Plastic Limit Lab Report

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The Liquid Limit was computed to be 42%. 3.2.2.2 PLASTIC LIMIT From determination point of view it is that water content at which a 3 mm thread of the soil sample does not crumble. Fig 3.7: Illustration for determination of Plastic Limit[7] Water was added to the soil and mixed thoroughly. A ball with about 8 g of this plastic soil mass was formed and rolled between the fingers and the glass plate with just sufficient pressure to roll the mass into a thread of uniform diameter throughout its length (with the rate of rolling between 80 and 90 strokes/min counting a stroke as one complete motion of the hand forward and back to the starting position again). The rolling was done till the threads of 3 mm diameter were obtained. The soil…show more content…
of soil was taken passing through 75 micron sieve was taken. Water was added to it to bring its moisture content to about 8% . The mould with base plate attached was weighed . The extension collar was attached with the mould. Then the moist soil in the mould was compacted in 3 equal layers, with 25 blows from the 2.6 Kg rammer on each layer. The extension was removed and the compacted soil was levelled off carefully to the top of the mould by means of a straight edge. Then the mould and soil was weighed. The soil was removed from the mould and a representative soil sample was obtained for water content determination. The process repeated again after adding suitable amount of water to the soil in an increasing order. The optimum moisture content was 14% 3.3 Soil Classification In the Indian Standard Classification System, classification of soil is done on the basis of their gradation characteristics and using Plasticity Index. Coarse grained soils that consist of more than 12% fines are classified as Silty Gravel or Silty sand if the fines are silty in character (i.e. it lies below the A-Line); They are classified as Clayey Gravel or Clayey sand if fines are clayey in character (i.e. the limits plot above the A-line on the Plasticity chart. Coarse grained soil having 5% to 12% fines are borderline cases and are given dual symbol. The first part of the dual symbol is indicative of the gradation, while the second part indicates the nature of fines. For example, a soil with a dual symbol SW-SC is a well graded sand with clayey fines which plot above the

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