PRACTICE VIII 



DETERMINATION OF THE EFFECT OF LIME ON PLASTIC SOILS 



Two students may work together on this experiment. 



Weigh out six 300-g. samples of a clay soil. 



To sample No. 1, check, add no lime. 



To No. 2 add 0.1 per cent, 0.3 g. of powdered quicklime. 



To No. 3 add 0.5 per cent, 1.5 g. of powdered quicklime. 



To No. 4 add 1.0 per cent, 3.0 g. of powdered quicklime. 



To No. 5 add 2.0 per cent, 6.0 g. of powdered quicklime. 



To No. 6 add 3 per cent, 10.0 g. of sand. 



Mix the clay and lime thoroughly in a soil pan and add just 

 enough water for maximum plasticity. Cover with a glass plate 

 to reduce loss by evaporation. Set aside to let the lime act for 

 at least twenty-four hours. 



Make a test of tenacity, as directed in Practice IX. 



After making the tenacity test fill the mold, first placing in it 

 a piece of damp cheesecloth to facilitate the removal of the clay. 

 Make duplicate bricks of each mixture, being careful to com- 

 press each to the same degree. Place the bricks on a cloth in 

 a soil pan and dry in an oven for five hours at 100 C. 



Test the strength of each brick by supporting the ends so as 

 to allow just 3 inches between the points of support. Suspend 

 weight bag in the middle of brick and determine the weight 

 necessary to break each by pouring shot into the bag. 



Explain the effect of lime. 



Why does the sand not have as much effect as lime on the 

 breaking strength ? 



How many tons of lime per acre do the above percentages rep- 

 resent, the surface 6| inches of soil weighing 2,000,000 pounds? 



REFERENCES. 



" Soils," Lyon and Fippin, pp. 116-117. 



" The Soil," Hall, pp. 40-41. 



" Physical Properties of Soils," Warington, pp. 25-35, especially p. 33. 



" The Soil," King, p. 30. 



" Soils," Hilgard, pp. 59-60. 



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