Below you can find some major causes of road crack and road defects. The page also provides what are the effects if these road defects are not properly addressed.
Alligator Cracking
Alligator cracking is a series of interconnecting cracks creating interconnected patterns on the road. The cracks start at the bottom of asphalt surface and propagate to the surface, initially as one or more longitudinal parallel cracks.
After repeated traffic loading, the cracks interconnect, forming many‐sided, sharp angled pieces that resemble chicken wire or the skin of an alligator. Alligator cracking occurs normally only in areas subjected to repeated traffic loading, such as wheel paths.
Possible Causes of Alligator Cracking
- Inadequate pavement thickness.
- Low modulus base.
- Brittle base or wearing course (e.g. cemented aged).
- Fatigue failure of asphalt pavement due to repeated traffic loading.
Transverse Cracking
Transverse cracks run perpendicular to the direction of traffic flow. Transverse cracks can start at the curb or shoulder, be contained in only one lane, or extend completely across the roadway. These cracks can also start in the middle of a lane or at the center line.
Possible Causes of Transverse cracks
Reflection of shrinkage crack or joint in underlying base(common with Portland cement concrete or cemented materials).
Construction joint or shrinkage crack (due to low temperatures or bitumen hardening) in asphalt surfacing.
Structural failure of Portland cement concrete base.
Longitudinal Cracking
Longitudinal cracks occur parallel to the direction of traffic flow. Longitudinal cracks can occur along the center line, in mid‐lane, in the wheel tracks and along the edge. Cracks can be relatively short in length or run the entire length of a pavement section.
Causes of Longitudinal Cracking
Reflection of shrinkage crack or joint in underlying base (common with Portland cement)
Concrete, cemented base of asphalt surfacing.
Poorly constructed paving lane joint in asphalt surfacing.
Daily temperatures cycle or asphalt hardening.
Effect of alligator,transverse and longitudinal cracking (if neglected)
Allows water to enter the pavement causing softening and weakening of the pavement and layers.
This may cause early failure of the pavement.
If severe, cause uneven ride for the motorist and may reduce traffic speed.
Pothole on the road surface
A defect on the surface of the paved (bitumen) roads.
Potholes are small bowl –shaped depressions on the pavement surface/base course, usually less than one meter in diameter.
They generally have sharp edges and vertical sides near the top of the hole. Their growth is accelerated by free water collecting inside the hole.
Potholes are reproduced when traffic abrades small pieces of pavement surface.
The pavement then continues to disintegrate because of poor surface quality, weak spots in the base or sub grade, or because of severe alligator cracking.
Most potholes are due to structurally related distress, and should not be confused with raveling and weathering.
When holes are created by high-severity alligator cracking, they should be identified as potholes.
Possible Causes of Pothole
- Asphalt content too low,
- Excessive heating of asphalt,
- Poor quality mixtures,
- Lack of compaction allowing ingress of water.
- Excessive axle loads,
- Mechanical damage to the road due to poor reinstatement of roads after services installations,
- Injury to pavement,
- Spills or leakages
Effect of pothole if not repaired
Allows water to enter the pavement causing softening and weakening of the pavement and lower layers, his may cause early failure of the pavement,
If left un-repaired, damage can rapidly expand,
Can create poor rides quality for motorist and may reduce traffic.
Reporting potholes
For reporting the potholes, you need quantification of length, width, depth and number of potholes.
You will need basic road inspection tools like measuring tape and camera.
Rutting/Deformation
Rutting is characterized by longitudinal depressions in the pavement surface that occur in the wheel paths of a roadway.
If water is able to penetrate into the body of the pavement, there will be a rapid increase in the degree of rutting, which often leads to cracking and the breaking up of the pavement, if excessive, can reduce serviceability and reduce vehicle travel speeds and in very severe cases, may be an accident risk.
Possible Rutting Causes:
- Inadequate pavement thickness,
- Inadequate compaction in surfacing or base,
- Inadequate strength (stability) in surfacing or base,
- Excessive bitumen in mix,
- Excessive axle loads.
Frost Heaving
Frost heaving is characterized by longitudinal depressions in the pavement surface.
Asphalt surface is more strongly cooled than other natural surface especially when snow is removed from the surface.
The defrection is caused by the ice lenz in the soil.
Possible Causes of Frost Heaving:
High grand water level
Water contents in the base course or road bed frozen and push pavement surface which caused surface defection.
Loss of the bearing force by melting ice in the pavement
High water contents in the base course
Effect (if neglected):
- Surface deflection
- Loss of bearing force of the pavement
- Destruction of the pavement
Thermal Crack/ Low Temperature Road Crack
Cracks caused by shrinkage of the asphalt mixture by low temperature. It is observed in the cold weather area.
Traverse crack at the equal interval of 10m to 20m is observed.
This crack is normally limited only surface course but required treatment such as sealing of the crack to avoid penetration of water.
Monitoring regular inspection is recommended.
Possible causes of thermal or low temperature crack include shrinkage of the asphalt mixture by low temperature or insufficient pavement thickness.
Reflection Road Crack
This crack happens due to existing crack of the under layer structure of the pavement such as joint of base course, crack of the cement stabilized course etc.
Also the reason can be a crack of the asphalt pavement which is paved over the old concrete pavement. Cracks of under layed concrete pavement cause the cracks
Cracks found on the overlay pavement which is constructed on the surface without sufficient remedy of the defects such as potholes.
If not properly repaired reflection crack can expand to larger defects such as pothole.
Possible Causes:
- Crack of underneath layer
- Possible by underground structures (pipe culvert etc.,)
Uneven Road Settlement
Normally longitudinal crack along the road at the border of embankment and cut cause of settlement of embankment.
Also observed at the concrete structure due to insufficient compaction.
If neglected it is possible to cause large scale slope failure.
Possible Causes:
- Difference of bearing force between cut and embankment
- Insufficient compaction at small area
- Loss of bearing force by penetrating of rain water into base course
- Consolidation
Road Corrugation
Plastic deformation of the surface with waving at small pitch on the longitudinal direction.
The deformation disturbs comfortablity of the drivers by giving vibration. If not repaired it may cause slide of surface layer, that may extend to the potholes.
Possible Causes of Road Corrugation:
Loss of the stability of asphalt mixture at high temperature
Insufficient construction of prime coat and tack coat
Excessive moisture in the base course and air void in the asphalt mix
Heaving/ Shoving
Usually heaving/shoving occurs on either side of the wheel tracks. The irregularities are associated with deformation and subsidence.
If neglected heaving may cause forcing up of weak materials as deformation occurs and progressive disintegration of the pavement.
Possible Causes of heaving
Ingress of water: reduced bearing capacity of the pavement.
Materials: of poor quality.
Workmanship: insufficient compaction.
Traffic: passage of vehicles which are too heavy for the pavement structure.
Pavement Stripping/Fretting
Stripping/fretting is the wearing away of the pavement surface caused by the dislodging of aggregate particle and loss of asphalt binder. This generally indicates that the asphalt binder has hardened significantly. Loss of coarse aggregate of a sprayed seal that leaves the binder exposed to tire contact can happen bit by bit, or over a localized area.
In long term this may cause progressive breaking away of chippings resulting in surfacing becoming more slippery and more permeable.
Possible Causes of stripping:
- Low binder content,
- Poor binder to stone adhesion (dirty aggregate, ineffective pre‐coating with adhesion agent or wet stone,
- Ageing or absorption of binder,
- Stone deterioration,
- Inadequate rolling before opening of seal to traffic,
- I incorrect bleeding of binder,
- Poor workmanship.
Road Surface Bleeding
Bleeding is a film of bituminous material that covers the pavement surface and which creates a shiny, glass like appearance. It occurs when asphalt fills the void of the mix during hot weather and then migrates to the pavement surface.
Due to this problem road surface becomes slippery and hazardous to traffic. Other problem can be separation and breaking away of surface layer due to traffic.
Possible causes of pavement bleeding include:
Excessive application of binder with respect to stone size.
Excessive prime coat incorporated into the seal
Excessive binder in underlying surface (patches or flushed area)
Prime seal covered before volatile material in primer binder evaporated.
Polishing
The condition of the surface with loss of slip resistance due to coarse aggregate and mortal is polished by vehicle. This may lead to loss of slip resistance and extend to pothole.
Possible causes of the polishing problem include use of aggregate with insufficient flakiness and excessive friction to the road surface by large vehicles (especially at curves).
Delaminate of binder, Slipping
Surface course is delaminated due to the sharing stress between layers, which may grow rapidly to the large defect or large deflection of the surface.
Possible causes include:
- Insufficient joint between pavement layers.
- Water penetration into the pavement layers.
- Excessive tack coat or insufficient tack coat
- Excessive difference of the elasticity between layers.
Pavement Edge Damage
Edge damage is a difference in elevation between the pavement edge and the shoulder and occurs along the edge of the pavement. It may cause rapid deterioration during rainy season and traffic will worsen this defect if not repaired.
Possible Causes:
- Shoulder wears (formation of step),
- Erosion by water,
- Insufficient compaction at edges of bituminous pavement.
- Road too narrow,
- Excessive axle loads.
Road Surface Waving
Undulations in road surface of a wavelength longer than corrugations. In hot weather, surface stripping can occur, that is reason of poor ride quality for motorists.
Possible causes of waving include:
- Poor quality material,
- Variation in compaction and bearing capacity of lower layers,
- Poor quality or lack of prime coat or tack coat,
- Material not suited to temperature range.
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