Novel utilization of waste concrete powder in alkali-activated binder.

This experimental study investigates a novel approach to utilize waste concrete powder (WCP) in conjunction with metakaolin as a precursor in the production of alkali-activated binder for sustainable consumption of construction and demolition waste. A Chapelle test confirms the presence of reactive silica in thermo-mechanically activated WCP. Different alkali-activated mixtures with metakaolin replacement ranging from 0 % to 80 % were prepared. The mixture with 40 % activated WCP, with a sodium silicate to sodium hydroxide ratio of 2, achieved better compressive strength than the reference sample without WCP. Mineralogical analysis of the mixture pastes revealed that activated WCP-based mixtures developed geopolymer gel and C-S-H gel, contributing to better strength properties in the case of the mixture with 40 % activated WCP. Life cycle analysis demonstrated that incorporating 40 % thermo-mechanically activated WCP by replacing metakaolin reduces carbon dioxide emissions by 49.5 % and 2.2 % compared to Portland cement and metakaolin-based binder, respectively. • Thermo-mechanical treated WCP promises an alternative binder in the alkali-activated based concrete. • Burned-Milled WCP (BMWCP) demonstrated high performance in reactivity compared to Milled WCP and as-received WCP. • In terms of mechanical performance, incorporating 50 % BMWCP improved compressive strength compared to the reference samples. • BMWCP based binder significantly decreases the environmental impact and the CO 2 emissions in general. [ABSTRACT FROM AUTHOR]