This paper was presented at the `Strategic investment alternatives for sustainable roadway materials' session. As pavement technology moves into the next century, pavements with modified materials will likely increase substantially. Although there is a considerable amount of information o mix formulation, properties and expected benefits of modified materials, there is very little available on field performance. This paper presents the findings of a recent study which devbeloped a technical/performance and economic model for assessing modified asphalt pavements. A Markov modeling prediction technique was used to develop performance models for both conventional and modified asphalts using rutting and Pavement Condition Index (PCI) as performance indicators. Actual rutting depth and PCI observations from a test site of a 6-lane freeway near London, Ontario were compared with the Markov predictions. Ontario Pavement Analysis of Costs (OPAC) 2000 predictions were also compared with the Markov conventional predictions and showed very good agreement. The Markov model for modified asphalts was then assumed to be validated. In general, the actual and predicted rut depths for the modified sections showed slight to significant improvements compared to conventional sections. Similar results were obtained for the PCI predictions. In some cases, modified section predictions save up to 10 years of additional service life, however, a maximum of six years was established for the economic analysis. A life-cycle cost analysis was performed using current Ontario unit costs. Results indicated that modified asphalts would be more cost effective on high volume, thicker pavement structures but not on low volume, thinner pavements. It is recommended, however, that the pavement designer should combine engineering judgment with life-cycle cost analysis in making specific project decisions. (A)
Abstract