emptying cement bin

emptying cement bin

Postby harberconcrete on Wed May 05, 2010 2:49 pm

I have been involved with a couple of projects that require the complete emptying/clean out of my cement bin. Currently I run almost all of the cement into out into a supersack and then climb into the bin and push the cement by hand to the sides of the bin so that the screw will catch it (repeating this step 2 or 3 times). Any one have a better way of cleaning the bin?
Brad
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Re: emptying cement bin

Postby smnstn on Mon May 10, 2010 3:19 pm

Yes, Brad -- the final technique may depend on the brand of machine you are working with, and what you are reloading with. But for most of those types of projects I have been involved with, contamination of one cement by another is not a problem. Generally speaking, I have supervised reloading with Rapid Set or Fondue cements for HP applications. Since you need to recalibrate for those projects anyway, simply load the new cement on top of what remains in your bin after emptying into a super sack. Then, if you are in your yard and have access to this super sack while re-calibrating for the project at hand, capture the first couple of runs and dump them into your super sack on top of your regular cement. When you reload the contents of the big bag, the specialty cement will be so dispersed, you won't notice it at all, yet you don't have to waste it or climb into the bin and inhale all the harmful silicates.

If you have the type of cement bin with the auger that conveys the cement to discharge directly into the mixer throat and not onto a belt or chain drag, it will take about 500 pounds of cement to recharge the tube if you have drawn it down to the point where no more cement will come out. You may have noticed this if you calibrate your cement for five trials to a specific count. Each successive trial is heavier than the last. I have had to run as many as 11 trials with some cements and equipment to get 3 consecutive consistent runs. This is due to the recharging, or "priming" of the new product to the point where it feeds consistently. You can also dump the cement from the calibration trials back into the top of the cement bin, and any of the original cement left over will become so diluted and dispersed among the new stuff, it will never be evident. So save your back and lungs. Unless you have a bin that retains over 1,000 pounds, or ten bags, of cement, I wouldn't worry about it. If the inspecting engineer has problems with your technique, accommodate him/her. But the likelihood of any detectable contamination from one cement to the other is not great.

Simon
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Re: emptying cement bin

Postby harberconcrete on Mon May 10, 2010 10:41 pm

Thanks Simon, unfortunately the materials I am using contain a fairly large percentage of dry color or are white cement which would most likely show up somewhere if I placed a regular mix for a slab. I had this happen on one job and although the customer was OK as they were going to tile over the concrete any way I guess I will continue to respirator up and climb in.
Thanks again.
Brad
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Re: emptying cement bin

Postby smnstn on Tue May 11, 2010 3:47 pm

Gadzooks! I guess I'd get the biggest shop vac I could find from Home Depot, or the equivalent. You might check Northern Tool or Harbor Freight as well. They might have larger capacity units than the conventional sources. I'd dedicate that device to suck cement only, and empty it into the super sack of the appropriate variety. I just can't imagine even color (or non-color) being actually visible after recalibration and/or dispersion, or recharging the discharge stream. I'm also serious about exposing yourself to silicosis. I hope that respirator is a real good one.

I will also take this opportunity to reiterate that, using the Cemen Tech machine as an example, if the cement in the bin is drawn down to a point at which the powder will no longer discharge down into the mixer throat or collection bucket, there cannot be more than 2-3 bags of stuff left in the corners of the bin. If the new cement is then loaded and the discharge tube recharged, CTI recommends a meter count of 1200-1500 to fully charge the system. In the model 100 machines they put out an average of .6 lbs per meter count, so you can estimate how much cement will be cycled through before you can be confident there's a consistent flow. The series 150 machines push out an average 1.0 pound per meter count. In either case, that's a lot of cement. If the new cement is also dragging the dregs of the old stuff with it, even if you dump it back into the top of the bin, the cross-augers will blend this stuff in so well you should never see it. So, without being there to witness what's going on, I can only speak from empirical experience. How's your mix angle when discharging concrete?

S.
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Re: emptying cement bin

Postby smnstn on Tue May 18, 2010 2:37 pm

I just re-read the above posts, and realized I had failed to mention making sure to run the vibrators when you're purging the bin under power. It's loud, so ear protection along with the respirator should be considered. I ignored it for convenience on several occasions and now wear two very powerful hearing aids ... just another maintenance problem. But if you use the vibrators, even hand triggering them, it should consolidate the remnants in the cement bin fairly quickly and expedite the process.

S.
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