Effects of micro-scale and molecular structure of modifiers on rheological response and compatibility for asphalt performances improvement

For pavement engineering, crumb rubber (CR)/styrene-butadiene-styrene (SBS) incorporate modified asphalt is an attractive binder with potential financial and environmental advantages. However, the phase segregation propensity and poor compatibility of CR/SBS polymers with asphalt, are significant issues that have a direct impact on the long-term stability of modified asphalt. The behavior of CR/SBS modified binders was investigated in relation to CR size and SBS structure. The results revealed that there exists an optimum value for the soft and hard segments of SBS molecular structure, which results in greatest modulus, viscosity, rutting factor and creep recovery rate of modified asphalt. Softening point difference, Han curve, and Cole-Cole plot were employed to further assess the influence on storage stability and compatibility between modifiers and asphalt. Suitable molecular configuration and CR size balance the hardness and flexibility. Under the action of high temperature and high shear, stable three-dimensional spatial network structure is constructed to improve the compatibility and viscoelastic characteristic of polymers modified asphalt through physical interaction (compatibility reaction and solubilization reaction) as well as chemical reaction (desulfurization and depolymerization reaction and cross-linking reaction). Differential Scanning Calorimetry (DSC) curves thermal analysis show that hybrid binder exhibits higher thermal stability compared with original asphalt. • SBS molecular architectures and rubber scale effect were explored for asphalt modification. • The relationship between polymer structure and viscoelasticity was elucidated. • Copolymers formed by binding of CR and SBS have synergistic effect on asphalt. • Suitable molecular configuration and CR size balance the hardness and flexibility of modified asphalt.