Effect of metakaolin and lime addition on geopolymerization of construction and demolition waste

Construction and demolition waste generates the largest amount of waste by volume, which threatens sustainable development and adversely affects the environment. These wastes contain a significant amount of aluminosilicates that have the potential to be used as building materials for value-added applications applicable to alternative construction materials. This study aims to synthesize geopolymers from brick powder using metakaolin/lime as additives and compare their physico-mechanical properties. The compressive strengths of the geopolymer products GP-1, GP-2, and GP-3 developed at 28 days from brick powder and metakaolin/lime with the activator solution were found to be 8.35, 21.30, and 25.0 MPa respectively, 2.55 and 2.99 times higher when metakaolin and lime were added. FTIR spectra and SEM-EDX micrographs of the reaction products showed structural changes and formation of aluminosilicate hydrate and calcium silicate hydrate gel with Al₂O₃/Na₂O ratios of 0.75, 1.67, and 1.98 respectively. The reaction products containing SiO₂/(SiO₂ + Al₂O₃ + Fe₂O₃) ratios of 0.70 and 0.76 were found to be desirable. The geopolymer product GP-3 was found to have a higher bulk density and mechanical strength than those of GP-1 and GP-2. These products are found to be very hard, with potential applications in construction industries to conserve the environment.