Block 33a SP 13

Rehab & Maint. HMA Overlays 1

Flexible Pavement Maintenance and Rehabilitation

HMA Overlays

Introduction and Functional Overlays

Senior/GraduateHMA Course


Pavement DataCollection

Projectevaluation

Select feasiblealternatives

ReconstructionRestorationRecyclingResurfacing

Life - cycle costs

Non- monetary factors

Select preferredalternatives

Detailed PS & E

Construction

MonitorPerformance

Steps In The Rehabilitation Process


Rehabilitation Feasibility

Preventive maintenance

Surface Treatment

Thin Overlay

ReconstructionCritical condition

AGE or ESAL

Thick Overlay

PAVEMENT CONDITION

Excellent

Failed


Pav

emen

t C

ondi

tion

Alt.-A

Alt.-B

Terminal Serviceability Index

Analysis Period

Analysis Period

RSL


Covered in this module

• HMA Overlays over HMA pavements– Functional – Structural

• HMA Overlays over PCC pavements


Overlay Types

• Functional overlays – Typically used to address surface

distresses or improve ride quality– Generally not designed and rely on past

experience• Structural overlays

– Correct structural deficiencies and are designed using the methods presented (or other methods)


Thin Overlay Thick Overlay

Surface Defects Structural Defects

Selection of an Overlay to Correct Deficiencies


Functional Overlays

• Remedy functional deficiencies• Minimum constructable thickness• May involve surface milling and repair with

overlay


Functional Deficiencies

• Adversely affect highway user– Poor surface friction– Hydroplaning– Excess surface distortion

• Rutting• Potholes• Faulting• Settlement


Surface Friction

• Force developed at tire-pavement interface that prevents sliding

• Factor influencing– Microtexture– Macrotexture– Transverse slope

• Poor friction can be caused by polishing or bleeding


Photo of poor surface friction


Hydroplaning

• Tires ride on thin film of water and lose contact with the pavement

• Hydroplaning is worsened by water standing on the pavement and is affected by the following – Wheelpath rutting– Lack of surface texture– Lack of cross slope


Photo of rutting in wheelpaths


Structural Overlays

Flexible Pavement Maintenance and Rehabilitation


Surface Roughness

• Irregularities in the pavement surface that adversely affect ride quality, safety, and vehicle maintenance costs

• HMA Pavements– Heaves, settlements– Deteriorated cracks– Potholes– Raveling

• PCC Pavements– Heaves, settlements– Spalling– Faulting– Curling/warping– Texture application


Photo of raveling


Options for Correcting Functional Deficiencies

• Thin overlay - 50 to 80 mm (2 to 3 in)• Milling plus thin overlay• Open-graded friction course• Full-depth or partial-depth repairs• Thin, hot-applied surfacing


Photo of milling


Structural Deficiencies

• Adversely affect the load-carrying capability of the pavement

• Indicators– Cracking– Distortion (rutting)– Disintegration


Photo of alligator cracking


Thickness Design

• Engineering judgment• Deflection• Layer deficiency• Mechanistic


Subgrade Soil

Base/Subbase

Surface

SUR

SUB

SUR

AxleLoad

Pavement Deflections


NDT SensorsNDTLoad

Measurement of Surface Deflection


NDT Load

“Strong”Pavement “Weak”

Pavement

Strong vs. Weak Pavements


Dynatest FWD

Load

Deflection measuring sensors


Options for Correcting Structural Deficiencies

• Structural overlay• Preoverlay repair and structural overlay• Recycling and structural overlay• Reconstruction

AASHTO procedure provides an overlay thickness to correct a structural deficiency


Considerations for Overlays

• Preoverlay repair• Overlay materials• Subdrainage• Reflection crack control• Traffic loadings• Pavement widening


Preoverlay Repairs

• Amount and type depends on– Type of overlay– Structural adequacy– Distress types and severity– Future traffic loadings– Physical constraints– Overall project funding


Preoverlay Repairs

• Consider trade-offs between– Overlay type– Overlay thickness– Preoverlay repair extent



Date post:	01-Jun-2015
Category:	Business
Upload:	chris-yarnell
View:	328 times
Download:	6 times

Block 33a SP 13

Business