Influence of capillary absorption and roughness of ceramic substrates on the adhesion of cement pastes

Abstrac This study assesses the joint influence of capillary absorption and substrate roughness on the adhesive strength of a cementitious matrix on brick substrate. One cementitious rendering and two substrates with different water absorption and roughness were used. The capillary absorption coefficient and the roughness coefficient were determined in 1cm2 test areas to then evaluate the matrix tensile bond strength and correlate it with the properties of the substrates. The results were validated by SEM and AFM analyses. Substrates with higher capillary absorption and lower roughness presented higher tensile bond strength. Micro and nanoscale analyses led us to conclude that, in the substrates used, the higher capillary absorption and the lower roughness generate a denser and less porous paste-substrate interface, suggesting a higher extent of contact between the hydrated paste and the substrate and, consequently, higher adhesive strength.