Design and Life Cycle Assessment of Retaining Wall with Used Foundry Sand as Backfill

Abstract

This life cycle assessment analysis in the present study compares energy consumption, carbon footprint, and environmental damages for the retaining wall backfilled with natural sand and used foundry sand (UFS). Utilization of UFS contributes toward lowering environmental impact in terms of waste management, ecological sustainability, and monetary benefits. This study consists of two sections, i.e., retaining wall design for modified backfill parameters, followed by a life cycle analysis (LCA) comparison study. Index and engineering properties of natural sand and UFS are determined for the retaining wall design based on codal specifications. As the study is aimed at evaluating life cycle assessment for construction instances where alternate materials like UFS are utilized, production, transportation, and utilization of conventional construction materials have been taken into consideration, along with the disposal of waste materials. The impact of variation in the height and type of wall is also studied. Environmental impact categories such as cumulative energy demand, human toxicity, and resource and ecosystem impact are evaluated for the cradle-to-gate variant. The software tool openLCA is used for environmental impact studies where the Ecoinvent database is considered with a mid-point approach. Factors of safety against external and internal stability of walls for different cases are considered and found to be above permissible limits. The impact categories are significantly affected and depict a loss in values when the UFS mixture is used as a retaining wall backfill. This is because UFS introduction in sand reduces earth pressure leading to savings in natural sand, concrete quantity, reinforcing steel, and fuel quantity consumed by building machines and vehicles transporting construction materials. The study concludes that in all examined impact categories, an alternative material provides a significant environmental benefit than the conventional material without compromising stability. The results demonstrate that the use of UFS is very effective as a sustainable alternative to natural sand for the backfill of retaining structures.