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-   -   Concrete - Control Joints (http://www.diychatroom.com/f19/concrete-control-joints-50203/)

AndrewF 08-03-2009 09:01 PM

Concrete - Control Joints
 
I am having my barn floor concrete poured Friday.

In the past, I have cut my control joints 24-48 hours after the pour and spaced them about 8-10' apart.

The contractor that is doing the pour this time, strongly recommends I have an early entry control joints cut. Supposedly they are "better".

Is this worth pay him an extra $250 to do the saw cuts the following morning with his early entry saw?

Or is my method of using a masonry saw fine? (This is what I used in my last pour and it was fine.)

Floor size: 40' x 68' 4" deep, 4000 psi.
Wire Mesh for reinforcement
Floor drains: 5

jomama45 08-03-2009 09:45 PM

Andrew, IMO there's no doubt that early entry sawing is superior to sawing within 24-48 hours. I cant say I've ever heard of a contractor charging more for it, though. I would automatically do it solely because I'm willing to put my name on my work, & it's often far easier than "selling" a crack to a customer later. Whether it's worth the extra money is beyond me, it has far more to do with you. What is acceptable to you as a finished product? With the weather this time of year, it makes early entry even more important IMO.

AndrewF 08-03-2009 10:03 PM

Ok, I just wanted to check and see if I was being blown some smoke or not.

Although I dont understand what makes it so special doing it the following morning (24 hours) vs me getting on it with a stihl saw 24 hours later.

concretemasonry 08-03-2009 10:15 PM

Many contractors will come back late the same day to saw the joints instead of waiting. Depending on the building situation, they may even be able to strip the slab forms at the same time.

No question about the superiority of a sawed joint compared to the sloppy tooled joint that will collect "junk".

All you are talking about is about $0.10/ sf, which is probably less than the cost of a coat of paint.

It is up to you but for something you expect to last for many years. The price should have been up front, but if you refuse the sawing, you could have some guarantee problems. Are you buying the materials and just paying for labor or do you have a contract with a performance contract?

Dick

jomama45 08-03-2009 10:26 PM

Andrew, what happens with fresh concrete is that the tensile stength of the curing concrete can exceed the comprehensive strength. Normally, cured concrete has great comprehensive strength & relatively low tensile strength.

In simple terms, the stresses of the shrinkage of the concrete exceeds the strength gain, resulting in random cracking. There are many elements that effect the curing pace of concrete including the concrete mix, low humidity, temperature, sbgrade, etc... That's why I said it's your call to make.

stadry 08-04-2009 07:10 AM

both dick & jo are spot on tho neither needs any support,,, having made a decent living for many yrs making 'green' cuts, the earliest 1 can saw jnts, the better,,, mesh adds some strength while the conc's in tension (green),,, after that state pass's, it only serves to hold the crk'd pieces together,,, steel adds only flexural strength but NO compressive strength.

$250's cheap enough altho we would've included it in the o'all cost of the work,,, we want our name on the work which'd incl jnt sawing so there'd be no random crk'ing,,, early-entry saws are meant to be used soon's the bleedwater's done but have seen some guys coming back the next day,,, too risky imo as micro-crk'ing could've already taken place.

AndrewF 08-06-2009 12:09 PM

Thanks All.

I am supplying the materials, the contractor is handling the pour and finish. We have a contract and he has provided proof of insurance.

I did the base, compacted ~4-5" of crushed limestone (304) and set the base grade. I am also building the forms in front of the 4 overhead doors and walk door.

I am putting the vapor barrier and wire mesh down tonight and have to tie it together, except for areas where it is overlapped one row.

The floor will have cuts, it just is a question of wether using an "early" entry saw is better than a traditional saw cut the next day.

I've done cuts in my floors before and never had any issues...the early entry saw soft cut is new to me and I wasnt sure if I really could justify the added cost.

This is just a floor in a pole-barn for parking the truck and storing other stuff in.

jomama45 08-06-2009 03:15 PM

Andrew,
There are literallly thousands of variables in the cure rate of concrete. (OK, maybe I'm exagerating a little!) Generally speaking, always saw within 24 hours, regardless of the tool used. The benefit of early entry sawing is it's designed to be used as early as 0-2 hours of the final finishing of the concrete with minimal chipping of the joints. There are other benefits, but they don't necessarily effect the long term of the concrete.

The reason I don't think twice about using an early entry are as follows: quieter, far less airborne dust, much cleaner & straighter joints, far better depth control (important with radiant heated floors), far better on one's back, & most importantly, they are better at controllin grandom cracking.

When it's all said & done, it's your money & only you can put a value on these things.

AndrewF 08-06-2009 04:41 PM

Thanks.

What threw me off was he said he would come back the next morning and do the early entry cut...what I read online was it was supposed to be done within hours.

If he is waiting until the next day, then I see no benefit of him doing it vs me.

I am spraying on a curing agent as well.

stadry 08-07-2009 07:40 PM

neither do i, andy,,, the benefit of the soff-cut saw's the ability to cut AS SOON AS THE BLEEDWTR'S OFF THE SLAB,,, we've done it both ways but i like a stihl demo saw on a cart w/asphalt ( not concrete ) diamond segments on the blade & slurcs - wet cut.

btw, early cutting also allows you to make shallower cuts - 3/4" on a 4" slab,,, the current spec's thickness/3 - 4" thickness / 3 = 1.333"

AndrewF 08-09-2009 02:42 PM

4 Attachment(s)
The concrete is poured and I cut the control joints in yesterday. Since it is just a pole barn I wasnt picky about the cuts and placement. If it was a more important area, I would have done the early entry route.


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