Used retarder on a job yesterday in between trucks where mud was going to be about 2 hrs old. threw it in the hopper, wet it a bit and circulated it about every 20 mins. Worked like a charm... much better than cleaning up and starting over or even worse losing system. Only complaint was when cleaning up, the "tight" spots in the hopper and around the valve were caked with set up mud. I don't have an agitator, so I guess thats to be expected. Did what I could with a shovel while waiting, but some places you can't get to. What do you guys do when your on a job for 4 + hours or so? 

i think that you got lucky,i would put into the truck on the last few yards so it could mix. if i waited 20 minutes to recirculate it would get hot and i would be dumping and washing, thats why you require waste containment. $40- bucks of mud is not worth a boom/line party.

 When i recirculate the pump i usualy pump the hopper low like just to cover the s tube. When i do it that way i dont get anny build up any where. But alot of times when im standing by the run is too long to be bringing the hose back to the hooper. What i do is soften my hooper then pump out my hooper running it dry for a bit alowing the air to push out as much mud as possible till the soft stuff comes out. Then suck all the line back to the outlet break off my pipe then hook up another elbow so that you can recirculate it right off of the the outlet. 

 What i notice when i do that is when pumping the hooper dry pushing the mud out with just the air it pushes out all the rocks well most of it. So after sucking it back and recirculating and making it soft it looks almost like grout. I keep recircuting it and adding water till it comes like slurry then when i started again i just put a little water in the first pipe befor hooking it up again. Works like a charm did it on a couple of 200 + foot runs never failed me.                                                                                    

I did a job a couple weeks ago in which I was told the cleanup mixer would be over an hour wait.  I sucked a sponge and cleaned out the hopper.  When the cleanup arrived (1 hr and 45 mins late) I primed and pumped away and finished the job.  I didn't want to deal with a bunch of hot mud in my system, since we were pouring a slab, and I didn't want to deal with a difficult hopper cleanout.

Der-Putz,

Man I am with you all the way.

Circulating mud, especially with a retarder is effective... but when you know it will be over an hour it isn't IMHO very wise.

Aside from the fact that cleaning out the old set-up crete is too damn hard and really sweaty work, well, it is dangerous.

Way too many accidents happen when you are doing the set-up crete chipping thing. Stupid "little" things that happen: smashed fingers are the most prevelent. A simple AVOIDABLE accident that is many times a LOST TIME accident that never had to happen in the first place.

WASH it out - sit on your azz - wait on the new fresh crete.

It never hurts to put some water in your hopper and stick a sponge in the end of your tip hose while waiting. It keeps the moisture in your boom and helps on the re-start.

And the clean out pile when properly raked down is a nice area to walk on.

Waiting on a load? turn your boom around as soon as the truck is pulling away. Circulate the mud, add some water if needed. get ready for the new stuff. After you have waited for a set amount of time, SUCK THE SPONGE. It is easy because the tip hose is right there and the mud is allready tempered up ti your specs.

Then clean out the hopper.

CHIPPING IS FOR CHUMPS with pumps.

;~)