Abstract
This study investigates the development of innovative high-performance natural seawater coral sand engineeredcementitious composites (HP-NSCS-ECC), with emphasis on early-age behavior, mechanical properties,shrinkage, heat of hydration, chloride ion penetration, and microstructural characteristics under coastal conditions(seawater, freshwater, and air). The optimized HP-NSCS-ECC exhibited outstanding mechanical performance,achieving an ultimate tensile strain of 8–10 %, more than double that of conventional silica sand ECC,and high strength, with tensile strength exceeding 10 MPa and compressive strength above 90 MPa. Crack widthswere tightly controlled below 80 μm, representing a ~35 % reduction compared to silica sand ECC, ensuringsuperior durability in harsh coastal environments. Seawater-mixed samples demonstrated an ~18 % increase inheat of hydration, with an earlier peak at 28.5 h (9 h earlier than freshwater mixtures), confirming acceleratedhydration and improved matrix densification. Under seawater curing, the shrinkage strain of ~3000 με observedin air-cured specimens was eliminated, inducing a beneficial self-stressing effect. The average free chloride-ionconcentration increased modestly by ~0.04 mol/L, yet remained ~40–50 % lower than typical values for silicasand ECC, indicating enhanced resistance to chloride ingress. Microstructural analysis revealed that coral sandmorphology and seawater ions promoted denser hydration products and stronger fiber–matrix interactions,enabling strain-hardening behavior with only 1.5 % PE fibers (12 mm length). Overall, HP-NSCS-ECC integrateshigh strength, exceptional ductility, shrinkage mitigation, and durability, offering a robust and sustainablematerial framework for marine and island construction, with clear potential to extend service life and reducemaintenance costs in offshore infrastructure applications.
NETL
NSTL
Elsevier