Explain your idea

The Mixer is currently very, very slow, and esp. with some of the suggested upcoming changes that encourage the use of liquid concrete, the mixer needs to be scaled out massively because it makes what feels like <10mB/t. I suggest scaling the processing amount per tick with the amount of recipe fluid, so if you have a full 8000mB tank of [input], it makes quickly, but the last few 10s of mB of [input] take longer to convert.

I'd suggest the square root of the volume, to give the best incentive, but for simplicity I doubt linear would matter that much. For sqrt(8000mB) + 1mB, it's 90mB/t, 4000mB it's ~64mB/t, etc, and for linear I'd suggest volume /100 + 1 - so max out at ~80mB/t and scaling down to something small.