Abrasion resistance and mechanical strength of underwater repair concrete curing under hydrostatic pressure

Damages of hydraulic concrete structures caused by erosion are a significant repair problem. Modern concrete enables performing the repair works without using the so-called dry dock. The repairs are often carried out at great depth. A special container, which could simulate placing and curing concrete under hydrostatic pressure, was used to study the concreting depth's influence on the concrete's future abrasion resistance. Two compositions of the underwater repair concrete were tested. The maximum grains size was 8 and 16 mm. Also, a viscosity-modifying admixture was used. The designed composites met the standard requirements in maintaining consistency in time and limiting the wash-out losses. The concrete specimens, taken for testing the abrasive resistance and compressive strength, were initially cured in the container for 28 days under pressure from 0 to 0.5 MPa. The pressure range corresponds to curing the concrete at a depth of up to 50 m. The abrasion tests were conducted using Böhme's disk. The results show that the hydrostatic pressure does not negatively affect the strength and abrasion resistance of the underwater concrete. The abrasion resistance is not directly related to compressive strength. It has been observed that the higher is hydrostatic pressure, the higher is abrasion resistance of the concrete's top layer compared to the bottom layer. The hydrostatic pressure acting when placing and curing the concrete mix causes releasing the bigger air voids. Therefore, the specimens taken from the top layer are less porous, which was confirmed by testing the apparent density.