Ternary Combination of Industrial Wastes for Sustainable Geopolymer Mortars

Abstract

AbstractConsidering the high carbon footprint, the adverse environmental impact of Portland cement has been evident over the past decades. On the other hand, the disposal of growing industrial waste is also an environmental concern. Industrial by-products, such as fly ash, ground granulated blast furnace slag (GGBS), ladle furnace slag (LS) and silica fume (SF), are gaining importance as an alternative to ordinary Portland cement to achieve sustainability in the construction industry. This research experimentally evaluated the effect of various industrial waste-based binders, alkali concentration, curing temperature and curing age on the compressive strength of geopolymer mortars. The mortar mixes used a ternary combination of binders in the range of GGBS 50–70%, LS 20–30% and SF 10–20% by mass. The sand, binder and alkaline activator ratio of 2.75:1:0.45 was maintained, and the strengths of alkaline solutions were 4, 6 and 8 M. The workability of fresh mortar was evaluated using the flow table test. After 24 h of casting, temperature curing at 60 °C and 80 °C was applied for 24 h. Following that, the samples were cured at ambient temperature, and the compressive strength was measured at the ages of 3 and 7 days. A set of the sample was cured at ambient temperature to compare the effect of heat curing. The effect of curing temperature on compressive strength was found to be more prominent than that of curing time. The result indicated 6 M alkaline is optimum, and using this, a sample with 60% GGBS, 20% LS and 20% SF in binder content gave the highest compressive strength (48.8 MPa) with 145 mm flow. In general, the ternary combination of waste binders with heat curing could be a sustainable option for the future of geopolymer concrete.KeywordsGeopolymer; ternary combination; ground granulated blast furnace slagLadle furnace slagSilica fume