Construction and demolition waste-based self-healing geopolymer composites for the built environment: An environmental profile assessment and optimization

Recycling construction and demolition waste (CDW) to produce “green” construction materials is an effort to decarbonize the built environment. However, due to the energy-intensive processes involved, it is essential to quantify and optimize its environmental implications in the early stages of development. This study performs a cradle-to-gate Life Cycle Assessment (LCA) of novel 100 % CDW-based self-healing geopolymers with the objective to optimize the environmental implication of the production process and product. The geopolymer binder developed is intended to replace ordinary Portland cement (OPC) in conventional concrete due to its significant global warming impacts caused by massive CO₂ emissions. The precursors for the geopolymer are red clay brick (RCB) waste, roof tile (RT) waste, hollow brick (HB) waste, concrete waste (C), and glass (G) waste and the aggregates are recycled concrete aggregate (RCA). Six scenarios based on a series of mixtures with varying compositions (e.g., with/without granulated blast furnace slag (S) addition in some cases) are studied. The Life cycle assessment (LCA) analysis provides the environmental impacts for producing 1 m³ of geopolymer during its experimental stage to make more sustainable decisions. Goal and scope definition, inventory analysis, impact assessment, and interpretation are made based on ISO 14040 standards. The global warming potential (GWP) of the mixtures is studied and ranges between 711 (for the mixture without sodium silicate (SS))-1180 kg CO₂ eq (for the mixture with SS). Other impact factors studied are Acidification Potential (AP), Eutrophication Potential (EP), Ozone Depletion Potential (ODP), Ecotoxicity of Air, Human Health Particulate Air (HHPA), and Smog. A sensitivity analysis is also performed with varying renewable sources of electricity such as photovoltaics, biomass, wind, and hydroelectricity.