The pavement must withstand repeated loads without failing or deforming when airports construct runways for huge planes. Throughout the 1970s, Newark International Airport in New Jersey hosted one of the biggest US operations using coal fly ash in a stabilised pavement base. The stuff wasn't just thrown underground. To make a cementitious base for flexible pavement, engineers used fly ash, lime, Portland cement, and sand. After 20 years or more, the Federal Highway Administration reported that the stabilised parts were still operating satisfactorily. This project was notable because it showed that a material derived from the burning of coal could be made into a structural layer for a large airport. It also provided an early example of the use of an industrial byproduct in the construction of long-life infrastructure.
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