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Steel Fibers
Steel Fibers have morphed through a number of
changes both in configuration and aspect ratio. Here is a listing of the Standard Cross Sections: The standard products either have a circular cross-section (ASTM A820 Type I) or a rectangular cross-section
(ASTM A820 Type II) or a shaved, modified Type I (ASTM A820 Type V). Other than the cross-section all of the other requirements
are precisely the same for all three. Type I and Type V steel fibers are also
identified as drawn wire steel fibers, while Type II is a slit sheet. The aspect ratio is important
indicator as to the ability of the steel fiber to disperse in the concrete. An aspect ratio of 60 is considered the upper
limit for most standard applications. Currently there are three
basic configurations of the steel fiber available: Continuously deformed (Types I, II and V), end deformed (Types I and II)
and hooked end (Type I). In general hooked end steel fibers produce higher post-first crack/toughness numbers and the continuously
deformed steel fibers produce higher flexural strength numbers. The end-deformed product will provide good results for both
the post-first crack and flexural strength. The steel fiber length
will range from ¾” (19mm) to 2” (50mm). Steel fibers at dosage levels of 40 lbs/yd3
or above, more realistically 50 lbs/yd3 or above will increase the flexural strength of the concrete. By increasing
the flexural strength the engineer has been provided an opportunity to either decrease the thickness of the slab-on-ground
or increase the load capacity when compared to the non-steel fiber designed slab. Finally, the engineer can also use this
increased load capacity as a Safety Factor. NMW’s engineer can assist in designing slabs-on-ground
that incorporate steel fiber using a proprietary program utilizing Westergaard and Myerhof methodology. ASTM Test Methods C1399, C1609 and C1550 can be
used to measure the post-first crack properties of the steel fiber reinforced concrete/shotcrete. Selecting the appropriate test is critical as is selecting the laboratory that can properly conduct the
test method selected. ASTM C1609 is typically chosen for Steel Fiber Reinforced
Concrete/Shotcrete. It is very important to the accuracy of the work that shotcrete
concrete test panels must be fabricated and the test specimens sawn from these panels.
Cast test beams are inappropriate for shotcrete. |
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NyGuard™ SF is the general label for a number of different steel
fiber products that NMW sells. All of our steel fibers meet the requirements of either ASTM A820 Type I (drawn wire)
or Type II (slit sheet) or Type V (modified cold drawn wire). Type I NMW has available a Type I (drawn wire) continuously deformed fiber as well
as two hooked-end products. We can provide both hooked end glued and loose. The NyGuard™ SF glued hooked
end products are manufactured to meet the same criteria as the ‘Superior’ and ‘Premium’ Bekaert-Dramix
steel fibers. Typically these Type I products are packaged in 50-pound bags and
boxes. Here availability is an issue. The time required from placing the order to access to the material is typically between
45 and 60 days. Therefore, it makes sense to get the P.O. as soon as possible when a Type I steel fiber is required. Type II We have two configurations of Type II steel fiber. The configurations are continuously deformed and end deformed. The Type II products are packaged in 50-pound boxes.
There is a disintegrating bag also available for an additional cost. The Type II products are generally available within 2
weeks of receipt of P.O. Type V Also available is a Type V continuously deformed fiber. This means the cross-section
is a segment of a circle. This product will also require a lead-time of 45-60 days from receipt of P.O. and delivery. |
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NMW,
Inc. ∙ 6553 West 400 North ∙ |
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