Temperature induced self-healing capability transition phenomenon of bitumens

Abstract

The temperature may induce the inconsistent order of self-healing capability between two bituminous materials, which could be called as the temperature induced self-healing capability transition phenomenon. To confirm this phenomenon, two base bitumens and four different styrene–butadiene-styrene polymer modified bitumen (SPMB) binders are selected to systematically investigate their self-healing capability through establishing the healing rate temperature (HR-T) curves and healing index temperature (HI-T) curves. Fluorescence microscopy (FM) is applied to study the internal morphology of different SPMB binders. The phase transition (PT) temperature range is determined by the differential scanning calorimeter (DSC) test. Within the PT temperature range, three kinds of special temperatures are discovered, i.e. healing peak temperature (HPT), healing critical temperature range (HCTR) and healing cross temperature (HCT). The HPT and HCTR are both lower than the high temperature PT range, followed by the softening point, and can be applied as the optimum healing temperature to guide the formulation of energy efficient pavement induction healing strategies. The HCT clearly divides the HR-T curves or HI-T curves of bitumens into different parts, thus leading to an opposite order of self-healing capability between two bitumens, which confirms the self-healing capability transition phenomenon. Therefore, the self-healing capability can not be evaluated comprehensively and accurately at only one given temperature. Most notably, it can be inferred that the temperature induced phase structure and property transition of bitumen is the essential reason for the self-healing capability transition phenomenon, which is significantly affected by the bitumen type, polymer type and content.