Abstract
The aggregate gradations specified by the Indiana Department of Transportation (INDOT) differ from those of the American Association of State Highway and Transportation Officials (AASHTO). Preliminary discussions suggest that adopting AASHTO standard gradation sizes could provide national alignment and simplify production for those operating in multiple states and supplying projects not subject to INDOT specifications. A comprehensive study was performed to evaluate the current INDOT specifications for coarse and fine aggregate gradations and to assess the potential impacts and feasibility of adopting AASHTO-specified gradations. A comparative analysis of INDOT gradations against AASHTO, ASTM International (ASTM), and those of neighboring states (Ohio, Illinois, Kentucky, and Michigan) was performed. Specifically, the study examined gradations used in concrete, asphalt, and unbound applications. Additionally, surveys and interviews were conducted with industry stakeholders (e.g., producers, contractors, and engineers) in the aggregate, concrete, and asphalt sectors to gain further insight. Results showed that AASHTO offers gradations similar to those currently used by INDOT. Industry stakeholders indicated that transitioning to AASHTO could provide uniform standards with neighboring states and other entities (e.g., ASTM, Federal Aviation Administration), generate economic benefits, improve production consistency, and enhance operational efficiency. Concrete and asphalt stakeholders suggested that adopting these gradations could provide greater flexibility for designing and optimizing mixtures. To shift to aggregate gradations specified by AASHTO, it is advisable to create a comprehensive, multistep plan to reduce disruptions to ongoing projects and the operational processes of industry stakeholders.
Keywords
aggregate gradation, INDOT, AASHTO, ASTM, mixture optimization, concrete pavements, asphalt pavements
Report Number
FHWA/IN/JTRP-2026/19
SPR Number
4914
Sponsoring Organization
Indiana Department of Transportation
Performing Organization
Joint Transportation Research Program
Publisher Place
West Lafayette, Indiana
Date of Version
2026
DOI
10.5703/1288284318648
Recommended Citation
Elgaali, H. H., Shah, A., & Olek, J. (2026). Evaluation of aggregate gradation specifications and the feasibility of harmonization with AASHTO standards (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2026/19). West Lafayette, IN: Purdue University. https://doi.org/10.5703/1288284318648
SPR-4914 Technical Summary