Enhancing Mechanical Performance of Geopolymer Concrete with Manufactured Sand: An Experimental Study

Concrete remains one of the most widely used and dependable construction materials globally. However, the rising demand for Ordinary Portland Cement (OPC) and natural river sand in the construction sector has led to significant environmental concerns. The production of OPC contributes heavily to CO₂ emissions—approximately one ton of CO₂ is released for every ton of OPC produced—due to limestone calcination and fossil fuel combustion. Additionally, the overexploitation of river sand has caused environmental degradation and supply shortages. This study explores a sustainable alternative by investigating the mechanical performance of geopolymer concrete (GPC) incorporating manufactured sand (M-sand) as a substitute for natural river sand. Geopolymer concrete, composed of Class F fly ash, ground granulated blast furnace slag (GGBS), and activated with alkaline solutions such as sodium silicate (Na₂SiO₃) and sodium hydroxide (NaOH), offers a viable replacement for OPC-based concrete. The mixes were prepared with NaOH molarities of 12M and 16M for G30 grade concrete. A sodium silicate to sodium hydroxide ratio of 2.5 and a SiO₂ to Na₂O ratio of 2 were maintained. Oven curing was conducted at 60°C. Manufactured sand was used as a partial and full replacement for natural sand at 0%, 50%, and 100%.