Internal curing effect of saturated coral coarse aggregate in high-strength seawater sea sand concrete

Abstract

This study characterizes the essential engineering properties of the coral coarse aggregate (CCA) and evaluated its potential utilization as an internal curing agent for high-strength seawater sea sand concrete (HS-SWSSC). The X-ray computed tomography (X-CT) scanning results indicate the internal structure of the CCA is mainly composed of open pores, and the pore diameter is in the range of 46 ∼ 382.1 µm. The water absorption of CCA reaches 15.7% at 24 h, and 90% of the absorbed water can be released at 97.5% relative humidity, which meets the requirements of ASTM C1761 for internal curing. Additionally, the workability and compressive strength of HS-SWSSC first increases and then decreases with the increasing CCA content. In contrast, the setting time of HS-SWSSC generally increases with CCA content. The incorporation of CCA can significantly enhance the internal relative humidity (IRH) of HS-SWSSC and prolong the saturation stage. Then the autogenous shrinkage of HS-SWSSC can be substantially reduced and completely eliminated when the CCA content reaches 20 vol%. The saturated CCA can also improve the hydration degree of HS-SWSCC and densify the interfacial transition zone (ITZ) between the CCA and the cement matrix. Based on the analysis above, the recommended CCA content used in HS-SWSSC is in the range of 10 ∼ 20 vol%. The findings from this study can serve as a valuable reference for utilizing CCA as an internal curing agent in HS-SWSSC.