Relationship between surface characteristics and superficial cohesion of concrete

Existing concrete surfaces have to be prepared before the application of a new layer. Different surface treatments (grinding, sandblasting, shotblasting, hand- and mechanical milling) have been performed and the quality of the preparation has been established on the base of three main parameters: surface roughness, superficial concrete microcracking and adhesion. Cracks have been systematically observed, in relation with surface treatment by means of Scanning Electron Microscope and Light Microscope. Finally, a repair mortar, with or without bond coat, has been applied on the concrete substrates and adhesion has been measured. Analysis of results clearly show the effect of roughness on adhesion in the case where no bond coat is used, the influence of the surface treatment on the waviness shape of the profile and the presence of microcracks in the near-to-surface layer, which is related to failure type.