The use of Trinidad Lake Asphalt on Airport Surfaces - A presentation by Mr. Alfred Grimaldi - Technical Consultant based in the United States.
The first installation of the blended asphalt pavement at a New York City airport was an aircraft apron at La Guardia Airport in 1981. This installation was 4 inches thick and consisted of a blend of Trinidad Lake Asphalt and Petroleum Asphalt. Marshall stability was 2700 pounds. Experiences gained from this project led to the use of the same TLA blend being used wherever flexible airport pavements experienced similar problems. These pavement deformities generally occurred at the intersections of taxiways and runways as a result of heavily loaded jets turning to take off on the runway.
In 1981, the same TLA blend was used at Newark International Airport in New Jersey, to correct similar pavement problems on a number of Taxiways. Runway 13L - 31 R at John F. Kennedy International Airport (JFKIA) in New York City was rehabilitated with the TLA modified asphalt in 1984. This runway is 10000 feet long and was originally constructed of Portland Cement Concrete and subsequently overlaid with about 7 inches of asphalt concrete. At the time of construction, the runway not only served both for takeoffs and landings, but also as a taxiway for aircrafts lined up for takeoffs on the cross runway.
In the summer heavy rutting would be experienced on the runway as a result of stopping and takeoff of aircraft lined up as far off on Runway 4 - 22. The rutting was caused by the action of aircraft tires as well as other factors. Repairs had to be performed to correct the pavement deficiency and make the runway operational. This had to be done more than once a year in some situations.
The rehabilitation of the runway included the removal of the asphalt and the installation of 6 inches bottom course, and 2 inches of top course with a 25 % TLA modified AC 20 binder. The Marshall stability tested at 2700 lbs. Transverse grooves (1/4 in. x 1/4 in. @ 1/2 in. o.c.) were cut in the finalised pavement surface for anti - hydroplaning purposes.
The Trinidad asphalt system corrected the pavement problem previously experienced and the transverse pavement grooves have remained straight indicating the system also corrected the rutting and shoving problem. Overall structural maintenance costs for the runway pavement have decreased compared to previous years.
The runway surface is periodically tested for skid resistance and continues to maintain good surface characteristics. A Saab Friction Tester is the type of equipment used for the evaluation.
A new taxiway was constructed parallel to the runway a number of years later. The purpose of this taxiway was to assist in reducing aircraft delays at the airport and to increase the capability of the runway, as well as provide more efficient access to the adjacent cargo area.
The taxiway is 150 feet wide and 6600 feet long. The surface course consisted of a TLA blended asphalt similar to Runway 13 - 31, and last reports indicated that both the runway and taxiway pavements are performing well.
In the fall of 1994, the TLA blended asphalt was used for the paving of the taxiway apron at the International Arrivals Building at JFKIA. This action was taken to correct pavement deformities in the apron pavement brought about by the heavy turning action of jet aircraft gear loads as they turned into gate positions for loading and unloading of passengers. The demonstrated high stability and resistance to pavement deformation of the Trinidad Asphalt resulted in the selection of this material.
Trinidad Asphalt continues to be used at the three New York city Airports whenever a pavement condition requires extraordinary materials.
In 1994 Trinidad Asphalt was used at Logan International Airport in Boston, Mass. In this case TLA was selected to correct a heavy rutting problem on a portion of a taxiway at the airport. The successful "track record" of these pavements has provided engineers with a valuable tool when dealing with the operation and maintenance of airfield pavements.
Commercial use and research to date have shown that Trinidad Lake Asphalt can provide structural and durability improvements which lead to extended pavement life. The study mentioned previously indicates that TLA can also provide economic advantages over conventional AC and PCC materials on airfield paving projects.
The results of one study indicated that the use of TLA in airfield pavements can be justified in the following situations:
Various research studies have shown asphalt concrete incorporating TLA exhibits improved mixture properties and extended service life in comparison to mixtures made strictly with petroleum - refined asphalt.
Trinidad Lake Asphalt has demonstrated that it's performance can be consistent when properly mixed and constructed. The potential structural and durability benefits offered by Trinidad Lake Asphalt include:
These benefits translate into improved pavement and longer pavement life which in turn, offer economic benefits. The use of Trinidad Lake Asphalt should be considered by design engineers and the project owner when evaluating pavement design and material alternatives