Comparative analysis of the retraction through the drying shrinkage of new and recycled polyester fibers

Abstract Analyzing the physical characteristics of the cementitious matrices, it is possible to highlight the shrinkage as one of the most influential in the durability. If not predicted or controlled, this has the potential to cause serious problems in systems, such as cracking. Due to the shrinkage effect of the matrix it is inevitable to encounter cracks in the early ages of the concrete due to the phenomenon of their volumetric variation. It is known that the addition of fibers affects the properties of the resulting composite, reducing its cracking potential. In this sense, this research evaluates the effects caused by the insertion of new and used polyester fibers in the drying retraction of concretes. The results of the compressive strength did not change with the addition of the polyester fibers in the reference concrete. By means of the restricted ring test it was possible to observe efficiency gains in the blends with the use of fibers, when it refers to the retraction by means of the reference matrix. The shrinkage stresses on drying were increased about twice with the inclusion of the fibrous reinforcements. It could be observed that the addition of recycled polyester fibers provided a reduction, about 80%, in the formation of cracks in the matrix when compared to the reinforcing effects in concrete with addition of the virgin fibers.