Determining Softening Point Of Bitumen

                                                                                   

                                                                           

Determining Softening Point Of Bitumen

This test is done to determine the softening point of asphaltic bitumen and fluxed native asphalt, road tar, coal tar pitch and blown type bitumen as per IS: 1205 – 1978. The principle behind this test is that softening point is the temperature at which the substance attains a particular degree of softening under specified condition of the test.
The apparatus required for this test :-
i) Ring and ball apparatus
ii) Thermometer – Low Range : -2 to 80^oC, Graduation 0.2^oC – High Range : 30 to 200oC, Graduation 0.5^oC

PREPARATION OF SAMPLE
i) The sample should be just sufficient to fill the ring. The excess sample should be cut off by a knife.

ii) Heat the material between 75 and 100^oC. Stir it to remove air bubbles and water, and filter it through IS Sieve 30, if necessary.

iii) Heat the rings and apply glycerine. Fill the material in it and cool it for 30 minutes.

iv) Remove excess material with the help of a warmed, sharp knife.

Procedure to determine Softening Point Of Bitumen
A) Materials of softening point below 80^o C:
i) Assemble the apparatus with the rings, thermometer and ball guides in position.

ii) Fill the beaker with boiled distilled water at a temperature 5.0 ± 0.5^oC per minute.

iii) With the help of a stirrer, stir the liquid and apply heat to the beaker at a temperature of 5.0 ± 0.5^oC per minute.

iv) Apply heat until the material softens and allow the ball to pass through the ring.

v) Record the temperature at which the ball touches the bottom, which is nothing but the softening point of that material.

B) Materials of softening point above 80^oC:
The procedure is the same as described above. The only difference is that instead of water, glycerine is used and the starting temperature of the test is 35^oC.

REPORTING OF RESULTS
Record the temperature at which the ball touches the bottom.

Determining Penetration of Bitumen

Determining Penetration of Bitumen

 

This test is done to determine the penetration of bitumen as per IS: 1203 – 1978. The principle is that the penetration of a bituminous material is the distance in tenths of a mm, that a standard needle would penetrate vertically, into a sample of the material under standard conditions of temperature, load and time. The apparatus needed to determine the penetration of bitumen is

i) Penetrometer

ii) Water bath

iii) Bath thermometer – Range 0 to 44^oC, Graduation 0.2^oC

SAMPLE
Bitumen should be just sufficient to fill the container to a depth of at least 15mm in excess of the expected penetration.

Procedure to determine the penetration of bitumen
i) Soften the bitumen above the softening point (between 75 and 100^oC). Stir it thoroughly to remove air bubbles and water.

ii) Pour it into a container to a depth of at least 15mm in excess of the expected penetration.

iii) Cool it at an atmospheric temperature of 15 to 30^oC for 1^1/2 hours. Then place it in a transfer dish in the water bath at 25.0 + 0.1^oC for 1^1/2 hrs.

iv) Keep the container on the stand of the penetration apparatus.

v) Adjust the needle to make contact with the surface of the sample.

vi) Adjust the dial reading to zero.

vii) With the help of the timer, release the needle for exactly 5 seconds.

viii) Record the dial reading.

ix) Repeat the above procedure thrice.

REPORTING OF RESULTS
The value of penetration reported should be the mean of not less than three determinations expressed in tenths of a mm.

Aggregate Impact Value (AIV)

AGGREGATE IMPACT VALUE

This test is done to determine the aggregate impact value of coarse aggregates as per IS: 2386 (Part IV) – 1963. The apparatus used for determining aggregate impact value of coarse aggregates is
Impact testing machine conforming to IS: 2386 (Part IV)- 1963,IS Sieves of sizes – 12.5mm, 10mm and 2.36mm, A cylindrical metal measure of 75mm dia. and 50mm depth, A tamping rod of 10mm circular cross section and 230mm length, rounded at one end and Oven.

Preparation of Sample
i) The test sample should conform to the following grading:
- Passing through 12.5mm IS Sieve – 100%

 ii) The sample should be oven-dried for 4hrs. at a temperature of 100 to 110^oC and cooled.

iii) The measure should be about one-third full with the prepared aggregates and tamped with 25 strokes of the tamping rod.

A further similar quantity of aggregates should be added and a further tamping of 25 strokes given. The measure should finally be filled to overflow, tamped 25 times and the surplus aggregates struck off, using a tamping rod as a straight edge. The net weight of the aggregates in the measure should be determined to the nearest gram (Weight ‘A’).

Procedure to determine Aggregate Impact Value
i) The cup of the impact testing machine should be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by 25 strokes of the tamping rod.
ii) The hammer should be raised to 380mm above the upper surface of the aggregates in the cup and allowed to fall freely onto the aggregates. The test sample should be subjected to a total of 15 such blows, each being delivered at an interval of not less than one second.
Reporting of Results
i) The sample should be removed and sieved through a 2.36mm IS Sieve. The fraction passing through should be weighed (Weight ‘B’). The fraction retained on the sieve should also be weighed (Weight ‘C’) and if the total weight (B+C) is less than the initial weight (A) by more than one gram, the result should be discarded and a fresh test done.
ii) The ratio of the weight of the fines formed to the total sample weight should be expressed as a percentage.
Aggregate impact value = (B/A) x 100%
iii) Two such tests should be carried out and the mean of the results should be reported.

DETERMINATION OF SPECIFIC GRAVITY

OBJECTIVE
Determine the specific gravity of soil fraction passing 4.75 mm I.S sieve by density bottle.

NEED AND SCOPE

The knowledge of specific gravity is needed in calculation of soil properties like void ratio, degree of saturation etc.

 DEFINITION

Specific gravity G is defined as the ratio of the weight of an equal volume of distilled water at that temperature both weights taken in air.

 APPARATUS REQUIRED

1. Density bottle of 50 ml with stopper having capillary hole.
2. Balance to weigh the materials (accuracy 10gm).
3. Wash bottle with distilled water.
4. Alcohol and ether.

  PROCEDURE

1. Clean and dry the density bottle  

1. wash the bottle with water and allow it to drain.
2. Wash it with alcohol and drain it to remove water.
3.  Wash it with ether, to remove alcohol and drain ether.

2. Weigh the empty bottle with stopper (W₁)

3. Take about 10 to 20 gm of oven soil sample which is cooled in a desiccator. Transfer it to the bottle. Find the weight of the bottle and soil (W₂).

4. Put 10ml of distilled water in the bottle to allow the soil to soak completely. Leave it for about 2 hours.

5. Again fill the bottle completely with distilled water put the stopper and keep the bottle  

    under constant temperature water baths (T_x⁰ ).

6. Take the bottle outside and wipe it clean and dry note. Now determine the weight of the bottle and the contents  (W₃).

7. Now empty the bottle and thoroughly clean it. Fill the bottle with only disttiled water and weigh it. Let it be W₄ at temperature (T_x⁰ C).

8. Repeat the same process for 2 to 3 times, to take the average reading of it.

  OBSERVATIONS 

S. No.	Observation Number	1	2	3
1 2   3   4	Weight of density bottle (W1 g) Weight of density bottle + dry soil (W2 g) Weight of bottle + dry soil + water at temperature T x0 C (W3 g) Weight of bottle + water (W4 g) at temperature Tx0 C
	Specific gravity G at  Tx0 C
	Average specific gravity at Tx0 C

CALCULATIONS




INTERPRETATION AND REPORTING

  Unless or otherwise specified specific gravity values reported shall be based on water at 27⁰C. So the specific gravity at 27⁰C = K�Sp. gravity at T_x⁰C.

       The specific gravity of the soil particles lie with in the range of 2.65 to 2.85. Soils containing organic matter and porous particles may have specific gravity values below 2.0. Soils having heavy substances may have values above 3.0.

CALIFORNIA BEARING RATIO TEST (CBR)

CALIFORNIA BEARING RATIO TEST 

OBJECTIVE

To determine the California bearing ratio by conducting a load penetration test in the laboratory. 

NEED AND SCOPE

The california bearing ratio test is penetration test meant for the evaluation of subgrade strength of roads and pavements. The results obtained by these tests are used with the empirical curves to determine the thickness of pavement and its component layers. This is the most widely used method for the design of flexible pavement.

This instruction sheet covers the laboratory method for the determination of C.B.R. of undisturbed and remoulded /compacted soil specimens, both in soaked as well as unsoaked state. 

PLANNING AND ORGANIZATION

Equipments and tool required.

1. Cylindrical mould with inside dia 150 mm and height 175 mm, provided with a detachable extension collar 50 mm height and a detachable perforated base plate 10 mm thick. 

2. Spacer disc 148 mm in dia and 47.7 mm in height along with handle. 

3. Metal rammers. Weight 2.6 kg with a drop of 310 mm (or) weight 4.89 kg a drop 450 mm. 

4. Weights. One annular metal weight and several slotted weights weighing 2.5 kg each, 147 mm in dia, with a central hole 53 mm in diameter. 

5. Loading machine. With a capacity of atleast 5000 kg and equipped with a movable head or base that travels at an uniform rate of 1.25 mm/min. Complete with load indicating device. 

6. Metal penetration piston 50 mm dia and minimum of 100 mm in length. 

7. Two dial gauges reading to 0.01 mm. 

8. Sieves. 4.75 mm and 20 mm I.S. Sieves.

9. Miscellaneous apparatus, such as a mixing bowl, straight edge, scales soaking tank or pan, drying oven, filter paper and containers. 

DEFINITION OF C.B.R.

It is the ratio of force per unit area required to penetrate a soil mass with standard circular piston at the rate of 1.25 mm/min. to that required for the corresponding penetration of a standard material.

C.B.R. = Test load/Standard load � 100

The following table gives the standard loads adopted for different penetrations for the standard material with a C.B.R. value of 100%

Penetration of plunger    (mm)	Standard load    (kg)
2.5 5.0 7.5 10.0 12.5	1370 2055 2630 3180 3600

          The test may be performed on undisturbed specimens and on remoulded specimens which may be compacted either statically or dynamically. 

PREPARATION OF TEST SPECIMEN

Undisturbed specimen

Attach the cutting edge to the mould and push it gently into the ground. Remove the soil from the outside of the mould which is pushed in . When the mould is full of soil, remove it from weighing the soil with the mould or by any field method near the spot.

Determine the density

Remoulded specimen

Prepare the remoulded specimen at Proctor�s maximum dry density or any other density at which C.B.R> is required. Maintain the specimen at optimum moisture content or the field moisture as required. The material used should pass 20 mm I.S. sieve but it should be retained on 4.75 mm I.S. sieve. Prepare the specimen either by dynamic compaction or by static compaction. 

Dynamic Compaction

Take about 4.5 to 5.5 kg of soil and mix thoroughly with the required water.

Fix the extension collar and the base plate to the mould. Insert the spacer disc over the base (See Fig.38). Place the filter paper on the top of the spacer disc.

   Compact the mix soil in the mould using either light compaction or heavy compaction. For light compaction, compact the soil in 3 equal layers, each layer being given 55 blows by the 2.6 kg rammer. For heavy compaction compact the soil in 5 layers, 56 blows to each layer by the 4.89 kg rammer.

Remove the collar and trim off soil.

Turn the mould upside down and remove the base plate and the displacer disc.

Weigh the mould with compacted soil and determine the bulk density and dry density.

Put filter paper on the top of the compacted soil (collar side) and clamp the perforated base plate on to it. 

Static compaction

Calculate the weight of the wet soil at the required water content to give the desired density when occupying the standard specimen volume in the mould from the expression.

                                       W =desired dry density * (1+w) V

Where W = Weight of the wet soil

            w = desired water content

           V = volume of the specimen in the mould = 2250 cm³ (as per the mould available in laboratory)

Take the weight W (calculated as above) of the mix soil and place it in the mould.

Place a filter paper and the displacer disc on the top of soil.

Keep the mould assembly in static loading frame and compact by pressing the displacer disc till the level of disc reaches the top of the mould.

Keep the load for some time and then release the load. Remove the displacer disc.

The test may be conducted for both soaked as well as unsoaked conditions.

If the sample is to be soaked, in both cases of compaction, put a filter paper on the top of the soil and place the adjustable stem and perforated plate on the top of filter paper.

Put annular weights to produce a surcharge equal to weight of base material and pavement expected in actual construction. Each 2.5 kg weight is equivalent to 7 cm construction. A minimum of two weights should be put.

Immerse the mould assembly and weights in a tank of water and soak it for 96 hours. Remove the mould from tank.

Note the consolidation of the specimen. 

Procedure for Penetration Test

Place the mould assembly with the surcharge weights on the penetration test machine. (Fig.39).

Seat the penetration piston at the center of the specimen with the smallest possible load, but in no case in excess of 4 kg so that full contact of the piston on the sample is established.

Set the stress and strain dial gauge to read zero. Apply the load on the piston so that the penetration rate is about 1.25 mm/min.

Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. Note the maximum load and corresponding penetration if it occurs for a penetration less than 12.5 mm.

Detach the mould from the loading equipment. Take about 20 to 50 g of soil from the top 3 cm layer and determine the moisture content. 

Observation and Recording

For Dynamic Compaction

Optimum water content (%)                                                                      

Weight of mould + compacted specimen g                                               

Weight of empty mould g                                                                          

Weight of compacted specimen g                                                              

Volume of specimen cm³                                                                            

Bulk density g/cc                                                                                       

Dry density g/cc                                                                                         

For static compaction

Dry density g/cc

Moulding water content %

Wet weight of the compacted soil, (W)g

Period of soaking 96 hrs. (4days). 

For penetration Test

Calibration factor of the proving ring                                                1 Div. = 1.176 kg

Surcharge weight used (kg)                                                                2.0 kg  per 6 cm construction

Water content after penetration test %

Least count of penetration dial                                                             1 Div. = 0.01 mm 

If the initial portion of the curve is concave upwards, apply correction by drawing a tangent to the curve at the point of greatest slope and shift the origin (Fig. 40). Find and record the correct load reading corresponding to each penetration.

                                         C.B.R. = P_T�/P_S � 100

where P_T = Corrected test load corresponding to the chosen penetration from the load penetration curve.

          P_S = Standard load for the same penetration taken from the table I. 

Penetration Dial	Load Dial	Corrected Load
Readings Penetration (mm)	proving ring reading Load (kg)

Interpretation and recording

C.B.R. of specimen at 2.5 mm penetration                              

C.B.R. of specimen at 5.0 mm penetration           

  C.B.R. of specimen at 2.5 mm penetration      

The C.B.R. values are usually calculated for penetration of 2.5 mm and 5 mm. Generally the C.B.R. value at 2.5 mm will be greater that at 5 mm and in such a case/the former shall be taken as C.B.R. for design purpose. If C.B.R. for 5 mm exceeds that for 2.5 mm, the test should be repeated. If identical results follow, the C.B.R. corresponding to 5 mm penetration should be taken for design.

DETERMINATION OF CONSISTENCY LIMITS

LIQUID LIMIT TEST
OBJECTIVE
1.Prepare soil specimen as per specification.
2.Find the relationship between water content and number of blows.
3.Draw flow curve.
4.Find out liquid limit.

NEED AND SCOPE

Liquid limit is significant to know the stress history and general properties of the soil met with construction. From the results of liquid limit the compression index may be estimated. The compression index value will help us in settlement analysis. If the natural moisture content of soil is closer to liquid limit, the soil can be considered as soft if the moisture content is lesser than liquids limit, the soil can be considered as soft if the moisture content is lesser than liquid limit. The soil is brittle and stiffer.

 THEORY

The liquid limit is the moisture content at which the groove, formed by a standard tool into the sample of soil taken in the standard cup, closes for 10 mm on being given 25 blows in a standard manner. At this limit the soil possess low shear strength.

 APPARATUS REQUIRED

 1. Balance   2. Liquid limit device  (Casagrende�s)   3. Grooving tool   4. Mixing dishes 

 5. Spatula   6. Electrical Oven  

PROCEDURE

1. About 120 gm of air-dried soil from thoroughly mixed portion of material passing 425   micron I.S sieve is to be obtained.

2. Distilled water is mixed to the soil thus obtained in a mixing disc to form uniform paste. The paste shall have a consistency that would require 30 to 35 drops of cup to cause closer   of standard groove for sufficient length.

3. A portion of the paste is placed in the cup of  LIQUID LIMIT device and spread into   portion with few strokes of spatula.

4. Trim it to a depth of 1cm at the point of maximum  thickness and return excess of soil to    the dish.

5. The soil in the cup shall be divided by the firm strokes of the grooving tool along the diameter through the centre line of the follower so that clean sharp groove of proper  dimension is formed.

6. Lift and drop the cup by turning crank at the rate of two revolutions per second until the  two halves of soil cake come in contact with each other for a length of about 1 cm by  flow only.

7. The number of blows required to cause the groove close for about 1 cm shall be recorded.

8. A representative portion of soil is taken from the cup for water content determination.

9. Repeat the test with different moisture contents at least three more times for blows between   10 and 40.  

OBSERVATIONS

Details of the sample:.......
Natural moisture content:........                Room temperature:..............

COMPUTATION / CALCULATION

Draw a graph showing the relationship between water content (on y-axis) and number of blows (on x-axis) on semi-log graph. The curve obtained is called flow curve. The moisture content corresponding to 25 drops (blows) as read from the represents liquid limit. It is usually expressed to the nearest whole number.

 INTERPRETATION AND RECORDING 

Flow index I_f = (W₂-W₁)/(logN₁/N₂) = slope of the flow curve.

Plasticity Index = w_l-w_p =

Toughness Index = I_p/I_f =

 

PLASTIC LIMIT TEST

NEED AND SCOPE  

Soil is used for making bricks , tiles , soil cement blocks in addition to its use as foundation for structures.

APPARATUS REQUIRED

1.Porcelain dish.
2.Glass plate for rolling the specimen.
3.Air tight containers to determine the moisture content.
4.Balance of capacity 200gm and sensitive to 0.01gm
5.Oven thermostatically controlled with interior of non-corroding material to maintain the temperature around 105⁰ and 110⁰C.

PROCEDURE

1. Take about 20gm of thoroughly mixed portion of the material passing through 425 micron  I.S.  sieve obtained in accordance with I.S. 2720 (part 1).

2. Mix it thoroughly with distilled water in the evaporating dish till the soil mass becomes   plastic enough to be easily molded with fingers.

3. Allow it to season for sufficient time  (for  24 hrs) to allow water to permeate throughout the soil mass

4. Take about 10gms of this plastic soil mass and roll it between fingers and glass plate with  just sufficient pressure to roll the mass into a threaded of uniform diameter throughout its   length. The rate of rolling shall be between 60 and 90 strokes per minute.

5. Continue rolling till you get a threaded of 3 mm diameter.

6. Kneed the soil together to a uniform mass and re-roll.

7. Continue the process until the thread crumbles when the diameter is 3 mm.

8. Collect the pieces of the crumbled thread in air tight container for moisture content  determination.

9. Repeat the test to at least 3 times and take the average of the results calculated to the nearest   whole number.

OBSERVATION AND REPORTING

Compare the diameter of thread at intervals with the rod. When the diameter reduces to 3 mm, note the surface of the thread for cracks.

PRESENTATION OF DATA

Average Plastic Limit=...............

Plasticity Index(Ip) = (LL - PL)=............        Toughness Index =Ip/I_F

SHRINKAGE LIMIT TEST

OBJECTIVE

To determine the shrinkage limit and calculate the shrinkage ratio for the given soil. 

THEORY

As the soil loses moisture, either in its natural environment, or by artificial means in laboratory it changes from liquid state to plastic state, from plastic state to semi-solid state and then to solid state. Volume changes also occur with changes in water content. But there is particular limit at which any moisture change does not cause soil any volume change. 

NEED AND SCOPE

Soils which undergo large volume changes with change in water content may be troublesome. Volume changes may not and usually will not be equal.

A shrinkage limit test should be performed on a soil.

  1. To obtain a quantitative indication of how much change in moisture can occur before any   appreciable volume changes occurs

  2. To obtain an indication of change in volume.

The shrinkage limit is useful in areas where soils undergo large volume changes when going through wet and dry cycles (as in case of earth dams)

 APPARATUS

1.  Evaporating Dish. Porcelain, about 12cm diameter with flat bottom.

2.  Spatula

3.  Shrinkage Dish. Circular, porcelain or non-corroding metal dish (3 nos) having a flat   bottom and 45 mm in diameter and 15 mm in height internally.

4.  Straight Edge. Steel, 15 cmm in length.

5.  Glass cup. 50 to 55 mm in diameter and 25 mm in height , the top rim of which is ground   smooth and level.

6.  Glass plates. Two, each 75 � 75 mm one plate shall be of plain glass and the other shall   have prongs.

7.  Sieves. 2mm and 425- micron IS sieves.

8.  Oven-thermostatically controlled.

9.  Graduate-Glass, having a capacity of 25 ml and graduated to 0.2 ml and 100 cc one �mark   flask.

10.Balance-Sensitive to 0.01 g minimum.

11.Mercury. Clean, sufficient to fill the glass cup to over flowing.

12.Wash bottle containing distilled water.

PROCEDURE

 Preparation of soil paste

1. Take about 100 gm of soil sample from a thoroughly mixed portion of the material passing  through 425-micron I.S. sieve.

2. Place about 30 gm the above soil sample in the evaporating dish and thoroughly mixed  with distilled water and make a creamy paste.

Use water content some where around the liquid limit.

 Filling the shrinkage dish

3. Coat the inside of the shrinkage dish with a thin layer of Vaseline to prevent the soil sticking to the dish.

4. Fill the dish in three layers by placing approximately 1/3 rd of the amount of wet soil with the help of spatula. Tap the dish gently on a firm base until the soil flows over the edges and no apparent air bubbles exist. Repeat this process for 2nd and 3rd layers also till the dish is completely filled with the wet soil. Strike off the excess soil and make the top of the dish smooth. Wipe off all the soil adhering to the outside of the dish.

5. Weigh immediately, the dish with wet soil and record the weight.

6. Air- dry the wet soil cake for 6 to 8hrs, until the colour of the pat turns from dark to light. Then oven-dry the to constant weight at 105⁰C to 110⁰C say about 12 to 16 hrs.

7. Remove the dried disk of the soil from oven. Cool it in a desiccator. Then obtain the weight of the dish with dry sample.

8. Determine the weight of the empty dish and record.

9. Determine the volume of shrinkage dish which is evidently equal to volume of the wet soil as follows. Place the shrinkage dish in an evaporating dish and fill the dish with mercury  till  it overflows slightly. Press it with plain glass plate firmly on its top to remove excess mercury. Pour the mercury from the shrinkage dish into a measuring jar and find the volume of the shrinkage dish directly. Record this volume as the volume of the wet soil pat.

 Volume of the Dry Soil Pat

10. Determine the volume of  dry soil pat by removing the pat from the shrinkage dish and immersing it in the glass cup full of mercury in the following manner.

 Place the glass cup in a larger one and fill the glass cup to overflowing with mercury. Remove the excess mercury by covering the cup with glass plate with prongs and pressing it. See that no air bubbles are entrapped. Wipe out the outside of the glass cup to remove the adhering mercury. Then, place it in another larger dish, which is, clean and empty carefully.

 Place the dry soil pat on the mercury. It floats submerge it with the pronged glass plate which is again made flush with top of the cup. The mercury spills over into the larger plate. Pour the mercury that is displayed by the soil pat into the measuring jar and find the volume of the soil pat  directly.

CALCULATION

CAUTION

Do not touch the mercury with gold rings.

  TABULATION AND RESULTS   

S.No	Determination No.	1	2	3
1 2 3 4 5 6 7 8       9 10	Wt. of container in gm,W1 Wt. of container + wet soil pat in gm,W2 Wt. of container + dry soil pat in gm,W3 Wt. of oven dry soil pat, W0 in gm Wt. of water in gm Moisture content (%), W Volume of wet soil pat (V), in cm Volume of dry soil pat (V0) in cm3  By mercury displacement method a.       Weight of displaced mercury b.      Specific gravity of the mercury Shrinkage limit (WS) Shrinkage ratio (R)

Field Density Test

* Procedure of Test

    First placed the field density plate on the place where the density should be measure.

    Then dig a pit having a depth around 6’’ and a diameter of the inner circle of the field density plate.

    Took the gravel from the dig and measured the weight.


    Measure the weight of the field density bottle.

    After that turn up down the bottle and kept the edge of the cone of the field density bottle on the plate and opened the tap at the neck and let the sand fill the pit.

    Then, measure the weight of the bottle with the rest of the sand retained in the bottle.

    Volume of sand filled the pit was calculated.

    The sand of the bottle should be passed through 1.18 mm sieve and retained on     0.6 mm sieve.

DETERMINATION OF MOISTURE CONTENT

 OBJECTIVE

Determine the natural content of the given soil sample.

NEED AND SCOPE OF THE EXPERIMENT

In almost all soil tests natural moisture content of the soil is to be determined. The knowledge of the natural moisture content is essential in all studies of soil mechanics. To sight a few, natural moisture content is used in determining the bearing capacity and settlement. The natural moisture content will give an idea of the state of soil in the field. 

DEFINITION

The natural water content also called the natural moisture content is the ratio of the weight of water to the weight of the solids in a given mass of soil. This ratio is usually expressed as percentage.

APPARATUS REQUIRED

    1. Non-corrodible air-tight container. 
    2. Electric oven, maintain the temperature between 1050 C to 1100 C.
    3. Desiccator.
    4. Balance of sufficient sensitivity. 

PROCEDURE

1. Clean the container with lid dry it and weigh it (W1).
2. Take a specimen of the sample in the container and weigh with lid (W2).
3. Keep the container in the oven with lid removed. Dry the specimen to constant weight maintaining the temperature between 1050 C to 1100 C for a period varying with the type of soil but usually 16 to 24 hours.
4. Record the final constant weight (W3) of the container with dried soil sample. Peat and other organic soils are to be dried at lower temperature (say 600 ) possibly for a longer period. 

  Certain soils contain gypsum which on heating loses its water if crystallization. If itb is suspected that gypsum is present in the soil sample used for moisture content determination it shall be dried at not more than 800 C and possibly for a longer time.

OBSERVATIONS AND RECORDING

Data and observation sheet for water content determination  

S.No.	Sample No.	1	2	3
1	Weight of container with lid W1 gm
2	Weight of container with lid +wet soil W2 gm
3	Weight of container with lid +dry soil W3 gm
4	Water/Moisture content W = [(W2-W3)/(W3-W1)]x100

   

INTERPRETATION AND REPORTING

  RESULT

The natural moisture content of the soil sample is ________

  GENERAL REMARKS

1. A container with out lid can be used, when moist sample is weighed immediately after placing the container and oven dried sample is weighed immediately after cooling in desiccator. 2. As dry soil absorbs moisture from wet soil, dried samples should be removed before placing wet samples in the oven.