This paper surveys the concrete technology issues of the SHRP C-201 project: Microstructure of Concrete. The purpose of this research is to generate knowledge which will enable improvement in the quality of highway concrete by controlling the development of the microstructure. This study emphasizes those features which will aid in the management of processing of fresh concrete and early curing of concrete in highway construction work. The specific program of the research in progress in an out growth of experience which has shown that the homogeneity and the workability of fresh concrete, and the conditions to which the concrete is exposed during its early curing, have a profound influence on the homogeneity and associated characteristics of the microstructure of the hardened concrete, and thereby on the durability of concrete structures. This research is therefore concentrating initially on an exploration of the principles of mixture proportioning of the concrete components which determine the packing characteristics of the concrete components as mixed, and also on the chemical reactions in the fresh cement paste, which influence its rheological characteristics. This knowledge is indispensable for the development of design methods, which can result in practical monitoring for optimum quality of the fresh concrete, forming the basis for the design of the corresponding monitoring methods. Other emphases of the research include the adaptation of methods for monitoring the early curing of concrete. This is important becasue thermal stresses originating during early curing may cause severe microcracking, and available systems for monitoring the curing appear to be adaptable for application to highway construction work. Finally, diagnostic methods for evaluation of the microstructure and associated properties are the focus of much of the current effort.
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