Iowa Department of Transportation
Iowa Highway Research Board
Jeramy Ashlockjashlock@iastate.edu email >
Faculty Affiliate, InTrans
Halil Ceylanhceylan@iastate.edu email >
Cassandra J. Rutherford
About the research
The goal of this project was to investigate the performance of granular road sections stabilized with quarry fines byproducts and perform a benefit-cost analysis (BCA) to find the most beneficial quarry fines options for stabilization.
Five sources of quarry fines were selected among 19 quarries across Iowa to build 3 test sections in Jones County, Iowa, and 4 sections in Boone County, Iowa. These two sites are among the most populated roads with relatively stiff subbase and subgrade layers, and they suffer from heavy traffic loads and freeze-thaw effects during winter and spring seasons. Construction and maintenance procedures for the test sections are detailed, and the associated costs of aggregate, hauling, and equipment are also documented in this report.
Extensive laboratory and field tests were performed before and after construction, as well as after one seasonal freeze-thaw period from 2019 to 2020, to evaluate and monitor the performance of the constructed sections. A BCA was performed using the documented construction and maintenance costs for service life scenarios of 20, 30, 40, and 50 years. A benefit-cost ratio (BCR) was calculated for each test section for different scenarios based on various performance measures including gravel content change, average fines content, total breakage, gravel-to-sand ratio, stiffness, shear strength, surface roughness, and dust emission. Performance measures were categorized into three overall mechanistic performance-based groups, and their BCRs were compared.
Overall, the results of this study showed that stabilization by quarry fines improved performance by providing binding between the surface aggregates, reducing dust emission and gravel loss, and increasing the stiffness and strength of the surface layers. Stabilization could be cost-effective by reducing the maintenance frequency depending on the material, hauling, and labor costs. The Limestone and Moscow Mine sections in Jones County, and Moscow and Ames Mine sections in Boone County had the best performance and cost-effectiveness among all stabilized sections. Although the Clay Slurry material was helpful to reduce dust emission compared to the rest of the sections, sections with the Clay Slurry were among the average-performance sections, and the increased construction costs made them a less cost-effective option for both counties.