Optimization and characterization of geopolymer binders from ceramic waste, glass waste and sodium glass liquid

Abstract

The development of ambient cured sustainable geopolymer binders was investigated throughout this study. Ceramic waste (CW), devitrified glass waste (DGW) and metakaolin (MK) were used as precursors, and sodium glass liquid (SGL) prepared from DGW as an alkali hardener. The chemical molar ratios of SiO2/Al2O3 and Na2O/SiO2, and the physical ratio of liquid/solid (L/S) were adjusted using an algorithmic mix design technique. This considered the chemical compositions and contents of precursors and hardeners. Produced binders were evaluated in fresh and hardened states using rotational viscometry, compressive strength measurements, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Fourier-Transform Infrared Spectroscopy (FTIR). The results demonstrated that, at a lower contribution of CW, binders develop lower yield stress and plastic viscosity; while the inclusion of SGL can cause reduced plastic viscosity if SiO2/Al2O3 values are not adjusted to reduce the extra soluble silica in the network. Additionally, the incorporation of 75%DGW +25%MK with CW precursor enhanced the compressive strengths of glass waste-based binders, whereas the use of 50%DGW +50%MK by CW replacement resulted in remarkable improvements in the strengths of ceramic waste-binders. The incorporation of SGL hardener in geopolymer binders containing ceramic waste, glass waste and metakaolin allowed high reductions in the commercial sodium silicate by 36%–76%. Also, it was possible to attain structural strengths equivalent to the control mixture without SGL, though this was valid only when an appropriate arrangement of silicate molecules was used in SGL hardener.