Dowel bars in concrete slab

Concrete has to face lot of hostile environmental forces. Concrete can expand or contract because of temperature, stresses due to various kind of load etc to maintain functional capacity in such way so that it does not get cracked, allow transfer of load without faulting at joints, in practice this is achieved by small steel rods called Dowel bars.

corrosion risk -dowel bars
                           Dowel bar

Dowel bars are place at transverse joints of concrete pavements to provide a connection between two slabs. Dowel bars are used in new construction like roads and rehabilitation projects such as slab replacement.

  1. Dowel bars are the device through which wheel loads are transferred from one slab of pavement to the next.
  2. Dowel Bars will significantly reduce the magnitude of the stresses and deflections at the slab joints.
  3. Dowel Bars prolong the useful life of concrete pavements.

 

Dowel bars  will extend service life of the project by improving load transfer and prevent faults at joints. Dowel bar of  30, 32, 36, 38 & 40 mm  Dia and 510 mm long are generally used.

 

Higher Corrosion Riskcorroded dowel bar in slab

Dowel bars are at higher risk of corrosion due to following reasons:

  1. Joints allow direct passage to aggressive agents like oxygen, moisture, chloride etc to the surface of dowel bar. It is further aggravated due to direct exposure to high and low temperature.
  2. Bond between dowel bar and concrete also allow easy diffusion to aggressive ions due to cyclic horizontal movements between the slabs.

 

Corrosion prevention

Dowel bars should be protected from corrosion although joints are sealed to keep water penetration to a minimum; water will seep over time and may corrode unprotected bars.

Typically dowel bars are protected from corrosion by application of epoxy coating or stainless steel clad bars. Epoxy coating’s smooth and almost friction-less surface provides easy horizontal movement in concrete so that slabs move independently which prevents slabs from excess stresses.

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