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Two-layer porous asphalt
      for urban roads
- The Øster Søgade project
           Lars Ellebjerg Larsen
              Hans Bendtsen
   Danish Road Institute/Road Directorate
Project goals
• To develop and test noise reducing pavements for
  urban roads

• Applying and improving Dutch two-layer concept for
  Danish conditions

• Investigate the clogging phenomenon of two-layer
  porous pavements

• Over the lifetime of the pavements to analyse:
   – The acoustical properties of the pavements
   – The clogging of the pavements
   – The structural properties of the pavements
Acknowledgements
Øster Søgade experiment financed by:
• Danish Ministry of Transport
• Danish Ministry of the Environment

Danish project group:
• Lene Michelsen, Danish Road Directorate
• Steen Kønigsfeldt and Michael Rasmussen, Municipality of
  Copenhagen
• Jørn Bank Andersen, Pavement Contractors Association / NCC
• Hans Bendtsen, Bent Andersen, Jørgen Kragh, Jørn Raaberg,
  Bjarne Schmidt and Lars Ellebjerg Larsen, Danish Road
  Institute/Road Directorate

The clogging project:
• Part of the Dutch IPG program
• Financial and technical support and cooperation of Road and
  Hydraulic Engineering Institute in the Netherlands (DWW)
• The DRI-DWW noise abatement programme
The test road
     Øster Søgade in Copenhagen:
     • Speed: 50 km/h
     • Traffic: 7000 AADT
     • HGV: 8 %
     • Length: 800 m
The test road 2
The porous pavements
Name     Section    Type         Total  Top layer    Bottom
                              thickness aggregate     layer
                                                    aggregate
                   Porous
PA8-70      I                 25+45 mm   5-8 mm     11-16 mm
                   asphalt

                   Porous
PA5-55     II                 20+35 mm   2-5 mm     11-16 mm
                   asphalt
                   Porous
PA5-90     III                25+65 mm   2-5 mm     16-22 mm
                   asphalt
                    Dense
DAC8
           IV       asphalt    30 mm     0-8 mm         -
(ref.)
                   concrete
The porous pavements 2
The test pavements
                         100
                                  AC8t
                         90       DA5
                                  DA8
                         80
                                  DA16
                         70       DA22
Percentage of material




                         60

                         50

                         40

                         30

                         20

                         10

                          0
                          0,001          0,01   0,1               1   10   100
                                                      Size (mm)
The test pavements 2

Material           PA5      PA8        PA16       PA22     DAC8
                   (top)    (top)    (bottom)   (bottom)   (ref.)

Stone material     95.0 %   95.5 %   97.0 %     97.5 %     97.5 %

Hydrated lime      1.5 %    1.5 %     1.5 %      1.5 %     1.5 %

Lime filler        3.5 %    3.0 %     1.5 %      1.0 %     1.0 %

Cellulose fibers   .25 %    .25 %     .25 %      .25 %

Bitumen            6.3 %    5.4 %     3.9 %      3.5 %     5.8 %

Marshall cavity    25.5 %   26.0 %   25.5 %     25.5 %     2.4 %
Pavement measurements

• On location
  – Texture – Laser measurements of MPD
  – Permeability – Becker’s tube method
  – Friction

• On drill cores
  –   Built-in voids
  –   Asphalt analyses
  –   Thin and plane sections
  –   CT-scans
Noise measurements

•   SPB
•   CPB
•   CPX
•   Sound absorption
    – Extended surface method [ISO 13472-1]
    – Impedance tube – Transfer-function
      method [ISO 10534-2]
Other surveys

• Noise annoyance
  – questionnaire survey


• Cost-benefit analyses
  – Comparison of pavements, barriers and
    façade insulation
Texture
Texture 2
                        PA8                    PA5                    DAC8
           3,000
                                                                     1999
                                                                     2001
                                                                     2002
           2,500                                                     2004
                                                                     2005
                                                                     Old pavement

           2,000
MPD (mm)




           1,500


           1,000


           0,500


           0,000
               0,000   0,100   0,200   0,300         0,400   0,500    0,600         0,700
                                        Positioning (km)
                                                                        [ISO 13473-1]
Permeability
Permeability - northbound lane
                                      70
Water draining time (seconds/10 cm)




                                      60

                                      50                                                  PA8-70 a
                                                                                          PA8-70 b
                                      40
                                                                                          PA8-70 c
                                      30                                                  PA5-55 a
                                                                                          PA5-55 b
                                      20                                                  PA5-55 c
                                                                                          PA5-90 a
                                      10
                                                                                          PA5-90 b
                                       0                                                  PA5-90 c
                                           0   10   20    30        40          50   60   70
                                                         Months after opening
Permeability - southbound lane
                                      70
Water draining time (seconds/10 cm)




                                      60

                                      50

                                      40
                                                                                          PA8-70 a
                                      30                                                  PA8-70 b
                                                                                          PA8-70 c
                                      20
                                                                                          PA5-55 a
                                      10                                                  PA5-55 b
                                                                                          PA5-55 c
                                       0                                                  PA5-90 a
                                           0   10   20    30        40          50   60   70
                                                                                          PA5-90 b
                                                         Months after opening             PA5-90 c
CT-scan of porous asphalt


7 years old PA from A12
CT-scan 2

                51 mm




33 mm
CT-Scan – Results
100%
           Bottom layer (PA16)             Top layer (PA8)              Voids
90%                                                                     Mortar
                                                                        Aggregate
80%

70%

60%

50%

40%

30%

20%

10%

 0%
       0    10           20      30         40               50    60               70
                                      mm
             33 mm                                                51 mm
Preparation of plane sections


            100 mm Drill Core


         Thin section 1    45 mm wide by 30 mm high   10 mm




                                                                      100 mm
                                                              40 mm
         Plane section (100 by 100 mm)                10 mm



         Thin section 2    45 mm wide by 30 mm high   10 mm
Acquiring the images

Plane section:
100 x 100 mm
Analyses of thin sections in microscope




        New               4 years old
SPB noise measurements
             1999   2000   2001        2002   2003    2004        2005

             75



             70
SPBI' [dB]




             65



             60
                     I            II            III          IV
Noise reduction

                 1999          2000                     2001              2002                    2003        2004                      2005
                       10

                        8
Noise reduction [dB]




                                            2.9                                   2.4                       6.0           2.3
                        6                                           4.9
                            4.5 4.6
                                                                          3.6                                     3.8
                        4             2.7         2.8                           2.7                                     2.7
                                            2.4                                       2.2
                                                        1.7
                        2                                     1.4                           1.3                                         1.4
                                                                                                  0.9 1.2                     1.0 1.1


                        0
                                                                                                                                              -0.2
                                             I                                         II                                     III
                       -2
Reference pavement – 8 or 11 mm
                                                 L_pA, max, fast, 7.5 m as a function of speed
                                               passenger cars, comparison of reference surfaces
                                     80
L_pA,max,fast,7.5m, [dB re 20 µPa]




                                     75



                                     70
                                                                                                  AC8d, Kgl
                                                                                                  AC11d(E), Kgl
                                                                                                  AC8d, SFr
                                     65
                                                                                                  AC11d, SFr
                                                                                                  AC11d, all, SFr
                                                                                                  AC11d, Ubh
                                     60
                                          40         50                   60              70
                                                          Speed, [km/h]
Questionnaire survey

• Questionnaire survey – before and after repaving
   – 240 questionnaires per survey
   – 72 and 65 percent returned



• Noise levels calculated with the Nordic Prediction
  Method for Road Traffic Noise
   – Levels before:
       • +1 dB for a worn and uneven pavement
   – Levels after:
       • -2.5 dB relative to before by the ref. pavement
       • -7.6 dB relative to before by the porous pavement
Noise annoyance with closed
  windows
100%

90%                             Cannot hear noise from
                                road traffic
80%                             Not annoyed

70%                             A little annoyed

60%                             Annoyed

50%                             Very annoyed

40%

30%

20%

10%

 0%
       Before           After                            Before            After
           Reference pavement                               P orous pavement
Noise annoyance with open
   windows
100%

90%                              Cannot hear noise from
                                 road traffic
80%                              Not annoying

70%                              A little annoying

60%                              Annoying

50%                              Very annoying

40%

30%

20%

10%

 0%
       Before            After                            Before            After
            Reference pavement                                P orous pavement
Dose-response – closed windows
                          100%
                                      Before repaving
                          90%
                                      After repaving
                          80%
                                      Dos e-res pons e curve
A little or more annoye




                          70%

                          60%

                          50%

                          40%

                          30%

                          20%

                          10%

                           0%
                                 45         50                 55                60               65     70   75
                                                               Nois e outs ide windows - L Aeq (dB(A))
Cost-benefit analysis

 Comparing 3 means:      3 cases:
 • Two-layer porous      • Central city street
   asphalt               • Ring road
 • Noise barriers        • Freeway
 • Sound insulation


 Net Present Value:      Comparing:
 • construction and      • Direct costs
   maintenance
                         • Costs/dB/dwelling
 • costs for a 30-year
   period
3 cases

 City street (50 km/h, AADT: 12.000)
     Apartments: 1st – 5th floor       15 m facade per apartment
     65 – 68 dB façade level           665 apartments (133/floor)


 Ring road (70 km/h, AADT: 30.000)
    Apartments: ground – 2nd floor     15 m facade per apartment
    73 – 74 dB façade level            399 apartments (133/floor)


 Freeway (110 km/h, AADT: 60.000)
    Detached houses in 5 rows          23 m road per house
    77 dB at the first row
    69/71 dB at the second row         435 houses (87/row)
    66/69 dB at the third row
    58/66 dB at the fourth row
    57/65 dB at the fifth row
Porous pavements

 Effect:                  Costs (net present value, €):

    City street:   4 dB      City street:   296,000

    Ring road:     5 dB      Ring road:     360,000

    Freeway:       6 dB      Freeway:       477,000
Noise barriers

Effect:                             Costs (net present value, €):

   City street:   Not possible         City street:   Not possible

   Ring road:     0-12 dB              Ring road:     1,335,000
                  Average: 3.9 dB

   Freeway:       1-12 dB              Freeway:       1,590,000
                  Average: 6.2 dB
Façade insulation

 Effect:                         Costs (net present value, €):

    9 dB on indoor levels with      City street:   2,685,000
    windows closed
                                    Ring road:     1,607,000

                                    Freeway:       2,890,000
Costs
                       3500
                                            P orous asphalt
                       3000
                                            Noise barrier
Costs (thousand Euro




                                            Facade insulation
                       2500

                       2000

                       1500

                       1000

                       500

                         0
                              City street   Ring road           Freeway
Costs per dB per dwelling
                         900
                               P orous asphalt
                         800
                               Noise barrier
                         700
Costs/dB/dwelling (Eur




                               Facade insulation
                         600

                         500

                         400

                         300

                         200

                         100

                          0
                               City street         Ring road   Freeway
Conclusion and perspective
• When new, the thickest porous pavement
  with 5 mm aggregate had the best noise
  reduction of 5-6 dB
• When old the porous pavement with 8 mm
  aggregate in the top-layer maintain a noise
  reduction of 1-2 dB
• In relation to 11 or 16 mm dense asphalt
  reduction is 1 to 2 dB higher
• The pavement with 8 mm aggregate clogs
  significantly less than the pavements with
  smaller aggregate
• The PA5 pavements are “dead” in 2005
Conclusions and perspective
• The perceived effect of noise reductions by
  porous asphalt matches the reduction in
  decibel level
• Compared to noise barriers and façade
  insulation porous asphalt gives a much higher
  noise reduction per invested Euro
• Analyses of thin and plane sections as well as
  the use of CT-scanning of drill cores will be
  used to evaluate the clogging process
• The working group are looking at possibilities
  for continuing the project with a renewal of
  the top layers with PA8

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Two Layer Porous Asphalt - Danish Experiences - BRRC Seminar 2005

  • 1. Two-layer porous asphalt for urban roads - The Øster Søgade project Lars Ellebjerg Larsen Hans Bendtsen Danish Road Institute/Road Directorate
  • 2. Project goals • To develop and test noise reducing pavements for urban roads • Applying and improving Dutch two-layer concept for Danish conditions • Investigate the clogging phenomenon of two-layer porous pavements • Over the lifetime of the pavements to analyse: – The acoustical properties of the pavements – The clogging of the pavements – The structural properties of the pavements
  • 3. Acknowledgements Øster Søgade experiment financed by: • Danish Ministry of Transport • Danish Ministry of the Environment Danish project group: • Lene Michelsen, Danish Road Directorate • Steen Kønigsfeldt and Michael Rasmussen, Municipality of Copenhagen • Jørn Bank Andersen, Pavement Contractors Association / NCC • Hans Bendtsen, Bent Andersen, Jørgen Kragh, Jørn Raaberg, Bjarne Schmidt and Lars Ellebjerg Larsen, Danish Road Institute/Road Directorate The clogging project: • Part of the Dutch IPG program • Financial and technical support and cooperation of Road and Hydraulic Engineering Institute in the Netherlands (DWW) • The DRI-DWW noise abatement programme
  • 4. The test road Øster Søgade in Copenhagen: • Speed: 50 km/h • Traffic: 7000 AADT • HGV: 8 % • Length: 800 m
  • 6. The porous pavements Name Section Type Total Top layer Bottom thickness aggregate layer aggregate Porous PA8-70 I 25+45 mm 5-8 mm 11-16 mm asphalt Porous PA5-55 II 20+35 mm 2-5 mm 11-16 mm asphalt Porous PA5-90 III 25+65 mm 2-5 mm 16-22 mm asphalt Dense DAC8 IV asphalt 30 mm 0-8 mm - (ref.) concrete
  • 8. The test pavements 100 AC8t 90 DA5 DA8 80 DA16 70 DA22 Percentage of material 60 50 40 30 20 10 0 0,001 0,01 0,1 1 10 100 Size (mm)
  • 9. The test pavements 2 Material PA5 PA8 PA16 PA22 DAC8 (top) (top) (bottom) (bottom) (ref.) Stone material 95.0 % 95.5 % 97.0 % 97.5 % 97.5 % Hydrated lime 1.5 % 1.5 % 1.5 % 1.5 % 1.5 % Lime filler 3.5 % 3.0 % 1.5 % 1.0 % 1.0 % Cellulose fibers .25 % .25 % .25 % .25 % Bitumen 6.3 % 5.4 % 3.9 % 3.5 % 5.8 % Marshall cavity 25.5 % 26.0 % 25.5 % 25.5 % 2.4 %
  • 10. Pavement measurements • On location – Texture – Laser measurements of MPD – Permeability – Becker’s tube method – Friction • On drill cores – Built-in voids – Asphalt analyses – Thin and plane sections – CT-scans
  • 11. Noise measurements • SPB • CPB • CPX • Sound absorption – Extended surface method [ISO 13472-1] – Impedance tube – Transfer-function method [ISO 10534-2]
  • 12. Other surveys • Noise annoyance – questionnaire survey • Cost-benefit analyses – Comparison of pavements, barriers and façade insulation
  • 14. Texture 2 PA8 PA5 DAC8 3,000 1999 2001 2002 2,500 2004 2005 Old pavement 2,000 MPD (mm) 1,500 1,000 0,500 0,000 0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700 Positioning (km) [ISO 13473-1]
  • 16. Permeability - northbound lane 70 Water draining time (seconds/10 cm) 60 50 PA8-70 a PA8-70 b 40 PA8-70 c 30 PA5-55 a PA5-55 b 20 PA5-55 c PA5-90 a 10 PA5-90 b 0 PA5-90 c 0 10 20 30 40 50 60 70 Months after opening
  • 17. Permeability - southbound lane 70 Water draining time (seconds/10 cm) 60 50 40 PA8-70 a 30 PA8-70 b PA8-70 c 20 PA5-55 a 10 PA5-55 b PA5-55 c 0 PA5-90 a 0 10 20 30 40 50 60 70 PA5-90 b Months after opening PA5-90 c
  • 18. CT-scan of porous asphalt 7 years old PA from A12
  • 19. CT-scan 2 51 mm 33 mm
  • 20. CT-Scan – Results 100% Bottom layer (PA16) Top layer (PA8) Voids 90% Mortar Aggregate 80% 70% 60% 50% 40% 30% 20% 10% 0% 0 10 20 30 40 50 60 70 mm 33 mm 51 mm
  • 21. Preparation of plane sections 100 mm Drill Core Thin section 1 45 mm wide by 30 mm high 10 mm 100 mm 40 mm Plane section (100 by 100 mm) 10 mm Thin section 2 45 mm wide by 30 mm high 10 mm
  • 22. Acquiring the images Plane section: 100 x 100 mm
  • 23. Analyses of thin sections in microscope New 4 years old
  • 24. SPB noise measurements 1999 2000 2001 2002 2003 2004 2005 75 70 SPBI' [dB] 65 60 I II III IV
  • 25. Noise reduction 1999 2000 2001 2002 2003 2004 2005 10 8 Noise reduction [dB] 2.9 2.4 6.0 2.3 6 4.9 4.5 4.6 3.6 3.8 4 2.7 2.8 2.7 2.7 2.4 2.2 1.7 2 1.4 1.3 1.4 0.9 1.2 1.0 1.1 0 -0.2 I II III -2
  • 26. Reference pavement – 8 or 11 mm L_pA, max, fast, 7.5 m as a function of speed passenger cars, comparison of reference surfaces 80 L_pA,max,fast,7.5m, [dB re 20 µPa] 75 70 AC8d, Kgl AC11d(E), Kgl AC8d, SFr 65 AC11d, SFr AC11d, all, SFr AC11d, Ubh 60 40 50 60 70 Speed, [km/h]
  • 27. Questionnaire survey • Questionnaire survey – before and after repaving – 240 questionnaires per survey – 72 and 65 percent returned • Noise levels calculated with the Nordic Prediction Method for Road Traffic Noise – Levels before: • +1 dB for a worn and uneven pavement – Levels after: • -2.5 dB relative to before by the ref. pavement • -7.6 dB relative to before by the porous pavement
  • 28. Noise annoyance with closed windows 100% 90% Cannot hear noise from road traffic 80% Not annoyed 70% A little annoyed 60% Annoyed 50% Very annoyed 40% 30% 20% 10% 0% Before After Before After Reference pavement P orous pavement
  • 29. Noise annoyance with open windows 100% 90% Cannot hear noise from road traffic 80% Not annoying 70% A little annoying 60% Annoying 50% Very annoying 40% 30% 20% 10% 0% Before After Before After Reference pavement P orous pavement
  • 30. Dose-response – closed windows 100% Before repaving 90% After repaving 80% Dos e-res pons e curve A little or more annoye 70% 60% 50% 40% 30% 20% 10% 0% 45 50 55 60 65 70 75 Nois e outs ide windows - L Aeq (dB(A))
  • 31. Cost-benefit analysis Comparing 3 means: 3 cases: • Two-layer porous • Central city street asphalt • Ring road • Noise barriers • Freeway • Sound insulation Net Present Value: Comparing: • construction and • Direct costs maintenance • Costs/dB/dwelling • costs for a 30-year period
  • 32. 3 cases City street (50 km/h, AADT: 12.000) Apartments: 1st – 5th floor 15 m facade per apartment 65 – 68 dB façade level 665 apartments (133/floor) Ring road (70 km/h, AADT: 30.000) Apartments: ground – 2nd floor 15 m facade per apartment 73 – 74 dB façade level 399 apartments (133/floor) Freeway (110 km/h, AADT: 60.000) Detached houses in 5 rows 23 m road per house 77 dB at the first row 69/71 dB at the second row 435 houses (87/row) 66/69 dB at the third row 58/66 dB at the fourth row 57/65 dB at the fifth row
  • 33. Porous pavements Effect: Costs (net present value, €): City street: 4 dB City street: 296,000 Ring road: 5 dB Ring road: 360,000 Freeway: 6 dB Freeway: 477,000
  • 34. Noise barriers Effect: Costs (net present value, €): City street: Not possible City street: Not possible Ring road: 0-12 dB Ring road: 1,335,000 Average: 3.9 dB Freeway: 1-12 dB Freeway: 1,590,000 Average: 6.2 dB
  • 35. Façade insulation Effect: Costs (net present value, €): 9 dB on indoor levels with City street: 2,685,000 windows closed Ring road: 1,607,000 Freeway: 2,890,000
  • 36. Costs 3500 P orous asphalt 3000 Noise barrier Costs (thousand Euro Facade insulation 2500 2000 1500 1000 500 0 City street Ring road Freeway
  • 37. Costs per dB per dwelling 900 P orous asphalt 800 Noise barrier 700 Costs/dB/dwelling (Eur Facade insulation 600 500 400 300 200 100 0 City street Ring road Freeway
  • 38. Conclusion and perspective • When new, the thickest porous pavement with 5 mm aggregate had the best noise reduction of 5-6 dB • When old the porous pavement with 8 mm aggregate in the top-layer maintain a noise reduction of 1-2 dB • In relation to 11 or 16 mm dense asphalt reduction is 1 to 2 dB higher • The pavement with 8 mm aggregate clogs significantly less than the pavements with smaller aggregate • The PA5 pavements are “dead” in 2005
  • 39. Conclusions and perspective • The perceived effect of noise reductions by porous asphalt matches the reduction in decibel level • Compared to noise barriers and façade insulation porous asphalt gives a much higher noise reduction per invested Euro • Analyses of thin and plane sections as well as the use of CT-scanning of drill cores will be used to evaluate the clogging process • The working group are looking at possibilities for continuing the project with a renewal of the top layers with PA8