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The deterioration of reinforced concrete structures caused by chloride‐induced corrosion is a major threat to their service life. Previous studies show that defects in the steel–concrete interface have a significant impact on the corrosion process of steel bars. Study on the chloride permeability of steel–concrete interface is very important for revealing the mechanism. In this article, we devised a new experimental method named chloride penetration depth test which was used to evaluate the chloride permeability along the steel–concrete interface. Two types of fresh concretes, normal concrete (NC) and lightweight aggregate concrete (LWAC) with obviously different stability, were designed to obtain specimens of various defect sizes in the steel–concrete interface. The results show that the chloride penetration depth measured with the new method increased with the defect size in the steel–concrete interface determined by backscattered electron (BSE) imaging and nanoindentation technology, indicating that the chloride permeability of steel–concrete interface could be identified by the method we proposed. [ABSTRACT FROM AUTHOR]

This study examines the potential of using calcium‐rich precursors to improve the strength of alkali‐activated slag (AAS) cement at low temperature. To achieve this target, the effect of calcium‐rich precursors on the early strength development of AAS mortars cured at 5°C was assessed. The strength development was investigated along with its internal temperature, microstructure and reaction products. It is found that the calcium‐rich precursors can improve the early strength of AAS around 35% and the group with Portland cement clinker gave the highest strength. Calcium oxide can also increase the compressive strength of AAS cement, but its effectiveness is not as good as the sample with clinker. Adding calcium sulfoaluminate can increase the early strength, while no significant contribution to 28‐day strength could be found. The results highlight that compressive strength of modified AAS mortar can reach 15 MPa at 6 h and 20 MPa at 24 h at 5°C, suggesting that this binder could be a valuable alternative for low temperature construction. [ABSTRACT FROM AUTHOR]