Compressive stress–strain behavior of slag-based alkali-activated seawater coral aggregate concrete after exposure to seawater environments

Abstract

The use of coral aggregates to replace traditional aggregate sources for preparing seawater coral aggregate concrete (CAC) in remote reef areas contributed to the reduced construction cost and construction period of offshore projects. However, the high chlorine salt content and porosity of coral aggregates will affect the durability and long-term performance of CAC and its structures. Therefore, this study employed alkali-activated materials (AAMs) instead of ordinary Portland cement (OPC) to prepare alkali-activated seawater coral aggregate concrete (AACAC), and investigated the effects of various exposure times (0, 6, 9, and 12 months) on the stress–strain behavior of CAC and AACAC under seawater immersion and wet-dry cycle environments. The deterioration mechanism in the mechanical properties of the concrete was evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The tested results reported that the mechanical properties of CAC were affected by the corrosive environment more than AACAC. When the specimens were exposed to seawater environments for 12 months, the cubic compressive strength, axial compressive strength, and elastic modulus of CAC were reduced by approximately 6.7 %, 8.4 %, and 3.3 %, respectively, while those of AACAC remained basically unchanged. In addition, this degradation in mechanical properties was also more severely affected by the seawater dry-wet cycle environment than the seawater immersion environment. It was concluded that the dense microstructure, excellent pore structure, and stable reaction products of AAMs are the reasons for their superior performance against seawater corrosion to cement-based cementitious materials.