Construction and instrumentation of full-scale geogrid-reinforced flexible pavement test sections

Nine low-volume flexible pavement sections were recently constructed at the Advanced Transportation Research and Engineering Laboratory (ATREL) at the University of Illinois, Urbana-Campaign (UIUC). The nine sections were divided into three categories based on the total thickness of the pavement system structure. The first category has 8 in. of aggregate base and 3 in. of hot-mix asphalt (HMA). The three sections in that category differ in aggregate reinforcement: one control and two reinforced with geogrids having different tensile strengths. The second category has a 15-in. pavement structure. Two sections were unreinforced, while one is reinforced with a geogrid. One of the unreinforced sections has a 5-in. HMA and 10-in. aggregate base. The remaining two sections have 12-in. aggregate base and 3-in. HMA. In the first two categories, the reinforcement was placed at the interface of the subgrade and granular base. The third category has a 16-in. aggregate base layer and 3-in. HMA: one control section, one reinforced at 5-in. below the HMA-aggregate interface, and the third is reinforced at the subgrade-aggregate interface as well as at 5 in. below the HMA-aggregate interface. The subgrade California Bearing Ratio (CBR) was maintained at 4% or lower throughout the sections. All pavement sections were instrumented for measuring pavement response to axle and environmental loading. More than 200 instruments were placed during construction. Instruments used include vertical and horizontal LVDTs for deformation measurements, pressure cells for measuring vertical pressures, HMA strain gages formeasuring transverse and longitudinal stains at the bottom of the HMA, time domain reflectometry (TDR) probes for measuring subgrade moisture contents, thermocouples for measuring pavement temperature profiles, and probes to measure pore-water pressure in the subgrade. Loading response instruments were placed in the center of the lane, where the wheel loading was expected; while environmental response instruments were installed at 3-ft from the centerline. Instrument locations were staggered with respect to the pavement profile. The first category was loaded using the Accelerated Testing Loading Assembly (ATLAS) at ATREL. 10 kips at 5-mph loading was applied until the pavement sections failed. This paper describes the pavement construction, instrumentation and the experimental program. Preliminary analysis of pavement responses to loading is presented.