Lightweight cementless composite of CaO-CaCl2-CaSO4-activated GGBFS developed as an alternative to lightweight gypsum composite

Gypsum binders have been widely used to develop lightweight composites; however, they are generally more expensive than Portland cement and less environmentally friendly than cementless binders. This study explored the use of a CaO-CaCl2-activated ground granulated blast furnace slag (GGBFS) binder system in replacing the conventional gypsum binders for manufacturing lightweight composites, as this cementless binder is more economical and environmentally friendly. CaSO4 and polyamide fibers were incorporated in mixtures to increase strengths. Expanded perlite (EP) and expanded vermiculite (EV) were used as lightweight aggregates. Overall, the developed composites exhibited comparable properties to conventional gypsum composites in terms of compressive and flexural strengths, lightweightness, thermal conductivity, whiteness, and non-flammability. However, compared to EP, the use of EV was less advantageous in achieving higher strengths, lower densities, and lower thermal conductivities, which was likely due to the unfavorable microstructure of EV: (1) the exfoliated lamellar structure of the EV seemed to be more susceptible to tearing or micro-buckling, and (2) its open structure likely absorbed more of the binder paste, which was heavier and had higher thermal conductivity than that of the EP. Lastly, trial boards were satisfactorily produced using one of the composites from this study. (C) 2020 Elsevier Ltd. All rights reserved.