EXPERIMENTAL STUDY OF SOIL STAILIZATION USING FLY ASH AND PLASTIC POWDER
Presented by:
N.C.Balakarthik
S.Ramkumar
ABSTRACT
Poor subgrade soil conditions can result in inadequate. Pavement support and reduce pavement life. Soils may be improved through the addition of class C fly ash & plastic powder. Such additives range from waste product’s to manufactured materials include class C fly ash & plastic powder. These additives can be used with a variety of soils to help improve their native engineering properties. The effectiveness of their additives depends on the soil treated and the amount of additive used.
The report contains a summary of the performance of class C fly ash and plastic fibre used with a wide range of soils. Laboratory tests have been carried out and results are reported in this paper. Each of the additives is combine with the soil of
10%,20%&30% to improve the texture, increase Strength, and reduce swell characteristics.
Plastic and flyash stabilized soils showed the most improvement in soil performance for both soils. The results showed that stabilized soils may be effective for construction of durable subgrades.
Geotechnical properties soils such as soft fine-grained and expansive soils are improved by various methods. The problematic soil is removed and replaced by a good quality material or treated using fly ash &plastic fibre.
Different methods can be used to improve and treat the geotechnical properties of the problematic soils (such as strength and the stiffness) by treating it in situ.These methods include densifying treatments (such as compaction or preloading), pore water pressure reduction techniques (such as dewatering or electro-osmosis), the bonding of soil particles (by ground freezing, grouting, and chemical stabilization), and use of reinforcing elements (such as geotextiles and stone columns).
The soil stabilization paper describes carried out to check the improvements in the properties of soil with flyash& plastic fibre in varying percentages.The soil stabilization is very important for many of the geotechnical engineering applications such as geotechnical engineering applications such as pavement structures, roadways. Building foundations, channel and reservoir linings, and irrigation systems. Water lines, and sewer lines to avoid the demage due to the settlement of the settlement of the soft soil or to the swelling action (heave) of the expensive soils.
Use of fly ash soil in soil stabilization. Soils can be treated with fly ash & plastic powder to modify engineering properties as well as produce rapid strength gain in unstable soils.
SOIL TYPE AND TESTING
INTRODUCTION
Soil can be described in many different ways, such as heavy, light, sandy, clay, loam, poor or good.Scientists typically describe soil according to its:
Ø Color
Ø Compaction
Ø Moisture content
Ø Organic content
Ø Ph
Ø Profile
Ø Structure
Ø Temperature, and
Ø Texture
Although each of these factors is important, three factors (texture, organic content and Ph.) are more important than the others. Regardless, we will provide a brief overview of all nine factors below.
Colour
Soil color can provide information about organic matter in the soil, drainage, biotic activity, and fertility. The chart below can give you some insight into the condition of your soil just from its appearance. To identify the color of your soil, you should take a garden spade or shovel, and dig a shallow hole, at least 3” – 4” deep and gauge the color (you should do this quickly before the sun can dry it out).
Condition
|
Dark color
|
Moderately dark color
|
Light color
| |
Organic matter
|
High
|
medium
|
Low
| |
Erosion factor
|
Low
|
medium
|
High
| |
Aeration
|
High
|
medium
|
Low
| |
Available nitrogen
|
High
|
medium
|
Low
| |
Fertility
|
High
|
medium
|
Low
| |
Compaction
To be healthy, a soil needs to be able to breath and water needs to be able to move through it reasonably easily. Compacted soils do not allow much air to circulate to the root zone and water (rainfall or irrigation) tends to be just run-off. This increases erosion and strips away vegetation and top soil. A normal, loosely compacted soil helps to absorb and retain water, releasing it slowly, and allows the root zone of plants to “breath”. These soils are generally more productive, since plants can grow much more readily. Dense, highly compacted soils typically have less plant growth, which increases runoff.
The rate of infiltration of water is an excellent indication of soil health. You can measure thev water infiltration rate very easily:
Ø First, get a large, empty coffee can cut off the bottom.
Ø Second, beginning about 3” up from the bottom, make the inside of the can every 3” with a permanent marker, being careful not to cut your hand on the edges of the can.
Ø Drive the can about 3” into the ground until the first mark is level with the ground (placing a board on the top of they can and pounding the board with a hammer will help drive into the ground. Be careful not to irrigate the area first, since this will prevent you from getting an accurate measurement of the infiltration rate.
Ø Fill the can with water clear to the top and begin timing the rate of infiltration .Measure the amount of water that has drained into the soil at the end of each minute for the first ten minutes. Determine the rate of infiltration in inches per minute by dividing the total number of inches of water that drained away in the can by 10 minutes .Knowing the actual water infiltration rate for your yard is critical if you want minimize the amount of water you use.
Ø Repeat the experiment at several areas around your yard, being careful to record each location and its infiltration rate. If the infiltration rates at each location vary considerably, then draw a quick sketch of your yard, and plot the infiltration rate for the aera. If you install an automated sprinkler system, you can adjust the emitters in each aera to only deliver the amount of water that can infiltrate in a given amount of time. This will eliminate irrigation run-off from your yard or garden, while ensuring adequate soil moisture for plants.
Moisture
The amount if moisture found in soil varies greatly with the type of soil, climate and the amount of humus in that soil. The types of organisms that can survive in your soil is largely determined by the amount of water available to them , since water acts as a means of nutrient transport and is necessary for cell survival. Soil moisture can also be determined by a soils laboratory. Soils labs typically dry a sample in an oven or a hot plate and compare the weight of the soil before drying to the weight after drying. The moisture content is reported as percent moisture on a weight basis. Several irrigation system manufacturers have developed soil moisture indicators that can be used to control irrigation more precisely , turning the system on only in areas where more water is needed and then only for the minimum time necessary to get the soil moisture back up to the desired level.
Organic content
The organic content of soil greatly influences the plant, animal and microorganisum populations in that soil. Decomposing organic materials provides many necessary nutrients to soil inhabitants. Without fresh additions of organic matter from time to time, the soil becomes deficient in some nutrients and soil populations decrease. The amount of organic materials can be determined by ignition. Organic materials is made of carbon compounds, which when heated to high temperatures are converted to carbon dioxide and water. In the inorganic process, a dry solid sample is heated to a high temperature. The results in a change in weight which allows for calculation of the organic content of the sample.
Soil pH
Most people thick that rainwater has a Ph 7, so it comes as something of a shock when they learn that rainwater has a normal Ph of about 6-6.5, which is slightly acidic. This is due to dissolved carbon dioxide from the air, which reacts with water to from a dilute acid, much like the carbon dioxide in soda. It should then come as no surprise that most plants grow their best at around the same pH*. You can determine the p H of your soil very easily using a universal indicator solution or pH paper, available at most hardware stores in the pool supplies section. To determine the pH , Just put a small amount of universal indicator over the soil, then match the color of the indicator solution with the p H Color chat. If you decide to use p H paper, pour a small amount of water on the soil sample. Touch the pH paper to the sample and match to color of the paper to the Ph color chart.
Soil profile
If you really want to know about your soil, the best way to start is to obtain a cross- section of the various layers. This can be done fairly easily if you use a soil oil core tool. A soil core tool is little more than a hollow tube 2 to 4 feet in length with a handle and cross piece like a shovel to help push it in. Once the tool has been inserted into the soil, it should be turned to loosen the soil and then pulled out. The resulting soil core can be easily examined to which is called a soil profile. To determine a soil horizon, you simply mark where the soil changes color and general appearance.
Soil structure
Soil structure tells how the soil affects the movement of water, air and root penetration into the soil. The geometric shapes of the soil determine how it is put together. Words such as blocky, columns, and plate-like, describe soil structures. To determine the structure of your soil, carefully break apart each layer and match its characteristics with the appropriate structural type shown below.
STRUCTURAL TYPE
|
WATER PENETRATION
|
DRINAGE
|
AERATION
|
columns
|
Good
|
good
|
Good
|
blocky
|
Good
|
good
|
Good
|
granular
|
Good
|
best
|
Best
|
Plate-like
|
Moderate
|
moderate
|
Moderate
|
Soil Temperature
Soil temperature has a significant role in helping to determine the rate of growth, and whether a plant will even survive. The temperature in your soil changes greatly with depth. To measure soil temperature, find an area that is not in direct sunlight. Using a thermometer, measure the air temperature at shoulder height. Hold the thermometer still for about one minute, read and record the air temperature. Next, measure the temperature at the surface of the surface of the ground. Put the thermometer flat on the ground and record the temperature after one minute. To determine the temperature below the ground surface, use a dowel into the ground till you reach the 1 inch mark. Remove the dowel and insert the thermometer for one minute, then remove the thermometer and quickly record the temperature. Repeat this procedure to obtain temperature readings at 2 inches, 6 inches and 12 inches. Take temperature reading at different times throughout the day at the same location. To compare with soil temperatures for areas in direct sun, just repeat using the same procedure but select an area that gets full sun. You will note that the soil temperatures in these areas are typically much higher than in the shaded areas.
Soil temperature
|
Conditions during growing season
|
Less than 400 F
|
No growth , bacteria and fungi are not very active
|
400 F to 650 F
|
Some growth
|
650 F to 700 F
|
Fastest growth
|
700 F to 850 F
|
Some growth
|
Above 850 F
|
No growth
|
Soil texture
Sandy soil absorbs more than two inches of water per hour. It is very porous, with large spaces between soil particles. Little water is retained and the sandy soil dries out quickly. Loam soil absorbs from 25 inches to 2 inches per hour. The soil is loose and porous and holds water quite well. Clay soil absorbs less than 25 inches of water per hour. Clay soil is dense with few air spaces between particles and holds water so tightly that little water is available for plants.
PROCEDURE
This chapter contains a description of the testing procedures followed as a part of this project standard procedures were used where possible. Adjustments to standard procedures are noted and non-standard procedures are described in detail.
Materials used
Native soil
Two different soils with type CH, CL, ML, SM, and SP were selected for use in the admixture evaluation. The native soil properties were determined according to ASTM standards list in table as described in the following sections. Soil from e the biomedical infrant of the college campus, and another place is near aeronotical department back side hill area were tested. Approximate source locations of the soil are shown in Figure.
Additives
TEST
|
ASTM
|
Grain Size Analysis
|
D 422
|
Atterberg Limits
|
D 4318
|
Specific Gravity
|
D 854
|
P H Lime stabilization
|
D 6276
|
Moisture – Density Relationship
|
D 629
|
Swell
|
KDOT in – house test method
|
Freeze - thaw
|
D 560
|
Wet – dry
|
D 559
|
Unconfined Compression
|
D 1633 , D 5102
|
The additives used for the stabilization and modification study included C fly ash & plastic powder. The soil were mixed with each of the additives for which there were reasonable expectations of improved engineering properties. Fly ash was fixed at 16%, which is the amount of cement required to lower the plasticity index to 10, with a maximum limit set at 9%. For soils with a native PI below 10, the amount of cement used was determined according to the Portland cement Association Soil-Cement Handbook (22). The enzymatic stabilizer was mixed at a dilution ratio of one ounce Permazyme to one of water in accordance with the manufactures recommendations (4).
Lab Testing
Soil – Preparation
Each soil was air- dried overnight in large pans and was then broken up to pass the 4.75 mm sieve. Samples of the soil were wet sieved according to ASTM D 2216 over a #40 sieve to remove the large particles. The #40 sieve was used instead of the #10 sieve because the Atterberg limits require materials passing through the 600 microns and retaining the 425 micron sieve size. After the material was broken then used for Atterberg Limits testing.
Atterberg Limits
The Atterberg limits were determined on the soil –lime using the KDOT Lime PI procedure. The lime was mixed with the soil and water was added to raise the moisture content of the soil – lime mixture to 5% above the native plastic limit. The soil –lime mixture was then allowed to mellow in a room at 22˚C for 48 hours. The sample and container were placed in an unsealed plastic bag with the opened end folded under the container. After the 48- hour moist curing the sample the sample was dried at 71˚C overnight. The Liquid limit, plastic limit and plasticity index of the soil - lime mixture were the determined in accordance with ASTM D 4318.
Fly ash
A weight of fly ash equivalent to the dry weight of soil was added for Atterberg limits testing. The fly ash was mixed with the soil to a uniform consistency. After complete mixing of the soil, fly ash and distilled water, the sample was covered and allowed for one hour. Atterberg limits were then determined.
Plastic powder
A weight of plastic powder equivalent to the dry weight of soil was added for Atterberg limits testing. The plastic powder was mixed with the soil a uniform consistency. After complete mixing of soil, plastic powder and distilled water, the sample was covered and allowed for one hour. Atterberg limits were then determined.
Moisture – Density Relationships (Proctor)
Fly ash
The fly ash percentage was based on the weight of dry soil. After the fly ash was added, the soil-fly ash mixture to a uniform consistency water was added to the soil-fly ash mixture was mixture was mixed to a uniform consistency. Water was added to the soil-fly ash mixture was placed in an airtight container for 1 hour to simulate a standard construction delay. Then it was compacted in a standard proctor mold and compacted with standard compaction.
Plastic powder
The plastic powder percentage was based on the weight of dry soil. After the plastic powder was added, the soil-plastic powder mixture to a uniform consistency water was added to the soil-plastic powder mixture was mixture was mixed to a uniform consistency. Water was added to the soil-plastic powder mixture was placed in an airtight container for 1 hour to simulate a standard construction delay. Then it was compacted in a standard proctor mold and compacted with standard compaction.
Unconfined Compression Testing
The soil sample that were compacted for the moisture-density relationships were cured for 14 days and then tested to determine their unconfined compressive strength. Reading were obtained at 10 minutes, 1 days, 7 days & 14 days after compaction.
TYPES OF TESTING
There are various tests are conducted for the soil stabilization.
Ø Sieve analysis
Ø Atterberg limits
Ø Specific gravity
Ø Procter compaction
Ø Field density method
Ø Un confined compression
Ø Permeability test
Sieve analysis
In the BS and ASTM standards, the sieve sizes are given in terms of the number of opening per inch. The number of opening per square inch is equal to the square of the number of the number of the sieve .In the Indian Standard (IS: 460-1962), the sieves are designated by the size of the aperture in mm. Table gives a list of sieves and their openings, for IS, and ASTM specifications. The complete sieve analysis can be divided into two parts – the analysis and fine analysis. An oven-dried sample of soil is separated into two fractions by sieving it through a 4.75 mm is sieve. The portion retained on it (+ 4.75 mm sieve size) it termed as the gravel fraction and is kept for the analysis, while the portion passing through it (- 4.75 mm sieve size) is subjected to fine sieve analysis. The following set of sieves used for coarse sieve analysis: IS: 100, 63, 20, 1O, and 4.75 mm. The sieves used for fine sieve analysis are : 2mm , 1.0 mm ,600 ,425 ,300 , 212 ,150 ,and 75 microns IS sieves.
Sieving is performed by arranging the various sieves one over the other in the order of their mesh opening – the largest aperture sieve being kept at the smallest aperture sieve at the bottom. A receiver is kept at the bottom and a cover is kept at the top of the whole assembly. The soil sample is put on the top sieve, and the whole assembly is fitted on a sieve shaking machine. The amount of shaking depends upon the shape and the number of particles. At least 10 minutes of shaking is desirable for soils with small particles. The portion of the soil sample retained on each sieve is calculated on the basis of the total mass of the soil sample taken and from these results, percentage passing through each sieve is calculated.
Atterberg limit
The Atterberg limits which are most useful for engineering purposes are liquid limit, and plastic limit. These limits are expressed as per cent water content.
Liquid limit
Liquid limit is the water content corresponding to the arbitrary limit between minimum water content at which the soil is still in the liquid state , but has a small shearing strength against flowing which can be measured by standard available means. With reference to the standard liquid limit content of which a part of soil cut. By a groove of standard dimension m, will flow together for a distance of 12 mm under impact of 25 blows in the device.
Plastic limit
Limit is the water content corresponding to an arbitrary limit between the plastic and the semi- solid states of consistency of the soil. It is defined as the minimum water content at which a soil will just begin to crumble when rolled into a thread approximately 3mm in diameter.
Determination of liquid limit
The liquid limit is determined in the laboratory with the help of the standard liquid limit apparatus designed by Casagrande. The apparatus consists of a hard rubber base of B.S. Hardness 21-25, over which a brass cup drops trough a desired height. The brass cup can be raised and lowered to fall on the cup can be adjusted with the help of adjusting screws. Before starting the test, the height of fall of the cup is adjusted to I cm. Two types of grooving tools are used (1) the Casagrande tool (2) ASTM tool. 11.0 mm wide at the top and 8 mm high while the ASTM tool cuts a groove 2 mm wide at bottom , 13.6 mm at the top and 10 mm deep . The ASTM tool is used only for sandy soils where Casagrande tool tends to tear the sides of the groove .About 100 g of the specimen passing through 425 microns sieve is mixed thoroughly with distilled water in the evaporation dish or on a marble plate to form a uniform paste. A portion of the paste is placed in the cup over the spot where the cup rests on the base, squeezed down and spread into position and the groove is cut in the soil pat when the groove should close in 25 blows, the liquid limit is determined by plotting a graph between number of blows, and corresponding the water content.
Plastic limit determination
To determine the plastic limit , the soil specimen , passing 425 microns sieve , is mixed thoroughly with distilled water until the soil mass becomes plastic soil mass should be left for enough time to allow water to permeate through the soil mass . A ball is formed with about 8 g of the plastic soil mass and rolled between the fingers and a glass plate with just sufficient pressure to roll the mass into a thread of uniform diameter throughout its length. When a diameter of 3 mm is reached, the soil is remolded again into a ball. This process of rolling and remolding is repeated until the thread until the thread starts just crumbling at a diameter of 3mm. The crumbled threads are kept for water content determination. The test is repeated twice more with fresh samples. The plastic limit is then taken as the average of three water contents
Specific gravity
Specific gravity G is defined as the ratio of the weight of a given volume of soil solids at a given temperature to the weight of an equal volume of distilled water at the temperature, both weights being taken in air. In other words, it is the ratio of unit weight of soil solids to that of water.
Determination of specific gravity by pycnometer
The object of the test is to determine the specific gravity of soil fraction passing 4.75mm IS sieve by pycnometer. 1) Pycnometer of about 900 ml capacity, with the conical brass cap and screwed at its top, 2) Balance sensitive to 1 kg, 3) Glass rod, 4) De aerated , distilled water
Test procedure
1) Clean the pycnometer and dry it. Find the mass of the pycnometer, brass cap and washer, accurate to 1kg
2) Take about 200 to 400 g of oven-dried soil and put it in the pycnometer. Find the mass of pycnometer plus soil etc..
3) Fill the pycnometer to half its height with distilled water and mix it thoroughly with glass rod. Add more water and stir it. Replace the screw top and fill the pycnometer flush with hole in the conical cap. Dry the pycnometer from outside, and find the mass.
4) Repeat steps 2 to 4 for two more determination of specific gravity.
Determination of field density of soil
The object of the test is to determine the dry density and dry unit weight of soil in- place by the core cutter.
Materials and equipment
1) Cylindrical core cutter of steel, 130 mm long and 10 cm internal diameter, with the wall thickness of 3 mm , beveled at one ended
2) Steel dolly, 2.5 cm high and 10 cm internal diameter, with a lip to enable it to be fitted on top of the core cutter,
3) Steel rammer, having mass of 9 kg
4) Straight edge
1) Palette knife
2) Balance accurate to 1 kg
Test procedure
1) Measure the inside dimension of the core cutter and calculate its volume find the mass of the core cutter accurate to 1 kg.
2) Expose the small area about 30 cm square, to be tested and level it. Put the dolly on the top of the core cutter and drive the assembly into soil with the help of the rammer until the top of the dolly protrudes about 1.5 cm above the surface.
3) Dig out the container from the surrounding soil, and allow some soil to project from the lower end of the cutter. With the trim flat the cutter. Take out the dolly and also trim flat the other end of the cutter
4) Find the mass of cutter full of soil.
5) Keep some representative specimen of soil for water content determination.
Permeability test
The property of a porous material which permits the passage or seepage of water through its interconnecting voids. A material having continuous voids is called permeability.
Determination of permeability by constant head test
The object of the experiment is to determine the coefficient of permeability of soil in the laboratory by constant head test using Jodhpur permeameter.
Material and equipment
1. Jodhpur permeameter complete with all accessories
2. De-aired water
3. Balanced to weigh to 1kg
4. 4.75 mm and 2 mm IS sieves
5. Mixing pan
6. Stop watch
7. Graduated measuring cylinder
8. Meter scale
9. Beaker
10. Thermometer
11. Container for water content determination
12. Straight edge knife
Test procedure:
Take 800 to 1000gm of specimen of soil and mix water to it so that its water content for the soil determined by proctors test
For the given volume of the moulds, calculate the mass of the soil mix so as to give the dry density
Assemble parameter for static compaction
Put the weighed quantity of soil into the moulds assembly
Maintain the load for about 1minute and then release it
Turn the mould assembly upside down and remove the 2.5cm pluck and collar
Place the mould assembly in the bottom tank and fill the bottom tank with water up to outlet
Connect the outlet tube of the constant head tank to the inlet nozzle of the permeameter, after removing the air in the flexible rubber tubing connecting the tube. Adjust the hydraulic head by either adjusting the relative heights of permeameter mould and the constant head tank
Start the stop watch, and the same time put a beaker under the outlet of the bottom tank. Run the test for some convenient time interval. Measure the quantity of water collected in the beaker during that time
Repeat the test twice, more under the same head and for the same time interval.
Standard Proctor Compaction Test General
The purpose of the standard Proctor compaction test is to determine the optimum water content and the maximum dry density that can be achieved with a certain compaction effort. The relationship between the moisture content and the density of the soil will be obtained in the process. Compaction effort designed in this laboratory test is comparable with that obtained in the field. Compaction is the process of increasing the bulk density of the soil or aggregate by driving out the air. For a given soil, for a given amount of compaction effort, the density obtained depends on the moisture content.
Scope
The method given in this standard is based on the standard proctor compaction test. Soil is compacted in a mould in three layers by dropping a 2.49 kg rammer a distance of 305mm. (Alternatively dropping a 2.5 kg rammer 300 mm). Dry density achieved by mixing soil with different water contents were determined to obtain the maximum dry density and the corresponding optimum moisture content.
There are four alternative procedures as listed below;
· A - With a 101.6 mm diameter mould for material passing 4.7.5 mm sieve,
· B - With a 152.4 mm diameter mould for material passing 4.7.5 mm sieve,
· C - With a 1-52.4 mm diameter mould for material passing 19.0 mm sieve,
· D- With a 1·52.4 mm diameter mould for material passing 19.0 mm Sieve,
Corrected by replacement for material retained on a 19.0 mm sieve,
Methods A and B
With methods A and/or B no oversize correction is required unless the material retained in 4.75 mm sieve is greater than 7%. In that case material retain in 4.75 mm sieve may be discarded. When material retained on 4.75 mm sieve is greater than 7%, method C should be used.
Method C
With method C unless the material retained in 19.0 mm sieve is greater than 10%, no oversize correction should be used. If the amount of material retained on 19.0 mm sieve is greater than 10%, method D should be used.
Method D
Material retained on 19.0 mm sieve should be passed through 75 mm sieve. Material retained on 75 mm sieve shall be discarded. Material passing the 75 mm sieve and retained on the 19 mm sieve shall he replaced with all equal amount of material passing a 19 mm sieve and retained 4.75 mm sieve. Material for replacement shall be taken from the unused portion of the sample.
Apparatus
The following apparatus are required,
a) Moulds - There shall be cylindrical moulds conforming to the moulds described above. The mould of diameter 101.6 mm shall have a height of 116.4 mm, and therefore will be of a volume 944 cm3.
The mold of 152.4 mm shall have a height of 116.4 mm, and therefore will be of a volume 2124 cm3.
The moulds shall be fitted with a detachable base plate and a removable extension approximately 50 mm high.
b) A metal Rammer - There shall be a metal rammer having a 50 mm diameter circular face, and weighing 2.49 kg. The rammer shall be equipped with a suitable arrangement for controlling the height of drop to 305mm. ( Alternatively there can be rammer of 2.5 kg weight with a drop 300 mm)
c) Balances - A balance readable and accurate to 1 g ( with a capacity 20 kg) and a balance readable and accurate to 0.01 g,
d) Sieves - A 75 mm sieve, a 19 mm sieve and a 4.75 mm sieve.
e) Mixing tools - Miscellaneous tools such as mixing pan, spoon, trowel, spatula etc.
f) Metal tray - A large metal tray ( 600 mm X 500 mm and 80 mm deep),
g) Straightedge - A Steel straightedge, 300 mm long, 25 mm wide, and 3 mm thick with one beveled edge,
h) Sample extruder - (Optional) An apparatus ( such as a jack) for extruding specimen from the mould,
i) An oven - Thermostatically controlled oven to provide temperature 105 -110 Co,
j) Cans - Cans to take samples for moisture content determination,
Procedure
1. Obtain approximately 3 kg of air – dried soil in the mixing pan, break all the lumps so that it passes the sieve given in method A, B, C and D
2. Add suitable amount of water (See Note 1)
3. Determine the weight of the empty mould without the base plate and the collar (M1) to the nearest 1g
4. Fix the collar and the base plate
5. Compact the moist soil in to the mould in three layers of approximately equal mass
(Each layer shall be compacted by 25 blows in the case of 101.6 mm diameter mould and 56 blows in the case of 152.4 mm diameter mould. Blows must be distributed uniformly over the surface of each layer so that the rammer always falls freely. The amount of soil must be sufficient to fill the mould, leaving not more than 6mm to be struck off when the extension is removed. (Note 03))
6. Detach the collar carefully without disturbing the compacted soil inside the mould and using a straight edge trim the excess soil leaving to the mould
7. Obtain the weight of mould with the moist soil (M2) after removing the base plate
8. Extrude the sample and break it to collect the sample for water content determination preferably at least two specimens one near the top and other near the bottom
9. Weigh an empty moisture can, M3 and weigh again with the moist soil obtained from the extruded sample in step 8 (M4)
Where;
M1 is the mass of the mould and base, in kg M2 is the mass of mould, base and soil, in kg
V is the volume of the mould in m3
|
10. Keep this can in the oven for water content determination
11. Repeat step 4 to 10. During this process weight M2 increases for some time with the increase in moisture and decreases thereafter. Conduct at least two trials after the weight starts to reduce.
12. After 24 hours get the weight of oven dried sample (M5)
Computations
The bulk density, ρ in kg/m3 of each compacted specimen shall be computed from the equation;
ρ = M2 – M1
V
|
w= M4 – M5
M4 – M3
|
Moisture content can be obtained from the equation;
ρ d = ρ
(1 + w)
|
Where w is the moisture content of the soil as a fraction.
The dry densities ρd, obtained in a series of determinations shall be plotted against the corresponding moisture content, w. A smooth curve shall be drawn through the resulting points and the position of the maximum on this curve shall be determined. Thus the maximum dry density and the corresponding water content should be obtained from the graph.
Presentation of Results
The maximum dry density shall be reported to the nearest kg /m3, and the optimum moisture content shall be reported to the nearest 0.01 %.
Ø Note 1 -
The amount of water to be added with air dried soil at the commencement of the test will vary with the type of soil under test. In general, with sandy and gravely soil a moisture content of 4% to 6% would be suitable, while with cohesive soils a moisture content of about 8% to 10% below the plastic limit of the soil, would be usually be suitable.
Ø Note 2 -
It is important that the water is mixed thoroughly and adequately with the soil, since inadequate mixing gives rise to variable test results. This is particularly important with cohesive soil when adding a substantial quantity of water to the air dried soil.
With clays of high plasticity, or where hand mixing is employed, it may be difficult to distribute the water uniformly through the air dried soil by mixing alone, and it may be necessary to store the mixed sample in a sealed container for a minimum period of about 16 hours before continuing with the test.
Ø Note 3 -
It is necessary to control the total volume of the soil compacted; since it has been found that if the amount of soil struck off after removing the extension is too great, the test results will be inaccurate.
Note 4 -
The water added for each stage of the test should be such that a the test it is often advisable to reduce the increments of water in the region of the optimum content range of moisture contents is obtained which includes the optimum moisture content. In general, increments of 1 % to 2% are suitable for sandy and gravely soils and of 2% to 4% for cohesive soils. To increase the accuracy of. Moisture
Calculation and Graphs
S.NO
|
Water content ml
|
Normal soil no of blows
|
20 % of fly ash + soil
|
30 % of fly ash + soil
|
70 % of fly ash + soil
|
1
|
20
|
31
|
26
|
24
|
15
|
2
|
25
|
22
|
20
|
18
|
10
|
3
|
30
|
15
|
8
|
14
|
8
|
4
|
35
|
7
|
6
|
10
|
6
|
5
|
40
|
3
|
0
|
4
|
2
|
6
|
45
|
0
|
0
|
0
|
0
|
LIQUID LIMIT SOIL – 1
LIQUID LIMIT OF SOIL -2
S.NO
|
Normal soil no of blowes
|
20 % of flyash + soil
|
30% of fly ash+ soil
|
70% of fly ash + soil
| |
1
|
20
|
70
|
50
|
30
|
23
|
2
|
25
|
50
|
20
|
15
|
15
|
3
|
30
|
35
|
15
|
5
|
10
|
4
|
35
|
10
|
10
|
2
|
5
|
5
|
5
|
3
|
0
|
0
|
0
|
6
|
0
|
0
|
0
|
0
|
0
|
Read more at http://joinedeyebrow.blogspot.com/#It8XWySj8mXtvLYe.99
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