the 2nd Cement reciepe is not realy 3 mandatory ores per craft, as Alumina can be created via processed and/or pellets, but yeah, its definatly more than the first one.
Ive never used washing for ores, most is done with direct sorting (sometimes to supplement indirect sorting), and I guess its up to what ores do you use elsewhere, and how easy they are produced.
In direct sorting, both Aluminium and Silicon use chunks, while iron is easier to get via simple crushed ore.
So with processed/pelleted Aluminium and easier iron, it uses less Silicon, which in this reciepe cant be upgraded since its direct ore.
I just ran the numbers for 100 cement each, and in raw (minable) ore, its 1:1,25. (when Alumina is made with pellets)
But it uses alot more byproducts, like sodium(s) in the almunia chain.
There is no easy way to find out if its worth it, since its only machine building material anyway, unless you wanna pave the world
Again, i have no clue about washing for ores, so this maybe is not the droid you looking for
I also never went for the T3 lead ingots, as lead is not really used that much that its worth it upgrading for less raw ore use.
Might try it, since im on a map with Madclowns science alternatives, which can use lead plates for SP1