From quarry to roadway: Putting underutilized materials to work on local roads

A 2015 Illinois Center for Transportation and Illinois Department of Transportation study estimated that Illinois quarries generated nearly 1 million tons of underutilized materials annually. Often stockpiled because of limited opportunities for use, these materials could offer a cost-effective way to maintain local roads without sacrificing performance.

Through an IDOT-sponsored project, ICT researchers examined whether quarry by-products could replace conventional aggregate in Otta seal, a protective road surface treatment that can incorporate locally available materials.

Erol Tutumluer and Ramez Hajj, University of Illinois Urbana-Champaign professors, led the project with Andrew Stolba and John Senger, IDOT’s chief geologist and bureau chief of research, respectively.

Originally developed to improve gravel roads without complete reconstruction, Otta seal helps protect road surfaces from moisture and traffic wear. The treatment involves applying liquid asphalt binder, spreading aggregate over it and rolling the particles into the binder.

Otta seal is particularly suited to low-volume roads.

According to design guidelines cited in the report, single-layer treatments can accommodate

up to 500 vehicles per day, while double-layer treatments can accommodate up to 2,000. In Europe and Africa, life of Otta seal treatments has been shown to last 8-10 years for a single layer and 12-15 years for a double layer. Unlike some conventional surface treatments, Otta seal can also use a broader range of aggregate sizes and qualities, allowing agencies to consider locally available materials.

Using underutilized quarry materials in Otta seal, however, presented challenges. Their many fine particles create more surface area for the binder to cover, making complete coating difficult. Materials also varied among quarries, requiring researchers to blend some with coarser aggregate.

The team developed a two-layer configuration, placing finer particles over the first binder application, then adding another binder application and coarser particles. This arrangement improved coating and left coarser material at the surface to provide texture for traction.

In laboratory tests simulating traffic wear and braking, the treatments containing underutilized quarry materials retained aggregate as well as or better than conventional Otta seal materials. The researchers also tested friction on wet surfaces and found that the treatments provided grip comparable to an existing asphalt pavement surface at ICT.

“For the traveling public, a low-cost maintenance approach could help agencies make better use of limited transportation budgets and potentially extend maintenance to more roadway miles,” Tutumluer said.

Stolba noted that underutilized quarry materials are produced across Illinois and that using them near their source could reduce hauling costs.

The researchers also developed preliminary guidance for IDOT on preparing road surfaces, applying materials, compacting the layers and monitoring performance. The guidance provides a starting point for evaluating the treatment under real-world conditions.

A follow-up ICT-IDOT project, R27-298: Field Implementation of Quarry By-Product based Otta Seal for Low-Volume Roads, will evaluate how the treatment performs under actual traffic and weather conditions. If successful, the approach could give Illinois communities another cost-effective option for maintaining local roads.

Read the report for the IDOT-sponsored research project, Quarry By-product Fines for Otta Seal Surfacing of Local Roads: https://doi.org/10.36501/0197-9191/26-013