Plastic Limit Research Paper

Plastic Limit

It is defined as the water content at which a soil would just start to crumble when rolled into a thread of 3mm diameter.

Procedure (Acc. to IS:2720 part 5) i) Take about 8gm of the soil and add some known quantity of water starting from lower value, if thread is broken add some more known quantity of water and repeat the process. roll it with fingers on a glass plate. The rate of rolling should be between 80-90 strokes per minute to form a diameter of 3mm. ii) If the dia. of the threads can be reduced to less than 3mm , without any cracks appearing , it means the water content is more than its plastic limit. Knead the soil to reduce the moisture content and roll it into a thread again. iii) Repeat the process of alternate

44.40% the soil will be classified as CI soil. 3.11 Free Swell Index Test

Free Swell Index is the increase in volume of soil without any external constraint when subjected to submergence in water. Free swell index test was performed as per IS :2720 (Part XL)- 1977.

Procedure (Acc. to IS:2720 part XL)- 1977

i) 2 specimens of 10gm each of the soil passing through 425µm IS sieve are taken and oven dried. ii) Each soil specimen is poured into a graduated cylinder of glass of capacity of 100ml. iii) Pour kerosene in one cylinder and distilled water in other up to 100 ml mark. iv) Entrapped air is removed by shaking or stirring with a glass rod gently.

v) The suspension is allowed to attain the state of equilibrium (for not less than 24 hrs.) vi )Final volume of soil in each of the cylinder should note

FIGURE - 3.9 Compaction of the soil sample FIGURE - 3.10 Compaction of the soil sample FIGURE 3.11Compacted soil after straight edge FIGURE 3.12 Wt. measurement of the sample Table -3.5 Standard Table of Proctor Density Test with Results of NBCS

Water Added in % 10% 12% 14% 16% 18% 20%

Volume of Mould (cm3) 1000 1000 1000 1000 1000 1000

Weight of Mould(Kg) 2.220 2.220 2.220 2.220 2.220 2.220

Weight of Mould + Compacted Soil (Kg) 4.000 4.035 4.110 4.165 4.235 4.230

Bulk Density ϒb =w/v 1.78 1.805 1.89 1.925 2.015 2.01

Water Content % 13.70% 15.30% 17.11% 18.72% 19.50% 21.36%

Dry Density ϒd 1.563 1.574 1.613 1.638 1.686 1.656

Graphical Representation of Proctor Density Test with Results of Natural Black Cotton