Multiscale Study on Low Temperature Crack Resistance Mechanism of Steel Slag Asphalt Mixture

The objective of this paper was to study low temperature crack resistance mechanism of steel slag asphalt mixture(SAM). Thermal stress restrained specimen test (TSRST) and three-point bending test were carried out to evaluate the low-temperature crack resistance of SAM and basalt asphalt mixture (BAM). Based on the digital image correlation technique (DIC), the strain field distribution and crack propagation of SAM were analyzed from the microscopic point of view, and a new index, crack length factor (C), was proposed to evaluate the crack resistance of the asphalt mixture. The crystal phase composition and microstructure of steel slag aggregate (SA) and basalt aggregate (BA) were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to explore the low-temperature crack resistance mechanism of SAM. Results show that the low-temperature crack resistance of SAM is better than that of BAM; SAM has good integrity and persistent elastic deformation, and its bending failure mode is a hysteretic quasi-brittle failure; The SA surface is evenly distributed with pores and has surface roughness. SA has the composition phase of alkaline aggregate-calcite (CaCO3), so it has good adhesion to asphalt, which reveals the mechanism of excellent low-temperature crack resistance of SAM.