What should I do about the corners? Do they require cement pillars? The garage is about 25' by 20'. What brand or type of cement is recoommended. Here in Texas, the ground shifts because of the high clay content. A car or SUV may be parked on the cement.
if ground shifts a lot why no use 3 inch thick patio slabs 3ft by 3 ft you would only need 24 of them and then you need to level with sand in this case if ground does shift all you would have to do is remove put down more sand and back to level again and if the garage needs to be reinforced then do so at the same time but make it a floating one
First off you won't just use cement you will need concrete. cement is a material that is used to make concrete. For a garage use a 6 bag half air mix. most garages are poured at a 4 in thickness at about a 4-5 in slump. 6 bag mix will give you about a 4000 psi if poured at a 4 in slump. the consitancy to your concrete is important to keep the strength this what I mean by slump. use wire mesh and an synthetic fiber to strengthen your concrete to help prevent cracking. if you have a 25x20x4 you will need 6.25 yards of crete. if your grade isn't good you may want to go with 6.5 yards. if using mesh which is a good idea you will need chairs too.
dig down 6 inches and fill with cement have fun
