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TOPIC 3: CONSTRUCTION OF ROAD LAYERS (Subbase (moisture content of +1 to…
TOPIC 3:
CONSTRUCTION OF ROAD LAYERS
Drainage Layer
laid on a prepared & acceptable
subgrade
materials: coarse aggregates and
fine aggregates
laid & compacted at moisture content
of +1 to -2% of OMC
Subbase
moisture content
of +1 to -2% of OMC
material: natural or artificial mixture of
locally available material
laid in 100-200mm compacted
thickness
compaction to produce density
greater than 95% MDD
Roadbase
material: crushed rocks, crushed
gravels
OMC +1 to -1%
laid in 100-200mm compacted
thickness
bituminous roadbase: conform to the quality
requirement in asphaltic concrete section
Coating
prime coat
liquid bitumen
on clean unbound
roadbase
tack coat
bitumen emulsion
on bituminous layer
Surfacing
Mix design or Job Mix
Formula
carried out in the lab under controlled conditions for each type of mix
Trial lay need to be conducted
to determine:
Thickness before compaction
Rolling pattern
Surface layer
Binder course layer is laid on the
road base after it is cleaned and
sprayed with prime coat
Tack coat is sprayed on the top of
binder course layer before laying
wearing course layer and compacted
Rolling
Layer of Compaction
Initial/Crushing/
breakdown
smooth wheel
Intermediate
pneumatic wheel
Finishing
smooth wheel
Shoulders
furnishing
compacting
shaping earth, gravel or
paved shoulder