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Author: Axel Schöler
Publisher: GRIN Verlag
ISBN: 3656258562
Category : Technology & Engineering
Languages : en
Pages : 147
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Book Description
Master's Thesis from the year 2012 in the subject Chemistry - Materials Chemistry, grade: 1,3, TU Bergakademie Freiberg (Institut für Glas, Keramik und Baustofftechnik), course: Bauchemie, language: English, abstract: The production of Portland cement clinker has a share of about 6% to 8% on the global CO2-emissions . Approximately 60% of those emissions are attributable to the decarbonation of limestone. A widespread approach for the reduction of the CO2-emissions is to replace the clinker in the cement by pozzolanic waste materials, e.g. fly ash. The reaction of fly ash is generally slow. Due to this slow reaction cement pastes mixed of Portland cement and fly ash have a slower strength development than pure Portland cement, at least at early ages up to 7 days. The goal of this study was to increase early strength properties of Portland cement/fly ash blends by increasing the early ettringite formation in order to decrease the porosity. Therefore various amounts of anhydrite and laboratory synthesised C3A were added to Portland cement/fly ash systems that contained 30% fly ash. The behavior of these systems in terms of kinetics, phase development and microstructure was studied by means of strength tests, isothermal calorimetry, thermogravimetric analysis, chemical shrinkage, X-ray diffraction, backscattered electron image analysis, mercury intrusion porosimetry and thermodynamic modeling. In addition the activation by Na2SO4 was investigated on certain systems. It was found that the amount of ettringite formed increases gradually with increasing amounts of anhydrite and C3A. The formation of ettringite was completed at approximately 1 day. Further the activation with Na2SO4 increased the amount of ettringite and shifted the completion of its formation to approximately 2 days. Due to the addition of anhydrite and C3A the porosity decreased corresponding to the amount of ettringite formed. The effects on the development of early strength were most distinct for very high additions and for systems activated by Na2SO4. All systems showed equal strengths at 7 d and 28 d. For later ages up to 90 days, the benefits at early ages were found to be inversed, leading to lower strength values compared to systems without or with low additions of anhydrite, C3A or Na2SO4. Eventually the increase in early strength was either too low to be significant or only relevant at very high additions of anhydrite and C3A with simultaneous system activation by Na2SO4. In terms of kinetics a remarkable impact of the added C3A was observed as this seemed to significantly accelerate the silicate reaction of the Portland cement.
Author: Axel Schöler
Publisher: GRIN Verlag
ISBN: 3656258562
Category : Technology & Engineering
Languages : en
Pages : 147
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Book Description
Master's Thesis from the year 2012 in the subject Chemistry - Materials Chemistry, grade: 1,3, TU Bergakademie Freiberg (Institut für Glas, Keramik und Baustofftechnik), course: Bauchemie, language: English, abstract: The production of Portland cement clinker has a share of about 6% to 8% on the global CO2-emissions . Approximately 60% of those emissions are attributable to the decarbonation of limestone. A widespread approach for the reduction of the CO2-emissions is to replace the clinker in the cement by pozzolanic waste materials, e.g. fly ash. The reaction of fly ash is generally slow. Due to this slow reaction cement pastes mixed of Portland cement and fly ash have a slower strength development than pure Portland cement, at least at early ages up to 7 days. The goal of this study was to increase early strength properties of Portland cement/fly ash blends by increasing the early ettringite formation in order to decrease the porosity. Therefore various amounts of anhydrite and laboratory synthesised C3A were added to Portland cement/fly ash systems that contained 30% fly ash. The behavior of these systems in terms of kinetics, phase development and microstructure was studied by means of strength tests, isothermal calorimetry, thermogravimetric analysis, chemical shrinkage, X-ray diffraction, backscattered electron image analysis, mercury intrusion porosimetry and thermodynamic modeling. In addition the activation by Na2SO4 was investigated on certain systems. It was found that the amount of ettringite formed increases gradually with increasing amounts of anhydrite and C3A. The formation of ettringite was completed at approximately 1 day. Further the activation with Na2SO4 increased the amount of ettringite and shifted the completion of its formation to approximately 2 days. Due to the addition of anhydrite and C3A the porosity decreased corresponding to the amount of ettringite formed. The effects on the development of early strength were most distinct for very high additions and for systems activated by Na2SO4. All systems showed equal strengths at 7 d and 28 d. For later ages up to 90 days, the benefits at early ages were found to be inversed, leading to lower strength values compared to systems without or with low additions of anhydrite, C3A or Na2SO4. Eventually the increase in early strength was either too low to be significant or only relevant at very high additions of anhydrite and C3A with simultaneous system activation by Na2SO4. In terms of kinetics a remarkable impact of the added C3A was observed as this seemed to significantly accelerate the silicate reaction of the Portland cement.
Author: Herbert Pöllmann
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110473720
Category : Science
Languages : en
Pages : 518
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Book Description
Aside from water the materials which are used by mankind in highest quantities arecementitious materials and concrete. This book shows how the quality of the technical product depends on mineral phases and their reactions during the hydration and strengthening process. Additives and admixtures infl uence the course of hydration and the properties. Options of reducing the CO2-production in cementitious materials are presented and numerous examples of unhydrous and hydrous phases and their formation conditions are discussed. This editorial work consists of four parts including cement composition and hydration, Special cement and binder mineral phases, Cementitious and binder materials, and Measurement and properties. Every part contains different contributions and covers a broad range within the area. Contents Part I: Cement composition and hydration Diffraction and crystallography applied to anhydrous cements Diffraction and crystallography applied to hydrating cements Synthesis of highly reactive pure cement phases Thermodynamic modelling of cement hydration: Portland cements – blended cements – calcium sulfoaluminate cements Part II: Special cement and binder mineral phases Role of hydrotalcite-type layered double hydroxides in delayed pozzolanic reactions and their bearing on mortar dating Setting control of CAC by substituted acetic acids and crystal structures of their calcium salts Crystallography and crystal chemistry of AFm phases related to cement chemistry Part III: Cementitious and binder materials Chemistry, design and application of hybrid alkali activated binders Binding materials based on calcium sulphates Magnesia building material (Sorel cement) – from basics to application New CO2-reduced cementitious systems Composition and properties of ternary binders Part IV: Measurement and properties Characterization of microstructural properties of Portland cements by analytical scanning electron microscopy Correlating XRD data with technological properties No cement production without refractories
Author: Axel Schöler
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Problem definition and research objectives 1. The production of Portland cement clinker causes approx. 5% to 8% of the annual man-made CO2 emissions. This is due to the usage of mainly fossil fuel (approx. 40 % of the total CO2) and because of the decarbonation of limestone as a main component of the raw meal (approx. 60 % of the total CO2). 2. Various strategies are applied in order to reduce the green-house gas-emissions, such as optimizing the process of clinker production, the use of alternative fuel and the partial substitution of the clinker in blended cement by so-called SCM (supplementary cementitious materials). Hereby blast-furnace slag, fly ash and limestone are the most used materials. 3. Quaternary systems containing three SCM simultaneously besides Portland cement contribute to the reduction of CO2 emissions due to the decrease of the clinker content. In addition, such systems allow to use blast-furnace slag and fly ash in the most economical way and provide the possibility to account for shortages of SCM on the market. 4. Blast-furnace slag and fly ash show similarities in their principal chemical compositions such that similar hydrates are formed during their reaction in presence of Portland cement. Compared to ternary systems based on blast-furnace slag or fly ash besides limestone, quaternary systems that contain both, blast-furnace slag and fly ash, simultaneously besides limestone, are expected to perform similar in terms of phase assemblage and strength development. 5. The use of SCM as cement replacing materials is limited due to their generally slower reaction compared to neat cement which also leads to lower strength development, especially in the early stage of the hydration up to 28 d. To account for this it is necessary to study the reactivity of SCM such as blast-furnace slag and fly ash in detail in order to develop strategies to enhance the reactivity and thereby the strength development of SCM-containing systems. 6. The early hydration of clinker phases is studied in detail, mainly in diluted systems. It is unclear if processes that were found to control the reaction of such model systems are also prevailing in concentrated cement pastes under realistic water-to-solid ratios. Deeper insight to this aspect is needed to better understand interactions of neat Portland cement and SCM in the first hours of hydration. State-of-the-art 7. Increasing Ca-concentrations lead to decreasing dissolution rates of C3S and C2S in diluted systems. 8. The hydration kinetics of C3S is controlled by the interplay of undersaturation with respect to C3S and oversaturation with respect to C-S-H. 9. Increasing Al-concentrations lead to a retardation of the hydration of C3S. It is unclear if the uptake of aluminum in C-S-H to form C-(A)-S-H which has a significantly lower growth rate than pure C-S-H or a retarding effect of Al on the dissolution of C3S causes this phenomenon. 10. The surface of limestone provides excellent conditions for the nucleation and growth of C-S-H such that significantly more C-S-H nuclei are formed in presence of limestone compared to other SCM. 11. The reactivity of blast-furnace slag and fly ash depends on the particle size as well as on the intrinsic reactivity of especially the amorphous phases. 12. An increase in network modifying oxides (e.g. CaO) in the chemical composition of amorphous (calcium)aluminosilicates leads to an increasingly depolymerized network which in turn causes increasing reactivity. The role of amphoteric oxides (Al2O3, Fe2O3) that can be present as network modifying oxides as well as network forming oxides is not completely solved. 13. CO2-containing AFm-phases are thermodynamically more stable than monosulfoaluminate. This indirectly stabilizes the voluminous ettringite which causes a higher total volume of hydrates and lower porosity whereby higher compressive strength is reached. 14. Only a few percent of limestone in blended cement reacts chemically dependent on the Al2O3 available for reaction. Al2O3 that is provided by the reaction of Portland cement but also by the dissolution of SCM, especially by fly ash, reacts to form hemicarboaluminate which is transformed to monocarboaluminate as the hydration proceeds. Methodology 15. The influence of SCM on the early hydration of Portland cement in binary (including blast-furnace slag or fly ash or limestone or quartz) and ternary (including fly ash and limestone) systems was investigated applying isothermal calorimetry and analysis of the pore solution chemistry. Calculated saturation indices and solubility products of relevant phases were correlated with heat development. Based on the gained data it was reviewed if mechanisms that control the hydration of pure phases in diluted systems are also prevailing in cement pastes under realistic conditions. 16. The influence of the chemical composition of synthetic glasses on their dissolution at high pH was investigated in highly diluted systems using ion chromatography. Pozzolanity tests were conducted on pastes using simplified model systems and glass-blended Portland cements. The process of the glass dissolution was investigated by isothermal calorimetry and by thermogravimetry. Correlation of experimentally determined total bound water with bound water determined by mass balance calculations as a function of amount of glass reacted allowed to estimate the degree of glass reaction in the pastes. Further on selective dissolution experiments were carried out to crosscheck the results of the bound water/mass balance approach. 17. The reaction kinetics of quaternary pastes containing blast-furnace slag and fly ash simultaneously in the presence of limestone were investigated up to 28 d using isothermal calorimetry and chemical shrinkage measurements. In addition strength tests on mortar bars were carried out. 18. Pastes of quaternary blends were also investigated in terms of hydrate assemblage at ages of up to 182 d. Thermodynamic calculations regarding total volume of hydrates as a function of limestone and fly ash/blast-furnace slag content were conducted. The calculations were supported by thermogravimetric determination of bound water and portlandite content as well as qualitative X-ray diffraction. The results were correlated with strength tests on mortar bars. 19. The pore solutions of hydrated quaternary blends were extracted and investigated by means of ion chromatography at ages of up to 728 d. Based on the ion concentrations in the solutions saturation indices were calculated for relevant phases. In order to gain better insight to the blast-furnace slag reaction sulphate speciation was carried out at two blast furnace slag levels (20 and 30 wt.%) for selected samples up to 91 d of hydration and at 91 d for the whole matrix under investigation. Main results 20. Investigations on the early hydration kinetics of binary systems showed a higher heat flow in presence of SCM compared to neat Portland cement. This is caused by the higher surface area that is available for the nucleation of hydrates and by the lower (over)saturation with respect to C-S-H. An increase in the Ca-concentration in the pore solution did not cause lower dissolution rates of C3S as was reported for pure phases in diluted systems. The highest dissolution was observed in the presence of limestone, i.e. at the highest Ca-concentration. The general trend of the reaction rate is inversely related to the degree of undersaturation with respect to C3S. The more undersaturated the faster the observed reaction. The presence of increasing Al-concentrations caused a retardation of the reaction which is in line with investigations on pure phases in diluted systems. Higher sulphate concentrations could be detected for the fly ash containing blend which possibly hindered ettringite precipitation and results in higher Al-concentrations. Correspondingly the low sulphate concentrations lead to lower Al-concentrations in the presence of quartz, blast-furnace slag and limestone compared to fly ash. 21. The early hydration kinetics of quaternary systems is significantly accelerated in the presence of limestone while fly ash leads to retardation. Compared to reference systems containing inert quartz, investigations by means of isothermal calorimetry and chemical shrinkage revealed an acceleration caused by blast-furnace slag. Additions of fly ash, limestone or mixtures thereof introduced another acceleration but differences are too small to be significant and clear distinguishing between the various SCM is not possible. 22. Investigations on the reactivity of synthetic glasses showed that increasing amounts of network modifying oxides caused an increase in reactivity and dissolution rates. The results reveal that Al2O3 acts mainly as network modifying oxide in all investigated glasses. Experimentally determined bound water (thermogravimetric experiments) in model systems and blended cements can be compared with bound water ...
Author: Herbert Pöllmann
Publisher: Walter de Gruyter GmbH & Co KG
ISBN: 3110473917
Category : Science
Languages : en
Pages : 557
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Book Description
Aside from water the materials which are used by mankind in highest quantities arecementitious materials and concrete. This book shows how the quality of the technical product depends on mineral phases and their reactions during the hydration and strengthening process. Additives and admixtures infl uence the course of hydration and the properties. Options of reducing the CO2-production in cementitious materials are presented and numerous examples of unhydrous and hydrous phases and their formation conditions are discussed. This editorial work consists of four parts including cement composition and hydration, Special cement and binder mineral phases, Cementitious and binder materials, and Measurement and properties. Every part contains different contributions and covers a broad range within the area. Contents Part I: Cement composition and hydration Diffraction and crystallography applied to anhydrous cements Diffraction and crystallography applied to hydrating cements Synthesis of highly reactive pure cement phases Thermodynamic modelling of cement hydration: Portland cements – blended cements – calcium sulfoaluminate cements Part II: Special cement and binder mineral phases Role of hydrotalcite-type layered double hydroxides in delayed pozzolanic reactions and their bearing on mortar dating Setting control of CAC by substituted acetic acids and crystal structures of their calcium salts Crystallography and crystal chemistry of AFm phases related to cement chemistry Part III: Cementitious and binder materials Chemistry, design and application of hybrid alkali activated binders Binding materials based on calcium sulphates Magnesia building material (Sorel cement) – from basics to application New CO2-reduced cementitious systems Composition and properties of ternary binders Part IV: Measurement and properties Characterization of microstructural properties of Portland cements by analytical scanning electron microscopy Correlating XRD data with technological properties No cement production without refractories
Author:
Publisher:
ISBN: 9780965231091
Category : Hydration
Languages : en
Pages : 326
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Book Description
Manual of integrated material and construction practices for concrete pavements.
Author: Wolfgang Hummel
Publisher: Universal-Publishers
ISBN: 1581126204
Category : Science
Languages : en
Pages : 589
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Book Description
The Nagra/PSI Chemical Thermodynamic Data Base 01/01 is an encyclopedia of thermodynamic data recommended for environmental studies. The data base focuses on elements commonly found as major solutes in natural waters, and on actinides and fission products relevant for radioactive waste disposal projects. It is the official chemical thermodynamic data base used in Swiss radioactive waste disposal projects. The detailed discussion of every number recommended in this encyclopedia is the result of a multi man-year project of the Paul Scherrer Institut (PSI), a Swiss National Lab. The five authors of this work have many years of experience in research, data base development and the application of thermodynamic data in environmental studies. The data included for many elements are based on their reviews of the basic literature. The data base also includes additional data selected by the authors from recommendations of other experts in ground- water geochemistry and of the international data base project of the Nuclear Energy Agency (NEA).This report is indispensable for every scientist working in the field of environmental studies as the comprehensive source of information on the quality of the thermodynamic data governing particular problems in environmental geochemistry, especially those concerned with the fate of hazardous substances. This enables graduate students, researchers and consultants, as well as regulators and reviewers of scientific papers to assess the scientific basis of environmental modeling studies. The encyclopedia can be used as a stand-alone source of knowledge but amplereferences are provided for readers who wish to go beyond the level of discussion in the book. An electronic version of the data base and a data base management program is available for download at our homepage (http://les.web.psi.ch/TDBbook.htm).
Author: P. Barnes
Publisher: CRC Press
ISBN: 0203477782
Category : Architecture
Languages : en
Pages : 584
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Book Description
Drawing together a multinational team of authors, this second edition of Structure and Performance of Cements highlights the latest global advances in the field of cement technology. Three broad categories are covered: basic materials and methods, cement extenders, and techniques of examination. Within these categories consideration has been given to environmental issues such as the use of waste materials in cement-burning as supplementary fuels and new and improved methods of instrumentation for examining structural aspects and performance of cements. This book also covers cement production, mineralogy and hydration, as well as the mechanical properties of cement, and the corrosion and durability of cementitious systems. Special cements are included, along with calcium aluminate and blended cements together with a consideration of the role of gypsum in cements. Structure and Performance of Cements is an invaluable key reference for academics, researchers and practitioners alike.
Author: G. C. Bye
Publisher: Thomas Telford
ISBN: 9780727727664
Category : Portland cement
Languages : en
Pages : 256
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Book Description
Portland cement is one of the most traditional of construction materials. Rising costs of the energy required for its manufacture and the increasing interest in understanding the mechanisms of concrete deterioration, as well as the importance of optimising the use of Portland cement in high quality concrete, have continued to sustain interest in this important material. This second edition of this popular book provides an up-to-date introduction to the raw materials and manufacturing processes of Portland cement. It gives an introductory account of cement composition, manufacture, quality assessment, hydration and the resulting microstructure-physical property relationships, and some mechanisms of the chemical degradation of hardened cement paste. The book is primarily intended for students of materials sciences and graduates in pure science or engineering entering the cement or concrete industries. However anyone requiring a good clear introduction to this material will find this book provides helpful information.
Author: Florence Bart
Publisher: Springer Science & Business Media
ISBN: 1461434459
Category : Technology & Engineering
Languages : en
Pages : 266
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Book Description
As the re-emergence of nuclear power as an acceptable energy source on an international basis continues, the need for safe and reliable ways to dispose of radioactive waste becomes ever more critical. The ultimate goal for designing a predisposal waste-management system depends on producing waste containers suitable for storage, transportation and permanent disposal. Cement-Based Materials for Nuclear-Waste Storage provides a roadmap for the use of cementation as an applied technique for the treatment of low- and intermediate-level radioactive wastes. Coverage includes, but is not limited to, a comparison of cementation with other solidification techniques, advantages of calcium-silicate cements over other materials and a discussion of the long-term suitability and safety of waste packages as well as cement barriers.
Author: Standards Association of Australia. Committee BD/10, Cement
Publisher:
ISBN:
Category : Cement
Languages : en
Pages : 8
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Book Description
