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Fiber reinforced concrete replace wire mesh?
3

Fiber reinforced concrete replace wire mesh?

Fiber reinforced concrete replace wire mesh?

(OP)
Hello everyone
Well I want to use polypropylene (or nylon) fiber as replacement of wiremesh in an elevated slab of composite metal decks. I just want to know is there any code or at least suggestions that suggest this substitution? (As manufacturer of the fiber recommend this)
Thanks

RE: Fiber reinforced concrete replace wire mesh?

At the top of the page, you can search for what you want in eng-tips. Type in "fibermesh" and proceed from there. There are numerous posts regarding this subject.

RE: Fiber reinforced concrete replace wire mesh?

Fibermesh is for crack control only.  If wire mesh is needed as bending reinforcement (for strength), the fiber mesh is not a substitute.

RE: Fiber reinforced concrete replace wire mesh?

RE: Fiber reinforced concrete replace wire mesh?

Fibers generally in low volumes are for crack control (dry shrinkage and temperature), however, large volumes of fibers - 0.5% can be used for strength.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

RE: Fiber reinforced concrete replace wire mesh?

Qshake, are there any building code evaluation reports that approve fibers for replacing structural rebar?  The ones I have seen explicitly state that this is not allowed.

RE: Fiber reinforced concrete replace wire mesh?

I'm still confused as to the benefits/uses of fibermesh, which is why I don't use it.  I was under the impression that the major benefit of fibermesh was to control plastic shrinkage cracking, and that it had little effect on temperature shrinkage or strength.  Is there an ACI publication that recommends design minimums for fiber reinforcing, to be used in lieu of Chapters 7 and 10 of ACI 318?

RE: Fiber reinforced concrete replace wire mesh?

I just thought you use fibermesh to increase your fc.  It has nothing to do with reinforcement.

RE: Fiber reinforced concrete replace wire mesh?

Synthetic fiber reinforcing is not used to increase the compressive strenght of concrete.

Go to www.fibermesh.com for more information.

RE: Fiber reinforced concrete replace wire mesh?

ACI 302.1R-96 "Guide for Concrete Floor and Slab Construction", Section 5.8 "Reinforcement", Section 5.8.3 "Synthetic Fibers":

"Synthetic fibers are used in floors to minimize plastic shrinkage cracking of concrete.  These fibers should not be used to replace temperature and shrinkage reinforcement because they have little impact on the behavior of concrete after it hardens."

RE: Fiber reinforced concrete replace wire mesh?

Please see my response at the bottom of this thread:  thread507-156960

RE: Fiber reinforced concrete replace wire mesh?

My apologies....I don't think there are any codes that allow full replacement or 1:1 replacement.  I didn't intend to mean or imply a full replacement.  But ACI 544 and related documents present the mechanics on FRC such that less conventional reinforcing can be used.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

RE: Fiber reinforced concrete replace wire mesh?

jmiec:  polypropylene fibres retard the release of bleed water and in the process provide a more uniform initial hydration.  This better disburses microcracking and hence improves shrinkage cracking... as I understand.

Dik

RE: Fiber reinforced concrete replace wire mesh?

dik-

I believe what you're referring to (and referred to in mbullism's post)is called "plastic shrinkage cracking" that occurs during the curing process, as opposed to shrinkage that occurs over months or years.

Aren't proper curing techniques supposed to prevent plastic shrinkage cracks?

RE: Fiber reinforced concrete replace wire mesh?

Bekaert has steel fiber products ,Dramix, Wiremix and DramixDuo that replace the traditional WWM. They also have a free computer program called DRAMIX DRAPRO that designs the slab for different types of loading.

RE: Fiber reinforced concrete replace wire mesh?

jmiec:  yes, but the PP fibres improve on this.  Little can be done for the long term shrinkage, except for a 'contained plastic flow' for lower strength concretes.  Over a period of time, lower strength concretes (<4500psi)exhibit a better plastic behaviour than elastic.  Higher strength concretes behave more elastically and more brittle.

Dik

RE: Fiber reinforced concrete replace wire mesh?

It is my understanding that fibers cannot be used to replace flexural steel required for negative moment over beams or girders. The composite deck acts as the positive moment steel. The fibers or WWF is for shrinkage and temperature only.

RE: Fiber reinforced concrete replace wire mesh?

I'd like to see this question put on a multiple choice test.

Choose the statement that you most closely agree with:

A. fibers are worthless
B. fibers help prevent plastic shrinkage cracking
C. fibers prevent long term shrinkage cracking
D. fibers prevent cracking due to temperature effects
E. fibers can be used to structurally reinforce concrete
F. fiber design is covered by the concrete institute
G. fiber design is covered by the metal deck institute
H. fibers increase the compressive strength of concrete

Apparently, I'm not the only one who is confused, and I think I know who is causing the confusion.

RE: Fiber reinforced concrete replace wire mesh?

B & D for a start... Dik

RE: Fiber reinforced concrete replace wire mesh?

B

D   (within limits)

F   (ACI 302, Paragraphs 3.2.4.1 and 3.2.4.2 - perhaps other documents, too)

G   "Steel Deck Institute Design Manual for Composite Decks, Form Decks and Roof Decks - No. 30" (as updated in 2003)

www.SlideRuleEra.net idea

RE: Fiber reinforced concrete replace wire mesh?

Fiber only enhances some of the properties of the CONCRETE.  It isn't intended to replace anything.

Agree with Dik and SRE.... and will add H..with reservations, as most of the fiber referred to these days is polypropylene fiber, which does little for compressive strength (and quite honestly...little for anything else), but steel fiber can be used very effectively for property enhancement, including an increase in compressive strength (though it gives a much higher percentage increase in flexural strength than it does in compressive strength)

RE: Fiber reinforced concrete replace wire mesh?

Fibers will increase fracture toughness, tensile strength, and flexural strength.  It will not have a significant effect on compressive strength.  

RE: Fiber reinforced concrete replace wire mesh?

PP fibers do nothing beyond plastic shrinkage cracking. Steel fibers are a different story but they vary widely in cost and effectiveness because of the way they are made. Bekaert makes several and theres a new one from this company, www.polytorx.com

RE: Fiber reinforced concrete replace wire mesh?

In 2002 Dr. Easterling, PhD at VA-Tech and Co-Author of "Desiging with Composite Metal Decking Assemblies" tested steel fibers as an alternate to welded wire fabric used for temperature and shrinkage reinforcement in CMDs.  The steel fibers performed very well and in 2003 the SDI ammendded their specifications, to include steel fiber with a minimum ARS of 80psi as an alternate to the welded wire on CMDs.  Any supplemental reinforcement, such as rebar over the beams to reinforce against the negative forces must remain. In 2005, Skanska utilized this option on the 1.5 million sf Census Bureau in Wash-DC.  (I had no idea how many people it takes to count.

Also, regarding welded wire fabric (W1.4, W2.0 or W2.9): What performance is expected from the light gage wwms? What formula supports it's use? I can only think of one, and it's the sub-grade drag formula; As = FLW/Fs, and this formula has been taken out of ACI 360.
For a good slab on grade, use a consertive control joint spacing to control the restraint drying shrinkage and fibers, either polypropylene, steel or a combination of the two, to enhance concrete properties that add to durability.  Throw the wwm in the river.

RE: Fiber reinforced concrete replace wire mesh?

Some polymeric fibers, like KevlarTM, carbon fiber and ultra-high molecular weight polyethylene have better tensile strength than steel. Nylon is up there too, but not stonger than steel .The normal polypropalene fibre used in slabs has no relevant stength. If you are going to use fibre use nylon its much stronger then polypropalene for any purpose.

Intrusion Prepakt
www.marineconcrete.com

RE: Fiber reinforced concrete replace wire mesh?

One of the reasons why you cannot use the fibers for reinforcement is because you cannot guarantee that the fibers are going to be evenly mixed throughout the concrete mix. You may have relatively few fibers at your critical stress region.

another reason is ductility. A 1 or 2" fiber can only stretch so far before it breaks!

RE: Fiber reinforced concrete replace wire mesh?

The list of answers should have "A" rephrased:
A. Not worth the cost and effort to obtain dependable results.
I then choose A.
The article cited by Parra-Montesinos say steel fibers were approved by ACI 318 for shear reinforcement in beams. Not found in my copy of ACI-318. Where do I look for this approval?

RE: Fiber reinforced concrete replace wire mesh?

There is one producer of synthetic fiber that can be used as flexural reinforcement on a slab on grade application.  Of course, the dosage rates to achieve this are pretty high, in the range of 7 lb/cu yd for a 6" slab.

There are no fiber producers that will tell you they can resist the negative moment above suspended deck supports.

RE: Fiber reinforced concrete replace wire mesh?

Testing by the Steel Deck Institute only adds to the confusion surrounding the fibers.  In my mind, concrete reinforcing is covered by ACI and CRSI, not the Steel Deck Institute.  The Steel Deck Institute should limit it's testing to metal deck.

The confusion continues when engineers take test data for steel fibers in elevated slabs on metal deck, and apply it to slabs-on-grade with polypropalene or nylon fibers.  

Test data that shows that steel fibers compare favorably to welded wire fabric doesn't carry a lot of weight, as welded wire fabric never did anything to enhance concrete to begin with.

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