Hot weather concrete curing according to ACI
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Question

Hot weather concrete curing according to ACI

Gus14 (Civil/Environmental)

(OP)

9 Aug 21 18:21

I searched this site for similar questions but my attempts were futile, so I hope I am not reposting. In local practice, during hot weather concreting it's common to start curing concrete by ponding with water after four hours of pouring. However, I am interested in finding out what ACI recommends, the read was difficult and I don't want to misinterpret the code so any notes on the following would be helpful.

Section 2.7 from ACI 308 states that the final curing method ( ponding and other methods ) should start when the surface would not be damaged by the curing material. This does not necessarily mean the final set but earlier the code stated that final curing should be done only after the final setting because otherwise it will increase the water-cement ratio, so now I am confused.

This is important because the final set at high temperatures according to the PCA table ends at 6.5 hours, and not the 4 hours rule of thumb.

HTURKAK (Structural) · Answer 1 · 2021-08-10 08:20:14

Maybe this: thread507-485901: Curing concrete by flooding with water - how long after placement?

and the links

https://www.concretenetwork.com/curing-concrete/

https://www.giatecscientific.com/education/curing-...

Gus14 (Civil/Environmental) · Answer 2 · 2021-08-10 13:51:46

Thank you HTURKAK for replying. The links were very helpful, as they confirmed my understanding, that final curing should be done after final setting has ended.

I think that the 4 hours rule of thumb comes from the fact they don't do any initial curing, which I think makes concrete reach final setting very early. Of course this is incorrect and it will decrease the concrete compressive strength. ACI clearly states that in hot weather, initial and intermediate curing is required immediately after placing.

BigH (Geotechnical) · Answer 3 · 2021-08-11 17:07:30

ACI 308-01

"Final curing refers to procedures implemented after final
finishing and after the concrete has reached final set. Examples
of final curing measures include application of wet coverings
such as saturated burlap, ponding, or the use of spray applied,
liquid membrane-forming curing compounds."

SlideRuleEra (Structural) · Answer 4 · 2021-08-11 18:38:09

Gus14 - In practice, determining when to start curing is straightforward. As a Bridge Contractor, our head Concrete Finisher monitored the surface to determine when workers can walk on it and curing methods can be deployed without any damage. Everyone involved, the Workers, the Contractor, Inspectors, the Engineer, and the Owner benefit from the timing being just right. I would, and have trusted an experienced finisher's judgement long before a well thought out but some what arbitrary time period.

I expect ACI is vague on when to begin curing is exactly for the reason I just posted... job site condition vary, an on-the-job qualified person is in the absolute best position to make a real-time decision.

www.SlideRuleEra.net idea

Gus14 (Civil/Environmental) · Answer 5 · 2021-08-11 19:48:07

Thank you BigH and SlideRuleEra for replying. The ACI quote puts in better words than mine to be fair.

Quote (SlideRuleEra)
I would, and have trusted an experienced finisher's judgment long before a well thought out but somewhat arbitrary time period.

I agree, I will not rely on specific timing, I will only rely on the setting state of concrete to determine when to start final curing.

Sanjay Roy (Industrial) · Answer 6 · 2021-09-21 05:05:10

Hot weather concreting is defined by ACI as “one or a combination of the following conditions that tends to impair the quality of freshly mixed or hardened concrete by accelerating the rate of moisture loss and rate of cement hydration, or otherwise causing detrimental results: high ambient temperature; high concrete temperature; low relative humidity; and high wind speed.

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Hot weather concrete curing according to ACI
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