The aim of this study was to relate the characteristics of interfacial transition zone (ITZ) "aggregate-cement paste" to the characteristics of porosity, water absorption, resistance and roughness of porous limestones.The first part of this work was to study the influence of moisture content and resistance of aggregates on the mechanical strength of mortars. The results show that, for porous and absorbent limestones, mortars made from dry aggregates are more resistant than those made from wet aggregates.The second part of this work was to study the ITZ of composites “rock-cement paste”. It was found that the surface roughness and the moisture content of rocks significantly affect the tensile and shear strengths of composites.The last part is devoted to the microstructure of ITZ by image analysis. The evolution of average porosity of ITZ is related to the mechanical properties of mortars by Féret’s law demonstrating that the compressive strength depends mainly on the mesoporosity of ITZ. The porosity gradient is related to the degree of hydration gradient and the W/C ratio gradient. These latter two are calculated by applying Powers’ model. The results show that for porous and absorbent limestones, the cement pastes and the ITZs of dry and wet aggregates mortars are not equivalent although initially we aimed to the same W/C ratio.
