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-   -   Pouring a patio without rebar???? (http://www.diychatroom.com/f19/pouring-patio-without-rebar-72774/)

luweee 06-03-2010 10:34 PM

Pouring a patio without rebar????
 
I have a person thats bidding my patio pour. He claims to be a 40 + year union worker in concrete... seems really knowledgeable. But he says he doesnt use rebar in his concrete for reinforcement. He uses fibrous mesh instead?

will this do the job and last as long? is it a correct way of doing it?

Thanks

stadry 06-04-2010 05:03 AM

so far he's right but ask him about jnt pattern, slump, wtr/cement ratio, insurance, license,,, whether or not he's ' union ' doesn't mean much but not necessarily a minus, either,,, neither mesh NOR fiber mean much in a 4" patio.

' correct ' means 1 method & his is,,, more interested in the ' why ' of HIS thinking,,, that would tell me more,,, we rarely use either - why spend the $ for no appreciable benefit in this project ?

better he's got enough people on hand who know what they're doing w/o being told,,, hate seeing a crew 1 man short so its nec to ' bless ' the mud before it gets away from them & makes proper finishing almost impossible :furious:

btw, sawing a proper jnt pattern at the correct time does more to eliminate random cracking in your conc than anything else :thumbsup:

PaliBob 06-04-2010 05:23 AM

Excellent advice in Post #2 from a Pro


Quote:

Originally Posted by luweee (Post 450911)
......will this do the job and last as long?....

City sidewalks and curbs do NOT have rebar.

.

posylane 06-04-2010 11:37 AM

I can't answer about the fiber since I don't know what he is actually using.

Metal mesh is junk. It will rust out in a few years (since it is thin) and won't be effective. Rebar is thick and will last a long time.

In Dallas sidewalks and curbs have rebar.

I don't think a decent fiber mesh will be as cheap as rebar. I'd ask him to provide the exact product name and then go research it. I have used fiber in all my hand done concrete (40 yards) but it is short (1" or so) loose fiber you put in the concrete as it is mixing. It is good stuff - I made 4" x 4" x 4' triangular concrete peices with just the fiber and you can pick them up in the middle and they won't break.

But I'd never substitute that for rebar on a patio - you want that to last a long time.

jlc791 06-04-2010 11:44 AM

I widened my driveway four years ago and poured 5" of fiberglass reinforced concrete at the recommendation of the concrete supplier. Only slightly more $$ than without the fiber but a lot cheaper - and faster - then setting up rebar. Not a single crack to date. :)

jlc

joed 06-04-2010 11:49 AM

Never used rebar in a patio.

posylane 06-04-2010 03:29 PM

Unless you are looking to spend as little money as possible or don't care about unconrolled cracking, I don't know why you wouldn't use rebar. If you don't use rebar (and you are using regular concrete) you are likely to get more and bigger cracks, and sections of the slab could crack/break and fall in relation to the rest of the slab.

Bad thinks like this are not certain to happen, depending on your ground, plants/trees near the work, ect., but you are opening the door. Rebar is cheep. A bad job is expensive.

Yoyizit 06-04-2010 03:46 PM

http://en.wikipedia.org/wiki/Carbon_grid

jomama45 06-04-2010 06:26 PM

Quote:

Originally Posted by posylane (Post 451193)
Rebar is cheep. A bad job is expensive.


I couldn't agree more with this. As of this point in time, I haven't discovered a way to retro-fit steel re-enforcement into concrete, so I stick to putting it in right away. As a professional, the minor cost of 3/8" rebar, and minimal labor to handle install it, is a meager few percentage of the cost of an entire job.

The transition to "Fibermesh" to replace all steel was made here 15 years ago. Ironically, every reputable contractor in my area has gone back to sttel re-enforcement in the last few years. If they didn't revert, the odds are that they wouldn't make it in business in this trade. The fiber has little to no effect in holding separate slabs together in my experience, which is a big deal when pouring over expansive soils that are subject to 4' of frost in the winter.

Now, this is just how we construct here in a cold climate with these soils, but I can honestly not see fibermesh having any long term advantages to steel. The advantage is a little cost savings at the time of installation due to slightly cheaper material & labor costs.

kwikfishron 06-04-2010 08:41 PM

I couldn’t agree with posy lane and 45 more. Bar is cheap, what 4-5 bucks a stick?

OP never said how big the patio was but what, 20, 40, 60 bucks of bar and 30 min. of labor for peace of mind?

The entry to the 100 + year old home I’m in now (who knows when the Crete was poured) has a 5’x25+’x 6”+ thick wrap around concrete porch, broke in two places with 1 ” gap at the top on hard clay soil. I look at it and think, if only there were a few sticks of bar in there.

Half of what I do in my business isn’t required, but I do it.

Tscarborough 06-05-2010 10:03 AM

Rebar does not prevent cracking in concrete. It holds the peices together, but that is not why it is there, it is there to increase flexural strength, which is not likely to apply to a patio unless you are in the habit of driving dumptrucks over it on a regular basis.

If your soils are extremely expansive (like Dallas), it is a good idea to use both Fibermesh (a brand name) and rebar. Poly fibers are not arranged in a mesh, they are chopped and distributed randomly through the concrete. They increase impact resistance and microcracking, as well as flexural strength.

All concrete cracks, the best you can do is to convice it to crack where you want it to, i.e. control joints.

stadry 06-05-2010 11:41 AM

'scar, they have ears but do not listen,,, they also have eyes but do not see :laughing:

adding bar at a d/w throat makes sense due to ' moment loading ' while its not needed 4' in from the st as the load's dynamic ( rolling ) & weighs less than if static ( parked ),,, using dble mats on a bdge makes sense yet senseless in a patio,,, conc usually cracks due to: 1, an improper jnt pattern; 2, early loading; 3, heavier-than-designed-to-support static/dynamic loads; OR 4, expansive soils.

when all's said & done, nothing beats thicker concrete :thumbup:

NJ Brickie 06-05-2010 02:03 PM

I also think rebar in a patio is usually not needed. With the soil in my area I only put rebar in patio/sidewalks (I know I am not suppose to put rebar in a sidewalk on city property) when there is a tree near by. Over the years the tree roots will lift the concrete and create a crack with separation of the two pieces. A stick or two of rebar will help to hold the two pieces together and hopefully you will have an arch to your sidewalk and not a tripping hazard. Tscar is right, rebar will not help prevent regular cracks in concrete that will eventually happen.

Red Squirrel 06-05-2010 04:00 PM

I'm no expert, but I think when it comes to non structural cement (it's just lying on the ground, it's not actually holding anything per say) the ground below is what is really important. It should be very well packed, and I'm sure there's proper processes and backfill materials that need to be used. I've seen people dig as deep as 4 feet to prepare the ground for interlocking stones so they don't buck and the ground does not shift under them. Similar should probably be done for a very good cement pour.

PaliBob 06-06-2010 04:12 AM

1 Attachment(s)
Two Thousand year old Concrete Dome
NO Rebar


http://en.wikipedia.org/wiki/Pantheon,_Rome
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