Plastic Shrinkage Evaluation of Self-Consolidating Concrete as Repair Materials Based on Restrained and Free Strain Measurements

Abstract

One of the most challenging problems that can confront a repair engineer is that the completed structure is a monolithic mass that is free from cracks, especially with regard to the plastic shrinkage cracking in concrete flatwork. The more roughness in the surface of substrate, there will be more bond strength between substrate and repair overlay. But, meanwhile, the more roughness, more restraints induced in overlay, which during shrinkage, tensile stresses will be generated in repair materials. The results of investigation reported herein concern the effect of the type of repair materials on free and restrained plastic shrinkage properties. Four types of repair materials were used in this work are plane self-consolidating concrete (SCC), SCC containing silica fume (SF), SCC containing SF and latex (Styrene Butadiene Rubber), and SCC containing SF, latex, and fiber. To roughen the surface of substrate base, dents were used to provide restraints. The panels were subjected to severe combination of wind, temperature, and relative humidity. The test program includes: settlement strain, free and restrained shrinkage strain, evaporation and bleeding rates, and crack characteristic measurements. The results show that, while the rates of evaporation and bleeding affect shrinkage, it is over shadowed by other factors, such as fiber type, binder type and use of latex. The results show that, a significant improvement was observed for SCC with latex and fiber exhibiting the lowest plastic settlement and shrinkage strains, as well as crack area and longest time to first cracking. The plane SCC exhibited almost twice the settlement and shrinkage strains than SCC with latex and fiber.