Optimum Use of Local Materials for Roadway Base and Subbase: Fid-Bau Portal

Optimum Use of Local Materials for Roadway Base and Subbase

Gautam, Biraj / Yuan, Deren / Nazarian, Soheil

Base materials that meet the specifications of many highway agencies are getting more difficult to acquire in many regions of the United States. Hauling higher-quality materials over long distances would significantly increase the costs associated with roadway construction. Lower-quality or marginally out-of-specification materials are usually available from local sources. If through appropriate treatment of the materials or/and structural design, the optimum use of local materials can be permitted, the construction can be accelerated and significant monetary benefits can be realized. Under many current specifications, a material can be considered low quality or out of specification for a variety of reasons such as improper gradation or inadequate plasticity. Because the limits set in most current specifications are experienced based, some of the criteria used to classify a base material may be less significant than others. This paper presents a combination of test protocols and simple structural analysis to guide pavement engineers in effective use of out of specification unbound aggregate base materials. The belief supported by many traditional design algorithms that the performance of a thicker low-quality granular unbound base is equivalent to a thinner high-quality one maybe inappropriate. Based on the test results from eight local pits in Texas, various cost-effective approaches to how a low-quality material can be used on low-volume roads and still get a quality foundation layer are presented.