Abstract
Many bonding failures between the substrate and repair mortar are attributed to too aggressive removal of the contaminated concrete and incorrect use of repair materials. To this end, in this study the effect of concrete removal techniques on substrates of different compositions and, as a result, on the bonding with repair mortar has been investigated. Substrate surfaces of different concrete compositions, micro-concrete (MC) and crushed stone concrete (CC), were treated by using three commonly used techniques: grit blasting (GB), jack-hammering (JH), and hydrodemolition/water-jetting (WJ). Automated Laser Measurements (ALM), sand patch tests and surface tensile strength measurements were applied to characterize the substrate surface. According to the results, the co-lateral effects of removal techniques such as WJ are dependent on the concrete mix composition. Moreover, WJ- and JH- treated samples achieved a lower surface tensile strength and bond strength compared to GB-treated slabs.
Highlights
Bond strength between concrete substrates and repair materials is influenced by parameters such as the saturation degree [1] and roughness [2] of the substrate surface, the applied removal technique [3], etc.Based on the removal depth, concrete removal techniques are categorized into different classifications
In this study, the value given in fig.6 for water jetting (WJ)-treated samples, is the highest roughness obtained in either X or Y
The former was to measure the surface tensile strength, and the latter was performed 28-days after the repair mortar was applied in order to evaluate the bond strength between the substrate and the repair material
Summary
Bond strength between concrete substrates and repair materials is influenced by parameters such as the saturation degree [1] and roughness [2] of the substrate surface, the applied removal technique [3], etc.Based on the removal depth, concrete removal techniques are categorized into different classifications. Concrete removal techniques like jack hammering (JH) or high-pressure water jetting (WJ) are usually used when a higher removal depth is the target [4]. These techniques, i.e. JH and WJ are usually referred to as “aggressive”. The former is claimed to create microcracks in the superficial layer of the substrate, and as a result, to weaken the bond strength [5,6,7]. Some research studies have reported the presence of microcracks caused by WJ [6,8], while others did not [9,10]
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