Experimental investigation on bond properties between rebar and concrete considering rebar corrosion and concrete deterioration caused by sulfate attack

Rebar corrosion induced by chloride erosion and concrete deterioration caused by sulfate attack are two critical factors that affect bond properties between rebar and concrete in marine environment. However, current studies about above two influencing factors on bond properties either consider rebar corrosion or sulfate attack. The bond properties between rebar and concrete considering the coupled effects of rebar corrosion and concrete deterioration caused by sulfate attack are required to further explored. In this paper, through the accelerate corrosion test, pull-out test and microscopic analysis (including scanning electron microscopy and X-ray diffraction measurements), the bond properties considering rebar corrosion and concrete deterioration caused by sulfate attack were investigated. A total of 88 RC specimens were designed to study the influences of rebar corrosion level, sulfate attack degree, sulfate ions associated cation types (sodium and magnesium ions) and concrete materials types (ordinary concrete and concrete incorporating fly ash and silica fume) on bond properties. The bond strength, bond-slip curve and failure mode were measured, and the effects of cracking width on bond properties were considered. Results show that the rebar corrosion level corresponding to the peak bond strength decreases with the increase of sulfate concentration. The bond strength decreases and the slip increases with the rise of sulfate concentration. Sodium sulfate attack causes the splitting failure, and severer magnesium sulfate attack leads to the transition from splitting failure to pull-out failure. The rebar corrosion level causing the concrete to crack decreases with the increase of sodium sulfate concentration. The higher the magnesium sulfate concentration, the less prone to produce rust-expansion cracks, but the worse cementing properties of RC bonding interface. Magnesium sulfate attack results in the severer attenuation of bond strength than sodium sulfate attack. The bond properties can be significantly improved by incorporating 20% fly ash and 5% silica fume. A prediction model of bond strength variation coefficient considering rebar corrosion level, sulfate ions concentration, sulfate ions associated cation types, and concrete materials types was established and verified.