51 / 2022-03-30 17:03:12

Stress-Stiffness Relationship of Repaired Concrete Considering Stress Relaxation Due to Drying Shrinkage

Re-deterioration,Ring test,Patch repair method

It has been reported that premature deterioration phenomena, such as interface peeling and surface cracking, occur in patched concrete members within 1-2 years of the repairing. It occurs despite using appropriate repair material for the deterioration factor of existing concrete, and even if it is performed again, there is a problem that the deterioration repeats over several years. The cause of premature deterioration has been considered the incompatibility in the deformation behavior (drying shrinkage) due to humidity fluctuations between the existing concrete and the repair material.

Since some previous studies have investigated predictive models for drying shrinkage rate and strain of concrete and repair material due to outside air temperature and humidity, the maximum shrinkage of repair materials and existing concrete can be predicted during their life service. If the generated stress on the patched concrete can be calculated for the predicted shrinkage strain, the required performance (tensile strength, etc.) of the repair material can be clarified considering the behavior of existing concrete in the design stage of the repair.

According to the above, to evaluate the compatibility of the deformation behavior in the repaired concrete member due to drying shrinkage, we conducted the Weiss ring test, which simulated the patched concrete member, to calculate stress considering relaxation on patched parts. It was assumed the drying shrinkage of repair material only, the restraint degree due to the rigidity ratio between concrete and repair material, and stress direction depending on the repair form. As a result, the maximum stress in the Weiss ring specimen was proportional to the ratio of the repair material to the concrete in the product of rigidity and thickness, regardless of the position of the restraint ring (inner and outer restraint) assuming concrete without drying shrinkage.