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LESSONS LEARNED FROM LABORATORY AND FIELD
EXPERIENCES ON THE USE OF DOUBLE TWIST STEEL WIRE
MESH AS A REINFORCEMENT FOR ASPHALT PAVEMENTS
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INTRODUCTION One of the oldest interface systems
used in flexible pavement is steel reinforcement.
The idea that appeared in the early 1950s was
based on the general concept that if hot-mix
asphalt (HMA) is strong in compression and weak
in tension, then reinforcement is definitely
needed. Steel reinforcement was abandoned in
the early 1970s after tremendous difficulties
were encountered in the installation. The idea
reappeared in the early 1980s with a new class of
steel reinforcement products in Europe many of
the early reported problems appear to be solved,
and successful experiences with the new class of
steel reinforcement were reported.
Installation of wire netting in Ontario (1960)
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WHAT IS ROAD MESH?
Road Mesh is manufactured from double twisted
steel wire mesh with transverse reinforcing rods
evenly spaced 16 cm centres. The hexagonal mesh
size is complying with EN 10223-3. The wire has
a zinc coating complying with EN 10244-2 Class A.
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WHAT IS ROAD MESH?
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MATERIALS FOR PAVEMENT REINFORCEMENT
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ROAD MESH APPLICATIONS
FATIGUE Crocodile \Alligator cracks
Road Mesh is able to absorb the horizontal
tensile stresses resulting from existing cracks
and traffic loads, thus increasing the pavement
life.
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ROAD MESH APPLICATIONS
RUTTING Channelisation
Road Mesh is installed at the base of the overlay
(gt 60 mm) thus intersecting the shear slip
circles, eventually reducing the surface rutting
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ROAD MESH APPLICATIONS
TRANSVERSE CRACKS Overlays on jointed concrete
pavements
The active joint is a discontinuity which tends
to propagate to the road surface. Road Mesh is
installed within the overlay to absorb the
tensile forces
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LABORATORY AND FIELD EXPERIENCESThe key
objective of the next slides is to review the
existing worldwide experiences on the application
of the double twist wire mesh reinforcement in
HMA.
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NOTTINGHAM UNIVERSITY (UK) The research
investigated the effectiveness of different
interlayer systems (geogrid, steel reinforcement
and fiberglass grid) in preventing the reflection
of cracks in HMA overlays. A repeated load shear
test was first used to evaluate the interface
shear strength and stiffness for unreinforced and
reinforced samples. Only steel reinforcement
provides interface shear stiffness comparable to
the unreinforced case both geogrid and glass
fibre caused a significant reduction in the
interface shear stiffness.
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NOTTINGHAM UNIVERSITY (UK) Pilot-scale pavement
tests carried out at the Nottingham Pavement Test
Facility enabled the model to be checked under
realistic conditions the pavement consisted of
two layers of asphalt with reinforcement between
them, overlying individual concrete slabs with
air gaps between them. The gaps acted as wide
cracks, inducing reflection cracking in the
overlying asphalt
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NOTTINGHAM UNIVERSITY (UK) The test results have
shown that steel reinforcement improves the
fatigue life by a factor up to 3, well above the
other materials performance
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CAGLIARI UNIVERSITY (I) The research investigated
the crack propagation process in the presence of
steel reinforcement based on a finite element
(ANSYS) model. The figure shows the crack
development as a function of the load cycles at
different frequencies (10 and 20 Hz) by making
reference to a crack 1 mm deep, the reinforcement
increases the pavement life by a factor variable
between 3 and 12 (at 20 Hz and 10 Hz
respectively).
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SMART ROAD (USA)
The Smart Road was conceived by the Virginia DOT
in conjunction with Virginia Techs
Transportation Institute and the Federal Highway
Administration and allows testing of various
hypotheses on pavement material performance and
characteristics. Pavement materials can be
tested under different environmental conditions
using the All Weather Testing facility. The
flexible pavement portion of the Smart Road
includes 12 sections 100 m long, closely
monitored through a complex array of sensors
located beneath the roadway and embedded during
construction.
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SMART ROAD (USA) All instruments were embedded in
the pavement section during construction and
included pressure cells, thermocouples and
specially made HMA strain gages.
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SMART ROAD (USA) In Section I the steel mesh was
installed on top of a surface mix base layer
(SM-9.5A) and underneath a BM-25.0 base mix layer
to investigate its capability as a reinforcing
system
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SMART ROAD (USA) Results of the FE models were
compared with actual stress and strain
measurements at the Smart Road. To quantify the
contribution of steel reinforcement to the
pavements service life, a classical fatigue law
(Arizona DOT) was adopted N 9.33 10-7
et-3.84 The improvement is pronounced at
intermediate and high temperatures and is
approximately 140 at the average temperature of
25 C both in the transverse and in the
longitudinal direction.
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SMART ROAD (USA) The Smart Road has provided the
design criteria for the calculation of the design
life of a Road Mesh reinforced pavement.
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CATANIA UNIVERSITY (I) The research focused on
the capacity of non-destructive pavement
measurement techniques to quantify the increase
in terms of resistance to deformation given to
flexible reinforced pavements by steel mesh, was
carried out elaborating data coming from a survey
conducted with Falling Weight Deflectometer (FWD)
and Ground Penetrating Radar (GPR) on an
experimental section 250 meters long on a
national road (SS 121) in West Sicily.
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CATANIA UNIVERSITY (I) Improvement of the
pavements service life To quantify the
contribution of steel reinforcement to the early
stages of a pavements service life, a classical
fatigue law (Asphalt Institute) was adopted N
0.0796 et-3.291 E-0.854 The presence of the Road
Mesh reinforcement provides a service life
increase variable between 36 (reinforcement
at 15 cm depth) and 52 (reinforcement at 8
cm depth)
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CONCLUSIONS
The performance of Road Mesh in asphalt pavement
layers have been thoroughly investigated in the
last 10 years through a number of research
projects carried out by Universities and Road
Authorities around the world, finalised to
develop an empirical design methodology for
reinforced pavements, validate FEM numerical
results with beam tests and field data and
evaluate the working life enhancement of a
reinforced pavement. The main results of the
researches in terms of FATIGUE LIFE IMPROVEMENT
due to the Road Mesh are quite similar in terms
of reinforcements effectiveness

• - Nottingham Univ. improvement factor 3
• - Cagliari Univ. improvement factor 3 - 12
• - Smart Road improvement factor 1.15 - 3.6
• - Catania Univ. improvement factor 1.36 -
  1.52