Effects of CaO-based expansive agent on carbonation resistance of marine concrete

Abstract

Marine concrete contains a high volume of supplementary cementitious materials, which benefits low-carbon concrete production. However, they may also increase the risk of cracking and accelerate the carbonation due to the pozzolanic reaction. Theoretically, the CaO-based expansive agent (CEA) can inhibit shrinkage cracks and introduce external calcium sources that aid in the carbonation resistance of concrete. A comprehensive understanding of the impact of CEA on the carbonation resistance of marine concrete is currently scarce. In this study, marine concretes with varying dosages of CEA were exposed to 20 % CO2 for 28 days. The carbonation depth, carbonation coefficient, air permeability, pore structure characteristics and CO2 buffer capacity of concrete were investigated. When the CEA dosage was less than 6 %, the carbonation resistance and air permeability approached the reference groups in normal-strength concrete (NSC) and high-strength concrete (HSC). However, more than 6 % CEA significantly decreased the carbonation resistance of concrete, particularly for HSC. For NSC, there was an excellent correlation between the carbonation coefficient and compressive strength, while for HSC, the carbonation coefficient correlated well with porosity. Also, CO2 buffer capacity was essential to assess the carbonation resistance of marine concrete.

Keywords

• CaO-based expansive agent
• Marine concrete
• Carbonation coefficient
• Capillary porosity
• CO2 buffer capacity