High ductility cementitious composites incorporating seawater and coral sand (SCS-HDCC) for offshore engineering: Microstructure, mechanical performance and sustainability

In support of sustainable development strategies, engineering construction on remote islands is conductive to promoting the development of marine resources and mitigating increasingly severe resource conflicts. However, marine engineering, facing extreme weather and natural disasters, necessitates concrete with high ductility, durability and crack control capacity. This study evaluates the feasibility of using seawater and coral sand instead of fresh water and river sand to prepare the high ductility cementitious composites (SCS-HDCC). The results indicate that increased coral sand substitution introduces defects and expands the aggregate-matrix interfacial zone due to its rough surface, high specific area, and low strength. Coral sand's internal curing enhances compactness and reduces harmful pores. The dual action of seawater and coral sand, SCS-HDCC matrix is more tenacious, and the damage and blockage during the fiber pull-out process becomes obvious, and the slip hardening coefficient of fiber-matrix interfacial zone increases. SCS-HDCC achieves satisfactory ductility (up to 1.18 %) with initial cracking strength of 4.18 MPa, ultimate tensile strength of 5.66 MPa, and crack width of 71.2 +/- 6.74 mu m, average crack spacing of 6.02 mm. The SCS-HDCCs prepared in this study offers economic and environmental benefits by reducing economic costs and carbon emissions through transporting raw materials from the continent. The research results have guiding significance for the construction of islands and reefs by SCSHDCC.