Study on the effect of recycled polyvinyl chloride powder on the properties of cementitious composite

A novel type of cementitious composite was proposed and studied, where recycled polyvinyl chloride (PVC) aggregate was employed as fine aggregate to partially replace the fine aggregates of sand in varying proportions. The fine aggregates of sand were replaced at five volume ratios (5 %, 10 %, 20 %, 30 %, and 50 %). A series of experiments were carried out to evaluate the workablity, mechanical properties and durability of the proposed cementitous coposites with PVC. The scanning electron microscopy (SEM) was applied to study the relationships between the mechanical properties and microstructures. The results showed that the fluidity increased by 12.5 % with a 50 % PVC replacement. However, the dry density decreased by 5 %, and water absorption increased with a higher PVC content. The compressive strength declined by 3.7 %, 6.1 %, 6.3 %, 11.5 %, and 28.8 % as the replacement ratio increased from 5 % to 50 %; while, the flexural strength decreased by 3.7 %, 6.8 %, 9.8 %, 17.0 %, and 23.5 %, respectively. The relative dynamic elastic modulus showed a 12.2 % reduction at 50 % PVC replacement. These decreases are attributed to the weaker bonding between PVC particles and the cement matrix, increased porosity, and micro-cracks at the interface transition zone, as confirmed by the SEM examination. The microstructural analysis revealed more porous and cracked interface zones with a higher PVC content, which impacted the mechanical properties of the composites. Despite the reduction in the mechanical strength, the durability of the composite improved significantly, with an enhanced resistance to chloride ion penetration and freeze-thaw cycles.