I have a $100\ \text{psi}, 300\ \text{cfm}$ air compressor that we use for running power tools, I need a way to inject mortar deep into a small opening and was wondering if anyone had experience with setups like this. From doing some research on the topic it sounds like historically it's pretty much what they did before the specialized concrete pumps we have now were around. I'm not worried about air mixing with the mortar but it would be interesting to know how much force this would have on the person at the operating end of the hose. I can't see it being more than a fire hose as long as we stick to a relatively small hose (the air input is $1"$ and I was planning on $1/2"$ for the output hose) All fittings and hoses are rated for $150\ \text{psi}$ and I was planning on buying a $200\ \text{psi}$ rated pressure tank. Am I missing anything here?

edit Just in case someone wanted to see my math here, I used the the following numbers density of (flowable grout) $= 128.7 \ \text{lbs/ft}^3 = 2061.6 \ \text{kg/m}^3$ Operating pressure $= 100\ \text{psi} = 689.476\ \text{kN/m}^2$

using $P =\rho*g*h$, we get $689476 = 2.0616*9.85*h$, where $h=\frac{689476}{2061.6*9.85} = 34\ \text{m}$ of pressure $= 111\ \text{ft}$ of available head (minus what's lost from friction with the hose/pipe/fittings) Should still be plenty enough pressure for what I need though also pressure at the nozzle would be $\frac{100}{0.7853} = 127.3\ \text{lbs}$, probably gonna bump that hose up to $3/4"$

Rough drawing of setup

edit - Drawing explanation As addressed in the comments I was just going to use ball valves at the grout intake air inlet and grout outlet, the pressure tanks I was looking at were 200 PSI 5 gallon water tanks that have like 8 ports already built into them. The mortar works out to about 4.7 gallons of flowable mortar/40# bag so it should work out for the smaller jobs we'd be using it for.

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    $\begingroup$ You should put your math into your original question - save people having to trawl through comments. $\endgroup$ – Solar Mike Feb 22 '18 at 12:41
  • $\begingroup$ The gravity feed - will that pressure exceed the pressure inside the tank? or else it gets blown back up... $\endgroup$ – Solar Mike Feb 22 '18 at 12:42
  • $\begingroup$ Gravity feed could have a checkvalve inline - you wouldn't be able to feed in while the compressor was running, but could pump in batches $\endgroup$ – Jonathan R Swift Feb 22 '18 at 14:59
  • $\begingroup$ Can you explain your drawing? if the air pressure isn't applied "behind" the mortar flow, it won't do anything useful. If all you want to do is empty the hole of "liquid" then use a vacuuum cleaner system to do so before pouring mortar. $\endgroup$ – Carl Witthoft Feb 22 '18 at 18:51
  • $\begingroup$ I understood the container in the drawing to be a storage tank, not the 'hole' $\endgroup$ – Jonathan R Swift Feb 22 '18 at 22:41

I would look at an auger extruder system like I've sketched out. They're good for extruding abrasive pastes like ceramics, mortar or grout. When the motor turns, the mortar would flow, when it stops flow stops. Crappy sketch of auger extruder


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