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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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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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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UK Pavement Design – Performance method

160mm

225mm

150MPa

350MPa

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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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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?

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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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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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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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A46 Newark to Widmerpool Improvement

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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

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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

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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%

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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

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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