Abstract
The thesis presents details of tests carried out to assess the effect of particle interaction on the mechanical properties of dense asphalt mixes. The degrees of particle interaction of a range of fine granular materials have been assessed quantitatively on the basis of packing characteristics and also the rate of discharge from an orifice. These have been shown to be related to the mechanical properties of sand asphalts assessed by means of the Marshall test. Tests have also been carried out to investigate the effects of aggregate type and grading on the properties of stone filled mixes, and their influence on Marshall stability, flow and void characteristics have been discussed. In particular, the separate contributions of the stone and sand to the load bearing properties of the mix have been examined, especially in relation to the shape of the Marshall test curves over a wide range of binder contents. Particular reference has been made to the behaviour of mixes in the range of binder contents below those more generally examined. The review of previous work includes a detailed examination of the mechanical tests available for bituminous materials, and a study of the various techniques provides a basis for assessing the mechanical properties of a material considered most relevant in its performance under load. The application of the various test procedures to mix design has been considered and the merits of the Marshall test discussed. Recommendations are given for an extension of the work reported, with especial reference to the correlation of results of laboratory tests on bituminous materials with their behaviour in road surfaces.