Bob Morrison wrote:
In a previous post Goedjn wrote...

I thought the point of the fiberglass was to limit spalling.
Does it really increase the tensile strength of concrete?



Some manufacturers claim it does. As I said earlier, the jury is still
out on whether or not fibermesh helps slabs resist random cracking.

I am of the opinion that it may help a little, but not enough to warrant
the cost. I prefer to increase the strength of the concrete the old
fashioned way: add cement and reduce water content. And, saw cut crack
control joints as soon the concrete is hard enough to walk on without
leaving marks (4-12 hours).


When I first came into contact with fibermesh (about 20 years
ago), it was limited to a couple of uses. We added it to
concrete for apartment balcony slabs and sometimes to
sidewalks. In the case of the balconies, we would pour these
at a thickness of 2" to 3". Not really enough room for any
other kind of reinforcement and chicken wire was way too
difficult to work with. The sidewalks had WWM, but the
fibermesh was added to help eliminate surface cracks.

In no way was it ever represented as a substitute for steel
reinforcement. Every time I hear that, I just have to laugh.

It may be ok in some areas, but here we have expansive soils,
rock, etc. that makes reinforcing steel absolutely necessary.

Someone mentioned that highways were constructed with
fibermesh only. They are building numerous highways here and
I have examined several of the projects under construction.
Here they use #5 rebars 1' OC with a 7" thickness, 5,000 PSI
concrete.

I will ask why they don't just use fibermesh. They could
probably use a good laugh.

--
Robert Allison
Rimshot, Inc.
Georgetown, TX