I used to do concrete design.
Industry standard for full strength is generally assumed at 28 days but by 3-7 days it should be up near 80-90% of full strength.
One thing you can do at this point is try to keep it wet. There is a misconception that concrete solidifies by drying out. It is actually a chemical reaction with the water combining with the cement to form a new substance. When originally poured, you want as little water in the mix as possible (while still allowing it to be worked) but once it's well set, you want to keep it moist so any free cement has water to react with (Back when I did this we had a cure room which had tanks of water and misters to keep samples constantly moist or wet).
For anyone looking at putting in a pad, avoid fast cure options. The concrete doesn't hold up as well. The primary use for it is in road construction where they can't justify closing a road for longer periods.
