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TYPICAL PAVEMENT DISTRESSES
(CLAYEY SUBGRADE???)
Dr. Venkaiah Chowdary
Assistant ProfessorDepartment of Civil Engineering
National Institute of Technology, WarangalEmail: [email protected]
Construction Practices of Pavements on Clayey Subgrade
G. Pulla Reddy Engineering College, Kurnool
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Pavement cross-section
Distresses in flexible pavements
Distresses in rigid pavements
Expansive soils as subgrade
Drainage measures
Geosynthetics
• Classification
• Functions
• Applications
Overview
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Pavement cross-section
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
GeosyntheticsGeosynthetics
•• ClassificationClassification
•• FunctionsFunctions
•• Applications Applications
Overview
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Flexible Pavement (MORTH, 2001)
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Rigid Pavement (MORTH, 2001)
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Conventional Flexible Pavements (Huang, 2004)
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
GeosyntheticsGeosynthetics
•• ClassificationClassification
•• FunctionsFunctions
•• Applications Applications
Overview
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Distresses in Flexible Pavements
Fatigue or Alligator Cracking
Bleeding
Block Cracking
Corrugation and Shoving
Depression
Joint Reflection Cracking
Longitudinal Cracking
Polished Aggregate
Potholes
Ravelling
Rutting
Transverse (Thermal) Cracking
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Fatigue or Alligator Cracking
Series of interconnected cracks caused by fatigue failure of HMA
surface under repeated traffic loading In thin pavements, crack initiates at the bottom of the HMA layer
where the tensile stress is high and propagates to the surface as oneor more longitudinal cracks ( Bottom-up cracks!!! )
In thick pavements, the cracksinitiate from the top in areas ofhigh localized tensile stressesresulting from tyre-pavementinteraction and asphalt binder
aging ( Top-down cracks!!! )
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Bleeding
A film of asphalt binder on the pavement surface
Usually creates a shiny, glass-like reflecting surface that can becomesticky
Bleeding occurs when asphalt binder fills the aggregate voids duringhot weather and then expands onto the pavement surface
This can be due to:
• Excess asphalt in HMA
• Less air voids in HMA
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Block Cracking
Interconnected cracks dividing the pavement into rectangular pieces
Larger blocks are classified as longitudinal and transverse cracks Block cracking normally occurs over a large portion of pavement
area but sometimes will occur only in non-traffic areas
Caused due to HMA shrinkageand daily temperature cycling
Typically caused by an inability ofasphalt binder to expand andcontract with temperature cyclesbecause of asphalt binder aging
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Corrugation and Shoving
A form of plastic movement typified by ripples (corrugation) or an
abrupt wave (shoving) across the pavement surface The distortion is perpendicular to the traffic direction
Usually occurs at points where traffic starts and stops (corrugation)or areas where HMA touches a rigid object (shoving)
Caused by starting and stoppingof vehicles combined with anunstable HMA layer (or) excessivemoisture in the subgrade
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Depression
Localized pavement surface areas with slightly lower elevations than
the surrounding pavement Depressions are very noticeable after a rain when they fill with water
Caused due to frost heave orsubgrade settlement resultingfrom inadequate compactionduring construction
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Joint Reflection Cracking
Cracks in a flexible overlay of a rigid pavement
Cracks occur directly over the underlying rigid pavement joints
Caused due to movement of thePCC slab beneath the HMAsurface because of thermal andmoisture changes
Generally not load initiated,however loading can acceleratedeterioration
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Longitudinal Cracking
Cracks parallel to the pavement centreline
Usually a type of fatigue cracking Caused due to poor joint construction/location; joints should be
constructed outside wheel path so that they are not frequently loaded
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Polished Aggregate
Areas of HMA pavement where the portion of aggregate extending
above the asphalt binder is either very small or there are no rough orangular aggregate particles
Causes decrease in skid resistance
Caused due to repeated trafficapplications
As the pavement ages, theprotruding rough, angularparticles becomes polished
This can occur quicker if theaggregate is susceptible toabrasion
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Potholes
Small, bowl-shaped depressions in the pavement surface that
penetrate all the way through the HMA layer down to the basecourse
They generally have sharp edges and vertical sides near the top ofthe hole
Potholes are most likely to occuron roads with thin HMA surfaces(25 to 50 mm) and may not occuron roads with 100 mm or deeperHMA surfaces
End result of alligator cracking
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Ravelling
The progressive disintegration of an HMA layer from the surface
downward as a result of the dislodgement of aggregate particles Caused due to loss of bond between aggregate particles and asphalt
binder
Ravelling may also be due tomechanical dislodging by certaintype of traffic (studded-tyres,tracked vehicles, snowplowblades, etc.)
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Rutting
Surface depression in the wheel path; pavement uplift (shearing) may
occur along the sides of the rut Ruts are particularly evident after a rain when they are filled with
water (hydroplaning); can be hazardous because ruts tend to pull a vehicle towards the rut path as it is steered across the rut
Caused due to permanentdeformation in any of thepavement layers or subgradeusually caused by verticalcompression or consolidation or
lateral movement of the materialsdue to traffic loading
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Transverse (Thermal) Cracking
Cracks perpendicular to the pavement centerline
A type of thermal cracking caused due to shrinkage of the HMAsurface due to low temperatures or asphalt binder hardening
May also be due to reflective cracking
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
GeosyntheticsGeosynthetics
•• ClassificationClassification
•• FunctionsFunctions
•• Applications Applications
Overview
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Distresses in Rigid Pavements
Blowup (buckling)
Corner break
Durability cracking (“D” cracking)
Faulting
Linear (panel) cracking
Popouts
Pumping
Patching
Polished aggregate
Reactive aggregate distresses
Shrinkage cracking
Spalling
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Blowup (Buckling)
A localized upward slab movement at a joint or crack
Usually occurs in summer and is the result of insufficient room forslab expansion during hot weather
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Corner Break
A crack that intersects the PCC slab joints near the corner
“Near the corner” is typically defined as within about 2 m A corner break extends through the entire slab and is caused by high
corner stresses.
It is due to severe corner stressescaused by load repetitionscombined with a loss of support,poor load transfer across thejoint, curling stresses and warping
stresses
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Durability Cracking (“D” Cracking)
Series of closely spaced, crescent-shaped cracks near a joint, corner
or crack; caused by freeze-thaw expansion of the large aggregate within the PCC slab
Durability cracking is a general PCC distress and is not unique toPCC pavements
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Faulting
A difference in elevation across a joint or crack usually associated
with undoweled JPCP Faulting is noticeable when the average faulting in the pavement
section reaches about 2.5 mm
Most commonly, faulting is aresult of slab pumping
Faulting can also be caused byslab settlement, curling and
warping
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Linear ( Panel) Cracking
Linear cracks not associated with corner breaks or blowups that
extend across the entire slab These cracks divide an individual slab into two to four pieces.
Caused due to a combination oftraffic loading, thermal gradientcurling, moisture stresses and lossof support
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Popouts
Small pieces of PCC that break loose from the surface leaving small
divots or pock marks Popouts range from 25-100 mm in dia. and from 25 - 50 mm deep
Popouts usually occur as a resultof poor aggregate durability
Poor durability can be a result ofa number of items such as: (i)poor aggregate freeze-thawresistance, (ii) expansiveaggregates, and (iii) alkali-aggregate reactions
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Pumping
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
Caused due to wateraccumulation underneath the slab
This can be caused by: a high water table, poor drainage, andpanel cracks or poor joint sealsthat allow water to infiltrate theunderlying material
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Patching
An area of pavement that has been replaced with new material to
repair the existing pavement A patch is considered a defect no matter how well it performs
Caused due to previous localizedpavement deterioration that hasbeen removed and patched
Also caused due to utility cuts
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Polished Aggregate
Areas of PCC pavement where the portion of aggregate on the
surface contains few rough or angular aggregate particles Caused due to repeated traffic applications
Generally, as a pavement ages theprotruding rough, angularparticles become polished
This can occur quicker if theaggregate is susceptible toabrasion or subject to excessivestudded tyre wear
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Reactive Aggregate Distress
Pattern or map cracking (crazing) on the PCC slab surface caused by
reactive aggregates Reactive aggregates are those that either expand or develop expansive
byproducts when introduced to certain chemical compounds
This type of distress is indicativeof poor aggregate qualities
Most commonly, it is a result ofan alkali-aggregate reaction
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Shrinkage Cracking
Hairline cracks formed during PCC setting and curing that are not
located at joints; they do not extend through entire depth of the slab Shrinkage cracks are considered a distress if they occur in an
uncontrolled manner (e.g., at locations outside of contraction jointsin JPCP or too close together in CRCP)
PCC will shrink as it sets andcures, therefore shrinkage cracksare expected in rigid pavementand provisions for their controlare made
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Spalling
Cracking, breaking or chipping of joint/crack edges
Usually occurs within about 0.6 m of joint/crack edge
Caused due to excessive stresses at the joint/crack caused byinfiltration of incompressible materials and subsequent expansion(can also cause blowups)
Caused due to disintegration ofthe PCC from freeze-thaw actionor “D” cracking
May also be due to misalignmentor corroded dowel
Also due to heavy traffic loading
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgrade
Drainage measuresDrainage measures
GeosyntheticsGeosynthetics
•• ClassificationClassification
•• FunctionsFunctions
••
Applications Applications
Overview
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Expansive Soils as Subgrade (IRC:37, 2001)• Top 500 mm portion of the roadway.
• Heavy compaction recommended for Expressways, NHs,SHs, and MDRs.
• Shall be compacted to 97% of dry density achieved withheavy compaction.
• Material used for subgrade shall have dry density not lessthan 1.75 g/cm3.
• CBR at most critical moisture conditions likely to occur in
the field.
• Use of expansive clay is not allowed for subgrade.
• If unavoidable, following procedure shall be adopted.
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• Expansive soils (black cotton soils, montmorillonite clays)
are characterized by extreme hardness and deep cracks when dry and tendency to heave during wetting.
• Moisture changes due to seasonal wetting and dryingcauses volumetric changes and leads to pavement
distortion, cracking, and unevenness.
• Volume changes in these soils depends on (i) dry densityof compacted soil, (ii) moisture content, and (iii) structure
of soil and method of compaction.• Expansive soils swell very little when compacted at low
densities and high moisture content; recommended tocompact the soils to slightly wet of OMC.
Expansive Soils as Subgrade (IRC:37, 2001)
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• Thickness design shall be based on 4-day soaked CBR.
Buffer Layer:
• Buffer layer made of non-expansive cohesive soil cushionof 0.6 to 1.0 m thickness:
i. prevents ingress of water into the underlyingexpansive soil,
ii. counteracts swelling and if the underlying expansivesoil heaves, movement will be more uniform.
• If buffer layer is not economically feasible, blanketcourse made of suitable material and thickness shall beprovided.
Expansive Soils as Subgrade (IRC:37, 2001)
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Blanket Course:
• At least 225 mm thickness.• Composed of coarse/medium sand (or) non-plastic
moorum with PI less than 5%.
•
Provided above expansive soil to serve as sub-base.• Extended over entire formation width.
• Alternatively, lime-stabilized black cotton sub-baseextending over entire formation width may be providedtogether with measures for efficient drainage.
• Improvement of drainage can significantly reduce themagnitude of seasonal heaves.
Expansive Soils as Subgrade (IRC:37, 2001)
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Drainage Measures:
• Provision must be made for lateral drainage of thepavement section.
• Granular sub-base/base shall be extended across the
shoulders.• Camber of 1:40 for BT surface and cross-slope of 1:20
for berms to shed-off surface run-off quickly.
•
Standing water not allowed on either side ofembankment.
Expansive Soils as Subgrade (IRC:37, 2001)
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Drainage Measures:
• Difference between subgrade level and highest watertable shall be at lest 1 m.
• 40 mm thick BT surfacing shall be provided to prevent
ingress of water through surface.• Shoulders shall be made of impervious material.
• Lime stabilized black cotton soil shoulder of 150 to 200
mm thickness is an economical option.
Expansive Soils as Subgrade (IRC:37, 2001)
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measures
GeosyntheticsGeosynthetics
•• ClassificationClassification
•• FunctionsFunctions
••
Applications Applications
Overview
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• Performance of a pavement can be affected by accumulation
of moisture in pavement• Measures to guard against poor drainage:
i. Proper camber
ii. Provision of surface and sub-surface drains
• Important when road is in cutting (or) built on low permeablesoils (or) situated in heavy rainfall/snowfall areas
• Difference between bottom of subgrade level and level of water table or high flood level should not be less than 0.6 to
1.0 m.
• In water logged areas where subgrade is within the capillarysaturation zone, suitable capillary cut-off may be installed
Drainage Measures (IRC:37, 2001)
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• When pavement is constructed over low permeable subgrade,
GSB layer shall be extended over entire formation width• Exposed ends of GSB layer should not be covered by soil
•
If GSB is of softer variety which may get crushed duringrolling leading to denser gradation and low permeability, thetop 100 to 150 mm shall be substituted by open gradedcrushed stone layer to ensure proper drainage
Drainage Measures (IRC:37, 2001)
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Requirements of drainage layer:
•
Criteria for high permeability drainage layer:
• To prevent entry of soil particles into drainage layer:
• Following materials are considered as good for drainage:
where, D85 is the size of sieve that allows 85% by weight of
material passing through it
5subgradeof D
layer drainageof D
15
15
5subgradeof D
layer drainageof Dand5,
subgradeof D
layer drainageof D
50
50
85
15
mm2.5Dand,D4D 21585
Drainage Measures (IRC:37, 2001)
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• Permeable sub-base when placed on soft erodible soils shall be
underlain by a layer of filter material to prevent intrusion ofsoil fines into the drainage layer
• Non-woven geosynthetic can be used as filter
Drainage Measures (IRC:37, 2001)
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• Base course shall be constructed 300 to 450 mm wider than
the bituminous surfacing so that run-off water disperses wellclear off the carriageway
• Shoulders shall have requisite cross-fall
• Shoulders shall not be at higher level than carriageway
Drainage Measures (IRC:37, 2001)
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
Geosynthetics
• Classification
• Functions
•
Applications
Overview
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
Geosynthetics
• Classification
•• FunctionsFunctions
••
Applications Applications
Overview
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Classification of GeosyntheticsClassification of Geosynthetics
Geotextiles
Geogrids
Geonets
Geomembranes
Geocomposites
Geosynthetic clay liners
Geopipes
Geocells
Geofoam
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
Geosynthetics
•• ClassificationClassification
• Functions
••
Applications Applications
Overview
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Functions of GeosyntheticsFunctions of Geosynthetics
Separation
Separates two layers of soilthat have different particlesize distributions
Used to prevent road basematerials from penetratinginto underlying soft subgradesoils
Prevents fine grainedsubgrade soils from being
pumped into permeablegranular road bases
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Reinforcement
Geotextiles and geogrids areused to add tensile strengthto a soil mass in order tocreate vertical or near-
vertical changes in grade
(reinforced soil walls)
Functions of GeosyntheticsFunctions of Geosynthetics
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Filtration
Acts similar to a sand filterby allowing water to movethrough the soil whileretaining all upstream soilparticles
Geotextiles are used toprevent soils from migratinginto drainage aggregate orpipes while maintaining flow
through the system
Functions of GeosyntheticsFunctions of Geosynthetics
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Drainage
Acts as a drain to carry fluidflows through less permeablesoils
Geotextiles are used todissipate pore waterpressures at the base ofroadway embankments
Functions of GeosyntheticsFunctions of Geosynthetics
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Type ofGeosynthetics
Separation Reinforcement FiltrationDrainag
eContainment
Geotextiles -
Geogrids - - - -
Geonets - - - -
Geomembranes - - - -
Geocomposites
Functions of GeosyntheticsFunctions of Geosynthetics
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Pavement crossPavement cross--sectionsection
Distresses in flexible pavementsDistresses in flexible pavements
Distresses in rigid pavementsDistresses in rigid pavements
Expansive soils as subgradeExpansive soils as subgrade
Drainage measuresDrainage measures
Geosynthetics
•• ClassificationClassification
•• FunctionsFunctions
•
Applications
Overview
G h i A li i i PG h i A li i i P
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Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
can be effectively used to reduce or avoid reflective cracking
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
G h i A li i i PG h i A li i i P
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works as a barrier to avoid pumping of soil fines
Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
G h i A li i i PG h i A li i i P
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can be effectively used to reduce asphalt cap thickness
Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
G h i A li i i PG h i A li i i P
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can be effectively used to reduce pavement thickness
Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
G h i A li i i PG h i A li i i P
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can be effectively used to increase the life of the pavement
can be effectively used to decrease the rut depth
Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
G h i A li i i PG h i A li i i P
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Dust particulate originates from the fines of the subgrade, which migrate upward into the unbound surface over time.
Vehicular traffic causes the fines in the unbound layer to bemobilized into the atmosphere.
Geotextile separators limit the migration of fines into theoverlying aggregate and also the intrusion of aggregate into the
subgrade.
Geosynthetics Applications in PavementsGeosynthetics Applications in Pavements
Source: http://www.geosyntheticssociety.org/Resources.aspx?pg=Education
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Thank You