Dive summary:

• Dark, glossy walls that reflect the area around the newly expanded St. Louis Art Museum comprise 23 tilt-up concrete panels made with a careful mix of Meramec gravel, glacial sand and trap rock aggregates and then polished to a high shine to give the look the architect wanted.
• Local contractor Concrete Coring Company did the finishing, putting on two crews a day for two months to work under tents during the winter and bring the finish to the gloss achieved by 1,500-grit screens.
• Workers had to grind deep into the mixture to properly expose the dark aggregates in the panels, which are each 22 feet high and range from 12 to 42 feet wide.

From the article:

“Consistent aggregate exposure was a key component of the architect’s vision,” says Carl Gregov, VP/COO at Concrete Coring Company. ...