## 4 Conclusions  
In this paper, the efficiency of the RCMT in assessing the chloride penetration resistance of concrete under submerged or wetting and drying conditions was analysed for a wide range of concretes with different w/b, types of aggregate and types and amounts of binder. To this end, the RCMT results were compared to those from the long-term IT and WDT, simulating real exposure conditions. This study covered a wide range of common NWC and LWAC for strength classes C20/25-C60/75 and LC20/22-LC60/66, respectively, which presented \(D_{d,RCMT}\) of 6-25 \(\times\) 10\({}^{-12}\) m\({}^{2}\)/s, representative of low to high chloride penetration resistance. The w/b was the most influential parameter in the chloride penetration resistance, regardless of the type of binder and aggregate. The RCMT and long-term tests were able to distinguish in the same manner significant alterations introduced by w/b in the concrete microstructure, following the same trend in the classification of concrete quality. Regarding the influence of the type of binder, a reasonable relation between the RCMT and the long-term tests was only achieved when concrete with FA was not considered. The incorporation of SF improved the chloride penetration resistance significantly from an early age, especially in low w/b concretes. The opposite behaviour was found with the incorporation of the quasi-inert LF. The same trends were found in both the RCMT and the long-term tests. However, the incorporation of FA was only effective in increasing  
Figure 18: Classification of chloride penetration resistance from \(D_{d,RCMT}\), based on \(D_{d,lT}\) (**a**) and \(D_{cl,WDT}\) (**b**). the chloride penetration resistance of concrete under long-term tests, where the chloride binding effect and the slow pozzolanic reactions were more relevant. Regarding the long-term tests, the reduction of \(D_{cl}\) was partly offset by the higher \(C_{s}\) in FA concrete. The RCMT carried out at 28 days showed to be inadequate in assessing the contribution of this addition in natural exposure conditions. Although more time-consuming, the RCMT at 90 days are recommended for FA concrete. In general, the \(D_{cl}\) was affected little by the type of aggregate. However, for LWAC with porous LWA and high w/b, the \(D_{cl}\) was higher, both in the RCMT and the long-term tests. The saturation conditions of surface LWA in long-term tests allowed their greater participation in chloride penetration. This participation was higher in the IT than in the WDT, because concretes were not allowed to dry since their production date. The differences between NWC and LWAC with porous LWA tended to be higher when the RCMT was related with \(K_{cr}\), because the \(C_{s}\) increased with the aggregate porosity in high w/b concrete. This confirmed the lower chloride penetration resistance of LWA with porous aggregates under short-exposure conditions. Noteworthy was the similar to better performance of LWAC with dense LWA compared to NWC, regardless of the concrete composition and exposure conditions. Similarly to the IT, for low w/b concrete, the \(D_{cl}\) was the predominant mechanism in the WDT. The WDT involved short-drying cycles, approximating to the exposure conditions of the IT. However, in high w/b concrete, the convection phenomenon was more relevant and the calculated \(D_{cl}\) tended to be higher in the WDT than in the IT. The difference between these tests was higher in \(K_{cr}\), because the \(C_{s}\) tended to increase in WDT. At least under the different exposure conditions considered in this study, reasonable correlations were obtained between the \(D_{cl,RCMT}\) and the \(D_{cl}\) or the \(K_{cr}\) from long-term tests, except for NWC with FA or LWAC with porous LWA and a w/b over 0.45. The correlation was higher between the \(D_{cl,RCMT}\) and the \(K_{cr}\) which is directly related with the chloride penetration resistance of concrete. The type of aggregate had less influence on the relation between tests than the type of binder.