john cook sci final presentation

8/10/2019 John Cook SCI Final Presentation

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Airfield Pavements

JOHN COOK Defence Infrastructure Organisation


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Airfield Pavement Management

Safety

Economic Maintenance

Minimise Disruption to Aircraft Operations

Three MainDrivers Surface Integrity, Fric tion,Strength, Evenness


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Surface Integrity


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Runway Friction


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New/Reconstruction/Extensions

Maintenance/Restoration

Cost Spli t - Maintenance/Restorationand New Works 1990-2000

1940s

1950s

Post1950s

Age of Airfield PavementSub Structures


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CHALLENGES

Balancing Maintenance and Funding

Increased Trafficking

Higher Rates of Wear and Fatigue

Limited Access for Technical Surveys/Tests andMaintenance


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Some Key Initiatives In respect of Use of Asphalt on MOD Airfields Aimed at

Addressing These Challenges

Use of PMBs in asphalt surfaces to improveperformance VFM - Standard Specification

plus additional end performance test methods

Use of proprietary spray treatments to extendlives of asphalt surface runways

For major restoration recycle existingpavement


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Use Of PMBs In Asphalt Mixes

Our Specifications for asphalt mix designdont effectively discriminate between useof standard grade binders and PMBs

new Tests Methods needed:-

Resistance to cold temperature cracking

Resistance to surface shear/scuffing atmedium/high temperatures


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Porous Friction Course UnmodifiedBinder

Porous Friction Course Modifiedbinder


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10mm

75mm

120mm

150mm

Semi Circular Bending TestEN 12697-44 (Crack

Propagation)


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prEN12697-44 : Crack propagation by semi-circular bending test(test performed at 0C)

0

0.05

0.1

0.15

0.2

0.25

0 1 2 3 4 5 6 7

Displacement (mm)

L o a

d p e r u n i

t t h i c k n e s s

( k N / m

m )

MSC_A_0CMSC_B_0CMSC_C_0CMSC_D_0C103_A_0C

103_B_0C103_C_0C103_D_0CSRB_A_0CSRB_B_0CSRB_C_0CSRB_D_0C


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Tentative Conclusions Use of PMBs in Asphalt for Airfield Pavements

Porous Friction Course with PMB 2 runways resur faced 2007 and 2010

Scuffing Test (TRL Report 176) highl ights a substantial improvement in in tegrity androbus tness that can be provided by a suitable PMB.

To retain duc til ity and durabili ty - Use of EN 12697-23 (ITST) to determine Deformation atBreak - ITVD (Indirect Tensile Vert ical Deformation) after ageing -test at 18 0C TentativeCriteria > 1.3mm

Torque/Shear/Bond Test ? Possible future criteria. Stone Mastic Asphalt w ith PMB 3 taxiways; 1 current runway project.

The Torque/Shear/Bond Test has provided a range of values for both straight gradebinders and PMBs probably reflecting the variation in integrity caused by severalfactors the binder, the adhesion between binder and aggregates and the surfacetexture and voids in the mix. Criteria (aged/un-aged) > ? Kpa

To retain/enhance ducti lity and durabili ty - Either Displacement at Break (based onEN12687-44) 0r Deformation at Break ITVD (Indirect Tensi le Vertical Deformation) afterageing at 18 0C > mm ?

Marshall Asphalt limited trials only.

Very robust and durable wi th straight grade binders.

We could benefit from improved resistance to reflection cracking


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AsphaltPreservatives/Rejuvenators

Low cost treatment to extend life ofasphalt surfaces

Speed and ease of application oftreatment to minimise disruption

Evaluation field experience andlaboratory testing


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Rejuvenator Spray Marshall Asphalt Application of bitumen emulsion spray 1 to 4 hour curing time

Application of fine dust (


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Eff i f A h l


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Effectiveness of AsphaltPreservatives/Rejuvenators - Stiffness

In sit u ageing, 5 10 yearsIn situ ageing, 3-5 years


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Experience and Tentative Conclusions Use of Asphalt Preservatives/Rejuvenators

Successfully used two types of treatments on runways:a. One classed as a rejuvenatorb. One classed as a penetrative preserver

Treatments have been applied to both Grooved Marshall

Asphalt (GMA) and Porous Friction Course (PFC). First runway treated over 4 years ago (PFC). Since that

time 1 further PFC runway and 4 GMA surfaced runwayshave been treated.

Initial results from laboratory testing programmecorroborate field experience.

More runways earmarked for treatment. Likely in futureto become standard practice reduce whole life costand disruption.


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Recycling Existing Pavements - Advantages

Minimise use of virgin materials Reduction of offsite haulage of materials Reduction of waist and landfill

Reduction of carbon dioxide emissions Reduction of cost and improved VFM

Sustainability can be defined as developmentthat meets the needs of the present generationwithout compromising the ability of futuregenerations to meet their needs


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Need to be Aware of Risks

Design long term performance Mix Design - Quality/Properties of

Secondary/recycled aggregates/componentmaterials and mix design -behaviour/performance of the mixed material structural, susceptibility to fatigue/reflectioncracking and durability

Construction Measured approach to development/applicationof new practices


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Foamed Bitumen

Inject cold water and air into hot bitumenat high pressure

Foaming bitumen increases volume andreduces viscosity for a short period

This enables a degree of coating of colddamp aggregate


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RAF Marham S TaxiwayFoamix - plant mix details

Bitumen 3.5% Cement 1.8% PFA 7.0%

Water 3.0%

0-10mm aggregate 51.0% 10-20mm aggregate 34.0%


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Foamix site laying Tack coat

application

Paver laid

The completed, tack coatedmat


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Summary of site ITSM testing


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Revised Grading Envelope


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Findings and Conclusions Inconsistencies with site cored specimens ie much lower stiffness than cylinder

mould samples At planning stage of a project - core exi sting pavements for laboratory test ing of

foam mixes range of densities. Construct ion Trial Area Densiti es. Comparison w ith laboratory results. At least

for early projects, dry coring at 14 days plus accelerated curing ITSM stif fness soaked/un-soaked - comparison wi th test data on moulded samples.

Stricter requirements on mix control limi ted scope Long term performance monitor future tests Anticipate future use with recycled tar asphal t planings Can lay large volumes quickly/continuously In Project Case Study a considerable cost saving made over conventional asphalt

base courses.

In Project Case Study saving in CO2 emiss ions over conventional asphalt basecourses was 60% ie 5000 tons. Also reducing waste, traffic movements and use ofnew materials /aggregates.

Confident in using on a firm foundation Low resistance to reflection cracking Confident in using to w ithin 100mm of surface I.e. min overlay 100mm dense

asphalt.


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Thank You

john cook sci final presentation

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