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Re: Hot Weather Concreting[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: tiger(--nospam--at)palaunet.com, seaint(--nospam--at)seaint.org
- Subject: Re: Hot Weather Concreting
- From: Rhkratzse(--nospam--at)aol.com
- Date: Wed, 27 Feb 2008 20:19:36 EST
ACI 305R "Hot Weather Concreting" recommends keeping concrete temperature as low as possible in hot weather, and provides a long list of detrimental effects due to hot weather and hot concrete.
I recall touring a nuclear power plant under construction west of Phoenix several decades ago and being informed that 90% of the water in their mix was in the form of ice. I assume there were good reasons to do that.
Ralph Hueston Kratz, S.E.
Richmond CA USA
In a message dated 2/27/08 4:41:21 PM, tiger(--nospam--at)palaunet.com writes:
I am hoping that someone on the listserver knows of literature that discusses the benefits of using crushed ice for concrete batching when sustained ambient temperatures for both placement and curing are in the range of 95 to 100 degrees F.
Let’s say I am placing concrete for two 8 inch precast walls (NOT mass concrete) in ambient temps of 95 to 100 deg F.
I use one mix design, but in one batch I replace some of the water with crushed ice (no change in W/C ratio) resulting in the temp of the concrete at discharge being less than 90 deg F. For the second batch I do not use ice and so the concrete at discharge is 95 deg F or a bit above. Both wall panels are shaded and moisture cured in exactly the same fashion at the same ambient temperature of 95 to 100 deg F for 28 days.
My question is, will the 28 day strength of the two panels differ significantly?
Based on literature I have been able to dig up, it would seem that there are two major problem areas with regard to placing concrete at these temps. First would be the placement itself, as the hot weather would tend to reduce workability and decrease set time. It seems to me that the addition of ice would help in this area by lowering the concrete temp at discharge.
Second problem area is overall decrease in ultimate concrete strength. Since the temp of the iced concrete would rise and match that of the uniced concrete within a few hours and stay at that level through almost all of the curing time, it seems to me that there would likely NOT be a significant benefit by adding ice in terms of 28 day concrete strength.
I searched the listserver archives and didn’t come up with anything on this topic. I am trying to determine if it is necessary to use ice at all, since other methods such as the addition of plasticizers to ensure workability could be used to address the first problem area. If, however, there is a noticeable effect on 28-day strength than keeping the ice requirement would be preferable.
Terangue *Tiger* Gillham, PE
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