Submicroscopic Evaluation Studies to Minimize Delayed Ettringite Formation in Concrete for a Sustainable Industry and Circular Economy

Abstract

AbstractThe high cost of maintenance, repair and retrofitting of concrete infrastructure to keep these structures durable and serviceable is not sustainable, so the design process needs to consider all aspects of deterioration mechanism/s that can potentially occur in a concrete structure. The ideal solution should contribute to sustainability by enhancing the durability of concrete elements and supporting a circular economy. We studied delayed ettringite formation (DEF), a potential deterioration mechanism, including mitigation measures, in various heat-cured cementitious systems. The results showed that continuously connected pore/crack paths at the submicroscopic level favor the transportation of DEF-causing ions in heat-cured systems. DEF increases the chance of developing cracks, which is a durability concern. To mitigate DEF, fly ash produced from an Australian bituminous coal-burning power station was incorporated in the binder to support the circular economy concept. Changes in heat-cured cementitious systems were evaluated using expansion, electrical resistivity, dynamic modulus, and microstructural studies. The pozzolanicity of fly ash was found to greatly enhance the formation of denser calcium-silica-hydrate, which in turn restricted the transportation of DEF-causing ions at the submicron level, leading to less DEF occurrence and enhancement of the durability and sustainability of concrete in field structures.