Low-Density Cellular Concrete as a Sustainable Replacement for Granular Fills in Bridge Approaches

Traditional construction of bridge approaches requires an enormous volume of aggregates. Because the materials needed for many of these projects require hauling from long distances, larger amounts result in increased construction costs and associated carbon footprint. Additionally, quarrying these huge volumes of aggregates has a destructive impact on the environment. As the push for sustainable construction increases, there is a need for more environmentally friendly construction materials. This study aims to assess the environmental benefits offered by using low-density cellular concrete (LDCC) as a substitute for granular fill materials for mechanically stabilized earth (MSE) walls used for bridge approaches. The life cycle assessment (LCA) technique is applied to appraise the global warming potential (GWP) for six LDCCs and two granular fill materials. LCA is conducted across three phases: material extraction, transportation, and construction of the selected fill material life cycle. The GWP is estimated for 250 cubic meters of fill materials. The estimated GWP of six LDCCs ranges from 46 to 118 tons of carbon dioxide equivalents (CO₂e), whereas the aggregates fill released 186 tons of CO₂e, and the soil fill caused 191 tons of CO₂e. Overall, the GWP reduction by substituting granular fill with LDCC is between 37% and 75%. LDCC construction requires lower transportation of raw materials to the construction site, resulting in a reduction of 80% of truck loads when compared to granular fills. The results from this work indicate that LDCC can be a sustainable replacement for the traditional granular fills; however, some design adjustments for MSE walls are necessary. The conclusions and outcomes generated from this paper will support practitioners in quickly assessing the environmental impacts of using different fill materials for MSE walls.