USE OF UNIVERSITY OF ILLINOIS TEST TRACK TO EVALUATE PAVEMENT PERFORMANCE

This paper correlates performance of pavements in the University of Illinois Pavement Test Track with findings from the AASHO Road Test and examines some of the fundamental factors influencing performance of flexible pavements. Forty test pavements were placed in the test track facility in 10 test sets and tested to failure under 4 and 6-kip (17.8 and 26.7-kN) axle loads on single-tire wheels. Serviceability trends for the pavements were recorded in terms of slope variance, rutting, cracking, and patching. Physical responses of the pavements to load were also recorded. Deflection under load and serviceability trends were compared with findings from comparable pavements in the AASHO Road Test. Regression analyses were made on the comparable data, and weighting functions were established between the AASHO Road Test and the University of Illinois Pavement Test Track for two service conditions: as placed and at a high degree of saturation. Results indicated that the University of Illinois Pavement Test Track is a useful tool for evaluating behavior and relative performance of pavement systems and that, within reasonable bounds, the facility can be used to predict performance of pavements in service. Moisture and density of the base, subbase, and subgrade materials all had a significant effect on the performance and behavior of the pavements. The effect of moisture in the granular base and subbase materials on pavement performance was profound; for example an increase of 1 pecent in the moisture content in the granular layers resulted in a ratio of the number of loads to failure of more than 700 to 1. Thus, even one load applied when the base and subbase are saturated would do as much damage as 700 loads applied at approximately optimum moisture content. This fact should be considered when regional environmental factors are established for pavement design. /Author/