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.
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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.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.
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