influential factors on the rheology of concrete, this study investigated the effect of mineral and chemical admixtures on the high-pressure rheology. A rheometer was fabricated that could measure the rheological properties while maintaining a high pressure to simulate the pumping process. The effects of superplasticizer, silica fume, nanoclay, fly ash, or ground granulated blast furnace slag were investigated when mixed with two control cement pastes. The water-to-cement ratios were 0.35 and 0.50. PMID:28773273

  3. Influence of Aggregate Coated with Modified Sulfur on the Properties of Cement Concrete

    Directory of Open Access Journals (Sweden)

    Swoo-Heon Lee

    2014-06-01

    Full Text Available This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to coat the aggregate surface at a speed of 20 rpm for 120 s. The MSCA with modified sulfur corresponding to 5% of the cement weight did not significantly affect the flexural strength in a prism concrete beam specimen, regardless of the water-cement ratio (W/C. However, a dosage of more than 7.5% decreased the flexural strength. On the other hand, the MSCA considerably improved the resistance to the sulfuric acid and the freezing-thawing, regardless of the sulfur dosage in the MSCA. The coating modified sulfur of 5% dosage consequently led to good results for the mechanical properties and durability of MSCA concrete.

  4. First real-time measurement of the evolving H-2/H-1 ratio during water evaporation from plant leaves

    NARCIS (Netherlands)

    Kerstel, ERT; van der Wel, LG; Meijer, HAJ

    We have studied the temporal behaviour of the deuterium isotope ratio of water vapour emerging from a freshly cut plant leaf placed in a dry nitrogen atmosphere. The leaf material was placed directly inside the sample gas cell of the stable isotope ratio infrared spectrometer. At the reduced

  5. The measurement of 129I for the cement and the paraffin solidified low and intermediate level wastes (LILWs), spent resin or evaporated bottom from the pressurized water reactor (PWR) nuclear power plants.

    Science.gov (United States)

    Park, S D; Kim, J S; Han, S H; Ha, Y K; Song, K S; Jee, K Y

    2009-09-01

    In this paper a relatively simple and low cost analysis procedure to apply to a routine analysis of (129)I in low and intermediate level radioactive wastes (LILWs), cement and paraffin solidified evaporated bottom and spent resin, which are produced from nuclear power plants (NPPs), pressurized water reactors (PWR), is presented. The (129)I is separated from other nuclides in LILWs using an anion exchange adsorption and solvent extraction by controlling the oxidation and reduction state and is then precipitated as silver iodide for counting the beta activity with a low background gas proportional counter (GPC). The counting efficiency of GPC was varied from 4% to 8% and it was reversely proportional to the weight of AgI by a self absorption of the beta activity. Compared to a higher pH, the chemical recovery of iodide as AgI was lowered at pH 4. It was found that the chemical recovery of iodide for the cement powder showed a lower trend by increasing the cement powder weight, but it was not affected for the paraffin sample. In this experiment, the overall chemical recovery yield of the cement and paraffin solidified LILW samples and the average weight of them were 67+/-3% and 5.43+/-0.53 g, 70+/-7% and 10.40+/-1.60 g, respectively. And the minimum detectable activity (MDA) of (129)I for the cement and paraffin solidified LILW samples was calculated as 0.070 and 0.036 Bq/g, respectively. Among the analyzed cement solidified LILW samples, (129)I activity concentration of four samples was slightly higher than the MDA and their ranges were 0.076-0.114 Bq/g. Also of the analyzed paraffin solidified LILW samples, five samples contained a little higher (129)I activity concentration than the MDA and their ranges were 0.036-0.107 Bq/g.

  6. Porosity and liquid absorption of cement paste

    DEFF Research Database (Denmark)

    Krus, M.; Hansen, Kurt Kielsgaard; Kunzel, H. M.

    1997-01-01

    be a slowing-down effect which is related to water because the absorption of organic liquids, such as hexane, is quite normal. Measurements of the porosity of hardened cement paste determined by helium pycnometry and water saturation show that water molecules can enter spaces in the microstructure which...... are not accessible to the smaller helium atoms. Considering the results of dilatation tests both before and after water and hexane saturation, it seems possible that a contraction of capillary pores due to moisture-related swelling of the cement gel leads to the non-linear water absorption over the square root...

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

    Science.gov (United States)

    Tishmack, Jody Kathleen

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

  8. Rheology of cement mixtures with dolomite filler

    Directory of Open Access Journals (Sweden)

    Martínez de la Cuesta, P. J.

    2000-06-01

    Full Text Available This experimental program has studied the behavior of fresh paste made up from cements mixed with dolomite filler. Through prior experiments the starting point is obtained for the designs 22 and 23 factorials. With these designs the governing equations are established that influence the specific surface of the filler, the filler percentage and the ratio water/(cement + filler, used as objective functions: test probe penetration, flow on table and shear stress in viscometer. Also the type of rheological conduct is determined and the influence over initial and final setting is observed.

    Este programa experimental estudia el comportamiento de las pastas frescas fabricadas a partir de cementos mezclados con filler dolomítico. En los experimentos previos se obtiene el punto central para los diseños 22 y 23 factoriales. Con estos diseños se establecen las ecuaciones que rigen la influencia de la superficie específica del filler, el porcentaje de filler y la relación agua/(cemento + filler, utilizando como funciones objetivos la penetración de sonda, la mesa de sacudidas y la tensión de corte en el viscosímetro. También se determina el tipo de conducta reológica y la influencia sobre el principio y fin de fraguado.

  9. Laboratory development and field application of novel cement system for cementing high-temperature oil wells

    Energy Technology Data Exchange (ETDEWEB)

    Wan, X.; Zhang, H.; Li, Y.; Yang, Y. [SINOPEC, Beijing (China); Shan, H.; Xiao, Z. [OPT, Beijing (China)

    2010-07-01

    The challenges that oil and gas well engineers face when cementing mid-to-high temperature exploration oil and gas wells were discussed. A newly developed cement system with an effective laminar-flow spacer was presented along with case histories that document the system's effectiveness for cementing high temperature exploration wells. The problems associated with cementing high temperature exploration wells include high bottom hole static temperature; very low pump rates; and very long job times. These challenges contribute to the operational risks during cement slurry placement in the wellbore as well as during cement sheath setting during the life of the well. The new cement formulation presented in this paper addresses these challenges. Eight jobs have been completed in the field with much success. The combination of a new retarder and fluid loss control additive improves the system performance considerably in terms of low fluid loss rate, minimal free water, proper rheology, predictable thickening time, high resistance to salt contaminations and no adverse effect on set cement strength. The drilling muds are effectively displaced by the laminar flow spacer, thus improving the cementing bond. 9 refs., 5 tabs., 6 figs.

  10. Dielectric properties of portland cement paste as a function of time since mixing

    Science.gov (United States)

    Camp, Paul R.; Bilotta, Stephen

    1989-12-01

    The dielectric properties of portland cement paste and mortar have been measured in the frequency range 100 Hz-7 MHz as a function of time since mixing. Over much of the spectrum, the ac conductance of the samples appears directly related to the amount of unbound water remaining in the sample and ionic conduction predominates. In addition, interesting structure was found in both the conductance and capacitance data at high frequencies as the free water content was reduced. We conclude that relatively simple measurements of this kind can be a useful tool in concrete research and may provide the basis for simple, in situ, nondestructive measurement of the degree of curing of concrete or for monitoring water migration in concrete structures. Measurements on sealed samples of partially or fully cured concrete reveal also the water-cement ratio of the original mix.

  11. Sr/Ca ratios in cold-water corals - a 'low-resolution' temperature archive?

    Science.gov (United States)

    Rüggeberg, Andres; Riethdorf, Jan-Rainer; Raddatz, Jacek; López Correa, Matthias; Montagna, Paolo; Dullo, Wolf-Christian; Freiwald, André

    2010-05-01

    One of the basic data to understand global change and past global changes is the measurement and the reconstruction of temperature of marine water masses. E.g. seawater temperature controls the density of seawater and in combination with salinity is the major driving force for the oceans circulation system. Geochemical investigations on cold-water corals Lophelia pertusa and Desmophyllum cristagalli indicated the potential of these organisms as high-resolution archives of environmental parameters from intermediate and deeper water masses (Adkins and Boyle 1997). Some studies tried to use cold-water corals as a high-resolution archive of temperature and salinity (Smith et al. 2000, 2002; Blamart et al. 2005; Lutringer et al. 2005). However, the fractionation of stable isotopes (delta18O and delta13C) and element ratios (Sr/Ca, Mg/Ca, U/Ca) are strongly influenced by vital effects (Shirai et al. 2005; Cohen et al. 2006), and difficult to interpret. Nevertheless, ongoing studies indicate the potential of a predominant temperature dependent fractionation of distinct isotopes and elements (e.g. Li/Ca, Montagna et al. 2008; U/Ca, Mg/Ca, delta18O, Lòpez Correa et al. 2008; delta88/86Sr, Rüggeberg et al. 2008). Within the frame of DFG-Project TRISTAN and Paläo-TRISTAN (Du 129/37-2 and 37-3) we investigated live-collected specimens of cold-water coral L. pertusa from all along the European continental margin (Northern and mid Norwegian shelves, Skagerrak, Rockall and Porcupine Bank, Galicia Bank, Gulf of Cadiz, Mediterranean Sea). These coral samples grew in waters characterized by temperatures between 6°C and 14°C. Electron Microprobe investigations along the growth direction of individual coral polyps were applied to determine the relationship between the incorporation of distinct elements (Sr, Ca, Mg, S). Cohen et al. (2006) showed for L. pertusa from the Kosterfjord, Skagerrak, that ~25% of the coral's Sr/Ca ratio is related to temperature, while 75% are influenced

  12. Shrinkage and Cracking Sensitivity of Cement Mortar Containing Fly Ash, Granulated Blast-furnace Slag and Silica Fume

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A laboratory study was undertaken to investigate drying shrinkage and cracking sensitivity subjected to restrained shrinkage of mortar containing fly ash (FA), granulated blast-furnace slag (GBFS) and silica fume (SF). Six mortar mixtures including control Portland cement (PC) and FA,GBFS and SF mortar mixtures were prepared. FA replaced the cement on mass basis at the replacement ratios of 20% and 35%, GBFS replaced the cement at the replacement ratios of 40%, SF replaced the cement at the replacement ratios of 8% and the blended mixtures with 20% FA, 20% GBFS and 8% SF. Water-cementitious materials ratio and sand-cementitious materials ratio were 0.4 and 2.0 for all mixtures, respectively. The mixtures were cured at 65% relative humidity and 20℃. The drying shrinkage value, initial cracking time and cracking width of the mortar samples were measured. The results show that all the mortar mixture containing FA exhibited the decrease of drying shrinkage.Moreover, initial cracking time was markedly delayed, and the crack width of the initial crack was reduced. However, the incorporations of various ratios of GBFS and SF led to an increase of drying shrinkage, initial cracking time and cracking width as compared to control mixture.

  13. 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.

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

    Science.gov (United States)

    Chowdhury, S; Maniar, A; Suganya, O M

    2015-11-01

    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.

  15. Simplified method for predicating consolidation settlement of soft ground improved by floating soil-cement column

    Institute of Scientific and Technical Information of China (English)

    龚晓南; 田效军; 胡文韬

    2015-01-01

    A simplified method is presented for predicting consolidation settlement of soft ground improved by floating soil−cement column on the basis of double soil-layer consolidation theory. Combining the axisymmetric consolidation model and equal strain assumption, the governing equation was derived for the consolidation of clayey subsoil reinforced by soil−cement column. By modifying the boundary condition of the interface between the improved layer and underlying layer on seepage and pore-water pressure, the analytical solution of consolidation of soft ground improved by floating soil−cement column was developed under depth-dependent ramp load. The results of the parameter analysis of consolidation behavior show that the consolidation rate is closely related with the depth replacement ratio by the column and the permeability of upper layer. The influence of column−soil constrained modulus ratio and radius ratio of the influence zone to the column on consolidation is also affected by depth replacement ratio. The column−soil total stress ratio increases with time and approaches the final value accompanied with the dissipation of excess pore water pressure.

  16. Competition among warm season C4-cereals influence water use efficiency and competition ratios

    Directory of Open Access Journals (Sweden)

    Amanullah

    2015-12-01

    Full Text Available Water use efficiency (WUE and competition ratio (CR response of three warm season C4-cereals (grasses viz. corn (Zea mays L., cv. Hybrid-5393 VT3, grain sorghum (Sorghum bicolor L. Moench, cv. Hybrid-84G62 PAT, and foxtail millets (Setaria italic, cv. German Strain R in pure and mixed stands under low and high water levels was investigated. The experiment was conducted in pot experiment at Dryland Agriculture Institute, West Texas A&M University, Canyon, Texas, USA, during spring 2010. The objective of this study was to know whether the differences in the competitive ability of different crop species influence WUE or not? The planned mean comparison indicated that the corn WUE was 20, 11, and 6% higher in the mixed stand than in pure stand at 30, 60, and 90 days after emergence (DAE, respectively. The corn plants in pure stand had 91, 72, and 81% higher WUE than the average WUE of sorghum and millets in pure stand at 30, 60, and 90 DAE, respectively. Grain sorghum in pure stand had 70, 32, and 36% higher WUE than that of millets in pure stand at 30, 60, and 90 DAE, respectively. The WUE of three crops in mixed stand was 10 and 8% higher than the two crops mixed stand at the two early stages; but the WUE was 24% less in the three crops mixed stand than the two crops mixed stand at 90 DAE. Corn-mixed stand in two crops (average of corn + sorghum and corn + millets had 78, 74, and 74% higher WUE than the mixed stand of sorghum and millets at 30, 60, and 90 DAE, respectively. Corn and millets mixed stand had 14, 10, and 26% higher WUE than the corn and sorghum mixed stand at 30, 60, and 90 DAE, respectively. The increase in water level decreased WUE at the two late growth stages in all three crop plants. At the early growth stage (30 DAE, WUE increased in all crops at the higher water level. On the basis of CR, corn was found the best competitor, while millets was declared the least competitor in the mixed stands (corn

  17. Suitable Types and Constituent Ratios for Clay-Pot Water Filters to Improve the Physical and Bacteriological Quality of Drinking Water

    Directory of Open Access Journals (Sweden)

    Watcharaporn Wongsakoonkan

    2014-06-01

    Full Text Available This study aimed to investigate suitable types and ratios of materials for making clay-pots, and their performance to improve the physical and bacteriological quality of drinking water. Synthetic water was prepared and used to select suitable types and ratios for clay-pot water filters. The clay-pots were prepared by combining clay with sand, coconut-shell charcoal, and rice-husk charcoal, at various ratios. The results indicated that all types and ratios could remove 100% of coliform bacteria and Escherichia coli, and were thus suitable for treating drinking water. However, for practical use, the system should have real-world application. Therefore, filtration rate/inner surface area/time was used as a criterion to determine suitable types and ratios. Different types of clay-plot water filter yielded significantly different filtration rates (p 0.01. A ratio with a maximal filtration rate of 60:40(0.38 ± 0.28 mL/cm2/hr was found to be suitable. The quality of filtered water was acceptable in terms of turbidity, coliform bacteria level, and Escherichia coli, according to WHO drinking-water quality guidelines.

  18. Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

    Directory of Open Access Journals (Sweden)

    Ayrton Alef Castanheira Pereira

    2016-02-01

    Full Text Available Abstract The water absorption behavior of the DGEBA/TETA epoxy system was evaluated as a function of the epoxy monomer to amine hardener ratio. Weight gain versus immersion time curves were obtained and the experimental points were fitted using Fickian and Non-Fickian diffusion models. The results obtained showed that for all epoxy monomer to hardener ratios analyzed water diffusion followed non-Fickian behavior. It was possible to correlate the water absorption behavior to the macromolecular structure developed when the epoxy/ hardener ratio was varied. All epoxy/hardener ratios present a two-phase macromolecular structure, composed of regions with high crosslink density and regions with lower crosslinking. Epoxy rich systems have a more open macromolecular structure with a lower fraction of the dense phase than the amine rich systems, which present a more compact two-phase structure.

  19. 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

  20. On the cross-sensitivity between water vapor mixing ratio and stable isotope measurements of in-situ analyzers

    KAUST Repository

    Parkes, Stephen

    2015-04-01

    In recent years there has been an increasing amount of water vapor stable isotope data collected using in-situ instrumentation. A number of papers have characterized the performance of these in-situ analyzers and suggested methods for calibrating raw measurements. The cross-sensitivity of the isotopic measurements on the mixing ratio has been shown to be a major uncertainty and a variety of techniques have been suggested to characterize this inaccuracy. However, most of these are based on relating isotopic ratios to water vapor mixing ratios from in-situ analyzers when the mixing ratio is varied and the isotopic composition kept constant. An additional correction for the span of the isotopic ratio scale is then applied by measuring different isotopic standards. Here we argue that the water vapor cross-sensitivity arises from different instrument responses (span and offset) of the parent H2O isotope and the heavier isotopes, rather than spectral overlap that could cause a true variation in the isotopic ratio with mixing ratio. This is especially relevant for commercial laser optical instruments where absorption lines are well resolved. Thus, the cross-sensitivity determined using more conventional techniques is dependent on the isotopic ratio of the standard used for the characterization, although errors are expected to be small. Consequently, the cross-sensitivity should be determined by characterizing the span and zero offset of each isotope mixing ratio. In fact, this technique makes the span correction for the isotopic ratio redundant. In this work we model the impact of changes in the span and offset of the heavy and light isotopes and illustrate the impact on the cross-sensitivity of the isotopic ratios on water vapor. This clearly shows the importance of determining the zero offset for the two isotopes. The cross-sensitivity of the isotopic ratios on water vapor is then characterized by determining the instrument response for the individual isotopes for a

  1. 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.

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

    Institute of Scientific and Technical Information of China (English)

    WU Di; CAI Si-jing

    2015-01-01

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

  3. Development of fluorapatite cement for dental enamel defects repair.

    Science.gov (United States)

    Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

  4. 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.

  5. 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)

  6. Cement compositions for cementing wells, allowing pressure gas-channeling in the cemented annulus to be controlled

    Energy Technology Data Exchange (ETDEWEB)

    Parcevaux, P.A.; Piot, B.M.; Vercaemer, C.J.

    1987-01-27

    The invention relates to cement compositions for cementing oil and geothermal wells. These compositions allow pressure gas-channeling to be effectively controlled up to more than about 485/sup 0/F. The compositions according to the invention comprise four essential constituents: a cement, a styrene-butadiene latex, a latex stabilizer, and water. The cement is a hydraulic cement belonging to any class among those currently used for cementing oil wells. The useful stabilizers according to the invention are anionic polyelectrolytes such as lignosulfanates and their desulfonated and/or resulfonated derivatives; sulfonated lignin-Kraft products; melamine-formaldehyde resins modified by a sulfonic acid or sulfite; formaldehyde/sulfonated naphthalene resins; or the condensation products of bi-nuclear sulfonated phenols and of formaldehyde. Preferred are the sodium salts of the condensation product of mononaphthalenesulfonic acid and of formaldehyde. The patent also includes a description of tests of various cement compositions of the invention, plus scanning electron microscope observations. 10 figs., 7 tabs.

  7. Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability.

    Science.gov (United States)

    Gomes, Filipa O; Pires, Ricardo A; Reis, Rui L

    2013-04-01

    Al-free glasses of general composition 0.340SiO2:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na2O:0.060P2O5 (a, b=0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements was evaluated using poly(acrylic acid) and water. We evaluated the influence of the poly(acrylic acid) molecular weight and glass particle size in the cement mechanical performance. Higher compressive strength (25±5 MPa) and higher compressive elastic modulus (492±17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and glass particle sizes between 63 and 125 μm. Cements prepared with glass formulation a=0.125 and b=0.000 were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer saline containing α-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial degradation. Zn release studies (concentrations between 413 μM and 887 μM) evidenced the necessity to tune the cement formulations to reduce the Zn concentration in the surrounding environment.

  8. Transport Properties of Carbon-Nanotube/Cement Composites

    NARCIS (Netherlands)

    Han, B.; Yang, Z.; Shi, X.; Yu, X.

    2012-01-01

    This paper preliminarily investigates the general transport properties (i.e., water sorptivity, water permeability, and gas permeability) of carbon-nanotube/cement composites. Carboxyl multi-walled carbon nanotubes (MWNTs) are dispersed into cement mortar to fabricate the carbon nanotubes (CNTs) rei

  9. Stabilization of chloro-organics using organophilic bentonite in a cement-blast furnace slag matrix.

    Science.gov (United States)

    Cioffi, R; Maffucci, L; Santoro, L; Glasser, F P

    2001-01-01

    The application of cement-based stabilisation/solidification treatment to organic-containing wastes is made difficult by the adverse effect of organics on cement hydration. The use of organophilic clays as pre-solidification adsorbents of the organic compounds can reduce this problem because of the high adsorption power of these clays and their compatibility with the cementitious matrix. This work presents an investigation of the effect on hydration kinetics, physico-mechanical properties and leaching behaviour of cement-based solidified waste forms containing 2-chlorophenol and 1-chloronapthalene adsorbed on organophilic bentonites. These were prepared by cation exchange with benzyldimethyloctadecylammonium chloride and trimethyloctadecylammonium chloride. The binder was a 30% pozzolanic cement, 70% granulated blast furnace slag mixture. Several binder-to-bentonite ratios and different concentrations of the organics on the bentonite were used. Kinetics of hydration were studied by measurement of chemically bound water and by means of thermal and calorimetric analyses. Microstructure and other physico-mechanical properties of the solidified forms were studied by means of mercury intrusion porosimetry, scanning electron microscopy and unconfined compressive strength measurement. Leaching was checked by two different leaching tests: one dynamic, on monolithic samples, and the other static, on powdered samples. This study indicates that the incorporation of the organic-loaded bentonite in the binder matrix causes modifications in the hardened samples by altering cement hydration. The effects of the two organic contaminants are differentiated.

  10. Study of peanut husk ashes properties to promote its use as supplementary material in cement mortars

    Directory of Open Access Journals (Sweden)

    J. Kreiker

    Full Text Available The properties of peanut husk ashes as a potential supplementary material in cement mortars were studied in the laboratory. The ashes were prepared in an electric furnace at 500, 650 and 800 ºC during 180 minutes and used without further treatment. The characterization of ashes includes X-Ray fluorescence, X-Ray diffraction, SEM, and determination of pozzolanic activity by conductivity. The ashes were tested in mortars as partial substitute of Portland cement, in a rate of 15 % of substitution. The compression strength of mortars was evaluated between 7 and 120 days, for probes prepared using a proportion of cement:sand of 1:3 on weight with water/cement ratio of 0,5 v/v. It was observed that the calcinations conditions influenced the behavior of the ashes, giving better results the ashes obtained at 500 ºC. The compression tests showed values near to 70% at 7 days but higher than 80% after 28 days for mortars prepared with ashes, respect to the cement mortar reference.

  11. Advanced high-temperature lightweight foamed cements for geothermal well completions

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, T.; Kukacka, L.E.; Galen, B.G.

    1986-04-01

    Foamed cement slurries that were prepared by mixing a cementitious material having a Class H cement-to-silica flour ratio of 1.0 in conjunction with a alpha-olefin sulfate foam surfactant and a coconut diethanolamide foam stabilizer were exposed in an autoclave at a temperature of 300/sup 0/C and a hydrostatic pressure of 2000 psi (13.79 MPa). One lightweight slurry having a density of 9.61 lb/gal (1.15 g/cc) yielded a cellular cement having a compressive strength at 24 hr of >1000 psi (6.9 MPa) and a water permeability of approx.10/sup -3/ darcys. The factors responsible for the attainment of these mechanical and physical properties were identified to be well-crystallized truscottite phases and a uniform distribution of discrete fine bubbles. The addition of graphite fiber reinforcement for the cement matrix significantly suppressed any segregation of foam caused by thermal expansion of the air bubbles and further improved the mechanical characteristics of the cured cements.

  12. Rechargeable calcium phosphate orthodontic cement with sustained ion release and re-release

    Science.gov (United States)

    Zhang, Ling; Weir, Michael D.; Chow, Laurence C.; Reynolds, Mark A.; Xu, Hockin H. K.

    2016-11-01

    White spot lesions (WSL) due to enamel demineralization are major complications for orthodontic treatments. Calcium phosphate (CaP) dental resins with Ca and P ion releases are promising for remineralization. However, previous Ca and P releases lasted for only weeks. Experimental orthodontic cements were developed using pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA) at mass ratio of 1:1 (PE); and PE plus 10% of 2-hydroxyethyl methacrylate (HEMA) and 5% of bisphenol A glycidyl dimethacrylate (BisGMA) (PEHB). Particles of amorphous calcium phosphate (ACP) were incorporated into PE and PEHB at 40% filler level. Specimens were tested for bracket-enamel shear bond strength, water sorption, CaP release, and ion recharge and re-release. PEHB+40ACP had higher bracket-enamel bond strength and ion release and rechargeability than PE+40ACP. ACP incorporation into the novel orthodontic cement did not adversely affect the bracket-enamel bond strength. Ion release and re-release from the novel ACP orthodontic cement indicated favorable release and re-release patterns. The recharged orthodontic cement could release CaP ions continuously for four weeks without further recharge. Novel rechargeable orthodontic cement containing ACP was developed with a high bracket-enamel bond strength and the ability to be repeatedly recharged to maintain long-term high levels of CaP ion releases.

  13. Effects of Total Hardness and Calcium:Magnesium Ratio of Water during Early Stages of Rare Minnows (Gobiocypris rarus).

    Science.gov (United States)

    Luo, Si; Wu, Benli; Xiong, Xiaoqin; Wang, Jianwei

    2016-01-01

    The ionic composition of water is important for all fish. In the present study, the effects of total hardness and Ca(2+):Mg(2+) ratio on early life stages of rare minnows (Gobiocypris rarus), a promising laboratory fish in China, were evaluated. Paired parent fish were transferred to spawning aquaria (16 L) containing water at different total hardness and Ca:Mg ratios, and their offspring were further cultured at 25 ± 1 °C and 12:12-h light:dark photoperiod. Fertilization rates were not affected by total hardness to 480 mg L(-1) CaCO3, but egg size decreased with increasing total hardness. Ca:Mg ratios less than 1:20 or greater than 8:1 had adverse influences on hatching, feeding, development, larval growth, and survival. Embryos and larvae incubated in Mg(2+)- and Ca(2+)-deficient waters exhibited high malformation rates and high mortality. Our results demonstrate that rare minnows can adapt to a wide range of total hardness and Ca:Mg ratios, although an imbalance between Ca(2+) and Mg(2+) in water is toxic to this species. To increase the comparability and usefulness of test results, we recommend the use of reconstituted or drinking water of defined total hardness and Ca:Mg ratio for the culture and toxicity testing of rare minnows.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-12-15

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

  15. Self-Shrinkage Behaviors of Waste Paper Fiber Reinforced Cement Paste considering Its Self-Curing Effect at Early-Ages

    Directory of Open Access Journals (Sweden)

    Zhengwu Jiang

    2016-01-01

    Full Text Available The aim of this paper was to study how the early-age self-shrinkage behavior of cement paste is affected by the addition of the waste paper fibers under sealed conditions. Although the primary focus was to determine whether the waste paper fibers are suitable to mitigate self-shrinkage as an internal curing agent under different adding ways, evaluating their strength, pore structure, and hydration properties provided further insight into the self-cured behavior of cement paste. Under the wet mixing condition, the waste paper fibers could mitigate the self-shrinkage of cement paste and, at additions of 0.2% by mass of cement, the waste paper fibers were found to show significant self-shrinkage cracking control while providing some internal curing. In addition, the self-curing efficiency results were analyzed based on the strength and the self-shrinkage behaviors of cement paste. Results indicated that, under a low water cement ratio, an optimal dosage and adding ways of the waste paper fibers could enhance the self-curing efficiency of cement paste.

  16. Organic Additive Implantation onto Cement Hydration Products

    Institute of Scientific and Technical Information of China (English)

    ZHU Jipeng; LI Zongjin; YANG Ruochong; ZHANG Yamei

    2014-01-01

    In polymer modified cementitious materials, it is hard to set up a chemical connection between the added polymer and the cement moiety. In this study FS (functional silane) was adopted to form this connection as a bridge component which has the functional group forming bonds with polymer. To testify the connection between FS and cement moiety, Q2/Q1 ratio (Qx:intensity ratio) investigation was carried out by the means of quantitative solid state 29Si MAS NMR. The results show that the Q2/Q1 ratio has increased with the addition of FS which indicates that the silicon chain length has increased, and the quantity of silicon atoms at site of Q2, chain site, has enhanced, showing that the silicon atom of FS has connected to the silicon chain of cement moiety by the bond“-Si-O-Si-”formation.

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

    Science.gov (United States)

    Wang, Xiao-Yong

    2017-01-26

    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.

  18. 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.

  19. Formulating a low-alkalinity cement for radioactive waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Coumes, C. Cau Dit; Courtois, S.; Leclercq, S.; Bourbon, X

    2004-07-01

    A multi-annual research program has been launched in January 2003 by CEA, EDF and ANDRA in order to formulate and characterize low-alkalinity and low-heat cements which would be compatible with an underground waste repository environment. Four types of bindings have been investigated: binary blends of Portland cement and silica fume or metakaolin, as well as ternary blends of Portland cement, fly ash and silica fume or metakaolin. Promising results have been obtained with a mixture comprising 37.5% Portland cement, 32.5% silica fume, and 30% fly ash: pH of water in equilibrium with fully hydrated cement is below 11. Moreover, silica fume compensates for the low reactivity of fly ash, while fly ash allows to reduce water demand, heat release, and dimensional variations of cement pastes and mortars. (authors)

  20. Carbonation process in lime pastes with different water/binder ratio

    Directory of Open Access Journals (Sweden)

    Álvarez, J. I.

    2006-03-01

    Full Text Available Most research on binder carbonation is based on the analysis of depth changes in the carbonation front. Moreover, previous studies have dealt with mortars, where aggregates play a role in the variations in carbonation patterns. In the approach adopted in the present study, carbonation was determined in terms of the variation in weight resulting from CO2 absorption, and a new parameter (independent of the drying process, denominated A, was established. This parameter was assessed in several lime pastes with different W/B (water/binder ratios and its variations were correlated to paste microstructure. Due to the type of porosity prevailing in lime pastes, diffusion took place according to Fick's law; water was retained not by capillarity but by surface adsorption. Drying did not retard carbonation in lime pastesLa mayoría de las investigaciones sobre el proceso de carbonatación en materiales conglomerantes estudia el movimiento del frente de carbonatación. Además, los trabajos previos han sido llevados a cabo en morteros, lo que implica variaciones en el comportamiento de la carbonatación debido a la presencia del agregado. En este trabajo, la carbonatación es discutida teniendo en cuenta la variación del peso como consecuencia de la absorción de CO2, al establecer un nuevo parámetro A (independiente del proceso de secado. Este parámetro ha sido evaluado en varias pastas de cal con distinta relación A/C (agua/conglomerante, y su variación se ha correlacionado con la microestructura de las pastas. Durante el proceso de la carbonatación, y debido al tipo de porosidad de las pastas de cal, tiene lugar la difusión de Fick: el agua no es retenida por capilaridad sino por adsorción sobre la superficie. El proceso de secado no retrasa la carbonatación en las pastas de cal.

  1. Links between purchase location and stable isotope ratios of bottled water, soda, and beer in the United States.

    Science.gov (United States)

    Chesson, Lesley A; Valenzuela, Luciano O; O'Grady, Shannon P; Cerling, Thure E; Ehleringer, James R

    2010-06-23

    This study investigated the impact of purchase location on the stable isotope ratios of beverages by measuring the delta(2)H and delta(18)O values of bottled water, soda, beer, and tap water collected across the contiguous United States. Measured beverage delta(2)H and delta(18)O values generally fit the Global Meteoric Water Line (GMWL), suggesting region-of-origin information is recorded in beverage water. Tap water delta(2)H and delta(18)O values were strongly correlated with the stable isotope ratios of bottled water and soda purchased in the same location. Beer water delta(2)H and delta(18)O values were also correlated with tap water, although not as strongly. Variability in delta(2)H and delta(18)O values among beverages purchased at a single location ranged from 2 to 41 per thousand and from 0.3 to 5.2 per thousand, respectively, but was generally moderate in most locations. It was concluded that the isotopic composition of local tap water is a reasonable proxy for consumers' fluid intake in most U.S. cities.

  2. Partial Replacement of Cement with Marble Dust Powder

    Directory of Open Access Journals (Sweden)

    Mr. Ranjan Kumar

    2015-08-01

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

  3. Holocene cemented beach deposits in Belize

    Science.gov (United States)

    Gischler, Eberhard; Lomando, Anthony J.

    1997-06-01

    Two types of cemented beach deposits occur on reef islands off the coast of Belize. These are (1) intertidal beachrock that is dominantly cemented by marine aragonite and high-magnesium-calcite cements, and (2) supratidal cayrock that is cemented mainly by vadose low-magnesium-calcite cements. Besides differences in position relative to present sea level and resulting early diagenesic features, beachrock and cayrock can be distinguished on the basis of differences in composition, texture, geographical position, and age. Whereas the composition of beachrock is similar to that of the adjacent marginal reef sediments, cayrock is enriched in benthic foraminifera. Intertidal beachrock is moderately to well sorted and well cemented, while supratidal cayrock is very well sorted, poorly cemented and friable. Beachrock occurs preferentially on windward beaches of sand-shingle Gays on the middle and southern barrier reefs and on the isolated platforms Glovers and Lighthouse Reefs. Cayrock only occurs on larger mangrove-sand Gays of the isolated platforms Turneffe Islands, Lighthouse Reef, and the northern barrier reef. 14C-dating of ten whole-rock and mollusk shell samples produced calibrated dates between AD 345 and AD 1435 for beachrock and between BC 1085 and AD 1190 for cayrock. The large-scale distribution of beachrock in Belize supports the contention that physical processes such as water agitation rather than biological processes control beachrock formation and distribution. Only on windward sides of cays that are close to the reef crest, where large amounts of seawater flush the beaches, considerable amounts of cements can be precipitated to produce beachrock. Cayrock forms due to cementation in the vadose zone and is only preserved on larger, stable mangrove-sand cays.

  4. The δ18O of Atmospheric Water Vapour is Recorded in the Oxygen Isotope Ratios of Leaf water and Organic Molecules at High Relative Humidity

    Science.gov (United States)

    Lehmann, M. M.; Goldsmith, G. R.; Schmid, L.; Siegwolf, R. T.; Gessler, A.; Saurer, M.

    2016-12-01

    The oxygen stable isotope ratios (δ18O) of water and organic molecules in plants hold information about plant physiology, ecohydrology, and environmental conditions. For instance, the δ18O ratio of leaf water reflects both the δ18O ratios of water in the soil and in the atmosphere. This water, which is incorporated into organic molecules at the time of synthesis, thus serves to record the environment in which the plant was growing. However, how δ18O of atmospheric water vapour affects the δ18O ratio of organic molecules remains poorly understood. In order to investigate the effects of fog and rain (e.g. high atmospheric water availability) on δ18O ratios of leaf water and organic molecules, we exposed oak tree saplings (Quercus robur) in wet and dry soil treatments to 18O-depleted water vapour at ca. 90% relative humidity for 5 h. We harvested plant material over 24 h to trace the movement of the isotopic label in water and organics throughout the plant from the leaves to the stem. The atmospheric water vapour caused a strong 18O-depletion in leaf and xylem water, as well as in leaf carbohydrates, with the most negative ratios observed at the end of the fogging. Moreover, the label was clearly observed in twig and stem phloem carbohydrates following a short delay. A detailed compound-specific isotope analysis of the leaf carbohydrates revealed that the label caused an 18O-depletion in fructose, glucose, and sucrose. Quercitol, an oak-specific alditol, did not show 18O-depletion. Clear soil moisture treatment effects were only observed for twig phloem carbohydrates, with a stronger 18O-depletion in wet plants than in dry plants, suggesting retarded leaf-to-phloem sugar export in trees under drought. We demonstrate that labelling with 18O-depleted water is a potential tool to trace the movement and incorporation of oxygen stable isotopes in plants. We clearly show that changes in δ18O of atmospheric water vapour are quickly imprinted on leaf water and

  5. Magnesia Modification of Alkali-Activated Slag Fly Ash Cement

    Institute of Scientific and Technical Information of China (English)

    SHEN Weiguo; WANG Yiheng; ZHANG Tao; ZHOU Mingkai; LI Jiasheng; CUI Xiaoyu

    2011-01-01

    A new type of magnesia modification alkali-activated cement was prepared, the strength, setting time, shrinkage ratio and cracking behavior, as well as the composition and structure of the hydration product were investigated. The results indicate that the setting time of this cement is similar to that of the ordinary commercial cements; its strength reaches the standard of 42.5 degree cement, its cracking resistance has been remarkably improved because of the micro-aggregate effect of fly ash and shrinkage compensating of magnesia.

  6. THE EFFECT OF NATURAL WATER WITH COW DUNG AND AGRICULTURAL WASTE RATIO ON BIOGAS PRODUCTION FROM ANAEROBIC CO-DIGESTION

    Directory of Open Access Journals (Sweden)

    NaponKeanoi

    2013-01-01

    Full Text Available Global warming caused by energy generation from fossil fuel has accelerated the deployment of renewable fuels such as biogas. In this study, batch fermentation (5L was studied to observe the effect of natural water, cow dung, rice straw and water hyacinth ratio on the biogas and methane production at ambient temperature (31°C, 7.1-7.4 of pH for 52 days. The five types of co-digestion were 2:1:1:1 (digester A, 1:1:1:1 (digester B, 0.5:1:1:1 (digester C, 1:1:1:0 (digester D and 1:1:0:1 (digester E, respectively. The result showed that the biogas production increased progressively with amount of natural water to raw material. The maximum biogas production and methane concentration was 1650 mL/days and 61.47% was obtained at substrate mixture 2:1:1:1 (digester A, which there are suitable of C:N ratio at 31.1:1. Natural water, cow dung, rice straw and water hyacinth was mixed for biogas production, have been found to improve highest biogas production compared to those of without rice straw and water hyacinth. Therefore, the mixing natural water, cow dung, rice straw and water hyacinth can improve both biogas production and content of methane in biogas.

  7. Factors affecting bond cement across casing leak zones in oil and gas wells

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, Mohamed; Edbeib, Said [Al-Fateh University, Tripoli (Libyan Arab Jamahiriya). Dept. of Petroleum Engineering

    2004-07-01

    Casing leaks have been a major concern to the oil industry because of their effect on lowering the production rate in many oil and gas wells. The leaks are the result of deterioration of the casing in the well, which is caused by severe corrosion due to the contact of the casing with high salinity foreign fluid. The objective of this study is to determine the factors influencing the mechanical properties of the hardened cement opposite the casing leak zones. This study is conducted by laboratory measurements of the compressive strength of the hardened cement when the cement slurry was mixed with different percentages of formation water and different concentrations of different cement additives. The results of this study indicate that the compressive strength readings obtained from the cement bond log and the cement evaluation tool against the casing leak zones are lower than those readings recorded in adjacent formations. The low cement compressive strength values observed across casing leak zones are due to the contamination of the cement with saline water present in these formations which, in turn, effects the hardening properties of the cement. The experimental results indicated that the salinity of the formation water when mixed with the cement slurry in the presence of cement additives, decreased the compressive strength of the bond cement and also decreased the thickening time of the cement slurry. It is concluded that casing leaks found in many wells observed in oil fields in Libya were due to the mixing of the cement with high salinity formation water present in the lost circulation zones. The high water salinity in these zones effects the setting time of the cement slurry which, therefore, decreased the hardening properties of the bond cement and caused cracks and channels in the hardened cement across lost circulation zones. (author)

  8. Identification of sources and production processes of bottled waters by stable hydrogen and oxygen isotope ratios.

    Science.gov (United States)

    Brencic, Mihael; Vreca, Polona

    2006-01-01

    Bottled water is a food product that considerably depends on the environment from which it originates, not only at the place where it is produced, but predominantly on the conditions in the recharge area of the wells captured for bottling. According to their source and the bottling process, bottled waters can be divided into natural and artificially sparkling waters, still and flavoured waters. These waters originate from various parts of the hydrological cycle and their natural origin is reflected in their hydrogen and oxygen stable isotopic compositions (delta(2)H and delta(18)O). A total of 58 domestic and foreign brands and 16 replicates of bottled waters, randomly collected on the Slovene market in September 2004, were analysed for delta(2)H and delta(18)O. The isotopic composition varied between -83 per thousand and -46 per thousand with an average of -66 per thousand for hydrogen, and between -11.9 per thousand and -7.5 per thousand with an average of -9.6 per thousand for oxygen. This investigation helped (1) to determine and test the classification of bottled waters, (2) to determine the natural origin of bottled water, and (3) to indicate differences between the natural and production processes. The production process may influence the isotopic composition of flavoured waters and artificially sparkling waters. No such modification was observed for still and natural sparkling waters. The methods applied, together with hydrological knowledge, can be used for the authentication of bottled waters for regulatory and consumer control applications.

  9. Influence of chloride in mortar made of Portland cement types II, III, and V on the near-field microwave reflection properties

    Science.gov (United States)

    Hu, Cairong; Benally, Aaron D.; Case, Tobias; Zoughi, Reza; Kurtis, Kimberly

    2000-07-01

    Corrosion of steel rebar in reinforced concrete structures, can be induced by the presence of chloride in the structure. Corrosion of steel rebar is a problematic issue in the construction industry as it compromises the strength and integrity of the structure. Although techniques exist for chloride detection and its migration into a structure, they are destructive, time consuming and cannot be used for the interrogation of large surfaces. In this investigation three different portland cement types; namely, ASTM types II, III and V were used, and six cubic (8' X 8' X 8') mortar specimens were produced all with water-to-cement (w/c) ratio of 0.6 and sand-to-cement (s/c) ratio of 1.5. Tap water was used when producing three of these specimens (one of each cement type). For the other three specimens calcium chloride was added to the mixing tap water resulting in a salinity of 2.5%. These specimens were placed in a hydration room for one day and thereafter left it the room temperature with low humidity. The reflection properties of these specimens, using an open-ended rectangular waveguide probe, were monitored daily at 3 GHz (S-band) and 10 GHz (X-band). The results show the influence of cement type on the reflection coefficient as well as the influence of chloride on the curing process and setting time.

  10. Leaching of metals from cement under simulated environmental conditions.

    Science.gov (United States)

    Lu, Huixia; Wei, Fang; Tang, Jingchun; Giesy, John P

    2016-03-15

    Leaching of metals from cement under various environmental conditions was measured to evaluate their environmental safety. A cement product containing clinker, which was produced from cement kiln co-processing of hazardous wastes, was solidified and leaching of metals was characterized using the 8-period test. Concentrations and speciation of metals in cements were determined. Effects of ambient environment and particle size on leachability of metals and mineralogical phases of cement mortars were evaluated by use of XRD and SEM. Results indicated that metals in cements were leachable in various media in descending order of: sea water, groundwater and acid rain. Cr, Ni, As, Co and V were leached by simulated sea water, while Cu, Cd, Pb, Zn, Mn, Sb and Tl were not leached in simulated sea water, groundwater or acid rain. When exposed to simulated acid rain or groundwater, amounts of Cr, Ni, As and V leached was inversely proportional to particle size of cement mortar. According to the one-dimensional diffusion equation, Cr was most leachable and the cumulative leached mass was predicted to be 9.6 mg kg(-1) after 20 years. Results of this study are useful in predicting releases of metals from cement products containing ash and clinkers cement kiln co-processing of hazardous wastes, so that they can be safely applied in the environment.

  11. Injectable bioactive calcium-magnesium phosphate cement for bone regeneration.

    Science.gov (United States)

    Wu, Fan; Su, Jiacan; Wei, Jie; Guo, Han; Liu, Changsheng

    2008-12-01

    Novel injectable and degradable calcium-magnesium phosphate cement (CMPC) with rapid-setting characteristic was developed by the introduction of magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The calcium-magnesium phosphate cement prepared under the optimum P/L ratio exhibited good injectability and desired workability. It could set within 10 min at 37 degrees C in 100% relative humidity and the compressive strength could reach 47 MPa after setting for 48 h, indicating that the prepared cement has relatively high initial mechanical strength. The results of in vitro degradation experiments demonstrated the good degradability of the injectable CMPC, and its degradation rate occurred significantly faster than that of pure CPC in simulated body fluid (SBF) solution. It can be concluded that the novel injectable calcium-magnesium phosphate cement is highly promising for a wide variety of clinical applications, especially for the development of minimally invasive techniques.

  12. Injectable Premixed Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

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

  13. Reuse of By-Products from Ready-Mixed Concrete Plants for the Production of Cement Mortars

    Directory of Open Access Journals (Sweden)

    Monika Zervaki

    2013-06-01

    Full Text Available This study was motivated by the necessity to recycle sludge water resulting from washing out concrete mixing trucks - a problem of both environmental and economic importance for the ready-mixed concrete industry. Sludge water from ready-mixed concrete plants as well as dry sludge, which is derived from the settling of the water, are hazardous for disposal due to their high pH value (pH>11.5. In this work, cement mortars were composed using either sludge water after various treatment, or dry sludge in several ratios. The cement mortars were tested for their workability and strength development. The purpose of this experimental design was to prove that sludge water, as well as sludge in a wet or dry form, can be used in the production of mortars without degrading any of their properties.

  14. EVOLUTION OF LIGHTWEIGHT FOAM CONCRETES BY WATER PROCEDURE

    Directory of Open Access Journals (Sweden)

    Eva Kuzielova

    2015-03-01

    Full Text Available The so called water procedure was used to prepare foam concrete samples with bulk density below 150 kg.m-3. Direct foaming method was applied by using of protein based foaming agent. The amount of Portland cement was decreased gradually along with the water-cement ratio maintenance. Degradation of foams occurred with reducing of cement content to 30 % of its original quantity regardless of water procedure included or not in the preparation procedure. Stability of the foam concrete samples prepared only from 30 % of cement was achieved after microwave and ultrasonic treatment of protein based foaming agent. The so prepared foam concretes were stable also after water procedure and exhibited final bulk density of 95 kg.m-3.

  15. Hydrogen isotope ratios in lunar rocks indicate delivery of cometary water to the Moon

    OpenAIRE

    Greenwood, James P.; Itoh , Shoichi; Sakamoto, Naoya; Warren, Paul; Taylor, Lawrence; Yurimoto, Hisayoshi

    2011-01-01

    Water plays a critical role in the evolution of planetary bodies, and determination of the amount and sources of lunar water has profound implications for our understanding of the history of the Earth-Moon system. During the Apollo programme, the lunar samples were found to be devoid of indigenous water. The severe depletion of lunar volatiles, including water, has long been seen as strong support for the giant-impact origin of the Moon. Recent studies have found water in lunar volcanic glass...

  16. Development of a novel cement by conversion of hopeite in set zinc phosphate cement into biocompatible apatite.

    Science.gov (United States)

    Horiuchi, Shinya; Asaoka, Kenzo; Tanaka, Eiji

    2009-01-01

    Synthetic bone cement that has zinc oxide core particles covered with hydroxyapatite (HAP) was developed; that is, the conversion of hopeite, the traditional zinc phosphate cement, into HAP was attempted. Here, hopeite is the final product of the reaction between powders and trituration liquid of the traditional zinc phosphate cement. This cement may have many advantages not only in terms of biological functions but also the setting process of the traditional cement and the mechanical properties of the developed compact if the hopeite can be converted into calcium phosphate (CP). In this study, calcium nitrate solutions of various concentrations were used for the conversion of hopeite crystals into CP. The products after the solution treatment were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR), and scanning electron microscope (SEM) observation. These results indicated that the converted scholzite crystals could be partially detected. Several types of set zinc phosphate cement with different P/L ratios were arranged. The surface products of the set cement after the solution treatment were analyzed by XRD. However, the crystal phase such as hopeite was not detected except for zinc oxide. The set cement, which was treated with the calcium nitrate solution, was immersed in simulated body fluid (SBF). HAP-like crystals on the set cement could be detected for the specimens immersed for 4 weeks. These findings suggested that the binding phase in the set cement could be converted into HAP by immersion in SBF.

  17. Root biomass, root/shoot ratio, and soil water content under perennial grasses with different nitrogen rates

    Science.gov (United States)

    Roots help in soil water and nutrient uptake and provide C input for soil C sequestration, but information on root biomass of bioenergy perennial grasses is lacking. Root/shoot ratios are used to estimate crop root biomass and C inputs, but the values for perennial grasses are also scanty. We examin...

  18. A comparison between wet canopy evaporation estimated by stable isotope ratios of water and canopy interception measured by water balance

    Science.gov (United States)

    Murakami, Shigeki; Hattori, Shohei; Uemura, Ryu

    2017-04-01

    Some papers proved that canopy interception is proportional to rainfall not only on a rain event basis but also on an hourly basis (e.g. Murakami, 2006, J. Hydrol.; Saito et al., 2013, J. Hydrol.). However, theoretically, evaporation does not depend on rainfall amount. These results are enigmatic and we need to reevaluate wet canopy evaporation. We measured gross rainfall and net rainfall in a plastic Christmas tree stand with a height of 165 cm placed on a 180-cm square tray as described in Murakami and Toba (2013, Hydrol. Res. Lett.). The measurement was conducted outside under natural rainfall. We also estimated wet canopy evaporation using stable isotope ratios of water. During a rain event, we manually sampled gross and net rainwater on an hourly basis. Evaporation was calculated using the difference between the δ18O (or δ2H) values in gross and net rainfall using isotope fractionation factor. Total gross rainfall in a target rain event in October, 2014, was 28.0 mm and net rainfall (discharge from the tray) was 22.7 mm, i.e. canopy interception was 5.3 mm (18.9% of gross rainfall). The δ18O (or δ2H) value in net rainfall was higher than that in gross rainfall because of fractionation by evaporation on wet canopy surface. Hourly evaporation calculated by the values of δ18O varied from 2% to 24% of gross rainfall, and the weighted average by hourly gross rainfall was 5.2% of gross rainfall. Further, we estimated rainfall interception using a tank model (Yoshida et al., 1993) assuming constant evaporation rate, i.e. 20% of gross rainfall. Total net rainfall calculated by the model was 23.1 mm, i.e. calculated canopy interception was 4.9 mm (17.5% of gross rainfall). Then, keeping the parameters of the model, we simulated net rainfall using hourly surface evaporation obtained by the δ18O values. Calculated net rainfall was 25.6 mm, i.e. wet canopy evaporation was only 2.4 mm (8.6% of gross rainfall). So far, possible explanation of the discrepancy between

  19. Radium Isotope Ratios as Tracers for Estimating the Influence of Changjiang Outflow Water to the Adjacent Seas

    Science.gov (United States)

    Kim, K.; Kim, S.

    2006-12-01

    In order to understand the influence of Changjiang (Yangtze River) outflow water to the adjacent seas during rainy and draught seasons, we studied the origin and mixing of surface water masses in the East China Sea and the South Sea of Korea. We used Ra-228/Ra-226 activity ratio and salinity as two conservative tracers in three end-members: Changjiang water (CW); Yellow Sea water (YSW); and Kuroshio water (KW). Radium isotopes in each 300-liter of surface water samples were extracted by passing through manganese-fiber cartridges, dissolved in hydroxylamine hydrochloride solution, coprecipitated as barium sulfate, dried and measured by gamma-ray spectroscopy. Results show that surface water of the East China Sea includes all three end-member waters during the rainy season, in the order of KW (50-80%), YSW (20-50%) and CW (5-15%). Surface water of the South Sea of Korea, however, includes a little fraction of, or almost no, CW in drought season. These are the preliminary results from an ongoing 6-year project ending in 2009 which aims to predict the influence of heavily polluted Changjiang outflow water to the adjacent seas after the completion of the gigantic Three Gorges (Sanxia) Dam.

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

    Science.gov (United States)

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

    2011-08-01

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

  1. Setting mechanisms of an acidic premixed calcium phosphate cement

    OpenAIRE

    2013-01-01

    Premixed calcium phosphate cements (pCPC), where glycerol is used instead of water as mixing liquid, present better handling characteristics than water-based cements. However, the setting mechanisms of pCPC have not been described thoroughly. The aim of this paper is to increase the understanding of the setting mechanism of pCPC. The investigated cement starts to set when glycerol is exchanged with water via diffusion of glycerol out to the surrounding body fluid and water into the material. ...

  2. Investigating Rheological Properties of High Performance Cement System for Oil Wells

    Directory of Open Access Journals (Sweden)

    Khalil Rehman Memon

    2013-10-01

    Full Text Available The main purpose of designing cement slurry for extreme and deep environment (HPHT wells is to develop high performance cement system in well bore to achieve zonal isolation. The primary objective of cement slurry is to improve rheological properties and displacement efficiency of cement system. Oil well slurries depend on its homogeneity of additive concentrations, quality and quantity to contribute the placement and success of a well drilling cementing operation. This research study is focused on the laboratory study of the High Performance Cement System (HPCS. This investigation of cement slurry was prepared with Silica Fume (SF and excess amount of water to decrease the slurry density in order to observe the rheological properties above 120C at different concentration of SF. Results indicates that the designed cement rheological properties are directly influenced by the shear rate and shear stress on the pump-ability of the cement with the increase of the SF concentration for the rheological improvement.

  3. Performance of cemented coal gangue backfill

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qin-li; WANG Xin-min

    2007-01-01

    Possibility of cemented gangue backfill was studied with gangue of Suncun Coal Mine, Xinwen Coal Group, Shandong,and fly ash of nearby thermal power plant, in order to treat enormous coal gangue on a large scale and to recovery safety coal pillars.The results indicate that coal gangue is not an ideal aggregate for pipeline gravity flow backfill, but such disadvantages of gangue as bad fluidity and serious pipe wear can be overcome by addition of fly ash. It is approved that quality indexes such as strength and dewatering ratio and piping feature of slurry can satisfy requirement of cemented backfill if mass ratio of cement to fly ash to gangue higher middle and long term comprehensive strength.

  4. 基于水泥水化模拟的水泥石毛细孔结构分析%Cement Hydration Simulation Based Analysis of Capillary Pore Structure in Cement Paste

    Institute of Scientific and Technical Information of China (English)

    吴芬; 郑建军; 周欣竹

    2015-01-01

    通过水泥水化模拟分析了水泥石毛细孔结构。基于水化动力学原理,模拟水泥水化全过程,将模拟所得的水化度与试验结果比较,验证了模拟方法的有效性。提出了水泥石毛细孔隙率和内表面积的数值方法,数值结果表明,孔隙率随着时间不断减小,内表面积先随着时间不断增大,到达峰值后随着时间逐渐减小,水灰比越小,出现峰值的时间越短。水化28 d 时,水灰比为0.3的水泥石毛细孔隙率和内表面积分别比水灰比为0.5的水泥石毛细孔隙率和内表面积小61%和11%。%The capillary pore structure in cement paste is analyzed through cement hydration simulation.Based on the principles of hydration kinetics,the whole process of cement hydration is simulated.The validity of the simulation method is verified by comparing the simulated degree of hydration with experimental results.A numerical method is presented for the porosity and internal surface area of capillary pores in cement paste.Numerical results show the cap-illary porosity decreases with time.The internal surface area of capillary pores first increases continuously with time and then decreases gradually with time after the peak value reached.The smaller the water/cement ratio is,the shorter the time corresponding to the peak value is.At the age of 28 days,the porosity and internal surface area of capillary pores in cement paste with a water/cement ratio of 0.3 is smaller than those with a water/cement ratio of 0.5 by 61%and 1 1%,respectively.

  5. Performance of RHA Cement Concrete under Marine Environment via Wetting and Drying Cyclic by Rapid Migration Test

    Directory of Open Access Journals (Sweden)

    Ramadhansyah Putra Jaya

    2013-12-01

    Full Text Available In this research, the performance of concrete containing rice husk ash (RHA under marine environment through wetting and drying cycles was investigated. Five levels of cement replacement (0%, 10%, 20%, 30% and 40% by weight were used. The total cementitious content used was 420 kg/m3. A water/binder ratio of 0.49 was used to produce concrete having a target compressive strength of 40MPa at the age of 28 days. The performance of blended cement concrete under marine environment was evaluated using rapid migration test (RMT.  The results clearly showed that RHA can be satisfactorily used as a cement replacement material in order to reduce the chloride penetration depth and hence increases the durability of concrete. Generally, the chloride penetration depth of concrete containing higher RHA replacement is decreased as the RHA replacement increases, resulting in concrete with higher resistance to seawater attack.

  6. Accuracy of Image Analysis in Quantitative Study of Cement Paste

    Directory of Open Access Journals (Sweden)

    Feng Shu-Xia

    2016-01-01

    Full Text Available Quantitative study on cement paste especially blended cement paste has been a hot and difficult issue over the years, and the technique of backscattered electron image analysis showed unique advantages in this field. This paper compared the test results of cement hydration degree, Ca(OH2 content and pore size distribution in pure pastes by image analysis and other methods. Then the accuracy of qualitative study by image analysis was analyzed. The results showed that image analysis technique had displayed higher accuracy in quantifying cement hydration degree and Ca(OH2 content than non-evaporable water test and thermal analysis respectively.

  7. Cement hydration from hours to centuries controlled by diffusion through barrier shells of C-S-H

    Science.gov (United States)

    Rahimi-Aghdam, Saeed; Bažant, Zdeněk P.; Abdolhosseini Qomi, M. J.

    2017-02-01

    Although a few good models for cement hydration exist, they have some limitations. Some do not take into account the complete range of variation of pore relative humidity and temperature, and apply over durations limited from up a few months to up to about a year. The ones that are applicable for long durations are either computationally too intensive for use in finite element programs or predict the hydration to terminate after few months. However, recent tests of autogenous shrinkage and swelling in water imply that the hydration may continue, at decaying rate, for decades, provided that a not too low relative pore humidity (above 0.7) persists for a long time, as expected for the cores of thick concrete structural members. Therefore, and because design lifetimes of over hundred years are required for large concrete structures, a new hydration model for a hundred year lifespan and beyond is developed. The new model considers that, after the first day of hydration, the remnants of anhydrous cement grains, gradually consumed by hydration, are enveloped by contiguous, gradually thickening, spherical barrier shells of calcium-silicate hydrate (C-S-H). The hydration progress is controlled by transport of water from capillary pores through the barrier shells toward the interface with anhydrous cement. The transport is driven by a difference of humidity, defined by equivalence with the difference in chemical potential of water. Although, during the period of 4-24 h, the C-S-H forms discontinuous nano-globules around the cement grain, an equivalent barrier shell control was formulated for this period, too, for ease and effectiveness of calculation. The entire model is calibrated and validated by published test data on the evolution of hydration degree for various cement types, particle size distributions, water-cement ratios and temperatures. Computationally, this model is sufficiently effective for calculating the evolution of hydration degree (or aging) at every

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

    Directory of Open Access Journals (Sweden)

    Ramírez-Arellanes, S.

    2012-09-01

    Full Text Available 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 setting times, reduces flow, slows cement hydration, and inhibits the formation of calcium hydroxide crystals in comparison with the control. Capillary absorption was significantly reduced in concrete containing mucilage, and chloride diffusion coefficients dropped up to 20% in the mixture with a mucilage/cement ratio = 0.30. The mixture with a mucilage/cement ratio = 0.45 displayed marginal reduction, and the mixture with mucilage/cement ratio = 0.60 exhibited a diffusion coefficient that was greater than the control for the specimens without moist curing.En esta investigación se evaluó el efecto de una solución de mucílago de nopal al 3% en los tiempos de fraguado, fluidez, hidratación y microestructura de pastas de cemento, y absorción capilar de agua y difusión de cloruros en concreto. La hidratación fue caracterizada por XRD y la microestructura por medio de SEM. Las relaciones solución de mucílago/cemento y agua/cemento fueron 0,30; 0,45 y 0,60. Los resultados en las pastas de cemento indican que el mucílago retarda los tiempos de fraguado, reduce la fluidez, retarda la hidratación del cemento, e inhibe la formación de cristales de hidróxido de calcio, comparados con los controles. La absorción capilar en concreto conteniendo mucílago se redujo significativamente y los coeficientes de difusión de cloruros disminuyeron hasta 20% en la mezcla mucílago/cemento = 0.30. En la relación mucílago/cemento = 0.45 la reducción fue marginal y

  9. THE OPTIMAL RATIO OF NILE TILAPIA (Oreochromis niloticus AND COMMON CARP (Cyprinus carpio FOR IMPROVING PRODUCTIVITY ON DEEP WATER POND

    Directory of Open Access Journals (Sweden)

    Imam Taufik

    2013-06-01

    Full Text Available Pond productivity can be increased by applied polyculture system in the deep pond. The purpose of this experiment is to examine the optimal ratio between nile tilapia and common carp, in order to increase the productivity. Nine concrete tanks (15 m2 with water depth of 2.2 m and were completed by water inlet, water outlet, and aeration. Both of nile tilapia and common carp with size ranging of 5-8 cm in total length were used. Stock density was 150 ind./m2. The difference ratio of both fish tilapia and carp of fish stocked as a treatment. The fish ratio this experiment were as followed: A 100%; B 80%:20%; C 60%:40%. Fish fed by pellet until at ad libitum. The duration of experiment was 100 days. Parameters such as survival, growth, and productivity were observed every ten days during the experiment period. Water quality parameters were also periodically observed. The results showed that survival of nile tilapia among the treatments were not significantly different (P>0.05 where survival of common carp at B treatment was better than C treatment (P<0.05. The highest of growth of absolute weight (94.86±2.85 g and total length (14.71±1 cm of nile tilapia at B treatment was found (P<0.05 where the best of growth of absolute weight (106.52±10.47 g and total length (11.57±1.78 cm of common carp was also found at B treatment (P<0.05. Biomass productivity at B treatment was the highest compared with A treatment (P<0.05. Combination between polyculture and the deep water pond technology could increase productivity. The polyculture system and the deep water pond technology would be able to keep constant water quality within in the threshold accordance with the regulation for fish culture.

  10. Why is the Ratio of Reflectivity Effective for Chlorophyll Estimation in the Lake Water?

    Directory of Open Access Journals (Sweden)

    Kazuo Oki

    2010-07-01

    Full Text Available The reasons why it is effective to estimate the chlorophyll-a concentration with the ratio of spectral radiance reflectance at the red light region and near infrared regions were shown in theory using a two-flow model. It was found that all of the backscattering coefficients can consequently be ignored by using the ratio of spectral radiance reflectance, which is the ratio of the upward radiance to the downward irradiance, at the red light and near infrared regions. In other words, the ratio can be expressed by using only absorption coefficients, which are more stable for measurement than backscattering coefficients. In addition, the band selection is crucial for producing the band ratio when the chlorophyll-a concentration is estimated without the effects of backscattering. I conclude that the two wavelengths selected must be close, but one must be within the absorption range of chlorophyll-a, and the other must be outside of the absorption range of chlorophyll-a, in order to accurately estimate the chlorophyll-a concentration.

  11. Beta-tricalcium phosphate release from brushite cement surface.

    Science.gov (United States)

    Alkhraisat, M Hamdan; Mariño, F Tamimi; Retama, J Rubio; Jerez, L Blanco; López-Cabarcos, E

    2008-03-01

    Different in vivo studies demonstrated that brushite cements are biocompatible, bioresorbable, and osteoconductive. However, the decay of brushite cements has been scarcely studied even though it may be of great concern for clinical applications in highly blood-perfused regions. This work was elaborated to elucidate factors that determine brushite cement surface disintegration. For that, brushite cements were modified using in their preparation different aqueous solutions of phosphoric, glycolic, tartaric, and citric acids in concentrations that were reported to improve the cement properties. Two-viscosity enhancing polysaccharides, chondroitin-4 sulfate and hyaluronic acid, were also assayed. Thereafter, pre- and set cement samples were immersed in distilled water for 24 h. The cement-solid weight loss, microstructure, liquid phase viscosity, mean size of the released particles, and zeta potential were analyzed using X-ray diffraction, FTIR spectroscopy, light scattering, scanning electron microscopy and optical microscopy. It was found that the particles released from the cement surface were beta-TCP, and their amount depends on the carboxylic acid used in the preparation of the cement. The addition of hyaluronic acid and chondroitin-4 sulfate decreased the amount of released particles from the surface of the set brushite cement made with citric acid. Furthermore, the hyaluronic acid increased significantly the viscosity of the citric acid solution and the cement paste prepared with this liquid phase showed a pronounced step down in particle release. In this study, we showed that the water solubility of calcium carboxylate and the viscosity of mixing liquid may dictate the superficial disintegration of brushite cements.

  12. Retrieval of water vapor mixing ratio from a multiple channel Raman-scatter lidar using an optimal estimation method.

    Science.gov (United States)

    Sica, R J; Haefele, A

    2016-02-01

    Lidar measurements of the atmospheric water vapor mixing ratio provide an excellent complement to radiosoundings and passive, ground-based remote sensors. Lidars are now routinely used that can make high spatial-temporal resolution measurements of water vapor from the surface to the stratosphere. Many of these systems can operate during the day and night, with operation only limited by clouds thick enough to significantly attenuate the laser beam. To enhance the value of these measurements for weather and climate studies, this paper presents an optimal estimation method (OEM) to retrieve the water vapor mixing ratio, aerosol optical depth profile, Ångstrom exponent, lidar constants, detector dead times, and measurement backgrounds from multichannel vibrational Raman-scatter lidars. The OEM retrieval provides the systematic uncertainties due to the overlap function, calibration factor, air density and Rayleigh-scatter cross sections, in addition to the random uncertainties of the retrieval due to measurement noise. The OEM also gives the vertical resolution of the retrieval as a function of height, as well as the height to which the contribution of the a priori is small. The OEM is applied to measurements made by the Meteoswiss Raman Lidar for Meteorological Observations (RALMO) in the day and night for clear and cloudy conditions. The retrieved water vapor mixing ratio is in excellent agreement with both the traditional lidar retrieval method and coincident radiosoundings.

  13. 水对水泥乳化沥青砂浆动态力学性能的影响%Effect of Water on Dynamic Mechanical Properties of Cement Emulsified Asphalt Mortar

    Institute of Scientific and Technical Information of China (English)

    田冬梅; 邓德华; 田青; 潘云瑞; 唐斯

    2013-01-01

    采用沥青与水泥的质量比为0.3的阴离子乳化沥青砂浆圆柱体试件,将其真空吸水饱和后经恒湿干燥法获得不同饱水度,再利用MTS 810疲劳试验机对基准试件和不同饱水度试件进行不同应力水平的疲劳试验,研究了水对水泥乳化沥青砂浆动态力学性能的影响。结果表明:与基准试件相比,吸水试件的极限疲劳强度显著降低,且饱水度越大,极限疲劳强度降低幅度越大;由于水泥乳化沥青砂浆中沥青相的动态黏弹性行为,使基准试件与吸水试件在不同应力水平下的应变均随着循环次数的增加而逐渐增大;基准试件的疲劳破坏形式为劈裂破坏,大多数为竖向裂缝,而在高频动荷载作用下吸水试件孔隙水形成超孔隙水压,对孔隙周围结构产生剪切作用,使其发生剪切破坏,裂缝呈倾斜状。%The mortar specimens with a mass ratio of asphalt/cement as 0.3 were prepared with anion emulsified asphalt. After being saturated by water in the vacuum chamber, these mortar specimens in a constant humidity dryer were dried to certain mois-ture contents, respectively. The fatigue test was carried on the reference specimen and specimens with different saturation values by MTS 810 fatigue machine. Effect of water on the dynamic mechanical properties of cement emulsified asphalt mortar was in-vestigated. The results show that the ultimate fatigue strength of the suction specimens decreases, compared to the reference specimen. The strain under a certain stress range increases with the increase of cycle number due to the dynamic viscoelastic be-havior of asphalt in the specimens for both reference and suction specimens. The vertical fatigue cracks appear in the reference specimen, meaning the splitting failure, but the sloping cracks appear in most various saturation specimens, reflecting the shear failure due to the shear effect of excess pore pressure on the surrounding

  14. Evaluation of the Katz-Thompson model for estimating the water permeability of cement-based materials from mercury intrusion porosimetry data

    Energy Technology Data Exchange (ETDEWEB)

    El-Dieb, A.S.; Hooton, R.D. (Univ. of Toronto, Ontario (Canada). Dept. of Civil Engineering)

    1994-01-01

    The permeability of concrete is becoming a focal characteristic with regard to the durability and performance of cement-based materials, pastes, mortars and concretes. Since it is mainly affected by the microstructure of the porous media, many models and theories have been developed relating the permeability of porous media to their microstructural parameters. One which proved to be useful in predicting the permeability of sedimentary rock, from mercury intrusion porosimetry data, is the Katz-Thompson theory. A review of this theory and its assumptions is presented, and its applicability to cementitious materials is investigated using two sets of data of various hardened cement pastes and concretes. Also, the major differences between cement-based materials and sedimentary rock from the microstructural point of view is reported.

  15. 5种常用减水剂对水泥砂浆耐久性的影响%Effects of Five Kinds of Water-Reducers on Durability of Cement Mortars

    Institute of Scientific and Technical Information of China (English)

    潘莉莎; 田政; 杜治光; 邱学青; 庞煜霞; 郑大锋

    2012-01-01

    Effects of five kinds of water-reducing agents, calcium lignosulfonate(CLS), modified calcium lignosulfonate(GCLl-6A) , amino-sulfonic based superplasticizer(ASP), sulfonated naphthalene formaldehyde(FDN) and sulfonated melamine urea formaldehyde resin(SMUF), on the durability of cement mortars were studied including impermeability, carbonization depth and shrinkage. The research results indicate that durability of cement mortar mixed with SMUF is the most excellent; durability of cement mortar mixed with GCL1-6A and FDN is next; that mixed with CLS is the weakest.%研究了木素磺酸钙(CLS)、改性木素磺酸钙(GCL1-6A)、氨基磺酸甲醛缩合物(ASP)、萘磺酸甲醛缩合物(FDN)和磺化三聚氰胺脲醛树脂(SMUF)这5种常用减水剂对水泥砂浆抗渗性、抗碳化性和收缩性等耐久性指标的影响.结果表明:掺SMUF的水泥砂浆其长期性和耐久性最优,其次是掺GCL1-6A,FDN的水泥砂浆,而掺CLS的水泥砂浆最差.

  16. The Application Study of Self-healing Cement in Shallow Water%自愈合水泥在浅海固井中的应用研究

    Institute of Scientific and Technical Information of China (English)

    陈大钧; 张直建; 雷鑫宇; 齐志刚

    2013-01-01

    According to the actual situation of the shallow cementing,the self-healing properties of self-healing cement is studied.The experiment used simulated seawater to slurry mixing,and tested the compressive strength recovery and the permeability declines of the cement under different curing temperature and medium.Under the curing temperature of 50 ℃ and 70 ℃,the cement,s compressive strength recovery and permeability decline under the simulated seawater conservation are more than 100% ; in crude oil curing,cement,s compressive strength recovery and permeability decreased more than 90%.%针对浅海固井的实际情况,研究了自愈合水泥的自愈合性能.实验利用模拟海水配浆,并测试了水泥石试件在模拟海水、原油、不同温度养护下的抗压强度的恢复情况及其渗透率的下降情况.实验结果表明,在50℃、70℃养护温度下,模拟海水养护中的水泥石试件抗压强度恢复和渗透率的下降均超过了100%;在原油养护下的水泥石试件抗压强度恢复和渗透率的下降均达到了90%以上.

  17. Dynamic Performance of High Bypass Ratio Turbine Engines With Water Ingestion

    Science.gov (United States)

    Murthy, S. N. B.

    1996-01-01

    The research on dynamic performance of high bypass turbofan engines includes studies on inlets, turbomachinery and the total engine system operating with air-water mixture; the water may be in vapor, droplet, or film form, and their combinations. Prediction codes (WISGS, WINCOF, WINCOF-1, WINCLR, and Transient Engine Performance Code) for performance changes, as well as changes in blade-casing clearance, have been established and demonstrated in application to actual, generic engines. In view of the continuous changes in water distribution in turbomachinery, the performance of both components and the total engine system must be determined in a time-dependent mode; hence, the determination of clearance changes also requires a time-dependent approach. In general, the performance and clearances changes cannot be scaled either with respect to operating or ingestion conditions. Removal of water prior to phase change is the most effective means of avoiding ingestion effects. Sufficient background has been established to perform definitive, full scale tests on a set of components and a complete engine to establish engine control and operability with various air-water vapor-water mixtures.

  18. Evaluation of super-water reducers for highway applications

    Science.gov (United States)

    Whiting, D.

    1981-03-01

    Super-water reducers were characterized and evaluated as potential candidates for production of low water to cement ratio, high strength concretes for highway construction applications. Admixtures were composed of either naphthalene or melamine sulfonated formaldehyde condensates. A mini-slump procedure was used to assess dosage requirements and behavior of workability with time of cement pastes. Required dosage was found to be a function of tricalcium aluminate content, alkali content, and fineness of the cement. Concretes exhibited high rates of slump loss when super-water reducers were used. The most promising area of application of these products appears to be in production of dense, high cement content concrete using mobile concrete mixer/transporters.

  19. A case study to detect the leakage of underground pressureless cement sewage water pipe using GPR, electrical, and chemical data.

    Science.gov (United States)

    Liu, Guanqun; Jia, Yonggang; Liu, Hongjun; Qiu, Hanxue; Qiu, Dongling; Shan, Hongxian

    2002-03-01

    The exploration and determination of leakage of underground pressureless nonmetallic pipes is difficult to deal with. A comprehensive method combining Ground Penetrating Rader (GPR), electric potential survey and geochemical survey is introduced in the leakage detection of an underground pressureless nonmetallic sewage pipe in this paper. Theoretically, in the influencing scope of a leakage spot, the obvious changes of the electromagnetic properties and the physical-chemical properties of the underground media will be reflected as anomalies in GPR and electrical survey plots. The advantages of GPR and electrical survey are fast and accurate in detection of anomaly scope. In-situ analysis of the geophysical surveys can guide the geochemical survey. Then water and soil sampling and analyzing can be the evidence for judging the anomaly is caused by pipe leakage or not. On the basis of previous tests and practical surveys, the GPR waveforms, electric potential curves, contour maps, and chemical survey results are all classified into three types according to the extent or indexes of anomalies in orderto find out the leakage spots. When three survey methods all show their anomalies as type I in an anomalous spot, this spot is suspected as the most possible leakage location. Otherwise, it will be down grade suspected point. The suspect leakage spots should be confirmed by referring the site conditions because some anomalies are caused other factors. The excavation afterward proved that the method for determining the suspected location by anomaly type is effective and economic. Comprehensive method of GRP, electric potential survey, and geochemical survey is one of the effective methods in the leakage detection of underground nonmetallic pressureless pipe with its advantages of being fast and accurate.

  20. Statistical Study on Cement-Soil Mixture Strength

    Institute of Scientific and Technical Information of China (English)

    YU Zhiqiang; CAO Yonghua; YAN Shuwang

    2005-01-01

    This paper presents an investigation on strength of cement deep mixing (CDM) mixture. Four typical works of offshore or land-based projects are introduced. With samples from these projects and laboratory tests, statistical analysis is made on the increment law of the strength of cement-soil mixture with different amount of cement, and strengths under different working conditions are compared. It is found that the amount of cement in the cement-soil mixture is closely related to the unconfined compressive strength of the mixture. At the age of 90 d,the unconfined compressive strength of the cement-soil mixture increased by 0.054 Mpa-0.124 Mpa with each cement increasing 10 kg/m3 in the cement-soil mixture, averagely increased by 0.085 Mpa, while that at the age of 120 d increased by 11% in comparison.The quality of the cement-soil mixture should be comprehensively evaluated in accordance with the trimmed average of strength, coefficient of variation and rock quality designation (RQD) indicators of sampling ratio.

  1. Minerals of expansive and non-shrinkage sulfomineral cements

    Directory of Open Access Journals (Sweden)

    Samchenko Svetlana V.

    2017-01-01

    Full Text Available Usually to obtain expansive cements sulfoaluminate clinker or mix aluminate clinker with calcium sulfates (gypsum, hemihydrate, anhydrate are used. For these cements ettringite is an important hydration product and kinetic reaction of this phase plays an important role in determinаting performance. The alternative aluminate phases may be ferrite containing ones. This article deals with the composition and properties of solid solution of calcium sulfoaluminate, sulfoferrite and sulfoaluminoferrite cements. It was studied an influence of calcium sulfate on structure and properties of calcium aluminate and ferrite phases, and their stability under high temperatures. Beside that the properties of cements containing these phases were studied. The investigation of hydration and properties of sulfomineral cements shows that ettringite and its analogies are formed in such way to provide expansion and compression of cement stone. Degree of expansion and self-stressing of cement stone depends not only on composition of sulfated minerals but on ratio and types of clinkers. The higher expansion is reached by the use of high alite containing Portland cement clinker together with sulfoaluminate or sulfoalumoferrite one, the lower expansion is reached by addition of sulfoalumoferrite and sulfoferrite clinkers. These cements are classified as self-stressing, expansive or shrinkage-compensating ones depend on the degree of their expansion after 28 days of curing.

  2. Spencer-Attix water/medium stopping-power ratios for the dosimetry of proton pencil beams.

    Science.gov (United States)

    Gomà, C; Andreo, P; Sempau, J

    2013-04-21

    This paper uses Monte Carlo simulations to calculate the Spencer-Attix water/medium stopping-power ratios (sw, med) for the dosimetry of scanned proton pencil beams. It includes proton energies from 30 to 350 MeV and typical detection materials such as air (ionization chambers), radiochromic film, gadolinium oxysulfide (scintillating screens), silicon and lithium fluoride. Track-ends and particles heavier than protons were found to have a negligible effect on the water/air stopping-power ratios (sw, air), whereas the mean excitation energy values were found to carry the largest source of uncertainty. The initial energy spread of the beam was found to have a minor influence on the sw, air values in depth. The water/medium stopping-power ratios as a function of depth in water were found to be quite constant for air and radiochromic film-within 2.5%. Also, the sw, med values were found to have no clinically relevant dependence on the radial distance-except for the case of gadolinium oxysulfide and proton radiography beams. In conclusion, the most suitable detection materials for depth-dose measurements in water were found to be air and radiochromic film active layer, although a small correction is still needed to compensate for the different sw, med values between the plateau and the Bragg peak region. Also, all the detection materials studied in this work-except for gadolinium oxysulfide-were found to be suitable for lateral dose profiles and field-specific dose distribution measurements in water.

  3. Hybridization morphology and dentin bond stability of self-etch primers with different ethanol/water ratios.

    Science.gov (United States)

    Fontes, Silvia T; Lima, Giana S; Ogliari, Fabrício A; Piva, Evandro; Moraes, Rafael R

    2012-07-01

    This study evaluated the influence of ethanol/water ratios on the bond strength to dentin of experimental two-step, self-etch adhesive systems. Self-etch primers were prepared with constant 40 mass % of solvents. The ethanol/water ratios tested were 7:1 (P1), 3:1 (P2), and 1:1 (P3); primers with only ethanol (PE) or water (PW) as solvent were also tested. The bond strength to the dentin was investigated through a microtensile bond strength test. Resin-dentin beam-shaped specimens were obtained and tested after 24 h, 6 months, and 1 year of storage in water at 37°C. The hybridization morphology was analyzed using SEM. For bond strength at 24 h, PE = P1, P1 = P2, and P2, P3 and PW > PE. After 6 months, PE = P1 6 months = 1 year. For P2, P3 and PW, 24 h = 6 months > 1 year. For PE and P1, adhesive failures were predominant at 24 h, mixed or adhesive failures after 6 months, and premature debonding was predominant after 1 year. For P2, mixed failures were predominant at 24 h and 6 months, and premature debonding after 1 year. For P3 and PW, mixed failures were predominant at all storage periods. The SEM analysis revealed no clear differences in the hybridization patterns yielded by the water-based primers; PE showed formation of irregular resin tags.

  4. Comparing Water Vapor Mixing Ratio Profiles and Cloud Vertical Structure from Multiwavelength Raman Lidar Retrievals and Radiosounding Measurements

    OpenAIRE

    Costa-Surós Montserrat; Stachlewska Iwona S.; Markowicz Krzysztof

    2016-01-01

    A study of comparison of water vapor mixing ratio profiles, relative humidity profiles, and cloud vertical structures using two different instruments, a multiwavelength Aerosol-Depolarization-Raman lidar and radiosoundings, is presented. The observations were taken by the lidar located in Warsaw center and the radiosoundings located about 30km to the North in Legionowo (Poland). We compared the ground-based remote sensing technology with in-situ method in order to improve knowledge about wate...

  5. Effects of elevated CO2 concentration on growth and water usage of tomato seedlings under different ammonium/nitrate ratios

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Increasing atmospheric CO2 concentration is generally expected to enhance photosynthesis and growth of agricultural C3 vegetable crops,and therefore results in an increase in crop yield.However,little is known about the combined effect of elevated CO2 and N species on plant growth and development.Two growth-chamber experiments were conducted to determine the effects of NH4+/NO3- ratio and elevated CO2 concentration on the physiological development and water use of tomato seedlings.Tomato was grown for 45 d in containers with nutrient solutions varying in NH4+/NO3- ratios and CO2 concentrations in growth chambers.Results showed that plant height,stem thickness,total dry weight,dry weight of the leaves,stems and roots,G value (total plant dry weight/seedling days),chlorophyll content,photosynthetic rate,leaf-level and whole plant-level water use efficiency and cumulative water consumption of tomato seedlings were increased with increasing proportion of NO3- in nutrient solutions in the elevated CO2 treatment.Plant biomass,plant height,stem thickness and photosynthetic rate were 67%,22%,24% and 55% higher at elevated CO2 concentration than at ambient CO2 concentration,depending on the values of NH4+/NO3- ratio.These results indicated that elevating CO2 concentration did not mitigate the adverse effects of 100% NH4+-N (in nutrient solution) on the tomato seedlings.At both CO2 levels,NH4+/NO3- ratios of nutrient solutions strongly influenced almost every measure of plant performance,and nitrate-fed plants attained a greater biomass production,as compared to ammonium-fed plants.These phenomena seem to be related to the coordinated regulation of photosynthetic rate and cumulative water consumption of tomato seedlings.

  6. Pu-239 and Pu-240 inventories and Pu-240/ Pu-239 atom ratios in the water column off Sanriku, Japan.

    Science.gov (United States)

    Yamada, Masatoshi; Zheng, Jian; Aono, Tatsuo

    2013-04-01

    A magnitude 9.0 earthquake and subsequent tsunami occurred in the Pacific Ocean off northern Honshu, Japan, on 11 March 2011 which caused severe damage to the Fukushima Dai-ichi Nuclear Power Plant. This accident has resulted in a substantial release of radioactive materials to the atmosphere and ocean, and has caused extensive contamination of the environment. However, no information is available on the amounts of radionuclides such as Pu isotopes released into the ocean at this time. Investigating the background baseline concentration and atom ratio of Pu isotopes in seawater is important for assessment of the possible contamination in the marine environment. Pu-239 (half-life: 24,100 years), Pu-240 (half-life: 6,560 years) and Pu-241 (half-life: 14.325 years) mainly have been released into the environment as the result of atmospheric nuclear weapons testing. The atom ratio of Pu-240/Pu-239 is a powerful fingerprint to identify the sources of Pu in the ocean. The Pu-239 and Pu-240 inventories and Pu-240/Pu-239 atom ratios in seawater samples collected in the western North Pacific off Sanriku before the accident at Fukushima Dai-ichi Nuclear Power Plant will provide useful background baseline data for understanding the process controlling Pu transport and for distinguishing additional Pu sources. Seawater samples were collected with acoustically triggered quadruple PVC sampling bottles during the KH-98-3 cruise of the R/V Hakuho-Maru. The Pu-240/Pu-239 atom ratios were measured with a double-focusing SF-ICP-MS, which was equipped with a guard electrode to eliminate secondary discharge in the plasma and to enhance overall sensitivity. The Pu-239 and Pu-240 concentrations were 2.07 and 1.67 mBq/m3 in the surface water, respectively, and increased with depth; a subsurface maximum was identified at 750 m depth, and the concentrations decreased with depth, then increased at the bottom layer. The total Pu-239+240 inventory in the entire water column (depth interval 0

  7. Transition of stable isotope ratios of leaf water under simulated dew formation.

    Science.gov (United States)

    Kim, Kyounghee; Lee, Xuhui

    2011-10-01

    Dew formation, a common meteorological phenomenon, is expected to intensify in the future. Dew can influence the H₂¹⁸O and HDO isotopic compositions of leaf water (δ(L) ), but the phenomenon has been neglected in many experimental and modelling studies. In this study, the dew effect on δ(L) was investigated with a dark plant chamber in which dew formation was introduced. The H₂¹⁸O and HDO compositions of water vapour, dew water and leaf water of five species were measured for up to 48 h of dew exposure. Our results show that the exchanges of H₂¹⁸O and HDO in leaf water with the air continued in the darkness when the net H₂¹⁶O flux was zero. Our estimates of the leaf conductance using the isotopic mass balance method ranged from 0.035 to 0.087 mol m⁻² s⁻¹, in broad agreement of the night-time stomatal conductance reported in the literature. In our experiments, the conductance of the C₃ species was 0.04 ± 0.01 mol m⁻² s⁻¹ and that of the C₃ plants was 0.10 ± 0.04 mol m⁻² s⁻¹. At the end of 16 h dew exposure, 72 (±17) and 94 (±11)% of the leaf water came from dew according to the ¹⁸O and D tracer, respectively. © 2011 Blackwell Publishing Ltd.

  8. Thermal performance of higher aspect ratio microchannels using TiO2-water nanofluids.

    Science.gov (United States)

    Raghuraman, D R S; Nagarajan, P K; Suresh, S

    2013-04-01

    An experimental setup was developed to study the heat transfer and fluid flow characteristics in rectangular copper microchannels with hydraulic diameter 29.4 microm using TiO2-Water nanofluids. The experimental facility is validated using existing correlations and subsequently tested with 0.1% and 0.3% concentrations of TiO2 nanofluids. The thermal resistance of heat sink with nanofluids is compared with the base fluid. It is inferred that 0.3% TiO2-Water nanofluids have 18% lower thermal resistance as compared to base fluid having for the same operating conditions.

  9. DEVELOPMENT OF POLYMER GEL SYSTEMS TO IMPROVE VOLUMETRIC SWEEP AND REDUCE PRODUCING WATER/OIL RATIOS

    Energy Technology Data Exchange (ETDEWEB)

    G. Paul Willhite; Stan McCool; Don W. Green; Min Cheng; Rajeev Jain; Tuan Nguyen

    2003-11-01

    Gelled polymer treatments are applied to oil reservoirs to increase oil production and to reduce water production by altering the fluid movement within the reservoir. This report describes the results of the first year of a three-year research program that is aimed at the understanding of the chemistry of gelation and the fundamental mechanisms that alter the flows of oil and water in reservoir rocks after a gel treatment. Work has focused on a widely-applied system in field applications, the partially hydrolyzed polyacrylamide-chromium acetate gel. Gelation occurs by network formation through the crosslinking of polyacrylamide molecules as a result of reaction with chromium acetate. The initial reaction between chromium acetate and one polymer is referred to as the uptake reaction. The uptake reaction was studied as functions of chromium and polymer concentrations and pH values. Experimental data were regressed to determine a rate equation that describes the uptake reaction of chromium by polyacrylamide. Pre-gel aggregates form and grow as the reactions between chromium acetate and polyacrylamide proceed. A statistical model that describes the growth of pre-gel aggregates was developed using the theory of branching processes. The model gives molecular weight averages that are expressed as functions of the conversion of the reactive sites on chromium acetate or on the polymer molecule. Results of the application of the model correlate well with experimental data of viscosity and weight-average molecular weight and gives insights into the gelation process. A third study addresses the flow of water and oil in rock material after a gel treatment. Previous works have shown that gel treatments usually reduce the permeability to water to a greater extent than the permeability to oil is reduced. This phenomenon is referred to as disproportionate permeability reduction (DPR). Flow experiments were conducted to determine the effect of polymer and chromium concentrations on

  10. The fluid-compensated cement bond log

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, T.H.; Leslie, H.D.; Wheelis, W.B.

    1984-09-01

    An experimental and numerical wave mechanics study of cement bond logs demonstrated that wellsite computer processing can now segregate wellbore fluid effects from the sonic signal response to changing cement strength. Traditionally, cement logs have been interpreted as if water were in the wellbore, without consideration of wellbore fluid effects. These effects were assumed to be negligible. However, with the increasing number of logs being run in completion fluids such as CaCl/sub 2/, ZnBr/sub 2/, and CaBr/sub 2/, large variations in cement bond logs became apparent. A Schlumberger internal paper showing that bond log amplitude is related to the acoustic impedance of the fluid in which the tool is run led to a comprehensive study of wellbore fluid effects. Numerical and experimental models were developed simulating wellbore geometry. Measurements were conducted in 5-, 7-, and 95/8-in. casings by varying the wellbore fluid densities, viscosities, and fluid types (acoustic impedance). Parallel numerical modeling was undertaken using similar parameters. The results showed that the bond log amplitude varied dramatically with the wellbore fluid's acoustic impedance; for example, there was a 70 percent increase in the signal amplitude for 11.5-lb/ gal CaCl/sub 2/ over the signal amplitude in water. This led to the development of a Fluid-Compensated Bond log that corrects the amplitude for acoustic impedance of varying wellbore fluids, thereby making the measurements more directly related to the cement quality.

  11. Clinical applications of glass-ionomer cements.

    Science.gov (United States)

    McLean, J W

    1992-01-01

    The use of glass-ionomer cements in clinical dentistry is now well established. They have a number of unique properties, including adhesion to moist tooth structure, biological compatibility, and anticariogenic properties due to their fluoride release. Their use in treating early carious or erosion lesions has been widely investigated. Established techniques include fissure filling and sealing, restoration of class 5 erosion lesions without cavity preparation, and the internal occlusal fossa or tunnel restoration. The "sandwich" technique using glass-ionomer cements as "dentin substitutes" has enabled composite restorations to be used with greater safety where pulpal damage may occur. The future probably lies in using a laminate technique where materials that attach to dentin and form a biological seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity leading to poor surface polish. Solving these problems is formidable, since inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this paper. In particular, clinical success depends upon early protection of the cement from hydration or dehydration, and the current use of light-cured bonding agents has largely solved this problem.

  12. Orbital and suborbital variability in North Atlantic bottom water temperature obtained from deep-sea ostracod Mg/Ca ratios

    Science.gov (United States)

    Cronin, T. M.; Dwyer, G.S.; Baker, P.A.; Rodriguez-Lazaro, J.; DeMartino, D.M.

    2000-01-01

    Magnesium/calcium (Mg/Ca) ratios were measured in the deep-sea ostracod (Crustacea) genus Krithe from Chain core 82-24-4PC from the western mid-Atlantic Ridge (3427 m) in order to estimate ocean circulation and bottom water temperature (BWT) variability over the past 200,000 years. Mg/Ca ratios have been used as a paleothermometer because the ratios are controlled primarily by ambient water temperatures at the time the organism secretes its adult carapace. Over the past two glacial-interglacial cycles, Mg/Ca values oscillated between about 7 mmol/mol and 12 mmol/mol, equivalent to a BWT range of 0 to > 3.5??C. The lowest values were obtained on specimens from glacial marine isotope stages (MISs) 2, 4 and 6; the highest values were obtained from specimens from the early part of the Holocene interglacial (MIS 1), and also from MISs 5 and 7. These trends suggest that BWTs in the North Atlantic Ocean fluctuate over orbital time scales. Suborbital variability in Mg/Ca ratios and BWT was also observed for the past 100,000 years. Ratios rose from ~8 mmol/mol to ~10 mmol/mol (implying a BWT increase of ~1 to 3??C) during 14 Mg/Ca excursions. The highest ratios were found in Krithe dated at approximately 32, 36-38, 43, 48, 73, 85 and 93 ka. Although the age model for the Chain 82-24-4PC and temporal resolution do not allow precise correlation, some of these deep-sea bottom temperature excursions appear to correspond to Heinrich events recorded in other regions of the North Atlantic and perhaps Dansgaard-Oeschger interstadial events recorded in Greenland ice cores. If confirmed, this would support the hypothesis that millennial-scale oscillations of climate in the North Atlantic are capable of affecting global climate via thermohaline circulation changes. (C) 2000 Elsevier Science B.V.

  13. Devitrification of ionomer glass and its effect on the in vitro biocompatibility of glass-ionomer cements.

    Science.gov (United States)

    Hurrell-Gillingham, K; Reaney, I M; Miller, C A; Crawford, A; Hatton, P V

    2003-08-01

    The effects of devitrification of an ionomer glass with a molar composition 4.5SiO(2).3Al(2)O(3).1.5P(2)O(5).3CaO.2CaF(2) on cement formation and in vitro biocompatibility were investigated. Differential thermal analysis was used to study the phase evolution in the glass, and to determine the heat treatments for production of glass-ceramics. X-ray diffraction patterns from glass frit heat-treated at 750 degrees C for 2h contained peaks corresponding to apatite (JCPDS 15-876), whereas for samples heat-treated at 950 degrees C for 2h apatite and mullite (JCPDS 15-776) were the major phases detected. Transmission electron microscopy (TEM) confirmed that apatite and apatite-mullite phases were present after heat treatments at 750 degrees C and 950 degrees C respectively. Glass and glass-ceramics were ground to prepare <45microm powders and glass ionomer cements were produced using a ratio of 1g powder: 0.2g PAA: 0.3g 10% m/v tartaric acid solution in water. In vitro biocompatibility was evaluated using cultured rat osteosarcoma (ROS) cells. Scanning electron microscopy (SEM) showed that cells colonised the surfaces of cements prepared using untreated ionomer glass and glass crystallised to form apatite (750 degrees C/2h). However, quantitative evaluation using MTT and total protein assays indicated that more cell growth occurred in the presence of cements prepared using ionomer glasses crystallised to apatite than cements prepared using untreated glass. The least cell growth and respiratory activity was observed on cements made with crystallised glass containing both apatite and mullite. It was concluded that the controlled devitrification of ionomer glasses could be used to produce GIC bone cements with improved biocompatibility.

  14. Strength development characteristics of concrete produced with blended cement using ground granulated blast furnace slag (GGBS) under various curing conditions

    Indian Academy of Sciences (India)

    SHAHAB SAMAD; ATTAULLAH SHAH; MUKESH C LIMBACHIYA

    2017-07-01

    To reduce the embodied carbon dioxide of structural concrete, Portland cement (PC) in concrete can be partially replaced with ground granulated blast furnace slag (GGBS). In this research effect of partial replacement of cement with GGBS on strength development of concrete and cured under summer and wintercuring environments is established. Three levels of cement substitution i.e., 30%, 40% and 50% have been selected. Early-age strength of GGBS concrete is lower than the normal PC concrete which limits its use in the fast-track construction and post-tensioned beams which are subjected to high early loads. The strength gainunder winter curing condition was observed as slower. By keeping the water cement ratio low as 0.35, concrete containing GGBS up to 50% can achieve high early-age strength. GGBS concrete gains more strength than the PC concrete after the age of 28 day till 56 day. The mechanical properties of blended concrete for various levels of cement replacement have been observed as higher than control concrete mix having no GGBS.

  15. SODIUM CITRATE INFLUENCE ON FORMATION OF CEMENT STONE IN THE ALUMINOUS BINDER

    Directory of Open Access Journals (Sweden)

    S. N. Leonovich

    2016-01-01

    Full Text Available The paper deals with the effect of sodium citrate on the formation of a cement stone in the aluminous binder. Formation of cement stone framework in cement hydraulic binder is accompanied with complicated physical and chemical processes of interphase interactions and dispersion, these processes are predicated on qualitative and quantitative composition of the cement mortar, continuous changes in its properties from preparation stage till curing. Addition of sodium citrate to tempering water enhances hydration of both Portland cement and calcium aluminate cement. Process pertaining to an increase of cement hydration rate is considered as a consequence of destruction in surface formations and exclusion of damping effect in respect of hydration rate and hydrolysis of products resulted from interaction of clinker material with tempering. It has been established that sodium citrate makes it possible to control processes of hydration, hydrolysis, binding and curing for cement mass. High degree of hydration of aluminous cement in the presence of sodium citrate provides fast binding and curing of binder, low porosity and rather high compression breaking strength of cement stone for all curing stages. An increase in concentration of sodium citrate in cement mixture up to 10 % of the cement mass exerts an influence not only on the process of cement mortar liquefaction, reduction of time for cement mass setting and hardening but also increases compression strength of cement stone. An analysis of the structure for cleavage surface of cement stone gives ground to declare that the addition of sodium citrate provides cement stone sealing and reduces its water absorption.

  16. Short-term Mechanical Properties of Glass Ionomer Cement

    Institute of Scientific and Technical Information of China (English)

    TANG Sanbao; XU Dongxuan

    2009-01-01

    The setting reaction of glass ionomer cement was studied by analyzing and comparing the short-tem mechanical properties of set cement stored in silicone oil,air and distilled water respectively at different temperatures.For the set cement stored at 37℃,the strength of the sample in the air reached the maximum value after 24 h,then decreased to about 210 MPa and kept steady.The strength of the sample in water increased continuously and slowly,however,the increasing rate of sample stored in silicone oil was higher than that in the water.At 20℃,the increasing rate of compressive strength for sample in air was higher than those in silicone oil and water.The diffusion speed and maintenance of water has significant effects on the mechanical properties of glass ionomer cements.

  17. Water-quality characteristics, including sodium-adsorption ratios, for four sites in the Powder River drainage basin, Wyoming and Montana, water years 2001-2004

    Science.gov (United States)

    Clark, Melanie L.; Mason, Jon P.

    2006-01-01

    The U.S. Geological Survey, in cooperation with the Wyoming Department of Environmental Quality, monitors streams throughout the Powder River structural basin in Wyoming and parts of Montana for potential effects of coalbed natural gas development. Specific conductance and sodium-adsorption ratios may be larger in coalbed waters than in stream waters that may receive the discharge waters. Therefore, continuous water-quality instruments for specific conductance were installed and discrete water-quality samples were collected to characterize water quality during water years 2001-2004 at four sites in the Powder River drainage basin: Powder River at Sussex, Wyoming; Crazy Woman Creek near Arvada, Wyoming; Clear Creek near Arvada, Wyoming; and Powder River at Moorhead, Montana. During water years 2001-2004, the median specific conductance of 2,270 microsiemens per centimeter at 25 degrees Celsius (?S/cm) in discrete samples from the Powder River at Sussex, Wyoming, was larger than the median specific conductance of 1,930 ?S/cm in discrete samples collected downstream from the Powder River at Moorhead, Montana. The median specific conductance was smallest in discrete samples from Clear Creek (1,180 ?S/cm), which has a dilution effect on the specific conductance for the Powder River at Moorhead, Montana. The daily mean specific conductance from continuous water-quality instruments during the irrigation season showed the same spatial pattern as specific conductance values for the discrete samples. Dissolved sodium, sodium-adsorption ratios, and dissolved solids generally showed the same spatial pattern as specific conductance. The largest median sodium concentration (274 milligrams per liter) and the largest range of sodium-adsorption ratios (3.7 to 21) were measured in discrete samples from the Powder River at Sussex, Wyoming. Median concentrations of sodium and sodium-adsorption ratios were substantially smaller in Crazy Woman Creek and Clear Creek, which tend to

  18. Spatial Variability of Nitrogen Isotope Ratios of Particulate Material from Northwest Atlantic Continental Shelf Waters

    Science.gov (United States)

    Human encroachment on the coastal zone has led to a rise in the delivery of nitrogen (N) to estuarine and near-shore waters. Potential routes of anthropogenic N inputs include export from estuaries, atmospheric deposition, and dissolved N inputs from groundwater outflow. Stable...

  19. Spatial Variability of Nitrogen Isotope Ratios of Particulate Material from Northwest Atlantic Continental Shelf Waters

    Science.gov (United States)

    Human encroachment on the coastal zone has led to a rise in the delivery of nitrogen (N) to estuarine and near-shore waters. Potential routes of anthropogenic N inputs include export from estuaries, atmospheric deposition, and dissolved N inputs from groundwater outflow. Stable...

  20. Temperature calibration of Mg/Ca ratios in the intermediate water benthic foraminifer Hyalinea balthica

    NARCIS (Netherlands)

    Rosenthal, Y.; Morley, A.; Barras, C.; Katz, M.E.; Jorissen, F.; Reichart, G.-J.; Oppo, D.W.; Linsley, B.K.

    2011-01-01

    Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and δ18O in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4°C and 13°C. This shallow infaunal species is primarily abundant in neritic to upper

  1. Temperature calibration of Mg/Ca ratios in the intermediate water benthic foraminifer Hyalinea balthica

    NARCIS (Netherlands)

    Rosenthal, Y.; Morley, A.; Barras, C.; Katz, M.E.; Jorissen, F.; Reichart, G.-J.; Oppo, D.W.; Linsley, B.K.

    2011-01-01

    Core top samples from Indonesian and northeast Atlantic depth transects were used to calibrate Mg/Ca and δ18O in tests of the calcitic benthic foraminifer Hyalinea balthica to bottom water temperature between 4°C and 13°C. This shallow infaunal species is primarily abundant in neritic to upper bathy

  2. The Evaluation of Material Properties of Low-pH Cement Grout for the Application of Cementitious Materials to Deep Radioactive Waste Repository Tunnels

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Seop; Kwon, S. K.; Cho, W. J.; Kim, G. W

    2009-12-15

    Considering the current construction technology and research status of deep repository tunnels for radioactive waste disposal, it is inevitable to use cementitious materials in spite of serious concern about their long-term environmental stability. Thus, it is an emerging task to develop low pH cementitious materials. This study reviews the state of the technology on low pH cements developed in Sweden, Switzerland, France, and Japan as well as in Finland which is constructing a real deep repository site for high-level radioactive waste disposal. Considering the physical and chemical stability of bentonite which acts as a buffer material, a low pH cement limits to pH {<=}11 and pozzolan-type admixtures are used to lower the pH of cement. To attain this pH requirement, silica fume, which is one of the most promising admixtures, should occupy at least 40 wt% of total dry materials in cement and the Ca/Si ratio should be maintained below 0.8 in cement. Additionally, selective super-plasticizer needs to be used because a high amount of water is demanded from the use of a large amount of silica fume. In this report, the state of the technology on application of cementitious materials to deep repository tunnels for radioactive waste disposal was analysed. And the material properties of low-pH and high-pH cement grouts were evaluated base on the grout recipes of ONKALO in Finlan.

  3. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Hasan KAPLAN; Hanifi BİNİCİ

    1995-01-01

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

  4. Development of nanosilica bonded monetite cement from egg shells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: huanzhou@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu (China); Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Division of Dentistry, The University of Toledo, Toledo, OH (United States)

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement.

  5. Hydration process in Portland cement blended with activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    Xian-ping LIU; Pei-ming WANG; Min-ju DING

    2011-01-01

    This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development.The hydration process was investigated by various means:isothermal calorimetry,thermal analysis,non-cvaporable water measurement,and X-ray diffraction analysis.The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend.The pozzolanic reaction occurs over a period of between 7 and 90 d,consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates.These hydrates are similar to those found in pure Portland cement.The results show that if activated coal gangue is substituted for cement at up to 30% (w/w),it does not significantly affect the final compressive strength of the blend.A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material.The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation.However,the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

  6. Influence of raw powder granulometry on the mechanical properties of a calcium phosphate bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Pittet, C. [Swiss Federal Inst. of Tech., Lausanne (Switzerland). Lab. de Technologie des Poudres; Hopital Orthopedique de la Suisse Romande, Lausanne (Switzerland); Grasso, P.; Lemaitre, J. [Swiss Federal Inst. of Tech., Lausanne (Switzerland). Lab. de Technologie des Poudres

    2002-07-01

    Brushite cement is a calcium phosphate cement obtained by mixing three powders with water. Starting powders are monocalcium phosphate monohydrate (MCPM), calcium sulfate hemihydrate (CSH) and {beta}-tricalcium phosphate ({beta}-TCP). The main phase obtained after setting is brushite (DCPD). The goal of this work was to mill the starting powders to obtain a finer and more homogeneous microstructure after setting, in order to enhance the mechanical properties of the cement. All three powders were milled and freeze-dried. The median diameters passed from 70.5 to 6.2 {mu}m for MCPM, 27.2 to 1.1 {mu}m for CSH, 2.4 to 1.5 {mu}m for {beta}-TCP. Specific surface areas of the powders increased on milling. Attrition of MCPM and CSH appeared to be beneficial to the maximum stresses the set cement can withstand. Cements prepared with raw powders showed 1.4 MPa indirect tensile strength and 4.4 MPa compressive strength. With milled MCPM and CSH, those values reached 4.1 and 22.1 MPa respectively. After these benefits, we tried to use the milled {beta}-TCP expecting further enhancement. To ensure wetting of all three powders and to keep the same paste rheology, the liquid/solid ratio had to be increased. The indirect tensile strength was seen to decrease by a factor of 3 when three milled powders were used at the same time. SEM of the fracture surfaces showed that milled {beta}-TCP formed clusters that did not react to form brushite. Lowering the maximum indirect tension stress is due to the fact that less brushite was formed, and to a higher porosity in the final product (mainly due to the higher liquid/solid ratio). (orig.)

  7. Sulfate deterioration of cement-based materials examined by x-ray microtomography

    Science.gov (United States)

    Naik, Nikhila N.; Kurtis, Kimberly E.; Wilkinson, Angus P.; Jupe, Andrew C.; Stock, Stuart R.

    2004-10-01

    Sulfate ions present in soil, groundwater, seawater, decaying organic matter, acid rain, and industrial effluent adversely affect the long-term durability of portland cement concrete, but lack of complete understanding of the nature and consequences of sulfate attack hamper our ability to accurately predict performance of concrete in sulfate-rich environments. One impediment to improved understanding of sulfate deterioration of cement-based materials has been the lack of appropriate non-destructive characterization techniques. Laboratory x-ray microtomography affords an opportunity to study in situ the evolution of physical manifestations of damage due to sulfate exposure. The influence of materials selection and mixture parameters - including water-to-cement ratio, cement type, and presence or absence of aggregate, as well as the influence of sulfate exposure conditions, including sulfate and cation type (i.e., Na2SO4 and MgSO4) and concentration - have been examined by microtomography to determine their influence on the rate and character of the sulfate-induced deterioration.

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

    OpenAIRE

    Natt Makul; Dinesh Kumar Agrawa

    2013-01-01

    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 a...

  9. Effects of chitosan on water resistance of magnesium phosphate cement%壳聚糖对磷酸镁水泥抗水性能影响∗

    Institute of Scientific and Technical Information of China (English)

    廖建国; 段星泽; 李艳群; 邹琴

    2015-01-01

    Magnesium phosphate cement (MPC)has excellent mechanical performance,which can be applied in civilian,military buildings and medical materials.However,the strength of MPC decreases fast because of wa-ter erosion.The method to improve the water resistance of MPC was an important research direction.This pa-per studied the influence of chitosan on setting time,strength and the crystalline structure of MPC paste.And the strength and structural change of MPC hardened paste was studied after soaked with different cycles in wa-ter(H2 O),simulated body fluid (SBF),phosphate buffered solution (PBS).The results show that:borax as a retarder can significantly prolong the setting time of MPC;unreacted borax and a large amount of over plus MgO exist in MPC and the main hydration products of MPC was MgKPO4•6 H2 O;the addition of chitosan can make the structure of MPC hardened paste more compact.Since chitosan improved the water resistance of MPC,the loss of strength of MPC due to water erosionwas significantly reduced.The biological activity of MPC hardened paste was confirmed by the formation of spherical bone-like apatite crystal on its surface after socked in SBF.%磷酸镁水泥(MP C )力学性能优异,在民用、军事建筑和医用材料领域都有广泛应用前景。但MP C 在经受水环境侵蚀时,强度损失较快,故改善MP C抗水性是一个重要的研究方向。研究了壳聚糖(CS)对MPC浆体凝结时间、强度及晶相结构影响,并研究了掺入CS后MPC硬化体在水、模拟体液(SBF)、磷酸盐缓冲溶液(PBS)中浸泡不同周期后强度及结构变化。结果表明,硼砂作为缓凝剂可明显延长 MP C的凝结时间;MPC 主要水化产物为 MgKPO4•6 H2 O,存在未参与反应硼砂和大量剩余 MgO;添加 CS 可使MP C硬化体结构更加致密,在经受水环境侵蚀时, MPC硬化体的强度损失明显减小,说明 CS 能提高MPC的抗水性;同时,由于 MPC 硬化体在 SBF 中浸泡后表面有球状类骨

  10. Evaluation of frost damage in cement-based materials by a nonlinear elastic wave technique

    Science.gov (United States)

    Eiras, J. N.; Kundu, T.; Popovics, J. S.; Monzó, J.; Soriano, L.; Payá, J.

    2014-03-01

    Frost resistance of concrete is a major concern in cold regions. RILEM (International union of laboratories and experts in construction materials, systems and structures) recommendations provide two alternatives for evaluating frost damage by nondestructive evaluation methods for concrete like materials. The first method is based on the ultrasonic pulse velocity measurement, while the second alternative technique is based on the resonant vibration test. In this study, we monitor the frost damage in Portland cement mortar samples with water to cement ratio of 0.5 and aggregate to cement ratio of 3. The samples are completely saturated by water and are frozen for 24 hours at -25°C. The frost damage is monitored after 0, 5, 10, 15 and 20 freezing-thawing cycles by nonlinear impact resonance acoustic spectroscopy (NIRAS). The results obtained are compared with those obtained by resonant vibration tests, the second alternative technique recommended by RILEM. The obtained results show that NIRAS is more sensitive to early stages of damage than the standard resonant vibration tests.

  11. Durability of cement-based materials: modeling of the influence of physical and chemical equilibria on the microstructure and the residual mechanical properties; Durabilite des materiaux cimentaires: modelisation de l'influence des equilibres physico-chimiques sur la microstructure et les proprietes mecaniques residuelles

    Energy Technology Data Exchange (ETDEWEB)

    Guillon, E

    2004-09-15

    A large part of mechanical and durability characteristics of cement-based materials comes from the performances of the hydrated cement, cohesive matrix surrounding the granular skeleton. Experimental studies, in situ or in laboratory, associated to models, have notably enhanced knowledge on the cement material and led to adapted formulations to specific applications or particularly aggressive environments. Nevertheless, these models, developed for precise cases, do not permit to specifically conclude for other experimental conclusions. To extend its applicability domain, we propose a new evolutive approach, based on reactive transport expressed at the microstructure scale of the cement. In a general point of view, the evolution of the solid compounds of the cement matrix, by dissolutions or precipitations, during chemical aggressions can be related to the pore solution evolution, and this one relied to the ionic exchanges with the external environment. By the utilization of a geochemical code associated to a thermodynamical database and coupled to a 3D transport model, this approach authorizes the study of all aggressive solution. The approach has been validated by the comparison of experimental observations to simulated degradations for three different environments (pure water, mineralized water, seawater) and on three different materials (CEM I Portland cement with 0.25, 0.4 and 0.5 water-to cement ratio). The microstructural approach permits also to have access to mechanical properties evolutions. During chemical aggressions, the cement matrix evolution is traduced in a microstructure evolution. This one is represented from 3D images similarly to the models developed at NIST (National Institute of Standards and Technology). A new finite-element model, validated on previous tests or models, evaluates the stiffness of the cement paste, using as a mesh these microstructures. Our approach identifies and quantifies the major influence of porosity and its spatial

  12. Internal Curing Using Water-releasing Material for High Strength Micro-expansive Concrete

    Institute of Scientific and Technical Information of China (English)

    LU Linnu; YANG Wen; HE Yongjia; WU Jing; HU Shuguang

    2009-01-01

    Due to its low water content,it is difficult for expansive agent to have an effective expansive effect on high strength concrete to compensate its extensive shrinkage and form a certain expansion.To solve this problem,water-releasing material with water storage and releasing characteristics was incorporated into high strength micro-expansive concrete to provide internal curing,and expansive effect of expansive agent was improved.Migration of water from initially saturated water-releasing material to the surrounding hydrating cement paste was investigated.Based on a given efficient diffusion distance of water stored in water-releasing material,the mass and real water-cement ratio of cured cement paste were estimated.At the same time,the effect of internal curing of water-releasing material on the volume deformation of high strength micro-expansive concrete was investigated.

  13. Evaporative Control on Soil Water Isotope Ratios: Implications for Atmosphere-Land Surface Water Fluxes and Interpretation of Terrestrial Proxy Records

    Science.gov (United States)

    Kaushik, A.; Noone, D. C.; Berkelhammer, M. B.; O'Neill, M.

    2014-12-01

    The moisture balance of the continental boundary layer plays an important role in regulating the exchange of water and energy between the land surface and atmosphere. Near-surface moisture balance is controlled by a number of factors including precipitation, infiltration and evapotranspiration. Measurements of stable isotope ratios in water can be exploited to better understand the mechanisms controlling atmosphere-land surface water fluxes. Understanding the processes that set sub-surface water isotope ratios can prove useful for refining paleoclimate interpretations of stable oxygen and hydrogen isotope-based proxies. We present in situ tower-based measurements of stable isotope ratios of water (δD and δ18O) in vapor, precipitation and soil from the Boulder Atmospheric Observatory, a semi-arid tall-tower site in Erie, Colorado, from July 2012 to September 2014. Near surface profiles from 0 to 10 m were measured approximately every ninety minutes. Soil profiles from 0 to 30 cm, the region of maximum variability, were sampled on a weekly basis and cryogenically extracted for stable water isotope measurement. Evaporation-proof bulk rain collectors provided precipitation samples at this site. Results show disequilibrium exists between surface vapor and soil water isotopes, with the top 10 cm of soil water approaching equilibrium with the surface vapor right after a rain event because of high infiltration and saturation at the surface. At this semi-arid site with little vegetation, evaporative exchange is the main driver for soil water fluxes as the soil dries, corroborated by soil Dexcess profiles showing progressive enrichment through evaporation. In addition, when nighttime surface temperatures are cooler than deep soil, as is the case in many arid and semi-arid environments, upward vapor diffusion from the soil leads to dew formation at the surface which then contributes to surface vapor values. We use these observations to constrain a Craig-Gordon evaporation

  14. Very high precision and accuracy analysis of triple isotopic ratios of water. A critical instrumentation comparison study.

    Science.gov (United States)

    Gkinis, Vasileios; Holme, Christian; Morris, Valerie; Thayer, Abigail Grace; Vaughn, Bruce; Kjaer, Helle Astrid; Vallelonga, Paul; Simonsen, Marius; Jensen, Camilla Marie; Svensson, Anders; Maffrezzoli, Niccolo; Vinther, Bo; Dallmayr, Remi

    2017-04-01

    We present a performance comparison study between two state of the art Cavity Ring Down Spectrometers (Picarro L2310-i, L2140-i). The comparison took place during the Continuous Flow Analysis (CFA) campaign for the measurement of the Renland ice core, over a period of three months. Instant and complete vaporisation of the ice core melt stream, as well as of in-house water reference materials is achieved by accurate control of microflows of liquid into a homemade calibration system by following simple principles of the Hagen-Poiseuille law. Both instruments share the same vaporisation unit in a configuration that minimises sample preparation discrepancies between the two analyses. We describe our SMOW-SLAP calibration and measurement protocols for such a CFA application and present quality control metrics acquired during the full period of the campaign on a daily basis. The results indicate an unprecedented performance for all 3 isotopic ratios (δ2H, δ17O, δ18O ) in terms of precision, accuracy and resolution. We also comment on the precision and accuracy of the second order excess parameters of HD16O and H217O over H218O (Dxs, Δ17O ). To our knowledge these are the first reported CFA measurements at this level of precision and accuracy for all three isotopic ratios. Differences on the performance of the two instruments are carefully assessed during the measurement and reported here. Our quality control protocols extend to the area of low water mixing ratios, a regime in which often atmospheric vapour measurements take place and Cavity Ring Down Analysers show a poorer performance due to the lower signal to noise ratios. We address such issues and propose calibration protocols from which water vapour isotopic analyses can benefit from.

  15. Post cementation sensitivity evaluation of glass Ionomer, zinc phosphate and resin modified glass Ionomer luting cements under class II inlays: An in vivo comparative study

    Directory of Open Access Journals (Sweden)

    Chandrasekhar V

    2010-01-01

    Full Text Available Objective: This study aims to compare the patient-perceived post-cementation sensitivity of class II metal restorations preoperatively, immediately after cementation, one week after cementation and one month after cementation with (1 Glass Ionomer luting cement (2 Zinc Phosphate cement and (3 Resin-modified Glass Ionomer luting cement. Materials and Methods: A total of 60 patients, irrespective of sex, in the age group of 15-50 years were selected and the teeth were randomly divided into three groups of 20 each. Twenty inlay cast restorations were cemented with three different luting cements. The criteria adapted to measure tooth sensitivity in the present study were objective examination for sensitivity.(1 Cold water test (2 Compressed air test and (3 Biting pressure test. Results: The patients with restorations cemented with Resin-modified Glass ionomer demonstrated the least postoperative sensitivity when compared with Glass Ionomer and zinc phosphate cement at all different intervals of time evaluated by different tests. Conclusion: The patients with restorations cemented with resin-modified Glass ionomer demonstrated the least postoperative sensitivity.

  16. 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.

  17. Characteristics and propierties of oil-well cements additioned with blast furnace slag

    Directory of Open Access Journals (Sweden)

    Sánchez, R.

    2011-06-01

    Full Text Available The present paper addresses the alkali activation of Portland cements containing blast furnace slag (20 and 30% of the cement by 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 activating solution 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. 29Si and 27Al MAS NMR and BSE/EDX studies, in turn, showed that the C-S-H gel forming in the alkali-activated cement/slag pastes contained Al in tetrahedral positions and low Ca/Si ratios.

    En el presente trabajo se ha estudiado la activación alcalina de cementos Pórtland con incorporación de escoria de horno alto (20% y 30% con respecto al peso de cemento para su posible aplicación en la construcción de pozos petrolíferos. Los estudios de hidratación realizados indican que en mezclas cemento/escoria, la disolución activadora de silicato sódico inhibe parcialmente la disolución de las fases silicato del cemento Pórtland originando un retraso de su hidratación así como la menor precipitación de productos de reacción. Dicha parcial inhibición de los procesos reactivos en las mezclas cemento/escoria originan resistencias mecánicas significativamente inferiores a las pastas de cemento Portland hidratadas con agua. Finalmente, los estudios de 29Si y 27Al RMN MAS y BSE/EDX indican que el gel C-S-H formado en pastas de mezcla cemento/escoria activadas alcalinamente presenta Al en posiciones tetraédricas y bajas relaciones Ca/Si.

  18. Aluminum-free glass-ionomer bone cements with enhanced bioactivity and biodegradability

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Filipa O.; Pires, Ricardo A., E-mail: rpires@dep.uminho.pt; Reis, Rui L.

    2013-04-01

    Al-free glasses of general composition 0.340SiO{sub 2}:0.300ZnO:(0.250-a-b)CaO:aSrO:bMgO:0.050Na{sub 2}O:0.060P{sub 2}O{sub 5} (a, b = 0.000 or 0.125) were synthesized by melt quenching and their ability to form glass-ionomer cements was evaluated using poly(acrylic acid) and water. We evaluated the influence of the poly(acrylic acid) molecular weight and glass particle size in the cement mechanical performance. Higher compressive strength (25 ± 5 MPa) and higher compressive elastic modulus (492 ± 17 MPa) were achieved with a poly(acrylic acid) of 50 kDa and glass particle sizes between 63 and 125 μm. Cements prepared with glass formulation a = 0.125 and b = 0.000 were analyzed after immersion in simulated body fluid; they presented a surface morphology consistent with a calcium phosphate coating and a Ca/P ratio of 1.55 (similar to calcium-deficient hydroxyapatite). Addition of starch to the cement formulation induced partial degradability after 8 weeks of immersion in phosphate buffer saline containing α-amylase. Micro-computed tomography analysis revealed that the inclusion of starch increased the cement porosity from 35% to 42%. We were able to produce partially degradable Al-free glass-ionomer bone cements with mechanical performance, bioactivity and biodegradability suitable to be applied on non-load bearing sites and with the appropriate physical characteristics for osteointegration upon partial degradation. Zn release studies (concentrations between 413 μM and 887 μM) evidenced the necessity to tune the cement formulations to reduce the Zn concentration in the surrounding environment. Highlights: ► We developed partially degradable, bioactive, Al-free glass-ionomer cements (GICs). ► Enhanced mechanical behavior was achieved using 63–125 μm glass particle size range. ► The highest mechanical resistance was obtained using poly(acrylic acid) of 50 kDa. ► Biodegradation was successfully tuned to start 8 weeks after GIC preparation. ► Zn

  19. Development of Polymer Gel Systems to Improve Volumetric Sweep and Reduce Producing Water/Oil Ratios

    Energy Technology Data Exchange (ETDEWEB)

    G. Paul Willhite; Stan McCool; Don W. Green; Min Cheng; Feiyan Chen

    2005-12-31

    Gelled polymer treatments are applied to oil reservoirs to increase oil production and to reduce water production by altering the fluid movement within the reservoir. This report describes the results of a 42-month research program that focused on the understanding of gelation chemistry and the fundamental mechanisms that alter the flows of oil and water in reservoir rocks after a gel treatment. Work was conducted on a widely applied system in the field, the partially hydrolyzed polyacrylamide-chromium acetate gel. Gelation occurs by network formation through the crosslinking of polyacrylamide molecules as a result of reaction with chromium acetate. Pre-gel aggregates form and grow as reactions between chromium acetate and polyacrylamide proceed. A rate equation that describes the reaction between chromium acetate and polymer molecules was regressed from experimental data. A mathematical model that describes the crosslinking reaction between two polymer molecules as a function of time was derived. The model was based on probability concepts and provides molecular-weight averages and molecular-weight distributions of the pre-gel aggregates as a function of time and initial system conditions. Average molecular weights of pre-gel aggregates were measured as a function of time and were comparable to model simulations. Experimental methods to determine molecular weight distributions of pre-gel aggregates were unsuccessful. Dissolution of carbonate minerals during the injection of gelants causes the pH of the gelant to increase. Chromium precipitates from solution at the higher pH values robbing the gelant of crosslinker. Experimental data on the transport of chromium acetate solutions through dolomite cores were obtained. A mathematical model that describes the transport of brine and chromium acetate solutions through rocks containing carbonate minerals was used to simulate the experimental results and data from literature. Gel treatments usually reduce the permeability

  20. 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.

  1. 磷酸钾镁胶结材料早期水稳定性调控技术研究%Control Technology Study of Early Water Stability of Magnesium Potassium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    邵云霞; 顾玉萍; 杨建明

    2013-01-01

    Effect of acid-base ratio and ash fly content on the early water stability of magnesium potassium phosphate cement (MKPC) was investigated through testing compressive strength,residual strength in water curing condition,and theirs effect mechanism were analyzed by testing hydration temperature rise of MKPC pastes and analyzing the pore structure of hardened MKPC pastes.The result indicated that,because of the composite retarder effectively relaying early hydration rate of MKPC paste,acid component in MKPC can be greatly improve and perfectly participated in hydration reaction,and the increase of proportion of base component can provide enough unreacted MgO grain cores insulting in the enhancement of micro-aggregate effect and improvement of pore structure.Because of adding some fly ash in MKPC with high proportion of base component,the spherical particles in fly ash can fill the pore in the hydrates and form good gradation with unreacted MgO grain cores insulting in the compact structure of hardened MKPC paste which hindered the infiltration of water dissolution of phosphates and hydrolysis of hydrates in water curing condition.The early water stability was obviously improved and met the demand of hydraulic binder.%通过测试磷酸钾镁胶结材料(MKPC)浆体的抗压强度和水养护剩余强度率,研究酸碱组份比例、粉煤灰掺量对MKPC浆体早期水稳定性的影响.通过测试MKPC浆体的初始水化温度和MKPC硬化体的吸水率,分析其影响机理,结果表明:由于复合缓凝剂有效延缓了MKPC浆体的早期水化反应速度,MKPC浆体组成结构中酸组份比例可大幅降低,有足量未反应的MgO颗粒存在起到微集料作用.在MKPC中掺适量粉煤灰且保证较高的碱组份比例,粉煤灰球形颗粒可填充水化物之间孔隙,且与足量未水化的MgO颗粒形成较好的级配搭配,使MKPC硬化体结构更加致密;在水养护条件下,水份不易渗入,磷酸盐及其水化物溶解和水解

  2. Spectral analysis software improves confidence in plant and soil water stable isotope analyses performed by isotope ratio infrared spectroscopy (IRIS).

    Science.gov (United States)

    West, A G; Goldsmith, G R; Matimati, I; Dawson, T E

    2011-08-30

    Previous studies have demonstrated the potential for large errors to occur when analyzing waters containing organic contaminants using isotope ratio infrared spectroscopy (IRIS). In an attempt to address this problem, IRIS manufacturers now provide post-processing spectral analysis software capable of identifying samples with the types of spectral interference that compromises their stable isotope analysis. Here we report two independent tests of this post-processing spectral analysis software on two IRIS systems, OA-ICOS (Los Gatos Research Inc.) and WS-CRDS (Picarro Inc.). Following a similar methodology to a previous study, we cryogenically extracted plant leaf water and soil water and measured the δ(2)H and δ(18)O values of identical samples by isotope ratio mass spectrometry (IRMS) and IRIS. As an additional test, we analyzed plant stem waters and tap waters by IRMS and IRIS in an independent laboratory. For all tests we assumed that the IRMS value represented the "true" value against which we could compare the stable isotope results from the IRIS methods. Samples showing significant deviations from the IRMS value (>2σ) were considered to be contaminated and representative of spectral interference in the IRIS measurement. Over the two studies, 83% of plant species were considered contaminated on OA-ICOS and 58% on WS-CRDS. Post-analysis, spectra were analyzed using the manufacturer's spectral analysis software, in order to see if the software correctly identified contaminated samples. In our tests the software performed well, identifying all the samples with major errors. However, some false negatives indicate that user evaluation and testing of the software are necessary. Repeat sampling of plants showed considerable variation in the discrepancies between IRIS and IRMS. As such, we recommend that spectral analysis of IRIS data must be incorporated into standard post-processing routines. Furthermore, we suggest that the results from spectral analysis be

  3. Influence of Cooling to Heating Load Ratio on Optimal Supply Water and Air Temperatures in an Air Conditioning System

    Science.gov (United States)

    Karino, Naoki; Shiba, Takashi; Yokoyama, Ryohei; Ito, Koichi

    In planning an air conditioning system, supply water and air temperatures are important factors from the viewpoint of energy saving and cost reduction. For example, lower temperature supply water and air for space cooling reduce the coefficient of performance of a refrigeration machine, and increase the thickness of heat insulation material. However, they enable larger temperature differences, and reduce equipment sizes and power demand. It is also an important subject to evaluate the effect of the supply water and air temperatures on energy saving and cost reduction on the annual basis by considering not only cooling but also heating loads. The purposes of this paper are to propose an optimal planning method for an air conditioning system with large temperature difference, and to analyze the effect of supply water and air temperatures on the long-term economics through a numerical study for an office building. As a result, it is shown that the proposed method effectively determines supply water and air temperatures, and the influence of the cooling to heating load ratio on the long-term economics is clarified.

  4. Stable carbon isotope ratios of archaeal GDGTs in the marine water column and surface sediments

    Science.gov (United States)

    Pearson, A.; Hurley, S.; Close, H. G.; Jasper, C. E.

    2016-12-01

    Archaeal glycerol dibiphytanyl glycerol tetraether (GDGT) lipids are ubiquitous throughout the marine environment and are preserved in sediments and sedimentary rocks on million-year timescales. Variations in the number of ring-containing GDGT isomers in sediments correlate with differences in overlying sea surface temperatures, a relationship formalized in the TEX86 paleotemperature proxy. Ammonia-oxidizing Thaumarchaeota are believed to be the major sources of these GDGTs, implying that the greatest production and export of GDGTs from the water column should be associated with the maximum expression of ammonia monooxygenase (amoA) genes and maximum number of thaumarchaeal cells, both of which occur in the subsurface NO2- maximum near a depth of ca. 80-250 m. To examine the relationship between production and export of GDGTs from the water column, we measured the concentrations and δ13C values of GDGTs in suspended particulate matter (SPM) of the western South Atlantic Ocean and compared them to values from pure thaumarchaeal cultures and from available sediment core-tops from other locations. Thaumarchaeota are believed to fix the majority of their carbon directly from dissolved inorganic carbon (DIC). However, both the SPM and core-top δ13C values in some cases are moderately more 13C-depleted than would be predicted based on the 13C content of local DIC and the previously-published biosynthetic isotope fractionation (ɛ). This indicates that the average metabolism of the planktonic archaeal community either is mixotrophic (≥ 25% organic carbon assimilation) or that the published ɛ value for the model organism Nitrosopumilus maritimus may not be representative of the total autotrophic community. In addition to this offset, δ13C values of GDGTs in SPM inversely mirror DIC profiles, with lowest values in the nitrite maximum and higher values in the deeper water column, similar to the overall trends for bulk SPM. Finally, while individual GDGTs in SPM samples

  5. Heavy cement slurries; Pastas pesadas de cimento

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Francisco Avelar da; Conceicao, Antonio C. Farias [PETROBRAS, XX (Brazil). Distrito de Perfuracao do Nordeste. Div. de Tecnicas de Perfuracao; Marins, Carlos Cesar Silva [PETROBRAS, XX (Brazil). Dept. de Perfuracao. Div. de Revestimento e Cimentacao

    1989-12-31

    When going deeper in a high pressure well, the only way to successfully cement your casing or linear is through the use of heavy cement slurry. In 1987 PETROBRAS geologists presented to the Drilling Department a series of deep, hot and high pressure wells to be drilled. The Casing and Cement Division of this department then started a program to face this new challenge. This paper introduces the first part of this program and shows how PETROBRAS is dealing with heavy weight slurries. We present the slurry formulations tested in laboratory, the difficulties found in mixing them in the field, rheology measurements, API free water and API fluid loss from both laboratory and field samples. (author) 3 tabs.

  6. Stimuli-responsive cement-reinforced rubber.

    Science.gov (United States)

    Musso, Simone; Robisson, Agathe; Maheshwar, Sudeep; Ulm, Franz-Josef

    2014-05-14

    In this work, we report the successful development of a cement-rubber reactive composite with reversible mechanical properties. Initially, the composite behaves like rubber containing inert filler, but when exposed to water, it increases in volume and reaches a stiffness that is intermediate between that of hydrogenated nitrile butadiene rubber (HNBR) and hydrated cement, while maintaining a relatively large ductility characteristic of rubber. After drying, the modulus increases even further up to 400 MPa. Wet/drying cycles prove that the elastic modulus can reversibly change between 150 and 400 MPa. Utilizing attenuated total reflection Fourier transform infrared spectroscopy), we demonstrate that the high pH produced by the hydration of cement triggers the hydrolysis of the rubber nitrile groups into carboxylate anions. Thus, the salt bridges, generated between the carboxylate anions of the elastomer and the cations of the filler, are responsible for the reversible variations in volume and elastic modulus of the composite as a consequence of environmental moisture exposure. These results reveal that cement nanoparticles can successfully be used to accomplish a twofold task: (a) achieve an original postpolymerization modification that allows one to work with carboxylate HNBR (HXNBR) not obtained by direct copolymerization of carboxylate monomers with butadiene, and (b) synthesize a stimuli-responsive polymeric composite. This new type of material, having an ideal behavior for sealing application, could be used as an alternative to cement for oil field zonal isolation applications.

  7. DEVELOPMENT OF POLYMER GEL SYSTEMS TO IMPROVE VOLUMETRIC SWEEP AND REDUCE PRODUCING WATER/OIL RATIOS

    Energy Technology Data Exchange (ETDEWEB)

    G. Paul Willhite; Don W. Green; Stan McCool; Min Cheng; Feiyan Chen

    2004-02-01

    The objectives of the research are to improve the effectiveness of polymer gels to increase volumetric sweep efficiency of fluid displacement processes and to reduce water production in production wells. The research is based on experimental data and conceptual and mathematical models developed from interpretation of experimental data. This report describes two types of mathematical models that were developed. One model type simulates the chemical reactions where polymer molecules are crosslinked to form a 3-dimensional network or gel. The model is based on statistical probabilities of reactions and yields molecular weights averages and distributions as functions of conversion. The second model type simulates the transport of chromium acetate, a common polymer crosslinker, through porous dolomite rock and includes the mechanisms of dolomite dissolution and chromium precipitation. The chromium transport model reasonably agreed with experimental data.

  8. Imbalances in the hardness/alkalinity ratio of water and Nile tilapia’s growth performance - doi: 10.4025/actascitechnol.v36i1.18995

    Directory of Open Access Journals (Sweden)

    Davi de Holanda Cavalcante

    2014-01-01

    Full Text Available The present work determined the effects of water with unbalanced calcium hardness/total alkalinity (CH/TA ratio on Nile tilapia growth performance. Two unbalanced CH/TA ratios were tested for 8 weeks using one indoor system with 30 circular polyethylene 100 L tanks and one outdoor system with 36 circular polyethylene 250 L tanks. The factors and their specific levels tested were the total alkalinity of water (TA; 50 and 100 mg L-1 CaCO3 and the CH/TA ratio of water (CH/TA; 1/2, 1/1 and 5/1. In the indoor system, the 5/1 CH/TA ratio tanks had higher total ammonia nitrogen (TAN than the 1/2 or 1/1 CH/TA ratio tanks. In the outdoor system, higher concentrations of TAN were found in the 1/2 CH/TA ratio tanks. The soil of the 5/1 CH/TA ratio indoor tanks had higher concentrations of organic carbon than the 1/2 or 1/1 CH/TA ratio tanks. The detrimental effects of the 5/1 CH/TA ratio on fish growth performance were stronger than those associated with the 1/2 CH/TA ratio. A significantly better food conversion ratio was observed in the 1/1 CH/TA ratio outdoor tanks regardless of the TA level of the water.

  9. Near-field microwave inspection and characterization of cement based materials

    Science.gov (United States)

    Bois, Karl Joseph

    The objective of this research project has been to investigate the potential of correlating the near-field microwave reflection coefficient properties of hardened cement paste (water and cement powder), mortar (water, cement powder and sand) and concrete (water, cement powder, sand and coarse aggregate) specimens to their various constituent make-up and compressive strengths. The measurements were conducted using open-ended rectangular waveguide probes operating at various microwave frequencies and in-contact with cubic specimens. For each material, various properties of the measured microwave reflection coefficient, such as the mean of the measured magnitude of reflection coefficient, and the standard deviation of the measured magnitude of reflection coefficient at various frequencies were monitored. Subsequently, the measurements were correlated to important parameters such as w/c ratio, s/c ratio, ca/c ratio, cure-state, constituent volume content and compressive strength. Other issues such as the detection of aggregate segregation in concrete as well as the detection chloride in cement paste and mortar were also addressed. Other related issues such as the detection of grout in masonry blocks were also investigated. In achieving these objectives, several theoretical modeling efforts were required, constituting significant contributions to the available literature. A complete analytical full wave expression (i.e. inclusion of higher-order modes) for the fields at the aperture of an open-ended waveguide probe radiating into a dielectric infinite half-space was derived. Also a novel two-port transmission line dielectric property measurement technique for granular and liquid materials was developed. A decision making process, based on the maximum likelihood scheme, was also implemented to determine w/c, s/c and ca/c ratios from the measured mean and standard deviation of reflection coefficient at two frequency bands. Finally, the issue of non-contact measurement was

  10. Assessment of optimum dilution ratio for biohydrogen production by anaerobic co-digestion of press mud with sewage and water.

    Science.gov (United States)

    Radjaram, B; Saravanane, R

    2011-02-01

    Anaerobic co-digestion of press mud with water or sewage at ratios of 1:7.5, 1:10 and 1:12.5 were performed in continuously fed UASB reactors for hydrogen production. At a constant hydraulic retention time of 30 h, the specific hydrogen production rate was 187 mL/g volatile solids (VS) reduced during maximum biohydrogen production of 7960 mL/day at a 1:10 ratio of press mud to sewage. Chemical oxygen demand (COD) and VS reductions of 61% and 59% were noted on peak biohydrogen yield. A pH range of 5-6 was suitable at ambient temperature for entire process; a lower pH was inhibitory. Co-digestion of acidic press mud with sewage controlled pH for fermentation. Hence press mud can be exploited for biohydrogen production.

  11. Cytotoxicity of commonly used luting cements -An in vitro study.

    Science.gov (United States)

    Trumpaite-Vanagiene, Rita; Bukelskiene, Virginija; Aleksejuniene, Jolanta; Puriene, Alina; Baltriukiene, Daiva; Rutkunas, Vygandas

    2015-01-01

    The study aimed to 1) evaluate the cytotoxicity of luting cements: Hoffmann's Zinc Phosphate (Hoffmann's ZP), GC Fuji Plus Resin Modified Glass Ionomer (Fuji Plus RMGI) and 3M ESPE RelyX Unicem Resin Cement (RelyX Unicem RC) and 2) test if pre-washing reduces the cements' cytotoxicity. In vitro human gingival fibroblast (HGF) culture model was chosen. The cytotoxicity was evaluated by MTT test, the cell viability -by staining the cells with AO/EB dye mixture. The means±SD of Cell Survival Ratio (CSR%) were compared among different cement types under two testing conditions, with or without cement pre-washing. The CSR%s were compared by ANOVA and linear multiple regression (LMR). Hoffmann's ZPC was less cytotoxic, while Fuji Plus RMGIC and RelyX Unicem RC were more cytotoxic (ANOVA, ptype of cement and cement pre-washing jointly explained 90% of cell survival (LMR, p<0.001, adjusted squared R=0.889). The commonly used luting cements such as Hoffmann's ZP, Fuji Plus RMGI and RelyX Unicem RC may have a cytotoxic potential.

  12. 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 oxide and Portland cement/lead oxide presented the highest radiopacity values and differed significantly from the other materials (p oxide presented the lowest radiopacity values of all mixtures (p < 0.05). All tested substances presented higher radiopacity than that of dentin and may potentially be added to the 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.