In the mid 1980s, the North Carolina Department of Transportation sponsored a two year study investigating the properties of high strength concrete using materials from North Carolina, including expanded slate aggregate. This study was conducted at North Carolina State University. One of the primary goals was to provide basic “round figure” data on certain “specialty” concretes such as lightweight concrete. “The purpose of this research was not so much to produce the absolute highest strengths attainable as it was to produce the highest strengths which could reasonably be attained in practice with more or less conventional materials and methods.”