Improving the Mechanical Properties of an Expansive Soil using Polyethylene Terephthalate and Recycled Concrete Aggregate

Abstract

A million tons of concrete are thrown away in the environment after the demolition of civil structures, each year. Similarly, polyethylene terephthalate is extensively used in plastic bottles, which is also discarded in the environment without any proper disposal system. This study tests the efficacy of polyethylene terephthalate and recycled concrete aggregate waste materials to improve the mechanical properties of expansive soil. To attain the study objectives, laboratory tests such as grain size, Atterberg limits, standard compaction, California Bearing Ratio, direct shear, and XRD tests were employed. The XRD test results show that the soil contains minerals such as montmorillonite and illite, which have a high affinity for water. The treated soil shows peak strength and CBR value at 15% PET and 15% RCA, which is due to the percentage increase in calcite after the treatment which is clearly observed in the XRD analysis of treated soil. The strength decreases with the wet-dry cycles, initially but it provides insignificant changes after 7th cycles. The treated soil provides maximum CBR of 17.1% at the optimal concentrations of additives, which is almost 76.68% more than the untreated soil. The untreated soil provides a California bearing ratio of 9.67 %, marginal to the road criteria for a minimum wet CBR of 7%. The study findings show that polyethylene terephthalate and recycled concrete aggregate materials are effective in improving the mechanical behaviour of the soil.