Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

3. Section-300
TABLE 306.1 THICKNESS OF LAYER FOR FLYASH EMBANKMENT CONSTRUCTION
Thickness of Layer Weight of static roller Weight of vibratory roller
(loose) in mm used in kN used in kN
Not exceeding 200 80 to 100
Not exceeding 400 80 to 100
250 60 to 80
100 to 150 10 to 15
5. Moisture content of fill material before commencement of compaction, shall be within (±) 2% of
the optimum moisture content when determined as per IS:2720 (Part-7). Moisture content of the
cover soil shall be maintained at OMC.
6. If water is required to be added to the fill material, the same shall be sprinkled from a water
bowser without flooding. The water shall be mixed thoroughly by blading, discing or harrowing.
7. Compaction of flyash should start as early as possible after spreading. Each layer of flyash shall
be thoroughly compacted to the specified density. When vibratory roller is used for compaction,
two passes without vibration followed by 5 to 8 passes with vibration shall normally be sufficient
to compact each layer.
8. The compaction of flyash core and earth cover on the sides shall proceed simultaneously. After
construction, flyash embankment shall conform to the following:
(i) Minimum dry density after compaction as percentage of
maximum dry density determined as per IS 2720 (Part-7) 98%
(ii) Minimum dry density after compaction, when used in
bridge abutments for embankment length equal to 1.5
times the height of the embankment, as percentage of
maximum dry density determined as per IS 2720 (Part 7) 100%
9. On the top of flyash embankment, at least 500 mm thick selected earth embankment shall be
provided, out of which top 300 mm shall be sub-grade as per sub-section 303.
10. Following precautions should be taken while handling flyash:
(i) Flyash (Pond Ash) should be delivered to site in covered dumper trucks to minimize loss of
moisture and dusting preferably during night.
(ii) Stockpiling of flyash at site should be avoided.
(iii) If stockpiling at site cannot be avoided, dusting shall be prevented by spraying water on
stockpiles at regular intervals and by keeping the stockpile covered with tarpaulin or a thin
layer of material not subject to dusting e.g. soil or granular material.
(iv) Traffic should be restricted in areas where flyash is temporarily stockpiled at site.
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