Effect of Surface Reinforcer on Compressive Strength and Microscopic Mechanism of Freeze–Thaw-Deteriorated Concrete

Abstract

Due to the deterioration caused by repeated freeze–thaw cycles, concrete materials in cold regions often develop cracks, which have serious effects and challenge the durability of concrete-based structures. Therefore, it is worthwhile to repair and strengthen freeze–thaw-damaged concrete to extend the service duration of the structure. In the present study, to investigate the restorative effect of surface reinforcer on freeze–thaw-deteriorated concrete specimens, the effects of the surface reinforcer type, its action duration, and the number of applications on the strength and deformation parameters of repaired specimens were systematically studied. Moreover, pore size distribution, pore structure at different depths, and the micromorphology characteristics were investigated by nuclear magnetic resonance (NMR), pore structure, and scanning electron microscope (SEM) tests to reveal the repair mechanism of different surface reinforcer types. The results indicated that the compressive strength of freeze–thaw-deteriorated concrete could be increased by up to 15.67% after the application of the surface reinforcer. Both the values of compressive strength and deformation modulus E50 increased with the increase in the action duration. In addition, the surface reinforcer could efficiently penetrate the interior of the deteriorated specimen and was able to decrease the total proportion of multi-harmful pores and harmful pores. Furthermore, the pore structure parameters could be significantly improved at a depth of 10 mm; however, the reparative effect of the surface reinforcer gradually decreased with the increase in the action depth. The surface reinforcer could efficiently promote the second hydration of cement and generate more cementitious materials to fill the microvoids, thereby improving the compactness and mechanical properties of the repaired specimens.