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

With the increasing depth of mining, 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, aiming to improve thermal insulation and promote sustainable waste utilization. Five mix designs were prepared with 0wt%, 5wt%, 10wt%, 15wt%, and 20wt% PVC dosages, and their thermo-mechanical behavior was systematically evaluated through uniaxial compressive strength (UCS) testing, thermal parameter measurements, energy evolution analysis, and SEM-based microstructural characterization. The results showed that 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. Thermal conductivity and specific heat capacity decreased progressively with increasing PVC content, with maximum reductions of 23.0% and 40.2% at 20wt% PVC, respectively. Microstructural analysis confirmed that moderate PVC addition reduced porosity and enhanced internal compactness, whereas excessive PVC likely inhibited C-S-H gel formation and weakened 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 may offer a practical strategy for mitigating thermal hazards in deep mining environments.