Determination of Load Damage Relationships through Accelerated Pavement Testing

Abstract

This paper describes the effects of increased wheel loads on the performance of thin asphalt pavements. Twelve instrumented full-scale test pavements were built inside a temperature/moisture controlled environment, and subjected to accelerated trafficking by means of a Heavy Vehicle Simulator (HVS). The test sections had constant geometry and materials, but the subgrade soil type and moisture content varied. Since tests are in progress, only eight test pavements were used to determine load damage exponents (LDEs). Each test pavement had six test sections for different load levels (22 to 103.5 kN). An LDE model was developed to predict rutting as a function of structural number (SN), load repetitions, and load intensity. Good correlations between the model prediction and measurements were found as at least four test pavements have an R2 value higher than 90%. Four test pavements had LDEs higher than 7.8, indicating significant impact of loading on rutting performance. It is believed that the high LDEs obtained in this study were attributed to low structural capacity (or structural number, SN) of the test pavements. Thus, it demonstrates that the well known 4th-power law (LDE=4) is too conservative for low SN pavements. With 10% overloading, 4th-power law will underestimate the damage of these light pavements by approximately 68% as compared to those from 8th-power law. A general trend was observed, based on available data, for A-2-4 and A-4 soils that LDE increases with increasing moisture content.