Balancing Sustainability and Cost in Concrete Production: LCA of Foam, Geopolymer, Slag, and Agricultural Waste Concretes
Muhammad Tamoor, Chunwei Zhang
Abstract
Cradle-to-gate LCA (IMPACT2002+ method, compliant with ISO 14040/44) compares the environmental and economic performance of nine concrete mixes, including concretes made with foam, geopolymer, metakaolin, slag, and rice husk ash. Significant differences are observed in global warming potential (GWP), acidification potential (AP), and particulate emissions. Foam concrete has the lowest environmental impact, with a negligible carbon footprint and minimal resource use, making it ideal for nonstructural applications. In contrast, despite being marketed as low-carbon, geopolymer and metakaolin concretes exhibit high GWP and AP due to the energy-intensive nature of their alkali activators and the production of calcined clays. These materials also incur substantial costs due to the energy-intensive production processes, including the use of activators, making them less economically competitive. Slag and rice husk ash concretes strike a balance between sustainability and cost-effectiveness, emerging as viable alternatives, especially in regions with abundant industrial byproducts. They provide reduced environmental impacts at an affordable cost. The study suggests that foam concrete is the most environmentally sustainable option, offering significant CO 2 reduction and cost benefits, particularly for nonstructural uses. While PCC remains the industry standard with the lowest environmental impact, GPC and MK, though economically competitive, require further standard formulations before their cost and environmental evaluations can be finalized. Self-healing concrete, although promising for long-term durability, presents high initial costs. Hemp concrete, while renewable and environmentally beneficial, has limited application due to its high processing energy requirements compared to foam concrete. This analysis guides the selection of concrete materials based on both cost-effectiveness and environmental impact, recommending foam concrete for low-strength applications and supplementary cementitious materials for general use, aligning concrete production with climate targets.