ABSTRACT
After placing a cementitious repair material on a concrete substrate, the moisture exchange between these two materials takes place. The concrete substrate absorbs water from the repair material. Since the repair material is still “liquid”, the water loss causes a reduction in the w/c ratio in the bulk repair material and at the interface. The resultant w/c ratio has two effects on the cement hydration of the repair material. On one hand, the reduced water content initially retards the cement hydration and affects the quality of the bond. On the other hand, a lower w/c ratio results in a lower porosity and a denser pore structure with probably higher strength of the repair material and the repair-substrate interface. Moreover, capillary absorption plays an important role in the mechanical interlocking, since it facilities the penetration of the liquid repair material into the cavities of the concrete substrate and increases the contact area between the two materials (Courard 2000).
