The project evaluated aggregate tests and, based on the results of laboratory tests, identified a set of nine aggregate tests that relate to performance of hot-mix asphalt concrete used in pavement construction and thus as predictors of pavement performance.

The properties of coarse and fine aggregates used in hot-mix asphalt concrete mixtures are very important to the performance of the pavement system in which they are used. For example, stripping and rutting of pavements can be traced directly to improper aggregate selection and use. Many 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 widespread use, familiarity, and a historical database have perpetuated the popularity of some tests, there was a need to evaluate existing aggregate tests, identify new tests that relate to performance, and develop better procedures for testing and selection of aggregate used in various hot-mix asphalt concrete applications.

Research included a review of relevant domestic and foreign literature, communications with highway agencies, and the conduct of laboratory tests to identify and evaluate aggregate properties that influence pavement performance, and recommend those tests that can be used as predictors of performance. NCHRP Report 405, "Aggregate Tests Related to Asphalt Concrete Performance in Pavements," documents the work performed under this project. The validity of the recommended tests will be evaluated by accelerated load tests and/or in-service pavement studies or other appropriate means under NCHRP Project 4-19(2).