EFFECTIVENESS OF ACCELERATED TEST METHODS USED TO EVALUATE THE RESISTANCE TO CHLORIDES PENETRATION ON COATED CONCRETE

Corrosion in reinforced concrete structures is leading to high maintenance and repair costs. In particular, chloride-induced corrosion, causing localized attacks, may affect the structural safety. Therefore, designers are encouraged to ensure a sufficient concrete quality in order to control the penetration of chlorides. Worldwide several different test standards are proposed in order to assess the resistance of concrete to the penetration of chlorides. Especially, accelerated tests are an important tool since they may provide, in a quite short time, input data to be used during the design phase to guarantee the required durability of the structure. To achieve this target, designer can also evaluate the possible use of additional protection techniques. However, the different test standards, generally, do not foresee the use of additional protection methods, such as concrete surface coatings, which are a promising opportunity to control reinforcement corrosion and prolongate the service life of the structure. Therefore, it would be interesting to evaluate whether the existing test standards may be used also to evaluate the resistance to the penetration of chlorides on coated concrete. In this work the applicability of two different accelerated test standards to coated concrete was tested. The selected standards were a unidirectional diffusion test (EN 12390-11:2015) and a chlorides migration test (ASTM C1202-19). The coatings used during this test were three different commercially available products: a hydrophobic pore-lining treatment, a polymer-modified cementitious coating and an acrylic film forming coating. A total amount of 12 concrete samples (8 coated and 4 left uncoated as control specimens) was realized. Eight samples were submitted to chlorides migration test and four to unidirectional diffusion test. The results of the two tests, thus the profiles of penetration of chlorides and the chlorides penetrability (expressed in passed charge during a 6 hours period) were compared for the different coating types. Also, a possible correlation between the test results from the different standards was evaluated. Results showed that chlorides migration test (ASTM C1202-19) underestimates the chlorides penetrability especially for coatings of polymeric nature, thus no correlation between the two different tests was observed. Thus, the importance of a careful selection of a suitable accelerated test method to be used to evaluate the penetration of chlorides on coated concrete was highlighted.