Water absorption and constraint stress analysis of polymer-modified cement mortar used as a patch repair material

Reinforced concrete structures are damaged by salt attack, concrete carbonation, and sulfate attack, etc. The expansion stress by the corrosion of reinforcing steel causes crack in the cover concrete. Patch repair method is commonly applied to deteriorated RC structures. Deterioration mechanism of a patch-repair method in reinforced concrete is investigated through the experiment and analysis. The repair material selected is polymer-modified cement mortar re-emulsified by polymer resin. Because the water absorption of the patch-repaired material varies, depending on the relative moisture content, the water-absorption coefficient was measured, which is obtained by the Boltzmann–Matano method. Two-dimensional coupled analysis (FEM) of water absorption, volume change, and mechanical properties were used to estimate qualitatively the factors responsible for the stress increment at the repair site, such as the nature of the repair materials and the substrate concrete, and conditions at the interface between the concrete and the repair material. The cracking mechanism after repair and the selection of repair materials are discussed.