Research on the performance of asphalt mixture with acid-treated steel slag based on microscopic properties

In order to investigate the expansion of steel slag and improving the performance of steel slag asphalt mixtures, 5 %, 10 % and 15 % concentrations of acetic acid solution were used for the pretreatment of steel slag. Fundamental physical-mechanical properties of steel slag were assessed, and the chemical composition and microscopic morphology of acid-treated steel slag were examined using XRF, SEM, EDS, and XRD analyses. Furthermore, steel slag asphalt mixtures were prepared by substituting the acid-treated steel slag for basalt aggregates, and the high-temperature performance, low-temperature performance, volume stability, water resistance, and fatigue behavior of asphalt mixtures incorporating acid-treated steel slag were investigated. Additionally, The comprehensive three-dimensional analysis of the pore structure in acid-treated steel slag asphalt mixtures was conducted to show the fundamental connection between their microscopic and macroscopic properties. The results reveal that the acetic acid pretreatment decreases the levels of f-MgO and f-CaO in steel slag effectively, thereby reducing its expansion. Moreover, the surface roughening induced by acetic acid pretreatment significantly enhances adhesion between asphalt and the steel slag surface. Meanwhile, acetic acid treatment also enhances road performance of steel slag asphalt mixtures, particularly exemplified by A15-AM (15 % acid-treated steel slag asphalt mixture). Additionally, the pore structure of the acid-treated steel slag asphalt mixture was refined, leading to an improvement in its road performance.