Waste Glass as Partial Binder Precursor and Fine Aggregate Replacement in Alkali Activated Slag/Fly ash System

Abstract

Fast increasing of generation and release of undesirable pollutants by the industrialization raise concerns about the environmental consequences of waste disposal. Among these waste materials, non-recycled waste glass constitutes one of the majority wastes produced in many European countries and sets a major environmental issue. Although glass could be recycled into the packaging stream without significantly changing its chemical and physical properties, there is still a significant proportion, which does not meet the strict criteria for packaging glass, to be sent to landfill. Waste glass is not a biodegradable material, which made landfilling waste glass become a highly unsustainable option. To find a better solution to reduce the environmental issues caused by disposal of waste glass, alkaline activation technology is introduced to use waste glass into alkali activated materials (AAMs) to produce construction materials. Waste glass is believed to have the potential to serve as precursor material in geopolymer production because of abundant amount of amorphous silica in a structure that does not reflect long range order. However, limited research has been conducted on waste glass as precursor material in AAMs, neither is the utilization of waste glass as replacement for binder precursor like fly ash. Currently, the feasibility of using waste glass in geopolymer systems is still largely unknown. This research project aims at a better understanding of the feasibility of using waste glass powder as partial binder precursor to create AAMs along with fly ash and slag and also the feasibility of using fine waste glass aggregate as partial aggregate replacement in geopolymer mortar. The main focus of this research is on the reactivity of waste glass powder and its influence on the microstructure development and gel formation, with correlation with mechanical strength. It has been found that: Waste glass powder, which is dominantly in irregular polygonal shape, has much finer particles size distribution and larger specific surface area compared with fly ash and slag. It has abundant amorphous Si and Ca, and has higher reactivity than fly ash. Waste glass powder serves as effective precursor replacement for fly ash in alkali activated slag/fly ash system. Fine waste glass aggregate is possible to be utilized to replace sand in alkali activated mortars when suitable workability is taken care off. This study provides a better insight on properties of waste glass powder as well as promotes understanding of the influence of waste glass powder on microstructure and gel formation, which is essential for future research and engineering application of this kind of waste material.