Danish Ministry of Transport and Energy
Danish Ministry of Transport and Energy
Danish Road Institute
Report 145
2005
Thin noise reducing
pavements
Road Directorate Guldalderen 12 P.O. Box 235 DK 2640 Hedehusene Denmark Telephone +45 4630 7000 Telefax +45 4630 7105 www Roadinstitute.dk
Title Thin noise reducing pavements - Experiences Dated November 2005
Copyright Road Directorate, all rights reserved Authors Hans Bendtsen, Bent Andersen Photo Hans Bendtsen
Published by Road Directorate, Danish Road Institute ISSN electronic 0909-1386
ISBN electronic 87-91177-70-7
Reports published by the Danish Road Directorate can be requested from the bookshop:
Telephone +45 4322 7300 Telefax +45 4363 1969 e-mail schultz@schultz.dk
Danish Road Institute
Report 145
2005
Hans Bendtsen
Bent Andersen
Danish Ministry of Transport and Energy Danish Ministry of Transport and Energy
Thin noise reducing
pavements
3
Contents
Abstract ... 5
Preface ... 6
1. Introduction ... 7
2. Test on urban road ... 8
2.1 Pavement types...8
2.2 Noise measurements...9
3. Test on Highway ... 11
3.1 Pavement types...11
3.2 Noise measurements...11
4. Conclusion and discussion ... 13
5. Acknowledgements ... 14
5
Abstract
Like porous pavements, thin layer pavements have a noise reducing potential on urban roads as well as on highways. In Denmark a project on urban roads was started in 2003. The goal was to develop and test thin layers as noise reducing pavements under Nordic conditions. This project is a part of the European SILVIA project started in September 2002. Another Danish project with test sections of thin layer pavements on a highway was started in the summer of 2004. 13 test sections have been constructed on urban roads and 5 on the highway. Different pavement types are included: 1. Open graded asphalt concrete. 2. Stone Mastics Asphalt. 3. A thin layer constructed as a combination pavement. Dense asphalt concrete pavements with maximum 8 or 11 mm aggregate size are included as reference pavements. Comprehensive measurement programs have started. Noise is measured by the SPB method. The pavements will be described together with the results of the first series of noise measurements. In 2004 a new research project on optimization of thin layers started as a co-operation between the Danish Road Institute / Road Directorate (DRI) and the Road and Hydraulic Engi-neering Institute in the Netherlands (DWW) called the DRI-DWW noise abatement program. This new project is focusing on optimising the noise reduction and to find the long-term noise reducing effects of thin layers. The project plan for this new pro-ject will also be presented.
6
Preface
This report contains an article written by Hans Bendtsen, Bent Andersen, for Forum Acusticum 2005 in Budapest, Hungary.
7
1. Introduction
Thin layer pavements have been used for 10 to 15 years in different European coun-tries as wearing courses on roads. Only in the last years there has also been a focus on this type of pavements as noise reducing pavements. The reasons for this is a wish to develop noise reducing pavements that are not porous and therefore will not have clogging and lifetime problems as porous pavements have, and at the same time to de-velop noise reducing pavements that are not very costly. The noise reducing effect of thin layers is related to the structure of the pavement surface. The goal is to create as smooth a pavement as possible in order to reduce the generation of vibration noise from the tires, and at the same time to create as open a pavement surface as possible in order to reduce the noise generated from air pumping, [4, 5].
In Denmark a project started in 2003 with the goal to develop and test noise reducing thin layers for urban roads. The project is called SILVIA.DK and is part of the EU project SILVIA [6]. Test sections have been constructed in 3 Danish cities (Copenha-gen, Aarhus and Randers) [4]. The first measurement results are presented in this arti-cle. In 2004 the Danish Road Directorate established a test site on a highway (M10 near Solrød) [3]. The first results from this site are also presented and discussed in this paper.
In 2004 co-operation between the Dutch (DWW) and the Danish (DRI) road institutes was started. The co-operation is called “The DRI-DWW noise abatement program” [1]. A total of 7 projects are carried out inside the framework of the program, which is a part of the large Dutch Innovation Program on Noise from Road Traffic, also called the IPG research program [2]. One of these projects is focussing on the acoustical as well as the structural lifetime of noise reducing thin layers. In order to get as long measurement series as possible measurements will be continued for some years on the SILVIA.DK and the Solrød test sites as a part of the DRI-DWW noise abatement pro-gram. New test sections with noise reducing thin layers will also be constructed in Denmark on highways with a speed limit of around 80 km/h and in the Netherlands on highways with speed limits around 110 km/h.
8
2. Test on urban road
2.1 Pavement types
The municipalities of Copenhagen, Randers and Aarhus participate in the SILVIA.DK project. They have agreed to provide test roads for the project and to finance the con-struction of the test pavements. The three urban test roads have a traffic flow of 6700 to 12500 vehicles pr. day, around 8 % of heavy vehicles and an average speed of 50-60 km/h [4]. The development and design of the recipes for the pavements to be tested in the project were based on a combination of the best available knowledge and tech-nology in Denmark combined with a study of the latest experiences in the Nether-lands, [7], and other European countries. The goal is to develop pavements fulfilling the following functional requirements:
• Pavements with as smooth a top surface as possible in order to minimize the noise
generated by vibrations in the tires. In order to achieve this, pavements with a maximum aggregate size of 6 mm have been selected.
• Pavements with as open a surface as possible in order to minimize the noise
gener-ated by the air pumping effect. In order to achieve this, pavements with a very open top structure have been selected. The pavements are open - but not porous (with an open structure in the whole layer thickness of the pavement). In one of the test pavements a certain amount of larger aggregate (size 5-8 mm) has been added, in order to increase the openness of the top surface.
Three different types of thin open pavements are included in the project:
1. Open graded asphalt concrete (AC-open) with a (built-in) Marshall air void of
approx. 8 - 14 %.
2. Stone Mastics Asphalt (SMA) with a (built-in) Marshall air void of approx.
4 - 8 %.
3. A thin layer constructed as a combination pavement (TP c). On the existing road
surface a thick layer of polymer modified bitumen emulsion (including water) is laid out. On the top of this a very open pavement (like porous asphalt) with a (built-in) Marshall air void of approx. 14 % or even more is applied. The bitumen layer “boils up” in the air voids of the pavement, leaving only the upper part of the structure open. This reduces the built-in air void of the pavement because the pores of the pavement are filled with bitumen.
Reference pavements constructed as dense asphalt concrete with 8 and 11 mm maxi-mum aggregate size are used. The bitumen will be in the soft end of the spectrum, in order to achieve a good lifetime for the pavements. Cement will be added to the bitu-men in order to improve the adhesion of the bitubitu-men. In some of the pavebitu-ments elas-tomer modified bitumen will be used in order to improve flexibility and durability. On the test sections in Aarhus and in Randers the same pavement types have been tested even though small modifications in the recipes have been made.
9
Table 1. Pavements tested on the Copenhagen test road [4]. Specified data.
Type Max. aggregate size Built-in air void Thickness approx. Weight AC11d (reference) 11 mm - 30 mm 70 kg/m2 AC8d (reference) 8 mm - 25 mm 55 kg/m2 AC6o 6 mm 8 – 14 % 20 mm 45 kg/m2 SMA6+ 6 mm +5/8 mm 4 – 8 % 20 mm 45 kg/m2 TP6c 6 mm 14 % 17 mm 35 kg/m2
2.2 Noise measurements
The noise has been measured when the pavements were new by the use of the Statisti-cal Pass-By method [8].
Table 2. Noise for passenger cars as LpA, fast, max, 7,5m at 60 km/h, and noise reduction relative to the
ref-erence pavement (AC11d) for each pavement type at the test sections in Copenhagen (in dB re 20 µPa).
AC11d AC8d AC6o SMA6+ TP6c
Passenger cars 72.6 71.6 70.3 70.6 69.5
Noise reducetion Ref. 1.0 2.3 2.0 3.1
Noise reduction Passinger cars
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5
AC8d AC6o SMA6 TP6c
dB
Figure 1. Noise reduction for passenger cars relative to the reference pavement (AC11d) for each pavement type at the Copenhagen test road (in dB re 20 µPa) at 60 km/h.
10
Figure 1 shows an overview of the noise reductions for passenger cars relative to the reference pavement (AC11d) for each pavement type at the test road at 60 km/h. On the background of these early results from the first measurement campaign when the pavements were around 6 month old, it seems that the combination pavements (TP6c) offers the best noise reducing potential of 3 dB followed by the open asphalt concrete (AC6o) and the SMA pavements with a noise reducing potential of 2 dB. As the dif-ferences are small no strong conclusions shall be drawn at this early stage on which pavement family that offers the best noise reductions. The measurements will be con-tinued in the coming years.
In Figure 2 the noise level (LpA, fast, max, 7,5m ) for passenger cars is shown for the test
sections included at 60 km/h. The noise from the reference pavements (AC11d) are around 72.6 dB. The dense asphalt concrete with 8 mm maximum aggregate size has a noise level which is 1 dB lower. This illustrates the importance of which reference pavement that are selected for an experiment with noise reducing pavements
Passenger cars 65,0 66,0 67,0 68,0 69,0 70,0 71,0 72,0 73,0 74,0 75,0
AC11d AC8d AC6o SMA6 TP6c
dB
Figure 2. Noise levels as LpA, fast, max, 7,5m for passenger cars at 60 km/h on
11
3. Test on Highway
3.1 Pavement types
In the summer of 2004 four test sections with thin layer pavements as well as a dense asphalt concrete reference surface with maximum 11 mm aggregate size were con-structed on the M10 highway near Solrød. The traffic volume is around 80.000 vehi-cles per day and the speed limit is 110 km/h. Generally the thin layers have an open surface structure and a small maximum aggregate size. The thin layers used on the highway are the following:
• SMA8: Stone Mastics Asphalt (SMA) with a (built-in) Marshall air void of approx.
12 %. The pavement is constructed like a porous pavement with a stone skeleton. The voids are filled with bitumen and filler, leaving only the surface structure open.
• AC8o: A dense, but very open graded asphalt concrete (AC-open) with a (built-in)
Marshall air void of approx. 15 %.
• TP 8c: A thin layer constructed as a combination pavement (TP c). On the existing
road surface a thick layer of polymer modified bitumen emulsion (including water) is laid out. On the top of this a very open pavement (like porous asphalt) with a (built-in) Marshall air void of approx. 14 % is applied. The bitumen layer “boils up” in the air voids of the pavement, leaving only the upper part of the structure open.
• SMA6+: Stone Mastics Asphalt (SMA) with maximum 6 mm aggregate size, but
with a small amount of 5/8 mm aggregate added.
Table 4. Pavements tested on the M10 highway [3]. Specified data.
Type Max.
aggre-gate size Built-in air void Thickness approx. Weight AC11d reference 11 mm 3 % 33 mm 80 kg/m2 SMA8 8 mm 12 % 29 mm 60 kg/m2 AC8o 8 mm 15 % 28 mm 60 kg/m2 TP8c 8 mm 14 % 22 mm 45 kg/m2 SMA6+ 6 mm + 5/8 mm 3 % 26 mm 60 kg/m2
3.2 Noise measurements
Also here the noise has been measured when the pavements were 4-5 month old by the use of the Statistical Pass-By method [8]. In the following the noise reduction is given relative to a dense asphalt concrete reference surface with maximum 11 mm aggregate size.
12
Table 5: Noise as LpA, fast, max, 7,5m and SPB index, and noise reduction relative to the reference pavement
(AC11d) for each pavement type (in dB re 20 µPa) [3]. Reference speed is 110 km/h for passenger cars and 85 km/h for trucks. For the standardized SPB index the traffic composition is 70 % pas-senger cars, 7.5 % dual-axle trucks and 22.5 % multi-axle trucks.
AC11d SMA8 AC8o TP8c SMA6+
Passenger cars 82.4 81.9 79.4 80.2 80.8 Noise reducetion 0.5 3.0 2.3 1.6 Dual-axle trucks 88.0 86.3 85.4 85.2 87.0 Noise reducetion 1.7 2.6 2.8 1.0 Multi-axle trucks 89.3 88.1 87.0 87.5 88.1 Noise reducetion 1.2 2.3 1.8 1.2 SPBI 86.3 85.3 83.8 84.3 85.1 Noise reducetion 0 1.0 2.5 2.0 1.2
It can be seen that the very open graded asphalt concrete (AC8o) has the best noise re-duction of 2.5 dB. The noise rere-duction for trucks is generally only a little smaller than for passenger cars, indicating that thin layers also has a good noise reducing effect on truck noise at highways with high speeds.
13
4. Conclusion and discussion
The noise reducing potential of different types of thin pavements has been measured on an urban test road (speed 60 km/h) and on a highway (speed 110 km/h). The meas-urements have been performed when the pavements were only about 6 month old. Three types of thin pavements have been included in the experiments. Stone Mastics Asphalt (SMA), open graded asphalt concrete (ACo) and combination pavement (TPc). Reference pavements constructed as dense asphalt concrete with 11 mm maxi-mum aggregate size is used (AC11d).
On the background of these early results from the first measurement campaign when the pavements were around 6 month old the following tendencies can be highlighted:
• Thin layer pavements with a small aggregate size offer a noise reducing potential
in relation to dense asphalt concrete (aggregate size 11 mm).
• It seems that for passenger cars on the urban roads at 60 km/h the combination
pavements (TP6c) offers the best noise reducing potential of 3 dB followed by the open asphalt concrete (AC6o) and the SMA pavements with a noise reducing po-tential of 2 dB.
• For the highway experiment the open graded asphalt concrete (AC8o) has the best
noise reduction of 2.5 dB for mixed traffic followed by the combination pavement with a noise reduction of 2 dB.
• The noise reduction for trucks on the highway is generally only a little smaller than
for passenger cars, indicating that thin layers also has a good noise reducing effect on truck noise at highways with high speeds.
As the differences are small no strong conclusions shall be drawn at this early stage on which pavement family that offers the best noise reductions. The measurements will be continued in the coming years.
14
5. Acknowledgements
The test of thin layers on urban Danish roads was originally financed as a part of the EU SILVIA project (2002 - 2005) and the Danish partners in this project. The mem-bers of the Danish project group have made excellent and important contributions to the whole project. These people are (besides the authors of this paper) Lene Michelsen from the Danish Road Directorate, Steen Kønigsfeldt and Michael Rasmussen from the Municipality of Copenhagen, Jørn Bank Andersen from the National Union of Pavement Contractors and NCC, Ole Grann Andersson from Skanska Asphalt, Jørn Raaberg from the Danish Road Institute / Road Directorate, Jørgen Horstmann from the Danish Environmental Protection Agency, Birte Nielsen from the Road Depart-ment, Municipality of Aarhus, Birgit Berggrein, Jonas H. Olesen, and Sven Aage Jen-sen from Road and Traffic department, Environmental Division, Municipality of Randers. The test of thin layers on a Danish highway was financed by the Danish Road Directorate (2004). This paper is partly produced as a part of the DRI-DWW noise abatement program which is a co-operation of Road and Hydraulic Engineering Institute in the Netherlands (DWW) inside the framework of the Dutch IPG program. In the coming years the measurements will be continued as a part of this programme.
15
References
[1] The DRI-DWW Noise Abatement Program - Project description. Note 24, 2005.
Danish Road Institute, Road Directorate. www.roadinstitute.dk.
[2] Noise Innovation Program for Road Traffic. (The IPG programme).
DWW report 2002-073.
[3] Measurement of road traffic noise from pavements on M10 near Solrød (Måling
af trafikstøj fra vejbelægninger på M10 ved Solrød, in Danish). Note 21, 2004. Danish Road Institute, Road Directorate. www.roadinstitute.dk.
[4] Thin Layer Test Pavements in Denmark – Project Description. Note 26, 2005.
Danish Road Institute, Road Directorate. www.roadinstitute.dk.
[5] Thin open layers as noise reducing pavements -an Inter-Noise 2004 presentation.
Report 135, 2004. Danish Road Institute, Road Directorate. www.roadinstitute.dk.
[6] The SILVIA homepage: www.trl.co.uk/silvia/.
[7] Dutch experience with thin layers as noise reducing pavements. Notes from a
study tour. SILVIA-DTF.ATKINS-004-01-WP4-07.05.03-Notes study tour Netherlands. 2003.
[8] ISO 11819-1:1997. Acoustics – Measurement of the influence of road surfaces on
Rapport / Report Nr.
No.
Titel/Title/Shortcut Forfatter/Author 128 Viden om drift af veje Gregers Hildebrand Charles Lykke Hansen SvendKold Johansen Birger Roland Jensen BjarneSchmidt, Jørn Raaberg 129 Crushed concrete from building demolition is a high
quality material for road construction
Knud A. Pihl Ole Milvang-Jensen Flemming Berg 130 Ubundne bærelag af knust beton
- efter europæiske standarder
Knud A. Pihl Flemming Berg Ole Milvang-Jensen 131 Ubundne bærelag af knust tegl
- efter europæiske standarder
Knud A. Pihl Flemming Berg Ole Milvang-Jensen 132 Ubundne bærelag af knust asfalt
- efter europæiske standarder
Knud A. Pihl Flemming Berg Ole Milvang-Jensen 133 Bundsikring af forbrændingsslagge
- efter europæiske standarder
Knud A. Pihl Flemming Berg Ole Milvang-Jensen 134 Noise emission from 4000 vehicle pass-bys
- an Inter-Noise 2004 presentation
Bent Andersen Hans Bendtsen 135 Thin open layers as noise reducing pavements
- an Inter-Noise 2004 presentation
Hans Bendtsen Bent Andersen 136 European co-operation in COST 347
- Bringing ALT activities closer together
Gregers Hildebrand Michael E. Nunn 137 Traffic management and noise reducing pavements
- Recommendations on additional noise reducing measures
Hans Bendtsen Jürgen Haberl, Johan Litzka Ernst Pucher Ulf Sandberg Greg Watts 138 Mechanistic Design of Semi-Rigid Pavements
- An Incremental Approach
Finn Thøgersen Christian Busch Anders Henrichsen 139 Holdbarhed af Drænasfalt Carsten Bredahl Nielsen Jørn Raaberg Erik Nielsen 140 Indbygning af skrivekridt - Et fuldskalaforsøg Sten Thorsen Poul Panduro Knud A. Pihl 141 Noise reducing pavements
- State of the art in Denmark
Hans Bendtsen Bent Andersen 142 Economic assessment of traffic noise in planning
- Danish experiences
Lars Ellebjerg Larsen Hans Bendtsen 143 Organising urban noise abatement
- New ideas
Hans Bendtsen Lene Nøhr Michelsen Brian Kristensen Lars EllebjergLarsen 144 Two-layer porous asphalt
- for urban roads
Hans Bendtsen Bent Andersen Jørn Raaberg Lars EllebjergLarsen Jørgen Kragh 145 Thin noise reducing pavements
- Experiences
Hans Bendtsen Bent Andersen
Road Directorate Niels Juels Gade 13 P.O. Box 9018 DK-1022 Copenhagen K Denmark Telephone +45 3341 3333 Telefax +45 3315 6335 Road Directorate Guldalderen 12 P.O. Box 235 DK-2640 Hedehusene Denmark Telephone +45 4630 7000 Telefax +45 4630 7105 Road Directorate Thomas Helsteds Vej 11 P.O. Box 529 DK-8660 Skanderborg Denmark Telephone +45 8993 2200 Telefax +45 8652 2013 vd@vd.dk Vejdirektoratet.dk
