Development of an Overlay Design Procedure for Composite Pavements

The composite overlay design procedure currently used by ODOT sometimes produces very large overlay thicknesses that are deemed structurally unnecessary, especially for composite pavements already with thick asphalt overlays. This study was initiated to investigate the cause(s) and to develop a revised procedure. The current ODOT pavement overlay thickness design procedure is based on the structural deficiency approach recommended by the 1993 AASHTO Pavement Design Guide. The current procedure uses a simple, closed form procedure to back-calculate the subgrade modulus and the effective modulus of the existing pavement structure from the measured Falling Weight Deflectometer (FWD) surface deflections. The simplistic treatment of the AC and PCC layers as a combined layer in the back-calculation model was found to significantly underestimate the moduli of the existing pavement. A three-layer elastic model is adopted in lieu of the two-layer model used in the current procedure for back-calculation. The three-layer model allows the composite pavement structure to be modeled more accurately. The elastic moduli of the asphalt concrete layer and the underlying Portland cement concrete can both be back-calculated, instead of being combined as one. A revised overlay design procedure has been developed. A comparison of the revised procedure and the current procedure shows that the three-layer model produces higher effective thickness than the two-layer model for the same pavement structure. Therefore, the required overlay thickness is reduced. The revised design software has been implemented into a design software program, which also offers an optional feature that takes into consideration the temperature effects on the asphalt concrete moduli.

• Record URL:
  http://cdm16007.contentdm.oclc.org/cdm/ref/collection/p267401ccp2/id/15849#img_view_text_container
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/35015
• Corporate Authors:

  University of Toledo, Ohio

  2801 West Bancroft Street
  Toledo, OH  United States  43606-3390

  Ohio Department of Transportation

  1980 West Broad Street
  Columbus, OH  United States  43223

  Federal Highway Administration

  Washington, DC  United States 
• Authors:
  • Hu, Liangbo
  • Chou, Eddie
• Publication Date: 2017-9

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Photos; References; Tables;
• Pagination: 98p

Subject/Index Terms

• TRT Terms: Asphalt concrete; Composite pavements; Falling weight deflectometers; Overlays (Pavements); Pavement design; Pavement layers; Portland cement concrete; Structural analysis
• Geographic Terms: Ohio
• Subject Areas: Design; Highways; Maintenance and Preservation; Pavements;

Filing Info

• Accession Number: 01663402
• Record Type: Publication
• Report/Paper Numbers: FHWA/OH-2017-23
• Contract Numbers: SJN 13483
• Files: TRIS, ATRI, USDOT, STATEDOT
• Created Date: Mar 21 2018 10:12AM