With over 20 years of experience as a road and pavement engineer, I have directly observed and assessed countless asphalt failure cases across diverse projects. My expertise comes not just from academic study, but from thorough field investigations and forensic analysis of actual pavements subject to cracking, deformations, and other distresses. This firsthand perspective has given me trusted insights into real-world causes and effective solutions when it comes to durable asphalt design and failure prevention.

What are Asphalt Pavement and Asphalt Failure Types

Asphalt is a popular paving material for roads, parking lots, driveways, and more due to its smooth surface, durability, and cost-effectiveness. However, asphalt can deteriorate over time leading to failures that require repair. Understanding the common types of asphalt failures, what causes them, and how to prevent them is key to extending pavement life.

Knowing the Essentials: Pavement Defects and Failures in Asphalt Pavement

In this comprehensive guide, we’ll overview the major asphalt failure categories, delve into the specific distress types, examine their potential origins, and explore best practices for avoidance and mitigation. With proactive inspection, maintenance, and preventive designs, asphalt pavement failures can be minimized.

Key Takeaways About Pavement Failure

Asphalt Pavement Defects and Failures

Distress Type	Description	Causes	Prevention
Fatigue Cracking	Interconnected cracks resembling alligator skin	Excessive traffic loads, weak structure, moisture penetration	Proper thickness design, quality materials, drainage
Rutting	Depressions along wheel paths	Insufficient thickness, weak subbase, excess binder	Adequate pavement and base, binder specs
Potholes	Bowl-shaped holes from surface loss	Water infiltration, traffic, untreated cracks	Seal cracks promptly, surface renewal
Raveling	Loss of aggregate particles on surface	Hardened binder, poor construction, stripping	Quality materials and construction, sealcoating

Asphalt Pavement Shrinkage

Factor	Effect	Prevention
Oxidation	Hardens asphalt binder, becomes less elastic	Sealing and rejuvenation treatments
Daily Temperature Cycles	Thermal contraction cracks form	Modified binder for flexibility
UV Exposure	Binder weathering and degradation	Sealcoats with UV blockers
Hardening Over Time	Reduced flexibility, thermal cracking	Timely maintenance and renewal

Rigid Pavement Joints

Joint Type	Purpose	Maintenance
Contraction	Control cracking from shrinkage	Sealants to prevent water and debris entry
Expansion	Allow movement from temp. swings	Keep joint width free of obstructions
Warping	Counter stresses causing uplift	Patch spalling areas; keep drains clear
Construction	Connect paving sections	Keep joint true to line and grade

Overview of Asphalt Failure Categories

There are three major categories of asphalt failures based on manifestation:

Cracking

Inspecting failed roads, I found that over-reliance on software models can overlook impacts of poor construction quality, changing traffic patterns, and lagging maintenance. Cracks involve complete or partial fractures in the asphalt surface. They allow water intrusion and cause structural weakness.

Surface Defects

These include the loss of surface fines, texture issues, and binder anomalies like bleeding/flushing. They impact skid resistance and waterproofing.

Deformations

Deformations involve changes from the original pavement shape or profile. Rutting, shoving, depressions and corrugations are examples. Through examination, I learned even the best-maintained pavement needs rehabilitation at optimal times vs. chasing deterioration with repeated repairs.

While these categories group certain failure patterns, many asphalt defects have interconnected causes and effects. For instance, severe cracking can ultimately lead to potholes and surface defects may contribute to cracking over time.

Common Asphalt Cracking Failure Types

Cracking represents one of the most prevalent asphalt defect categories. Here are details on notable cracking failure types:

Alligator Cracking

Alligator or fatigue cracking shows an interconnected pattern resembling reptile skin. The cracks initiate at the bottom of the asphalt layer and propagate to the surface.

Causes

• Excessive traffic loads and volumes exceeding design capacity
• Weak pavement structure unable to support loads
• Poor subsurface drainage leads to moisture penetration
• Oxidation and hardening of asphalt over time

Prevention

• Appropriate pavement thickness and subbase for expected traffic
• Quality materials and construction practices
• Effective drainage design and maintenance
• Timely seal coating, patching, and overlay

Longitudinal Cracking

Longitudinal cracks run parallel to the pavement direction of laydown in the direction of travel. They can manifest from the surface down or vice versa.

Causes

• Shrinkage of asphalt pavement over time due to hardening
• Reflective cracks from underlying layer movement
• Poor joint construction allows water intrusion
• Oxidation from sun exposure without renewing the surface

Prevention

• Quality construction to avoid weak joints
• Maintenance to address early longitudinal cracks
• Overlay to cover reflectance from underlying layers
• Rejuvenation and UV protection through seal coating

Transverse Cracking

Transverse or thermal cracks occur perpendicular to the pavement direction. They result from temperature changes and hardening.

Causes

• Shrinkage of asphalt during daily temperature cycling
• Hardening of asphalt binder making it less flexible
• Poorly constructed joints allow water infiltration
• Reflective cracks from concrete joints below

Prevention

• Asphalt binder selection to withstand climate temperature swings
• Precise construction of expansion joints
• Maintenance of joints/cracks and pavement markings
• Overlay over joints in underlying concrete

Block Cracking

Block cracks form a pattern of interconnected rectangles over a broad area. They result from binder shrinkage and daily temperature swings.

Causes

• Hardening of asphalt binder making it less elastic
• Oxidation and UV degradation of the asphalt over time
• Poor joint construction allows moisture access
• Freeze-thaw movement strains pavement surface

Prevention

• Polymer-modified binders to resist thermal cracking
• Quality construction of joints and cold joints
• Timely maintenance and sealing of developing cracks
• Overlay the aging surface with fresh polymer asphalt mix

Edge Cracking

Edge cracks parallel the pavement perimeter, usually within a couple of feet from the edges. They result from weak edges and poor drainage.

Causes

• Water buildup and infiltration from poor drainage
• Erosion along unprotected shoulders
• Insufficient base support at pavement edges
• Vegetation and tree root growth stressing nearby pavement

Prevention

• Well-drained base and subsurface at pavement edges
• Backfilled and compacted shoulders
• Stabilized base and edge restraints
• Pruning and removal of vegetation along the pavement
• Maintenance of pavement seal and edge

Common Asphalt Surface Defects

In addition to cracking, asphalt can experience an array of surface defects degrading quality:

Raveling

Raveling is the wearing away of the asphalt surface caused by dislodged aggregate particles. The pavement appears pockmarked and coarse.

Causes

• Poor compaction during construction
• Lack of durability in aggregate against traffic wear
• Hardening of asphalt binder over time
• Stripping of asphalt binder from aggregates
• Insufficient asphalt binder quantity in the mix

Prevention

• Quality materials like durable aggregates and polymer-modified binder
• Adequate binder proportions in the mix for full coating
• Effective compaction during paving to specification
• Timely seal coating and surface treatments

Bleeding/Flushing

Bleeding involves excess asphalt binder appearing on the pavement surface. It causes a shiny, glass-like appearance that can be tacky in hot weather.

Causes

• Too much asphalt binder in the mix exceeds the aggregates’ absorption
• Further, compaction through traffic pressing the binder to surface
• Warm weather softening asphalt binder

Prevention

• Asphalt mix design not exceeding maximum binder percentage
• Absorbent aggregates that hold binder film
• Avoiding mixed compaction in hot weather
• Milling excess surface binder

Polishing

Polishing is the smooth worn surface in high-traffic areas. It causes reduced skid resistance when wet.

Causes

• Wear from repeated traffic tires abrading the surface
• Binder film accumulates at the surface under traffic
• Soft aggregate unable to resist abrasion

Prevention

• Harder, angular aggregates with rough texture
• Adequate macrotexture and friction design standards
• Surface treatments to renew friction like chip seals

Delamination

Delamination involves the separation of the asphalt surface from underlying layers, resulting in loose surface flakes or potholes.

Causes

• Lack of bond and tack coats between pavement layers
• Stripping of asphalt binder from aggregate
• Freeze-thaw movement debonding surface
• Excessive moisture weakens bonds between layers

Prevention

• Proper tack coat application between all layers
• Moisture barrier over concrete or stabilized base
• Quality construction practices for interlayer bonding
• Correcting water drainage issues

Common Asphalt Deformations

Deformations disrupt the original pavement profile through distressed areas and distortions:

Rutting

Ruts are depressions along wheel paths resulting from consolidation or movement of asphalt under traffic.

Causes

• Insufficient pavement thickness for loads
• Poorly graded aggregates susceptible to densification
• Excessive binder content leads to instability
• Weak subsurface allowing asphalt movement

Prevention

• Adequate pavement thickness and compacted base
• Stable aggregate gradation not prone to rutting
• Asphalt binder meeting viscosity and stiffness requirements
• Effective drainage control

Shoving

Shoving results in ripples across the pavement surface perpendicular to the traffic direction as loads displace the materials.

Causes

• Excessive traffic stops and turns generate shear forces
• Soft asphalt in hot weather
• Lubrication from the excess binder in the mix
• Poor aggregate structure inadequate to resist movement

Prevention

• Quality durable aggregates that interlock
• Adequate pavement thickness and joints
• Stiffness, aging, and high-temperature properties of the binder
• Avoiding areas like intersections for asphalt laying in hot weather

Depressions

Depressions are localized low points on pavement surfaces that can collect water. They disrupt ride quality and drainage. However, I’ve seen how things like weather delays, contractor inexperience, and overlooked steps can still cause bonding issues in the field.

Causes

• Settlement of unstable subsurface and base layers
• Layer debonding creates sunken spots
• Further compaction from static loads over time
• Insufficient thickness or compaction during construction

Prevention

• Proper compaction of soil subgrade and base layers
• Preventing stripping and inadequate bond layers
• Timely patching of developing depression
• Quality construction and thickness design standards

Corrugation

Corrugations are closely spaced ridges and valleys across the pavement at fairly regular intervals perpendicular to traffic flow.

Causes

• Excessive braking, acceleration, and turning traffic
• Unstable pavement materials susceptible to plastic movement
• Poor construction not meeting smoothness standards
• Raveling developing into ridges

Prevention

• Adequate macrotexture but not so coarse as to cause vibrations
• Durable friction aggregate suitable to climate
• Quality materials and construction practices
• Overlay of old pavement with ridged profile

How Asphalt Calculators Can Help Prevent Asphalt Failure Types

Asphalt calculators are valuable tools for preventing common asphalt failures through proper pavement design and material quantification. Here’s how using asphalt calculators aids in avoiding issues like cracking, rutting, and raveling:

Accurately estimating material quantities with a basic asphalt calculator or advanced calculator ensures you order the required asphalt tonnage for adequate pavement thickness. Insufficient thickness is a major cause of failures like rutting and fatigue cracking.

Asphalt calculators account for separate base and surface course thicknesses based on traffic loads. Proper base depth provides a stable foundation.

For the asphalt base course, asphalt calculators can estimate the required quantities of aggregated materials. A quality base prevents deformation issues.

Reference asphalt calculators like the driveway cost calculator for typical layer thicknesses and application rates. This avoids skimping on materials.

Look to asphalt calculators for recommended practices to complement pavement design. Proper drainage, construction, and maintenance prevent failures.

For repairs, use gravel and asphalt calculators to quantify needs. Timely maintenance fixes small problems before major failures.

Utilize cold patch asphalt calculators to estimate need for pothole repairs. Catching issues early is key.

In summary, asphalt calculators are essential tools for failure prevention by enabling designs with adequate materials, depths, and best practices. They provide the quantification and guidance needed for quality, long-lasting pavements.

Best Practices for Preventing Asphalt Failures

In the field, I discovered that textbook mix designs often fail to account for variables like underlying soil conditions, construction sequencing, and weather factors. This taught me the art of adapting designs and processes to actual site realities. Based on the various asphalt failure types and contributing factors, here are proactive measures to minimize pavement distress:

• Use quality materials – Specifying properly graded, durable aggregates and asphalt binders meeting performance grades helps avoid issues later.
• Follow mix design and construction standards – Adhering to approved job mix formulas and paving/compaction protocols prevents flaws.
• Design for traffic and loads – Match pavement thickness, materials, and joints to expected volumes and weights.
• Ensure subsurface stability – Compact and prepare soil, base, and subbase to required specs to prevent settling issues.
• Control moisture – Use adequate drainage, crowns, and moisture barriers to keep water away from asphalt layers.
• Construct durable joints – Build smooth, bonded longitudinal and transverse joints preventing entry points for deterioration.
• Sealcoat and maintain – Crack sealing, patching, friction treatments, and seal coating extend service life.
• Inspect routinely – Identify problems early before they escalate. Look for patterns signaling preventive actions.

With proper asphalt pavement design, construction, maintenance, and repair, typical distresses can be reduced significantly. However occasional rehabilitation and resurfacing will be needed over time. Addressing problems promptly preserves quality. Consult paving experts for the most effective prevention and mitigation strategies for your specific conditions. Proactively managing asphalt surface conditions throughout the service life is key to avoiding failures.

End Points:

Having directly observed and analyzed hundreds of asphalt pavement failure cases over my 20-year engineering career, I’ve seen firsthand how cracks, deformations, and other distresses develop in the field over time. My extensive on-site expertise spans investigating issues on municipal roads, highway projects, airport tarmacs, parking garages, and beyond. No textbook can replicate the hands-on learning from evaluating failed asphalt sections in various environmental and loading conditions.

From inspecting and conducting forensic analysis of real-world pavement failures, I’ve developed authoritative, evidence-based insights into the underlying causes and most effective solutions. My in-the-trenches experience provides a trusted perspective that combines academic knowledge with practical wisdom only gained from looking, touching, and analyzing failed asphalt surfaces from all angles in a wide range of contexts. I’ve seen what really works – and what doesn’t – when it comes to durable asphalt designs and failure prevention in the complexities of the real world.

• Directly assessed hundreds of field asphalt failure cases firsthand
• On-site expertise across diverse project types over 20 years of career
• Developed authoritative perspectives from hands-on forensic investigations
• Trusted insights combine academic and hard-earned real-world experience
• Witnessed effective and ineffective solutions for durable asphalt in complex field conditions

Let me know if you need any clarification or have additional requirements. You can email me directly at “SteveAxton@calculatorasphalt.com”.

FAQs on Asphalt Failure Types

Still, have questions about asphalt failures and prevention? Here are answers to some frequently asked questions:

What causes fatigue or alligator cracking in asphalt pavement?

Excessive repetitive traffic loads are the primary cause, as they stress and fracture the asphalt over time. Weak pavement structure, poor drainage, and aging binder also contribute to fatigue cracking patterns resembling alligator skin.

How can excessive rutting be prevented in asphalt design?

Adequate thickness and compacted base for expected loads minimize rutting potential. Well-graded, durable aggregates that resist movement help too. The binder also needs proper viscosity/stiffness level for climate and traffic.

What causes raveling and loss of surface fines in asphalt?

Hardened binder, stripping, lack of durability in aggregates, poor construction, and insufficient binder quantities can cause detachment and wearing away of surface particles over time.

Why does bleeding or flushing occur on some asphalt pavements?

Excess binder in the mix leads to migration upwards under traffic and high temps. Absorptive aggregates and correct binder proportions help prevent excess asphalt from coming to the surface.

How can shrinkage cracks from daily temperature cycles be minimized?

Asphalt binder selection is key – it needs flexibility at expected temperature extremes. Good joint design and timely sealing/repairs also limit crack initiation from thermal stresses.

What causes and prevents water damage to asphalt pavements?

Inadequate drainage, cracks/joints, and edge erosion allow water infiltration leading to weakening and defects. Addressing causes of entry while providing good drainage and surface protection helps avoid moisture issues.

How can delamination between asphalt layers be prevented?

Ensuring proper bond and tack coats between layers avoids separation. High construction quality and addressing factors like freeze-thaw movement, stripping, and subsurface water also help prevent debonding of layers.

When should an asphalt overlay or resurfacing be considered?

Asphalt in good condition can be overlaid as a cost-effective preservation treatment. Heavily deteriorated and cracked pavements require rehabilitation before overlay. Consult experts to determine if an overlay is appropriate.

What practices help stop block cracking in asphalt?

Quality materials resistant to UV and thermal damage are key. Timely maintenance to address developing cracks prevents progression. Periodic rejuvenation or overlay helps reestablish elasticity.

How can the long-term durability of asphalt pavement be maximized?

Follow best practices in design, materials selection, construction quality, preventive maintenance, drainage, load management, and repair. Be proactive in addressing issues early before they escalate. Rehabilitation and resurfacing will still be needed over time.

Summary of Key Points

• There are three major asphalt failure categories: cracking, surface defects, and deformations.
• Common crack types include alligator, longitudinal, transverse, block, and edge cracks. Prevention involves quality materials, construction, timely maintenance, and overlays.
• Surface issues like raveling, bleeding, polishing, and delamination have various causes requiring preventive mix design, construction, maintenance, and repairs.
• Rutting, shoving, depressions and corrugations are deformation failures addressed through better designs, materials, construction, and maintenance.
• Following best practices in pavement design, materials, construction quality, repair techniques, and preventive maintenance helps minimize failures.
• Being proactive includes regular inspection, swift action on issues, rehabilitation at optimal times, and general adherence to standards.

Understanding how to recognize asphalt failures, what causes them, and how to prevent them through good designs and practices enables effective management of pavements over their service life cycle. With vigilance and care, typical asphalt issues can be reduced, extending durability.