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Old 05-01-2013, 11:46 AM   #1
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Concrete pour rate


A question for those astute to the wilds of concrete. I am working with some formulas for lateral pressure on concrete form. I understand the formulas and terms used in the formulas but, how is the pour rate determined?

The pour rate in feet per hour (rate of rise in the forms) would be variable for a particular volume etc. Apparently this is calculated from the flow rate of the mix out of the truck and the given volume of your job. That's what I'm looking for.

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Old 05-01-2013, 02:53 PM   #2
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Concrete pour rate


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A question for those astute to the wilds of concrete. I am working with some formulas for lateral pressure on concrete form. I understand the formulas and terms used in the formulas but, how is the pour rate determined?

The pour rate in feet per hour (rate of rise in the forms) would be variable for a particular volume etc. Apparently this is calculated from the flow rate of the mix out of the truck and the given volume of your job. That's what I'm looking for.
Don't know if this is what your looking for.

rate, or how fast a form is filled with concrete can be a very important issue. The specified time that is allowed from batch to placement in the form is on the order of 1.5 hours. Considering delivery time for a transit mixer truck, it is usually advisable to plan to empty the truck in no more than one-half of an hour. The supply company may have a jobsite time limit stipulation that requires standby time be paid for the truck after a short period allowed for discharging the concrete. A wall pour 27 feet long and 1 foot thick uses only 1 cyd of concrete per vertical foot of height. Unless short transit mixer loads are used, the form should be designed to accept at least 10 ft of concrete pour rate per hour. Another solution is to have more than one such pour scheduled simultaneously so that an 8 or 10 cyd transit mixer can deposit a partial load into each form so the average pour rate is held to a reasonable rise. A crane can handle 10 to 50 cyd/hour of concrete by bucket. A concrete pump can vary up to 100 cyd yards per hour with an effective average of about 50 cyd per hour. Most commercial batch plants are capable of producing 80 to 100 cyd of concrete per hour.
A very large pour in plan, say 54 feet long by 12 feet wide, contains 24 cyd per foot. A 4-foot-an-hour pour rate would require 96 cyd per hour delivery and placing. Special arrangements with the batch plant and extra cranes and/or pumps may be required. Massive foundation mats theoretically fill at less that one foot per hour, but the side forms should still be designed for a full liquid head of concrete. The reason for this is that the placement of concrete should proceed from one end in a set of staggered 2-foot lifts. This method allows for simultaneous pour, screed, finish and curing operations. It also reduces the risk of cold joints and reduces the time the concrete lift must be continuously manned. But what happens is in any given stretch the form will be filled to the top in less than an hour.
ACI (American Concrete Institute) publishes some excellent books on formwork. They generally recommend a maximum wall pressure design of 1,500 psf. Columns are designed up 3,000 psf because they will be filled in a matter of a few minutes. It is recommended by the author that most forms be designed for no less than 750 psf or liquid head, whichever is less. The form should be stiff enough to resist the impact of concrete pouring and the unbalanced loadings that can occur during placement operations.

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Old 05-01-2013, 08:40 PM   #3
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Concrete pour rate


That's an interesting read.

In the real world, pour rate on commercial/state jobs is determined by an engineer. In residential jobs, it's determined by how quick the mixers can empty out.
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Old 05-02-2013, 10:22 AM   #4
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Concrete pour rate


Years ago when i first started driving ready mix, a salesman from symonds forms was trying to sell a set of forms to a customer of our's without too much success,finally our customer said to the symonds guy,if you can show me that the forms won't blow out when i pour all of the concrete into the forms at once,i'll buy them.
The Symonds salesman had a set of forms sent out,our customer's guy's set them up, using wire form ties and walers,no bracing of any kind,and had 24 yards on 4 trucks sent out one truck for each corner, had us wet up each load with the same amount of water, and all of us discharge our loads as fast as we could,the forms held with no blow out or floating,the contractor wrote the check for the forms on the spot,i seem to remember it was for 10 or 12 thousand dollars at the time,how's that for flow rate.
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Old 05-02-2013, 10:30 AM   #5
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Concrete pour rate


Thanks for all the info Canarywood1. I did find alot of informative PDFs online and am sorting and saving for further research. I'm looking more intently at the ICF forms, and I'm seeing that most of the formulas and math involved is rather specific to a particular form system.

One thing that is still a bit unclear is -

when you consolidate the concrete, via hand-roding for instance, I'm reading that when the bottom of the rod should be able to penetrate the top of the first "lift" a few inches or so, then its time to place the second lift. Is there a definitive formula for this "few inches" or does an experienced concrete guy just develop a feel for this?

Also, what kinda time is involved per lift Vs height of lift for this "setting" to take place before the next lift to be placed? I know temperature would be an obvious variable there.
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Old 05-02-2013, 08:12 PM   #6
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Concrete pour rate


"when you consolidate the concrete, via hand-roding for instance, I'm reading that when the bottom of the rod should be able to penetrate the top of the first "lift" a few inches or so, then its time to place the second lift."

Haven't seen that done in years,viabrators are what's used,must be something really old your reading.



Also, what kinda time is involved per lift Vs height of lift for this "setting" to take place before the next lift to be placed? I know temperature would be an obvious variable there.


Thought that was discussed in the first post??
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Old 05-02-2013, 08:26 PM   #7
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Concrete pour rate


Is the question about the ability of the forms to take the load of wet concrete or the quality of the final concrete itself?

Pouring too fast can result in bad concrete or bowed forms, especially with too much slump.

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Old 05-02-2013, 10:33 PM   #8
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Concrete pour rate


Mostly about the forms. I can't see how the quality of the concrete would be effected by pouring faster or slower.
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Old 05-02-2013, 11:01 PM   #9
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Concrete pour rate


This is where the guy doing the pouring (pumper) comes into play. Your pour rate is a function of how fast they can get the concrete out of the truck....and where the put it. In the real world, they don't just dump it in one spot....good concrete guys are spreading it out. If your doing deep forms, they have a vibrator....

The bottom line is that they work their way around....so the flow rate to any one area is a big variable.....
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Old 05-03-2013, 05:55 AM   #10
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Concrete pour rate


My last question was referring to the time lapse "between" lifts at which point the previous lift is considered stiff enough to begin the next lift. The top of the previous lift would still be wet enough to incorporate the next lift.

I wrote "consolidating", but I meant "sounding". Sounding is the process of using a rod (re-bar) to check the firmness of the top of the previous lift.

Hand roding is still used around here though for consolidating on relatively small jobs.
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Old 05-03-2013, 10:04 AM   #11
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My last question was referring to the time lapse "between" lifts at which point the previous lift is considered stiff enough to begin the next lift. The top of the previous lift would still be wet enough to incorporate the next lift.

I wrote "consolidating", but I meant "sounding". Sounding is the process of using a rod (re-bar) to check the firmness of the top of the previous lift.

Hand roding is still used around here though for consolidating on relatively small jobs.
The only time i can think about having to use that process would be pouring something like a silo when slip forming is used,and the rate of pour is minimized to maybe 1 foot per hour,since the inital set time for concrete is 2 hours,you can be sure it's firm enough at that point in time,also the slump is very important ,as is the amount of concrete that the truck mixers can hold because of time constraints of unloading.
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Old 05-04-2013, 08:59 AM   #12
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Concrete pour rate


When I used to do set-time tests, I'd use a penetrometer to get the psi of the fresh concrete and monitor the time it took to set (by the way, probably the most boring job in the history of the world).

I can't remember how long it took to get it to even register (100psi or so), but I do remember it was longer than it took to do a lift when pouring walls.

Practicality would be an issue also, since a penetrometer is small enough to fit in your hand, so it'd be tough to get into a wall form, if you've got a lift that is a few feet from the top.

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