Some aspects of the mechanical testing of hot rolled asphalt surfacings.

Hot Rolled Asphalt Wearing course mixtures, containing up to 55% by mass of coarse aggregate, were tested over a range of binder contents using the following test methods: Marshall Test Indirect-Tensile Test Wheel-Tracking Test. The results obtained were used to assess the ability of each of these methods to (i) assist in the selection of an optimum mixture composition, from the point of view of resistance to deformation (ii) predict the resistance to deformation of the various mixturestested. It was found that the results obtained by all three test methods could be used to define an ''optimum binder content" for a given set of constituents, and that both Marshall Stability and Marshall Quotient were closely related to resistance to deformation, as measured in the Wheel-Tracking Test. In the light of the results obtained, the Marshall Test would appear to be most suitable of the three (from the practical point of view) for application to the design of Hot Rolled Asphalt Mixture s.However, before total confidence can be placed in the results obtained by this method, there are several improvements which must be made.