A universal gradation for highway pavement base course materials

Around the world, several standards and guidelines exist for the construction of highway pavement base courses. In the current global construction environment, an engineer may be dealing with a highway project sitting in a place far away from the construction site, and there may be an urgent need to work on a preliminary analysis and design of the pavement. In such situation, it would be advantageous to have a universal gradation of the base course materials. Therefore, this study aims to develop such a gradation, considering the standard guidelines being adopted in several countries including Australia, Brazil, various European nations, India, Iran, New Zealand, South Africa and USA. The analysis has resulted in three different particle-size distribution (PSD) ranges; however, one of the three has been proposed as the universal gradation in view of the most common or widespread practice. The gradation has been developed both in the form of a PSD curve, as well as in a tabular form. It was observed that the universal gradation consists of the largest particle size of 50 mm and permissible fines (particles smaller than 0.075 mm) content of 2-8%.