Month: August 2024

In civil engineering, several studies showed that organic soils may show considerably low bearing capacities, and considered them as soft soils due to their high settlement values indeed under relatively applied loads. Consequently, there’s a tendency in the field of construction to avoid executing any projects above this type of problematic soils.
when exposed to structure’s loads, especially that wide areas of the area are covered with fine granulated soils containing different rates of organic matter. It is very necessary to know whether soil is organic or not. However, organic matter can also decrease the efficiency of compaction because the organic matter absorbs some of the energy transmitted to the sample. As per MORT& H specification , organic soil can not be used in road construction. Here is procedure how to find out the organic percentage in soil.

Determination of total Organic matter in soils.

Sample Preparation:

1. Total weight of original soil sample (Oven dried) – W1
2. Sieve the sample on 10 mm IS sieve and weighed the passing material – W2
3. Then sieve the sample on 425 micron IS sieve and take the soil sample for the test – Approximately 5 grams – W3 grams.

Preparation of Reagents:

1. Potassium Dichromate Normal solution: Dissolve 49.035 grams of Potassium Dichromate in one liter of distilled water.
2. Ferrous Sulphate 0.5 N solution: Dissolve 140 grams of Ferrous Sulphate in 0.5 N Sulphuric acid to make one liter of solution (Add 14 ml of concentrated Sulphuric acid to distilled water to make one liter of solution for 0.5 N Sulphuric acid).
3. Concentrated Sulphuric acid: Gr 1.83.
4. Ortho Phosphoric acid: Gr 1.70 to 1.75.
5. Indicator: 25 grams of Sodium Diphemylamine-Sulphonate dissolved in 100 ml of distilled water.

Standardization of Ferrous Sulphate Solution:

1. Take 10 ml of Normal Potassium Dichromate solution in to 500 ml conical
2. Add 20 ml concentrated Sulphuric acid and swirled and allowed to cool for some
3. Add 200 ml of distilled water, 10 ml of Ortho Phosphoric acid and 1ml of the Indicator and the mixture shall be shaking thoroughly.
4. Ferrous Sulphate solution added through burette in 0.5 ml increments, up to the solution changes from blue to
5. Add 5 ml Potassium Dichromate, then solution changing the color back to blue.
6. And then Ferrous Sulphate added drop by drop until the color of the solution changes from blue to Measure the total volume of Ferrous Sulphate solution in ml and recorded it as ‘X’.

Procedure:

1. Take 5 grams of soil sample of 425 micron IS sieve passing in 500 ml conical
2. Add 10 ml of Potassium Dichromate
3. Add 20 ml of concentrated Sulphuric acid and allowed to 30 minutes on a heat insulating surface like asbestos
4. Add 200 ml distilled water, 10 ml of Ortho Phosphoric acid, 1 ml of the Indicator and the mixture shall be shake
5. Ferrous Sulphate solution added through burette in 0.5 ml increments, up to the solution changes from blue to
6. Add 5 ml Potassium Dichromate, then solution changing the color back to blue.
7. And then Ferrous Sulphate added drop by drop until the color of the solution changes from blue to Measure the total volume of Ferrous Sulphate solution in ml and recorded it as ‘Y’.

Calculations:

1. The Volume of Potassium Dichromate used to oxidize organic, V= 5(1 – Y/X).
2. Percentage of Organic Matter in soil = (0.67W2V) / (W1W3)

The expansion of soil containing high sulphates occurs during ambient temperature drops from daytime temperatures of roughly 30 degree to below 5 degree at night. This expansion caused structural damage to single storey house in particular and to interior concrete bottoms and asphalt driveways. This phenomena, herein appertained to as” salt heave,” . Only by early recognition of the presence of water-soluble sulphate in the soil to control structural damage building or pavement. The final test procedure described herein provides a system to estimate soils containing sodium sulfate.  In this session we will learn how to determine total soluble sulphates by volumetric system as per( IS 2720 – Part – 27).

Object: Determine total soluble sulphates by volumetric method as per  (IS : 2720 – Part – 27)

Sample Preparation: Take about 100 grams of oven dried soil sample and sieve it in a 425 micron IS Sieve.

Preparation of Reagents:

1. Barium Chloride Solution (N/4): Dissolve 5 grams Barium chloride in one liter of distilled water.
2. Potassium Chromate Solution (N/4): Dissolve 275 grams of Potassium chromate in a small amount of distilled water. Add few drops of Silver Nitrate solution to it to remove any Chloride, filter and dilute to 250 ml.
3. Silver Nitrate Indicator: Dissolve 500 mg of Silver Nitrate in 100 ml of distilled water.
4. Dilute Solution of Ammonium Hydroxide: (Sp.Gr 0.888) Mix Ammonium Hydroxide and distilled water in the ratio of 1:2.
5. Concentrated Hydrochloric acid: Gr 1.11.

Test Procedure:

1. 10 grams of soil sample taken in to
2. Add 50 ml water, stir well, allow decanting and
3. Take 10 ml filtrate sample by pipette in a conical
4. Make it slightly acidic by adding concentrated hydrochloric acid (i.e.: few drops) and heat to
5. Add Barium Chloride solution (N/4) from the burette till the precipitation is complete, measure the volume in ml and recorded it as ‘X’.
6. Neutralize the solution with Ammonium hydroxide (i.e.: few drops).
7. Titrate the excess of Barium chloride against Potassium Chromate solution(N/4), measure the volume in ml and recorded it as ‘Y’. the end point may be confirmed, if considered necessary, by using Silver nitrate solution as an external indicator.

Calculations:

Sulphates as Sodium Sulphate in Soil, percent by mass = 0.0177 x (X – Y)