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How to Make Sweaty, Freezing, Versatile Bituminous Materials

Different roads like highways and residential streets need different materials.

There’s a method to my pavement material testing for both summer and winter extremes. 

Zhanping You uses models, material testing and construction projects to show that a road is not all it’s cracked up to be. You is the 2019 Michigan Tech Research Award winner and a professor of transportation engineering. He studies asphalt, and more sustainable options, for ensuring that roads do not crack in the first place.

Along with his code-savvy and dirt-under-the-fingernails lab group, You digs deep into the mechanical and chemical properties that affect the longevity of roadways. You and his group have laid down over 10 miles of test projects in Michigan and also applied his research work in Minnesota and Texas. They help county and state project managers sort out challenges with climate and construction resources on a local level; their numerical modeling of particles — discrete element method — provides global insight for road infrastructure.

Discrete Element Method

Old transportation material models used to approximate the elasticity of an asphalt mix — that’s the flex in the material, how bendy it is. While road rash would lead us to believe otherwise, roads are indeed made of flexible materials that change shape over time, affected by temperature and traffic load. Hot days, cold snaps and heavy trucks put wear and tear on roads.

However, elasticity alone is too simple. Models improved when they could measure the viscoelasticity of pavement — that’s both the flex and flow of the material over time and temperature. You has been able to model with a third component, plasticity — that’s the ability to undergo stress and permanent deformation without cracking. Viscoelastoplasticity helps engineers like You truly understand how to prevent roads from cracking, or what finally pushes them over the edge and makes them crack.

“Models help us understand the fundamental mechanisms of material behavior and performance,” You said. “And while testing practices can be generalized, the most shareable part of our research is modeling. A model is universal; if you use the model, it can be applied to similar materials and structures by entering different parameters.”

Hit the Road

Models need ground-truthing. In this case, validation for transportation material discrete element method modeling comes in the form of many stretches of highway test beds. You’s group has laid down 10 miles of test material in Michigan and the group also monitor hundreds of miles in Michigan and other states.

Last summer, You led a project downstate with the Road Commission of Kalamazoo County, funded by the Michigan Department of Environment, Great Lakes, and Energy (EGLE), the former Michigan Department of Environmental Qualify (MDEQ). The project’s goal was to assess recycled rubber materials made out of scrap tires. They laid down six lane miles of test track on W Avenue from the Schoolcraft Village limits to Portage Road, Schoolcraft Township – Kalamazoo, Michigan. It is split into four sections: hot rubber thin overlay (HRTO), conventional thin overlay, hot rubber chip seal (HRCS) and conventional chip seal.

“The purpose of the project was to evaluate the new reacted and activated rubber to investigate the applicability of such rubber, mainly composed of finely ground scrap tires,” You said. “The aim is to create more cost-effective, long-lasting, safe and environmentally friendly mixes for pavements.”

This summer the team will be checking on the old tires made anew; preliminary results showed the recycled rubber was quieter and smoother than conventional methods, and the team wants to determine how well it stood up to summer and winter fluctuations. They’re also installing a similar test section in Iron Mountain in June and You is coordinating material installation with the MnROAD test track in Albertville, Minnesota. 

Interdisciplinary Bituminous

You is a pavement powerhouse. But he says he could not do this work alone.

“I like working with other people to get a new perspective,” he said, listing his collaborators in his home Department of Civil and Environmental Engineering as well as many other departments, including materials science, chemical engineering, mechanical engineering, mathematics and the School of Forest Resources and Environmental Science. And teaching is an equally important venue for building teams.

“I focus a lot on the sustainability of construction,” You said. “I’m training the next generation of decision-makers … in my lab, students are not just lab technicians.”

Michigan Technological University is a public research university founded in 1885 in Houghton, Michigan, and is home to more than 7,000 students from 55 countries around the world. Consistently ranked among the best universities in the country for return on investment, Michigan’s flagship technological university offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, computing, forestry, business and economics, health professions, humanities, mathematics, social sciences, and the arts. The rural campus is situated just miles from Lake Superior in Michigan's Upper Peninsula, offering year-round opportunities for outdoor adventure.