blast furnace slag, which means an industrial waste product has been substituted for virgin material (in our case, that means more than seven cubic yards of recycled material). The slag will make the concrete denser and harder once it has fully cured.
The steel anchor bolts will hold the steel columns in place. The bolts are embedded deeply enough (20" - 27") to secure the house, even during a category 5 hurricane. Some of the bolts moved a bit during the concrete pour, so they'll need to be "adjusted" with a sledge hammer before the columns can be erected.
The notch at the edge of the slab is an interesting detail. The insulated wall panels we're using will sit in the notch, which will have the primary benefit of shedding rain water away from the house, to prevent it from penetrating at the floor level. We've interrupted the notch at all of the door openings, where the slab edge will support each door's threshold.
front porch (the rectangular patch of dirt will be the porch).