- 2076 Asoj · 8 marks
Repair vs rehabilitation; rigid pavement failures
Short answer
Repair fixes localized defects (e.g., patching potholes) for short-term function; rehabilitation restores structural capacity along a whole length (e.g., overlay) for long-term improvement. Typical rigid pavement failures: transverse and longitudinal cracking, corner breaks, punch-outs, faulting, pumping, spalling, blow-up, scaling, and joint seal failure, caused by load, temperature, and poor support.
Differentiate between Repair and Rehabilitation of highways. Explain about different types of typical rigid pavement failures. Draw a sketches wherever applicable.
Repair vs rehabilitation of highways
| Basis | Repair | Rehabilitation |
|---|---|---|
| Meaning | Correcting local defects to restore function | Restoring or upgrading the structural capacity of a whole length |
| Scale | Localised: patches, crack sealing, joint resealing | Extended: overlay, slab replacement, recycling |
| Cause | Isolated damage | General structural deterioration or increased traffic |
| Cost and effect | Low cost, short-term effect | High cost, long-term effect |
| Example | Patching potholes; repairing spalled joints | 100 mm bituminous overlay; concrete overlay; replacement of failed slabs |
Types of failure of rigid pavement
Typical types of failure of a cement concrete pavement:
| Failure | Description | Cause |
|---|---|---|
| Transverse cracking | Cracks across the slab | Late sawing of joints, joint spacing too long, thin slab, restrained shrinkage |
| Longitudinal cracking | Cracks along the lane | Differential settlement, warping, thin slab, poor subgrade support |
| Corner break (corner crack) | A triangular piece cut off at the slab corner by a crack meeting both edges, usually within about 1.5 m of the corner | Load at an unsupported corner, loss of support (pumping), poor load transfer |
| Diagonal cracking | Crack at about 45 degrees | Heavy corner loads, settlement |
| Punch-out / shattered slab | Slab breaks into many pieces | Heavy repeated loads, weak sub-base |
| Faulting | Step between slabs at a joint | Pumping, poor load transfer (dowel failure) |
| Pumping | Ejection of water and fines at joints | Water under the slab, loose subgrade, heavy traffic |
| Spalling | Breaking of joint edges | Incompressible material in joints, weak concrete, dowel misalignment |
| Blow-up (buckling) | Slab lifts and shatters in hot weather | Blocked expansion joints, insufficient expansion gap |
| Scaling and crazing | Flaking and map cracks on the surface | Over-finishing, poor curing, freeze-thaw |
| Joint seal failure | Loss of sealant, weeds in joints | Aged sealant, poor installation |
Faulting at a joint Corner break
______ +-------------+
______| step | |
joint | |
| crack -> /
+-----------/-+
Remedies include full-depth repair, slab replacement, dowel retrofit, grinding of faults, crack and joint resealing, undersealing (grouting) to fill voids, and improving drainage.
✓ Answer checked by Claude Opus 5.5 (high effort)
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