in general, concrete protects steel against corrosion. however, this protection is sometimes destroyed during the life of a structure and visible signs of distress such as rust staining, cracking and spalling of the concrete appear. although this usually occurs before the integrity of a structure is threatened, it would be advantageous to detect corrosion at an earlier stage. unfortunately, it is difficult to detect corrosion before visible signs of distress appear. the trrl has been evaluating testing techniques which can be used to assess the risk of corrosion of steel in concrete. this report describes the application of a number of these techniques to five reinforced concrete structures. in each case the work was initiated by some form of visible distress. it is shown that by careful application of a number of complementary techniques it is possible to obtain sufficient information about the condition of a structure to make a qualitative assessment of the corrosion risk. the development of techniques for measuring the strength and permeability of in situ concrete would enable a more reliable assessment to be made.(a)

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