Determining the suitability of a particular soil requires knowing the proportion of each of the ingredients in the soil and also whether the particular material has the required properties.
For example, a road soil that is 95 percent sand will not form, and soil that does not have cohesive properties is useless as a road material and will do nothing but form dust.
Therefore it is necessary to do some field tests before using clay in road work. The following 4 filed tests can be carried out to check its suitability for road work.
1. To determine the proportion of sand in soil
Take a sample of dry soil and weigh it. Pour it into a glass and fill it with water. Stir it and remove the soil. Do this several times until nothing but sand remains in the glass. Dry the sand and weigh it. The result will give the percentage of sand in the soil. The rest is clay and silt.
2. To determine the ratio of clay to silt
The silt is usually darker in color than the clay and a sample that has a very high percentage of silt will not have the characteristic brown soil color. Silt freezes more quickly than clay. If the sample is poured into a glass and mixed with water and the soil is allowed to settle, the soil will remain muddy while the silt will settle within a few minutes. A sample that is cleaned too quickly contains a lot of silt. This type of soil has to be mixed with a little clay before it can be used as a road material.
3. To determine soil quality
Pure clay is very resistant to moisture and becomes plastic and unstable when wet, and as it erodes easily, producing all the dust when dry. The extent to which these objections come depends on whose soil is slaking or non-slaking Diversity. The moldy variety is undesirable as it is muddy in the wet season and dusty in the dry season. Perform slaking tests as described below to determine the properties of different soils.
Make several balls of the same size from different clays and dry them. Place them in water so that they are completely covered. Balls that hold their shape the longest after being placed in water have the highest resistance to slaking, and that soil is preferred for use in road construction. It is important in this test that if different soils are being compared, the proportion of sand in each sample should be the same and should not exceed 25 percent. If there is excess sand, it should be removed before performing the slaking test.
If the soil is of loose type, the balls will almost disintegrate as soon as they are put in water, such soil is not suitable for road work. Samples that contain a lot of silt will not show good non-slaking properties and will break down at once in water. Before using such soil, clay has to be mixed in it.
4. To determine the suitability of sand
Place a sample of sand in a vessel containing water and stir the water until the sand is completely in suspension. Then when the sand is allowed to settle, add water gradually. Good quality sand will not be carried with the water, but will remain in the pot until practically all the water is drained. Poor quality sand will not meet this test and is not suitable for use in road works.