Time required for CIP Anchor Bolt to fully set in concrete 1

[amain002]

Wanted to get some opinion on how long does a cast in place anchor take to fully set in concrete (foundation/pier). I have a situation where the contractors wants to go ahead and start installing steel columns asap. The concrete is only 3 days old but has reached it 75% capacity.
Having said that, the concrete is still in the process of curing say until 28 days and not sure of the CIP anchors has fully bonded with concrete and reached it full capacity.

Also, the other important concern is that the anchor bolts sees pullout or uplift load immediately after installing the steel due to its fixed base and cantilevered conditions. Therefore, in my opinion I would like to wait at least for 7 days but prefer 28 days to be on safe side. But the contractors don't agree with me on this. So in your opinion, how long do you think we need to wait until we reach the full capacity of the anchor bolts. Thank you all for your opinion.

 

[Lomarandil]

To fully set, the concrete must reach it's design strength.

But I'd be on the side of the contractor here. I don't know the details of the installation, but have you checked whether full concrete strength is required for the anchorage to perform at the needed level for construction to continue?

----
just call me Lo.

 

[amain002]

Lo, thank you for the input.

At this phase the loads will be just the dead load. Thus like you said not 100% required capacity is required. However my concern is that, concrete at 3 to 4 days, its still green and in the process of hardening. So even if the concrete has reached 100% strength, it is still in the process of curing and not sure how it impacts the CIP anchors.

 

[Enable]

I think you may be misunderstanding what the curing process actually entails. Curing technically never ends and if we said we couldn't move on until the mix has cured we'd still be in the basement of all structures from the 1900s! We call it a day at 28-day strength because that is...well...what we've done. Now, you also seem to be under the impression that even if the concrete reaches the specified design strength at an earlier date, the mechanical properties of bond and adhesion will somehow be less, and that is wrong. If your mix reaches 35 mPa at 3 days that will have the same bond properties to the anchors as a mix that does the same in 14 days, all else being equal (assuming mix designs are same here). EDIT - I should say to within reasonable limits that you might care about. I mean, temperature and other things during the cure can effect bond, etc. But in the typical scenario what I said holds true. Moreover, if your anchors are cast-in-place most of what they are relying on is not direct bond itself but concrete break-out / bearing which is a linear function of compressive strength and hence time to strength is irrelevant.

BTW dead load is NOT your only concern. Construction loads and impact therefrom are a massive concern at this stage of construction and you do not want to neglect that when reviewing capacity to proceed.

 

[sbisteel]

OSHA requires concrete reach 75% of design strength determined by ASTM standard tests before steel erection can begin, see 1926.752(a)(1).

They also allow a lower strength if it is "sufficient to support the loads imposed during construction", but we generally stick to the 75%.

 

[dik]

I generally allow them to be loaded (lightly) after 7 days.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[canwesteng]

I usually allow steel erection after 3 days, provided the breaks look ok, enough to support loads and at least 3000 psi. But I also make sure they have a plan for curing the concrete for the full 7 days while erecting the steel.

 

[phamENG]

OSHA also requires that column anchorages be capable of resisting a dead load moment of of 5.4K-in, so you'll have some tension there, too.

Each column anchor rod (anchor bolt) assembly, including the column-to-base plate weld and the column foundation, shall be designed to resist a minimum eccentric gravity load of 300 pounds (136.2 kg) located 18 inches (.46m) from the extreme outer face of the column in each direction at the top of the column shaft.

 

[cvg]

your extra cylinders have met "75% capacity", not the foundation pier. this is one reason why you may want to exercise some caution and wait for 7 days.