Effect of polypropylene plastic fibers length on cracking resistance of high performance concrete at early age

•The properties of HPC reinforced with different length of fibers were studied.•The increasing length of fibers reduced absolute value of autogenous shrinkage.•The increase in fibers length reduced the tensile creep of HPC.•The increase in fibers length reduced cracking resistance of HPC. Fibers reinforcement which is an effective mean to improve the cracking resistance of high performance concrete (HPC) is widely applied in practice. The early-age cracking resistance is improved by the addition of polypropylene plastic fibers, which is also affected by the length of fibers. Although investigations on the effect of content of polypropylene plastic fibers on the properties of HPC were carried out, investigations on the effect of length of polypropylene plastic fibers on the cracking resistance of HPC remain lacking. In present study, the effect of length of polypropylene plastic fibers on the early-age properties of HPC was investigated by Temperature Stress Test Machine. The test results and corresponding analysis indicated that: (1) the increasing length of polypropylene plastic fibers reduced the temperature drop at cracking time of HPC; (2) the increasing length of polypropylene plastic fibers reduced the absolute value of autogenous shrinkage of HPC; (3) the increasing length of polypropylene plastic fibers reduced the ratio of cracking stress to axial tensile strength and stress reserve of HPC; (4) the increasing length of polypropylene plastic fibers reduced the specific tensile creep of HPC; (5) the increasing length of polypropylene plastic fibers reduced the cracking resistance of HPC.