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Highlights • Sulphoaluminate cement (SAC) lower the surface pH of artificial reef concrete (ARC). • Both marine sand and seawater improve the mechanical properties of SAC-based ARC. • Cement types play key roles in the properties of ARC with seawater and marine sand. Abstract To promote the extensive application of artificial reefs, developing a type of economical and low-alkaline artificial reef concrete (ARC) where marine organisms can grow quickly is necessary. A grade C30 ARC with sulphoaluminate cement (SAC), sea water and marine sand is proposed. The workability, mechanical properties, surface pH and microstructure (scanning electron microscopy (SEM), X-ray diffraction (XRD) and pore structure) of this ARC were studied. The influences of the cement type (ordinary Portland cement (OPC), SAC and a mixed SAC and OPC cement), water type (freshwater and sea water) and sand type (river sand and marine sand) on the properties of ARC are discussed. In terms of the mechanical properties and surface pH of ARC with sea water and marine sand, SAC performed better than OPC. However, a mixed SAC and OPC cement had significantly negative effects on the workability and mechanical properties of the sea water and marine sand-based ARC. Marine sand and sea water displayed positive effects on the mechanical properties but no obvious effects on the surface pH of SAC-based ARC. Compared to ARC with OPC, river sand and freshwater, the proposed ARC has superior mechanical properties, a better microstructure, a lower surface pH and a lower cost. [ABSTRACT FROM AUTHOR]

• Proposed artificial reef concrete (ARC) possess high penetration resistance. • Sulphoaluminate cement (SAC) reduce the steel rebar corrosion in proposed ARC. • The feasibility of using marine sand and seawater in SAC-based ARC is verified. To reduce the surface alkalinity of artificial reef concrete (ARC) and save fresh water and natural aggregate resources, a new artificial reef concrete (NARC) made with sulphoaluminate cement (SAC), sea water and marine sand was proposed in our previous work. However, the steel corrosion as a major concern associated with NARC has not been explored. In this paper, the effects of cement type (SAC, ordinary Portland cement (OPC), mixed cement of OPC and SAC) on the chloride permeability and capillary water absorption of sea water and marine sand-based ARCs were studied. The anodic polarization and loss of steel rebar weight were used to evaluate the effects of the cement type and corrosion inhibitor on the corrosion of steel rebars in ARCs. The results of the present work show that for sea water and marine sand-based ARC, SAC significantly improves the microstructure and decreases the chloride penetration and the water absorption rate. Meanwhile, due to the high chloride binding rate of SAC, the corrosion degree of rebars in NARC is less than that of sea water and marine sand-based ARC with OPC and mix cement of OPC and SAC. Compared with ordinary ARC (ARC made OPC, fresh water and river sand), the steel rebar corrosion in NARC is more serious. Nevertheless, a 2% dosage of corrosion inhibitor (TEA) can significantly decrease the steel rebar corrosion in NARC to a similar corrosion degree of ordinary ARC. The feasibility of using marine sand and seawater in SAC-based ARC is verified. [ABSTRACT FROM AUTHOR]