Taking a good mix and adding larger rock and more admix for a 300 yard floor pour tomorrow.  State of Indiana engineer drew up mix design.  She is new at her job too.  Wish me luck and they ordered the pump not the belt.

Just larger rock? Didn't change the batch weight? Theoretically, it should still pump, as now there is less surface area for the paste to cover/lubricate. If you could get the specifics of the mix and post, and let us know your experience.

I'll get all the info since my brother in-law is batchman.  Most of the low curl mixes I've seen are not pump friendly.

Buddy I think I would have your belt on stand by parked next to your Boom Pump just in case.

whats a low curl mix?

I am such a worrier.  Jocky was right and it pumped without a hitch. Old dogs can learn new tricks.  Another 300 to do Wednesday if the finishers aren't sent to another job.

how large is large rock over there

I'm with Murf on this, just what is a "low curl mix" ? As for the larger agg ,just how much larger is it? We pump a lot of 50mm stone here on civil work to achieve strength from the stone and not the cement to reduce thermal cracking.

The rock used in this mix is Indiana limestone #4 which runs a top size of about 43mm. The problem begins when admix is used in excess and cement is minimized.  Todays mix contained fly ash and is being used as a water treatment tank floor.

I once belted a 300cy floor that the company had a propritary admixture they put in the mud. The floor was ultra flat,but the big selling point is not one control joint cut anywhere. It was for A Sysco foods warehouse with forklifts running on it so they didn't want any curling at the saw joints. Whatever they put in the mud worked because I looked at a floor they did a year previous which showed no visible cracking. Also this mud was poured at about a 7" slump.