## 4 Conclusions
The RCMT and the WDT, which involved different penetration mechanisms, showed a poorer correlation. Based on the results of this study the chloride penetration resistance of concrete was sorted into recommended RCMT classes, which are able to distinguish concretes of different quality. In general, the same ranking of chloride penetration resistance suggested from \(D_{cl,RCMT}\) was valid for \(D_{cl}\) and \(K_{cr}\), from both long-term tests considered in this study. However, further research is needed, especially in the range of high quality concretes. In general, the RCMT was a reasonable indicator of the chloride penetration resistance of concrete, having been able to distinguish concrete produced with different types of aggregate and paste compositions, under distinct long-term exposure conditions. Conceptualisation, J.P., J.A.B. and S.R. ; methodology, J.P., J.A.B. and S.R. ; software, J.P.; validation, J.P., J.A.B. and S.R. ; formal analysis, J.P., J.A.B. and S.R. ; investigation, J.P., J.A.B. and S.R. ; resources, J.P., J.A.B. and S.R. ; data curation, J.P., J.A.B. and S.R. ; writing--original draft preparation, J.P., J.A.B., S.R. and A.S.; writing--review and editing, J.P., J.A.B. and S.R. ; funding acquisition, J.P. and J.A.B. All authors have read and agreed to the published version of the manuscript. This research was funded by the Portuguese Foundation for Science and Technology (FCT), through scholarship SFRH/BD/111278/2015. Not applicable. The first author wishes to thank the financial support of the Portuguese Foundation for Science and Technology (FCT), through scholarship SFRH/BD/111278/2015. The authors wish to acknowledge CERIS/IST for supporting the research, and the companies SECIL, CentralTermoelectrica do Pego, Saint-Gobain Weber Portugal, Salite, and BASF for supplying the materials used in the experiments. The authors declare no conflict of interest. * Nordtest Method (1999) Nordtest Method. _Concrete, Mortar and Cement-based Repair Materials: Chloride Migration Coefficient from Non-Steady-State Migration Experiments_; NT Build 492; Nordtest Method: Helsinki, Finland, 1999. * [PERSON] and [PERSON] (2009) [PERSON]; [PERSON]. Analysis of the Rapid Chloride Migration test. In Proceedings of the 3 rd International PhD Workshop on Modelling the Durability of Reinforced Concrete, Guimaraes, Portugal, 22-24 October 2009; [PERSON], [PERSON], [PERSON]; RILEM Publications SARL: Guimaraes, Portugal, 2009. * [PERSON] et al. (2012) [PERSON]; [PERSON]; [PERSON] [PERSON]. RCM: A new model accounting for the non-linear chloride binding isotherm and the non-equilibrium conditions between the free- and bound-chloride concentrations. _Constr. Build. Mater._**2012**, _27_, 293-304. [CrossRef]
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