Paving the Way
Even though they’re no longer rolling, scrap tires might still find their way to Georgia’s roadways, depending on the results of a study by Georgia Southern civil engineering professor Junan Shen.
Shen wants to find out if a relatively new type of paving mix – rubberized asphalt – will save the state money and landfill space. He has been selected by the Georgia Department of Transportation (DOT) to determine if the performance of the mix, derived from scrap tires and considered a “green” material, is a viable alternative for building roads.
“With our study, we want to determine if crumb rubber is a practical, stable solution. The world is using more and more green materials – which crumb rubber is – made from scrap tires,” Shen said.
Part of the study will look at the permeability of the new materials’ rubberized Open Graded Friction Course (OGFC). Also, said Shen, “As a driver, is your visibility improved? Is the pavement safer to drive on during the rain? Does the rain accumulate on the roadway, or does it drain off, making it safer for drivers?
Another potential advantage of the new mix is that noise could also be reduced on the roadway, he said.
The project, the first awarded by the DOT to the University, will determine how rubberized asphalt’s performance compares to polymer-modified asphalt pavements. As part of the study, Jeremy Todd Earnest, a Georgia Southern senior civil engineering technology major from Marietta, Ga., will assist Shen on the nearly $75,000 project.
Test sections on I-75 near Perry and I-20 in Augusta were paved three years ago with OGFC and stone matrix asphalt, respectively, using the “dry” process of modifying asphalt cement with crumb rubber. In the dry process, crumb rubber is concurrently blended with mix aggregates and asphalt cement at the plant, while in the “wet” process, crumb rubber is blended with the asphalt cement before the blended cement is mixed with aggregates. So far, the performance of these test sections has not been formally evaluated, nor has research on the dry process generally been documented. The wet process has been successfully evaluated and implemented by other states.
Shen’s findings will be used in a second, more comprehensive phase of the overall project, which would include field evaluations.
“There are going to be additional phases of the DOT research,” said Shen. “The second phase will be a more comprehensive study on the test sections of the rubberized pavement to determine changes in the roadway, such as cracking and rutting.
“Through this study we will provide best-practice recommendations to the Georgia DOT for consideration as they look at road construction alternatives,” said Shen. “Our ultimate goal is to save money on road construction and this study is just the first phase of a much larger project that could have major benefits for Georgia taxpayers.”
“I am excited to work with Dr. Shen on this study for the Georgia DOT,” said Earnest, who hopes to become a structural engineer. “The opportunity to do research while being an undergraduate is incredible. It will give me real-world experience, and help me compete in a very competitive job market. I would not necessarily have had this opportunity at another university.”
States actively using crumb rubber for their roadways are Arizona, California, Texas and Florida, said Shen. “It’s a way to recycle and use green materials. The state of Georgia produces approximately 9 million scrap tires every year. What are we going to do with them? This is a smart alternative.”