two layer porous asphalt - danish experiences - brrc seminar 2005
DESCRIPTION
Danish experiences with two-layer porous asphalt on Øster Søgade in CopenhagenTRANSCRIPT
Two-layer porous asphalt for urban roads
- The Øster Søgade projectLars Ellebjerg Larsen
Hans BendtsenDanish Road Institute/Road Directorate
• 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
Project goals
AcknowledgementsØster 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 roadØster 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
thickness Top layer aggregate
Bottom layer
aggregate
PA8-70 I Porous asphalt 25+45 mm 5-8 mm 11-16 mm
PA5-55 II Porous asphalt 20+35 mm 2-5 mm 11-16 mm
PA5-90 III Porous asphalt 25+65 mm 2-5 mm 16-22 mm
DAC8 (ref.) IV
Dense asphalt
concrete30 mm 0-8 mm -
The porous pavements 2
0
10
20
30
40
50
60
70
80
90
100
0,001 0,01 0,1 1 10 100
Size (mm)
Per
cent
age
of m
ater
ial
AC8tDA5DA8DA16DA22
The test pavements
The test pavements 2
Material PA5(top)
PA8(top)
PA16(bottom)
PA22(bottom)
DAC8(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
0,000
0,500
1,000
1,500
2,000
2,500
3,000
0,000 0,100 0,200 0,300 0,400 0,500 0,600 0,700
Positioning (km)
MP
D (m
m)
19992001200220042005Old pavement
PA8 PA5 DAC8
[ISO 13473-1]
Permeability
Permeability - northbound lane
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
Months after opening
Wat
er d
rain
ing
time
(sec
onds
/10
cm)
PA8-70 aPA8-70 bPA8-70 cPA5-55 aPA5-55 bPA5-55 cPA5-90 aPA5-90 bPA5-90 c
Permeability - southbound lane
0
10
20
30
40
50
60
70
0 10 20 30 40 50 60 70
Months after opening
Wat
er d
rain
ing
time
(sec
onds
/10
cm)
PA8-70 aPA8-70 bPA8-70 cPA5-55 aPA5-55 bPA5-55 cPA5-90 aPA5-90 bPA5-90 c
CT-scan of porous asphalt
7 years old PA from A12
CT-scan 2
33 mm
51 mm
CT-Scan – Results
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 10 20 30 40 50 60 70
mm
VoidsMortarAggregate
Top layer (PA8)Bottom layer (PA16)
33 mm 51 mm
100
mm
40 m
m
10 mm
10 mm
10 mm
Thin section 1
Thin section 2
Plane section (100 by 100 mm)
100 mm Drill Core
45 mm wide by 30 mm high
45 mm wide by 30 mm high
Preparation of plane sections
Acquiring the images
Plane section: 100 x 100 mm
Analyses of thin sections in microscope
New 4 years old
SPB noise measurements
60
65
70
75
I II III IV
SP
BI'
[dB
]
1999 2000 2001 2002 2003 2004 2005
Noise reduction
4.5 4.9
6.0
4.63.6 3.8
2.7 2.7 2.72.4 2.2
1.0
2.8
1.3 1.11.7
0.91.41.4 1.2
-0.2
-2
0
2
4
6
8
10
I II III
Noi
se re
duct
ion
[dB
]
1999 2000 2001 2002 2003 2004 2005
2.9 2.32.4
Reference pavement – 8 or 11 mmL_pA, max, fast, 7.5 m as a function of speed
passenger cars, comparison of reference surfaces
60
65
70
75
80
40 50 60 70Speed, [km/h]
L_pA
,max
,fast
,7.5
m, [
dB re
20
µPa]
AC8d, KglAC11d(E), KglAC8d, SFrAC11d, SFrAC11d, all, SFrAC11d, Ubh
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
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Before After Before After
Reference pavement Porous pavement
Cannot hear noise fromroad traffic
Not annoyed
A little annoyed
Annoyed
Very annoyed
Noise annoyance with openwindows
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Before After Before After
Reference pavement Porous pavement
Cannot hear noise fromroad traffic
Not annoying
A little annoying
Annoying
Very annoying
Dose-response – closed windows
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
45 50 55 60 65 70 75
Noise outs ide windows - LAeq (dB(A))
A li
ttle
or
mo
re a
nn
oye
Before repaving
After repaving
Dose-response curve
Cost-benefit analysis
Comparing 3 means:• Two-layer porous
asphalt• Noise barriers• Sound insulation
Net Present Value:• construction and
maintenance• costs for a 30-year
period
3 cases:• Central city street• Ring road• Freeway
Comparing:• Direct costs• Costs/dB/dwelling
3 cases
City street (50 km/h, AADT: 12.000)Apartments: 1st – 5th floor65 – 68 dB façade level
Ring road (70 km/h, AADT: 30.000)Apartments: ground – 2nd floor73 – 74 dB façade level
Freeway (110 km/h, AADT: 60.000)Detached houses in 5 rows77 dB at the first row69/71 dB at the second row66/69 dB at the third row58/66 dB at the fourth row57/65 dB at the fifth row
15 m facade per apartment665 apartments (133/floor)
15 m facade per apartment399 apartments (133/floor)
23 m road per house435 houses (87/row)
Porous pavements
Effect:
City street: 4 dB
Ring road: 5 dB
Freeway: 6 dB
Costs (net present value, €):
City street: 296,000
Ring road: 360,000
Freeway: 477,000
Noise barriers
Effect:
City street: Not possible
Ring road: 0-12 dBAverage: 3.9 dB
Freeway: 1-12 dBAverage: 6.2 dB
Costs (net present value, €):
City street: Not possible
Ring road: 1,335,000
Freeway: 1,590,000
Façade insulation
Effect:
9 dB on indoor levels with windows closed
Costs (net present value, €):
City street: 2,685,000
Ring road: 1,607,000
Freeway: 2,890,000
Costs
0
500
1000
1500
2000
2500
3000
3500
City street Ring road Freeway
Cost
s (t
housa
nd E
uro
Porous asphaltNoise barrierFacade insulation
Costs per dB per dwelling
0
100
200
300
400
500
600
700
800
900
City street Ring road Freeway
Cost
s/dB/
dw
ellin
g (
Eur
Porous asphaltNoise barrierFacade insulation
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 mmaggregate 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