Selecting a Rut Resistant Hot Mix Asphalt for Boston-Logan International Airport: Fid-Bau Portal

Selecting a Rut Resistant Hot Mix Asphalt for Boston-Logan International Airport

Pelland, Robert J. / Gould, Jonathan S. / Mallick, Rajib B.

Hot weather pavement rutting and moisture induced damage have become problematic on several taxiways and aprons that are subject to slow moving and standing aircraft loads at Logan International Airport in Boston, MA. The Massachusetts Port Authority is evaluating the performance of seven mix designs that are presently in service by the testing of field cores at the Worcester Polytechnic Institute (WPI). Three mixes were tested for rutting and moisture susceptibility: a Trinidad Lake Asphalt (TLA)/latex modified P-401, a PG 64-28 P-401, and Densiphalt, a semi-flexible pavement. Four mixes were selected for more extensive testing: a PG 76-28 modified P-401, a reclaimed asphalt pavement (RAP)/latex modified P-401, a latex modified stone matrix asphalt (SMA), and a Rosphalt 50 modified P-401. Laboratory studies included use of loaded wheel track tests for determination and comparison of rutting and moisture induced damage at 60°C (140°F); determination of resilient modulus with the universal testing machine (UTM); determination of volumetric properties; and determination of the high temperature PG rating of the binders. Results indicate that significant improvement in rutting resistance can be achieved by providing a higher performance grade asphalt, a modified binder, or coarser gradation. The modification of mix designs comes with an increased cost of production. Not surprisingly, the two most expensive mixes, Densiphalt and Rosphalt 50, tested very well; they may be most cost effective in locally troublesome areas. Based on Massport's field experience, Densiphalt, and probably Rosphalt 50, must be installed on a very stable subbase. These mixes may thus be best suited as the wearing course of new construction as opposed to an overlay or inlay of existing pavements. The TLA mix shows good rut resistance in the laboratory, but is prone to cracking and susceptibility to moisture after four to five years of service. The PG 64-28 P-401 also proved to be susceptible to moisture. Both mixes are no longer used at Logan Airport. The RAP mix has performed very well in the field through two summers and tested well in the laboratory. The PG 76-28 and SMA mixes have shown slight indications of rutting in the field. These last three mixes are the least costly to produce and should be studied further. It is recommended that long-term field performance of these mixes be evaluated, and that accelerated loading and testing of these mixes be conducted. Using the results of this program, proper specifications and quality control tests can be developed for assuring design and construction of economical and stable mixes.