Performance evaluation of asphalt pavement types E, F, and G Noble-Garfield counties (OK-97-03) 2270

Abstract

In 1991 the Oklahoma Department of Transportation (ODOT) initiated an experimental project investigating the performance of three asphalt mix designs; Types E, F, and G. Type Eis a relatively fine aggregate mix with lOOo/o passing the 12.5 mm (Yl inch) sieve. Type F is more coarsely graded with 100°/o passing the 38 mm (1 Yi in) sieve. And Type G is a very coarse mix with 100°/o passing the 76 mm (2Yl in) sieve. (Full gradations in Appendix A.) It was hoped that a Type E surface course over a large aggregate base course would resist rutting. The large aggregate mixes (F and G) provided problems from the beginning. The top size aggregate had to be removed and replaced with smaller aggregate before they would fit properly in the standard density molds. Therefore, the test results were not representative of actual field densities. During construction, segregation was evident and field compaction densities were essentially not comparable to laboratory densities. Placement of the Type E (fine aggregate) surface course went smoothly. After one year, rutting had begun. Coring revealed major stripping in the large aggregate mixes; as evidenced by the presence of loose aggregate only partially coated with asphalt. Rutting worsened each year and other distresses, including raveling and spot bleeding, became increasingly serious. Because of the poor performance of the underlying large aggregate base courses, the Type E surface course could not be properly evaluated. The problems encountered with F and G mixes were many and serious; thus, both mixes were removed from the ODOT Specifications and are currently not used.