Perry's about got it. We use 75 instead of 80 ( did the 80 more than once and we seem to come up short with the truck ). 4" is 3.5", use 2 X 4s for your forms. Put either a steel pin or wood stake every 2 to 3 feet ( closer of you are turning or adding ). Put an "added" 2 to 3 inches at the garage slab to help the transition.
Use 1/2 paper at 3 inches and crack it 10 X 10 ( unless you are fighting cracking, then 8 X 8 ). Either crack it or cut it with a saw while it is still green.
Use 6000 PSI over compressed sand will run you about $100 to $125 per yard here in Metro Detroit. Probably more in other areas. All you need to do is call the ready mix place and ask for 5 yards. Then ask for the Cartage costs.
Hope this helps, poured a lot of cement.
