Effect of Polypropylene Fibers in the Early Curing Stages of Concrete

摘要

The report documents the effect of small percentages of polypropylene fibers on controlling internal microcracking and, thus, increasing the tensile strength of concrete. When concrete is restrained from shrinkage, internal stresses will increase until tension failure occurs, causing internal microcracks to develop. These internal shrinkage cracks tend to coalesce into large, through-thickness cracks and weaken the material. Research tests included shrinkage, restrained shrinkage, and modulus of rupture tests. Results have revealed that the presence of relatively small percentages of polypropylene fibers, whether fibrillated or monofilament, has an effect on potential shrinkage cracking in that the fibers reduce the tendency for the internal shrinkage cracks to coalesce into large, through-thickness cracks, and to keep the crack faces closer together when cracking occurs. It was also concluded that the fibers have little if any effects on reduced shrinkage or strength improvement during the early curing stages.