How long do you have to wait to pour new concrete against new concrete? 1

[Kom3]

Hi, I have a 120'x20' mat foundation designed for a bunch of equipment. I need to develop a localized drainage plan for various equipment. Having a drainage pipe go below the 2' thick foundation isn't feasible since I don't have the necessary slope to pull that off. Hence, I plan on adding drainage trenches that leads to a catch basin. The drainage trench would cut through the 120'x20' mat foundation so I plan on just breaking the 120' pad into 4 separate foundations. I would then have (4) 30'x20' pad separated by drainage trenches. However, I am wondering what is the impact to the schedule if I do this. Is there a waiting time before new concrete can be poured against one another? This is a time sensitive project so I may have to find a different plan if the construction time takes too long. Regards.

 

[BridgeSmith]

If you want it to bond, the sooner the better. If you don't want it to bond to the previously placed concrete, you'll need a bond breaker of some kind, regardless of how long you wait.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[SlideRuleEra]

In warm weather and assuming a suitable concrete mix design, the next day will be fine. A example more extreme than your plan is for jump forming of tall structures such as chimneys and silos... a pour a day, and that is on top of the day old concrete.

Unless the floor surface has reason to be "level", slope top to the slabs (in one dimension) toward the drainage trenches. For positive drainage, slope in the 1% to 2% range is suitable. In our experience expecting less slope to work is wishful thinking. We learned and started using 2% slope for the ground floor of our electric generating stations, our consultant's "howled" but we did it anyway and have been happy with the results (for many years).

 

[Tomfh]

ASAP if you want it to stick.

 

[dik]

and roughen the bonding surface (1/2" amplitude).

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik