COLLAbORATE: Performance of alkali-activated slag concrete as cover to rebar against penetration of chloride

This project is aimed to evaluate the performanCe Of alkaLi-activated sLag concrete As cOver to Rebar Against peneTration of chloridE (COLLAbORATE). Alkali-activated materials (AAMs) have emerged as eco-friendly alternatives to OPC due to lower embodied energy and CO2 emission. Reinforced concrete structures using alkali-activated slag (AAS) as the binder have been appearing in different regions of the world. The penetration of chloride is the main reason for the corrosion of reinforcing steel in cold-winter or marine climates. However, the performance of AAS as protection of rebar against chloride penetration has not been well understood. The existing knowledge on chloride binding and transport in plain AAS investigated in lab conditions does not allow a realistic estimation of the service life of reinforced AAS concrete in practice, where restraint by rebar, drying and contact with water can all make substantial differences. COLLAbORATE will first evaluate the cracking profile of AAS concrete cover due to the restrained autogenous and drying shrinkage by rebar. In-situ nano X-ray computed tomography combined with Digital Volume Correlation will be utilized to monitor the cracking development. The products and microstructure modification due to leaching caused by contact with water will then be characterized by advanced techniques. The effects of cracking and leaching on water convection, chloride binding and chloride transport will be quantified. These results will be used as inputs to build chloride transport model. Non-destructive techniques such as wireless iCOR will be used to inspect the initiation of corrosion as validation of the model. Service life of the reinforced AAS concrete can be then predicted. This project will lay the knowledge base to establish design methods of reinforced AAS concrete and contribute to standardisation for related concrete structures, which is of great significance for a wider application of sustainable AAMs.