Study on Time-Dependent Behavior of RC Beams with Flexural Cracks Generated at Early Age

Abstract

In this research, to clarify the time-dependent deformational behavior of RC beams with flexural cracks generated at an early age, continuous flexural loading of RC beams was conducted, and the effects of shrinkage property, age of cracking, and environmental conditions were experimentally investigated. A calculation method of total crack width utilizing the results of numerical simulation was proposed. Using this method, tensile deformation of RC beams at an early age was analyzed.

The results of this study demonstrated that compressive deformation of concrete due to drying creep causes a significant increase in the tensile stress of reinforcement. Especially under high compressive stress/strength ratio, large creep deformation, which might be due to micro-cracks generated at ITZ between the cement paste and aggregate, should be properly considered in numerical simulation. Furthermore, deterioration of the bond between compressive reinforce-ment and the surrounding concrete might be another reason for the large creep deformation.

Moreover, it was assumed that concrete between flexural cracks generated at a very early age could deform with less bond deterioration following the deformation of tensile reinforcement. This might be due to the generation of mi-cro-cracks at ITZ between the cement paste and aggregate, which might prevent internal cracks around reinforcement leading to deterioration of the bond.