Performance Testing: Cracking Group Experiment. Randy West Director, National Center for Asphalt Technology

Transcription

1 Performance Testing: Cracking Group Experiment Randy West Director, National Center for Asphalt Technology

2 Outline What are Performance Tests? Why do we need them? When should we use them? What are we doing to move toward implementation?

3 What are Performance Tests" Additional tests beyond volumetric properties Intended to indicate a mix's resistance to particular distresses (i.e. field performance) May or may not yield an engineering property

4 Performance testing is the art of molding materials we do not wholly understand into shapes we cannot precisely analyze, so as to withstand forces we cannot assess, in such a way that the community at large has no reason to suspect our ignorance. Source unknown

5 Recycled Shingles With the current volumetric mix design system Sulfur pellets Fractionated RAP Recycling agents Recycled Tire Rubber Aramid & Polyolefin fibers

6 Uses of Performance Tests For Research Purposes To evaluate new materials or design strategies As Part of Mix Design Process (i.e. Balanced Mix Design) To identify mixtures prone to performance problems To gain confidence on Warranty projects For Quality Assurance Purposes To assess how plant mix could impact performance and use in pay adjustment factors

7 Important Test Aspects 1. Strong relationship to performance 2. Practical: cost, time, complexity 3. Repeatable, reproducible

8 Rutting Tests E* and Fn irlpd APA Hamburg Shear Stiffness AASHTO TP 79 AASHTO TP 116 AASHTO TP 63 AASHTO T 324 AASHTO T 320

9 Moisture Damage Susceptibility Tests Tensile Strength Ratio AASHTO T 283 Hamburg Wheel Tracker AASHTO T 324

10 Moisture Damage Susceptibility Testing AASHTO T 283, Tensile Strength Ratio Procedure is well established for mix design approval and verification of plant mix 1 week to complete the test Precision statistics Single-operator d2s = Multi-lab d2s = Pass/Fail criteria on TSR Some states also have minimum conditioned tensile strength AASHTO T 324, Hamburg Wheel Tracking Test Specified by a growing number of states and used by numerous researchers 1 to 2 days to complete test $60,000+ equipment cost Precision statistics unknown, suspected to be poor Pass/Fail criteria on SIP

11 Modes of Cracking Fatigue Top-Down Reflection Thermal Block Load Related Environment Related

12 Fatigue Tests Beam Fatigue AASHTO T 321 Simplified Visco-Elastic Continuum Damage Texas Overlay Tester TEX 248-F

13 Low Temperature Cracking Tests IDT Creep Compliance AASHTO T 322 Semi-Circular Bend Disk-Shaped Compact Tension TSRST

14 Top-Down Cracking Tests SCB-LA SCB-IL OT-TX OT-NCAT Energy Ratio Nflex Factor Cantabro

15 Validation of Performance Tests Researchers generally develop methods independently Many tests lack a regional or national validation effort with field pavements Most have unknown precision statistics Laboratory aging protocols are still being researched

16 MnROAD + NCAT Cracking Group Experiments

17 Scope of Experiments NCAT Test Track Top-down cracking MnROAD Low-temperature cracking

18 Cracking Group Sponsors Washington Oregon Nevada California Montana Idaho Wyoming Utah Colorado North Dakota South Dakota Nebraska Kansas Minnesota Iowa Wisconsin Missouri Michigan (upper pennisula) Illinois Michigan Indiana Kentucky Tennessee Ohio New York Pennsylvania West Virginia Vermont New Hampshire Delaware Maryland Virginia North Carolina Maine Massachusetts Rhode Island Connecticut New Jersey FHWA Arizona New Mexico Oklahoma Arkansas Mississippi Alabama (DOT & DEM) Georgia South Carolina Texas Louisiana Florida

19 Top-Down Cracking Sections Cracking Group sections ft. sections each section instrumented Surface Layer 1.5 Intermediate Layer 2.25 Base Layer 2.25 Granular base 6 Stiff track subgrade infinite HiMA mix 21

20 Top-Down Cracking Tests SCB-LA IFIT OT-TX OT-NCAT Energy Ratio NCAT is conducting these tests on both LMLC and PMLC samples that are aged and unaged.

21 CG Performance to Date March 15, MESALs Section Description Rutting (mm) Δ IRI (in/mi.) Δ MTD (mm) Cracking (% of lane) N1 20% RAP (Control) N1 Control w/ High Density N5 Low AC, Low Density N8 20% RAP 5% RAS S5 35% RAP PG S6 Control w HiMA S13 AZ Rubber Mix

22 Energy Ratio on Unaged PMLC Specimens 24 based on field cores aged in service UF recommended criteria 1.95 for 1 MESAls per year

23 SCB on Unaged PMLC Specimens on LTOA specimens LADOTD criteria as of kj/m 2 for 3 MESALS for 20 yr. design 0.6 kj/m 2 for 3 MESALS for 20 yr. design

24 OT on Unaged PMLC Specimens NJDOT criteria as of for PG surface mixes 175 for PG surface mixes TXDOT criteria not clear, changing 300 for some mixes

25 OT-NCAT Mod. on Unaged PMLC Specimens 27 similar ranking at Texas OT

26 IFIT on Unaged PMLC Specimens Preliminary Flexibility Index criteria = 8 28

27 MnROAD Cracking Group Test Section Update

28 MnROAD Test Sections Cracking Group Cells

29 Asphalt Mixtures CELL NO BINDER GRADE ABR % RAS 16 64S Yes 17 64S Yes 18 64S No 19 64S No 20 52S No 21 58H No H No 23 64E No All mixes are 12.5 mm NMAS All mixes are Ndes = 80 and target air voids = 4.0% except cell 19 which has Ndes = 100 and target air voids = 3.0% 1 Cell 22 limestone aggregate in mix 2 Highly modified asphalt binder

30 Cracking Modes and Testing Types of cracking investigated Low temperature Top-down likely Fatigue also possible PMLC testing Low temp: DCT-MN and IDT Creep or SCB-MN Intermediate temp: IFIT, OT, BBF E*, TSR, Hamburg, loose mix, cores Sampling for other research studies

31 DCT Results

32 Hamburg Results SIP = 7500 Passes

33 TSR Results TSR C16 C17 C18 / C19 C20 C21 C22 C23 Design TSR PMLC TSR

34 IFIT Results

35 Next Steps Aging protocol established: loose mix C Laboratory testing of all mixes (unaged and aged) to be completed by next spring Test sections will remain in place until we have separation of performance.

36 Thank You