Chloride ingress in concrete – Results from over 20 years’ field exposure in Swedish marine environment
Paper in proceedings, 2014
This paper presents the results from a number of research projects dealing with chloride ingress in concrete exposed to Swedish marine environment after exposure up to over 20 years. In the beginning of the 1990s, some 40 types of concrete slabs were exposed to seawater at the Träslövsläge field site on the west coast of Sweden. The concrete slabs were periodically sampled for chloride ingress profiles after exposure for 0.5–2, 5, 10 and 20 years. These chloride profiles were used for validation of prediction models for chloride ingress. Two models, one empirical and another mechanism-based, were compared with the measured chloride profiles. The results show that the chloride ingress is in general more severe in the submerged zone than in the other zones. Multi-pozzolanic additions such as fly ash and silica fume can effectively reduce chloride ingress. The mechanism-based model gives reasonable prediction of chloride ingress from 1 up to 20 years whilst the empirical model based on short-term field data underestimates chloride ingress in concrete with low water-binder ratios and pozzolanic additions. From the predictions of the mechanism-based model, it has been demonstrated that the best measure to achieve 100 years’ service life with a cover thickness of for example 60 mm is to use either 5% silica fume or 20% fly ash with reduced water-binder ratio ≤ 0.30, or to use a combination of both fly ash and silica fume (w/b 0.35). It seems that a water-binder ratio lower than 0.30 does not further reduce chloride ingress.