The dowel bars in a rigid pavement are provided at ____.

A. Transverse joints

B. Longitudinal joints

C. Expansion joints

D. Contraction joints

Answer: Option C – Expansion joints


Contraction joint:

Contraction joint is a transverse joint.

The purpose of contraction joint is to control cracking due to pavement contraction caused by shrinkage and temperature fluctuations.

Expansion joint:

The purpose of the expansion joint is to allow the expansion of the pavement due to rise in temperature with respect to construction temperature. 

Normally, a structure exceeding 45 m in length is provided with expansion joints.

The maximum spacing between the expansion joint is 140 m.

Expansion joints in rigid pavements are provided for the expansion/contraction of the concrete slab due to temperature variation and subgrade moisture variation.

Construction joints:

Construction joints are transverse header joints put in at the end of each day’s run or longitudinal joints between lanes of multiple lane pavement. The purpose of such joints is to divide large pavement areas into convenient size for paving. Longitudinal construction joints are usually provided with deformed tiebars.

A transverse construction joint may serve as a contraction or expansion joint if its location coincides with that of a planned transverse joint.

Longitudinal joints:

Longitudinal center joints are joints in the direction of paving and are provided in all street and highway pavement built in lanes over ahout 15 ft wide. These center joint s are intended to relieve the transverse stresses which develop from wheel loads and slab curling or warping due to moisture and temperature difference in the pavement and variable subgrade support resulting from soil swelling or shrinking.

Dowel bar:

Dowel bars are provided at expansion joints.

Dowel bar is used to transfer the load between two concrete slabs.

Dowel bars in concrete pavement are placed in the longitudinal direction of the traffic.

Dowel bars keep the two slabs in same height and reduce the differential deflection between slabs.

Mild steel rounded bars having diameter > 25mm are used that are bonded on one side and free on other side.

Shear Stress, Bending Stress and Bearing Stress develop in Dowel Bars.

Tie bar:

Tie bars tie two slabs and don’t transfer load.

Tie bars must be deformed and anchored into the concrete to function properly.

Tie bars are smaller than dowel bars.

The spacing between tie bars is more than dowel bars.

Tie bars are provided across longitudinal joints.

Its initial setting time is 5 mins and final setting time is 30 mins.

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