Integrated Evaluation Of Volume Changes Of High Strength Concrete

In high strength concrete (HSC) structures, a phenomenon that the concrete is cracked at early ages can be observed frequently. It has become an important issue that will be resolved as soon as possible to control early cracking. Therefore, this paper presents a systematic study on the strain and stress due to volume changes of HSC. The time-dependent change of mechanical properties and the components of volume change and its restrained stress of HSC were investigated experimentally. The restrained stresses have been analyzed with creep analysis method, based on the measured values of mechanical properties and shrinkage behavior of HSC.The results show that mechanical properties of HSC, including compressive strength, axial compressive strength and Young's modulus, increase faster than those of common concrete at early ages. Autogenous shrinkage of HSC develops very fast at early ages; the value of autogenous shrinkage strain at the age of 1 day is about 35% of that at 28 days and 30% of that at 90 days. After 60 days, autogenous shrinkage showed a tendency to converge and the contribution of autogenous shrinkage strain to total shrinkage is about 70%. It is clear that autogenous shrinkage stress is the greatest portion of total shrinkage stress according to the result of separation of restrained stresses and the other components such as dying shrinkage stress and thermal stress cannot be neglected also. Therefore, it is necessary to integrate the influence of autogenous shrinkage, thermal...