Presentation on theme: "Selecting the Correct PG Asphalt for Your Airport Project"— Presentation transcript:
1Selecting the Correct PG Asphalt for Your Airport Project A Driving Force In Asphalt29th Annual FAA Airports ConferenceHershey, PAMarch 2, 2006Ronald CorunCITGO Asphalt Technical Support ManagerCITGO Petroleum Corporation
2What is SUPERPAVE? New Asphalt Binder specification New Mix Design procedure using a new laboratory compaction device
3We Have Three Asphalt Binders Q. How do we determine which asphalt binder is best for our project?A. The asphalt binder that gives the best performanceABC
4Performance ? Q. What areas of poor performance do we want to avoid ? Or, in other words, how do our asphalt pavements fail ?
12Problem with one temperature grading According to the Penetration system:According to the Viscosity System:
13Asphalt bindersQ. Are the properties of asphalt binders constant over a pavements performance life?A. NO! An asphalt binder’s response to loading is a function of three factors. . .AgeTemperatureRate of Loading
14Asphalt binder’s response to loading is a function of. . . 1. age
15AgingAsphalt binders undergo aging through the loss of volatiles (a.k.a. loss of light ends) and oxidation.From the standpoint of determining an asphalt binder's performance there are three key ages we need to address.
16Key Aging New material - no aging During construction Aging in the plantAging during placementLate in the pavement's lifeyears of service
17Aging - How ?Early: To simulate the aging that occurs due to construction and initial service, we are going to employ the Rolling Thin-Film Oven (RTFO). This is a standard AASHTO test method, T 240.Spec.: 85 minutes, 163°C, 400 ml of air per minute, 15 rpm
18Rolling Thin Film Oven163°Ccontrolsfanbottle carriageair jet
21Aging - How ?Long term: To simulate the aging that occurs due to oxidation over a pavement's life, we are going to subject the RTFO residue to time, temperature, and pressure. For this we are going to develop a pressure aging vessel, (PAV).
22Aging - How ? Long term, Spec.: AASHTO PP1. According to PP1, our RTFO residue is subjected to:Temperature: 90 to 110°CTime: hoursPressure: kPa
40DSR provides G* and G*, Complex Shear Modulus , Phase Angle G* / sin Correlates to rutting resistance.G* sin Correlates to fatigue resistance.
41Rutting Specification - Minimum Stiffness @ T(high) G* / sin > 1.00 kPa on unaged binderG* / sin > 2.20 kPa on RTFO aged binder
42Pavement Age Low Temp Fatigue Cracking Cracking Construction Rutting [DTT][RV][DSR][BBR]Pavement AgeRTFO - agingNo agingPAV - aging
43Fatigue Cracking Specification - Maximum Stiffness @ T(inter) G* sin < 5000 kPa on PAV aged binder
44Pavement Age Low Temp Fatigue Cracking Cracking Construction Rutting [DTT][RV][DSR][BBR]Pavement AgeRTFO - agingNo agingPAV - aging
45Superpave Binder Specification Low Temperature Characterization The Bending Beam Rheometer (BBR) determines the Creep Stiffness (S) of an asphalt binder at low temperatures.If a binder is too stiff at service temperatures, you can expect low temperature cracking.
55Bending Beam Rheometer, BBR Deflection(t)simulates stiffness after2 hours at 10 °C lower temp60 secTime
56BBR Data - Relaxation slope = m-value 60 sec Log Creep Stiffness, S PG Specslope = m-valueLog Loading Time60 sec
57Low Temperature Cracking Specification Maximum Creep Stiffness Value (S)S < 300 MPaMinimum m-valuem > 0.300
58Other PG Binder Tests . . . Q. What about Construct-ability ? A. A better word might be Pump-ability. A concern raised during SHRP was the need to address modified systems. Heavily modified systems can literally burn-out pumps. To address this, we will use ASTM D 4404, "Brookfield Rotational Viscometer."
59Pavement Age Low Temp Fatigue Cracking Cracking Construction Rutting [DTT][RV][DSR][BBR]Pavement AgeRTFO - agingNo agingPAV - aging
80What is SBS? Styrene-Butadiene-Styrene Styrene provides stiffness at high temperaturesButadiene gives flexibility at low temperaturesComplete dispersion of SBS in asphalt provides best performance
81How is PMA Produced? Start with PG 64-22 Test Asphalt Properties Dissolve and Cross-link SBS MoleculesReaction TimeConstant AgitationConstant HeatTest Asphalt PropertiesPerformance PropertiesHomogenous MaterialConsistency
85Superpave Plus Binder Specifications Used to ensure polymer-modificationExample: PG Plus Maximum phase angle of 75 degreesTest methodsDSR Phase Angle (Engineering value)Amount of Stretch and/or Recovery (Empirical)
87PG Binder Selection for Airports How do we get from ESALs to Airplanes?Airfield Asphalt Pavement Technology Program (AAPTP)Research funded by AIR-21Managed by Auburn UniversityPrimarily will research adapting Superpave to airfieldsUntil research is complete – common sense guidelines developed by FAA and DOD
88FAA and DoD General Guidelines for Binder Grade Selection on Airfields Consult with local DOTDetermine grades that are typically being used and are available for the particular areaDetermine the “Standard Grade”Typically used for highways with less than 10 million ESALsSufficient on most GA airportsConsider ‘Bumping’ for top 5 inches if concernedPast performance?High tire pressures?Standing or slow traffic (stacking on TWs)?Channelized traffic (alleyways)?
89Grade Bumping Example - Airfields For Aircraft < 12,500 lbs PG 64-22For Aircraft < 100,000 lbs PG or PG 76-22For Aircraft > 100,000 lbs PG or PG 82-22Need to Consider Traffic Flow
90The higher the Grade, the stiffer the binder. The more rut resistance. Rule # 1PG 82PG 76PG 70PG 64PG 58The higher theGrade, the stifferthe binder.The more rutresistance.
91The lower the number, the more resistant to thermal cracking. Rule # 2PG - 22- 28-34The lower thenumber, the moreresistant tothermal cracking.
92The greater the difference Rule # 3PG 82O 22OPG 76O 22OPG 70O 22OPG 64O 28OPG 64O 22OPG 58O 28O104O98O92O86OMix Cost %Mix Cost %The greater the differencethe higher the cost.
93CONCLUSIONSTraining needed for everyone if SUPERPAVE is to be used successfullyPG Grade System provides the right asphalt for varying climate and traffic conditionsSUPERPAVE places more tools in the Pavement Designers’ Tool BoxDesigners can solve pavement problems they were unable to in the past using SUPERPAVESUPERPAVE