Skeptics say it's nearly impossible to build a superflat floor when a dry shake floor hardener is also specified. Success is even less likely if workers have never built a superflat floor. But the skeptics are quiet now; it's been done on a General Motors expansion project in Flint, Michigan. The project included more than half a million square feet of 8-inch-thick superflat floors, and an additional 615,000 square feet of floor required to be only half as flat.
A mechanized finishing system was used for the floor. It included three pieces of equipment:
- A rotating eccentric shaft vibratory screed strikes off and consolidates the concrete.
- A hydraulic-driven material spreader with a vane feeder spreads the floor hardener.
- A tamper screed embeds the floor hardener.
Special finishing equipment included a long-handled straightedge with an adjustable head that allowed the finisher to vary the angle of the handle for cutting high spots or filling low spots.