2.2.1 Atterberg limits tests
Liquid limit (LL), plastic limit (PL) and plasticity index (PI) were obtained following the method given in the ASTM D4318 (2000). Variations in the plasticity index of untreated clayey soils before and after addition of hydrated lime were then studied. The air-dried soil sample (passing through No. 40 sieve) was initially mixed with the required quantity of hydrated lime in a dry state. De-ionized water was added to the soil-hydrated lime mixture. To let the water permeate through the soil mixture, the paste was allowed to stand in an airtight container for about 24 hours before testing in the laboratory. After that, the paste was remixed with the stabilizer thoroughly for at least 15 min before performing the first laboratory test. The plastic limit tests were performed on the same mixture prepared for the liquid limit test. Both of liquid and plastic limit tests were conducted at room temperature.