A New Test for Asphalt Quality: Asphalt Binder Cracking Device (ABCD)

Transcription

1 A New Test for Asphalt Quality: Asphalt Binder Cracking Device (ABCD) Sang-Soo Kim, Ohio University Ohio Asphalt Paving Conference February 6, 2008

2 2 Scope Background ABCD Concept: Operating Principle Development Of ABCD Laboratory Validation Field Validation Application

3 3 ABCD: Asphalt Binder Cracking Device NCHRP-IDEA #99 ABCD: To minimize Low Temperature Thermal Cracking, one of major failure types of asphalt pavements. Nationally, tens of billion dollars are spent to fix the cracked pavement every year.

4 4 AASHTO M320 (Table 1) Assumes Strength & CTE are constant Cracking temperature depends on binder stiffness (BBR) Does not work for modified binders; a(t) Thermal Stress, Strength Soft Stress Strength Stiff Temperature

5 5 AASHTO M320 (Table 2) Assumes CTE is constant; Strength is not constant Cracking temperature depends on binder stiffness (BBR) and strength (DTT) Thermal Stress, Strength Strength Stress Temperature

6 6 ABCD Concept: Operating Principle invar ring electrical strain gauge asphalt Coefficient of Thermal Expansion/Contraction Asphalt = 200 x 10-6 m/m/c Invar Ring = 1.4 x 10-6 m/m/c When temperature drops, asphalt shrinks 100 times or more than the ABCD invar ring. Asphalt compresses the ring. The Electrical Strain Gauge measures this compression. When it cracks, the compression disappears.

7 7 Current ABCD Silicone Mold with Protrusions / Invar Ring Presence of hole in the sample significantly reduced variability

8 8 Stress Distribution on Specimen Prepared with Silicone Mold (for 1.0 MPa Average Stress) Invar Ring 0.82 MPa 0.64 MPa 2.02 MPa 1.57 MPa Asphalt Stress Distribution Hole in Sample

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10 10 ABCD Development Current ABCD Silicone Mold & Invar Ring One Hole in Specimen Start right after trimming at room temperature Cooling: 20C -20C in 1 hr; From -20C, 10C/hr Tcr Standard Deviation = 0.5~1.0C

11 ABCD Test: Typical Results 11

12 12 Advantage of ABCD Simple procedure Single equipment Stiffness, strength, CTE are accounted for close to field conditions Test is forgiving Simultaneous testing of several samples

13 LAB STUDY #1: FHWA Modified Binders 9 Fracture Stress (ABCD), MPa ESI Polymer Modified SBS L EV A G SBS L G SBS R G EV A Flux CMCRA Air-Blow n MRL 191 Unm No Polymer Except CMCRA Unm ABCD Fracture Temperature, C 13

14 Role of Polymer Average (Max) Fracture Stress (ABCD), MPa Polymer Modified PG Binder (FHWA) PG Binder (CA) Roofing Flux Roofing Coat silicone mold, invar ring, 10C/hr ABCD Fracture Temperature, C 14

15 15 Pearson Correlation: FHWA Modified Binders ABCD M320-2 (ABCD) M320-2 M320-1 S m ABCD 1 M320-2 (ABCD) M M S (BBR) m-value (BBR) TSRST

16 16 LAB STUDY #2: Polymer Concentration Binder M320-1 ABCD PG Grade Tcr C Strain, με (strength) Base Base+2% SBS Base+3% SBS Base+4% SBS Base+5% SBS Binders were prepared by ExxonMobil ABCD results Triplicate samples

17 ABCD on SBS Concentration ABCD Fracture Strain, micros 60 5% % 3% 2% SBS Base ABCD Cracking Temp, C 17

18 SBS Concentration vs. Cracking Temp -35 M320-1 ABCD Cracking Temp, C SBS Content, % 18

19 19 Polymer Modification Field Trials (138 data) Asphalt Institute, Engineering Report -215, (2005) Quantification of the Effects of Polymer-Modified Asphalt (page 18)

20 20 Validation #1: Pennsylvania Test Road Constructed in 1976 using 6 AC-20 binders Sections T1 & T5 cracked 4 month later Air Temperature = -29C Pavement Temperature = -23C Sections T2, T4, T6 cracked after 4 years Section T3 never cracked for 7 years Overlaid 1984

21 ABCD Results: PA RTFO Residue RTFO (1 st Try) RTFO (2nd Try) 1 2 Avg Avg T Broken T T T T T

22 ABCD Results: PA PAV Residue PAV Sections 1 2 Avg T T T T T T Trimming error 2. Eccentricity: Ring was off-centered by about 1 mm. 22

23 23 Errors in Sample Preparation Excessive Trimming

24 24 Cracking Index (7yr) vs ABCD (PAV) Cracking Index (7yr) 100 y = 8.91x T1 80 R 2 = 0.94 T T2 T4 20 T6 0 T ABCD (PAV) Tcr, C

25 25 Cracking Index (7yr) vs M320-1 (PAV) Cracking Index (7yr) y = 4.93x R 2 = AASHTO M320; BBR (PAV) Tcr, C

26 26 Cracking Index (7yr) vs BBR Stiffness (PAV) Cracking Index (7yr) y = 7.14x R 2 = BBR Stiffness (PAV) Tcr, C

27 TSRST VS ABCD (PAV) FHWA Study PA Study y = 0.74x R 2 = 0.85 TSRST, C y = 0.54x R 2 = ABCD (PAV) 27

28 Validation #2: Lamont Test Road y = x R 2 = Thermal Cracks /km (2003) Lamont Test Road ABCD Tcr, C 28

29 29 Validation #3: Highway 17 (SPS-9A) near Petawawa Ontario Highway 17, Ontario y = x R 2 = Crack/km (2003) ABCD Tcr, C

30 30 Critical Temperature vs. Cracking Index of Test Pavements Coefficient of Determination (R 2 ) Test Roads ABCD M320-1 M320-2 Elk Co, PA Lamont Highway

31 31 ABCD Commercialization Timeline Commercialization by EZ Asphalt Technology, LLC. through Highways for LIFE Technology Partnership Program $239,000 Grant Ruggedness Test by October 2008 ABCD Commercial Products by End of 2008 Round Robin Tests (10 labs) During 2009

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34 34 Summary Good correlation between ABCD and Pennsylvania Test Road performance Good correlation between ABCD and TSRST Able to characterize polymer modified binders Improved repeatability: ~1.0C or less for binders tested ABCD test is simple and forgiving Sturdy ABCD ring

35 Acknowledgement NCHRP-IDEA #99 (Inam Jawed, Ed Harrigan) David Powers (Ohio DOT) Highways for LIFE (Julie Zirlin, Sarah Tarpgaard) Tom Harman (FHWA) Aroon Shenoy (FHWA) Jack Youtcheff (FHWA) John D Angelo (FHWA) Dean Maurer (Penn DOT) Kai Tam (Ontario MOT) Simon Hesp (Queen s Univ.) Olga Puzic (ExxonMobil) Asphalt Institute 35

36 Thank You! 36