Moisture equilibrium of cement based materials containing slag or silica fume and exposed to repeated sorption cycles

Water vapor sorption isotherms are essential data in models to predict the service life of cement based structures. This study investigates the influence of water to binder ratio (0.4, 0.5 and 0.6), and the presence of two SCMs (70% slag and 10% silica fume) on sorption isotherms, both in the hygroscopic and in the super-hygroscopic relative humidity (RH) ranges.In the present paper desorption isotherms are divided into different parts based on the Jennings CM-II model of the C–S–H structure. The samples with silica fume and slag have higher moisture content than OPC samples, but with a higher amount of gel pores and lower amount of capillary pores. At low RHs all samples have similar desorption curves and the introduction of SCMs induces only a slight increase in the BET surface area.