Question 1:
a) What is road maintenance? /Qu’est
ce que c’est l'entretien d’une route? (4pts)
b) Give different main reasons
of the road maintenance/Donnez les différentes raisons
principales de l’entretien d’une
route. (6pts)
Answer 1:
a) Road maintenance is defined
as the act of preserving roadway structures and
other facilities as nearly as possible in their
original condition to prolong their
useful lives. Pavements which are left to deteriorate
without timely maintenance
treatment are likely to require major rehabilitation
and reconstruction much
sooner than those which are properly maintained.
(4pts)
b) Main reasons of road maintenance:
- To reduce the rate of road deterioration;
(2pts)
- To lower the vehicle operating
cost; (2pts)
- To keep the road open on a continuous
basis(2pts)
Question 2:
Give the purpose and explain briefly different
classifications of road
markings/ Donnez le but et expliquez brièvement des différentes catégories
de marquages
routiers. (15pts)
Answer 2:
a) The purpose of road markings
is to control, warn, or guide road users. (3pts)
b) Road markings are classified
as follows:
Longitudinal markings – dividing
lines, lane lines and edge lines (4pts)
Transverse markings – stop line,
give way line and pedestrian crossings (4pts)
Other markings – arrows, restricted
areas, text and symbols (4pts)
Question 3:
Give five types of flexible pavement failures/defects,
their causes and
remedial measures / Donnez cinq types de défaillances ou défauts des chaussées asphalté,
leurs causes et les mesures correctives.
(25pts)
Answer 3:
a) Corrugation/shoving:
These are in the form of
plastic movements typified by ripples (corrugation)or an abrupt
wave (shoving) across the
pavement surface. (2pt)
Causes: - mix contamination; (1pt)
- poor mix design (segregation). (1pt)
Repair: resurfacing (1pt)
b) Bleeding:
It is a film of
asphalt binder on the pavement surface which usually create a
shiny, glass-like reflecting surface that can become sticky when
dry and slippery
when wet. (2pt)
Causes: - Excessive asphalt binder in the surface layer (poor mix
design);
(0.5pt)
-Law surface layer, air void content. (0.5pt)
Repair: - Minor
bleeding can often be corrected by applying coarse sand to
blot up the excess asphalt binder; (1pt)
-Major bleeding can be corrected by cutting off excess asphalt and
resurfacing. (1pt)
c) Polished aggregates:
This is characterized
by the areas of the wearing course with the portion of
the aggregate extending above the asphalt binder being either very
small or they are
no rough angular aggregate particles. (2pt)
Causes: - Repeated traffic applications; (0.5pt)
- Use of aggregates susceptible to abrasion. (0.5pt)
Repair: - Slurry sealing; (0.5pt)
-Resurfacing; (0.5pt)
-Non-structural overlay. (1pt)
d) Alligator cracking:
These are series of interconnected cracks caused by fatigue of the
surface layer under
repeated traffic loading. (2pt)
Causes: - Repeated traffic loading; (0.5pt)
- Stripping; (0.5pt)
- Poor construction (inadequate compaction). (0.5pt)
Repair: - Sealing; (0.5pt)
-Overlaying; (0.5pt)
-Patching. (0.5pt)
e) Block cracking:
These are interconnected cracks that divide the pavement up into
rectangular pieces.
Larger blocks are generally classified as longitudinal or
transverse cracking. (2pt)
Causes: - asphalt binder aging; (1pt)
-Poor choice of asphalt binder in the mix design. (0.5pt)
Repair: - Crack sealing; (0.5pt)
- Slurry sealing; (0.5pt)
- Overlaying. (0.5pt)
f) Patching:
It is an area of the pavement that has been replaced with new
material to repair the
existing pavement. A patch is considered a defect no matter how
well it performs.
(2pt)
Causes: - Previous localized pavement deterioration that has been
removed and
replaced; (1pt)
-Utility cuts. (1pt)
Repair: They are themselves a repair action. The only way they can
be removed from
a pavement surface is by either structural or non-structural
overlaying. (1pt)
g) Stripping:
It is the loss of bond between aggregates and asphalt binder that
typically begins at
the bottom of the surface layer and progresses upwards.
When the loss of bond between the aggregates and the asphalt
binder begins at the
surface and progresses downwards, it is called raveling. (2pt)
Causes: - Poor aggregate surface chemistry; (1pt)
-Water in the surface layer causing moisture damage. (1pt)
Repair: The stripped surface needs to be removed and replaced
after correction of
any subsurface drainage issues. (1pt)
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