The Effects of Micro and Macro Synthetic Fibers on Drying Shrinkage of Restrained Concrete

When concrete loses its moisture, it shrinks and results in cracking. In addition to undesirable effects on the appearance of concrete, cracks reduce its strength and durability. Fibers are used in concrete in order to control shrinkage cracks. The goal of this study is to evaluate the effects of micro and macro synthetic fiber in reducing the drying shrinkage and cracking under restrained conditions. For this purpose, in the first phase of the study, the effects of two types of microfibers, polypropylene and double-part, were selected. The results of the first phase of the study showed that polypropylene fibers have a better performance in improving initial cracking time and reducing the maximum crack width. The second phase of the study investigated the effect of macro synthetic fibers as well as the micro and macro synthetic fibers, hybrid mixes, in reducing the drying shrinkage of restrained conditions. The experimental results obtained in the second phase showed that the presence of macro synthetic fibers, due to the high modulus of elasticity, had a significant effect on drying shrinkage. The results also showed that the hybrid mixes had the best performance