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
lead to the loss of traction and thus prevent the vehicle from responding to
control inputs such as steering, braking or accelerating). It also decreases
the splash and spray from vehicles in wet weather. It serves as a drainage
channel for water to flow beneath the pavement surface.
Friction course has larger texture depth and this enhance improved skid
resistance for vehicles traveling at high speed. It also has other benefits
like the reduction of noise generated by vehicle tyres.
4. Why do some countries have reservation on the use of friction
course as bituminous surface layers? (RS2)
Owing to the porous nature of friction course, its deterioration rate is faster
than conventional bituminous materials and the durability of friction course
is a main concern form users. The service life of friction course is reported
to be around 8-10 years.
The main durability problem of friction course is associated with raveling of
friction course and stripping of underlying layers. Raveling of friction course
occurs as a result of lack of cohesion between aggregates. Stripping of
underlying layers is attributed by inadequate drainage of water through the
friction course. With the use of polymer in friction course, it permits the use
of higher air void (allows for better drainage) and higher binder content.
5. What is the purpose of tar in bituminous materials? (BM1)
Tar is commonly incorporated in bituminous materials because of the
following reasons:
(i) Blending of tar with bitumen possesses better binding performance with
roadstone than bitumen.
(ii) Resistance to fuel oil erosion is high. Tar is used in roads where there is
frequent spillage of fuel from vehicles.
6. What are the different functions of aggregates, filler and binder in
bituminous pavement? (BM2)
In bituminous materials, course aggregates perform the bulking action of
the mixture and contributes to the stability of resulting mix. Fine aggregates
form the major proportion of mortar.
Filler: it stiffens and strengthens the binder.
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