Volume-IF - JantERmantER

DCPL-K4A02
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Grading Size of Sieve Percent by weight
Classi- screenings designation passing the sieve
fication
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A 12.5 mm 12.5 mm 100
10.0 mm 90-100
4.75 mm 10-30
150 micron 0-8
B 10 mm 10 mm 100
4.75 mm 85-100
150 micron 10-30
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3.4.2.5 Binding Material
Binding material to be used for water bound macadam construction shall
comprise of a suitable material approved by the Engineer having plasticity
index value of less than 6 as determined in accordance with IS:2720 (Part
V).
Application of binding material may not be necessary, when the
screenings used are of crushable type such as moorum or gravel.
3.4.3 Construction Operations
3.4.3.1 Preparation of Base
The subgrade/sub-base to receive the water bound macadam coarse shall
be prepared to the specified grade and camber and made free of dust and
other extraneous material. Any ruts or soft yielding places shall be corrected
in an approved manner and rolled until firm. Where water bound macadam
is to be laid over an existing black topped surface, 50 mm x 50 mm furrows
shall be cut at an angle of 45 degrees to the centre line of the road at 1
metre intervals in the latter before laying the coarse aggregate.
3.4.3.2 Inverted Choke
If the water bound macadam is to be laid directly over the sub-grade,
without any other intervening pavement course, a 25 mm course of
screenings (Grading B) shall be spread on the prepared subgrade before
application of the coarse aggregates is taken up.
3.4.3.3 Spreading Coarse Aggregate
(PCA.775.S034sca7) V.II-D2/S-VII : 11