Evaluation of the maximum load value and cracking load in fiber-reinforced concrete

Abstract In fiber-reinforced fluid concrete (FRFC), it is possible to use the casting flow of the concrete to guide the fibers in the places and directions of greater stresses, which is a relevant aspect when you want to use the fiber-reinforced concrete (FRC) for structural purposes. However, the normative instructions referring to the sizing aspects of the FRC still do not verify the validity of this preferential orientation of the fibers since they consider that the maximum load corresponds to the cracking load when using dispersed fibers in the matrix, and they base their studies on this hypothesis. In view of this and knowing the significant change that the preferential orientation of the fibers can provide to the FRC, it is necessary to carry out a study regarding the relationship between this orientation and the resistance load of the concrete. From this, a study is presented associated with the relationship between the maximum load and the cracking load of a sample of concrete reinforced with steel fibers (SFRC) and another of concrete reinforced with polymeric fibers (PFRC), both with the preferential orientation of the fibers that will be used later for structural applications. According to the study, it was observed that when the element exhibits hardening behavior and the fiber has a high modulus of elasticity, there is no statistically significant difference between the loads. However, when the element exhibits softening behavior and the fiber has a low modulus of elasticity, there is a statistically significant difference between the loads. Thus, it can be concluded that, when using the preferential orientation of the fibers in the composite, the maximum load may not correspond to the cracking load, making it necessary later to determine the design load and, consequently, the possible variations in the dimensioning aspects.