Fiber strengthener in concrete worth it?
Ken Schumm
to concrete that were supposed to strengthen the concrete and reduce
cracking.
Anyone here have any experience with this stuff? What's it called?
Does it work well? Is it worth it?
My builder is saying it costs $3-4 more per cubic yard, but he has
no experience with it.
TIA
Daniel Hicks
In theory it stops the "micro-cracks" that eventually widen into large
cracks. It is effective when properly used, but there's not a lot
experience with it to know what "proper use" is. One negative is that
it sometimes leaves the concrete surface a little fuzzy, until the
surface fibers wear off.
I'd probably use it if I was putting in a new driveway, sidewalk, patio,
etc (but then I like to experiment with things like this). It would
serve no real purpose for things like poured foundations, however.
technochallenged
been years since I worked concrete and I noted the concrete set up much
faster than what I remembered. Not sure if that was due to the fibers, or
new chemicals being used in the mix.
Didn't notice any "fuzz", but I finished it with a broom for anti-skid
properties.
Since that time, I"ve had a fully loaded cement truck, backhoes, and dump
trucks drive repeatedly across the 4" thick driveway, and have no cracks at
all. I am well pleased with the product.
Daniel Hicks <danh...@ieee.org> wrote in message
news:37D9B842...@ieee.org...
Bob Sovereign
steel fibres used as well. Excellent durability as discussed.
Finishing and trowelling (especially power trowelling can be tough. I'm
surprised that the additional cost is that low. I think it is much
higher here in W Canada.
Ken Schumm wrote:
> Awhile back on a TV home show I saw them adding some sort of fibers
> to concrete that were supposed to strengthen the concrete and reduce
> cracking.
>
> Anyone here have any experience with this stuff? What's it called?
> Does it work well? Is it worth it?
>
> My builder is saying it costs $3-4 more per cubic yard, but he has
> no experience with it.
>
> TIA
dnhudson
>
> You're probably talking about fibreglass fibres, although I have seen
> steel fibres used as well. Excellent durability as discussed.
> Finishing and trowelling (especially power trowelling can be tough. I'm
> surprised that the additional cost is that low. I think it is much
> higher here in W Canada.
>
> Ken Schumm wrote:
>
> > Awhile back on a TV home show I saw them adding some sort of fibers
> > to concrete that were supposed to strengthen the concrete and reduce
> > cracking.
> >
> > Anyone here have any experience with this stuff? What's it called?
> > Does it work well? Is it worth it?
The fibermesh people claim that it controls bleeding and in my
experience it sure does...even very wet concrete shows almost no
bleeding.
Wet concrete is not a good thing; it makes for weak concrete.
Other than than, I have not seen the finishing problems that some folks
claim. Usually, fibers are used for flatwork (driveways, patios) and
those don't need power troweling (bull float and fresno is plenty with a
little hand troweling around the edges). Use a broom finish.
The key to good performance of the finished product is to control the
water in the mix (no more than a 4-5 inch slump), use of control joints,
and proper curing. Without control joints or proper curing, or if your
concrete is too wet, you can get cracking no matter whether you use mesh
or fiber.
Also, be sure to seal your control joints.
> >
> > My builder is saying it costs $3-4 more per cubic yard, but he has
> > no experience with it.
> >
> > TIA
Watch your builder. Builders generally hire really cheap subs who wet
up the concrete (placing and finishing is hard work and wet concrete
makes placement easier) and who don't even know what control joints
are. Your builder may not either. If your builder resists, hire an
engineer out of your own pocket if you must, but get it right the first
time.
As for your original question, fiber appears to be a good alternative
mesh and easier to control quality. Mesh placement is the problem and
it is usually not placed in the optimum position.
C. Brunner
wrote:
>Ken Schumm wrote:
>> Awhile back on a TV home show I saw them adding some sort of fibers
>> to concrete that were supposed to strengthen the concrete and reduce
>> cracking.
>> Anyone here have any experience with this stuff? What's it called?
>> Does it work well? Is it worth it?...
>In theory it stops the "micro-cracks" that eventually widen into large
>cracks. It is effective when properly used, but there's not a lot
>experience with it to know what "proper use" is. One negative is that
>it sometimes leaves the concrete surface a little fuzzy, until the
>surface fibers wear off.
...
Last year, our contractor used it for our front porch, back patio, and
driveway slabs. His justification was that he didn't want the
concrete subs tearing up their rubber boots by walking on metal
reinforcing wire, so he used fiber-reinforced concrete instead. Guess
what? We were working on a cost-plus basis, and he never mentioned
there was a price difference. (We were too naive to ask, and the
contract didn't say anything about it.) Based on what y'all have
said, we'd have been better off to buy the guys new rubber boots. We
have cracks in the porch and cracks in the driveway slabs, all at
predictable stress spots. And the stuff is nearly impossible to sweep
clean with a broom.
C. Brunner
dnhudson
Surface fuzziness is an indication of overworking the concrete, at least
according to the fibermesh folks. In the 12 test slabs I've poured,
I've seen none.
The fibers exposed to sunlight will degrade and break off, so your
sweeping problem should disappear soon.
Your contractor's concern for his subs is a first, but I don't recall
any big problem with ruining rubber boots during my tenure in the
business.
Sean Smith
news:37dd7abf...@news.duc.auburn.edu...
> On Sat, 11 Sep 1999 02:10:26 GMT, Daniel Hicks <danh...@ieee.org>
> wrote:
> >Ken Schumm wrote:
> >> Awhile back on a TV home show I saw them adding some sort of fibers
> >> to concrete that were supposed to strengthen the concrete and reduce
> >> cracking.
> >> Anyone here have any experience with this stuff? What's it called?
> >> Does it work well? Is it worth it?...
> >In theory it stops the "micro-cracks" that eventually widen into large
> >cracks. It is effective when properly used, but there's not a lot
> >experience with it to know what "proper use" is. One negative is that
> >it sometimes leaves the concrete surface a little fuzzy, until the
> >surface fibers wear off.
> driveway slabs. His justification was that he didn't want the
> concrete subs tearing up their rubber boots by walking on metal
> reinforcing wire, so he used fiber-reinforced concrete instead. Guess
> what? We were working on a cost-plus basis, and he never mentioned
> there was a price difference. (We were too naive to ask, and the
> contract didn't say anything about it.) Based on what y'all have
> said, we'd have been better off to buy the guys new rubber boots. We
> have cracks in the porch and cracks in the driveway slabs, all at
> predictable stress spots. And the stuff is nearly impossible to sweep
> clean with a broom.
Sounds like a B.S. excuse. They're not supposed to WALK on the mesh
after it has been put into place.
Sean
Bruce Birbeck
>
> C. Brunner <bru...@vetmed.auburn.edu> wrote
> > ........... His justification was that he didn't want the
> > concrete subs tearing up their rubber boots by walking on metal
> > reinforcing wire, so he used fiber-reinforced concrete instead.
> > (snip)
> > C. Brunner
>
> Sounds like a B.S. excuse. They're not supposed to WALK on the mesh
> after it has been put into place.
>
> Sean
So, exactly HOW are they to place the concrete? Sky hooks and belt
loops?
How many slabs have you seen placed?
I do agree that the boot excuse is a load of BS, but I've never seen a
slab done without workers IN the mud. With boots on.
Besides, if you want reinforced concrete, use rebar, not mesh.
(ducking and running away)
--
BBB
Take out the NOSPAM to reply, unless it's already gone...
Sean Smith
news:37DE75...@tidewater.net...
The ones I have seen done placed 2x12's over many ares to provide
"catwalks" to do the work to avoid having any problems with placing the
concrete and/or tripping over the placed reinforcement. Then again, the
only slabs I have seen that are of any size requiring catwalks have used
rebar for reinforcement. Anything done with mesh was typically done for
sidewalks and driveway slabs, which must be done in sections and therefore
walking on them can be avoided since the sections are typically small enough
to simply use standard long-handled tools. I would assume that large
commercial buildings that they'd have to walk on the reinforcement since the
pour is so large but this is alt.HOME.repair and most jobs are small enough
to avoid having to walk all over the rebar and/or mesh you so carefully
placed.
Sean
Tim Werbstein
>
> Sean Smith wrote:
> >
> > C. Brunner <bru...@vetmed.auburn.edu> wrote
>
> > > ........... His justification was that he didn't want the
> > > concrete subs tearing up their rubber boots by walking on metal
> > > reinforcing wire, so he used fiber-reinforced concrete instead.
> > > (snip)
> > > C. Brunner
> >
> > Sounds like a B.S. excuse. They're not supposed to WALK on the mesh
> > after it has been put into place.
> >
> > Sean
>
> So, exactly HOW are they to place the concrete? Sky hooks and belt
> loops?
> How many slabs have you seen placed?
>
> I do agree that the boot excuse is a load of BS, but I've never seen a
> slab done without workers IN the mud. With boots on.
> Besides, if you want reinforced concrete, use rebar, not mesh.
> (ducking and running away)
> BBB
> Take out the NOSPAM to reply, unless it's already gone...
In my opinion, on narrow slabs it's no problem to stand outside the
pour. On wide expanses a properly equipped contractor has long-handled
spreaders and floats. Only a few times have I seen a condition (using
mesh) where you can't reach from the sides of the pour. After all, your
placement areas are limited by the distance between expansion joints,
which is best under 15 feet.
Bruce Birbeck
I guess I was thinking in terms of basements and garages, not driveways.
Usualy, the guys pull the mesh up as they leave. On big commercial jobs,
they run the buggies over plywood, or pump it. Either way, the crew
walks over the field.
On radiant jobs, they leave the mesh on the bottom, with the tubing
tied to it. As I said, the rebar will stand walking on/over. And, a
trip-splat is so amusing...
Bruce Birbeck
>
> Bruce Birbeck <rocNoS...@tidewater.net> wrote in message
> news:37DE75...@tidewater.net...
>
> "catwalks" to do the work to avoid having any problems with placing the
> concrete and/or tripping over the placed reinforcement. Then again, the
> only slabs I have seen that are of any size requiring catwalks have used
> rebar for reinforcement. Anything done with mesh was typically done for
> sidewalks and driveway slabs, which must be done in sections and therefore
> walking on them can be avoided since the sections are typically small enough
> to simply use standard long-handled tools. I would assume that large
> commercial buildings that they'd have to walk on the reinforcement since the
> pour is so large but this is alt.HOME.repair and most jobs are small enough
> to avoid having to walk all over the rebar and/or mesh you so carefully
> placed.
>
> Sean
Yeah, but how did the concrete get there? In wheelbarrows, over the cat
walks? How was it distributed? By moving the 2x12s around? How was it
screeded? At some point people walk in the mud. Basements and garages
have 'big' slabs, and the guys seem to use chutes, boots, and hoes to
place the mix.
Even if you pumped the concrete, a screed has to be in the mud, attached
to a concrete finisher, to begin the floating process.
In the 6x6 mesh slabs I've seen done, the mesh was in the bottom of the
slab, and foot traffic during the pour wasn't a problem. An attempt to
pick the mesh up before screeding was usually made, unless an agreement
was reached in advance to leave the mesh (with the radiant tubing on it)
at/near the bottom of the slab.
chrome__d...@my-deja.com
Ken Schumm <kwsc...@qsolv.com> wrote:
> Awhile back on a TV home show I saw them adding some sort of fibers
> to concrete that were supposed to strengthen the concrete and reduce
> cracking.
>
> Anyone here have any experience with this stuff? What's it called?
> Does it work well? Is it worth it?
>
> no experience with it.
>
> TIA
>
it to me, just get a higher psi concrete if you want something
stronger, the cost is very minimal
Sent via Deja.com http://www.deja.com/
Share what you know. Learn what you don't.
Daniel Hicks
> Besides, if you want reinforced concrete, use rebar, not mesh.
> (ducking and running away)
Well, many years ago my parents remodeled an old farmhouse and had what
was, I'd guess, a 10x40 front porch poured. The crew that poured it
used mesh with no expansion joints, and when I last saw it about 15
years later it was still crack-free.
(Of course, the crew that poured it had the previous week been pouring
military runways and used left-over mesh from that job. I think the
mesh was welded from 1/4" rod. And they had the chairs for it.)
technochallenged
<chrome__d...@my-deja.com> wrote in message
news:7rn2i0$jcf$1...@nnrp1.deja.com...
Bruce Birbeck
>
> In article <Voyager.990910182312.30903C@QSolv>,
> Ken Schumm <kwsc...@qsolv.com> wrote:
> >
> > My builder is saying it costs $3-4 more per cubic yard, but he has
> > no experience with it.
> >
> > TIA
> >
> thats more then doubleing the price of the concrete, doesnt sound worth
> it to me, just get a higher psi concrete if you want something
> stronger, the cost is very minimal
Uh, that's 3 to 4 dollars a yard, not $34 a yard.
Good point about strength, tho...
Tim Werbstein
> BBB
> Take out the NOSPAM to reply, unless it's already gone...
Unfortunately, mesh in the bottom of a slab is almost useless... most
subject to rust and cannot properly perform its functions of either
supporting bending loads or anti-crack because there's insufficient
coverage or "bite" on the mesh reinforcing. Just look at the design
drawings for mesh. It's supposed to be in the middle of slabs.
Yes, it's a difficult problem and requires proper placement of chairs
(hopefully rustproof) and walking gangways to keep the mesh in place.
Lifting mesh afterward is also a pretty good way to assure that it's in
the wrong place when the concrete sets, such as too close to the
surface. If you can pull up the mesh, the concrete mix is probably too
watery, air voids will be added, and there is more segregation of
aggregate size distribution.
dnhudson
>
> In article <Voyager.990910182312.30903C@QSolv>,
> Ken Schumm <kwsc...@qsolv.com> wrote:
> > to concrete that were supposed to strengthen the concrete and reduce
> > cracking.
> >
> > Anyone here have any experience with this stuff? What's it called?
> > Does it work well? Is it worth it?
> >
> > no experience with it.
> >
> > TIA
> >
> thats more then doubleing the price of the concrete, doesnt sound worth
> it to me, just get a higher psi concrete if you want something
> stronger, the cost is very minimal
$3-$4 per cubic yard is not doubling. Concrete costs $50 - $60 per
cubic yard in our area without fiber. The extra cost of the fiber is
roughly a tradeoff with the elimination mesh, at least on larger
projects.
Sean Smith
Mesh at the bottom is the wrong place for it, it provides no useful
purpose at that point. The concrete is typically poured through a chute,
whether off a truck or off the mixer, typically right where it needs to be.
I know I can reach across 6' with a typical hoe, can't you?
Sean
Bruce Birbeck
(hack thread remains)
>
> Unfortunately, mesh in the bottom of a slab is almost useless... most
> subject to rust and cannot properly perform its functions of either
> supporting bending loads
That is one of its' functions? We are talking about 6x6 WWF? Temperature
stress, shrinkage cracking, and crack size limitation are what I recall.
> or anti-crack because there's insufficient
> coverage or "bite" on the mesh reinforcing. Just look at the design
> drawings for mesh. It's supposed to be in the middle of slabs.
Indeed. Getting it there and keeping it there is the problem.
>
> Yes, it's a difficult problem and requires proper placement of chairs
> (hopefully rustproof) and walking gangways to keep the mesh in place.
What are the walkways resting on, and how are they moved without anyone
getting on the feild?
>
> Lifting mesh afterward is also a pretty good way to assure that it's in
> the wrong place when the concrete sets, such as too close to the
> surface.
And bent.
If you can pull up the mesh, the concrete mix is probably too
> watery, air voids will be added, and there is more segregation of
> aggregate size distribution.
Yep. I don't agree with the technique of lifting, just sharing what I've
seen. Up here, they 'pour cement', and don't 'place concrete'.
And again, when I attach my tubing to the mesh, it becomes a part of
the heating system, remains on the bottom, and I suggest to the concrete
sub/ general contractor that they put down another layer of mesh, or
properly reinforce with rebar.
Bruce Birbeck
>
(slash the rest)
>
> Mesh at the bottom is the wrong place for it, it provides no useful
> purpose at that point. The concrete is typically poured through a chute,
> whether off a truck or off the mixer, typically right where it needs to be.
> I know I can reach across 6' with a typical hoe, can't you?
>
> Sean
Yep. What should I do when the basement is 34 x 46, and surrounded by 8'
walls? Get a longer hoe?
The guys are all over that job, working their way out, and walking all
over the mesh/rebar.
How is the chute adjusted unless someone is down there at the end of
it? How can you move the horses holding up the chute without getting on
the feild?
And the mesh with radiant tubing on it stays on the bottom (1"
coverage), the best place to be for an even surface temperature.
Needless to say, this can produce a lot of 'discussion'....
chrome__d...@my-deja.com
recently priced concrete, and 3500psi was 61.95 yd, it was only 1.5
more (63.45 yd) to upgrade to 4000 psi.
Tim Werbstein
>
> Yep. What should I do when the basement is 34 x 46, and surrounded by 8'
> walls? Get a longer hoe?
> The guys are all over that job, working their way out, and walking all
> over the mesh/rebar.
> How is the chute adjusted unless someone is down there at the end of
> it? How can you move the horses holding up the chute without getting on
> the feild?
> And the mesh with radiant tubing on it stays on the bottom (1"
> coverage), the best place to be for an even surface temperature.
> Needless to say, this can produce a lot of 'discussion'....
> --
> BBB
> Take out the NOSPAM to reply, unless it's already gone...
I agree, it's a tough problem and I have no blanket solution (without
upping costs). Perhaps a staged placement of slabs with bonded
construction joints would make it possible? Perhaps using fibermesh.
Perhaps omitting the rebar (it's a basement) and using very low-slump
concrete, wet curing for two full weeks, and SHOOTING any one damaging
the curing membrane. I think your recommendation of using mesh above
the pipe is very good.
My 50-year old basement slab is smooth, hard, and crack free - placed
long before fibermesh. Of course, portland cement was weaker then and
more was used than we need today for the same compressive strength.
However, with fewer "fines" as provided by cement, our modern concrete
is much less dense and less durable. Now, we add things like
microsilica to replace the fines and density we naturally had because of
weaker portland cement!
Pardon me... I could go on about this!