FIRST DEMONSTRATION PROJECT IN USA

Within the stated goal of the Board of County Road Commissioners of the County of Kalamazoo is using their expertise, energy and funds to provide the safest and most convenient road system possible, and to contribute to economic development and high quality of life throughout the county, it is not a surprise that when Michigan Technological University (MTU) had an idea of who to contact with an idea, the Road Commission of Kalamazoo County (RCKC) came to mind. Together it was decided to investigate the usage of new technologies to enhance the future cost benefits of preserving our infrastructure and provide future advancement of using scrap tires in Michigan. A joint grant application to the Michigan Department of Environmental Quality (DEQ) Scrap Tire Development Grant was funded.

The first RARX (www.rarx.net) test sections, placed under the leadership of the RCKC in Michigan, USA, were, in my opinion, was one of best organized events of this kind, I have ever been a part of. Weekly calls organized by Joanna I. Johnson, the Managing Director, prior to the test section itself, the coordination at the job site and the yard, the great “can do” spirit of all the personnel of the RCKC, MTU, asphalt contractor and bitumen suppliers created an environment of positive thinking, productivity and innovation that are, for me, the best I have ever had the pleasure of participating. RCKC’s leadership made sure everyone knew exactly what was going to happen and what was expected from each participant. Simply FANTASTIC! As we know if any construction project, the preparation is important and the flexibility of adapting to changes in the field is also critical to delivering successful projects.

The purpose of the two RARX test sections were to investigate the applicability of the usage of the new reacted and activated rubber (mainly composed of finely grinded used car and truck tires) to create more cost effective, long lasting, safe and environmentally friendly mixes and surface treatments.

The test sections were supported by the grant from a proposal elaborated by RCKC and Professor Zhanping You from MTU. CONSULPAV Lda (www.consulpav.com) cooperated with MTU in the formulation of a new kind of paving mix incorporating large amounts of recycled rubber and recycled paving material yet reaching rutting resistances and flexural fatigue lives with performances much higher than most mixes used in USA. This mix was denominated RARX-THINGAP. It contains about 6% RAP (reclaimed asphalt pavement), regular PG 58-28 bitumen, about 4.5 % RARX and the rest is selected natural aggregate (% by weight of the mix). RARX was provided by CIRTEC (www.cirtec.es). Efforts by CONSULPAV were covered by the SILENT RUBBER PAVE project (http://silentrubberpave.eu/).

The asphalt contractor, Lakeland Asphalt, (http://lakelandasphalt.com/) was very cooperative, enthusiastic, and inventive in adapting the mixing process to incorporate the RARX material never used in the USA.

Placing RARX in the conveyor belt at Lakeland Asphalt's plant

Even the bitumen supplier Bit Mat Products (http://www.bitmatproductsofindiana.com) went out of its way to provide bitumen at higher than normal temperature, so that we could minimize the heating time at the chip seal test section where RARX was directly blending into the bitumen of the Bearcat RARX Distributor (http://www.bearcatmfg.com/). Bearcat designed a new kind of distributor to accommodate the capabilities of this new pre-reacted and activated rubber with an extra auger inside the tank to insure fast mixing of the RARX in the bitumen. Virtually immediately after blending the asphalt rubber binder is ready to spray. RCKC innovative spirit shinned as they provided an easy way to introduce the RARX into the distributor tank. This was also a first in the USA. The coordination provided by Travis Bartholomew, Operations Director and Mark Worden, Project Superintendent and the cooperative, professional, friendly attitude of all the RCKC personnel made possible to the success of this project. Professor You and students participated in a very active role and were also vital for the success of the project.

Loading system developed by RCKC to place RARX into the distributor

The cost effectiveness of paving is clearly in the mind of the paving industry in Michigan. See below a truck with 50 tons of RARX THINGAP mix unloading into the paver.

Below we can appreciate the general aspect of the section of the road, a surface texture close-up and the stone on stone structure of the RARX-THINGAP mix.

The RCKC team is very experienced in using chip seals in their annual preventive maintenance strategies and they have had great success using them. The purpose of the test section was to see if they can even be more successful in making more long-lasting surface treatment. The video below shows the chip seal application operation. I call your attention for the rollers that were specially designed by RCKC. Again, it shows RCKC desire for cost effectiveness as wider paving rollers minimize the number of roller operators and number of passes allowing faster operation.  The chip seal trial was difficult and posed challenges to properly apply the material in the beginning of the project. The good story was that it eventually went well with quite some team effort.  There are certainly something we can do to improve the equipment and training prior construction as well as other opportunities to refine this process in the future.

Chip seal paving

The weather in Michigan is challenging, and requires that water be prevented from entering into the pavement to minimize freeze thaw damage. Furthermore the snow removal equipment is very demanding on the surface of those surface treatments. Only after the first winter we will see how the new RARX rubber chip seal resist those harsh conditions. For now they look good and they are expected to out-last existing chip seal maintenance procedures.

Furthermore, I am convinced that RCKC and the industry may be able to advance and adapt the aggregate gradation selection to accommodate this new rubberized binder and make it fit into their special requirements. With the higher viscosity and with the much higher binder elasticity they are able to place more binder, that if the market will support, may be less expensive, and secure more aggregate retention and resistance to reflective cracking while being also less prone to aging.

It was very exciting and gratifying participating in this very important first RARX demonstration project in the USA. As the Rubberized Asphalt Foundation (RAF) is a research foundation dedicated to the science and practical use of recycled tire rubber in asphalt. RAF serves as a comprehensive, expert resource to provide technical knowledge and awareness that will enhance the development and broad use of rubberized asphalt. The foundation is comprised of renowned international experts from academia, government and industry who are leading the scientific development of recycled rubber for asphalt applications. This project confirmed that recycled materials can potentially create a sustainable circular economy where RARX recycled rubber can be used for asphalt applications. A potential mix of fixes in future sustainability of our infrastructure. The RARX THINGAP mix placed by RCKC is likely to be one of the quietest mixes most cost effective, environmentally friendly and safe mixes ever placed in USA.

As Joanna Johnson stated “we are pleased to be part of a first use of this product; learning during the preparation and application process. Now we will monitor and potentially this could be the beginning of something new “.

	Dr. Jorge B. Sousa Director Rubberized Asphalt Foundation