Considerations on the effect of sample size for the critical chloride content in concrete

In order to perform reliable service life predictions of reinforced concrete structures, realistic values for the critical chloride content are needed. With regard to the large scatter in the literature as well as the development of modern cement types, agreement has been reached that the test methods for this parameter must be improved. Many of the setups in use are not practice-related. In the present work, the effect of the size of reinforced concrete samples is discussed. It is shown that this parameter is not critical when considering electrochemical or physical aspects of the corrosion mechanism. From a probabilistic point of view, on the other hand, it has some implications since the critical chloride content decreases with increasing rebar length. Further research should concentrate on finding the critical sample size, i.e. the minimal specimen size that is required to give proper critical chloride contents. Moreover, some aspects of evaluating experimental results are pointed out.