Pavement Distresses Flexible 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 Counties

MN LRRB • Distress Identification for the Long Term Pavement Performance Program SHRP

Identifying the Distress is the 1 st 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