AMPT Cyclic Fatigue Test Y. Richard Kim Jimmy D. Clark Distinguished University Professor Alumni Distinguished Graduate Professor NC State University North East Asphalt User/Producer Group Meeting October 18, 2017
Outline q AMPT Cyclic Fatigue Test Method q Material Properties q FlexMAT TM and FlexPAVE TM q Field Validation q Applications q Summary
AMPT Cyclic Fatigue Test Method (AASHTO TP 107)
Asphalt Mixture Performance Tester
100 mm Dia. Specimen 100 mm 38 mm Dia. Specimen 38 mm 150 mm 110 mm 178 mm 6 gyratory specimens needed 100 mm 2 gyratory specimens needed 150 mm
Advantages of 38 mm Geometry q Saving materials (asphalt mixture and glue) and time (16 hrs curing time vs. less than 1 hr) q Lower load capacity needed q Five-minute epoxy strong enough q Allows testing field cores by horizontal coring of cores
AMPT E* and Cyclic Fatigue Tests q Modulus Axial compression dynamic modulus test (AASHTO T 378) Dynamic modulus mastercurve and time-temperature shift function q Cracking Resistance AMPT cyclic fatigue test (AASHTO TP 107) Damage characteristic curve ü Defines how fatigue damage grows under cyclic loading Energy-based failure criterion ü Defines when test specimen fails
TP 107 Test Protocol q Controlled actuator displacement cyclic test Range of number of cycles to failure between 10,000, and 100,000 cycles q On-specimen strains measured by LVDTs q Total test time for characterization of 1 mixture (3 specimens): within 1 day Strain Stress (kpa) 1.5E-03 1.2E-03 9.0E-04 6.0E-04 3.0E-04 0.0E+00 2000 1500 1000 500 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4-500 -1000 Actuator 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Time (s) Time (s) On-specimen
Material Properties
S-VECD Model for Cracking E* (MPa) 100000 10000 C 1000 1.0 0.8 0.6 0.4 Reduced Frequency (Hz) 70000 stress/strain amplitudes, and different loading histories. CX_7C 60000 CX_13C 0.2 Damage Characteristic Curve 0.0 0.E+00 2.E+05 4.E+05 6.E+05 8.E+05 S Log Shift Factor 100-4.0-5.0 E* Mastercurve -6.0 These characteristic relationships remain the same under 10-7.0 1E-08 1E-05 1E-02 1E+01 1E+04-20 -10 0 10 20 30 40 50 60 Sum (1-C) to Failure 4.0 3.0 2.0 1.0 0.0-1.0-2.0-3.0 50000 40000 30000 20000 10000 0 COS_13C CS_13C Time-Temperature Shift Factor different modes of loading, different temperatures, different Temperature ( C) y = 0.5283x R² = 0.98704 Energy-Based Failure Criterion 0 20000 40000 60000 80000 100000 120000 Number of Cycles to Failure
Predicted Nf Fatigue Life Prediction 10 Hz, 100 700 microstrains, three temperatures 1000000 100000 10000 S9.5C VTe00LC VTe30LC VTe40LC LOE 1000 1000 10000 100000 1000000 Measured Nf N " = K % ε ( ) * E ).
S app as an Index Property S app 16 14 12 10 8 6 4 2 0 (a) NH6420-opt NH6420opt S app 16 14 12 10 8 6 4 2 0 (b) NH6440-opt NH6440opt NH6440+opt Sapp 1 æ 1 R ö = ç D 10000 èc11 ø 1 C 12
FlexMAT TM Excel-Based Analysis of AMPT Data
Import Data from AMPT
FlexMAT TM Analysis E* Mastercurve Damage Characteristic Curve Failure Criterion Rutting Shift Model
Export Data to FlexPAVETM
FlexPAVE TM 1.0 Pavement Performance Analysis
EICM in FlexPAVETM
Material Properties
Traffic Data
Damage Contour
Field Validation
Validation Sections Validated using 65 asphalt mixtures, including WMA, RAP, and PMA mixtures, from 61 pavement sections
FlexPAVE TM Simulation NCAT Test Track (f) OGFC (c) FW (b) AW OGFC Foam Evotherm (a) Control (d) RW (e) R Control RAP+WMA High RAP
RAP Performance in Pavements NCAT Test Track 7 RAP Mixtures FHWA-ALF 4 RAP Mixture Aggregate Base Aggregate Base % Cracking Measured 60 50 40 30 20 10 0 O FW AW C RW R 5 7 9 11 13 15 % Damage Predicted % Damage Predicted by FlexPAVE TM 60 50 40 30 20 40% RAP PG64-22 20% RAP PG58-28 20% RAP PG64-22 Control PG64-22 0 100000 200000 300000 400000 500000 600000 No. of Cycles @ 600" Crack Length
Applications
Forensic Investigation NC-24 with Observed TDC US-74 with Observed BUC
Performance-Engineered Mix Design Volumetric Final optimum Cracking Resistance Rutting Resistance Minimum Required % AC Minimum Required Candidate Performance Optimum
FHWA PRS Framework Sampling of Mixtures/ Data from Paving Project Performance Tests in AMPT FlexMAT TM Excel-Based Data Analysis FlexPAVE TM Pavement Performance Analysis Performance Monitoring & Feedback Incentives/ Disincentives Application of Pay Factors to Life Difference Prediction of Life for As- Designed vs. As- Constructed
Current Status q Ruggedness and inter-laboratory study on TP 107 under FHWA project (both 100 mm and 38 mm geometries) q Shadow projects for PRS specifications Maine DOT Missouri DOT Maryland DOT New Jersey DOT Ontario Ministry of Transportation FHWA/Federal Lands of Highway North Carolina DOT
Summary q q q q AMPT cyclic fatigue test (TP 107) is an efficient test method based on sound mechanistic principles. The AMPT cyclic fatigue test and accompanying models have been validated using over 60 pavements and 60 mixtures, including RAP, WMA, and PMA. Applications include: Determination of endurance limits Prediction of thermal, bottom-up, and top-down cracking Performance-engineered mixture design Local calibration of Pavement ME Design Performance-related QA specifications Forensic investigation of cracking in pavements AMPT cyclic fatigue test can be used to integrate mix design, pavement design, and performance-related QA specifications.
Thank you! Questions?