Early-age autogenous shrinkage and tensile creep of concrete reinforced with polypropylene macro fiber

Early-age autogenous shrinkage and thermal shrinkage developed in concrete may lead to cracking when the stress induced by restrained shrinkage is higher than the tensile strength of concrete. Early-age tensile creep (TC) of concrete can mitigate the tensile stress generated in concrete induced by restrained shrinkage. Characterizing the TC of concrete at early age is important for cracking resistance evaluation. The early-age autogenous shrinkage and TC of concrete with various proportions of polypropylene (PP) macro fiber (0%, 0.3%, 0.6%, and 0.9%) were investigated utilizing the Temperature Stress Test Machine. Fiber dispersion and the microstructure of concrete mixtures were also analyzed. Test results indicated that PP macro fiber reinforcement led to the improvement of mechanical properties and mitigation of autogenous shrinkage. TC behavior of concrete at early age including TC, TC coefficient, and specific TC decreased with the inclusion of PP macro fiber. A modified model for the prediction of the early-age specific TC of concrete reinforced with PP macro fiber was proposed.