Failures in Rigid Pavements

Hi,

Failures in cement concrete pavements are recognized mainly by the formation of the structural cracking.

Failures occur due to two factors:

(a) Deficiency of pavement materials.

(b) Structural in-adequacy of the pavement system.

Deficiency of the Pavement Materials:

Soft aggregates
Poor workmanship in joint construction
Poor joint filler or sealer material
Poor surface finish
Improper and insufficient curing.

Here are the various defects that creep in due to the causes above:

Dis-integration of the cement concrete
Formation of cracking
Spalling of joints.
Poor riding surface
Slippery surface
Formation of shrinkage cracks
Ingress of surface water and further progressive failures.

Also Read: Failures in Flexible Pavements

Structural in-adequacy of Pavement System:

Inadequate sub-grade support, less pavement thickness would be a major cause of developing the structural cracking in pavements. Following are the causes and types of failure which develop:

Inadequate pavement thickness
In-adequate sub-grade support and poor subgrade soil
The incorrect spacing of joints.

Above would give rise to the failures of the following types:

Cracking of the slab corners
Cracking of the pavement longitudinally
Settlement of slabs
Widening of joints
Mud Pumping.

Now here are the typical pavement failures which occur in the rigid pavements and will be discussed here are details:

Scaling of the cement concrete
Shrinkage cracks
Spalling of joints
Warping cracks
Mud Pumping
Structural cracking

Scaling of Cement Concrete:

Whenever there are deficiencies in the concrete mix or presence of some chemical impurities may result in the scaling of the cement concrete. Also when excessive vibrations are given to the mix, cement mortar will come on top during the construction and thus with use the cement mortar gets abraded exposing the aggregates of the mix. This makes the pavement surface rough and shabby in appearance.

Shrinkage Cracks: During the curing operation of cement concrete pavement immediately after the construction, the shrinkage cracks normally develop. The placement of cracks is in longitudinal as well in the transverse direction.

Spalling of Joints:

Sometimes when pre-formed filler materials are placed during the casting of pavement slabs, the placement is somehow dislocated and filler is thus placed at an angle. The concreting is completed without noticing this faulty alignment of the filler material. Thus this forms an overhang of a concrete layer on the top side and the joint, later on, shows excessive cracking and subsidence.

Also Read: Failures in Flexible Pavements

Warping Cracks:

If the joints are not well designed to accommodate the warping of slabs at edges, this results in the development of excessive stresses due to warping and the slab develops cracking at the edges in an irregular pattern. Hinge joints are generally provided for relieving the slabs of warping stresses. There is no structural defect due to warping cracks if proper reinforcement is provided at the longitudinal and transverse joints as it takes care of the structural in-adequacy.

Thanks!!

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