By looking at it I do assume it weighs a ton it doesn’t look like a board at allI might have misunderstood, but the soffit board is usually light weight, I assume that's because it's overhanging. A 50mm thick concrete slab 30cm wide (say) would weigh a ton by the time you went round the house, surely?
Edit - just seen the pics
I’ll be taking it easy with the SDS in case it cracks and falls taking me with it