Larry@stinescorner,another question

I always was told the soupier the concrete the weaker it would be. What about these concrete pumps doesn't have to be soup to pump it?

no , it dont have to be like soup , can still meet a slump test

they have admixtures and pumping agents to help with the flowability. Yes the more water you add to a mix other than it's designed amounts can reduce it's strenght thats why if a concrete contractor needs to wet it up a beyond it's designed slump they would talk to the supplier about using a placticizer or order a 4000# mix where a 3000# mix is needed knowing they are going to wet it up enough to reduce it's strenght but still be within the desired breaking strength to meet the jobs specs. I work for a Redi mix Companey batching trucks and delivering Crete and see it all the time

Not Larry, BUT they do have Super Plasticizer for a mix - Makes it "flow" better and keep W/C and strengh.

Question is - Why didn't they move the pump truck back as the pour progressed?
Pumping concrete drives water and air entraining agents out - pariculary at that angle of the pump truck.

Don't see any concrete trucks backed up?

just got home ,but the answers were better than I can type ..Larry

350 loads 4AM til at least 3PM

Looks like it's gonna be nice swimmin pool--

The soup is for the chap who is too cheap to hire a pump, especially on house foundations, wet it up so it flows around, nobody sees the separation when it is dry, that is a good reason to have it supervised. They also have a habit of leaving the reo sitting on the bottom, rather defeats its purpose.When the house cracks down the line, nobody is around.

2 things, takes too long to move, and once your pumping crete you keep pumping, if it starts to dry in the pipes then it sucks the water out of the new crete and plugs up the pipes, thats when you see ask holes and elbows all over the place. lol.

All the jobs I worked on, a pump mix design is submitted for approval, whether it has admixtures, or lower slump, the compressive strength has to meet the specifications for the job, test cylinders are to be taken, said contractor will know this up front, if the mix design fails, they eat it. Adding water to any great extent in the field is not something I like to see.

Regardless, you tell a contractor that each pour or every so many yards, test cylinders will be taken, in addition to their responsibility for the material attaining its specified strength, as per a contract, you usually don't get any problems, can still happen, but they know not to fool with it, eyes are on them.

There's a bunch of admixtures out there, modern mix designs for all kinds of purposes, like I've said before, and has been said by others here as well, that W/C ratio is key, you can't deviate very much from it and still get the intended results.

not a concrete expert but i've heard so many do's and don'ts about it, enough to make one really wonder how much of it is smoke blowing, one case in point is pouring into a hole without a trim tube the aggregates will separate from falling force if so what effect does the vibrators use to settle it and force out the air have on the aggregates.

I would say that, most of what you may think is smoke, is a legitimate concern.

To become more educated on concrete, I would suggest ASTM reference material and ACI (American Concrete Institute) and 03300 C.S.I. specifications, (Construction Specification Institute)

You can separate the aggregates, or settle them out. There is a limit to the drop distance, I think its 8'-0", from that height and beyond you need to use a chute, its common to see that in 03300 specifications.

Vibrator needs to be used in increments within a form, never still in one place, touch and go, just to settle and eliminate voids, especially a wall or similar component. You don't fill a form and then use a vibrator, you do it in increments until you reach the top of the form, or you could cause a blow out, too much settling at once, I've seen it happen.

Another seemingly obscure specification with concrete ready mix trucks, is there is a counter that tells you how many times the barrel has turned, more than 300 times and the load is rejected, can settle out the aggregate, not sure about additional air entrainment, but there is a reason for the counter and it comes from ACI or ASTM.

P.S. Never forget that this material is caustic, and will burn your skin in short order.

too many revs on a mixer will beat out some of the air, and cause the crete to set up faster also. but will also help to stiffen up the crete.