Strength properties of fine aggregate concretes reinforced by polyamide fibers

Reinforcing concrete with fiber is one of the most effective methods to improve the properties of cement-based materials. In this study, the effect of using two different polyamide fibers (i.e. PA6 and PA66) as reinforcement in fine aggregate concretes was investigated. The effects of the fiber length and type of supplementary cementitious materials (SCM) were also studied. Three-point bending test, pullout, and compression tests were carried out on the cementitious composites. The effect of embedment length was also investigated on pullout behavior. Pseudo-strain hardening behavior was obtained in the fiber-reinforced concretes. Although there was no significant difference in the flexural properties of composites containing PA66 and PA6 fibers, the pullout load and energy which were obtained by PA66 fibers were 36% and 45% higher than PA6 fibers, respectively. It was found that an increase in PA66 fiber embedment length up to 10 mm leads to an increase in pullout energy. The compressive strength of more than 90 MPa was obtained using PA66 fibers, which were considerably higher than ordinary concrete and PVA fiber-reinforced concrete.