Effect of synthetic and functionalized waxes on bituminous binders: From the glassy state to the intermediate viscoelastic domain

A 50/70 bitumen was modified with five different commercial waxes, including Fischer-Tropsch, Montan and functionalized waxes. Thermal and morphological properties were investigated through Differential Scanning Calorimetry (DSC) and polarized optical microscopy (POM). Dynamic and continuous rheological tests were carried out to analyse the mechanical response of wax-modified bitumens (WMB). Theories behind possible mechanisms of asphalt/wax interaction are discussed. The entire frequency/temperature domain was divided into two macro-regions. The first one covers the glassy state, with independent waxy structures, where the bitumen mainly determines the mechanical response. The second macro region develops along the intermediate viscoelastic domain and propagates towards high temperatures/low frequencies. Within this domain, all WMB exhibits a complex mechanical response, with gel-like characteristics, thus suggesting the existence of physical networks and interconnections between contiguous wax crystalline segments.