Carbonation resistance of low-carbon mortar blended with belitic calcium sulfoaluminate (BCSA) cement and its impact on initial corrosion of steel

Abstract

The blend of ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement has been well-established as a promising low-carbon binder in terms of matrix properties. However, the application in reinforced structures raises questions regarding its protective ability for the embedded steel, particularly concerning corrosion performance in carbonation environments. This study aims to evaluate the carbonation resistance of OPC-CSA blended mortar and investigate the related corrosion behavior of the embedded steel upon accelerated carbonation. The experimental findings indicate that, compared to OPC mortar, the reinforced blended mortar exhibited a deeper carbonation depth in the mortar matrix and a comparable corrosion rate of the embedded steel throughout the carbonation process. Although the OPC-CSA blended mortar showed higher overall porosity before and after carbonation compared to OPC mortar, the lower pore volume in the diameter range larger than tens of nanometers confirmed the finer pore size distribution of the blended mortar. Despite the negligible corrosion rates of the embedded steel, consistently below 0.1 μA cm⁻² for both mortars during the carbonation process, the characteristic of steel-mortar interface was found to influence the initial formation of corrosion stains.