A Closer Look at Prevailing Civil Engineering Practice - European ...

A Closer Look at Prevailing Civil Engineering Practice, What, Why and How
Vincent T. H. CHU
(ii) It aids in the cutting of paving blocks near edge courses because
paving blocks could lie over edge courses and the positions of
cutting could be marked accurately without any difficulty. However, if
a wall instead of edge courses is located adjacent to the pavement,
it is practically difficult to position the paving block over the gap
because of the physical hindrance of the wall.
(iii) It could be designed as surface drainage channel to convey
stormwater to a discharge point.
(iv) It acts as a frame which defines the shape of pavement.
20. For compaction of paving blocks, should the jointing sand be
applied before or after the compaction process
The common practice is to apply jointing sand at the first place followed by
subsequent compaction. However, there are several potential problems
associated with this method. Firstly, the presence of sand provides support
to paving blocks leading to inadequate compaction. Secondly, the excess
jointing sand may be crushed during compaction and leaves stains on the
surface of paving blocks. Thirdly, damaged paving blocks appear to be
difficult for removal owing to frictional grip by jointing sand.
The alternative method is to carry out compaction firstly and then followed
by application of joint sand and then re-compaction is carried out again.
This method eliminates all the shortcomings of the first method described
above. However, it suffers from the demerit of two passes of compaction
instead of a single stage of compaction is required. Moreover, the
compaction operation tends to be noisier because of the absence of the
infilling sand which helps to reduce noise level. The direct contact between
individual paving blocks is more vulnerable to spalling during compaction.
21. Can the sand bedding be omitted in paving block pavement
In the paving block pavement, it normally consists of the following main
elements: sub-base, sand bedding and paving blocks. Sub-base is the
main structural element to take up traffic load and spread it into larger area
so that the traffic stress is small enough for subgrade to sustain. Sand
bedding is used for providing correct line and level for paving blocks to lie
on. To achieve this, screeding of bedding layer is implemented so that the
paving blocks could be laid directly on it without the need of further leveling.
The large range of particle sizes associated with sub-base renders it
unsuitable to provide a uniform surface with correct level for paving blocks
to lie on.
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