pH TEST TO DETERMINE LIME REQUIREMENTS FOR
D-1. Materials. Lime to be used for soil stabilization.
D-2. Apparatus. Apparatus include pH meter (the pH meter must be
equipped with an electrode having a pH range of 14), 150-milliliter (or
larger) plastic bottles with screw-top lids, 50-milliliter plastic beakers,
distilled water that is free of CO,, balance, oven, and moisture cans.
a. Standardize pH meter. Standardize the pH meter with a buffer
solution having a pH of 12.45.
b. Weight samples. Weigh to the nearest 0.01 gram representative
samples of air-dried soil, passing the No. 40 sieve and equal to 20.0 grams of
c. Pour samples. Pour the soil samples into 150-milliliter plastic bottles
with screw-top lids.
d. Add lime. Add varying percentages of lime, weighed to the nearest
0.01 gram, to the soils. (Lime percentages of 0, 2, 3, 4, 5, 6, 8, and 10, based
on the dry soil weight, may be used.)
e. Mix. Thoroughly mix soil and dry lime.
f. Add distilled water. Add 100 milliliters of distilled water that is
CO,-free to the soil-lime mixtures.
g. Snake soil-lime and water. Shake the soil-lime and water for a
minimum of 30 seconds or until there is no evidence of dry material on the
bottom of the bottle.
h. Shake bottles. Shake the bottles for 30 seconds every 10 minutes.
i. Transfer slurry. After 1 hour transfer part of the slurry to a plastic
beaker and measure the pH.
j. Record pH. Record the pH for each of the soil-lime mixtures. The
lowest percent of lime giving a pH of 12.40 is the percent required to
stabilize the soil. If the pH does not reach 123.40, the minimum lime
content giving the highest pH is required to stabilize the soil.