Performance of fly ash/GGBFS based geopolymer concrete with recycled fine and coarse aggregates at hot and ambient curing

The incorporation of recycled aggregates in geopolymer concrete (GPC) exhibits higher environmental sustainability due to its ability to utilize industrial by-products and construction and demolition (C&D) waste. This study investigates the combined effect of fine and coarse recycled aggregates on the behavior of GPC. In this research, fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as binder, whereas sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used as alkaline activators. Recycled fine aggregates (RFA) were used at 30%, 60% and 100% replacement of natural fine aggregates (NFA) and recycled coarse aggregates (RCA) were used at 0%, 50% and 100% replacement of natural coarse aggregates (NCA). To study the effect of curing temperature, two types of curing regimes, i.e. hot and ambient curing, were employed. Performance of developed GPC was evaluated in terms of workability, mechanical properties (compressive strength, splitting tensile strength, and flexural strength) and durability properties such as water absorption, sorptivity, resistance against acid attack, resistance against marine environment and electrical resistivity. It was found that the behavior of GPC is improved when the samples were cured at high temperature for 24 h, as compared to the samples cured under ambient curing conditions. Furthermore, NFA can be replaced up to 100% with NCA, and up to 60% in the presence of 50% RCA and up to 30% in the presence of 100% RCA. It was also found that with an increase in the percentage of recycled aggregates, durability performance gradually declined. The results showed that GPC can be developed with inclusion of both recycled fine and coarse aggregates, which can help to preserve valuable natural resources, reduce CO2 emission, and dispose C&D waste.