EXPERIMENT NO 4 : PLASTIC LIMIT TESTINTRODUCTION Plastic Limit Test is conducted to determine the moisture content at the point of translation from plastic to semisolid state. The plastic limit is defined as minimum water content at which a soil will just begin to crumble when rolled into a thread of 3.2 mm in diameter. OBJECTIVE The objective of this experiment is to determine the plastic limit of soil sample and then to calculate plasticity index. PROBLEM STATEMENT Classification of a fine grained soil requires quantification of the soil plasticity index. Plastic limit is required for the determination of plasticity index. Hence accurate determination of soil plastic limit is required for determination of reliable plasticity index. APPARATUS 1. 2. 3. 4. 5. 6. Spatula Moisture containers Wash bottle containing distilled water Electronic balance sensitive to 0.1 g Large glass plate Drying oven MATERIALS Fine grained soil sample PROCEDURE If at this point the thread begins to act brittle and crumbles then the plastic limit has been reached. The rate of rolling have to be decreased for very fragile soils. 3.1. The soil paste were shaped into a ball shape. 50 g of dried soil were mixed with water sufficiently and soil paste were made. The test was repeated for two more determinations DISCUSSION . The soil thread that have been crumbled was collected and kept in the airtight container for water determination. The process was continued until the thread just crumble at 3mm diameter. The provided 3mm diameter rod was used as a reference. 4. If the plastic limit has not been reached then fold and knead the thread into a ball again and repeat the rolling process. and rolled on to the glass plate with the hand pressure at rate 0f 80 – 90 strokes per minute. 2. The mass was rolled into a thread of uniform diameter throughout its length until the thread reaches a diameter of approximately 3mm. Semi-Solid. we must be careful when using the apparatus in the lab in order to elude from any incident occurred in the lab. after the originator of the test procedures. DATA AND OBSERVATION: . Wash the apparatus until it’s clean and throw the soil or any materials in the dustbin. For the third time testing. Besides that. operators frequently do not carry out testing using the tips of the fingers (as specified in the Bristish Standard) since these are eminently unsuited to the task. After calculate the average.67%. along with shrinkage limit are referred to as the "Atterberg Limits".86%. the percentage of water content was 42. This is because we need to avoid any dangerous especially when using the oven or any chemical. Its primary use is in association with the other Atterberg limits in soil identification and classification.liquid unlit.Solid State Atterberg Limits and Indices. In order to avoid any mistakes.liquid limit. in addition. We must consider any possibility of error that can be happen during the experiment.11%. We have to wear gloves when dealing with the hot oven. Semi-Solid . we found that the plastic limit of soil was 31. From the values we can see that the percentage of water content in the third time testing shows extremely different from the first and second time testing. Atterberg limit is quite unreliable since the test method often give a wide range or error. also known as the lower plastic limit. we should be more careful and follow all the procedures. however the low levels of accuracy coupled with high cost tend to discourage use. we determined the plastic limit of the soil. plastic limit. For the first and second. The extensive use of plasticity testing can be most rewarding. along with shrinkage limit are referred to as the "Atterberg Limits". StagySolid State Atterbera Limits and Indices. plastic limit.The following moisture conditions . We mixed the soil with water.81% and 26. ball it and rolled the ball gently until it form crumble. we repeat the procedures for three times. In this experiment. When considering the plastic limit test. In this experiment. The following moisture conditions . is the water content at which a soil changes from the plastic state to a semisolid state. The plastic limit. amount of finger pressure used and the shape of the tips of fingers varies to a great extent and. the value of water content was 23. after the originator of the test procedures. Plastic limit.6 1.1 0.67% w = [(mass of water) / (mass of solids + mass of water)] x 100 = [(0.8 + 0.4 0.3 Mass of water (g) 0. w = [(mass of water) / (mass of solids + mass of water)] x 100 = [(0.6)] x 100 = 42.81% w = [(mass of water) / (mass of solids + mass of water)] x 100 = [(0. 1.7 14.4)/ (1.5)] x 100 w = 23.8 15. The value plastic limit.1 + 0.5 Mass of dry soil (g) 1.5)/ (1. PL is the average of the three water contents.6)/ (0.9 Mass of container + dry soil (g) 16.Determination No.6 Mass of container (g) 14. 1 2 3 1 2 3 Mass of container + wet soil (g) 17. Sample Of Calculations: Water content for specimen of container no.4)] x 100 w = 26.86 Container number 1.0 16.8 Water content (%) 23. .2 15.67 42.81 26.6 + 0.5 15.9 14.86% w 2.5 0. 12 % CONCLUSION .23 – 31.3. PL = Liquid Limit – Plastic Limit = 40.81 + 26.86) / 3 PL = 31.67 + 42. PL = (23.11 % Plasticity index.11 = 13. For the second and third test. we can conclude that the objectives of this experiment were achieved. The difference between the liquid limit and plastic limit is the plasticity index. we found that the plastic limit of soil was 31. we just do the experiment for liquid limit and plastic limit. In the lab. it wills past through the liquid limit. So. we determined the plastic limit of the soil. plastic. plastic limit.67% and 42.12 %. we found the plastic limit of sample soil is less than 50%.Plastic limit is conducted to determine the moisture content at the point of transition from plastic to semisolid state. the value of water content was 26. the percentage of water content was only 23. After plotting the graph.11%. semisolid and solid. After do the calculation using the formula.2 mm in diameter.86%. Its primary use is in association with the other Atterberg limits in soil identification and classification. The liquid. So. We use Cassagrande method to determine the liquid limit of the sample soil. After we have done the experiment (Liquid Limit and Plastic Limit Tests). For the first time testing. In this experiment. we found that the plastic index of the soil is equal to 13. ATTACHMENT . If a soil in the liquid state is gradually dried out. The dividing line between liquid and plastic states is the liquid limit. The plastic limit is defined as the minimum water content at which a soil will just begin to crumble when rolled into a thread of 3. plastic state. from all the values we can see that the percentage of water content not show the extremely different. and after calculate the average.81%. plastic and shrinkage limits are therefore quantified in terms of the water content at which a soil changes from the liquid to the plastic state. The four states of consistency in Atterberg limits are liquid.. semisolid state and shrinkage limit and reach the solid stage. we found that the liquid limit of soil sample 44. the dividing line between plastic and semisolid states is the shrinkage limit. From the chart we found that the type of soil was falling under silt intermediate (MI) (below A-line). Because the liquid limit and plastic limit are the two most commonly used Atterberg limits. The plastic limit is the lower boundary range of the plastic behaviour of a given soil.23 % and it shows that the soil had a lot of water content. Figure 1.0 Ellipsoidal soil mass. .0 Apparatus in experiment Figure 2. 0 Thread reach until 3mm .Figure 3. Figure 4.0 Roll into uniform diameter. 2013 R. 3. Craig’s Soil Mechanics.F.REFERENCES 1.html . Soil Mechanics Laboratory Manual. http://civilengineeringlaboratory. Craig. Spon Press. Department of Civil Engineering Version 1 May 2.com/2012/02/liquid-limit-and-plastic-limittests.blogspot. 7th Edition.