Two things you can try one be a larger diameter of hose or pipe or you can throw a small box of laundry detergent in each load and mix for about 3 minutes

Its not so much a plasticizer as a VMA   you need a high range viscosity modifier.  have used it to pump where there are no or low fines    

use a pump with 5 inch cylinders (tk50) so there is no reduction in your delivery system. also VMA (vmar) is Gods gift to concrete pumping, i carry my own jug just for emergency

light weight concrete and plasticizer does not work period. it wont take the place of water. and if the rock is not soaked thru. all the moisture is absorbed when pressure is put on it. crack open the rock with a hammer and if its dry on the inside its not soaked well enuff. good luck to you

Sounds like the plug is definitely a bleed problem at the valve at higher velocity and increase in delivery pressure. Pumpatube has a point if the valve and spectacle plate is that of a big mouth perhaps the reduction is too great over a small distance for this particular mix design. If you getting slow volume without hassle maybee the solution may be a pump with smaller diameter inlet valve and spectacle plate to try keep the surface area of the valve and seal to a minimum.

Dipstick I never got into light weigh concrete but a good freind told me the best way to get water inside light weigh was the use of a vaccum chamber it pulls all the air out of the rock then when water is injected the rock will pull the water in,thats what I was told, just soaking it in water is not enough when you start pumping no more water thats in the mix under pressure it starts taking up what water there is that my two cents worth , You guys are the best in the world pumping concrete.

If you could get the mix des and a sieve on the agg   i could look at it and tell you what would need to be done to pump it       ?how many feet of line, ?temp of agg, ?Ambiient temp?      sounds like the VMA will help but your building heat on the push   harder you push more heat and acts like fales set   with low water and high plasticizer your concrete will start forming set cystals in you line    you might need some retarder to make things work. just remember water is are pipe lube and you to have some  but then with friction you will have the slump loss that will be the water evaporation and the water/cement ratio will still be the same if you slump up a bit on a long push.      Im a concrete pumper first and a readymix producer 2nd :)   

I did a 19 story highrise with lightweight concrete. It was also plasticized. We had to experiment a lot to get it to pump. We ended up adding water a bit at a time then the plasticizer. We ended up with a 4-5" slump and then plasticizing it to an 8-9 to get it to pump 19 stories.

I also did another project that pored a lightweight material with 800ft of 5" line. It had a similar problem as yours. The result was an incompatibility with all the chemicals in the mud. It was a new mix design and went to total crap if bumper over 300ft. The ready mix changed the chemicals to come from the same company and it went better but not great. We could then pump it 500ft with out issue but still not good enough.

Another project, a tunnel project, had an issue with micro fiber. The micro fiber was dosed at 3 times the manufacturer recommendation. We reduced the fiber and it went better. We could then pump the mix 500+ft instead of 200ft.

air entrainment , whats your percentage ?

and what is happening is a type of segregation , more air entrainment will help with this , and if possible may want to back off the plasticizers some to get the slump down.

usually if you can get 5% +- 1 it would help , If I am having segregation problems I alway increase air , but to me it actually sounds like the cement or flyash content coud go up 40 pounds a yard and this may solve all your problems , more rock =needing more cementuous material to be pumpable.

the amount of cement is about 675 pound a yard. i don't think the amount of cement is the problem

Time to go to 6 inch line and reduce down at your placer.  i know its an extra cost but from what you are saying with no extra weight added to mix design and an air content of 4.5 max. Larger line which will slow the velocity of the concrete and provide you with the ability to speed up without the pressure problems.  Use the nomograph in the manual it will help you

Soak the aggregate pile at concrete plant the night before the pour with a sprinkler.  Lightweight stone absorbs water big time.   If it's not soaked, extra pumping pressure will force all your fluids into the stone.  I've seen 4-5" of slump lost from mixer to end of line from this.  Also, back the throttle down to roughly 1100 RPMS and bump your volume control up to increase pour rate if you're not already doing so, to hell keep the pressure/friction to a minimum in your system. .good luck!  

Use a Putz Kattkreter with 5 inch barrels rated at 54 cu. per hour and add 16-20 ounces of VMA per cu. yd. = Smooth flow with no reduction in your delivery system & Prime with 3 x 80lb bags of masons mortar mix = problem solved

Not sure if this was mentioned but if the moisture of the concrete isnt at a min 80-90mm slump before SuperP then your gonna have a rough time...

We have one project here that has a strict no water added rule, only SuperP, but the SuperP needs a certain amount of moisture to work properly just like everything else in your mixes.

Is there any other additves being added to the mix, like calcium or corrosion inhibitor or Xypex?

Dipstick you guys are not afraid to tackle anything I have to hand it to you.

You all when to a lot of hard work building your pipe line,

what if you would have had enough barges to build a floating

concrete plant so you could have cut your long distance pumping in half.

Anyway you guys are tops in my book GOOD WORK