Environmentally Friendly Stabilization of Unpaved Shoulders

Researchers at Iowa State University have investigated several alternatives for the stabilization of granular shoulder materials. Soybean oil soap-stock (SOS) appears to be an effective and environmentally friendly treatment. The stabilizer used in field studies is a proprietary formulation of SOS called "DUSTLOCK." SOS is a by- product of the refining process of soybean oil. Being a by-product, it is relatively inexpensive, though several other uses exist. It is also attractive because it can be applied at ambient temperatures with distributor trucks and fits the equipment and labor skill set that is available in many state Department of Transportation (DOT) shops and local jurisdictions. SOS shows promise in certain cases. In previous testing, some sections performed very well. Continuing research is investigating the traffic levels and materials where SOS stabilization can be both successful cost-effective. Iowa State University researchers are working with Iowa Department of Transportation (IDOT) personnel to investigate application techniques and alternative equipment configurations so that SOS might be used in as many situations as possible. In the summer and fall of 2011, ISU researchers worked with IDOT to test application procedures in locations with differing traffic levels and using various application techniques. Ongoing research is monitoring the performance of the stabilized shoulders over time.