Life Cycle Assessment of Geopolymer Materials Utilizing Construction and Demolition Waste

Abstract

This study assessed the environmental impacts of construction and demolition waste (CDW)-based geopolymers. For analysis, the cradle-to-gate system boundary was established. Two different geopolymer mixtures were evaluated: one composed entirely of CDW-based precursors-(CDW100), and another incorporating supplementary cementitious materials-(SCMs) as a 20 % replacement of CDW-based precursors-(CDW80SCM20). Raw materials were sourced from a diverse range of demolition waste. NaOH and Ca(OH)2 were employed as activators. Additionally, a cementitious mixture with comparable strength was included in the analysis as a benchmark for comparison with the geopolymers. The results of the impact analyses revealed that CDW80SCM20 had a greater environmental impact across various categories compared to CDW100. The relatively higher environmental impacts of the CDW80SCM20 mixture are largely attributed to the transport-related environmental burdens associated with the inclusion of SCMs. The largest differences were for land occupation and global warming, at 30.8 % and 16.9 %, respectively. Moreover, the results indicated that the environmental impacts of the CDW-based mortars were significantly lower than those of the cementitious system, with the exception of aquatic eutrophication and ozone layer depletion. The increase in ozone layer depletion is mainly associated with the production of NaOH via the chlor-alkali process, which contributes to emissions affecting stratospheric ozone. The advantages of geopolymers in terms of environmental impact made it possible to reduce the effects of global warming by 48.1 %, aquatic acidification by 22.1 %, land occupation by 45.2 %, and nonrenewable energy consumption by 1.83 %. However, aquatic eutrophication and ozone layer depletion were found to be higher compared to cementitious mortar.