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Sample records for cement components hydration

  1. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2001-01-01

    Ordinary Portland Cement (OPC) is often used for the solidification/stabilization (S/S) of waste containing heavy metals and salts. These waste components will precipitate in the form of insoluble compounds on to unreacted cement clinker grains preventing further hydration. In this study the long te

  2. Modelling the effects of waste components on cement hydration

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    2000-01-01

    Ordinary Portland Cement (OPC) is often used for the Solidification/Stabilization (S/S) of waste containing heavy metals and salts. These waste componenents will precipitate in the form of insoluble compounds onto unreacted cement clinker grains preventing further hydration. In this study the long t

  3. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

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

  4. Structural Investigations of Portland Cement Components, Hydration, and Effects of Admixtures by Solid-State NMR Spectroscopy

    DEFF Research Database (Denmark)

    Skibsted, Jørgen Bengaard; Andersen, Morten D.; Jakobsen, Hans Jørgen

    2006-01-01

    for the C-S-H phase formed during hydration. It will be demonstrated that Al3+ and flouride guest-ions in the anhydrous and hydrated calcium silicates can be studied in detail by 27Al and 19F MAS NMR, thereby providing information on the local structure and the mechanisms for incorporation of these ions...... in the cement phases. The role of flouride ions is of special interest for mineralized Portland cements and it demonstrated that the location of these anions in anhydrous and hydrated Portland cements can be clarified using 19F MAS or 29Si{19F} CP/MAS NMR despite these cements contain only about 0.2 wt...

  5. 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

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

    International Nuclear Information System (INIS)

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

  7. Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement

    Indian Academy of Sciences (India)

    Rohan Jadhav; N C Debnath

    2011-08-01

    The importance of computed X-ray diffraction patterns of various polymorphs of alite (3, 1, ), belite (, ), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are 3-alite phase and -belite phase, respectively. Both cubic and orthorhombic phases of C3A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with / ratio, 0.5 and the results are interpreted in the light of difference in phase compositions viz. -C2S/C3S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C3S hydration.

  8. Mesoscale texture of cement hydrates.

    Science.gov (United States)

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

    2016-02-23

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

  9. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

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

  10. A new geopolymeric binder from hydrated-carbonated cement

    OpenAIRE

    Paya Bernabeu, Jorge Juan; Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Soriano Martinez, Lourdes; Mitsuuchi Tashima, Mauro

    2012-01-01

    This paper evaluates the use of hydrated Portland cement as the raw material in the production of geopolymers. The silicon and aluminium oxides needed for the geopolymerization process were produced by the carbonation of hydrated Portland cement, which transforms CSH and CAH (Portland cement hydrates) into silica and alumina gels. Hydrated-carbonated Portland cement was alkali activated with a NaOH/waterglass solution. Pastes and mortars were prepared, and micro-structural and mechanical prop...

  11. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  12. Experimental techniques for cement hydration studies

    Directory of Open Access Journals (Sweden)

    Andreas Luttge

    2011-10-01

    Full Text Available Cement hydration kinetics is a complex problem of dissolution, nucleation and growth that is still not well understood, particularly in a quantitative way. While cement systems are unique in certain aspects they are also comparable to natural mineral systems. Therefore, geochemistry and particularly the study of mineral dissolution and growth may be able to provide insight and methods that can be utilized in cement hydration research. Here, we review mainly what is not known or what is currently used and applied in a problematic way. Examples are the typical Avrami approach, the application of Transition State Theory (TST to overall reaction kinetics and the problem of reactive surface area. Finally, we suggest an integrated approach that combines vertical scanning interferometry (VSI with other sophisticated analytical techniques such as atomic force microscopy (AFM and theoretical model calculations based on a stochastic treatment.

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

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

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

  14. 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.

  15. 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.

  16. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...... seven days, dilatometers were manually recorded during at least 56 days. The dispersion model was applied to fit chemical shrinkage results and to estimate the maximum (or ultimate) value for calculation of degree of hydration. Except for a pure Portland cement best fits were obtained by the general...

  17. Hydration of Portland cement with additions of calcium sulfoaluminates

    Energy Technology Data Exchange (ETDEWEB)

    Le Saout, Gwenn, E-mail: gwenn.le-saout@mines-ales.fr [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Lothenbach, Barbara [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hori, Akihiro [DENKA Chemicals GmbH, Wehrhahn-Center, Cantadorstr. 3, D-40211 Duesseldorf (Germany); Higuchi, Takayuki [Denki Kagaku Kogyo Kabushiki Kaisha (DENKA), Omi, Itoigawa, Niigata, 949-0393 (Japan); Winnefeld, Frank [Empa, Swiss Federal Laboratories for Materials Science and Technology, Concrete and Construction Chemistry Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland)

    2013-01-15

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

  18. Hydration of Portland cement with additions of calcium sulfoaluminates

    International Nuclear Information System (INIS)

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

  19. Rheological and hydration characterization of calcium sulfoaluminate cement pastes

    OpenAIRE

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

    2012-01-01

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

  20. Notes on hydrated cement fractals investigated by SANS

    Energy Technology Data Exchange (ETDEWEB)

    Ficker, T [Faculty of Civil Engineering, Physics Department, Technical University, Zizkova 17, CZ-602 00 Brno (Czech Republic); Len, A [Budapest Neutron Centre, Konkoly Thege 29-33, H-1525 Budapest (Hungary); Nemec, P [Faculty of Civil Engineering, Physics Department, Technical University, Zizkova 17, CZ-602 00 Brno (Czech Republic)

    2007-07-07

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

  1. Hydration of calcium sulfoaluminate cements - Experimental findings and thermodynamic modelling

    International Nuclear Information System (INIS)

    Calcium sulfoaluminate cements (CSA) are a promising low-CO2 alternative to ordinary Portland cements and are as well of interest concerning their use as binder for waste encapsulation. In this study, the hydration of two CSA cements has been investigated experimentally and by thermodynamic modelling between 1 h and 28 days at w/c ratios of 0.72 and 0.80, respectively. The main hydration product of CSA is ettringite, which precipitates together with amorphous Al(OH)3 until the calcium sulfate is consumed after around 1-2 days of hydration. Afterwards, monosulfate is formed. In the presence of belite, straetlingite occurs as an additional hydration product. The pore solution analysis reveals that straetlingite can bind a part of the potassium ions, which are released by the clinker minerals. The microstructure of both cements is quite dense even after 16 h of hydration, with not much pore space available at a sample age of 28 days. The pore solution of both cements is dominated during the first hours of hydration by potassium, sodium, calcium, aluminium and sulfate; the pH is around 10-11. When the calcium sulfate is depleted, the sulfate concentration drops by a factor of 10. This increases pH to around 12.5-12.8. Based on the experimental data, a thermodynamic hydration model for CSA cements based on cement composition, hydration kinetics of clinker phases and calculations of thermodynamic equilibria by geochemical speciation has been established. The modelled phase development with ongoing hydration agrees well with the experimental findings.

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

    International Nuclear Information System (INIS)

    Calcium silicate cements are widely used for low- and intermediate-level radioactive waste conditioning. However, wastes produced by nuclear activities are very diverse and some of their components may chemically react with cement phases. For instance, ashes resulting from the incineration of technological wastes including neoprene and polyvinylchloride may contain substantial amounts of soluble zinc chloride. This compound is known to strongly delay or inhibit Portland cement setting. One approach to limit adverse cement-waste interactions is to select a binder showing a better compatibility with the waste while keeping cement matrix advantages (low cost, simple process, hydration with water provided by the waste...). This work thus investigates the potential of calcium sulfo-aluminate cement for zinc Zn(II) immobilization. Four aspects were considered: hydration (kinetics and products formed), properties of hydrated binders, mechanisms of zinc retention and durability of the cement pastes (based on leaching experiments and modelling). The influence of three main parameters was assessed: the gypsum content of the cement, the concentration of ZnCl2 and the thermal evolution at early age. It follows that materials based on a calcium sulfo-aluminate cement containing 20% gypsum are interesting candidates for zinc Zn(II) stabilization/solidification: there is no delay in hydration, mineralogy of the hydrated phases is slightly dependent on thermal history, mechanical strength is high, dimensional changes are limited and zinc Zn(II) is well immobilized, even if the cement paste is leached by pure water during a long period (90 d). (author)

  3. Early hydration cement Effect of admixtures superplasticizers

    Directory of Open Access Journals (Sweden)

    Puertas, F.

    2001-06-01

    Full Text Available Early hydration of portland cement with superplasticizer admixtures of different nature has been studied. These admixtures were: one based on melamine synthetic, other based on vinyl copolymer and other based on polyacrylate copolymers. The dosage of the formers were constant (1% weigth of cement and for the third, the influence of admixture dosage was also evaluated, giving dosage values among 1-0.3%. The pastes obtained were studied by conduction calorimetry, XRD and FTIR. Also the apparent fluidity was determined by "Minislump" test. The main results obtained were: a superplasticizers admixtures used, regardless of their nature and for the polycarboxilate one the dosage, retard the silicate hydration (specially, alite phase, b The ettringite formation is affected by the nature of the admixture. cA relationship between the dosage of admixture based on polycarboxilates and the time at the acceleration has been established. A lineal relation (y = 11.03 + 16.05x was obtained. From these results is possible to know, in function of dosage admixture, the time when the masive hydration products and the setting times are produced. Also the total heat releases in these reactions is independent of the nature and dosage of admixture, saying that in all cases the reactions are the same.

    En el presente trabajo se ha estudiado la hidratación inicial de un cemento portland aditivado con superplastificantes de diferente naturaleza. Dichos aditivos fueron: uno basado en melaminas sintéticas, otro en copolímeros vinilicos y otro en policarboxilatos. La dosificación de los dos primeros se fijó constante en 1% en peso con relación al cemento, mientras que para el tercero se evaluó, también, la influencia de la dosificación, tomando proporciones desde el 1% hasta el 0,3%. Las pastas obtenidas se estudiaron por: calorimetría de conducción, DRX y FTIR. También se determinó la fluidez de la pasta a través del ensayo del "Minislump ". Los

  4. Effect on Hydration and Hardening of Tricalcium Phosphate Bone Cement

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The bioactive α-Ca3 (PO4)2 bone cement was studied by XRD , SEM and isothermal calorimetric measurements. The results showed that a mixed pattern of TCP and hydroxylapatite were obtained after hydration and hardening. The mechanism of hydration and hardening of the α-Ca3 ( PO4 )2 was dissolution-precipitation,(NH4) H2 PO4 was the best set accelerator to the α-Ca3 ( PO4 )2 cement, and the HAP powers and the(NH4) H2 PO4 concentration had a great effect on the hydration rate of α-Ca3 ( PO4 )2.

  5. A new quantification method based on SEM-EDS to assess fly ash composition and study the reaction of its individual components in hydrating cement paste

    Energy Technology Data Exchange (ETDEWEB)

    Durdziński, Paweł T., E-mail: pawel.durdzinski@gmail.com [Laboratory of Construction Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, CH-1015 Lausanne (Switzerland); Dunant, Cyrille F. [Laboratory of Construction Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, CH-1015 Lausanne (Switzerland); Haha, Mohsen Ben [HeidelbergCement Technology Center GmbH (HeidelbergCement AG), Rohrbacher Str. 95, 69181 Leimen (Germany); Scrivener, Karen L. [Laboratory of Construction Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, CH-1015 Lausanne (Switzerland)

    2015-07-15

    Calcareous fly ashes are high-potential reactive residues for blended cements, but their qualification and use in concrete are hindered by heterogeneity and variability. Current characterization often fails to identify the dominant, most reactive, amorphous fraction of the ashes. We developed an approach to characterize ashes using electron microscopy. EDS element composition of millions of points is plotted in a ternary frequency plot. A visual analysis reveals number and ranges of chemical composition of populations: silicate, calcium-silicate, aluminosilicate, and calcium-rich aluminosilicate. We quantified these populations in four ashes and followed their hydration in two Portland-ash systems. One ash reacted at a moderate rate: it was composed of 70 vol.% of aluminosilicates and calcium-silicates and reached 60% reaction at 90 days. The other reacted faster, reaching 60% at 28 days due to 55 vol.% of calcium-rich aluminosilicates, but further reaction was slower and 15 vol.% of phases, the silica-rich ones, did not react.

  6. 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.

  7. Research on Hydration of Steel Slag Cement Activated with Waterglass

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper studied the hydration and strength influence factors of Steel Slag Cement (SSC),such as the quantity of steel slag and slag and the dosage of additive.The results show that:(a) In the process of hydration of SSC,steel slag and slag activate each other;(b) Waterglass's structure forms the preliminary skeleton of SSC,and the hydration products of SSC link or fill in the skeleton;(c) Sodium in waterglass is the catalytic and its concentration does not change in the process of hydration.(d) Structure of activation is a significant factor to the property of SSC.

  8. Evolution of the hydration in cements with additions

    OpenAIRE

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

    2002-01-01

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

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

    OpenAIRE

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

    2013-01-01

    The main objective of this work is to study the hydration and properties of calciumsulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied paramet...

  10. Active iron-rich belite sulfoaluminate cements: clinkering and hydration.

    Science.gov (United States)

    Cuberos, Antonio J M; De la Torre, Angeles G; Alvarez-Pinazo, G; Martín-Sedeño, M Carmen; Schollbach, Katrin; Pöllmann, Herbert; Aranda, Miguel A G

    2010-09-01

    Ordinary Portland cement (OPC) is an environmentally contentious material, as for every ton of OPC produced, on average, 0.97 tons of CO2 are released. Conversely, belite sulfoaluminate (BSA) cements are promising eco-friendly building materials, as their production may deplete CO2 emissions up to 35% (compared to OPC). However, the hydration rate of belite is slow. Here, we report the clinkering of iron-rich BSA materials, their activation with B2O3, and establishing a methodology to measure their improved reactivities. Nonactivated BSA clinker contained only beta belite phase, 52 wt %. Meanwhile, BSA clinkers activated with 1 and 2 wt % of B2O3 contained 28 wt % of beta and 25 wt % of alpha'H; and 54 wt % of alpha'H phase, respectively. Therefore, activation of BSA has been proved as alpha'H-belite is stabilized. The hydration of the cements has been studied by laboratory and synchrotron X-ray powder diffraction (using Rietveld method and chemical constraints), calorimetry, and environmental scanning electron microscopy. Cement pastes have different hydration rates. For nonactivated BSA cement, 20 and 48% of the belite reacted after one and three months, respectively. Conversely, 37-49% after one month and 52-62% after three months of overall belite reactivities have been measured for BSA cements activated with B2O3. PMID:20701316

  11. Porous and adsorption properties of hydrated cement paste

    Directory of Open Access Journals (Sweden)

    Marina Biljana S.

    2004-01-01

    Full Text Available Adsorption isotherms of benzene on hydrated cement pastes prepared by cement ground with and without the addition of grinding aids, triethanol amine (TEA and ethylene glycol (EG were investigated. The adsorption isotherms were interpreted by means of the Dubinin-Astakhov (DA and Dubinin-Radushkevich-Stoeckli (DRS equations. The microporous structure of cement gel (C-S-H in the cement pastes, and changes in the Gibbs free energy of adsorption were determined. The mechanical properties of the cement pastes were also measured. It was evident that pastes with additives had different parameters of the DRS and DA equations: the volume and dimensions of the gel pores, the distribution of the dimensions, the characteristic energy of adsorption, and the change in the Gibbs free energy of adsorption. The mechanical properties were also different. The dispersity of the additive-containing ground cements had a favorable effect on the hydration processes. When applying TEA, it was also necessary to analyze its influence on the chemical behavior of hydration in the starting period.

  12. Dry-grinded ultrafine cements hydration. physicochemical and microstructural characterization

    Directory of Open Access Journals (Sweden)

    Foteini Kontoleontos

    2013-04-01

    Full Text Available The aim of the present research work was the evaluation of the physicochemical and microstructural properties of two ultrafine cements, produced by dry grinding of a commercial CEM I 42.5N cement. The effect of grinding on particle size distribution was determined by laser scattering analyzer. All cements were tested for initial and final setting times, consistency of standard paste, soundness, flow of normal mortar and compressive strengths after 1, 2, 7 and 28 days. The effect of the fineness on the heat of hydration was also investigated. The hydration products were determined by X-ray diffraction analysis and by Fourier transform infrared spectroscopy, at 1, 2, 7 and 28 days. The microstructure of the hardened cement pastes and their morphological characteristics were examined by scanning electron microscopy. Porosity and pore size distribution were evaluated by mercury intrusion porosimetry. The effects of greater fineness on compressive strengths were evident principally at early ages. After the first 24 hours of hydration, the compressive strength of the finest cements was about 3 times higher (over 48 MPa than the corresponding of CEM I 42.5N (15.1 MPa.

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

    OpenAIRE

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

    2014-01-01

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

  14. 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.

  15. Mesoscopic structure of cerium waste loaded hydrated cement by SANS

    International Nuclear Information System (INIS)

    Cementation is one of the most commonly used methods for conditioning radioactive wastes. It provides a cost-effective solution for encapsulation of low and intermediate level radioactive wastes into suitable solid form for long term safety storage. Cerium is used for decontamination of alpha contaminated metallic waste and after this decontamination process, secondary wastes with corrosion products are created, which must be managed properly and cemented for near surface disposal. In the present work, modification of mesoscopic structure in hydrated cement due to addition of simulated cerium waste at different concentrations has been investigated by small-angle neutron scattering (SANS). Structural modifications, in mesoscopic length scale, have been observed. The scattering profiles for three kinds of cement blocks (virgin, 10 g/l and 20 g/l of corrosion product (C.P.) with 4 mm thickness) are shown. Data have been analyzed in the light of polydisperse spherical particles model assuming a log-normal distribution. Widely separated bimodal particle size distributions best represent the present data. Further, it has been observed that the scattering profile obeys power-law (Q-n) behaviour in two domains of Q, which reflects the self-similar/self-affined morphology of the inhomogeneities. Estimated parameters from SANS data are tabulated. A comparison is shown mentioning the value of scattering radius of gyration, exponent values (η) and average particle size for each kind of hydrated cement sample. (author)

  16. Advances in understanding hydration of Portland cement

    Energy Technology Data Exchange (ETDEWEB)

    Scrivener, Karen L., E-mail: Karen.scrivener@epfl.ch [Laboratory of Construction Materials, Ecole Polytechnique Fédérale de Lausanne, 1015 (Switzerland); Juilland, Patrick [Sika Technology AG, Zürich (Switzerland); Monteiro, Paulo J.M. [Department of Civil and Environmental Engineering, University of California at Berkeley (United States)

    2015-12-15

    Progress in understanding hydration is summarized. Evidence supports the geochemistry dissolution theory as an explanation for the induction period, in preference to the inhibiting layer theory. The growth of C–S–H is the principal factor controlling the main heat evolution peak. Electron microscopy indicates that C–S–H “needles” grow from the surface of grains. At the peak, the surface is covered, but deceleration cannot be attributed to diffusion control. The shoulder peak comes from renewed reaction of C{sub 3}A after depletion of sulfate in solution, but release of sulfate absorbed on C–S–H means that ettringite continues to form. After several days space becomes the major factor controlling hydration. The use of new analytical technique is improving our knowledge of the action of superplasticizers and leading to the design of molecules for different applications. Atomistic modeling is becoming a topic of increasing interest. Recent publications in this area are reviewed.

  17. Zeolites as structure formation products of alkalineous cements hydration

    OpenAIRE

    Kryvenko, Р. V.; Runova, R. F.; Rudenko, I. I.

    2014-01-01

    The paper concerns analysis of theoretical and experimental studies, according to which, in conditions of artificial stone making for buildings purposes (cement, concrete), synthesis of alkaline aluminosilicates similar to natural minerals of zeolitic group occurs. Presence of such new formations in hydration products of standartized type alkaline cements provides their high running abilities and durability. Наведено аналіз теоретичних і експериментальних досл...

  18. Effect of curing temperatura on hydration process of different cement

    OpenAIRE

    Elkhadiri, I.; Palacios, M.; Puertas, F.

    2009-01-01

    [EN]Hydration was studied in two cements (CEM I 42.5R and CEM II/A-V 42.5R) cured at temperatures ranging from 4 to 85°C. Hydration was monitored with a number of instrumental techniques: X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Backscattered Electron (BSE) imaging in conjunction with Energy Dispersive X-ray analysis (EDX) and Nuclear Magnetic Resonance (MAS NMR). The mechanical strength of the pastes was likewise determined at different ages, while mercury int...

  19. Heavy Metal Desorption From Cement Hydrates Caused by Chloride Solutions

    OpenAIRE

    Hayashi, Akihiko; Ogawa, Yuko; Kawai, Kenji

    2014-01-01

    After the demolition of concrete structures, it is expected to recycle the whole of the demolished concrete. As of now, however, it is difficult to recycle the fine powders generated in the processes of demolition of concrete and manufacture of recycled aggregate because these powders may contain heavy metals exceeding the soil environmental standard, and such powders are disposed finally. It is well known that heavy metals are easily adsorbed on cement hydrates. To promote the total recyclin...

  20. HYDRATION AND PROPERTIES OF BLENDED CEMENT SYSTEMS INCORPORATING INDUSTRIAL WASTES

    Directory of Open Access Journals (Sweden)

    Heikal M.

    2013-06-01

    Full Text Available This paper aims to study the characteristics of ternary blended system, namely granulated blast-furnace slag (WCS, from iron steel company and Homra (GCB from Misr Brick (Helwan, Egypt and silica fume (SF at 30 mass % pozzolanas and 70 mass % OPC. The required water of standard consistency and setting times were measured as well as physico-chemical and mechanical characteristics of the hardened cement pastes were investigated. Some selected cement pastes were tested by TGA, DTA and FT-IR techniques to investigate the variation of hydrated products of blended cements. The pozzolanic activity of SF is higher than GCB and WCS. The higher activity of SF is mainly due to its higher surface area than the other two pozzolanic materials. On the other side, GCB is more pozzolanic than WCS due to GCB containing crystalline silica quartz in addition to an amorphous phase. The silica quartz acts as nucleating agents which accelerate the rate of hydration in addition to its amorphous phase, which can react with liberating Ca(OH2 forming additional hydration products.

  1. 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 .

  2. Hydration of Hybrid Alkaline Cement Containing a Very Large Proportion of Fly Ash: A Descriptive Model

    Directory of Open Access Journals (Sweden)

    Inés Garcia-Lodeiro

    2016-07-01

    Full Text Available In hybrid alkaline fly ash cements, a new generation of binders, hydration, is characterized by features found in both ordinary portland cement (OPC hydration and the alkali activation of fly ash (AAFA. Hybrid alkaline fly ash cements typically have a high fly ash (70 wt % to 80 wt % and low clinker (20 wt % to 30 wt % content. The clinker component favors curing at ambient temperature. A hydration mechanism is proposed based on the authors’ research on these hybrid binders over the last five years. The mechanisms for OPC hydration and FA alkaline activation are summarized by way of reference. In hybrid systems, fly ash activity is visible at very early ages, when two types of gel are formed: C–S–H from the OPC and N–A–S–H from the fly ash. In their mutual presence, these gels tend to evolve, respectively, into C–A–S–H and (N,C–A–S–H. The use of activators with different degrees of alkalinity has a direct impact on reaction kinetics but does not modify the main final products, a mixture of C–A–S–H and (N,C–A–S–H gels. The proportion of each gel in the mix does, however, depend on the alkalinity generated in the medium.

  3. The Early Strength of Slag Cements with Addition of Hydrate Microcrystals

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effect of hydrate microcrystals such as calcium silicate hydrates (CSH) and ettringite on the early strength of slag cements was studied.The authors explored the possibility of improving the early strength of the slag cement by applying crystal seed technology.It is shown that slag crystal seeds make the early strength of the cement increased due to the action of hydrate crystal seeds,which speed up the hydration of clinker minerals in the nucleation of ettringite.Therefore,the early strength of the slag cement is obviously improved.

  4. Silicate anion structural change in calcium silicate hydrate gel on dissolution of hydrated cement

    International Nuclear Information System (INIS)

    High pH conditions of aqueous solutions in a radioactive waste repository can be brought about by dissolution of cementitious materials. In order to clarify the mechanisms involved in maintaining this high pH for long time, we investigated the dissolution phenomena of OPC hydrate. In the present research, leaching tests on powdered cement hydrates were conducted by changing the ratio of mass of leaching water to mass of OPC hydrate (liquid/solid ratio) from 10 - 2,000 (wt/wt). Ordinary Portland Cement hydrate was contacted with deionized water and placed in a sealed bottle. After a predetermined period, the solid was separated from the solution. From the results of XRD analysis on the solid phase and the Ca concentration in the aqueous phase, it was confirmed that Ca(OH)2 was preferentially dissolved when the liquid/solid ratio was 10 or 100 (wt/wt), and that C-S-H gel as well as Ca(OH)2 were dissolved when the liquid/solid ratio was 500 (wt/wt) or larger. 29Si-NMR results showed that the silicate anion chain of the C-S-H gel became longer when the liquid/solid ratio was 500 (wt/wt) or greater. This indicates that leaching of OPC hydrate results in a structural change of C-S-H gel. (author)

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

    Directory of Open Access Journals (Sweden)

    Viveka Nand Dwivedi

    2008-12-01

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

  6. Interaction of calcium silicate hydrates (C-S-H), the main components of cement, with alkaline chlorides, analogy with clays; Interaction des silicates de calcium hydrates, principaux constituants du ciment, avec les chlorures d'alcalins. Analogie avec les argiles

    Energy Technology Data Exchange (ETDEWEB)

    Viallis-Terrisse, H

    2000-10-06

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

  7. 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.

  8. Micromotion of cemented and uncemented femoral components.

    Science.gov (United States)

    Burke, D W; O'Connor, D O; Zalenski, E B; Jasty, M; Harris, W H

    1991-01-01

    We evaluated the initial stability of cemented and uncemented femoral components within the femoral canals of cadaver femurs during simulated single limb stance and stair climbing. Both types were very stable in simulated single limb stance (maximum micromotion of 42 microns for cemented and 30 microns for uncemented components). However, in simulated stair climbing, the cemented components were much more stable than the uncemented components (76 microns as against 280 microns). There was also greater variation in the stability of uncemented components in simulated stair climbing, with two of the seven components moving 200 microns or more. Future implant designs should aim to improve the initial stability of cementless femoral components under torsional loads; this should improve the chances of bony ingrowth. PMID:1991771

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

    Science.gov (United States)

    Chaunsali, Piyush

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

  10. Mitigating the effects of system resolution on computer simulation of Portland cement hydration

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2008-01-01

    CEMHYD3D is an advanced, three-dimensional computer model for simulating the hydration processes of cement, in which the microstructure of the hydrating cement paste is represented by digitized particles in a cubic domain. However, the system resolution (which is determined by the voxel size) has a

  11. A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste

    Science.gov (United States)

    Jo, Byung-Wan; Chakraborty, Sumit

    2015-01-01

    To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

  12. 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.

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

    International Nuclear Information System (INIS)

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

  14. The crucial effect of early-stage gelation on the mechanical properties of cement hydrates

    Science.gov (United States)

    Ioannidou, Katerina; Kanduč, Matej; Li, Lunna; Frenkel, Daan; Dobnikar, Jure; Del Gado, Emanuela

    2016-07-01

    Gelation and densification of calcium-silicate-hydrate take place during cement hydration. Both processes are crucial for the development of cement strength, and for the long-term evolution of concrete structures. However, the physicochemical environment evolves during cement formation, making it difficult to disentangle what factors are crucial for the mechanical properties. Here we use Monte Carlo and Molecular Dynamics simulations to study a coarse-grained model of cement formation, and investigate the equilibrium and arrested states. We can correlate the various structures with the time evolution of the interactions between the nano-hydrates during the preparation of cement. The novel emerging picture is that the changes of the physicochemical environment, which dictate the evolution of the effective interactions, specifically favour the early gel formation and its continuous densification. Our observations help us understand how cement attains its unique strength and may help in the rational design of the properties of cement and related materials.

  15. Influence of ultra-fine fly ash on hydration shrinkage of cement paste

    Institute of Scientific and Technical Information of China (English)

    GAO Ying-li; ZHOU Shi-qiong

    2005-01-01

    Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.

  16. 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.

  17. INFLUENCE OF POZZOLANA ON THE HYDRATION OF C4AF RICH CEMENT IN CHLORIDE ENVIRONMENT

    Directory of Open Access Journals (Sweden)

    IRMANTAS BARAUSKAS

    2013-03-01

    Full Text Available This study investigated the influence of natural pozzolana - opoka additive on the hydration of C4AF rich cement and the effects of chloride ions on the hydrates formed. In the samples, 25 % (by weight of the sintered C4AF rich cement and OPC was replaced with pozzolana. The mixtures were hardened for 28 days in water, soaked in a saturated NaCl solution for 3 months at 20°C. It was estimated that under normal conditions, pozzolana additive accelerates the hydration of calcium silicates and initiates the formation of CO32- - AFm in the Brownmillerite rich cement. However, the hydration of Brownmillerite cement with opoka additive is still slower to compare with hydration of Portland cement. Also, opoka decreases total porosity and threshold pore diameter of Brownmillerite cement paste after two days of hydration. After 28 days of hydration threshold pore diameter became smaller even to compare with threshold pore diameter of Portland cement. Opoka additive promotes the formation of Friedel’s salt in Brownmillerite samples treated in saturated NaCl solution, because CO32-–AFm affected by saturated NaCl solution become unstable and takes part in reactions producing Friedel’s salt.

  18. 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.

  19. 53rd Cement Technical Conference. Cement hydration 3; Dai 53 kai semento gijutsu taikai. Semento no suiwa 3

    Energy Technology Data Exchange (ETDEWEB)

    Hanehara, Shunsuke [Taiheiyo Cement Corp., Tokyo (Japan)

    1999-08-10

    Osawa et al. reported the quantitative reaction rate of fly ash in cement paste by using the unreacted quartz quantitative method using hydrochloric acid and sodium carbonate in regard of the fly ash reaction rate in the fly ash cement hydration. Miyahara et al examined the influence of potassium chloride on the hydration speed of 4 type clinker minerals in regard of the cement hydration in addition of potassium chloride. Morioka et al examined the influence of various expansion materials on C{sub 3}A hydration and reported that a reason to delay the C{sub 3}A hydration in the CSA and quartz system expansion materials was high mole ratio of SO{sub 3}/Al{sub 2}O{sub 3}. Tsuyumoto et al examined the noncontacting monitoring in the hardening process of the cement- admixture ingredient- water system by means of the quasi-elasticity laser scattering method. Nakada et al examined the measurement of cement hydration rate in combination of the selective dissolution method and the X-ray powder diffraction. (NEDO)

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

    DEFF Research Database (Denmark)

    Moesgaard, Mette; Poulsen, S.L.; Herfort, D.;

    2012-01-01

    This work investigates the hydration of blended Portland cement containing 30 wt.% Na2O-CaO-Al2O3-SiO2 (NCAS) glass particles either as the only supplementary cementitious material (SCM) or in combination with limestone, using 29Si MAS NMR, powder XRD, and thermal analyses. The NCAS glass...... of hydration. The hydrated glass contributes to the formation of the calcium-silicate-hydrate (C-S-H) phase, consuming a part of the Portlandite (Ca(OH)2) formed during hydration of the Portland cement. Furthermore, the presence of the glass and limestone particles, alone or in combination, results...... in an accelerated hydration for alite (Ca3SiO5), the main constituent of Portland cement. A higher degree of limestone reaction has been observed in the blend containing both limestone and NCAS glass as compared to the limestone – Portland mixture. This reflects that limestone reacts with a part of the alumina...

  1. Reverse extraction of early-age hydration kinetic equation from observed data of Portland cement

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The early-age hydration of Portland cement paste has an important impact on the formation of microstructure and development of strength.However,manual derivation of hydration kinetic equation is very difficult because there are multi-phased,multi-sized and interrelated complex chemical and physical reactions during cement hydration.In this paper,early-age hydration kinetic equation is reversely extracted automatically from the observed time series of hydration degree of Portland cement using evolutionary computation method that combines gene expression programming and particle swarm optimization algorithms.In order to reduce the computing time,GPUs are used for acceleration in parallel.Studies have shown that according to the extracted kinetic equation,simulation curve of early-age hydration is in good accordance with the observed experimental data.Furthermore,this equation still has a good generalization ability even changing chemical composition,particle size and curing conditions.

  2. Evolution of the hydration in cements with additions

    Directory of Open Access Journals (Sweden)

    Bonavetti, V. L.

    2002-12-01

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

    En el presente trabajo se analizó el mecanismo de hidratación de pastas de cemento portland normal con la incorporación de caliza, cuarzo y puzolana natural (proporción 80/20 en peso, por medio de la evaluación del contenido de agua no evaporable, la actividad puzolánica por vía química y la formación de productos de hidratación por DRX. Los resultados obtenidos permitieron determinar un aumento de la cantidad de productos de hidratación inicial debidos al efecto filler en todas las pastas. En las pastas con caliza se evidenció el efecto de dilución a edades avanzadas, en tanto que en las pastas con cuarzo y puzolana, este efecto fue menos predominante debido a la contribución de la reacción puzolánica.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

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

    International Nuclear Information System (INIS)

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

  5. A sample holder for the study of isothermal heat of hydration of cement

    DEFF Research Database (Denmark)

    Hansen, Per Freiesleben; Jensen, Ole Mejlhede

    1998-01-01

    Different techniques for measuring heat of hydration of cement are discussed, and a sample holder designed specially for measuring isothermal heat of hydration is described. A particular characteristic of the sample holder is the vacuum mixing technique which ensures a momentary and homogeneous...

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

    Science.gov (United States)

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

    2011-10-30

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize wastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl(2) mixing solution was characterized over one year as a function of the gypsum content of the binder and the thermal history of the material. Blending the CSA clinker with 20% gypsum enabled its rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrates assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, strätlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the gypsum content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes. PMID:21889260

  7. Chemo-physical modeling of cement mortar hydration: Role of aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jena, E-mail: jeong@profs.estp.fr [Université Paris-Est, Institut de Recherche en Constructibilité, ESTP, 28 Avenue Président Wilson, 94234 Cachan (France); Ramézani, Hamidréza, E-mail: hamidreza.ramezani@univ-orleans.fr [CRMD, CNRS FRE 3520-Research Center on Divided Materials, École Polytechnique de l’Université d’Orléans, 8 rue Léonrad de Vinci, 45072 Orléans Cedex 2 (France); Leklou, Nordine, E-mail: nordine.leklou@univ-nantes.fr [LUNAM Université, Université de Nantes-IUT Saint-Nazaire, GeM, CNRS UMR 6183, Research Institute in Civil Engineering and Mechanics, 58 rue Michel Ange BP 420 44606 Saint Nazaire Cedex (France); Mounanga, Pierre, E-mail: pierre.mounanga@univ-nantes.fr [LUNAM Université, Université de Nantes-IUT Saint-Nazaire, GeM, CNRS UMR 6183, Research Institute in Civil Engineering and Mechanics, 58 rue Michel Ange BP 420 44606 Saint Nazaire Cedex (France)

    2013-07-20

    Graphical abstract: - Abstract: After mixing of the cement with water, most of the anhydride products sustain the hydration process and this leads to the hydrate products, e.g. CSH, Ca(OH){sub 2}, Afm and Aft. The mentioned hydration process is a highly complex phenomenon involving the chemically based thermo-activation inside the cement mortars during the early age hydration process. The chemo-thermal hydration reactions drasticaly increase at the early age of hydration after the mixing action and then it becomes less important and turns to be nearly asymptotic. The progress of the hydration phenomenon drives the material properties change during the very early age of cement hydration. Regarding the mortar and concrete, such hydration process would not be homogeneous through the cement matrix due to the aggregates presence. These inclusions will affect the temperature distribution as well as degree of hydration. In the current contribution, the chemical and thermal hydration have been firstly investigated by means of SEM observations using replica method and secondly by the 3D-FEM numerical experiments including two different case studies using glass beads as aggregates. The numerical experiments match fairly good the experimental measurements obtained using a pseudo-adiabatic testing setup for the case studies herein. The scanning electron microscopy (SEM) images observation demonstrates the gap spaces around the glass beads next to the external surfaces. These gaps can be essentially seen for the multi-glass beads case study. The role of the temperature and degree of hydration gradients are clearly obtained using the numerical samples. Some fresh routes and outlooks have been afterwards discussed.

  8. Radon exhalation of hardening concrete: monitoring cement hydration and prediction of radon concentration in construction site

    Energy Technology Data Exchange (ETDEWEB)

    Kovler, Konstantin [National Building Research Institute, Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 32000 (Israel)]. E-mail: cvrkost@technion.ac.il

    2006-07-01

    The unique properties of radon as a noble gas are used for monitoring cement hydration and microstructural transformations in cementitious system. It is found that the radon concentration curve for hydrating cement paste enclosed in the chamber increases from zero (more accurately - background) concentrations, similar to unhydrated cement. However, radon concentrations developed within 3 days in the test chamber containing cement paste were {approx}20 times higher than those of unhydrated cement. This fact proves the importance of microstructural transformations taking place in the process of cement hydration, in comparison with cement grain, which is a time-stable material. It is concluded that monitoring cement hydration by means of radon exhalation method makes it possible to distinguish between three main stages, which are readily seen in the time dependence of radon concentration: stage I (dormant period), stage II (setting and intensive microstructural transformations) and stage III (densification of the structure and drying). The information presented improves our understanding of the main physical mechanisms resulting in the characteristic behavior of radon exhalation in the course of cement hydration. The maximum value of radon exhalation rate observed, when cement sets, can reach 0.6 mBq kg{sup -1} s{sup -1} and sometimes exceeds 1.0 mBq kg{sup -1} s{sup -1}. These values exceed significantly to those known before for cementitious materials. At the same time, the minimum ventilation rate accepted in the design practice (0.5 h{sup -1}), guarantees that the concentrations in most of the cases will not exceed the action level and that they are not of any radiological concern for construction workers employed in concreting in closed spaces.

  9. Mössbauer, XRD, and Complex Thermal Analysis of the Hydration of Cement with Fly Ash

    OpenAIRE

    Vili Lilkov; Ognyan Petrov; Yana Tzvetanova; Plamen Savov; Milen Kadiyski

    2013-01-01

    Hydration of cement with and without fly ash is studied with Mössbauer spectroscopy, XRD, and thermal analysis. Iron in cement is present as Fe3+-ions and occupies two octahedral positions, with close isomer shifts and quadrupole splittings. Iron in fly ash is present as Fe2+ and Fe3+, and the Mössbauer spectra display three doublets—two for Fe3+ in octahedral coordination and one for Fe2+. A third doublet was registered in the hydrating plain cement pastes after the 5th day, due to Fe3+ in t...

  10. Early and late hydration of supersulphated cements of blast furnace slag with fluorgypsum

    OpenAIRE

    Bazaldúa-Medellín, M. E.; Fuentes, A. F.; Gorokhovsky, A.; Escalante-García, J. I.

    2015-01-01

    The hydration, strength development and composition of hydration products of supersulphated cements were characterized from the first 48 hours up to 360 days. Two compositions of 80% Blast furnace slag, 10–15% Fluorgypsum and 10–5% Portland cement were cured in dry and wet conditions. The main hydration products were ettringite and C-S-H since the first hours and up to 360 days as evidenced by X-ray diffraction, thermal analysis and electron microscopy. The strength was favored by higher fluo...

  11. Hydrated phases and pore solution composition in cement solidified saltstone waste forms

    International Nuclear Information System (INIS)

    The mineral phases and pore solution composition of hydrated cement solidified synthetic saltstone waste forms are quantified using thermogravimetric analysis, quantitative X-ray powder diffraction, and inductively coupled plasma atomic emission spectroscopy. Although the synthetic waste contained additional sulfate, the overall chemistry of the system suppressed the formation of sulfate-bearing mineral phases. This was corroborated by the pore solution analysis that indicated very high sulfur concentrations. After one year of hydration, the mineral phases present and the composition of the pore solution are stable, and are generally consistent with expectations based on the hydration of high volume portland cement replacement mixtures. (authors)

  12. Model Analysis of Initial Hydration and Structure Forming of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The auto efficiently hydration heat arrangement and the non-contacting electrical resistivity device were used to test the thermology effect and the resistivity variation of Portland cement hydration.The structure forming model of Portland cement initial hydration was established through the systematical experiments with different cements, the amount of mixing water and the chemical admixture. The experimental results show that, the structure forming model of cement could be divided into three stages, i e, solution-solution equilibrium period, structure forming period and structure stabilizing period. Along with the increase of mixing water, the time of inflexion appeared is in advance for thermal process of cement hydration and worsened for the structure forming process. Comparison with the control specimen, adding Na2SO4 makes the minimum critical point lower, the flattening period shorter and the growing slope after stage one steeper. So the hydration and structure forming process of Portland cement could be described more exactly by applying the thermal model and the structure-forming model.

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

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

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

  14. Relation between the Rheology Characteristic and Initial Hydration Structure of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, the influence of cement kinds and the chemical admixtures on the initial rheology characteristic and structure forming and developing of cement hydration was studied. The relationship between the rheology characteristic, the initial hydration structure forming and the hydration process at very early ages was analyzed by macro properties and microstructure tests. The results showed that, the storage modulus, acted as S, could be described more subtle distinction accompanying with hydration of fresh paste model at very early period. Combining the resistivity alterations, a sudden change on structure forming emerged when the hydration of cement becoming inducing age. The rheology characteristic was interrelated to the hydration structure forming, development and the physical mechanics properties. The sudden change on storage modulus moved up due to the addition of retarder, but the structure forming and developing was retarded to a certain extent.

  15. Rate of CO2 attack on hydrated Class H well cement under geologic sequestration conditions.

    Science.gov (United States)

    Kutchko, Barbara G; Strazisar, Brian R; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

    2008-08-15

    Experiments were conducted to study the degradation of hardened cement paste due to exposure to CO2 and brine under geologic sequestration conditions (T = 50 degrees C and 30.3 MPa). The goal was to determine the rate of reaction of hydrated cement exposed to supercritical CO2 and to CO2-saturated brine to assess the potential impact of degradation in existing wells on CO2 storage integrity. Two different forms of chemical alteration were observed. The supercritical CO2 alteration of cement was similar in process to cement in contact with atmospheric CO2 (ordinary carbonation), while alteration of cement exposed to CO2-saturated brine was typical of acid attack on cement. Extrapolation of the hydrated cement alteration rate measured for 1 year indicates a penetration depth range of 1.00 +/- 0.07 mm for the CO2-saturated brine and 1.68 +/- 0.24 mm for the supercritical CO2 after 30 years. These penetration depths are consistent with observations of field samples from an enhanced oil recovery site after 30 years of exposure to CO2-saturated brine under similar temperature and pressure conditions. These results suggest that significant degradation due to matrix diffusion of CO2 in intact Class H neat hydrated cement is unlikely on time scales of decades. PMID:18767693

  16. 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.

  17. Effect of three natural pozzolans in portland cement hydration

    Directory of Open Access Journals (Sweden)

    Rahhal, V.

    2003-03-01

    Full Text Available Natural pozzolans have been used since ancient times and continues to be used today. The chemistry and morphological composition of natural pozzolans and their particle size distribution allows classifying them as more or less reactive pozzolan. In this research several techniques have been used to study the influence of pozzolan on portland cement hydration as much as to evaluate the mechanical and durable properties of concretes, mortars and pastes containing pozzolans. This paper describes the effect of incorporating three natural pozzolans to two cements with very different mineralogical composition. The techniques used were: conduction calorimetry and Fratini test. Results proved that pozzolanic activity and the acceleration and retardation of hydration reaction depend on the mineralogical composition of the portland cernent used. Effects of dilution, stimulation, acceleration or retardation reactions, behavior into areas of heat dissipation and pozzolanic activity depend on the percentage of pozzolan used and the age in which it has been analyzed.

    El uso de las puzolanas naturales se remonta a la antigüedad, no obstante, actualmente continúa su utilización. La composición química y morfológica de las puzolanas naturales, sumado al tamaño de sus partículas, las califican como más o menos reactivas. En el estudio de las mismas, se han aplicado variadas técnicas para el análisis de sus interferencias en las reacciones de hidratación de los cementos portland; así como para la evaluación de las propiedades resistentes y duraderas que pueden conferirle a los hormigones, morteros o pastas de los que formen parte. Este trabajo versará sobre los efectos que produce la incorporación de tres puzolanas naturales a dos cementos portland de muy diferente composición mineralógica. Las técnicas aplicadas para su estudio han sido: la calorimetría de conducción y el ensayo de Fratini. Los resultados obtenidos permiten determinar

  18. 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 .

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

    Science.gov (United States)

    Fujikura, Yusuke; Oshita, Hideki

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

  20. Dry-grinded ultrafine cements hydration. physicochemical and microstructural characterization

    OpenAIRE

    Foteini Kontoleontos; Petros Tsakiridis; Apostolos Marinos; Nikolaos Katsiotis; Vasileios Kaloidas; Margarita Katsioti

    2013-01-01

    The aim of the present research work was the evaluation of the physicochemical and microstructural properties of two ultrafine cements, produced by dry grinding of a commercial CEM I 42.5N cement. The effect of grinding on particle size distribution was determined by laser scattering analyzer. All cements were tested for initial and final setting times, consistency of standard paste, soundness, flow of normal mortar and compressive strengths after 1, 2, 7 and 28 days. The effect of the finene...

  1. Strength development, hydration reaction and pore structure of autoclaved slag cement with added silica fume

    Energy Technology Data Exchange (ETDEWEB)

    Xi, Y. [China Building Materials Academy, Beijing (China); Siemer, D.D. [LITCO, Idaho Falls, ID (United States); Scheetz, B.E. [Pennsylvania State Univ., University Park, PA (United States). Materials Research Lab.

    1997-01-01

    Under continuous hydrothermal treatment the strength of portland cement paste decreases with curing time and the pore structure coarsens. It was found in this study that the compressive strength of slag cement paste containing 67.5 wt.% ggbfs also decreases with time after 24 hour hydrothermal processing, but with a small addition of silica fume to the slag cement, the cement strength increases and the pore structure densifies when processed under comparable conditions. Based on observations XRD and SEM, these changes are attributed to: (1) changes in the hydration reactions and products by highly reactive silica fume, such that amorphous products dominate and the strength reducing phase {alpha}-C{sub 2}SH does not form; (2) slower hydration of slag, partially caused by the decreased pH of the pore solution, favors the formation of a dense pore structure; and (3) the space filling properties of the micro particles of silica fume.

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

    Science.gov (United States)

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

    2012-12-01

    Wellbore Cement studies have been ongoing for decades. The studies vary from efforts to reduce permeability and resistance to corrosive environment to issues with gas migration also known as Sustained Casing Pressure (SCP). These practical issues often lead to health and safety problems as well as huge economic loss in oil and gas industry. Several techniques have been employed to reduce the impact of gas leakage. In this study we purely focus on expandable liners, which are introduced as part of oil well reconstruction and work-overs and as well abandonment procedures that help in prevention of SCP. Expandable liner is a tube that after application of a certain tool can increase its diameter. The increase in diameter creates extra force on hydrated cement that results in reducing width of interface fractures and cement-tube de-bonding. Moreover, this also causes cement to change its microstructure and other porous medium properties, primarily hydraulic conductivity. In order to examine changes before and after operations, cement pore structure must be well characterized and correlated to cement slurry design as well as chemical and physical environmental conditions. As modern oil well pipes and tubes contain iron, it is difficult to perform X-ray tomography of a bulk measurement of the cement in its wellbore conditions, which are tube wall-cement-tube wall. Neutron imaging is a complementary technique to x-ray imaging and is well suited for detection of light elements imbedded in metallic containers. Thus, Neutron Imaging (NI) is investigated as a tool for the detection of pore structure of hydrated wellbore cement. Recent measurements were conducted at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) neutron imaging facility. NI is is highly sensitive to light elements such as Hydrogen (H). Oil well cements that have undergone a full hydration contain on average 30%-40% of free water in its pore structure. The unreacted water is the main

  3. Study on the hydration and microstructure of Portland cement containing diethanol-isopropanolamine

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Suhua, E-mail: yc982@163.com; Li, Weifeng; Zhang, Shenbiao; Hu, Yueyang; Shen, Xiaodong

    2015-01-15

    Diethanol-isopropanolamine (DEIPA) is a tertiary alkanolamine used in the formulation of cement grinding-aid additives and concrete early-strength agents. In this research, isothermal calorimetry was used to study the hydration kinetics of Portland cement with DEIPA. A combination of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC)–thermogravimetric (TG) analysis and micro-Raman spectroscopy was used to investigate the phase development in the process of hydration. Mercury intrusion porosimetry was used to study the pore size distribution and porosity. The results indicate that DEIPA promotes the formation of ettringite (AFt) and enhances the second hydration rate of the aluminate and ferrite phases, the transformation of AFt into monosulfoaluminate (AFm) and the formation of microcrystalline portlandite (CH) at early stages. At later stages, DEIPA accelerates the hydration of alite and reduces the pore size and porosity.

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

    DEFF Research Database (Denmark)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Kaziliunas A.

    2013-12-01

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

  6. Laser Radiation CO2 Effects in Cement Paste at Different Hydration Stages after Preparation

    OpenAIRE

    Moreno-Virgen M.R.; Soto-Bernal J.J.; Ortiz-Lozano J.A.; Frausto-Reyes C.; Bonilla-Petriciolet A.; González-Mota R.; Rosales-Candelas I.; Pineda-Piñón J.

    2011-01-01

    In this work the changes occurring in cement pastes irradiated by 10.6µm CO2 laser at diff erent stages of hydration after preparation are presented. Raman spectroscopy, X-ray diffraction and Scanning Electronic Microscopy (SEM) techniques were used to observe molecular structural changes. Intensity of cement paste Raman peaks after laser irradiation was monitored in samples irradiated 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 days after their preparation. Applied laser power changed Raman peaks inte...

  7. Polycarboxylate superplasticiser admixtures: effect on hydration, microstructure and rheological behaviour in cement pastes

    OpenAIRE

    Puertas, F.; Santos, H.; Palacios, M.; Martínez-Ramírez, Sagrario

    2005-01-01

    A study was conducted on the effect of a polycarboxylate (PC) admixture on the mechanical, mineralogical, microstructural and rheological behaviour of Portland cement pastes. It was observed that the presence of PC admixture retards the initial cement hydration reactions, although this effect may be offset by possible increased diffusion in later stages. Additionally, the PC admixtures produce a few alterations in the structure and composition of the formed C–S–H gel. The addition of 1% PC...

  8. A nanoscale study of dissolution and growth processes in cement hydrates

    OpenAIRE

    Rheinheimer, Vanessa

    2012-01-01

    This thesis aims at providing new knowledge on the, otherwise poorly known, molecular-scale mechanisms that operate during hydration of cement phases and dissolution of their hydrates. In order to pursue this objective, a novel approach has been followed, including the development of a new procedure to synthesize thin films of calcium silicates, real time characterization of grain growth and dissolution with liquid-cell atomic force microscopy, and monitoring of their chemical evolution by X-...

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

    Directory of Open Access Journals (Sweden)

    Bonavetti, V. L.

    2014-09-01

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

  10. Individual and combined effects of chloride, sulfate, and magnesium ions on hydrated Portland-cement paste

    International Nuclear Information System (INIS)

    Ground water with a high concentration of magnesium ion is known to cause deterioration to portland cement concretes. A proposed mechanism for this deterioration process published previously involves an approximate 1:1 replacement of Ca ions by Mg ions in the crystalline phases of hydrated cement. The current study was undertaken to determine which ions, among magnesium, chloride, and sulfate, cause deterioration; whether their deleterious action is individual or interdependent; and to relate this mechanism of deterioration to the outlook for a 100-yr service life of concretes used in mass placements at the Waste Isolation Pilot Plant. Loss of Ca ion by cement pastes was found to be strongly related to the concentration of Mg ion in simulated ground-water solutions in which the paste samples were aged. This was true of both salt- containing and conventional cement pastes. No other ion in the solutions exerted a strong effect on Ca loss. Ca ion left first from calcium hydroxide in the pastes, depleting all calcium hydroxide by 60 days. Some calcium silicate hydrate remained even after 90 days in the solutions with the highest concentration of Mg ion, while the paste samples deteriorated noticeably. The results indicated a mechanism that involves dissolution of Ca phases and transport of Ca ions to the surface of the sample, followed by formation of Mg-bearing phases at this reaction surface rather than directly by substitution within the microstructure of hydrated cement. Given that calcium hydroxide and calcium silicate hydrate are the principal strength-giving phases of hydrated cement, this mechanism indicates the likelihood of significant loss of integrity of a concrete exposed to Mg-bearing ground water at the WIPP. The rate of deterioration ultimately will depend on Mg-ion concentration, the microstructure materials of the concrete exposed to that groundwater, and the availability of brine

  11. Effect of Nano-TiO2 Addition on the Hydration and Hardening Process of Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; LI Hainan; MEI Junpeng; OUYANG Pei

    2015-01-01

    The influences of nano-TiO2 on the setting time, hydration process, hydration products and morphology of sulphoaluminate cement were studied by Vicat apparatus, isothermal calorimetry, X-ray diffraction (XRD), thermal analysis and scanning electron microscopy (SEM). The experimental results show that the incorporation of nano-TiO2 can obviously promote the setting and hardening process of sulphoaluminate cement, and shorten the interval between the initial and ifnal setting time, the hydration induction period of sulphoaluminate cement is significantly shortened and the acceleration period begins immediately, but the hydration exothermic rate at hydration stationary phase is not obviously impacted. The nano-TiO2 additives have inlfuence on the formation rate and degree of crystallinity, but do not affect the type of hydration process. The structure of hydration products is compact at middle age, but their content and microstructure do not change.

  12. The effect of sulfate activation on the early age hydration of BFS:PC composite cement

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C., E-mail: nick.collier@sheffield.ac.uk; Li, X.; Bai, Y.; Milestone, N.B.

    2015-09-15

    Blast furnace slag/Portland cement composites are routinely used for immobilising intermediate level nuclear wastes in the UK. Using high cement replacement levels reduces hydration exotherm and lowers pH. Although a lower grout pH will be beneficial in reducing the corrosion of certain encapsulated reactive metals such as aluminium, the degree of slag reaction will also be lower which may result in the formation of less hydration products and which in turn may reduce the capacity to immobilise waste ions. Adding neutral salts such as calcium and sodium sulfate to the composite cement can potentially increase slag activation without significantly altering the pH of the cement matrix. Thus the corrosion of any encapsulated metals would not be affected. This paper describes some of the properties of a hydrated 9:1 blast furnace slag:Portland cement matrix containing added sulfates of calcium and sodium. The findings show that all additives caused an increase in the amount of slag that reacted when cured for up to 28 days. This produced more material able to chemically bind waste ions. Activation with gypsum produced the highest rate of slag reaction.

  13. Mössbauer, XRD, and Complex Thermal Analysis of the Hydration of Cement with Fly Ash

    Directory of Open Access Journals (Sweden)

    Vili Lilkov

    2013-01-01

    Full Text Available Hydration of cement with and without fly ash is studied with Mössbauer spectroscopy, XRD, and thermal analysis. Iron in cement is present as Fe3+-ions and occupies two octahedral positions, with close isomer shifts and quadrupole splittings. Iron in fly ash is present as Fe2+ and Fe3+, and the Mössbauer spectra display three doublets—two for Fe3+ in octahedral coordination and one for Fe2+. A third doublet was registered in the hydrating plain cement pastes after the 5th day, due to Fe3+ in tetrahedral coordination in the structure of the newly formed monosulphate aluminate. In cement pastes with fly ash, the doublet of tetrahedral iron is formed earlier because the quantity of ettringite and portlandite is low and more monosulphate crystallizes. No Fe(OH3 phase forms during hydration of C4AF. The fly ash displays pozzolanic properties, which lead to lowering of the portlandite quantity in the cement mixtures and increasing of the high temperature products.

  14. The effect of sulfate activation on the early age hydration of BFS:PC composite cement

    International Nuclear Information System (INIS)

    Blast furnace slag/Portland cement composites are routinely used for immobilising intermediate level nuclear wastes in the UK. Using high cement replacement levels reduces hydration exotherm and lowers pH. Although a lower grout pH will be beneficial in reducing the corrosion of certain encapsulated reactive metals such as aluminium, the degree of slag reaction will also be lower which may result in the formation of less hydration products and which in turn may reduce the capacity to immobilise waste ions. Adding neutral salts such as calcium and sodium sulfate to the composite cement can potentially increase slag activation without significantly altering the pH of the cement matrix. Thus the corrosion of any encapsulated metals would not be affected. This paper describes some of the properties of a hydrated 9:1 blast furnace slag:Portland cement matrix containing added sulfates of calcium and sodium. The findings show that all additives caused an increase in the amount of slag that reacted when cured for up to 28 days. This produced more material able to chemically bind waste ions. Activation with gypsum produced the highest rate of slag reaction

  15. A combined QXRD/TG method to quantify the phase composition of hydrated Portland cements

    Energy Technology Data Exchange (ETDEWEB)

    Soin, Alexander V.; Catalan, Lionel J.J. [Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1 (Canada); Kinrade, Stephen D., E-mail: stephen.kinrade@lakeheadu.ca [Department of Chemistry, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1 (Canada)

    2013-06-15

    A new method is reported for quantifying the mineral phases in hydrated cement pastes that is based on a combination of quantitative X-ray diffractometry (QXRD) and thermogravimetry (TG). It differs from previous methods in that it gives a precise measure of the amorphous phase content without relying on an assumed stoichiometric relationship between the principal hydration products, calcium hydroxide (CH) and calcium silicate hydrate (C–S–H). The method was successfully applied to gray and white ordinary Portland cements (GOPC and WOPC, respectively) that were cured for up to 56 days. Phase distributions determined by QXRD/TG closely matched those from gray-level analysis of backscattered scanning electron microscope (BSEM) images, whereas elemental compositions obtained for the amorphous phase by QXRD/TG agreed well with those measured by quantitative energy dispersive X-ray spectroscopy (EDS)

  16. The Mechanical Properties and Hydration Characteristics of Cement Pastes Containing Added-calcium Coal Gangue

    Institute of Scientific and Technical Information of China (English)

    LI Dongxu; SONG Xuyan

    2008-01-01

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

  17. Component analysis of the protein hydration entropy

    Science.gov (United States)

    Chong, Song-Ho; Ham, Sihyun

    2012-05-01

    We report the development of an atomic decomposition method of the protein solvation entropy in water, which allows us to understand global change in the solvation entropy in terms of local changes in protein conformation as well as in hydration structure. This method can be implemented via a combined approach based on molecular dynamics simulation and integral-equation theory of liquids. An illustrative application is made to 42-residue amyloid-beta protein in water. We demonstrate how this method enables one to elucidate the molecular origin for the hydration entropy change upon conformational transitions of protein.

  18. Effect of the addition of nanosilica on white cement hydration at 25°C

    Directory of Open Access Journals (Sweden)

    Sáez del Bosque I.F.

    2014-04-01

    Full Text Available The cement industry is keen on reducing natural resource consumption, reusing waste that would otherwise be sent to a rubbish tip and lowering its CO2 emissions. In pursuit of those objectives, the addition of materials such as silica fume, ceramic waste, rice husk and precipitated or colloidal nanosilica, in the various stages of cement manufacture has become increasingly common. That practice inspired the present study (using isothermal conduction calorimetry, 29Si and 27Al MAS NMR, XRD and DTA/TG of the effect of precipitated amorphous nanosilica (10 wt% on white portland cement (WPC hydration. The isothermal conduction calorimetry findings, which were consistent with the NMR and DTA/TG results, showed that adding amorphous nanosilica altered reaction kinetics, expediting alite and belite hydration. The addition also intensified the heat flow attributed to alumina phase hydration and brought the respective peak forward. Although no general consensus has been reached in the literature on the attribution of the third peak appearing on the calorimetric curve for WPC, based on the present findings, the main aluminate hydrate product is monosulfoaluminate. Furthermore, a pre-peak inflection point on the profile of the first exothermal peak on the WPC calorimetric curve was interpreted as the beginning of the pozzolanic reaction, which accelerates alite hydration, consuming portlandite and raising the heat released. C-S-H gel nanostructure was also modified. The results revealed a linear relationship in both the blended and the pure cement pastes between the degree of hydration and the number of Q1 and Q2 units in the gel. The presence of Q2 units was much greater and of Q1 units slightly lower in the former than in the latter.

  19. Influence of Plasticizer Amount on Rheological and Hydration Properties of CEM II Type Portland Cements

    Science.gov (United States)

    Šeputytė-Juciké, J.; Pundienė, I.; Kičaitė, A.; Pranckevičienė, J.

    2015-11-01

    The article analyzes the effect of plasticizer (based on polycarboxilates) amount (0.3 - 1.2% wt. of cement) on the rheological and hydration properties of two Portland cements pastes: CEM II/A-S 42.5N and CEM II/A-LL 42.5N. Increase of plasticizer amount reduces viscosity of CEM II/A-LL 42.5N cement paste from 3 to 12 times, where viscosity of CEM II/A-S 42.5N cement paste reduces from 5 to 20 times. The optimum plasticizer dose (0.3%) in case of CEM II/A-S 42.5N and (1.2%) in case of CEM II/A-LL 42.5N was established. Calorimetry studies have shown that plasticizer reduces the wetting heat release rate in CEM II/A-LL 42.5N cement twice and in CEM II/A-S 42.5N cement - by 25%. Plasticizer prolongs the maximum heat release rate time by 16 h in CEM II/A-LL 42.5N samples and reduces heat release rate by 19%. In CEM II/A-S 42.5N cement samples plasticizer prolongs maximum heat release rate time by 14.5 h and increases heat release rate by 15%. The goal of this study is to analyze the effect of the dosage of the most widely used plasticizer on solubility characteristics, rheological and hydration properties of two cements CEM II/A-S 42.5N and CEM II/A-LL 42.5N to establish the optimum dose of plasticizer in cements pastes.

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

    Directory of Open Access Journals (Sweden)

    N. Mohamed Sutan

    2015-01-01

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

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

    Science.gov (United States)

    Rechkalov, Denis; Chernogorlov, Sergey; Abyzov, Victor

    2016-01-01

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

  2. Hydration kinetics of cements by Time-Domain Nuclear Magnetic Resonance: Application to Portland-cement-derived endodontic pastes

    International Nuclear Information System (INIS)

    Time-Domain Nuclear Magnetic Resonance (TD-NMR) of 1H nuclei is used to monitor the maturation up to 30 days of three different endodontic cement pastes. The “Solid–liquid” separation of the NMR signals and quasi-continuous distributions of relaxation times allow one to follow the formation of chemical compounds and the build-up of the nano- and subnano-structured C–S–H gel. 1H populations, distinguished by their different mobilities, can be identified and assigned to water confined within the pores of the C–S–H gel, to crystallization water and Portlandite, and to hydroxyl groups. Changes of the TD-NMR parameters during hydration are in agreement with the expected effects of the different additives, which, as it is known, can substantially modify the rate of reactions and the properties of cementitious pastes. Endodontic cements are suitable systems to check the ability of this non-destructive technique to give insight into the complex hydration process of real cement pastes.

  3. Early and late hydration of supersulphated cements of blast furnace slag with fluorgypsum

    Directory of Open Access Journals (Sweden)

    Bazaldúa-Medellín, M. E.

    2015-03-01

    Full Text Available The hydration, strength development and composition of hydration products of supersulphated cements were characterized from the first 48 hours up to 360 days. Two compositions of 80% Blast furnace slag, 10–15% Fluorgypsum and 10–5% Portland cement were cured in dry and wet conditions. The main hydration products were ettringite and C-S-H since the first hours and up to 360 days as evidenced by X-ray diffraction, thermal analysis and electron microscopy. The strength was favored by higher fluorgypsum contents and lower Portland cement contents. These cements generated heats of hydration of 40–57 KJ/Kg after 28 hours, which are lower than portland cement.Se realizó la caracterización de la hidratación, desarrollo de resistencia y la composición de los productos de hidratación de los cementos supersulfatados durante las primeras 48 horas y hasta 360 días. Se estudiaron dos composiciones de 80% de Escoria de alto horno, 10–15% de Fluoryeso y 10–5% de Cemento portland, se curaron en condiciones secas y húmedas. Los principales productos de hidratación fueron etringita y C-S-H desde las primeras horas y hasta 360 días, como se evidenció por difracción de rayos X, análisis térmico y microscopía electrónica de barrido. La resistencia se favoreció con mayor contenido de fluoryeso y bajos contenidos de cemento portland. Estos cementos generaron calores de hidratación de 40–57 KJ/Kg después de 28 horas, los cuales resultan más bajos que los generados por el cemento portland.

  4. The influence of silanized nano-SiO{sub 2} on the hydration of cement paste: NMR investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bede, A., E-mail: Andrea.Bede@phys.utcluj.ro; Pop, A.; Ardelean, I. [Technical University of Cluj-Napoca, Department of Physics and Chemistry, 400114 Cluj-Napoca (Romania); Moldovan, M. [“Babes-Bolyai” University, “Raluca Ripan” Chemistry Research Institute, Department of Polymer Composites, 400294 Cluj-Napoca (Romania)

    2015-12-23

    It is known that by adding a small amount of nanoparticles to the cement-based materials a strong influence on the workability, strength and durability is obtained. These characteristics of the material are fundamentally determined by the hydration process taking place after mixing the cement grains with water. In the present study the influence introduced by the addition of nano-silica with silanized surfaces on the hydration process was investigated using low-field nuclear magnetic resonance (NMR) relaxometry. The cement samples were prepared using gray cement at a water-to-cement ratio of 0.4 and a 5% addition of nanosilica. The surface of the nanoparticles was modified using a coating of Silane A174. The cement pastes were monitored during their standard curing time of 28 days. It was established that, by using unmodified nanosilica particles, an acceleration of the hydration process takes place as compared with the pure cement paste. On the other side, by adding silanized nanoparticles, the dormancy stage significantly extends and the hydration process is slower. This slowing down process could enhance the mechanical strength of cement based materials as a result of a better compaction of the hydrated samples.

  5. Interfacial chemistry of epoxy adhesives on hydrated cement paste

    OpenAIRE

    Djouani, Fatma; CONNAN, Carole; CHEHIMI, Mohamed M; BENZARTI, Karim

    2008-01-01

    Epoxy resins [diglycidylether of bisphenol A, (DGEBA)] are the main adhesives used in civil engineering for the repair of damaged concrete structures (bridges, walls) or for assembly applications. Their interfacial molecular interactions with cement-type substrates are thus of prime importance and require surface- and interface-sensitive characterisation tools. In this context, we report an XPS, FTIR and differential scanning calorimeter (DSC) study of the interfacial chemistry of stoichiomet...

  6. Chemical Composition and Microstructure of Hydration Products of Hardened White Portland Cement Pastes Containing Admixtures

    Institute of Scientific and Technical Information of China (English)

    LI Qiu

    2015-01-01

    This study investigated the nature of hydration products of white portland cement (WPC) containing 20 mM malic acid or 1 M calcium chloride hydrated for 11 years. The study identiifed the hydration products and characterized the chemical composition, morphology, micro/nano structure of C-S-H and the main binding phase in cementitious materials. Calcium hydroxide (CH), ettringite and C-S-H were identiifed in WPC with 20 mM malic acid paste hydrated for 11 years. WPC with 1 M calcium chloride paste hydrated for 11 years contained the same phases, but with less CH, and the presence of Friedel’s salt (Ca2Al(OH)6Cl·2H2O). There were still small amount of anhydrous cement particles remaining in both pastes after 11 years hydration according to the SEM and29Si MAS NMR results. The hydration products of paste containing malic acid had a lower porosity than those prepared with calcium chloride upon visual inspection under SEM. The morphology of the outer product (Op) C-S-H was coarse ifbrillar and the inner product (Ip) C-S-H had a very ifne microstructure in both pastes under TEM. Both Ip and Op C-S-H formed in paste containing malic acid had lower Ca/Si and higher Al/Si than those in paste containing calcium chloride. C-S-H in paste containing calcium chloride had longer MCL and less percentage of bridging tetrahedra occupied by aluminum in silicon/aluminum chains due to relatively lessQ1 and moreQ2. A new type of silicon tetrahedra,Q2B, was introduced during deconvolution of29Si MAS NMR results. Ip and Op C-S-H in both pastes had aluminum substituted tobermorite-type and jennite-type structure, and all the charges caused by aluminum substituting silicon bridging tetrahedra were balanced by Ca2+.

  7. WOOD PRE-TREATMENT INFLUENCE ON THE HYDRATION OF PORTLAND CEMENT IN COMBINATION WITH SOME TROPICAL WOOD SPECIES

    Directory of Open Access Journals (Sweden)

    Nusirat Aderinsola SADIKU

    2014-06-01

    Full Text Available The influence of three pre-treatment methods on the hydration characteristics of Portland cement in combination with three tropical hardwood species was investigated. The maximum hydration temperature and time to reach maximum hydration temperature were analysed for the wood-cement-water mixtures of the three species after removing inhibitory extractives of wood samples by extraction with 5% Sodium hydroxide (NaOH, cold and hot water after removing inhibitory extractives of wood samples. There were differences in the hydration reaction of the wood species with Portland cement using the different pre-treatment methods. The compatibility of the wood species with Portland cement improved following pre-treatment. Sodium hydroxide pre-treatment had the most significant effect followed by hot water. Terminalia ivorensis (Idigbo, and Antiaris africana (Oriro species showed considerable improvement in their compatibility with Portland cement at 5% Sodium hydroxide pre-treatment with maximum hydration temperature of 65oC where Arere had 60.5oC where both cold and hot water were unable to raise the hydration temperature beyond 55.5oC . This study shows that the wood species requires more than cold and hot water extraction to make them suitable for wood cement composite materials as extraction with sodium hydroxide (1% solution was found to be the most effective treatment for the wood species under investigation.

  8. 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.

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

    Directory of Open Access Journals (Sweden)

    Mohamed Heikal

    2015-03-01

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

  10. Laser-radiation scattering by cement in the process of hydration: simulation of the dynamics and experiment.

    Science.gov (United States)

    Gorsky, M P; Maksimyak, P P; Maksimyak, A P

    2012-04-01

    This paper discusses simulation of speckle-field dynamics during coherent light scattering by a cement surface in the process of hydration. Cement particles are represented by the spheres whose sizes and reflection indices are changing during the hydration process. The study of intensity fluctuations of scattered coherent radiation is a suitable technique for the analysis of both fast and slow processes of mineral binder hydration and formation of polycrystalline structures in the process of hardening. The results of simulation are in good agreement with the experimental data.

  11. Carbonation Behavior of Pure Cement Hydrates under Supercritical Carbon Dioxide Conditions - 12199

    International Nuclear Information System (INIS)

    Carbonation of cement-based waste forms using a supercritical carbon dioxide (SCCO2) is a developing technology for the waste immobilization of radioactive and non-radioactive wastes. However, the detail carbonation behaviors of cement matrices under the SCCO2 condition are unknown, since cement matrices forms very complex phases. In this study, in order to clarify the crystal phases, we synthesized pure cement hydrate phases as each single phases; portlandite (Ca(OH)2), ettringite (Ca6Al2(SO4)3(OH)12.26H2O), and calcium silicate hydrate (n CaO---m SiO2 ---x H2O), using suspensions containing a stoichiometric mixture of chemical regents, and performed carbonation experiments using an autoclave under supercritical condition for carbon dioxide. The XRD results revealed both the carbonate phases and co-product phases depending on the initial hydrate phases; gypsum for Ettringite, amorphous or crystalline silica for calcium silicate hydroxide. Thermogravimetric analysis was also performed to understand carbonation behaviors quantitatively. According to the experimental results, it was found that the major reaction was formation of calcium carbonate (CaCO3) in all cases. However, the behaviors of H2O and CO2 content were quietly different: Portlandite was most reactive for carbonation under SCCO2 conditions, and the CO2 content per one molar CaO was ranged from 0.96 ∼ 0.98. In the case of Ettringite, the experiment indicates partial decomposition of ettringite phase during carbonation. Ettringite was comparatively stable even under the SCCO2 conditions. Therefore, a part of ettringite remained and formed similar phases after the ettringite carbonation. The CO2 content for ettringite showed almost constant values around 0.86 ∼ 0.87. In the case of calcium silicate hydrate, the carbonation behavior was significantly influenced by the condition of SCCO2. The CO2 content for the calcium silicate hydrate had values that ranged from 0.51 ∼ 1.01. The co-products of the

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

    OpenAIRE

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

    2009-01-01

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

  13. Structural characterization of magnesium silicate hydrate: towards the design of eco-sustainable cements.

    Science.gov (United States)

    Tonelli, M; Martini, F; Calucci, L; Fratini, E; Geppi, M; Ridi, F; Borsacchi, S; Baglioni, P

    2016-02-28

    Magnesium-based cement is one of the most interesting eco-sustainable alternatives to standard cementitious binders. The reasons for the interest towards this material are twofold: (i) its production process, using magnesium silicates, brine or seawater, dramatically reduces CO2 emissions with respect to Portland cement production, and (ii) it is very well suited to applications in radioactive waste encapsulation. In spite of its potential, assessment of the structural properties of its binder phase (magnesium silicate hydrate or M-S-H) is far from complete, especially because of its amorphous character. In this work, a comprehensive structural characterization of M-S-H was obtained using a multi-technique approach, including a detailed solid-state NMR investigation and, in particular, for the first time, quantitative (29)Si solid-state NMR data. M-S-H was prepared through room-temperature hydration of highly reactive MgO and silica fume and was monitored for 28 days. The results clearly evidenced the presence in M-S-H of "chrysotile-like" and "talc-like" sub-nanometric domains, which are approximately in a 1 : 1 molar ratio after long-time hydration. Both these kinds of domains have a high degree of condensation, corresponding to the presence of a small amount of silanols in the tetrahedral sheets. The decisive improvement obtained in the knowledge of M-S-H structure paves the way for tailoring the macroscopic properties of eco-sustainable cements by means of a bottom-up approach. PMID:26781557

  14. Application of a sub-lattice model to predictions of cement hydrate chemistry

    International Nuclear Information System (INIS)

    The incongruous dissolution of C-S-H gel is central to the performance of the chemical barrier in a deep geological disposal repository for nuclear wastes. Numerous thermodynamic models have been developed with which the dissolution of C-S-H gel may be simulated. One of the limitations in many of these models is their inflexibility in terms of incorporating additional chemical elements into the C-S-H gel structure. This paper reports the application of a sublattice model for C-S-H gel, allowing for example, substitution of alumina, sulphate or heavy metals into the structure. Comparisons are drawn between the sub-lattice representation and other models, illustrating the inherent flexibility of this approach. Examples are presented comparing the solubility of arsenic phases in the solid and aqueous solutions as calculated using the sub-lattice method. The partitioning of arsenic between solid and aqueous phases is explored over a range of activities and temperatures, ultimately bounded by the appearance of solubility limiting phases. Extending this approach to more realistic cement mineral assemblages introduces both stoichiometric hydrates and an additional solid solution representing hydro-garnet. Two cement types are used for the final examples; an ordinary Portland cement and a blended Portland-blast furnace slag, typical of a UK encapsulation grout. Simulations of their dissolution by percolating groundwater illustrate the influence of these cements in controlling the local chemical environment through their service life. (authors)

  15. Laser Radiation CO2 Effects in Cement Paste at Different Hydration Stages after Preparation

    Directory of Open Access Journals (Sweden)

    Moreno-Virgen M.R.

    2011-07-01

    Full Text Available In this work the changes occurring in cement pastes irradiated by 10.6µm CO2 laser at diff erent stages of hydration after preparation are presented. Raman spectroscopy, X-ray diffraction and Scanning Electronic Microscopy (SEM techniques were used to observe molecular structural changes. Intensity of cement paste Raman peaks after laser irradiation was monitored in samples irradiated 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 days after their preparation. Applied laser power changed Raman peaks intensity at 187.5cm-1, 563cm-1, 695cm-1, 750cm-1, 897cm-1, 1042cm-1 and 1159cm-1 that correspond to compounds already present in cement pastes. X-ray diffraction, SEM images and changes in the Raman peaks confirm the recrystalization of cement paste compounds into new phases (alite and belite after irradiation. The produced changes show a clear dependence on the applied laser power density and age of samples.

  16. Study on the hydration product of cement in early age using TEM

    Institute of Scientific and Technical Information of China (English)

    HAN Song; YAN PeiYu; LIU RengGuang

    2012-01-01

    The morphology,crystallization and elemental composition of cement hydration products in early age including Ca(OH)2,CSH gel,AFt and AFm were investigated by transmission electron microscopy (TEM).Compared with the results from SEM and XRD,the TEM method and its advantage in the investigation of early hydration products were discussed.The results showed that TEM method is more accurate and reliable than SEM in the investigation of early hydration products.The CSH gel was confirmed to be amorphous foil-like shape product with a lot of crumples in early hydration age.Its Ca/Si ratio is 1.3±0.2.The morphology difference of AFt and AFm was clarified.AFt and AFm are both poly-crystal with layered structure,composed of disordered nano crystal.The size of nano crystal is less than 20 nm.The difference of Ca/Si ratio results between SEM and TEM was investigated,and its reason was explained.

  17. Chromium behavior during cement-production processes: a clinkerization, hydration, and leaching study.

    Science.gov (United States)

    Sinyoung, Suthatip; Songsiriritthigul, Prayoon; Asavapisit, Suwimol; Kajitvichyanukul, Puangrat

    2011-07-15

    The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca(6)Al(4)Cr(2)O(15), Ca(5)Cr(3)O(12), Ca(5)Cr(2)SiO(12), and CaCr(2)O(7), with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca(5)(CrO(4))(3)OH, CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr(3+) from Ca(6)Al(4)Cr(2)O(15) and Cr(6+) from CaCr(2)O(7), CaCrO(4)·2H(2)O, and Al(2)(OH)(4)CrO(4), were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.

  18. Chromium behavior during cement-production processes: A clinkerization, hydration, and leaching study

    Energy Technology Data Exchange (ETDEWEB)

    Sinyoung, Suthatip [Department of Environmental Engineering, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Songsiriritthigul, Prayoon [Synchrotron Light Research Institute, PO Box 93 Nakhon Ratchasima, 30000 (Thailand); School of Physics, Suranaree University of Technology, Nakhon Ratchasima, 30000 (Thailand); Asavapisit, Suwimol, E-mail: suwimol_s@hotmail.com [Environmental Technology, School of Energy and Materials, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); National Center of Excellence for Environmental and Hazardous Waste Management, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Kajitvichyanukul, Puangrat, E-mail: puangratk@nu.ac.th [National Center of Excellence for Environmental and Hazardous Waste Management, Faculty of Engineering, King Mongkut' s University of Technology Thonburi, Bangkok, 10140 (Thailand); Department of Civil Engineering, Faculty of Engineering, Naresuan University, Phitsanulok, 65000 (Thailand)

    2011-07-15

    Highlights: {yields} Behavior of chromium during cement-production processes. {yields} Formation of new chromium compounds in clinker with chromium oxidation states of +3, +4.6, +5, and +6. {yields} Addition of chromium altered the composition of the clinker phases, setting time, and compressive strength of hydrated mixes. {yields} Cr{sup 3+} and Cr{sup 6} were leached during leaching tests, whereas other species remained in the mortar. - Abstract: The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM/EDS, and TG/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca{sub 6}Al{sub 4}Cr{sub 2}O{sub 15}, Ca{sub 5}Cr{sub 3}O{sub 12}, Ca{sub 5}Cr{sub 2}SiO{sub 12}, and CaCr{sub 2}O{sub 7}, with chromium oxidation states of +3, +4.6, +5, and +6, respectively, was detected. After the hydration process, additional chromium compounds were identified in the mortar matrix, including Ca{sub 5}(CrO{sub 4}){sub 3}OH, CaCrO{sub 4}.2H{sub 2}O, and Al{sub 2}(OH){sub 4}CrO{sub 4}, with chromium oxidation states of +4.6, +6, and +6, respectively. Additionally, some species of chromium, such as Cr{sup 3+} from Ca{sub 6}Al{sub 4}Cr{sub 2}O{sub 15} and Cr{sup 6+} from CaCr{sub 2}O{sub 7}, CaCrO{sub 4}.2H{sub 2}O, and Al{sub 2}(OH){sub 4}CrO{sub 4}, were leached during leaching tests, whereas other species remained in the mortar. The concentrations of chromium that leached from the mortar following U.S. EPA Method 1311 and EA NEN 7375:2004 leaching tests were higher than limits set by the U.S. EPA and the Environment Agency of England and Wales related to hazardous waste disposal in landfills. Thus, waste containing chromium should not be allowed to mix with raw materials in the cement manufacturing process.

  19. Study of cements silicate phases hydrated under high pressure and high temperature; Etude des phases silicatees du ciment hydrate sous haute pression et haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Meducin, F.

    2001-10-01

    This study concerns the durability of oil-well cementing. Indeed, in oil well cementing a cement slurry is pumped down the steel casing of the well up the annular space between it and the surrounding rock to support and protect the casing. The setting conditions of pressure and temperature may be very high (up to 1000 bar and 250 deg C at the bottom of the oil-well). In this research, the hydration of the main constituent of cement, synthetic tri-calcium silicate Ca{sub 3}SiO{sub 2}, often called C{sub 3}S (C = CaO; S = SiO{sub 2} and H H{sub 2}O), is studied. Calcium Silicate hydrates are prepared in high-pressure cells to complete their phase diagram (P,T) and obtain the stability conditions for each species. Indeed, the phases formed in these conditions are unknown and the study consists in the hydration of C{sub 3}S at different temperatures, pressures, and during different times to simulate the oil-well conditions. In a first step (until 120 deg C at ambient pressure) the C-S-H, a not well crystallized and non-stoichiometric phase, is synthesized: it brings adhesion and mechanical properties., Then, when pressure and temperature increase, crystallized phases appear such as jaffeite (Ca{sub 6}(Si{sub 2}O{sub 7})(OH){sub 6}) and hillebrandite (Ca{sub 2}(SiO{sub 3})(OH){sub 2}). Silicon {sup 29}Si Nuclear Magnetic Resonance (using standard sequences MAS, CPMAS) allow us to identify all the silicates hydrates formed. Indeed, {sup 29}Si NMR is a valuable tool to determine the structure of crystallized or not-well crystallized phases of cement. The characterization of the hydrated samples is completed by other techniques: X- Ray Diffraction and Scanning Electron Microscopy. The following results are found: jaffeite is the most stable phase at C/S=3. To simulate the hydration of real cement, hydration of C{sub 3}S with ground quartz and with or without super-plasticizers is done. In those cases, new phases appear: kilchoanite mainly, and xonotlite. A large amount of

  20. Probing the hydration of composite cement pastes containing fly ash and silica fume by proton NMR spin-lattice relaxation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Proton NMR spin-lattice relaxation (T1) was used as a prober for observing the hydration process of composite cement pastes blending fly ash and silica fume during the early age.The distribution at initial time,evolution curves and signals intensity of T1 were shown in this paper.Results demonstrate that the T1 distribution curves at initial time exhibit two peaks,which are regarded as two different water phases in the pastes.The evolution curves of T1 are in good agreement with the hydration process of composite pastes and could be roughly divided into four stages:initial period,dormant period,acceleration period and steady period.The hydration mechanism for each stage was discussed.The hydration of the composite cement pastes was retarded by the addition of fly ash and silica fume when compared to that of pure cement.However,the hydration degree of the cement in the blends was promoted.

  1. Compressive Strength and Hydration Process of Self Compacting Concrete (SCC) mixed with Sea Water, Marine Sand and Portland Composite Cement

    OpenAIRE

    Tjaronge, Wihardi; Irmawaty, Rita

    2014-01-01

    In order to eliminate the main problems of shortage of clean water and fine aggregate in the low land areas and the distant islands, this research utilized sea water and marine sand and Portland composite cement to produce high performance of Self Compacting Concrete (SCC). Portland composite cement containing of fly ash. The evaluation result on the mix design, workability (slumpflow, segregation), mechanical properties (compressive strength-static modulus) and hydration process of SCC were ...

  2. Analysis of Femoral Components of Cemented Total Hip- Arthroplasty

    CERN Document Server

    Singh, Shantanu

    2014-01-01

    In cemented Total Hip Arthroplasty (THA), material chosen for femoral stem and cross section of stem itself, proved to be critical parameters for, stress distribution in the femoral components, interfacial stresses and micro movements. Titanium alloy (Ti6Al4V), when used as a material for femoral stem, recorded large displacement as compared to Chromium alloy (CoCrMo) stems. This large displacement in case of Ti6Al4V caused the stem to bend inside the cement mantle, thus destroying it. Thus, CoCrMo proved to be a better in cemented THA. Failure in THA may occur at cement-stem or cement-bone interface, thus interfacial stresses and micro movements were analysed in the present study. Comparison between trapezium and circular cross section showed that, femoral stem with trapezium cross section underwent lesser amount of sliding and debonding, at both interfaces, as compared to circular cross section. Moreover, trapezium cross section also generated lower peak stresses in femoral stem and cortical femur. The pres...

  3. Pore solution analysis of cement pastes and nanostructural investigations of hydrated C3S

    International Nuclear Information System (INIS)

    Pore solution investigations of cement pastes which had been prepared with the addition of ethanolamine showed that the ethanolamine had not been bound by cement during hydration and remained more or less completely dissolved in the capillary water, which can (theoretically) be expressed. This suggests that no significant binding of ethanolamine had occurred, neither chemically nor by way of adsorption and that the physically bound water (gel water) could not act as a solvent for the ethanolamine. The latter seems to be in contrast to the frost theory according to which a part of the gel water is mobile [M. Setzer, Micro ice lens formation, in: M.J. Setzer (Ed.), Proceedings of the 3rd International Bolomey Workshop 'Pore Solution in Hardened Cement Paste', University of Essen, June 1998, AEDIFICATIO Publishers, Freiburg, 2000, pp. 89-112]. This shows that a better understanding of structural details in the nanometer range of hardened cement is necessary. Therefore, small-angle neutron scattering (SANS) experiments were performed to study this part of the structure using C3S. SANS studies allow a nondestructive description of statistically representative microstructures in the scale range from micrometer to nanometer. In contrast to the established methods for microstructural investigations like MIP or BET, nondried samples can be used. Moreover, the scattering signals can be analyzed in a variety of ways, and therefore, a more detailed insight can be provided into the very complex cement paste microstructure. In this study, the signals were evaluated with respect to the specific inner surface and the particle-size distribution in the investigated nanometer range up to ∼100 nm

  4. Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

    Energy Technology Data Exchange (ETDEWEB)

    De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr [MINES ParisTech, PSL Research University, Centre de Géosciences, 35 Rue St-Honoré, 77305 Fontainebleau Cedex (France); Bertron, Alexandra; Larreur-Cayol, Steeves; Escadeillas, Gilles [University of Toulouse, UPS/INSA/LMDC, 135 Av. de Rangueil, 31077 Toulouse Cedex 04 (France)

    2015-03-15

    Interactions of short-chain organic acids with hydrated cement phases affect structure durability in the agro-food and nuclear waste industries but can also be used to modify cement properties. Most previous studies have been experimental, performed at fixed concentrations and pH, without quantitatively discriminating among polyacidity effects, or complexation and salt precipitation processes. This paper addresses such issues by thermodynamic equilibrium calculations for acetic, citric, oxalic, succinic acids and a simplified hydrated CEM-I. The thermodynamic constants collected from the literature allow the speciation to be modeled over a wide range of pH and concentrations. Citric and oxalic had a stronger chelating effect than acetic acid, while succinic acid was intermediate. Similarly, Ca-citrate and Ca-oxalate salts were more insoluble than Ca-acetate and Ca-succinate salts. Regarding aluminium complexation, hydroxyls, sulfates, and acid competition was highlighted. The exploration of acid mixtures showed the preponderant effect of oxalate and citrate over acetate and succinate.

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

    International Nuclear Information System (INIS)

    This work attempts to investigate the modelling of radioisotopes (Cs+, Pb2+, Eu3+) immobilization in cement matrix, in the frame of the design of engineered barrier of a deep radwaste repository. The model development concept consists of three major steps: - surface chemistry modelling of the calcium silicate hydrate CSH, used to simulate hydrated cement behaviour; - solid analysis of the batch sorption experiments: identification of the uptake mechanism; - both previous steps are used, with isotherm data, in the modelling of the radioisotopes immobilization in the CSH matrix. Final results: (all modelling are available for all the range of studied Ca/Si ratios and have been validated with predictive calculations). - A thermodynamic modelling of the CSH surface chemistry has been developed. The labile calcium and proton sorption constants on silanol sites (>SiOH) have been extracted. - Cs+ is sorbed on two sites. The silanol site (weak site) has a high site density (10 sites.nm-2), which accounts for the CSH unsaturation in high [CS+]. A strong site is also identified. - Pb2+ immobilization in CSH matrix is modelled with surface equilibria and solubility equilibrium. - Eu3+ fixation has been investigated with solid analysis: Site-Selective anti Time-Resolved Luminescence Spectroscopy, XPS and SEM-EDS. Eu3+ thus does not precipitate in CSH water but is sorbed on the CSH surface (high hydroxylated environment). Europium is also (minority site) inserted in the CSH framework. (author)

  6. Effect of Additives on the Morphology of the Hydrated Product and Physical Properties of a Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    Xiupeng WANG; Jiandong YE; Yingjun WANG

    2008-01-01

    The morphology of a hydrated calcium phosphate cement (CPC) doped with several normally used additives was investigated by scanning electron microscopy (SEM) and the compressive strength of the cement was determined in this study. The hydrated products of CPC without additives was rod-like hydroxyapatite (HA) grains with around 2-5 μm in length and 100 nm in width. The addition of Sr obviously decreased the crystal size of the rod-like grains. CPCs containing carbonate, collagen and gelatin showed flake-like crystal morphology. Crylic acid-containing CPC presented flocculus-like structure. And malic acid-containing CPC exhibited oriented flake-like structure. The X-ray diffraction (XRD) analysis showed that the additives used in this study did not alter the hydration products of the cement. The compressive strength tests indicated that the compressive strength of the cement with rod-like morphology HA crystals was much higher than that of the cement with flake-like morphology HA crystals, and the cement with oriented flake-like morphology HA crystals .exhibited the poorest compressive strength.

  7. Reproducibility of the uptake of U(VI) onto degraded cement pastes and calcium silicate hydrate phases

    International Nuclear Information System (INIS)

    The U(VI) uptake in degraded cement pastes was undertaken in the laboratories of CEA/L3MR and SUBATECH in order to check the reproducibility of the study. Two well hydrated cement pastes, CEM I (ordinary portland cement, OPC) and CEM V (blast furnace slag (BFS) and fly ash added to OPC) were degraded using similar protocols. Equilibrium solutions and solid materials were characterised for three degradation states for each paste. All samples are free of portlandite and the pH of the equilibrated cement solutions vary in the range 9.8-12.2. Three calcium silicate hydrate phases (C-S-H) were synthesised in order to compare the sorption properties of degraded cement pastes and of hydrate phases in similar pH conditions. In order to avoid precipitation processes, the operational solubility limit was evaluated before batch experiments. These solubility values vary significantly in the pH range [9-13] with a 2.4 x 10-7 mol L-1 minimum at pH close to 10.5. In batch sorption experiments, the distribution ratio Rd values are high: 3 x 104 - 1.5 x 105 mL g-1. The uptake of U(VI) increases when comparing the least and the most degraded cement pastes whereas the initial composition of cement has relatively insensitive effect. Sorption isotherms, expressed as a log [U(VI)solid]/log[U(VI)solution] plots are linear. A slope of 1 is calculated indicating the predominance of sorption processes. As sorption and desorption values are close, the uptake mechanism seems reversible. The Rd values measured in C-S-H suspensions are in good agreement with Rd values of degraded cement pastes, and C-S-H materials could be one of the cementitious phases which control U(VI) uptake in cement pastes. (orig.)

  8. Caesium sorption by hydrated cement as a function of degradation state: experiments and modelling.

    Science.gov (United States)

    Ochs, M; Pointeau, I; Giffaut, E

    2006-01-01

    To provide reliable K(d) data for Cs required for the performance assessment of cement-based radioactive waste repositories, two complementary approaches were followed. First, Cs sorption was determined on a range of hydrated cement paste (HCP) and mortar samples of CEM I and CEM V for different degradation states and solution compositions, as well as on some single mineral phases. Second, a surface complexation-diffuse layer model previously developed by Pointeau et al. [Pointeau, I., Marmier, N., Fromage, F., Fedoroff, M., Giffaut, E., 2001. Cs and Pb uptake by CSH phases of hydrated cement. Material Research Society Symposium Proceedings, 663, 105-113] for Cs sorption on synthetic CSH phases was simplified to facilitate its application to whole HCP and mortars or concrete, following re-assessment of the model parameters. All measurements were compared with model predictions. The sorption data obtained on the different solid phases as a function of conditions corroborate that CSH minerals are the main sorbing phase for Cs in HCP. The data also clearly show the important influence of pH and the dissolved concentration of Na, K and Ca on K(d). It is further suggested that a decrease of pH is concomitant with a decrease of the Ca/Si ratio and a corresponding increase in surface sites with high affinity for Cs and, thus, K(d). Elevated concentrations of cations able to compete with Cs for these sites lead to a decrease of K(d), on the other hand. The simplified model was applied to the sorption measurements performed within this study as well as to a variety of literature data, mainly K(d) values for a variety of fresh HCP and mortar or concrete samples based on different samples of Ordinary Portland Cement as well as blended cements. The results show that the model can be applied reasonably well to a very large variety of conditions in terms of solid and solution compositions that cover a range of K(d) values from 10(-4) to ca. 3.2m(3)/kg. The large scatter

  9. Hydration of a silica fume blended low-alkali shotcrete cement

    Science.gov (United States)

    Lothenbach, Barbara; Rentsch, Daniel; Wieland, Erich

    Ettringite and C-S-H are the main hydrates formed during the hydration of the low-alkali cement “ESDRED” consisting of 60% CEM I, 40% microsilica and 4.8% set accelerator. Small quantities of portlandite and hemicarbonate present as intermediate phases destabilise within a few weeks. The use of a set accelerator leads to massive ettringite precipitation, a moderate decalcification of C-S-H and reduction of pH due to presence of dissolved formate. The slow reaction of the silica fume during hydration decalcifies the C-S-H and decreases the alkali concentration to 30 mM and the pH value of the pore solution to 11.5 after 1 year and longer. The further reaction of the silica fume is expected to be slow and to result in a decrease of pH to 11. Further, the destabilisation of ettringite to thaumasite is expected. The long-term stability of C-S-H and the pH of approximately 11 make ESDRED a good candidate for usage in contact with the clay-based barriers of a repository for radioactive waste.

  10. Effect of temperature on the hydration of Portland cement blended with siliceous fly ash

    International Nuclear Information System (INIS)

    The effect of temperature on the hydration of Portland cement pastes blended with 50 wt.% of siliceous fly ash is investigated within a temperature range of 7 to 80 °C. The elevation of temperature accelerates both the hydration of OPC and fly ash. Due to the enhanced pozzolanic reaction of the fly ash, the change of the composition of the C–S–H and the pore solution towards lower Ca and higher Al and Si concentrations is shifted towards earlier hydration times. Above 50 °C, the reaction of fly ash also contributes to the formation of siliceous hydrogarnet. At 80 °C, ettringite and AFm are destabilised and the released sulphate is partially incorporated into the C–S–H. The observed changes of the phase assemblage in dependence of the temperature are confirmed by thermodynamic modelling. The increasingly heterogeneous microstructure at elevated temperatures shows an increased density of the C–S–H and a higher coarse porosity. -- Highlights: •The reaction of quartz powder at 80 °C strongly enhances the compressive strength. •Almost no strength increase of fly ash blended OPC at 80 °C was found after 2 days. •Siliceous hydrogarnet is formed upon the reaction of fly ash at high temperatures. •Temperature dependent change of the system was simulated by thermodynamic modelling. •Destabilisation of ettringite above 50 °C correlates with sulphate content of C–S–H

  11. Performances of hydrated cement treated crushed rock base for Western Australian roads

    Directory of Open Access Journals (Sweden)

    Suphat Chummuneerat

    2014-12-01

    Full Text Available The resilient modulus (RM of hydrated cement treated crushed rock base (HCTCRB affected by amount of hydration periods, compaction and dryback processes was presented using repeated load triaxial tests. The related trends of RM corresponding to the different hydration periods still cannot be concluded. Instead, It is found that the moisture content plays more major influence on the RM performance. Higher additional water during compaction of HCTCRB, even at its optimum moisture content and induced higher dry density, led to the inferior RM performance compared to the sample without water addition. The RM of damper samples can be improved through dryback process and superior to that of the sample without water addition at the same moisture content. However, the samples without water addition during compaction deliver the comparable RM values even its dry density is lower than the other two types. These results indicate the significant influence of moisture content to the performances of HCTCRB with regardless of the dry density. Finally, the experimental results of HCTCRB and parent material are evaluated with the K-θ model and the model recommended by Austroads. These two models provide the excellent fit of the tested results with high degree of determination.

  12. Microstructure and Composition of Hydration Products of Ordinary Portland Cement with Ground Steel-making Slag

    Institute of Scientific and Technical Information of China (English)

    LI Yong-xin; CHEN Yi-min; ZHANG Hong-tao; HE Xing-yang; WEI Jiang-xiong; ZHANG Wen-sheng

    2003-01-01

    The effect of ground steel-making slag on microstructure and composition of hydration products of ordinary Portland cement (OPC) was investigated by mercury intrusion porosimetry ( MIP ), X- ray diffraction (XRD) and differential thermal analysis (DTA). Results show that ground steel-making slag is a kind of high activity mineral additives and it can raise the longer-age strength of OPC mortar. The total porosity and average pore diameter of OPC paste with groand steel-making slag increase with the increase of the amount of ground steelmaking slag replacing OPC at various ages, while after 28 days most pores in OPC paste with ground steel-making slag do not influeace the strength because the diameter of those pores is in the rang of 20 to 50nm. The hydration mechanism of ground steel-making slag is similar to that of OPC but different from that of fly ash and blast furnace slag. The hydration products of ground steel-making slag contain quite a lot of Ca( OH)2 in long age.

  13. Study of the action of phosphate ions contained in the mixing water on the hydration of a Portland cement

    International Nuclear Information System (INIS)

    Cementation is considered as the most attractive solution for the conditioning of low and intermediate radioactive wastes. The species contained in these wastes can strongly influence the reactivity of the cement pastes, it is in particular the case of the ortho-phosphate ions which are found in the evaporation concentrates. The aim of our work was to determine the influence of these ions on the hydration and the rheological properties of the cement pastes at early age as well as the mechanical and physical properties on the hardened material. (author)

  14. Improvement of Cement Strength by Induction Method

    Institute of Scientific and Technical Information of China (English)

    YANG Li-yuan; LIN Zong-shou

    2004-01-01

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

  15. Crystal chemistry of portland cement hydrates as radioactive waste hosts. Final report, June 15, 1983-June 14, 1984

    International Nuclear Information System (INIS)

    Portland cement hydrates have been used as encapsulant/host phases in radioactive waste management. However, their phase chemistry and stability relationships are poorly defined. Therefore, on occasion, they have not performed as well as expected. As a result, their use has been mainly limited to low-level waste disposal. Since this knowledge gap existed, we had begun to investigate the crystal chemistry of the portland cement hydrates. It was our objective to identify potential hydrate host phases which were not only suitable for isolating radioactive-waste species but also inexpensive, easily processed, low-temperature materials. Initially, we were concentrating upon two areas of interest: the fixation of iodine by the calcium aluminate hydrates and the feasibility of using Stratling's compound as a host phase for cesium and strontium fixation. In both cases, a phase equilibrium study was initiated in order to identify phase relations and consequences of adding the species of interest to the system. An iodine-containing analogue of calcium monosulfoaluminate hydrate (C3A.CaI2.xH2O) was identified as a possible host phase. CsOH was added to formulations in the neighborhood of Stratling's compound, in order to establish phase relations and identify the fixation ability of Stratling's compound and its associated hydrates. 11 figures, 9 tables

  16. Crystal chemistry of portland cement hydrates as radioactive waste hosts. Progress report, June 15, 1983-February 7, 1984

    International Nuclear Information System (INIS)

    Portland cement hydrates have been used as encapsulant/host phases in radioactive waste management. However, their phase chemistry and stability relationships are poorly defined. Therefore, on occassion, they have not performed as well as expected. As a result, their use has been mainly limited to low-level waste disposal. Since this knowledge gap exists, we have begun to investigate the crystal chemistry of the portland cement hydrates. It is our objective to identify potential hydrate host phases which are not only suitable for isolating radioactive-waste species but also inexpensive, easily processed, low-temperature materials. Initially, we have been concentrating upon two areas of interest: The fixation of iodine by the calcium aluminate hydrates and the feasibility of using Straling's compound as a host phase for cesium and strontium fixation. In both cases, a phase equilibrium study has been initiated in order to identify phase relations and consequences of adding the species of interest to the system. An iodine-containing analogue of calcium monosulfoaluminate hydrate (C3A.CaI2.xH2O) has been identified as a possible host phase. CsOH and Sr(OH)2 are being added to formulations in the neighborhood of Stratling's compound, in order to establish phase relations and identify the fixation ability of Stratling's compound and its associated hydrates. 10 figures, 6 tables

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

    International Nuclear Information System (INIS)

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

  18. Intrinsic differences in atomic ordering of calcium (alumino)silicate hydrates in conventional and alkali-activated cements

    International Nuclear Information System (INIS)

    The atomic structures of calcium silicate hydrate (C–S–H) and calcium (–sodium) aluminosilicate hydrate (C–(N)–A–S–H) gels, and their presence in conventional and blended cement systems, have been the topic of significant debate over recent decades. Previous investigations have revealed that synthetic C–S–H gel is nanocrystalline and due to the chemical similarities between ordinary Portland cement (OPC)-based systems and low-CO2 alkali-activated slags, researchers have inferred that the atomic ordering in alkali-activated slag is the same as in OPC–slag cements. Here, X-ray total scattering is used to determine the local bonding environment and nanostructure of C(–A)–S–H gels present in hydrated tricalcium silicate (C3S), blended C3S–slag and alkali-activated slag, revealing the large intrinsic differences in the extent of nanoscale ordering between C–S–H derived from C3S and alkali-activated slag systems, which may have a significant influence on thermodynamic stability, and material properties at higher length scales, including long term durability of alkali-activated cements

  19. Analysis of Femoral Components of Cemented Total Hip Arthroplasty

    Science.gov (United States)

    Singh, Shantanu; Harsha, A. P.

    2015-10-01

    There have been continuous on-going revisions in design of prosthesis in Total Hip Arthroplasty (THA) to improve the endurance of hip replacement. In the present work, Finite Element Analysis was performed on cemented THA with CoCrMo trapezoidal, CoCrMo circular, Ti6Al4V trapezoidal and Ti6Al4V circular stem. It was observed that cross section and material of femoral stem proved to be critical parameters for stress distribution in femoral components, distribution of interfacial stress and micro movements. In the first part of analysis, designs were investigated for micro movements and stress developed, for different stem materials. Later part of the analysis focused on investigations with respect to different stem cross sections. Femoral stem made of Titanium alloy (Ti6Al4V) resulted in larger debonding of stem at cement-stem interface and increased stress within the cement mantle in contrast to chromium alloy (CoCrMo) stem. Thus, CoCrMo proved to be a better choice for cemented THA. Comparison between CoCrMo femoral stem of trapezium and circular cross section showed that trapezoidal stem experiences lesser sliding and debonding at interfaces than circular cross section stem. Also, trapezium cross section generated lower peak stress in femoral stem and cortical femur. In present study, femur head with diameter of 36 mm was considered for the analysis in order to avoid dislocation of the stem. Also, metallic femur head was coupled with cross linked polyethylene liner as it experiences negligible wear compared to conventional polyethylene liner and unlike metallic liner it is non carcinogenic.

  20. Effect of Fly Ash and Silica Fume on Hydration Rate of Cement Pastes and Strength of Mortars

    Institute of Scientific and Technical Information of China (English)

    LIU Jun; ZHANG Yun; LIU Runqing; ZHANG Bing

    2014-01-01

    The effect of fly ash and silica fume on hydration rate and strength of cement in the early stage was studied. Contrast test was applied to the complex cementitious system to investigate the hydration rate. Combined with mechanical strength, the influence of fly ash and silica fume during the hydration process of complex binder was researched. The peak of the rate of hydration heat evolution and the mechanical strength decreased as the ratio of fly ash increased, however, as the ratio of silica fume increased, the peak of the rate of hydration heat evolution and the mechanical strength increased obviously. When the ratios of fly ash and silica fume are 10%and 5%, the peak of the rate of hydration heat evolution is the highest. At the same time 7 days of flexural and compressive strength are the highest as 8.89 MPa and 46.52 MPa, respectively. Fly ash and silica fume are the main factors affecting the hydration rate and the mechanical property.

  1. The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, J.M. [Departamento de Física Aplicada, Universitat Politècnica de València, Camino de Vera, 46022, Valencia (Spain); Fita, I.C., E-mail: infifer@fis.upv.es [Departamento de Física Aplicada, Universitat Politècnica de València, Camino de Vera, 46022, Valencia (Spain); Soriano, L.; Payá, J.; Borrachero, M.V. [ICITECH, Instituto de Ciencia y Tecnología del Hormigón, Universitat Politècnica de València (Spain)

    2013-08-15

    In this paper, mortars and pastes containing large replacement of pozzolan were studied by mechanical strength, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP) and electrical impedance spectroscopy (EIS). The effect of metakaolin (35%) and fly ash (60%) was evaluated and compared with an inert mineral addition (andalusite). The portlandite content was measured, finding that the pozzolanic reaction produced cementing systems with all portlandite fixed. The EIS measurements were analyzed by the equivalent electrical circuit (EEC) method. An EEC with three branches in parallel was applied. The dc resistance was related to the degree of hydration and allowed us to characterize plain and blended mortars. A constant phase element (CPE) quantified the electrical properties of the hydration products located in the solid–solution interface and was useful to distinguish the role of inert and pozzolanic admixtures present in the cement matrix.

  2. Effect of hydrated lime and cement on moisture damage of recycled mixtures with foamed bitumen and emulsion

    OpenAIRE

    Nosetti, R.A.; Pérez Jiménez, Félix Edmundo; Martínez Reguero, Adriana Haydée; Miró Recasens, José Rodrigo

    2016-01-01

    Cold recycling with foamed bitumen can be used as a sustainable and cost-effective rehabilitation technique. This paper focuses on the evaluation of the resistance to the water action in mixtures with reclaimed asphalt pavement (RAP) and foamed bitumen by means of indirect tensile test, comparing the effect of two active fillers: cement and hydrated lime. Additionally, mixtures recycled with RAP and asphalt emulsions were also tested in order to compare the response of both technologies. Resu...

  3. Substitution of the clayey mineral component by lignite fly ash in portland cement clinker synthesis

    OpenAIRE

    Jovanović Nataša; Komljenović Miroslav; Petrašinović-Stojkanović Ljiljana; Baščarević Zvezdana; Bradić Violeta; Rosić Aleksandra

    2006-01-01

    Fly ash from four power plants in Serbia (PP "Morava" - Svilajnac, PP "Kolubara" - Veliki Grijani, PP "Kostolac" - units B1 and B2 - Kostolac and PP "Nikola Tesla" - units A and B - Obrenovac) was utilized as the starting raw component for Portland cement clinker synthesis. Limestone and quartz sand from the "Holcim - Serbia, a.d." cement factory were the other two starting raw components. Based on the chemical composition of the raw components and from the projected cement moduli, the amount...

  4. Non-Isothermal, Multi-phase, Multi-component Flows through Deformable Methane Hydrate Reservoirs

    CERN Document Server

    Gupta, Shubhangi; Wohlmuth, Barbara

    2015-01-01

    We present a hydro-geomechanical model for subsurface methane hydrate systems. Our model considers kinetic hydrate phase change and non-isothermal, multi-phase, multi-component flow in elastically deforming soils. The model accounts for the effects of hydrate phase change and pore pressure changes on the mechanical properties of the soil, and also for the effect of soil deformation on the fluid-solid interaction properties relevant to reaction and transport processes (e.g., permeability, capillary pressure, reaction surface area). We discuss a 'cause-effect' based decoupling strategy for the model and present our numerical discretization and solution scheme. We then identify the important model components and couplings which are most vital for a hydro-geomechanical hydrate simulator, namely, 1) dissociation kinetics, 2) hydrate phase change coupled with non-isothermal two phase two component flow, 3) two phase flow coupled with linear elasticity (poroelasticity coupling), and finally 4) hydrate phase change c...

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

    Directory of Open Access Journals (Sweden)

    Hiroshi Suzuki

    2016-01-01

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

  6. Effect of hydrating water on the physical characteristics and the diffusion release of cesium nitrate immobilized in cement

    International Nuclear Information System (INIS)

    The effect of the preparation procedure --- variable amounts of hydrating water on the leachability of a soluble contaminant (CsNO3) from cement samples immersed in water, as well as the physical characteristics of cement samples such as density, pore volume, and compressive strength --- were considered in this paper. Leach tests of cement specimens containing 2% in weight of cesium nitrate (CsNO3), prepared at different water-to-cement ratios, W/C = 0.35, 0.40, 0.45, and 0.55, were curred for 60 degrees C, 98% RH, for eleven days. The leaching standard procedure suggested by the International organization for Standardization (ISO) was used to follow the kinetics for the Cs+, NO3-, and Ca3+ releases from cement right cylinders, 20 mm in diameter and 20 mm high, leached in water at a solid surface-to-liquid volume (S/V) = 0.1/cm. The results of the cumulative fraction release (CFR) versus time (t) in days indicate that the leaching of soluble elements like NO3- and cesium follows a diffusion mechanism

  7. Non-Isothermal, Multi-phase, Multi-component Flows through Deformable Methane Hydrate Reservoirs

    OpenAIRE

    Gupta, Shubhangi; Helmig, Rainer; Wohlmuth, Barbara

    2015-01-01

    We present a hydro-geomechanical model for subsurface methane hydrate systems. Our model considers kinetic hydrate phase change and non-isothermal, multi-phase, multi-component flow in elastically deforming soils. The model accounts for the effects of hydrate phase change and pore pressure changes on the mechanical properties of the soil, and also for the effect of soil deformation on the fluid-solid interaction properties relevant to reaction and transport processes (e.g., permeability, capi...

  8. Measurement and modeling of the surface potential evolution of hydrated cement pastes as a function of degradation

    International Nuclear Information System (INIS)

    Hydrated cement pastes (HCP) have a high affinity with a lot of (radio)toxic products and can be used as waste confining materials. In cementitious media. elements are removed from solution via (co)precipitation reactions or via sorption/diffusion mechanisms as surface complexation equilibria. In this study, to improve the knowledge of the surface charge evolution vs the degradation of the HCP particles, two cements have been studied: CEM-I (ordinary Portland cement, OPC) and CEM-V (blast furnace slag and fly ash added to OPC). Zeta potential measurements showed that two isoelectric points exist vs HCP leaching, i.e., pH. Zeta potential increases from -17 to +20 mV for pH 13.3 to pH 12.65 (fresh HCP states) and decreases from 20 to -8 mV for pH 12.65 to I I (degraded HCP states). The use of a simple surface complexation model of C-S-H, limited in comparison with the structural modeling of C-S-H in literature, allows a good pr?diction of the surface potential evolution of both HCP. Using this operational modeling, the surface charge is controlled by the deprotonation of surface sites (> SO-) and by the sorption of calcium (> SOCa+), which brings in addition a positive charge. The calcium concentration is controlled by portlandite or calcium silicate hydrate (C-S-H) solubilities. (authors)

  9. Calcium-aluminum-silicate-hydrate "cement" phases and rare Ca-zeolite association at Colle Fabbri, Central Italy

    Science.gov (United States)

    Stoppa, F.; Scordari, F.; Mesto, E.; Sharygin, V.; Bortolozzi, G.

    2010-06-01

    Very high temperature, Ca-rich alkaline magma intruded an argillite formation at Colle Fabbri, Central Italy, producing cordierite-tridymite metamorphism in the country rocks. An intense Ba-rich sulphate-carbonate-alkaline hydrothermal plume produced a zone of mineralization several meters thick around the igneous body. Reaction of hydrothermal fluids with country rocks formed calcium-silicate-hydrate (CSH), i.e., tobermorite-afwillite-jennite; calcium-aluminum-silicate-hydrate (CASH) — "cement" phases - i.e., thaumasite, strätlingite and an ettringite-like phase and several different species of zeolites: chabazite-Ca, willhendersonite, gismon-dine, three phases bearing Ca with the same or perhaps lower symmetry of phillipsite-Ca, levyne-Ca and the Ca-rich analogue of merlinoite. In addition, apophyllite-(KF) and/or apophyllite-(KOH), Ca-Ba-carbonates, portlandite and sulphates were present. A new polymorph from the pyrrhotite group, containing three layers of sphalerite-type structure in the unit cell, is reported for the first time. Such a complex association is unique. Most of these minerals are specifically related to hydration processes of: (1) pyrometamorphic metacarbonate/metapelitic rocks (natural analogues of cement clinkers); (2) mineralization between intrusive stocks and slates; and (3) high-calcium, alkaline igneous rocks such as melilitites and foidites as well as carbonatites. The Colle Fabbri outcrop offers an opportunity to study in situ complex crystalline overgrowth and specific crystal chemistry in mineral phases formed in igneous to hydrothermal conditions.

  10. Optimization of growth medium for Sporosarcina pasteurii in bio-based cement pastes to mitigate delay in hydration kinetics.

    Science.gov (United States)

    Williams, Sarah L; Kirisits, Mary Jo; Ferron, Raissa Douglas

    2016-04-01

    Microbial-induced calcium carbonate precipitation has been identified as a novel method to improve durability and remediate cracks in concrete. One way to introduce microorganisms to concrete is by replacing the mixing water with a bacterial culture in nutrient medium. In the literature, yeast extract often has been used as a carbon source for this application; however, severe retardation of hydration kinetics has been observed when yeast extract is added to cement. This study investigates the suitability of alternative carbon sources to replace yeast extract for microbial-induced calcium carbonate precipitation in cement-based materials. A combination of meat extract and sodium acetate was identified as a suitable replacement in growth medium for Sporosarcina pasteurii; this alternative growth medium reduced retardation by 75 % (as compared to yeast extract) without compromising bacterial growth, urea hydrolysis, cell zeta potential, and ability to promote calcium carbonate formation. PMID:26795346

  11. Effect of temperature on the hydration process and strength development in blends of Portland cement and activated coal gangue or fly ash

    Institute of Scientific and Technical Information of China (English)

    Pei-ming WANG; Xian-ping LIU

    2011-01-01

    This paper describes the results of an investigation into the effect of the variation of curing temperatures between 0 and 60 ℃ on the hydration process,pore structure variation,and compressive strength development of activated coal gangue-cement blend (ACGC).Hardened ACGC pastes cured for hydration periods from 1 to 360 d were examined using the non-evaporable water method,thermal analysis,mercury intrusion porosimetry,and mechanical testing.To evaluate the specific effect of activated coal gangue (ACG) as a supplementary cementing material (SCM),a fly ash-cement blend (FAC) was used as a control.Results show that raising the curing temperature accelerates pozzolanic reactions involving the SCMs,increasing the degree of hydration of the cement blends,and hence increasing the rate of improvement in strength.The effect of curing temperature on FAC is greater than that on ACGC.The pore structure of the hardened cement paste is improved by increasing the curing temperature up to 40 ℃,but when the curing temperature reaches 60 ℃,the changing nature of the pore structure leads to a decrease in strength.The correlation between compressive strength and the degree of hydration and porosity is linear in nature.

  12. Predicting the Impact of Multiwalled Carbon Nanotubes on the Cement Hydration Products and Durability of Cementitious Matrix Using Artificial Neural Network Modeling Technique

    Directory of Open Access Journals (Sweden)

    Babak Fakhim

    2013-01-01

    Full Text Available In this study the feasibility of using the artificial neural networks modeling in predicting the effect of MWCNT on amount of cement hydration products and improving the quality of cement hydration products microstructures of cement paste was investigated. To determine the amount of cement hydration products thermogravimetric analysis was used. Two critical parameters of TGA test are PHPloss and CHloss. In order to model the TGA test results, the ANN modeling was performed on these parameters separately. In this study, 60% of data are used for model calibration and the remaining 40% are used for model verification. Based on the highest efficiency coefficient and the lowest root mean square error, the best ANN model was chosen. The results of TGA test implied that the cement hydration is enhanced in the presence of the optimum percentage (0.3 wt% of MWCNT. Moreover, since the efficiency coefficient of the modeling results of CH and PHP loss in both the calibration and verification stages was more than 0.96, it was concluded that the ANN could be used as an accurate tool for modeling the TGA results. Another finding of this study was that the ANN prediction in higher ages was more precise.

  13. The degree of hydration assessment of blended cement pastes by differential thermal and thermogravimetric analysis. Morphological evolution of the solid phases

    Energy Technology Data Exchange (ETDEWEB)

    Monteagudo, S.M., E-mail: sm.monteagudo@alumnos.upm.es [Departamento de Ingeniería Civil: Construcción, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid 28040 (Spain); Moragues, A., E-mail: amoragues@caminos.upm.es [Departamento de Ingeniería Civil: Construcción, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid 28040 (Spain); Gálvez, J.C., E-mail: jaime.galvez@upm.es [Departamento de Ingeniería Civil: Construcción, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid 28040 (Spain); Casati, M.J., E-mail: mariajesus.casati@upm.es [Departamento de Vehículos Aeroespaciales, Escuela de Ingeniería Aeronáutica, Universidad Politécnica de Madrid (Spain); Reyes, E., E-mail: encarnacion.reyes@upm.es [Departamento de Ingeniería Civil: Construcción, Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos, Universidad Politécnica de Madrid, Madrid 28040 (Spain)

    2014-09-20

    Highlights: • A proposal of hydration degree calculation for blended cement pastes is presented. • The method is based both on the contributions of various authors and on DTA–TG results. • Paste and mortar specimens with BFS, FA and SF mineral admixtures were used. • The evaluation of CH gives information on hydration and pozzolanic reactions. • The assessment of α provides an insight into future strength evolution. - Abstract: The degree of hydration assessment of cement paste from differential thermal and thermogravimetric analysis data has been performed by several authors that have offered a number of proposals for technical application to blended cements. In this paper, two calculation methods are studied in detail. Then, a proposal of the degree of hydration calculation for blended cements, based on the analysis of experimental results of DTA–TG, is presented. The proposed method combines the contributions of the authors and allows straightforward calculation of the degree of hydration from the experimental results. Validation of the methodology was performed by macroscopic and microstructural tests through paste and mortar specimens with blast furnace slag, flying ash and silica fume mineral admixtures bei(g)ng used. Tests of scanning electron microscopy with an energy dispersive analyser on paste specimens, and of mechanical strength on mortar specimens with the same percentages of substitution, were performed. They showed good agreement with the information derived from the differential thermal and thermogravimetric analysis data.

  14. Effect of calcium sulfates on the early hydration of calcium sulfoaluminate cement and the stability of embedded aluminium

    International Nuclear Information System (INIS)

    Conventional Portland cement-based systems have been considered unsuitable for immobilising nuclear wastes containing reactive metals, such as aluminium, due to the high pH of the pore solution (usually around 12.5) and free moisture. On the contrary, calcium sulfo-aluminate cement (CSA) produces a lower pH (10.5-12) environment and has an excellent water binding capability as a result of the formation of its main hydration product, ettringite. Therefore, it offers a good potential to immobilise aluminium. However, the pore solution pH and ettringite formation depend largely on the raw materials used to formulate the CSA, which is usually a blend of 75%-85% of CSA clinker and 15-25% of calcium sulfate (in the form of gypsum or anhydrite). In this paper, it was found that, compared to anhydrite, gypsum (15% wt of the blend) demonstrated the highest reduction in the corrosion of embedded Al, possibly due to its lower initial pH (around 10.5) and self-desiccating nature at the early stage of hydration. Whilst the CSA/anhydrite had a higher Al corrosion rate, the initial set was more acceptable than CSA/gypsum. Nonetheless, overall, it was concluded that CSA with gypsum (15% wt) should be considered as a base formulation for the encapsulation of Al waste. The unfavorable rapid set and high heat generation, however, demonstrated that modifications are required, potentially by using mineral additions. (authors)

  15. Study of the relation between hydrated portland cement composition and leaching resistance

    NARCIS (Netherlands)

    Eijk, van R.J.; Brouwers, H.J.H.

    1998-01-01

    The present paper addresses cement compositions that have an optimal resistance against acid attack and hence, low leaching rates and optimal waste containment. To this end a shrinking core leaching model is used that describes the leaching of metals from a cement sample. This process is directly re

  16. Acid attack on hydrated cement — Effect of mineral acids on the degradation process

    Energy Technology Data Exchange (ETDEWEB)

    Gutberlet, T.; Hilbig, H.; Beddoe, R.E., E-mail: robin.beddoe@tum.de

    2015-08-15

    During acid attack on concrete structural components, a degraded layer develops whose properties as a protective barrier are decisive for durability. {sup 29}Si NMR spectroscopy and {sup 27}Al NMR spectroscopy were used with XRD to investigate the degraded layer on hardened cement paste exposed to HCl and H{sub 2}SO{sub 4}. The layer comprises an amorphous silica gel with framework silicates, geminate and single silanol groups in which Si is substituted by Al. Amorphous Al(OH){sub 3} and Fe(OH){sub 3} are present. The gel forms by polycondensation and cross-linking of C-A-S-H chains at AlO{sub 4} bridging tetrahedra. In the transition zone between the degraded layer and the undamaged material, portlandite dissolves and Ca is removed from the C-A-S-H phases maintaining their polymer structure at first. With HCl, monosulphate in the transition zone is converted into Friedel's salt and ettringite. With H{sub 2}SO{sub 4}, gypsum precipitates near the degradation front reducing the thickness of the transition zone and the rate of degradation.

  17. Substitution of the clayey mineral component by lignite fly ash in portland cement clinker synthesis

    Directory of Open Access Journals (Sweden)

    Jovanović Nataša

    2006-01-01

    Full Text Available Fly ash from four power plants in Serbia (PP "Morava" - Svilajnac, PP "Kolubara" - Veliki Grijani, PP "Kostolac" - units B1 and B2 - Kostolac and PP "Nikola Tesla" - units A and B - Obrenovac was utilized as the starting raw component for Portland cement clinker synthesis. Limestone and quartz sand from the "Holcim - Serbia, a.d." cement factory were the other two starting raw components. Based on the chemical composition of the raw components and from the projected cement moduli, the amounts of raw components in the raw mixtures were calculated. Six different raw mixtures were prepared - each one consisted of limestone, sand and different fly ash. A raw mixture from the industrial production of the "Holcim - Serbia, a.d." cement factory was used as the reference material. The prepared raw mixtures were sintered in a laboratory furnace at 1400°C. The chemical and mineralogical compositions of the synthesized clinkers were determined. The characteristics of clinkers, based on fly ash, were compared to the characteristics of the industrial Portland cement clinker from the "Holcim - Serbia, a.d." cement factory. The results of the investigation showed that fly ash from power plants in Serbia can be suitable for Portland cement clinker synthesis.

  18. The effects of citric acid on the hydration of calcium phosphate cement

    Institute of Scientific and Technical Information of China (English)

    DAI Hong-lian; YAN Yu-hua; WANG You-fa; LI Shi-pu

    2001-01-01

    @@ INTRODUCTION Calcium phosphate cements (CPC) overcome the practical disadvantages of blocks or granulesl can be handled as a paste and sit in situ. Their structure and composition close to that of HAP make them biocompatible materials. 2 The conventional calcium phosphate cement had some problems such as long setting time (30~60 min) and low compressive strength, etc. In our system, an α-TCP/TTCP powder mixture was mixed with water containing citric acid to control the setting time and compressive strength. In this paper, the effects of various concentration citric acid solutions on the properties of the cement are reported.

  19. Effect of different retarders on the hydration of calcium sulfoaluminate eco-cement pastes

    OpenAIRE

    García-Maté, Marta; De la Torre, Ángeles G.; Aranda, Miguel A. G.; Santacruz, Isabel

    2014-01-01

    The manufacture of Calcium SulfoAluminate (CSA) cements is more environmentally friendly than that of OPC [1] as their production releases up to 40% less CO2 than the latter. The main performances of CSA cements are fast setting time, good-chemical resistance properties and high early strengths. CSA cements are prepared by mixing CSA clinker with different amounts of a calcium sulfate set regulator such as gypsum (CaSO4•2H2O), bassanite (CaSO4•½H2O), or anhydrite (CaSO4), or mixtures of th...

  20. Crystallographic characterization of cement pastes hydrated with NaCl; Caracterizacao cristalografica de pastas de cimento hidratadas com NaCl

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Carina Gabriela de Melo e; Martinelli, Antonio Eduardo; Melo, Dulce Maria Araujo; Melo, Marcus Antonio de Freitas; Melo, Vitor Rodrigo de Melo e [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil)

    2012-07-01

    One of the major current challenges faced by oil companies is the exploration of pre salt basins. Salt layers deposited upon the evaporation of ocean water and continental separation are mainly formed by NaCl and isolate immense oil reservoirs. The mechanical stability and zonal isolation of oil wells that run through salt layers must be fulfilled by cement sheaths saturated with NaCl to assure chemical compatibility between cement and salt layer. The present study aimed at evaluating the effect of NaCl addition on the hydration of oil well cement slurries as well as identifying the nature of crystalline phases present in the hardened cement. To that end, cement slurries containing NaCl were mixed, hardened and characterized by X-ray diffraction. The results revealed that the presence of NaCl affects the formation of hydration products by the presence of Friedel's salt. The intensity of the corresponding peaks increase as the contents of NaCl in the slurry increase. High concentrations of NaCl in Portland slurries increase the setting time of cement and the presence of Friedel's salt decreases the strength of the hardened cement. (author)

  1. Thermodynamic and structural characteristics of cement minerals at elevated temperature

    International Nuclear Information System (INIS)

    We have instituted an experimental and including program designed to elucidate the structural and thermodynamic response of cement minerals to elevated temperature. Components of the program involve: (a) synthesis of hydrated Ca-silicates; (b) structural analysis of cement phases induced by heating and dehydration/rehydration; (c) mechanistic and thermodynamic descriptions of the hydration/dehydration behavior of hydrated Ca-silicates as a function of temperature, pressure and relative humidity; (d) study of naturally occurring hydrated Ca-silicates; and (e) measurements of thermodynamic data for hydrated Ca-silicates

  2. Altered cement hydration and subsequently modified porosity, permeability and compressive strength of mortar specimens due to the influence of electrical current

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.

    2014-01-01

    This paper reports on the influence of stray current flow on microstructural prop-erties, i.e. pore connectivity and permeability of mortar specimens, and link these to the observed alterations in mechanical properties and cement hydration. Mortar specimens were partly submerged in water and calcium

  3. Experimental Research and Analysis of Hydration Heat of Cement%水泥水化热试验研究分析

    Institute of Scientific and Technical Information of China (English)

    冀伟

    2016-01-01

    Hydration heat of cement is one of main factors affecting concrete works and is regarded as one of main reasons of early stage cracking of concrete.This paper selects different kinds of Portland cement to carry out the test of hydration heat of cement,and researches influences of different kinds of cement,coal ash and water reducer on hydration heat of cement based on the test results.%水泥水化热是影响混凝土工程的一个主要因素,且被认为是混凝土早期开裂的主要原因之一.选取不同种类的硅酸盐水泥进行水泥水化热试验,并基于试验结果,研究不同水泥种类、粉煤灰和减水剂对水泥水化热的影响.

  4. 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

  5. Modelling the effect of electrical current flow on the hydration process of cement-based materials

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.; Koenders, E.A.B.

    2014-01-01

    Stray current is essentially an electrical current “leakage” from metal conductors and electrical installations. When it flows through cement-based systems, electrical energy is converted to thermal energy that causes increasing temperature due to Joule heating phenomena. The aim of this paper is to

  6. 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.

  7. Analysis and Study of Cement Hydration Heat Test Method%水泥水化热测试方法的分析研究

    Institute of Scientific and Technical Information of China (English)

    龚英; 丁晶晶

    2015-01-01

    水泥水化热是大体积混凝土产生裂缝的主要影响因素,是工程选用水泥考察参数之一。本文对比研究了3种测试方法,认为与直接法(标准规范)相比,溶解热法和TAM AIR测试法操作较简便、测试精度较高、试验误差较小;TAM AIR测试法可直接提供水泥水化放热速率曲线,而溶解热法仅提供特定龄期的水泥水化热。%The cement hydration heat is the main influence factor of massive concrete cracks,which is one of the cement expedition parameters selected for project. In the paper,three test methods are comparatively researched. It is believed that dissolution thermal method and TAM AIR test method are characterized by relatively simple operation,high test precision and low experimental error compared with direct method (standard specification).TAM AIR test method can directly offer cement hydration heat rate curve,while dissolution thermal method only provides cement hydration heat of specific age.

  8. 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.

  9. Immobilization of radioactive waste in cement based matrices

    International Nuclear Information System (INIS)

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

  10. Monitoring the Methane Hydrate Dissociation by the Offshore Methane Hydrate Production Tests using Multi-component Seismic

    Science.gov (United States)

    Asakawa, Eiichi; Hayashi, Tsutomu; Tsukahara, Hitoshi; Takahashi, Hiroo; Saeki, Tatsuo

    2013-04-01

    We developed a new OBC (Ocean Bottom Cable), named as 'DSS' (Deep-sea Seismic System). The sensor has 3-component accelerometer and a hydrophone applicable for four-component (4C) seismic survey. Using the DSS, the methane hydrate dissociation zone will be tried to be monitored at the water depth of around 1000m during JOGMEC offshore methane hydrate production test in early 2013. Before the DSS, we had developed the RSCS (Real-time Seismic Cable System) with 3-component gimbaled geophones, and carried out a reflection seismic survey in the Nankai Trough in 2006. Referring this successful survey, we improved the RSCS to the DSS. The receiver size is reduced to 2/3 and the receiver case has a protective metallic exterior and the cable is protected with steel-screened armouring, allowing burial usage using ROV for sub-seabed deployment at the water depth up to 2000m. It will realize a unique survey style that leaves the system on the seabed between pre-test baseline survey and post-test repeated surveys, which might be up to 6 months. The fixed location of the receiver is very important for time-lapse monitoring survey. The DSS has totally 36 sensors and the sensor spacing is 26.5m. The total length is about 1km. We carried out the pre-test baseline survey between off Atsumi and Shima-peninsula in August, 2012.We located the DSS close to the production test well. The nearest sensor is 63m apart from the well. A newly developed real-time 3-D laying simulation system consisting of ADCP (Acoustic Doppler Current Profiler), transponders attached to the DSS, and real-time 3-D plotting system for transponder locations have been adopted. After we laid the cable, we buried the DSS using ROV (Remotely Operated Vehicle). The baseline survey included 2D/3D seismic surveys with shooting vessel and cable laying/observation ship. The resultant 2D section and 3D volume shows the good quality to delineate the methane hydrate concentrated zone. After the baseline survey, we have left

  11. Is there evidence for accelerated polyethylene wear in uncemented compared to cemented acetabular components? A systematic review of the literature

    NARCIS (Netherlands)

    van der Veen, Hugo; van Jonbergen, H.P.W.; Poolman, R.W.; Bulstra, S.K.; van Raay, J.J.A.M.

    2013-01-01

    Joint arthroplasty registries show an increased rate of aseptic loosening in uncemented acetabular components as compared to cemented acetabular components. Since loosening is associated with particulate wear debris, we postulated that uncemented acetabular components demonstrate a higher polyethyle

  12. Application of the electrical characterization to the study of the hydrated phases of the cement with coal bottom ash; Aplicacion de la caracterizacion electrica al estudio de las fases hidratadas de cemento con adicion de escorias de centrales termicas

    Energy Technology Data Exchange (ETDEWEB)

    Menendez, E.; Frutos, J. de; Alvaro, A. M.

    2014-02-01

    The present paper investigates the influence of using Bottom and Fly Ash as partial replacement of cement in the hydration process. Through measurements of electrical impedance spectroscopy (EIS) and X -ray diffraction (XRD), we analyze from the early stages to the hydration process to the end. Values of EIS, XRD and its relation, are used to determine transformation of hydrated phases, and for each of the substitutions, is indicated as modified the hydrated phase as a function of time and compared it with the reference material. It also proves the relevance of using EIS measures in real time, and as non destructive testing to characterize the hydration process of these materials. (Author)

  13. Grinding Characteristics of Multi-component Cement-based Material

    Institute of Scientific and Technical Information of China (English)

    LU Difen; TAO Longzhong; LI Ning; HU Haipeng

    2005-01-01

    The grinding characteristics of two or multi-component material of clinker with limestone, blast furnace slag and fly ash were studied. Investigation was carried out on the particle size distribution, the Blaine fineness and the sieve residue of the separate and interground products. The relative contents of clinker and limestone in different size fractions of the interground product were examined, and the interaction of two components, which have different grindabilities, was analyzed. The results show there exists a selective grinding effect during intergrinding, one component can help or hinder the grinding of the other. Making good use of this interaction appropriately not only enhances the grindabilities of two or multi-component mixtures, which can promote the grinding process of clinker with industrial wastes, but also improves their particle size distribution and properties.

  14. 21 CFR 888.3320 - Hip joint metal/metal semi-constrained, with a cemented acetabular component, prosthesis.

    Science.gov (United States)

    2010-04-01

    ... cemented acetabular component, prosthesis. 888.3320 Section 888.3320 Food and Drugs FOOD AND DRUG..., prosthesis. (a) Identification. A hip joint metal/metal semi-constrained, with a cemented acetabular component, prosthesis is a two-part device intended to be implanted to replace a hip joint. The...

  15. Development of Ocean Bottom Multi-component Seismic System for Methane Hydrate Dissociation Monitoring

    Science.gov (United States)

    Takahashi, H.; Asakawa, E.; Hayashi, T.; Inamori, T.; Saeki, T.

    2011-12-01

    A 2D multi-component seismic survey was carried out in the Nankai Trough using the RSCS (Real-time Seismic Cable System) system in 2006. The RSCS is the newly developed ocean bottom cable system which is usable in more than 2000m water depth. The results of the PP and data PS components gave us much information of the methane hydrates bearing zone. Based on RSCS technology, we are developing a new monitoring system using multi-component seismic sensors to delineate the methane hydrate dissociation zone for the offshore methane hydrate production test scheduled in FY2012. Conventional RSCS is composed of three component gimbaled geophones which require a large volume inside the receiver. We will adopt accelerometers to achieve a small receiver that is 2/3 the size of conventional RSCS. The accelerometer data can be corrected into horizontal or vertical directions based on the gravity acceleration. The receiver case has a protective metallic exterior and the cable is protected with steel-screened armoring, allowing for burial usage using ROV for sub-seabed deployment. It will realize a unique survey style that leaves the system on the seabed between pre-test baseline survey and post-test repeated survey, which might be up to 6 months. The fixed location of the receiver is very important for time-lapse monitoring survey. We name the new system as DSS (Deep-sea Seismic System). A feasibility study to detect the methane hydrate dissociation with the DSS was carried out and we found that the methane hydrate dissociation could be detected with the DSS depending on the area of the dissociation. The first experiment of the DSS performance test in a marine area is planned in November 2011. The main features of DSS are described as follows: (1) Deep-sea /Ultra Deep-sea Operation Methane hydrate exists in equilibrium temperature and pressure holds at water depths greater than 500m. The system water depth resistance target up to 2000m. The receiver case has a protective

  16. Immobilisation of radwaste in cement based matrices

    International Nuclear Information System (INIS)

    The solubilities and influence on cement pH are reported for calcium aluminate and aluminosulphate hydrates. The solubility of Ca(OH)2 is reported to 700 bars. Polymerization of C-S-H is investigated by NMR. Specific interactions of U6+ and iodine (I-, IO3-) with cement components are described. The impact of radiation on cements and the influence of higher temperature are documented. The role of dissolved Ca and CO2 in groundwaters as dissolution media for cements are reported. (author)

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

    Directory of Open Access Journals (Sweden)

    Tatiana Pyatina

    2016-05-01

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

  18. Remagnetization and Cementation of Unconsolidated Sediments in the Mallik 5L-38 Well (Canadian Arctic) by Solute Exclusion During Gas Hydrate Formation

    Science.gov (United States)

    Hamilton, T. S.; Enkin, R. J.; Esteban, L.

    2007-05-01

    Bulk magnetic properties provide a sensitive measure of sedimentary diagenesis related to the stability and growth of gas hydrates. The deposit at Mallik (Mackenzie Delta, Canadian Arctic) occurs in unconsolidated Tertiary sands, but is absent in interstratified silt layers. A detailed sampling of the JAPEX/JNOC/GSC Mallik 5L-38 core tested the use of magnetic properties for detecting diagenetic changes related to the hydrate. Petrographic studies reveal that the sands are well sorted and clean, with quartz > chert >> muscovite and little fines content. Excepting a few rare bands of indurated dolomite in the midst of the gas hydrate zone, there is little or no cementation in the sands. Detrital magnetite is the dominant magnetic mineral, comprising up to a few percent of the sand grain population. In contrast, the muddier layers have a somewhat different detrital grain composition, richer in lithic (sedimentary and metamorphic) grains, feldspar, and clays. They are extensively diagenetically altered (to as much as 30- 40%) and cemented with carbonates, clays, chlorite and the iron sulphide greigite (the dominant magnetic mineral). The greigite is recognized by its isotropic creamy-white reflectance, cubic to prismatic habit, and characteristic tarnish to faintly bluish bireflectant mackinawite. Habits range from disseminated cubes and colliform masses to inflationary massive sulphide veins and clots. Rare detrital grains of magnetite were observed among the silt grains, but never in a reaction relationship or overgrown. Instead the greigite has nucleated separately, in tensional fractures and granular masses up to 4 mm across. In this particular sediment sequence, being so quartz and chert rich, there is insufficient local source for the introduced cements (calcite, dolomite, greigite, clays, jarosite), so ions must have been introduced by fluid flow. Magnetic studies reveal a bi-modal character related to the lithology (sands versus silts) and their magnetic

  19. Early age hydration and pozzolanic reaction in natural zeolite blended cements: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction

    International Nuclear Information System (INIS)

    The in situ early-age hydration and pozzolanic reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 oC. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C3S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C3S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.

  20. A literature review of mixed waste components: Sensitivities and effects upon solidification/stabilization in cement-based matrices

    International Nuclear Information System (INIS)

    The US DOE Oak Ridge Field Office has signed a Federal Facility Compliance Agreement (FFCA) regarding Oak Ridge Reservation (ORR) mixed wastes subject to the land disposal restriction (LDR) provisions of the Resource conservation and Recovery Act. The LDR FFCA establishes an aggressive schedule for conducting treatability studies and developing treatment methods for those ORR mixed (radioactive and hazardous) wastes listed in Appendix B to the Agreement. A development, demonstration, testing, and evaluation program has been initiated to provide those efforts necessary to identify treatment methods for all of the wastes that meet Appendix B criteria. The program has assembled project teams to address treatment development needs in a variety of areas, including that of final waste forms (i.e., stabilization/solidification processes). A literature research has been performed, with the objective of determining waste characterization needs to support cement-based waste-form development. The goal was to determine which waste species are problematic in terms of consistent production of an acceptable cement-based waste form and at what concentrations these species become intolerable. The report discusses the following: hydration mechanisms of Portland cement; mechanisms of retardation and acceleration of cement set-factors affecting the durability of waste forms; regulatory limits as they apply to mixed wastes; review of inorganic species that interfere with the development of cement-based waste forms; review of radioactive species that can be immobilized in cement-based waste forms; and review of organic species that may interfere with various waste-form properties

  1. A literature review of mixed waste components: Sensitivities and effects upon solidification/stabilization in cement-based matrices

    Energy Technology Data Exchange (ETDEWEB)

    Mattus, C.H.; Gilliam, T.M.

    1994-03-01

    The US DOE Oak Ridge Field Office has signed a Federal Facility Compliance Agreement (FFCA) regarding Oak Ridge Reservation (ORR) mixed wastes subject to the land disposal restriction (LDR) provisions of the Resource conservation and Recovery Act. The LDR FFCA establishes an aggressive schedule for conducting treatability studies and developing treatment methods for those ORR mixed (radioactive and hazardous) wastes listed in Appendix B to the Agreement. A development, demonstration, testing, and evaluation program has been initiated to provide those efforts necessary to identify treatment methods for all of the wastes that meet Appendix B criteria. The program has assembled project teams to address treatment development needs in a variety of areas, including that of final waste forms (i.e., stabilization/solidification processes). A literature research has been performed, with the objective of determining waste characterization needs to support cement-based waste-form development. The goal was to determine which waste species are problematic in terms of consistent production of an acceptable cement-based waste form and at what concentrations these species become intolerable. The report discusses the following: hydration mechanisms of Portland cement; mechanisms of retardation and acceleration of cement set-factors affecting the durability of waste forms; regulatory limits as they apply to mixed wastes; review of inorganic species that interfere with the development of cement-based waste forms; review of radioactive species that can be immobilized in cement-based waste forms; and review of organic species that may interfere with various waste-form properties.

  2. Aggregation of Calcium Silicate Hydrate Nanoplatelets.

    Science.gov (United States)

    Delhorme, Maxime; Labbez, Christophe; Turesson, Martin; Lesniewska, Eric; Woodward, Cliff E; Jönsson, Bo

    2016-03-01

    We study the aggregation of calcium silicate hydrate nanoplatelets on a surface by means of Monte Carlo and molecular dynamics simulations at thermodynamic equilibrium. Calcium silicate hydrate (C-S-H) is the main component formed in cement and is responsible for the strength of the material. The hydrate is formed in early cement paste and grows to form platelets on the nanoscale, which aggregate either on dissolving cement particles or on auxiliary particles. The general result is that the experimentally observed variations in these dynamic processes generically called growth can be rationalized from interaction free energies, that is, from pure thermodynamic arguments. We further show that the surface charge density of the particles determines the aggregate structures formed by C-S-H and thus their growth modes. PMID:26859614

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

    International Nuclear Information System (INIS)

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

  4. 公路粉煤灰水泥水化过程的研究%Studies on Hydrated Process of High Road Fly Ash Cement

    Institute of Scientific and Technical Information of China (English)

    付兴华; 孙景旭; 董友军; 文福民

    2001-01-01

    The hydrated products and pore size distribution of high road fly ash cements were studied by means of XRD,DTA,Mercury porosimeter,etc.,The experiment results showed that C-S-H gel,AFt were the main hydrated products in high road fly ash cement,but the contents of Ca(OH)2 were lower.The exothermic peaks of the formation of AFt and AFm appeared in hydrated exotermic curves of this cements,while the peaks of C-H-S gel and Ca(OH)2 were not.Although the total porosity of this cement stone were higher,the volume porosity of large pores which sizes were more than 1000A。 were lower after 7 days,the micropores and gel pores which size were little than 500A。 were higher.Thus,the cement stone was fine and close in texture,properties were also higher in late ages.%采用X-射线衍射、差热分析、微量热计及压汞测孔仪对公路粉煤灰水泥的水化产物、水化放热曲线、孔尺寸分布进行了研究。实验结果表明,公路粉煤灰水泥的主要水化产物是C-S-H凝胶、AFt及少量的Ca(OH)2。在该水泥的1天水化放热曲线上仅出现了AFt及AFm的形成放热峰,未出现C-S-H凝胶及Ca(OH)2的快速形成放热峰。尽管该水泥的空隙率较高,但水化7天以后大于1000A。的连通大孔体积率较低,而小于500A。的微孔及凝胶孔体积率较高,因此水泥石的结构致密,后期性能较好。

  5. Revision total hip replacement with a cemented long femoral component: minimum 9-year follow-up results.

    OpenAIRE

    So, Kazutaka; Kuroda, Yutaka; Matsuda, Shuichi; Akiyama, Haruhiko

    2013-01-01

    [Background] Surgical revision after failed total hip replacement is a technically challenging procedure. The aim of this study was to analyze the long-term results of revision total hip replacement using a cemented long femoral component and identify factors that influence the results. [Methods] We retrospectively reviewed 34 hips in 33 patients who had undergone revision total hip replacement using a cemented long femoral component between 1994 and 2001. Hip function was evaluated according...

  6. EXPERIMENTAL INVESTIGATION ON GAS HYDRATE FORMATION IN PRESENCE OF ADDITIVE COMPONENTS

    Institute of Scientific and Technical Information of China (English)

    SUN Zhigao; FAN Shuanshi; GUO Kaihua

    2003-01-01

    Additives were used to increase gas hydrate formation rate and storage capacity. Experimental tests of methane hydrate formation were carried out in surfactant water solutions in a high-pressure cell.Sodium dodecyl sulfate (SDS) and alkyl polysaccharide glycoside (APG) were used to increase hydrate formation. The effect of SDS on hydrate formation is more pronounced compared APG. Cyclopentane (CP) also improves hydrate formation rates while it cannot increase methane gas storage capacity.

  7. Influence of The Activated Qatari Attapulgite Clay Admixture on The Mechanical Properties and Hydration Kinetics of Ordinary Portland Cement

    OpenAIRE

    Al-Noaimi, Kawkab Kh. [كوكب النعيمي

    2001-01-01

    Blended cements are types of cements containing additives other than those used m Portland cement, which have considerable technological interest, because such addition increases the chemical resistance to sulfate and chloride attack. The present investigation represents a laboratory study, which provides a unique opportunity to introduce an effective practical attempt to deal with the problem of concrete deterioration m Qatar and the Arabian Gulf region, and to provide a solution to the prob...

  8. Low pH cements based on CAC for underground repositories of HLW: long-term hydration and resistance against ground water aggression

    International Nuclear Information System (INIS)

    Cementitious materials play an important role in the structural stability and integrity of a purpose built repository for the geological disposal of high level waste. However, the expected generation of an alkaline plume from the concrete by the ingress of groundwater would have detrimental effects on the intended use of a bentonite buffer. To limit this risk, low-pH cementitious materials are being developed to have a target pH < 11 corresponding to the upper stability limit of bentonite. This paper deals with the modifications generated in the chemical composition of the pore solutions of low-pH cement pastes based on Calcium Aluminates Cements (CAC) and in their solid phases after 2 years of hydration. The results show a high stability of the solid phases formed in short-term (90 days). The main modifications in the pore solution composition and in the solid phases occur before 90 days of hydration and, after that, their properties keep quite stable. This paper also deals with the resistance of these low-pH cementitious materials to long-term groundwater aggression using two types of aggressive agents: deionized water and groundwater from the real site of Aespoe (Sweden). Low-pH concretes based on CAC plus silica fume have been evaluated. It appears that their behaviour depends on the leaching agent composition but, with the 2 agents tested in this work, the produced low-pH concretes show a good resistance

  9. Intrusion Characteristics of Three Bone Cements for Tibial Component of Total Knee Arthroplasty in a Cadaveric Bone Model.

    Science.gov (United States)

    Walden, Justin K; Chong, Alexander C M; Dinh, Nam L; Adrian, Scott; Cusick, Robert; Wooley, Paul H

    2016-01-01

    The purpose of this study was to evaluate and compare the intrusion characteristics of Simplex-HV to Simplex-P and Palacos-R in cadaveric proximal tibial bone. Eighteen fresh-frozen cadaver proximal tibiae were examined with standard arthroplasty tibial cuts. Each tibia was randomly assigned to receive one of the three bone cements for use with finger packing technique. Sagittal sections were prepared and analyzed using digital photography and stereoscopic micrographs to evaluate cement intrusion characteristics. The cement penetration depth was measured from the tibial bone cut surface, which did not include the cement thickness under the tibial base plate. Significant differences were detected in the bone cement penetration between the three cements. Penetration was increased using the Simplex-HV (average, 2.7 mm; range, 2.0-3.0 mm) compared with Simplex-P (average, 2.2 mm) and Palacos-R (average, 1.8 mm). These depths approximate to 3.7, 3.2, and 2.8 mm of total cement penetration, respectively. The data suggest that high-viscosity bone cement may provide good fixation of the tibial component of a total knee arthroplasty when using the finger packing technique. PMID:27518289

  10. CO{sub 2} reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures

    Energy Technology Data Exchange (ETDEWEB)

    Barbara G. Kutchko; Brian R. Strazisar; Nicolas Huerta; Gregory V. Lowry; David A. Dzombak; Niels Thaulow [United States Department of Energy, Pittsburgh, PA (United States). National Energy Technology Laboratory

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO{sub 2} and CO{sub 2}-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO{sub 2} storage integrity. The pozzolan additive chosen, Type F flyash, a by-product of coal combustion, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO{sub 2} and CO{sub 2}-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO{sub 2}-saturated brine and supercritical CO{sub 2} after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO{sub 2}, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 {mu}D. Analyses of 50:50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO{sub 2}, which are consistent with our laboratory findings. 16 refs., 4 figs., 1 tab.

  11. CO2 reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures.

    Science.gov (United States)

    Kutchko, Barbara G; Strazisar, Brian R; Huerta, Nicolas; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing, wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 microD. Analyses of 50: 50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings.

  12. CO2 reaction with hydrated class H well cement under geologic sequestration conditions: effects of flyash admixtures.

    Science.gov (United States)

    Kutchko, Barbara G; Strazisar, Brian R; Huerta, Nicolas; Lowry, Gregory V; Dzombak, David A; Thaulow, Niels

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing, wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolan-cement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm for both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 microD. Analyses of 50: 50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings. PMID:19544912

  13. Surface energies of hardened cement pastes and their mineral hydrate components

    OpenAIRE

    BENZARTI, K; Perruchot, C.; CHEHIMI, MM

    2004-01-01

    Concrete is the most common material in the fields of construction and civil engineering. Damaged concrete structures are often repaired by gluing stiff reinforcements on the damaged zones (such as steel or composite plates), using epoxy adhesives. A good wettability of the mineral surface by the epoxy resin is usually required in order to promote an accurate level of adhesion. Therefore, the surface energy of the cementitious substrate can be considered as an important parameter for the dura...

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

    OpenAIRE

    Kara, P

    2013-01-01

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

  15. CO2 Reaction with Hydrated Class H Well Cement under Geologic Sequestration Conditions: Effects of Flyash Admixtures

    Energy Technology Data Exchange (ETDEWEB)

    Kutchko, Barbara G. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering; Strazisar, Brian R. [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Huerta, Nicolas [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Univ. of Texas, Austin, TX (United States); Lowry, Gregory V. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering; Dzombak, David A. [Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering; Thaulow, Niels [RJ Lee Group, Inc., Monroeville, PA (United States)

    2009-05-15

    The rate and mechanism of reaction of pozzolan-amended Class H cement exposed to both supercritical CO2 and CO2-saturated brine were determined under geologic sequestration conditions to assess the potential impact of cement degradation in existing wells on CO2 storage integrity. The pozzolan additive chosen, Type F flyash, is the most common additive used in cements for well sealing in oil-gas field operations. The 35:65 and 65:35 (v/v) pozzolancement blends were exposed to supercritical CO2 and CO2-saturated brine and underwent cement carbonation. Extrapolation of the carbonation rate for the 35:65 case suggests a penetration depth of 170-180 mm far both the CO2-saturated brine and supercritical CO2 after 30 years. Despite alteration in both pozzolan systems, the reacted cement remained relatively impermeable to fluid flow after exposure to brine solution saturated with CO2, with values well below the American Petroleum Institute recommended maximum well cement permeability of 200 mu D. Analyses of 50:50 pozzolan-cement cores from a production well in a sandstone reservoir exhibited carbonation and low permeability to brine solution saturated with CO2, which are consistent with our laboratory findings.

  16. Development of methodology for evaluation of long-term safety aspects of organic cement paste components

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, M.; Holgersson, S. (Chalmers University of Technology, Goeteborg (Sweden)); Ervanne, H. (Helsinki Univ. (Finland)) (and others)

    2008-12-15

    Long-term safety aspects of superplasticizers (SP) and other cement paste components were studied in this joint Nagra - NUMO - SKB - Posiva project with aim to develop a methodology for the evaluation of the long-term safety aspects of superplasticizers (SP) and other organic components of cement pastes. The study also evaluated the effects of SPs and other cement paste components that have already been used or that are most likely to be used in the construction of the high-level nuclear waste repositories in Sweden, Switzerland, Finland and Japan. The main long-term safety issue of concern is whether the superplasticizers and/or other organic components of cement pastes might affect the transport properties of radionuclides. A full evaluation of whether the superplasticizers can be used in a high-level nuclear waste repository cannot be answered based on the studies but a classification of the superplasticizers based on their impact on sorption of radionuclides has been done. The basic methodology for testing, leaching and analyzing of leachants and solid samples of different types was developed at CRIEPI. Two different methodologies for studying the impact of SPs on the sorption of Eu on crushed rock were tested and developed by Helsinki University (HU) and Chalmers University of Technology (CTH). Methods for analyzing organics leaching from grouts were successfully tested by CRIEPI and CTH (Chalmers University of Technology). At CRIEPI the total organic content (TOC) of the leachants was analyzed by Infrared absorption spectrometry (IR) followed by Gel Permeation Chromatography (GPC) for the identification of the organic compounds. At CTH several different analytical methods were tested (e.g. IR, UV spectroscopy, NMR, MALDI-TOF), but these methods still require improvement. In addition to SPs, organics are present in several components of cement pastes, for example in cement grinding aid (CGA) and micro silica slurry. The results suggests that the main high

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

    Directory of Open Access Journals (Sweden)

    I. R. Oliveira

    2007-03-01

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

  18. Potential Use Of Carbide Lime Waste As An Alternative Material To Conventional Hydrated Lime Of Cement-Lime Mortars

    OpenAIRE

    Al Khaja, Waheeb A.

    1992-01-01

    The present study aimed at the possibility of using the carbide lime waste as an alternative material to the conventional lime used for cement-lime mortar. The waste is a by-product obtained in the generation of acetylene from calcium carbide. Physical and chemical properties of the wastes were studied. Two cement-lime-sand mix proportions containing carbide lime waste were compared with the same mix proportions containing conventional lime along with a control mix without lime. Specimens wer...

  19. Chemical alteration of cement materials in a radioactive waste repository environment. 1. Thermodynamic modelling for the dissolution and precipitation of calcium silicate hydrates

    International Nuclear Information System (INIS)

    Cementitious material, a potential waste packaging and backfilling material for the disposal of radioactive waste, is expected to provide both physical and chemical containment. In particular the ability to provide high-pH conditions, which depends on the solubility of the constituent hydrated minerals in cement matrices, is a very important parameter when considering the release of radionuclides from radio active wastes. For long-term safety assessment, it is necessary to develop a series of predictive calculation models. Several models have been proposed for the incongruent dissolution of calcium silicate hydrate (C-S-H) gel, which is the principal product of hydrated cement phases. In the repository, the re-precipitation of minerals would follow their dissolution when an equilibrated solution moves to the other regions and equilibrates with the constituent minerals there. However, previous models have not yet adequately quantitatively evaluated the re-precipitation or interaction of other minerals with the dissolution of C-S-H gel. In this study, therefore, a thermodynamic dissolution and precipitation model of C-S-H gel is proposed assuming a binary non-ideal solid solution of Ca(OH)2 and Si02. Dissolution and precipitation experiments on C-S-H gel were performed. C-S-H precipitates were prepared using two techniques. One was based on hydrolysis in a mixture of Ca and Si solutions and produced homogeneous gels. With the other technique, precipitates were prepared by contacting Ca(OH)2 solution with C-S-H gel with low Ca/Si ratios (0.47, 0.65, 0.9). The results were well predicted by the proposed model. Dissolution experiments on C-S-H gel coexisting with ettringite were also carried out. At Ca/Si>l.2 in C-S-H gel, the equilibrated pH and Ca and Si concentrations are nearly the same as those for C-S-H gel alone. At lower Ca/Si, interaction between ettringite and C-S-H dissolution was observed more clearly. The measured pH and Ca and Si concentrations were

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

    Energy Technology Data Exchange (ETDEWEB)

    Pointeau, I

    2000-09-01

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

  1. Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

    Energy Technology Data Exchange (ETDEWEB)

    Schroefl, Christof, E-mail: christof.schroefl@tu-dresden.de [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Mechtcherine, Viktor [Technische Universität Dresden, Fakultät Bauingenieurwesen, Institut für Baustoffe, DE-01062 Dresden (Germany); Vontobel, Peter; Hovind, Jan; Lehmann, Eberhard [Paul Scherrer Institut, Laboratory for Neutron Scattering and Imaging, CH-5232 Villigen/AG (Switzerland)

    2015-09-15

    Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1.

  2. Sorption kinetics of superabsorbent polymers (SAPs) in fresh Portland cement-based pastes visualized and quantified by neutron radiography and correlated to the progress of cement hydration

    International Nuclear Information System (INIS)

    Water sorption of two superabsorbent polymers in cement-based pastes has been characterized by neutron radiography. Cement pastes with W/C of 0.25 and 0.50 and one additionally containing silica fume (W/C = 0.42) were investigated. The SAPs differed in their inherent sorption kinetics in extracted cement pore solution (SAP 1: self-releasing; SAP 2: retentive). Desorption from SAP 1 started very early after paste preparation. Hence, its individual non-retentiveness governs its behavior only. SAP 2 released water into all matrices, but its kinetics were different. In the paste with the highest W/C, some moderate water release was recorded from the beginning. In the other two pastes, SAP 2 retained its stored liquid during the dormant period, i.e., up to the percolation threshold. Intense desorption then set in and continued throughout the acceleration period. These findings explain the pronouncedly higher efficiency of SAP 2 as internal curing admixture as compared to SAP 1

  3. Study of the action of phosphate ions contained in the mixing water on the hydration of a Portland cement; Etude de l'action des phosphates presents dans l'eau de gachage sur l'hydratation d'un ciment Portland

    Energy Technology Data Exchange (ETDEWEB)

    Benard, Ph

    2005-12-15

    Cementation is considered as the most attractive solution for the conditioning of low and intermediate radioactive wastes. The species contained in these wastes can strongly influence the reactivity of the cement pastes, it is in particular the case of the ortho-phosphate ions which are found in the evaporation concentrates. The aim of our work was to determine the influence of these ions on the hydration and the rheological properties of the cement pastes at early age as well as the mechanical and physical properties on the hardened material. (author)

  4. 磷石膏基水泥的早期水化性能研究%Early hydration properties of phosphogypsum-based cement

    Institute of Scientific and Technical Information of China (English)

    袁继峰; 刘彬; 董晓进

    2014-01-01

    研究了原样磷石膏、200℃煅烧磷石膏、800℃煅烧磷石膏制备的磷石膏水泥的力学性能(对应编号分别为:MPC-1、MPC-2和MPC-3),进行了不同改性磷石膏基水泥早期水化放热速率及28 d水化产物的测试分析。结果表明:煅烧磷石膏尤其高温煅烧磷石膏可发挥更好的硫酸盐激发效果,有效提高磷石膏基水泥的强度,尤其是早期强度。800℃煅烧磷石膏水泥MPC-3试样3、28 d强度分别为20.1、44.7 MPa,达到42.5R水泥强度等级要求;煅烧磷石膏基水泥的早期水化进程明显加快,相对MPC-1试样,MPC-2、MPC-3第二放热峰出现时间分别提前约10 h和17 h;磷石膏基水泥的水化产物主要为钙矾石和C-S-H凝胶,高温煅烧磷石膏基水泥水化产物更为密集。%Influence of phosphogypsum,200 ℃ calcined phosphogypsum and 800 ℃ calcined phosphogypsum on paste strength of modified phosphogypsum-based cement(No.:MPC-1 MPC-2 and MPC-3) were tested;Furthermore,early hydration exothermic rate and 28 d hydration products were systematically compared.Results showed that calcined phosphogypsum ,especially high temperature calcined phosphogypsum can play better stimulate sulfate effect,effectively improve strength of MPC,especially early strength.800 ℃ calcined phosphogypsum-based cement with the compressive strength 20.1 MPa at 3 d and 44.7 MPa at 28 d can meet the standard of Portland ce-ment of 42.5R grade in strengths.Early hydration process of MPC accelerated markedly ,the second exothermic peak of MPC-2 and MPC-3 can respectively advance for 10 h and 17 h relative to MPC-1.Hydration products of phosphogypsum-based cement were mainly ettringite and C-S-H gel,which were more intensive for MPC-2 and MPC-3.

  5. Evaluation of Ohio fly ash/hydrated lime slurries and Type 1 cement sorbent slurries in the U.C. Pilot spray dryer facility. Final report, September 1, 1993--August 31, 1994

    Energy Technology Data Exchange (ETDEWEB)

    Keener, T.C.; Khang, S.J.; Meyers, G.R. [Cincinnati Univ., OH (United States)

    1995-02-01

    The objectives of this year`s work included an evaluation of the performance of fly ash/hydrated lime as well as hydrated cement sorbents for spray drying adsorption (SDA) of SO{sub 2} from a simulated high-sulfur flue gas. These sorbents were evaluated for several different hydration methods, and under different SDA operating conditions. In addition, the physical properties of surface area and porosity of the sorbents was determined. The most reactive fly ash/hydrated lime sorbent studied was prepared at room temperature with milled fly ash. Milling fly ash prior to hydration with lime did have a beneficial effect on calcium utilization. No benefit in utilization was experienced either by hydrating the slurries at a temperature of 90{degrees}C as compared to hydration at room temperature, or by increasing hydration time. While the surface areas varied greatly from sorbent to sorbent, the pore size distributions indicated ``ink bottle`` pores with surface porosity on the order of 0.5 microns. No correlation could be drawn between the surface area of the sorbents and calcium utilization. These results suggest that the composition of the resulting sorbent might be more important than its surface area. The most effective sorbent studied this year was produced by hydrating cement for 3 days at room temperature. This sorbent provided a removal efficiency and a calcium utilization over 25 percent higher than baseline results at an approach to saturation temperature of 30{degrees}F and a stoichiometric ratio of 0.9. A maximum SO{sub 2} removal efficiency of about 90 percent was experienced with this sorbent at an approach to saturation temperature of 20{degrees}F.

  6. The influence of acetabular inclination angle on the penetration of polyethylene and migration of the acetabular component: a prospective, radiostereometric study on cemented acetabular components.

    Science.gov (United States)

    Kadar, T; Furnes, O; Aamodt, A; Indrekvam, K; Havelin, L I; Haugan, K; Espehaug, B; Hallan, G

    2012-03-01

    In this prospective study we studied the effect of the inclination angle of the acetabular component on polyethylene wear and component migration in cemented acetabular sockets using radiostereometric analysis. A total of 120 patients received either a cemented Reflection All-Poly ultra-high-molecular-weight polyethylene or a cemented Reflection All-Poly highly cross-linked polyethylene acetabular component, combined with either cobalt-chrome or Oxinium femoral heads. Femoral head penetration and migration of the acetabular component were assessed with repeated radiostereometric analysis for two years. The inclination angle was measured on a standard post-operative anteroposterior pelvic radiograph. Linear regression analysis was used to determine the relationship between the inclination angle and femoral head penetration and migration of the acetabular component. We found no relationship between the inclination angle and penetration of the femoral head at two years' follow-up (p = 0.9). Similarly, our data failed to reveal any statistically significant correlation between inclination angle and migration of these cemented acetabular components (p = 0.07 to p = 0.9).

  7. 电阻率法测定硅酸盐水泥水化活化能%Activation Energy of Portland Cement Hydration by Electrical Resistivity Measurement

    Institute of Scientific and Technical Information of China (English)

    魏小胜; 肖莲珍

    2011-01-01

    研究了温度对水泥水化时电阻率的影响情况,建立了用于估算电阻率极大值的双曲线方程,提出根据不同温度时的电阻率可以计算孔隙液相活化能(Eas)和水化反应的活化能(Ear).试验所用水泥浆体试样的水灰比分别为0.30、0.35、0.40、0.45和0.55,养护温度分别为15、20℃和30℃,测试时间均为72h.为消除温度对孔隙液相离子迁移的影响,在15℃和30℃测得的电阻率值分别以20℃为基准进行了校正,分析了温度对水泥水化产物形成的影响.研究表明:当水灰比从0.55减小到0.30时.Eas从16.5kJ/mol增大到25.7kJ/mol,这是因为低水灰比水泥浆体的液相离子浓度较大.计算表明:硅酸盐水泥水化反应的活化能Ear为37.2 kJ/mol,这与ASTM C1074的推荐值(40 kJ/mol)比较接近.在不同养护温度下得到的电阻率双曲线方程表明:在所测试的温度范围内,温度越低,电阻率的极大值越大.%Temperature effect on the electrical resistivity of Portland cement pastes during first 72 h was investigated. The experiments were conducted on the cement pastes with various water cement ratios of 0.30, 0.35, 0.40, 0.45, 0.55 at different curing temperatures of 15, 20 and 30 ℃. The hyperbolic equation for each sample was established to estimate the ultimate resistivity. The electrical resistivity at various temperatures can determinate the activation energy for the liquid solution in pores (Eas) and the activation energy for hydration reaction (Ear). The electrical resistivities at 15 and 30 ℃ are obtained based on the value at 20 ℃ to eliminate the effect of temperature on the ionic mobility in the liquid solutions. The Eas increased with the decrease of water cement ratio due to a higher ion concentration in a lower water cement ratio paste solution, and the Eas ranged from 16.5 to 25.7 kJ/mol. The activation energy of cement hydration determined was 37.2 k J/mol, which was similar to the value recommended by the

  8. [Finite element analysis of a cemented ceramic femoral component for the assembly situation in total knee arthroplasty].

    Science.gov (United States)

    Schultze, Christine; Klüss, Daniel; Martin, Heiner; Hingst, Volker; Mittelmeier, Wolfram; Schmitz, Klaus-Peter; Bader, Rainer

    2007-08-01

    The femoral components of the total knee replacements are generally made of metal. In contrast, ceramic femoral components promise improved tribological and allergological properties. However, ceramic components present a risk of failure as a result of stress peaks. Stress peaks can be minimised through adequate implant design, proper material composition and optimum force transmission between bone and implant. Thus, the quality of the implant fixation is a crucial factor. The objective of the present study was to analyse the influence of the cement layer thickness on stress states in the ceramic femoral component and in the femur. Two- and three- dimensional finite element analyses of an artificial knee joint with cement layers of different thickness and with an unbalanced cement layer thickness between the ceramic femoral component and the femur were performed. Higher stress regions occurred in the area of force transmission and in the median plane. The maximum calculated stresses were below the accepted tensile strength. Stresses were found to be lower for cement layer thickness of <2.0 mm. PMID:17691864

  9. Early-age acoustic emission measurements in hydrating cement paste: Evidence for cavitation during solidification due to self-desiccation

    DEFF Research Database (Denmark)

    Lura, Pietro; Couch, J.; Jensen, Ole Mejlhede;

    2009-01-01

    . According to these experimental results, the acoustic emission measured around setting time was attributed to cavitation events occurring in the pores of the cement paste due to self-desiccation. This paper shows how acoustic emission might be used to indicate the time when the fluid–solid transition occurs...

  10. General model for the heat of isothermal hydration of cement%水泥恒温水化放热统一模型

    Institute of Scientific and Technical Information of China (English)

    李占印; 董继红

    2011-01-01

    The heat of hydration of reference cement curing at isothermal temperature is measured by dissolution heat standard in this paper. According to the characteristics of hydration heat monitoring data. Testing datas were fitting respectively in the way of hyperbolic function,power function, combined-expon-ential function and logarithmic function. Data coincidence and scope of application of its fitting function model were estimated based on coefficient and connotation value and extension value. In the end of this paper combined-exponential model based on activation energy and equivalent time was provided. Which given a synthetic consideration to effects of temperature rise on the hydration heat reaction rate. Furthermore,its discrete model was deduced. In favor of applied in finit-difference method resolving on temperature rise at massive concrete.%按照溶解热法测试基准水泥在恒温养护条件下的水化热,根据监测的水化热数据特征,分别按照双曲函数表达式、幂函数表达式、复合指数表达式和对数函数表达式拟合试验数据,根据相关系数以及函数表达式的外延值评价拟合函数的吻合度和适用范围.最后,提出基于活化能和等效时间的复合指数模型,该模型综合考虑了温升对水泥水化放热规律的影响,并推导出其离散模型,方便表达式在大体积混凝土水化热温升差分法解析时的应用.

  11. Influence of latex on the hydration products and microstructure of oil well cement pastes%胶乳对油井水泥水化产物和硬化浆体微结构的影响

    Institute of Scientific and Technical Information of China (English)

    刘仍光; 周仕明; 陶谦; 阎培渝; 丁士东

    2015-01-01

    利用XRD和SEM⁃EDS对胶乳油井水泥水化产物及硬化浆体微结构进行了研究。结果表明胶乳并没有改变油井水泥水化产物的种类;微观形貌显示,胶乳的掺入使得水化产物表面形成一层绒状的物质结构,堆积紧密的六方叠片状的Ca( OH)2晶体形貌变得松散薄片状分布。%The microstructure and hydration products of latex oil well cement pastes were investigated by means of XRD and SEM⁃EDS. The results show that adding latex doesn’ t change the type of hydration products of oil well cement. The morphology shows that a layer of fluffy material is formed on the surface of hydration products due to the incorporation of latex. The calcium hydroxide crystal, which is hexagonal plate⁃like and accumulates tightly in hardened neat cement paste, becomes looser and laminar in the hardened latex oil well cement paste.

  12. Research on Hydration Properties of Blended Cement based on Thermal Activated Coal Gangue%热活化煤矸石——水泥复合体系水化性能分析

    Institute of Scientific and Technical Information of China (English)

    何燕

    2012-01-01

    By specific strength concept, the pozzolanic effect of activated coal gangue could be investigated. Through the content of Ca (OH)2 surplus and the amount of chemically combined water, the hydration degree of activated coal gangue-cement system could be investigated. By means of X-ray diffraction and Differential Thermal Analysis etc, the hydration process of the cement system with activated coal gangue could be analyzed. The results shows that, coal gangue, calcined under the temperature of 750℃ and held for 4 hours, makes a good contribution to the pozzolanic effect of the hardened cement pastes and the activated coal gangue-cement system shows high hydration degree, with fewer Ca(OH)2 surplus and more chemically combined water. The main hydration products are C-S-H gel, Ca(OH)2 and sulfoaluminate hydrate ettringite.%采用比强度法对活化煤矸石的火山灰效应进行评定,通过Ca(OH)2剩余量和化学结合水量的测定,分析活化煤矸石-水泥体系的水化程度,并采用X射线衍射分析,差热分析对其水化过程进行研究.结果表明:煅烧温度为750℃,保温时间为4h的热活化煤矸石对水泥体系的火山灰贡献率较高;该体系Ca(OH)2剩余量较少,化学结合水量较多,其水化产物主要以C-S-H凝胶,Ca(OH)2和钙矾石为主.

  13. EFFECT OF SHRINKAGE REDUING ADMIXTURE ON HYDRATION AND PORE STRUCTURE OF CEMENT-BASED MATERIALS%减缩剂对水泥基材料水化和孔结构的影响

    Institute of Scientific and Technical Information of China (English)

    张志宾; 徐玲玲; 唐明述

    2009-01-01

    The effect of shrinkage reducing admixture (SPA) on hydration process and pore structure of cement-based materials was studied. The hydration heat, chemically combined water and Ca(OH)2 content of cement paste and pore structure of mortar were measured by isothermal calorimeter, gravimetric method, X-ray diffraction and mercury intrusion porosimetry. The results indicate that the SPA has a slight retarding effect on hydration of cement, and the hydration of paste with and without the SPA tended to be the same with increasing the curing time. The appearance time of exothermic peak can be delayed, and the peak value as well as the hydration heat of cement can be lowered by adding the SPA. The chemically combined water of the SPA paste is less than that of the controlled sample. A difference of hydration between the controlled paste and the SPA paste is shortened with hydration age. The Ca(OH)2 content of the SPA paste is less than that of the controlled paste at 3 d, but they are similar at 28 d. Furthermore, the pore volume can be reduced and the innocuous pores can be increased by the SPA used. In addition, the resultant formation of the SRA in pore solution of cement-based materials was supposed.%通过对水泥净浆水化放热量、Ca(OH)2的含量和化学结合水量及水泥砂浆的孔结构的测定,研究减缩剂对水泥基材料水化和孔结构的影响.结果表明:减缩剂会延缓水泥的水化,且随着龄期的发展,延缓作用渐弱.具体表现为减缩剂会降低水泥水化放热的峰值,延迟峰值出现的时间,减小水化放热量;减缩剂能够减小水泥净浆的化学结合水量;龄期为3d时,掺减缩剂的净浆中Ca(OH)2的含量明显低于空白样的,28d时与空白样的相当;减缩剂能够减小水泥砂浆中多害孔和有害孔的孔体积,增加无害孔的孔体积.另外还对减缩剂在水泥基材料中存在的形态提出设想.

  14. The use of electrical impedance spectroscopy for monitoring the hydration products of Portland cement mortars with high percentage of pozzolans

    OpenAIRE

    Cruz González, José Mª; Fita Fernández, Inmaculada Concepción; Soriano Martinez, Lourdes; Paya Bernabeu, Jorge Juan; Borrachero Rosado, María Victoria

    2013-01-01

    In this paper, mortars and pastes containing large replacement of pozzolan were studied by mechanical strength, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM), mercury intrusion porosimetry (MIP) and electrical impedance spectroscopy (EIS). The effect of metakaolin (35%) and fly ash (60%) was evaluated and compared with an inert mineral addition (andalusite). The portlandite content was measured, finding that the pozzolanic reaction produced cementing systems with all ...

  15. Adhesive strength of total knee endoprostheses to bone cement - analysis of metallic and ceramic femoral components under worst-case conditions.

    Science.gov (United States)

    Bergschmidt, Philipp; Dammer, Rebecca; Zietz, Carmen; Finze, Susanne; Mittelmeier, Wolfram; Bader, Rainer

    2016-06-01

    Evaluation of the adhesive strength of femoral components to the bone cement is a relevant parameter for predicting implant safety. In the present experimental study, three types of cemented femoral components (metallic, ceramic and silica/silane-layered ceramic) of the bicondylar Multigen Plus knee system, implanted on composite femora were analysed. A pull-off test with the femoral components was performed after different load and several cementing conditions (four groups and n=3 components of each metallic, ceramic and silica/silane-layered ceramic in each group). Pull-off forces were comparable for the metallic and the silica/silane-layered ceramic femoral components (mean 4769 N and 4298 N) under standard test condition, whereas uncoated ceramic femoral components showed reduced pull-off forces (mean 2322 N). Loading under worst-case conditions led to decreased adhesive strength by loosening of the interface implant and bone cement using uncoated metallic and ceramic femoral components, respectively. Silica/silane-coated ceramic components were stably fixed even under worst-case conditions. Loading under high flexion angles can induce interfacial tensile stress, which could promote early implant loosening. In conclusion, a silica/silane-coating layer on the femoral component increased their adhesive strength to bone cement. Thicker cement mantles (>2 mm) reduce adhesive strength of the femoral component and can increase the risk of cement break-off. PMID:25781660

  16. Numerical predictions of the thermal behaviour and resultant effects of grouting cements while setting prosthetic components in bone.

    Science.gov (United States)

    Quarini, G L; Learmonth, I D; Gheduzzi, S

    2006-07-01

    Acrylic cements are commonly used to attach prosthetic components in joint replacement surgery. The cements set in short periods of time by a complex polymerization of initially liquid monomer compounds into solid structures with accompanying significant heat release. Two main problems arise from this form of fixation: the first is the potential damage caused by the temperature excursion, and the second is incomplete reaction leaving active monomer compounds, which can potentially be slowly released into the patient. This paper presents a numerical model predicting the temperature-time history in an idealized prosthetic-cement-bone system. Using polymerization kinetics equations from the literature, the degree of polymerization is predicted, which is found to be very dependent on the thermal history of the setting process. Using medical literature, predictions for the degree of thermal bone necrosis are also made. The model is used to identify the critical parameters controlling thermal and unreacted monomer distributions. PMID:16898219

  17. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Tobermorite and xonotlite, two synthetic calcium silicate hydrates, improve the Cs retention of cement matrices for Cs, when incorporated at the 6 to 10% level. A kinetic and mechanistic scheme is presented for the reaction of fine grained, Cs-loaded clinoptilolite with cement. The Magnox waste form reacts quickly with cement, leading to an exchange of carbonate between waste form and cement components. Carbonation of cements leads to a marked improvement in their physical properties of Cs retentivity. Diffusion models are presented for cement systems whose variable parameters can readily be derived from experimental measurements. Predictions about scaled-up behaviour of large immobilized masses are applied to extrapolation of laboratory scale results to full-size masses. (author)

  18. Identification and Structures of Two Main Unknown Components in the By-product from the Hydration Synthesis of Camphor

    Institute of Scientific and Technical Information of China (English)

    吴梭; 李兆基; 康遥; 覃业燕; 唐艳红; 姚元根; 钟庆有; 林镜福; 林晓晴; 王镇中

    2000-01-01

    Two main unknown components in the by-product of camphor hydration synthesis were separated and identified by fine fractional distillation and spectroscopic analyses. The components with different ratios of unknown components A and B were collected by the further distillation. The combined spectral results of GC, MS,GC-MS and 13C NMR of the collected samples revealed that A is exo-2, 2, 3-trimethylbicyclo[2, 2, 1 ]heptane, and B is endo-2, 2, 3-trimethylbicyclo[2, 2, 1 ]heptane.

  19. Prediction of chloride ingress and binding in cement paste

    DEFF Research Database (Denmark)

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

    2007-01-01

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

  20. 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

  1. International Workshop Sustainable and Science-driven Engineering of Cement-based Materials (SSEC 2011)

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    On fundamental scientific research, the thermodynamics and kinetics of hydration of cements are introduced and used to optimize the formation of cement hydrates and accordingly the microstructure of cement-based materials.

  2. Portland Cement (KS and API Class G) and Relative Quantitative Analysis

    Science.gov (United States)

    LEE, Seung-Woo; CHAE, Gi-Tak; KIM, Taehee

    2015-04-01

    Portland cement is a common component consisting of a sealing material for wellbores for geological carbon storage to prevent vertical fluid migration and provide mechanical support. Portland cement was reacted with carbon dioxide (CO2) in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate a cement-CO2 reaction along the wellbore from the carbon injection depth to the near surface. The reaction of the cement phase with CO2 can lead to important changes in its structure and properties. In this study, two types of cement were used: KS Portland cement and API Class G Portland cement. The hydrated cement sample columns (14 mm diameter X 90 mm long; water-to-cement ratio = 0.5) were reacted with CO2 in the saturated and the unsaturated condition. Fly-ash was used as additives to promote carbonation. These conditions were maintained under high pressure (8 MPa) and temperature (40 degree Celsius) for 10 and 100 days. To analyze the degree of carbonation after cement carbonation, relative quantitative analysis was proposed. And Rietveld method were conducted to evaluate a relative quantitative analysis (RQA) with an aragonite-calcite equation. This method can be an alternative to the general quantitative analysis method to identify the state of cement carbonation between Portland cement and CO2. Based on an understanding of cement carbonation and its relative quantification, we propose that our method should be used to select the optimized cement for CO2 storage. Using our method, KS (Korea Standard) Portland cement (type I) and API Class G Portland cement have been compared with respect to the characterization of each cement and to the cement carbonation of each cement.

  3. 全尾砂新型充填胶凝材料开发及其水化机理探讨%Discussion on exploitation of new backfilling cementing materials with unclassified tailings and associated hydration mechanisms

    Institute of Scientific and Technical Information of China (English)

    李茂辉; 杨志强; 高谦; 王有团

    2015-01-01

    Based on the characteristics of unclassified tailings in the Sijiaying iron mine, experimental research on exploitation of new backfilling cementing materials that can replace the cement was carried out using lime, desulfurization gypsum, slag, and other solid wastes. Using scanning electron microscopy ( SEM) and X⁃ray diffraction ( XRD) analysis, the hydration mechanisms of the new backfilling cementing materials were analyzed, and the optimum ratio of activators was determined. The results show that the strength of the new backfilling cementing materials can meet the filling body strength requirements for safe mining in the Sijiaying iron mine when the mass fractions of slurry, lime, and desulfurization gypsum are 68%, 3. 5%, and 16. 0%, respectively, and the cement⁃sand ratio is 1∶8. The results also show that the new backfilling cementing materials have a more compact structure and coarser occurrence when compared with the cement. The hydration products of the new backfilling cementing materials are mainly AFt crystals and C⁃S⁃H gel, which greatly increases the age strength of the new backfilling cementing materials.%针对司家营铁矿全尾砂,利用石灰、脱硫石膏、矿渣等固体废弃物开展替代水泥的新型充填胶凝材料试验研究,并通过电镜扫描( SEM)和X射线衍射( XRD)分析,研究新型充填胶凝材料激发剂的水化机理,确定激发剂优化配比。研究表明,当料浆质量分数为68%、胶砂比为1∶8、石灰质量分数为3.5%、脱硫石膏质量分数为16.0%时能够满足司家营铁矿南区嗣后充填法采矿对充填体强度的要求。结果显示,新型充填胶凝材料胶砂体与水泥胶砂体相比,结构更致密、产状更粗大,水化产物主要为AFt晶体和无定型C⁃S⁃H凝胶,从而大幅度提高了新型充填胶凝材料胶砂体的龄期强度。

  4. 三乙醇胺对水化过程中水泥浆体液相离子浓度的影响%Influence of Triethanolamine on Elemental Concentrations in Aqueous Phase of Hydrating Cement Pastes

    Institute of Scientific and Technical Information of China (English)

    孔祥明; 路振宝; 闫娟; 刘辉; 王栋民

    2013-01-01

      采用电感耦合等离子体发射光谱仪(ICP–OES)测定水化过程中水泥浆体液相中元素组成,研究三乙醇胺(triethanolamine,TEA)对水泥浆体液相中离子浓度的影响。结果表明:TEA的加入明显提高了水化过程中水泥浆体液相中的Fe、Ca和 Al的浓度,同时提高了S、Si和OH–的浓度。另外,水化热测试表明:0.1%掺量的TEA提高了水泥第一个水化放热峰,延长了水泥水化诱导期。采用总有机碳测试法跟踪测试TEA加入到水泥浆体后,在浆体液相中的浓度变化,结果发现:TEA的消耗主要发生在水泥水化加速期,表明TEA通过化学反应或物理吸附进入了水泥水化产物中。将TEA加入到饱和Ca(OH)2溶液及含有Ca(OH)2沉淀的饱和Ca(OH)2溶液中,对溶液电导率的测试证实了TEA可以和钙离子形成络合物的推测。%The influence of triethanolamine (TEA) on the elemental concentrations in the aqueous phase of hydrating cement pastes was investigated via inductively coupled plasma atomic emission spectroscopy (ICP–OES). The results show that the TEA increases the concentrations of Fe, Ca, and Al, as well as those of S, Si, and OH–in the aqueous phase of the fresh pastes. The isothermal calo-rimetry experiment indicates that the TEA addition of 0.1%increases the first peak of cement hydration and extends the induction period. The total organic carbon (TOC) results show that the TEA in the aqueous phase of the hydrating cement pastes is rapidly con-sumed in the acceleration period of cement hydration, suggesting that TEA could be incorporated into the hydration products via ei-ther chemical reaction or physical adsorption. The measurement of conductivity of saturated Ca(OH)2 solution confirms the formation of the complex between the TEA and calcium ions.

  5. EFFECT OF INORGANIC SALTS ON DEGREE OF HYDRATION AND PORE STRUCTURE OF CEMENT PASTES%无机盐对水泥石水化程度和孔结构的影响

    Institute of Scientific and Technical Information of China (English)

    杨文萃; 葛勇; 袁杰; 张宝生

    2009-01-01

    采用压汞法研究了水灰比为0.3和0.5的掺加无机盐外加剂[CaCl2,Na2SO4,NaNO2和Ca(NO3)2]水泥石在3 d和28d时的孔结构,并测试化学结合水含量.结果表明:CaCl2,Na2SO4 NaNO2能促进水泥水化:CaCl2促进水泥水化作用最为明显,并可降低水泥石大孔和毛细孔孔隙率;Na2SO4增大了大孔孔隙率;NaNO2能显著减小28d时毛细孔连通孔径和毛细孔孔隙率;Ca(NO3)2在前3d对水泥水化没有明显的作用,在3d时水泥石中大孔和毛细孔孔隙率以及毛细孔连通孔径增大.%The pore structures of cement paste with a water-cement ratio of 0.3 and 0.5 in mass, containing inorganic salts admixture (CaCl2, Na2SO4, NaNO2 and Ca(NO3)2) were studied by mercury intrusion porosimetry at 3 d and 28 d. The hydration degree of ce-ment pastes was also analyzed. The results show that CaCl2, Na2SO4 and NaNO2 can improve the hydration of cement. The accelerat-ing effect of CaCl2 is dominant, compared to the other salts. CaCl2 can also reduce the porosity of the coarse pores and capillary pores of the pastes, and Na2SO4 can increase the porosity of the coarse pores in cement pastes. The throat size of an interconnected capillary net-work and the porosity of the capillary pores in pastes with NaNO2 at 28 d decrease. Ca(NO3)2 does not improve the cement hydration during 3 d, but it can increase the porosity of the coarse pores or the capillary pores as well as the throat size in the paste at 3 d.

  6. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Lachowski, Eric E.;

    1999-01-01

    Vapour phase hydration of purl cement clinker minerals at reduced relative humidities is described. This is relevant to modern high performance concrete that may self-desiccate during hydration and is also relevant to the quality of the cement during storage. Both the oretical considerations and...... experimental data are presented showing that C(3)A can hydrate at lower humidities than either C3S or C2S. It is suggested that the initiation of hydration during exposure to water vapour is nucleation controlled. When C(3)A hydrates at low humidity, the characteristic hydration product is C(3)AH(6...

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

    OpenAIRE

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

    2015-01-01

    Calcium carbide residue (CCR) is a waste by-product from acetylene gas production. The main component of CCR is Ca(OH)2, which can react with siliceous materials through pozzolanic reactions, resulting in a product similar to those obtained from the cement hydration process. Thus, it is possible to use CCR as a substitute for Portland cement in concrete. In this research, we synthesized CCR and silica fume through a chemical combustion technique to produce a new reactive cementitious powder (...

  8. Effects of the Component and Fiber Gradient Distributions on the Strength of Cement-based Composite Materials

    Institute of Scientific and Technical Information of China (English)

    YANG Jiu-jun; HAI Ran; DONG Yan-ling; WU Ke-ru

    2003-01-01

    The effects of the component gradient distribution at interface and the fiber gradient distribution on the strength of cement-based materials were studied.The results show that the flexural strength and compressive strength of the mortar and concrete with interface component and fiber gradient distributions are obviously improved.The strengthes of the fiber gradient distributed mortar and concrete (FGDM/C) are higher than those of fiber homogeneously distributed mortar and concrete (FHDM/C).To obtain the same strength,therefore,a smaller fiber volume content in FGDM/C is needed than that in FHDM/C.The results also show that the component gradient distribution of the concrete can be obtained by means of multi-layer vibrating formation.

  9. Fly and bottom ashes from biomass combustion as cement replacing components in mortars production: rheological behaviour of the pastes and materials compression strength.

    Science.gov (United States)

    Maschio, Stefano; Tonello, Gabriele; Piani, Luciano; Furlani, Erika

    2011-10-01

    In the present research mortar pastes obtained by replacing a commercial cement with the equivalent mass of 5, 10, 20 and 30 wt.% of fly ash or bottom ash from fir chips combustion, were prepared and rheologically characterized. It was observed that the presence of ash modifies their rheological behaviour with respect to the reference blend due to the presence, in the ashes, of KCl and K2SO4 which cause precipitation of gypsum and portlandite during the first hydration stages of the pastes. Hydrated materials containing 5 wt.% of ash display compression strength and absorption at 28 d of same magnitude as the reference composition; conversely, progressive increase of ash cause a continuous decline of materials performances. Conversely, samples tested after 180 d display a marked decline of compression strength, as a consequence of potassium elution and consequent alkali-silica reaction against materials under curing.

  10. Characterization of cement-based ancient building materials in support of repository seal materials studies

    International Nuclear Information System (INIS)

    Ancient mortars and plasters collected from Greek and Cypriot structures dating to about 5500 BC have been investigated because of their remarkable durability. The characteristics and performance of these and other ancient cementitious materials have been considered in the light of providing information on longevity of concrete materials for sealing nuclear waste geological repositories. The matrices of these composite materials have been characterized and classified into four categories: (1) gypsum cements; (2) hydraulic hydrated lime and hydrated-lime cements; (3) hydraulic aluminous and ferruginous hydrated-lime cements (+- siliceous components); and (4) pozzolana/hydrated-lime cements. Most of the materials investigated, including linings of ore-washing basins and cisterns used to hold water, are in categories (2) and (3). The aggregates used included carbonates, sandstones, shales, schists, volcanic and pyroclastic rocks, and ore minerals, many of which represent host rock types of stratigraphic components of a salt repository. Numerous methods were used to characterize the materials chemically, mineralogically, and microstructurally and to elucidate aspects of both the technology that produced them and their response to the environmental exposure throughout their centuries of existence. Their remarkable properties are the result of a combination of chemical (mineralogical) and microstructural factors. Durability was found to be affected by matrix mineralogy, particle size and porosity, and aggregate type, grading, and proportioning, as well as method of placement and exposure conditions. Similar factors govern the potential for durability of modern portland cement-containing materials, which are candidates for repository sealing. 29 references, 29 figures, 6 tables

  11. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    OpenAIRE

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Robert J. Flatt; D'Espinose De Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measuremen...

  12. Performance of Non-Cemented, Hemispherical, Rim-Fit, Hydroxyapatite Coated Acetabular Component.

    Science.gov (United States)

    John, Thomas K; Ghosh, Gaurav; Ranawat, Chitranjan S; Ranawat, Amar S; Meftah, Morteza

    2015-12-01

    The purpose of this study was to assess the durability of a non-cemented, hemispherical rim-fit, hydroxyapatite coated cup with a highly cross-linked polyethylene in 223 total hip arthroplasties. At 6-years follow-up (range, 5-9), there were no cup revisions for osteolysis or loosening. Radiologic evidence of osseointegration was based on presence of Stress Induced Reactive Cancellous Bone and radial trabeculae, seen in 47% and 93% of cups, respectively; both were most prevalent in Zone 1. There was no interference demarcation in any zones. Two cups were revised (0.9%): one for dislocation and another for infection. The Kaplan-Meier survivorship for cup revision for any failure (infection, dislocation) was 99% and for mechanical failure (osteolysis, loosening) was 100%. This design has excellent safety, efficacy and durability. PMID:26235521

  13. Distinguishing between hydrated, partially hydrated or unhydrated clinker in hardened concrete using microscopy

    NARCIS (Netherlands)

    Valcke, S.L.A.; Rooij, M.R. de; Visser, J.H.M.; Nijland, T.G.

    2010-01-01

    Hydration of clinker particles is since long a topic of interest in both designing and optimizing cement composition and its quantity used in concrete. The interest for carefully observing and also quantifying the type or stage of clinker hydration in hardened cement paste is twofold. Firstly, the c

  14. Interaction-component analysis of the hydration and urea effects on cytochrome c

    Science.gov (United States)

    Yamamori, Yu; Ishizuka, Ryosuke; Karino, Yasuhito; Sakuraba, Shun; Matubayasi, Nobuyuki

    2016-02-01

    Energetics was analyzed for cytochrome c in pure-water solvent and in a urea-water mixed solvent to elucidate the solvation effect in the structural variation of the protein. The solvation free energy was computed through all-atom molecular dynamics simulation combined with the solution theory in the energy representation, and its correlations were examined over sets of protein structures against the electrostatic and van der Waals components in the average interaction energy of the protein with the solvent and the excluded-volume component in the solvation free energy. It was observed in pure-water solvent that the solvation free energy varies in parallel to the electrostatic component with minor roles played by the van der Waals and excluded-volume components. The effect of urea on protein structure was then investigated in terms of the free-energy change upon transfer of the protein solute from pure-water solvent to the urea-water mixed solvent. The decomposition of the transfer free energy into the contributions from urea and water showed that the urea contribution is partially canceled by the water contribution and governs the total free energy of transfer. When correlated against the change in the solute-solvent interaction energy upon transfer and the corresponding changes in the electrostatic, van der Waals, and excluded-volume components, the transfer free energy exhibited strong correlations with the total change in the solute-solvent energy and its van der Waals component. The solute-solvent energy was decomposed into the contributions from the protein backbone and side chain, furthermore, and neither of the contributions was seen to be decisive in the correlation to the transfer free energy.

  15. Comparative Hydration Behavior of Metakaolin-Microfine System

    OpenAIRE

    Sood, Vivek; Kumar, Ashok; Agarwal, S. K.

    2014-01-01

    In the present study comparative hydration behaviour of cement with metakaolin and-microfine (ultra fine slag) system has been investigated. Various properties like pozzolanic activity, compressive strength, heat of hydration, XRD of control, hydrated and blended metakaolin/microfine-cement compositions has been compared. With 5%, 7.5% and 10% replacement of cement by metakaolin and microfine, pozzolanic activity increases about 22%, 27%,13% for metakaolin and 23%,35%,20% for microfine compar...

  16. Comparison on Heat of Hydration between Current Concrete for NPP and High Fluidity Concrete including Pozzolan Powders

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Jea Myoung; Cho, Myung Sug [KEPCO Research Institute, Daejeon (Korea, Republic of)

    2010-10-15

    Nuclear power plant (NPP) concrete structures are exposed to many construction factors that lower the quality of concrete due to densely packed reinforcements and heat of hydration since they are mostly constructed with mass concrete. The concrete currently being used in Korean NPPs is mixed with Type I cement and fly ash. However, there is a demand to improve the performance of concrete with reduced heat of hydration and superior constructability. Many advantages such as improving workability and durability of concrete and decreasing heat of hydration are introduced by replacing cement with pozzolan binders. Therefore, the manufacturing possibility of high fluidity concrete should be investigated through applying multi-component powders blended with pozzolan binders to the concrete structure of NPPs, while the researches on properties, characteristic of hydration, durability and long-term behavior of high fluidity concrete using multi-component cement should be carried out. High fluidity concrete which is made using portland cement and pozzlonan powders such as fly ash and blast furnace slag has better properties on heat of hydration than the concrete currently in use for NPPs

  17. Isothermal Calorimetry Study of Blended Cements and its Application in Numerical Simulations

    NARCIS (Netherlands)

    Xiong, X.; Van Breugel, K.

    2001-01-01

    Apparent activation energy (E) is generally used to consider the effect of temperature on the kinetics of cement hydration in the numerical simulation of cement hydration processes. This paper deals with an experimental study on the kinetics of Portland cement and blast furnace slag cement using iso

  18. Terahertz spectroscopy of concrete for evaluating the critical hydration level

    Science.gov (United States)

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Sasmal, Saptarshi; Pesala, Bala

    2014-03-01

    Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

  19. 水泥基材料极早期水化机理及微观结构分析%Early Hydration Mechanism and Microstructural Analysis of Cement-based Materials

    Institute of Scientific and Technical Information of China (English)

    张文强; 李海玉; 陈帅

    2014-01-01

    The issue about the study of ion concentration of pore solution in hydration of cement will try to explain the very early hydration process and its mechanism of hydration.In addition,the issue uses the method of corrupting fly ash by alkaline solution to simulate the impact of pore solution alkalinity reacting hydration and hydration products. The results show that the basic trend of the ion concentration is consistent,which mixed 0,10%,20% of ash respec-tively.Its change is different to the ion concentration of pore solution,because in the beginning stages of hydration,it is mainly controlled by the alkaline soluble substances.Additionally to AFM observation,the change of microstructure of fly ash is closely related to the concentration of alkali ions.%测试了水泥浆体中孔溶液离子浓度在水化极早期的演变规律;运用原子力显微镜(AFM),采用碱性模拟溶液腐蚀粉煤灰的方法来研究了水化过程中孔溶液碱度对粉煤灰化学反应活性以及水化反应和水化产物生成的影响。研究结果表明:粉煤灰掺量分别为0、10%、20%的三种水泥水化孔溶液各离子浓度随水化时间的推移,其变化趋势基本是相同的。水化最开始的阶段孔溶液离子浓度主要是由碱性物溶解控制,其变化呈现差异性。AFM观察结果表明,碱性溶液可以侵蚀粉煤灰颗粒表面,改变其微观结构,改变的程度与侵蚀溶液碱离子浓度密切相关。经侵蚀的粉煤灰颗粒表面有纤维状水化产物形成。

  20. Cements with low Clinker Content

    Science.gov (United States)

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

    2015-11-01

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

  1. 蒸养条件下不同种类外加剂对水泥水化进程的影响%Effect of Different Kinds of Admixture on Process of Cement Hydration under Steam-curing

    Institute of Scientific and Technical Information of China (English)

    肖茜; 伍勇华; 南峰; 何廷树; 李论

    2013-01-01

    用直接测温法、X射线半定量分析方法,系统研究了蒸养条件下高效减水剂(聚羧酸高效减水剂、萘系高效减水剂)、早强剂(硫酸钠)和引气剂(十二烷基硫酸钠)对硅酸盐水泥的放热量和蒸养强度的影响.研究结果表明,聚羧酸高效减水剂延缓了水化放热温峰出现的时间,水化热和Ca(OH)2生成量明显减少;萘系高效减水剂和硫酸钠使水化热温峰出现的时间提前并随水化热量的增多蒸养强度提高,Ca(OH):生成量增加;十二烷基硫酸钠对水泥水化热几乎没有影响,蒸养强度随十二烷基硫酸钠掺量的增加而降低,Ca(OH)2生成量没有明显变化.%By using direct thermometry and X-ray diffraction technique,the influences of superplasticizer (such as polycarboxylate superplasticizer and naphthalene superplasticizer),early strength agent(such as Na2SO4)and air-entraining agent(such as sodium dodecyl sulfate)on cement hydration heat and strength under steam curing were investigated.The results showed that polycarboxylate superplasticizer could postpone the temperature peak,and reduce the hydration heat and the quantity of Ca (OH)2.Nfaphthalene superplasticizer and Na2SO4 used could obviously advance the temperature peak.With the increase of hydration heat,the strength under steam curing obviously was improved and the quantity of Ca (OH) 2 increased.The sodium dodecyl sulfate had little effect on the hydration heat of the cement.The strength under steam curing was reduced with the increase of dosage of Sodium dodecyl sulfate and the quantity of Ca(OH)2 had no clear change.

  2. Control of structurization processes in wood-cement systems at fixed pH

    Science.gov (United States)

    Subbotina, Natalia; Gorlenko, Nikolay; Sarkisov, Yuriy; Naumova, Ludmila; Minakova, Tamara

    2016-01-01

    The paper presents a study of structurization processes in the wood-cement systemmixed with the buffer solutions and the improvement of service properties of products produced therefrom. Infrared spectroscopy, X-ray phase analysis, and pH measurements show that structurization processes in wood-cement systems depend on the acidity of aqueous solution, the behavior of hydration, neutralization, and polycondensation reactions with the formation of polymer products including those with cement grout components and functional groups of wood. It is shown that phosphate buffer solutions used for mixing wood-cement compositions improve their strength properties and reduce water absorption. The optimum acidity of the buffered medium for service properties of the wood-cement systemis pH = 4.8.

  3. 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

  4. Study on the hardening mechanism of cement asphalt binder

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The hydration and hardening mechanism of cement asphalt binder(CAB) was studied.The early hydration process,hydration products and paste microstructure of CAB made by Portland cement and anionic asphalt emulsion were investigated by calorimetry,X-ray diffraction,and environmental scanning electron microscopy.The early hydration process of CAB can be characterized as 5 stages similar to those of Portland cement.There is no chemical reaction detected between cement and asphalt,hence no new hydration products other than those of Portland cement are produced.The hardening of CAB begins with the hydration of cement.When the hydration of cement comes into the acceleration period and its exothermic rate comes to the maximum,the coalescence of asphalt particles in asphalt emulsion is triggered.In the hardened system of CAB,it was found that the hydration products of cement form the skeleton and are covered by the continuous asphalt film.They formed an interpenetrating network system.The emulsifiers in the asphalt emulsion may retard the hydration process of cement.

  5. Do Rerevision Rates Differ After First-time Revision of Primary THA With a Cemented and Cementless Femoral Component?

    DEFF Research Database (Denmark)

    Gromov, Kirill; Pedersen, Alma B; Overgaard, Søren;

    2015-01-01

    Worldwide use of cementless fixation for total hip arthroplasty (THA) is on the rise despite some evidence from the world's registries suggesting inferior survivorship compared with cemented techniques. The patterns of bone loss associated with failed cementless and cemented THAs may prejudice...

  6. Correlation between the degree of conversion and the elution of leachable components from dental resin-based cements

    Directory of Open Access Journals (Sweden)

    KOSOVKA OBRADOVIĆ-DJURIČIĆ

    2011-09-01

    Full Text Available This study examined the possible correlation between the degree of conversion (DC and the amount of substances eluted from three commercial cured resin-based cements. The DC of the various resin-based cements was measured by Raman spectroscopy, while the quantity of unreacted monomers released from the cement matrix (triethylene glycol dimethacrylate, TEGDMA, urethane dimethacrylate, UDMA, 2-hydroxyethyl methacrylate, HEMA and bisphenol A was determined by high pressure liquid chromatography (HPLC. The obtained results, after multiple statistical evaluation (one way ANOVA, LSD post hoc test, showed no significant differences in the DC values between the resin cements. On the contrary, the results of the HPLC analysis depicted statistically significant differences between the three materials with respect to the amount of leached monomers. In addition, no correlation between the DC and the amount of eluted substances from the tested cured composite cements was found.

  7. Early stage hydration law of cement pastes under the coupling effect" of cellulose ether and expanded perlite%纤维素醚-膨胀珍珠岩耦合作用下水泥浆体早期水化规律

    Institute of Scientific and Technical Information of China (English)

    苏雷; 马保国; 蹇守卫; 赵志广; 刘敏

    2012-01-01

    Early hydration law of cement pastes modified with hydroxypropyl methyl cellulose ether and expanded perlite and their mechanism in cement pastes were studied by hydration exothermic rate, XRD, FT-IR, DTG and Ca(OH)2 content. The results show that hydroxypropyl methyl cellulose ether can significantly reduce the peak of hydration exothermic rate of cement paste in early stage. Hydration induction period and acceleration period of cement pastes were delayed. It had little retarding influence on middle and late period hydration of cement paste. The peak hydration exothermic rate of cement pastes modified with expanded perlite was decreased. The effect was worse than the hydroxypropyl methyl cellulose. Expanded perlite had no retarding effects on cement hydration. It had obvious coupling effect under combined action of hydroxypropyl methyl cellulose ether and expanded perlite. Hydroxypropyl methyl cellulose ether and expanded perlite can significantly reduce the content of Ca(OH)2 after 12h hydration. The content of Ca(OH)2 in cement pastes respectively decreased by 43.6% and 9.1% than blank samples. After 24 and 72h hydration, the trendy of decreasing of Ca (OH)2 content in cement paste became very slow with both hydroxypropyl methyl cellulose ether and expanded perlite mixing.%利用水化放热速率、XRD、FT-IR、DTG和Ca(OH)2含量测试手段,研究了羟丙基甲基纤维素醚和膨胀珍珠岩两种保水因子单掺和耦合作用条件下水泥浆体的早期水化规律及二者的作用机理。结果表明羟丙基甲基纤维素醚能够显著降低水泥浆体早期水化放热速率峰值,且能延缓诱导期和加速期出现的时间,对水泥浆体中后期水化没有明显的延缓效应。膨胀珍珠岩可以降低早期水化放热速率峰值,效果较羟丙基甲基纤维素醚差,但对水泥水化无延缓效应。当二者耦合作用时,具有显著的叠加效应。水化12h时,羟丙基甲基纤维素醚和膨

  8. The search for negative amplitude components in quasi-continuous distributions of relaxation times: the example of 1H magnetization exchange in articular cartilage and hydrated collagen

    International Nuclear Information System (INIS)

    When inverting nuclear magnetic resonance relaxation data in order to obtain quasi-continuous distributions of relaxation times for fluids in porous media, it is common practice to impose a non-negative (NN) constraint on the distributions. While this approach can be useful in reducing the effects of data distortion and/or preventing wild oscillations in the distributions, it may give misleading results in the presence of real negative amplitude components. Here, some examples of valid negative components for articular cartilage and hydrated collagen are given. Articular cartilage is a connective tissue, consisting mainly of collagen, proteoglycans and water, which can be considered, in many aspects, as a porous medium. Separate T1 relaxation data are obtained for low-mobility ('solid') macromolecular 1H and for higher-mobility ('liquid') 1H by the separation of these components in free induction decays, with α denoting the solid/liquid 1H ratio. When quasi-continuous distributions of relaxation times (T1) of the solid and liquid signal components of cartilage or collagen are computed from experimental relaxation data without imposing the usual NN constraint, valid negative peaks may appear. The features of the distributions, in particular negative peaks, and the fact that peaks at longer times for macromolecular and water protons are at essentially the same T1, are interpreted as the result of a magnetization exchange between these two spin pools. For the only-slightly-hydrated collagen samples, with α>1, the exchange leads to small negative peaks at short T1 times for the macromolecular component. However, for the cartilage, with substantial hydration or for a strongly hydrated collagen sample, both with α1H ratio, α. The solid-to-liquid exchange times are found to be in the range from 10 ms to a few tens of ms at all hydration levels. The results may be of interest for the application of magnetization exchange contrast in the imaging of articular cartilage

  9. Mechanical property and hydration mechanism of slag blended magnesium phosphate cement%矿渣磷酸镁水泥的力学性能和水化机理

    Institute of Scientific and Technical Information of China (English)

    侯磊; 李金洪; 王浩林

    2011-01-01

    以高炉矿渣作为磷酸镁水泥(MPC)的活性混合材料,研究了MPC的凝固时间、力学性能、物相组成和显微结构,并探讨了矿渣MPC的作用机理.实验固定磷镁比为25%,硼镁比为7.5%,矿渣掺量分别为磷镁总质量的0%、10%、20%、30%和40%.结果表明,矿渣参与了水化反应并提高了MPC的胶凝性能,随着矿渣掺量增大,矿渣MPC的抗压强度提高,但矿渣水化产生的膨胀应力会破坏MPC的内部结构,因此其抗折强度随矿渣掺量增大而降低.矿渣MPC的主要水化产物为六水合磷酸镁铵(MgNH4PO4·6 H2O),矿渣的掺入使凝胶相增加,并有部分Ca2+进入MgNH4PO4·6 H2O品格,使水化产物的形貌、大小发生变化.样品中剩余较多死烧镁和矿渣颗粒,可起骨料作用.%Blast-furnace slag was used as an active addition of magnesium phosphate cement. The influence of blast-furnace slag on the setting time, mechanical property, mineral phase and microstucture of slag blended magnesium phosphate cement (MPC) was studied. The prescription was designed as follows: the ratio of monoammonium phosphate to magnesia was 25% in mass, the borax additive amount to magnesia was 7.5% , the additive amount of blast-furnace slag was 0% , 10%, 20%, 30% and 40% separately in the ratio of total amount of dead burned magnesia and monoammonium phosphate to MPC. The results show that slag might participate the hydration, which improves the bonding of MPC, and the compressive strength of slag-blended MPC is improved with the increasing additive amount of slag. However, slag might results in expansion stress during hydration process, which causes lattice disturbance in hardened MPC, so the flexual strength decreases with the increasing additive amount of slag at the same time. The main hydration product of slag blended MPC is struvite (MgNH4PO4·6 H2O), the content of amorphous phase might increase after being mixed with slag in MPC, and Ca2+ ions in slag can result

  10. 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.

  11. Using bio-based polymers for curing cement-based materials

    OpenAIRE

    Zlopasa, J.; Koenders, E.A.B.; Picken, S.J.

    2014-01-01

    Curing is the process of controlling the rate and extent of moisture loss from the surface of cement based materials. It is the final stage in the production of cement-based materials and it is the essential part for achieving continuous hydration of cement, while avoiding cracking due to drying shrinkage. Continuous cement hydration also guarantees a strong bond between aggregate, fewer voids, and depercoliation of capillary pores. Thus, a properly cured cement-based material is prepared for...

  12. Characteristics and propierties of oil-well cements additioned with blast furnace slag

    OpenAIRE

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

    2011-01-01

    The present paper addresses the alkali activation of Portland cements containing blast furnace slag (20 and 30% 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. D...

  13. Clinker mineral hydration at reduced relative humidities

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    1998-01-01

    This report deals with gas phase hydration of pure cement clinker minerals at reduced relative humidities. This is an important subject in relation to modern high performance concrete which may self-desiccate during hydration. In addition the subject has relevance to storage stability where...

  14. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates.

    Science.gov (United States)

    Pustovgar, Elizaveta; Sangodkar, Rahul P; Andreev, Andrey S; Palacios, Marta; Chmelka, Bradley F; Flatt, Robert J; d'Espinose de Lacaillerie, Jean-Baptiste

    2016-01-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of (29)Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured. PMID:27009966

  15. Understanding silicate hydration from quantitative analyses of hydrating tricalcium silicates

    Science.gov (United States)

    Pustovgar, Elizaveta; Sangodkar, Rahul P.; Andreev, Andrey S.; Palacios, Marta; Chmelka, Bradley F.; Flatt, Robert J.; D'Espinose de Lacaillerie, Jean-Baptiste

    2016-03-01

    Silicate hydration is prevalent in natural and technological processes, such as, mineral weathering, glass alteration, zeolite syntheses and cement hydration. Tricalcium silicate (Ca3SiO5), the main constituent of Portland cement, is amongst the most reactive silicates in water. Despite its widespread industrial use, the reaction of Ca3SiO5 with water to form calcium-silicate-hydrates (C-S-H) still hosts many open questions. Here, we show that solid-state nuclear magnetic resonance measurements of 29Si-enriched triclinic Ca3SiO5 enable the quantitative monitoring of the hydration process in terms of transient local molecular composition, extent of silicate hydration and polymerization. This provides insights on the relative influence of surface hydroxylation and hydrate precipitation on the hydration rate. When the rate drops, the amount of hydroxylated Ca3SiO5 decreases, thus demonstrating the partial passivation of the surface during the deceleration stage. Moreover, the relative quantities of monomers, dimers, pentamers and octamers in the C-S-H structure are measured.

  16. Electrical Measurement to Assess Hydration Process and the Porosity Formation

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; XIAO Lianzhen; LI Zongjin

    2008-01-01

    The change of electrical resistivity with time at early ages was used to investigate the hydration process and the porosity development. Porosity reduction process of cement-based materials hydration was developed by a proposed method. The porosity reduction is fast at the setting period. The results find that the pore discontinuity occurs faster at lower water/cement ratios than at higher water/cement ratios which is similar to the results of the Percolation method.

  17. Energetically Modified Cement (EMC) - Performance Mechanism

    Energy Technology Data Exchange (ETDEWEB)

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

    2003-03-01

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

  18. In situ synchrotron X-ray powder diffraction study of the early hydration of α-tricalcium phosphate/tricalcium silicate composite bone cement

    Energy Technology Data Exchange (ETDEWEB)

    Morejon-Alonso, Loreley; Correa, Jose Raul, E-mail: lmorejon@fq.uh.cu [Departamento de Quimica General, Facultad de Quimica, Universidad de La Habana, UH (Cuba); Motisuke, Mariana [Universidade Federal de Sao Paulo (UNIFESP), Sao Jose dos Campos, SP (Brazil); Carrodeguas, Raul Garcia [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Laboratorio de Avaliacao e Desenvolvimento de Biomateriais do Nordeste; Santos, Luis Alberto dos [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Escola de Engenharia. Departamento de Materiais

    2015-01-15

    Bioactivity, osteogenicity and mechanical properties of α-tricalcium phosphate (α-TCP) based phosphates cements can be improved by adding tricalcium silicate (C{sub 3}S); however, the addition of C{sub 3}S delays the precipitation and growth of calcium deficient hydroxyapatite (CDHA). Thus, the aim of this work was the study of in situ setting reaction of α-TCP/C{sub 3}S composite bone cement under high energy X-ray generated by a synchrotron source within the first 72h. The results showed that the addition of C{sub 3}S induces the precipitation of nanosized CDHA at early times depending on the added content. Calculated crystallite sizes showed that the higher the content of C{sub 3}S, the smaller the crystal size at the beginning of the precipitation. These results are different from those obtained by conventional XRD method, suggesting that the proposed technique is a powerful tool in determining the composition and extent of reaction of CPCs surfaces in real time. (author)

  19. The Use of Supersulfated Cement(SSCin Mass Concrete

    Directory of Open Access Journals (Sweden)

    Wang Shu

    2016-01-01

    Full Text Available This paper isfocused on the use of Supersulfated Cement (SSC in mass concrete. The physicalproperties and mechanicalproperty was tested. Contrast with the common cement, this paper studied the temperature rise of hydration and the heat of hydration to obtain the advantage of SSC, which will provide the basis for the use of SSC in mass concrete.The micro properties were tested through Scanning Electron Microscope (SEM. The test shows that the SSC shows better workingperformance than ordinary cement. The compressive strength of SSC under standard curing condition is higher than that under room curing condition. The compressive strength of SSC is increasing with time and the rate of increasing is decreasing. The temperature rise of hydration of SSC are lower than that of ordinary cement. Different with the ordinary cement, the main hydrated products of SSC areettringite and scalycalcium silicate hydrate.

  20. Effect of silica fume additions on the hydration behaviour of calcium aluminates

    OpenAIRE

    Fumo, Daniel A.; Segadães, Ana M.

    1997-01-01

    In the recent refractory castables technology, the calcium aluminate cement is being replaced in increasing proportion by very fine matrix components, such as silica fume and colloidal alumina. More efficient particle packing and the resulting lower water requirements have been the proposed explanation for the improved green density and strength, without sacrificing the castable workability. However, the aluminates are still responsible for the hydraulic setting of the castable. The hydration...

  1. The search for negative amplitude components in quasi-continuous distributions of relaxation times: the example of {sup 1}H magnetization exchange in articular cartilage and hydrated collagen

    Energy Technology Data Exchange (ETDEWEB)

    Fantazzini, Paola; Galassi, Francesca [Department of Physics, University of Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy); Bortolotti, Villiam [Department of DICAM, University of Bologna, Viale del Risorgimento 2, 40136 Bologna (Italy); Brown, Robert J S [953 West Bonita Avenue, Claremont, CA 91711-4193 (United States); Vittur, Franco, E-mail: paola.fantazzini@unibo.it [Department of Life Sciences, University of Trieste, via Giorgeri 1, 24137 (Italy)

    2011-06-15

    When inverting nuclear magnetic resonance relaxation data in order to obtain quasi-continuous distributions of relaxation times for fluids in porous media, it is common practice to impose a non-negative (NN) constraint on the distributions. While this approach can be useful in reducing the effects of data distortion and/or preventing wild oscillations in the distributions, it may give misleading results in the presence of real negative amplitude components. Here, some examples of valid negative components for articular cartilage and hydrated collagen are given. Articular cartilage is a connective tissue, consisting mainly of collagen, proteoglycans and water, which can be considered, in many aspects, as a porous medium. Separate T{sub 1} relaxation data are obtained for low-mobility ('solid') macromolecular {sup 1}H and for higher-mobility ('liquid') {sup 1}H by the separation of these components in free induction decays, with {alpha} denoting the solid/liquid {sup 1}H ratio. When quasi-continuous distributions of relaxation times (T{sub 1}) of the solid and liquid signal components of cartilage or collagen are computed from experimental relaxation data without imposing the usual NN constraint, valid negative peaks may appear. The features of the distributions, in particular negative peaks, and the fact that peaks at longer times for macromolecular and water protons are at essentially the same T{sub 1}, are interpreted as the result of a magnetization exchange between these two spin pools. For the only-slightly-hydrated collagen samples, with {alpha}>1, the exchange leads to small negative peaks at short T{sub 1} times for the macromolecular component. However, for the cartilage, with substantial hydration or for a strongly hydrated collagen sample, both with {alpha}<<1, the behavior is reversed, with a negative peak for water at short times. The validity of a negative peak may be accepted (dismissed) by a high (low) cost of NN in error of fit

  2. 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.

  3. CaCl2-Accelerated Hydration of Tricalcium Silicate: A STXM Study Combined with 29Si MAS NMR

    Directory of Open Access Journals (Sweden)

    Qinfei Li

    2015-01-01

    Full Text Available The effect of calcium chloride (CaCl2 on tricalcium silicate (C3S hydration was investigated by scanning transmission X-ray microscopy (STXM with Near Edge X-ray Absorption Fine Structure (NEXAFS spectra and 29Si MAS NMR. STXM is demonstrated to be a powerful tool for studying the chemical composition of a cement-based hydration system. The Ca L3,2-edge NEXAFS spectra obtained by examining C3S hydration in the presence of CaCl2 showed that this accelerator does not change the coordination of calcium in the calcium silicate hydrate (C-S-H, which is the primary hydration product. O K-edge NEXAFS is also very useful in distinguishing the chemical components in hydrated C3S. Based on the Ca L3,2-edge spectra and chemical component mapping, we concluded that CaCl2 prefers to coexist with unhydrated C3S instead of C-S-H. In Si K-edge NEXAFS analysis, CaCl2 increases the degree of silicate polymerization of C-S-H in agreement with the 29Si CP/MAS NMR results, which show that the presence of CaCl2 in hydrated C3S considerably accelerates the formation of middle groups (Q2 and branch sites (Q3 in the silicate chains of C-S-H gel at 1-day hydration.

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

    Directory of Open Access Journals (Sweden)

    Jagmeet Singh

    2016-04-01

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

  5. Manufacture and properties of fluoride cement

    Science.gov (United States)

    Malata-Chirwa, Charles David

    This research work aimed at characterising composition, hydration and physical properties of fluoride cement, by studying samples of the cement obtained from Malawi, and comparing them to ordinary Portland cement. By confirming the suitable characteristics of fluoride cement through this work, the results of the research work provide a good basis for the wider adoption of fluoride cement as an alternative to ordinary Portland cement, especially in developing economies. Numerous accounts have been cited regarding the production and use of fluoride cement. Since there have not been conclusive agreement as to its properties, this study was limited to the theories of successful incorporation of fluoride compounds in the manufacture of fluoride cement. Hence, the properties and characteristics reported in this study relate to the cement currently manufactured in Malawi, and, on a comparative basis only, to that manufactured in other parts of the world. Samples of the fluoride cement used in the study were obtained by synthetic manufacture of the cement using common raw materials for the manufacture of fluoride cement that is limestone, silica sand, and fluorspar. These samples were subjected to several comparative tests used to characterise cements including examination under x-ray diffractometer, scanning electron microscopy and tests for setting time and compressive strength. Under similar laboratory conditions, it was possible to prove that fluoride cement hardens more rapidly than ordinary Portland cement. Also observed during the experimental work is that fluoride cement develops higher compressive strengths than ordinary Portland cement. The hardening and setting times are significantly different between the two cements. Also the nature of the hydration products, that is the microstructural development is significantly different in the two cements. The differences brought about between the two cements are because of the presence of fluorine during the clinkering

  6. Effect of Nano-Silica Agglomeration on Hydration and Hardening of Cement%纳米二氧化硅团聚特性对水泥水化硬化性能的影响

    Institute of Scientific and Technical Information of China (English)

    孔德玉; 杜祥飞; 杨杨; Surendra P Shah

    2012-01-01

    Effect of nano-silica agglomeration on the hydration and hardening of cement was investigated by using precipitated silica (PS) with much larger agglomerates and nano-silica (NS) powder with much smaller ones as additives. The results reveal that the PS exhibits a higher pozzolanic reactivity at early ages and a better accelerating effect on the cement hydration though it possesses some larger agglomerates and a little lower pozzolanic reactivity at late ages rather than NS. The observation by scanning electron micros- copy indicates that the cementitious property of the pozzolanic C-S-H gels from the agglomerates was limited. There even existed an interfacial transition zone between the reacted agglomerates and bulk hardened cement paste (HCP). The MIP results show that the NS addition can reduce the capillary and the gel pore of the HCP in the range of 20nm-10 μm more effectively, compared to the PS addition. It is suggested that the effect of nano-silica addition on the microstmcture improvement of the HCP could be resulted fi'om the filling and water adsorbing effects of the agglomerates in the powder rather than the seeding effect.%以团聚粒径很大的沉淀二氧化硅(PS)和团聚粒径较小的纳米二氧化硅(NS)为原材料,研究了纳米二氧化硅团聚特性对水泥水化硬化特性的影响。结果表明:与 NS 相比,虽然 PS 团聚粒径很大,后期火山灰活性较低,其早期火山灰活性却较大,对水泥水化的促进作用也更明显。扫描电子显微镜分析表明,NS 和 PS 的火山灰反应产物的胶结作用有限,其与水泥水化产物本体之间甚至存在明显的界面过渡区。压汞分析表明:掺 PS 和NS 均可有效降低硬化水泥石毛细孔率;与掺 PS 相比,掺 NS 对减小 20 nm~10 μm 的凝胶孔和毛细孔体积更有利。掺纳米二氧化硅对硬化水泥石微观结构的影响主要是由于团聚颗粒对水泥分散体系的填充效应和吸水

  7. Durability of Cement Composites Reinforced with Sisal Fiber

    Science.gov (United States)

    Wei, Jianqiang

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

  8. Evaluation of long-term interaction between cement and bentonite for geological disposal (2) XAFS analysis of calcium silicate hydrate precipitates at cementitious and bentonite material interface

    International Nuclear Information System (INIS)

    Document available in extended abstract form only. Numerical analyses of the long-term alteration of the engineered barriers used for the disposal of TRU waste predicted precipitation of C-S-H minerals at the interface between the cementitious materials and the bentonite-based buffer. When the C-S-H precipitates at this interface, the diffusion coefficient in the engineered barriers will decrease, resulting in reduced mass transport, which feeds back to reduce the rate of subsequent alteration. The C-S-H predicted to form at the cement-bentonite interface could not be identified directly using conventional analytical tools, including XRD, due to its low crystallinity. The authors propose that XAFS analysis, which provides spectra sensitive to the valency and coordination of the element of interest regardless of its crystallinity, would be capable of characterizing the C-S-H. The presence of the C-S-H precipitated as a secondary mineral has already been confirmed by applying chemical and XAFS analyses to bentonite specimens collected from the compacted bentonite-cement interface. However, because of the limitations on the width of specimens that can be collected by cutting from block samples, i.e. approximately 1 mm, detailed concentration profiles could not be obtained for this secondary C-S-H. In this study, XAFS spectra of thin specimens were measured using an X-ray detector in order to obtain detailed concentration profiles for the C-S-H formed at the interface between the cementitious material and the bentonite-based buffer. The X-ray detector used in the XAFS analysis consists of 1024 photodiodes arranged in line with a 0.025 mm pitch (photodiode array; PDA). Ca-K-edge XAFS measurements were conducted at the Photon Factory of the KEK. The synchrotron was operated in top-up mode with 450 mA during the measurements. Specimens were taken from a contact sample of compacted bentonite (Kunigel V1; dry density of 1.6 g/cm3) and hardened OPC (w/c = 0.6) immersed in

  9. Neutron Scattering Studies of Cement

    Science.gov (United States)

    Allen, Andrew

    2010-03-01

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

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

    Directory of Open Access Journals (Sweden)

    Hongfang Sun

    2015-02-01

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

  11. Do cement nanoparticles exist in space ?

    CERN Document Server

    Bilalbegovic, G; Mohacek-Grosev, V

    2014-01-01

    The calcium-silicate-hydrate is used to model properties of cement on Earth. We study cementitious nanoparticles and propose these structures as components of cosmic dust grains. Quantum density functional theory methods are applied for the calculation of infrared spectra of Ca4Si4O14H4, Ca6Si3O13H2, and Ca12Si6O26H4 clusters. We find bands distributed over the near, mid and far-infrared region. A specific calcium-silicate-hydrate spectral feature at 14 microns, together with the bands at 10 and 18 microns which exist for other silicates as well, could be used for a detection of cosmic cement. We compare calculated bands with the 14 microns features in the spectra of HD 45677, HD 44179, and IRC+10420 which were observed by Infrared Space Observatory and classified as remaining. High abundance of oxygen atoms in cementitious nanoparticles could partially explain observed depletion of this element from the interstellar medium into dust grains.

  12. Application of Recycled Concrete Aggregates Containing Waste Glass Powder/Suspension and Bottom Ash as a Cement Component in Concrete

    OpenAIRE

    Kara, P

    2013-01-01

    The growing environmental concerns and the increasing scarcity of landfills encourage the recycling of industrial wastes and adopting environmentally friendly practices by rational usage of natural resources. The production of concrete with recycled aggregate and reduced cement volume is the most desirable form of achieving a closed life cycle as an ecological constructional material. This paper describes results of a study undertaken to examine the influence of recycled aggregates obta...

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

    International Nuclear Information System (INIS)

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

  14. Cement degradation and the alteration of host rocks. Studies within the Grimsel Test Site Project.

    Science.gov (United States)

    Soler, J. M.

    2009-04-01

    Cement is a major component of the engineered barrier system in proposed underground repositories for low- and intermediate-level radioactive waste. Cement grouting of highly-conductive fractures in the vicinity of such repositories is also planned. The interaction between the hyperalkaline solutions derived from the degradation of cement and the rocks hosting such repositories may change the physical and chemical properties of the host rocks. The HPF project (Hyperalkaline Plume in Fractured Rock; ANDRA-FR-, DOE-USA-, JAEA-JP-, NAGRA-CH-, POSIVA-FI-, SKB-SE-) studied the alteration of a fractured granite due to the circulation of a synthetic high-pH solution. A significant decrease in fracture permeability was observed both in the laboratory (core infiltration experiment; decimeter scale) and in the Grimsel Test Site (circulation along a fracture; meter scale), despite the relatively minor mineralogical alteration. Coupling of mineralogical alteration and permeability changes was incorporated into reactive transport modeling of the experiments. The hydration and degradation of cement are being explicitly incorporated into the new LCS (Long-Term Cement Studies; JAEA-JP-, NAGRA-CH-, NDA-GB-, POSIVA-FI-) project at Grimsel. New laboratory and field experiments including a cement source are being designed. Reactive transport modeling of the degradation of cement, causing the formation of hyperalkaline solutions and the alteration of the host rock, will be an essential part of the experiment.

  15. Chloride binding of cement-based materials subjected to external chloride environment - A review

    OpenAIRE

    Yuan, Q.; Shi, C; Schutter, G. de; Audenaert, K.; Deng, D.

    2009-01-01

    This paper reviews the chloride binding of cement-based materials subjected to external chloride environments. Chloride ion exist either in the pore solution, chemically bound to the hydration products, or physically held to the surface of the hydration products. Chloride binding of cement-based material is very complicated and influenced by many factors, such as chloride concentration, cement composition, hydroxyl concentration, cation of chloride salt, temperature, supplementary cementing m...

  16. Cement content influence in rebar corrosion in carbonated mortars

    OpenAIRE

    Américo, P. O.; A.A. Nepomuceno

    2003-01-01

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

  17. Clean Development Mechanism: Laterite as Supplementary Cementing Material (SCM

    Directory of Open Access Journals (Sweden)

    Syed Zaighum Abbass

    2013-02-01

    Full Text Available Carbon dioxide (CO2 a major Green House Gas (GHG in the atmosphere, is believed to be largely responsible for global climate change through industrial emissions. The level of CO2 concentration has exponentially increased from about 280 ppm at the start of the industrial revolution to about 380 ppm to date. Although Kyoto protocol has bound industrialized nations to reduce green house gas emissions by 5.2% below 1990 levels around year 2008-2012, but violation continues. The cement industry is one of the major emitter of green house gases, particularly CO2 due to its energy intensive production process. It is estimated that approximately 1 tone of CO2 is released during the manufacturing of each tone of Portland cement. Most of CO2 emissions originate from burning fossil fuels and de-carbonization of limestone in a cement plant. During past several decades, the use of by-product materials in concrete, either as components of blended cements or as admixtures, has increased significantly. In this study, another alternate Supplementary Cementing Material (SCM, Laterite has been used with the objectives: to evaluate the performance of cement containing different percentages of laterite (5, 10, 15, 20, 25, and 30 %; to identify the optimum replacement percentage; and to investigate the effects of different concentrations of laterite on various properties of cement. For that purpose, laterite was tested: before blending (for elemental and mineralogical composition by using XRF, SEM and XRD: after blending (Elemental analysis using XRF, fineness test by using Blaine’s air permeability test and for particle size % on 45, 90 and 200 µ sieve, respectively; and after hydration (for mineralogical analysis using SEM. Furthermore, physical tests of manufactured cement, i.e., water consistency, setting time, Le-Chatlier-expansion and compressive strength were also evaluated and compared with limestone and fly-ash cement blends. The results show that with the

  18. 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.

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

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

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

  20. Increase in the strength characteristics of Portland cement due to introduction of the compound mineral supplements

    Science.gov (United States)

    Il'ina, Liliia; Gichko, Nikolai; Mukhina, Irina

    2016-01-01

    At the initial phase of hardening it is the limestone component that plays a major role in the hardening process, which acts as the substrate for the crystallization of hydrate tumors due to its chemical affinity with the products of Portland cement hydration. After 7 days, the diopside supplement influences the processes more significantly. Diopside has a high modulus of elasticity compared to the cement paste. As a result, stresses are redistributed within the cement paste and the whole composition is hardened. An increase in the quantity of diopside in the compound supplement to more than 66.7% does not provide a substantial increase in the strength of the cement paste. As the hardness of diopside is higher than the hardness of limestone, much more energy is required to grind it down to a usable component. Therefore, a further increase in the quantity of diopside in the compound supplement is not economically feasible. An evaluation of the optimum quantity of input compound mineral supplements can be made based on the ideas of close packing of spherical particles and the Pauling rules. The optimum content of the supplement is 8-8.5% provided that its dispersion and density are close to the dispersion and density of the binder. An increase in the dispersion of the supplement reduces its optimal quantity.

  1. Geomechanical Modeling of Gas Hydrate Bearing Sediments

    Science.gov (United States)

    Sanchez, M. J.; Gai, X., Sr.

    2015-12-01

    This contribution focuses on an advance geomechanical model for methane hydrate-bearing soils based on concepts of elasto-plasticity for strain hardening/softening soils and incorporates bonding and damage effects. The core of the proposed model includes: a hierarchical single surface critical state framework, sub-loading concepts for modeling the plastic strains generally observed inside the yield surface and a hydrate enhancement factor to account for the cementing effects provided by the presence of hydrates in sediments. The proposed framework has been validated against recently published experiments involving both, synthetic and natural hydrate soils, as well as different sediments types (i.e., different hydrate saturations, and different hydrates morphologies) and confinement conditions. The performance of the model in these different case studies was very satisfactory.

  2. 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.

  3. Investigation on the Effect of Recycled Asphalt Shingle (RAS in Portland Cement Mortar

    Directory of Open Access Journals (Sweden)

    Jinwoo An

    2016-04-01

    Full Text Available Tear-off roofing shingle, referred to as Reclaimed asphalt shingle (RAS, is the byproduct of construction demolition and it is a major solid waste stream in the U.S. Reuse of this byproduct in road construction sector can contribute to the success of materials sustainability as well as landfill conservation. Ground RAS has similar particle distribution as sand and its major component includes aggregate granules, fibers, and asphalt. To promote the beneficial utilization of RAS, this study evaluates the effect of RAS in cement mortar when used as replacement of sand. In addition, the study investigates how cellulose fibers from RAS behave under high alkaline environment during cement hydration process, which may significantly affect mortar’s strength performance. The laboratory study includes measurements of physical, mechanical, and durability behaviors of cement mortar containing RAS replacing sand up to 30%. It was found that the optimum mixture proportions are 5% and 10% for compressive strength and toughness, respectively.

  4. Role of aluminous component of fly ash on the durability of Portland cement-fly ash pastes in marine environment

    International Nuclear Information System (INIS)

    The durability, of mixtures of two kinds of Spanish fly ashes from coal combustion (ASTM class F) with 0, 15 and 35% replacement of Portland cement by fly ash, in a simulated marine environment (Na2SO4+NaCl solution of equivalent concentration to that of sea water: 0.03 and 0.45 M for sulphate and chloride, respectively), has been studied for a period of 90 days. The resistance of the different mixtures to the attack was evaluated by means of the Koch-Steinegger test. The results showed that all the mixtures were resistant, in spite of the great amount of Al2O3 content of the fly ash. The diffusion of SO42-, Na+ and Cl- ions through the pore solution activated the pozzolanic reactivity of the fly ashes causing the corresponding microstructure changes, which were characterized by X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). As a result, the flexural strength of the mixtures increased, principally for the fly ash of a lower particle size and 35% of addition

  5. The influence of cement type and temperature on chloride binding in cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

    1998-01-01

    cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear......This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  6. Gas hydrates

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    Content-Type text/plain; charset=UTF-8 43 Gas Hydrates T. Ramprasad National Institute of Oceanography, Dona Paula, Goa-403 004 rprasad@nio.org A gas hydrate is a crystalline solid; its building blocks consist of a gas molecule... surrounded by a cage of water molecules. Thus it is similar to ice, except that the crystalline structure is stabilized by the guest gas molecule within the cage of water molecules. Many gases have molecular sizes suitable to form hydrate, including...

  7. 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 ...

  8. Hardening of calcium hydroxide and calcium silicate binders due to carbonation and hydration

    OpenAIRE

    Cizer, Özlem; Campforts, J; Balen, Koenraad Van; Elsen, Jan; Gemert, Dionys van

    2006-01-01

    Hardening of calcium hydroxide and calcium silicate binders composed of cement, rice husk ash (RHA) and lime in different compositions were studied with mechanical strength, mercury intrusion porosimetry, thermal analysis and SEM. When cement is partially replaced with RHA and lime, hardening occurs as a result of combined hydration, pozzolanic reaction and carbonation reaction. While hydration of cement contributes to the early strength development of the mortars, carbonation is much more pr...

  9. Portland cement hydration: study of various techniques

    Directory of Open Access Journals (Sweden)

    Triviño Vázquez, F.

    1974-06-01

    Full Text Available Not availableLa complejidad de la química del cemento es motivo de que aún hoy día permanezcan sin aclarar muchos procesos que transcurren durante el fraguado y posterior endurecimiento de la pasta. La industria de la construcción precisa de un conocimiento técnico más sólido, ya que al saber el modo de actuar de los componentes de la pasta del cemento puede conseguir de este material: facilidad y economía en su empleo, resistencias mecánicas elevadas e inalterabilidad y duración en las obras realizadas. Cualquier nuevo conocimiento sobre la química de la pasta, por ello, suele tener inmediata aplicación o sirve como base para ulteriores investigaciones, que en su día darán nuevas propiedades prácticas al cemento o incluso a otros materiales diferentes. El comportamiento de la pasta durante las primeras 24 horas ha sido el motivo de este estudio. Se efectuaron medidas térmicas, de conductividad, de contenidos de productos solubles en agua, de productos cristalinos y de variaciones de solicitación de agua, por los métodos que veremos a continuación.

  10. Topics in Cement and Concrete Research

    OpenAIRE

    Brouwers, H. J. H.

    2006-01-01

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

  11. The suitability of a supersulfated cement for nuclear waste immobilisation

    Science.gov (United States)

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

    2014-09-01

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

  12. Characteristics of hydration products and pore structure in cement-based material with ultra fine slag at early ages%掺超细矿粉水泥基材料早龄期水化产物及孔结构特性

    Institute of Scientific and Technical Information of China (English)

    张亚梅; 余保英

    2011-01-01

    选用超细矿粉配制水泥基材料,比较了其与普通矿粉对水泥浆体的力学性能影响.分别通过XRD和MIP分析了硬化水泥浆体的水化产物、最可几孔径及孔隙率.分析结果表明,粒径明显偏小的超细矿粉具有较高的火山灰反应活性,1d时水化产物中Ca( OH)2的衍射峰明显低于纯水泥浆体和掺普通矿粉的水泥浆体,超细矿粉能显著促进水泥基材的早龄期水化.MIP分析发现,早龄期时掺超细矿粉的水泥浆体的最可几孔径和累积孔隙率均小于掺普通矿粉的水泥浆体和纯水泥浆体,表明超细矿粉在早龄期时就起到了细化浆体孔结构、提高密实度的作用.%The early age mechanical performance of cement-based material incorporated with ultra fine slag and ordinary slag were comparatively investigated. The hydration products, pore size and porosity of cement-based material were tested with XRD (X-ray diffraction) and MIP (mercury intrusion porosimetry) , respectively. The low peak strength of Ca( OH)2 obtained from XRD analysis show that ultra fine slag with significantly smaller particle size than ordinary slag has higher pozzalanic activity than ordinary slag, which suggests that the addition of ultra fine slag can promote the hydration process of cement-based material at early ages. Results from MIP test reveal that the addition of ultra fine slag to cement paste can reduce both the characteristic pore size and the porosity and hence optimize the pore structure and increase the density of hardened cement paste.

  13. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    OpenAIRE

    Nediljka Gaurina-Međimurec; Davorin Matanović; Gracijan Krklec

    1994-01-01

    During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures) and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production...

  14. The Application of SCC-DV-Xα Computational Method of Quantum Chemistry in Cement Chemistry

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    It has been explored why quantum chemistry is applied to the research field of cement chemistry. The fundamental theory of SCC-DV-Xα computational method of quantum chemistry is synopsized. The results obtained by computational quantum chemistry method in recent years of valence-bond structures and hydration activity of some cement clinker minerals, mechanical strength and stabilization of some hydrates are summarized and evaluated. Finally the prospects of the future application of quantum chemistry to cement chemistry are depicted.

  15. Studies on cement matrix used at the radioactive waste treatment plant for radwaste conditioning

    International Nuclear Information System (INIS)

    Full text: The research activities performed by the Department of Radioactive Waste Management is focused on the LLAW treatment products obtained by chemical precipitation and on the conditioning of these products by cementation. The individual mechanisms involved in the chemical precipitation process are directly dependent on the precipitate properties and structure, which are connected with the initial system composition and the precipitation procedure, i.e. reagent concentration, rate and orders of chemical addition, mixing rate and time and ageing conditions. In the case of conditioning by cementation, the chemical nature and proportion of the sludges or concentrates affect both the hydrolysis of the initial cement components and the reactions of metastable hydration constituents, as well as the mechanical strength and chemical resistance of the hardened cemented matrix. Generally, the study of the precipitation products and their behaviour during cementation and the long-term disposal is extremely difficult because of the system complexity (phase composition and structure) and the lack of non-destructive analytical methods. The experience accumulated by the countries who developed nuclear programs in military and socioeconomic fields and which produced important volumes of radioactive wastes, lead us to study some of mineral additives to be used in the conditioning and disposal technology. It is well known that mineral additives are diminishing the leaching rate of the radionuclides in the disposal environment. The studies have the purpose to obtain the most propitious mixture of cement-bentonite and cement-volcanic tuff which have the mechanical properties similar to the cement paste used for the conditioning of radioactive waste. Taking into consideration the characteristics of these mineral binders, namely a very good plasticity and capacity of adsorption, which lead to the decrease of porosity, in the future, the mixture is planned to be used at the

  16. Studies on cement matrix materials used at the Radioactive Waste Treatment Plant for radwaste conditioning

    International Nuclear Information System (INIS)

    The research activities performed by Department of Radioactive Waste Management is focused on the treatment of LLAW products obtained by chemical precipitation and on the conditioning of these products by cementation. The individual mechanisms implied in the chemical precipitation processes are directly dependent on the precipitate properties and structure, which in turn are connected with the initial system composition and the precipitation procedure, i.e. reagent concentration, rate and orders of chemical addition, mixing rate and time and ageing conditions. In case of conditioning by cementation, the chemical nature and proportion of the sludges or concentrates affect both the hydrolysis of the initial cement components and the reactions of metastable hydration constituents, as well as the mechanical strength and chemical resistance of the hardened cemented matrix.Generally, the study of the precipitation products and their behaviour during cementation and the long-term disposal is extremely difficult because of the system complexity (phase composition and structure) and the lack of the non-destructive analytical methods. The experience accumulated by the countries who advanced nuclear programmes in military and socio-economic fields and which produced important volumes of radioactive wastes, leads us to study some of mineral additives to be used in the conditioning and disposal technology. Is well known that some mineral additives can diminish the leaching rate of the radionuclides in the disposal environment.The studies have the purpose to obtain the most propitious mixture of cement-bentonite and cement-volcanic tuff, which have the mechanical properties similar to the cement paste used for the conditioning of radioactive waste.Taking into account the characteristics of these mineral binders, namely a very good plasticity and capacity of adsorption, which lead at the decrease of porosity, the mixture is planned to be used in the future, at the Radioactive

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

    Institute of Scientific and Technical Information of China (English)

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

    2016-01-01

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

  18. Curing time effect on the fraction of 137Cs from cement-ion exchange resins-bentonite clay composition

    Directory of Open Access Journals (Sweden)

    Plećaš Ilija

    2010-01-01

    Full Text Available To assess the safety of disposal of radioactive waste material in cement, curing conditions and time of leaching radionuclides 137Cs have been studied. Leaching tests in cement-ion exchange resins-bentonite matrix, were carried out in accordance with a method recommended by IAEA. Curing conditions and curing time prior to commencing the leaching test are critically important in leach studies since the extent of hydration of the cement materials determines how much hydration product develops and whether it is available to block the pore network, thereby reducing leaching. Incremental leaching rates Rn[cm/d] of 137Cs from cement-ion exchange resins-bentonite matrix after 240 days were measured. The results presented in this paper are examples of results obtained in a 30-year concrete testing project which will influence the design of the engineer trenches system for future central Serbian radioactive waste storing centre.

  19. Using bio-based polymers for curing cement-based materials

    NARCIS (Netherlands)

    Zlopasa, J.; Koenders, E.A.B.; Picken, S.J.

    2014-01-01

    Curing is the process of controlling the rate and extent of moisture loss from the surface of cement based materials. It is the final stage in the production of cement-based materials and it is the essential part for achieving continuous hydration of cement, while avoiding cracking due to drying shr

  20. THE INFLUENCE OF ORTHOPHOSPHATES ON THE PROPERTIES OF PORTLAND CEMENT

    OpenAIRE

    Antanas Kaziliunas

    2014-01-01

    The article continues the research of input reduction of phosphogypsum preparation for the production of building materials. Desiccated apatite (2.18 % P2O5 in gypsum) makes the least changes in the properties of Portland cement: it prolongs the cement setting times and reduces the compressive strength about 10 %. The apatite formation in the pastes of soluble orthophosphate-cement occurs during the formation of X-ray amorphous colloidal calcium orthophosphate hydrate, which prolo...

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

    OpenAIRE

    Blanco-Varela, M. T.; Martínez-Ramírez, S.; Gener, M.; Vázquez, T.

    2005-01-01

    Volcanic pozzolans owe their pozzolanic activity chiefly to the presence of vitreous or zeolitic material rich in SiO2, and Al20y compounds that react with the portlandite produced during cement hydration to generate amorphous gels with cementitious properties. The present study analyzes the modifications taking place in the composition, structure and micro structure of the hydra ted cement paste when 20% of the cement by we...

  2. Synthesis of pure Portland cement phases

    DEFF Research Database (Denmark)

    Wesselsky, Andreas; Jensen, Ole Mejlhede

    2009-01-01

    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases...... in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the The process of solid state synthesis are is described in general including practical advice on equipment and techniques. Finally In addition, some exemplary mix compositions...

  3. INFLUENCE OF GLASS CULLET IN CEMENT PASTES

    Institute of Scientific and Technical Information of China (English)

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

    2006-01-01

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

  4. Influence of Fly Ash on Zeta Potential and Conductivity of Early Polycarboxylate Superplasticizer-Cement Hydration%粉煤灰对水泥-聚羧酸减水剂体系早期Zeta电位和电导率的影响研究

    Institute of Scientific and Technical Information of China (English)

    温勇; 邓雷; 韩国旗

    2015-01-01

    粉煤灰作为常用的活性矿物掺合料,在当前配制绿色高性能混凝土中得到了广泛的应用。本文采用电声法zeta电位仪测定了不同掺量的粉煤灰与不同掺量的聚羧酸减水剂(PCA)对水泥水化早期zeta电位的影响,并同时测定水泥水化溶液体系的电导率,以此来判定粉煤灰按照一定比例替代水泥后对水泥-减水剂体系水化早期Zeta电位的影响情况。结果表明,粉煤灰总体会降低水泥水化早期的zeta电位值,在水化体系的zeta电位和电导率测试结果中粉煤灰与聚羧酸减水剂表现出一定的协同作用效果,有助于改善混凝土的和易性。%Fly ash, as commonly used active mineral admixture of concrete, has been widely used in green high performance concrete. In this paper, it has measured the zeta potential values of different dosages of fly ash with different amounts of polycarboxylic acid water reducing agent(PCA) to the influence of the cement hydration at early age by the electro-acoustic method, and measured the electrical conductivity in the system of cement hydration solution at the same time. The results showed that, fly ash can reduce the zeta potential of early cement hydration, fly ash with polycarboxylic acid water reducing agent showed certain synergy effect in measured of the zeta Potential and conductivity, and contribute to the improvement of the workability of concrete.

  5. Influence of Li-slag on Zeta potential and conductivity of early polycarboxylate superplasticizer-cement hydration%锂渣对水泥-聚羧酸减水剂体系早期Zeta电位和电导率的影响研究

    Institute of Scientific and Technical Information of China (English)

    赵桂娟; 温勇; 周晓梅; 王衡

    2014-01-01

    Lithium slag,is the solid industrial waste that scale emissions from Xinjiang industrial factory ,it could be used in concrete in-dustry in Xinjiang as an active mineral admixture. However ,it will have a certain influence on the early performance of fresh concrete after mixed with the lithium slag. Therefore,it has measured the Zeta potential values of different dosages of lithium slag with different super-plasticizer amounts to the influence of the cement hydration at early age by the electro-acoustic method ,and measured the electrical con-ductivity in the system of cement hydration solution at the same time. The results showed that although the Zeta potential values of lithium itself close to zero,the Zeta potential of early cement hydration increased after its addition and the polycarboxylate superplasticizer parti-cles could preferential adsorption on the surface of lithium slag particles.%锂渣是新疆规模排放的固体工业废弃物,可作为混凝土用的活性矿物掺合料,在新疆混凝土工业中得到了一定的应用。但混凝土中掺入锂渣往往会对混凝土早期新拌性能产生一定的影响,为此,采用电声法测定了不同掺量的锂渣与不同掺量的聚羧酸减水剂对水泥早期水化Zeta电位的影响,并同时测定水泥水化溶液体系的电导率。结果表明,虽然自身Zeta电位值接近于零的锂渣掺入水泥后却提高了水泥水化早期的Zeta电位值,并且聚羧酸减水剂分子可能优先吸附与锂渣颗粒表面。

  6. Degree of Hydration of OPC and OPC/Fly ash Paste Samples Conditioned at Different Relative Humidity

    Directory of Open Access Journals (Sweden)

    Nasir Shafiq

    2011-05-01

    Full Text Available Degree of hydration of cement paste controls many properties of hardened concrete and/or mortar such as compressive strength. During the drying process, the degree and the rate of hydration of cement paste in concrete/mortar samples are significantly affected by the ambient relative humidity of the exposure conditions. There are various parameters such as the amount of calcium hydroxide, Ca(OH2 in the paste, quantity of the chemically bound water, specific gravity of the paste, fraction of un-hydrated cement, liberated heat of hydration and strength of the hydrated cement may be used to determine the degree of hydration of the cement paste. This paper presents the results of the experimental investigation for the determination of the degree of hydration of 100% cement paste and fly ash blended cement pastes. After 28 days moist curing, the samples were conditioned in 100%, 75%, 65%, 40% and 12% relative humidity. Conditioning of samples in different relative humidity had significant effects on the compressive strength of the mortar samples and the degree of hydration of the paste samples. Conditioning of samples in 100% RH resulted in higher compressive strength and the degree of hydration. Because of the 28 days moist curing and 12 weeks moisture conditioning in different RH, fly ash based samples showed better compressive strength than the OPC samples.

  7. Conditioning of radioactive waste solutions by cementation

    International Nuclear Information System (INIS)

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

  8. Flow assurance intervention, hydrates remediation

    Energy Technology Data Exchange (ETDEWEB)

    Mancini, Christopher S. [Oceaneering International Inc., Houston, TX (United States)

    2012-07-01

    This paper addresses the issues of removing hydrates in sub sea flow lines and associated equipment with an Remotely Operated Vehicle (ROV) of opportunity and a multi-service-vessel (MSV). The paper is split into three topics: the equipment used with the ROV, assessing the interface points and handling fluids produced from drawing down the pressure. Each section is explained thoroughly and backed up with real world experience. The equipment section details information from actual jobs performed and why the particular components were utilized. The system is generally contained in an ROV mounted skid. Pumps are utilized to draw down the pressure inside the hydrated section of equipment, removing one of the three necessary components for hydrates formation. Once the section is pumped down, several options exist for handling the fluids pumped out of the system: pumping to surface, re-injection into the well, or injection into an operating flow line. This method of hydrates remediation is both economical and timely. Hydrate blockages form in low temperatures and high pressures. Reducing the pressure or increasing the temperature so the conditions lie to the right of the hydrate dissociation curve will slowly decompose the blockage. Depressurization and the use of MEG or methanol will give favorable conditions to remove the hydrate plug. Oceaneering has the capabilities to remove hydrates using the FRS in conjunction with an installation vessel to dispose of the gas and fluid removed from the flow line. Hydrate remediation techniques should be implemented into the initial design to reduce costs later. The cost of stopped production combined with the day rate for equipment needed for hydrate removal outweighs the costs if no technique is utilized. (author)

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

    Directory of Open Access Journals (Sweden)

    A.B. Tchamba

    2015-06-01

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

  10. Thermal analysis of cement pastes with superabsorbent polymers

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Jensen, Ole Mejlhede; Lukosiute, Irena;

    2013-01-01

    Thermal analysis of cement systems is very helpful in the understanding of many different properties of cementitious compounds, both for the original reacting compounds, and also for the resulting hydration products. Superabsorbent polymers can be added to cement systems with many different reasons......, so it is relevant that fundamental knowledge of this new compound on the development of hydration is well understood [1-3]. This paper reports research on thermal analysis of cement pastes with superabsorbent polymers. We have studied several parameters: the concentration of SAP in the system...... and understanding of cementitious materials when internal curing is active. [1] Luís P. Esteves, On the hydration of water-entrained cement–silica systems: Combined SEM, XRD and thermal analysis in cement pastes, Thermochimica Acta, 2011, vol. 518: pp. 27–35. [2] Luís P. Esteves, Superabsorbent Polymers...

  11. PRINCIPLES OF RE-ENGINEERING METHODOLOGY FOR TECHNOLOGICAL PROCESS IN PROCESSING OF RAW MATERIAL COMPONENTS WHILE PRODUCING CEMENT AND SILICATE PRODUCTS

    Directory of Open Access Journals (Sweden)

    I. A. Busel

    2014-01-01

    necessity to modernize technological equipment used for grinding raw material components with the purpose to improve efficiency and quality, power- and resource saving. The possibility of using various grinding aids that permit to increase grinding productivity is shown in the paper. The paper studies an automation concept of the control system which used for grinding process of mineral raw material. A conceptual model for complexation of various methods grinding aids has been proposed in the paper. The paper presents methodological principles for simulation of technological process used for processing of mineral raw material while producing cement and silicate products. The parameters which are to be controlled and which are necessary for development of computer simulations of technological grinding process have been determined in the paper. The paper justifies an application of imitation simulation for creation of computer models. Methodology for imitation simulation of the technological process has been studied in the paper. The paper confirms the possibility to use analytical and probability methods. Imitation simulations of a grinding mill operation have been developed on the basis of experimental data and probability functions. The possibility of controlling technological process of raw material grinding has been demonstrated in the paper.While implementing the proposed complex of organizational and technical recommendations it is possible to increase grinding productivity up to 30-50 % and significantly reduce и существенно снизить energy consumption for mineral raw material grinding during production of cement and silicate products. The combined reengineering methodology for grinding process including all the mentioned intensification methods substantially increases quality of final products and reduces its self-cost that will favour its compatibility and attractiveness for consumers.

  12. Seismic investigation of gas hydrates in the Gulf of Mexico: 2013 multi-component and high-resolution 2D acquisition at GC955 and WR313

    Science.gov (United States)

    Haines, Seth S.; Hart, Patrick E.; Shedd, William W.; Frye, Matthew

    2014-01-01

    The U.S. Geological Survey led a seismic acquisition cruise at Green Canyon 955 (GC955) and Walker Ridge 313 (WR313) in the Gulf of Mexico from April 18 to May 3, 2013, acquiring multicomponent and high-resolution 2D seismic data. GC955 and WR313 are established, world-class study sites where high gas hydrate saturations exist within reservoir-grade sands in this long-established petroleum province. Logging-while-drilling (LWD) data acquired in 2009 by the Gulf of Mexico Gas Hydrates Joint Industry Project provide detailed characterization at the borehole locations, and industry seismic data provide regional- and local-scale structural and stratigraphic characterization. Significant remaining questions regarding lithology and hydrate saturation between and away from the boreholes spurred new geophysical data acquisition at these sites. The goals of our 2013 surveys were to (1) achieve improved imaging and characterization at these sites and (2) refine geophysical methods for gas hydrate characterization in other locations. In the area of GC955 we deployed 21 ocean-bottom seismometers (OBS) and acquired approximately 400 km of high-resolution 2D streamer seismic data in a grid with line spacing as small as 50 m and along radial lines that provide source offsets up to 10 km and diverse azimuths for the OBS. In the area of WR313 we deployed 25 OBS and acquired approximately 450 km of streamer seismic data in a grid pattern with line spacing as small as 250 m and along radial lines that provide source offsets up to 10 km for the OBS. These new data afford at least five times better resolution of the structural and stratigraphic features of interest at the sites and enable considerably improved characterization of lithology and the gas and gas hydrate systems. Our recent survey represents a unique application of dedicated geophysical data to the characterization of confirmed reservoir-grade gas hydrate accumulations.

  13. Gradient Acid Dissolving Test Study and Identification of Geopolymer and Cement Hydration Products%梯度酸溶法区分地聚合物与水泥水化产物

    Institute of Scientific and Technical Information of China (English)

    郭晓潞; 施惠生; 林茂松

    2013-01-01

    Gradient acid dissolving tests were made to divide geopolymer and hydration product quantificationally.The feasibility of gradient acid dissolving test was investigated on the basis of the dissolution rates of geopolymer/hydration product and X-Ray diffraction (XRD), Fourier transform infrared spectroscopy(FTIR) analyses.The results show the behaviors of dissolution of the geopolymer and the hydration product in the same gradient acid are different, and the acid point to divide geopolymer and hydration product is pH = 3.The gradient acid dissolving test is an effective method to divide geopolymer and hydration product.%采用梯度酸溶解试验方法来定量区分地聚合物与普通水化产物,结合产物溶解率与残渣微观分析验证了该方法的可行性.研究结果表明,地聚合物与普通水化产物在梯度酸中的酸溶性存在较大差异,区分地聚合物与普通水化产物的酸临界点为pH=3,梯度酸溶解试验能较好地区分两者.

  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......−liquid reactions are discussed, as are the influences of particles sizes on clinker phase formation. Furthermore, a mechanism for clinker phase formation in an industrial rotary kiln reactor is outlined....

  15. Applications of Moessbauer spectroscopy in cement studies

    International Nuclear Information System (INIS)

    In the last two decades Moessbauer spectrometer has been employed to investigate cement and its clinker. In this work some of these investigations are exhibited briefly hoping that this would facilitate further investigations. It has already been seen that Moessbauer spectroscopy gives good information about some vague points which were present before using this technique as a tool in cement studies such as clinker formation, iron solubility, the iron states in the different phases of clinker as well as the effect of hydration at different times on the states of iron cement pastes, methods for the quality control of the manufactured clinker, the evaluation of the degree of hydration and the compressive strength have been assessed. A concept about the Moessbauer spectroscopy is presented. (author)

  16. Elastic properties of gas hydrate-bearing sediments

    Science.gov (United States)

    Lee, M.W.; Collett, T.S.

    2001-01-01

    Downhole-measured compressional- and shear-wave velocities acquired in the Mallik 2L-38 gas hydrate research well, northwestern Canada, reveal that the dominant effect of gas hydrate on the elastic properties of gas hydrate-bearing sediments is as a pore-filling constituent. As opposed to high elastic velocities predicted from a cementation theory, whereby a small amount of gas hydrate in the pore space significantly increases the elastic velocities, the velocity increase from gas hydrate saturation in the sediment pore space is small. Both the effective medium theory and a weighted equation predict a slight increase of velocities from gas hydrate concentration, similar to the field-observed velocities; however, the weighted equation more accurately describes the compressional- and shear-wave velocities of gas hydrate-bearing sediments. A decrease of Poisson's ratio with an increase in the gas hydrate concentration is similar to a decrease of Poisson's ratio with a decrease in the sediment porosity. Poisson's ratios greater than 0.33 for gas hydrate-bearing sediments imply the unconsolidated nature of gas hydrate-bearing sediments at this well site. The seismic characteristics of gas hydrate-bearing sediments at this site can be used to compare and evaluate other gas hydrate-bearing sediments in the Arctic.

  17. Low-temperature fabrication of macroporous scaffolds through foaming and hydration of tricalcium silicate paste and their bioactivity

    OpenAIRE

    Huan, Z.; Chang, J.; Zhou, J.

    2009-01-01

    A low-temperature fabrication method for highly porous bioactive scaffolds was developed. The two-step method involved the foaming of tricalcium silicate cement paste and hydration to form calcium silicate hydrate and calcium hydroxide. Scaffolds with a combination of interconnected macro- and micro-sized pores were fabricated by making use of the decomposition of a hydrogen peroxide (H2O2) solution that acted as a foaming agent and through the hydration of tricalcium silicate cement. It was ...

  18. 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.

  19. Handbook of gas hydrate properties and occurrence

    Energy Technology Data Exchange (ETDEWEB)

    Kuustraa, V.A.; Hammershaimb, E.C.

    1983-12-01

    This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

  20. X-ray diffractometry of steam cured ordinary Portland and blast-furnace-slag cements

    International Nuclear Information System (INIS)

    This work studies some aspects of the phases produced by hydration of ordinary and blast-furnace-slag cements, at normal conditions and steam cured (60 and 950 C), using an X-ray diffraction technique. The blast-furnace-slag cement was a mixture of 50% of ordinary Portland cement and 50% of blast-furnace-slag (separately grinding). After curing the X-ray diffraction reveals that, in relation to ordinary Portland cement, the main phases in blast-furnace-slag cement are hydrated silicates and aluminates, hydro garnet, etringitte and mono sulphate. After steam curing the hydration of blast-furnace-slag cement proceeds. This is a result of the slag activation by the curing temperature. (author). 8 refs., 3 figs., 1 tab

  1. Mechanical properties of sand, silt, and clay containing tetrahydrofuran hydrate

    Science.gov (United States)

    Yun, T.S.; Santamarina, C.J.; Ruppel, C.

    2007-01-01

    The mechanical behavior of hydrate-bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes, drilling and coring operations, and the analysis of certain small-strain properties of these sediments (for example, seismic velocities). This study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 MPa confining pressure on sand, crushed silt, precipitated silt, and clay specimens with closely controlled concentrations of synthetic hydrate. The results show that the stress-strain behavior of hydrate-bearing sediments is a complex function of particle size, confining pressure, and hydrate concentration. The mechanical properties of hydrate-bearing sediments at low hydrate concentration (probably 50% of pore space), the behavior becomes more independent of stress because the hydrates control both stiffness and strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination, cementing particles together, and filling the pore space. The cementation contribution to the shear strength of hydrate-bearing sediments decreases with increasing specific surface of soil minerals. The lower the effective confining stress, the greater the impact of hydrate formation on normalized strength.

  2. Study on Strength and Microstructure of Cement-Based Materials Containing Combination Mineral Admixtures

    Directory of Open Access Journals (Sweden)

    Meijuan Rao

    2016-01-01

    Full Text Available The compressive strength of complex binders containing two or three blended mineral admixtures in terms of glass powder (GP, limestone powder (LP, and steel slag powder (SP was determined by a battery solution type compressive testing machine. The morphology and microstructure characteristics of complex binder hydration products were also studied by microscopic analysis methods, such as XRD, TG-DTA, and SEM. The mechanical properties of the cement-based materials were analyzed to reveal the most appropriate mineral admixture type and content. The early sample strength development with GP was very slow, but it rapidly grew at later stages. The micro aggregate effect and pozzolanic reaction mutually occurred in the mineral admixture. In the early stage, the micro aggregate effect reduced paste porosity and the small particles connected with the cement hydration products to enhance its strength. In the later stage, the pozzolanic reaction of some components in the complex powder occurred and consumed part of the calcium hydroxide to form C-S-H gel, thus improving the hydration environment. Also, the produced C-S-H gel made the structure more compact, which improved the structure’s strength.

  3. 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

  4. Soft X-ray Microscopy of Green Cements

    Science.gov (United States)

    Monteiro, P. J. M.; Mancio, M.; Kirchheim, A. P.; Chae, R.; Ha, J.; Fischer, P.; Tyliszczak, T.

    2011-09-01

    The present status of the cement and concrete industry is not sustainable. The production of Portland cement is responsible for 7% of the CO2 emissions in the world and existing reinforced concrete infrastructure is deteriorating at a fast pace. The change in the existing technology requires new developments in our understanding of the nanostructure of hydration products and the complex deterioration reactions. We have been developing an elaborate research program to advance the existing cement and concrete science by characterizing its nanostructure by synchrotron radiation. A new generation of green cements is being studied using high-resolution soft x-ray microscopy at the nano-level.

  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. First-principles elasticity of monocarboaluminate hydrates

    KAUST Repository

    Moon, J.

    2014-07-01

    The elasticity of monocarboaluminate hydrates, 3CaO·Al2O3·CaCO3·xH2O (x = 11 or 8), has been investigated by first-principles calculations. Previous experimental study revealed that the fully hydrated monocarboaluminate (x = 11) exhibits exceptionally low compressibility compared to other reported calcium aluminate hydrates. This stiff hydration product can contribute to the strength of concrete made with Portland cements containing calcium carbonates. In this study, full elastic tensors and mechanical properties of the crystal structures with different water contents (x = 11 or 8) are computed by first-principles methods based on density functional theory. The results indicate that the compressibility of monocarboaluminate is highly dependent on the water content in the interlayer region. The structure also becomes more isotropic with the addition of water molecules in this region. Since the monocarboaluminate is a key hydration product of limestone added cement, elasticity of the crystal is important to understand its mechanical impact on concrete. Besides, it is put forth that this theoretical calculation will be useful in predicting the elastic properties of other complex cementitous materials and the influence of ion exchange on compressibility.

  7. Self-cementing Mechanism of CFBC Coal Ashes at Early Ages

    Institute of Scientific and Technical Information of China (English)

    SONG Yuanming; QIAN Jueshi; WANG Zhi; WANG Zhijuan

    2008-01-01

    The self-cementing mechanism at early ages of circulating fluidized bed combustion (CFBC) coal ashes was studied by X-ray diffraction (XRD), infrared (IR) spectroscopy and chemical method. The results indicate that the amorphous phase is predominant in CFBC coal ashes. The polymerization degree of [SiO4] and [AlO6] of CFBC desulphurization coal ashes is lower than that of those without desulphurization. The contents of the components with fast hydration rate of CFBC desulphurization coal ashes are significantly greater than those of the ashes without desulphurization. This work confirms that the amorphous minerals with high chemical activity are the main causes of the self-cementing property of CFBC desulphurization coal ashes at early ages.

  8. Cement/slag chemistry studies

    International Nuclear Information System (INIS)

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

  9. Pressurization of bioactive bone cement in vitro.

    Science.gov (United States)

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

    1999-01-01

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

  10. Methane gas hydrate effect on sediment acoustic and strength properties

    Science.gov (United States)

    Winters, W.J.; Waite, W.F.; Mason, D.H.; Gilbert, L.Y.; Pecher, I.A.

    2007-01-01

    To improve our understanding of the interaction of methane gas hydrate with host sediment, we studied: (1) the effects of gas hydrate and ice on acoustic velocity in different sediment types, (2) effect of different hydrate formation mechanisms on measured acoustic properties (3) dependence of shear strength on pore space contents, and (4) pore pressure effects during undrained shear. A wide range in acoustic p-wave velocities (Vp) were measured in coarse-grained sediment for different pore space occupants. Vp ranged from less than 1 km/s for gas-charged sediment to 1.77–1.94 km/s for water-saturated sediment, 2.91–4.00 km/s for sediment with varying degrees of hydrate saturation, and 3.88–4.33 km/s for frozen sediment. Vp measured in fine-grained sediment containing gas hydrate was substantially lower (1.97 km/s). Acoustic models based on measured Vp indicate that hydrate which formed in high gas flux environments can cement coarse-grained sediment, whereas hydrate formed from methane dissolved in the pore fluid may not. The presence of gas hydrate and other solid pore-filling material, such as ice, increased the sediment shear strength. The magnitude of that increase is related to the amount of hydrate in the pore space and cementation characteristics between the hydrate and sediment grains. We have found, that for consolidation stresses associated with the upper several hundred meters of sub-bottom depth, pore pressures decreased during shear in coarse-grained sediment containing gas hydrate, whereas pore pressure in fine-grained sediment typically increased during shear. The presence of free gas in pore spaces damped pore pressure response during shear and reduced the strengthening effect of gas hydrate in sands.

  11. Natural Gas Hydrates

    OpenAIRE

    Ersland, Geir

    2010-01-01

    The experimental set-up with the MRI monitoring apparatus was capable of forming large quantities of methane hydrates in sandstone pores and monitor hydrate growth patterns for various initial conditions. Spontaneous conversion of methane hydrate to carbon dioxide hydrate occurred when methane hydrate, in porous media, was exposed to liquid carbon dioxide. The MRI images did not detect any significant increase in signal in the hydrate saturated cores that would indicate the presence of free w...

  12. HYDRATING CHARACTERISTICS OF MODIFIED PORTLAND WITH Ba-BEARING SULPHOALUMINATE MINERALS

    OpenAIRE

    Chenchen Gong; Jibao Xin; Shoude Wang; Lingchao Lu

    2016-01-01

    The hydrating characteristics of modified Portland cement with Ba-bearing sulphoaluminate minerals were studied in this paper. Scanning Electron Microscopy-Energy Dispersive Spectrometer (SEM-EDS), mercury intrusion porosimeter (MIP) and compressive strength were determined to characterize hydrating products and microstructure. Results show that basic physical properties of modified Portland cement with Ba-bearing sulphoaluminate minerals (SMPC) are similar with PC except the shorter setting ...

  13. Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mauricio Martínez-Alanis

    2016-01-01

    Full Text Available Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD at an early age (first hours of hydration. The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

  14. Evaluation of Hydrated Lime Filler in Asphalt Mixtures

    OpenAIRE

    Mohammed Abbas Hasan Al-Jumaily

    2008-01-01

    Mineral filler is one of important materials and affecting on properties and quality of asphalt mixtures .There are different types of mineral filler depended on cost and quality , the matter encourages us to achieve this study to evaluate hydrated lime filler effects on properties of asphalt mixes related with strength and durability. Conventional asphaltic concrete mixtures with Portland cement and soft sandstone fillers and mixtures modified with hydrated lime were evaluated for their fund...

  15. 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.

  16. Leaching Behavior and Mechanism of Cement Solidiifed Heavy Metal Pb in Acid Medium

    Institute of Scientific and Technical Information of China (English)

    ZHOU Mingkai; WANG Caiping; CHEN Yan; CHEN Xiao

    2015-01-01

    The relationship between Pb leaching concentration and the solution’s pH with time was analyzed when cement in its solidiifed form was leached in an acid medium. The effects of the particle size of the solidified form, the cement adding method, and the hydration degree on Pb solidification were also investigated. The experimental results indicate that cement is quickly dissolved and hydrated in the acid medium, forming a C-S-H gel or silicic acid sol with good adsorption. When cement-Pb solidified form is leached in an acetate solution, the hydrated product erodes with time, so the Pb concentration increases slightly in the beginning. Then, some of the Pb ions are absorbed by the newly generated silicic acid sol, C-S-H. Others produce Pb(OH)2 precipitation for secondary solidification, leading to a gradual decrease in the Pb concentration in a leaching time of more than two hours. Moreover, the particle size of the solidiifed form has important effects on the Pb dissolution. When the amount of added cement is low, with a pH of less than 9.5, the solidiifcation affects the sequence of the original cement powder, the cement hydrated powder, and the cement-Pb solidiifed form. When the added amount of cement increases with a pH of more than 11, the effect of adding methods on solidiifcation decreases, and the solidiifed form is a little better than others.

  17. Radionuclide and metal sorption on cement and concrete

    CERN Document Server

    Ochs, Michael; Wang, Lian

    2016-01-01

    Cementitious materials are being widely used as solidification/stabilisation and barrier materials for a variety of chemical and radioactive wastes, primarily due to their favourable retention properties for metals, radionuclides and other contaminants. The retention properties result from various mineral phases in hydrated cement that possess a high density and diversity of reactive sites for the fixation of contaminants through a variety of sorption and incorporation reactions. This book presents a state of the art review and critical evaluation of the type and magnitude of the various sorption and incorporation processes in hydrated cement systems for twenty-five elements relevant for a broad range of radioactive and industrial wastes. Effects of cement evolution or ageing on sorption/incorporation processes are explicitly evaluated and quantified. While the immobilisation of contaminants by mixing-in during hydration is not explicitly addressed, the underlying chemical processes are similar. A quantitativ...

  18. Study on activity evaluation of activated coal-gangue and the hydration process

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Chemical compositions, mineral compositions and the activated mechanism of the coal-gangue were analyzed. And pozzolana activities of the coal-gangue were evaluated after activated. Moreover, hydration heat and hydration compositions of activated coal-gangue-calcium oxide system, as well as hydration degree and hardened paste microstructures of activated coal-gangue-cement system were studied. Results show that pozzolana activities of the activated coal-gangue root in amorphous SiO2 and activated Al2 O3. With the exciting of gypsum, the reaction of activated coal-gangue and Ca(OH)2 would produce hydration products as ettringite, calcium silicate hydrate, and calcium aluminate. The relationship between the curing age and the content of Ca(OH)2 in coal-gangue-cement system was ascertained. Unhydrated particles in the coal-gangue-cement paste were more than that in the neat cement paste at the same hydration periods, and even existed at the later stage of hydration. Furthermore, the activated coal-gangue could inhibit growth and gathering of the calcium oxide crystal, and improve the structure of hardened cement paste.

  19. Immobilization of radioactive waste in cement-based matrices

    International Nuclear Information System (INIS)

    Model studies of the behaviour of cement systems have been advanced by considering the nature of the phases formed during hydration and deriving pH-composition models for the CaO-SiO2-H2O system. Preliminary results of Esub(h) measurements are also reported. Leach tests on Sr from cements are interpreted in terms of Sr retention mechanisms. Present results indicate that the aluminate phases in OPC contribute to the chemical retentivity. Studies on cement-clinoptilolite reactions, made using coarse grained clinoptilolite are reported: ferrierite also reacts chemically with cement. Two critical surveys are presented, together with new data: one on the potential of blended cements, the other on cement durability in CO2-containing environments. (author)

  20. Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

    Science.gov (United States)

    Tsukada, K.; Kusaka, T.; Saari, M. M.; Takagi, R.; Sakai, K.; Kiwa, T.; Bito, Y.

    2014-05-01

    We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization-magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water are mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility.

  1. Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

    Energy Technology Data Exchange (ETDEWEB)

    Tsukada, K., E-mail: tsukada@cc.okayama-u.ac.jp; Kusaka, T.; Saari, M. M.; Takagi, R.; Sakai, K.; Kiwa, T. [The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530 (Japan); Bito, Y. [Central Research Lab., Hitachi. Ltd., 1-280 Higashi-Koigakubo, Kokubunji, Tokyo 185-8601 (Japan)

    2014-05-07

    We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization–magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water are mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility.

  2. Effects of Static Magnetic Fields on the Physical, Mechanical, and Microstructural Properties of Cement Pastes

    Directory of Open Access Journals (Sweden)

    Juan J. Soto-Bernal

    2015-01-01

    Full Text Available This paper presents the results of an experimental study carried out to comprehend the physical, mechanical, and microstructural behavior of cement pastes subjected to static magnetic fields while hydrating and setting. The experimental methodology consisted in exposing fresh cement pastes to static magnetic fields at three different magnetic induction strengths: 19.07, 22.22, and 25.37 Gauss. The microstructural characterization makes evident that there are differences in relation to amount and morphology of CSH gel; the amount of CSH is larger and its morphology becomes denser and less porous with higher magnetostatic induction strengths; it also shows the evidence of changes in the mineralogical composition of the hydrated cement pastes. The temperature increasing has no negative effects over the cement paste compressive strength since the magnetostatic field affects the process of hydration through a molecular restructuring process, which makes cement pastes improve microstructurally, with a reduced porosity and a higher mechanical strength.

  3. STUDY OF THE INFLUENCE OF COMPLEMENTARY HYDRATION ON THE MECHANICAL PROPERTIES OF SELF-REDUCING PELLETS

    Directory of Open Access Journals (Sweden)

    Felippe de Oliveira Sousa

    2015-06-01

    Full Text Available This study has investigated how different methods and time of complementary hydration affects the cold strength of self-reducing pellets. Identical pellets had been made by the addition of pellet feed, coal, cement and lime and have been subjected to hydration by water immersion or in a moist chamber for different periods. A group of non-hydrated pellets was used as reference for evaluation the effect of hydration. The pellets were then characterized by mechanical tests of compression and tumbling strength. The results have shown an increase in the mechanical properties of pellets and have proved that the hydration by moist chamber was the most efficient method.

  4. Chemical and mineralogical characterization of two commercial cements and its evolution in function of time

    International Nuclear Information System (INIS)

    Mineralogical evolution of Portland cement is studied during hydration process using materials characterization techniques as X-ray diffraction (XRD) and scanning electron microscopy (Sem) in order to analyze the changes in the various cement minerals as alite, belite, celite, during processing to the hydrated phases of tobermorite gel, portlandite and ettringite, respectively, in the cement paste setting at different ages (3, 7 and 28 days). It was found that the hydration process occurs differently in each mineral because of their reaction rates or changes they experience in their crystals during processing of anhydrous to hydrated phase. You may notice changes in the appearance of the dough as you go hydration and the formation of tobermorite gel, portlandite and ettringite. (Author)

  5. Effect of Aggregate Gradation with Fuller Distribution on Properties of Sulfoaluminate Cement Concrete

    OpenAIRE

    Gong, Chenchen; Jie ZHANG; Wang, Shoude; Zong, Wen; Lu, Lingchao

    2014-01-01

    Aggregate, the main ingredient of concrete, has a great effect on mechanical property and durability of concrete. Sulfoaluminate cement has lots of special properties such as high early-age compressive strength, fast hydration and setting rate, and hydration with slight swelling. But effect of aggregate gradation with Fuller distribution on properties of sulfoaluminate cement concrete was seldom studied. Hence, in this paper, experimental investigations on mechanical property and durability o...

  6. Self-healing ability of fly ash-cement systems

    Energy Technology Data Exchange (ETDEWEB)

    Pipat Termkhajornkit; Toyoharu Nawa; Yoichi Yamashiro; Toshiki Saito [Lafarge Research Centre, Quentin Fallavier (France). Reactive Components Department

    2009-03-15

    Concrete is susceptible to cracking due to both autogenous and drying shrinkage. Nevertheless, most of these types of cracks occur before 28 days. Because fly ash continues to hydrate after 28 days, it is likely that hydrated products from fly ash may modify microstructure, seal these cracks, and prolong the service life. This research investigates the self-healing ability of fly ash-cement paste. Compressive strength, porosity, chloride diffusion coefficients, hydration reactions and hydrated products were studied. The research focuses on behavior after 28 days. According to the experimental results, the fly ash-cement system has the self-healing ability for cracks that occur from shrinkage. The self-healing ability increased when the fraction of fly ash increased.

  7. 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

  8. Effect of mixing water magnetic activation cycle on cement stone structure

    Science.gov (United States)

    Kugaevskaya, S. A.; Abzaev, Yu A.; Safronov, V. N.; Sarkisov, Yu S.; Gorlenko, N. P.; Ermilova, T. A.

    2015-01-01

    The paper presents results of investigations of hydration processes and structure formation of the cement paste matrix mixed with water activated by magneto static field using water treatment cycle technology. It is shown that crystallization of phases occurs in the cement-water system at different rates, and phase redistribution in the structure of the cement paste matrix is described before and after magnetic activation of mixing water. Also, modeling of the cement-water system and calculations of amorphous and crystalline phases using the Rietveld refinement method before and after magnetic activation show that strength properties of the cement paste matrix depend not only on quantitative but also qualitative relationship between phases.

  9. Heat of Hydration of Low Activity Cementitious Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Nasol, D. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-07-23

    During the curing of secondary waste grout, the hydraulic materials in the dry mix react exothermally with the water in the secondary low-activity waste (LAW). The heat released, called the heat of hydration, can be measured using a TAM Air Isothermal Calorimeter. By holding temperature constant in the instrument, the heat of hydration during the curing process can be determined. This will provide information that can be used in the design of a waste solidification facility. At the Savannah River National Laboratory (SRNL), the heat of hydration and other physical properties are being collected on grout prepared using three simulants of liquid secondary waste generated at the Hanford Site. From this study it was found that both the simulant and dry mix each had an effect on the heat of hydration. It was also concluded that the higher the cement content in the dry materials mix, the greater the heat of hydration during the curing of grout.

  10. Hydration studies of ye’elimite by using Ptychographic X-ray nano-tomography

    OpenAIRE

    Cuesta, Ana; da Silva, Julio C; Diaz, Ana; Holler, Mirko; De la Torre, Ángeles G.; García Aranda, Miguel Ángel

    2015-01-01

    CSA (Calcium SulfoAluminate) cements may have variable compositions but all of them contain ye’elimite(Ca4Al6O12SO4). The manufacture of CSA cements is more environmentally friendly than that of ordinary Portland cements as their production releases up to 40% less CO2. The hydration of ye’elimite leads to crystalline ettringite (AFt) and amorphous aluminum hydroxide (AH3•nH2O). Ptychographic X-ray computed nanotomography (PXCT) has been used here to study the hydration of ye’elimite-contai...

  11. Experimental characterization and modelling of acoustic velocity and electrical resistance in hydrate bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Y.; Zhang, W.; Liu, Y.; Ren, S. [China Univ. of Petroleum, Dongying (China). Inst. of Petroleum Engineering

    2008-07-01

    In the development of gas hydrate resources, characterization of natural gas hydrate bearing sediments is important. Solid hydrates fill the voids of the matrix formed by sand grains and change their cementation condition, which have a significant impact on the resistance and sound velocity of the sand matrix. Acoustic velocity and electrical resistivity are important methods in well-logging of conventional oil/gas reservoirs. They can also be effectively utilized in the characterization of gas hydrate-bearing sediments. Solid hydrates fill the voids between sand grains and change the cementation condition of the sand matrix, which can enhance the propagation of sounds, increasing the sound velocity. Since electric ions are excluded in hydrate, hydrate formation can change the distribution and mobility of electrolytes in sub sea sediments, which will affect the resistance of the sand matrix. This paper presented a study that involved experiments that measured the acoustic P-wave velocity and electrical properties of sandpacks with methane hydrate formed under simulated subsea sediment conditions. The paper discussed the key findings of the experiments in order to correlate the resistivity and acoustic P-wave velocity with hydrate saturation in porous media. The effects of hydrate on the resistivity and ultrasonic velocity of hydrate bearing sand matrix were revealed and modeled. It was concluded that the resistivity of the sandpack bearing with hydrate slightly decreased when hydrate saturation was low, probably because of the hydrate's ion exclusion effect. An increased resistivity with higher hydrate saturation could be explained by a blockage mechanism of hydrates formed in the pores. 11 refs., 1 tab., 8 figs.

  12. Literature survey on phase composition of hardened cement paste containing fly ash

    International Nuclear Information System (INIS)

    The purpose of this literature survey is to collect the knowledge on the effect of fly ash in hardened cement paste and the information about evaluation of physicochemical performance based on phase composition of hardened cement paste. The performance of hardened cement paste containing fly ash is affected by the property of fly ash, hydration of cement and pozzolanic reaction of fly ash. Some properties of fly ash such as density and chemical composition are reflected in phase composition, showing the progress of cement hydration and pozzolanic reaction. Therefore clarification of the relationship of phase composition and performance will lead to appropriate evaluation of the property of fly ash. The amount of pore, chemical shrinkage, pore solution, compressive strength, Young modulus and alkali silica reaction have relations to the phase composition of hardened cement paste. It is considered as future subject to clarify the relationship of phase composition and performance for various properties of fly ash. (author)

  13. Influence of the use of nanoscale siliceous cement system on the strength

    OpenAIRE

    KOSACH Anatoliy Fyodorovich; DANILOV Sergey Valeryevich; GUTAREVA Natalya Anatolyevna; KOROTAEV Maksim Aleksandrovich

    2014-01-01

    The article is devoted to creation of scientific basis for cement stone structure formation, development of optimal compositions and technology for manufacturing building materials based on the waste of fine-grained pure quartz production. This technology provides significant pore filling, formation of new crystallization centers which act as an dditional reinforcement of cement hydration products, and increase of physical and mechanical properties.

  14. Comparison of observed and simulated cement microstructure using spatial correlation functions

    NARCIS (Netherlands)

    Igarashi, S.; Chen, W.; Brouwers, H.J.H.

    2009-01-01

    The microstructure of cement pastes, as revealed by SEM-BSE image analysis, was compared with a simulated structure generated by the University of Twente version of the CEMHYD3D hydration simulation model. The spatial array of unhydrated cement particles was simulated by the model. However, spatial

  15. In-situ Mechanical Manipulation of Wellbore Cements as a Solution to Leaky Wells

    Science.gov (United States)

    Kupresan, D.; Radonjic, M.; Heathman, J.

    2013-12-01

    Wellbore cement provides casing support, zonal isolation, and casing protection from corrosive fluids, which are essential for wellbore integrity. Cements can undergo one or more forms of failure such as debonding at cement/formation and cement/casing interface, fracturing and defects within cement matrix. Failures and defects within cement will ultimately lead to fluids migration, resulting in inter-zonal fluid migration and premature well abandonment. There are over 27,000 abandoned oil and gas wells only in The Gulf of Mexico (some of them dating from the late 1940s) with no gas leakage monitoring. Cement degradation linked with carbon sequestration can potentially lead to contamination of fresh water aquifers with CO2. Gas leaks can particularly be observed in deviated wells used for hydraulic fracking (60% leakage rate as they age) as high pressure fracturing increases the potential for migration pathways. Experimental method utilized in this study enables formation of impermeable seals at interfaces present in a wellbore by mechanically manipulating wellbore cement. Preliminary measurements obtained in bench scale experiments demonstrate that an impermeable cement/formation and cement/casing interface can be obtained. In post-modified cement, nitrogen gas flow-through experiments showed complete zonal isolation and no permeability in samples with pre-engineered microannulus. Material characterization experiments of modified cement revealed altered microstructural properties of cement as well as changes in mineralogical composition. Calcium-silicate-hydrate (CSH), the dominant mineral in hydrated cement which provides low permeability of cement, was modified as a result of cement pore water displacement, resulting in more dense structures. Calcium hydroxide (CH), which is associated with low resistance of cement to acidic fluids and therefore detrimental in most wellbore cements, was almost completely displaced and/or integrated in CSH as a result of

  16. Assessment of cement durability in repository environment

    International Nuclear Information System (INIS)

    The present research aimed at investigating the durability of cement paste under nuclear waste repository conditions using accelerated tests. Cement paste samples are examined after being exposed to the environmental conditions that are expected to prevail in the repository environment and the results are compared with those obtained with unexposed specimens or specimens exposed to reference conditions. The following exposure conditions were selected: a) Immersion in salt solution, distilled water, or kept in dry storage; b) Room temperature (20 C. degrees) or high temperature (60 C. degrees); c) Immersion time of 30 days or 60 days (not for dry storage); d) Irradiation to a dose of (400 kGy) or background radiation (0 kGy). After exposure to the stressing conditions, the effects of each factor on the cement paste samples were observed by changes in their characteristics. Compressive strength tests were performed on all samples and some of them were investigated in terms of changes in mineralogy by X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). With the results obtained so far it was possible to point out the following conclusions. First, after a period of immersion in water, cement paste samples further hydrated and presented higher mechanical resistance, as expected. Secondly, dry storage did not allow a complete hydration as a consequence of pore water evaporation. High temperatures intensified this process and led to the ettringite decomposition to meta-ettringite. Thirdly, higher temperature accelerated hydration kinetics and promoted higher mechanical resistance in samples kept under immersion. Fourthly, the irradiation dose applied was unable to change the mineralogy of cement paste samples and fifthly, no statistically significant differences were observed between 30 or 60 days exposure time, for the test conditions

  17. The effect of temperature rise on microstructural properties of cement-based materials: correlation of experimental data and a simulation approach

    NARCIS (Netherlands)

    Susanto, A.; Koleva, D.A.; Van Breugel, K.

    2015-01-01

    This work reports on the influence of stray current flow on temperature rise in hardening cement-based materials and consequently altered cement hydration. To simulate stray current, different levels of electrical current were applied to cement paste and mortar specimens immediately after casting. I

  18. 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.

  19. Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

    Science.gov (United States)

    Walling, Sam A; Provis, John L

    2016-04-13

    This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis. PMID:27002788

  20. The In-situ Reinforcement of Calcium Phosphate Cement and Its Micro-structural Analysis

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Carbon nanotubes ( CNTs ) and polyacrylic acid were employed to modify the setting process and hydration products of β- TCP/ TTCP calcium phosphate cement. The micro-structure of hydration product and the fashion of how additives and hydration particles interconnected were investigated. With the modification effect of CNTs, the setting particles and CNTs got winded and interconnected and thus made the composite more compact and denser.

  1. Experimental determination of carbonation rate in Portland cement at 25°C and relatively high CO2 partial pressure

    Science.gov (United States)

    Hernández-Rodríguez, Ana; Montegrossi, Giordano; Huet, Bruno; Virgili, Giorgio; Orlando, Andrea; Vaselli, Orlando; Marini, Luigi

    2016-04-01

    The aim of this work is to study the alteration of Portland class G Cement at ambient temperature under a relatively high CO2 partial pressure through suitably designed laboratory experiments, in which cement hydration and carbonation are taken into account separately. First, the hydration process was carried out for 28 days to identify and quantify the hydrated solid phases formed. After the completion of hydration, accompanied by partial carbonation under atmospheric conditions, the carbonation process was investigated in a stirred micro-reactor (Parr instrument) with crushed cement samples under 10 bar or more of pure CO2(g) and MilliQ water adopting different reaction times. The reaction time was varied to constrain the reaction kinetics of the carbonation process and to investigate the evolution of secondary solid phases. Chemical and mineralogical analyses (calcimetry, chemical composition, SEM and X-ray Powder Diffraction) were carried out to characterize the secondary minerals formed during cement hydration and carbonation. Water analyses were also performed at the end of each experimental run to measure the concentrations of relevant solutes. The specific surface area of hydrated cement was measured by means of the BET method to obtain the rates of cement carbonation. Experimental outcomes were simulated by means of the PhreeqC software package. The obtained results are of interest to understand the comparatively fast cement alteration in CO2 production wells with damaged casing.

  2. Accelerated growth of calcium silicate hydrates: Experiments and simulations

    International Nuclear Information System (INIS)

    Despite the usefulness of isothermal calorimetry in cement analytics, without any further computations this brings only little information on the nucleation and growth of hydrates. A model originally developed by Garrault et al. is used in this study in order to simulate hydration curves of cement obtained by calorimetry with different known hardening accelerators. The limited basis set of parameters used in this model, having a physical or chemical significance, is valuable for a better understanding of mechanisms underlying in the acceleration of C-S-H precipitation. Alite hydration in presence of four different types of hardening accelerators was investigated. It is evidenced that each accelerator type plays a specific role on one or several growth parameters and that the model may support the development of new accelerators. Those simulations supported by experimental observations enable us to follow the formation of the C-S-H layer around grains and to extract interesting information on its apparent permeability.

  3. Synthesis of partial-stabilized cement (PSC) via sol-gel process.

    Science.gov (United States)

    Wang, Wen-Hsi; Lee, Yuan-Ling; Lin, Chun-Pin; Lin, Feng-Huei

    2008-06-15

    The traditional method of preparing partial-stabilized cement (PSC), which is a kind of calcium silicate cement, is through power mixing method. Low reaction efficiency and initial strength limited the application of PSC as a dental root-end filling material. This study provides a one-step sol-gel process for the synthesis of PSC. A complexing ligand is used for tuning down the activity of aluminum sec-butoxide (ASB) in order to avoid possible self-polymerization. After the modification with complex ligand, there is no residue of reactant observed on the analysis of SDT, and bonding between metal atoms is observed in the FTIR spectrum. Each component of PSC is identified using XRD. The hydration product, which is called portlandite, of sol-gel-synthesized PSC is observed after 1 day of hydration, and crystallinity of portlandite increases much faster than that of traditional PSC. The initial strength of sol-gel-synthesized PSC achieves detectable level 24 h earlier than that of traditional PSC; microhardness value of sol-gel-synthesized PSC at 7th day is 2.98 HV, which is much higher than that of traditional PSC (2.05 HV). PSC is successfully synthesized and the initial strength of PSC is improved by this modified sol-gel process.

  4. Corrosion-resistant Foamed Cements for Carbon Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Gill, S.; Pyatina, T., Muraca, A.; Keese, R.; Khan, A.; Bour, D.

    2012-12-01

    The cementitious material consisting of Secar #80, Class F fly ash, and sodium silicate designed as an alternative thermal-shock resistant cement for the Enhanced Geothermal System (EGS) wells was treated with cocamidopropyl dimethylamine oxide-based compound as foaming agent (FA) to prepare numerous air bubble-dispersed low density cement slurries of and #61603;1.3 g/cm3. Then, the foamed slurry was modified with acrylic emulsion (AE) as corrosion inhibitor. We detailed the positive effects of the acrylic polymer (AP) in this emulsion on the five different properties of the foamed cement: 1) The hydrothermal stability of the AP in 200 and #61616;C-autoclaved cements; 2) the hydrolysis-hydration reactions of the slurry at 85 and #61616;C; 3) the composition of crystalline phases assembled and the microstructure developed in autoclaved cements; 4) the mechanical behaviors of the autoclaved cements; and, 5) the corrosion mitigation of carbon steel (CS) by the polymer. For the first property, the hydrothermal-catalyzed acid-base interactions between the AP and cement resulted in Ca-or Na-complexed carboxylate derivatives, which led to the improvement of thermal stability of the AP. This interaction also stimulated the cement hydration reactions, enhancing the total heat evolved during cement’s curing. Addition of AP did not alter any of the crystalline phase compositions responsible for the strength of the cement. Furthermore, the AP-modified cement developed the porous microstructure with numerous defect-free cavities of disconnected voids. These effects together contributed to the improvement of compressive-strength and –toughness of the cured cement. AP modification of the cement also offered an improved protection of CS against brine-caused corrosion. There were three major factors governing the corrosion protection: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS

  5. Pore Structure of Cement Pastes Blended with Volcanic Rock

    Institute of Scientific and Technical Information of China (English)

    YU Lehua; ZHOU Shuangxi; LI Liling

    2016-01-01

    The pore parameters of cement pastes blended with volcanic rock at the curing age of 1, 28 and 90 d were de-termined by a mercury intrusion porosimetry. The pore structure of the pastes was characterized through the analysis of porosity, average pore diameter, the most probable pore aperture, pore size distribution, as well as total pore volume. For the improvement of mechanical property and durability of cement-based material, the correlation of the formed pore structure with hydration time and replacement level of volcanic rock for cement was revealed. The results indicate that volcanic rock can diminish porosity and reduce pore size in cement paste when curing time prolongs, which is particu-larly prominent with replacement level of less than 20% in late period. The more harmful pores (i.e., capillary pore) are gradually transformed into harmless pore (i.e., gel pores or micropore), even fully filled and disappeared when hydration products increase. The pore structure of the cement paste is thus refined. The beneficial effect of volcanic rock on the pore structure of cement paste could enhance the mechanical property and durability of cement-based material.

  6. Effect of supplementary cementing materials on the concrete corrosion control

    International Nuclear Information System (INIS)

    Failure of concrete after a period of years, less than the life expected for which it was designed, may be caused by the environment to which it has been exposed or by a variety of internal causes. The incorporation of supplementary materials has at the Portland cement the purpose of improving the concrete microstructure and also of influence the resistance of concrete to environmental attacks. Different mineral by-products as ground granulated blast furnaces slag (GGBS), silica fume (SF), meta kaolin (MK), fly ash (FA) and other products have been used as supplementary cementing materials. This paper is about the behavior of concrete in the presence of mineral additions. Compared to Portland cements, blended cements show lower heat of hydration, lower permeability, greater resistance to sulphates and sea water. These blended cements find the best application when requirements of durability are regarded as a priority specially on high performance concrete: (Author) 11 refs

  7. 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...

  8. Treatment and recycling of asbestos-cement containing waste

    Energy Technology Data Exchange (ETDEWEB)

    Colangelo, F. [Department of Technology, University Parthenope, Naples (Italy); Cioffi, R., E-mail: raffaele.cioffi@uniparthenope.it [Department of Technology, University Parthenope, Naples (Italy); Lavorgna, M.; Verdolotti, L. [Institute for Biomedical and Composite Materials - CNR, Naples (Italy); De Stefano, L. [Institute for Microelectronics and Microsystems - CNR, Naples (Italy)

    2011-11-15

    Highlights: {yields} Asbestos-cement wastes are hazardous. {yields} High energy milling treatment at room temperature allows mineralogical and morphological transformation of asbestos phases. {yields} The obtained milled powders are not-hazardous. {yields} The inert powders can be recycled as pozzolanic materials. {yields} The hydraulic mortars containing the milled inert powders are good building materials. - Abstract: The remediation of industrial buildings covered with asbestos-cement roofs is one of the most important issues in asbestos risk management. The relevant Italian Directives call for the above waste to be treated prior to disposal on landfill. Processes able to eliminate the hazard of these wastes are very attractive because the treated products can be recycled as mineral components in building materials. In this work, asbestos-cement waste is milled by means of a high energy ring mill for up to 4 h. The very fine powders obtained at all milling times are characterized to check the mineralogical and morphological transformation of the asbestos phases. Specifically, after 120 min of milling, the disappearance of the chrysotile OH stretching modes at 3690 cm{sup -1}, of the main crystalline chrysotile peaks and of the fibrous phase are detected by means of infrared spectroscopy and X-ray diffraction and scanning electron microscopy analyses, respectively. The hydraulic behavior of the milled powders in presence of lime is also tested at different times. The results of thermal analyses show that the endothermic effects associated to the neo-formed binding phases significantly increase with curing time. Furthermore, the technological efficacy of the recycling process is evaluated by preparing and testing hydraulic lime and milled powder-based mortars. The complete test set gives good results in terms of the hydration kinetics and mechanical properties of the building materials studied. In fact, values of reacted lime around 40% and values of compressive

  9. Treatment and recycling of asbestos-cement containing waste

    International Nuclear Information System (INIS)

    Highlights: → Asbestos-cement wastes are hazardous. → High energy milling treatment at room temperature allows mineralogical and morphological transformation of asbestos phases. → The obtained milled powders are not-hazardous. → The inert powders can be recycled as pozzolanic materials. → The hydraulic mortars containing the milled inert powders are good building materials. - Abstract: The remediation of industrial buildings covered with asbestos-cement roofs is one of the most important issues in asbestos risk management. The relevant Italian Directives call for the above waste to be treated prior to disposal on landfill. Processes able to eliminate the hazard of these wastes are very attractive because the treated products can be recycled as mineral components in building materials. In this work, asbestos-cement waste is milled by means of a high energy ring mill for up to 4 h. The very fine powders obtained at all milling times are characterized to check the mineralogical and morphological transformation of the asbestos phases. Specifically, after 120 min of milling, the disappearance of the chrysotile OH stretching modes at 3690 cm-1, of the main crystalline chrysotile peaks and of the fibrous phase are detected by means of infrared spectroscopy and X-ray diffraction and scanning electron microscopy analyses, respectively. The hydraulic behavior of the milled powders in presence of lime is also tested at different times. The results of thermal analyses show that the endothermic effects associated to the neo-formed binding phases significantly increase with curing time. Furthermore, the technological efficacy of the recycling process is evaluated by preparing and testing hydraulic lime and milled powder-based mortars. The complete test set gives good results in terms of the hydration kinetics and mechanical properties of the building materials studied. In fact, values of reacted lime around 40% and values of compressive strength in the range of 2

  10. 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

  11. Study on Acceleration Mechanism of Liquid Alkali-free Accelerating Components%液体无碱速凝组分的速凝机理探讨

    Institute of Scientific and Technical Information of China (English)

    贺雄飞; 张迅

    2014-01-01

    The acceleration mechanism of liquid alkali-free accelerating components,including aluminum sulfate and aluminum fluoride,is discussed by testing on the setting time of cement paste mixed with aluminum sulfate and aluminum fluoride respectively,as well as by XRD analysis on the cement paste mixed with accelerating components after final setting,1-day hydration and 7-day hydration.The study results show that,due to the large amount of ettringite generated and the C3 S hydration caused by calcium ion reduction and hydration heat,the setting of the cement paste is accelerated when aluminum sulfate solution is mixed into the Portland cement;due to the C3 AH6 generated,the setting of the cement paste is accelerated by aluminum fluoride solution;the aluminum ion in the aluminum fluoride solution accelerates the hydration of the cement paste;the fluoride ion in the aluminum fluoride solution retards the setting of the cement paste.The paper can provide a theoretical basis for developing and promoting the application of high-performance liquid alkali-free accelerator.%通过测试单独掺入液体无碱速凝组分硫酸铝和氟化铝后水泥浆的凝结时间以及对掺速凝组分后达到终凝、水化1d及水化7 d 的水泥浆体进行XRD图谱分析,深入探讨液体无碱速凝剂组分硫酸铝和氟化铝对水泥的速凝机理。试验结果表明:硅酸盐水泥中掺入硫酸铝溶液因生成大量的钙矾石,同时因消耗大量的钙离子及水化热的作用促进C3 S的水化作用导致浆体快速凝结;氟化铝溶液主要通过形成C3 AH6而导致水泥浆体速凝,氟化铝溶液中铝离子对水泥水化起速凝作用,而氟离子起缓凝作用。

  12. Determination of the Physical Properties of Sediments Depending on Hydrate Saturation Using a "Quick Look" Method

    Science.gov (United States)

    Strauch, B.; Schicks, J. M.; Spangenberg, E.; Seyberth, K.; Heeschen, K. U.; Priegnitz, M.

    2015-12-01

    Seismic and electromagnetic measurements are promising tools for the detection and quantification of gas hydrate occurrences in nature. The seismic wave velocity depends among others on the hydrate quantity and the quality (e.g. pore filling or cementing hydrate). For a proper interpretation of seismic data the knowledge of the dependency of physical properties as a function of hydrate saturation in a certain scenario is crucial. Within the SUGAR III project we determine such dependencies for various scenarios to support models for joint inversion of seismic and EM data e.g. for the shallow gas hydrate reservoirs in the Danube Delta. Since the formation of artificial lab samples containing pore filling hydrate from methane dissolved in water is a complex and time consuming procedure, we developed an easier alternative. Ice is very similar to hydrate in some of its physical properties. Therefore it might be used as analogous pore fill in a "quick look" experiment to determine the dependency of rock physical properties on hydrate content. We used the freezing point depression of a KCl solution to generate a dependency of ice saturation on temperature. The measured seismic wave velocity in dependence on ice saturation compares very well with data measured on a glass bead sediment sample with methane hydrate formed from methane dissolved in water. We could also observe that ice, formed from a salt solution in the pore space of sediment, behaves similar to methane hydrate as a non-cementing solid pore fill.

  13. Three-dimensional Microstructure Simulation Model of Cement Based Materials,

    NARCIS (Netherlands)

    Ye, G.; Van Breugel, K.

    2003-01-01

    This paper describes a computer-based numerical model for the simulation of the development of microstructure during cement hydration. Special emphasis is on the algorithm for characterizing the pores. This includes the porosity and the pore size distribution and the topological properties of the po

  14. PHYSICO-CHEMICAL MODIFICATION OF MONOLITHIC CONCRETE CEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2015-10-01

    Full Text Available Purpose. The paper is aimed to the development of scientific bases of the technology of modified concrete of new generation for special facilities by managing the processes of structure formation of modified cement system in conditions of hardening. Methodology. For the achievement the goal: 1 the research of rheological characteristics of modified concrete mixes for special facilities purpose and processes of structure formation of modified cement system of natural curing concrete was conducted; 2 there were defined methods of reliable evaluation of concrete strength at the removal time of formwork and transmission of loads to the constructions where the concrete has not reached the designed strength. Findings. The author found that the structure formation process develops in the hydrating modified cement system as a result of interaction of various macroions. In this process its active parts prevail, which considerably exceed its dissipative part compared to normal conditions of hardening. Originality. There were established the regularities of structure formation of modified cement system, reinforced with synthesized, well crystallized helical filamentary crystals, mechanical grip of which is considered as a principal source of strength in combination with an additional coupling achieved due to cross-germination of crystals. Practical value. In the study the increased binding capacity of cement in high strength concretes and the use of modified cement systems in the special conditions of concreting were considered. The organo-mineral modifying complex that provides the dispersed reinforcement of concrete cement matrix which allows modifying the process of cement matrix structure formation by changing the nature of the surface of binder and modifier was developed. The temperature factor has no negative influence on the hardening concrete and complex modifier provides the improved physico-mechanical characteristics of cement matrix and concrete

  15. Application progress of solid 29Si, 27Al NMR in the research of cement-based materials

    International Nuclear Information System (INIS)

    Background: The solid-state Nuclear Magnetic Resonance (NMR) is an effective method for the research of cement-based materials. Now it focuses on using solid 29Si and 27Al NMR to research the hydration structure of the cement-based materials in cement chemistry. Purpose: A theoretical guidance is proposed for solid 29Si and 27Al NMR technology used in cement chemistry research. Methods: We reviewed the application of solid 29Si and 27Al NMR in the cement-based materials and analyzed the problem among the researches. Results: This paper introduced an fundamental, relevant-conditions and basic parameters of NMR, and studied the technical parameters of solid 29Si and 27Ai NMR together with the relationship among the hydration structure of cement based material. Moreover, this paper reviewed the related domestic and overseas achievements in the research of hydration structure of the cement-based materials using solid 29Si and 27Al NMR. Conclusion: There were some problems in the research on cement-based materials by technology of solid 29Si and 27Al NMR. NMR will promote the Hydration theory of cement-based material greatly. (authors)

  16. HYDRATION AND ENZYME ACTIVITY

    OpenAIRE

    Poole, P.

    1984-01-01

    Hydration induced conformation and dynamic changes are followed using a variety of experimental techniques applied to hen egg white lysozyme. These changes are completed just before the onset of enzyme activity, which occurs before all polar groups are hydrated, and before monolayer coverage is attained. We suggest that these hydration induced changes are necessary for the return of enzyme activity.

  17. Life Origination Hydrate Theory (LOH-Theory) and Mitosis and Replication Hydrate Theory (MRH-Theory): three-dimensional PC validation

    Science.gov (United States)

    Kadyshevich, E. A.; Dzyabchenko, A. V.; Ostrovskii, V. E.

    2014-04-01

    Size compatibility of the CH4-hydrate structure II and multi-component DNA fragments is confirmed by three-dimensional simulation; it is validation of the Life Origination Hydrate Theory (LOH-Theory).

  18. Study of P-350 cement setting kinetic by nuclear magnetic resonance

    Directory of Open Access Journals (Sweden)

    Duque Fernández, Gabriel L.

    1993-12-01

    Full Text Available A kinetic study of cement setting process is presented in this paper A new method which allows the microscopic research of the evolution of the cement hydration applied to the study of three P-350 cuban cements is used. The initial and final values of the specific surfaces of the hydration products and cement were obtained, and the different periods of the hydration process of cement pastes were characterized. The influence of the cement phase composition on the surface development of the hydrated cement stone is discussed.

    En el presente trabajo se presenta el estudio de la cinética del proceso de fraguado del cemento empleando un método novedoso que permite investigar microscópicamente la evolución de la hidratación del cemento, el cual fue aplicado al estudio de tres cementos cubanos P-350. Se obtuvieron los valores iniciales y finales de las superficies específicas de los productos de hidratación y del cemento. Se caracterizaron los diferentes períodos del proceso de hidratación de las pastas de cemento. Se muestra la influencia de la composición fásica del cemento sobre el desarrollo superficial de la pasta hidratada.

  19. 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.

  20. 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

  1. Phase Transition of Methane Gas Hydrate and Response of Marine Gas Hydrate Systems to Environmental Changes

    Science.gov (United States)

    Xu, W.

    2003-12-01

    Gas hydrates, which contain mostly methane as the gas component in marine sediment, are stable under relatively high pressure and low temperature conditions such as those found along continental margins and permafrost regions. Its stability is mostly controlled by in-situ pressure, temperature and salinity of pore fluid. Environmentally introduced changes in pressure and temperature can affect the stability of gas hydrate in marine sediment. While certain changes may enhance the process of gas hydrate formation, we are much more interested in the resultant dissociation processes, which may contribute to sub-marine slope instability, seafloor sediment failure, formation of mud volcanoes and pock marks, potential vulnerability of engineering structures, and the risk to drilling and production. We have been developing models to quantify phase transition processes of marine gas hydrates and to investigate the response of marine gas hydrate systems to environmental changes. Methane gas hydrate system is considered as a three-component (water, methane, salt) four-phase (liquid, gas, hydrate, halite) system. Pressure, temperature and salinity of pore fluid constrain the stability of gas hydrate and affect phase transition processes via their effects on methane solubility and fluid density and enthalpy. Compared to the great quantity of studies on its stability in the literature, in-depth research on phase transition of gas hydrate is surprisingly much less. A method, which employs pressure, enthalpy, salinity and methane content as independent variables, is developed to calculate phase transition processes of the three-component four-phase system. Temperature, an intensive thermodynamic parameter, is found not sufficient in describing phase transition of gas hydrate. The extensive thermodynamic parameter enthalpy, on the other hand, is found to be sufficient both in calculation of the phase transition processes and in modeling marine gas hydrate systems. Processes

  2. Cement Based Batteries and their Potential for Use in Low Power Operations

    Science.gov (United States)

    Byrne, A.; Holmes, N.; Norton, B.

    2015-11-01

    This paper presents the development of an innovative cement-electrolyte battery for low power operations such as cathodic protection of reinforced concrete. A battery design was refined by altering different constituents and examining the open circuit voltage, resistor loaded current and lifespan. The final design consisted of a copper plate cathode, aluminium plate anode, and a cement electrolyte which included additives of carbon black, plasticiser, Alum salt and Epsom salt. A relationship between age, temperature and hydration of the cell and the current it produced was determined. It was found that sealing the battery using varnish increased the moisture retention and current output. Current was also found to increase with internal temperature of the electrolyte and connecting two cells in parallel further doubled or even tripled the current. Parallel-connected cells could sustain an average current of 0.35mA through a 10Ω resistor over two weeks of recording. The preliminary findings demonstrate that cement-based batteries can produce sufficient sustainable electrical outputs with the correct materials and arrangement of components. Work is ongoing to determine how these batteries can be recharged using photovoltaics which will further enhance their sustainability properties.

  3. Use of industrial byproducts as alumina sources for the synthesis of calcium sulfoaluminate cements.

    Science.gov (United States)

    Pace, Maria Lucia; Telesca, Antonio; Marroccoli, Milena; Valenti, Gian Lorenzo

    2011-07-15

    Calcium sulfoaluminate (CSA) cements show some desirable environmentally friendly features that include the possibility of using several industrial byproducts as raw materials in their manufacturing process. Alumina powder, from the secondary aluminum manufacture, and anodization mud, from the production process of anodized aluminum, have proved to be suitable as partial or total substitutes for an expensive natural material like bauxite. CSA clinker generating raw mixtures, containing limestone, natural gypsum, bauxite, and/or one of the alumina-rich byproducts, were heated 2 h in a laboratory electric oven at temperatures ranging from 1150 to 1300 °C. Conversion of reactants into 4CaO·3Al(2)O(3)·SO(3) (the key component of CSA cements), evaluated using X-ray diffraction (XRD) analysis, increased with an increase of both burning temperature and byproduct concentration. When examined through differential thermogravimetric and XRD analyses, a synthetic CSA clinker (made from the raw mixture incorporating alumina powder as a total replacement of bauxite) mixed with 20% gypsum showed a hydration behavior almost similar to that of an industrial CSA cement containing the same amount of gypsum. PMID:21707122

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

    Science.gov (United States)

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

    2009-04-01

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

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

    Science.gov (United States)

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

    2011-05-01

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

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

    Institute of Scientific and Technical Information of China (English)

    于文金; 罗永传; 弓子成; 丁庆军

    2011-01-01

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

  7. Utilization of Iron Ore Tailings as Raw Material for Portland Cement Clinker Production

    Directory of Open Access Journals (Sweden)

    Li Luo

    2016-01-01

    Full Text Available The cement industry has for some time been seeking alternative raw material for the Portland cement clinker production. The aim of this research was to investigate the possibility of utilizing iron ore tailings (IOT to replace clay as alumina-silicate raw material for the production of Portland cement clinker. For this purpose, two kinds of clinkers were prepared: one was prepared by IOT; the other was prepared by clay as a reference. The reactivity and burnability of raw meal, mineralogical composition and physical properties of clinker, and hydration characteristic of cement were studied by burnability analysis, differential thermal analysis, X-ray diffraction, and hydration analysis. The results showed that the raw meal containing IOT had higher reactivity and burnability than the raw meal containing clay, and the use of IOT did not affect the formation of characteristic mineralogical phases of Portland cement clinker. Furthermore, the physical and mechanical performance of two cement clinkers were similar. In addition, the use of IOT was found to improve the grindability of clinker and lower the hydration heat of Portland cement. These findings suggest that IOT can replace the clay as alumina-silicate raw material for the preparation of Portland cement clinker.

  8. Inference of the phase-to-mechanical property link via coupled X-ray spectrometry and indentation analysis: Application to cement-based materials

    Energy Technology Data Exchange (ETDEWEB)

    Krakowiak, Konrad J.; Wilson, William [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States); James, Simon [Schlumberger Riboud Product Center, 1 Rue Henri Becquerel, Clamart 92140 (France); Musso, Simone [Schlumberger-Doll Research Center, 1 Hampshire St., Cambridge, MA 02139-1578 (United States); Ulm, Franz-Josef, E-mail: ulm@mit.edu [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139-4307 (United States)

    2015-01-15

    A novel approach for the chemo-mechanical characterization of cement-based materials is presented, which combines the classical grid indentation technique with elemental mapping by scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS). It is illustrated through application to an oil-well cement system with siliceous filler. The characteristic X-rays of major elements (silicon, calcium and aluminum) are measured over the indentation region and mapped back on the indentation points. Measured intensities together with indentation hardness and modulus are considered in a clustering analysis within the framework of Finite Mixture Models with Gaussian component density function. The method is able to successfully isolate the calcium-silica-hydrate gel at the indentation scale from its mixtures with other products of cement hydration and anhydrous phases; thus providing a convenient means to link mechanical response to the calcium-to-silicon ratio quantified independently via X-ray wavelength dispersive spectroscopy. A discussion of uncertainty quantification of the estimated chemo-mechanical properties and phase volume fractions, as well as the effect of chemical observables on phase assessment is also included.

  9. Evaluation of Hydrated Lime Filler in Asphalt Mixtures

    Directory of Open Access Journals (Sweden)

    Mohammed Abbas Hasan Al-Jumaily

    2008-01-01

    Full Text Available Mineral filler is one of important materials and affecting on properties and quality of asphalt mixtures .There are different types of mineral filler depended on cost and quality , the matter encourages us to achieve this study to evaluate hydrated lime filler effects on properties of asphalt mixes related with strength and durability. Conventional asphaltic concrete mixtures with Portland cement and soft sandstone fillers and mixtures modified with hydrated lime were evaluated for their fundamental engineering properties as defined by Marshall properties , index of retained strength , indirect tensile strength , permanent deformation characteristics , and fatigue resistance .A typical dense graded mixture employed in construction of surface course pavement in Iraq in accordance with SCRB specifications was used .The materials used in this study included mineral aggregate materials (coarse and fine sizes were originally obtained from Najaf Sea quarries and two grades of asphalt cements produced from Daurah refinery which are D47 and D66 . The physical properties , stiffness modulus and chemical composition are evaluated for the recovered asphalt cement from prepared asphalt mixes containing various filler types .The paper results indicated that the addition of hydrated lime as mineral filler improved the permanent deformation characteristics and fatigue life and the use of hydrated lime will decrease the moisture susceptibility of the asphalt mixtures.

  10. Reaction kinetics of dual setting α-tricalcium phosphate cements.

    Science.gov (United States)

    Hurle, Katrin; Christel, Theresa; Gbureck, Uwe; Moseke, Claus; Neubauer, Juergen; Goetz-Neunhoeffer, Friedlinde

    2016-01-01

    Addition of ductile polymers to calcium-deficient hydroxyapatite (CDHA)-forming bone cements based on α-tricalcium phosphate (α-TCP) is a promising approach to improve the mechanical performance of α-TCP cements and extend their application to load-bearing defects, which is else impeded by the brittleness of the hardened cement. One suitable polymer is poly-(2-hydroxyethylmethacrylate) (p-HEMA), which forms during cement setting by radical polymerisation of the monomer. In this study the hydration kinetics and the mechanical performance of α-TCP cements modified with addition of different HEMA concentrations (0-50 wt% in the cement liquid) was investigated by quantitative in situ XRD and four-point bending tests. Morphology of CDHA crystals was monitored by scanning electron microscopy. The hydration of α-TCP to CDHA was increasingly impeded and the visible crystal size of CDHA increasingly reduced with increasing HEMA concentration. Modification of the cements by adding 50 wt% HEMA to the cement liquid changed the brittle performance of the hardened cement to a pseudoplastic behaviour, reduced the flexural modulus and increased the work of fracture, while lower HEMA concentrations had no significant effect on these parameters. In such a composite, the extent of CDHA formation was considerably reduced (34.0 ± 1.8 wt% CDHA with 50 % HEMA compared to 54.1 ± 2.4 wt% CDHA in the reference formed after 48 h), while the general reaction kinetics were not changed. In conclusion, while the extent of CDHA formation was decreased, the mechanical properties were noticeably improved by addition of HEMA. Hence, α-TCP/HEMA composites might be suitable for application in some load-bearing defects and have adequate properties for mechanical treatment after implantation, like insertion of screws. PMID:26610924

  11. Rheological Properties of Cemented Tailing Backfill and the Construction of a Prediction Model

    OpenAIRE

    Liu Lang; KI-IL Song; Dezheng Lao; Tae-Hyuk Kwon

    2015-01-01

    Workability is a key performance criterion for mining cemented tailing backfill, which should be defined in terms of rheological parameters such as yield stress and plastic viscosity. Cemented tailing backfill is basically composed of mill tailings, Portland cement, or blended cement with supplementary cement material (fly ash and blast furnace slag) and water, among others, and it is important to characterize relationships between paste components and rheological properties to optimize the w...

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

    Science.gov (United States)

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

    2014-01-01

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

  13. Macrodefect-free cements: chemistry and impact of the environment

    Energy Technology Data Exchange (ETDEWEB)

    Drabik, M.; Galikova, L.; Mojumdar, S.C. [Slovak Academy of Sciences, Bratislava (Slovakia). Inst. of Inorganic Chemistry

    2002-07-01

    To control and improve the moisture resistance is a long felt necessity of the MDF cements, chemical approaches together with material science contribute to the progress. Present results support our previous hypothesis about the impregnation or barier effect of poly-P on the MDF cements and enlarge the validity of this hypothesis to the blends of SAFB clinker, Portland cement and HPMC or poly-P. Compactness of Al(Fe)-O-P cross-links increases the intrinsic density and, consequently, impregnates the system against the uptake of moisture. In a sense of the theory of functional polymers, the intensity of grafting of polymer chains to the surface of grains increases if poly-P is used and with the prolonged processing. The scope of moisture attack on MDF cements synthesized from the blends of SAFB clinker, Portland cement and HPMC or poly-P, as quantified using mass changes as measure of moisture resistance, is strongly affected by the nature of polymer. The addition of Portland cement in the raw mix improves the moisture resistance of MDF cements. Thermal analysis shows: (i) the irreversible mass gain of 3 - 10% is arisen from carbonation and secondary hydration of cement grains and (ii) the Al(Fe)-O-C(P) cross-links remain intact in the moist environment at either ambient or extreme levels of humidity. (orig.)

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

    Directory of Open Access Journals (Sweden)

    Fakhim Babak

    2014-01-01

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

  15. Relationship between chloride diffusivity and pore structure of hardened cement paste

    Institute of Scientific and Technical Information of China (English)

    Guo-wen SUN; Wei SUN; Yun-sheng ZHANG; Zhi-yong LIU

    2011-01-01

    Based on effective media theory, a predictive model, relating chloride diffusivity to the capillary pores, gel pores,tortuosity factor, and pore size distribution of hardened cement, is proposed. To verify the proposed model, the diffusion coefficient of chloride ions, the degree of hydration, and peak radius of capillary pores of cement paste specimens were measured. The predicted results for chloride diffusivity were compared with published data. The results showed that the predicted chloride diffusivity of hardened cement paste was in good agreement with the experimental results. The effect of the evolution of pore structures in cement paste on chloride diffusivity could be deduced simultaneously using the proposed model.

  16. Multi-scale simulation of capillary pores and gel pores in Portland cement paste

    OpenAIRE

    Gao, Peng; YE, guang; Wei, Jiangxiong; Yu, Qijun

    2015-01-01

    The microstructures of Portland cement paste (water to cement ratio is 0.4, curing time is from 1 day to 28 days) are simulated based on the numerical cement hydration model, HUMOSTRUC3D (van Breugel, 1991; Koenders, 1997; Ye, 2003). The nanostructures of inner and outer C-S-H are simulated by the packing of monosized (5 nm) spheres. The pore structures (capillary pores and gel pores) of Portland cement paste are established by upgrading the simulated nanostructures of C-S-H to th...

  17. Experimental Research on Performances of Dry-grinding Fine Cement for Grouting

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The performances of dry-grinding fine cement (DFC) in grouting procedure were experimentally studied.The measurement of its fineness and simulated test for injectability showed that this DFC could be used to inject rock mass with micro-fissure.In order to improve the grouting quality,the water-cement ratio and discarding time of slurry should be controlled precisely.If the water-cement ratio is over 2∶1 in slurry that is made from DFC,it is not suitable to grout.Finally,the influence of different mixing times on strength of hydrated cement made from the DFC is explained by microstructure analysis with SEM.

  18. [Comparison of fixation effects of heavy metals between cement rotary kiln co-processing and cement solidification/stabilization].

    Science.gov (United States)

    Zhang, Jun-li; Liu, Jian-guo; Li, Cheng; Jin, Yi-ying; Nie, Yong-feng

    2008-04-01

    Both cement rotary kiln co-processing hazardous wastes and cement solidification/stabilization could dispose heavy metals by fixation. Different fixation mechanisms lead to different fixation effects. The same amount of heavy metal compounds containing As, Cd, Cr, Cu, Pb, Zn were treated by the two kinds of fixation technologies. GB leaching test, TCLP tests and sequential extraction procedures were employed to compare the fixation effects of two fixation technologies. The leached concentration and chemical species distribution of heavy metals in two grounded mortar samples were analyzed and the fixation effects of two kinds of technologies to different heavy metals were compared. The results show the fixation effect of cement rotary kiln co-processing technology is better than cement solidification/stabilization technology to As, Pb, Zn. Calcinations in cement rotary kiln and then hydration help As, Pb, Zn contained in hazardous wastes transform to more steady chemical species and effectively dispose these heavy metals compounds. Cr3+ is liable to be converted to much more toxic and more mobile Cr6+ state in cement rotary kiln. And so Cr wastes are more fit for treatment by cement solidification/stabilization technology. The work could provide a basis when choosing disposal technologies for different heavy metals and be helpful to improve the application and development of cement rotary kiln co-processing hazardous wastes.

  19. The effect of fly ash and coconut fibre ash as cement replacement materials on cement paste strength

    Science.gov (United States)

    Bayuaji, R.; Kurniawan, R. W.; Yasin, A. K.; Fatoni, H. AT; Lutfi, F. M. A.

    2016-04-01

    Concrete is the backbone material in the construction field. The main concept of the concrete material is composed of a binder and filler. Cement, concrete main binder highlighted by environmentalists as one of the industry are not environmentally friendly because of the burning of cement raw materials in the kiln requires energy up to a temperature of 1450° C and the output air waste CO2. On the other hand, the compound content of cement that can be utilized in innovation is Calcium Hydroxide (CaOH), this compound will react with pozzolan material and produces additional strength and durability of concrete, Calcium Silicate Hydrates (CSH). The objective of this research is to explore coconut fibers ash and fly ash. This material was used as cement replacement materials on cement paste. Experimental method was used in this study. SNI-03-1974-1990 is standard used to clarify the compressive strength of cement paste at the age of 7 days. The result of this study that the optimum composition of coconut fiber ash and fly ash to substitute 30% of cement with 25% and 5% for coconut fibers ash and fly ash with similar strength if to be compared normal cement paste.

  20. Asphalt cement poisoning

    Science.gov (United States)

    ... petroleum material that hardens when it cools. Asphalt cement poisoning occurs when someone swallows asphalt. If hot ... found in: Road paving materials Roofing materials Tile cements Asphalt may also be used for other purposes.

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

    Science.gov (United States)

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

    2012-07-01

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

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Nik Khairul Irfan Bin Nik Ab. Lah.

    2013-05-01

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

  4. The Properties of Cement Mortars Modified by Emulsified Epoxy and Micro-fine Slag

    Institute of Scientific and Technical Information of China (English)

    CHEN You-zhi; WANG Hong-xi; MA Zhi-yong; LI Qing-hua

    2003-01-01

    The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro-fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg-intrusion micromeritics.The experimental results indicate that the series effects of water-reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro-fine slag endowed cement-based materials with perfect performances.The main hydration products in the system are C-S-H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH)2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro-pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.

  5. Galvanic corrosion of Mg-Zr fuel cladding and steel immobilized in Portland cement and geopolymer at early ages

    Science.gov (United States)

    Rooses, Adrien; Lambertin, David; Chartier, David; Frizon, Fabien

    2013-04-01

    Galvanic corrosion behaviour of Mg-Zr alloy fuel cladding and steel has been studied in Ordinary Portland cement and Na-geopolymer. Portland cements implied the worse magnesium corrosion performances due to the negative effects of cement hydrates, grinding agents and gypsum on the galvanic corrosion. Galvanic corrosion in Na-geopolymer paste remains very low. Silicates and fluoride from the geopolymer activation solution significantly improve the corrosion resistance of the magnesium alloy while coupling with a cathode.

  6. Feasibility of using phase change materials to control the heat of hydration in massive concrete structures.

    Science.gov (United States)

    Choi, Won-Chang; Khil, Bae-Soo; Chae, Young-Seok; Liang, Qi-Bo; Yun, Hyun-Do

    2014-01-01

    This paper presents experimental results that can be applied to select a possible phase change material (PCM), such as a latent heat material (LHM), to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests) were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH)2 · 8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  7. Feasibility of using phase change materials to control the heat of hydration in massive concrete structures.

    Science.gov (United States)

    Choi, Won-Chang; Khil, Bae-Soo; Chae, Young-Seok; Liang, Qi-Bo; Yun, Hyun-Do

    2014-01-01

    This paper presents experimental results that can be applied to select a possible phase change material (PCM), such as a latent heat material (LHM), to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests) were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH)2 · 8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete. PMID:25133259

  8. Feasibility of Using Phase Change Materials to Control the Heat of Hydration in Massive Concrete Structures

    Directory of Open Access Journals (Sweden)

    Won-Chang Choi

    2014-01-01

    Full Text Available This paper presents experimental results that can be applied to select a possible phase change material (PCM, such as a latent heat material (LHM, to control the hydration heat in mass concrete structures. Five experimental tests (microconduction, simplified adiabatic temperature rise, heat, and compressive strength tests were conducted to select the most desirable LHM out of seven types of inorganic PCM used in cement mortar and to determine the most suitable mix design. The results of these experimental tests were used to assess the feasibility of using PCM to reduce hydration heat in mass concrete that was examined. The experimental results show that cement mortar containing barium- [Ba(OH2·8H2O] based PCM has the lowest amount of total hydration heat of the cement pastes. The barium-based PCM provides good latent heat properties that help to prevent volume change and microcracks caused by thermal stress in mass concrete.

  9. Gas hydrate nucleation

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-12-31

    The overall aim of the project was to gain more knowledge about the kinetics of gas hydrate formation especially the early growth phase. Knowledge of kinetics of gas hydrate formation is important and measurements of gas hydrate particle size and concentration can contribute to improve this knowledge. An experimental setup for carrying out experimental studies of the nucleation and growth of gas hydrates has been constructed and tested. Multi wavelength extinction (MWE) was the experimental technique selected for obtaining particle diameter and concentration. The principle behind MWE is described as well as turbidity spectrum analysis that in an initial stage of the project was considered as an alternative experimental technique. Details of the experimental setup and its operation are outlined. The measuring cell consists of a 1 litre horizontal tube sustaining pressures up to 200 bar. Laser light for particle size determination can be applied through sapphire windows. A description of the various auxiliary equipment and of another gas hydrate cell used in the study are given. A computer program for simulation and analysis of gas hydrate experiments is based on the gas hydrate kinetics model proposed by Skovborg and Rasmussen (1993). Initial measurements showed that knowledge of the refractive index of gas hydrates was important in order to use MWE. An experimental determination of the refractive index of methane and natural gas hydrate is described. The test experiments performed with MWE on collectives of gas hydrate particles and experiments with ethane, methane and natural gas hydrate are discussed. Gas hydrate particles initially seem to grow mainly in size and at latter stages in number. (EG) EFP-94; 41 refs.

  10. Acrylic Bone Cements Modified with Starch

    OpenAIRE

    Krilova, V; Vītiņš, V

    2010-01-01

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

  11. Preventing Coal and Gas Outburst Using Methane Hydration

    Institute of Scientific and Technical Information of China (English)

    吴强; 何学秋

    2003-01-01

    According to the characteristics of the methane hydrate condensing and accumulating methane, authors put forward a new technique thought way to prevent the accident of coal and gas outburst by urging the methane in the coal seams to form hydrate. The paper analyzes the feasibility of forming the methane hydrate in the coal seam from the several sides, such as, temperature,pressure, and gas components, and the primary trial results indicate the problems should be settled before the industrialization appliance realized.

  12. Osteogenesis Capacity of a Novel BMP/α-TCP Bioactive Composite Bone Cement

    Institute of Scientific and Technical Information of China (English)

    YANG Wei-zhong; ZHOU Da-li; YIN Shao-ya; YIN Guang-fu; GAO Li-da; ZHANG Yun

    2004-01-01

    To improve the osteogenesis ability of α-tricalcium phosphate (α-TCP) bone cement,a novel BMP/α-TCP composite bone cement was prepared.By measuring the setting time and compressive strength,the hydration characteristic of bone cement was evaluated.Animal experiments including histological observation,radiographic investigation as well as digital image analyses reveal the difference of osteogenesis ability among BMP,α-TCP bone cement and BMP/α-TCP composite bone cement.Results show that α-TCP bone cement possesses excellent hydration and setting properties as well as high mechanical property.Comparison experiments show that BMP/α-TCP composite bone cement has a stronger osteogenesis ability.The gross observation of the implant site does not exhibit any inflammation or necrosis.Histological analyses reveal that the material has good osteointegration with host bone,and new bone formation is detected within the materials,which are degrading.Strong osteogenesis ability of the composite is due to not only the excellent osteoconductive potential but also the osteoinductive potential contributed by active BMP releasing and the material degradation.Large skull defect could be well-healed by filling BMP/α-TCP composite bone cement.This novel material proves itself to be an absorbable and bioactive bone cement with an osteogenesis ability.

  13. An effective medium inversion algorithm for gas hydrate quantification and its application to laboratory and borehole measurements of gas hydrate-bearing sediments

    Science.gov (United States)

    Chand, S.; Minshull, T.A.; Priest, J.A.; Best, A.I.; Clayton, C.R.I.; Waite, W.F.

    2006-01-01

    The presence of gas hydrate in marine sediments alters their physical properties. In some circumstances, gas hydrate may cement sediment grains together and dramatically increase the seismic P- and S-wave velocities of the composite medium. Hydrate may also form a load-bearing structure within the sediment microstructure, but with different seismic wave attenuation characteristics, changing the attenuation behaviour of the composite. Here we introduce an inversion algorithm based on effective medium modelling to infer hydrate saturations from velocity and attenuation measurements on hydrate-bearing sediments. The velocity increase is modelled as extra binding developed by gas hydrate that strengthens the sediment microstructure. The attenuation increase is modelled through a difference in fluid flow properties caused by different permeabilities in the sediment and hydrate microstructures. We relate velocity and attenuation increases in hydrate-bearing sediments to their hydrate content, using an effective medium inversion algorithm based on the self-consistent approximation (SCA), differential effective medium (DEM) theory, and Biot and squirt flow mechanisms of fluid flow. The inversion algorithm is able to convert observations in compressional and shear wave velocities and attenuations to hydrate saturation in the sediment pore space. We applied our algorithm to a data set from the Mallik 2L–38 well, Mackenzie delta, Canada, and to data from laboratory measurements on gas-rich and water-saturated sand samples. Predictions using our algorithm match the borehole data and water-saturated laboratory data if the proportion of hydrate contributing to the load-bearing structure increases with hydrate saturation. The predictions match the gas-rich laboratory data if that proportion decreases with hydrate saturation. We attribute this difference to differences in hydrate formation mechanisms between the two environments.

  14. DEVELOPING A NEW GENERATION OF HIGH PERFORMANCE COMPOSITE CEMENT

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper proposed a new generation of high performance composite cement which is designed according to the optimization of composition and structure of cement paste and is manufactured by blending the different components with special composite techniques. Each of these components has its different special property, and should be compatible with each other and match each other, and the properties of them are complementary mutually. At present, such kind of high performance composite cement can be manufactured with high reactivity cement clinker, ground granulated blast-furnace slag, high grade fly ash, silica fume etc.

  15. 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)

  16. Influence of nano-dispersive modified additive on cement activity

    Energy Technology Data Exchange (ETDEWEB)

    Sazonova, Natalya, E-mail: n.a.sazonova@mail.ru; Badenikov, Artem, E-mail: rector@agta.ru; Ivanova, Elizaveta, E-mail: lisik-iva@mail.ru [Angarsk State Technical University, 60, Tchaykovsky St., 665835, Angarsk (Russian Federation); Skripnikova, Nelli, E-mail: nks2003@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation)

    2016-01-15

    In the work the influence of single-walled carbon nanotubes (SWCNT) on the cement activity and the processes of structure formation of the hardened cement paste in different periods of hydration are studied. The changes in the kinetic curves of the sample strength growth modified with SWCNT in amount of 0.01 and 0.0005 % are stipulated by the results of differential scanning colorimetry, scanning electronic and ionic microscopy, X-ray-phase analysis. It was found that the nano-modified additive may increase in the axis compressive strength of the system by 1.4–6.3 fold relatively to the reference samples and may reach 179.6 MPa. It may intensify the hydration process of calcium silicates as well as influence on the matrix of hardened cement paste. The studies are conducted on the structural changes in the hardened cement paste, the time periods of increase and decrease of the compressive strength of the samples, the amount of the calcium hydroxide and tobermorite-like gel as well as the degree of hydration C{sub 3}S and β-C{sub 2}S.

  17. Influence of nano-dispersive modified additive on cement activity

    Science.gov (United States)

    Sazonova, Natalya; Badenikov, Artem; Skripnikova, Nelli; Ivanova, Elizaveta

    2016-01-01

    In the work the influence of single-walled carbon nanotubes (SWCNT) on the cement activity and the processes of structure formation of the hardened cement paste in different periods of hydration are studied. The changes in the kinetic curves of the sample strength growth modified with SWCNT in amount of 0.01 and 0.0005 % are stipulated by the results of differential scanning colorimetry, scanning electronic and ionic microscopy, X-ray-phase analysis. It was found that the nano-modified additive may increase in the axis compressive strength of the system by 1.4-6.3 fold relatively to the reference samples and may reach 179.6 MPa. It may intensify the hydration process of calcium silicates as well as influence on the matrix of hardened cement paste. The studies are conducted on the structural changes in the hardened cement paste, the time periods of increase and decrease of the compressive strength of the samples, the amount of the calcium hydroxide and tobermorite-like gel as well as the degree of hydration C3S and β-C2S.

  18. METHANE HYDRATE PRODUCTION FROM ALASKAN PERMAFROST

    Energy Technology Data Exchange (ETDEWEB)

    Richard Sigal; Kent Newsham; Thomas Williams; Barry Freifeld; Timothy Kneafsey; Carl Sondergeld; Shandra Rai; Jonathan Kwan; Stephen Kirby; Robert Kleinberg; Doug Griffin

    2005-02-01

    part of the Ugnu and throughout the West Sak. No hydrate-bearing zones were identified either in recovered core or on well logs. The base of the permafrost was found at about 1260 ft. With the exception of the deepest sands in the West Sak and some anomalous thin, tight zones, all sands recovered (after thawing) are unconsolidated with high porosity and high permeability. At 800 psi, Ugnu sands have an average porosity of 39.3% and geometrical mean permeability of 3.7 Darcys. Average grain density is 2.64 g/cc. West Sak sands have an average porosity of 35.5%, geometrical mean permeability of 0.3 Darcys, and average grain density of 2.70 g/cc. There were several 1-2 ft intervals of carbonate-cemented sandstone recovered from the West Sak. These intervals have porosities of only a few percent and very low permeability. On a well log they appear as resistive with a high sonic velocity. In shallow sections of other wells these usually are the only logs available. Given the presence of gas in Hot Ice No. 1, if only resistivity and sonic logs and a mud log had been available, tight sand zones may have been interpreted as containing hydrates. Although this finding does not imply that all previously mapped hydrate zones are merely tight sands, it does add a note of caution to the practice of interpreting the presence of hydrates from old well information. The methane hydrate stability zone below the Hot Ice No. 1 location includes thick sections of sandstone and conglomerate which would make excellent reservoir rocks for hydrates and below the permafrost zone shallow gas. The Ugnu formation comprises a more sand-rich section than does the West Sak formation, and the Ugnu sands when cleaned and dried are slightly more porous and significantly more permeable than the West Sak.

  19. 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.

  20. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job

  1. Hydrothermal Characteristics of Blended Cement Pastes Containing Silica Sand Using Cement Kiln Dust as an Activator

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The hydrothermal reactivity of silica sand was studied using cement kiln dust (CKD) as an activator in addition to the Portlandcement fraction of El-Karnak cement (a blend of ordinary Portland cement and ground sand). Autoclaved El-Karnak cementpastes were studied at pressures of 0.507, 1.013 and 1.520 MPa of saturated steam with respect to their compressive strength,kinetics of hydrothermal reaction and the phase composition of the formed hydrates. The role of CKD in affecting thephysicochemical and mechanical properties of El-Karnak cement pastes was studied by autoclaving of several pastes containing5, 7.5, 10 and 20% CKD at a pressure of 1.013 MPa of saturated steam. CKD was added either as a raw CKD (unwashed) orafter washing with water (washed CKD). The results of these physicochemical studies obtained could be related as much aspossible to the role of CKD (raw or washed) in affecting the hydrothermal reactivity of silica sand in El-Karnak cement pastes.

  2. Kinetics of strength gain of biocidal cements

    Directory of Open Access Journals (Sweden)

    Rodin Aleksandr Ivanovich

    Full Text Available Biocorrosion becomes the determinative durability factor of buildings and constructions. Damages of construction materials caused by bacteria, filamentous fungi, actinomycetes constitute a serious danger to the constructions of a building or a structure and to the health of people. Biodeteriorations are typical both in old and new constructions. A great quantity of destruction factors of industrial and residential buildings under the influence of microorganisms was established in practice. Providing products and constructions based on concretes fungicidal and bactericidal properties is an important direction of modern construction material science. The most efficient way to solve this task is creation of biocidal cements. The article presents the results of experimental studies of kinetic dependences of strength gain by biocidal cements by physico-mechanical and physico-chemical analysis methods. The identical velocity character of initial hydration of the developed compositions of biocidal cements is set, as well as a more calm behavior of hardening processes at later terms. It has been established that the compositions of biocidal cements modified by sodium sulfate and sodium fluoride possess the greatest strength.

  3. Study of transformations of hydrated high alumina cement by means of ray diffraction, infrared spectroscopy and thermal analysis. Influence of carbon anhydride, temperature, humidity and the addition of powdered limestone (continuation

    Directory of Open Access Journals (Sweden)

    Vázquez, T.

    1975-09-01

    Full Text Available Not availableLa espectroscopia de absorción I.R. (designada al principio de este trabajo con las siglas E.I. es una técnica de amplia utilización dentro de la Química Orgánica. Tan sólo en los últimos años se ha extendido mucho a la Química Inorgánica. Dentro del campo del cemento y más particularmente del aluminoso, el estudio ha sido realmente restringido. El primer trabajo aparecido fue en el año 1965 y efectuado por A. Braniski (29 que estudió por I.R. la hidratación del AC entre las edades de 1 y 7 días. Mucho más estudiadas han sido las fases individuales, los aluminatos de calcio que componen (o pueden componer el producto anhidro e hidratado del cemento aluminoso; como trabajo de interés en este aspecto, está la Tesis Doctoral de J. Volant (31, que versó sobre la espectrometría infrarroja de los aluminatos de calcio hidratados. El autor, como técnica de preparación de muestras, utiliza la suspensión del producto en un líquido oleaginoso apropiado. En el presente trabajo se ha escogido la técnica de las "pastillas de BrK" como idónea para la conservación de la muestra y la posibilidad, por lo tanto, de repetición del espectro en un futuro. Asimismo facilita el análisis cuantitativo.

  4. Cement and Concrete Nanoscience and Nanotechnology

    Directory of Open Access Journals (Sweden)

    Taijiro Sato

    2010-02-01

    Full Text Available Concrete science is a multidisciplinary area of research where nanotechnology potentially offers the opportunity to enhance the understanding of concrete behavior, to engineer its properties and to lower production and ecological cost of construction materials. Recent work at the National Research Council Canada in the area of concrete materials research has shown the potential of improving concrete properties by modifying the structure of cement hydrates, addition of nanoparticles and nanotubes and controlling the delivery of admixtures. This article will focus on a review of these innovative achievements.

  5. Hydration Assessment of Athletes

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ KEY POINTS · Although there is no scientific consensus for 1 ) howbest to assess the hydration status of athletes, 2)what criteria to use as acceptable outcome measurements, or 3) the best time to apply practical assessment methods, there are methods that can be used toprovide athletes with useful feedback about their hydration status

  6. Authigenic gypsum found in gas hydrate-associated sediments from Hydrate Ridge, the eastern North Pacific

    Institute of Scientific and Technical Information of China (English)

    WANG Jiasheng; Erwin Suess; Dirk Rickert

    2004-01-01

    Characteristic gypsum micro-sphere and granular mass were discovered by binocular microscope in the gas hydrate-associated sediments at cores SO143-221 and SO143/TVG40-2A respectively on Hydrate Ridge of Cascadia margin, the eastern North Pacific. XRD patterns and EPA analyses show both micro-sphere and granular mass of the crystals have the typical peaks and the typical main chemical compositions of gypsum, although their weight percents are slightly less than the others in the non-gas hydrate-associated marine regions. SEM pictures show that the gypsum crystals have clear crystal boundaries, planes, edges and cleavages of gypsum in form either of single crystal or of twin crystals. In view of the fact that there are meanwhile gas hydrate-associated authigenic carbonates and SO42(-rich pore water in the same sediment cores, it could be inferred reasonably that the gypsums formed also authigenically in the gas hydrate-associated environment too, most probably at the interface between the downward advecting sulfate-rich seawater and the below gas hydrate, which spilled calcium during its formation on Hydrate Ridge. The two distinct forms of crystal intergrowth, which are the granular mass of series single gypsum crystals at core SO143/TVG40-2A and the microsphere of gypsum crystals accompanied with detrital components at core SO143-221 respectively, indicate that they precipitated most likely in different interstitial water dynamic environments. So, the distinct authigenic gypsums found in gas hydrate-associated sediments on Hydrate Ridge could also be believed as one of the parameters which could be used to indicate the presence of gas hydrate in an unknown marine sediment cores.

  7. PURIFIED WASTE FCC CATALYST AS A CEMENT REPLACEMENT MATERIAL

    Directory of Open Access Journals (Sweden)

    Danute Vaiciukyniene

    2015-06-01

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

  8. Applicability of the Waste Fibres in Cement Paste

    Directory of Open Access Journals (Sweden)

    Regina KALPOKAITĖ DIČKUVIENĖ

    2013-09-01

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

  9. Role of different superplasticizers on hydrated lime pastes and mortars

    OpenAIRE

    Alvarez, J. I.; Fernandez, J M; Sirera, R. (Rafael); Perez-Nicolas, M. (María); Navarro-Blasco, I. (Íñigo); Duran, A

    2015-01-01

    The behaviour of different superplasticizers admixtures was assessed for hydrated lime pastes and mortars. Sometimes, air lime pastes and mortars were modified with two supplementary cementing materials (SCMs), namely nanosilica (NS) and metakaolin (MK). Two different polycarboxylate ethers, a lignosulfonate and a naphthalene condensed sulfonate superplasticizer were added to lime pastes and mortars and their effects on fresh-state properties as well as on the mechanical strengths were evalua...

  10. Monitoring of sulphate attack on hardened cement paste studied by synchrotron XRD

    Science.gov (United States)

    Stroh, J.; Meng, B.; Emmerling, F.

    2015-10-01

    The complex matter of external sulphate attack on cement-based construction materials is still not completely understood. The concentration of sulphate is a crucial factor for the formation of secondary phases and phase transitions of cement hydrates due to sulphate ingress into the microstructure. The sulphate attack on building materials for high and low sulphate concentrations was monitored by laboratory experiments. Hardened cement paste consisting of ordinary Portland cement (CEM I) were exposed to aqueous solutions of sodium sulphate for 18 months. Three sample compositions were used for this research, including different supplementary cementitious materials (SCM). The phase composition was determined for different time spans by high resolution synchrotron X-ray diffraction. Cross sections of exposed cement prisms were investigated as a representation of the microstructural profile. Based on the data, a temporal and spatial determination of the stages of the sulphate attack and the deterioration course was possible. Cement matrices blended with slag showed the highest resistance against sulphate attack.

  11. Stabilization of chromium salt in ordinary portland cement

    Indian Academy of Sciences (India)

    Damir Barbir; Pero Dabić; Petar Krolo

    2012-12-01

    Ordinary Portland cement (OPC) samples containing the chromium salt have been investigated using differential microcalorimetry, conductometry and Fourier transform infrared spectroscopic analysis. The effect of chromium on OPC hydration was evaluated by continuous observing of early hydration. The microcalorimetrical results show that with increasing the share of chromium salt, heat maximums assume lower values and the occurrence of the maximum registered in the earlier hydration times. Conductometrical measurements show that with increasing addition of chromium salt, curve did not show any specific shape, immediate drop in specific conductivity is noticed and the maximum is reached earlier. This coincides with microcalorimetrical results. It can be concluded that the addition of chromium does not affect the mechanism of the hydration process, but it does affect the kinetic parameters and dynamics of the cement hydration process. It was found that chromium salt addition to the cement–water system is acceptable up to 2 wt.%. According to standard EN 196-3 for OPC, the beginning of binding time should occur after 60 minutes. Increased amount of chromium over 2 wt.% significantly accelerate the beginning of binding time and for the system it is not acceptable.

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

    Institute of Scientific and Technical Information of China (English)

    HOU Haobo; HE Xinghua; ZHU Shujing; ZHANG Dajie

    2006-01-01

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

  13. Treatment and recycling of asbestos-cement containing waste.

    Science.gov (United States)

    Colangelo, F; Cioffi, R; Lavorgna, M; Verdolotti, L; De Stefano, L

    2011-11-15

    The remediation of industrial buildings covered with asbestos-cement roofs is one of the most important issues in asbestos risk management. The relevant Italian Directives call for the above waste to be treated prior to disposal on landfill. Processes able to eliminate the hazard of these wastes are very attractive because the treated products can be recycled as mineral components in building materials. In this work, asbestos-cement waste is milled by means of a high energy ring mill for up to 4h. The very fine powders obtained at all milling times are characterized to check the mineralogical and morphological transformation of the asbestos phases. Specifically, after 120 min of milling, the disappearance of the chrysotile OH stretching modes at 3690 cm(-1), of the main crystalline chrysotile peaks and of the fibrous phase are detected by means of infrared spectroscopy and X-ray diffraction and scanning electron microscopy analyses, respectively. The hydraulic behavior of the milled powders in presence of lime is also tested at different times. The results of thermal analyses show that the endothermic effects associated to the neo-formed binding phases significantly increase with curing time. Furthermore, the technological efficacy of the recycling process is evaluated by preparing and testing hydraulic lime and milled powder-based mortars. The complete test set gives good results in terms of the hydration kinetics and mechanical properties of the building materials studied. In fact, values of reacted lime around 40% and values of compressive strength in the range of 2.17 and 2.29 MPa, are measured. PMID:21924550

  14. ULTRA-LIGHTWEIGHT CEMENT

    International Nuclear Information System (INIS)

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

  15. Exploitation of subsea gas hydrate reservoirs

    Science.gov (United States)

    Janicki, Georg; Schlüter, Stefan; Hennig, Torsten; Deerberg, Görge

    2016-04-01

    Natural gas hydrates are considered to be a potential energy resource in the future. They occur in permafrost areas as well as in subsea sediments and are stable at high pressure and low temperature conditions. According to estimations the amount of carbon bonded in natural gas hydrates worldwide is two times larger than in all known conventional fossil fuels. Besides technical challenges that have to be overcome climate and safety issues have to be considered before a commercial exploitation of such unconventional reservoirs. The potential of producing natural gas from subsea gas hydrate deposits by various means (e.g. depressurization and/or injection of carbon dioxide) is numerically studied in the frame of the German research project »SUGAR«. The basic mechanisms of gas hydrate formation/dissociation and heat and mass transport in porous media are considered and implemented into a numerical model. The physics of the process leads to strong non-linear couplings between hydraulic fluid flow, hydrate dissociation and formation, hydraulic properties of the sediment, partial pressures and seawater solution of components and the thermal budget of the system described by the heat equation. This paper is intended to provide an overview of the recent development regarding the production of natural gas from subsea gas hydrate reservoirs. It aims at giving a broad insight into natural gas hydrates and covering relevant aspects of the exploitation process. It is focused on the thermodynamic principles and technological approaches for the exploitation. The effects occurring during natural gas production within hydrate filled sediment layers are identified and discussed by means of numerical simulation results. The behaviour of relevant process parameters such as pressure, temperature and phase saturations is described and compared for different strategies. The simulations are complemented by calculations for different safety relevant problems.

  16. Evaluation of Type I cement sorbent slurries in the U.C. pilot spray dryer facility. Final report, November 1, 1994--February 28, 1996

    Energy Technology Data Exchange (ETDEWEB)

    Keener, T.C.; Khang, S.J.

    1996-07-31

    This research was focused on evaluating hydrated cement sorbents in the U. C. pilot spray dryer. The main goal of this work was to determine the hydration conditions resulting in reactive hydrated cement sorbents. Hydration of cement was achieved by stirring or by grinding in a ball mill at either room temperature or elevated temperatures. Also, the effects of several additives were studied. Additives investigated include calcium chloride, natural diatomite, calcined diatomaceous earth, and fumed silica. The performance of these sorbents was compared with conventional slaked lime. Further, the specific surface area and pore volume of the dried SDA sorbents were measured and compared to reactivity. Bench-scale tests were performed to obtain a more detailed picture of the development of the aforementioned physical properties as a function of hydration time.

  17. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

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

    International Nuclear Information System (INIS)

    The early age hydration by borate solution of 3 calcium sulfo-aluminate cements (CSA), containing respectively 0%, 10% and 20% of gypsum by weight of cement was studied using isothermal calorimetry and dynamic mode rheo-metry. XRD and TGA analysis were carried out on pastes with increasing hydration degrees (up to 90 days) to specify the mineralogy and to figure out the mechanisms of borate immobilisation. It has been shown that the retarding effect of borate anions is due to the precipitation of the amorphous calcium borate C2B3H8; borate anions were then incorporated in Aft-type phases. The macroscopic properties of hydrated binders (compressive strength, length change) were also followed during 180 days. It appears that the mechanical strength continuously increases with the hydration degree. Length changes under wet-curing and sealed bag remain moderate and seem to be stabilized after 180 days

  19. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    Energy Technology Data Exchange (ETDEWEB)

    Steshenko, Aleksei, E-mail: steshenko.alexey@gmail.com; Kudyakov, Aleksander; Konusheva, Viktoriya [Tomsk State University of Architecture and Building, 2 Solyanaya Sq., Tomsk, 634003 (Russian Federation)

    2016-01-15

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  20. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    Science.gov (United States)

    Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya

    2016-01-01

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  1. Electrical properties of methane hydrate + sediment mixtures: The σ of CH4 Hydrate + Sediment

    Energy Technology Data Exchange (ETDEWEB)

    Du Frane, Wyatt L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Stern, Laura A. [U. S. Geological Survey, Menlo Park, CA (United States); Constable, Steven [Scripps Institution of Oceanography, La Jolla, CA (United States); Weitemeyer, Karen A. [Scripps Institution of Oceanography, La Jolla, CA (United States); National Oceanography Centre Southampton (United Kingdom), Univ. of Southampton Waterfront Campus, Southampton (United Kingdom); Smith, Megan M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, Jeffery J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-30

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  2. Cement content influence in rebar corrosion in carbonated mortars

    Directory of Open Access Journals (Sweden)

    Américo, P. O.

    2003-12-01

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

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

  3. Hydraulic Conductivity of Residual Soil-Cement Mix

    Science.gov (United States)

    Govindasamy, P.; Taha, M. R.

    2016-07-01

    In Malaysia, although there are several researches on engineering properties of residual soils, however study on the hydraulic conductivity properties of metasedimentary residual soils is still lacking. Construction of containment walls like slurry wall techniques can be achieved with hydraulic conductivity of approximately 5 x 10-7cm/sec. The objectives of the study were to determine the physical properties of metasedimentary residual soils and to determine the influence of 1%, 3%, 5% and 10% of cement on hydraulic conductivity parameters. The coefficient of hydraulic conductivity of the soil naturally and soil-cement mixtures were determined by using the falling head test. According to the test, the hydraulic conductivity of the original soil was 4.16 x 10-8 m/s. The value decreases to 3.89 x 10-8 m/s, 2.78 x 10-8 m/s then 6.83 x 10-9 m/s with the addition of 1%, 3% and 5% of cement additives, respectively. During the hydration process, cement hydrates is formed followed by the increase in pH value and Ca(OH)2 which will alter the modification of pores size and distribution. When the quantity of cement increases, the pores size decrease. But, the addition of 10% cement gives an increased hydraulic conductivity value to 2.78 x 10-8 m/s. With 10%, the pore size increase might due to flocculation and agglomeration reaction. The generated hydraulic conductivity values will indirectly become a guide in the preliminary soil cement stabilization to modify the properties of the soil to become more like the properties of a soft rock.1. Introduction

  4. Preferential adsorption of polycarboxylate superplasticizers on cement and silica fume in ultra-high performance concrete (UHPC)

    Energy Technology Data Exchange (ETDEWEB)

    Schroefl, Ch.; Gruber, M.; Plank, J., E-mail: sekretariat@bauchemie.ch.tum.de

    2012-11-15

    UHPC is fluidized particularly well when a blend of MPEG- and APEG-type PCEs is applied. Here, the mechanism for this behavior was investigated. Testing individual cement and micro silica pastes revealed that the MPEG-PCE disperses cement better than silica whereas the APEG-PCE fluidizes silica particularly well. This behavior is explained by preferential adsorption of APEG-PCE on silica while MPEG-PCEs exhibit a more balanced affinity to both cement and silica. Adsorption data obtained from individual cement and micro silica pastes were compared with those found for the fully formulated UHPC containing a cement/silica blend. In the UHPC formulation, both PCEs still exhibit preferential and selective adsorption similar as was observed for individual cement and silica pastes. Preferential adsorption of PCEs is explained by their different stereochemistry whereby the carboxylate groups have to match with the steric position of calcium ions/atoms situated at the surfaces of cement hydrates or silica.

  5. Compatibility of Pretreated Coir Fibres (Cocos nucifera L.) with Portland Cement to Produce Mineral Composites

    OpenAIRE

    Ferraz, Joana M.; Cláudio H. S. Del Menezzi; Mario R. Souza; Okino, Esmeralda Y. A.; Martins, Sabrina A.

    2012-01-01

    The objectives of the present work were to evaluate the chemical compatibility between coir (Cocos nucifera L.) and cement and to study treatment methods to improve this compatibility. In the inhibition test, cement hydration temperature evolution was measured in the absence and presence of untreated and treated coir fibres (cold water, hot water and NaOH), besides the addition of 4% of CaCl2. The chemical characterization of untreated and treated coir fibres was done by determining the conte...

  6. On the effect of mixing on property development of cement pastes

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Bøhm, Anja; Kjeldsen, Ane Mette

    2006-01-01

    The method of mixing may affect the degree of agglomeration of particles in cement-based materials and thus the properties of the materials in their fresh, hardening, and hardened state. Paste (w/c=0.35) of white Portland cement with and without 10% silica fume and 0.65% superplasticizer were mixed...... was observed. The effect of mixing on development of hydration was not reflected in the resistance to migration of chloride ions in 28 days old samples....

  7. The interaction between nuclear waste glass and cement

    International Nuclear Information System (INIS)

    The interaction between simulated reference waste glasses SON68 and SM539 and cement has been studied in suspensions of Ordinary Portland Cement and synthetic young cement water with pH 13.5 at 30 C. The cement appears to trigger glass dissolution by consumption of glass matrix components. This leads to fast glass dissolution at a constant rate with formation of a porous gel layer on the glass. This is probably due mostly to the reaction of Si from the glass with portlandite, forming CSH phases. After consumption of the portlandite, the glass alteration rate is expected to decrease. (authors)

  8. The lithification of ultramafic dominated till with magnesium silicate hydrate: a new green concrete

    Science.gov (United States)

    de Ruiter, Lisa; Olav Austrheim, Håkon; Hu, Depan; Dysthe, Dag Kristian; Ulven, Ole Ivar

    2016-04-01

    The Feragen Ultramafic Body located near the town of Røros in Eastern Norway gives rise to a unique phenomenon: A lithification process involving natural cement of magnesium silicate hydrate (M-S-H). The ultramafic body is covered with moraine deposits that form tills throughout the area. The tills consist mainly of variably serpentinized ultramafic rock fragments, with additional quartz and feldspar grains transported to the area with the glaciers that formed the till. This provides the exceptional combination of ultramafic and Si-rich rocks. Throughout the area, multiple spots can be found where natural cement has resulted in the lithification of the till, forming tillite. This mainly occurs close to mine tailings of ancient chromium mines, as the mine tunnels provide air flow that increases the evaporation and thus the precipitation of the cement. The Weichselian glaciation constrains the age of the moraines to less than 10 ka and the formation of the concrete related to mine tailings suggests that the lithification took place after the termination of the mining activity in 1927. Thus, the cement is formed in-situ at its current location, indicating that it forms in a subarctic climate. EMP and SEM analysis indicate that the cement is a hydrated magnesium silicate phase, cementing together quartz, feldspar and serpentine grains to form a natural concrete. The cement consist of 31 wt% of MgO and 49 wt% of SiO2. Quartz and feldspar grains are partly dissolved in the concrete while the resulting pore space is filled with cement, indicating that the Si in the cement originated from the quartz and feldspar phases. Weathering of the ultramafic body involves the dissolution of brucite to create a high pH, Mg-rich fluid, which subsequently can dissolve the quartz and be the source for the M-S-H cement. A dissolution-precipitation process involving the dissolution of both brucite and quartz thus results in the formation of the cement. Future TEM analysis should give

  9. Synthesis and characterization of cement slurries additives with epoxy resins - kinetics, thermodynamic and calorimetric analysis

    International Nuclear Information System (INIS)

    Cement has been used in the world, presenting a wide versatility. However, due to its chemical nature, it is subject to several types of chemical damages, especially for agents of acidic nature. With the purpose of increase its life-time, new cement slurries have been modified with the addition of specific additives. The objective of this work is to modify cement slurries with epoxy resins, which promote higher resistance of those materials in relation to acid attacks. Three cement slurries were synthesized with epoxy resins and a standard slurries, which was composed by cement and water. After 30 days of hydration, the samples were characterized by XDR, FTIR and thermal analysis (TG and DSC). The hydration processes of the cement slurries were studied by heat-conduction microcalorimetry. A kinetic study of HCl interaction with the new slurries were performed by the batch methodology at 25, 35, 45 e 55 deg C. It was verified that the addition of the polymers delayed the processes of hydration of the slurries, decreasing the flow of heat released as a function of the amount of added resin and, increased the resistance of those slurries to the acid attack. (author)

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

    Institute of Scientific and Technical Information of China (English)

    LIN Zongshou; ZHAO Qian

    2009-01-01

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

  11. Withdrawing Nutrition, Hydration

    Science.gov (United States)

    Module eleven of the EPEC-O Self-Study Original Version discusses the general aspects of withholding or withdrawing of life-sustaining therapies, and presents a specific application to artificial nutrition and hydration.

  12. Hydrate morphology: Physical properties of sands with patchy hydrate saturation

    Science.gov (United States)

    Dai, S.; Santamarina, J.C.; Waite, William F.; Kneafsey, T.J.

    2012-01-01

    The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

  13. High-temperature cementing materials for completion of geothermal wells. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kalyoncu, R.S.; Snyder, M.J.

    1981-05-01

    Several portland cement types, oil well cements, and various additives and admixtures were evaluated during the course of development of a number of promising compositions suitable for geothermal applications. Among the cements and various materials considered were portland cement Types I, III, and V; oil well cement Classes G, H, and J; and additives such as silica flour, blast furnace slags, pozzolan, hydrated lime, perlite, and aluminum phosphate. Properties of interest in the study were thickening time, compressive strength, cement-to-metal bond strength, and effects of the cements on the corrosion of steel well casings. Testing procedures and property data obtained on a number of compositions are presented and discussed. Several cementing compositions comprised of Class J oil well cement, pozzolan, blast furnace slags, and silica flour were found to possess properties which appear to make them suitable for use in geothermal well completions. Five of the promising cementing compositions have been submitted to the National Bureau of Standards for additional testing.

  14. Spent FCC catalyst for improving early strength Portland cement

    OpenAIRE

    Borrachero Rosado, María Victoria; Monzó Balbuena, José Mª; Paya Bernabeu, Jorge Juan; Vunda, Christian; VELÁZQUEZ RODRÍGUEZ, SERGIO; Soriano Martinez, Lourdes

    2014-01-01

    Spent fluid catalytic cracking (FCC) catalyst from the petrol industry has proven to be a very active pozzolanic material. This behavior leads to an additional increase in the strength of the mortar that contains this catalyst. Pozzolanic effects tend to be considered for periods above three days, whereas in shorter times, the influence of pozzolan is usually negligible. The reactivity of FCC is so high, however, that both pozzolanic effects and acceleration of cement hydration are evident in...

  15. Impact of Compound Hydrate Dynamics on Phase Boundary Changes

    Science.gov (United States)

    Osegovic, J. P.; Max, M. D.

    2006-12-01

    systems include pipeline blockages and natural hydrate concentrations associated with upwelling fluids in marine sediments. 3) In open systems, mass can either flow into or out of a system. In such situations compound hydrate will form or decompose to re-establish chemical equilibrium. This is accomplished by 1) loading/consuming a preferred hydrate former to/from the surroundings, 2) lowering/raising the temperature of the system, and 3) increasing the local pressure. Examples of this type of system include hydrate produced for low pressure transport, depressurized or superheated hydrate settings (pipeline remediation or energy recovery), or in an industrial process where formation of compound hydrates may be used to separate and concentrate gases from a mixture. The relationship between composition and the phase boundary is as important as pressure and temperature effects. Composition is less significant for simple hydrates where the hydrate behaves as a one-component mineral, but for compound hydrate, feedback between pressure, temperature, and composition can result in complex system behavior.

  16. A Study of Metal-Cement Composites with Additives

    Directory of Open Access Journals (Sweden)

    Mironov Victor

    2014-12-01

    Full Text Available The application of small-sized metal fillers (SMF provides a combination of high bulk density, increased durability and ferromagnetic properties of composite materials on the cement basis. However, the total strength of the composite can be compromised by poor adhesion of metal particles with the cement matrix. The use of versatile additives like microsilica and metakaolin is able to improve the structural integrity and mechanical properties of heavy concretes. The paper considers the results of a study using specimens of heavy concretes with SMF aiming to estimate its strength, structural features and ultrasonic parameters. It was found that the contact of SMF particles with the cement was not perfect, since the voids appeared between them and the cement matrix during the cement hydration process (exothermal reaction. Due to the border porosity, the specimens with the metal fillers have lower compressive strength, lower ultrasound velocity and increased frequency slope of attenuation. Microsilica and metakaolin additives facilitate better contact zone between the cement matrix and metal fillers.

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

    Institute of Scientific and Technical Information of China (English)

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

    2003-01-01

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

  18. Tympanoplasty with ionomeric cement

    DEFF Research Database (Denmark)

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

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

  19. Study on molasses in retarding and water reducing properties of cement pastes%甘蔗糖蜜对水泥缓凝和减水的性能研究

    Institute of Scientific and Technical Information of China (English)

    刘金芝; 冉千平; 张建纲; 江姜

    2012-01-01

    Molasses is not only retarding but also water reducing on cement paste. Colloidal component and Non -colloidal component of molasses were separated by alcohol coagulation method. This paper explains the reasons of property of retardation and water reduction of molasses on cement paste by way of cement hydration heat, surface tension and adsorption performance. All studies show that colloidal component Qf molasses is mainly for dispersion and that Non-colloidal component is mainly for retardation.%甘蔗废糖蜜对水泥同时具有缓凝和减水作用.采用酒精凝聚法分离废糖蜜得到胶体和非胶体组份:从水泥水化热、表面张力以及吸附性能阐述了其对水泥减水和缓凝的原因.结果表明,糖蜜中的胶体组份主要起分散作用,而非胶体组份主要起缓凝作用.

  20. 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.

  1. Mechanism of Calcined Phosphogypsum for the Volume Change of Blended Cement

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The paper describes an investigation into the volume change of cement mortar specimen at the three kinds of different curing schedules including 20℃ and 5% Na2SO4 solution curing, tap water standard curing, 50% RH curing for 90 days. The testing results of hydration heat, chemical shrinking and XRD prove that calcined phosphogypsum has evident excitation effect on the activity of high calcium ash and steel slag. Simultaneously, calcined phosphogypsum has the function of decreasing volume shrinkage to blended cement possessing steel slag and high calcium ash. In sulfate curing, calcined phosphogypsum can avoid the phenomenon of protrude apex of the blended cement.

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

    International Nuclear Information System (INIS)

    The potential of calcium sulfoaluminate (CSA) cement was investigated to solidify and stabilize radwastes containing large amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration). Hydration of pastes and mortars prepared with a 0.5 mol/L ZnCl2 mixing solution was characterized over one year as a function of the gypsum content of the binder and the thermal history of the material. Blending the CSA clinker with 20% gypsum enabled rapid hydration, with only very small delay compared with a reference prepared with pure water. It also improved the compressive strength of the hardened material and significantly reduced its expansion under wet curing. Moreover, the hydrate assemblage was less affected by a thermal treatment at early age simulating the temperature rise and fall occurring in a large-volume drum of cemented waste. Fully hydrated materials contained ettringite, amorphous aluminum hydroxide, straetlingite, together with AFm phases (Kuzel's salt associated with monosulfoaluminate or Friedel's salt depending on the gypsum content of the binder), and possibly C-(A)-S-H. Zinc was readily insolubilized and could not be detected in the pore solution extracted from cement pastes, or in their leachates after 3 months of leaching by pure water at pH 7. The good retention of zinc by the cement matrix was mainly attributed to the precipitation of a hydrated and well crystallized phase with platelet morphology (which may belong to the layered double hydroxides family) at early age ≤ 1 day), and to chemisorption onto aluminum hydroxide at later age. (author)

  3. SETTING AND HARDENING OF AGRO/CEMENT COMPOSITES

    Directory of Open Access Journals (Sweden)

    Amal Hanafy Abdel-Kader

    2010-02-01

    Full Text Available In this study, the use of bagasse fiber (BF and unbleached bagasse pulp (BP in a cement matrix, as a raw material, to produce lightweight construction materials is reported. The bagasse was used as partial replacement of cement at different levels: 0% (control cement, 1%, 2% 3%, and 4% by weight. The average size of bagasse fibers was less than 2 mm. Although a reduction in the physical and mechanical strength was observed, the incorporation of either fiber or pulp increased the water of consistency and setting time. A composite containing 4% of bagasse fibers can be used for lightweight concrete. FT-IR spectra showed that the BF or BP adversely affect the rate of calcium silicate hydrate (CSH formation by decreasing its promotion.

  4. Study on Utilization of Carboxyl Group Decorated Carbon Nanotubes and Carbonation Reaction for Improving Strengths and Microstructures of Cement Paste

    Directory of Open Access Journals (Sweden)

    Xiantong Yan

    2016-08-01

    Full Text Available Carbon nanotubes (CNTs have excellent mechanical properties and can be used to reinforce cement-based materials. On the other hand, the reaction product of carbonation with hydroxides in hydrated cement paste can reduce the porosity of cement-based materials. In this study, a novel method to improve the strength of cement paste was developed through a synergy of carbon nanotubes decorated with carboxyl group and carbonation reactions. The experimental results showed that the carboxyl group (–COOH of decorated carbon nanotubes and the surfactant can control the morphology of the calcium carbonate crystal of carbonation products in hydrated cement paste. The spindle-like calcium carbonate crystals showed great morphological differences from those observed in the conventional carbonation of cement paste. The spindle-like calcium carbonate crystals can serve as fiber-like reinforcements to reinforce the cement paste. By the synergy of the carbon nanotubes and carbonation reactions, the compressive and flexural strengths of cement paste were significantly improved and increased by 14% and 55%, respectively, when compared to those of plain cement paste.

  5. Effect of metakaolin on strength and efflorescence quantity of cement-based composites.

    Science.gov (United States)

    Weng, Tsai-Lung; Lin, Wei-Ting; Cheng, An

    2013-01-01

    This study investigated the basic mechanical and microscopic properties of cement produced with metakaolin and quantified the production of residual white efflorescence. Cement mortar was produced at various replacement ratios of metakaolin (0, 5, 10, 15, 20, and 25% by weight of cement) and exposed to various environments. Compressive strength and efflorescence quantify (using Matrix Laboratory image analysis and the curettage method), scanning electron microscopy, and X-ray diffraction analysis were reported in this study. Specimens with metakaolin as a replacement for Portland cement present higher compressive strength and greater resistance to efflorescence; however, the addition of more than 20% metakaolin has a detrimental effect on strength and efflorescence. This may be explained by the microstructure and hydration products. The quantity of efflorescence determined using MATLAB image analysis is close to the result obtained using the curettage method. The results demonstrate the best effectiveness of replacing Portland cement with metakaolin at a 15% replacement ratio by weight.

  6. 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.

  7. Strength Development and Microstructure of Hardened Cement Paste Blended with Red Mud

    Institute of Scientific and Technical Information of China (English)

    PAN Zhihua; ZHANG Yanna; XU Zhongzi

    2009-01-01

    Red mud was activated to be a mineral admixture for Portland cement by means of heating at different elevated temperatures from 400 ℃ to 700 ℃. Results show that heating was ef-fective, among which thermal activation of red mud at 600 ℃ was most effective. Chemical analysis suggested that cement added with 600 ℃ thermally activated red mud yielded more calcium ion dur-ing the early stage of hydration and less at later stage in liquid phase of cement water suspension sys-tem, more combined water and less calcium hydroxide in its hardened cement paste. MIP measure-ment and SEM observation proved that the hardened cement paste had a similar total porosity and a less portion of large size pores hence a denser microstructure compared with that added with original red mud.

  8. The encapsulation of Mg(OH){sub 2} sludge in composite cement

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C.; Milestone, N.B. [University of Sheffield, Sheffield (United Kingdom). Dept. of Material Engineering

    2010-03-15

    A range of magnesium hydroxide waste sludges arising from the re-processing of nuclear fuel exist in the UK and require safe long-term disposal. Similar wastes undergo a cementation process in order to immobilise radioactive material prior to disposal. Simulant magnesium hydroxide sludges have been prepared and their subsequent interactions with composite cement systems based on the partial replacement of ordinary Portland cement with blast furnace slag and pulverised fuel ash have been studied. This work has concluded that there was little reaction between the sludge and any of the composite cements during hydration. Apart from a small quantity of a hydrotalcite-type phase containing magnesium from the sludge, the main phases detected were C-S-H and unreacted brucite. This indicates that the magnesium in the sludges is encapsulated by the cement, rather than being immobilised or chemically bound within the hardened matrix.

  9. Binary effect of fly ash and palm oil fuel ash on heat of hydration aerated concrete.

    Science.gov (United States)

    Mehmannavaz, Taha; Ismail, Mohammad; Radin Sumadi, Salihuddin; Rafique Bhutta, Muhammad Aamer; Samadi, Mostafa; Sajjadi, Seyed Mahdi

    2014-01-01

    The binary effect of pulverized fuel ash (PFA) and palm oil fuel ash (POFA) on heat of hydration of aerated concrete was studied. Three aerated concrete mixes were prepared, namely, concrete containing 100% ordinary Portland cement (control sample or Type I), binary concrete made from 50% POFA (Type II), and ternary concrete containing 30% POFA and 20% PFA (Type III). It is found that the temperature increases due to heat of hydration through all the concrete specimens especially in the control sample. However, the total temperature rises caused by the heat of hydration through both of the new binary and ternary concrete were significantly lower than the control sample. The obtained results reveal that the replacement of Portland cement with binary and ternary materials is beneficial, particularly for mass concrete where thermal cracking due to extreme heat rise is of great concern.

  10. Model of Coherent Interface Formation in Cement-Based Composites Containing Polyblend of Polyvinyl Alcohol and Methylcellulose

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA),methylcellulose (MC) and their polyblend in an amount of 10 wt % with respect to cement,as well as the texture of dehydrated bodies of PVA,MC,and the polyblend solutions,were investigated with SEM.The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehydrated bodies of PVA and MC.The network texture has restrained the movement of polyblend molecules in the cement mortar but is helpful to forming a coherent interface between cement paste and quartz.The key factor of forming the coherent interface is not the neutralization reaction between H+ from hydrolysis of quartz and OH- from hydration of cement,but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and anions from hydrolysis of quartz and hydration of cement,respectively.The model of the coherent interface formation is that excessive [HSiO3]- and [SiO3]2- anions are bonded with the hydrated cations such as Ca2+ and Al3+,which is confirmed by the gel containing Ca and Si on the quartz surface.

  11. Properties of MSW fly ash-calcium sulfoaluminate cement matrix and stabilization/solidification on heavy metals.

    Science.gov (United States)

    Qian, G R; Shi, J; Cao, Y L; Xu, Y F; Chui, P C

    2008-03-21

    In this paper, investigations were undertaken to formulate the properties of fly ash-calcium sulfoaluminate (CSA) cement matrix by blending MSW fly ash with CSA cement. The compressive strength, pore structure, hydration phases, and leaching behavior of Zn and Pb doped MSW fly ash-CSA cement matrices were determined by XRD, MIP, DSC, FTIR, EDX, TCLP leaching test and other experiments. The results showed that the addition of MSW fly ash to form fly ash-CSA cement matrix reduced the compressive strengths of matrices and made the pore distribution of matrices coarser, compared to that of pure CSA cement matrix. However, fly ash-CSA cement matrix could effectively immobilize high concentration of heavy metal such as lead and zinc with much lesser leaching of TCLP. Besides ettringite AFt, Friedel phase was a new hydration phase formed in the matrix. The formation of these hydration phases was responsible for huge reservoir of heavy metal stabilization by chemical fixing. Therefore, it could be postulated that MSW fly ash-CSA cement matrix was a potential new constituent of S/S matrix for high concentration of heavy metals such as Zn and Pb ions. PMID:17728061

  12. Statistical Analyses of Optimum Partial Replacement of Cement by Fly Ash Based on Complete Consumption of Calcium Hydroxide

    Directory of Open Access Journals (Sweden)

    Ouypornprasert Winai

    2016-01-01

    Full Text Available The objectives of this technical paper were to propose the optimum partial replacement of cement by fly ash based on the complete consumption of calcium hydroxide from hydration reactions of cement and the long-term strength activity index based on equivalent calcium silicate hydrate as well as the propagation of uncertainty due to randomness inherent in main chemical compositions in cement and fly ash. Firstly the hydration- and pozzolanic reactions as well as stoichiometry were reviewed. Then the optimum partial replacement of cement by fly ash was formulated. After that the propagation of uncertainty due to main chemical compositions in cement and fly ash was discussed and the reliability analyses for applying the suitable replacement were reviewed. Finally an applicability of the concepts mentioned above based on statistical data of materials available was demonstrated. The results from analyses were consistent with the testing results by other researchers. The results of this study provided guidelines of suitable utilization of fly ash for partial replacement of cement. It was interesting to note that these concepts could be extended to optimize partial replacement of cement by other types of pozzolan which were described in the other papers of the authors.

  13. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

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

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

    Science.gov (United States)

    Arjunan, P.

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

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

    International Nuclear Information System (INIS)

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

  16. 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.

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

    International Nuclear Information System (INIS)

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

  18. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2003-01-31

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

  19. A preliminary study of CO2 sequestration of cement paste

    Science.gov (United States)

    Choi, Y.; Lee, H.; Hwang, J.; Oh, J.; Lee, J.

    2013-12-01

    Recently, CO2 capture and storage technologies to reduce CO2 concentration in the atmosphere have been extensively studied because global warming is a worldwide issue. Waste cement is a potential raw material for mineral carbonation. In general, carbonation refers a calcite forming reaction in hydrated cement. The carbonation of portlandite in hydrated cement is very straightforward. However, the carbonation of CSH (calcium silicate hydrate: CaO-SiO2-H2O) composing the largest portion of hydrated cement involved in complex reactions and is a key to increase the carbonation efficiency of waste cement. The present study was conducted to have basic information for utilizing waste cement as a raw material for CO2 sequestration. Cement paste was made with W:C= 6:4 and stored for 28 days in water bath. The prepared cement paste was pulverized, and fine grains sizing less than 0.15mm was used for experiment. For the direct aqueous carbonation experiment, 15g of sample is reacted with 200 ml of 1M NaHCO3 in 500ml HDPE bottle. 1M NaCl and 0.25 M MgCl2 was used for additives after leaching test with 0.25, 0.5, 1.0 and 1.5M NaCl and MgCl2 solutions, and the carbonation efficiency of these additives was evaluated. After reaction, the reacted cement paste and supernatant solution were separated from centrifuging at 5000rpm. The reacted cement paste was analyzed with XRD, DSC/TGA and SEM/EDS. The supernatant solution was filtered with 0.45um membrane filter, and nitric acid was added to lower 2 for preventing calcite precipitation. Then, chemical composition of solution was analyzed with ICP-OES. The leaching of Ca ion is increased with increasing NaCl concentration and is maximized at 1M solution. Extremely small leaching of Si ion indicates that NaCl feebly affect on the carbonation of CSH. The leaching of Ca ion in MgCl2 solution is 10 times greater than in NaCl solution and is maximized at 0.5M solution. The increased Ca leaching is probably caused by the decalcification of

  20. Hydration mechanism and leaching behavior of bauxite-calcination-method red mud-coal gangue based cementitious materials.

    Science.gov (United States)

    Zhang, Na; Li, Hongxu; Liu, Xiaoming

    2016-08-15

    A deep investigation on the hydration mechanism of bauxite-calcination-method red mud-coal gangue based cementitious materials was conducted from viewpoints of hydration products and hydration heat analysis. As a main hydration product, the microstructure of C-A-S-H gel was observed using high resolution transmission electron microscopy. It was found that the C-A-S-H gel is composed of amorphous regions and nanocrystalline regions. Most of regions in the C-A-S-H gel are amorphous with continuous distribution, and the nanocrystalline regions on scale of ∼5nm are dispersed irregularly within the amorphous regions. The hydration heat of red mud-coal gangue based cementitious materials is much lower than that of the ordinary Portland cement. A hydration model was proposed for this kind of cementitious materials, and the hydration process mainly consists of four stages which are dissolution of materials, formation of C-A-S-H gels and ettringite, cementation of hydration products, and polycondensation of C-A-S-H gels. There are no strict boundaries among these four basic stages, and they proceed crossing each other. Moreover, the leaching toxicity tests were also performed to prove that the developed red mud-coal gangue based cementitious materials are environmentally acceptable. PMID:27131457

  1. Protein hydration and dynamics

    International Nuclear Information System (INIS)

    Inelastic neutron scattering can measure the protein thermal fluctuations under the physiological aqueous environment, especially it is powerful to observe the low-energy protein dynamics in THz region, which are revealed theoretically to be coupled with solvations. Neutron enables the selective observation of protein and hydration water by deuteration. The complementary analysis with molecular dynamics simulation is also effective for the study of protein hydration. Some examples of the application toward the understanding of molecular basis of protein functions will be introduced. (author)

  2. Surface characterization of the cement for retention of implant supported dental prostheses: In vitro evaluation of cement roughness and surface free energy

    Energy Technology Data Exchange (ETDEWEB)

    Brajkovic, Denis [Clinic for Dentistry, Department of Maxillofacial Surgery, Faculty of Medical Sciences, University of Kragujevac, Svetozara Markovica 69, 34000 Kragujevac (Serbia); Antonijevic, Djordje; Milovanovic, Petar [Laboratory for Anthropology, Institute of Anatomy, School of Medicine, University of Belgrade, Dr. Subotica 4/2, 11000 Belgrade (Serbia); Kisic, Danilo [Laboratory for Atomic Physics, Institute of Nuclear Sciences “Vinca”, University of Belgrade, Belgrade (Serbia); Zelic, Ksenija; Djuric, Marija [Laboratory for Anthropology, Institute of Anatomy, School of Medicine, University of Belgrade, Dr. Subotica 4/2, 11000 Belgrade (Serbia); Rakocevic, Zlatko, E-mail: zlatkora@vinca.rs [Laboratory for Atomic Physics, Institute of Nuclear Sciences “Vinca”, University of Belgrade, Belgrade (Serbia)

    2014-08-30

    Graphical abstract: - Highlights: • Surface free energy and surface roughness influence bacterial adhesion. • Bacterial colonization causes periimplantitis and implant loss. • Zinc-based, glass-ionomers and resin-cements were investigated. • Glass-ionomers-cements present the lowest values of surface free energy and roughness. • Glass-ionomer-cements surface properties result with reduced bacterial adhesion. - Abstract: Background: Material surface free energy and surface roughness strongly influence the bacterial adhesion in oral cavity. The aim of this study was to analyze these two parameters in various commercial luting agents used for cementation of implant restorations. Materials and methods: Zinc-based, glass-ionomers, resin modified glass-ionomer and resin-cements were investigated. Contact angle and surface free energy were measured by contact angle analyzer using Image J software program. Materials’ average roughness and fractal dimension were calculated based on Atomic Force Microscope topography images. Results: Zinc phosphate cements presented significantly higher total surface free energy and significantly lower dispersive component of surface free energy compared to other groups, while resin-cements showed significantly lower polar component than other groups. The surface roughness and fractal dimension values were statistically the highest in the zinc phosphate cements and the lowest for the glass-ionomers cements. Conclusion: Glass-ionomers-cements presented lower values of surface free energy and surface roughness than zinc phosphate and resin cements, indicating that their surfaces are less prone to biofilm adhesion. Practical implications: Within limitations of an in vitro trial, our results indicate that glass-ionomers-cements could be the cements of choice for fixation of cement retained implant restorations due to superior surface properties compared to zinc phosphate and resin cements, which may result in reduced plaque formation

  3. Surface characterization of the cement for retention of implant supported dental prostheses: In vitro evaluation of cement roughness and surface free energy

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Surface free energy and surface roughness influence bacterial adhesion. • Bacterial colonization causes periimplantitis and implant loss. • Zinc-based, glass-ionomers and resin-cements were investigated. • Glass-ionomers-cements present the lowest values of surface free energy and roughness. • Glass-ionomer-cements surface properties result with reduced bacterial adhesion. - Abstract: Background: Material surface free energy and surface roughness strongly influence the bacterial adhesion in oral cavity. The aim of this study was to analyze these two parameters in various commercial luting agents used for cementation of implant restorations. Materials and methods: Zinc-based, glass-ionomers, resin modified glass-ionomer and resin-cements were investigated. Contact angle and surface free energy were measured by contact angle analyzer using Image J software program. Materials’ average roughness and fractal dimension were calculated based on Atomic Force Microscope topography images. Results: Zinc phosphate cements presented significantly higher total surface free energy and significantly lower dispersive component of surface free energy compared to other groups, while resin-cements showed significantly lower polar component than other groups. The surface roughness and fractal dimension values were statistically the highest in the zinc phosphate cements and the lowest for the glass-ionomers cements. Conclusion: Glass-ionomers-cements presented lower values of surface free energy and surface roughness than zinc phosphate and resin cements, indicating that their surfaces are less prone to biofilm adhesion. Practical implications: Within limitations of an in vitro trial, our results indicate that glass-ionomers-cements could be the cements of choice for fixation of cement retained implant restorations due to superior surface properties compared to zinc phosphate and resin cements, which may result in reduced plaque formation

  4. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Kaplan, Hasan; Hanifi BİNİCİ

    1995-01-01

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

  5. Formation of porous gas hydrates

    CERN Document Server

    Salamatin, Andrey N

    2015-01-01

    Gas hydrates grown at gas-ice interfaces are examined by electron microscopy and found to have a submicron porous texture. Permeability of the intervening hydrate layers provides the connection between the two counterparts (gas and water molecules) of the clathration reaction and makes further hydrate formation possible. The study is focused on phenomenological description of principal stages and rate-limiting processes that control the kinetics of the porous gas hydrate crystal growth from ice powders. Although the detailed physical mechanisms involved in the porous hydrate formation still are not fully understood, the initial stage of hydrate film spreading over the ice surface should be distinguished from the subsequent stage which is presumably limited by the clathration reaction at the ice-hydrate interface and develops after the ice grain coating is finished. The model reveals a time dependence of the reaction degree essentially different from that when the rate-limiting step of the hydrate formation at...

  6. Influence of Ultrafine 2CaO·SiO2 Powder on Hydration Properties of Reactive Powder Concrete

    OpenAIRE

    Hongfang Sun; Zishanshan Li; Shazim Ali Memon; Qiwu Zhang; Yaocheng Wang; Bing Liu; Weiting Xu; Feng Xing

    2015-01-01

    In this research, we assessed the influence of an ultrafine 2CaO·SiO2 powder on the hydration properties of a reactive powder concrete system. The ultrafine powder was manufactured through chemical combustion method. The morphology of ultrafine powder and the development of hydration products in the cement paste prepared with ultrafine powder were investigated by scanning electron microscopy (SEM), mineralogical composition were determined by X-ray diffraction, while the heat release characte...

  7. Evaluation of Compatibility between Beetle-Killed Lodgepole Pine (Pinus Contorta var. Latifolia Wood with Portland Cement

    Directory of Open Access Journals (Sweden)

    Ian D. Hartley

    2010-12-01

    Full Text Available The compatibility of wood from mountain pine beetle (Dendroctonus ponderosa killed lodgepole pine (Pinus contorta var. latifolia with Portland cement was investigated based on time-since-death as a quantitative estimator, and the presence of blue-stained sapwood, brown rot, or white rot as qualitative indicators. The exothermic behavior of cement hydration, maximum heat rate, time to reach this maximum, and total heat released within a 3.5–24 h interval were used for defining a new wood-cement compatibility index (CX. CX was developed and accounted for large discrepancies in assessing wood-cement compatibility compared to the previous methods. Using CX, no significant differences were found between fresh or beetle-killed wood with respect to the suitability for cement; except for the white rot samples which reached or exceeded the levels of incompatibility. An outstanding physicochemical behavior was also found for blue-stained sapwood and cement, producing significantly higher compatibility indices.

  8. 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.

  9. Estimating the chloride transport in cement paste

    Directory of Open Access Journals (Sweden)

    Princigallo, A.

    2012-06-01

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

    Se ha desarrollado un método para medir el coeficiente de difusión de los iones cloruro en la pasta de cemento, partiendo de una aplicación analítica de la segunda ley de Fick en un sistema de coordinadas cilíndrico. Este método, que es natural, demostró ser capaz de producir resultados de difusividad en tan solo un mes. Se consiguió reducir el tiempo de ensayo mediante el aprovechamiento de la tridimensionalidad del flujo desde el exterior al interior de la probeta. A fin de determinar la concentración de saturación, se sometieron las pastas de cemento Portland a una disolución de cloruros concentrada. Este método resultó ser útil en el estudio de los cambios del coeficiente de difusión de la pasta de cemento provocados por las reacciones de hidratación que tienen lugar en esta.

  10. Hydrated coefficient of clathrates and its applications in determination of aqueous inclusions with multivolatile components%气水化合物的水合常数及其在水溶液包裹体多组分挥发分测定中的应用

    Institute of Scientific and Technical Information of China (English)

    刘斌; 徐金明

    2007-01-01

    During the microthermometric measurement (cooling) of aqueous inclusions with multivolatile components, solid crystals of gas clathrates often occur with snow-flower- or soft-ice appearances. The structural formula of these solids is M · nH2O (where n ≥5.67 ). Many hydrocarbons, related compounds and their binary or multi-component mixtures may generate gas clathrates. This phenomenum is of fundamental importance to the study of inclusions with hydrocarbon aqueous solutions, because this is related to the determination of inclusion parameters and the computation of thermodynamic parameters.In the nature most aqueous inclusions contain not merely one volatile component but multi-volatile components. Therefore, the measurement of aqueous inclusions with multivolatile components is of universal significance and great importance. There have been many studies and available formula or figures about the computation of thermodynamic parameters for aqueous inclusions with one volatile component. Nevertheless, there are few studies concerning with multivolatile components and it is very difficult to computate thermodynamic parameters for aqueous inclusions with these components.In this paper, hydrated coefficient K is introduced. Ki is the ratio of molar fraction of component i in the gas phase to that in the gas clathrate, or Ki = yi/xi. Because K is a function of temperatures and pressures, it can be used to evaluate the temperature-pressure conditions on the phase behavior with multivolatile components.Based on the regression analysis of available experimental data, the authors have developed computational expression of hydrated coefficients in relation to temperature and pressure for most hydrocarbons and other volatile components, which is helpful to conveniently compute thermodynamic parameters on stability state for clathrates with volatile components. As aqueous inclusions with multivolatile components are common in the nature, by the use of final melting

  11. Basic properties of calcium phosphate cement containing different concentrations of citric acid solution

    Institute of Scientific and Technical Information of China (English)

    戴红莲; 闫玉华; 冯凌云; 李世普; 贺建华

    2002-01-01

    The properties of calcium phosphate cement consisting of α-tricalcium phosphate (α-TCP) and tetracalcium phosphate (TTCP) have been investigated by using a cement liquid that contained citric acid with concentration of 0.05 mol/L or higher. The relationship between the setting time of the system cement and the concentration of citric acid solution shows concave type curve. When solution concentration was 0.2 mol/L, the setting time was 8 min, which was the shortest. While the relationship between 24 h compressive strength of the cement and the citric acid concentration shows convex type curve. When solution concentration was 0.2 mol/L, the compressive strength was 39.0 MPa, which was the highest. Afterwards, the microstructure of the hardening product was observed by SEM, the effect of citric acid on the exothermic rate of hydrate reaction was studied by microcalorimeter, and the crushed specimens were subjected to X-ray diffraction. The results verified that the low citric acid concentration can accelerate the hydrate reaction rate of the α-TCP/TTCP system. However, the high citric acid concentration inhibited hydroxyapatite formation and retarded the rate of hydrate reaction of the α-TCP/TTCP cement.

  12. Chemical and dimensional evolution of cationic ions exchange resins in cement pastes

    International Nuclear Information System (INIS)

    Ion exchange resins (IERs) are widely used by the nuclear industry to decontaminate radioactive effluents. After use they are usually encapsulated in cementitious materials. However, the solidified waste forms can exhibit a strong expansion, possibly leading to cracking. Its origin is not well understood as well as the conditions when it occurs.In this work, the interactions between cationic resins in the Na+ or Ca2+ form and tricalcium silicate (C3S), Portland cement (CEM I) or Blast furnace slag cement (CEM III/C) are investigated at an early age in order to gain a better understanding of the expansion process.The results show that during the hydration of a paste of C3S or CEM I containing IERs in the Na+ form, the resins exhibit a transient expansion of small magnitude due to the decrease in the osmotic pressure of the interstitial solution. This expansion, which occurs just after cement setting, is sufficient to damage the material which is poorly consolidated for several reasons: small hydration degree, precipitation of less cohesive sodium bearing C-S-H, heterogeneous microstructure with highly porous zones and lastly cleavable crystals of portlandite at the interface between resins and paste. This expansion can be prevented by performing a calcium pretreatment of the resins or by using a CEM III/C cement with a slower rate of hydration than that of Portland cement. (author)

  13. Order and disorder in calcium–silicate–hydrate

    International Nuclear Information System (INIS)

    Despite advances in the characterization and modeling of cement hydrates, the atomic order in Calcium–Silicate–Hydrate (C–S–H), the binding phase of cement, remains an open question. Indeed, in contrast to the former crystalline model, recent molecular models suggest that the nanoscale structure of C–S–H is amorphous. To elucidate this issue, we analyzed the structure of a realistic simulated model of C–S–H, and compared the latter to crystalline tobermorite, a natural analogue of C–S–H, and to an artificial ideal glass. The results clearly indicate that C–S–H appears as amorphous, when averaged on all atoms. However, an analysis of the order around each atomic species reveals that its structure shows an intermediate degree of order, retaining some characteristics of the crystal while acquiring an overall glass-like disorder. Thanks to a detailed quantification of order and disorder, we show that, while C–S–H retains some signatures of a tobermorite-like layered structure, hydrated species are completely amorphous

  14. Stabilization/solidification of selenium-impacted soils using Portland cement and cement kiln dust.

    Science.gov (United States)

    Moon, Deok Hyun; Grubb, Dennis G; Reilly, Trevor L

    2009-09-15

    Stabilization/solidification (S/S) processes were utilized to immobilize selenium (Se) as selenite (SeO(3)(2-)) and selenate (SeO(4)(2-)). Artificially contaminated soils were prepared by individually spiking kaolinite, montmorillonite and dredged material (DM; an organic silt) with 1000 mg/kg of each selenium compound. After mellowing for 7 days, the Se-impacted soils were each stabilized with 5, 10 and 15% Type I/II Portland cement (P) and cement kiln dust (C) and then were cured for 7 and 28 days. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the effectiveness of the S/S treatments. At 28 days curing, P doses of 10 and 15% produced five out of six TCLP-Se(IV) concentrations below 10mg/L, whereas only the 15% C in DM had a TCLP-Se(IV) concentration pozzolan doses up to 10 times less than the treatments that established the BDAT. Neither pozzolan was capable of reducing the TCLP-Se(VI) concentrations below 25mg/L. Se-soil-cement slurries aged for 30 days enabled the identification of Se precipitates by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX). XRD and SEM-EDX analyses of the Se(IV)- and Se(VI)-soil-cement slurries revealed that the key selenium bearing phases for all three soil-cement slurries were calcium selenite hydrate (CaSeO(3).H(2)O) and selenate substituted ettringite (Ca(6)Al(2)(SeO(4))(3)(OH)(12).26H(2)O), respectively.

  15. Stabilization/solidification of selenium-impacted soils using Portland cement and cement kiln dust

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Deok Hyun, E-mail: dmoon10@hotmail.com [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Department of Environmental Engineering, Chosun University, Gwangju 501-759 (Korea, Republic of); Grubb, Dennis G. [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Schnabel Engineering, LLC, 510 East Gay Street, West Chester, PA 19380 (United States); Reilly, Trevor L. [W.M. Keck Geoenvironmental Laboratory, Center for Environmental Systems, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)

    2009-09-15

    Stabilization/solidification (S/S) processes were utilized to immobilize selenium (Se) as selenite (SeO{sub 3}{sup 2-}) and selenate (SeO{sub 4}{sup 2-}). Artificially contaminated soils were prepared by individually spiking kaolinite, montmorillonite and dredged material (DM; an organic silt) with 1000 mg/kg of each selenium compound. After mellowing for 7 days, the Se-impacted soils were each stabilized with 5, 10 and 15% Type I/II Portland cement (P) and cement kiln dust (C) and then were cured for 7 and 28 days. The toxicity characteristic leaching procedure (TCLP) was used to evaluate the effectiveness of the S/S treatments. At 28 days curing, P doses of 10 and 15% produced five out of six TCLP-Se(IV) concentrations below 10 mg/L, whereas only the 15% C in DM had a TCLP-Se(IV) concentration <10 mg/L. Several treatments satisfied the USEPA TCLP best demonstrated available technology (BDAT) limits (5.7 mg/L) for selenium at pozzolan doses up to 10 times less than the treatments that established the BDAT. Neither pozzolan was capable of reducing the TCLP-Se(VI) concentrations below 25 mg/L. Se-soil-cement slurries aged for 30 days enabled the identification of Se precipitates by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX). XRD and SEM-EDX analyses of the Se(IV)- and Se(VI)-soil-cement slurries revealed that the key selenium bearing phases for all three soil-cement slurries were calcium selenite hydrate (CaSeO{sub 3}.H{sub 2}O) and selenate substituted ettringite (Ca{sub 6}Al{sub 2}(SeO{sub 4}){sub 3}(OH){sub 12}.26H{sub 2}O), respectively.

  16. Immobilisation of ion exchange resins in cement

    International Nuclear Information System (INIS)

    Over the last seven years, Low Oxidation State Metal Ion reagents (LOMI) have been used to decontaminate the 100 MW(e) Steam Generating Heavy Water Ractor (SGHWR) at Winfrith. The use of these reagents has resulted in a dilute ionic solution containing activation products which are produced by corrosion of metallic components in the reactor. It has been demonstrated that the amount of activity in the solution can be reduced using organic ion exchanger resins. These resins consist of a cross linked polystyrene with sulphonic acid or quaternary ammonium function groups and can be successfully immobilised in blended cement systems. The formulation which has been developed is produced from a 9 to 1 blend of ground granulated blast furnace slag (BFS) and ordinary Portland cement (OPC) containing 28% ion exchange resin in the water saturated form. If 6% Microsilica is added to the blended cement the waste loading can be increased to 36 w/o. (author)

  17. Chemical and mineralogical characterization of two commercial cements and its evolution in function of time; Caracterizacion quimica y mineralogica de dos cementos comerciales y su evolucion en funcion del tiempo

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez B, O.

    2014-07-01

    Mineralogical evolution of Portland cement is studied during hydration process using materials characterization techniques as X-ray diffraction (XRD) and scanning electron microscopy (Sem) in order to analyze the changes in the various cement minerals as alite, belite, celite, during processing to the hydrated phases of tobermorite gel, portlandite and ettringite, respectively, in the cement paste setting at different ages (3, 7 and 28 days). It was found that the hydration process occurs differently in each mineral because of their reaction rates or changes they experience in their crystals during processing of anhydrous to hydrated phase. You may notice changes in the appearance of the dough as you go hydration and the formation of tobermorite gel, portlandite and ettringite. (Author)

  18. Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities

    Science.gov (United States)

    Lee, Myung W.

    2008-01-01

    Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.

  19. Use of the “red gypsum” industrial waste as substitute of natural gypsum for commercial cements manufacturing

    Directory of Open Access Journals (Sweden)

    Gázquez, M. J.

    2012-06-01

    Full Text Available The main objective of this research has been the valorisation of a waste from the TiO2 production process (sulphate method, called red gypsum, in the production of cements. This waste is mainly formed by di-hydrate calcium sulphate and iron hydroxides. To cover this objective it has been necessary to perform the physico-chemical characterisation of the red gypsum as well as the main components in the production of cements and of the new cements generated. Moreover, for the red gypsum, has been analyzed its radioactive content because it is generated in a NORM (Naturally Occurring Radioactive Materials industry. Finally, the most important properties of the obtained cements with different proportions of red gypsum in their composition have been studied by comparing them with the standard ones obtained in a Portland cement. Lastly, we have demonstrated that the new cements fulfil all the quality tests imposed by the European legislation.

    El objetivo de esta investigación ha sido analizar la valorización de un residuo generado en el proceso de producción de dióxido de titanio (vía sulfato, denominado yeso rojo, en la producción de cementos. Dicho residuo está compuesto fundamentalmente por sulfato de calcio di-hidratado e hidróxidos de hierro. Para ello, ha sido necesaria la caracterización físico-química del yeso rojo, así como la de los otros componentes fundamentales en la fabricación de cementos y de los cementos generados con el mencionado residuo. Además, en el caso del yeso rojo, se ha analizado su contenido radiactivo al generarse éste en una industria NORM (Natural Occurring Radioactive Materials. Posteriormente, se han estudiado las propiedades más importantes de los cementos producidos con diferentes porcentajes de yeso rojo añadido, comparando estas mezclas con las propiedades de un cemento Portland comercial, comprobándose que se cumplen todas las normas Europeas de calidad exigibles.

  20. Alternative Fuel for Portland Cement Processing

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-06-30

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