Modifying Surface Properties of Model and Pavement Aggregates with Silanes

Adhesion between binder and aggregate is a major concern when studying bituminous mixtures’ mechanical performances. Many parameters are to be taken into account, for instance chemical composition of binder and aggregate, interface roughness, etc. Isolating each parameter for a comprehensive approach of adhesion phenomenon can be very challenging but necessary. This paper is a first step of a larger study to isolate the role of surface chemical properties of aggregates in binder/aggregate interface. In order to alter only the very surface of aggregate and its chemical composition, a simple 3-step-procedure for chemical surface modification at molecular scale using two different hydrophobic organosilanes is given. Two substrates proposed here are made of classical rock (microdiorite) for pavement construction from a French quarry, and of glass as model material. The change of physicochemical properties of modified substrates is then assessed through contact angle method on smooth plates, while the nano-coating’s composition is assessed with X-Ray Photoelectron Spectroscopy (XPS) on aggregates. Contact angle method significantly revealed hydrophobic properties for both modified substrates, up to a 30 degrees’ increase. XPS analysis show that the coating is a success on both substrates, and probably with a strong siloxane bond.