Combined effect of internal curing and hydration promotion on concrete performances: Contributions of roof-tile waste aggregate and chloride-based accelerator

Abstract

Internal curing (IC) of concrete has recently been the subject of research due to its advantages, particularly in long-term performance. However, IC often decreases early-age strength and requires sufficient external curing time to be most effective. On the contrary, a chloride-based accelerator (CA) is well-known for accelerating early-age cement hydration and strength development. Therefore, this study aimed to investigate the combined effect of IC using roof-tile waste aggregate and CA using sea salt on concrete performance. Several concrete mixtures were cast with single or combined effects under poor and standard curing conditions. Roof-tile waste was used to partially replace normal coarse or fine aggregate to provide IC for concrete. Subsequently, the compressive strength and carbonation rate, as mechanical and durability indices, respectively, were measured until approximately 8 years of age. The combined effect resulted in significant strength improvement compared with the single effects under the same curing conditions. At approximately 8 years, under standard curing conditions, the IC effect increased the compressive strength by 40%, while the combined effect increased it by 60% compared to normal concrete. Concrete with combined effects also performed better in terms of durability tests but with a smaller magnitude than the strength index.