Research Pays Off: Low-Cost and Environment-Friendly Asphalt-Treated Mixtures: Louisiana Tests Designs

Asphalt cement materials are costly, and asphalt mixtures have environmental impacts. Alternatives are needed to reduce the cost and to decrease the emissions generated in production and construction without compromising performance.

Asphalt-treated mixtures (ATMs) offer one alternative; however, state transportation agencies’ specifications for ATMs adversely affect the economic competitiveness of ATMs and limit their use in pavement construction.

The Louisiana Department of Transportation and Development (DOTD) initiated research to develop a design methodology for ATMs that would be durable, stable, cost-effective, and environmentally friendly.

The results of the loading wheel test, indirect tensile strength, and flow number tests demonstrated a laboratory performance similar to that of conventional base course hot-mix asphalt (HMA) mixtures at high and intermediate temperatures. In addition, the asphalt-treated base mixtures demonstrated a several-fold improvement over unbound granular base materials in stiffness and in permanent deformation resistance.

The research findings contributed to the development of a guideline for designing low-cost ATMs.

In roadway shoulder and low-volume road applications Louisiana DOTD use of ATMs saved approximately $7.20 per ton or about 16 percent compared to conventional low-volume HMA. In addition, a life-cycle assessment showed that in low-volume roads the new generation of ATMs reduces energy consumption by up to 29 percent, water consumption by 39 percent, and hazardous waste generation by 42 percent when compared with conventional HMA mixtures.