$\rightarrow$ (MU – Dec. 12, May 13, May 14)

Following are the various failure occurs in rigid pavement:

1. Shrinkage cracks.

• After casting of the cement concrete pavements, the next procedure on next day is curing for getting strength.

• During curing process, the shrinkage cracks are generally developed in longitude and transverse direction.

2. Scaling of cement concrete.

• Scaling is caused by the deficiency in the mix or presence of chemical impurities and scaling is also caused by excessive vibration given to the mix.

• This vibration brings the cement slurry or cement mortar on the top surface during construction. Due to deficiency, chemical impurities and excessive vibration, pavement surface becomes more rough in appearance.

3. Warping cracks.

• Improper design of joints makes warping of slab at edges. Due to this, there is development of excessive stresses producing the cracks at the edges.

• Warping cracks are prevented by providing the hinge joints.

4. Mud pumping.

$\rightarrow$ Mud pumping.

When the soil slurry comes out through the joints and cracks of cement concrete pavement due to heavy wheel loads, then it is called as Mud pumping.

• Mud pumping makes downward movement of slab under the heavy load of vehicles.

• Following are the various factor which are more responsible for mud pumping.

1. Amount of free water.

2. Slab deflection.

3. Sub grade soil type.

4. Lack of support.

Fig. 7.2.9 shows slurry comes out through the joints due to Lack of support.

Fig. 7.2.10 (a) and (b) shows there is progressive increase in the wheel load in the pavement slab because of reduction in sub-grade support which develops the cracks and mud pumping and finally pavement fails.