Enhancing passing ability of coral aggregate concrete by optimising wet packing density

This study employed sea sand (SS) and coral aggregate (CA) to completely replace river sand and natural coarse aggregate in the production of seawater sea sand coral aggregate concrete (SSCAC). However, the porous characteristics of CA increase the surface friction between the cement paste, SS and CA, adversely impacting the workability of SSCAC. For mitigation, it is essential to optimise the rheology of SSCAC. This can be accomplished by partially substituting cement with fly ash (FA), limestone powder (LS) or silica fume (SF), and with a suitable superplasticiser (SP) dosage to enhance the wet packing density (WPD) of SSCAC. A total of 86 SSCAC specimens were prepared with varying replacement ratios of FA (15–35%), LS (15–35%) and SF (5–15%), as well as combinations of FA and SF with varying SP dosages. These specimens were evaluated for their flowability, L-box passing ability (PL), segregation index, WPD and the 28-day and 91-day compressive strength. The results indicated that the addition of SF enhanced the maximum PL limit by way of the higher WPD achieved. On the other hand, only slight enhancement of PL by LS or FA substitution was observed.