Download or read book Influence of Superplasticizers on the Early Hydration of Portland Cement and Cement Compounds written by Christopher John Duston and published by . This book was released on 1982 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Superplasticizers on the Early Hydration of Portland Cements and Cement Compounds written by Christopher John Duston and published by . This book was released on 1982 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Superplasticizers written by Vangipuram Seshachar Ramachandran and published by Natural Resources Canada, Canada Centre for Mineral and Energy Technology. This book was released on 1997 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book has been prepared with the aim of integrating information about the chemistry and application of concrete superplasticizers in a manner relevant to concrete engineers and technologists. The opening chapter introduces basic aspects of concrete science as background for what follows. Chapters 2-4 discuss the chemical synthesis of superplasticizers, methods used to characterize those chemicals, and techniques for evaluation of their effect in cementitious systems. Subsequent chapters cover: the influence of superplasticizers on hydration of cement materials; rheology of cementitious systems; issues related to the mode of action and compatibility of superplasticizers; the effect of superplasticizers on fresh concrete; mechanical properties and durability of concrete; innovative applications of superplasticizers in concrete; superplasticizer dispensing, specifications, and standards; patents related to superplasticizers; and current and future trends in the use of superplasticizers in concrete.
Download or read book Slump Loss and Retempering of Superplasticized Concrete written by J. Francis Young and published by . This book was released on 1983 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Retarding Effects on Cement and Tricalcium Silicate Hydration Induced by Superplasticizers written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Superplasticizers are utilized both to improve the fluidity during the placement and to reduce the water content of concretes. Both effects have also an impact on the properties of the hardened concrete. As a side effect the presence of superplasticizers affects the strength development of concretes that is strongly retarded. This may lead to an ecomomical drawback of the concrete manufacturing. The present work is aimed at gaining insights on the causes of the retarding effect of superplasticizers on the hydration of Portland cement. In order to simplify the complex interactions occurring during the hydration of Portland cement the majority of the work focuses on the interaction of superplasticizer and tricalcium silicate (Ca3SiO5 or C3S, the main compound of Portland cement clinker). The tests are performed in three main parts accompanied by methods as for example isothermal conduction calorimetry, electrical conductivity, Electron Microscopy, ICP-OES, TOC, as well as Analytical Ultracentrifugation. In the first main part and based on the interaction of cations and anionic charges of polymers, the interactions between calcium ions and superplasticizers are investigated. As a main effect calcium ions are complexed by the functional groups of the polymers (carboxy, sulfonic). Calcium ions may be both dissolved in the aqueous phase and a constitute of particle interfaces. Besides these effects it is furthermore shown that superplasticizers induce the formation of nanoscaled particles which are dispersed in the aqueous phase (cluster formation). Analogous to recent findings in the field of biomineralization, it is reasonable to assume that these nanoparticles influence the crystal growth by their assembly process. Based on the assumption that superplasticizers hinder either or both dissolution and precipitation and by that retard the cement hydration, the impact on separate reactions is investigated. On experiments that address the solubility of C-S-H phases and portlandite, it is shown that complexation of calcium ions in the aqueous phase by functional groups of polymers increases the solubility of portlandite. Contrary, in case of C-S-H solubility the complexation of calcium ions in solution leads to decrease of the calcium ion concentration in the aqueous phase. These effects are explained by differences in adsorption of polymers on C-S-H phases and portlandite. It is proposed that adsorption is stronger on C-S-H phases compared to portlandite due to the increased specific surface area of C-S-H phases. Following that, it is claimed that before polymers are able to adsorb on C-S-H phases the functional groups must be screened by calcium ions in the aqueous phase. It is further shown that data regarding the impact of superplasticizers on the unconstrained dissolution rate of C3S does not provide a clear relation to the overall retarding effect occurring during the hydration of C3S. Both increased and decreased dissolution rate with respect to the reference sample are detected. If the complexation capability of the superplasticizers is considered then also a reduced dissolution rate of C3S is determined. Despite the fact that the global hydration process is accelerated, the addition of calcite leads to a slower dissolution rate. Thus, a hindered unconstrained dissolution of C3S as possibly cause for the retarding effect still remains open for discussion. In the last section of this part, the pure crystallization of hydrate phases (C-S-H phases, portlandite) is fathomed. Results clearly show that superplasticizers prolong the induction time and modify the rate of crystal growth during pure crystallization in particular due to the complexation of ions in solution. But this effect is insufficient to account for the overall retarding effect. Further important factors are the blocking of crystal growth faces by adsorbed polymers and the dispersion of nanoscaled particles which hinders their agglomeration in order to build up crystals. In the last main part of the work, the previously gathered results are utilized in order to investigate hydration kinetics. During hydration, dissolution and precipitation occur in parallel. Thereby, special attention is laid on the ion composition of the aqueous phase of C3S pastes and suspensions in order to determine the rate limiting step. All in all it is concluded that the retarding effect of superplasticizers on the hydration of tricalcium silicate is based on the retardation of crystallization of hydrate phases (C-S-H phases and portlandite). Thereby, the two effects complexation of calcium ions on surfaces and stabilization of nanoscaled particles are of major importance. These mechanisms may partly be compensated by template performance and increase in solubility by complexation of ions in solution. The decreased dissolution rate of C3S by the presence of superplasticizers during the in parallel occuring hydration process can only be assessed indirectly by means of the development of the ion concentrations in the aqueous phase (reaction path). Whether this observation is the cause or the consequence within the dissolution-precipitation process and therefore accounts for the retarding effect remains a topic for further investigations. Besides these results it is shown that superplasticizers can be associated chemically with inhibitors because they reduce the frequency factor to end the induction period. Because the activation energy is widely unaffected it is shown that the basic reaction mechanism sustain. Furthermore, a method was developed which permits for the first time the determination of ion concentrations in the aqueous phase of C3S pastes in-situ. It is shown that during the C3S hydration the ion concentration in the aqueous phase is developed correspondingly to the heat release rate (calorimetry). The method permits the differentiation of the acceleration period in three stages. It is emphasized that crystallization of the product phases of C3S hydration, namely C-S-H phases and portlandite, are responsible for the end of the induction period.
Download or read book Concrete Admixtures Handbook 2nd Ed written by V.S. Ramachandran and published by William Andrew. This book was released on 1996-12-31 with total page 1183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the publication of the first edition ten years ago, significant developments have occurred in the use of admixtures in concrete. Eight new chapters and a full update of the preceding ten chapters bring this book up to date; reflecting the relative advances made in the science and technology of different groups of admixtures. The increased role and development of admixtures in concrete technology is evidenced by a number of conferences, publications, and novel admixtures available in the market place. These developments in the field caused the modification of many chapters in the first edition in order to reflect the advances. Although individual chapters refer to standards and specifications of admixtures, those only interested in the standards or techniques used in investigating admixtures will find the second chapter (Research Technologies, Standards, and Specifications) useful. Admixtures are not as inert as may be presumed. They may chemically interact with the constituents of concrete and affect the properties of the fresh and hardened concrete and its durability. The third chapter deals with these aspects. It was important to devote a chapter to recent attempts in developing new admixtures.
Download or read book Application of Admixtures in Concrete written by A.M. Paillere and published by CRC Press. This book was released on 2004-03-01 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a thorough review of the properties and use of the principal chemical admixtures for use in concrete. Concise and clearly presented, the book includes extensive references to key sources of information. The presentation of each admixture is in a standard format, which helps the reader to find relevant information easily.
Download or read book Science and Technology of Concrete Admixtures written by Pierre-Claude Aïtcin and published by Woodhead Publishing. This book was released on 2015-11-12 with total page 668 pages. Available in PDF, EPUB and Kindle. Book excerpt: Science and Technology of Concrete Admixtures presents admixtures from both a theoretical and practical point-of-view. The authors emphasize key concepts that can be used to better understand the working mechanisms of these products by presenting a concise overview on the fundamental behavior of Portland cement and hydraulic binders as well as their chemical admixtures, also discussing recent effects in concrete in terms of rheology, mechanics, durability, and sustainability, but never forgetting the fundamental role played by the water/binder ratio and proper curing in concrete technology. Part One presents basic knowledge on Portland cement and concrete, while Part Two deals with the chemical and physical background needed to better understand what admixtures are chemically, and through which mechanism they modify the properties of the fresh and hardened concrete. Subsequent sections present discussions on admixtures technology and two particular types of concrete, self-consolidating and ultra-high strength concretes, with final remarks on their future. Combines the knowledge of two leading authors to present both the scientific and technology of admixtures Explains what admixtures are from a chemical point-of-view and illustrates by which mechanisms they modify the properties of fresh and hardened concrete Presents a fundamental, practical, and innovative reference book on the topic Contains three detailed appendices that can be used to learn how to use admixtures more efficiently
Download or read book Cement and Concrete Chemistry written by Wieslaw Kurdowski and published by Springer Science & Business. This book was released on 2014-04-24 with total page 705 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph describes cement clinker formation. It covers multicomponent systems, clinker phase structures and their reactions with water, hydrate composition and structure, as well as their physical properties. The mineral additions to cement are described as are their influence on cement-paste properties. Special cements are also discussed. The microstructure of concrete is then presented, and special emphasis is given to the role of the interfacial transition zone, and the corrosion processes in the light of cement-phase composition, mineral additions and w/c ratio. The admixtures' role in modern concrete technology is described with an emphasis on superplasticizer chemistry and its cement-paste rheological modification mechanism. Cement with atypical properties, such as calcium aluminate, white, low energy and expansive cements are characterized. The last part of the book is devoted to special types of concrete such as self compacting and to reactive powders.
Download or read book Influence of Superplasticizers on the Hydration of Cement written by Ramachandran, V. S. (Vangipuram Seshachar) and published by . This book was released on 1981 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Superplasticizers and Other Chemical Admixtures in Concrete written by and published by . This book was released on 2006 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Developments in the Use of Superplasticizers written by V. M. Malhotra and published by . This book was released on 1981 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemistry and Microstructure of Solidified Waste Forms written by Roger D. Spence and published by CRC Press. This book was released on 1992-12-15 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chemistry and Microstructure of Solidified Waste Forms presents a comprehensive summary of mechanisms of immobilization in cementitious waste forms and the effect of waste species on cement chemistry and morphology. The book introduces the well-known chemistry and microstructure of cement pastes, in addition to common mechanisms of immobilization of waste species in cementitious waste forms. The fundamental chemical and microstructural fate of waste species is reviewed, and a technique for studying cementitious waste forms using scanning transmission electron microscopy (STEM) is described with examples of its application. Chemistry and Microstructure of Solidified Waste Forms also presents evidence to prove that chromium in waste becomes part of the cement matrix, and the potentially harmful effect of this process is discussed. Data for interpretations are included so that other researchers can analyze the data and draw their own conclusions. The book also discusses how solubility and solubility theory can be combined with leach theory and diffusion theory to predict the leaching performance of cementitious waste forms. Chemistry and Microstructure of Solidified Waste Forms will prove invaluable to hazardous waste professionals, engineers, environmental engineers, chemical engineers, waste disposal managers, waste form developers and researchers, and regulators.
Download or read book Hydration of Portland Cement Compounds written by Robert Herman Bogue and published by . This book was released on 1934 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Admixtures on the Composition of the Liquid Phase and the Early Hydration Reactions in Portland Cement Pastes written by M. H. Roberts and published by . This book was released on 1968 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Superplasticizers and Other Chemical Admixtures in Concrete written by and published by . This book was released on 1989 with total page 684 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Changes in the Early Hydration Behavior of Portland Cement Used in the Solidification of Hazardous Chemicals written by Frank P. Frey and published by . This book was released on 1988 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract.
