Development and characterization of binary recycled ceramic tile and brick wastes-based geopolymers at ambient and high temperatures

Abstract Although construction and demolition waste usually include more than one type of material in in-situ conditions, it has rarely been studied combined in geopolymer systems. This paper explored an experimental approach to combine recycled brick (RBW) and recycled ceramic tile (RCT) wastes in binary geopolymer binders prepared fully at ambient temperature. In order to optimize their physical and chemical parameters, the binary geopolymers were designed at 20 to 80% of RBW and RCT, reduced liquid/solid ratio (L/S), and pre-estimated chemical factors of SiO2/Al2O3 and Na2O/SiO2 of the entire composition. The interrelation between the preselected design factors and the flowability, setting time, compressive strength, and microstructure of binary RBW + RCT binders was explored. Also, metakaolin (M), ground granulated blast furnace slag (GGBS), fly ash-C (FC) and fly ash-F (FF) partially replaced (RBW + RCT) at 15, 30 and 45% to explore another method of improvement in the ambient environment. The effect of the curing temperature was considered by treating the optimized binary mixtures at 50, 75, and 100 °C curing temperatures for the initial 24 h after casting. In addition, microstructural studies with X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-Ray spectroscopy (SEM-EDS), and Fourier transformed infrared (FTIR) spectroscopy were completed to depict microstructural changes at different design parameters and curing conditions. In addition to precursor powder contents of 20% RBW and 80% RCT, SiO2/Al2O3 and Na2O/SiO2 ratios of 10.0 and 0.24, respectively, were required to reach enhanced compressive strengths at room and high temperatures. Incorporating 45% FC in ternary mixtures contributed to achieving a very strong improvement of 88% in compressive strength at 28 days. Along with N-A-S-H formations, the amount of C-A-S-H/C-S-H dominated the level of geopolymerization and resulted in considerable compressive strengths of the binary and ternary binders.