Within three to five years following construction of asphalt pavements, reflected cracks may be observed, one of the primary forms of distress in hot-mix asphalt overlays of flexible pavements. Reflected cracks affect ride quality when rolled down and allow water to penetrate into the pavement and the base, causing the asphalt mix to deteriorate and the base to soften. Consequently, the service life of pavements is reduced. Cold in-place recycling (CIR) provides an economical rehabilitation method that mitigates crack reflection by pulverizing the asphalt pavement surface, thus destroying the old crack pattern in the recycled layer. While the performance of recycled roads is generally good, there is some inconsistency. Several years after recycling, some roads are in excellent condition, while more cracking and rutting is observed on other roads. These differing behaviors can be observed on roads constructed in the same county by the same contractor in the same construction season. Thus, the difference in performance is probably not from such factors as weather, equipment, contractor experience, and construction procedures. Rather, other factors more prominently affect pavement performance, such as recycled pavement age, traffic volume, support conditions, and aged engineering properties of the CIR materials. This paper discusses a partially completed investigation to identify how aged engineering properties of the CIR materials and other factors affect pavement performance. A selection matrix consisting of 18 sample roads was developed based on previous study. These 18 sample roads represent various ages (young/medium/old), traffic volumes (high/medium/low), and support conditions (strong/weak) in a geographically balanced sampling in Iowa. Pavement condition index (PCI) ratings were collected using an automated pavement distress digital image collection and analysis system. Engineering properties of CIR materials (density, compressive strength, indirect tensile strength, resilient modulus, and asphalt and aggregate content) will be examined through field and lab tests. Statistical analysis will be conducted to describe the relationships between pavement performance and the prominent factors. It is expected that the conclusions and recommendations from this study can be used to improve the performance of future CIR projects in Iowa and other states.
Abstract