It is now possible to produce architectural concrete containing aggregate of any color. Researchers have been working to develop plastic aggregates that can replace conventional mineral aggregates in concrete. They have discovered that an engineering thermoplastic called polybutylene terephthalate (PBT) had the greatest potential. Its high mechanical strength, low moisture absorption, and good dimensional stability contribute to its excellent performance as an aggregate. In laboratory test, concrete containing an aggregate mix of virgin and recycled PBT had a 28-day compressive strength of 5500 psi. Because plastic aggregate absorbs little moisture, the concrete also performed well in freeze-thaw durability tests. Also, almost any color shade is possible.
The first installation of plastic aggregate concrete was at the General Electric "Living Environments" concept house built in Pittsfield, Massachusetts, in 1989. The concept house features plastic aggregate concrete in several areas. Concrete floors in the basement contain various colors of plastic aggregate and have a terrazzo-style finish produced by wet grinding. A concrete patio contains a mix of gray, white, and black plastic aggregate. Plastic aggregate even tops the home's kitchen counters.