Analysis of the feasibility of using tunnel dreg-based recycled sand and powder for concrete production in a high-altitude region through lab-scale tests.

The utilization of tunnel dreg-based recycled sand (TDRS) concrete in high-altitude regions kills four birds with one stone by reducing carbon emissions, addressing raw material shortages, promoting the value-added utilization of building solid waste, and encouraging recycling in construction. Herein, concrete incorporating varying amounts of TDRS powder (4-12%) and sand ratios (37-43%) was prepared and real high-altitude environment exposure tests were carried out. The mechanical properties, drying shrinkage, microstructure, carbon footprint, and costs were systematically analyzed. Results show that compressive strength and drying shrinkage initially increase then decrease with rising TDRS contents, attributed to TDRS concrete's dense microstructure with ∼ 50 nm pore size. A modified drying shrinkage model for TDRS concrete achieved prediction errors within ± 10%. Replacing natural sand with TDRS reduces carbon emissions by 11.204 kgCO2/t, and shortens transport distances, yielding at least 13.7% reduction in costs. Future systematic research on the durability and long-term performance of TDRS concrete is essential for advancing its practical application.