AMPT Cyclic Fatigue Test

Transcription

1 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

2 Outline q AMPT Cyclic Fatigue Test Method q Material Properties q FlexMAT TM and FlexPAVE TM q Field Validation q Applications q Summary

3 AMPT Cyclic Fatigue Test Method (AASHTO TP 107)

4 Asphalt Mixture Performance Tester

5 100 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

6 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

7 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

8 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 E E E E E Actuator Time (s) Time (s) On-specimen

9 Material Properties

10 S-VECD Model for Cracking E* (MPa) C Reduced Frequency (Hz) stress/strain amplitudes, and different loading histories. CX_7C CX_13C 0.2 Damage Characteristic Curve E+00 2.E+05 4.E+05 6.E+05 8.E+05 S Log Shift Factor E* Mastercurve -6.0 These characteristic relationships remain the same under E-08 1E-05 1E-02 1E+01 1E Sum (1-C) to Failure COS_13C CS_13C Time-Temperature Shift Factor different modes of loading, different temperatures, different Temperature ( C) y = x R² = Energy-Based Failure Criterion Number of Cycles to Failure

11 Predicted Nf Fatigue Life Prediction 10 Hz, microstrains, three temperatures S9.5C VTe00LC VTe30LC VTe40LC LOE Measured Nf N " = K % ε ( ) * E ).

12 S app as an Index Property S app (a) NH6420-opt NH6420opt S app (b) NH6440-opt NH6440opt NH6440+opt Sapp 1 æ 1 R ö = ç D èc11 ø 1 C 12

13 FlexMAT TM Excel-Based Analysis of AMPT Data

14 Import Data from AMPT

15 FlexMAT TM Analysis E* Mastercurve Damage Characteristic Curve Failure Criterion Rutting Shift Model

16 Export Data to FlexPAVETM

17 FlexPAVE TM 1.0 Pavement Performance Analysis

18 EICM in FlexPAVETM

19 Material Properties

20 Traffic Data

21 Damage Contour

22 Field Validation

23 Validation Sections Validated using 65 asphalt mixtures, including WMA, RAP, and PMA mixtures, from 61 pavement sections

24 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

25 RAP Performance in Pavements NCAT Test Track 7 RAP Mixtures FHWA-ALF 4 RAP Mixture Aggregate Base Aggregate Base % Cracking Measured O FW AW C RW R % Damage Predicted % Damage Predicted by FlexPAVE TM % RAP PG % RAP PG % RAP PG64-22 Control PG No. of 600" Crack Length

26 Applications

27 Forensic Investigation NC-24 with Observed TDC US-74 with Observed BUC

28 Performance-Engineered Mix Design Volumetric Final optimum Cracking Resistance Rutting Resistance Minimum Required % AC Minimum Required Candidate Performance Optimum

29 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

30 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

31 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.

32 Thank you! Questions?