This document reports the results of a comprehensive study pertaining to the determination of causes and mechanisms resulting in a reduction of strength in concrete mixtures containing Synthetic air entraining admixtures. The study involved experimentation with concrete mixtures containing both the Synthetic and Vinsol resin admixtures. Tests involved determination of air content for fresh concrete and air bubble characteristics including size and distribution for hardened concrete. Compressive strength of concrete samples were determined at ages 7, 14, 28 and 56 days.
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
An admixture is any material other than water, aggregates, and hydraulic cement that is used as an ingredient of a concrete or mortar mixture and added to the batch immediately before or during mixing. 4 types of admixtures are discussed: (1) accelerators, the most common of which is calcium chloride; (2) air-entraining, to protect the concrete against the damage it may suffer if the paste becomes saturated with water and then freezes; (3) retarders and water reducers, which extend setting time 30 to 50 percent to compensate for placement temperatures, to avoid cold joints, or to avoid undesirable effects of displacements and deflections; and (4) pozzolans, which react with hydroxides to form compounds with cementitious properties, and usually produce a lower cost concrete.
This study evaluated the impacts of construction on the air content and air-void system structure of Portland cement concrete pavements. The primary intent was to quantify the air content of fresh concrete before and after it has gone through the slipform paver. The air-void system parameters of hardened concrete were then assessed using cast and extracted core specimens. The results of the air content testing on fresh concrete and the concrete cylinder specimens cast in the field suggested that there is some loss of air as the concrete passes through the paver. Laboratory testing performed on cores extracted from the pavement did not provide any conclusive evidence that entrained air is lost during the slipform paving process. In fact, many of the extracted cores had measured air content values that were much higher than the specification requirement. If excessive, this could result in increased permeability and low-strength related issues. Although a rigorous statistical analysis was not performed, the results suggest that the air content testing on fresh concrete is not capturing the true air content of the concrete placed with a slipform paver. The fresh concrete air content is generally lower than the air content measured in the cores.
The Concrete Construction Engineering Handbook, Second Edition provides in depth coverage of concrete construction engineering and technology. It features state-of-the-art discussions on what design engineers and constructors need to know about concrete, focusing on - The latest advances in engineered concrete materials Reinforced concrete construction Specialized construction techniques Design recommendations for high performance With the newly revised edition of this essential handbook, designers, constructors, educators, and field personnel will learn how to produce the best and most durably engineered constructed facilities.
Based on the Institute of Concrete Technology's Advanced Concrete Technology Course, these four volumes are a comprehensive educational and reference resource for the concrete materials technologist. An expert international team of authors from research, academia and industry has been brought together to produce this unique series. Each volume deals with a different aspect of the subject: constituent materials, properties, processes and testing and quality. With worked examples, case studies and illustrations throughout, the books will be a key reference for the concrete specialist for years to come. - Expert international authorship ensures the series is authoritative - Case studies and worked examples help the reader apply their knowledge to practice - Comprehensive coverage of the subject gives the reader all the necessary reference material
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