Reflection cracking is one of the main distresses in hot-mix asphalt (HMA) overlays. It has been a serious concern since early in the 20th century. Since then, several models have been developed to predict the extent and severity of reflection cracking in HMA overlays. However, only limited research has been performed to evaluate and calibrate these models. In this dissertation, mechanistic-based models are calibrated to field data of over 400 overlay test sections to produce a design process for predicting reflection cracks. Three cracking mechanisms: bending, shearing traffic stresses, and thermal stress are taken into account to evaluate the rate of growth of the three increasing levels of distress severity: low, medium, and high. The cumulative damage done by all three cracking mechanisms is used to predict the number of days for the reflection crack to reach the surface of the overlay. The result of this calculation is calibrated to the observed field data (severity and extent) which has been fitted with an S-shaped curve. In the mechanistic computations, material properties and fracture-related stress intensity factors are generated using efficient Artificial Neural Network (ANN) algorithms. In the bending and shearing traffic stress models, the traffic was represented by axle load spectra. In the thermal stress model, a recently developed temperature model was used to predict the temperature at the crack tips. This process was developed to analyze various overlay structures. HMA overlays over either asphalt pavement or jointed concrete pavement in all four major climatic zones are discussed in this dissertation. The results of this calculated mechanistic approach showed its ability to efficiently reproduce field observations of the growth, extent, and severity of reflection cracking. The most important contribution to crack growth was found to be thermal stress. The computer running time for a twenty-year prediction of a typical overlay was between one and four minutes.

Master of Science / Department of Civil Engineering / Mustaque A. Hossain / Preventive maintenance strategies are applied to pavement to bring it back to appropriate serviceability when it starts to deteriorate soon after construction due to several factors, e.g., traffic loading, deterioration of pavement materials, and climatic effects. In recent years, more and more highway agencies are adopting preventive maintenance strategies and moving away from rehabilitation actions since rehabilitating pavements at near failure is not a cost-effective pavement management technique. A variety of preventive maintenance treatments or thin surface treatments are available to bring pavements back to appropriate serviceability for road users. The Kansas Department of Transportation (KDOT) has adopted several preventive maintenance treatments including thin overlay, ultra-thin bonded asphalt surface (Nova Chip), chip seal, and slurry seal. This thesis discusses the effectiveness of thin surface or preventive maintenance treatments applied in 2007 on 16 highway sections in Kansas. Three types of thin surface treatments, 25-mm Hot-Mix-Asphalt (1” HMA) overlay, ultra-thin bonded asphalt surface (Nova Chip), and chip seal, were examined in this study. These treatments were applied on three types of surface preparation, namely, bare surface, 25-mm surface recycle (1” SR), and 50-mm surface recycle (2” SR). Effectiveness of the thin surface or preventive maintenance treatments for mitigating typical distresses and enhancing pavement performance was evaluated by conducting before-and-after (BAA) comparisons. All data required for this study were extracted from the Pavement Management Information System (PMIS) database of KDOT. It was observed that transverse and fatigue cracking significantly decreased and rutting conditions were improved after the thin surface treatments were applied. Roughness conditions were observed to be better on the highway test sections treated with 25-mm (1”) HMA and Nova Chip, while the effects of chip seals on reducing roughness were not as obvious. Benefit and performance levels of the pavements were observed to rise after the thin surface treatments were applied. The Hamburg Wheel-Tracking Device (HWTD) test was conducted on core samples taken from the highway sections under this study. Laboratory test results showed that most projects exceeded the maximum rut-depth limit (20 mm) specified for 20,000 wheel passes, 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 25-mm (1”) HMA, carried 20,000 wheel passes without exceeding the maximum rut limit of 20 mm (0.8 inch). Pair-wise comparisons or contrasts among the treatments were also performed with the statistical analysis software, SAS. Air void of the HWTD test cores was found to be a significant factor affecting performance of thin surface treatments. The results also revealed that performance was significantly affected by the type of treatment and surface preparation.