Life Cycle Assessment of Construction Demolition Waste-Based Geopolymer Binder Within the Framework of Sustainability

Abstract

In today's world, where the population is rapidly increasing and natural resources are decreasing accordingly, the concept of Life Cycle Assessment (LCA) is becoming increasingly important in the fight against climate change and global warming. According to International Organization for Standardization (ISO) 14040/44 standards, life cycle analysis is an environmental assessment method that brings a holistic perspective to the life cycle of products or services. It identifies the environmental aspects and potential impacts associated with a product, process or activity by identifying and quantifying the energy and materials used and the emissions and waste generated by all processes. In this way, LCA aims to reduce resource consumption, reduce environmental emissions and thus reduce their impacts. In this LCA study, cradle-to-gate system boundary was determined and SimaPro software and the Impact 2002+ method was used. Within this thesis’s scope, geopolymer binders with lower environmental impacts were considered and life cycle analyses were carried out to develop environmentally friendly materials. The geopolymer binder systems were created using construction demolition waste (CDW), which has reached levels that cannot be ignored worldwide, thereby ensuring that CDW is controlled in the most environmentally appropriate way possible. In this study, in which construction demolition wastes such as hollow brick, red clay brick, roof tiles, concrete waste and glass waste were used, 2 types of geopolymer mortar mixtures, a completely CDW-based geopolymer mortar (CDW100) and supplementary cementitious materials (SCM) substituted geopolymer mortar (CDW80SCM20), were created and their environmental impacts were evaluated with LCA. Then, in order to observe the negative effects of cement on the environment, a cementitious mortar mix was also included in the system and compared with the geopolymer mortar mixes. According to the findings of impact assessments, CDW-based geopolymer mortars exhibited significantly lower environmental impacts except for aquatic eutrophication and ozone depletion. The advantages of geopolymer mortars in terms of environmental impacts made it possible to reduce the global warming effect by 48.1%, aquatic acidification by 22.1%, land occupation by 45.2% and non-renewable energy by 1.83%. However, aquatic eutrophication and ozone depletion were higher compared to ordinary Portland cement (OPC) mortar. Compared to CDW100, CDW80SCM20 showed a slightly higher impact in the environmental impact categories. The largest difference in this comparison is for land occupation and global warming with 30.8% and 16.9% respectively. These outputs revealed that the geopolymer system containing only CDW is more advantageous in terms of environmental impact, while the potential disadvantage caused by the use of SCM retains its advantage compared to OPC mortar (except for non-renewable energy).