HIGH TIRE PRESSURE AND TEMPERATURE EFFECTS ON HOT MIX ASPHALT CONCRETE PERMANENT DEFORMATION USING CUSTOMIZED ASPHALT PAVEMENT ANALYZER April 22, 2010 Injun Song, Ph.D. SRA International, Inc. 2010 FAA WORLDWIDE AIRPORT TECHNOLOGY TRANSFER CONFERENCE ATLANTIC CITY, NEW JERSEY, USA

FAA William J. Hughes Technical Center AUTHORS Injun Song, Ph.D. SRA International, Inc. Phone: (609) 601-6800; Fax: (609) 601-6801 INJUN_SONG@SRA.COM Navneet Garg, Ph.D. FAA William J. Hughes Technical Center Phone: (609) 485-4483; Fax: (609) 485-4845 NAVNEET.GARG@FAA.GOV

OBJECTIVES High tire pressure / temperature effects on Hot Mix Asphalt (HMA) permanent deformation using Asphalt Pavement Analyzer (APA). Conducting research into the design of HMA to resist damage from high pressure aircraft tires. Test results will be compared with the FAA’s full scale test data.

ICAO ANNEX 14 Annex 14 - Aerodromes. Volume I - Aerodrome Design and Operations. 2.6 Strength of pavements 2.6.6 Information on pavement type for ACN-PCN… a) Pavement type for ACN-PCN determination:… b) Subgrade strength category:… c) Maximum allowable tire pressure category: Code no pressure limit W pressure limited to 1.50 MPa X pressure limited to 1.00 MPa Y pressure limited to 0.50 MPa Z

FAA CUSTOMIZED APA The 100 psi (0.69 MPa) and 104°F (40°C) are adopted for APA test conditions. Simulating highway traffic (load) and environment conditions. FAA customized APA that is capable of applying tire pressures representative of a heavy commercial aircraft (250 psi +).

FAA CUSTOMIZED APA

APA TEST CONDITIONS Three test conditions are selected to simulate effects from high tire pressures and high pavement temperatures in airport pavements. All tests conducted in dry condition. Pneumatic cylinders applied 100 lbf load at 60 Hz frequency. Contact Pressure, psi / Temperature, °F 100 / 140 (= 0.69 MPa / 60°C) 250 / 70 (= 1.72 MPa / 21°C) 250 / 140 (= 1.72 MPa / 60°C)

TEST SPECIMENS High Tire Pressure (HTP) pavement test area at the FAA’s National Airport Pavement Test Facility (NAPTF). 6-inch diameter by 3-inch high cylindrical samples are used for APA testing after cored from HTP area. The top 3-inch (76 mm) from 6-inch high core was used for the testing. FAA’s P401 specification based on Marshall mix design procedure was used for the HMA mix design. PG 64-22 is selected and used for the HTP test area construction.

P-401 GRADATION

DATA ANALYSIS Direct comparisons of rut depth, rut depth slope, and rut rate respectively. Adopted VESYS method (pavement structure) to predict permanent deformation for extended APA stroke numbers. Effects from high tire pressures and temperatures are relatively compared.

RUT DEPTH COMPARISONS Temperatures effects under high contact pressure of 250 psi (1.72 MPa): 70°F (21°C) and 140°F (60°C). Contact pressure effects under high test temperature of 140°F (60°C): 100 psi (0.69 MPa) and 250 psi (1.72 MPa). Manual rut depth measurements shows about ±0.25 mm differences from APA monitored rut depth.

TEMPERATURE EFFECTS ON HMA RUT DEPTH

CONTACT PRESSURE EFFECTS ON HMA RUT DEPTH

RUT SLOPE COMPARISONS Rut slope changes at different APA test conditions. Rut slope is computed by D (rut depth) / D (pass number). Significant effects by high contact pressure and temperatures.

RUT SLOPE CHANGES at DIFFERENT APA TEST CONDITIONS

RUT RATE COMPARISONS (at Steady State) Pressure, psi Temperature, °F Rut Rate (between 1500 and 5000 passes), mm/pass number 100 (0.69 MPa) 140 (60°C) 0.000475 250 (1.72 MPa) 70 (21°C) 0.000294 0.000622* *The rut rate would be 0.000275 mm/pass with the secondary stage

RUTTING STAGES USING APA TEST DATA Secondary Primary Tertiary

VESYS METHOD VESYS method (pavement structure) was adopted to predict permanent deformation for extended APA stroke numbers. Effects from high tire pressures and temperatures are relatively compared. System rutting formulation considering the pavement system as a whole structure including all the layers as shown in following equation

VESYS METHOD (continued) Permanent deformation was predicted for extended APA stroke numbers until 15000 passes. Assumed the sublayers are all metal plates (no permanent deformation during the APA testing) to simulate APA test conditions.

CONCLUSIONS FAA customized APA equipment is capable of applying tire pressure representative of a heavy commercial aircraft. APA tests at high tire pressures and temperatures were conducted and the acquired data was analyzed. These test results will be used to augment the full scale testing program at the NAPTF. Rut depth increased significantly with higher contact pressures and temperatures. The permanent deformation was more sensitive to temperature than to the contact pressure changes.