A Study of Effectiveness of Thin Surface Treatments Using Hamburg Wheel Tracking Device

In recent years, more and more highway agencies are adopting preventive maintenance strategies or thin surface treatments to bring pavements back to appropriate serviceability for road users. This paper discusses the effectiveness of several thin surface or preventive maintenance treatments on sixteen highway test sections in Kansas. The treatments studied include thin Hot-Mix Asphalt (HMA) overlay, ultra-thin bonded asphalt surface (Nova Chip), and chip seal. These treatments were applied with three different types of surface preparation- bare surface, 1" surface recycle (hot in-place recycling), and 2" surface recycle. Hamburg Wheel-Tracking Device (HWTD) test was conducted on the cores from the test sections with thin surface treatments under this study. The laboratory test results show that most projects exceeded the maximum rut depth limit (20 mm) specified in the study and the number of wheel passes to failure varied significantly among the projects. Cores from only three projects, two treated with Nova Chip and one with 1" HMA overlay, carried 20,000 wheel passes without exceeding maximum rut depth limit. Pair-wise comparisons or contrasts among the treatments were performed with the statistical analysis software, SAS. Air void of the HWTD test cores was found to be a significant factor affecting the performance of thin surface treatments. Since the Hamburg test samples (62 mm tall) consisted mostly of underlying layer materials, it was concluded that quality of this layer is the major determinant of performance of pavements with thin surface treatments.