The necessity of repair efficiency evaluation is stressed in many standards and guidelines related to repair of concrete structures. For this purpose, besides of pull-off test, non-destructive methods based on propagation of stress waves are usually recommended, e.g. ultrasonic methods and impact echo method.

In this work an effect of concrete substrate surface quality on stress wave propagation in repair system was investigated. Three substrate types, made from concrete of strength classes: C30/37, C40/50 and C50/60 were tested by impact-echo method. Four surface treatments (polishing, sandblasting, scabbling and hydro-jetting) were performed to obtain different quality of concrete substrate. The quality of the preparation was characterized on the basis of three main groups of parameters: surface geometry parameters, superficial concrete microcracking and adhesion strength. The surface geometry was characterized using patch test and opto-morphology technique. The quality of the superficial zone of concrete and cracks were systematically observed, in relation to the given surface treatment type. Commercial repair mortar was applied on concrete substrates after surface treatments. The impact-echo measurements and bond strength tests were carried out after 28 days of repair material hardening. The effects of concrete substrate strength and surface geometry characteristic on frequency spectrum were discussed. The potential relationships between parameters of stress wave propagation in repair system and the bond strength as well as the quality of bond interface were analyzed.

The research project was financially supported by the Government of Poland (KBN) and the Regional Government of Wallonia (DRI), Belgium. Part of experiments has been done in the framework of project granted by Polish Scientific Research Committee - grant number KBN 4 T07E 027 27.

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1. Computer simulation of stress wave propagation in repair systems
2. Characterization of concrete surface geometry by laser profilometry
3. A new method for concrete surface roughness characterization by opto-morphology technique
4. On the usability of wavelet analysis for non-destructive assessment of repair efficiency by impact-echo method