Life Cycle Assessment and Carbon Footprint Analysis of Recycled Aggregates in the Construction of Earth-Retaining Walls During Reconstruction

Abstract

AbstractIn a nation, reconstruction is needed to provide resiliency and maintain economic growth. To remedy the damage done on roads and highways after an event, the reconstruction of earth-retaining walls (ERWs) before road/highway rehabilitation is of great importance. This would provide land transportation routes from airports or emergency personnel services to save lives and transport supplies/materials to disaster-stricken areas. It is one of the most common structures in civil engineering designed to retain earth pressure on roads and highways. It is constructed using concrete, a widely used construction material with high material consumption and carbon footprint. Aside from these, construction and demolition wastes (CDW) arise from the damaged ERWs and any concrete materials contributing to adverse impacts on the environment. These alarming facts are some of the many reasons for evaluating construction materials, such as using life cycle assessment (LCA) on CDWs. This paper investigates the use of ERWs using concrete from cradle-to-gate with natural aggregates (NAs) and recycled aggregates (RAs) from CDW. It considers three ERW types, such as gravity wall, cantilever wall, and mechanically stabilized earth (MSE) wall. It was found that the construction of MSE walls, among other types of earth retaining structures, is found to be 50–70% of less impact than other types of ERWs in this study. The utilization of RA in the production of concrete is up to 15% less impactful than NA, even with the additional 10% increase in cement content to compensate for the strength loss from the use of RA to NA. In ideal condition, the transport distances of NA and RA should be around 15–20 km from extraction of raw materials and processing, to concrete pouring. A limit of 100 km transport distance for RA must also be considered so that the environmental benefits from the use of RA would not be outweighed. Further studies on the economic aspect and the sustainability of its supply chain during the reconstruction are recommended.KeywordsLife cycle assessmentRecycled aggregateRetaining wallConcreteConstruction and demolition waste