Often mistakenly referred to as a steel fibre, people in our industry wrongly label Helix Micro-Rebar. This couldn’t be any further from the truth. The facts and information shown on this page we categorically show you how and why Helix Micro-Rebar is a much stronger and much more reliable concrete reinforcement system for all manner of structural concrete building and foundation purposes than the various configurations of steel fibre on the market.
Point of Difference – Helix Micro-Rebar vs. Macro Steel Fibre
The descriptor ‘Micro-Rebar’ has not been chosen by accident to describe Helix 5-25 Twisted Steel Micro- Rebar (TSMR). It is exactly what it claims to be; a replacement for mesh and rebar in structural concrete applications. As such, less Helix is needed per m3 to achieve the same performance as steel fibre in concrete applications where they are used primarily for temperature and shrinkage control.
However, the use of Helix TSMR also greatly increases the bond strength with the concrete matrix. Because of its patented twisted geometry, it provides a torsional resistance rather than a pull-out resistance, much like the difference between trying to pull a screw from a piece of timber as opposed to a nail (steel fibre). This provides a concrete section with greater ductility (shear strength).
Figure 3. Comparison of pull-out response of high-strength straight, hooked-end, and twisted fibres embedded in high-strength concrete (Willie, K., Naaman, A.E., “Pullout behavior of high-strength steel fibers embedded in ultra-high-performance concrete”. ACI Materials Journal, July-August 2012, Title no. 109-M46, pp: 479-488).
Because Helix is coated with zinc, it forms zinc oxide when in contact with the cement paste, thus self-coating the entire TSMR in a protective rust inhibiting layer. “(Black steel reinforcement corrosion) will initiate after 15 years, while for galvanized steel attack initiates after 44 years. This indicates a theoretical extension of life of 3 times for galvanized bar over black steel bar”, and “(the) extension of life of galvanized steel is usually somewhat longer that the 3 times factor” (Yeomans, S.R., 2004. “Galvanized Steel Reinforcement in Concrete: An Overview”. University of New South Wales, Canberra, Australia). In fact, the electroplated zinc layer increases the adhesive bond with the concrete (Yeomans, 2004).
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Naaman, A.E., 2008. “High Performance Fibre Reinforced Cement Composites”. High-performance Construction Materials: Science and Applications, Vol. 1 of Engineering Materials for Technological Needs, Shi, C. & Mo, Y.L. editors, pp: 91-154.
Naaman, A.E., 2003. “Engineered steel fibres with optimal properties for reinforcement of cement composites”. Journal of Advanced Concrete Technology, Vol. 1, No. 3, pp: 241-252.
Naaman, A.E., 1998. “New Fiber Technology”. Concrete International, July 1998, pp: 57-62.
Ng, T.S., Htut, T.N.S., Foster, S.J., 2012. Fracture of steel fibre reinforced concrete – The Unified variable engagement model. School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia.
Park, S.H., Kim, D.J., Ryu, G.S., Koh, K.T., 2012. “Tensile behavior of Ultra High Performance Hybrid Fiber Reinforced Concrete”. Journal – Cement & Concrete Composites, Vol. 34, pp: 172–184.
Willie, K., Naaman, A.E., “Pullout behavior of high-strength steel fibers embedded in ultra-high-performance concrete”. ACI Materials Journal, July-August 2012, Title no. 109-M46, pp: 479-488.