Abstract
Reliable bond of steel fiber in concrete is a key problem relating to the reinforcing effect of steel fiber on concrete matrix and for the guide in significance for the optimal design of the geometry and mechanical properties of steel fiber. In this paper, on the basis of multi-indices of evaluation for the bond properties of single hooked-end steel fiber, the indices for the evaluation of synergistic bond properties of different deformed steel fibers are proposed. The pull-out tests were carried out for different deformed steel fibers embedded in mortar wet-sieved from self-compacting SFRC with manufactured sand. Fourteen types of steel fibers were used, including six hooked-end, two crimped, four indentation, one milling, and one large-end. The bond strength, bond energy, and bond toughness of single and per unit weight steel fiber were evaluated with the correspondence to the loading status of cracking resistance, normal serviceability, and ultimate bearing capacity of concrete. Results show that the deformed steel fibers presented different bond behaviors, hooked-end, and crimped steel fibers with circular cross-sections and a tensile strength of higher than 1150 MPa have excellent effects of strengthening, energy dissipation, and toughening capacity on self-compacting concrete with a cubic compressive strength of 60 MPa at normal serviceability and ultimate bearing capacity. Indentation, milling, and large-end steel fibers are more suitable for reinforcing the concrete strength due to the rigid bond before concrete cracking. The synergistic working of steel fibers with concrete matrix should be concerned to realize the effects of only or simultaneously reinforcing the strength and toughness of concrete.
Highlights
Steel fiber reinforced concrete (SFRC) is a concrete admixing short and random distributed steel fibers [1,2,3]
Even though some comparative studies focused on several types of steel fiber, the bond properties were always evaluated separately and without a suitable method [28,30], except for a study in which the pull-out energy per unit volume of steel fiber was used to compare the pull-out energies of steel fibers with different embedded volumes [30]. This leads to the fact that the manufacture of steel fiber is only based on a basic cognition of SFRC, and no in-depth studies have been done on the mechanism of synergistic working of steel fibers with concrete matrix
The mortar was wet sieved from fresh self-compacting SFRC to keep consistent with the bond performance of steel fiber in concrete matrix
Summary
Steel fiber reinforced concrete (SFRC) is a concrete admixing short and random distributed steel fibers [1,2,3]. To determine the reinforcement effects on concrete strength and toughness, the bond behaviors of steel fiber is essential to the rational application of deformed steel fibers This is important to upgrade the mix proportion design of SFRC with high-performance coming from the matching up of steel fibers with concrete [1,2,3,4,16,17,18]. Even though some comparative studies focused on several types of steel fiber, the bond properties were always evaluated separately and without a suitable method [28,30], except for a study in which the pull-out energy per unit volume of steel fiber was used to compare the pull-out energies of steel fibers with different embedded volumes [30] This leads to the fact that the manufacture of steel fiber is only based on a basic cognition of SFRC, and no in-depth studies have been done on the mechanism of synergistic working of steel fibers with concrete matrix.
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