I suggest you look into a diaphragm mud pump.
They have a Briggs and Stratton type motor turning, through a built in reduction gearbox, a large crank that cycles a connecting rod up and down.
The bottom of the connecting rod is fixed to the center of an approx. 20" diameter reinforced rubber sheet diaphragm.
The pumping chamber is on the bottom side of the diaphragm and has an inlet and an outlet each running through flapping rubber one-way valves so that when the rod pulls up on the diaphragm it will suck in through the suction valve and when the rod pushes down on the diaphragm it will expell through the outlet valve.
It will pump sticks, leaves, sand, gravel, mud, and any other kind of debris that happens to be small enough to fit through the inlet hose strainer.
I have no doubt it will pump papercrete without hesitation.
We rented them from the local construction equipment rental company.
Dan
Dan 520-834-4176 I10 and Twin Peaks
Fundamentals first.
What is the head rating of the pump?
How high are you pumping?
If the pump is rated at 6' head, and you are attempting 10' you are headed for failure even if its pure water.
if you laid the out pipe on the ground does the mix make it thru? You might need to rent a bucket lift.
Hope it helps.
McGinnis
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