You can use the tool developed by NIST (https://www.nist.gov/el/materials-and-structural-systems-division-73100/inorganic-materials-group-73103/virtual-rapid) to determine (VERY ROUGHLY) the expected range of RCPT values or you can consult the literature for some ranges of results. In any case, such a measurement is affected, substantially, by the pore solution composition and conductivity (RCPT values need to be corrected for pore solution resistivity), leaching or degree of saturation, among many other things. Therefore, finding a certain number in the literature that represents a mix with "cement 300 to 350 kg/m3, w/c 0.38 to 0.40" does not mean in any way that you will find a similar result for your mix. To add up to this, there is no certain constant correlation between RCPT values and chloride diffusion coefficients and different authors seem to find different correlations. An estimate of the diffusion coefficient can be achieved using an approach such as that in Weiss et al., (2017): (https://www.researchgate.net/publication/312029942_Toward_Performance_Specifications_for_Concrete_Durability_Using_the_Formation_Factor_for_Corrosion_and_Critical_Saturation_for_Freeze-Thaw)

This, however, demands a knowledge of the pore solution conductivity and the chloride binding isotherm. Even if the diffusion coefficient is estimated in such a way, a knowledge of the surface chloride concentration would be required to determine the chloride profiles. Furthermore, even if the profiles are determined, a knowledge of the chloride threshold, required to initiate corrosion, and the corrosion propagation rate are required in order to answer the question of: would my structure last for 50 years if my RCPT value is x?

Conference Paper Toward Performance Specifications for Concrete Durability: U...

Andrew

Thanks for the reply and will look at the publications.

Regards

Raman