Long-Lasting Open Graded Friction Course (OGFC) for Surfacing New Mexico Roads

The New Mexico Department of Transportation (NMDOT) uses open graded friction course (OGFC) material/layer for surfacing its high-volume traffic roads, however additional research is needed to identify whether OGFC is performing adequately considering the environmental and climatic conditions throughout the state. OGFC is typically designed with a high percent air void content (> 19%) to increase permeability, which allows faster removal of roadway surface moisture. Traditional dense graded pavement are designed with air void content at 5.5% as well as to enhance the International Roughness Index (IRI) and Skid Resistance. Currently, NMDOT uses only one type of performance grade binder: PG 70-28+ (or rubberized 70-28R+) throughout NM, irrespective of climatic/environmental conditions where PG selection should be location/climate specific. There is a national trend where state DOTs are moving towards performance-based mix designs; whereas currently, the NMDOT uses only a volumetric method for designing OGFC. Recently OGFC is suspected to play significant roles in statewide top-down cracking problems in New Mexico, because the high air content in OGFC leads to accelerated aging due to higher accessibility of air, which results in brittle OGFC that promotes initial cracking within the thin OGFC layer which then propagates into the lower hot mix asphalt (HMA) layers. The main objectives of this research are to: (1) Examine whether NMDOT can utilize alternative binder types in OGFC. (2) Determine if NMDOT can add additional performance testing requirements for OGFC mix designs. The study will develop a performance based OGFC specification. In addition to drain down, permeability, and abrasion tests, researchers will develop inter-phase shear (specialized test), aging, moisture susceptibility, and semicircular-notched type fracture tests.