Peculiarities of Bond Strength Degradation in Reinforced Concrete Induced by Accelerated Electrochemical Methods

Reinforced concrete (RC) structures are long-term operated objects with service life of 50–100 years. During their operation they subject to continuous ambient effects (cyclic temperature changes, acid rains, de-icing salts) and service loads (e.g. traffic) which effect on structural integrity of the composite and lead to worsening of structures serviceability. One of the reasons for strength loss of RC members is bond degradation between rebar and concrete. It could be caused by two different factors: overprotection of RC and reinforcement corrosion. These effects were simulated in the laboratory conditions by the electrochemical methods, applying of impressed cathodic current and accelerated corrosion tests respectively. It was shown that applied anode polarization causes not only concrete cracking due to internal pressure of corrosion products at the interface, but also due to their expansion far from rebar, for a distance comparative with a specimen thickness, evidently into preliminary formed cracks. Since intensive corrosion of steel reinforcement decreases its diameter and corrosion products can migrate from the rebar surface into a depth of concrete these factors could weaken bond in RC installations up to a total loss of cohesion between rebar and concrete. The influence of cathodic polarization of steel embedded in concrete is commonly seemed to consist in its possible hydrogen embrittlement and ions redistribution in concrete matrix. In this paper the effect of hydrogen recombined at the rebar–concrete interface on bond weakening and concrete cracking is considered.