Question: what is the difference between 20 mpa and 25 mpa concrete?
Answer: 20mpa is weaker than 25mpa concrete, 32mpa and 40mpa concrete and so on. As a rule of thumb 20mph concrete is fine for foot traffic, I.e., footpaths and house slabs, depending on your sub base, whilst 25 mph is more appropriate for driveways and light traffic.