Feasibility of Granular Road and Shoulder Recycling Phase II: Gradation Optimization for Improved Performance

The previous IHRB project TR-685 “Feasibility of Granular Road and Shoulder Recycling” (Li et al. 2018a, 2018b) involved construction and testing of several granular road and shoulder test sections in which existing surface materials were recycled and blended with virgin materials. One of the most useful outcomes of the TR-685 Phase I project is the Gradation Optimization tool (Figure 1), a spreadsheet that allows engineers to determine the optimum mixture of existing granular surface materials with up to three virgin quarry materials (along with a selected thickness of subgrade for plasticity if desired). Conceptually, the optimum gradation is the one that comes as close as physically possible to a design target gradation having the tightest particle packing (Figure 2), which should give the highest strength and minimize particle breakage. However, the Gradation Optimization tool was developed based on actual California Bearing Ratio (CBR) tests of low-strength crushed limestone aggregates from southwest Iowa, and it hypothesized that the design gradation should be different for other aggregates that have different strengths, angularities, and geologic origins. Additionally, the freeze-thaw performance and long-term stiffness and permanent deformation should be considered in the design of the optimized gradations.

• Record URL:
  • https://ideas.iowadot.gov/subdomain/ideas-main/end/node/3070?qmzn=iKFrYf#Active

Language

• English

Project

• Status: Active
• Funding: $214,843.00
• Contract Numbers:

  TR-797

• Sponsor Organizations:

  Iowa Department of Transportation

  800 Lincoln Way
  Ames, IA  United States  50010
• Managing Organizations:

  Iowa Department of Transportation

  800 Lincoln Way
  Ames, IA  United States  50010

  Iowa Highway Research Board

  Iowa Department of Transportation
  800 Lincoln Way
  Ames, IA  United States  50010
• Project Managers:

  Goetz, Vanessa

• Performing Organizations:

  Iowa State University, Ames

  Center for Transportation Research and Education
  2711 South Loop Drive, Suite 4700
  Ames, IA  United States  50010-8664

  Michigan State University, East Lansing

  Department of Civil & Environmental Engineering
  Institute for Community Development
  East Lansing, MI  United States  48824-1226
• Principal Investigators:

  Ashlock, Jeramy

  Cetin, Bora

• Start Date: 20210915
• Expected Completion Date: 20251031
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Aggregate gradation; Gravel roads; Recycling; Road shoulders
• Geographic Terms: Iowa
• Subject Areas: Highways; Materials; Pavements;

Filing Info

• Accession Number: 01945648
• Record Type: Research project
• Source Agency: Iowa Department of Transportation
• Contract Numbers: TR-797
• Files: RIP, STATEDOT
• Created Date: Feb 12 2025 6:47PM