Enhancing the performance of basic magnesium sulfate cement-based coral aggregate concrete through gradient composite design technology

The porous nature of coral aggregate challenges the manufacturing of high performance coral concrete, which obstacles its development and application. By using gradient composite design technology, this study reports an environmentally friendly and economical method to modify coral aggregates. This improvement can overcome the technical bottleneck of manufacturing high performance coral concrete. Innovatively, citric acid was used to clean coral aggregate particles, and basic magnesium sulfate cement (BMSC) was used to coat coral aggregates. Subsequently, BMSC was used as binder to manufacture the high performance coral aggregate concrete. The acid cleaning removed loose attachments and soft layer on the surface of coral aggregates. It enhanced the filling effect of BMSC coating into pores and improved the interfacial bonding between the coral aggregate surface and the cement coating. The gradient composite design technology modified the interfacial transition zone of coral concrete, successfully solved the problem of poor interface between coral aggregates and mortar. Comparing to the concrete prepared with original coral aggregates, the concrete prepared using the proposed new method improved workability by 35.3%, flexural strength by 20.5% and compressive strength by 31.8%, and significantly reduced capillary water absorption