Development of optimized binary ceramic tile and concrete wastes geopolymer binders for in-situ applications

Abstract This study explored the development of an optimized binary geopolymer system of ceramic tile waste (CTW) and concrete waste (CW) for more sustainable use in in-situ applications. The geopolymer binders were synthesized based on a physico-chemical method of different CTW and CW combinations, between 20% and 80%, predetermined liquid-to-solid (L/S) and chemical parameters of SiO 2/Al2O3 and Na2O/SiO2 ratios, while using curing at room temperature. The flow spread diameters, setting times, compressive strengths and microstructural investigations of binary compositions were performed at various CTW and CW contents and preselected oxide values. Meanwhile, the effect of short-term elevated temperatures on the optimum strength combinations was also considered under 50 °C, 75 °C, and 100 °C. Moreover, further optimization was tried at ambient curing by incorporating supplementary cementitious materials (SCM) in ternary CTW-CW-SCM compositions including 15%, 30% and 45% of metakaolin (MK), ground granulated blast furnace slag (GGBS), Class C fly ash (FC) and Class F fly ash (FF). X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) were performed to investigate the effect of the mentioned parameters on geopolymer formations. The results indicate that the optimum binary CTW + CW composition can be reached at 40% CTW + 60% CW and SiO 2/Al2O3 and Na2O/SiO2 of 12.3 and 0.18, respectively. Adding 45% GGBS content in ternary mixtures helped attain very high strength binders of more than 100 MPa at normal conditions. Along with the designed physical and chemical ratios, the amount of Ca2+ played a dominant role in enhancing the degree of geopolymerization and the properties of C-A-S-H/C-S-H and N-A-S-H reaction products.