Improved material specifications for unsealed roads

Abstract

Performance-related specifications for the selection of gravel materials for use in unsealed roads were developed in South Africa in the late 1980's along with associated deterioration models. The implementation of these has shown that, when the material fully complies with these specifications, and the materials are compacted to a high density, the actual performance of the road is even better than predicted by the models. These specifications have subsequently been tested and implemented in other countries in the southern African region. However, American Standard Test Methods (ASTM), the test methods used in other countries are often based upon the British Standard (BS) methods. The inherent differences in these test methods need to be taken into account so that the specifications can be effectively applied. A revised material selection guide and performance prediction chart have been developed for use when the materials are tested using the British Standard test methods.