Flexible Base Ride Specification Development and Evaluation (0-4760-1)

The Texas Department of Transportation (TxDOT) is implementing a ride specification that uses profile data collected with inertial profilers for acceptance testing of the finished surface. The ride specification, Item 585, is applicable for either hot-mix asphalt or Portland cement concrete pavements and uses the international roughness index computed from profile measurements to quantify the level of ride quality achieved from construction. Prior to this project, TxDOT did not have a standard ride specification for surface treatments over flexible base courses. Since this pavement type comprises a significant percentage of the state highway network, improving the ride quality of surface treatments is of concern to TxDOT engineers responsible for achieving ride quality standards within their districts. To this end, a standard ride specification was necessary to assure (among other factors) that surface treatments are built with acceptable levels of ride quality. This report documents the work performed to establish applicable criteria for a flexible base ride specification. Through a cooperative effort with TxDOT engineers, researchers evaluated proposed criteria using ride data collected from district projects and investigated the effect of texture on ride quality measurements. Based on the analyses of data collected from laboratory and field tests, researchers found that the requirements given in the flexible base ride specification are appropriate to use for acceptance testing of the ride quality of flexible base on surface treatment projects. Applicable recommendations for implementing the specification are provided in the report.