57 th Annual NJ Asphalt Paving Conference Iselin, NJ March 25, Ronald Corun Director- Asphalt Technical Services Axeon Specialty Products

Transcription

1 57 th Annual NJ Asphalt Paving Conference Iselin, NJ March 25, 2014 Ronald Corun Director- Asphalt Technical Services Axeon Specialty Products

2 John D Angelo, Ph.D. P.E. D Angelo Consulting LLC R. Michael Anderson, P.E. Asphalt Institute

3 PG test system uses Dynamic Shear Rheometer to measure stiffness Testing performed at high pavement temperature for pavement location

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5 Construction Rutting Fatigue Cracking Low Temp Cracking [DTT] [RV] [DSR] [BBR] Pavement Age No aging RTFO - aging PAV - aging

6 Place asphalt sample between two steel plates Apply a oscillating shear stress Measure strain Calculate a materials modulus Modulus = Stress / Strain A measure of material stiffness

7 G *, Complex Shear Modulus, Phase Angle G * / sin Correlates to rutting resistance A measure of stiffness

8 G * / sin > 1.00 kpa on unaged binder G * / sin > 2.20 kpa on RTFO aged binder

9 Traffic conditions Weights Speed

10 60 C 1 hour 25 C 1 hour 10 hours

11 RTFO DSR, kpa PG PG Spec 2.2 kpa Test Temperature, ºC 50 mph (10 rad/s) 20 mph (4 rad/s) 5 mph (1 rad/s)

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14 Rut 5000 passes of ALF 11 58ºC mm 24 mm 20 Rut Depth, mm mm AC-10 AC-20 PMA 0 PG PG PG Asphalt Binder Grade

15 Same mix - different binders PG modified no rutting PG unmodified 15mm rutting

16 We currently test a PG at 76 C 170 F Pavements and asphalt binders do not reach 170 F Testing binders at artificially high temperatures which may distort performance PG test high temperature grading does not correlate with field rutting performance

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19 SHRP research used only unmodified asphalts and current test does not measure benefits of elastomeric polymers Most modified asphalts contain an elastomeric polymer Elastomeric material bounces back after load is removed recovers

20 Any new specification must be blind to modification. A new specification must identify the rutting potential of all binder types under multiple conditions. Incorporate a rest period after loading the sample to measure recovery

21 Research looked for a material property other than Stiffness Modulus (G*) that would correlate with pavement rutting Discovered rutting correlation with nonrecoverable compliance (J nr ) J nr is inverse of stiffness

22 Non-recoverable compliance (J nr ) describes stress dependency of the binder For neat asphalts, flow is linear and not sensitive to stress level For polymer-modified asphalts, response is not linear and is sensitive to stress level of the test Perform MSCR testing at two stress levels (100 Pa and 3200Pa) to check how sensitive the asphalt binder response is to stress level

23 Test Procedure Apply 100 Pa Stress for a 1 second Creep period Remove the Stress for a 9 second Recovery period Repeat for 10 cycles Apply 3200Pa Stress for a 1 second Creep period Remove the Stress for a 9 second Recovery period Repeat for 10 cycles

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31 Stiffness Modulus G = Stress/ Strain Compliance J = Strain/Stress J nr and G are inverse values G*/sinδ = 2.2 for RTFO material 1 / /J nr G*/sinδ J nr 0.4 established from research correlating J nr values to mix testing and field performance Research and field data showed cutting J nr in half cut rutting in half

32 Environmental grade plus traffic level designation Four Traffic Levels S = Standard < 10 million ESALs and standard traffic loading H = Heavy million ESALs or slow moving traffic V = Very Heavy > 30 million ESALs or standing traffic E = Extreme > 30 million ESALs and standing traffic

33 PG has 4 grades based on traffic (Standard, Heavy, Very Heavy, Extreme) PG becomes PG 64-22S J nr 4.0 PG becomes PG 64-22H J nr 2.0 PG becomes PG 64-22V J nr 1.0 PG becomes PG 64-22E J nr 0.5 Test temperature is 64 C for all grades and J nr changes for each grade Old PG system the stiffness requirement remains the same, but test temperature changes

34 yr Jnr 3.2 kpa binder mod true grade rut mm 70C Ultrapave SBR Styrelf SB GTR Sealoflex SBS Multigrade Cryo Rubber Control y = x R 2 =

35 Jnr Jnr 12.8kPa PG PG PG y = x R 2 = rut mm

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38 MSCR J nr addresses the high temperature rutting for both neat and modified binders, but many highway agencies require polymers for rutting, cracking and durability Most agencies using polymermodified asphalt use a test in addition to the PG testing to ensure polymer modification PG+ tests are empirical methods to determine the presence of an elastic material Stretch tests Recovery tests

39 PG+ tests in use Phase Angle Elastic Recovery Forced Ductility Toughness and Tenacity PG+ test procedures may vary widely from one agency to another Mold shape Amount of stretch Hold time Test temperature Multiple tests and procedures are burden for suppliers selling to multiple states

40 PG+ tests may determine presence of elastomeric polymer, but not how effectively it is blended with the polymer MSCR % Recovery can identify presence of elastomeric polymer and its effectiveness

41 Strain % 7 6 γ p = Peak strain 5 4 γ r = recovered strain % recovery= (γr / γp) X 100 γ u = un-recovered strain time s

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45 UDOT Elastic Recovery, % AASHTO T301-mod RTFO, 25 C, 20 cm pull and then cut h 200-2h 188-4h 200-4h 188-6h 200-6h 188-6h+X 200-6h+X

46 % Recovery MSCR Recommended Min % Recovery PGXX V Recommended Min % Recovery PGXX H h 200-2h 188-4h 200-4h 188-6h 200-6h 188-6h+X 200-6h+X

47 Mixing Temperature and cross-linking affect the properties of polymer modified binders. The Elastic Recovery showed little difference between the different processing methods. The MSCR J nr and MSCR % Recovery indicated larger differences than the current PG and ER tests. The Larger differences were verified by the Florescence Microscopy. MSCR can replace the ER Single protocol Quick and easy Fundamental property

48 PG Grade PG Grade (J nr ) J nr Spec J nr Value % Recovery Spec % Recovery Value Hamburg Rut Depth (10,000 passes) PG PG 64E NA NA 7.1 mm PG PG 64H NA NA 3.57 mm PG PG 64V >50% 55.8% 1.68 mm PG PG 64E >66% 78.5% 1.55 mm Current Axeon SP Asphalt Binders PG and PG are neat asphalts PG and PG are polymer modified

49 NEAUPG states agreed to implement MSCR grading on polymer-modified grades in 2014 NJDOT specifies PG Testing on current PG binders indicates they are PG 64E-22 NJDOT and other NEAUPG states will specify PG 64E-22 in place of PG For first year Axeon SP will label as follows: PG (PG 64E-22)

50 MSCR research indicates J nr is a major improvement in high temperature PG asphalt testing Much better correlation with rutting in the roadway MSCR % Recovery does a much better job of measuring the presence of polymer and the effectiveness of the polymer in the asphalt than current PG+ tests

51 Questions?