Title says it all; I’m sure a thin layer of cement will be left over after they poor it all, and I would imagine that thin layer would harden and then the next time they use the mixer another thin layer would be leftover and so on and so forth. After a while I would imagine it would accumulate to the point where it renders the mixer unusable.
Why is this not the case?
In: Engineering
My great grandfather worked for a ready-mix plant when he came home from WWII. He mentioned having to using a small of dynamite on occasion when they’d have to clean a drum out.
Times I worked construction, they would figure what they ordered pretty close. Nobody wants to pay for what they can’t use. I’ve seen the drivers, if it’s a small amount, flush it with a bunch of water where they can end up dumping basically sand and gravel on the ground. The trucks carry water where they can rinse down. Or just back the truck up to a different spot and dump it where it isn’t a problem.
Excellent answers.
I will add that sugar greatly prolongs concrete setting. Worried about concrete in the barrel starting to set, dump in a bottle of full sugar cola. That will extend setting time so you can hopefully get to where you can safely offload it.
It’s also used in the oilfield when you need to prevent the cement you’ve vacuumed up from setting in the truck before you’ve offloaded it
I met a roided out bodybuilder years ago who delivered us a load of concrete, and he said he climbed into the drums of trucks and would jack hammer them out. Which sounds like the worst job in the world.
This was a big deal when drivers went on strike not too long ago. Mid shift union called a strike so they all left with trucks full of cement. Company’s sued the unions for damages.
No one carries around a 50# bag of sugar just in case?
I’m not gonna scroll down all the way to see if someone has already said this.
After a clean dump the driver hoses everything down with water including inside the mixer. What’s left is diluted enough to not set up. In case a pour goes bad and it looks like they’re gonna get caught with a load in danger of setting up, sugar. Sugar will stop the chemical process that hardens the cement. I’ve seen them dump bags of sugar, kept ready just in case, into the mixer itself. Just keep adding sugar and water until it’s safe. I do oilfield work and normally there’s a roll off container or a half round tank that the operator dumps the diluted load into. Then they have vac trucks clean it up and dispose of. In smaller pours gone wrong ive seen operators even dumping bottles of mountain dew in it to slow the reaction. If that’s not done then yeah, hammer n chisel time.
About 0.5 m3 is left in the drum from the normal 8.5 m3 load. It doesn’t accumulate because they wash the drum after the mixer returns to the plant.
I was on a job years ago and it did harden. They cut the mixer off the truck with torches, dug a hole and buried it right there. You can’t drive the truck after the mud hardens because it will flop over with dead weight.
I have zero authority on the matter, but I was told that concrete trucks have a barrel of reserve water so that if you hit the time limit the driver can dump the water in. It ruins the batch of concrete but saves the truck.
I also once met a financial planner from the mid West. He built his whole practice on concrete companies….they can only be a max of 45 min drive from each other. He set up and run all their retirement plans. Genius!
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