Sulfate-Induced Corrosion of Carbon Steel Reinforcement in Fresh Calcium Sulfoaluminate Binders

Ordinary Portland cement (OPC) is the main hydraulic construction material, the fabrication of which is an important source of carbon dioxide. Presently, alternative binders are attracting a lot of interest as a way to minimize their environmental impact. Calcium sulfoaluminate cements (CSAs) show massive potential for emissions reduction and possess unique properties. Nevertheless, there is an essential knowledge gap concerning the durability of CSA structures in terms of reinforcement corrosion. This work studies the corrosion behavior of plain carbon steel in media of fixed and variable composition that simulate the liquid phase of fresh CSA-based materials at different stages of binder hydration. The findings of electrochemical and nonelectrochemical techniques suggest that sulfate-induced corrosion of mild steel starts at early stages of hydration in pure CSA and in blended CSA-OPC binders. Once initiated, corrosion of reinforcement would continue regardless of favorable conditions found in the hydrated state in both systems, even though short-term repassivation was observed. In addition, the origin and possible solutions to tackle the corrosion problem are discussed.