Controlled Low Strength Material with Waste Materials for Trench Filling in Expansive Soils and Contaminated Sites

Abstract

Abstract Expansive soils exerting swelling pressures can lead to structural damage in underground utilities like foundations and pipelines. To address this issue, non-swelling materials can be used as substitutes for backfilling trenches. Controlled Low-Strength Material (CLSM) serves as a suitable alternative and can be prepared using industrial wastes and by-products. The objective of this research work is to replace the conventional filling materials with CLSM, especially in areas where swelling soils exert pressure on sewer pipes, water pipes, and structure footings. To ensure sustainability, industrial wastes like crumb rubber, arecanut fiber, and coconut fiber are incorporated to create the CLSM. From the compression tests, the ideal CLSM mixture identified was 1:10:25 of Cement: Flyash: Sand, with 5% Rubber, 0.2% Arecanut fiber, and 0.2% Coconut fiber. The swelling pressure of black cotton soil estimated by constant volume method was 317.65 kPa, which is relatively high. Consequently, replacing the swelling soils with CLSM emerges as a viable solution to prevent structural damages in lightweight structures. The utilization of CLSM in contaminated soils was also studied as the pollutants in the soil may cause structural damages to the foundation materials. The soil and CLSM materials were filled in trenches and the leaching tests were conducted with copper and zinc solutions of 1000 ppm. From the results, it was found that the CLSM prepared using waste materials is effective in reducing the migration of metals through it and hence it can be effectively used as a trench filling material in contaminated sites.