CPD SEMINAR ON CAUSES OF PREMATURE ROAD FAILURE CAUSES OF PREMATURE ROAD FAILURE AND STRATEGIES ADOPTED FOR REPAIR AND STRATEGIES ADOPTED FOR REPAIR

AND RE-HABILITATION AND RE-HABILITATION

Engr. Muhammad Uzair, Executive Engr. Muhammad Uzair, Executive Engineer C&W DepartmentEngineer C&W Department

November 7, 2012November 7, 2012

ByBy

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SEQUENCE OF PRESENTATIONSEQUENCE OF PRESENTATION IMPORTANCE OF THE SUBJECTIMPORTANCE OF THE SUBJECT

CAUSES OF PREMATURE ROAD CAUSES OF PREMATURE ROAD

FAILUREFAILURE

STATEGIES FOR RE-HABILITATION STATEGIES FOR RE-HABILITATION

QUESTION & ANSWER SESSIONQUESTION & ANSWER SESSION

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The Seminar on the subject will help: The Seminar on the subject will help: TO SENSITIZE THE ROAD ENGINEERS AGAINST THE TO SENSITIZE THE ROAD ENGINEERS AGAINST THE

POTENTIAL CAUSES OF ROAD FAILURE AND TO POTENTIAL CAUSES OF ROAD FAILURE AND TO ACQUAINT ACQUAINT

THEM WITH APPROPRIATE REMEDIAL TOOLSTHEM WITH APPROPRIATE REMEDIAL TOOLS

TO IMPART AWARNESS REGARDING THE MENACE OF TO IMPART AWARNESS REGARDING THE MENACE OF

OVER- LOADING AND AXLE CONTROL REGIMEOVER- LOADING AND AXLE CONTROL REGIME

TO CONCENTRATE MORE ON DESIGN & QUALITY ISSUES TO CONCENTRATE MORE ON DESIGN & QUALITY ISSUES

FOR PRESERVATION OF PRECIOUS ROAD NETWORK FOR PRESERVATION OF PRECIOUS ROAD NETWORK

IMPORTANCE OF THE SUBJECTIMPORTANCE OF THE SUBJECT

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CAUSES OF PREMATURE CAUSES OF PREMATURE ROAD FAILUREROAD FAILURE

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Following are the major causes of Following are the major causes of Premature road failure:Premature road failure:

IN-ADEQUATE PAVEMENT IN-ADEQUATE PAVEMENT DESIGNDESIGN FAULTY CONSTRUCTIONFAULTY CONSTRUCTION IMPEDED DRAINAGE IMPEDED DRAINAGE OVER-LOADINGOVER-LOADING LACK OF PROPER & TIMELY LACK OF PROPER & TIMELY REPAIRREPAIR

MAJOR CAUSES OF PREMATURE ROAD MAJOR CAUSES OF PREMATURE ROAD FAILUREFAILURE

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IN-ADEQUATE PAVEMENT DESIGNIN-ADEQUATE PAVEMENT DESIGN

Under-estimation or carelessness in design Under-estimation or carelessness in design parameters leads to in-adequate pavement parameters leads to in-adequate pavement design which results into premature road design which results into premature road failure much before the predicted design life.failure much before the predicted design life.

It may be due to :It may be due to :

Incorrect traffic count or traffic analysis.Incorrect traffic count or traffic analysis.

Incorrect assessment of Subgrade materialIncorrect assessment of Subgrade material Incorrect selection of design parameters like Incorrect selection of design parameters like

serviceability indices, Reliability, and drainage serviceability indices, Reliability, and drainage

coefficient etc. coefficient etc. 7

FAULTY CONSTRUCTIONFAULTY CONSTRUCTIONEffective Quality control at the time of Effective Quality control at the time of construction is the essence of good quality construction is the essence of good quality work. The design specification, if not followed work. The design specification, if not followed in construction as well as in selection of in construction as well as in selection of materials, will obviously lead to some type of materials, will obviously lead to some type of distress resulting into premature road failure.distress resulting into premature road failure.

It may be due to:It may be due to:

Use of Sub-standard materialsUse of Sub-standard materials

Poor workmanship.Poor workmanship.

In-adequate Compaction of various pavement layers In-adequate Compaction of various pavement layers

Deviation from specified construction methodology Deviation from specified construction methodology

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IMPEDED DRAINAGE IMPEDED DRAINAGE Surface drainage is the most important factor Surface drainage is the most important factor affecting the performance and serviceability of affecting the performance and serviceability of flexible pavement. A well-designed and well-flexible pavement. A well-designed and well-constructed road with poor drainage system constructed road with poor drainage system will fail much ahead of its design life.will fail much ahead of its design life.

Water damage is initially caused by hydraulic Water damage is initially caused by hydraulic pressure.pressure.

This pressure pushes the water down into the This pressure pushes the water down into the road road fabrics and break it up.fabrics and break it up.

Freezing & Thawing phenomena during winter Freezing & Thawing phenomena during winter season season further aggravate the situation.further aggravate the situation.

Eventually, the water descends into the Subgrade Eventually, the water descends into the Subgrade layer, layer, lowers its CBR and results into the deep seated lowers its CBR and results into the deep seated road road failure.failure.

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OVER-LOADINGOVER-LOADINGThe most dangerous cause of premature road The most dangerous cause of premature road failure is the overloaded vehicles carrying load failure is the overloaded vehicles carrying load much heavier than the legal weight anticipated much heavier than the legal weight anticipated in the pavement design.in the pavement design.

The failure on this account is usually very fast as The failure on this account is usually very fast as the the damaging factor used in the pavement design damaging factor used in the pavement design has a 4has a 4thth degree exponential effect.degree exponential effect. This phenomenon results into severe rutting This phenomenon results into severe rutting under the under the wheel track particularly during hot weather.wheel track particularly during hot weather.

The over-loading needs to be checked through an The over-loading needs to be checked through an effective Axle control regime as this menace effective Axle control regime as this menace itself is itself is sufficient for destruction of an ideal roadsufficient for destruction of an ideal road

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LACK OF PROPER & TIMELY MAINTENANCELACK OF PROPER & TIMELY MAINTENANCE

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SRATEGIES FOR REPAIR & SRATEGIES FOR REPAIR & REHABILITATIONREHABILITATION

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SRATEGIES FOR REPAIR & REHABILITATIONSRATEGIES FOR REPAIR & REHABILITATION

Once the distress is noticed in the road pavement, Once the distress is noticed in the road pavement, the same should be repaired immediately with the same should be repaired immediately with appropriate technique otherwise the damages will appropriate technique otherwise the damages will multiply with the passage of traffic and subsequent multiply with the passage of traffic and subsequent rainy spills.rainy spills.

While selecting an appropriate mode of repair or re-While selecting an appropriate mode of repair or re-habilitation, the following factors should be kept in habilitation, the following factors should be kept in mind:mind:

Type of roadType of road

Type and volume of traffic Type and volume of traffic

Material availabilityMaterial availability

Economic considerationsEconomic considerations

Before discussing various repair techniques, lets Before discussing various repair techniques, lets through some light on the types of Distresses. through some light on the types of Distresses.

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TYPES OF ROAD FAILURETYPES OF ROAD FAILUREThe following distresses usually develop in flexible The following distresses usually develop in flexible pavements due to premature road failure : pavements due to premature road failure :

CrackingCracking (Alligator, Longitudinal and Transverse cracks)(Alligator, Longitudinal and Transverse cracks)

RuttingRutting

SettlementSettlement

ShovingShoving

RavelingRaveling

FrettingFretting

BleedingBleeding

Potholes & PatchesPotholes & PatchesDetails of these failures and their repair/ re-Details of these failures and their repair/ re-habilitation are mentioned in the next slides:- habilitation are mentioned in the next slides:- 16

CRACKINGCRACKINGCRACKING is the most significant distress causing roughness CRACKING is the most significant distress causing roughness

and leading to water infiltration deep into the underlying pavement and leading to water infiltration deep into the underlying pavement layers. Cracks should be sealed as soon as possible with appropriate layers. Cracks should be sealed as soon as possible with appropriate Crack seals, Fog seals or Slurry seals according to their intensity, Crack seals, Fog seals or Slurry seals according to their intensity, nature and locations. Cracks are further sub divided into the nature and locations. Cracks are further sub divided into the following categories: following categories:

Alligator CrackingAlligator CrackingThese are series of interconnected cracks formed due to These are series of interconnected cracks formed due to fatigue failure of Asphalt surface generally caused by fatigue failure of Asphalt surface generally caused by repeated traffic loading. These may be “Bottom –up” or “Top-repeated traffic loading. These may be “Bottom –up” or “Top-Down” cracking depending upon the thickness of Asphalt Down” cracking depending upon the thickness of Asphalt concrete. concrete. The cracked area should be cold milled and re-filled The cracked area should be cold milled and re-filled with fresh HMA layers.with fresh HMA layers.

Longitudinal CrackingLongitudinal CrackingThese cracks are formed parallel to the road centerline; These cracks are formed parallel to the road centerline; caused usually due to fatigue action or faulty construction caused usually due to fatigue action or faulty construction joint.joint.

Transverse CrackingTransverse Cracking These cracks are formed perpendicular to the road centerline; These cracks are formed perpendicular to the road centerline; caused due to shrinkage of Asphalt in low temperatures. caused due to shrinkage of Asphalt in low temperatures. Longitudinal and transverse cracks when interconnect, Longitudinal and transverse cracks when interconnect, become Block cracking.become Block cracking.

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18Longitudinal Crack

19Transverse Crack

20Alligator Crack

21Alligator Cracking

22Block Cracking

RUTTINGRUTTING Rutting usually occurs under the wheel track during hot Rutting usually occurs under the wheel track during hot weather when weather when the Asphalt concrete in the wheel path softens and the Asphalt concrete in the wheel path softens and displaces to both displaces to both sides forming longitudinal humps and depressions along the sides forming longitudinal humps and depressions along the traffic traffic flowflow. . The rutted area should be removed and reconstructed The rutted area should be removed and reconstructed with the with the required pavement layers according to its severity. required pavement layers according to its severity.

Rutting is of two types:Rutting is of two types:Mix RuttingMix RuttingSubgrade RuttingSubgrade Rutting

Rutting is caused due to:Rutting is caused due to:

Over loadingOver loading Excessive mineral fillerExcessive mineral filler High Asphalt contentHigh Asphalt content

Deficiency of angular aggregate in the Deficiency of angular aggregate in the

mixmix Insufficient compaction of HMA layers Insufficient compaction of HMA layers during during

construction.construction.

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QUESTIONS ?QUESTIONS ?

SETTLEMENTSETTLEMENT

This is the most serious road failure caused due to This is the most serious road failure caused due to faulty design, sub-standard construction, poor drainage faulty design, sub-standard construction, poor drainage or excessive over-loading.or excessive over-loading.In this type of failure, the damage extends down to the In this type of failure, the damage extends down to the subgrade bottom. subgrade bottom. It can be rehabilitated through It can be rehabilitated through complete reconstruction only.complete reconstruction only.

SHOVINGSHOVING

It is a form of plastic movement typified by ripples It is a form of plastic movement typified by ripples or corrugations visible as an abrupt wave across the or corrugations visible as an abrupt wave across the pavement surface. The distortion is usually pavement surface. The distortion is usually perpendicular to the traffic direction and occurs at perpendicular to the traffic direction and occurs at points where traffic starts or stops. It is caused by points where traffic starts or stops. It is caused by traffic action coupled with poor JMF or mix traffic action coupled with poor JMF or mix contamination. contamination. It is corrected through cold milling and It is corrected through cold milling and re-laying of Fresh HMA or resurfacing.re-laying of Fresh HMA or resurfacing.

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27SHOVING

28COLD MILLING

29COLD MILLING

30COLD MILLING ON MARDAN –SWABI ROAD

31TACK COAT APPLIED TO MILLED SURFACE

32FILLING OF MILLED SURFACE WITH ASPHALT CONCRETE

RAVELING RAVELING

This is the progressive disintegration of This is the progressive disintegration of Bituminous layers as a result of the dislodgement of Bituminous layers as a result of the dislodgement of aggregate particles. It leads to surface roughness due aggregate particles. It leads to surface roughness due to loose debris on the pavement and loss of skid to loose debris on the pavement and loss of skid resistance. resistance. Raveling may be treated with appropriate Raveling may be treated with appropriate Bituminous Surface Treatment(BST)Bituminous Surface Treatment(BST)

BLEEDINGBLEEDING

It is the formation of a thin film of Asphalt binder It is the formation of a thin film of Asphalt binder due high Asphalt content commonly observed in hot due high Asphalt content commonly observed in hot weather. It usually creates a shiny surface that can weather. It usually creates a shiny surface that can become quite sticky. become quite sticky. Minor bleeding can often be Minor bleeding can often be corrected by applying coarse sand to blot up the excess corrected by applying coarse sand to blot up the excess asphalt binder. asphalt binder. Major bleeding can be treated by cutting off excessive Major bleeding can be treated by cutting off excessive asphalt with motor grader. If the resulting surface asphalt with motor grader. If the resulting surface become excessively rough, resurfacing may be become excessively rough, resurfacing may be necessary.necessary.

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FRETTING FRETTING

This is a phenomenon in which the surface material This is a phenomenon in which the surface material gradually loose its control with the surface due to ageing or gradually loose its control with the surface due to ageing or overheated mixture causing premature ageing. It not only overheated mixture causing premature ageing. It not only causes undulated surface but also invite ponding of water in causes undulated surface but also invite ponding of water in the fretted out surface. the fretted out surface. Such type of damage can Such type of damage can economically be restored with single or double coat of economically be restored with single or double coat of surface dressing according to its severity.surface dressing according to its severity.

POTHOLES & PATCHES POTHOLES & PATCHES

Small Bowl-shaped depressions in the pavement Small Bowl-shaped depressions in the pavement surface that penetrate all the way through the HMA layers surface that penetrate all the way through the HMA layers down to the base course are called potholes. They generally down to the base course are called potholes. They generally have sharp edges and vertical sides near the top. Serious have sharp edges and vertical sides near the top. Serious vehicular damage can result from driving across potholes at vehicular damage can result from driving across potholes at higher speeds. Potholes are the end result of alligator higher speeds. Potholes are the end result of alligator cracking. cracking. For repair, the potholes should be trimmed to For repair, the potholes should be trimmed to geometrical shape and filled with base and/or Asphalt geometrical shape and filled with base and/or Asphalt concrete. Interconnected potholes can be combined to form a concrete. Interconnected potholes can be combined to form a patch and treated in the same way as that of individual patch and treated in the same way as that of individual pothole.pothole.

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35Extensive Cracking and potholesExtensive Cracking and potholes

CRACK SEALSCRACK SEALS

Crack seal products are used to fill individual pavement Crack seal products are used to fill individual pavement cracks to prevent entry of water or non-compressible cracks to prevent entry of water or non-compressible substance such as sand, dirt or weeds. Crack sealant is substance such as sand, dirt or weeds. Crack sealant is typically used on early stage longitudinal cracks ,transverse typically used on early stage longitudinal cracks ,transverse cracks ,reflection cracks and block cracks. Alligator cracks are cracks ,reflection cracks and block cracks. Alligator cracks are most often too extensive to warrant filling with crack sealer; most often too extensive to warrant filling with crack sealer; they usually require an area treatment such as MILL & FILL or they usually require an area treatment such as MILL & FILL or reconstruction. Crack filler material is typically some form of reconstruction. Crack filler material is typically some form of rubberized asphalt or sand slurry.rubberized asphalt or sand slurry.

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FOG SEALSFOG SEALSA fog seal is a light application of a diluted slow-A fog seal is a light application of a diluted slow-

setting asphalt emulsion to the surface of an aged(oxidized) setting asphalt emulsion to the surface of an aged(oxidized) pavement surface. Fog seals are low-cost and are used to pavement surface. Fog seals are low-cost and are used to restore flexibility to an existing HMA pavement surface. restore flexibility to an existing HMA pavement surface. They may be able to temporarily postpone the need for a They may be able to temporarily postpone the need for a surface treatment or non-structural overlay for an year or surface treatment or non-structural overlay for an year or two.two.

SLURRY SEALSSLURRY SEALS

A slurry seal is a homogeneous mixture of A slurry seal is a homogeneous mixture of emulsified asphalt, water, well-graded fine aggregate emulsified asphalt, water, well-graded fine aggregate and mineral filler that has a creamy fluid-like and mineral filler that has a creamy fluid-like appearance when applied. Slurry seals are used to fill appearance when applied. Slurry seals are used to fill existing pavement surface defects as either a existing pavement surface defects as either a preparatory treatment for other maintenance preparatory treatment for other maintenance treatments or as a wearing course. There are three treatments or as a wearing course. There are three basic aggregate gradations used in slurry seals:basic aggregate gradations used in slurry seals:

Type I : Fine Slurry Seals Type I : Fine Slurry Seals (with aggregate size upto 0.25 (with aggregate size upto 0.25 in)in)

Type II : General Slurry SealsType II : General Slurry Seals(with aggregate size upto (with aggregate size upto 0.25 in)0.25 in)

Type III: Coarse Slurry SealsType III: Coarse Slurry Seals(with aggregate size upto (with aggregate size upto 0.25 in)0.25 in)

The performance of Slurry seals can further be improved with The performance of Slurry seals can further be improved with thetheaddition of polymers for specialized cases; the process being addition of polymers for specialized cases; the process being calledcalled Micro surfacingMicro surfacing..

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BITUMINOUS SURFACE TREATMENT (BST)BITUMINOUS SURFACE TREATMENT (BST)

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Bituminous surface treatment, also known as a Bituminous surface treatment, also known as a seal coat or chip seal, is a thin protective wearing seal coat or chip seal, is a thin protective wearing surface that is applied to a pavement or base surface that is applied to a pavement or base course. BSTs can provide the following functions:course. BSTs can provide the following functions:

A waterproof layer to protect the underlying pavement.A waterproof layer to protect the underlying pavement.

Increased skid resistance.Increased skid resistance.

A fill for existing cracks or raveled surfaces.A fill for existing cracks or raveled surfaces.

A anti-glare surface during wet weather and an increased A anti-glare surface during wet weather and an increased reflective surface for night driving.reflective surface for night driving.

BST can be Single Surface Treatment (SST), Double Surface BST can be Single Surface Treatment (SST), Double Surface Treatment(DST) or Triple Surface Treatment (TST) Treatment(DST) or Triple Surface Treatment (TST) depending upon the number of coats needed to restore a depending upon the number of coats needed to restore a worn out surface. worn out surface.

39BITUMINOUS SURFACE TREATMENT (BST)BITUMINOUS SURFACE TREATMENT (BST)

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SUMMARY OF FAILURES, CAUSES AND CURES

S.No Type of Failure

Causes Cures

1 CrackingCracking Fatigue failure of HMA, Loss of pavement supporting characteristics and Temperature cycling.

Crack seals, Fog seals, Slurry seals or ultimately “MILL & FILL” for severe alligator cracking.

2 RuttingRutting In-adequate pavement design, Excessive mineral filler, high asphalt content, in-adequate compaction and over-loading

Cold milling and relaying of fresh HMA layers OR Bituminous Surface Treatment (BST)

3 SettlemeSettlementnt

Faulty pavement design, Sub-standard materials, impeded drainage and in-adequate compaction

Removal of damaged layers and reconstruction as per fresh pavement design

4 ShovingShoving Traffic action and faulty JMF Cold milling and relaying of fresh HMA layers OR Bituminous Surface Treatment (BST)

5 RavelingRaveling Dust coating on aggregate, segregation of aggregate, Sub standard asphalt binder and in-adequate compaction

Bituminous Surface Treatment (BST) with single or double coats as per surface condition

6 FrettingFretting Dust coating on aggregate, Sub standard asphalt binder and in-adequate compaction

Bituminous Surface Treatment (BST) with single or double coats as per surface condition

7 BleedingBleeding Excessive Asphalt content in HMA, excessive application of binder in BST or low HMA air voids

Sand blotting OR in severe cases the excessive Asphalt is removed through motor grader and surface rectified through BSTs.

8 Potholes Potholes & &

Patches Patches

Final result of Alligator cracking or sometimes due to utility cuts.

Filling of potholes with Base and Asphalt as needed.

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THANK THANK YOUYOU

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