Performance of Chip Seals Using Local and Minimally Processed Aggregates for Preservation of Low Traffic Volume Roadways

摘要

Many roadways in the world are in locations without high quality aggregates. Therefore, high quality aggregates must be transported to these locations when pavement construction or preservation activities are needed. This transportation increases the cost of pavement construction and preservation in these areas of the state. Increased costs often mean that timely pavement preservation activities are postponed. This postponement leads to deterioration of the infrastructure and, ultimately, increased costs. In addition, many of the pavements requiring preservation are low volume facilities. These low volume roads may not require the very high quality aggregates necessary on higher traffic volume facilities. Therefore, if more economical local aggregates could be demonstrated to perform acceptably, pavement preservation could be accomplished within budget at appropriate intervals. This would save costs in both the short and the long terms. Chip seals are used extensively by many road authorities for extending pavement life. Chip seals utilizing locally available and minimally processed aggregates should be a more economical pavement preservation treatment than chip seals constructed with higher quality, more expensive aggregates. Although chip seals constructed on high traffic roadways require high quality, crushed and approximately single-sized aggregates, low traffic roadways may not demand such materials to perform acceptably. Therefore, an experiment was designed to demonstrate the performance of chip seals constructed using two different aggregates on two low volume state highways. The control aggregate was the material routinely used for chip seal construction and the second aggregate was a material that did not meet specifications for gradation or fracture. Construction of the test sections was conducted by agency maintenance forces in 2009. Condition surveys were performed to determine pre-chip seal condition and then periodically for the next three years to track performance. Two five hundred foot long evaluation sections were located within each test pavement for each aggregate resulting in two thousand lane-feet of test area for each roadway. Results of the experiment after three years of service indicate no significant difference in performance between the aggregates. Distress in both pavements is limited to a return of transverse and longitudinal cracks, but with low percentages of chip loss. Some limited areas of the pavements also contain longitudinal flushing streaks where distributor nozzles may not have been adjusted correctly and higher quantities of asphalt were applied. Based on the results of this research it appears that locally available, minimally processed aggregates can be successfully applied as chip seal aggregate on low volume roadways. The report includes a recommended chip seal design procedure, aggregate and construction specification for low traffic volume roadways.