Control Joint advice

[premierjax]

Hey guys just poured a 60 x 36 yesterday, the temp down here in Florida right now is mid 50's. We were done pouring around noon yesterday and the guys left around 6 pm. They kept power troweling but the concrete didnt seem to set. When they were leaving you could still touch it and leave a finger print. So one of the guys said he would leave and take his partner home and then swing by again to try and water polish it. He stopped by about 45 min later and it still wasnt right. He is coming by this morning to water polish again and then burn it in. My big question is I know control joints should be cut sooner than later but they say instead of cutting them today we should cut tomm. because if the concrete is wet it will chip when they cut it. Will this be okay? or should I insist on cutting today?

 

[Ross/Kzoo]

They're the experts. If there's any problem then there's only one person to blame.

 

[MG44]

They cut my 105x60 a day and a half later, no cracks

 

[premierjax]

yes your right Ross, but its alot easier not dealing with problems, wouldnt you say?

 

[nehog]

Mine was cut the day after the pour/finish. But... I think they said the main factor was just that it is easier to cut when you cut it early.

 

[Gary S]

Same here. I poured mine one day and cut it the next day (in the rain).

 

[Kevin54]

My cuts were always done the next day.

 

[Engineer61]

Sounds like they don't want to cut it yet because it's still hasn't fully set and is too soft. Cutting early is just faster and easier on the equipment as concrete continues to harden and strengthen the longer it is given to cure. So cutting it early is easier as the concrete isn't yet as strong as it will be later. But you do have to let the concrete harden enough to let the equipment grind it away in the cut instead of just pushing the soft concrete around.

 

[MG44]

My dad and I poured a 30x15 patio behind my house about 7 years ago. We cut it about 4 days after with no ill effect. Don't sweat it.

Ever drill a hole in 6" concrete even 3 weeks after its poured? (I have, multiple holes). The bottom of the concrete was still wet. Its not going to crack anytime soon.

 

[ConCretin]

Control joints should be cut as early as possible. The purpose of control joints is to avoid random cracks, which typically occurs early when the concrete is shrinking the most but hasn't developed much tensile strength. The longer you wait, the greater the chance of random cracking.

With that said, some methods of cutting joints allow you to get on the slab sooner than others. A standard concrete saw requires that the concrete gain considerable strength to avoid 'raveling' of the joint. This occurs when the blade tears our aggregate as it cuts and results in a ragged looking joint. This type of equipment often requires you to wait as long as 24 hours.

An 'early entry saw' has a blade that spins into the cut and has a plate that holds the concrete surface down. You can use these saws immediately after the slab is finished.

The timing of the joints depends on the equipment being used and the weather. Obviously the chances of random cracks is greatly reduced with the use of early entry saws but it depends on what your guy has. As you noted, concrete sets slower as the temp drops so this has to be taken into account as well.

 

[soapii]

Our sawcut guy was always a day behind the production crew.

--Joe

 

[dirttracker18]

FWIW we have hot summers and very cold winters with deep frost and no one uses control joints here for garages. I have a 30 X 36 with no cuts, 5 years old and no cracks.

People are really hung up on control cuts but the evidence doesn't support the need.

 

[Shadowdog500]

my cuts were always done the next day.

+1! ......