Influence of Steel and Macro-Synthetic Fibers on Concrete Properties

Abstract

Fiber addition has become one of the most prevalent methods for enhancing the tensile behavior of concrete. Fibers reduce cracking phenomena and improve the energy absorption capacity of the structure. On the other hand, the introduction of fibers can introduce a negative impact on concrete workability, whose loss is influenced by different parameters (among which are fiber content and fiber type). In this context, an exploratory study on the influence of steel (high stiffness) and macro-synthetic (low stiffness) fibers on the fresh properties of concrete was carried out, considering workability and air content, as well as resultant mechanical performance. Four fiber types at two volume fractions (0.5% and 1.0%) were studied in two base concretes with different water-to-cement ratios (0.45 and 0.50) by using the slump test, DIN flow table test and air content meter. An additional parameter for the DIN flow table test is proposed herein to quantify the potential preferential flow direction caused by fiber orientation and entanglement. Air meter results showed that the fibers caused only a slight increase in concrete air content; this agreed well with the results of mechanical testing, which showed no apparent effect on measured compressive strength. In addition, it was captured that, for a given fiber volume fraction, steel fibers more adversely affected Fiber Reinforced Concrete (FRC) workability as compared to polypropylene ones, while the opposite result was obtained considering FRC toughness.Fibers 2018, 6, 47 2 of 14 mixing, placing and compacting. In addition, there can be challenges in dispersion, where fibers entangle and result in non-uniform distribution in the concrete matrix. Consequently, an FRC that cannot be placed and compacted easily will affect constructability and will not lead to the required strength or durability characteristics of the material and, consequently, of the overall structure [28]. This aspect underscores the importance of carefully evaluating the fresh properties of FRC related to workability. Workability is influenced by different factors, among which are water content, cement content, aggregate characteristics, admixtures, fiber type and content.In comparison to the numerous studies present in the literature about the hardened properties of FRC, only a relatively small number of studies are focused on its workability [25,[29][30][31][32][33][34][35][36][37][38]. In addition, most of these studies are focused on steel fibers [25,[29][30][31][32][33][34][35][36][37][38], while macro-synthetic fibers were studied only in [34]. In these investigations, different test methods were adopted to measure the fresh properties related to workability, including slump [25,[29][30][31][32][33][34]37,38], Vebe test [25,29,30,33,[36][37][38], inverted cone test [29,33,34,36], compacting factor test [36], DIN flow table test [34,35] and rheometers [34,36]. All these tests were mainly developed for Plain Concrete (hereafter PC). The slump test is the most common method for both PC and FRC, even i...

Mechanical and Durability Characteristics of Latex‐Modified Fiber‐Reinforced Segment Concrete as a Function of Microsilica Content

“…e concrete made with the steel fiber showed lower load, and decreasing load after initial crack loading, than the macro synthetic fiber, and strain softening occurred [41]. However, the flexural toughness of mixes made with steel fiber at the same fiber volume fraction was greater [44,45]. Hence, for equivalent flexural toughness, the fiber volume fraction of the macro synthetic fiber must be higher than that of the steel fiber [44,45].…”

“…However, the flexural toughness of mixes made with steel fiber at the same fiber volume fraction was greater [44,45]. Hence, for equivalent flexural toughness, the fiber volume fraction of the macro synthetic fiber must be higher than that of the steel fiber [44,45]. In this study, the target performance for segment concrete was only design compressive strength.…”

“…e effects of blends of fibers (hybrid fiber reinforcement) were evaluated with respect to possible improvement of the performance of the latex-modified fiberreinforced segment concrete. Blends of fibers of different lengths, diameters, and types are also known to improve the performance of concrete because they can effectively control the micro-and macrocracks that form in the concrete [19,34,45,46]. Accordingly, using hybrid fibers in concrete can help to optimize the performance of the concrete [19,34,45,46].…”

“…Blends of fibers of different lengths, diameters, and types are also known to improve the performance of concrete because they can effectively control the micro-and macrocracks that form in the concrete [19,34,45,46]. Accordingly, using hybrid fibers in concrete can help to optimize the performance of the concrete [19,34,45,46]. Previous studies showed that the flexural behavior and cracking are suppressed when the macro synthetic fiber and the micro PP fiber are hybridized and applied compared with cases where only a single type of fiber is used [34].…”

Effect of High Temperature on the Mechanical Properties of Steel Fiber-Reinforced Concrete

“…Chalioris and Panagiotopoulos [27] evaluated the flexural response of steel fiber-reinforced concrete (SFRC) by a numerical approach. Guerini et al [28] studied the effect of steel fibers and synthetic macrofibers on the workability and mechanical performance of concrete. Chalioris, Kosmidou, and Karayannis [29] investigated the influence of steel fiber addition on the mechanical behavior of reinforced beams submitted to cyclic loading.…”