Mechanisms and Significant Parameters

Measuring the resistivity on a very local scale inside concrete using small embedded electrodes has been shown to be a good method for measuring and monitoring the effects of water uptake and drying, as a function of depth, binder type and environment [42, 43]. 

Each of the transport processes that leads to corrosion of the reinforcement and then governs its kinetics can be characterized by a parameter (D, S, K, p) that depends on the concrete properties and can be determined experimentally. Table 2.5 shows the parameters that are relevant to different situations. At least theoretically, these parameters can be used in the design of concrete structures to calculate the evolution in time of corrosion (initiation or propagation) or any other type of degradation as a function of concrete properties and environmental conditions. 

Correlations. Kinetics of the different transport processes that can take place in concrete, and thus the parameters that define them, are correlated among themselves because they depend on the porous structure of concrete. These correlations, however, are not of a general nature, but vary in relation to the composition or 

Protection of rebar - chloride ingress v Type of cement 

Other properties of concrete. For example, for concrete made with a certain type of cement, correlations between the water permeability and the diffusion coefficient of chlorides, that is between K and D, can be established. Nevertheless, when variations are made in the type of cement used, for example, changing from Portland cement to blended cement, the relationships are no longer valid (D may vary even two orders of magnitude with no corresponding variation in K [3]). 

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