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 search for: 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.
R
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.
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 on it.
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 the 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 been around a long time and is widely used. My stamped concrete patio was done using it.
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 structural strength.
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 driveway.
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 sidewalk.
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 a bonus.
I'm just an amateur, so consider my advice accordingly...
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.
Only one so far, two others have been over and I'm waiting to receive their quotes. 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.
Location is SE Wisconsin. Not sure of composition since we just moved into the house that was built in 2006. Normal for this area is a mix of clay and who knows what else.
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 both.
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 willing.
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.
Now one more update. The $4,700 asphalt guy said they will compact with a 5 ton roller. The $7,050 asphalt guy gave me this answer: "After our grading crew fine grades the driveway to ensure positive drainage, the grading crew will use a large steel drum vibratory compaction roller to compact the existing gravel." Thoughts?
Obviously, because of cost, I'm leaning toward asphalt vs. the 10, 11 $12k quotes I've been given for concrete. It's Wisconsin, so I don't know if every 3 years to seal and patch it will be an accurate timetable, but if it lasts 15 years, sealing it every 3 years, I'll be happy or, dead, or in a nursing home by then.
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