Study on Microstructure and Rheological Properties of Cement-Chemical Admixtures-Water Dispersion System at Early Stage


Book Description

This thesis studies the effects of superplasticizers, polyacrylate latexes and asphalt emulsions, which differ in molecular/particle size from nanometers to microns, on the rheological properties of fresh cement pastes (FCPs), as well as the action mechanisms involved. It systematically investigates the rheological properties and microstructure of cement-based materials, and elucidates the adsorption behaviors of polycarboxylate polymers with different functional groups and their effects on cement hydration. Moreover, it reveals how the working mechanism of naphthalene sulfonate formaldehyde (NSF) differs from that of polycarboxylate ether-based (PCE) superplasticizers. Lastly, it develops a conceptual microstructure model and two rheological equations. These findings lend theoretical support to the development of new chemical admixtures and new, higher-performance, cement-based composites.




Effect of Chemical Admixtures on Rheology of Cement Paste at High Temperature


Book Description

Placement of cement-based materials in hot weather conditions encounters many problems due to the rapid evaporation of mixing water and the accelerated hydration of cement. Such materials are also adversely affected at elevated temperatures by an increased water demand, shorter setting time, and more rapid slump loss. These problems can be mitigated using adequate chemical admixtures. However, technical data on such admixtures are commonly developed at normal temperatures, and there is a real need to investigate their performance at hot temperatures. In the current research, the rheological properties of portland cement pastes with a water-cement ratio (w/c) of 0.35 and 0.50 are investigated at different temperatures in the range of 20 to 45°C using an advanced shear-stress/shear-strain controlled rheometer. The influence of water-reducing and retarding admixture, polycarboxylate, naphthalene sulfonate, and melamine-based high-range water-reducing admixtures (HRWR) in addition to mid-range water-reducing admixtures (MRWR) on the rheological properties of cement paste at various temperatures was also examined. The paper aims at formulating recommendations for the effective use of chemical admixtures at high temperature, which should enhance the rheological properties of cement-based materials in hot weather conditions.




The Rheology of Fresh Concrete


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Understanding the Rheology of Concrete


Book Description

Estimating, modelling, controlling and monitoring the flow of concrete is a vital part of the construction process, as the properties of concrete before it has set can have a significant impact on performance. This book provides a detailed overview of the rheological behaviour of concrete, including measurement techniques, the impact of mix design, and casting. Part one begins with two introductory chapters dealing with the rheology and rheometry of complex fluids, followed by chapters that examine specific measurement and testing techniques for concrete. The focus of part two is the impact of mix design on the rheological behaviour of concrete, looking at additives including superplasticizers and viscosity agents. Finally, chapters in part three cover topics related to casting, such as thixotropy and formwork pressure. With its distinguished editor and expert team of contributors, Understanding the rheology of concrete is an essential reference for researchers, materials specifiers, architects and designers in any section of the construction industry that makes use of concrete, and will also benefit graduate and undergraduate students of civil engineering, materials and construction. Provides a detailed overview of the rheological behaviour of concrete, including measurement techniques, casting and the impact of mix design The estimating, modelling, controlling and monitoring of concrete flow is comprehensively discussed Chapters examine specific measurement and testing techniques for concrete, the impact of mix design on the rheological behaviour of concrete, particle packaging and viscosity-enhancing admixtures




Brittle Matrix Composites 7


Book Description

The International Symposium in Brittle Matrix Composites October 13-15, 2003 covers a wide spectrum of topics including cement based composites, ceramic composites and brittle polymer matrix composites. In the papers various topics and issues are considered such as: analytical and numerical studies related to the design of composites, prediction of behaviour and verification of strength and stability, testing methods, manufacturing processes and repair, environmental effects and durability assessment. The present volume of 55 papers proves that there are still many problems in the field of brittle matrix composites deserving theoretical and experimental investigations and that new solutions to these problems are needed for practical application in civil engineering, industrial structures, machinery and other domains.







Proceedings fib Symposium in Stuttgart


Book Description




Rheology of Fresh Cement-Based Materials


Book Description

This book introduces fundamentals, measurements, and applications of rheology of fresh cement-based materials. The rheology of a fresh cement-based material is one of its most important aspects, characterizing its flow and deformation, and governing the mixing, placement, and casting quality of a concrete. This is the first book to bring the field together on an increasingly important topic, as new types of cement-based materials and new concrete technologies are developed. It describes measurement equipment, procedures, and data interpretation of the rheology of cement paste and concrete, as well as applications such as self-compacting concrete, pumping, and 3D printing. A range of other cement-based materials such as fiber-reinforced concrete, cemented paste backfills, and alkali-activated cement are also examined. Rheology of Fresh Cement-Based Materials serves as a reference book for researchers and engineers, and a textbook for advanced undergraduate and graduate students.




Active Rheology Control of Cementitious Materials


Book Description

This book reports on cutting-edge research within the new field of active rheology control of cementitious materials, presenting new ideas developed within the ERC Advanced Grant Project, SmartCast (hosted at Ghent University), which extend the possibilities of admixtures and additions beyond current options. The research presented here develops a new method of actively controlling the rheology of fresh concrete during casting operations by incorporating specially designed responsive components. This results in real-time changes to the rheological behaviour of the cementitious material, allowing the user to intervene actively after the cementitious material has left the mixing phase. This newly gained agility contributes to increased processing speed and placement reliability in the case of traditional casting methods and can also facilitate advanced 3D concrete printing. The different routes followed to achieve this Active Rheology Control are explained within. The book suits researchers and innovative practitioners and is the first comprehensive text to present these new findings. The Open Access version of this book, available at http://www.taylorfrancis.com, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license.