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Laid between subgrade and pavement.Laid between subgrade and pavement.
To serve as an effective drainage layer to drain To serve as an effective drainage layer to drain off the water entering in to the pavement layers.off the water entering in to the pavement layers.
To serve as the structural component of the To serve as the structural component of the flexible pavement structure by distributing wheelflexible pavement structure by distributing wheel load stresses transmitted through the surface course and granular base course.load stresses transmitted through the surface course and granular base course.
To prevent moisture migration from subgrade.To prevent moisture migration from subgrade.
Crushers are mainly used to reduce the size of large stone or rock to Crushers are mainly used to reduce the size of large stone or rock to smaller uniform sized aggregates. smaller uniform sized aggregates.
They are set up in the nearby stone quarries to reduce transportation cost.They are set up in the nearby stone quarries to reduce transportation cost.
(wearing due to frictional rubbing)
1.Pressure1.Pressure2. Impact2. Impact3. Attrition3. Attrition4. A combination of these 4. A combination of these operationsoperations..
Tipper is a very large truck designed to carry heavy loads and can be emptied by rais ing front of the carrier to allow
the contents to sl ide out from the back using hydraulic arm attached to the carrier
In Granular Sub-Base (GSB) construction, aggregates are needed to be distributed according to their sizes.
This purpose is fulfilled by using a machine known as aggregate distributor.
Motor Grader is a machine usedto spread the sub-base materialto uniform thickness and specifiedcross slope by adjusting the bladeof the grader.
Granular Sub-Base layer is watered to Optimum Moisture Content and
then it is compacted by rolling.
If the compacted thickness of the layer is 100mm or lesser, an ordinary
smooth wheeled roller is used.
For compacted thickness exceeding 100mm, compaction is done by
Vibratory roller of static weight 10 tons or more. Rolling is done starting from the lower edge proceeded towards
the upper edge of divided carriageway with rolling speed limited to
5 KMPH.
Rolling is continued till at least 98% of the maximum density of the
material is achieved.