Initial Ride Quality of Hot-Mix Asphalt Pavements (05-1453)**
Mary Stroup-Gardiner, Gardiner Technical Services, LLC
Alan Carter, Universite du Quebec, Canada
Priyabrata (Thomas) Das, Auburn University
Brian Bowman, Auburn University

Ride quality assessed with an inertial profiler on flexible pavement was used to provide initial information on the following key issues: repeatability associated with IRI values for a wide range of hot mix asphalt (HMA) material variables, timing of acceptance testing for initial ride quality, IRI changes with type of roadway, influence of stops and starts in the paving operation on ride quality, identification of “bump”, and effect of grinding on IRI. IRI was calculated for 25-foot intervals instead of the standard 0.1 mi (528 feet) for all testing in order to highlight local anomalies such as bumps due to paving stoppages. Results indicate that the standard deviation of three replicate passes with an inertial profiler is 5 in/mi (includes 46 HMA mixes). IRI measurements with time suggest that initial acceptance testing can be conducted within 7 days, thereby allowing more flexibility in scheduling by the agency. Limited traffic also slightly reduces the IRI values, which is to the contractor’s advantage. IRI values are defined for two-lane county roads, medium to high traffic facilities. Separate IRI ranges are suggested for each of these categories based on the type of HMA construction: new, repair and overlay, and mill and overlay. These ranges are set for best and good practices (continuous paving, no stoppages; consistent supply of trucks, very short stops). IRI values greater than 125 in/mi in any given 25-foot interval indicate a bump; bumps can be ground so that these areas have IRI values of less than 100 in/mi.