Excavation and Piers

Here's where we're up to to date. Excavation was done a little over a week ago. Piers have been installed. I was expecting traditional bored holes filled with concrete, however, they appear to use blade piers. These are steel tubes with a corkscrew style blade on the end that are twisted into the ground until they reach the solid ground. Our soil is very clay heavy. I'm not sure how I feel about the blade piers. From what I have read on the net, they are stronger than concrete, are faster to install, and avoid the need to remove spoil, get a council inspection etc. I'm not sure how they go with corrosion. From some reports they're good for 40 years, longer if they are galvanised. They don't appear to be galvanised. Anyway, they'll outlast me, so....