Sustainable repurposing of polyvinyl chloride waste as aggregates in limestone-calcined clay cement

This research addresses the urgent need for sustainable construction practices by presenting an innovative approach to mitigate the environmental burden associated with Polyvinyl Chloride (PVC) waste disposal. This study offers a dual benefit of waste management and resource conservation by repurposing PVC as aggregates in cementitious systems. The study aims to explore the impact of substituting natural aggregates with up to 100 vol% of two types of PVC—soft PVC from electric wire coverings and hard PVC from water pipes—on the fresh properties, mechanical strength, physical performance and environmental impact of the limestone-calcined clay cement (LC3) system. Incorporating both hard and soft PVC reduced the flowability significantly. In addition, flexural and compressive strength of LC3 mortars declined by around 52% and 48% for H-PVC, and by around 64% and 87% for S-PVC mixes, respectively. However, completely substituting natural aggregates with PVC enhanced thermal insulation by up to 60% compared to control samples. The thermal conductivity of LC3 containing 100 S-PVC achieves the requirements of RILEM to be considered as an insulating lightweight cementitious material. PVC incorporation exhibited mixed effects on sound insulation. On the other hand, the total absorbed energy increased significantly by 290% and 305% for 100% hard (HPVC) and 100% soft (SPVC) samples, respectively, compared to the control sample. Conversely, the peak impact force slightly decreased for LC3 with HPVC, while LC3 with 100% SPVC showed a reduction of about 53%. The use of PVC aggregates remarkably diminished the carbon footprint of the selected mix designs, suggesting that recycling PVC into aggregate for cementitious materials offers a sustainable solution for both load-bearing (HPVC) and non-load-bearing (SPVC) applications.