Development of Water-Cured Alkali-Activated Concrete with a High Volume of Silica-Rich Waste Limestone Powder and GGBS and Fly Ash Materials: Strength, Durability, and Life Cycle Assessment

Significant amounts of finely ground waste powder are produced during the heating process of silica-rich limestone aggregates in asphalt concrete plants. This resulting by-product poses challenges and opportunities in the scope of environmental sustainability, waste management, and resource utilization. Some attempts were made to utilize limestone powder in concrete production; however, its use was limited to a small quantity. Thus, this paper explores the feasibility of utilizing a high proportion of silica-rich waste limestone powder (LSP) in combination with ground granulated blast furnace slag (GGBS) and fly ash (FA) as precursor materials in producing alkali-activated mixtures. A series of experiments were conducted to evaluate the mechanical properties, durability characteristics, and microstructural analysis of the developed water-cured alkali-activated mortars and concrete. The results showed that the mixtures having a high volume of LSP (40%-50%) and GGBS/FA as precursor materials demonstrated adequate flowability (186-240 mm), satisfactory compressive strength (33-45 MPa), and good durability (water absorption was in the range of 2.6%-3.8%). In addition, the microstructural analysis in terms of scanning electron microscope (SEM), energy dispersive spectroscope (EDS), and Fourier transform infrared (FTIR) spectrometer revealed a dense microstructure with gel formation, which was correlated to mechanical strength. Finally, the environmental impact based on the life cycle assessment was evaluated, and the developed mixtures exhibited an average emission reduction of 63% compared with traditional concrete. The findings of this study suggest that waste LSP, typically disposed in landfills, can be effectively utilized up to 50% in the production of environmentally sustainable concrete.