Basic mechanical behaviours and deterioration mechanism of RC beams under chloride-sulphate environment

This paper investigates the basic mechanical behaviour of reinforced concrete (RC) beams using chloride corrosion-damaged steel reinforcements and subjected to sulphate ions environment. To this end, ten RC beams were studied which contained 5% sodium chloride and implemented by a series of drying-immersion cycling (15% sodium sulphate immersion solution). Test results indicated that the flexural capacity, ductility, and stiffness of the beams were improved at early stage of the corrosion. This was attributed to the fact that concrete strength and steel-concrete interfacial bond were enhanced. The former is for the filling effects of micro-expansive Ettringite and gypsum sulphate, while the latter is due to the slight surface corrosion pits of steel bars at the stage. However, the mechanical properties of the beams decreased subsequently for the deteriorations in the concrete strength due to excessive expansion of Ettringite and gypsum sulphate, and the degradation of self-property of reinforcement and its interface bond with the concrete. Based on the study, the deterioration mechanism of RC beams under chloride-sulphate environment was discussed and its main determining factors at different stages were analysed.