Garage project

[whitedogone]

I have seen rebar tele thru 4" slabs before. It's just a Garage! Just put down a VB and use 6 Gauge 6 X 6 Flat Remesh on chairs and pour 5-6" of 4000# fiber mix on top. NO expansion joint at perm (the slab will shrink 1/6-1/8"). Spray it with curing compound and cut it into 1/4's a day or 2 after pour. The best thing you can do for the strength (besides the w/c ratio) is to keep it curing for the full 28 days after pour. I might put a 1/2" bar across the door area where I cut it down for the "Door Weep Pocket"
http://www.tractorbynet.com/forums/build-yourself/152236-idea-keep-rain-fron-getting-2.html

 

[Builder]

Probably because the rebar was set too high in the slab.

It may be "just a garage", but cracked floors that settle in garages suck, too.

TBN guys love their garages. Cracked settled shop/garage floors are unacceptable.

I would think in the 1-100 chance that telegraphing did show (hopefully we're talking about the same thing - "shadows" or stains indicating where the rebar is) He could apply a concrete finish on the floor.

Personally, I've never seen this happen on any concrete.

Look at where strength is a must-rebar is used liberally.

 

[whitedogone]

Probably because the rebar was set too high in the slab.

It may be "just a garage", but cracked floors that settle in garages suck, too.

nope....on chairs in center of pour. I know for sure because I made them tear out 10,000 sf

 

[whitedogone]

http://www.tkproduct.com/Curing Concrete.PDF

 

[Builder]

Concrete is strong in compression, poor in tension.
Rebar, or steel, is the opposite.

By combining the two, you develop a product that is superior
and complimentary to the strengths and weaknesses of the individual materials.

 

[Builder]

http://www.tkproduct.com/Curing%20Concrete.PDF

I agree with those curing methods. It is amazing how much better the product turns out when a curing membrane is used.

I'm sure you know your stuff, but I do what works for me and I've poured a sh_t-load of concrete.

Here's a good article in laymans terms about reinforcing concrete. The last few paragraphs explain how rebar helps. http://www.askthebuilder.com/NH055_Concrete_Cracks.shtml

 

[whitedogone]

Concrete is strong in compression, poor in tension.
Rebar, or steel, is the opposite.

By combining the two, you develop a product that is superior
and complimentary to the strengths and weaknesses of the individual materials.

He may as well go with a Post-tensioned concrete haunched slab design.

The superstructure could be designed for two (2) load groups. The first load group consists of the
standard AASHTO loads, MS-18, MS-22.5 and HL-93. LFD (Load Factor Design) is used
for MS-18 and MS-22.5 designs; LRFD (Load Resistance Factor Design) is used for HL-93
design. The allowable concrete stresses used for the service conditions are:

Tension in concrete:
0 for 110 % of MS -18 load
0.25 F'c for MS - 22.5 or HL - 93 loads
Compression in concrete:
0.4F'c for MS -18 and MS - 22.5 loads
0.6F'c for HL - 93 load

Now that would be a garage floor!

 

[dieselsmoke1]

Just got home and found my plumbing rough in approval in the box. Time to lock and load on this floor.

 

[Gary Fowler]

I have seen the shadow effect or telegraphing as you guys are calling it in lots of wet concrete but seldom does it show in cured concrete. This is generally caused by overvibrating and the slurry just forms on top of the rebar. I dont believe that it is harmful to the strength of the concrete at least for house slabs as long as your W/C ratio is .45 or less. The best way to assure that you have good concrete is to let the concrete supplier know that you WILL be taking test cylinders of the concrete and it had better meet the spec or he will be breaking it out and replacing it. I have personally seen batch plants use left over concrete as part of the next batch when they know it is going to a house slab and normally isnt tested like it is in heavy construction. You may spec out 3500 or 4000 psi but may only be getting 2500 concrete due to the batch plant operator wanted to safe a few bucks. Get a certified test lab to take the samples and test them if you are at all concerned with strength and cracking. Also the cooler the weather that will delay the set of the concrete some, the stronger the concrete will be when finally cured. Ideal pouring temperature is about 38 F. Hot weather will cause hair line cracks on the surface just about everytime even with a curing compound applied.

 

[dieselsmoke1]

I have seen rebar tele thru 4" slabs before. It's just a Garage! Just put down a VB and use 6 Gauge 6 X 6 Flat Remesh on chairs and pour 5-6" of 4000# fiber mix on top. NO expansion joint at perm (the slab will shrink 1/6-1/8"). Spray it with curing compound and cut it into 1/4's a day or 2 after pour. The best thing you can do for the strength (besides the w/c ratio) is to keep it curing for the full 28 days after pour. I might put a 1/2" bar across the door area where I cut it down for the "Door Weep Pocket"

No expansion joints at the perimeter, as in just turn the VB up and trim it off flush with the mud when dry? I'd really like that for two reasons, nice plastic covering so the brick doesn't get spattered while pouring and no big nasty expansion joint beside the wall forever. Will my inspector freak if he sees no expansion joint?