Investigation on the wetting behavior of asphalt emulsion on aggregate for asphalt emulsion mixture

Abstract

The wetting behavior of asphalt emulsion on aggregate greatly influences the physical bonding interface between asphalt emulsion and aggregate. However, the wetting behavior of asphalt emulsions has not been widely considered. In this work, the wetting behavior of asphalt emulsion on aggregate was investigated in terms of dynamic contact angle. Firstly, the quantitative indicators for evaluating the wetting behavior are proposed. Then, the factors influencing the wetting behavior are analyzed, such as emulsifier dosage, asphalt dosage, wetting agent dosage, aggregate type and surface roughness. Finally, the primary factor affecting the wetting behavior is analyzed using the grey correlation method. The result shows that the wetting process of asphalt emulsion on the aggregate surface could be divided into two stages: the initial linear rapid wetting stage driven by inertial force, the second slow wetting stage driven by viscous forces, which the development of dynamic contact angle can be well illustrated by the power function. The equilibrium contact angle (θe) and wetting velocity (v) are recommended as quantitative indicators of wetting behavior. Grey correlation analysis shows that the emulsifier dosage and wetting agent dosage can significantly affect the wetting behavior. Increasing the emulsifier dosage can increase the equilibrium contact angle and decrease the wetting velocity. Adding the wetting agent can reduce the equilibrium contact angle and increase the wetting velocity. Therefore, to guarantee the good wetting behavior, the emulsifier dosage should not be too high, provided that good emulsification effect is achieved and the wetting agent can be added in asphalt emulsion.