Innovations in HMA Performance Testing John D’Angelo D’Angelo Consulting, LLC Canadian User Producer Group for Asphalt Moncton 2009

Materials Testing The HMA is tested in some fashion to simulate the real world. The HMA is tested in some fashion to simulate the real world. The tests go from simple to sophisticated. The tests go from simple to sophisticated. From Empirical to Fundamental. From Empirical to Fundamental.

What is a performance test? It is a test that directly or indirectly relates to the performance characteristics of the material. It is a test that directly or indirectly relates to the performance characteristics of the material. These tests can be Empirical or Fundamental or a combination of both. These tests can be Empirical or Fundamental or a combination of both. Empirical tests relate results to past experience. Empirical tests relate results to past experience. Fundamental tests relate stress, strain, and temperature to past performance. Fundamental tests relate stress, strain, and temperature to past performance.

APA Sample APA Sample Small sample with loading very unlike the real world. Must be correlated over a narrow range of conditions and material to the real world.

Hamburg Tester Unrealistic loading. Again must be correlated over a narrow range of conditions and material to the real world.

Next Generation of Performance Testers New tests have a closer relationship to fundamental properties of the mix. New tests have a closer relationship to fundamental properties of the mix. Measured material properties tied to performance models to estimate distress. Measured material properties tied to performance models to estimate distress.

SST Device Developed during SHRP to evaluate mix performance. Expensive, complicated, difficult to interpret results.

8 Simple Performance Tests (SPTs) Development 9-19Identification of SPTs and Protocol Development (Complete) 9-29Equipment Specification and Development for SPTs (Active) 9-33 A Mix Design Manual for Hot Mix Asphalt (Active)

AC Mix Performance Tester The test can evaluate the rutting and fatigue response of the AC mix. The equipment is relatively inexpensive and easy to use. Test results are inputs for the Mechanistic Empirical Pavement Design Guide.

Sample Preparation IPC ServoPac Superpave Gyratory Compactor 180 – 190 mm Ht. 180 – 190 mm Ht. Va = 9.5%

Sample Preparation Test Specimen Va = 8%

Performance Tests E* – Dynamic Modulus Fn – Flow Number (Repeated Load) Ft – Flow Time (Static Load)

Dynamic Modulus E* Load Displacement 75 ~ 125 µε   Loading Frequency Phase Angle * 0 0    E 0  0  = dynamic stress = recoverable axial strain

|E*| Master Curve

3 f3 2 f2 1 k k t 1ff E 11 kN                    321 fff ;  ; Calibration Factors Fatigue Cracking Model

HMA Performance Tester Dynamic Creep Dynamic Creep Simulates Traffic Load Simulates Traffic Load Loading on 0.1 sec Loading on 0.1 sec Load off for 0.9 sec Load off for 0.9 sec Repeat sequence Repeat sequence Cumulative axial strains recorded Cumulative axial strains recorded

Flow Number Test (Fn) Dynamic Creep Simulates Traffic Load Loading – 0.1 sec Rest – 0.9 sec

Repeated Load Test Results Laboratory test run at 53.4°C

Repeated Load Axial Test Actual test parameters are still being developed. Actual test parameters are still being developed. Parameters are based on stress conditions in the pavement. Parameters are based on stress conditions in the pavement.

Beam Fatigue Test Test provides loss of modulus with load repetitions. This is empirically compared to field performance. Test is time consuming to run and loading relation to the real world questionable.

Axial Fatigue Test New push pull test allows fatigue testing in the AMPT with inputs to the VEPCD model.

IDT Testing Indirect Tensile test- Used for low temperature properties of the mix Expensive, easy to setup and run. Use Creep Strain and Strength

Use of the BBR device to test mix Main obstacle: the use of smaller size specimens that may not capture overall behavior of pavement Volume of material tested may not be representative Asphalt mixtures contain aggregate sizes larger than smallest dimension of beam

Use of the BBR for Low Temperature Mix Testing Previous research at University of Minnesota suggested use of simpler test method based on creep tests of thin beams in three-point bending Thin beams (6.25 x 12.5 x 100mm) can be used to investigate effect of surface aging, microcracking, and compaction on mechanical properties of asphalt pavements

Loading Procedure Predict Lowest Temperature Creep Stiffness

Performance Testing We have new tools that provide results closer to the real world. We have new tools that provide results closer to the real world. New modeling procedures allow us to do a better job of interpreting the results. New modeling procedures allow us to do a better job of interpreting the results. We can do a better job of estimating performance. We can do a better job of estimating performance.

In the end we still have to build it right

THANK YOU QUESTIONS