Measurement and modeling of creep property of high-strength concrete considering stress relaxation effect

Abstract

Measurement of concrete creep under constant sustained stress conditions is usually a long process. The external load applied on the specimen may relax gradually during this long process due to the time-dependent properties of concrete and test set-up, which would lead to an improper assessment of concrete creep without considering the stress relaxation effect. This study developed a theoretical method based on the linear superposition principle to derive the specific creep of concrete from the compressive creep test results where a certain amount of stress has relaxed. Three types of high-strength concretes were cast for the creep tests. In addition, the workability, mechanical properties, and shrinkage of the three concretes were measured. Then the application of the existing models including the ACI model, CEB-FIP model, GL2000 model, and B4 model to predict the creep and shrinkage of high-strength concrete was discussed. The results reveal that the specific creep of concrete used in this study without considering the stress relaxation effect decreases by 4.3%∼11.0% when 6.7%∼13.1% of the applied stresses relax during the creep tests. Both creep and shrinkage of high-strength concrete exposed to drying decrease with increasing curing age. It is found that the CEB-FIP model can predict the shrinkage of high-strength concrete well and the B4 model can give a predicted result relatively close to the measured creep of high-strength concrete.