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The behavior of steel fiber reinforced concrete (SFRC) is highly dependent on mix design, where the properties of its components, such as cementitious matrix and fibers, impact the physical and mechanical properties of the composite. Incorporating steel fibers into concrete modifies its physical properties, potentially leading to fiber segregation and resulting in a nonuniform distribution of the fibers within the material. In experimental studies, an increase in fiber volume has been found to change the failure mode of SFRC beams from shear to flexure, and numerical investigations have shown that randomness in fiber distribution can significantly influence the behavior of the composite. Therefore, this study aims to develop a numerical model that considers variations in material properties to simulate the change in the failure mode of SFRC beams due to variations in fiber volume. The failure and yielding parameters were initially established and integrated into the concrete damaged plasticity (CDP). Subsequently, the response of both steel and concrete to tension or compression stresses was ascertained. Finally, the appropriate meshes and finite elements were chosen for the simulation. In the final approach, two methods were employed to introduce randomness into the beam. One divided the beam into different vertical segments: 30, 45, and 90, and the other combined vertical and horizontal segments: 30 vertical with 4 horizontal, 45 vertical with 5 horizontal, and 90 vertical with 10 horizontal. A script was developed in Python to automatically insert the properties. The numerical model successfully captured the change in failure mode from shear to flexure resulting from fiber volume increase. Vertical and horizontal segments increased toughness due to crack deviation, better predicting cracking pattern and loading capacity for the highest fiber contents. [ABSTRACT FROM AUTHOR]

The construction industry requires concrete with adequate post-cracking behavior for applications such as tunnels, bridges, and pavements. For this reason, polypropylene macrofibers are used, which are synthetic fibers that fulfill the function of providing residual strength to concrete. In this study, an experimental plan is carried out to evaluate the bending behavior of concrete reinforced with polypropylene fibers using the four-point bending test according to ASTM C1609. Three fiber dosages (3.6, 7.2 and 10.8 kg/m3) and three fiber lengths (40, 50, and 60 mm) were used. The use of macro polypropylene fibers increased the post-cracking behavior of concrete. In addition, based on the experimentally obtained results and available literature data, a multivariable equation was developed to predict the concrete toughness as a function of the volume, slenderness, and modulus of elasticity of the fibers. A Pearson's correlation coefficient, r of 0.90, showed a strong correlation between the developed equation and the experimental data. From this equation, it was possible to determine the participation of the following parameters in calculating toughness. The participation or weight of the fiber's modulus of elasticity on the concrete's tenacity is 26%, the volume of the fiber is 39%, the slenderness is 19%, and the reinforcement index is 16%. [ABSTRACT FROM AUTHOR]

Recently, fiber-reinforced concrete (FRC) creep behavior has become a much addressed topic, and the main gap found in the literature is whether cracked FRC is stable in the serviceability limit state. Therefore, this work aims to investigate the creep behavior of steel and polypropylene (PP) FRC by analyzing the growth of the crack opening displacement over time in prismatic specimens subjected to sustained bending. Sustained load tests were also performed on FRC constituents and on the fiber matrix interface in order to evaluate individually their long-term response, and to understand their contribution in bending. Based on a model proposed, the rotation in a plastic hinge located in the crack area could be calculated considering the three mechanisms evaluated—fiber pullout, concrete compression, and shrinkage. It could be concluded that the fiber pullout mechanism plays a primary role in creep deformation in precracked elements subjected to sustained bending loads. [ABSTRACT FROM AUTHOR]

The work in hand presents results of an experimental and numerical research on the post-heating residual strength of a basalt textile refractory composite submitted to tensile loading. The tensile tests were performed after a preheating process at temperatures ranging from 25 to 1000 °C. The mechanical performance and cracking mechanisms were discussed and compared to that obtained at room temperature. Image analysis by means of digital image correlation method was used to obtain the evolution of crack width which was subsequently correlated with the stress response for all target temperatures. Scanning electron microscopy was used to investigate the damage processes in the fiber–matrix interfaces after exposure to high temperatures. A finite difference model was used to simulate the tension stiffening behavior of TRC (Textile Reinforced Concrete) systems predicting their crack spacing and stress vs. strain responses. The obtained results indicated that due to the coating decomposition the reliability of basalt TRC can only be guaranteed from room temperature to 150 °C. [ABSTRACT FROM AUTHOR]

• Positive influence on the fiber addition on fatigue life of the composite. • Three parameter Weibull distribution successfully allows to estimate fatigue life of pre-cracked SFRC. • New methodology verifies fatigue deterioration through bending tests and damage equations. • Two novel empirical correlations successfully estimated damage evolution and energy release rate. The present research proposes a novel methodology for estimating mechanical degradation for steel fiber reinforced concrete. An experimental campaign was carried out in order to characterize the fatigue response of the cementitious composite and to determine fatigue life using S-N curves based on Weibull distribution. Using the experimental results, two empirical correlations were proposed to estimate damage evolution and energy release growth rate as a function of the number of cycles. Both use the initial stiffness and the energy release of the studied material as an input, which are both evaluated as the flexural strength at 0.50 mm of crack mouth opening displacement. [ABSTRACT FROM AUTHOR]

• Half-hooked fibers presented energy dissipation capacity similar to hooked fibers. • Optimal fiber content was found to be 0.75% for the investigated composites. • Half-hooked fibers had more pullout sensitivity to the presence of fibers in the matrix. • Embedment length had no conclusive influence on the pullout load. The work in hand reports an experimental work on the pullout behavior of hooked-end, half-hooked and straight steel fibers from a High-Strength Fiber-Reinforced Self-Compacting Concrete (HSFRSCC). The influence of three matrix fiber contents on pullout was investigated and compared to an unreinforced control matrix. It was found that half-hooked fibers had the best capacity during the friction regime and can dissipate more energy than hooked-end fibers. Also, the presence of fibers in the matrix had the most beneficial effect on the composite with a fiber content of 0.75%, explained by the improved confinement of the reinforced matrix, fiber to fiber interlock, and better control of splitting cracks for fiber with mechanical anchorage. Further increase in fiber content (V f = 1%) had a deleterious effect reducing the bond performance. In General, the half-hooked fibers were the only ones presenting better dissipation capacity than the unreinforced matrix. There was no evidence that the increase in embedment length increases the pullout load. [ABSTRACT FROM AUTHOR]