Comparative life cycle assessment analysis of mono, binary and ternary construction and demolition wastes-based geopolymer binders

Abstract

The global construction industry is in high demand of sustainable building materials that are cost-effective and simultaneously have a low carbon footprint and energy consumption. As a result, geopolymeric materials primarily derived from construction and demolition wastes (CDWs) have become more attractive sustainable alternatives to ordinary Portland cement (OPC)-based cementitious materials. This paper aims to comparatively analyze the life cycle assessment (LCA) of CDW-based geopolymers comprising recycled brick powder (RBP), recycled ceramic tile powder (RTP) and recycled concrete powder (RCP) at the mono, binary and ternary geopolymer (GP) binder systems. The mono GP binders were synthesized based on pre-targeted design chemical parameters of SiO2/Al2O3 and Na2O/SiO2 molar ratios and liquid-to-solid (L/S) ratio, while the binary and ternary combinations considered different RBP, RTP and RCP precursor contents at the optimized SiO2/Al2O3 and Na2O/SiO2 molar ratios of each constituent CDW precursor in the geopolymer matrices. The LCA analysis was performed through experimental results in terms of embodied energy (E-energy) consumption (Ef), and embodied carbon dioxide (E-CO2) emissions (Cf) as indicators of the global warming potential (GWP) of these GP systems while considering ambient curing. Interesting results were attained in terms of improved sustainable environmental impact of the ternary integration of CDW materials than their mono and binary counterparts when used as precursors in geopolymer binders. The synthesis of the optimal ternary composition of BTC-20:40:40 synthesized at SiO2/Al2O3, Na2O/SiO2 and L/S ratios of 10.2, 0.18 and 0.30, respectively resulted in the lowest embodied CO2 emission of Cf = 5.58 kg/ton/MPa and embodied energy of Ef = 18.61 MJ/ton/MPa, indicating 110.8% and 157.9% reduction in terms of embodied carbon dioxide and embodied energy, respectively, as compared to the reference Portland cement (OPC) binder with equivalent strength at 28 days.