Cracking of high strength concrete around deformed reinforcing bar due to shrinkage

Abstract

High Performance Concrete is particularly sensitive to self-desiccation of the cement paste during the hydration process, which leads to autogenous shrinkage. If a restraint is present, autogenous shrinkage may lead to high self-induced stresses, possibly causing surface and even through cracks and potentially jeopardizing the durability of the concrete structure. It is a matter of vital importance to grasp the characteristic of high performance concrete, especially in the case of RC. Two different super-high-strength concretes whose water to binder ratio is 0.15 and compressive cylinder strength at 28 days is more than 120 N/mm are developed. One of these is conventional super high strength concrete that shows very large autogenous shrinkage, namely about 800μ, and the other shows about 200 μ at 28 days due to adding expansive additive and shrinkage reducing agent. Subsequently experimental results of shrinkage induced stress in RC, using two different concrete mentioned above, whose reinforcement ratio is 8.6% are reported. Additionally an evidence of crack at the vicinity of reinforcement of SHSC when the reinforcement ratio is about 8.6% is reported and its effect on mechanical behavior of RC is discussed.