Thermomechanical and microstructural characteristics of cemented backfill incorporating low-dosage polyvinyl chloride powder

With the increasing mining depth, heat hazards have become a critical challenge in deep underground operations. This study explores the incorporation of polyvinyl chloride (PVC) powder as a partial cement replacement in cemented backfill to improve thermal insulation and promote sustainable waste utilization. Five mix designs were prepared with 0, 5wt%, 10wt%, 15wt%, and 20wt% PVC, and their thermomechanical behaviors were systematically evaluated through uniaxial compressive strength (UCS) testing, thermal parameter measurements, energy evolution analysis, and microstructural characterization via scanning electron microscopy. The results showed that the UCS and energy absorption capacity first increased and then decreased with PVC addition, reaching an optimum at 10wt% PVC, which achieved an 87.5% higher strength and improved energy dissipation compared with the control. The thermal conductivity and specific heat capacity progressively decreased with increasing PVC content, with the maximum reductions of 23.0% and 40.2%, respectively, for 20wt% PVC. Microstructural analysis confirmed that moderate PVC addition reduced the porosity and enhanced the internal compactness, whereas excessive PVC likely inhibited calcium silicate hydrate gel formation and weakened the structural integrity. A PVC dosage of 10wt% was identified as the optimal replacement level, providing a favorable balance between strength and thermal insulation. This study provides new insights into sustainable backfill design and offers a practical strategy for mitigating thermal hazards in deep mining environments.