Dry-mix drum?

[speedy]

Has anybody ever heard of loading a drum with the dry constituents of concrete into the drum, driving several hour in sweltering heat or freezing cold and having FRESH concrete on-site? Reich has mixer drums that can do this.

www.reichpumps.com/pdf/dtm98c.pdf

Kind of a neat concept, but exactly how do you load it? Obviously not through the funnel. Maybe the funnel will swing out of the way and you load it with a high-speed belt?

And how do you keep the water injection nozles clean?

I like the concept, but you're still stuck with the mix design. whereas with the 'mobile mixers' you can alter the mix, and you can still have fresh mud.

What are your thoughts?

[Matt]

I have heard of the mobile mixers that you mentioned that serve this same purpose, but never a mixer drum that could accomplish the same. As to how the water injection nozzles stay clean or how the water system feeding those nozzles is mounted in a rotating drum is beyond me. I would imagine it would load the same way you "dry batch" a normal mixer truck. In fact, if you added the separate water tank with additives to a regular mixer truck, and emptied that tank into a dry batched load on site, it would seem to serve the same purpose.

Those are my thoughts. ;D

[Driver]

Oh boy can I see alot of dry loads with this set up ;D
Not sure I would want this config added to any fleet.
All tho if they are building them someone must be buying em.
I can see how the nozzles would stay clean with water injection,,operator would have to be sure he cleans em out..but what about the wear on the piping system??? Sure the shop would have a nightmare keeping water lines intact?

Another thought is with dry batch ya still have moisture in your aggraragtes causing meat balls in the mix??

[batchmaster]

I've heard of loads being chemically altered to endure long hauls through heat and cold, but nothing like this. I would imagine like driver says it's going to be a mechanical nightmare. Also the moisture in the agg has to start the hydration process...I wouldn't imagine it could be good, unless everything is stored seperate, agg, cement and water.

[batchmaster]

On Reich's site, it talks about reusing wash water??? wouldn't this add water to your dry agg? and unless they are batching oven dry material? seems confusing to me, you'd have to be a sucker to believe there is no moisture in the mix just by adding the water on site. unless they don't divulge top secret information or something, doesn't seem feasible.

[speedy]

I do think that the cement powder is separate. If you look at the graphic is shows different layers of materials in the drum.

The drum must be loaded with a high-speed conveyor, I don't think that you could keep separation with a top-load through the funnel.

The water tank is large enough for the batch water and wash water. There are separate tanks for admix.

I've seen mixer trucks hauling crushed rock before and discharging it without a problem, but I have to wonder about the ability to start a full drum of dry aggregates turning.

And you would think that the aggregates must be dried if it was to go any distance, especially in the winter.

[batchmaster]

On the diagram it says cement and agg, leading me to believe that they are together, I think that just for the illustration purposes they show different layers so you can see the different materials, but if it had different compartments in the drum for different materials, that would lead to gates and that in the drum that would have to open to put the material together, and I would imagine it would have to load through two different openings, unless they put some kind of diverter in to send the materials different directions.

[Driver]

I gotta beleive its all blended also..I dont see seprate comparents for each stone and sand..kinda think that would throw the barrel a bit off balance and right off the mounting rails..
I dont see much use for this,,think the mobile mixers like Matt talked about would be a better conf.
I think we have 1 maybe 2 (mobile mixers)of these in our area but dont see them much and have only poured along side 1 once..It seemed to work well (or at least ok)
Not even sure if mobile mixer is the right name for these trucks,,kinda look like a stone slinger,, product is mixed on site as needed and is dispensed off a conveyor belt

[speedy]

The usual configuration of a 'mobile mixer' is to have 2 aggregate compartments, one for sand, the other for rock. There is a common belt underneath these two compartments and the blend is controlled by adjusting the gate openings. There is a cement powder tank that dispenses by auger and a highly accurate water injection system too, plus admix dispensing pumps too. Some also dispense fibre for reinforcement, and have coloured concrete capability too.

This is 'volumetric' concrete batching as opposed to 'gravimetric' (weight). Just like mixing in a mortar mixer.... 4 parts sand, 3 parts rock, 2 parts cement powder, & a pail of water, only it's continual.

All this drops into a mixing auger to blend it all together. And the mix comes out the end & down a short chute, to which you can add extensions. The mixing auger can be raised or lowered to extend the mixing time, and slewed left & right.

This mix is very FRESH, so the slump is somewhat deceiving as the cement has had the time is needs to stabilize the absorption of water, hence, it may seem too wet. Another quirk of this fresh mix is 'false set'. Soon after it is placed, it seems as if it is 'flash setting'. There have been admixtures developed to counter this, although there is nothing wrong with the mix, this also happens in a mixer drum, but you never get to see it.

I would imagine it takes an especially good man to properly operate one of these, as he has to be a batchman and mixer driver. Cool thing is that you can change the mix on the fly, sandy, rocky, wet, dry, high strength, low strength. A lot going on there.

Here's a link to a manufacturer: www.globalmixer.com/

[batchmaster]

I've never seen a mobile mixer pour but we have loaded one up here when we had some highway work going on close. I think they were doing some kind of latex job or something, the guy was talking about how nasty it was.

[advancemixer]

it would be like gunite and look what that does to the barrel. hydration from the sand has happened.

[batchmaster]

exactly, unless they are baking their materials, not possible.

[vegastom69]

hey guys just to let you know it can be done in vegas we have rear discharge mixers ,back a few years we took loads 4 hours away up to beaty the trucks were all loaded dr batch with drum in slow agg the sand was put in 1st sand 2nd cement and fly ash 3rd the sand and rock was left in seprate pilles for days to make sure they were dry not hard to do in vegas,rotated the drum as slow as possiable you all know we did not want any flat spots on drums (lol) after we arrived on job water was added to loads from a water truck, belive me all my years driving this was a 1st for me but worked out well . but if you stop and think what they are doing it make sence layer the agg and sand keep power from sand you will be fine . and well all know that todays concrete is crete on drugs thumbs up to master builders

[batchmaster]

but that was in regular mixers right, didn't need anything special, i went to a little school at a local cement supplier, and mb was talking about those loads in vegas, they didn't say anything about dry batching the loads, they made it seem like their chemicals did the trick, retarded the mix until it got there, like a four hour run. but if you were actually there then...but even slow turning the drum, going to mix up some right, did the load off load fine, or did you have any balling?

[intruder473]

We did it 5 nights a week for a month 10 trucks 105 miles oneway its no fun