Yes, 6" should be sufficient and EMAWican is correct about the importance of your subgrade. If using WWF (wire mesh) reinforcing, make sure it is 6"x6" and a heavier, paving grade like W4.7xW4.7. Also, when you cut your concrete, don't go any bigger than 12'x12' panels and cut about 1 1/2" deep for 6" paving.