Fiber Reinforcement in Residential Slabs

[Atomic25]

If you spec out a fiber for a typical 4" residential slab on grade, normal soils, how do you typically do it? Do you spec a manufacturer and dosage rate? I dont want to call out something that will be a premium, yet I want decent results.

In commercial applications we typically use Strux 90/40, but I've been told it's not really for residential applications.

 

[concretemasonry]

Since you will be obtaining the concrete locally, find out what the local experience and common materials used are.

Just because you spec a product does not mean you will get it if the local producers do not have the experience and mix designs for your specied product.

If it was a commercial project, it would be large enough to do some testing and/or special mix designs. For a residential project, it is a different story if you want predictability and performance without a premium for an unusual specification.

Dick

 

[Atomic25]

It's a residential application, but for about 500 homes.

 

[concretemasonry]

500 home may be substantial if all are built in one year, but there never is a guarantee in residential construction. With residential projects and an undertermined time/volume guarante, you could pay a small premiuim for one specified material since it would require some extra costs, experimentation and quality control exposure as compared to the traditional materials currently used.

Because delivery is a high portion of the concrete cost, I would check with the local suppliers to see what they currently use and have dispesing equipment for. The products currently available may be satisfactory for your purposes and you could eliminate the problems with a learning curve. Delivery/agitating times can be quality factors as are the dispensing accuracy, dosing timing and the technical support from the fiber supplier.

If it were a large commercial project with a defined schedule and competitive bidding, I would specify your usual materials and see if there were proposals for "or equals".

Dick

 

[flamby]

What requirement in a residential structure prompts you to go for fiber? You say, you expect decent results. What results? The fibers are for strength, abrasion or fire protection?

Ciao.

 

[Atomic25]

Contractor doesnt want to use WWF. They know as well as us that it gets walked down easily into the subgrade unless they go through a lot of hassle.

I want something that wont clump together, will provide shrinkage reinforcing, and wont create a hairy slab. If you go use some noname brand, Ive been told you get what you pay for.

This is a military base, they're all getting built at once.

 

[Lion06]

This has been addressed on this forum before. Fiber reinforcement is not a substitute for WWF for T & S.

 

[jike]

Check out

http://www.fibermesh.com/application.aspx?ID=2173

and then call several suppliers that you commonly work with and ask what is regularly available to them.

 

[concretemasonry]

Atomic25 -

Since it is a military base, you may be able to research the military facilities specifications to see what they spec (if they do) for other projects. It can make everything smoother.

I would be leery of a contractor that does not think he can handle a time proven material in a construction environment.

 

[nackra]

TM 822-7 Appendix C

http://www.usace.army.mil/publications/armytm

 

[Atomic25]

This project isn't ruled by military specs, but rather the state building code. Not sure if it's a new thing or what.

Thanks for the help guys.

StructEIT, please provide link to said discussion. I cant find it. The whole premise of synthetic fibers is to replace WWF.

 

[Qshake]

Don't forget to check out ACI 544 to see what the benefits of fiber reinforcing are and what it can and cannot do.

Regards,
Qshake

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

 

[archeng59]

the fibermesh SALESMEN want you to believe the fibers can replace WWF or rebar. Those sales guys have done a good job convincing the contractors that fibermesh can replace reinforcing. But if you read ALL of the literature prepared by the fibermesh manufacturer, the literature contains a disclaimer stating the fibers are intended to help reduce the amount of shrinkage cracking and is not intended to replace reinforcing in the slab.

 

[vmirat]

Atomic25,
Are you doing work on existing MFH units or is this a privatization contract? If these are existing, then you should be using UFGS 03 20 01.00 10 which has a section in it on fiber reinforcement. If this is a privatization contract, then they are probably requiring you to comply with local codes instead of military specs. However, the UFGS that I quoted isn't too far off from what we see around here locally, so you might be safe using what it requires anyway. That way, the military will be happy cause you're matching their spec.

 

[pinehurst]

If I had a nickel every time a contractor wanted to use fibres in lieu of WWM...
In our experience, substitution of WWF with fibres is acceptable depending upon the application and type of fiber. Polypropelene fibres are for plastic shrinkage control only; they do nothing for drying shrinkage and certainly do not contribute to flexural strength. However, for slab-on-grade applications, certain types of fibres from manufacturer's have sufficient tensile strenght and high enough modulus that they can compete with WWM applications for slab-on-grade applications. In my own practice, I have often used steel fibres in lieu of WWM and with improvements in fiber technology also used cetain polymer (note: not polypropelene)fibers.

In specific answer to your question, we spec. a fiber type and a dosage based on weight per cubic yard of concrete based on input from the manufacturer, the subgrade type, and the loading conditions. Do your homework on the recommended fiber type for your application and accept alternates only at your own peril.

 

[Atomic25]

Yes, this is a privatization project, hence local codes, brand new single family homes, about a 7 year major project.

It looks like I have no choice but to require the only manufacturer that I know of that specifically states their product replaces WWF, Strux 90/40 by Grace.

http://www.na.graceconstruction.com/template.cfm?page=/toplevel_pages/news_detail.html&nid=400