Buckgnarly
Well-known member
What's a safe time to wait before installing a lift? 5", 4k slab with rebar and Bendpack 10k if it matters. I believe Bendpak says one month.....
Cure time before drilling for lift
- Thread starter Buckgnarly
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lakeroadster
Well-known member
Call the mix plant that delivered your concrete, they'll have the best answer for you.
The standard answer is 28 days..
Oh.. and opinions vary: http://precast.org/2013/10/28-day-myth/
The standard answer is 28 days..
Oh.. and opinions vary: http://precast.org/2013/10/28-day-myth/
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if the slab is poured, wait. If it is not, price out an admixture like " high early".
28 days is standard, though many mix designs will achieve and even pass their design strengths early. John had good advice, your supplier can give you the mix design with data logs for their breaks. They may be getting their 4k break in as little as 10 days.
28 days is standard, though many mix designs will achieve and even pass their design strengths early. John had good advice, your supplier can give you the mix design with data logs for their breaks. They may be getting their 4k break in as little as 10 days.
OP
Buckgnarly
Well-known member
I am in no rush, it will be poured in about 2 weeks, but the framing and finish work will take until mid July probably....I'd just want to be safe, rather than sorry.
bcradio
Well-known member
28 days
matt_i
Well-known member
I'd wait until you have a roofed structure. That can happen quickly but no sense letting the pre-drilled holes fill up with junk that has to be (should be!) removed later.
ms fowler
Well-known member
Since you HAVE the time, wait.
Concrete does not magically become strong at 28 days; it is a continual process which begins when the materials are mixed and continues nearly forever. The rate of strength-gain is quite high at first, and then slows. After 56 days the rate is VERY slow. 28 days is just the convention that has been agreed to for concrete strength. The typical curve --if there is such a thing would show about 2/3 to 3/4 of the 28 day strength at 7 days. The use of NewCem will make the 7 day strength a little lower. Some High/Earl mixes might reach their "28 day strength" in 24 to 72 hours.
Most lift manufacturers require 3000 PSI. Since you are using a 4000 PSI mix, unless you have other admixtures, your concrete should attain 3000 PSI in 7 days or less.
If it was me, I'd wait at least the 7 days, and since you have the time, you could wait the full 28 days. There is no real benefit to not waiting.
Oh, and if the Contractor is Soft-Cutting the joints, have him do it, as soon as the slab will bear weight--probably 4 to 6 hours after it was batched--and one more--DO NOT ALLOW EXTRA WATER-- beyond the mix design to be added by the Contractor. The crew will likely want to "give it a little drink"--it makes it easier for them, but they should stick with the Contract--they bid it to place the concrete at the specified slump ( water-cement ratio) and they should stick to it--making it "easier" is not your problem.
Concrete does not magically become strong at 28 days; it is a continual process which begins when the materials are mixed and continues nearly forever. The rate of strength-gain is quite high at first, and then slows. After 56 days the rate is VERY slow. 28 days is just the convention that has been agreed to for concrete strength. The typical curve --if there is such a thing would show about 2/3 to 3/4 of the 28 day strength at 7 days. The use of NewCem will make the 7 day strength a little lower. Some High/Earl mixes might reach their "28 day strength" in 24 to 72 hours.
Most lift manufacturers require 3000 PSI. Since you are using a 4000 PSI mix, unless you have other admixtures, your concrete should attain 3000 PSI in 7 days or less.
If it was me, I'd wait at least the 7 days, and since you have the time, you could wait the full 28 days. There is no real benefit to not waiting.
Oh, and if the Contractor is Soft-Cutting the joints, have him do it, as soon as the slab will bear weight--probably 4 to 6 hours after it was batched--and one more--DO NOT ALLOW EXTRA WATER-- beyond the mix design to be added by the Contractor. The crew will likely want to "give it a little drink"--it makes it easier for them, but they should stick with the Contract--they bid it to place the concrete at the specified slump ( water-cement ratio) and they should stick to it--making it "easier" is not your problem.
mike93lx
ALLIANCE MEMBER
If the manufacturer has provided a wait time, why wouldn't you follow it?
wssix99
Well-known member
The longer you wait, the better.
Unless you are using a very exotic, engineered concrete, no one will recommend anything less than 28 days because that is typically the length of time where the initial strength of concrete is measured. The material gets stronger as time goes on.
Unless you are using a very exotic, engineered concrete, no one will recommend anything less than 28 days because that is typically the length of time where the initial strength of concrete is measured. The material gets stronger as time goes on.
This...and you should not strip the forms for 7 for structural areas...
6768rogues
Banned
Agree, design strength is 28 days.