In 2009, Illinois used 38,881 tons of fly ash in highway construction; IDOT reported spending $1.75 million while reducing landfill use and cement demand

Illinois highways are increasingly integrating fly ash, a byproduct of coal combustion, as a sustainable option for road construction. This practice not only diverts waste from landfills but also conserves millions by minimizing the reliance on energy-demanding Portland cement. However, recent modifications in power plant technology are limiting the availability of fly ash, prompting the exploration of alternative materials amid the dwindling use of coal.