Mixture design and performance-based specification recommendations for cold patching mixtures
Cold patching asphalt mixtures constitute an essential element for the maintenance and rehabilitation of pavement infrastructure. Although this maintenance technique is both expensive and time consuming, it can minimize further damage and costly future repairs as well as increase user and vehicle safety. As a result, cold patching mixture performance is critical. Unfortunately, there is a lack of standard mixture design guidelines for homemade mixtures and performance-based mixture specifications for both homemade and containerized mixtures to ensure satisfactory field performance. This thesis develops a homemade mixture design for cold and wet weather areas by identifying the failure mechanisms of cold patching mixtures and analyzing the effects of gradation, aggregate shape, binder content and viscosity, curing time, temperature, and admixtures on the mixture workability and stability. Laboratory and accelerated pavement testing (APT) procedures are specifically defined for use with cold patching mixtures. Protocols and procedures are also defined for the field evaluations of these mixtures. Results from field evaluations are used as overall relative measures of field performance and as validation for those results obtained from laboratory and accelerated pavement tests. Furthermore, testing results, in conjunction with testing procedures developed as part of this thesis, are used to provide recommendations for performance-based specifications for homemade and containerized cold patching mixtures. Such recommendations provide interim guidelines for the rejection or approval of such mixtures. Overall, the protocols and testing procedures developed herein help ensure the material characteristics necessary for desired patch performance in the field, which in turn reduces the failure rate and makes cold patching a more cost-effective maintenance operation.