Interrelation between wet packing density and passing ability of concrete containing coral aggregates

This study investigates the use of sea sand (SS) and coral aggregate (CA) as substitutes for river sand and natural coarse aggregate in the production of seawater sea sand coral aggregate concrete (SSCAC). The inherently porous structure of CA increases interfacial friction between the cement paste, SS, and CA, thereby influencing the workability of SSCAC. To address this issue, the rheological properties of SSCAC were optimised by partially replacing cement with limestone powder (LS), incorporating crushed coral aggregate (CCA), and adjusting the superplasticiser (SP) dosage to improve the wet packing density (WPD). A total of 45 SSCAC mixtures were prepared with varying contents of LS, CA, CCA, and SP. These mixtures were evaluated for flowability, L-box passing ability (PL), segregation index, WPD, and compressive strength at 28 and 91 days. The results demonstrated that the inclusion of LS and CCA effectively enhanced the WPD of SSCAC, thereby improving segregation resistance, flowability, and PL. A strong positive correlation was identified among flowability, PL, and WPD, confirming the critical role of particle packing in optimising SSCAC rheology.