Mechanical properties of hybrid fiber‐reinforced concretes made with low dosages of synthetic fibers

Abstract

Recent advances made in concrete fibers have made them one of the concrete's recommended ingredients, mainly to eliminate the drawbacks associated with the weakness of cementitious materials, such as concrete, in tension. The addition of fibers, however, introduces extra cost and labor requirements, while selecting an appropriate choice and dosage of fibers has still remained a standing question. To address the outlined issues, the current study investigates the development of fiber‐reinforced concrete (FRC) mixtures with a focus on achieving superior mechanical properties with a low dosage of synthetic fibers. For this purpose, three choices of macrofibers were examined. The investigations spanned four dosages of each macrofiber mixed with three dosages of a microfiber included to ensure adequate resistance to early‐age, shrinkage‐induced strains. The experiments conducted on the developed hybrid FRC mixtures systematically measured workability, as well as compressive, splitting tensile, and flexural strength properties. The test results were then paired with the micro‐scale monitoring of the bond between individual macrofibers and the concrete matrix through scanning electron microscope images. The outcome shed light on how each of the macrofibers of choice contributed to improving the FRC's mechanical properties. This paved the way to benefit from a minimum dosage of them to achieve the expected structural response, while avoiding crack formation and propagation in various applications.

Ultra‐high performance concrete under direct tension: Investigation of a hybrid of steel and synthetic fibers

“…The PP fibers were also noted to have a (relatively) high water absorption, mainly due to their porous structure. 44,45 On the other hand, the water absorption capacity of the PVA fibers was (relatively) low, i.e., in the range of 0.1%-1.0%, 46 while the water absorption capacity was even lower (i.e., to a negligible level) for AR glass and carbon fibers. A comparison of the mixtures made with synthetic fibers indicated that the workability improved from nylon to PP, carbon, PVA, and AR glass fibers.…”

“…The water absorption of nylon fibers has been reported to be as high as 3.0% (or more) by weight, 43 thus reducing the water available for achieving the desired flow. The PP fibers were also noted to have a (relatively) high water absorption, mainly due to their porous structure 44,45 . On the other hand, the water absorption capacity of the PVA fibers was (relatively) low, i.e., in the range of 0.1%–1.0%, 46 while the water absorption capacity was even lower (i.e., to a negligible level) for AR glass and carbon fibers.…”

Concrete for Living Walls: Current Status and a New Design Recommendation

“…In the second stage (laboratory test Series 2), 24 additional prismatic specimens (20 × 90 × 400 mm) were prepared by using a constant dosage of macrofibres (12 kg/m 3 ) and varying microfiber (Crackstop ® Ultra, Adfil, Belgium) content from 0 to 3 kg/m 3 (Figure 3b). The main research question concerned the determination of whether microfibers can improve the structural toughness on the macro scale, as fairly controversial results have been reported elsewhere in the literature [23][24][25]. The results obtained from the second experimental stage are presented in Figure 3d.…”

Optimization design of functionally graded ultra‐high performance cementitious composite on flexural behavior

“…10 Previous studies suggested that increasing the content of steel fiber is an effective method to improve the flexural behavior of UHPCC. 11,12 However, its application is limited due to high cost of steel fibers and corrosion risk for fibers closed to the concrete surface. Consequently, seeking a method to improve the fiber utilization efficiency and the flexural property of UHPCC is particularly important.…”

“…In addition, fiber content reveals a strong dependency on tensile strength 10 . Previous studies suggested that increasing the content of steel fiber is an effective method to improve the flexural behavior of UHPCC 11,12 . However, its application is limited due to high cost of steel fibers and corrosion risk for fibers closed to the concrete surface.…”