Corrosion Behavior of Carbon Steel Rebar in Calcium Sulfoaluminate CSA-Based Systems

The use of ordinary binders to manufacture structural concrete for construction sector does not fully fit with the interests of cement industries, which are seeking to reduce the impact of cement production on environment, CO2 emissions and consumption of raw materials and energy. Therefore, alternative binders are developed and studied, such as calcium sulfoaluminate (CSA) cement, which combines rapid hardening, high-early strength, with less CO2 emission due to the lower temperature used for clinker production. Several studies regarding the mechanical and rheological properties of concretes manufactured with CSA cement are reported, whereas research on durability and corrosion behavior of carbon steel in such admixtures is still lacking. Compared with ordinary Portland cement (OPC), the hydration of CSA cement shows important difference that can influence durability of reinforced concrete structures, because it does not produce Ca(OH)2. Consequently, less alkaline pH is expected, which significantly affects corrosion behavior of steel reinforcing bars. Furthermore, purpose of this work is the evaluation of the alkalinity level of concretes manufactured with CSA cement using pH sensible probes, pH indicators alternative to phenolphthalein and other techniques. Likewise, in order to investigate the corrosion behavior of carbon steel during different stages of hydration of calcium sulfoaluminate based cementitious systems, tests in simulating pore solutions at different pH and 〖SO〗_4^(2-) concentration were carried out.