Fly ash is a byproduct of coal-burning electric plants. The ash is trapped and collected, then used as a partial substitute for Portland cement. While it is true that this process creates what is now considered a green building material, questions remain about how safe fly ash truly is. Title: Comparison of Class C Versus Class F Fly Ash for Concrete Pavement Author: WisDOT Research & Library Unit Subject: 0092-12-04, 2015. This project brief summarizes the Wisconsin Highway Research Program project, Laboratory Study for Comparison of Class C Versus Class F Fly Ash for Concrete Pavement. A New Approach to the Production of Bricks Made of 100% Fly Ash Kedsarin Pimraksa, Matthias Wilhelm, Michael Kochberger and Werner Wruss Vienna University of Technology, Institute for Chemical Technology of Inorganic Materials, Getreidemarkt 9/161 Boral’s Carbon Burn-Out technology is used to improve the quality of fly ash produced at coal-fueled electric generating stations, making the ash suitable for use in concrete and other high-value applications.