Still getting estimates on paving the remainder of my driveway. Latest
concrete guy comes in and says they no longer use wire mesh, it ends up
rusting and then popping the concrete, so they mix a fiber mesh right into
the concrete before they pour it. 4 inches.
I'm skeptical, but not against new technology. Any opinions because I've
never heard of this, or seen it. I've always just seen wire mesh laid down.
Called 4 asphalt contractors and not one has returned my calls so far. I
thought contractors and the economy are hurting?
3 concrete guys so far. Two with wire mesh and the above mentioned guy.
Two at 4" and one at 5".
Check out the alt.building.construction newsgroup archives and do a
Bob Morrison concrete slab
Bob is no longer with us, and his presence and knowledge are sorely
missed. I am of like mind in that concrete slab longevity is pretty
much impossible without proper sub-grade preparation. The fiberglass
mesh reduces surface cracking, but it is not a true reinforcement such
as rebar (and to some extent wire mesh). The problem with
reinforcement is that people believe it will prevent the slab from
cracking, which is not true. It will prevent the slab pieces from
moving differentially after the slab cracks. Only proper sub-grade
preparation and attention to the concrete mix will minimize cracking.
Control joints are cut in while the concrete is still green to allow
the slab to crack where you want it, and not randomly.
4" for a driveway is light - that's what's usually poured for a
sidewalk. Code requires slab reinforcement to have 3" of concrete
cover to prevent the reinforcement from rusting out. Wire mesh
usually won't pop the concrete unless it is too close to the surface -
again, attention to detail during placing of the concrete is the key.
The thing that will differentiate almost any choice between
contractors in almost any trade is the attention paid before the
"real" work starts. The quality and longevity of a painting job is
80% in the prep work. Concrete is probably not quite that high, but
not far off. Ask any driveway contractor what they are doing to
prepare the sub-grade. If you don't hear the word "compacted" then
I'd keep looking.
Our condo association in Breckenridge, CO used the fibre-glass
reinforced concrete for replacing several walkways a couple of years
ago. They still cracked, even though the base was well-packed. I
think the trick is to have the driveway poured and then scored in
several sections, with expansion room for those hot summer days.
There will be cracking, at least that way it is controlled and doesn't
look so bad.
Some contractors are busy.
I had spoken to my asphalt guy last year and checked him out.
Then a week ago he popped up and said he was doing a neighborhood road
near us and we could get a special deal while all his equipment was
here. Four of us out of the 20 houses in our neighborhood took him up
Last year, at this time, it was my tree guy. He was really backed up.
I think while new construction is way down, lot of contractors are busy
with repairs and upgrades for us folks that are not moving.
Can't answer your concrete question but do know a bit about fiber
reinforced composites. Concrete has good compressive strength but poor
tensile strength and is better when reinforced. Is there a difference
between wire mesh and rebar? I would think that if rebar were used, it
would take many years to rust to the point of uselessness. I had pinned
some concrete bumpers with rebar to the back of my drive over 30 years
ago and when moved for the new driveway, the rebar was still intact.
Yes, wire mesh is just that. Basicly heavy gauge wire arranged
in a cross pattern, resulting in squares that are a few inches across.
It comes rolled up.
Rebar is steel rods about 1/2" in diameter.
It isn't that the rebar has to disintegrate so that the rebar has no
strength left for the problems to occur. If water makes it's way
into the concrete over time, the steel rusts and expands. That
can cause the concrete to then start to crack. That's probably what
contractor was referring to in recommending the fiber concrete
vs using mesh or rebar. Of course for the contractor,
eliminating the steel reinforcement saves time, money, etc and
lets him come in at a lower bid. Any many people won't be
aware enough to even know to question the difference.
Not sure in what applications you can get away with just using
the fiber reinforced concrete. Or the exact tradeoffs. But it's
around a long time and is widely used. My stamped concrete
patio was done using it.
Without specific knowledge of the OP's location and soil conditions,
and even allowing for that, I don't see how you can make that
assertion. Rebar is a two-edged sword, and the common belief that
throwing rebar into concrete will always make it a better installation
is a fallacy.
Wire mesh is primarily used to hold concrete together WHEN it cracks. It
won't prevent cracking. To be effective, the mesh must be placed in the
middle of the slab. Unfortunately, the wire is often layed on the ground
and "pulled up" as the concrete is poured. Obviously, this probably won't
result in accurate placement of the wire mesh. Since you can bend wire
mesh with your fingers, it clearly doesn't add much in the way of
In contrast, fiberglass mesh essentially adds thousands of little bridges
where cracks may occur. Since it is mixed into the concrete, there are no
placement issues like you can have with wire mesh. It won't prevent
cracking either, but it does offer more connections to keep potential
cracks from getting larger.
Rebar provides some crack control like the mesh options, but is typically
used more for reinforcement. Concrete is very strong in compression, but
very weak in tension. If you span a slab of concrete supported only at
the ends, it will break easily in the middle when weight is added (i.e.
driving on it). Rebar adds strength to the slab and allows it to support
more weight across gaps like that without breaking. But it can still
crack from shrinkage and other movement.
I used fibermesh in our 24'x28' garage slab, with no other mesh or
reinforcing. I did not want any control joints in the floor, so it's a
single large slab. It is now 11 years later and there's only a minor
hairline crack near one of the doors. It wouldn't even be noticeable
except for some discoloring where water came in (I have since
waterproofed the slab edge to keep water out). However, we did install
and compact a 4" layer of rock and vapor barrier before having the slab
poured. One thing to consider is the mesh makes it harder to get a
perfectly smooth troweled finish. But this probably isn't an issue for a
We used quite a bit of rebar in our foundation footings and stemwalls (as
required by code). This helps strengthen the wall from settling, pressure
from the earth around the foundation, and seismic movements.
I also used a couple lengths of rebar in our sidewalks as these were
placed over backfill around the house. While I tried to compact the earth
as much as possible, there's still a chance the ground could settle. The
rebar should help minimize any cracking if voids develop under the
For the sake of comparison, my parents poured several concrete parking
slabs and sidewalks with no reinforcement of any kind (no mesh, fiber, or
rebar). As far as I know, those slabs are still intact today with no
problems. Most city sidewalks are poured with no reinforcements either.
So anything you can add to strengthen and reinforce the concrete would be
I'm just an amateur, so consider my advice accordingly...
Only one so far, two others have been over and I'm waiting to receive their
Anyway, first concrete guy is 2950 sq ft and $11,500.
First asphalt was $4,950. Still waiting for an answer on how thick the
asphalt will be after compression. Two more asphalt contractors supposedly
coming out next week for quotes.
Are they talking about "macro fibers"? macro fibers are the new
thing, the old thing was micro fibers. Macro are thin filaments of a
plastic sort of material about 2 - 3 inches long. One question to
ask them is what percent of fiber they will be using and how does that
compare to the manufacturers recommendations. The have been several
advantages found for using fiber instead of mesh or rebar in the major
construction industry. One big difference is that with mesh or rebar
you will get larger cracks farther apart. With fiber the cracks will
tend to be smaller and closer together, usually they will be pretty
tight. Even though the fibers don't usually add compressive strength
to the concrete they do make it "tougher". And since they are not
metal they don't rust and cause problems. If the dosage rate meets
the manufacturers recommendations I would not hesitate to use it.
I had a large residential concrete job done last fall, costing about
$22,000. The best and most respected contractors, one of whom I chose to
do the job, recommended the same approach using fiber material added to
the mix instead of rebar or steel mesh. It has been in less than a year
so I can't tell if the approach was ultimately a good one, but a lot of
satisfied customers from the past apparently have found this to be a
good solution. Time will tell.........
Just to update...lowest quote so far for concrete is $11,500. Two more at
$12,500 and $13,000. A little variance in the way they measure, but all
around 2,900-3,100 sq ft. It's not a conventional shaped drive.
Two asphalt quotes so far. One at $4,700 and the other at $7,050. Both say
they will grade and compress existing aggregate then pave 3" on upper
course. Not sure why the big price difference? Still getting more bids for
There's such a thing as diminishing returns in soliciting bids. You
won't be necessarily getting additional information or a better
completed job, and more likely it will just muddy the water and waste
your and the contractors' time. I'd figure, looking at it from the
cheap seats, that you should first make up your mind whether you need
or want concrete. That's largely determined by where you are as
climate has a lot to do with it, and of course your budget.
After that it's a question of getting a couple or three bids on the
exact same project, and/or knowing how to balance the bids. To a very
large degree the determining factor should be the contractor's
reputation, company longevity and their willingness to take care of
problems on their nickel. When you ask for references, ask for a
reference for a project that needed some corrective work. That might
be a tough reference to get from some contractors, but if you explain
that you want to know how they service a job, they should be more
As far as the sub-grade preparation, it's compaction, not
compression. Using the wrong words will peg you as a newb that is
trying to come across as knowing more than they actually do - in other
words, either a mark or a potential pain in the ass. The compaction
itself is a major factor in any paving project. Nail down the
contractors on exactly how they prepare and compact the sub-grade.
Some contractors will drive a truck up and down the driveway and call
that compacted, some will use a plate compactor, and some will have a
ride on roller (aka steamroller). The best would be a combination of
the last two, the first is an immediate, "Next!"
No problem. Compaction is one of those large grey areas where
miscommunication (or scams) enter the picture. Correct compaction may
require doing it in stages - 6" of fill, compact, repeat. That's a
much better way to do it than just dumping all of the fill and just
compacting the top.
I'm not clear on whether you're repaving or paving a previously
unpaved section. If it was paved, and you'll be pulling the old
paving, what needs to be done is entirely dependent on why the first
paving job died. If it just cracked from age and then winter got to
it or something like that, then the base is probably okay and it can
be regraded and compacted. If the old paving job died because it
settled and cracked, then you might very well have to pull up the old
aggregate excavate some more, and then fill/compact/fill/compact until
it's at the right grade.
Correct preparation will determine if the new driveway will last ten
or fifteen years or twenty five. That has a big effect on which
contractor's price will appear more attractive.
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