Durability Aspects of Stabilized Quarry By-product Pavement Base and Subbase Applications

Recent research conducted at the Illinois Center for Transportation (ICT-R27-168) evaluated sustainable applications of quarry by-products (QB) or QB blended with coarse-recycled aggregates as chemically stabilized base and subbase layers. The research proved that stabilized QB pavement applications have satisfactory pavement performance. This project (ICT-R27-SP38) investigates the durability aspects of previously evaluated stabilized base/subbase QB applications due to fluctuations in temperature and moisture content, which induce freeze-thaw cycles during winter and wetting-drying conditions in the stabilized QB layers. Durability tests were conducted on samples extracted from field test sections previously evaluated with Accelerated Pavement Testing (APT) as well as on new samples compacted in the laboratory with the same material types and combinations. Field-extracted samples were exposed to multiple cycles of freezing and thawing and wetting and drying over three years in the field. Both laboratory and field samples were evaluated following the AASHTO T 135 wet-dry and AASHTO T 136 freeze-thaw durability test protocols, respectively. Results of durability testing indicated better wet-dry durability performance of QB samples when compared to freeze-thaw durability, particularly for samples stabilized with Type I Portland cement. The majority of field and laboratory samples had a cumulative soil-cement loss of 10% or lower following 12 cycles of wetting and drying indicating satisfactory performance. Note that 10% soil-cement loss is used in Illinois DOT practice to determine the percentage of stabilizing agent that ensures durability. Results also indicated that cement-stabilized QB materials benefited from long-term curing in the field, while fly ash–stabilized QB materials were less durable after exposure to multiple freeze-thaw and wet-dry cycles during and after APT testing. Further, durability samples having QB materials from dolomitic aggregate sources, i.e. having higher percentages of magnesium in their chemical composition as determined by X-Ray Fluorescence (XRF), exhibited better field performance trends than QB materials with primarily limestone (calcium oxide content) fines. This durability improvement was linked to the cementation observed in the dolomitic fines after exposure to freeze-thaw cycles in the field. Further, higher density and improved packing of QB materials observed in samples compacted at or near maximum dry density resulted in consistently better durability.