We are extending our house and having a retaining wall built of bricks and mortar to make room for it. The architect has specified 'sulphate-free hardcore' to backfill. I suppose this is because of possible sulfate attack on the mortar.
Our builder is going to use rubble from the demolition of a 70s concrete block utility room as the fill. This doesn't contain any plasterboard but the walls were plastered. Should I be concerned?
Leo