A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
when the cracks are open due to the contraction of concrete. The groove
location is a plane of weakness and the groove acts as a potential
crack-inducing device where any potential cracks due to shrinkage and
thermal contraction may form will be confined to the base of the groove. It
will not cause any unpleasant visual appearance on the exposed surface of
unreinforced concrete pavement.
The above-mentioned contraction joints can be designed as unsealed.
These grooves are very narrow so that stones can hardly get into these
grooves even when the joint undergoes contraction. The fine particles or
grit entering into the groove are likely to be sucked out by the passing
vehicles. The joints can be self-cleansing and it may not be necessary to
seal the joints for fear of attracting the accumulation of rubbish and dirt
[55].
8. What is the difference between tie bars and dowel bars in concrete
carriageway? (RJ5)
Tie bars are deformed rebars or connectors used for holding faces of rigid
slabs in contact to maintain aggregate interlock. Tie bars are not load
transferring device. For instance, tie bars are used in longitudinal joints in
concrete pavement.
Dowel bars are smooth round bars which mainly serve as load transfer
device across concrete joints. They are placed across transverse joints of
concrete pavement to allow movement to take place. Where movement is
purposely designed for longitudinal joints, dowel bars can be adopted.
9. In concrete pavement, keyway joint are sometimes adopted in
longitudinal joint. Why? (RJ6)
Longitudinal joints are installed in concrete pavement to prevent differential
settlement between adjacent concrete panels. Moreover, it serves to
control cracking from stresses caused by volumetric changes of concrete
owing to moisture and thermal gradients. In essence, the joint contains tie
bars to enhance efficient load transfer between adjacent concrete panels.
Sometimes keyway joint are designed in longitudinal joint to improve the
performance of the joint. Though the installation of keyway joint does not
appear to increase the load transfer efficiency of longitudinal joint, it proves
to help reduce the deflection of concrete pavement. Keyways are not
recommended for thin slab (less than 250mm thick) because of the
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