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RE: Fibermesh Topping Slab[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Fibermesh Topping Slab
- From: "Sprague, Harold O." <spragueho(--nospam--at)bv.com>
- Date: Fri, 3 Oct 2003 09:35:18 -0500
Your observation is a good one. I have seen many products that performed very well in the laboratory to only fail miserably in the field. The Sarabond example I pointed out led to millions of dollars in law suits. It did very well in the lab. It performed miserably in the field, but only after about 5 years or so. The result was thousands of projects being constructed that were doomed to failure. There were several lawyers and a couple of testing labs in Chicago that got very rich due to Sarabond. At one time, HUD specified Sarabond in their specifications.
While my hands-on experience with this is limited to
laboratories, my impression is that steel "dogbone" fibers are most
effective when used WITH polypropylene fibers? The mix and placement
required care to disperse the fibers adequately, but the synthetic fibers did
well resisting the small cracks from developing while the steel fibers did well
in resisting the larger cracks and providing some strength in tensioned areas.
I have done the steel fiber deal, too. They perform very well. The only down side is the potential for balling in the truck. But if you can get them dispersed in the mix, they perform very well. But that is a big if.
I would never use polypropylene fibers for anything except to reduce rebound in shotcrete, but you have to use them at 15 pounds per cubic yard or more in that application. And even then, I would prefer steel fibers.
The biggest lesson is to look at all vendors with a suspicious eye. I normally require a test placement with new concrete products. But you only find the problems with something like polypropylene fibers when you do a full scale placement. And then it is too late. On the plus side, polypropylene fibers create almost as much work for lawyers and repair specialists as did Sarabond. Good news for lawyers is bad news for engineers.
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