Advancements in Characterization of Modified Bitumens. H. Bahia The University of Wisconsin-Madison

Transcription

1 Advancements in Characterization of Modified Bitumens H. Bahia The University of Wisconsin-Madison

2 Lecture Outline Targets of bitumen modification Types of bitumen modifications Traditional methods of testing PMBs New methods for evaluating modified bitumens: Production and construction Performance related Future trends

3 The Targets of Modification 1- Temperature Sensitivity Thermal Cracking Fatigue Cracking Rutting Mixing & Construction Stiffness, G* Typical bitumen Ideal (modified) bitumen Temperature

4 Targets of Modification 2- Better Failure Envelop Log Stress Temp. Unmodified bitumen Modification Stronger, More Ductile Modified bitumen log Strain

5 Enhanced Performance of HMA by Use of Polymer Modification (H. Von Quintus AMAP Meeting 2/ % less Cracking

6 Enhanced Performance of HMA by Use of Polymer Modification (H. Von Quintus AMAP Meeting 2/ % less Rutting

7 Target Distresses that would justify modifiers- 52 Agencies Rutting 39/52 Low temperature cracking 28/52 Fatigue Cracking 21/52 Aging 14/52 Moisture Damage 14/52

8 Modifier Identification of Asphalt Modifiers Terrel and Epps, 1989 Romine et al., 1991 Peterson 1993 Reference Moratzai Moulthrop 1993 McGennis 1995 Isacsson & Lu 1995 Banasiak and Geistlinger Thermoplastic P. X X X X X X X 2.Thermoset P. X X X X X X X 3.Fillers/Reinf. 4.Agents/Extenders X X X X X X X X X 5.Adhesion Prom. X X X X X X 6.Catalysts X X X X X X 7.Aging Inhibitors X X X X X X X 8.Others X X X X Total number * *(27 ASA): Antistripping Additives

9 Asphalt Modification Variables With additives Monomer types and combinations Molecular architecture Amount used Method of mixing with asphalt Third component additives Without additives Oxidation (process) Multi grade Acids (catalysts)

10 Modifiers in Bitumen - Microscopic Observations Neat SBR Oxidized EVA SBS PE No Satbilizer

11 Modifiers Most Commonly Used Highway Agencies in U.S Generic Type Total No. of Users ELASTOMERIC POLYMRES 69 (54%) PLASTOMERIC POLYMERS 13 (10%) MINERAL FILLERS 13 (10%) ANTI-OXIDANTS 13 (10%) HYDROCARBONS 12 ( 9%) PROCESS-BASED 8 ( 7%)

12 Modifiers Most Commonly Used Polymer Modifiers POLYMERS - ELASTOMERS Styrene Butadiene Styrene (SBS) 28 Styrene Butadiene Rubber Latex (SBR) 17 Styrene Butadiene (SB) 16 Styrene Isoprene Styrene (SIS) 1 Styrene Ethylene Butylene Styrene (SEBS) 1 Polyisoprene (natural and synthetic) 1

13 2004 Survey in USA By AMAP Mr. John Casola

14 Specifications & Tests of Modified Bitumen / First Generation AASHTO-AGC-ARTBA-~ Task Force 31 Polymer Modified Asphalts Table 1 - Styrene Block Copolymers Table 2 - Styrene Butadiene Rubber Latexes or Neoprene Latex Table 3 - Ethylene Vinyl Acetate or Polyethylene

15 Pre- PG grading Specifications Task Force 31: Polymer Modified Asphalts- Table 2 Styrene Butadiene Rubber Latexes or Neoprene Latex 2-A 2-B 2-C Penetration, 77 F, 100 g, 5 sec min Viscosity, 140 F, Poises min Viscosity, 275 F, cst max Ductility, 39.2, 5 cpm, cm min Flash Point, F min Solubility, % min Toughness, 77 F, 20 ipm, in-lbs min Tenacity, 77 F, 20 ipm, in-lbs min RTFOT or TFOT Residue: Viscosity, 140 F, Poises max Ductility Retention, 39.2 F, 5cpm, cm min Toughness, 77 F, 20 ipm, in-lbs min Tenacity, 77 F, 20 ipm, in-lbs min

16 Traditional Tests for Modified Asphalts Isacsson and Lu Elastic 25 C Toughness and 25 C Not a Stan dard Not a stan dard Tensile (extensional) Properties An index of the capability for elastic recovery. Measured using the conventional ductility set up but sample is stretched and then cut to measure recovery of cut ends. Method has been modified several times and is run using sliding plate rheometer, ARRB Elastometer, Consistometer, and torsional loading set-up. One of the most widely used to determine if modified binder includes elastomers. Used in North America, Australia and Europe. An index of energy to failure used to detect modifiers and assess their contribution to toughness. A hemispherical head is inserted in an asphalt container and then pulled out. The area under the load deformation curve is divided into an initial peak area and a terminal tenacity area. The sum is the toughness. Elastomeric modifiers could have a significant effect particularly if they are cross linked.

17 Elastic Recovery USA Ductility & Australian Elastometer

18 Toughness and Tenacity

19 1993- SHRP Performance- Grading Does it apply for PMBs? Binder Grades Climatic Basis for Spec Unaged (tank) binder Aged (construction) binder Aged (pavement) binder PG 58 PG 64 PG 70 Performance Grade Average 7-day Maximum Pavement Design Temperature, C (a) < 58 < 64 < 70 Minimum Pavement Design Temperature, C >-10 >-20 >-30 >-40 >-10 >-20 >-30 >-40 >-10 >-20 >-30 Original Binder Flash Point, AASHTO T48, minimum, C Viscosity, ASTM D4402 (Brookfield): 230 Max, 2 Pa-s (2000 cst) Test Temp, C 165 Dynamic Shear, SHRP B-003: G*/sin delta, min 1.0 kpa (0.145 psi) Test 10 rad/s, C Rolling Thin Film Oven Test (AASHTO T240, ASTM D2872) Residue Mass Loss, max, % Dynamic Shear, SHRP B-003: 0.3 G*/sin delta, min 2.0 kpa (0.290 psi) Test 10 rad/s, C PAV Aging Temperature, C Dynamic Shear, SHRP B-003: G* sin delta, max, 3000 kpa (435 psi) Test 10 rad/s, C Creep Stiffness, SHRP B-002 (b): S, max, 2 E05 kpa, (29000 psi) m-value, min, 0.35 Test 60 s, C Direct Tension, SHRP B-006: Failure Strain, min, 1.0% Test 1.0 mm/min, C Tests/Criteria Test Temp

20 What are the new challenges? We are not sure.. What temperatures to use in mixing and Compaction! Why modified binders are better for rutting! Not sure what is fatigue and how binders affect it! If Modifiers affect moisture damage If MP1a (DTT strength) makes a Difference! What to do about the RTFO and PAV for modified binders!

21 New / advanced testing needed for modified bitumens Thermal Fatigue Cracking Cracking 4. Fracture 3. Binder strength fatigue strain at failure glass transition Permanent Deformation 2. Binder repeated creep 5. SAFT 6. Cohesion PAV RTFO (mixing & compaction) 1. Viscosity at variable shear rate Pavement Temperature, C

22 New Testing for Modified Bitumens Screening Testing: LAST: Storage stability with/ without agitation PAT : Particulate Additives Mixing and compaction temperatures Performance Related Replace G*/sinδ with a binder rutting test Replace G*sinδ with a binder fatigue test Thermal Cracking Tgtesting Strain and stress at failure

23 Storage Stability The Lab Asphalt (bitumen) Stability Test (LAST) Electric Motor 2000 RPM Temperature Probe Purge (N 2 ) Sampling Temperature Controller (Brookfield) Insulation Time, Temperature, & Agitation Baffle (4) Internal Heater Propeller (4 Blades) External Heater

24 Particulate Additive Test (PAT)

25 Mixing and Compaction Temperatures Viscosity as a function of shear rate ZSV Viscosity, cps 6.E+05 5.E+05 4.E+05 3.E+05 2.E+05 1.E+05 1.E+03 Modified - 1 Modified -2 Unmodified Shear Rate, 1/s

26 Old vs. New Compaction Temperatures C Lower Temp. C Compaction T: /s Compaction T: 3000 ZSV

27 Rutting: Do We Need to Change G*/Sin d, and How? For Modified Binders YES we do!

28 Current Test: Cyclic Loading Could be OK only if elasticity is low Strain 2% Strain 25% Strain 50% Stress/ Strain Can only give total energy: Torque (stress) Total W dissipated = π.τ i2.sin δ/ G* = W elastic + W delayed elastic+ W viscous γ 2 τ 2 This could be OK for conventional bitumens because they are mostly viscous. But not for modified elastic bitumens

29 Why is loading mode so important? Truck Load Current b) DSR Traffic Repeated creep a) Time Time Paveme nt Strain Elastic + Delayed Elastic (Recoverable) Viscous (Permanent) Time Cannot Separate Permanent from Recovered!!! Can Time

30 Binder Rutting Test (DSR) Accumulated Strain Strain (mm/mm) Test data Fit Cycles Time (seconds)

31 To Separate non-recoverable Four-Element (Burgers) Model Strain τ0 Elastic Response γ1 G0, γ1 γ2 Delayed -Elastic Response G1, γ2 η1, γ2 γ1 γ 3 η0, γ3 Time Viscous Response τ0

32 Simplest Analysis Method to where Separate Permanent Strain J ( t) = 1 G 0 = + J e 1 G J e = elastic compliance, 1 J de (1 ( t) e tg 1 J / η1 J de = delayed elastic compliance, and + J v = viscous compliance. + v ) ( t) + 1 η 0 t SS Steady State Viscosity

33 Modification Can Reduce Damage Creep Tests at 70C, 300 Pa shear stress (Loading 1s Recovery 9s) 100 cycles Strain, mm/mm Accumulated Strain PG 82- Oxidized PG82- PEs PG-82- SBSr No Additive Plastomer (s) Time, sec Elastomer

34 Multiple Stress Creep Recovery Test of Asphalt Binder Using a Dynamic Shear Rheometer (MSCR) AASHTO TP67 Note: taken from D Angelo 2005 [3]

35 Modified binders can improve resistance to RUTTING

36 Fatigue Do we need to change G*.Sinδ? Yes For all Binders

37 Perpetual Pavements 4 to 6 Zone Of High Compression SMA, OGFC or Superpave High Modulus Rut Resistant Material (Varies As Needed) Max Tensile Strain Flexible Fatigue Resistant Material 3-4 Pavement Foundation

38 Binders Vary Significantly In Fatigue Behavior 1.6E+07 G*, Pa 1.4E E E+07 G* (Pa) 8.0E+06 What 6.0E+06 is measured 4.0E+06 initially is not 2.0E+06 maintained with time/cycles E Cycles Number of Cycles in the DSR

39 Determination of Fatigue Life of Binders Using the DSR Stress τ max Strain γ max

40 Dissipated Energy Ratio Pronk (DWW) defined the Ratio of dissipated energy (R de ) as follows: R de In which W n = the total sum of the dissipated energy up to cycle n, and W n = the dissipate energy at cycle n. = W n W n

41 Bitumen Damage Behavior As Related to Fatigue Dissipated Energy Ratio Np No. of Cycles

42 Work on Binder Fatigue Edge effects or fatigue 5-15 MPa range Anderson et al. Nynas (Soenen & Redelius ) Compare standard Parallel Plate to other geometry/method. Asphalt mastic (Little,Lytton, et al.) Mini mixture High stiffness Rilem TG1 Round Robin study

43 Thermal Cracking Visco-elasticity Failure Stress Failure Strain Glass Transition

44 What Causes Thermal Cracking? Due to cooling, asphalt is subjected to stress. t dε( τ ) σ ( t) = E( ξ ξ ) dτ dτ 0 Volume Change With Temperature From Tg From BBR Cracking occurs if stress exceeds strength, or if strain exceeds strain tolerance

45 How Does Volume Change? Glass Transition Measurements 0 Sample Tv0 (C) =40 v=c v +a g (T-T g )+R(a l -a g )ln{1+exp[(t-t g )/R]} Specific Volume Change (1e-6ml/g) -10,000-20,000-30,000-40,000 c v = T g (C) = R = a g (10-6 /C) = a l (10-6 /C) = R 2 = α g T g 1 α l Cell 0 Cell 1 Precision Capillary Tube -50, Temperature (C) Polypropylene Washer Average Fit Silicon Rubber O-ring Stainless Steal Fitting Housing Base Cup Binder Specimen Silicon Paper

46 Difference in Glass Transition 0 Specific Volume Change (1e-6ml/g) -10,000-20,000-30,000-40,000-50,000-60, Temperature (C)

47 Typical Direct Tension Data As a function of Temperature σ f T0 /T (MPa) C -12 C -18 C -24 C Stress Fit -6 C -12 C -18 C -24 C Strain Fit Strength Failure Strain Ductility ε f (%) Reflective Tape Measurement section Load 11 mm 18 mm 11 mm Load Temperature Temperature (C)

48 Future Trends Thermal Cracking Tensile restrained test, Ring test S. Kim Fracture test in bending Hesp and Marasteanu Aging German Flask Test (DIN) SAFT Anderson and Glover Adhesion / Cohesion Thin Film Tackiness Konitpong and Bahia

49 Aging Procedures For Modified Bitumen X Yes SAFT

50 Cohesion or Thin Film Tack (TFT) Testing with DSR 0.01 mm/s Solid Surface Asphalt

51 Effect of Polymer Additives on Tackiness Binder C T [s*n] Force (N) PG58-28(original): 56 PG58-28(0.5%Morlife): 48 PG64-28(SB): 110 PG64-28(SBS): 126 PG64-28(Elvaloy): Time (s)

52 Asphalt Research Post SHRP --> Damage Resistance Elastic SHRP Hard Post SHRP Strong Weak Pen-Vis Soft Viscous

53 Concluding Remarks Modification can improve Performance of Pavements significantly. Selection of modifiers should be measured using damage behavior. Linear visco-elastic testing (current Superpave) is not sufficient. Some modified asphalts require special handling and construction procedures.

54 Thank You for this Opportunity Questions!