Main causes of cracks in Asphalt Pavement
November 11th, 2021
There are many reasons for asphalt pavement cracking, which can be divided into three categories:
One is the structural damage crack caused by the action of driving load. Under the action of wheel load, when the tensile stress at the bottom of pavement structure layer is greater than the tensile strength of its material, the crack is called load type crack.
The second is the temperature cracks caused by the temperature change of asphalt surface, including low-temperature shrinkage cracks and temperature fatigue cracks, which are called non load cracks.
Third, there are often transverse cracks at both ends of bridges and culverts, or long longitudinal joints on road sections, which are mainly caused by consolidation settlement of fill or foundation settlement, which is called settlement cracks. Although there are many causes and forms of cracks in asphalt pavement, the driving load and the temperature change of asphalt pavement are the main causes of cracks.
Transverse crack
(1) temperature shrinkage cracking of asphalt pavement;
(2) the cracking of semi-rigid base course, especially cement stabilized macadam, is reflected to the asphalt surface course;
(3) horizontal crack of pavement caused by excavation of some base courses, embedding of pipelines and frost crack of Subgrade in frozen areas;
(4) during the construction of surface course, the construction joint is not handled well, the joint is not tight and the combination is poor.
(5) consolidation or foundation settlement caused by filling on both sides of bridges, culverts or channels.
Longitudinal crack
(1) the non-uniformity of filling materials and filling, and the compactness of filling can not meet the design requirements. After a period of natural settlement, especially after rain soaking, the subgrade strength decreases, and the bearing capacity of some Subgrade along the slope also decreases, and longitudinal cracks will appear.
(2) during construction, the cold joints at the joints of the front and rear pavements are not handled carefully according to the requirements of relevant specifications, and the combination is not tight and separated;
(3) settlement due to poor compaction quality of backfill in longitudinal trench;
(4) the soil layer at the junction of new and old pavement in the widened section is not treated thoroughly, and the uneven settlement causes longitudinal cracking;
(5) the slope value is less than the design value, and the longitudinal cracking caused by landslide due to insufficient slope compaction and too deep side ditch.
Reticular crack
(1) cracks caused by insufficient compactness of subgrade or local looseness of base course materials, which reduces the bearing capacity of pavement;
⑵ the quality of asphalt and asphalt mixture is poor. Asphalt has low ductility and poor crack resistance. Cracks caused by too long mixing time, too high mixing temperature or too long storage time in the storage bin, which hardens the asphalt and is sensitive to tensile strain;
(3) the asphalt layer has insufficient thickness, poor interlayer bonding and water infiltration, resulting in cracks;
(4) fatigue cracks caused by repeated driving load.
(5) local network cracks caused by external causes such as pollution and corrosion.
Reflection crack
(1) cover the cracked old asphalt and cement concrete pavement with asphalt surface. Due to the change (decrease) of temperature, the cracks of the old pavement continue to expand, giving an additional stress to the new asphalt surface which is also in temperature shrinkage, so that the new pavement is disconnected at the old crack.
⑵ reflection cracks caused by temperature shrinkage and dry shrinkage cracking of semi-rigid base.
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