Study of effect of reference time of chloride diffusion coefficient in numerical modelling of durability of concrete

Abstract

The results of numerical calculations on the resistance of the reinforced concrete bridge deck to chlorides are compared with a different approach to the diffusion coefficient of the input parameter, and presented. The aim is to point out the necessity of a correct model adjustment in the case of using diffusion parameters obtained differently at different measurement times. The diffusion parameter, as a typical concrete material constant, was derived from electrical resistivity measurements and using the least-squares method from a direct chloride test. Due to the different times of obtaining the concrete parameters, a control calculation was performed, which showed that the numerical model for calculating the initiation of reinforcement corrosion in chloride-exposed reinforced concrete requires the application of not only a suitable diffusion parameter but also an adequate reference time. The article points out the need to use an adequate reference time introduced in the numerical calculation of the durability of reinforced concrete with respect to aggressive substances. The results show that the most appropriate reference time value is derived from the average measurement time related to the lifetime of the concrete.