Comparative Field Evaluation of Shale Oil–Modified Asphalt with Polymer-Modified Asphalts

Abstract

Since the discovery, patenting by Western Research Institute, and licensing to The New Paraho Corporation of a concept for the use of an asphalt modifier that can be produced from western shale oil, nine test strips have been constructed in five states in the United States. Performance evaluations were conducted on three shale oil–modified asphalt (SOMAT) test pavements that were laid in Utah and Wyoming. In all cases the performance of the test pavements was compared with pavement sections that were constructed using polymer-modified asphalts. The results of the evaluation of the pavement performance at the three project sites in general show that rutting, fatigue cracking, and thermal cracking properties of the SOMAT (test) pavements are comparable to the AC-20R and PBA-6a (control) pavements. However, with respect to moisture susceptibility and in-service aging, the SOMAT pavements are less prone to moisture damage and are aging at a slower rate than the control pavements. A life cycle cost analysis was conducted on the SOMAT and AC-20R pavements laid south of Moab, Utah, on U.S. Highway 191. The projected terminal service life for the two pavements, assuming that no remedial actions are taken, is 28 years for the SOMAT test strip and 7 years for the AC-20R control section. The cost of these remedial actions was estimated on the basis of the realization that remedial actions would be conducted and assuming a 30-year service life. The total estimated cost for the SOMAT pavement was $171,218/lane-mile, and for the AC-20R pavement it was $315,639/lane-mile.