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
Joint sealant: it seals the joint width and prevents water and dirt from
entering the joint and causing dowel bar corrosion and unexpected joint
stress resulting from restrained movement.
Joint filler: it is compressible so that the joint can expand freely without
constraint. Someone may doubt that even without its presence, the joint
can still expand freely. In fact, its presence is necessary because it serves
the purpose of space occupation such that even if dirt and rubbish are
intruded in the joint, there is no space left for their accommodation.
Dowel bar: This is a major component of the joint. It serves to guide the
direction of movement of concrete expansion. Therefore, incorrect
direction of placement of dowel bar will induce stresses in the joint during
thermal expansion. On the other hand, it links the two adjacent structures
by transferring loads across the joints.
PVC dowel sleeve: It serves to facilitate the movement of dowel bar. On
one side of the joint, the dowel bar is encased in concrete. On the other
side, however, the PVC dowel sleeve is bonded directly to concrete so that
movement of dowel bar can take place. One may notice that the detailing
of normal expansion joints in Highways Standard Drawing is in such a way
that part of PVC dowel sleeve is also extended to the other part of the joint
where the dowel bar is directly adhered to concrete. In this case, it appears
that this arrangement prevents the movement of joint. If this is the case,
why should designers purposely put up such arrangement? In fact, the
rationale behind this is to avoid water from getting into contact with dowel
bar in case the joint sealant fails. As PVC is a flexible material, it only
minutely hinders the movement of joint only under this design.
Bond breaker tape: As the majority of joint sealant is applied in liquid form
during construction, the bond breaker tape helps to prevent flowing of
sealant liquid inside the joint .
Cradle bar: It helps to uphold the dowel bar in position during construction.
3. What is the purpose of using movement accommodation factor for
joint sealant? (J2)
Movement accommodation factor is commonly specified by manufacturers
of joint sealants for designers to design the dimension of joints. It is defined
as the total movement that a joint sealant can tolerate and is usually
expressed as a percentage of the minimum design joint width [12]. Failure
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