In 2022, California put plastic from discarded printer cartridges into a 500-foot Highway 99 lane; after thousands of trucks in hot and cold weather, it had no cracking or rutting

California tested asphalt that contained recycled plastic from discarded printer toner cartridges on State Route 99 in Elk Grove, south of Sacramento in 2022. The project began with a test on a highway shoulder before the modified asphalt was placed across all lanes of a 500-foot section. Granite Construction later reported that thousands of heavy trucks traveled across the section through hot and cold weather without visible cracking or rutting.The plastic came from printer cartridgesThe recycled material came from used printer toner cartridges, which is a waste stream that can be rather difficult to recycle. Granite Construction worked with researchers from the University of Nevada, Reno to develop an asphalt binder that contained modified toner polymer, or MTP. The mix incorporated 10% recycled plastic by weight of the binder.The highway project conducted an earlier test in a commercial parking lot in 2021, where Granite had used the post-consumer plastic material there before moving to the highway application. The State Route 99 section provided a test under regular traffic, which included heavy trucks and seasonal temperature changes. The work was part of the Cosumnes Bridge Replacement Project in Sacramento County, and researchers were interested in whether the modified asphalt could maintain its performance under conditions that cause conventional pavement to deform or crack.Thousands of trucks crossed the test sectionThousands of heavy trucks were exposed to the Highway 99 section during the field trial, with Granite reporting that the pavement experienced both high temperatures and freezing conditions during the monitoring period. Its 2022 sustainability report said that the section had no cracking or rutting after the early testing period. According to the University of Nevada, Reno, a levee breach flooded the test section during a winter atmospheric-river storm. Researchers inspected the pavement afterward and reported that the plastic-modified asphalt remained intact, despite the additional water exposure and traffic loads. The test therefore gave researchers another set of conditions under which to examine the pavement’s performance.The laboratory work pointed to some changes in the asphalt binder as the amount of toner plastic increased. Granite reported higher stiffness and viscosity in the modified binder, which are properties that can affect how asphalt responds to heat and heavy loading. The researchers were also examining how those changes could influence the material’s resistance to deformation and cracking under different pavement conditions.The test did not establish long-term performanceThe early results were promising, but the Highway 99 project was still a field trial. The University of Nevada, Reno said that researchers continued laboratory and field testing to study the material's long-term resistance to cracking and rutting. Granite also calculated potential environmental benefits from using recycled plastic in asphalt, with its report estimating that the modified mixture could reduce the mix's global warming potential by at least 5% compared with a similar mixture without recycled plastic. Those figures were Granite's calculations for the larger mixture and should not be treated as a measurement of the 500-foot Highway 99 section alone.The project put a waste material from printer cartridges into a conventional road-building application and tested it using regular highway traffic. The early inspection found no visible cracking or rutting after thousands of trucks had crossed the test area, but longer-term monitoring was still needed to determine how the material would perform over a normal pavement life.You use AI every day. Now get your AI Quotient. Take the AIQ test.