Development of Preplaced Alkali-Activated Coral Concrete for a Marine Environment

The use of coral aggregate (CA) in marine concrete can greatly reduce project costs and periods. An environmentally friendly alkali-activated material (AAM) was used to grout CA to produce preplaced alkali-activated coral concrete (PAACC), reducing the binder amount and achieving environmental benefits. The alkali-activated grout (AAG) determined the performance of PAACC and acted as the main load-bearing structure, and the size of the CA slightly affected the PAACC. The compressive strength of PAACC reached about 55% that of AAG, ranging between 35 and 46 MPa at 28 days, with low chloride content (0.006%–0.016%), meeting the requirements for most marine structures. Additionally, PAACC had accelerated early strength development (approximately 5% higher than grout) due to the moisture released from the CA. PAACC had an excellent interfacial transition zone, with strengthened CA in the concrete composite, potentially increasing the practical use of PAACC.