An investigation on the mechanical properties of granular materials in interface with asphaltic concrete

• A multi-disciplinary research approach involving Geotechnical Eng. and Pavement Eng.
• A better approximation of interaction value between sand and asphalt concrete materials.
• Using the direct shear and Marshal test results simultaneously to achieve more reliable results.

Asphaltic concrete has been used as waterproofing core in embankment dams, since 1948. In this application, granular materials are used around the asphaltic concrete as filter, which makes a complicated behaviour in the interface and needs to be researched by experiments and modelling. This paper describes experimental work and the results of investigating the mechanical behaviour of the interface between aggregates and asphaltic concrete. Small scale shear strength test has been used in this study, in which the shear surface is considered as the interface. The effect of bitumen penetration grade, moisture, density and angularity of aggregates on the shear strength parameters at different levels of normal stresses and a constant shear rate have been studied. The results show that the shear strength parameters increases with increasing the density and normal stress level. It is also shown that the shear parameters decrease with increasing moisture content in the interface. The penetration grade of bitumen does not have a significant effect on the parameters. It is also demonstrated that the ratio of interaction between the aggregate and asphalt concrete decreases in a certain range of variation.