The rapid chloride migration test (RCM) is a commonly used accelerated test for the determination of the chloride diffusion coefficient in concrete. Nevertheless, the initial development and further experience with the RCM test concern mainly the ordinary Portland cement system. Therefore, the objective of this work is to analyse the application of this test method for other types of binders, by performing and analysing the RCM test results for mortars prepared with additions of supplementary cementitious materials. A comparison is given between the total chloride concentration profiles measured in concrete after the RCM test and the colourimetric test results. The presented results show that the accuracy of the silver nitrate colourimetric technique is sufficient for the determination of the chloride penetration front and that the RCM test is a suitable method also for the determination of chloride diffusion coefficient in mortars with blended cements.