Rate dependent short-term creep and creep recovery of normal concrete

Understanding the rate effect is crucial for enhancing the safety assessment of concrete structures. It has been observed that creep of cement paste exhibits rate dependency at the micron scale. This study investigates the rate-dependent behavior of short-term creep and creep recovery in concrete at the macroscopic level. Short-term creep tests under varying loading rates were conducted in the study, using two different concrete mix proportions. The experimental results reveal that the creep strain, residual strain, and recovery strain of concrete increase with the loading and unloading rates. The study also introduces a modified fractional-order viscoelastic model, which accurately fits the experimental results of creep and creep recovery. The research concludes that as the loading time increases, the creep strain increases, mainly in the form of an increase in irrecoverable strain. The linear correlation between residual strain and creep strain is associated with the rate of loading and unloading. At a loading rate of 7 kN/s, there is a nonlinear escalation observed in the residual strain.