CE Materials Part I: Highway Materials Aggregates References: Roberts et.al, “Hot Mix Asphalt Materials, Mixture Design, and Construction” NAPA Education Foundation, 1996. WSDOT Pavement Guide available at http://training.ce.washington.edu/WSDOT/ Atkins 2003 Aggregates Natural Soil vs. Aggregates? Aggregate: usually refers to a coarse- grained soil that has in some way been processed or sorted.