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
expansion joints is to minimize the frictional resistance between the bar
and its surrounding concrete. This is the reason why plain round bars are
usually used instead of deformed bars which provide mechanical interlock
with concrete and hence it hinders the free movement of the dowel bar.
Both bituman-based paint (debonding agent) and plastic sleeve could
serve the purpose of reducing friction between dowel bar and surrounding
concrete. From practical point of view, the use of plastic sleeve (e.g. PVC
dowel sleeve) around dowel bars can well prepared off-site and
manufactured well in advance, thus saving the time of construction.
4. For unreinforced concrete carriageway, what is the sequence of
closing and opening of expansion joints and contraction joints?
Let’s take an example to illustrate the sequence of closing and opening of
joints (Ministry of Transport (1955)). For instance, an unreinforced concrete
carriageway is constructed in winter. When temperature rises in the
following summer, the section between expansion joints will expand as a
whole single element resulting in the closure of expansion joints. This
section of concrete pavement will move outwards from the mid-point
between the expansion joints. In the next winter, each bay (i.e. concrete
pavement between adjacent contraction joints) of concrete contracts about
the midpoint of its length with opening of contraction joints.
Fig. Movement of joints in summer and winter
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