The headline race Sunday is expected to draw more than 190,000 people to the track. Forty-eight people remained hospitalized Tuesday with injuries from Saturday night's collapse. Two were listed in critical condition. Tindall Corp. of Spartanburg, S.C., which made the slabs for the walkway, has dispatched an engineer and a private firm to investigate the collapse. The track's own engineers also are investigating.
Wet concrete is poured around stretched steel cables to make slabs.
After the slabs dry, the tension on the cables is released, strengthening the concrete. The design is widely used for all kinds of structures, engineers said. We don't know exactly what did, but we are fairly confident that that was not a cause. It is one of the most bizarre things I have ever seen. All 11 cables buried in the concrete were corroded, causing the bridge to bow and then snap, said Don Goins, the state's chief engineer.