last week im pouring a roof slab the hose man says pump more but the foreman says stop, i followed the hoseman (the hoseman thinks he will fill the blockholes manually)and the problem is this, a lot of concrete on the roof and they cant bring the concrete down so they get a crane with a bucket to work with,

yesterday im pouring garage floor,the hoseman wants the hosetip close to the concrete, when i resume pumping the switch is in reverse and i noticed that my hose sucks the concrete back, just thinking why i didnt do it when i pour the roof slab that they want the concrete back in the truck, and my question is this is it ok to suck back the concrete as i soak my tip hose?

based on youre experiences,is this applicable? i keep on reading the manual for the pump i cant find any instruction that this can be permissible

1. You'd make a huge mess of the ass end of your pump

2. Depending on the boom position I don't think the pump will have the power in reverse to suck concrete up over the top of the highest point.

3. Safety? No idea if it's safe or not, never thought about doing it.

I have had customers mention this to me towards the end of a pour as i am shutting it off in advance to make sure they dont get too much before. Telling me how good this one operator was because when he got too much in the pour he just sucked it back. Now I have never tried it but my answer to them was " If he was such a good operator he wouldnt have put too much in the pour in the first place." Thats what i think about it.

chongliyan

Would it work in theory? YES.

The problem with that is that [1] your tip hose would need to remain open and not collapse [2] you would need to keep the suction portion immersed in the crete to such an extent that concrete and not air was acted on by the negative pressure.

Think about your hopper; if it is less than 1/2 full, it is liable to "suck air"

Good in theory, not very functional in reality. ;~)

Bob has the logical approach and true.

I shouldn't say this but I have done this more than one time,believe me.When this situation happens to me I walk over and chat with hose man.After this chat w/witnesses he decides he still wants more,he gets it.When the crew figures out the root cause I simply tell him told ya.

The simple fact in cases like that you are following instructions (your job).If the hose man is stuck on stuipid perhaps a career change would be in order.Then again you most likely haven't been doing this as long as me.

Happy Trails

I've done it once were it worked on a raft slab.  The area that we finished in was about 4 or 5 feet thick and for some reason the guy's doing the first pass had not filled it up.  We were able to stick the hose in about 5 feet deep and sucked up about a half a meter.  What a mess at the back of the pump though.  Even at that depth we needed people pushing at the mud with their feet to stop the air holes.

even in theory it wil not work

atmospheer presure 1 bar= 400 inch water kolom

= 167 inch concreet kolom

if you suck back to absoluut vacuem you never reach the top of your tip hose

sorry for the bad englich  

I know for a fact that you can empty a lake. Talk about a good water wash!!!

thank you guys for sharing youre idea's. great help and knowledge for me.

I have done this with a line pump but never a boom. you can only suck up as high as 14.7 lbs (atmospheric pressure) will push it. If you are pouring at a higher elevation than your truck. How ever if you dont have the room in the hopper a big mess will result. Seth

LOL Bob I have done that many times works awsome!

I been pack'n around a plastic barrel cut in 1/2 for 9 or 10 years. Suck'n a bucket! Do it every single job, less water, less mess, Contractors love it so has every outfit I've worked for. They start out sceptics But they eventually see the light. You'll NEVER rock a boom off this way. I'll make a video(ha ha ha)