Coal Reject

23
CHAPTER-1 INTRODUCTION The pavement system provides a smooth surface over which the vehicle may safely pass under all weather condition and satisfy all the requirements for which it is intended. As considering the geotechnical aspect, pavement is strongly influenced by material properties, moisture and other environmental factors. Water migrates into the soil in various ways. It goes through cracks in surface or inadequate shoulders (edge inflow), capillary rise in fine grained foundation soil (underlying groundwater table).in cold season the moisture may undergo seasonal freeze/thaw cycles. It reduces the strength and stiffness of unbound materials and promotes contamination of coarse granular material due to fines migration which causes the swelling of the soil. COMPONENT OF A PAVMENT SYSTEM: The pavement is a combination of base, sub base, surface course placed on subgrade in order to transmit the traffic load to the roadbed uniformly. This figure represents the modern pavement system.

description

The pavement system provides a smooth surface over which the vehicle may safely pass under all weather condition and satisfy all the requirements for which it is intended.As considering the geotechnical aspect, pavement is strongly influenced by material properties, moisture and other environmental factors. Water migrates into the soil in various ways. It goes through cracks in surface or inadequate shoulders (edge inflow), capillary rise in fine grained foundation soil (underlying groundwater table).in cold season the moisture may undergo seasonal freeze/thaw cycles. It reduces the strength and stiffness of unbound materials and promotes contamination of coarse granular material due to fines migration which causes the swelling of the soil.

Transcript of Coal Reject

Page 1: Coal Reject

CHAPTER-1

INTRODUCTION

The pavement system provides a smooth surface over which the vehicle may safely pass under

all weather condition and satisfy all the requirements for which it is intended.

As considering the geotechnical aspect, pavement is strongly influenced by material properties,

moisture and other environmental factors. Water migrates into the soil in various ways. It goes

through cracks in surface or inadequate shoulders (edge inflow), capillary rise in fine grained

foundation soil (underlying groundwater table).in cold season the moisture may undergo

seasonal freeze/thaw cycles. It reduces the strength and stiffness of unbound materials and

promotes contamination of coarse granular material due to fines migration which causes the

swelling of the soil.

COMPONENT OF A PAVMENT SYSTEM:

The pavement is a combination of base, sub base, surface course placed on subgrade in

order to transmit the traffic load to the roadbed uniformly. This figure represents the

modern pavement system.

Fig-1 Basic components of a typical pavement system.

Page 2: Coal Reject

The sub grade is a natural soil layer in which we put the materials to construct a pavement.it is

essential to observe that in no case it should be overstressed. The pressure which is coming from

the top of the road is transmitted by sub grade within allowable limit. It should not be deformed

beyond the elastic limit. While constructing a pavement we have to consider that sub grade soil

is well compacted at least 50cm layer with optimum moisture content (OMC) and maximum dry

density (MDD). It is the top surface of road bed upon which pavements structure and shoulders

are constructed. It is also called as a platform for the construction of pavement and to support the

pavement without undue deflection that would impact the pavement’s performance. The upper

layer of this natural soil may be compacted or stabilized to increase its strength, stiffness and

stability.

The Sub base is a layer or layers of specified or selected materials of sub grade to support a base

course. The sub base is the lower quality than the base layer. The sub base may be treated with

Portland cement, asphalt, lime, fly ash or combination of these admixtures to increase its strength

and stiffness. A sub base layer is used where the sub grade quality is very poor. So it is very

expensive. Without a sub base layer we can design the pavement. Basically a sub base layer is

not included with rigid pavement. Selected granular material is also used in sub bas

Base is a layer of high stability and density. Its main purpose is to distribute the stresses which is

created by wheel loads acting on the wearing surface so that the stresses transmitted to the

subgrade will not be sufficiently great to result in excessive deformation or displacement of that

foundation layer. The base must also such character that it is not damaged by capillary water or

frost action. Example of base may be composed of gravel , crushed rock or any granular

material.

Finally, the surface course is provided a smooth riding surface. It provides resistance which is

exerted by the tyre of the vehicle and takes up wear and tear due to traffic. Wearing course also

prevent the surface infiltration. Plate bearing test and Benkelman beam test are also sometimes

used for the evaluating the wearing course. The surface layer may consist of asphalt in “flexible

pavement” or Portland cement concrete in “rigid pavement”. The top layer of the flexible

pavement is wearing course. The surface layer must minimize the infiltration of surface water,

provide a smooth, uniform and skid resistant riding surface and offer durability against traffic

abrasion and the climate.

Page 3: Coal Reject

Fig-2: SHOWS THE COMPONENT LAYER OF THE PAVEMENT

SOME GEOTECHNICAL ISSUES ON PAVMENT CONSTRUCTION:

1. A wearing surface is the part of a pavement which provide sufficient smoothness,

frictional resistance, and sealing and drainage of surface water (i.e., to minimize

hydroplaning).

The asphalt and cement concrete is like the bound structural layer that provides sufficient

load-carrying capacity to water intrusion into the underlying unbound materials

2. A subgrade that provides a uniform and sufficiently strong, hard foundation for the

overlying layers.

3. Drainage system is provided for quickly extract the water from pavement system before

the water degrades the properties of unbound layers and subgrade.

4. Remedial measures, in some cases, such as soil improvement/stabilization or

geosynthetics to increase strength, stiffness and/or drainage characteristics of various

layers or to provide separation between layers(e.g., to prevent fines contamination).

The location, assessment, procurement of construction materials are major considerations for

engineering usually given priority consideration. The final analysis the selection of the materials

to be used will mainly depend upon availability , cost inherent properties such as strength and

durability.-

Page 4: Coal Reject

As we know the cost of wellknown construction material like crushed rock and clean gravel has

increased their cost day by day. So recent times led to their use being restricted to very expensive

and highly founded project. Later on which forced to the search for replaceable, in expensive

and locally available alternatives has become an intergal part of devloping countries. Even in

developed countries the growing scarcity of good quality construction materials has forced

research scientist and engineers to look towards the use of alternative materials which possess

the acceptable engineering properties in order to satisfy the durability and safety requirements

for which they are intended for.

The waste resulting from the separation of genuine coal from a jumble of other mined out

materials is known as “coal reject”.

The coal reject has variety of constituents which include fragment of shells, mud stones, sand

stones, and fine coal particles. The shapes of these fragments are variable and the surface exhibit

rough texture. The main components of coal rejects are quartz (55.6%), feldspar, clay(35.4%),

mica(3.3%). other minor component of coal reject are lime, soda , potash, titanium

oxide ,magnesium.

Unfortunately in the natural state of coal reject do not meet their specific requirement for many

construction purposes. In this an attempt has been made to utilize coal reject as an alternate civil

engineering material. To augment the property of coal reject to make it suitable as civil

engineering material Portland cement has been also used a stabilizing agent.

Page 5: Coal Reject

CHAPTER-2

TEST METHODS & TESTING PROCEDURES:

INTRODUCTION:

As the objective of the present study is to characterize coal reject as an alternate pavement material, tests pertaining to both coarse aggregate and subgrade materials are conducted on it. In this chapter the testing procedure of aggregate test, and soil test has been explained.

COAL REJECTS AS A ROAD AGGREGRATE:

TEST FOR ROAD AGGREGRATE:

CRUSHING TEST:

The aggregate crushing value provides resistance to crushing under gradually applied compressive loads.

TESTING PROCEDURE:

The apparatus which is necessary for testing of crushing test are a steel cylinder 15.2cm diameter, a base plate and, plunger, compression testing machine, cylindrical measure of diameter 11.5cm and height 18cm.

1. Dry aggregate has taken which was passing through 12.5mm sieve and retained on 10mm sieve.

2. A cylinder has filled with dry aggregate in three equal layers which is tamped by 25 times.

3. The plunger placed on the top of the specimen and a load is applied of 40 tonnes per minute.

4. The crushed aggregate has removed in the compression machine and passing on 2.36mm sieve.

5. The aggregate crushing value is the percentage of the crushed material passing 2.36mm sieve in terms of original weight of thee specimen.

Page 6: Coal Reject

Fig-3: COMPRESSIVE STRENGTH MACHINE USED FOR CRUSHING TEST

IMPACT TEST:

Aggregate is subjected to impact due to moving wheel loads. The aggregate impact test is carried out for determining the resistance to impact of aggregate.

The aggregate impact testing machine consists of a metal base and a cylindrical steel cup of internal diameter 10.2cm and depth 5cm in which the aggregate placed.

2. This test consist of a metal hammer of weight of 13.5-14.0 kg having a free fall from a height 38cm is arranged to drop through a vertical guides.

3. It has been taken the aggregate which was passing through the 12.5mm sieve and retained on 10mm sieve.

4. It is filled in the cylindrical measure in three layers by tamping each layer by 25 blows.

5. The sample transferred from th cup of the aggregate impact testing machine and compacted by tamping 25 times.

Page 7: Coal Reject

6. The hammer raised to a height of 38cm and allowed to fall freely on th specimen.

7. Then the crushed aggregate e sieved through the 2.36mm sieve.

8. The aggregate impact value is expressed as the percentage of the final formed in terms of the total weight of the sample.

Fig-4: SHOWS THE IMPACT INSTRUMENT

FLAKINSS INDEX:

The flakiness index of aggregate is the percentage by weight of aggregate particles whose least dimension thickness is less than three fifth or .6 of their mean dimension.

2. The test has done whose particle size larger than the 6.3mm sieve.

3. The sample of aggregate tested through a set of sieve and separated on specified size rang.

4. Total weight of th sample has taken as (W) and the flaky material passed through the appropriate slot from ach size range of test aggregate are added which is expressed in terms of(w).

5. Flakiness index=100W/w

ELONGATION INDEX:

The elongation index of an aggregate is defined by the weight of particle whose greater dimension or length is greater than one and four fifth or 1.8 times of their mean dimension.

Page 8: Coal Reject

1. The sample of aggregate tested through a set of sieve and separated into a specified range.

2. The aggregate from each size of the range is passed through an appropriate gauge length.

3.The portion of th elongated aggregate having length greater than the specified gauge from each range weighted and total weight of th elongated coal rejects is expressed as a percentage of the total weight of the sample to get the elongation index.

SPECIFIC GRAVITY:

Specific gravity is used to determine the quality or strength of the material.

1.2kg of dry aggregate sample has taken in wire basket and immersed in 24 hours.

2. The sample weighted in water and buoyant weight found.

3. The weight of dry aggregate has taken after drying it 24 hours.

4. The specific gravity calculated by dividing the dry aggregate by weight of an equal volume of water.

COAL REJECT AS A SUBGRADE

RESEARCH PROCEDURE OF COAL REJECTS:

The coal reject was collected from……………….

We have carried oth labrotary test of coal reject to determine the geotechnical properties of the

material both in its natural state and mixed with Portland cment.we have done th test like specific

gravity, grain size distribution, linear shrinkage, compaction, CBR, and shear strength.

Compaction test were done in both natural coal rject and adding various cement content with

coal reject. CBR value is obtained in soked condition. we were adding the OMC w.r.to M.D.D

and soked 4 days. then the CBR value was determined.shear strength also carried out by

unconfined compressive strength and direct shear method. both test were carried out by adding

various percentage of cement.

SAMPLE PREPARATION AND TESTING PROCEDURE:

The coal reject has brought from…… It is mixed with some impurities. To discard this

impurities at first the coal reject has properly washed and ovndrying 24 hours. Then the sample

has fully prepared for testing. As it behaves like a coarse aggregate for determining the test like

CBR, compaction, specific gravity it has crushed in crusher machine.

Page 9: Coal Reject

3.The portion of th elongated aggregate having length greater than the specified gauge from each range weighted and total weight of th elongated coal rejects is expressed as a percentage of the total weight of the sample to get the elongation index.

SPECIFIC GRAVITY:

Specific gravity is defined by the ratio of the mass of a given volume of solids to the mass of an

equal volume of distilled water with a stated temperature. The specific gravity experiment has

done in pycnometer method. The equipment used in th experiment like pycnometer, balance,

vacuum pump, funnel, spoon.

1. Recorded the weight of clean dry pycnometer.

2. Put the 50gm of soil mass on pycnometer and weighted the pycnometer with soil mass

3. Added the water up to three-fourth of pycnometer and shacked properly.

4. Put it on a vacuum up to 15 to 20minutes to reduce the entrapped void.

5. After cooled it we have added the distilled water up to a mark level and cleaned the exterior

surface and recorded the weight of pycnometer with soil and water

6. After cleaning the pycnometer it filled with only water up to the mark level.

Fig-5(a) SHOWS SPECIFIC GRAVITY APPARATUS Fig-5(b) SHOWS BALANCE

COMPACTION:

Compaction is done to determine the relationship between the moisture content and dry density

of a specified soil in a specified compactive effort. The compactive effort is the amount of

Page 10: Coal Reject

mechanical energy that is applied to the soil. There are various methods used to compact soil in

the field like tamping, kneading, vibration, and static load compaction. R.R.PROCTOR has

developed impact compaction method using some equipment and methodology in labrotary. Two

types of compaction are there.1.standard proctor test.2 .modified proctor test.

We have done the experiment using standard proctor test which is also known as light

compaction method.

1.2.5 Kg of dry soil has taken which was passing through the 4.75mm sieve.

2. This material is a type of coarse aggregate .so we have started the adding of water content

from 8%.

3. The soil mixed thoroughly and covered with a wet cloth and left for maturing about 15 to 30

minutes.

4. The soil compacted by a 5.5 lb. hammer falling a distance of one foot into a soil filled mould. The mould is filled with three equal layers of soil, and each layer is subjected to 25 drops of the hammer. 5. The standard mould has 4 inches in diameter and has a volume of about 1/30 ft3 (944 cm3),6. The soil has filled up to the cylinder and last compacted layer must extend above the collar joint.7. we removed the collar and levelled it properly and weighted.8. Accordingly moisture content has taken top, middle, bottom of the soil and oven dried it 24 hours9. Repeated the process in 5 steps until the weight of the soil mass has not reduced.

Fig-6(a) COAL REJECT AS COMPACTION Fig-6(b) SHOWS COMPACTION APPARATUS

Page 11: Coal Reject

CBR: California bearing ratio(CBR) test is a type of test developed by the California division of

highways in 1929.The test is used to determine the suitability of subgrade and th materials used

in sub-base and se course.

1. The test conducted on a prepared specimen in a mould .

2. The labrotary CBR apparatus consist of a mould 150mm diameter and 175mm high, having a

separate base plate and a collar.

3. The load is applied by a loading frame through a plunger of 50mm diameter.

Dial gauges are used for measurement of the expansion and penetration.

4. The plunger penetrate the specimen at the rate of 12.5mm per minute

5. The penetration of 2.5mm and 5mm recorded by a proving ring attached to the plunger.

6. The load expressed as a percentage of standard load at the respective deformation level which

is known as CBR value.

Fig-7: SHOWS COAL REJECT AS CBR

Page 12: Coal Reject
Page 13: Coal Reject

PERMEABILITY:

Permeability refers to which the water flows through the soil. This property needs to calculate

the seepage through earth dams or under sheet pile walls and the calculation the seepage rate

from waste storage facilities. We have done the experiment in falling head test. The permeametre

mould has used as same as th constant head.

1. A vertical graduated stand pipe of known diameter is fitted to the top of the permeametre.

2. The test started by allowing the water in th stand pipe to flow through the sample to the

constant had chamber from which it overflows and spills out

3. As the water flows through the soil, the water level in the stand pipe falls.

4. The time required for the water level to fall from a known initial head (h1) to a known

final head (h2) determined.

5. The head is measured with reference to the difference of level of water

Fig-9: SHOWS FALLING HEAD PERMEABILITY APPARATUS

UNCONFINED COMPRESSION TEST:

The primary purpose of this test is to determine the unconfined compressive strength, which is

then used to calculate the unconsolidated undrained shear strength of the clay under unconfined

conditions. According to the ASTM standard, the unconfined compressive strength (qu) is

Page 14: Coal Reject

defined as the compressive stress at which an unconfined cylindrical specimen of soil will fail in

a simple compression test. In addition, in this test method, the unconfined compressive strength

is taken as the maximum load attained per unit area, or the load per unit area at 15% axial strain,

whichever occurs first during the performance of a test.

1. The soil sample is extracted by shell by tube sampler. Cut the soil specimen so that the

ratio of (l/d) is approximately between 2 and2.5

2. We measured the exact diameter of the specimen in both top and bottom.

3. Measured the exact length of the specimen at three locations.

4. We weighted the sample and recorded on the data sheet

5. Then calculating the deformation corresponding the 15% strain.

6. Carefully the sample is placed in compression device and applied the load and recorded

the deformation respective to the strain.

7. Remove the sample from compression device and put it in oven for determination of

water content.

Fig-10: SHOWS COAL REJECT AS UNCONFINED COMPRESSION

DIRECT SHEAR TEST:

1. A direct shear test conducted on a soil specimen in a shear box which splits into two halves

along a horizontal plane at its middle.

Page 15: Coal Reject

2. The box is divided horizontally such that the dividing plane passes through the centre.

3. The prepared specimen is directly compacted with the direct box.

4. Due to our test is undrained the gripper plate without perforation kept at right angle to the

direction of shear.

5. The soil sample is prepared and normal load is applied in differently.

6. The reading of dial gauge and proving ring has taken till the specimen failed

7. The failure indicated when the proving ring begins to recede after having reached the

maximum value.

8. At the end of the test, the specimen removed and water content found

9. A graph between normal stress and shear stress has plotted.

Fig-11 SHOWS DIRECT SHEAR APPARATUS