Impact of addition of polyvinyl chloride on the properties of clayey soil using experimental approach and optimization for geotechnical engineering applications

In geotechnical engineering, soil stabilization is essential for improving the properties of clayey soils in infrastructure projects. This study explores the use of response surface methodology to optimize the utilization of polyvinyl chloride (PVC) waste as a stabilizing agent in proportions ranging from 2.5 to 30%. The percentages of clay and PVC served as input parameters, while the outputs included the CBR index, compressibility coefficient (Cc), swelling coefficient (Cs), and swelling pressure (Ps). Experimental results showed that replacing up to 30% of clay soil with the PVC improved key properties, such as the methylene blue value which had a relative decrease of 24.9%, consistency limits (LL, LP, and IP) underwent significant reductions of approximately 15.94%, 13.44%, and 17.2%, respectively, compaction parameters OMC and MDD show reductions of 52.38% and 10.32%, and consolidation characteristics Cc, Cs, and Ps show significant reductions of 92.55%, 43.64%, and 77.04%. For mechanical performance, including soaked CBR with a significant increase of 159.69% and penetration pressure, a 10% PVC replacement was identified as optimal. A quadratic predictive model was developed to optimize these responses, achieving a high coefficient of determination (R² > 0.97) and statistically significant P-values (< 0.0001) for all outputs. These results underscore the model's reliability and the potential of using PVC waste as a sustainable stabilization material. The approach is cost-effective, scalable, and eco-friendly, utilizing the PVC waste to stabilize soils, reduce environmental impacts, and enable sustainable infrastructure.