Help With Concrete Slab - 1st Timer

[midnightscape]

Hi all, newB here.

I'm pouring a 31x7 slab adjacent to the end of a garage for a storage shed and occasional boat parking. Have the forms 3 sides in using 2x4s on the 7' foot ends and 2x6s on the 31' span. My question is do I need to use some kind of expansion joint material between the concrete garage floor already there and the new? Also, should I section off the 31' span into like 3 smaller sections and pour them individually (my concern here would be trying to screed the concrete along the 31' length with no 2x4 to use on the garage side to stay level) If I do all 31' at a time, how often do I cut in a joint?

Sorry for the long post...first time with concrete and want to be sure.
Thank you in advance.
Jason

[Rich]

You should have 1/2" expansion joint between old and new. If this is your first time pouring a large slab I would section off the slab into 3 pours - to take care of the screed against the garage side you can use the expansion material as your screed line by nailing it into the edge of concrete. You could also rent a laser level and do wet screeds.
If you pour the whole thing at once put control joints every 8'-10'.

[midnightscape]

Thanks for the reply Rich.

I think I'm going to do 3 pours just to make me feel better about the whole thing.

What should I use for expansion joint material, I know there are a few different materials. Do I need to put it between the 3 pours or will I not need to worry about them since they are done separate they naturally have their own joint?

[Rich]

It's kind of 1/2 dozen one six the other. There are so many variables that can affect one adversely one time and not the next. If it were mine I would probably only put the expansion material against the existing slab.

[midnightscape]

Rich,

I've found some 1/2" expansion material...but a neighbor who recently poured a slab for a patio said he used treated 2x4's between his foundation and the slab. Is this acceptable? Also as far as the pour goes, with my schedule I'm thinking I won't have the time (or expertise) to do it. Any idea what it would cost to have someone (contractor) come in just for the pour? I realize concrete delivery costs will vary, but as far as labor for the size of slab I'm looking at?

Jason

[Rich]

You're probably looking at somewhere between 800 and 1000 (labor and material). Those treated 2x4's sure look nice... for about a year. Most treated wood is pretty wet when you get it and when it dries out you'll have a pretty large gap that's going to be unsightly (IMO). This ends up allowing water to flow pretty easily right down the face of your foundation. I'm not saying that 1/2" expansion won't allow some water to flow down there also but at least it's a stable product. Water, sun, and the rest of the elements won't bother it too much.
But that's just my opinion :)

[midnightscape]

I will go with the expansion material...thanks for your opinion.

And...just so I understand you right...800 to 1000 for them to just come out and pour the concrete, screed and float it? Not doing the forms...those are already in, they just have to come in and pour.

[mjpliv]

If your slab is exposed to the elements I would suggest that you add a shallow slope to direct water away from the shed.

If you are in an area that is subjected to freeze and thaw cycles, consider ordering your concrete with 3-4% air (this means the batch plant adds a chemical that forms tiny bubbles in the concrete). This will reduce the chances of stress fractures due to uneven expansion and contraction. It will also help prevent spalling (surface flaking).

[Rich]

Entrained air is the umm.. not so un-technical term :)

[Rich]

Here's a good link regarding entrained air from PCA
http://www.cement.org/basics/concretebasics_airentrained.asp

[mjpliv]

If I used the proper term I would probably get empty stares back from the trades involved. Around here we just order "air". I would probably get the same response if I used the term "addmixture".

Here is a true storey about shortcuts for words or acronyms -

My cel phone stopped holding a battery charge so I took it into my Telus dealer to get it and the charger checked out. He informed me that the charger had packed it in but it was covered by warrenty so he said it would be replaced.

He took out a warrenty form and took my name and address and then he asked, "What is your PCS number?"

I said, "What is a PCS number?"

He said, "Its the number for your PCS."

I said, "As far as I know, I don't have a PCS."

This kid rolled his eyes and in a tone I didn't really care for he says, "What is the number people dial to get a hold of you?"

I said, "You mean my phone number?"

"It's called a PCS", he lectured me at this point, "a Personal Communication System! The are not called telephones anymore!"

This guy was actually serious!!!!! Having run out of patience, I gave him my number and he filled in the rest of the form in silence.

After he presented me with my new charger I said,"Is that everything?" to which he replied, " Yes".

I asked, "Can I go to my CCTD now?"

Puzzled he asked, "What is a CCTD?"

I said, "My Cross Country Transportation Device ----- Have a nice day!".

He just stood there with his mouth open so I turned around and headed for my CCTD (car) but as I was leaving I could hear about 4 or 5 people laughing to kill themselves in the offices behind the service counter.

Man that guy burned me!! :D

[midnightscape]

Thanks for the replies.

I'm in Minnesota so I did plan on ordering entrained concrete. I also put in a slight slope (probably 1 1/2" drop on the 7 1/2' span) away from the garage/existing concrete for drainage.

I didn't really get a reply back from Rich though on the cost. Was the 800 to 1000 really just for the labor of doing the actual pour, screed, and float? Or is that the whole job, including putting in the forms?

Jason

[Rich]

That's the whole job - labor, concrete, rebar, forming, etc.
A rough idea of cost is take the cubic yards plus waste times the cost per cubic yard and take that number times 3. It'll be in the ballpark.