Assessing Concrete Damage in Reinforced Concrete

It has been shown that there can be a relationship between corrosion behavior and acoustic emission (AE) activity. This is particularly true for corrosion initiation in reinforced concrete. In fact, some investigators have concluded that continuous AE monitoring could detect the onset of rebar corrosion earlier that other methods such as galvanic corrosion, half-cell potential, or polarization resistance measurements. The results were based on tests carried out during corrosion experiments in which reinforced concrete specimens, typical of those used in ASTM G109, were used. However, most of the concrete damage occurs after corrosion initiation, sometimes quite a while after. Moreoever, the rate of continuing corrosion can vary significantly after corrosion initiation. In such cases, corrosion rate information and galvanic current information may be more useful in assessing corrosion behavior and resulting concrete damage. When AE testing was used on reinforced concrete specimens that had suffered varying degrees of corrosion and concrete damage, it was found that there was a relationship between concrete damage due to corrosion and the number of pulses generated. This was based on one-time tests, not continuous monitoring. It was generally observed that the greater the damage, the lower the number of pulses. This suggests that this technique may be used to assess concrete damage in certain cases where electrochemical information is difficult to determine. In addition, it may mean that this test might be used as a stand-alone test to determine the degree of concrete damage, once a database of information about similar structures has been developed.

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