Use of SMA in Europe
Egbert Beuving

Secretary General of EAPASMA – Japan - January / February 20181

Introduction
•
•
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•
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What is EAPA
Types of asphalt used in Europe
Introduction into Stone Mastic Asphalt - SMA
Current developments
European Standards for SMA
Conclusions

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2

EAPA
EAPA is a non-profit association– Founded in 1973 and nowadays– Based in Brussels, Belgium

EAPA represents the majority of the European asphalt paving industry– The manufacturers of asphalt and asphalt paving companies– Material and equipment suppliers

EAPA’s mission– To promote the good use of asphalt and the maintenance of a sustainable European road
network
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Objectives••••

Represent its members in the institutions of the EU
Promote the effective and sustainable use of asphalt and new developments
Participate in European standardisation and legislation activities
Collect, exchange and promote knowledge
as well as best practices• Improve the image of ‘’asphalt ‘’ in Europe

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Activities

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Activities
Asphalt in Figures

EAPA Newsletter

Position Papers

Providing Statistical Data on www.eapa.org

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Asphalt used in Europe
In million tonnes
per year

Total Production of Hot and Warm Mix Asphalt in Europe from 2000 to 2016
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Asphalt used in Europe• European countries > 10 million tons/year
Country

2016

FranceGermany
Great Britain
Italy
PolandSpain
TurkeyEurope

34
41
22
23
19
13
40
282

Japan
USA

± 42
340

Picture of Asphalt in Figures 2016

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Surface layers used in Europe
Data of Asphalt in Figures 2016

picture of Asphalt in Figures 2016

Country
Belgium
Croatia
Czech
Republic
Denmark
Estonia
Finland
Hungary
Lithuania
Netherlands
NorwaySlovakia
Slovenia
Spain
TurkeySurface
BinderBasecourse [%] course [%] course [%]
55
0
45
63
2
36

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56
50
63
91
69
47
37
80
72
55
73
30

24
5
28
0
23
24
9
10
16
7
19
41

20
45
9
9
8
29
54
10
12
38
8
29
9

Mostly used Surface Layers in Europe
Country
Austria
Belgium
Croatia
Czech Republic
Denmark
Estonia
FinlandGermany
Hungary
Lithuania
Netherlands
Slovakia
Slovenia
Spain
Turkey% of total annual hot and warm mix asphalt production in 2016
Asphalt Concrete
SMA
Porous Asphalt
33
38
59
49
36
61
73
20
61
40
18
68
49
62
27

6
14
3
6
13
2
12
9
6
5
10
5
6
1
4

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0
1
10
0
0
0

9
0
0

10

Introduction - SMA – Stone Mastic Asphalt••••

It was developed in Germany in the mid-1960s
Studded tyres were widely used -> wear
Asphalt Concrete not good enough
Mastic asphalt expensive and labour intensive to lay

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•
•
•

German standard for SMA in 1984
Since then used in Europe and across the world
European standard (EN 13108-5) in 2006
This standard specifies a technical framework which allows national application
documents in each country

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Introduction• Stone Mastic Asphalt (SMA) used in many countries• Used for surface and binder courses of highways, roads, airports, harbours, etc.
• In all countries except Ireland: SMA is used for runway surfaces; mostly SMA 11
Widely used because of its• High stability• High durability• Ability to be applied in thin layers• Noise reduction• Lower Rolling resistance

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Functional Pavement Characteristics
The main functional characteristics of SMA are:
• Skid resistance, evenness (transverse and longitudinal), visibility and aquaplaning• Resistance to permanent deformation “stability” (pavement performance) anddurability• Noise reducing surface and recyclable / recycling.

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Skid resistance
Depends on:• Selection of aggregate type
– Polished Stone Value for skid resistance for long(er) period– Level depends on local aggregate availability and experience of use• Design of surface texture– Aggregate size
– Degree of mortar filling of the voids– Larger aggregate: more texture depth– Smaller aggregate: less Rolling resistance

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Skid resistance• Important to ensure mixes are not overfilled with mastic.
• Otherwise loss of skid resistance, loss of texture under traffic and rutting.
• SMA mixes have thicker binder film than most conventional mixtures.
• In some countries for improving initial skid resistance (during first few weeks) they
apply a bit grit (aggregates 1- 3mm) to surface during the final passes of compaction

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Aquaplaning• The high (negatively) surface texture gives more capacity to store / remove water.

• Good riding comfort (because it is smooth pavement)• Low Rolling Resistance

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Stability• It is so called Stone-skeleton mixture• High resistance to rutting/ permanent deformation• It was developed for this reason

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Durability• SMA is durable, wear-resistant material• Is impervious due mastic mortar• Mortar / mixture has high binder content

Difference in structure between Asphalt Concrete (AC), SMA, BBTM (Thin Layers ofAsphalt Concrete) and Porous Asphalt (PA)SMA – Japan - January / February 201818

Durability of Surface Layers

Source: EAPA Position Paper Long Life Pavement (1997)
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Durability of Surface Layers

Source: EAPA Position Paper Long Life Pavement (1997)
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Noise• For reducing tyre-road noise: macrotexture and porosity of the road surface areimportant• The relatively open surface texture of SMA and the smoothness (negative texture)offers the advantageous noise reducing properties• SMA pavements with a maximum aggregate size of 11 mm (0/11 mm) or less (0/6mm) have given up to 2 - 3 dB(A) less noise compared with dense asphalt concrete

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Recycling• SMA can be 100% reused / recycled• Reclaimed asphalt back in SMA difficult due accurate control of grading

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SMA for Heavy Duty Pavements• SMA used in heavy duty pavements because of its stone-skeleton• High quality aggregate used
• For heavy duty pavement the structure below SMA needs to be good (too)Applied thickness: at least 2.5 x nominal aggregate size
• So for SMA 6: ≥ 15 – 20 mm
andfor SMA 16:≥ 40 – 50 mm

In some cases Polymer modified Bitumen (PmB) is used:• To be on the safe side
• In case a higher rutting resistance is needed
For low volume road normal Paving grade bitumen is used
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Practice of SMA in Europe• General - grading’s used in Europe• Drainage Inhibitors• Modified Binders• Mixture Design

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Practice of SMA in Europe
All countries using SMA have / report very positive experiences with SMA
The major SMA types are SMA 8, SMA 11 and SMA 16.
• There are national preferences for other grading’s• Germany and the Netherlands they also use SMA 5• Sweden also uses SMA 4• In the Nordic countries often SMA 16 to give increased resistance to studded tyres
Generally, crushed aggregates are recommended for both the coarse and fine mineral
fractions• For the fine fractions sometimes partly uncrushed aggregate (natural sand) is used
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Practice of SMA in Europe
Mixture composition requirements for various grading’s
SMA Type

5–6
8
9.5 – 10
11 – 1214
16

Percentage
passing sieve
63 µm

Percentage passing
sieve 2 mm

6 – 12
6 – 12
6 – 11
6 – 11
6 – 11
5 – 1027 – 40
20 – 35
21 – 32
18 – 32
15 – 30
15 – 30

Binder content, %On 100%aggregate
5.6 – 8.0
6.5 – 7.5
5.3 – 6.8
5.3 – 7.5
6.5
6.4

“in”
mixture5.3 – 7.4
6.1 – 7.0
5.0 – 6.4
5.0 – 7.0
6.1
6.0

The mixture design is generally based on the volumetric properties
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Mixture Design
The essential characteristics of SMA concept are the volumetric parameters• SMA is gap graded bituminous mixture with an aggregate skeleton, formed byrelatively coarse aggregate particles, which is filled by a mastic of bitumen, filler andfine aggregate (sand),• It is essentially to determine the right volumetric proportion of the constituent
materials• The right distribution of skeleton voids (VCA) and mastic portions.
A higher void content in the aggregate structure can be achievedby creating a larger gap in the aggregate grading
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Drainage Inhibitors
The mastic in SMA is a filler-sand mixture which is overfilled with binder andtherefore a drainage inhibitor needed
The remaining void content in the final SMA mixture generally is in general 3 - 6% (byvolume)Due to the thick binder film required in SMA: drainage inhibitor is necessary• In general fibres are used such as cellulose and specific organic materials• Drainage inhibitors are active during: storage, transport and laying of hot SMA• After compaction: no influence to the performance of the mixture

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Drainage Inhibitors• Cellulose fibres are added mostly in pelletised form
• Dosed (automatically or manually) in the mixer through pipe for better distribution• The required amount of inhibitor is based on practical experience.
• To measure drainage inhibiting capacity for SMA: binder drainage test (EN 12697-18)
Schellenberg test.

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Grading SMA versus Asphalt Concrete

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Modified Binders
Modified binders are used in SMAs

• To increase the resistance to permanent deformation• To increase the durability of the pavement surface• To reduce application and damage risks especially in cases of very thin layers• Use of PmB can reduce need for drainage inhibitor (although this can still benecessary with some PMBs)

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Production, Laying and Compaction
Batch plants and drum mixers can be used for producing SMA• SMA is sensitive to overfilling of the aggregate structure with mastic• Therefore accurate aggregate supply control is important because of volumetric
design• The addition of the fibres can take place in several ways.
• Automatic dosing• Pelletized fibres easy to use

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Production, Laying and Compaction
Before the start of the project a trial production of SMA is recommended

No special attention needed during laying
Laying by hand is not recommended• Due to the high internal cohesion of the mixture• Difficult to obtain the optimum evenness, durability and density of the mixture

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Production, Laying and Compaction
For SMA surface courses only steel wheel rollers are to be selected• Start with a static pass
• Followed by one oscillating pass to give satisfactory intermediate compaction• Number of total passes depends on specified voids and density• Use a trial section to verify process and to check compaction equipment achieves
the required/specified density• Thin layers -> quick cooling -> early compaction

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Current Developments• SMA Binder Courses (SMA BC)• SMA as base course layer / Triple SMA• Noise-Reducing SMA (SMA NR)

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SMA Binder Courses••••

Rutting in pavements often due to binder layer (layer just below surface layer)
Due to high shear stresses in that layers due to truck loadings
SMA has good rutting resistance due to stone-skeleton
SMA is also impermeable (Important for binder courses)• Sections in Sweden and Germany: SMA for Binder Courses• Promising solution for highly stressed binder courses• SMA binder courses can be used as temporarily surface layer

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SMA Base Courses
Traditional pavement design: strain level at the bottom of theasphalt structure• Strain level at the bottom of the base layer• More bitumen -> better fatigue• SMA –> more bitumen -> better fatigue• Rich bottom layer concept-> Perpetual pavement in Poland

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Triple SMA• Innovative triple SMA layer for heavy duty pavements:
service roads at a refinery in Gdansk (Poland)• Slow moving traffic• They used
• 60 mm highly modified SMA anti-fatigue base course layer(SMA 16 PmB 45/80-80)• 90 mm binder course of SMA 22 PmB 25/55-80• 50 mm surface course SMA 16 PmB 45/80-80.

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Noise-Reducing SMA
Tire/road surface interaction noise important in many countries
SMA mixture design with improved noise reduction (SMA NR) successfully applied ine.g. Austria, Denmark and Germany. In Germany more than 4 dB(A)Mixture design: higher void content + optimised surface texture (small aggregate)
No gritting
Characteristics of Layer
Paving thickness
Compaction degree
Void content
Evenness (4 m section of
measurements)

mm%Vol.-%

SMA 8 S (NR)
25 – 40≥ 97
9.0 – 14.0

SMA 5 S (NR)20 – 30≥ 97
9.0 – 14.0

mm

≤ 3.0

≤ 3.0

Characteristics of Noise Reducing SMA (FGSV, Germany, 2014)
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User / Environmental Benefits•

Longer service life and lower maintenance -> lower CO2 footprint• Less user delays and congestions• Reduced risk of aquaplaning• Low levels of traffic noise.
• 100% recyclable

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Cost EffectivenessInitial material costs/tonne can be higher than of standard Asphalt Concrete (AC):• due to higher binder content• need for high quality aggregates• requirement for a drainage inhibitor (and modified bitumen• Reduced production capacity, if extra mixing time is required for drainage inhibitor
But:• SMA can be applied in thinner layers compared to AC• Longer performance life than AC• Less maintenance costs, less user delay costs etc.
• In the end SMA is cheaper
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European Asphalt Standards• Product standards (EN 13108 series)• Standards for Test Methods (EN 12697 series)

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EN 13018-5 - SMA

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EN 13018-5 - SMA
The test methods
are shown in the
EN 12697 series

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EN 13018-5 - SMA

EN 13108-20 = Type Testing
EN 13108-21 = Factory Production Control

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SMA Product Standard EN 13108-5
SMA
Passing sieve (% by weight)
31.5 mm22.4 mm

D4

D5

D6

D8

D10

D11

D12

D14

20.0 mmD16100

16.0 mm100

14.0 mm
11.2 mm100

10.0 mm100

8.0 mm

100

6.3 mm

100

100

100

90 - 100

90 - 100

D20

D22

100

100
90 - 100

90 - 100

90 - 100

90 - 100

90 - 100

90 - 100

90 1005.6 mm100

90 - 100

4.0 mm90 –100
25 – 45

20 - 40

20 - 40

20 - 40

20 - 35

20 - 35

20 - 35

15 – 30

15 – 30

15 – 30

15 – 30

5 - 145 - 145 - 145 - 145 - 135 - 135 - 135 - 12

5 - 12

5 - 12

5 – 122.0 mm
0.063 mm
Min. binder content % by weight

Bmin 5.0 – 7.6

Void content Marshall % by volume
Vmax 3.0 – 8.0
Vmin 1.5 – 6.0

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Conclusions
SMA has several advantages compared to other asphalt (surface) mixture• SMA is safe - good skid resistance, good evenness and minimized aquaplaning.
• SMA is noise reducing• SMA can have low Rolling Resistance• SMA has high resistance to permanent deformation• SMA is durable and sustainable -> greener• SMA has longer service life and gives good return on investment• SMA is economically attractive - less maintenance costs and convincing life-cycle
costs

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www.eapa.org
beuving@eapa.org

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