The project identified aggregate properties that influence the performance of portland cement concrete in the various highway applications, evaluated existing aggregate tests to assess their ability to predict pavement performance, and presented a plan for further evaluating potential aggregate tests and recommending a set of aggregate tests that relate to the performance of portland cement concrete used in pavement construction.

The properties of coarse and fine aggregates used in portland cement concrete mixtures are very important to the performance of the highway pavements in which they are used, and proper aggregate selection is necessary for attaining desired performance. However, many of the currently used aggregate tests were developed empirically to characterize an aggregate without, necessarily, understanding the direct relationship to the performance of the final product. Although widespread use, familiarity, and a historical database have perpetuated the popularity of some tests, the highway industry may be better served by other tests that would provide a clearer relationship with performance. Thus, research is needed to evaluate existing aggregate tests, identify new tests that relate to performance, and develop better procedures for testing and selection of aggregates used in portland cement concrete pavements. This project provided the first step in the process for achieving this objective. Further research will be performed under NCHRP Projects 4-20A and 4-20B.

Research included a review of relevant domestic and foreign literature, an analysis of state highway agency practices relevant to the testing and evaluation of aggregates, and an evaluation of potential aggregate tests.