around here we can get it either way
pure portland cement, which comes in 80 or 90lb bags, must be mixed with sand and gravel and of course water
is much more expensive,, maybe 12 bucks of so
then there is concrete, basically premixed which comes in 60lb bags, you just mix it with water it has the sand and gravel
already in there. it is about 2 bucks and change a bag
one bag of portland cement will make alot of concrete when mixed with the required sand and gravel.
i don't remember but i think a couple of bags of portland cement will make up about a yard of concrete.
bob g