The mechanical behaviour of Recycled Aggregate Concrete (RAC) is investigated by reporting the main results of experimental tests intended at understanding the influence of Recycled Concrete Aggregates (RCAs) on the resulting mechanical properties of concrete. The focus is placed on the higher porosity of RCAs and their higher water absorption capacity. Consequently, the role of the initial moisture conditions of RCAs at mixing is also unveiled and its consequences on both the hydration reaction and the time evolution of compressive strength are highlighted. The influence of processing procedures intended at reducing the aforementioned porosity is also discussed