Using surface free energy method to study the cohesion and adhesion of asphalt mastic

In order to improve the road performance of asphalt mixture, the cohesion and adhesion of asphalt mastic which is the most important component of asphalt mixture were studied. The surface free energy of asphalt was tested using sessile drop method, and the surface free energy of fillers was measured using column wicking method. The work of cohesion and adhesion between asphalt and fillers were calculated through using their surface free energy parameters. The results show that the neat asphalt has higher surface free energy than the modified asphalt. The van der Waals force of surface free energy plays a more important role. The polarity power of modified asphalt is higher than the neat asphalt. The Lewis acid–alkali forces of different fillers have a big difference, while the van der Waals forces are nearly the same. Limestone filler has the biggest surface free energy and the components, and granite filler has the smallest intermolecular forces, and andesite filler has the smallest Lewis acid–alkali force. The specific surface area is an important parameter effecting the interfacial interaction between asphalt and fillers. The work of adhesion at a constant volume ratio has a better regularity than at a constant specific surface area regardless of whether the condition is dry or damp, whether the asphalt is modified or not, and the order is granite filler > andesite filler > limestone filler. A good correlation exists between complex modulus G∗ and work of adhesion.