Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

3. Section-400
409. LIME-FLYASH STABILIZED SOIL SUB-BASE
The Lime-Flyash Stabilized Soil is a mixture of soil and flyash, when stabilized with lime.
A. Methodology
1. Before receiving the lime-flyash stabilized soil sub-base, the subgrade should be shaped to the
desired profile and checked for line, grade and cross-section. Any irregularities beyond the
permitted tolerance, soft and yielding spots should be corrected and adequately compacted.
2. The soil free from any organic or deleterious material should conform to the pulverization
requirements as under:
Percent weight of soil passing IS Sieve 26.5 mm - 100%
Percent weight of soil passing IS Sieve 5.6 mm - 80%
Where required, suitable equipment like tractor-towed disc harrows should be deployed for
meeting the pulverization requirements.
3. On the prepared sub-grade, the pulverized soil should be spread uniformly, the uncompacted
thickness being about one-third more than the specified compacted thickness, determined through
field trials.
4. Lime and Flyash in the required quantities should be spread uniformly over the soil, taking care
to prevent raising of dust.
5. A tractor-towed Rotavator or similar equipment should be used for mixing. The process of mixing
should be continued till the required uniformity of mixing has been obtained.
6. Prior to compaction, the specified moisture content should be (±) 2 percent of the optimum moisture
content. Where required, water should be added uniformly using a Water Bowser fitted with a
Sprinkler.
7. Water should be uniformly mixed with the soil-lime-flyash mix by discing or harrowing using
tractor-towed disc harrows or similar equipment.
8. Manual mixing, when permitted by the Engineer shall be carried out as per Clause 409.5.4 of
MoRD Specifications.
9. Immediately after spreading, grading and leveling of the mixed material, compaction should be
carried out, till 100% of the maximum dry density of the material as per IS:2720 Part 7 is achieved.
10. Not more than 60 minutes should elapse between the start of moist mixing and start of the
compaction process. Normally, compaction should be completed within 3 hours of mixing.
11. Curing of the compacted layer should be carried out for a minimum period of 7 days by spreading
moist straw/wet gunny bags or sand and periodically sprinkling water.
12 At the end of the day’s work, a transverse construction joint for full depth should be made by
chamfering at an angle of 30 0 .
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