European Research into Granular Material for Pavement Bases and Subbases

Two transnational European research projects in the area of granular materials for road pavements are described. The results are used to illustrate the state of practice as compared to the state of the art and are placed within the setting of a broad picture of national research within Europe. Discussed are the direction of European research, its implementation, those areas that will continue to be problematic, and the findings and strategies that suggest better-practice for non-European users. The use of the repeated-load triaxial test is shown to be an important aspect. Although the test is shown to have limitations for practical purposes, it illustrates the nature of material behavior that may be expected in situ. It is shown that a fundamental engineering understanding has been applied to granular material pavement layer technology but that there remain issues of in situ assessment, analytical methods, and variability of in situ conditions that hinder full application of current understanding.