Experiences with PA in the Netherlands

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Experiences with Porous Asphalt in the
Netherlands
Jan Voskuilen Project Manager Asphalt
Road and Hydraulic Engineering
Institute Ministry of Transport, Public Works
and Water Management
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TOPICS

• History of Porous Asphalt (PA)
• 2. Mix design and requirements
• 3. Advantages and disadvantages of PA
• 4. Problems and solutions
• 5. Maintenance
• 6. New developments

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History of PA
PA developed during 2nd world war for air
fields Rediscovered in the Netherlands in the
seventies Since 1987 limited application of PA
for safety In 1990 the policy changed
application of PA on all motorways because of
noise reduction In 2005 65 of our motorways
have PA as wearing course
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Increasing part of PA on motorways
Percentage growth of PA on the Dutch motorways
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Mix Design Components

• Standard PA 0/16 consists of
• crushed stones 6 to 16 mm
• crushed sand between 2 and 0.063 mm
• filler lt 0.063 mm containing 25 Ca(OH)2
• pen grade bitumen 70/100
• no RA allowed
• no drainage inhibitors are used

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Mix design of PA 0/16 (mass )
On sieve desired max. min. 16.0 mm
0.0 7.0 11.2 mm 15.0 30.0 8.0
mm 50.0 65.0 5.6 mm 70.0
85.0 2.0 mm 85.0 0.063 mm
95.5 Bitumen 70/100 4.5 ( on 100
aggregate)
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Grading of PA 0/16
120
100
min. grading
80
max. grading
percentage on sieve
60
40
20
0
C16
C11,2
C8
C5,6
2 mm
63 um
sieve
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Mix design procedure
Compact 4 Marshall specimens PA (2 50 blows)
Determine the void content of the
specimens The minimum void content must be at
least 20 Determine the mean composition
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Popular research test methods for PA
Test temperature is 20 degree C. The resistance
to ravelling is expressed as the total amount of
loose material after 24 hours of testing
Rotating Surface Abrasion Test
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Popular research test methods for PA
Rotating Surface Abrasion Test (RSAT)
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Other research test methods for PA
(Retained) Indirect Tensile Test
(ITT) Wehner Schulze
Retain conditions 68 hours in water of 40 degree
C.

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Other research test methods for PA
Semi Circular Bendig Test
(SCB) Wehner Schulze

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Other research test methods for PA
Cantabro

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Performance based contracts

• Guarantee period is 7 years
• Functional requirements before opening,
  during the guarantee period and at the end of the
  guarantee period for
• - ravelling
• - cracks
• - void content
• - drainability
• - layer thickness
• - longitudinal evenness
• - rutting

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Disadvantages of PA

• After laying lower initial skid resistance
• Sometimes winter maintenance problems
• Ravelling can cause broken wind screens
• Higher costs
• Clogging
• Sensitive for damage

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Early life dry skid resistance

• Accident in 1991 on new PA
• Longer braking distance
• Tests on different road surfaces

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Monitoring skid resistance

• Gap-graded mixes
• Initial dry friction, deceleration test (100
  slip)
• initial wet friction (86 slip)
• wet friction during service life once in two
  years (86 slip)

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Brake test (100 slip, dry surface)
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86 slip trailer (wet skid resistance)
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86 slip trailer (wet surface)
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Characteristic values for braking deceleration
Braking deceleration must be gt 6.5 m/s2
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Cause of the initial low dry skid resistance of PA

• In contrast with Dense Asphalt no crushed sand or
  fine aggregate is sprinkled on PA surface to
  improve initial skid resistance
• After laying the PA aggregate is covered with a
  bitumen film
• During 100 slip alarm stop (without ABS) the
  bitumen film weakens due to increasing
  temperature (bitu-planing)
• Melted bitumen forms a sliding surface
• Important
• Problem only occurs with vehicles without
  ABS-system
• Motorists dont expect this of new asphalt!!!

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Policy from 1991
If the braking deceleration (BD) is lt 5.2 m/s2
there is a speed limitation of 70 km/h. If BD is
between 5.2 and 6.5 m/ s2 the sign longer
braking distance new road surface has to be
placed (time 3 to 6 months depending on traffic
and climate)
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BD in m/s2
6
5
0
12
6
months
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Policy from 1991

• Warn road users with special sign longer braking
  distance new road surface
• Carry out research to improve initial dry skid
  resistance

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Winter maintenance problems
The problem is that de-icers drain in the pores
of PA Solutions - good information for car
drivers (radio, television) - sprinkling higher
amount de-icer - closure of lanes Lab research
Safe cote and CMC
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Road safety investigation
On PA road sections happen as much accidents as
on Dense Asphalt road sections!!! Cause
motorists drive faster on PA during rainfall, so
the extra safety of PA is consumed! As a
consequence of this, the capacity of PA road
sections during rainfall is higher
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Advantages of PA

• Noise reduction
• No rutting problems
• During rainfall
• - no aqua planing
• - reducing of splash and spray
• higher capacity
• road markings stay visable
• Comfortable
• Better quality of run off water
• High appreciation of car drivers!

Dense Asphalt Concrete
Porous Asphalt
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Performance of standard PA 0/16

• Service life of PA
• average service life of fast lane is 16 years
• average service life of slow lane is 12 years
• 3 dB(A) noise reduction in comparison with DA

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Maintenance techniques for PA
The following maintenance techniques are
available Seal technique before ravelling
starts an emulsion with a rejuvenator is spread
on the PA surface If the ravelling process has
already started an open emulsion sand asphalt
mixture is applied in the upper part of PA (see
paper about Via-Ral, Kneepkens et all, EE,
Vienna 2004) In/out at the end of service
life milling of old PA and laying new PA
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Maintenance techniques for PA
Start of ravelling
Serious ravelling problems, end of service life
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Tensile strength
2
3
Service life
1
Time for preventive maintenance (seal technique)
2
Time for temperory maintenance (Via-Ral)
3
Time to mill old PA and lay new PA
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New developments (PA Plus)
Results of evaluation of test sites PA with 5.5
bitumen has a longer service life in comparison
with standard PA with 4.5 pen grade
bitumen. Service life of PA with PMB and PA with
pen grade bitumen with drainage inhibitors is
equal.(see paper Voskuilen et all, EE, Vienna
2004) Recommendation Use PA with 5.5 pen grade
bitumen with drainage inhibitors
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Two-layer PA constructions
NEW DEVELOPMENTS

• Standard construction
• 25 mm top layer PA 4/8
• 45 mm bottom layer PA 11/16
• Alternative construction
• 20 mm top layer PA 2/6
• 50 mm bottom layer PA 11/16

Noise reduction is 5 to 6 dB(A)
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Limiting conditions for Two-layer PA
NEW DEVELOPMENTS

• Only top layer 4/8
• No noise barriers needed
• Locations with normal clogging
• Realization road-width without traffic
• Laying period 1 May 1 October
• Good weather conditions

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Thank you!
Current
Future