A Study On Autogenous Shrinkage Stress Of High Performance Concrete

In order to evaluate autogenous shrinkage stress of high performance concrete (HPC) due to autogenous shrinkage exactly, it is necessary to develop effective stress analysis method and study deeply time-dependence of compressive strength, Young's modulus, creep and autogenous shrinkage. In this paper, the behavior of autogenous shrinkage strain and stress of HPC was investigated experimentally, and the influence of curing temperature and water-cement ratio on mechanical properties, autogenous shrinkage strain and stress was discussed. The creep stress based on step-by-step methods was applied for estimating autogenous stress, and comparison was made with the values from investigation.The conclusions derived from the study are as follows: (1)The development of compressive Young's modulus of HPC is rapider than the compressive strength development, especially at early 3 days, the lower water-cement ratio and the higher curing temperature, the more significant the phenomenon. (2) The lower water-cement ratio and higher curing temperature, the more rapidly autogenous shrinkage strain and stress developed. (3) The development of the autogenous shrinkage stress is slower than development of the strain due to creep of concrete at early ages. (4) In the case of 20℃curing temperature, the development of calculation results of autogenous shrinkage stress present a simlar tendency to that of experimental results, based on step-by-step method. Autogenous shrinkage stress was overestimated by computing at early age, but the calculation results agreed with experimental results later. (5) In the case of 35℃and 5℃curing temperature, the behavior of autogenous shrinkage stress can not be discribed by calculation results, due to neglecting the influence of temperature on tensile creep model used in this paper. (6) It is clear that tensile creep model is more appropriate for evaluating autogenous shrinkage stress than comparessive creep model.