Corrosion Kinetics of Steel in Carbonated Pore Solutions Containing Chlorides and Sulphates

Abstract

The carbonation of cementitious materials is often attributed to be one of the major causes of corrosion in reinforced concrete, possibly leading to premature deterioration. When assessing the effect of carbonation on corrosion, most studies are limited to measuring the carbonation rates of different concretes. From these, replacing clinker with supplementary cementitious materials – one of the main strategies to reduce CO2 emissions – was found to increase the rate of carbonation. However, a more urgent question concerns the actual corrosion kinetics of steel in carbonated systems, accounting for factors such as the pore solution composition, microstructure, and moisture of the cementitious matrices. To address this topic, this study focuses on the effect of carbonated pore solutions on the kinetics of steel corrosion. Steel samples were immersed in artificial pore solutions representative of carbonated binders, at pH 8.1, under aerated conditions. Furthermore, the role of aggressive species, such as chlorides and sulphates, was examined to assess their potential significance in carbonated media. The steel-solution systems were monitored through open circuit potential (OCP) and polarization resistance (Rp). Understanding the isolated impact of the pore solution on steel corrosion will support further studies combined with the microstructure and moisture states of carbonated reinforced concretes, crucial to safely assure the durability of environmentally friendly structures.