Durability of seawater coral aggregate concrete under seawater immersion and dry-wet cycles

Abstract

Coral aggregates replace traditional aggregate sources to prepare coral aggregate concrete (CAC) in remote island or reef areas contributing to reduced construction costs and periods of offshore projects. However, the high porosity of coral aggregates provides a channel for external corrosion solutions to penetrate into the concrete, rendering the CAC and its structures prematurely exposed to durability-related problems during service in marine environments. Therefore, this paper performed the mechanical properties and durability of CAC under seawater immersion and dry-wet cycle environments, and the deterioration mechanisms in the mechanical characteristics of CAC after seawater environment exposure were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The experimental results reported that the mechanical properties of CAC after exposure to seawater environments gradually declined with increasing exposure temperature and exposure age. After being exposed to seawater dry-wet cycle environments at 60 °C for 12 months, there was a reduction of approximately 14.4%, 13.0%, and 16.9% in the cubic compressive strength, elastic modulus, and axial compressive strength of CAC, respectively. This performance degradation was mainly attributed to the chemical reaction between the internal hydration products of the concrete and the corrosive ions in seawater. Additionally, compared with seawater immersion environments, the deterioration in mechanical properties of CAC was more significantly affected by seawater dry-wet cycle environments.