Preparation and Mix Design of Usual-Temperature Synthetic Pitch-Modified Cutback Asphalt

Usual-temperature synthetic pitch (USP) is a modifier that can efficiently reduce the mixing temperature and improve the overall engineering properties of warm-mix asphalts; however, few studies are reported for its application in cold patch asphalt. In this article, cutback asphalts were prepared with USP, bitumen, biodiesel, an antistripping agent, and a tackifier. Referring to a series of single-factor analyses on the cutback asphalt viscosity, the reasonable dosage ranges for the USP, antistripping agent, and tackifier were first determined. Based on these, a four-factor and four-level orthogonal test plan was proposed to guide the selection of some potential appropriate mix design schemes. The recommended mix design schemes were then screened out by successively examining the physical properties, adhesion, workability, Marshall stability, high- and low-temperature rheological properties, and compatibility. Two design schemes with mass proportions of 6:18:0.3:6 (Scheme 1) and 6:20:0.4:2 (Scheme 2) for USP, diluent, antistripping agent, and tackifier, respectively, were finally selected. The engineering properties of the prepared specimens meet the standard requirements. Compared with Scheme 1, Scheme 2 presents better Marshall stability and high- and low-temperature performance. The proposed mix design schemes can guide the preparation of USP-modified cold patch asphalts and promote their application in practice.