Pavement Distresses Flexible Pavement Sponsored by: Minnesota LTAP Center Presented by: Michael Marti, P.E. SRF Consulting Group, Inc. Dan Wegman, P.E.

Pavement DistressesFlexible Pavement

Sponsored by: Minnesota LTAP Center

Presented by: Michael Marti, P.E.SRF Consulting Group, Inc.

Dan Wegman, P.E.SemMaterials

Various Rating Manuals

• Pavement Rehabilitation:A Guide for Minnesota Cities and CountiesMN LRRB

• Distress Identification for the Long Term Pavement Performance Program SHRP

Identifying the Distress is the 1st Step in the Process

Identifying Distresses Includes:

• Name• Severity• Amount

“Rate what you see and not what you think.”

Cracking

• Types– Fatigue– Thermal/Transverse – Block– Edge– Longitudinal– Reflection – Slippage

Fatigue Cracking

• Causes– Insufficient strength– End of pavement life– Too heavy of loads

• Cures– Remove and replace– Mill and overlay

Thermal Cracking (Transverse)

• Causes–Contraction and

Expansion of Pavement with Changing Temperatures

• Cures–Crack Filling–Full-Depth Reclamation–Thick Overlay

Block Cracking

• Causes– High Void Content– Oxidative Hardening of the AC– Thermal Cracking

• Cures– Crack Filling/Sealing– Seal Coat– Full-Depth Reclamation– Thick Overlay

Edge Cracking

• Causes– Soil Movement Beneath

Pavement

• Cures– Crack Filling/Sealing– Full-Depth Reclamation

Longitudinal Cracks

• Causes– Low Temperatures

• Cures– Crack Sealing– Thick Overlay

Reflective Cracking• Causes

– Existing cracks or joints in the underlying structure

– Concrete slab movements

• Cures– Crack Filling– Extensive Pre-Overlay Repair– Rubblizing– Crack & Seat– Saw & Seal– Interlayer

Slippage Cracking

• Description– U-shaped cracks in areas of braking, turning, accelerating

• Causes– Poor bond between asphalt surface and underlying layer

• Cures– Crack Filling/Sealing– Full-Depth Reclamation

Surface Defects• Rutting• Shoving• Bleeding• Polished Aggregate• Raveling• Potholes• Patching

Rutting• Causes

– Low Air Voids• Asphalt content

too high– Smooth, Rounded Aggregate

• Excessive amounts of natural sand

– Excess Dust

• Cures– Remove/Replace 100 mm (4 inches)– Micro-surfacing

Shoving

• Causes– Unstable Mix– Braking, stopping or

accelerating traffic

– Slippage between layers • Cures

– Remove and Replace– Mill and Overlay– Thick Overlay

Bleeding

• Causes– Too high asphalt content

• too rich a plant mix• improperly constructed

seal coat• too heavy prime or tack

coat

• Cures– Sand blot– Micro-surfacing– Seal coat

Polished Aggregate

• Causes– Soft aggregate– Heavy traffic

• Cures– Seal coat– Micro-surfacing– Thin Overlay

Raveling• Causes

– Asphalt binder unable to hold aggregate in place

• dusty aggregates• segregation • low in-place density• aged asphalt binder• Stripping

• Cures– Seal Coat– Micro-surfacing– Thin Overlay

Potholes

• Causes – Raveling of cracks– Moisture damage– Freeze-thaw– Insufficient strength

• Cures– Patch

Patch Deterioration

• Causes– Poor bonding to existing

pavement– Improper compaction– Poor materials– Propagation of

original distress

• Cures– Remove and replace– Re-patch– Assess original distress

Miscellaneous Distresses

• Lane-to-shoulder Drop off• Water Bleeding and

Pumping

Lane to Shoulder Drop off

• Cause– Differences in materials

used for lane and shoulder– Differential settlement– Insufficient compaction of

base

• Cures– Wedge/leveling overlay– Micro-surfacing

Water Bleeding and Pumping

• Causes– Cracks– Inadequate drainage

• Cures– Full-depth patch– Crack seal