Advances in Tes,ng of Asphalt Pavements & Materials. Randy West NCAT Director

Transcription

1 Advances in Tes,ng of Asphalt Pavements & Materials Randy West NCAT Director 1

2 Some Tests I ll Talk About Bond Strength Three- Wheel Polishing Device Load- Related Cracking Tests Bending Beam FaDgue Texas Overlay Tester IDT Fracture Energy IDT Energy RaDo Simplified ViscoelasDc ConDnuum Damage Semi- Circular Bend Test 2

3 Interlayer Bond Strength Test Overlay Existing Pavement Bonded Interface Simple shear method to evaluate strength of bond between pavement layers Op,mize tack coat materials and applica,on rates for different pavement surfaces Forensic evalua,ons General criteria of 100 psi min. bond strength 3

4 3- Wheel Polishing Machine Simulated trafficking of pavement surfaces to evaluate changes in texture and fricdon Used with Dynamic FricDon Tester and Circular Texture Meter Assess uldmate fricdon results in a few days 4

5 3- Wheel Polishing Machine Simulated trafficking of pavement surfaces to evaluate changes in texture and fricdon Used with Dynamic FricDon Tester and Circular Texture Meter Assess uldmate fricdon results in a few days 4

6 3- Wheel Polishing Machine Simulated trafficking of pavement surfaces to evaluate changes in texture and fricdon Used with Dynamic FricDon Tester and Circular Texture Meter Assess uldmate fricdon results in a few days 4

7 Tests for FaDgue Cracking Test Method Bending Beam FaDgue AASHTO T 321 Simplified ViscoelasDc ConDnuum Damage AASHTO PP Texas Overlay Tester Semi- Circular Bend IDT Energy RaDo Disc- Shaped Compact Tension Test TEX F LTRC UF ASTM 5

8 Why we need a reliable cracking test? Economics drive us to use lower asphalt contents and more recycled binders which tend to reduce strain tolerance. TradiDonal mix criteria have weak reladonships to performance and restrict innovadon. 6

9 Bending Beam FaDgue TesDng AASHTO T 321 Temperature: 20 C Frequency: 10 Hz 3 beams at 3 strain magnitudes 200 to 800 με Beam size 2.5 x 2 x 15 7% air voids 50% s,ffness reduc,on 7

10 Bending Beam FaDgue Results 8

11 FaDgue Endurance Limit 9

12 IDT Fracture Energy Simple sample preparadon Quick test, monotonic loading, 4 strain measurements 10 C test temperature Analysis is straight forward Specimens long- term aged prior to tesdng Stress, σ instant of fracture Fracture Energy Strain, ε 10

13 IDT Fracture Energy CorrelaDon with fadgue cracking at WesTrack R. Kim and H. Wen, AAPT

14 Texas Overlay Tester (Tex F) Test for fa,gue or reflec,ve cracking Developed to simulate overlay on horizontal joint movements of PCC Specimen cut from field core or SGC specimen Repeated direct tension, triangular 10 sec. waveform (5 sec loading and 5 sec unloading) 12

15 Texas Overlay Tester 93% Load ReducDon 13

16 Energy RaDo Developed at U of FL to determine top- down cracking poten,al Three IDT tests required: Resilient modulus Creep compliance Fracture energy 10 C Criterion: ER > 1.95 for trafficking less than 1,000,000 ESALs 14

17 S- VECD (AMPT FaDgue) TesDng AASHTO PP Drag procedure by NCSU Cyclic load: 10 Hz 19 C (or based on MAAT) E* needed first to esdmate strain levels 4+ replicates of AMPT sample Failure defined as a sharp reducdon in phase angle Two failure targets: 1,000 and 10,000 cycles 15

18 SVECD (AMPT Fa,gue) Test PseudosDffness versus damage curve (C vs. S) NCSU program allows user to characterize fadgue life for any strain level, temperature, and frequency 16

19 Summary of S- VECD FaDgue PredicDon 45% RAP PG % RAP PG Virgin 17

20 Consumer Reports Style Much beper than average Beper than average Average Less than average Probably a liability 18

21 Tests for FaDgue Cracking Test Std. Method Field Verified Eqmt. Cost Time to Result Best Buy BBF SVECD Overlay Tester SCB Energy RaDo Fracture Energy 19

22 Thank You 20