Impact of initial chloride contaminations on the corrosion rate evolution of reinforced Belite-Ye'elimite-Ferrite (BYF) cement mortars

Portland cement has become an essential building material in the last century. Its production unfortunately leads to noticeable CO₂-emissions. The development of Belite-Yeelimite-Ferrite (BYF) cement as alternative binder is a promising solution with a decrease of 20-30% in CO2 emissions. One important issue for this new cement is its ability to passivate mild steel. Only few results about it are currently available due to the relatively new nature of the technology. This paper discusses the electrochemical behavior of steel in a BYF matrix. The impact of chloride (present in raw materials as permissible impurities) was considered too. An ordinary Portland cement was used as reference. Mortar specimens with embedded steel rebar were cast with varying chloride contents (0.0, 0.2, 0.4 and 1.0% of chloride by mass of cement). Electrochemical techniques such as half-cell readings, linear polarization resistance (LPR) and large potentiodynamic polarizations were carried out. Specimens contaminated by chloride up to 0.4% showed low corrosion rate (< 1 μm/year) during the first year of measurements. High corrosion activity (>5 μm/year) was yet observed with a chloride content of 1.0% by mass of cement. Therefore steel embedded in BYF mortar passivates and a chloride content up to 0.4% by mass of cement can be tolerated. The contamination by 1% of chloride by mass of cement (not allowed for reinforced concrete made with Portland cement according to the European standard EN 206) leads to active corrosion.