1 Creep, Shrinkage and Cracking of Restrained Concrete at Early Age Salah A. Altoubat and David A. Lange University of Illinois at Urbana-Champaign Department of Civil and Environmental Engineering Urbana, IL 61801 ABSTRACT Creep and shrinkage of concrete under restrained conditions during the first days after casting have been characterized by experiments that provide data on shrinkage and tensile creep strains, restrained shrinkage stress and the extent of stress relaxation by tensile creep mechanisms. Effects of fiber reinforcement (steel and polypropylene), w/c ratio, drying conditions and curing conditions on restrained shrinkage behavior of normal and high performance concrete are discussed. 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 about 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. Keywords: tensile creep, shr inkage, cracking, early age behavior, fiber reinforcement, restrained shrinkage, steel fibers, polypropylene fibers, shrinkage stress, curing