Damage evolution of steel slag asphalt mixtures under freeze–thaw cycles: a combined DIC and AE analysis

In order to comprehensively reveal the freeze‒thaw (F‒T) damage mechanism of warm mix steel slag rubber powder-modified asphalt mixtures (CR-WSAM). This study is based on acoustic emission (AE) characteristic parameters and digital image correlation (DIC) strain cloud maps. To analyse the CR-WSAM damage evolution process under the action of different F–T cycles. A Markov chain damage model is built to predict damage states. The results show a consistent effect of synergistic monitoring of AE and DIC. F‒T cycles weaken the mixture's resistance to damage, significantly reducing the acoustic emission energy and b-value, resulting in the formation of numerous primary microcracks in the specimens. The solution enters the cracks and has a stripping effect on the asphalt aggregate interface. Tensile damage dominates in pure Type I cracking, but shear damage is still present. The damage is divided into three stages, and stage III shear damage is more pronounced. Shear damage accounted for less than 10% at −10°C. Shear action had a positive effect on the damage resistance of the asphalt mixtures. According to the damage stages, a damage prediction model based on the Markov chain is proposed, which can accurately reflect the damage state of asphalt mixtures.