Corporación de Desarrollo Tecnológico

Transcription

1 Corporación de Desarrollo Tecnológico Conferencia Tecnológica: Asfalto Espumado; la experiencia australiana y su aplicación en Chile 28 de agosto de 2013 Foamed bitumen mix design and thickness design: research to improve current processes Geoff Jameson Investigador en ARRB Group Corporación de Desarrollo Tecnológico 45 páginas

2 Foamed bitumen mix design and thickness design : research to improve current processes Geoff Jameson Chief Scientist, Pavements ARRB Group Chilean Construction Chamber Wed 28 August Advancing safety and efficiency in transport through knowledge research consulting technology

3 Presentation Outline Objectives of the foamed bitumen research Development of mix design method Improve thickness design method Field performance studies 3

4 Australia Population: 23 million 7 states 2 territories 4

5 National highway: 18,600 km Total road length: 813,000 km Population: 23 million Sealed: 323,000 km Unsealed: 490,000 km 5

6 Climate and Rainfall Dry interior Wet along coastline 6

7 95% Australian sealed road network, thin bituminous surfaced granular pavements Bituminous binder & aggregate Unbound granular base Unbound granular subbase Subgrade 7

8 Unbound granular base 8

9 In situ foamed bitumen stabilisation increased over last 10 years typically 3.5% bitumen and 1.5% quicklime limited use of cement, concerns about cracking now trialling 2.5% bitumen 9

10 Four year national research project ( ) The purpose of this project is: To improve and harmonise national mix design procedures To improve thickness design procedures does material fatigue crack? 10

11 Foamed Bitumen Stabilisation Working Group A very important element in the success of the project is the close collaboration between road agencies, contractors and the researchers Project guided by a Working Group comprising: State road agencies Stabilisation industry contractors Researchers ARRB Group 11

12 Mix design mix design test methods vary throughout Australia need for harmonisation need to relate mix design properties to field performance 12

13 Mix design based on indirect tensile modulus 13

14 National working group developing test methods T301 T305 Determination of Foaming Properties of Bitumen Mixing of Foamed Bitumen Stabilised Materials (includes method of establishing mixing moisture content) T310 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures : Part 1 Dynamic compaction using Marshall drop hammer T311 Compaction of Test Cylinders of Foamed Bitumen Stabilised Mixtures : Part 2 Gyratory compaction T313 Compaction of Test Slabs of Foamed Bitumen Stabilised Mixtures T320 T321 T330 T340 Curing of Test Cylinders of Foamed Bitumen Stabilised Mixtures Curing of Test Slabs of Foamed Bitumen Stabilised Mixtures Resilient Modulus of Foamed Bitumen Stabilised Mixtures Deformation Resistance of Foamed Bitumen Stabilised Mixtures by the Wheel Tracking Test 14

15 Lack of national test methods hindering progress 50 blows Marshall hammer Gyratory compaction to field density 15

16 Compaction method major influence on modulus 16

17 Research in 2013/14 Effect of compaction method (Marshall, Standard drop hammer, gyratory) on modulus and density Effect of mixing moisture content on compactibility and modulus 17

18 Also the link between laboratory and field properties not well understood 18

19 Coring pavement in early life measuring comparing modulus with laboratory mix design results 19

20 Calder Freeway example 20

21 Improve modulus specifications usefulness of initial modulus in terms of the rutting on opening to traffic selecting a design modulus is bitumen stripping an issue and how useful is retained modulus ratio 21

22 Thickness design 22

23 Mechanistic approach Assumption is that foamed bitumen stabilised material is susceptible to fatigue cracking 23

24 Thickness design of FBS layers current thickness design based on modified asphalt fatigue relationship need to verify 24

25 Field performance monitoring Monitoring of in service roads six existing pavements were identified heavily trafficked roads Construction and monitoring of under-designed roads constructed three pavements designed such that they are predicted to fatigue crack with in 3 years another under-designed pavement will be constructed early 2014 foamed bitumen stabilisation thicknesses mm 25

26 Performance under-designed pavements, colder climates more susceptible to fatigue Kwinana Freeway Port Wakefield Road Calder Freeway 26

27 1. Calder Freeway constructed March 2013 collaboration between road agency, contractors and researchers 27

28 4 th March FBS construction 100 m length 4.8 m width slow lane and part shoulder 2 x 2.4 m widths crushed rock base stabilised to depth of 150 mm 3.5 % bitumen & 1.5% quicklime 28

29 Mix design Research task compare modulus of material sampled from road bed and compacted in lab with laboratory-manufactured materials compare field core moduli with moduli of laboratorymanufactured specimens Compaction test specimens in the field? 29

30 Research task Early-life characteristics rutting and ravelling strength gain surface deflections modulus of field cores usefulness of initial modulus 30

31 Research tasks Performance over 3 years rutting roughness cracking modulus 31

32 Condition after 1 month of trafficking 2 coat chip seal surface 32

33 FWD deflections were measured 8 days & 1 month after FBS construction Deflections measured in loaded and unloaded areas of pavement to estimate modulus changes with time and loading: on the edge line in the outer wheel path between the wheel paths 33

34 Curvatures low and consistent There is a need to develop a temperature adjustment procedure 0.10 Calder Freeway Woodend foamed bitumen stabilised material 8 days post construction pavement temperature 29 C 0.10 Calder Freeway Woodend foamed bitumen stabilised materials 1 month post construction pavement temperature 12 C Curvatures (D0-D200) 0.05 at 566 kpa (mm) 0.04 Outer wheelpath Between wheelpaths 0.06 Curvatures (D0-D200) 0.05 at 566 KPa (mm) Outer wheelpath Between wheelpaths Chainage (m) Chainage (m) 8 days, 29 C 1 month, 12 C 34

35 Coring along edge line at 8 days & 1 month after FBS construction 35

36 Predicted to fatigue crack with 3 years 36

37 2. Port Wakefield Road constructed early 2011, as part of 1km long project heavily trafficked road 75 m section stabilised to 150 mm depth 950 m section stabilised to depth of 200 mm 3% bitumen + 1% hydrated lime 37

38 Port Wakefield Road fatigue cracking fatigue cracking observed after 18 months of trafficking in reasonable agreement with thickness design model 38

39 Monitoring measured deflections 39

40 Field cores 40

41 3. Kwinana Freeway Perth Constructed in m trial section with reduced thickness, 150 mm FBS asphalt surfaced with underlying geotextile reinforced seal 41

42 No cracking apparent yet surface deflections regularly being measured may identify fatigue damage prior to surface cracking 42

43 Adding another project early in 2014 Newell Highway 43

44 4 year national research project involvement of road agencies, contractors and researchers objectives Summary four year national research project ( ) development of national mix design procedures refinement of modulus specifications using field performance data calibration of thickness design procedures 44

45 Gracias! 45