Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior

Abstract

The aim of this work is to present an approach, inspired by the way in which a compass needle maintains a consistent orientation under the action of the Earth's magnetic field, for manufacturing a cementitious composite reinforced with aligned steel fibers. Aligned steel fiber reinforced cementitious composites (ASFRC) were prepared by applying a uniform electromagnetic field to fresh mortar containing short steel fibers, whereby the short steel fibers were driven to rotate in alignment with the magnetic field. The degree of alignment of steel fibers in hardened ASFRC was assessed both by counting steel fibers in fractured cross-sections and by X-ray computed tomography analysis. The results from the two methods show that the steel fibers in ASFRC were highly aligned while the steel fibers in non-magnetically treated composites were randomly distributed. The aligned steel fibers had a much higher reinforcing efficiency, and the composites, therefore, exhibited significantly enhanced flexural strength and toughness. The ASFRC is thus superior to SFRC in that it can withstand greater tensile stress and more effectively resist cracking.

Investigation on Fracture Behavior of Cementitious Composites Reinforced with Aligned Hooked-End Steel Fibers

“…After finishing the fracture test, the specimens were broken into two sections along the crack at the notch. In order to analyze the orientation of steel fibers, the manual fibercounting method was used to record the angle between the steel fiber and the axis of the specimen according to [32]. The angles were divided into four zones, namely, 0-15 • , 15-45 • , 45-75 • , and 75-90 • .…”

An investigation of magnetic field distribution for assembly of magnets and its effect on alignment of steel fiber in aligned steel fiber-reinforced concrete

“…In this method, the mixture is placed inside an empty interior chamber looped by a square solenoid coil and the steel fibers are aligned by the uniform magnetic field offered by the solenoid. The orientation coefficient of ASFRC prepared by the square solenoid coil can exceed 0.9, and the ASFRC exhibits flexural strengths of 88% greater than SFRC when the fiber volume fractions are 0.8% (Mu et al, 2018). According to Qing et al (Qing et al, 2019), the dosage of steel fibers can be decreased by at least 40% if the tensile strength of ASFRC utilizing aligned steel fiber technology is equal to that of SFRC (it may even be somewhat greater).…”

Experimental study on the flexural tensile properties of aligned steel fiber–reinforced reactive powder concrete members

“…Generally, the distribution direction of steel fibers can be adjusted by changing the pouring method and pouring sequence [7][8][9] as well as applying an electromagnetic field. [10][11][12] Yoo et al 13,14 prepared reactive powder concrete (RPC) members with a maximum fiber orientation efficiency factor of 0.66 by pouring concrete at the end of a test mold and letting it flow freely to fill the mold. The quasi-static loading test results indicated that larger fiber orientation efficiency factor produced higher flexural strength, deformation capacity, and increased toughness.…”

“…The three-point bending test results showed a tenfold post-cracking flexural strength difference for cutting angles of 0 and 90 relative to the radial direction. Mu et al [10][11][12] designed a small electromagnetic field device to adjust the fiber distribution, to which a steel fiber-reinforced cement mortar with a fiber orientation efficiency factor of about 90% was fabricated. After adjusting the fiber direction, the flexural tensile strength of the specimen could be increased by 146% and the residual strength could be increased by 150% and 200% at deflections of l/150 and l/600, respectively.…”

“…It has been reported that a parallel distribution of steel fibers to the main stress direction can effectively improve their utilization rate. Generally, the distribution direction of steel fibers can be adjusted by changing the pouring method and pouring sequence 7–9 as well as applying an electromagnetic field 10–12 . Yoo et al 13,14 prepared reactive powder concrete (RPC) members with a maximum fiber orientation efficiency factor of 0.66 by pouring concrete at the end of a test mold and letting it flow freely to fill the mold.…”