Concrete Overlay Design of Flexible Pavement Using the NCHRP 1-37A Design Guide —A Case Study—

Abstract

A pavement evaluation and concrete overlay design was completed for a 10- mile section of flexible pavement on Interstate 35 of the Kansas Turnpike. A records review, visual condition survey, rutting measurements, and testing with a falling weight deflectometer (FWD) was conducted. Coring was also performed to establish the condition of underlying hot mixed asphalt (HMA) layers. The results were used to evaluate the conditions of the in-place pavement and to design rehabilitation alternatives. The evaluation indicated that the existing flexible pavement had deteriorated to a state that requires rehabilitation. A requirement of the design was to maintain the existing surface elevation, thus, the design portland cement concrete (PCC) overlay thickness would be milled off from the existing 330-mm (13-in) HMA layer thickness. Several alternative concrete overlays were designed and evaluated using the new Mechanistic-Empirical Pavement Design Guide (ME PDG) from NCHRP 1-37A. A variety of informative sensitivity results are shown including an optimized concrete overlay design for the I-35 project and comparison is made with the 1993 AASHTO procedure. In addition, designs are also presented for lower traffic conditions to illustrate its impact on design. The results demonstrate the practical use, reasonableness, and benefits of the new M-E PDG for PCC overlay design.