Case Study
US 90 North: HiMA Breakthrough in Midway, FL
Introduction
In Midway, Florida, there are two large truck stops on US 90 serving traffic from I-10, just west of Tallahassee. In 2018, an average of 1,326 trucks per day traveled on US 90 north (west) of I-10, while 1,665 trucks per day used this highway south (east) of I-10 toward Tallahassee.
Challenge
Trucks entering and leaving the Pilot and Flying J Travel Centers slow and stop to turn into one of the stores, or slowly accelerate as they leave. The combination of heavy axle loads and slow-moving traffic led to severe rutting on US 90 -over 5 cm (2 in). As a result, the Florida Department of Transportation (FDOT) planned to reconstruct this highway section using the Portland cement concrete pavement.
Resolution
As a stopgap measure, FDOT decided to remove and replace about 6.4 cm (2 ½ in) of hot mix with a dense-graded, 12.5 mm nominal maximum aggregate size “Friction Course” mixture using HiMA. FDOT engineers had observed the excellent performance of test sections with mixtures using HiMA at the National Center for Asphalt Technology test track. They decided to try it out on this demanding highway section where the asphalt never worked well before. C.W. Roberts Contracting, Inc. (Tallahassee, Florida) was the contractor on this project, which was built in August 2015. Even though the contractor was only allowed to compact the mixture using equipment operated in static mode, they achieved the target in-place density.
In 2020, the HiMA mixture is still in place and performing very well with minimal rutting. The project’s success prompted FDOT to initiate several studies that evaluate HiMA using aggregates and mixtures commonly used in Florida (details below). Since the Midway project in 2014 through 2019, over 385,000 tons of hot mix asphalt requiring the use of high polymer were let to contract by FDOT. As of March 2020, seven terminals are listed on FDOT’s Approved Products List for supplying high polymer for FDOT projects.