Most of concrete deterioration processes depend on deleterious substances penetrating from the surrounding environment into the bulk of the concrete through its surface. So, enhancing both transport and microstructure of the concrete in the exposed outer layer of the structure must be insured. This research investigates the sorptivity, nature and amount of hydration products and capillary porosity of OPC matrix containing different contents of rice husk ash (RHA). The effects of water-binder ratio and curing regime on sorptivity of OPC/RHA matrix were also outlined. The test results showed that incorporating RHA in OPC concrete has led to a significant reduction in the volume of interconnected pores of diameters more than 30 nm (capillary porosity) and amount of C-H, a notable enhancement in sorptivity, and an increase in C-S-H content. These effects are pronounced with increasing RHA content. However, the enhancement in the fluid transport characteristic of OPC/RHA matrix is mainly dependent on the considered w/b ratio and curing regime.