Designing corrosion resistant systems with alternative cementitious materials

Alternative cementitious materials (ACMs) may exhibit superior mechanical properties and durability to certain environments, and that also may be produced with relatively less environmental impact compared to traditional portland cement. Differences in ACM composition, reaction products, and microstructure produces variations in their performance, including their resistance to fluid and ion and to corrosion of embedded steel. Understanding relationships between composition, structure, and corrosion performance in ACM systems is essential for designing durable reinforced concrete from these materials. Here, five commercially available ACMs are evaluated and compared against ordinary portland cement (OPC). The five ACMs include one calcium aluminate cement (CAC); one ternary blend of calcium aluminate, portland cement, and calcium sulfate (CACT); one calcium sulfoaluminate cement (CSA) as well as the same CSA cement with polymer-modification (CSAP); and one activated aluminosilicate binder system (AA). Water sorption, chloride ion ponding, bulk conductivity, formation factor measurements, and accelerated corrosion tests were performed to evaluate the porosity, mass transport, chloride ion binding capacity, and resistance to corrosion of embedded reinforcement. The results demonstrate that mixtures with high pore structure interconnectivity and low binding capacity (such as CSA and CAC investigated in this paper) or mixtures with significantly low binding capacity (such as AA investigated in this paper) should be avoided to minimize damage due to chloride-induced corrosion. Polymer addition could be an important strategy to improve the corrosion resistance of mixtures that have high interconnectivity. Overall, one ACM, CACT, evaluated in this study showed the best corrosion resistance among the materials considered – including OPC.