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-   -   driveway hack jobs? (http://www.diychatroom.com/f105/driveway-hack-jobs-176781/)

pman6 04-10-2013 05:08 PM

driveway hack jobs?
 
Hack or not?

I called several contractors for a driveway job.
Standard 4" thick.

A few of them said they use wire mesh, some use rebar.

but they don't use dobies or rebar chairs.
They pull up on the mesh/rebar after the concrete is poured.

Then they walk all over it, making the mesh and rebar sink back to the bottom.

In wet 3000 psi concrete, wouldn't the rebar slowly sink to the bottom, making the reinforcement useless?

These are licensed contractors who have been doing it this way for years.

One contractor told me he doesn't use dobies because that 2"x2" spot ends up being weak. I'm thinking, big deal. that one space occupied by a dobie is solid enough, and will hold up a rebar grid even if you step on it.

It doesn't even take much time to tie a few dobies here and there.
If you put one dobie every 4 square feet, It would only cost me an extra $50 in materials for a 600 sq.ft driveway.


proper....
http://naturalstone.graniterock.com/...obie-rebar.jpg

Nailbags 04-10-2013 06:13 PM

The old school way was to rake it up and then hope it stay up and in the right place. a cross section would look like a wave of mesh high and lows in it. floating the rebar in bad thing to do. I have done it working for others who insisted on it. does not give the streagnth it should have. Use rebar do the ties right and use chairs. using wire heavy gage mesh use the cement blocks. Simple may add to the cost by say 80 to 100 dollars big whoop.

pman6 04-10-2013 06:50 PM

Quote:

Originally Posted by Nailbags (Post 1156401)
The old school way was to rake it up and then hope it stay up and in the right place.


ah no wonder. These guys I called were old. got their license in the late 1980's.

back then, they used mesh.

these days, more people are using rebar. Probably no difference as far as holding things together.

itsreallyconc 04-10-2013 06:51 PM

why any steel at all in a 4" driv eway ? http://www.diychatroom.com/f105/why-...r-conc-176648/ ,,, you'll find this has been recently discuss'd.

that being said, at the d/w throat & garage pad, we do place #4 bar to add flexural strength,,, HOWEVER, the d/w is generally 6" thick for the 1st 10' to give extra strength when shock loads ( cars driving in & rebounding on their shocks ) are applied,,,
you should know steel doesn't add compressive strength,,, ACI recommends 2" of conc above AND below anysteel.

you'll get a much better job IF the contractor installs a proper jnt pattern @ the correct time AND sees that the conc cures correctly,,, wire mesh is for ...

:censored:why would anyone use 3K compressive strength conc ?,,askeered of a few more $$ in the d/w ?

' licensed & doing it this way for years ' means little 'cause they can't see YOUR house from their house :laughing: sounds as if someone's peeing on your leg & trying to tell you its raining:eek:

Nailbags 04-10-2013 07:08 PM

you can toss rebar in it for a drive way yes use #4 rebar and use 4,000 psi mud with fiber mesh added and put your pre stressed joints in it. you should be fine.

jomama45 04-10-2013 10:11 PM

The biggest reason chairs/dobies aren't used in residential construction here has nothing to do with the material cost, but logistics. It's not uncommon to pull a ready-mix truck into the forms to spout the concrete out, or use a wheelbarrow, or use a power buggy. If placing by these methods, it's simply not realistic to chair the re-inforcement up.

I've been putting rebar in flatwork for 14 years now, and I've yet to encounter all of the downsides that have been mentioned so far, at least on a regular basis. Sure, I've seen mesh in or near the bottom of the pour, but it certainly wasn't the reason we were replacing the concrete. We've also removed enough of our own work for me to witness that the rebar doesn't sink to the bottom w/o chairs............

pman6 04-11-2013 10:49 AM

Quote:

Originally Posted by itsreallyconc (Post 1156427)


:censored:why would anyone use 3K compressive strength conc ?,,askeered of a few more $$ in the d/w ?

higher psi cracks more easily if not properly babysat, supposedly.


Quote:

Originally Posted by jomama45 (Post 1156570)
We've also removed enough of our own work for me to witness that the rebar doesn't sink to the bottom w/o chairs............


that's a little more reassuring. I still would like dobies in the corners of each grid at least.


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