Presentation Given by Akbar on Pavement Faults

8/9/2019 Presentation Given by Akbar on Pavement Faults

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Rigid Pavement

Distress


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1-Blowup (Buckling)


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Blowup (Buckling)


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Blowup (Buckling)

Description:Description:

A localized upward slab movement and shattering at ajoint or crack. It is the result of insufficient room forslab expansion during hot weather.

Problem:Problem:

Roughness, moisture infiltration, in extreme cases (as inthe second photo) can pose a safety hazard

Possible Causes:Possible Causes:

During cold periods (e.g., winter) PCC slabs contractleaving wider joint openings. If these openings becomefilled with incompressible material (such as rocks orsoil), subsequent PCC slab expansion during hot periods(e.g., spring, summer) may cause high compressivestresses. If these stresses are great enough, the slabsmay buckle and shatter to relieve the stresses.


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2-Faulting


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Faulting


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Faulting


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FaultingDescription:

A difference in elevation across a joint or crack. Usually theapproach slab is higher than the leave slab due topumping, the most common faulting mechanism.

Faulting is noticeable when the average faulting in thepavement section reaches about 2.5 mm (0.1 inch).When the average faulting reaches 4 mm (0.15 in), somerehabilitation measures should be considered.

Problem:

Roughness (an expression of irregularities in the pavement surface that adversely

affect the ride quality of a vehicle)

Possible Causes:

Most commonly, faulting is a result of slabpumping. Faulting can also be caused by slabsettlement.


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3-Linear (Panel) Cracking


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Linear (Panel) Cracking


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Linear cracks not associated with corner breaks or blowups

that extend across the entire slab. Typically, these cracks

divide an individual slab into two to four pieces.

Problem:Problem:

Roughness, allows moisture infiltration leading to erosion of

base/sub-base support.


Usually a combination of traffic loading, thermal changes,

moisture stresses and loss of support.


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44--PopoutsPopouts


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PopoutsPopouts


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PopoutsPopouts


Small pieces of PCC that break loose from the surface leaving small

divots or pock marks. Popouts range from 25 - 100 mm (1 - 4 inches)

in diameter and from 25 - 50 mm (1 - 2 inches) deep.

Problem:Problem:

Roughness, usually an indicator of poor material


Popouts usually occur as a result of poor aggregate durability. Poor

durability can be a result of a number of items such as:

Poor aggregate freeze-thaw resistance

Expansive aggregates

Alkali-aggregate reactions


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55--PumpingPumping

Pumping in action


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Pumping damage


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Broken slabs with pumping evidence


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PumpingPumping


Movement of material underneath the slab or ejection of material

from underneath the slab as a result of water pressure. Water

accumulated underneath a PCC slab will pressurize when the slab

deflects under load. This pressurized water can do one of the

following:

Move about under the slab.

Move from underneath one slab to underneath an adjacent

slab. This type of movement leads to faulting.

Move out from underneath the slab to the pavementsurface. This results in a slow removal of base, subbase and/or

sub-grade material from underneath the slab resulting in

decreased structural support.


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Problem:Problem:

Decreased structural support of the slab, which can lead to

cracking and faulting.


Water accumulation underneath the slab. This can be caused bysuch things as:

a high water table,

poor drainage,

and panel cracks or

poor joint seals

which allow water to infiltrate the underlying material.


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Distresses in

FlexiblePavements


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Fatigue (Alligator) Cracking


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Alligator Cracking


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Fatigue (Alligator) CrackingFatigue (Alligator) Cracking


Series of interconnected cracks caused by fatigue failureunder repeated traffic loading.

In thin pavements, cracking initiates at the bottomasphalt layer where the tensile stress is the highest thenpropagates to the surface as one or more longitudinal

cracks. This is commonly referred to as "bottom-up" or"classical" fatigue cracking.

In thick pavements, the cracks most likely initiate fromthe top in areas of high localized tensile stressesresulting from tire-pavement interaction and asphalt

binder aging (top-down cracking). After repeatedloading, the longitudinal cracks connect forming many-sided sharp-angled pieces that develop into a patternresembling the back of an alligator or crocodile.


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Problem:Problem:

Indicator of structural failure, cracks allow moistureinfiltration, may further deteriorate to a pothole

Possible Causes:Possible Causes:Inadequate structural support, which can be caused

by many things. A few of the more common onesare listed here:

Decrease in pavement load supportingcharacteristics Loss of base, subbase or subgrade support (e.g., poor

drainage or thaw resulting in a less stiff base).

Increase in loading (e.g., more or heavier loads

than anticipated in design) Inadequate structural design

Poor construction (e.g., inadequate compaction)


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Potholes


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PotholesPotholesDescription:Description:

Small, bowl-shaped depressions in the pavement surface that penetrate allthe way through the layer down to the base course. They generally have

sharp edges and vertical sides near the top of the hole. Potholes are

most likely to occur on roads with thin asphalt surfaces (25 to 50 mm (1

to 2 inches)) and seldom occur on roads with 100 mm (4 inch) or deeper

asphalt surfaces.

Problem:Problem:

Roughness (serious vehicular damage can result from driving across

potholes at higher speeds), moisture infiltration. Pavement roughness is generallydefined as an expression of irregularities in the pavement surface that adversely affect the ride quality of a

vehicle (and thus the user).


Generally, potholes are the end result ofalligator cracking. As alligator

cracking becomes severe, the interconnected cracks create small chunks

of pavement, which can be dislodged as vehicles drive over them. The

remaining hole after the pavement chunk is dislodged is called a pothole.


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PotholesPotholes


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Pothole


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Rutting


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RuttingRuttingDescription:Description:

The depressions all along the length of the road are called ruts.Surface depression in the wheelpath. Pavement uplift

(shearing) may occur along the sides of the rut. Ruts areparticularly evident after a rain when they are filled withwater.

There are two basic types of rutting:

i. mix rutting

ii. subgrade rutting

Mix rutting occurs when the subgrade does not rut yet thepavement surface exhibits wheelpath depressions as aresult of compaction/mix design problems.

Subgrade rutting occurs when the subgrade exhibitswheelpath depressions due to loading. In this case, thepavement settles into the subgrade ruts causing surfacedepressions in the wheelpath.


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Problem:Problem:

Ruts filled with water can cause vehicle hydroplaning, canbe hazardous because ruts tend to pull a vehicletowards the rut path as it is steered across the rut.

Possible Causes:

Insufficient compaction of pavement layers during construction. If

it is not compacted enough initially, pavement may continue todensify under traffic loads.

Subgrade rutting (e.g., as a result of inadequate pavement

structure)

Improper mix design or manufacture (e.g., excessively high asphaltcontent, excessive mineral filler, insufficient amount of angular

aggregate particles)


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Plastic Flow Rutting


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Rutting in Asphalt Layer


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Rutting in Sub-grade or Base


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BleedingBleeding


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Bleeding


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Bleeding


A film of asphalt binder on the pavement surface. It usually creates a shiny,glass-like reflecting surface that can become quite sticky.

Problem:Problem:

Loss ofskid resistance when wet


Bleeding occurs when asphalt binder fills the aggregate voids during hot

weather and then expands onto the pavement surface. Since bleeding is not

reversible during cold weather, asphalt binder will accumulate on the

pavement surface over time. This can be caused by one or a combination of

the following:

Excessive asphalt binder in the asphalt concrete (either due to mix design or

manufacturing)

Excessive application of asphalt binder during BSTBST (bituminous surface

treatment) application


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Corrugation and ShovingCorrugation and Shoving


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Corrugation and ShovingDescription:Description:

A form of plastic movement typified by ripples (corrugation) oran abrupt wave (shoving) across the pavement surface. Thedistortion is perpendicular to the traffic direction. Usuallyoccurs at points where traffic starts and stops (corrugation)or areas where Hot mix asphalt (HMA) abuts a rigid object(shoving).

Problem:Problem:Roughness


Usually caused by traffic action (starting and stopping)combined with:

An unstable (i.e. low stiffness) HMA layer (caused by mixcontamination, poor mix design, poor HMA manufacturing,or lack of aeration of liquid asphalt emulsions)

Excessive moisture in the subgrade


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Polished AggregatePolished Aggregate


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li h dli h d


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Polished AggregatePolished Aggregate


Areas of HMA pavement where the portion ofaggregate extending above the asphalt binder iseither very small or there are no rough or angularaggregate particles.

Problem:Problem:

Decreased skid resistancePossible Causes:Possible Causes:

Repeated traffic applications.

Generally, as a pavement ages the protruding rough,

angular particles become polished. This can occurquicker if the aggregate is susceptible to abrasionor subject to excessive studded tire wear.


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Raveling


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RavelingDescription:Description:

The progressive disintegration of an HMA layer from thesurface downward as a result of the dislodgement of

aggregate particles.

Problem:Problem:

Loose debris on the pavement, roughness, water collecting inthe raveled locations resulting in vehicle hydroplaning, loss

ofskid resistance


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Several including:

Loss of bond between aggregate particles and the

asphalt binder as a result of:

A dust coating on the aggregate particles that forces the

asphalt binder to bond with the dust rather than the

aggregate

Inadequate compaction during construction. High density is

required to develop sufficient cohesion within the HMA.

Mechanical dislodging by certain types of traffic(studded tires, snowplow blades or tracked vehicles).

R li


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Raveling

SOURCES OF PREMATURE PAVEMENT FAILURE


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SOURCES OFPREMATURE PAVEMENT FAILURE

ConstructionPractices&

Quality Control

Inadequately Designed Pavements Will Fail Prematurely Inspite

OfBest Quality Control & Construction Practices


Quality Control


Quality Control


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Thank YouThank You


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ANSWER & QUESTION

SESSION

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Presentation Given by Akbar on Pavement Faults