Quote:
Originally Posted by kayosthery
It can be pumped, but may require different additives to do so, namely Super Plasticizer "Super P", to make it fluid enough. If the contractor is pouring a lot of the vertical work at one time, it will usually pump the concrete. Every time you place concrete with a pump though you have to order enough to lose in the pipe that runs from the stationary pump on Lower Lower Wacker all the way to the tip of the pump. All of that unplaced concrete gets blown back through the pipe to a concrete truck when finished. So, you need to be placing enough that your production gained through pumping is offsetting the cost of the time to crane and bucket, as well as the lost concrete in the pipe. There's a lot of other considerations too, for example, the crane might be busy doing other things, and pumping is the only option.
To the last part of your comment... I wasn't saying pumping changes the mix. I meant that you cannot be sure when the mix you want reaches the end of the placing boom and when the truck delivering that mix runs out. Not saying it can't be done, but it's a lot easier and faster to crane and bucket the vertical mix.
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With pumping, I thought there was a plug, something called a "pig" that was put in the end of the line (at the pump end) so the material that is in the pipe/hose could be pumped to the work area. I don't have any practical experience with this, but it seems like it should be a fairly easy calculation to figure out how much concrete is needed for any formed work, like a wall or a column, and also how much concrete is in the pipe/hose. I realize there would be some waste or overage but I would assume that also happens with the crane and bucket method.
With a crane and bucket it seems like there would be a huge amount of lost time between one bucket and the next------a crane can only do one pick at a time, and the higher the work site grows the longer the time would be between bucket deliveries.
I know that the crane usage is planned out very carefully, so maybe there are times when it makes sense/cents to do both pumping and bucket work. If the crane isn't being used for anything else it might as well be hauling concrete.
What union handles the placement of concrete in the vertical forms, is it the same one as does the slabs? I would imagine that the workers can do "X" amount in a certain time and once they are on the site its the managers job to be able to put them to work for the full day.
This to me is another example of the construction dance----balancing how much concrete a mix truck can deliver, how long it takes to get the concrete to where its needed, how much manpower is needed to place the concrete, time it takes to move from one pour spot to the next one (after all they are 10' to 16' up in the air above the slab) how to allow for break and lunch times, how to use the labor for as much of the day as possible but to avoid overtime whenever possible. And do all this while the rest of the construction is taking place all around the site. It still is very impressive to me.
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