Building on the work performed under NCHRP Project 4-20, the project identified aggregate properties that influence the performance of portland cement concrete pavements and the laboratory tests that can be used to determine these properties. The project also proposed a plan for a laboratory study to further evaluate potential aggregate tests and recommend a set of aggregate tests that relate to performance of portland cement concrete used in pavement construction and thus can be used as predictors of pavement performance.

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. Because wide spread use, familiarity, and a historical database have perpetuated the popularity of some tests, there is a need 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 a step in the process for achieving this objective. Further research will be performed under NCHRP Project 4-20B.

Research included a review of relevant domestic and foreign literature, communications with selected state highway agency, an evaluation of potential aggregate tests, and development of a plan for a laboratory study. The consultant's report describes the work performed under this project.