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

本项目旨在评价碱矿渣混凝土作为钢筋保护层的抗氯离子渗透性能(协作性)。碱激发材料(AAM)由于具有较低的能耗和二氧化碳排放，已成为OPC的环保型替代品。用碱激发矿渣(AAS)作为粘结剂的钢筋混凝土结构已在世界不同地区出现。在寒冷的冬季或海洋气候条件下，氯离子的渗透是钢筋锈蚀的主要原因。然而，AAS作为钢筋防止氯离子渗透的性能还没有被很好地理解。在实验室条件下调查的现有关于普通AAS中氯结合和迁移的知识不能在实践中现实地估计钢筋AAS混凝土的使用寿命，在实践中，钢筋约束、干燥和与水接触都会产生很大的差异。Collaborate将首先评估由于钢筋抑制自生和干燥收缩而导致的AAS混凝土保护层的裂缝分布。将利用原位纳米X射线计算机层析成像和数字体积相关技术来监测裂纹的发展。然后，将用先进的技术来表征由于与水接触而导致的浸出产物和微观结构的改变。裂解和淋滤对水对流、氯离子结合和氯离子迁移的影响将被量化。这些结果将被用作建立氯迁移模型的输入。非破坏性技术，如无线ICOR，将被用来检查腐蚀的开始作为模型的验证。从而可以预测AAS混凝土的使用寿命。该项目将为建立钢筋AAS混凝土的设计方法奠定基础，并有助于相关混凝土结构的标准化，对可持续AAM的更广泛应用具有重要意义。

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.