Enhanced Compaction to Improve Durability and Extend Pavement Service Life: A Literature Review

This literature review was conducted to provide information to support the Federal Highway Administration Asphalt Pavement Technology Program strategic direction on extending pavement service life through enhanced field compaction. The results from the past studies clearly indicate the effect of low in-place air voids on the fatigue and rutting performance of asphalt pavements. A 1% decrease in air voids was estimated to improve the fatigue performance of asphalt pavements between 8.2 and 43.8% and the rutting resistance by 7.3 to 66.3%. In addition, a 1% reduction in in-place air voids can extend the service life by conservatively 10%. Based on these results, a life cycle cost analysis (LCCA) was conducted on two alternatives in which the exact same asphalt overlay would be constructed to 93% and 92% densities to illustrate the effect of in-place air voids on the life cycle cost of asphalt pavements. The LCCA results show that the user agency would see a net-present-value cost savings of $88,000 on a $1,000,000 paving project (or 8.8%) by increasing the minimum required density by 1%. Due to its significant effect, the cost of providing increased in-place density can be significantly less than the operation, maintenance, and road user cost savings realized due to extended service life of the pavements. In an AASHTO survey of state agencies' targets for field compaction conducted in 2007, the majority of states responding to the survey had a compaction target of 92%, but over one-third of the responding agencies had compaction targets less than 92%. Most of these in-place density requirements currently adopted by states were determined based on what levels of in-place density could be achieved in the past using prior construction technologies. Since in-place density has a significant impact on the performance of asphalt pavements, agencies may consider implementing a higher in-place density requirement that can be achievable by following best practices and adopting new asphalt pavement technologies and knowledge gained from recent research. Some of these technologies and knowledge, including warm mix asphalt, intelligent compaction, improved construction joints, and improved agency specifications to incentivize achieving higher in-place densities, are briefly discussed in this report.