National Concrete Pavement Technology Center

Project description

A majority of Ohio Department of Transportation's (ODOT's) 4-lane and interstate highways are composite pavement; with the vast majority being Portland cement concrete (PCC) pavement overlaid with asphalt concrete (AC). Each year, ODOT rehabilitates several hundred miles of existing AC/PCC pavements by additional overlay. It is important to have an effective means to evaluate the existing AC/PCC pavements and to design the overlay thickness required to carry anticipated future traffic loading. The pavement overlay thickness design procedure currently exercised by ODOT works well for both flexible and rigid pavements, but it tends to produce overly conservative designs for composite pavements. For composite pavements with relatively thick asphalt overlays, the current design procedure consistently recommends very high overlay thickness that is deemed structurally unnecessary. Research is needed to evaluate and verify the assumptions used for composite pavements in the current overlay design procedure and provide modifications as needed or to develop a new deflection based overlay design procedure for composite pavements. The proposed study investigates the possible cause(s) and finds solution(s) to address the problem within the composite overlay design procedure and to verify and validate the revised procedure through actual pavements. The goals and objectives of this project are to: (1) develop and validate a Falling Weight Deflectometer ‰ÛÜ(FWD) deflection-based overlay design procedure for composite pavements and incorporate it into the most current version of ODOT's overall design software; and (2) provide ODOT with the ability to mechanistically determine the effective thickness of the PCC slab portion of a composite pavement for use in the U.S. Army Corps of Engineers' equation for the design of unbonded concrete overlays.