Pheidole are known to do excellently in ytong nests, but Solenopsis are capable of chewing through the ytong, destroying it and potentially escaping, so I wouldn't recommend using a ytong nest for them
What about Pheidole pallidula, will they chew the ytong?
I'm in the process of deciding what formicarium to build / buy for my Pheidole pallidula and, apart of not giving them tiny holes where they can escape from, it also has to be nom nom proof.
Not sure about what exact kind of Pheidole they are, but the ones I have on my garden have chewed through my brick and cement house and infested it several times, so ytong...
Or Paris plaster, would that work out or just be something they can sharpen their mandibles on? It can be mixed with different proportions of water to make it harder.