M, H and P class slabs

That's correct Mel_house, there are also supposedly mixtures so you can get a M/H or H/E....but ususally it's M, H or P these days

M - Moderately reactive - silt or clay sites, which can experience moderate ground movement from moisture changes

H - Highly reactive - clay sites, with high ground movement etc.

E - Extremely reactive - extreme ground movement etc.

P - Problem sites which include soft soils, eg. soft clay or silt or loose sand, landslip, mine, subsidence, collapsing soils, erosion, abnormal moisture or those that cant be classified otherwise.

There are various internal beam requirement for M, H, E & P slabs. Therefore you would think that the P class slab would be the strongest suitable for the site.

Whoops...sorry *P* didn't scroll down to see you'd already answered....