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Various Cause of Disintegration of Water Bound Macadam and Surface Treated (Asphalt Roads):
1. Inadequate stability or strength
2. Loss of binding action
3. Loss of base course materials
4. Inadequate Weaving Course
5. Use of inferior materials
6. Lack of lateral confinement for the granular base course.
1. Inadequate Stability or Strength:
Poor Mix proportioning or inadequate thickness are main reasons for the lack of stability or strength of sub-base or base course.
2. Loss of Binding Action:
Due to internal movements of aggregate in sub-base a base course layers under the stress applications, the component structures of the layer get disturbed. There is also loss of binding action resulting in low stability and poor load transmitting property of the pavement layer.
3. Loss of base course materials
The loss of base course materials is only possible when either the base course is not covered with a weaving course or the weaving course has completely worn out. This causes removal of binding material in WBM base and the stons aggregator are left in a loose state.
4. Inadequate weaving course
Absence of weaving course or inadequate thickness or stability of weaving course expose the base course to the damaging effect of climatic variation mainly due to rains, frost action and the traffic.
5. Use of inferior materials
Many failures, mainly structural failure are attributed due to use of inferior materials in the passing jobs.
6. Lack of lateral confinement for the granular base course:
Due to lack of lateral confinement of granular base course, deterioration occurs.
Main faults occurring in WBM and surface treated (asphalt) roads:
- Alligator Cracking
- Consolidation of pavement layers
- Shear failure
- Longitudinal cracking
- Frost Heaving
- Lack of binding to lowers course
- Reflection crushing
- Formation of waves and corrugation
