Evaluation of time-dependent chloride parameters for assessing reinforced concrete bridges

Chloride diffusivity of concrete is an important input parameter in service life prediction models. Diffusion coefficient is influenced by mix proportions, curing, compaction, pore size distribution, time, relative humidity and temperature, and decreases over time. However, many life time prediction models still consider this parameter as a constant, resulting in overly conservative durability designs, especially when GGBS or Fly ash are present in concrete mix. Some of the models proposed so far for estimating this parameter are time-dependent, while others are based on mix proportions. A laboratory program is reported, and a novel numerical model is sought for to estimate the degree of hydration as determined from the heat of hydration of concrete. Diffusion coefficients are measured using Nordtest rapid migration test; and a correlation is sought for, between the two. Tests are performed at regular intervals to allow for characterization of the influence of the aforementioned parameters.