Implementation of the Bitumen Performance Grading System in Estonia

Transcription

1 Implementation of the Bitumen Performance Grading System in Estonia Pouya Teymourpour Hussain U. Bahia University of Wisconsin-Madison Tallinn, Estonia Feb 19, 2015

2 Outline How US has reached to currently valid Superpave standards. On-going research in bitumen and asphalt mixtures. What should be the bitumen properties in pavements. What should be the composition of asphalt mixtures to ensure a year long lifespan of pavements. Comments on study of bitumen sources used in Estonia Concluding Remarks

3 Bitumen Standards USA Overview 1930 s Pen grading 1960 s Viscosity grading Superpave testing system proposed PG grading implemented PG (Plus) more complex Damage Resistance Testing NCHRP 9-10: 2008 ( MSCR ) 2011 (BBS) 2013 (LAS) 2014 (SENB, BYET, DSR-ER)

4 Common Targets for Bitumen Specifications - Performance Based Grading Constructability Performance Rutting Durability Fatigue Cracking Thermal Cracking

5 Properties of Asphalt Binders elastic Stiffness (Response to Load) Asphalt binder is a temperature-susceptible viscoelastic material elastic solid viscous fluid viscous Temperature C Cold climates ==> use soft-grade asphalts Warm climates ==> use hard-grade asphalts Change in stiffness with temperature dictates inservice response to loading. High strain/stress behavior dictates performance.

6 Historical Specifications Pen & Vis 0 sec 5 sec penetration 100 g 100 g vacuum hard Consistency (pen or vis) soft -15 pen vis vis Temperature, C A, B, C are same grade! A B C

7 Pen at 25 C, Viscosity at 60C Conventional Asphalt Grades- 1930s 1990s Penetration Grades AC 40 AC 20 AC 10 AC 5 AC 2.5 AR AR 8000 AR 4000 AR 2000 AR

8 Performance Grading Should: Include measures describing stress-strain relationships under field climate and loading. Consider pavement conditions: Temperature (pavement) Traffic speed and volume, Pavement structure, and aging. Include acceptance limits derived from factual field performance/experience.

9 Asphalt Behavior Visco-elastic Lower Temp Shorter loading time (High Traffic Speed) Hard Elastic Viscous Soft Higher Temp Longer loading time Slower Traffic Speed

10 Fundamental Rheology Tests PG System Thermal Cracking Thermal Cracking Fatigue Cracking Fatigue Cracking Rutting Permanent Deformation Production (mixing & compact) PAV RTFO Pavement Temperature, C

11 Important Considerations: Traffic and Pavement Structure Effect of traffic Volume & Speed Pavement Damage ESALS and Speed limits! Weak vs. Strong base!

12 Current Performance Grading System- PG 1. Climate 2. Traffic conditions- Indirectly 3. Reliability Performance Grade PG Summer Average 7-day max pavement design temp Winter Min pavement design temp

13 PG Grades and Binder Modification Reasons for Modified Binders 1. Extreme Climates (i.e. AZ or WI) 2. Slow/Standing Traffic 3. Poor subgrade Support

14 The New Grading System- MP19 PG xx(z)-yy 1. Climate: xx-yy 2. Traffic conditions- Trucks (S,H,V,E) 3. Reliability, and 4. Modification Performance Grade PG 64(V)-10 Summer Average 7-day max pavement design temp Traffic Volume & Speed Winter Min pavement design temp

15 New / advanced testing needed for modified asphalts Thermal Cracking Fatigue Cracking Permanent Deformation (mixing & compaction) 4. Fracture (SENB) glass transition 3. Binder fatigue- LAS 5. DSR - Ductility 2. Binder repeated creep - MSCR 1. Viscosity at variable shear rate PAV RTFO Pavement Temperature, C

16 HMA Basics: Rocks + Asphalt + Air Voids Stability of HMA: 1.Rock- to rock contacts 2.Binder rheology

17 Aggregate Structure in Mix is very Important Digital Image Aggr. Skeleton Stress Distrib. How can we measure it? Can we specify it? What factors control it?

18 Mixture Response to Load and Climate Stiffness Response to Load elastic Mixtures = Asphalt (5-6 % ) + Aggregates (94-5%) + Voids Temperature, C Viscous/ Plastic

19 Shearing Behavior of Aggregate Shear Stress, t Mohr-Coulomb Theory failure envelope f c Normal Stress, s

20 Aggregate gradation and voids between aggregates Packing Voids will 1. reduce stiffness (modulus) 2. Increase amount of cement / asphalt required (cost) 3. Increase permeability 4. Affect workability

21 Shearing Behavior of Aggregate angle of repose Cubical Aggregate Rounded Aggregate

22 Deformation in Asphalt Layers deformation Elastic/ Delayed elastic Viscous/plastic loads

23 Mix Design and Testing Progress Earlier methods Marshall Mix Design, Hveem Mix Design In the s Texas Gyratory Mix Design, other Empirical Strength Testing In the 1990 s Superpave Gyratory and Aggregate testing system ( 1994 ) In 2000 Hamburg, APA, SPT In 2010s AMPT, Bailey Method, Imaging

24 Superpave Mixture Performance Tests AMPT Uni-axial/tri-axial Test : E*, FN, Nf Pavement Temperature, C

25 1. Traffic 2. Aggregates Properties 3. Gyrations 4.Densification N ini, Ndes Va@ N max 5. Durability Dust/Bind, VFA TSR Example of Mixture Specification Wisconsin DOT

26 MARC studies: We Measure aggregate structure ipas1 ipas2 (Image Processing and Analysis Software) ipas: A tool to identify aggregate structure. Give statistics about Packing Connectivity Orientation Spatial segregation Contact Length Contact Zone Stress Path

27 Aggregate Packing Characterization 2D to represent 3D - Stereology ipas2 output used to quantify packing: Aggr. Proximity Index API= Total aggregate to aggregate Proximity length Cutting sections

28 Can we control Mixture Rutting: Effect of Aggregate Gradation and Binder Modification Unmodified- coarse, Fine GTR- Coarse, Fine Elastomer- Coarse, Fine Plastomer- Coarse, Fine

29 Internal Aggregate Structure (API) Can explain the differences in FN Neat Binder GTR Binder Elastomer Binder GTR Binder Lower Density Plastomer Binder

30 Estonia Cold Climate Thermal Cracking Thermal cracking of pavements remains one of the most challenging distress in pavements to predict, and reduce, in North America.

31 Cold Temperature Mixture Test Methods: Two types 1. Fracture Tests SCB IDT* IDT* SENB DCT 2. Modulus & Failure Tests TSRST ATCA Load Cell *IDT can be performed with notch (fracture), without notch (failure) or in creep mode.

32 ATCA: Asphalt Thermal Cracking Analyzer LVDTs Un-restrained beam Load cell Rollers Restrained beam Un-restrained (top) l 1 1 g T g Restrained (bottom)

33 ATCA: Asphalt Thermal Cracking Analyzer s f 1 l Tc 1 g T g LVDTs Un-restrained beam Load cell Rollers Restrained beam

34 Aggregate Type Effect on Contraction Coefficients and Tg Linear Strain (1e-6mm/mm) ,000-1,400-1,800-2,200-2,600-3,000-3,400-3,800-4,200-4,600-5,000-5,400-5,800-6,200-6,600-7,000-7,400-7,800 v=cv+ g(t-tg)+r( l- g)ln{1+exp[(t-tg)/r]} Mix Type cv = Tg(C) = R0 = g(10-6 /C) = l(10-6 /C) = R 2 = Binder AC AF NC NF AC AF NC NF Sample Temperature (C) AF: Crushed Limestone Fine AC: Crushed Limestone Coarse NF: Gravel Fine NC: Gravel Coarse same binder and similar binder content

35 G f Mixture (J/m 2 ) Binders vs. Mixtures FENIX SCB Spanish Aggregates UPC Granite PFS-I Limestone PFS-I G f Binder (J/m 2 ) Fenix Test (Mixtures)

36 Developing Material Selection Criteria SCB, Fract. Energy [J/m^2] If 200 ft/500 ft of transverse cracking after 5 years is acceptable Transverse cracking, ft/500ft Acceptable Mixtures: All granite and limestone with binder G f > 15 mj/m 2 G f Mixture, J/m G f Binder, J/m 2 Limestone Low Temp Granite Low Temp Limestone Int Temp Granite Int Temp Unacceptable Mixtures: limestone with binder G f < 15mJ/m 2

37 Estonia Study Hypothesis & Objectives Hypothesis: Variety of available bitumen types in Estonia does not adequately cover the varying climatic needs. Objectives: Conduct Superpave performance grading testing protocol to determine the PG grades of Estonian binders. Compare the grades of available binders with those required for existing climatic conditions. Investigate the production of needed grades through feasible modification techniques.

38 New Methods for Modified Binder Evaluation Damage Based Characterization Thermal Cracking Fatigue Cracking Permanent Deformation SENB LAS MSCR Pavement Temp, C

39 Required PG Grades

40 Materials Binders designations provided from different crude sources Binder Code Description Crude Oil PG A Pen Venezuela B Pen Russia C Pen Russia D Pen Russia E Pen Russia F Pen Venezuela G Pen Russia H Shale Oil Estonia 52-4

41 Low Service temperature Available vs. Required PG Grades Available PG Needed, Unavailable PG High Service Temperature

42 Modification Alternatives: Oils + Polymers Base Modified Modification Binder Binder Code PG A 5% Oil-A M-A B 10% Oil-B + 2% Plastomer M-B C 8% Oil-B + 3% Elastomer M-C D 8% Oil-B + 2% Plastomer M-D E 11% Oil-A M-E E 8% Oil-B M-E F 8% Oil-B + 4% Plastomer M-F G 8% Oil-B + 5% Elastomer M-G Oil A: Bio Oil Oil B: Refined Waste Oil Elastomer: SBSx Plastomer: Functionalized Polyethylene (Titan 7686) Selection of the dosage of oil modifier based on the required low temperature performance grade

43 Test Methods Test Methods Selected for Binder Evaluation Engineering Property of the Binder Conventiona l Binder Test Advanced Binder Test 1 Rutting resistance DSR HT PG Fatigue Cracking Resistance DSR IT PG Linear Amplitude Sweep (LAS) 3 Thermal Cracking Resistance Bending Beam Rheometer (BBR) Single Edge Notched Beam (SENB) 4 Chemical Content Spectrum --- Gel Permeation Chromatography (GPC)

44 Results High Temperature Grading-Unmodified Binders Un-Aged RTFO Aged Narrow range of Performance Grades between provided Binders

45 Results High Temperature Grading-Continuous Grade binders with same pen grade (i.e binder A to E) showed different behavior at high temperatures and cover a range of three different PG grades adding lubricating oils decrease the high temperature properties of the original binder

46 Results Intermediate Temperature Continuous Grade Reduction in the IT grade of binders by 6 to 15 C by binder modification Superpave Max IT Grade: PG 58-28: 19 C PG 58-34: 16 C PG 58-40: 13 C

47 Effect of Oils on LT Binder Properties

48 Results Low Temperature Grading-Continuous Grade Considering the high temperature grade of these binders to be kept the same level, selected modifications were capable of expanding the performance range of binders by shifting the lower band up to 10 C

49 Complex Modulus [MPa] Shear Stress [MPa] Fatigue Life from LAS Specification based on Binder Nf Rheology Frequency Sweep m Unmodified Modified Frequency [Hz] Slope B N f = A (γ max ) B Damage Resistance Continuous Amplitude Sweep Shear Strain [%] VECD A Unmodified Modified

50 Results Linear Amplitude Sweep (LAS) Test 2.5%Strain Amplitude 5%Strain Amplitude Increase in Fatigue Life Lubricating oils improve the fatigue resistance at different strain levels Same IT PG grade can resist fatigue significantly different

51 Single Edge Notched Bending (SENB) 51

52 Fracture Properties and Strain Tolerance 52

53 Results Single Edge Notched Bending LT Grade Marginal difference between unmodified and modified binders Test is performed at LT grade of the binders

54 Concluding Remarks- Binder Study Estonia will need to use Oil modification to improve performance of pavements Oils could result in lower rutting resistance; need polymers to offset this effect Fatigue resistance varies significantly based on oils Impact of oils and polymers vary based on oil type and the crude source of binder

55 Concluding Results General Roads are built with mixtures, not Binders! Thermal Cracking & rutting are affected by: aggregate structure and binder properties. Suggestion for Mixture studies: Internal structure and resistance to rutting Ipas and FN Coefficient of thermal contraction- ACTA Fracture properties Moisture damage Wet Hamburg

56 Thank You! Questions? Hussain Bahia Pouya Teymourpour

57 Results High Temperature Grading-Aging Susceptibility Aging effect of different recycling agents are not the same The difference in aging index for different recycling agents comes from their different chemical components Values will change if the binder is exposed to long term aging

58 Results Aging Vs. Elemental Analysis RTFO Aged G /sinδ Aging Index = Un aged G /sinδ Aging Susceptibility has fair relationship to Vanadium Content

59 GPC Parameters MW: weight-average molecular weight influences the bulk properties and toughness of the material Mn: number-average molecular weight influences the thermodynamic properties of the molecule Mz: z-average molecular weight Mp: peak molecular weight

60 Gel Permeation Chromatograph (GPC) Simple separation technique available that responds to molecular size alone and not to chemical structure. Analogous to a type of sieve analysis of sample. LMS MMS SMS GPC spectrum divided into 13 equal elution time areas.

61 Results GPC Results Different patterns of chromatograms and GPC clearly distinct the different molecular size distribution of different binders

62 Results Rheological Vs. Chemical Properties-High Temp. Increase in larger molecules portion of the binder More asphaltene and higher stiffness at higher temperatures

63 Results Rheological Vs. Chemical Properties-Low Temp. Relationship between the binder stiffness measured during BBR and the average molecular weight (Mz) in binders Decrease Mz corresponds to increments in lighter molecular weight components of the binders More presence of lighter molecule sizes Part of maltenes reach their glass transition region at higher temperatures More brittle behavior

64 Results Extended BBR Samples were conditioned at their LT+10 C for 72 hours BBR testing after 24 hr and 72 hr Binders tested in 3 categories based on LT grade: -12 C -18 C -24 C A D G M-B M-E-2 B C E F M-A M-C M-D M-F M-G

65 Results Extended BBR -24 C Overall performance improvement (less hardening susceptibility) by using modifications Higher polymer content showed to be more effective (M-F & M-G)