Effect of lithology on the freeze-thaw damage behavior of tunnel slag concrete: Experimental and numerical investigations

The application of tunnel slag in the production of concrete raw materials can significantly alleviate the shortage of natural sand aggregates, reduce the costs associated with transporting raw materials, and contribute to environmental protection. However, the influence mechanisms of the lithology for tunnel slag products (coarse aggregate, fine aggregate, and stone powder) on the basic properties and frost resistance of concrete remain unclear. This study initially experimentally investigated the slump, compressive strength before freeze-thaw cycles (FTCs), as well as mass loss rate, relative dynamic elastic modulus, and pore structure after FTCs for the concrete incorporating tunnel slag products (tunnel slag concrete, TSC), including granite, limestone, and gneiss TSC. Furthermore, the cohesive zone model was adopted to explore the freeze-thaw damage of TSC and validated through the aforementioned tests. Based on this model, the freeze-thaw failure patterns and residual compressive strength of concrete containing varying lithological tunnel slag products and stone powder contents were examined after FTCs. Finally, a freeze-thaw damage prediction model for TSC with an initial porosity greater than 0.78 % was established. The results indicated that the number of FTCs required for granite and limestone TSC to reach the same damage was 25–50 greater than that of gneiss specimen with same amount of stone powder, and reducing the stone powder content can significantly enhance frost resistance of TSC. Additionally, the freeze-thaw damage of TSC was directly related to its initial porosity, and the damage prediction model based on initial porosity provided a more accurate forecast of freeze-thaw damage in TSC. This study aims to offer a feasible solution for the resource utilization of tunnel slag and ensure the durability of TSC structures in cold regions.