GRAIN SIZE ANALYSIS.( IS : 2720 – PART – 4 )

GRAIN SIZE ANALYSIS.

( IS : 2720 – PART – 4 )

INTRODUCTION:

Most of the methods for soil identification and classification are based on certain physical properties of the soils. The commonly used properties for the classification are the grain size distribution, liquid limit and plasticity index. These properties have also been used in empirical design methods for flexible pavements, and in deciding the suitability of sub grade soils.

The soils received from the field are divided into two parts: one, the fraction retained on 2mm sieve and the other passing 2mm sieve. The sieve analysis also may be carried out separately for these two fractions. The fraction retained on 2mm sieve may be subjected to dry sieving using bigger sieves and that passing 2mm sieve may be subjected to wet sieving; however if this fraction consists of single grained soil with negligible fines passing 0.075mm size, dry sieving may be carried out.

Apparatus:

Various apparatus include set of standard sieves of different sieve sizes, balance, rubber covered pestle and mortar, oven, riffle and sieves shaker.

Procedure:

(a) For the fraction retained on 2.0mm sieve: Sufficient quantity of the dry soil retained on 2.0mm sieve is weighed out. The quantity of sample taken may be increased when the maximum size of particles is higher. The sample is separated into various fractions by sieving through the set of sieves of sizes 100, 63, 20, 6, 4.75 and 2 mm IS sieves. Additional sieve size may also be introduced if necessary. After initial sieving, the material retained on each sieve is collected, the lumps broken down using mortar and rubber covered pestle and is re-sieved thus the soil fraction retained on each sieve is carefully collected and weighed.

(b) For the fraction passing 2.0mm sieve and retained on 0.075mm sieve: Dry sieving may be done in the case of soils which are cohesion less, single grained and without lumps. Rifling or quartering method takes the required quantity of soil sample, dried in oven at 105⁰ to 110⁰C and is subjected to dry sieve analysis using a set of sieves with sieve openings 2.0, 0.6, 0.425, 0.15 and 0.075 mm, pan and lid, additional sieves may be used or any of the sieves removed, depending upon the requirement of the test. The material retained on each sieve and on the pan are separately collected and weighed.

Wet sieving may be adopted in the case of clayey or cohesive soils. Required quantity of sample taken by riffling is weighed. The sample is spread in a tray or bucket and covered with water. In case of soils having fractions that are likely to flocculate a dispersing agent like sodium hexametaphosphate (2.0g) or sodium hydroxide (1.0g) and sodium carbonate (1.0g) per liter of water may be added to the water. The mix is stirred and left for soaking. The soaked soil specimen is placed over the set of sieves of sizes with the finest sieve and pan at the bottom and washed thoroughly. Washing is continued till the water passing each sieve is substantially clean. The fraction of each sieve is emptied carefully without loss of material in separate trays, oven dried at 105⁰ to 110⁰C and each fraction weighed separately.

Calculations:

The weight of dry soil fractions retained on each sieve is calculated as a percentage of the total dry weight of the sample taken.

Results:

The results are plotted on a semi-logarithmic graph with the grain size or sieve size on the X-axis in log. scale and the percentage finer of each sieve on the Y-axis in ordinary scale. The smooth curve joining the points thus obtained is known as the particle size distribution curve or diagram.

Uniformity coefficient of soil, C_u = D₆₀ / D₁₀

Coefficient of curvature, C_c = (D₃₀)² / (D₁₀ X D₆₀)

Where, D60, D30 and D10 are particle sizes corresponding to 60, 30 and 10 percent finer.

FREE SWELL INDEX TEST.( IS : 2720 – PART – 40 )

FREE SWELL INDEX TEST.

( IS : 2720 – PART – 40 )

Object:

To determine the free swell index of soils.

Apparatus:

1) 425 micron IS sieve

2) Glass graduated cylinders – 2 nos 100ml capacity

3) Distilled water and kerosene.

Procedure:

Take two 10 grams soil specimens of oven dry soil passing through 425-micron IS sieve. Each soil specimen shall be poured in each of the two glass graduated cylinders of 100ml capacity. One cylinder shall then be filled with kerosene oil and the other with distilled water up to the 100ml mark. After removal of entrapped air the soils in both the cylinders shall be allowed to settle. Sufficient time (not less than 24 hours) shall be allowed for the soil sample to attain equilibrium state of volume without any further change in the volume of the soils. The final volume of soils in each of the cylinders shall be read out.

Calculations:

The level of the soil in the kerosene-graduated cylinder shall be read as the original volume. The soil samples, kerosene being a non-polar liquid does not cause swelling of the soil. The level of the soil in the distilled water cylinder shall be read as the free swell level. The free swell index of the soil shall be calculated as follows:

                                                      (Vd – Vk)

Free swell index, percent       =      ----------- X 100

                                                            Vk

Where,       Vd =           the volume of soil specimen read from the graduated cylinder  

                                    containing distilled water.

                   Vk =           the volume of soil specimen read from the graduated cylinder 

                                    containing kerosene.  

 

FLASH AND FIRE POINT TEST.( IS : 1209 – 1978 )

                                                   FLASH AND FIRE POINT TEST.

                                                             ( IS : 1209 – 1978 )

INTRODUCTION:

Bituminous materials leave out volatiles at high temperatures depending upon their grade. These volatile catch fire causing a flash. This condition is very hazardous and it is therefore essential to qualify this temperature for each bitumen grade.

Flash point: The flash point of a material is the lowest temperature at which the vapour of substance momentarily takes fire in the form of a flash under specified condition of test.

Fire point: The fire point is the lowest temperature at which the material gets ignited and burns under specified condition of test.

Object:

To determine the flash and fire point of bitumen by Pensky-Martens closed tester.

Apparatus:

a) Pensky-Martens closed tester consist of cup, lid, stirrer device, shutter, flame exposure device.

b) Thermometer ( 0 – 350⁰C) – sensitivity – 0.1⁰C.

Procedure:

The material is filled in the cup up to a filling mark. The lid is placed to close the cup in a closed system. All accessories including thermometer of the specified range are suitably fixed. The bitumen sample is then heated. The test flame is lit and adjusted in such a way that the size of a bleed is of 4mm diameter. The heating is done at the rate of 5⁰C to 6⁰C per minute. The stirring is done at a rate of approximately 60 revolutions per minute. The test flame is applied at intervals depending upon the expected flash and fire points. First application is made at least 17⁰C below the actual flash point and then at every 1⁰C to 3⁰C. The stirring is discontinued during the application of the test flame.

Results:

The flash point is taken as the temperature read on the thermometer at the time of the flame application that causes a bright flash in the interior of the cup in closed system. For open cup it is the instance when flash appears first at any point on the surface of the material. The heating is continued until the volatiles ignite and the material continues to burn for 5 seconds. The temperature of the sample material when this occurs is recorded as the fire point.    

Limits: The flash point for all grades of bitumen materials is 175⁰C, minimum.

DUCTILITY TEST.( IS : 1208 – 1978 )

                                                                        DUCTILITY TEST.

                                                                        ( IS : 1208 – 1978 )

INTRODUCTION:

In the flexible pavement construction where bitumen binders are used, it is of significant importance that the binders form ductile thin films around the aggregates. This serves as a satisfactory binder in improving the physical interlocking of the aggregates.

Object:

To determine the ductility of the bituminous material.

Apparatus:

a) Ductility machine.

b) Briquette moulds.

c) Knife.

Procedure:

The bitumen sample is melted to a temperature of 75 to 100⁰C above the approximate softening point until it is fluid. It is strained through 90 micron sieve, poured in the mould assembly and placed on a brass plate, after a solution of glycerin and dextrin is applied at all surfaces of the mould exposed to bitumen. After 30 to 40 minutes, the plate assembly along with the sample is placed in water bath maintained at 27⁰C for 30 minutes. The sample and mould assembly are removed from water bath and leveling the surface using hot knife cuts off excess bitumen material. After trimming the specimen, the mould assembly-containing sample is replaced in water bath maintained at 27⁰C for 85 to 95 minutes. The sides of the mould are now removed and the clips are carefully hooked on the machine with out causing any initial strain.

The pointer is set to zero, the machine is started and the two clips are pulled apart horizontally at a uniform speed of 50 +/- 2.5mm per minute. While the test is in operation, it is checked whether the sample is immersed in water at depth of at least 10mm. The distance, at which the bitumen thread of each specimen breaks, is recorded (in cm) to report as ductility value.

Results:

The distance stretched by the moving end of the specimen up to the point of breaking of thread measured in centimeters is recorded as ductility value.

Limits: The minimum ductility value of A35 & S35 grade bitumen is 50 cm at 27⁰C.

              All other grades, the ductility value is 75 cm at 27⁰C.  

DELETERIOUS CONTENTS OF SOILS.(IS : 2720 – Part – 27)

DELETERIOUS CONTENTS OF SOILS.

I. Determination of Total Soluble Sulphates by Volumetric Method: (IS : 2720 – Part – 27)

Object:

Determination of total soluble sulphate content of soil by Volumetric method.

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 30.5 grams Barium chloride in one liter of distilled water.

2. Potassium Chromate Solution (N/4): Dissolve 24.275 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: Sp.Gr 1.11.

Test Procedure:

1. 10 grams of soil sample taken in to beaker.

2. Add 50 ml water, stir well, allow decanting and filtered.

3. Take 10 ml filtrate sample by pipette in a conical flask.

4. Make it slightly acidic by adding concentrated hydrochloric acid (i.e.: few drops) and heat to boiling.

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)

II. DETERMINATION OF ORGANIC MATTER IN SOILS ( IS: 2720 – Part – 22)

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Total weight of original soil sample (Oven dried) – W1 grams.

2. Sieve the sample on 10 mm IS sieve and weighed the passing material – W2 grams.

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: Sp.Gr 1.83.

4. Ortho Phosphoric acid: Sp.Gr 1.70 to 1.75.

5. Indicator: 0.25 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 flask.

2. Add 20 ml concentrated Sulphuric acid and swirled and allowed to cool for some times.

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 green.

5. Add 0.5 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 green. 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 flask.

2. Add 10 ml of Potassium Dichromate solution.

3. Add 20 ml of concentrated Sulphuric acid and allowed to 30 minutes on a heat insulating surface like asbestos sheet.

4. Add 200 ml distilled water, 10 ml of Ortho Phosphoric acid, 1 ml of the Indicator and the mixture shall be shake vigorously.

5. Ferrous Sulphate solution added through burette in 0.5 ml increments, up to the solution changes from blue to green.

6. Add 0.5 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 green. 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= 10.5(1 – Y/X).

2. Percentage of Organic Matter in soil = (0.67W2V) / (W1W3)

III. DETERMINATION OF CHLORIDE AND SALINITY IN SOILS

Object:

Determination of total Organic matter in soils.

Sample Preparation:

1. Take the oven dried soil sample and sieve it on 2 mm IS sieve.

2. Take 50 grams of 2mm passing material in conical flask and add the distilled water with 1:5 ratio, allowed to 16 hrs, so that the salts are extracted by the distilled water completely.

Preparation of Reagents:

1. Chloride free distilled water.

2. Potassium Chromate – color Indicator.

3. Standard Silver Nitrate (0.0141N / 0.0156N): Dissolved 2.395 grams Silver Nitrate in one liter of hot distilled water to prepare 0.0141N solution. Alternatively, dissolve 2.65 grams of Silver Nitrate in one liter of hot distilled water to prepare 0.0156N  solution. 

Procedure:

1. Take 25 ml of filtered sample in a conical flask.

2. Adjust the PH in the range of 7 to 8 by adding Sulphuric acid or Sodium Hydroxide solution.

3. Add 1 ml of Potassium Chromate – Yellow color develops.

4. Take 0.0156N Silver Nitrate solution in burette and titrate till brick red color develops. Measure the volume in ml and recorded it as ‘X’.

Calculations:

1. Chloride(mg/l or ppm),  Y = (X x 35.46 x 1000 x 0.0156) / (ml of sample taken)

2. Salinity (ppt or gms/lt) = 0.03 + 1.806 x Chlorides in g/lt.

3. Total Chlorides in soil sample = 5 x Y.