LAUSR

Abstract The investigation of the effect of surface preparation on the adhesion of underwater repair concretes to the horizontal surfaces has been carried out. A special chamber was used that made it possible to place the repair concrete on the concrete substrate under the water and its curing under hydrostatic pressure. Three types of underwater repair concrete were tested with the maximum aggregate grain size up to 8 mm. As a reference, the first repair concrete has been designed with an anti-washout admixture and superplasticizer. The second concrete was modified with the addition of the polypropylene fibers, and the third concrete contained the styrene-acrylic copolymer as an admixture. The surface of the concrete substrates was initially treated mechanically by hammering and sand-blasting. The SRI index characterized the degree of surface treatment. The substrates with the repair concretes were cured under hydrostatic pressure inside the specially built pressure chamber. After curing, the bond strength of the repair concretes to the substrates was tested by the pull-off method. The results of these tests, together with the compressive strength tests, were the basis for analyzing the influence of the surface preparation and hydrostatic pressure on the adhesion of the repair concretes to the horizontal surfaces of the concrete substrates with various degree of treatment. The most significant effect of hydrostatic pressure was observed for the repair concrete containing copolymer admixture.