pavement road defects 807


There are many types of roads but pavement roads are the most popular specifically those with asphalt or tarmac. in this article we will cover the most common defects and their causes :-

  1. Alligator cracking – This is a pavement defect brought about by poor drainage, weak base, sub grade  or just excessive loading in the road. it forms cracks that resemble an alligators skin.  I recommend a full depth patch. 
  2. longitudinal cracks – This are cracks that form longitudinally across the surface of the pavement road parallel to the center line. They are brought about by pavement fatigue, shrinkage of asphalt layer, temperature cycles or poor joint crack. I recommend maintenance of drainage and remove source of water. Seal crack with asphalt emulsion slurry or light grade asphalt mixed with fine sand.
  3. transverse cracking – this resembles longitudinal cracking but at this instance the crack is perpendicular to center line. Its causes are just like the longitudinal cracks. I recommend maintenance of drainage and remove source of water. Seal crack with asphalt emulsion slurry or light grade asphalt mixed with fine sand.
  4. block cracking – This are block shaped cracks along the road surface. They are caused by old and dry mix, mix placed dry, Fine aggregate mix & low penetration asphalt absorptive aggregates but unlike alligator cracking its not brought by excessive loading in the road but by low traffic volume. I recommend a surface treatment or thin overlay. 
  5. Edge cracks – This are cracks forming across edges or in shoulders. They are caused by lacking lateral support, weak base or sub grade, frost, poor drainage, soil shrinkage, settlement, vegetation along edge, heavy traffic along edge. I recommend removal of vegetation across edge, improved drainage, Fill cracks with asphalt emulsion slurry or emulsion asphalt crack seal or fill. 
  6. Joint reflection cracks – its a combination of transverse and longitudinal cracks criss-crossing i.e forming a joint. it caused by disparity in movement between the asphalt and concrete layers with deteriorates further under heavy traffic.I recommend a crack seal or fill. 
  7. slippage cracking – This are skid marks left on surface of pavement. They are brought by lack of tack coat use, high sand content mixture, Lack of a good bond between surface layer and the course beneath it. I recommend partial or full depth patch.
  8. pot holes – This are pot shaped holes across the surface of the road. They arise from deterioration of another type of distress, poor surface mix, weak points in base or sub grade. I recommend partial, full depth or injection patching. 
  9. depressions – This form indentations in asphalt and are also known as bird baths. They come from lack of good road construction methods, settlement in lower pavement layers. I recommend cold mill and overlay, thin surface patch or Infrared patch. 
  10. rutting – they are channeled depressions in the wheel tracks. They are caused by lack of compaction, weak asphalt mixtures, moisture causing weakness, lateral movement of any of the pavement layers or the sub grade under heavy traffic. I recommend cold mill and overlay or thin surface patch.
  11. shoving – This is the formation of ripples in the road surface. it is also known as wash boarding. its caused by too high fine aggregate content, incorrect asphalt grade, low air voids, mixtures too high in asphalt. I recommend deep or full-depth patch.  
  12. corrugations – This are uneven spots in road surface almost similar to shoving. its caused by too high fine aggregate content, incorrect asphalt grade, low air voids, mixtures too high in asphalt. I recommend deep or full-depth patch.  
  13. upheaval –  This is upward movement in a pavement. is caused by swelling of the sub grade, expansion of soils or frost heave. I recommend Full-depth patch.
  14. Ravelling – This is the weathering of the road which arises by a combination of traffic and water. it brought about by poor quality of mixture, asphalt binder hardening. I recommend surface treatment or thin overlay. 
  15. Bleeding – This is the colour change or fading of the road. it comes from too much asphalt in a mix, heavy tack coat, much sealant in the cracks or joints under an overlay & traffic. I recommend chip Seals, sandwich Seals or thin overlay. 
  16. longitudinal, transverse streaking – This is the formation of lines in the road surface either parallel or perpendicular to center line respectively. It is formed by changing spray bar height as the distributor load decreases, nozzle control linkage problem, improper application temperature of asphalt, aggregate not spread immediately. I recommend re-sealing of the surface with proper procedure & adjustment of equipment.  

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