Evaluation of crack sealing techniques in Alaska's asphalt concrete pavements

Abstract

Thermal cracking is one of the most prevalent asphalt concrete (AC) pavement distresses in northern states and countries. Every year in Alaska, a substantial amount of funding is spent on sealing cracks according to the practices of the Alaska Department of Transportation and Public Facilities (ADOT&PF) Maintenance and Operations (M&O) division. However, to date there are no specific guidelines available that clearly outline the best timing for crack sealing or even what conditions necessitate crack sealing in a consistent manner. There is a need to evaluate the effectiveness and best practices for using the crack sealing techniques on AC pavements in Alaska. In response to this research need, a pavement preservation project was conducted and found that although crack sealing is a very common practice in Alaska, it is unclear how and why M&O decides to seal cracks since some are sealed and some are not. This motivated further evaluation of 91 field sections that represent the various climate regions of Alaska. A new survey method, "special thermal crack evaluation (STCE) ", was developed to answer critical questions related to road thermal cracks and to provide guidance for crack sealing practices. The new STCE method was conducted along with two other field survey methods, the Long Term Pavement Performance (LTPP) program and the Pavement Surface and Evaluation Rating (PASER). Results between methods were then correlated. Finally, regression analyses were conducted to determine factors that significantly influence crack development and crack sealing practices in Alaska. Significant influencing factors on crack development include pavement temperature, freezing index, and rut depth. Crack frequency, freezing index, pavement age, PASER rating, PASER transverse crack severity level, and certain STCE questions can significantly contribute to the decision making for current sealing practices. It was found that the STCE method could generate direct recommendations on crack sealing practices. STCE, in combination with the LTPP and PASER methods, provides specific analysis about asphalt thermal cracking and sealing of these cracks so that informed decisions can be made for a positive impact on ADOT&PF's maintenance budget. It is recommended to use STCE along with the LTPP and PASER methods and to use the findings of influencing factors of this study to develop more specific plans for future crack sealing practices.