Interchange Materials Lab
February 2024
Vol. 52, Iss. 2
Put to the test: asphalt, concrete, paint and steel The following was originally published in the August 2018 edition of Interchange. WYDOT Public Affairs sat down with the Materials Program and learned that it’s been business as usual for State Materials Engineer Greg Milburn and his 41 person staff. “There’s not a lot of changes in our industry,” Milburn said. “Obviously, there have been various upgrades over time such as new mix design procedures, modernized equipment, and implementing new specifications. But fundamentally, we’re doing what we’ve been doing for 100 years, which is testing materials and designing roads.”
Photo: Mark Horan/WYDOT
From recommending which highway sections need work the most, to the final check to make sure all materials used to build a highway have been tested and certified, WYDOT’s Materials Program is involved in projects from start to finish. The program has laboratories that test virtually all materials used by the department, from the components of asphalt or concrete pavement to the reinforcing steel and bolts used in bridges and the paint used to stripe the completed highways. “Essentially, anything that is incorporated into a project that’s materials related has to be tested and/or certified, from barbed wire to bridge girders,” State Materials Engineer Greg Milburn said. “We test lots of different materials and products in-house. We test how thick the galvanization is on the wire used in fences. We test bridge paint. We even test the roundness of glass beads used to increase reflectivity of traffic paint.” But the program’s responsibilities go beyond testing materials. Its Pavement Management System is one of the primary tools used to decide if and when a project is added to the State Transportation Improvement Program. The PMS rates the condition of pavements based on roughness, rutting, cracking and friction using information gathered by consultants and Materials technicians who drive the state’s highways annually with special testing equipment.
Photo: Mark Horan/WYDOT
Job Lopez, in the Asphalt Laboratory, prepares a binder specimen in the Dynamic Shear Rheometer to evaluate specification compliance.
Terrence Gavagan, in the Soils and Surfacing Laboratory, demonstrating sieve analysis of fine aggregate.
The pavement condition ratings are used to predict the future performance of the pavement based on computer models. That helps WYDOT determine which highway sections need work the most and the appropriate rehabilitation strategies to use. Once a project is added to the STIP, engineers in the Materials Program begin working to find what kind of surfacing materials should be used and how thick each layer needs to be. The recommended pavement thickness depends on current and projected traffic volumes, particularly for trucks, the stability of the soil and geology under the route and how long the pavement is expected to last. “Whether it’s concrete or asphalt, or if the project is for maintenance, rehabilitation, reconstruction or new construction, we design it for a particular life,” Milburn said. “We design for 10-year, 20-year and 30-year life spans.” For highways with relatively consistent traffic volumes, the recommended thickness of the pavement can vary widely based on the soil conditions under the road. “We need to know how strong the roadbed will be,” Milburn said. “Geology drills it and sends us samples to test. We have arMaterials continued on page 3