Life-cycle cost analysis of SMA pavements and SMA application guidelines

Abstract

The objective of this research project was to provide a comparative cost analysis of pavements constructed using stone matrix asphalt (SMA) mixtures versus those built with Wisconsin Department of Transportation's (WisDOT?s) conventional hot-mix asphalt (HMA) mixtures, based on parallel life-cycles (inclusive of any required maintenance) and resultant performance. The research entailed a thorough evaluation of SMA and conventional HMA mixture performance on Wisconsin highways, collection and review of SMA and conventional HMA unit costs, and full-scale life-cycle costing to determine the cost-effectiveness of SMA pavements. Performance analysis, consisting of Pavement Distress Index (PDI) and International Roughness Index (IRI) threshold-based life projections combined with survival analysis techniques, resulted in SMA and HMA overlay service life estimates when placed on three groups of like pavements: (1) low-volume asphalt pavements on U.S./State routes, (2) high-volume jointed reinforced concrete (JRC) pavements on Interstate/U.S. routes, and (3) moderate-volume JRC pavements on U.S./State routes. Based on the results of the performance analysis, pavement life-cycle models were developed for SMA and HMA overlays corresponding to each group. Using the life-cycle models and historical-based best estimates of pay item unit costs, deterministic and probabilistic life-cycle cost analyses (LCCAs) were conducted. For group 1 overlay applications, SMA was found to be more cost-effective than conventional HMA, leading to the recommendation that SMA mixture use under this scenario be considered on a case-by-case basis. For group 2 and 3 overlay applications, the reverse was observed, with HMA found to be more cost-effective. However, a similar recommendation for SMA use under these scenarios was given, based on indications that the SMA overlays examined in the study were placed on rougher (possibly more deteriorated) pavements.