Purpose: This paper aims to reduce the cost, limit the time and increase raw material source availability, coral aggregate seawater concrete (CASC) composed of coral, coral sand, seawater and cement can be widely used for the construction of ports, levees, airports and roads to achieve practical engineering values. However, the naturally porous coral structure and abundant Cl⁻ in the seawater and coral lead to extremely severe reinforcement corrosion for CASC. It is well known that Cl⁻ is the main cause of reinforcement corrosion in the marine environment. Therefore, it is necessary to research the reinforcement corrosion of CASC in the marine environment. Design/methodology/approach: In this study, linear polarization resistance was adopted to test the linear polarization curves of reinforcement in CASC with different exposure times. E_corr, R_p, I_corr and V_corr were calculated according to the weak electrochemical polarization theory and Stern–Geary formula. The effects of concrete cover thickness, exposure time, reinforcement types and inhibitor on reinforcement corrosion in CASC were analysed. The reinforcement corrosion degradation rule was determined, which provided theoretical support for the durability improvement, security assessment, service life prediction and service quality control of CASC structures in marine islands and reef engineering. Findings: The corrosion resistance was enhanced with increased concrete cover thickness, and the concrete cover thickness for organic new coated steel should be at least 5.5 cm to reduce the reinforcement corrosion risks in CASC structures. The corrosion resistance of different types of reinforcements followed the rule: 2205 duplex stainless steel > 316 stainless steel > organic new coated steel > zinc-chromium coated steel > common steel. In the early exposure stage, the anti-corrosion effectiveness of the calcium nitrate inhibitor (CN) was superior to that for the amino alcohol inhibitor (AA). With the extension of exposure time, the decreasing rate of anticorrosion effectiveness of CN was higher than that of AA. Originality/value: Reinforcement corrosion of CASC in a marine environment was studied. Concrete cover thickness, exposure time, reinforcement type and inhibitor influenced the reinforcement corrosion were investigated. New technique of reinforcement anti-corrosion in marine engineering was proposed. Possible applications of CASC in marine engineering structures were suggested.

The present work investigates the microstructural evolution process of concrete under chemical attack by magnesium sulfate solution or a composite solution (sodium sulfate and magnesium chloride), salt crystallization attack through dry–wet cycles, and bending stress. The composition and microstructure are studied in detail using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of the relative dynamic elastic modulus and visual inspection analysis indicate that damage and deterioration of concrete from the composite solution are more serious than those from magnesium sulfate. Moreover, damage and deterioration of concrete under chemical attack are remarkably accelerated by salt crystallization and bending stress. According to the microstructural analysis, crack initiation elements (a new concept) are present in the concrete, which are expected to lead to crack generation and expansion in the concrete. After the corrosion of concrete under chemical attack, salt crystallization attack and bending stress for 903 days, several crack initiation elements are found in the SEM photographs of the concrete, and a grouping of microcracks appears in the concrete. These microcracks form a network by diffusion and connection. The results show that the composite solution is a more severe corrosion medium than magnesium sulfate, according to a comparison of the crack width.