Reinforced concrete repairs in beams

Abstract

The effectiveness of reinforced concrete repairs may be established in terms of their ability to restore the structural integrity of the reinforced concrete element and to protect the reinforcement from severe weathering conditions. Therefore, 18 large scale reinforced concrete beams were cast and subject to an accelerated corrosion mechanism in a chloride environment. The beams were repaired using two different materials for comparison purposes, namely an OPC mortar and a free flowing micro-concrete. Twelve beams were tested just after the repair material has cured, and the remaining beams were subjected to an aggressive weathering cycle for 6 months after which structural and electrochemical testing were conducted. This paper presents the results of both structural load testing of all beams, and physical and electrochemical performance of repaired beams before and during the accelerated weathering. The results of structural testing showed that in short-term situation both materials behaved very similar to each other and were able to restore 60–70% of the beams’ capacity. But in long-term situation the OPC mortar beams has deteriorated badly showing extensive cracking, while the free flowing micro concrete beams have shown very little cracking. The former restored only 40–50% of the capacity while the latter restored approximately 90%. The electrochemical monitoring data provided a useful comparison of two repair systems in terms of inhibitive influence of repairs on steel reinforcement and electrochemical interactions between the repaired and unrepaired areas. The protection afforded to the corroded rebars and subsequent reduction in corrosion rate was more significant with free flowing micro-concrete repair material than with OPC mortar. Incipient anodes were formed at the repair/concrete interfaces soon after the repair. Under accelerated weathering conditions, free flowing micro-concrete has been found to offer better resistance to chloride ingress from an external source than OPC mortar. A significant increase in corrosion rate and concrete surface weathering was observed in the climatic chamber, hence suggesting that a long term performance of a repair material can be assessed in a short time scale under these conditions.