Evaluation of long-term performance of cold in-place recycled asphalt roads
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Asphalt pavements deteriorate over time. Typically three to five years following construction, reflected cracks, one of the primary forms of distress in hot-mix asphalt overlays of flexible pavements, may be observed. When rolled downed, reflected cracks affect ride quality. In addition, reflected cracks allow the penetration of water into the pavement and the base. The water causes 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. However, recycled roads have inconsistent performance. Several years after recycling, some roads are still in excellent condition with only a few minor cracks while extensive cracking and rutting were observed on other roads. These opposite behaviors can be observed on roads that were constructed in the same county, by the same contractor in the same construction season. Thus the difference in performance is probably not turn such factors as weather, equipment, contractors' experiences, and construction procedures. Rather, other factors become more prominent in affecting pavement performance, such as: age of the recycled pavement; traffic volume; support conditions; and aged engineering properties of the CIR materials;This dissertation investigates how aged engineering properties of the CIR materials and other factors affect pavement performance. Twenty-four sample roads were selected to represent various ages, traffic volumes, and support conditions 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 were examined through field and lab tests. Statistical analyses were conducted to descript the relationships between the pavement performance and the prominent factors. The conclusions and recommendations were presented in this dissertation.