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Overview, including less common optionsPresented by Dr Cliff NichollsSenior Academy Fellow – 15 Oct. 2009
SCI/IAT/IHT Seminar – Cases for and against hot mix road surfacings
Page 2
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Material Types
Mixtures defined by standards
BS 594 and BS 4987 replaced by BS EN 13108
Page 3
Material Types
BS EN 13108-1 Asphalt concrete (AC)- Includes macadams, Marshall asphalt and EME2
BS EN 13108-2 Asphalt concrete for very thin layers (BBTM)
BS EN 13108-3 Soft asphalt (SA)
BS EN 13108-4 Hot rolled asphalt (HRA)
BS EN 13108-5 Stone mastic asphalt (SMA)
BS EN 13108-6 Mastic asphalt (MA)
BS EN 13108-7 Porous asphalt (PA)
prEN 13108-9 Ultra-thin layer asphalt concrete (UTLAC)
Page 4
Page 5
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Similarities
All made from the same component materials
Different proportions- Aggregate gradings
- Binder contents
How different are the gradings?
BS EN 13108 overall envelope for target gradings- 10 mm size for comparison
Asphalt concrete AC 10 gradings
0
10
20
30
40
50
60
70
80
90
100
Po
po
rtio
n p
assin
g (
%)
Sieve Size (mm)
AC10
0.063 0.25 0.5 2.0 6.3 10 14
Page 7
AC 10 and BBTM 10 gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10A
BBTM10B
BBTM10C
BBTM10D
0.063 0.25 0.5 2.0 6.3 10 14
Page 8
AC 10 and BBTM 10 gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
0.063 0.25 0.5 2.0 6.3 10 14
Page 9
AC 10, BBTM 10 and SMA 10 gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
0.063 0.25 0.5 2.0 6.3 10 14
Page 10
AC 10, BBTM 10, SMA 10 and MA 10 gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
MA10
0.063 0.25 0.5 2.0 6.3 10 14
Page 11
AC 10, BBTM 10, SMA 10 and PA 10 gradings
0
10
20
30
40
50
60
70
80
90
100
Po
po
rtio
n p
assin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
0.063 0.25 0.5 2.0 6.3 10 14
Page 12
AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
HRA15/10F
0.063 0.25 0.5 2.0 6.3 10 14
Page 13
AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
HRA30/10F
0.063 0.25 0.5 2.0 6.3 10 14
Page 14
AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
HRA0/10F
0.063 0.25 0.5 2.0 6.3 10 14
Page 15
AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
HRA55/10F
0.063 0.25 0.5 2.0 6.3 10 14
Page 16
AC 10, BBTM 10, SMA 10, PA 10 and HRA gradings
Page 17
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10
BBTM10
SMA10
PA10
HRA55/10C
0.063 0.25 0.5 2.0 6.3 10 14
AC 10, BBTM 10, SMA 10 or PA 10 grading
0
10
20
30
40
50
60
70
80
90
100P
op
ort
ion
pa
ssin
g (
%)
Sieve Size (mm)
AC10 or BBTM10 or SMA10 or PA10?
0.063 0.25 0.5 2.0 6.3 10 14
Page 18
Similarities
Grading envelopes overlap
What is the “common” mixture like?
Do not know, but expect:- Relatively open macadam, thin surfacing or SMA
- Relatively impermeable PA
Mixture types relatively arbitrary classifications
Page 20
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Properties Required of Surfacings
The envelopes do have differences
Effect on properties of surfacings?(taken from TRL Report TRL250)
Suitability for re-profiling
Deformation resistance
Resistance to cracking
Spray reduction
Noise reduction
Skid resistance
Texture depth
Durability
Quality of ride
Initial cost
Speed of construction
Sustainability
Page 21
Performance of Surfacings (1)
Material Re-profiling Deformation Cracking
Hot rolled asphalt( )
Porous asphalt
Macadam
Mastic asphalt
Stone mastic asphalt
Thin surf. (26-39 mm)
Thin surf. (18-25 mm)
Thin surf. (< 18 mm)
Page 22
Performance of Surfacings (2)
Material Spray Noise Skid
Hot rolled asphalt
Porous asphalt
Macadam
Mastic asphalt
Stone mastic asphalt
Thin surf. (26-39 mm)
Thin surf. (18-25 mm)
Thin surf. (< 18 mm)
Page 23
Performance of Surfacings (3)
Material Texture Durability Ride
Hot rolled asphalt
Porous asphalt
Macadam
Mastic asphalt
Stone mastic asphalt
Thin surf. (26-39 mm)
Thin surf. (18-25 mm)
Thin surf. (< 18 mm)
Page 24
Performance of Surfacings (4)
Material Cost Speed
Hot rolled asphalt
Porous asphalt
Macadam
Mastic asphalt
Stone mastic asphalt
Thin surf. (26-39 mm)
Thin surf. (18-25 mm)
Thin surf. (< 18 mm)
Page 25
Differences
Some properties also dependant on aggregate size
No mixture is best for all properties
No mixture is worst for all properties
Engineering judgement for each situation
“Horses for courses”
Overall durability- Wild variations with workmanship
- Workmanship in design, manufacture and laying
- To UK specifications
Page 26
Expected Service Life of Different Surfacings
Type Category Expected LifeThin surfacing BBTM 11 to 15 years
SMA 10 to 16 yearsUltra-thin 8 to 11 yearsMultiple surface dressing 4 to 8 yearsMicro-surfacing 2 to 6 years
Hot rolled asphalt High & medium stability 14 to 24 yearsLow stability 8 to 13 years
Asphalt concrete DBM 10 to 16 yearsOpen graded macadam 6 to 10 yearsMarshall asphalt 15 to 25 years
Porous asphalt 7 to 10 years
Page 28
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Porous asphalt - Concept
Porous asphalt - History
PSA developed friction course for airfields 1950s
First TRL road trial 1967
Pervious macadam incorporated into BS 4987 1988
HA 50/93 issued 1993
Porous asphalt incorporated into SHW 1994
Still in SHW but not preferred material
Page 30
UK trials of porous asphalt
Page 31
0
5
10
15
20
Num
ber
of T
rials
20 mm Unmodified 20 mm Modified
16 & 14 mm Unmodified 14 & 16 mm Modified
10 mm Unmodified 10 mm Modified
89-91
8688
8385
8082
7779
7476
7173
6870
6567
Service life of porous asphalt
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Pro
po
rtio
n o
f se
rvic
ab
le s
ect
ion
s
Life (years)
Ultimate life
Spray-reducing life
Page 32
Identification of failure
Failure can be sudden
Literally “There one day, gone the next”
Identify potential
Estimate for paving grade binders
Polymer-modified binders different slope
Page 33
0
20
40
60
80
100
120
140
0 2 4 6 8 10 12
Pre
dic
ted
re
cove
red
pe
ne
tra
tio
n
(0.1
mm
)
Time from laying (years)
40/60 pen
70/100 pen
160/220 pen
Brittle failure
Advantages of porous asphalt
Less traffic noise in both dry and wet conditions
Less splash and spray in wet conditions
Reduced possibility of aquaplaning
Reduced surface glare
Reduced rolling resistance
Page 34
Disadvantages of porous asphalt
Reduced structural strength
Requires positive edge drainage details
Requires extra lighting
Requires tighter tolerances
Care needed to ensure no barriers within mat
Tendency for the pores to clog
Maintenance operations limited to avoid creating dams
Winter maintenance regimes need adjustment
Concerns over durability
High cost
Page 35
Uses for porous asphalt
High prestige sites
Sites not needing long durability
Sites with spray problems
Sites where excessive surface water with heavy rainfall
Not necessary for sites with noise problems
Therefore uses will be limited …
… but there are still some uses
Page 36
Page 37
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Mastic asphalt
Basic components:- Stiff binder
- Aggregate in powdered or finely crushed form
- High binder content
Heated and mixed together to form a pudding or porridge-like product
Capable of being poured and trowelled or screeded out to level
“Poured asphalt”
Two sub-categories
Page 38
Mastic asphalt
Mastic asphalt- Voidless with the consistency of a pudding
- Screeded by hand
- Used in UK, France and Mediterranean
Gussasphalt- Relies on a graded aggregate structure
- Flows into place, albeit assisted by compaction
- Laid by machine
- Germany, Northern Europe and Scandinavian countries
Page 39
Mastic asphalt
Good waterproofing
Primary uses:- Tunnels
- Concrete bridge decks
- Steel bridge decks
- Footpaths
- Flat roofs
Page 40
Page 41
Table of contents
Material types
Similarities
Porous asphalt
Mastic asphalt
Conclusions
1
2
3
4
5
6
Differences
Conclusions
Page 42
Mixture types are relatively arbitrary
But are still useful
No mixture is best for all properties
No mixture is worst for all properties
Engineering judgement for each situation
Appropriate choice is important
But …
… care and attention (workmanship) can be as important
Asphalt Surfacings
All that there is to know …
… about the details of all asphalt types
Page 43
Conclusions
Page 44
Porous asphalt- Widely used on airfields
- Not widely used on highways
- Good for sites with spray problems or where excessive surface water with heavy rainfall
- Limited durability
Mastic asphalt- Highly impermeable
- Several specialist uses
- One of the few options for long steel bridge decks
- High costs
Page 45
Do YouHave Any Questions?
But You WillJust Have To Wait!
Page 46
Thank youSCI/IAT/IHT Seminar
“Overview, including less common options”
Presented by Dr Cliff NichollsSenior Academy Fellow – 15 October 2009
Tel: 01344 770276Email: cnicholls@trl.co.uk