Structural performance monitoring of an unstabilized fly ash-based road subbase

Beneficial utilization of stabilized fly ash as a structural layer in pavement construction is a common practice in the United States. At the same time, application of untreated and unstabilized fly ash in such cases is relatively rare. One such application was demonstrated at an Industry Access Truck Route in the state of Illinois. Approximately 60,000 m 3 of F-fly ash, compacted in place, was used to construct the subbase for the 7.3 m wide and 3.4 km long road. The entire road was built into three control sections, i.e., ACl, fly ash, and AC2. Control Section AC1 was 0.75 km long and was built on fine sand subgrade; the fly ash control section was 2.2 km long and was built on silty/clayey subgrade using fly ash as subbase; Control Section AC2 was 0.45 km long and was built on clayey subgrade. This paper presents the long-term postconstruction structural performance results of the fly ash control section, as compared to Control Sections AC1 and AC2. Falling weight deflectometer studies performed on the truck route have indicated all the sections of the truck route to be performing satisfactorily. The fly ash control section in particular has exhibited very good structural performance.