When it comes to road maintenance and repair, state and local officials are looking for cost-effective, sustainable solutions that perform. A product made with U.S. Soy offers just that. Researchers at Iowa State University, with support from the United Soybean Board and the Iowa Soybean Association, developed a soy-based solution that can help extend the life of asphalt pavement. The 2022 Farm Progress Show in Iowa generated excitement about a product that is not only sustainable but can add to farmers’ bottom line (see sidebar).
Roads and highways are a vital gateway for all Americans for traveling to school or work, hauling soybeans to the grain elevator or transporting goods across the country. According to the Federal Highway Administration, there are more than 4 million miles of paved roads in the U.S. — 94% of which are surfaced with asphalt. By using soybean oil to replace a portion of the petroleum traditionally used in road products, soy-biobased alternatives can simultaneously help shrink the environmental footprint of road and highway maintenance work, save money and support local farmers. Importantly, soy-biobased product allows for greater use of reclaimed asphalt pavement (RAP) and lowers the amount of virgin asphalt required in the mix and provides a new source for aggregate.
Ames, Iowa-based Colorbiotics has commercialized Invigorate Additive, which was developed at Iowa State University. Together they have tested the performance of the soybean oil-derived rejuvenator on projects across the country. Invigorate triggers chemical reactions inside recycled binder to break down asphaltene aggregation and reverse the effects of
oxidation. The product attacks aged binder at the molecular level to transform recycled material from the inside out, resulting in a binder that can stand up to standard asphalt specifications and extend road life. Another product — Invigorate Topical — is a waterborne, spray-applied version also made with soy, that extends the service life of aging pavement with minimal traffic disruption. The company also offers another soy-based asphalt product called Biomag and an asphalt shingle rejuvenator called Peak 301.
According to the Federal Highway Administration, “recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. Reclaimed asphalt pavement (RAP) is a useful alternative to virgin materials because it reduces the need to use virgin aggregate, which is a scarce commodity in some areas of the United States. It also reduces the amount of costly new asphalt binder required in the production of asphalt paving mixtures.”
Here are a few examples provided by Colorbiotics about how Invigorate is helping communities save money with a high-performing, sustainable product.
Heartland Asphalt, Inc. of Mason City, Iowa ran trials on a county road in northern Iowa that featured mixes with several different levels of RAP content. The control sample was mixed with 20% RAP, while a representative range of RAP content — 30%, 40% and 45% — was mixed both with and without Invigorate. The mixes were laid in 600- to 700-ton strips.
The Invigorate Additive significantly lowered the virgin oil content required.
“The 45% high RAP content mix with 5% Invigorate brought virgin oil content to 61.7% with 38.3% of binder coming from the RAP,” said Rich Millard, quality control manager for Heartland Asphalt. “This can result in economic savings.”
George Jessen, president and general manager of Heartland Asphalt, added, “If using the rejuvenator is cost-efficient and good for the environment, that makes us more competitive, so it makes a lot of sense to consider using more RAP.”
All States Materials Group (ASMG) used Invigorate Additive on a low-volume town road in Deerfield, Massachusetts. They compared the following asphalt mixes on a 2-inch overlay:
- PG 58-28 binder and Invigorate to produce 800 tons of 9.5 mm surface mix with 30% RAP
- PG 64- 28 binder with no rejuvenator to produce 9.5 mm Massachusetts DOT-approved 15% RAP mix (control mix)
The test samples from the Invigorate mix performed comparably to the control mix in the Hamburg Wheel Tracking Test for rutting and Illinois Flexibility Index Test (I-FIT) for cracking. In the Indirect Tensile Asphalt Cracking Test (Ideal-CT) the Invigorate mix performed significantly better than the control mix.
According to Jon Pepyne, technical manager for All States Asphalt, a division of ASMG, “Virgin asphalt is the most expensive part of the mix. Every tenth of virgin asphalt you can take out helps save money. We would definitely be interested in using it again. Every plant in the Northeast has a mountain of RAP they are sitting on. So, the more RAP you can use, the better. If we can stop the pile from getting bigger or reduce the pile, that would not only be good for the environment but also cost-wise.”
E&B Paving conducted a trial with Invigorate Additive on an asphalt parking lot in Indianapolis and the results were positive. The trial included 300 tons each of a 9.5 mm surface mix with:
- 40% RAP content using Invigorate
- A second biopolymer with another rejuvenator
- A smaller amount of a standard 9.5 mm surface mix with 25% RAP and no rejuvenator as a control section.
Prior to paving, the top 1.5 inches of the lot’s asphalt surface were milled and recycled. The paving crew followed with a 1.5-inch overlay compacted of the three different mix designs.
According to Stephen Perkey, a paving foreman with E&B Paving, the Invigorate mix was very workable, even with a 40% RAP content. “A lot of times a mix with high RAP content can be tough to work with, and it will lose temperature fast,” Perkey said. “I’ve noticed this mix has been very easy to move, it has similar workability to our traditional 9.5 mm mix, it’s got a really good shine, and looks slick on the top like we want.”
In addition, the Invigorate mix test samples performed well in the Hamburg Wheel Tracking Test for rutting, and the two different tests for cracking.
“The specimens with Invigorate passed all tests,” said Elizabeth Pastuszka, HMA design and Q.C. coordinator for E&B Paving. “We also analyzed rejuvenator cost compared to RAP content and found Invigorate to be a cost-effective solution for running higher RAP mixes.”