Performance evaluation of green mortars developed from a ternary eco-cement of industrial solid wastes

Abstract

The performance of green mortars (GMs) incorporating an eco-cement made from various proportions of rice husk ash (RHA), ground granulated blast-furnace slag (GGBFS) and circulating fluidised bed combustion fly ash (CFA) was evaluated. Different RHA contents (15 wt%, 30 wt% and 45 wt%) were used to replace GGBFS (by weight) and these mixtures were activated by 15 wt%, 20 wt% and 25 wt% CFA by the total weight of GGBFS and RHA. The engineering properties of the mortars were examined by compressive strength, splitting tensile strength, water absorption, porosity and dynamic Young's modulus tests. Sulfate resistance tests and scanning electron microscopy (SEM) were conducted to evaluate the durability and microstructure of the GMs. The test results demonstrated that the content of RHA and CFA strongly impacted the properties of the GMs. The mortars with 20 wt% CFA and <30 wt% RHA showed the best performance at later ages. CFA decreased the sulfate resistance of the GMs, while RHA increased sulfate resistance and significantly reduced thermal conductivity. SEM images of the samples showed amorphous gels and the ettringite crystal-like phase, leading to a dense microstructure of the mortars.