Nanoscale study on adhesion performance and aging degree prediction of warm mix asphalt under UV aging condition

Compared with hot mix asphalt, warm mix asphalt ( WMA) has inferior adhesion performance, and ultraviolet (UV) aging will further weaken the adhesion performance of WMA. There are, however, few investigations on the aging mechanism under conditions of single UV radiation, and the majority of current research on UV aging is conducted under the combined action of UV radiation and oxygen. In this paper, an indoor accelerated experimental equipment for UV aging was developed, and two experimental schemes of oxygen isolation condition and light-oxygen coupling condition were designed. The developed UV aging tests were carried out on WMA this for 0–50–100–150 and 200 h. The nano adhesion properties were studied by atomic force microscopy ( AFM) and gel permeation chromatography ( GPC) experiments. The characterization method of WMA nano adhesion performance was proposed using correlation analysis. In addition, the nonlinear differential equations between nano-indexes and aging time were established by the Verhulst model. The results showed that the generation of microcracks and the increase of large molecular weight during UV aging will decrease WMA adhesion performance, and the degradation is more significant under the light-oxygen coupling conditions. Moreover, the correlation coefficients between large molecular weight and nano-adhesion under two UV aging conditions were higher than 0.90, showing that large molecular weight could characterize the degradation of nano-adhesion of WMA after UV aging. The saturation characteristics of the honeycomb structure area ratio were prominent, and the coefficient of determination of the nonlinear equations were higher than 0.93 for both two UV aging conditions. The aging model can be used to accurately characterize and predict the WMA UV aging state through the variation of honeycomb structure area ratio.