FIBER reinforced CONCRETE (FRC) has been used widely due to its advantages over plain CONCRETE such as high energy absorption, post cracking behavior, flexural and impact strengths, arresting shrinkage crack.This research discusses the effect of increasing the percentage of polypropylene FIBER on flexural toughness and strength of FRC. Three percentages of polypropylene FIBER were substituted in 1% STEEL FIBER reinforced CONCRETE (SFRC). Finally, the mechanical properties of three types of hybrid FIBER reinforced CONCRETEs were compared with each other and with STEEL FIBER reinforced CONCRETE by measuring their flexural toughness and flexural strength. A four-point bending test was adopted to determine the effect of hybrid FIBERs on crack arresting and post crack behavior.The research results show that the more the percentage of polypropylene FIBER which is substituted in SFRC is, the less the amount of energy absorption and flexural toughness with FRC will be.

CONCRETE incorporating STEEL FIBERs poses difficulty in mixing, transporting, placing and compacting that may lead to voids in hardened CONCRETE. The determination of fresh FIBER reinforced CONCRETE properties is therefore, important for satisfactory performance in hardened state. The present experimental study investigates effect of three FIBER properties volume fraction of FIBER, aspect ratio of FIBER and diameter of FIBER- on the rheological properties of high performance CONCRETE with a parallel plate rheometer. The test result shows that yield stress and plastic viscosity are adversely affected by all the three parameters. FIBER volume concentration has the highest effect on the measured rheological parameters whereas FIBER diameter has the least effect.

In developing countries, usage of STEEL FIBER-reinforced cementitious composites is widely expanding in structures, due to their high mechanical performance and flexibility. In this paper, the behavior of STEEL FIBER-reinforced CONCRETE exposed to corrosive environments has been investigated. Three test programs were conducted: one dealt with the effect of corrosion on STEEL FIBER-reinforced mortar specimens, next considered the effects of using pre-corroded FIBER in mortar specimens, and the other dealt with the effect of corrosion on the behavior and the failure modes of a single FIBER pull-out test. Different exposure periods, types of solutions and the temperature of environment were taken into account.

In order to select the most suitable CONCRETE for the construction of high-rise buildings, method of analytic hierarchy process (AHP) based on expert knowledge has been used.In this study conducted a series of laboratory works, to compare the effect of STEEL FIBERs used in various categories of resistance on CONCRETE behavior parameters. Mixing the samples is set for the three categories of resistance 25, 35 and 45 MPa. Strength parameters that are chosen to identify CONCRETE actions are tensile strength, impact strength, compressive strength and flexural strength. Also the samples in each resistance category are made with four FIBERs quantity: without FIBERs, 15, 25 and 35 kg FIBERs per cubic meter. The results suggest that using of STEEL FIBERs, increases the impact resistance, time of the first crack and ultimate strength of CONCRETE significantly. Also the addition of this type of FIBERs, increases tensile strength and flexuralstrength but don’t have significant effect on the compressive strength of CONCRETE.

Cementitious matrices are the fragile materials that possess a low tensile strength. The ‎addition of FIBERs randomly distributed in these matrices improves their resistance to ‎cracking, substantially. However, the incorporation of FIBERs into a plain CONCRETE ‎disrupts the granular skeleton and quickly causes problems of mixing as a result of the ‎loss of mixture workability that will be translated into a difficult CONCRETE casting in ‎site. This study was concerned on the on hand with optimizing the FIBERs reinforced ‎CONCRETE mixes in the fresh state, and on the other hand with assessing the mechanical ‎behavior of this mixture in the hardened state, in order to establish a compromise ‎between the two states. In the first part of this paper, an experimental study of an ‎optimization method of FIBERs reinforced CONCRETE while taking into account of some ‎parameters related to the matrix e.g. volume of the admixture, volume of incorporated ‎FIBERs and the volume of water and, cement (W, C) in function of workability time are ‎presented. Finally, test specimens of mixture optimized by this method have been ‎tested in compression and tension due to bending. The results have been compared ‎with those of mixture test specimens optimized by Baron-Lesage method‏.‏

Adding STEEL FIBERs to reinforced CONCRETE improves the active mechanisms on crack surface including tension and shear transfer mechanisms. In STEEL FIBER Reinforced CONCRETE (SFRC), tensile stresses are developed in FIBERs and deformed reinforcing bars just after crack initiation. With this beneficial effect, CONCRETE tensile strength is improved and crack spacing decreases. In this research, SFRC member behavior is analytically investigated under pure tension and in order to verify the model, the results are compared with some recent experimental results. From the viewpoint of constitutive modeling of RC elements, there are two main approaches, discrete crack and continuum level models. The major disadvantage that adheres to discrete crack models is the fact that these models focus on the local crack behavior and seek to detect the crack paths, which of course requires a high computational cost. By contrast, continuum level models take advantage of the spatially averaged models between two primary transverse cracks. In a process of developing average constitutive models, it is important to model local mechanisms, these mechanisms in a reinforced CONCRETE domain are related to initiation and propagation of cracks.In this article, the tension stiffening model is developed considering all effective local stress transfer mechanisms including tension behavior of deformed bar, FIBERs pullout, tension softening of plain CONCRETE and bond slip-stress between the reinforcing bar and CONCRETE matrix. Straight and end hooked FIBERs have different mechanisms during pullout such as debonding, friction and mechanical anchorage of end hooked FIBERs. To predict the FIBER tensile behaviors, it is necessary to define FIBER stress transfer mechanism on the crack surface. The most important parameters that affect FIBERs behavior are material properties, size and geometry, distribution and orientation of FIBERs. The model used in this research considers a uniform random distribution forFIBER’s geometrical location and inclination angle. In this model, the slip occurred in the FIBER is considered on both sides of FIBER embedded in CONCRETE. The bond slip- stress behavior of straight FIBER is defined as linear before the bond stress reaches to the bond strength, then the bond stress is considered constant until the complete pullout. In end-hooked FIBERs, in addition to debonding and friction, the end mechanical anchorage of the FIBER has also an important effect on the bearing capacity. In fact, in the process of FIBER pullout, hooked part of FIBER most have plastic deformation. To simulate it, a parabolic model is used. In order to solve the algorithm, an iterative analysis method is applied to calculate tension stress-elongation of specimen. To increase the accuracy of the model, the local yielding of reinforcing bars and matrix damage at the crack surface are also numerically simulated. Model verification is carried out by comparing the computational predictions with available experimental results. The results show good agreement with the test results. The proposed model is also shown to be useful in considering the effect of various percentages of FIBERs on average stress-strain behavior of deformed bar, total load elongation of specimen, crack spacing and CONCRETE tension stiffening. By increasing FIBER percentage, crack spacing will decrease so the average stress- strain behavior of deformed rebar becomes more similar to the bare bar.

STEEL fibres have gained popularity in recent decades for use in CONCRETE at relatively low volume fractions. They are mainly used to enhance toughness, flexural strength and resistance to shrinkage-induced cracking. However, little information is available about the effects of FIBERs on permeability and porosity, which play an important role in long –term durability of CONCRETE materials. This paper presents the results of an experimental study that was carried out to examine The influences of STEEL FIBER addition on the permeability and porosity of a CONCRETE prepared mainly from local materials. The test results are discussed in this paper, the interpretation of the test results is reported as well as conclusions regarding the effects of STEEL FIBERs on the Water and gas permeability of CONCRETE.