The project identified test procedures for measuring aggregate shape, texture, and angularity characteristics that are likely to influence performance of hot-mix asphalt and hydraulic cement concrete mixtures and unbound materials used in highway pavements, discussed the merits and deficiencies of these procedures, and presented a plan for further evaluating potential procedures and recommending suitable methods for use in central and field laboratories.

The properties of coarse and fine aggregates used in hot-mix asphalt and hydraulic cement concrete and unbound base and subbase layers are very important to the performance of the pavement system in which they are used. Particle shape, texture, and angularity are among the aggregate properties that have significant effects on performance. These properties vary widely with the type and source of aggregates and processing techniques. However, current aggregate specifications do not address in a direct manner the measurement of these properties, thus leading to inconsistent interpretation and use of test results. While several methods for measuring aggregate shape, texture, and angularity characteristics were developed in recent years, and others are being developed as part of ongoing research efforts, an evaluation of these methods--with respect to their practicality, labor requirements, ease of use, cost, versatility, field applicability, use in multiple ratio shape analysis, and other factors--has not been performed. Thus research is needed to evaluate potential test methods and identify or develop suitable test methods for measuring relevant properties in central and field laboratories, and to develop recommendations to help improve specifications for aggregates used in highway pavements. Further research will be performed under NCHRP Project 4-30A.

Research included a review of relevant domestic and foreign literature; identification of available test methods for characterizing aggregate shape, texture, and angularity; and an evaluation of potential test methods.