Creep, Shrinkage, and Cracking of Restrained Concrete at Early Age

In this study, uniaxial restrained shrinkage tests were conducted on plain and fiber-reinforced concrete (FRC) samples to provide data on shrinkage stresses, shrinkage strain, and tensile creep at early age. The influences of water-cement ratio (w/c), fiber reinforcement, and curing conditions on restrained shrinkage behavior of concrete were investigated. It was found that tensile creep relaxed shrinkage stresses by 50% and doubled the failure strain capacity. Both the magnitude and time history of the shrinkage stress influence the time of cracking, which in this study occurred at approximately 80% of the static tensile strength. Steel fibers substantially delay the shrinkage cracking, but without influencing the stress at failure. Finally, it was found that sealing of the concrete specimens did not eliminate the early age shrinkage, and that wet curing effectively relaxed shrinkage stresses.