Effect of recycled fine aggregates on alkali-activated slag concrete properties

Abstract

Normally, recycled fine aggregate (RFA) is an unwanted by-product of construction demolished waste crushing, with high contaminant content. The presence of RFA is highly restricted in ordinary Portland cement (OPC) concrete production because of the poor durability and mechanical performance. This paper presents a study of the effect of RFA on the mechanical and durability of alkali activated slag concrete (AASC). Results indicated that RFA can be used as fine aggregate in AASC with superior early age compressive strength compared to river sand in AASC. It is caused by the presence of non-hydrated cement paste attached to the RFA with alkali activate property, which is equivalent to increase the quantity of alkali activator, and accelerate the hydration of ground granulated blast furnace slag (GGBFS) especially in the early age. In later age, the mechanical properties of AASC incorporating RFA are slightly lower than conventional AASC due to the larger porosity in the concrete.