More than five decades ago, engineers in northern Illinois tried something that was unusual for highway construction at the time: instead of using hundreds of thousands of cubic yards of traditional soil and aggregate, they built the core of a major road embankment with 246,000 cubic yards of coal fly ash.
The experiment took place near Waukegan in 1972, beneath a roughly 7,500-foot section of expressway. More than 50 years later, the project has become an important example of how an industrial waste product could be transformed into a useful construction material.
