Influence of surface roughness and tensile bond strength in clay hollow block-paste adhesion

The adhesion of coating mortars is influenced by various factors, with the roughness of the substrates being particularly important. Surface roughness encompasses irregularities, including peaks and valleys, which can impact the adhesive properties between the cementitious matrix and the substrate. This study quantitatively analyses the roughness, topography, and interface area influence between ceramic substrates and cementitious coating on tensile bond strength. A single type of paste was applied to 400 surfaces of clay hollow blocks with varying roughness levels. The ceramic substrates were characterized using 3D laser profilometry to assess roughness. The study’s findings reveal crucial insights into average tensile bond strengths concerning specific roughness parameters, notably average valley area (AVA) and average valley height (AHV). It was observed that deeper valleys necessitated broader lake expansions for optimum adhesion. Remarkably improved average tensile bond strength was achieved at AHV values ranging from 2.16 to 2.78 µm and at 0.98 µm, beginning from an AVA of 0.19 mm². Furthermore, even at an AVA of 0.07 mm², a notable increase in adhesion was observed. In conclusion, this study highlights the profound influence of roughness parameters, AVA and AHV, on the adhesion between clay hollow blocks and cementitious matrices. The comprehensive analysis of surface roughness and its impact on adhesion provides valuable insights for optimizing coating mortar applications in construction and engineering practices.