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The reinforcement exposed during repair has to be cleaned so that protective treatment can be applied. Even if no protective treatment is to be applied cleaning has to be carried out so that the steel surface is in intimate contact with the new concrete or mortar. The only effective methods of cleaning reinforcement are by grit blasting and water jetting. Other methods, such as wire brushing, even by mechanical means, do not clean to the necessary standard. Grit blasting and water jetting are also the only methods that can reach the backs of bars and the difficult locations where bars cross.
Once the reinforcement has been cleaned it should be examined to check whether sufficient cross-sectional area remains. As a rule of thumb, any bar that has lost more than 20% of its area should be replaced but the amount of steel required for structural reasons should be checked. If additional bars are provided they need to have an adequate lap to existing bars or be adequately anchored into sound concrete
All reinforcement, both original and new, should be firmly fixed in position before reinstatement takes place.
Acknowledgement: The Concrete Society
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