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Deterioration of Bituminous Roads. 2 Surface Treatment Base, Surface and Material Types Granular Base Asphalt Base Asphalt Pavement Base Stabilized Base.

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Presentation on theme: "Deterioration of Bituminous Roads. 2 Surface Treatment Base, Surface and Material Types Granular Base Asphalt Base Asphalt Pavement Base Stabilized Base."— Presentation transcript:

1 Deterioration of Bituminous Roads

2 2 Surface Treatment Base, Surface and Material Types 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 Asphalt Mix

3 3 Surface Type Base Type Pavement Type Asphalt Mix Granular Base Asphalt Base Stabilized Base Asphalt Pavement AMGB AMAB AMSB AMAP Surface Treatment Granular Base Asphalt Base Stabilized Base Asphalt Pavement STGB STAB STSB STAP Pavement Classification System

4 4 Base and Surface Types Over Time

5 5 Distress Modes Surfacing Distress  Cracking  Ravelling  Potholing  Edge-Break Deformation Distress  Rutting  Roughness Pavement Surface Texture Distress  Texture Depth  Skid Resistance Drainage Distress  Drainage

6 6 Distress Modes

7 7

8 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 Cracking o 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 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 m 2. 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 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 11 International Roughness Index Bump Integrator Trailer TRRL Quarter-car Index Index Present Serviceability Index IRI m/km BI mm/kmQI counts/km PSI BI = 360 IRI^1.12 QI = 13 IRI SI = 5 e^(-0.18 IRI) IRI = BI^0.89 IRI = QI / 13 IRI = 5.5 ln (5.0/SI) Good Paved Poor Paved Poor Unpaved Good Unpaved Roughness Scales

12 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 13 SURFACE A B C D HARSH POLISHED T ~ 0.35mm T ~ 2mm SCALE OF TEXTURE MICROMACRO COARSE D T ~ 2mm D FINE D D T ~ 0.35mm FINE SFC ~ 0.4 SFC ~ 0.6 SFC ~ 0.4 SFC ~ Texture Depth and Skid Resistance

14 14 Drainage: Drainage condition (excellent, good, fair, poor or very poor), which defines the drainage factor. Drainage Distress

15 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 16 SURFACE CONDITION DEFECTCDS Dry (brittle)Nominally 10% 0.5 less than optimum binder content NormalOptimum binder 1.0 content Rich (soft)Nominally 10% 1.5 more than optimum binder content Construction Defects Indicator for Bituminous Surfacings - CDS

17 17 Measures the strength of a pavement Takes into account the thickness and strength coefficient of each pavement layer AASHTO Structural Number

18 18 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 HDM-III Modified Structural Number ASSHTO Structural Number

19 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. SNP d = SNBASU d + SNSUBA d + SNSUBG SNBASU = contribution from surface and base layers SNSUBA = contribution from sub-base layers SNSUBG = contribution from subgrade S = season HDM-4 Adjusted Structural Number

20 20 The average annual SNP used in the models is derived from the dry season SNP d, and the lengths of the dry season SNP = f s * SNP d f s = function of SNP w / SNP d 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] SNP w / SNP d = f = function of DF, rainfall, surface distress SNP and Drainage Effects

21 21 Benkelman or FWD Deflection if base is not cemented SNPk = 3.2 DEF^-0.63 if base is cemented SNPk = 2.2 DEF^-0.63 if base is not cemented DEF = 6.5 SNPk^-1.6 if base is cemented DEF = 3.5 SNPk^-1.6 Adjusted Structural Number Adjusted Structural Number and Benkelman or FWD Deflection

22 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 23 ASSET CONDITION EXCELLENT POOR TIME Minimum Acceptable Standard (TRIGGER) Decay in Condition (DETERIORATION) Treatment Applied What We are Trying to Predict (1) Predict asset condition

24 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 Road Condition Rehabilitation Time (years) or Traffic Loading Maintenance Standard Pavement Performance Curve Good Poor

25 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 26 Start Point Critical For Predictions

27 27 Deterministic 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 Probabilistic 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 28 Usually based on Markov-Chain Probabilistic Models (1)

29 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 30 Empirical based on statistical analysis of locally observed deterioration trends Mechanistic uses fundamental theories of pavement behaviour for their development Structural mechanistic-empirical approach based on identifying the functional form and primary variables and then applying various statistical techniques to quantify their impacts using empirical data (HDM-4 Models) Deterministic Models (1)

31 31 Mechanistic based models  Greater flexibility than regression models  More easily transferred to different pavements or conditions  Data intensive Structured empirical approach  Knowledge of how pavements perform used to set framework for statistical analysis  Much less data intensive  Used in HDM Deterministic Models (2)

32 32 Types of Deterministic Models (1) Absolute models predict the condition at a particular point in time as a function of independent variables and the road condition at construction time Incremental recursive models predict 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 33 Absolute  Predicts the future condition o CONDITION = f(a0, a1, a2)  Limited to conditions model developed for  Problems with calibration  Used on HDM-4 for concrete roads Incremental  Predicts the change in condition from the current condition: o  CONDITION = f(a0, a1, a2)  Can use any start point so much more flexible  Used in HDM-4 for Bituminous Roads Types of Deterministic Models (2)

34 34 BituminousConcreteBlock*Unsealed Cracking Rutting Ravelling Potholing Roughness Edge break Surface texture Skid resistance Cracking Joint spalling Faulting Failures Serviceability rating Roughness Rutting Surface texture Roughness *not in current release Gravel loss Roughness Plus deterioration of drains Pavement Defects Modelled in HDM-4

35 35 POTHOLING CRACKING Structural Thermal Reflection ROUGHNESS Cracking Rutting Potholing Structural Patching Environment RAVELLING RUTTING Structural Deformation Plastic Deformation Surface Wear Initial Densification Deterioration Models - Bituminous

36 36 t 1 t 1 Water ingress Further cracking Patches Shear Uneven surface Spalling Faster deformation ROUGHNESS Potholes Patches Time Uneven Surface Lower strength Area of Cracking Rut depth Interaction Mechanisms

37 37 Models are structured empirical Individual distresses modelled separately Relationships are incremental and recursive dY = K a 0 f(X 1, X 2, X 3, etc) Modelled sequentially through to roughness Maintenance intervention at end of each year Principles Of Deterioration Models

38 38 Input pavement strength, condition, age for initial analysis year Compute traffic loading Compute roughness increment Compute surface distress increment Scheduled maintenance? Y N Condition responsive? Y N Patching? Y N Compute post-maintenance condition, strength, age Compute maintenance effects Year Loop Paved Roads Deterioration Sequence

39 39 Roughness = F(age, strength, traffic loading, potholes, cracking, ravelling, rutting, environment) Roughness (IRI) Treatment Do Nothing Year Roughness

40 40 Roughness at the Beginning of the Year Roughness at the End of the Year IRIa IRIb IRIb1 = IRIb0 + dIRI + dIRIoper Roughness Increment during the analysis year dIRI Analysis Year Maintenance Operation Effect dIRIoper Maintenance Effects

41 41 Annual Change in Roughness

42 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 to Structural Deterioration

43 43 dRIc = a0 * dACRA dACRA = f(annual increase in cracking) dRIr = a0 * dRDS dRDS = f(annual increase in rutting) dRIt = a0 * dPOT dPOT = f(annual increase in potholes) Roughness Increment Due to Surface Distress

44 44 dRIe = Kgm * m * RIa Kgm = calibration factor (#) m = environmental coefficient (#) RIa = Roughness at start of the year (IRI, m/km) Roughness Increment Due to Environment

45 45 Moisture Classification

46 46 Temperature Classification

47 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 48 Modelled as ‘All’ and ‘Wide’ cracking Cracking Initiation - years Time 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 49 Initiation Progression Cracking Initiation and Progression

50 50 Cracking Initiation Model (1) ICA=K cia {CDS 2 *a 0 exp[a 1 SNP+a 2 (YE4/SN 2 ) +CRT} ICAtime to cracking initiation, in years  CDSconstruction quality  SNPstructural number of pavement  YE4traffic loading  K cia calibration factor  CRTeffect of maintenance

51 51 Cracking Initiation Model (2)

52 52 CRP = retardation of cracking progression due to preventive treatment Progression of All cracking commences when  tA > 0 or ACAa > 0 Cracking Progression Model (1)

53 53 Cracking Progression Model (2)

54 54 Time to Initiation of Thermal Cracking - ICT Progression of Thermal Cracking - NCT NCT converted to ACT (area of thermal cracking) Total Area of Cracking - ACRA ACRA = ACA + ACT Modelled as No. of transverse cracks Transverse Thermal Cracking

55 55 Transverse Thermal Cracking

56 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 57 Rut Depth Progression (2)

58 58 Rutting = F(age, traffic, strength, compaction) Pavement Age (Years) Rutting (mm) Weak Pavement Strong Pavement Rut Depth Progression (3)

59 59 Time to Initiation of Ravelling (years) IRV Progression of Ravelling (area of carriageway) ARV Ravelling

60 60 Ravelling Initiation

61 61 Ravelling Progression

62 62 Time to Initiation of Potholes (years) IPT Progression of Potholing (number of potholes) NPT Potholing

63 63 Potholing Initiation

64 64 Pothole progression is affected by the time lapse between the occurrence and patching of potholes - TLF Maintenance FrequencyTLF < 2 weeks month months months months months months1.00 Potholing Progression (1)

65 65 Potholes caused by: Cracking Ravelling Enlargement Potholing Progression (2)

66 66 Potholing Progression (3)

67 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 68 Edge Break (2)

69 Bituminous Road Work Effects

70 70 Road Work Effects Condition Traffic / Time Reconstruct Overlay

71 71 Road Works

72 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 73 Can group pavement deterioration into:  Surface  Structural 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 74 Road Work Classification Preservation  Routine o Patching, Edge repair o Drainage, Crack sealing  Periodic o Preventive treatments o Rehabilitation o Pavement reconstruction  Special o Emergencies o Winter maintenance Development  Improvement s  Widening  Realignment  Off-carriageway works  Construction  Upgrading o New sections

75 75 Road Works Activities (1)

76 76 Road Works Activities (2)

77 77 Scheduled  Fixed intervals of time between interventions  Interventions at fixed points of time Responsive  Pavement condition  Pavement strength  Surface age  Traffic volumes/loadings  Accident rates Maintenance Interventions

78 78 Depending on distress maintenance has different effects Maintenance Effects

79 79 Maintenance May Affect Pavement strength Pavement condition Pavement history Maintenance cost REMEMBER … the type of treatment dictates what it will influence

80 80 Works Duration – One Year

81 81 Works Duration – Up to Five years

82 82 Hierarchy of Roads Works

83 83 Pavement Type After Maintenance

84 84 HDM Series – Volume 4


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