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"This report presents a recommended procedure for evaluating air-entraining admixtures used in highway concrete. The procedure involves the testing of non-air-entrained concrete and concrete containing the air-entraining admixture under simulated field conditions. Criteria are proposed for acceptance of admixtures for use in either highway pavements or structures. The recommended procedure and acceptance criteria will guide materials engineers in evaluating and selecting air-entraining admixtures that should contribute to appropriate freeze-thaw durability and thus to good performance and long service life. The content of the report will be of immediate interest to materials engineers, researchers, and others concerned with the design of concrete mixtures for use in highway pavements and structures."--taken from Foreword, page [v].
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.
"TRB's National Cooperative Highway Research Program (NCHRP) 749: Methods for Evaluating Fly Ash for Use in Highway Concrete presents suggested changes to coal fly ash specifications and test protocols contained in American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Transportation Materials and Methods of Sampling and Testing (AASHTO M 295). The changes suggested include modifications to the test methods currently specified for evaluating acceptability of fly ash for use in highway concrete as well as the introduction of new test methods for enhancing such evaluations. Attachment C: Details of the Research into Methods for Evaluating Fly Ash Use in Highway Concrete is only available online."--Publisher description.

Admixtures in Concrete

National Research Council (U.S.). Highway Research Board. Committee on Chemical Additions and Admixtures for Concrete

Published: 1971

Total Pages: 60


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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.
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
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.
Introductory technical guidance for civil engineers and others interested in evaluation of corrosion mitigation technologies for concrete repairs. Here is what is discussed: 1. GENERAL 2. PRODUCTS 3. EXECUTION.