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Using cementitious materials for sustainable pavement solutions
Ian Gibb22nd February 2012
Pavement Design
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UK Pavement Design –Old method
• Prescriptive
• Based on CBR of subgrade
• Limited range of CBM
permitted
• Structural contribution of HBM
not maximised
• Only C32/40 concrete
considered
• CBM characterised by early
age (7 day) strength
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Concrete Show 2012
UK Pavement Design – Performance method
Class 1 = 50MPa
Class 2 = 100MPa
Class 3 = 200MPa
Class 4 = 400MPa
• Four foundation classes
defined by long-term surface
modulus
• Allows wide range of materials
• Locally won
• Recycled
• Industrial by-products
• Allows structural benefit of
HBM to be utilised (in both
foundation and upper layers)
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Concrete Show 2012
UK Pavement Design – Performance method
• Four foundation classes
defined by long-term surface
modulus
• Allows wide range of materials
• Locally won
• Recycled
• Industrial by-products
• Allows structural benefit of
HBM to be utilised (in both
foundation and upper layers)
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Concrete Show 2012
UK Pavement Design – Performance method
160mm
225mm
150MPa
350MPa
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Concrete Show 2012
Hydraulic Binders (EN 14227)
• Range of binders permitted
including
• CEM I
• Slag
• Fly ash
• Can be specified with
• different strengths
• different gradings
• 360-day values of stiffness
modulus now used
CBGM C20mm; 14mm, 10mm well-
graded
CBGM B31.5mm well-graded mixture
CBGM AWide-graded mixtures
Suggested Designation
Aggregate limitations
FABM 2SBM B220, 14, 10 mm well-graded mixtures
SBM B3
SBM B1-2
Slag Bound
FABM 3
FABM 1
Fly Ash Bound
Sand mixtures
31.5 mm well-graded mixtures
Aggregate limitations
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Pavement Design
CBM 5
CBM 4
CBM 3
CBM 2
CBM 1
Old Terminology
1 (C12/16)B1 (C12/16)B (C12/15)15MPa
B1 (C15/20)
B1 (C9/12)
A or B3 (C6/8)
A or B4 (C3/4)
SBM
B (C16/20)
B (C10/12)
A (C5/6)
A (C5/6)
CBGM
1 (C15/20)
1 (C9/12)
3 (C6/8)
4 or 5 (C3/4)
FABM
20MPa
10MPa
7MPa
4.5MPa
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Case Studies
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A46 Newark to Widmerpool Improvement
• Scope
• 28km Dual two lane trunk road
• 5km online widening
• 8 grade separated junctions
• 15 overbridges
• 4 underbridges
• 90,000m3 concrete
• 5,000T reinforcement
• £220 million ECI contract awarded
to Balfour Beatty in March 2004
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Concrete Show 2012
A46 Newark to Widmerpool Improvement
• Challenge – what to do with 68,000 tonnes
of carriageway planings
• Balfour Beatty have zero waste to landfill
policy
• Five potential applications identified
(4 unbound, 1 bound)
• Tests on existing pavement showed varying
levels of Polycyclic Aromatic Hydrocarbons
(PAH) – Coal Tar?
Concrete Show 2012
Regulatory position
’… ensuring that waste management is carried out without endangering human health, without harming the environment and in particular:
(i) without risk to water, air, soil, plants or animals; (ii) without causing a nuisance through noise or odours; and (iii) without adversely affecting the
countryside or places of special interest.’
Waste tar bound road planings are hazardous waste where level
of coal tar >0.1%
EA will permit use of waste tar bound
planings without environmental permit :
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Concrete Show 2012
A46 Newark to Widmerpool Improvement
• Trials conducted
• Varying binder content
• Varying blend of scalpings:planings
• Leaching characteristics evaluated to
standard EA NEN 7375 (The Tank Test)
• Proved planings could be used in HBM
• URS produced Materials Management Plan
acceptable to EA
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Concrete Show 2012
A46 Newark to Widmerpool Improvement
Planings
(%)
Scalpings
(%)
Use if
PAH
(mg/kg)
Comment
100 < 400 Acceptable in
unbound layer
50 50 < 1350
40 60 < 8000
30 70 < 20000
> 20000 Unlikely but
would require
lower ratio or
off-site disposal
URS demonstrated that
site testing using
Ultraviolet Fluorescence
(UVF) could estimate PAH
concentration
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Concrete Show 2012
A46 Newark to Widmerpool Improvement
Concrete Show 2012
Airport pavement design, Isle of Man Airport
• Existing taxiways inadequate to deal with future traffic loading
• URS conducted extensive site investigation for COLAS
• Two layers of tar bound material identified
• No hazardous waste landfill locally
Concrete Show 2012
Airport pavement design, Isle of Man Airport
• Cold mix HBM chosen for pavements in need of strengthening
• HBM option used cold in-situ recycling of 250-265mm of existing
pavement with 100mm new asphalt surfacing
Concrete Show 2012
Airport pavement design, Isle of Man Airport
• Sustainable solution with substantial reductions in cost (40%), energy consumption (44%) and carbon dioxide emissions (32%), compared against the conventional reconstruction design, was achieved
-99%
-73%
-6000
Concrete Show 2012
Trans-European Motorway, RomaniaPavement Foundation Optimisation
• Optimising the pavement foundation design of a 415km of Motorway to produce a cost effective sustainable solution
• The Spingbox was used to optimise the local material properties, with different binder contents
• Silty clay subgrade, local sand and gravel materials
• Crushed rock sub-base and cement treated base materials
• The effect of high moisture content on materials stiffness was also investigated
• Substantial cost and environmental benefits are achieved using local materials
15802% binder
(only swelled)
120150Silty Clay Soil
100135---Sand &
Gravel
110160Negligible
Reduction
425500Crushed Rock
(Andesite)
No Binder
&
Saturated
No
Binder
Binder &
Saturated
2%
Binder
4%
Binder
Material type
Stiffness for different binder content (MPa)
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There’s more to sustainability…..
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Noise
• Concrete pavements are noisy
• Skid resistance provided by
• Sand in laitance
• Transverse brush marks
• American experience showed
longitudinal grooves can
• Reduce noise
• Improve skid resistance
• Trialled in UK, e.g. A12 and A14
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Sustainability
• Working with clients to
• Reduce embodied CO2
• Explore advantages of grinding and
grooving new pavements
• Using specialist tools
• WLCC (in-house developed) –
evaluates whole life financial costs
and carbon emissions for different
road maintenance options
• CHANGER (developed by IRF) –
evaluates carbon footprint for
alternative designs, construction
methods and materials
Concrete Show 2012
Environmental Benefits
• Marginal, secondary, local and recycled
aggregates can be used in pavement
foundation
• A wide range of binders including slag and
fly ash can be used
• Reduction in foundation and upper layer
thickness will result in lower material
production and transportation to site (vehicle
movements)
• Thinner pavement reduces project
construction time, resources requirements
and disruption to the public
• Performance specification produces a better
quality construction, improved long-term
performance and reduced maintenance
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Questions