Concrete Mixertruck Cleaning

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yogi
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Concrete Mixertruck Cleaning

Post by yogi » 22 Dec 2017, 14:24

They are building a house down the street from me. Today they poured the concrete foundation. As I watched them I began to wonder how they clean out the inside of that concrete mixer truck. It must accumulate a lot of old concrete after a while. Well ... this is one way: https://www.youtube.com/watch?v=SlUWwHkHfpI

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Kellemora
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Re: Concrete Mixertruck Cleaning

Post by Kellemora » 22 Dec 2017, 15:25

I drove a mixer for a short while, we were not allowed to let any buildup remain in the truck between loads, else it gets really hard to get out.
Even so, there is always some buildup that once it accumulates it grows fast.
Mainly on the back side of the screw not visible from the top.
Unless a truck breaks down and has no way to empty the load before it sets, it's not all that hard to keep a mixer clean.
Besides the Eco-Friendly cleaners, which don't work worth a diddly squat, we used muriatic acid or hydrochloric acid.
Sometimes we even used dry ice, or metal blocks to break up heavy buildup.
The company I drove for had us load dry sand and let the mixer run for about an hour, after our last load before the weekend started. Kept the insides nice and shiny. If they weren't we got fired, hi hi...

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pilvikki
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Re: Concrete Mixertruck Cleaning

Post by pilvikki » 22 Dec 2017, 15:55

but... where does all cement juice go, just down the drain? :eek:

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yogi
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Re: Concrete Mixertruck Cleaning

Post by yogi » 22 Dec 2017, 18:11

Good question. I'm guessing that it goes into the sewer system or into the surrounding ground. It's toxic.
Last edited by yogi on 23 Dec 2017, 18:30, edited 1 time in total.

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Kellemora
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Re: Concrete Mixertruck Cleaning

Post by Kellemora » 23 Dec 2017, 13:05

Oh heck no, OSHA would shut them down in an instant. The aggregate is screened, washed, dried, and reused.
The water left over is filtered and the limestone wet powdery goo from the process gets added to the next batch.
The wastewater is fairly clear and used in the next batch also.
The only time waste goes into the ground and possibly into a sewer, is when we wash the trucks on sight after a delivery. Nothing really toxic about it at that point of release.
The only real problem we have is when they cannot use the amount of concrete we brought.
In this case, we add water to the mixer and boogie back to the plant for our next load.
If we don't have another load going out, what is left in the truck goes through the process I first mentioned, and reused.
I rarely had that problem, because I had a few friends who always needed a little concrete for this or that, and I would call to see if they could take what I had left. Most of the time, one of them was ready and waiting for it when I swung by.
The boss didn't mind because it saved him money if we didn't bring it back, hi hi...

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yogi
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Re: Concrete Mixertruck Cleaning

Post by yogi » 23 Dec 2017, 18:36

I didn't realize concrete could be recycled so easily. Plus, I figured there was a chemical bond between the limestone and the clay which is what makes it cement.

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Kellemora
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Re: Concrete Mixertruck Cleaning

Post by Kellemora » 24 Dec 2017, 16:19

Well their sorta is Yogi. The cement part of concrete is the glue that bonds with the aggregate.
The cement also hardens as it cures. A little lime added to the mix makes it set faster.
Cement by itself isn't very strong at all. Cement and Sand make Mortar, add gravel and you have Concrete.

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yogi
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Re: Concrete Mixertruck Cleaning

Post by yogi » 24 Dec 2017, 18:16

I was thinking that once the cement hardens (chemically binding the limestone and the clay) it cannot be easily undone. Then again, my only experience with the stuff is a bag of Sakrete. LOL

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Kellemora
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Re: Concrete Mixertruck Cleaning

Post by Kellemora » 25 Dec 2017, 17:00

It does bond and is hard to break up to get out of a mixer. Crawling inside and using a jack-hammer is about the only way to break it all loose.
The only real problem we had with build-up was behind the screw blades. And if it got too bad, we had to use the iron blocks bouncing around to knock much of it loose. Then the stronger acid to get it good and clean.
Sometimes they used dry ice which caused the metal to shrink faster than the concrete, and this allowed a lot to break free from the back of the screw.
We had really old trucks, nothing like the modern ones of today, which are much easier to keep clean.
I hear those new ones that dump to the front, have silicone inside. I've not seen that written anywhere though. Seems it would tear up real quick, so maybe I misunderstood what someone said.
Even so, it seems like our technology has advanced enough that they could come up with something to make keeping mixers clean inside.

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