Durability of Stabilized Quarry By-Products in Base and Subbase Applications

Abstract

AbstractThis paper presents findings from a research project conducted at the Illinois Center for Transportation (ICT) to study durability aspects of chemically stabilized Quarry By-product (QB) materials. The studied applications include chemically stabilized QB fines or blends of QB with coarse-recycled aggregates in base and subbase layers. The material combinations studied were evaluated with Accelerated Pavement Testing (APT) by constructing and loading full-scale pavement test sections utilizing stabilized QB mixes in base and subbase layers. All evaluated QB pavement applications showed satisfactory pavement performance trends, i.e., low subgrade stress levels and low surface rutting accumulation compared to a conventional pavement section used as control. QB samples were extracted from seven field sections constructed using cement and Class C fly ash stabilizers for different material combinations and were subjected to freeze–thaw and wet-dry cycles in a controlled laboratory environment. Prior to conducting the durability study, the field-extracted samples were exposed to multiple cycles of freezing/thawing and wetting/drying over the course of three years. Samples were evaluated by AASHTO T 135 and AASHTO T 136 for wet-dry and freeze–thaw durability tests, respectively. The results of durability testing indicated that cement-stabilized QB materials benefited from the 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 in the field. Field samples compacted at or near their maximum dry densities consistently showed better performance trends for durability. Further, samples made with dolomitic QB fines benefited from having higher magnesium oxide content and exhibited better durability performance than those of limestone QB materials having higher calcium oxide content. This was linked to more cementation observed in the dolomitic fines after being exposed to freeze–thaw cycles over three winters in the field.KeywordsQuarry by-productQuarry finesDurabilityFreeze–thawWet-dryChemical stabilizationAggregatesRecycled materialsSustainability