Back-Calculated Pavement Layer Modulus Values of Geogrid Reinforced Test Sections

A study was conducted on full-scale pavement test sections to assess base reinforcement with geogrid in flexible pavements. Two thicknesses of asphalt and two thicknesses of base course were tested. Four test sections were reinforced with geogrid placed at the base/subgrade interface, and there were four matching control sections constructed on one subgrade. A heavy vehicle simulator loaded all the test sections. After construction, the subgrade was conditioned to a lower modulus value by adding water to the test sections, and the response was monitored using falling weight deflectometer (FWD) testing. In addition, FWD testing was also performed immediately prior to and after traffic loading in order to monitor the modulus of the subgrade and base layers. The subgrade modulus values were greatly affected by water content, but also experienced a significant decrease from immediately before to immediately after application of traffic. The modulus values then recovered over time. The base modulus values demonstrated a similar response when traffic was applied. The average modulus values for the base courses reinforced with geogrid were on average 1.34 times those for the base courses in the control sections throughout the project.