Applying multi-criteria decision-making on alternatives for earth-retaining walls: LCA, LCC, and S-LCA

Abstract

The aim of this research is to assess the sustainability performance of different concrete and stone walls being used in residential buildings in Malaysia in terms of environmental issues, economic concerns, and social aspects. The concrete walls consist of crib wall (CW), cantilever reinforced concrete wall (CRCW), and keystone wall (KW), while stone walls include gabion wall (GW) and rubble masonry wall (RMW). Four different assessment criteria such as global warming potential (GWP), ozone layer depletion (OLD), cost present value (CPV), and social impacts (SI) were considered. In this study, life cycle assessment (LCA) was conducted to evaluate the considered walls based on individual criteria of GWP and OLD, while life cycle cost (LCC) and social life cycle assessment (S-LCA) were performed based on CPV and SI, respectively. In S-LCA, three main social indicators such as workers, local community, and society were taken into account. Then, a multi-criteria decision-analysis (MCDA) approach is implemented to assess and prioritize alternative walls, which is resulted from LCA, LCC, and S-LCA, by considering combination of abovementioned criteria. The primary results of LCA for GWP criterion shows that the GW and RMW are the best options with respective emissions of 12784 KG CO2eq and 20020 KG CO2eq. On the other hand, the result for OLD indicates that the best alternatives are GW and RMW with respective emissions of 178.99 CFC-11 eq and 224.88 CFC-11 eq. The results of LCC declare that RCW is the best option by 595600 MYR which is 14% less than the second-best option (RMW). The S-LCA results show that the CW is the best option with 10% better than the second option (KW). The MCDA results revealed that the sustainability performance of the GW was the highest among alternatives followed by RWW, RCW, KW, and CW. The presented approach in this research has been successfully applied on a case study. It provides valuable insight on the assessment of earth-retaining systems assisting decision makers in prioritizing and selecting the most sustainable retaining walls to be used in residential buildings in Malaysia and other countries with similar climate conditions.