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
4. In concrete pavement, why is the requirement of 95% by mass of
quartz grains are specified in contract?
In General Specification of Civil Engineering Works (1992 Edition), in
Clause 10.09 it states “Fine aggregate for concrete shall be natural
river-deposited sand consisting of at least 95% by mass of quartz grains”.
The aim of such specification is to control the quality of river sand. As
quartz is a durable and hard material, using a high percentage of quartz in
aggregates of concrete can enhance the strength and durability of the
surface texture of concrete carriageway.
In addition, such specification requires a high percentage of quartz content,
thereby reducing the probability of presence of impurities like shell.
5. Should joints of concrete kerbs be in line with the joints in concrete
carriageway? (PS2)
In normal practice, joints are provided in road kerbs to cater for concrete
expansion and contraction. However, the location of joints in kerbs is not
arbitrary and they should match with joints in concrete carriageway.
Otherwise, it is very likely that cracks may form in concrete kerbs at
location of pavement joints (Ministry of Transport (1955)).
6. Can a sub-base layer serve as a drainage layer to remove water
from pavement? (PS3)
Besides providing load distribution in post-construction stage and working
platform in construction stage, sub-base can also serve as a drainage layer
to remove water coming from the pavement. For thick layers of road
pavement, it is likely that the water leakage from pavement is insignificant
and therefore the sub-base layer mainly serves to support the traffic
stresses. However, for thin pavement layers, water penetration is quite
substantial and therefore sub-base may also act as a drainage layer to
remove these water.
7. If there is a delay of bituminous laying on top of sub-base, should
tack coat be applied on the top surface of sub-base? (PS4)
When there is a delay between bituminous laying of different bituminous
layers (i.e. roadbase, base course etc.), a tack coat is applied on top of the
bituminous layers because it helps to enhance better bonding between
bituminous materials. If there is insufficient bonding between adjacent
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