Washington, May 31 : A new research program in the US is finding ways of making asphalt more environmentally sustainable.
Called the Asphalt Research Consortium (ARC), the research program is the Federal Highway Administration's first major consortium to improve asphalt technology since the Superpave effort of the early 1990s.
According to University of Wisconsin-Madison civil engineering professor Hussain Bahia, more than 90 percent of US roadways are paved with asphalt, which means any modifications that boost its recycled content, lengthen its life, or cut the energy needed to manufacture it could have a big impact on the environment and our pocketbooks.
One of his first goals is to develop so-called "cold mix" asphalts for widespread introduction into the United States.
Places like Africa and India have used them for decades, and research shows they can save up to seven times the energy of their hot mix counterparts.
Studies by Canada's Office of Energy Efficiency and others have found that paving with these cold mixes, also called emulsions, saves significant amounts of energy, especially when combined with recycling efforts.
These asphalts also cut emissions of carbon dioxide and other gases. But, a number of issues remain, and this is where Bahia hopes his research will make a difference.
"At US refineries today, there are very mature, established specifications for hot binders - our paving grade asphalts," he said. "But for emulsions, there is no clear agreement on how to define the quality. So, we have emulsions already, but we don't produce them as much because the specifications aren't as clear," he added.
Bahia first wants to develop quality control tests and standards that will encourage US engineers, chemists and road builders to adopt cold mix asphalts, or at least give them a try.
This means first defining the critical ways in which these asphalts fail, and designing systems for detecting the failures.
"We can then determine the chemistry or physics that will give us a larger margin of safety from these failures," said Bahia.
The final step will involve simulating various climate conditions in the laboratory to see how failure limits change with freezing cold or blazing heat.