Deterioration of Bituminous Roads

2Sur

face

Tre

atm

ent

• Granular Base• Asphalt Base• Asphalt Pavement

Base• Stabilized Base

• Asphalt Concrete• Hot Rolled Modified Asphalt• Rubberized Asphalt• Polymer Asphalt Concrete• Soft Bitumen Mix (Cold Mix)• Porous Asphalt• Stone Mastic

• Cape Seal• Double Bituminous Surface Dressing• Single Bituminous Surface Dressing• Slurry Seal• Penetration Macadam

Base, Surface and Material Types

Asp

halt

Mix

3

Surface Type Base Type Pavement TypeAsphalt Mix Granular Base

Asphalt BaseStabilized BaseAsphalt Pavement

AMGBAMABAMSBAMAP

Surface Treatment Granular BaseAsphalt BaseStabilized BaseAsphalt Pavement

STGBSTABSTSBSTAP

Pavement Classification System

4

Base and Surface Types Over Time

5

Distress Modes

• Surfacing DistressCrackingRavellingPotholingEdge-Break

• Deformation DistressRuttingRoughness

• Pavement Surface Texture DistressTexture DepthSkid Resistance

• Drainage DistressDrainage

6

Distress Modes

7

Distress Modes

8

Surfacing Distress

• Cracking Area: Sum of rectangular areas circumscribing manifest distress (line cracks are assigned a width of 0.5 m), expressed as a percentage of carriageway area.

Structural Crackingo Narrow Cracking (1-3 mm crack width)o Wide Cracking (> 3 mm crack width)

Thermal Transverse Cracking• Ravelling Area: Area of loss of material from

wearing surface, expressed as a percentage of carriageway area.

9

Surfacing Distress

• Number of Potholes: Number of potholes per kilometer expressed in terms of the number of ‘standard’ sized potholes of area 0.1 m2. A pothole being defined as an open cavity in road surface with at least 150 mm diameter and at least 25 mm depth.

• Edge Break Area: Loss of bituminous surface material (and possibly base materials) from the edge of the pavement, expressed in square meters per km.

HDM-4 assigns a depth of 100 mm to potholes and edge break area

10

Deformation Distress

• Rutting: Permanent traffic-associated deformation within pavement layers which, if channelised into wheelpaths, accumulates over time and becomes manifested as a rut, expressed as the maximum depth under 2 m straightedge placed transversely across a wheelpath.

• Roughness: Deviations of surface from true planar surface with characteristic dimensions that affect vehicle dynamics, ride quality, dynamic loads and drainage, expressed in the International Roughness Index, IRI (m/km).

11

International RoughnessIndex

Bump Integrator

Trailer TRRL

Quarter-car IndexIndex

Present ServiceabilityIndex

IRI m/km BI mm/km QI counts/km PSI

0 0 0 5.01 700 13 4.22 1400 26 3.53 2200 40 3.04 3000 50 2.45 3800 65 2.06 4700 80 1.78 6500 100 1.2

10 8300 130 0.612 10000 156 016 14000 21020 18000 26024 22000 310

BI = 360 IRI^1.12QI = 13 IRISI = 5 e^(-0.18 IRI)

IRI = 0.0032 BI^0.89IRI = QI / 13IRI = 5.5 ln (5.0/SI)

Good Paved

Poor Paved

Poor Unpaved

Good Unpaved

Roughness Scales

12

• Texture Depth: Average depth of the surface of a road expressed as the quotient of a given volume of standardized material (sand) and the area of that material spread in a circular patch on the surface being tested.

• Skid Resistance: Resistance to skidding expressed by the sideways force coefficient (SDF) at 50 km/h measured using the Sideways Force Coefficient Routine Investigation Machine (SCRIM).

Pavement Surface Texture Distress

13

SURFACE

A

B

C

D

HARSH

HARSH

POLISHED

POLISHED

T ~ 0.35mm

T ~ 2mm

SCALE OF TEXTURE

MICROMACRO

COARSE

D

COARSE

T ~ 2mmD

FINE

D

DT ~ 0.35mm

FINE

SFC ~ 0.4

SFC ~ 0.6

SFC ~ 0.4

SFC ~ 0.650

50

50

50

Texture Depth and Skid Resistance

14

• Drainage: Drainage condition (excellent, good, fair, poor or very poor), which defines the drainage factor.

Drainage Distress

15

• Poor construction quality: Results in greater variability in material properties and road performance. Defined by construction quality parameters.

Relative compaction of the base, sub-base and selected subgrade layers – COMP

Construction defects indicator for bituminous surfacings - CDS (based on binder content)

Construction defects indicator for the base -CDB based on gradation of material, aggregate shape (0 no defects, 1.5 several defects)

Construction Quality

16

SURFACE CONDITION DEFECT CDSDry (brittle) Nominally 10% 0.5

less than optimumbinder content

Normal Optimum binder 1.0content

Rich (soft) Nominally 10% 1.5more than optimumbinder content

Construction Defects Indicator for Bituminous Surfacings - CDS

17

• Measures the strength of a pavement• Takes into account the thickness and strength

coefficient of each pavement layerStructural Number Example 1 Structural Number Example 2

A B A*B A B A*BThickness Coefficient Total Thickness Coefficient Total

Pavement Layer (mm) (#) (mm) Pavement Layer (mm) (#) (mm)Surface 25 0.20 5.0 Surface 50 0.40 20.0Base 100 0.14 14.0 Base 150 0.14 21.0Subbase 150 0.10 15.0 Subbase 200 0.10 20.0Total (mm) 34.0 Total (mm) 61.0Total (inches) = Structural Number = 1.3 Total (inches) = Structural Number = 2.4

Structural Number Example 3 Structural Number Example 4A B A*B A B A*B

Thickness Coefficient Total Thickness Coefficient TotalPavement Layer (mm) (#) (mm) Pavement Layer (mm) (#) (mm)Surface 100 0.40 40.0 Surface 150 0.40 60.0Base 200 0.14 28.0 Base 250 0.14 35.0Subbase 250 0.10 25.0 Subbase 300 0.10 30.0Total (mm) 93.0 Total (mm) 125.0Total (inches) = Structural Number = 3.7 Total (inches) = Structural Number = 4.9

AASHTO Structural Number

18

∑=

=n

1iiihaSN

SNC = SN + SNSG

• The HDM-III Modified Structural Number includes the strength contribution of the sub-grade that is a function of the sub-grade CBR

ASSHTOStructuralNumber

43.1)(log85.0)(log51.3 21010 −−= CBRCBRSNSG

HDM-III Modified Structural Number

19

• The strength of bituminous pavements on HDM-4 is characterised by the adjusted structural number – SNP

• The SNP includes the strength contribution of the sub-grade that is a function of the sub-grade CBR

• The SNP applies a weighting factor to the sub-base and sub-grade contributions which reduces with increasing depth, so that the pavement strength for deep pavements is not over-predicted.

SNPd = SNBASUd + SNSUBAd + SNSUBG

SNBASU = contribution from surface and base layersSNSUBA = contribution from sub-base layersSNSUBG = contribution from subgrade

HDM-4 Adjusted Structural Number

20

• The average annual SNP used in the models is derived from the dry season SNPd, and the lengths of the dry season

SNP = fs* SNPd

fs = function of SNPw / SNPd and length of dry season

• Drainage effect on pavement strength is modelled through the changes in the drainage factor DF [1 excellent - 5 very poor]

SNPw / SNPd = f = function of DF, rainfall, surface distress

SNP and Drainage Effects

21

Benkelman or FWD

Deflection

if base is not cementedSNPk = 3.2 DEF^-0.63

if base is cementedSNPk = 2.2 DEF^-0.63

if base is not cementedDEF = 6.5 SNPk^-1.6

if base is cementedDEF = 3.5 SNPk^-1.6 Adjusted

StructuralNumber

Adjusted Structural Number andBenkelman or FWD Deflection

22

• Road investment decision support systems must have some form of pavement deterioration modelling capability

• Objective is to predict the future condition and the effects of maintenance

Road Deterioration Modelling

23

ASSETCONDITION

EXCELLENT

POOR TIME

Minimum Acceptable Standard(TRIGGER)

Decay in Condition(DETERIORATION)

Treatment Applied

What We are Trying to Predict (1)

• Predict asset condition

24

What We are Trying to Predict (2)

• Predict long term pavement performance• Predict effects of maintenance standards• Calculate annual costs: Road Agency + Road User

Roa

d C

ondi

tion

Rehabilitation

Maintenance Standard

Time (years) or Traffic Loading

PavementPerformanceCurve

Good

Poor

25

Road Deterioration Depends On

• Original design• Material types• Construction quality• Traffic volume and axle loading• Road geometry and alignment• Pavement age• Environmental conditions• Maintenance policy

26

Start Point Critical For Predictions

27

DeterministicDeterministic• Predict that there is

a set outcome of an event

• Used for network or project analyses

• Give detailed work program for a section

• HDM-4

ProbabilisticProbabilistic• Predict that there is

a probability of an outcome

• Used for network analyses

• Cannot give detailed work program for a section

Types of Models

28

• Usually based on Markov-Chain

CurrentCondition

Cracked

Not Cracked

Not Cracked

Cracked

Not Cracked

Cracked

Not Cracked

Cracked

10%

90%

20%

80%

40%

60%

70%

30%

Cracked100%

Probability

Time

Probabilistic Models (1)

29

• Good for getting overall network investment needs

• Cannot be used for planning investments on specific roads i.e.Link X needs treatment Y in year Z

Probabilistic Models (2)

30

• Empiricalbased on statistical analysis of locally observed deterioration trends

• Mechanisticuses fundamental theories of pavement behaviour for their development

• Structural mechanistic-empirical approachbased on identifying the functional form and primary variables and then applying various statistical techniques to quantify their impacts using empirical data (HDM-4Models)

Deterministic Models (1)

31

• Mechanistic based models Greater flexibility than regression modelsMore easily transferred to different pavements or conditions Data intensive

• Structured empirical approachKnowledge of how pavements perform used to set framework for statistical analysisMuch less data intensiveUsed in HDM

Deterministic Models (2)

32

Types of Deterministic Models (1)

• Absolute modelspredict the condition at a particular point in time as a function of independent variables and the road condition at construction time

• Incremental recursive modelspredict the change in condition from an initial state as a function of independent variables and the road condition at the beginning of the year

33

• AbsolutePredicts the future condition

o CONDITION = f(a0, a1, a2)Limited to conditions model developed forProblems with calibrationUsed on HDM-4 for concrete roads

• IncrementalPredicts the change in condition from the current condition:

o Δ CONDITION = f(a0, a1, a2)Can use any start point so much more flexibleUsed in HDM-4 for Bituminous Roads

Types of Deterministic Models (2)

34

Bituminous Concrete Block* Unsealed

CrackingRuttingRavellingPotholingRoughness

Edge breakSurface textureSkid resistance

CrackingJoint spallingFaultingFailuresServiceability ratingRoughness

RuttingSurface textureRoughness

*not in current release

Gravel lossRoughness

Plus deterioration of drains

Pavement Defects Modelled in HDM-4

35

POTHOLING

CRACKINGStructuralThermalReflection

ROUGHNESS

CrackingRuttingPotholing

Structural

PatchingEnvironment

RAVELLING

RUTTING Structural DeformationPlastic DeformationSurface Wear

Initial Densification

Deterioration Models - Bituminous

36

t 1 t 1

Wateringress

Furthercracking

Patches

Shear

Unevensurface

Spalling

Fasterdeformation

ROUGHNESS

Potholes

Patches

Time Time

UnevenSurface

Lower strength

Area ofCracking

Rutdepth

Interaction Mechanisms

37

• Models are structured empirical • Individual distresses modelled separately• Relationships are incremental and

recursivedY = K a0 f(X1, X2, X3, etc)

• Modelled sequentially through to roughness

• Maintenance intervention at end of each year

Principles Of Deterioration Models

38

Input pavement strength,condition, age for initialanalysis year

Compute traffic loading

Compute roughness increment

Compute surface distress increment

Scheduled maintenance?YN

Condition responsive?Y

N

Patching?Y

NCompute post-maintenance condition, strength, age

Compute maintenance effects

Year Loop

Paved Roads Deterioration Sequence

39

• Roughness = F(age, strength, traffic loading, potholes, cracking, ravelling, rutting, environment)

0

2

4

6

8

10

12

14

1 6 11

Year16

Rou

ghne

ss (I

RI)

Treatment

Do Nothing

Roughness

40

Roughness at theBeginning of the Year

Roughness at theEnd of the Year

IRIaIRIa

dIRI

Analysis Year

IRIbIRIb

IRIb1 = IRIb0 + dIRI + dIRIoper

Roughness Incrementduring the analysis year

dIRI

Analysis Year

MaintenanceOperationEffect

dIRIoper

Maintenance Effects

41

ΔRI = Kgp [ΔRIs + ΔRIc + ΔRIr + ΔRIt ] + ΔRIewhere

ΔRI = total incremental change in roughness during analysis year, in m/km IRI

Kgp = calibration factor for roughness progression

ΔRIs = incremental change in roughness due to structural deterioration during analysisyear, in m/km IRIΔRIc = incremental change in roughness due to cracking during analysis year, in m/kmIRIΔRIr = incremental change in roughness due to rutting during analysis year, in m/kmIRIΔRIt = incremental change in roughness due to potholing during analysis year, in m/kmIRI

ΔRIe = incremental change in roughness due to environment during analysis year, inm/km IRI

Annual Change in Roughness

42

dRI = 134 * Exp (m * Kgm * AGE3) * [1 + SNPKb]^-5 * YE4

m = environmental coefficient (#)Kgm = calibration factor (#)AGE3 = pavement age (years)SNPKb = adjusted structural number function

of surface distress (#)YE4 = annual number of equivalent standard

axles (million ESA/lane/year)

Roughness Increment Due toStructural Deterioration

43

dRIc = a0 * dACRAdACRA = f(annual increase in cracking)

dRIr = a0 * dRDSdRDS = f(annual increase in rutting)

dRIt = a0 * dPOTdPOT = f(annual increase in potholes)

Roughness Increment Due toSurface Distress

44

dRIe = Kgm * m * RIaKgm = calibration factor (#)m = environmental coefficient (#)RIa = Roughness at start of the year (IRI,

m/km)

Roughness Increment Due toEnvironment

Temperature Classification

Moisture

Classification

Tropical Sub-

tropical hot

Sub-tropical

cool

Temperatecool

Temperatefreeze

Arid 0.005 0.010 0.015 0.025 0.040 Semi-arid 0.010 0.015 0.025 0.035 0.060

Sub-humid 0.020 0.025 0.040 0.060 0.100 Humid 0.025 0.030 0.060 0.100 0.200

Per-humid 0.030 0.040 0.070

45

MoistureClassification

Description ThornthwaiteMoisture

Index

AnnualPrecipitation

(mm) Arid Very low rainfall,

High evaporation-100 to -61 < 300

Semi-arid Low rainfall -60 to -21 300 to 800

Sub-humid Moderate rainfall, orstrongly seasonalrainfall

-20 to +19 800 to 1600

Humid Moderate warmseasonal rainfall

+20 to +100 1500 to 3000

Per-humid High rainfall, or verymany wet-surface days

> 100 > 2400

Moisture Classification

46

Temperature Description Temperature range(C)

Tropical Warm temperatures in small range 20 to 35Sub-tropical -hot

High day cool night temperatures,hot-cold seasons

- 5 to 45

Sub-tropical -cool

Moderate day temperatures, coolwinters

-10 to 30

Temperate -cool

Warm summer,shallow winter freeze

- 20 to 25

Temperate -freeze

Cool summer,deep winter freeze

- 40 to 20

Temperature Classification

47

• Structural Cracking: This is effectively load and age/environment associated cracking.

• Transverse Thermal Cracking: This is generally caused by large diurnal temperature changes or in freeze/thaw conditions, and therefore usually occurs in certain climates.

For each type of cracking, separate relationships are given for predicting the time to initiation and the rate of progression.

Cracks Modeling

48

Modelled as ‘All’ and ‘Wide’ cracking

Cracking Initiation - yearsTime to initiation of ‘All’ cracking - ICA

Time to initiation of ‘Wide’ cracking - ICW

Cracking Progression - % of total carriageway area

Progression of ‘All’ cracking - ACA

Progression of ‘Wide’ cracking - ACW

Structural Cracking

49

0

20

40

60

80

100

120

0 5 10 15 20 25

Year

Are

a (%

)

InitiationProgression

Cracking Initiation and Progression

50

Cracking Initiation Model (1)

ICA=Kcia{CDS2*a0exp[a1SNP+a2(YE4/SN2)+CRT}

ICA time to cracking initiation, in yearsCDS construction quality

SNP structural number of pavement

YE4 traffic loading

Kcia calibration factor

CRT effect of maintenance

51

0

2

4

6

8

10

12

14

0.0 0.2 0.4 0.6 0.8 1.0

Axle Loading (MESAL/year)

All

Cra

ck In

itiat

ion

Perio

d (y

ears

)

SNP = 5

SNP = 2

CDS = 1.25

CDS = 1.00

CDS = 0.75

Cracking Initiation Model (2)

52

• CRP = retardation of cracking progression due to preventive treatment

• Progression of All cracking commences when δtA > 0 or ACAa > 0

dACA = Kcpa

Cracking Progression Model (1)

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

CDSCRP zA [(zA*a0*a1*δtA*YE4*SNPa2

+ SCAa1 )1/a1 - SCA]

53

0

20

40

60

80

100

0 2 4 6 8 10 12 14 16 18

Time Since Crack Initiation (years)

Are

a of

Stru

ctur

al C

rack

ing

(%)

All Cracking

Wide Cracking

SNPd = 6YE4 = 1.0

SNPd = 3YE4 = 0.1

Cracking Progression Model (2)

54

Time to Initiation of Thermal Cracking - ICT

Progression of Thermal Cracking - NCTNCT converted to ACT (area of thermal cracking)

Total Area of Cracking - ACRAACRA = ACA + ACT

Modelled as No. of transverse cracks

Transverse Thermal Cracking

55

Transverse Thermal Cracking

0

20

40

60

80

100

120

0 5 10 15 20

Surface Age (Years)

Tran

sver

se T

herm

al C

rack

ing

(No/

km)

temperate freezehumid

sub-tropical hotarid

56

HDM-4 Rut Depth model based on four components

• Initial Densification - RDO

• Structural Deformation - RDST

• Plastic Deformation - RDPD

• Wear from Studded Tyres -RDW

Rut Depth Progression (1)

57

Age

Rut

Dep

th

Initial Densification (First Year)

Densification - No Cracking

Structural Deterioration - With Cracking

Rut Depth Progression (2)

58

• Rutting = F(age, traffic, strength, compaction)

Pavement Age (Years)

Rut

ting

(mm

) Weak PavementWeak Pavement

Strong PavementStrong Pavement

Rut Depth Progression (3)

59

Time to Initiation of Ravelling

(years)

IRV

Progression of Ravelling

(area of carriageway)

ARV

Ravelling

60

Ravelling Initiation

0

2

4

6

8

10

12

14

16

18

0 1000 2000 3000 4000 5000

AADT

Rav

ellin

g In

itiat

ion

Per

iod

(yea

rs)

CDS = 1.0

CDS = 0.75

CDS = 1.25

61

Ravelling Progression

0

10

20

30

40

50

60

70

80

90

100

0 2 4 6 8 10 12 14 16

Time Since Ravelling Initiation (years)

Are

a of

Rav

ellin

g (%

)

CDS = 1.25CDS = 0.75 CDS = 1.0

62

Time to Initiation of Potholes

(years)

IPT

Progression of Potholing

(number of potholes)

NPT

Potholing

63

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7 8 9 10

Traffic (million axles/lane/year)

Tim

e to

Pot

hole

Initi

atio

n (y

ears

)

Granular baseMMP = 100 mm/month

HS = 20 mm

HS = 50 mm

HS = 100 mm

HS = 150 mm

Potholing Initiation

64

Pothole progression is affected by the time lapse between the occurrence and

patching of potholes - TLFMaintenance Frequency TLF

< 2 weeks 0.021 month 0.062 months 0.123 months 0.204 months 0.286 months 0.4312 months 1.00

Potholing Progression (1)

65

Potholes caused by:

• Cracking

• Ravelling

• Enlargement

Potholing Progression (2)

66

0

200

400

600

800

1000

0 1 2 3 4 5 6 7 8 9 10

Traffic (million axles/lane/year)

Pot

holin

g (n

o/km

/yea

r)

Granular baseACW = 40%MMP = 100 mm/monthTLF = 1

HS = 25 mm HS = 50 mm

HS = 100 mm

Potholing Progression (3)

67

Edge Break (1)

Loss of surface, and possibly base materials from the edge of the pavement

Commonly arises on narrow roads with unsealed shoulders

HDM-4 predicts the volume of material loss

68

Edge Break (2)

0

10

20

30

40

50

60

70

80

90

0 500 1000 1500 2000

AADT

Edg

e B

reak

(m3/

km/y

ear)

Edge Step = 50 mmAverage Speed = 50 km/hRainfall = 200 mm/month

Width = 3.5 m

Width = 4.5 m

Width = 5.5 m

Bituminous Road Work Effects

70

Road Work Effects

Condition

Reconstruct

Overlay

Traffic / Time

71

Road Works

72

• Timing of works over the analysis period

• Calculation of the physical quantities or amounts of works to be undertaken

• Estimating the costs of works

• Resetting / changing one or more of the characteristics that define the road

Road Works Modelling

73

• Can group pavement deterioration into:

SurfaceStructural

• Surface deterioration can be halted at almost any point by maintenance

• Structural deterioration rates can be reduced by maintenance, but never halted

Road Work Effects

74

Road Work Classification

PreservationRoutine

o Patching, Edge repairo Drainage, Crack sealing

Periodico Preventive treatmentso Rehabilitationo Pavement reconstruction

Specialo Emergencieso Winter maintenance

DevelopmentImprovements

WideningRealignmentOff-carriageway works

ConstructionUpgrading

o New sections

75

Works Class Works Type Works Activity / OperationRoutineMaintenance

RoutinePavement

patching, edge-repair, crack sealing,spot-regravelling, shoulders repair,etc.

Drainage culvert repairs, clearing side drainsRoutineMiscellaneous

vegetation control, markings, signs

PeriodicMaintenance

PreventiveTreatment

fog seal, rejuvenation

Resurfacing surface dressing, slurry seal, capeseal, regravelling

Rehabilitation overlay, mill and replace, inlayReconstruction partial reconstruction, full pavement

reconstructionSpecial Emergency clearing debris, repairing

washout/subsidence, traffic accidentremoval, etc.

Winter snow removal, salting, gritting, etc

Road Works Activities (1)

76

Works Class Works Type Works Activity /OperationWidening partial widening, lane addition,

Improvement

Realignment horizontal and vertical geometricimprovements, junctionimprovement

Off-carriageway

shoulders addition, shouldersupgrading, NMT lane addition,side drain improvement, etc.

ConstructionUpgrading upgrading by changing the

surface classNew section dualisation of an existing section,

new section (link)

Road Works Activities (2)

77

• ScheduledFixed intervals of time between interventionsInterventions at fixed points of time

• ResponsivePavement conditionPavement strengthSurface ageTraffic volumes/loadingsAccident rates

Maintenance Interventions

78

• Depending on distress maintenance has different effects

Pothole Crack Surface Repair Sealing Treatment

Time or Traffic

Cracking IRIRutting

DistressQuantity

Maintenance Effects

79

Maintenance May Affect

• Pavement strength• Pavement condition• Pavement history• Maintenance cost

REMEMBER … the type of treatment dictates what it will influence

80

Cb1

Cb4Cb2 = Ca3

Years0 4321

Percenttotalcosts

100

Ca2

Cao

Roadvariable

0 4321 Years

Cbo = Ca1

Scheduled intervention

Responsiveintervention

Note:Cay = Variable at the beginning of year yCby = Variable at the end of year y

Cb1

Cb4Cb2 = Ca3

Years0 4321 Years0 4321

Percenttotalcosts

100

Ca2

Cao

Roadvariable

0 4321 Years0 4321 Years

Cbo = Ca1

Scheduled intervention

Responsiveintervention

Note:Cay = Variable at the beginning of year yCby = Variable at the end of year y

Works Duration – One Year

81

Cb4 = Ca5

Cb3

Ca4

Cb1 = Ca2Cbo = Ca1

Cao

Years0 4321

Cb2 = Ca3Road

variable

Percenttotal

costs

0 4321 Years

40

30

Scheduled intervention

Responsiveintervention

Note:Cay = Variable at the beginning of year yCby = Variable at the end of year y

Cb4 = Ca5

Cb3

Ca4

Cb1 = Ca2Cbo = Ca1

Cao

Years0 4321 Years0 4321

Cb2 = Ca3Road

variable

Percenttotal

costs

0 4321 Years0 4321 Years

40

30

Scheduled intervention

Responsiveintervention

Note:Cay = Variable at the beginning of year yCby = Variable at the end of year y

Works Duration – Up to Five years

82

Works Type Works Activity / Operation Hierarchy Unit CostNew section Dualisation of an existing section 1 per km Upgrading Upgrading to a new surface class 2 per km Realignment Geometric realignment 3 per km Widening Lane addition 4 per m2 or per km

Partial widening 5 per m2 or per km Reconstruction Pavement reconstruction 6 per m2 or per kmRehabilitation Mill and replace 7 per m2

Overlay rubberised asphalt 8 per m2Overlay dense-graded asphalt 9 per m2Overlay open-graded asphalt 10 per m2Inlay 11 per m2Thin overlay 12 per m2

Resurfacing Cape seal with shape correction 13 per m2(Resealing) Cape seal 14 per m2

Double surface dressing with shape correction 15 per m2Double surface dressing 16 per m2Single surface dressing with shape correction 17 per m2Single surface dressing 18 per m2Slurry seal 19 per m2

Preventive Fog sealing 20 per m2Treatment Rejuvenation 21 per m2Routine Edge repair* 22 per m2Pavement Patching* 22 per m2

Crack sealing* 22 per m2

Hierarchy of Roads Works

83

Existing Pavement TypeAMGB AMSB AMAB AMAP STGB STSB STAB STAP

Routine works AMGB AMSB AMAB AMAP STGB STSB STAB STAPPreventive Treatment AMGB AMSB AMAB AMAP STGB STSB STAB STAPReseal STAP STAP / STSB * STAP STAP STGB STSB STAB STAPOverlay AMAP AMAP / AMSB * AMAP AMAP AMGB AMSB AMAB AMAPInlay AMGB AMSB AMAB AMAP STGB STSB STAB STAPMill & replace to intermediate surface **AP **AP **AP **AP N/A **SB **AB **APMill & replace to base **GB **SB **AB **AP **GB **SB **AB **AP* will depend on the ‘critical’ thickness (Hmin) of the existing bituminous surfacing** indicates that this is dependent on the specific works activity (i.e., operation) and the surface material

Pavement Type After Maintenance

84

HDM Series – Volume 4