Ham Surfacing Utility Works

“Surfacing Utility Works” (Maintaining Trenches) by

Introduction

Professor Alan R. Woodside Transport & Road Assessment Centre (TRAC) University of Ulster MSc Infrastructure Engineering April 2008

What do we mean by Maintenance? • Funding an off-spring! • Funding a former wife! • Oxford dictionary definition “….? “

Northern Ireland’s meaning “…….this we will maintain ! …..”

Dictionary definition of “Maintenance” 1. ..the act of maintaining or the state of being maintained.. 2. .. a means of support: livelihood … 3. .. the interference in a legal action by a person having NO interest in it as by providing funds to continue the action … 4. .. a provision ordered to be made by way of periodical payments or a lump sum, as for a spouse after a divorce 5. .. relating to the maintaining of buildings machinery etc. …

What will we Maintain • Highways. Roads.Streets. • Infrastructure • NIRAUC or HAUC

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Pavement Life 120

Question What will cause Maintenance?

Pavement serviceability

Percentage

100

80

60

40

20

0

Years

Faults causing an increase in Maintenance • • • • • •

Failure in design Alteration in Specification Unforeseen circumstances Limited sampling T’s ignored Slackness in Supervision

D isintegration

Answer Faults and Failures

Failures in bituminous surfacings

• D isintegration • I nstability • F racture / fatigue • S kidding loss resistance

D isintegration

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D isintegration • • • • •

Ravelling Pitting Spalling Pot-holing Stripping

Disintegration

Instability

D isintegration • Minimised by high binder contents which thoroughly bind the particles and reduce the rate of weathering of the binder films • but stability may be reduced

I nstability Instability

• • • • •

Rutting Shoving Corrugation Deformation Flowing

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Instability Instability

Highway problems - Java

Instability

Stability • Dependant on: – Inter-particle friction – Binder flow characteristics

F racture / Fatigue

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Fracture / fatigue

Fracture / fatigue

Highway problems - Canada

F racture / fatigue • The resistance of road materials to cracking as a result of repeated loads

F racture / fatigue • “Crocodile” cracking or • “Chicken-wire” cracking

Two main causes of cracking • Traffic induced stressing • Thermal stressing

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Use of fabrics to limit reflective cracking

S kidding Resistance loss

Relative Performance of Wearing Courses (more * the better)

S kidding resistance loss

Surfacing type Structural Rutting Cracking Ride Suitable texture Skidding - Early - Normal Noise dB(A) Spray Contract risk Durability Speed Cost

On-site controls • • • • • •

•

•

Taking samples for mix compliance • Bitumen content and aggregate grading Temperature Taking cores – thickness Density / compaction • Mix density and PRD Evenness • 3m edge and rolling straight edge Texture depth • Rate of spread of chips • Sand patch test Skid resistance • Portable skid resistance tester - SRV • SCRIM - SFC Porosity - RHC

Surface dressing nil nil * nil **

HRA

Porous asphalt ** **** *** **** *****

Safepave

ULM

SMA

**** *** ***** *** ***

* **** ** ***** *****

** ***** *** **** ****

*** ***** *** **** ****

***** ***** 82 ** *** ** ***** £1.00

**** **** 80 *** **** ***** ** £3.50

*** **** 74 ***** ** **** *** £6.75

*** **** 76 **** *** **** **** £3.50

*** **** 76 *** *** **** *** £3.80#

*** **** 76 *** **** ***** *** £3.80#

Assessment of Trenches • • • • • • •

Settlement / Compaction Surface Thickness of Blacktop Surface regularity Surface Texture Skid Resistance Shape Steps

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Assessment of Trenches for Mercury Communications

Trench Reinstatements

• Requirements 1. In – narrower trench 2 Up – pipe/duct higher in the trench 3 Down – bring the price down

Assessment of Trenches

Trench Reinstatements • • • • • • •

Trench Reinstatements Failures (thickness only) 70% Fail

Settlement / Compaction Surface Thickness of Blacktop Surface regularity Surface Texture Skid Resistance Shape Steps

Trench Reinstatements Failures (thickness only)

50% Fail

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Trench Reinstatements

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Temperature

On-site controls • • • • • •

Temperature Texture depth Skid resistance Porosity Evenness etc.

• Temperature measurement is one of the most important aspects of laying and compacting bituminous materials. • Delivery and compaction. • Wind-chill needs to be considered > rate of heat loss. • Layer thickness / ability to retain heat for compaction.

Taking cores • • • • • •

Visual analysis Composition analysis Layer thickness Density Compaction Mix properties – stiffness, wheel tracking

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Core drilling

Use of Nuclear Density Gauge

• Most direct method of assessment is to cut a specimen from the area to be checked. • Core drilling is fast and simple. • Gives a specimen of adequate size and quality. • Core may be assessed for density, degree of compaction, wheel-track rate.

Nuclear Density Gauges advantages • • • •

Density related to compaction Fast - two minutes Non destructive - no cores Work with the roller driver to maximise compaction levels • Allows piece of mind • Most contracts now use them

MOT Straight Edge

Nuclear Density Gauges disadvantages • Uses a radioactive source • Restrictions on their use - what do you do in Nuclear Free Zones? • A lot of records required • Operators need close control - x-ray badges • What do you do if you “accidentally” drive over one with a roller?

Anything straight can do!

• 3m in length • Used to determine lateral surface regularity - usually transverse (<3mm allowed) • Equally supported at edge end giving a set height between road and beam • Vertical irregularity measured using an incremented wedge

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Rolling straight edge

Rolling Straight Edge

• 3 metre long • Used to check for surface irregularities - longitudinal • Sensing unit connected to independent wheel • 4mm or 7mm noted • None > 10mm permitted • Measured in sections of 300m or 75m parallel to edge • Cat A. Road - 20 4mm per 300m • Cat. B. Road - 40 4mm per 300m

Rate of spread of chippings

HRA texture depth

• • • •

Relates to texture depth Uses a 300mm square tray Calibrated spring balance Determine rate of spread of chippings in kg/m2 • Trays positioned in front of spreader • After the machine has passed over the tray is lifted and the rate of spread read directly from the balance

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Sand patch test

Polishing

Skid-resistance • Same equipment as used in PSV test but with wider slider • Used to measured localised skid-resistance • Spring-loaded rubber slider mounted on a pendulum arm • Arm may be adjusted vertically • Pendulum swings across surface for a set distance • Gives SRV - skid-resistance value

Skid resistance of over-banding

SFC measurement using SCRIM

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SFC measurement using SCRIM

Surface porosity - for PA

• SFC - sideways force coefficient • SCRIM - sideways force coefficient routine investigation machine • Allows skid resistance measurement of road network • Minimum levels of SFC specified according to site conditions i.e. location, number of c.v.d per lane

Relative hydraulic conductivity • • • •

Measures porosity Cylinder of water Pull plunger Time how long it takes to empty • PA - a few seconds • HRA - all day!

THE END - Thank you for listening

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