Study on the Evaluation of Influence of Creep on Autogenous Shrinkage Stress

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The following concepts were clarified on the compressive and tensile creep, the evaluation method of creep under changing stress and the calculation method of autogenous shrinkage stress of high strength concrete in early ages.1. Creep is proportion to a stress to the extent of 40 % of stress-strength ratio, at least.2. A significant difference is not recognized with compressive and tensile creep.3. Creep characterisitic changes greatly near by the age of 1 or 2 days, and the change is small after the age of 3 days.4. Basic creep function for high strength concrete in early age can be given by the product of final creep value and creep progress function.5. Creep value right after the stress reversal estimated by the method of superposition is grater than the measured a little, yet the estimated value generally agree well with the measured value.6. There are no remarkable differences between the estimated values by the time hardning rule and the strain hardning rule, and the estimated vales are fairly small compared with the measured value, especially right after the stress reversal.7. The time hardining rule and the time hardning rule require some appropriate correction considering the softning due to the stress reversal.8. The autogenous shrinkage stress of 1.5N/mmィイD12ィエD1 at the age of 7 days and 2.2N/mmィイD12ィエD1 at the age of 60 days were measured by using JCI method in high strength concrete having water-cement ratio of 30%.9. The autogenous shrinkage stress can be estimated by the increment method using the effective Young's modulus calculated from measured creep coefficient of high strength concrete having water-cement ratio of 30%.10. The Young's modulus reduction coefficient for calculation of autogenous shirinkage stress is a little smaller than that for thermal stress calculation