CONTENTS

1.INTRODUCTION

2.LITERATURE REVIEW

3.HLL(Hindustan Latex Ltd) LIFECARE LTD.

3.1.Introduction

3.2.Effluent Treatment Plant

3.2.1. Collection Tank/Equalisation tank

3.2.2. Lime Mixing Channel

3.2.3 FeCl3 mixing Channel

3.2.4 Mixing Channel

3.2.5 Primary Settling Tank

3.2.6 Aeration Tank

3.2.7 Secondary Settling Tank

3.2.8 Sludge Recirculation Sump

3.2.9 Chemoxidation Tank

3.2.10 Pressure Sand Filter

3.2.11 Treated effluent water collection tank

3.2.12.Recycling of treated effluent water

3.2.13.Sludge Drying Beds

3.3.Characteristics of treated water

4.BRICKS

4.1.Composition of good brick earth

4.2.Properties of good bricks

4.3.Standard Size and weight of bricks:

4.4.Manufacture of Bricks

4.4.1.Raw materials

4.4.2.Manufacturing Process

4.5.Tests on Burnt Clay Building Bricks

4.5.1.Test for Compressive Strength of Bricks [Ref: IS 3495 (Part 1):1992]

4.5.2.Water Absorption test of Building Bricks (Ref: IS 3495 (Part 2)-1992

4.6.Types of bricks

5.MATERIALS AND METHODS USED

5.1.Moisture Content

5.2.Specific Gravity

5.3.Preparation of bricks

5.3.1. Sieving

5.3.2.Mixing

5.3.3.Drying

5.3.4.Burning

5.3.5.Testing

6.RESULTS AND DISCUSSIONS

6.1.Proportioning

1.INTRODUCTION

A large quantity of sludge is generated each year from various industries. Large amount of waste water is produced from various processes within the industry like manufacturing processes, cleaning processes, kitchen wastes etc. for discharging this wastewater into the specified water bodies, certain standard specified by the Regulatory Authorities have to be met. For this purpose. The wastewater has to be subjected to various treatment processes. As a result of these treatment processes, sludge is produced. The quantity of the sludge produced depends upon the amount of wastewater and the type of treatment adopted for treating the wastewater. Common method adopted for disposing the sludge is land filling. Landfill disposal of the sludge has drawbacks like high cost of transportation, difficulty in getting suitable sites for land filling, heavy metal contamination of the land, emission of foul gases etc. so, disposal of sludge has become a major issue. Efforts are being made to utilize the sludge for making useful materials. This is a win-win strategy because it not only converts the wastes into useful materials but it also alleviates the disposal problem. The use of sludge in construction industry is considered to be the most economic and environmentally sound option.

This study focuses on the possibility of using sludge as a brick material. The sludge for this study was collected from HLL Lifecare Limited; peroorkada. The main raw material used in this industry is Latex. A latex is a colloidal suspension of very small polymer particles in water. Natural latex is produced from the rubber tree (Hevea brasilienesis) and is the protective fluid contained beneath the bark. It is a cloudy white liquid, similar in appearance to cow milk. It is collected by cutting a thin strip of bark from the tree and allowing the latex to exude into a collecting vessel over a period of few hours.

2.LITERATURE REVIEW

Different industries produce sludge of different quality and in different quantities. This may be due to difference in the manufacturing processes and treatment given to the wastewater. Disposal of sludge has become a major issue. Efforts are being made to utilise the sludge for making useful materials. Major research is being conducted in the field of utilization of sludge in brick manufacturing. The quality and type of brick made depends on various factors like composition of sludge, additives used, temperature at which the brick is fired, water content etc.

A study was conducted on the use of recycled paper processing residues in making porous brick with reduced thermal conductivity by Mucahit Sutcu et.al. Mixtures containing brick raw materials and the paper waste were prepared at different proportions (upto 30 wt%). The granulated powder mixtures were compressed in a hydraulic press, and the green bodies were dried before firing at 1100°C. Dilatometric behaviours, drying and firing shrinkages were investigated as well as the loss on ignition, bulk density, apparent porosity, water absorption and thermal conductivity values of the fired samples. Their mechanical and microstructural properties were also investigated. The results obtained showed that the use of paper processing residues decreased the fired density of bricks down to 1.25 g/cc. compressive strengths of the brick samples produced in this study were higher than that required by the standards. Thermal conductivity of the porous brick produced in this study (<0.4 W/m K) showed more than 50% reduction compared to local brick of the same composition (0.8 W/m K). Conversion of this product to a perforated brick may reduce its thermal conductivity to very low values.

Another study conducted by Chih-Huang Weng et.al. investigated the influence of sludge proportion and the firing temperature in determining the brick quality. Increasing the sludge content results in a decrease of brick shrinkage, water absorption and compressive strength. Results also showed that the brick weight loss in ignition was mainly attributed to the organic matter content in the sludge being burnt out during the firing process. With upto 20% sludge added to the bricks, the strength measured at temperatures 960 and 1000°C met the requirements of the Chinese National Standards. Toxic characteristic leaching procedure (TCLP) tests of bricks also showed that the metal leaching level is low. The conditions for manufacturing good quality bricks is 10% sludge with 24% of moisture content prepared in the moulded mixtures and fired at 880-960°C.

The study conducted by Chihpin et al. investigated yhe use of sludge as partial substitute for clay in brick manufacturing. In this study, four different series of sludge and clay proportioning ratios were studied, which exclusively involved the addition of sludge with ratios 50, 60, 70 and 80% of the total weight of sludge-clay mixture. Each series involved the firing of bricks at 950, 1000, 1050 1nd 1100°C, giving 16 different brick types. The physical properties of produced bricks were then determined and evaluated according to Egyptian Standard Specifications and British standards. From the obtained results, it was concluded that by operating at the temperature commonly practiced in the brick kiln, 50% was the optimum sludge addition to produce brick from sludge-clay mixture. The produced brick properties were superior to those available in the Egyptian market.

3.HLL (Hindustan Latex Ltd.) LIFECARE LTD.

3.1.Intoduction

Hindustan Latex Limited or HLL Lifecare Limited is a Government of India undertaking, Ministry of Health and Family Welfare, Government of India which started as a corporate entity in March 1966. Their product ranges from contraceptive aids and healthcare aids to social marketing products. HLL is one of the largest manufacturers of male contraceptives in the country.

HLL commenced its operation and established a plant at Trivandrum, the capital city f the natural rubber rich state of Kerala on 5th April 1969. HLL started working at Peroorkada, Trivandrum with an annual production capacity of 144 million pieces in 1969, which was doubled to 288 million pieces in 1976, by putting additional manufacturing lines to the existing plants. In 1986, two additional plants with latest Japanese technology were commissioned one at Trivandrum and other at Kangala near Belgaum, Karnataka making the total production capacity to 608 million pieces. In Trivandrum, HLL has two factories; one at Peroorkada and other at Akkulam. In the Akkulam factory the products are Copper T. IUDs, blood transfusion bags, Surgical Sutures and Hydrocephalous Shunt. Peroorkada factory produces condoms. With a vast array of innovative products and social programmes HLL is year after taking a step. HLL has grown today into a multi-product, multi-unit organization addressing various public health challenges facing humanity.

HLL has been declared a Mini Ratna Company by the Government of India and is upgraded as a Schedule B PSU. HLL has set its sights to be Rs1000 crore company by the year 2010. HLL Lifecare Limited is the only company in the world manufacturing and marketing the widest range of contraceptives. It is unique in providing a range of Condoms, including Female Condoms, Intra Uterine Devices, Oral Contraceptive Pills- Steroidal, Non-steroidal and Emergency Contraceptive Pills and Tubal Rings. HLL’s healthcare products range includes Blood Collection Bags, Surgical Sutures, Auto Disable Syringes, Vaccines, In-Vitro Diagnostic Test Kits, Pharma Products for Women, Natural Products, Hydrocephalous Shunt, Tissue Expanders, Surgical and Examination Gloves, Blood Banking Equipment, Neonatal Equipment, Blood Transfusion and Intravenous Sets, Vending Machines, Iron and Folic Acid Tablets, Sanitary Napkins, Oral Rehydration Salts and Medicated Plasters.

HLL has introduced Closed System Blood Bags that are integrated with Leukocyte Filter called LD Bags. These bags are intended for Leuko-depletion immediately upon collection of blood from donors at blood banks. In collaboration with the Female Health Company (FHC) of US, HLL is marketing FC female condom in India. The female condom is the only female

controlled prevention technology approved by the US FDA and the WHO. FC is distributed in over 100 countries around the world.

HLL has launched several initiatives in the services sector for medical infrastructure development, diagnostic centres and procurement consultancy. These have been conceived to bring about a whole new realm of accessible, affordable healthcare delivery to every citizen.

Over the years each of the initiatives taken up by HLL has been targeted towards making quality healthcare available at the doorstep of every family. Associate Institutions of HLL namely HLFPPT and Lifespring Hospitals have ensured that healthcare delivery.

HLL gives emphasis on effective quality control at every manufacturing stage right from the raw material to the final product, during its various production stages. I n recognition of its quality and manufacturing process, the company got ISO 9002 certificate from NQA Quality System Register Limited in1996 and ISO 14001 in 2000. Also HLL got approval from the Federal Drugs Administration (FDA) and South African Bureau of Standards (SABS).

3.2.Effluent Treatment Plant

The Effluent Treatment Plant (ETP) is installed for clear water discharge from production line since 1969. Present ETP can handle up to 1000Kl/day of wastewater.

3.2.1. Collection Tank/Equalisation tank

The function of the equalisation tank is to collect effluent from the different streams and to keep uniform characteristics for the effluent stream. Effluents from various sections of the plant, which includes latex, filtrate from Nutsche filter, wash water and canteen effluent are collected in this tank. Four such collection tanks are installed to collect wastewaters from the three plants A, B and C.

3.2.2. Lime Mixing Channel

PH of the raw effluent ranges from 9-10. Hydrated lime, i.e., 1% solution of lime (10Kg of lime mixed with 1000litres of water, agitated for 1min and allowed to settle for another 1min) is therefore added to the effluent in order to make the pH 12. This enhances floc formation. Lime is allowed to flow into the channel under gravity.

3.2.3 FeCl3 mixing Channel

Next FeCl3 reagent stored in Sintex tank is transferred under gravity and is added to the effluent at the rate of 150-1000ml/min. This neutralizes the pH and brings the pH level to 6-8.

Provision is given to add chemicals at overflow mixing tank also. If incoming effluent is acidic, lime addition is increased to bring down acidity. If pH is less than 7, after lime and FeCl3 addition; FeCl3 dosage is reduced and if pH is more, dosage is increased.

3.2.4 Mixing Channel

The combined effluent from the equalisation tank is pumped to the mixing box of mixing channel where chemicals are added at adequate dosages. General flow rate of raw effluent is 7 to 20 litres per second. The mixing channel is a baffled type mixing channel. Here flocs are formed, precipitation and coagulation takes place and flocs grow denser.

3.2.5 Primary Settling Tank

Water from mixing tank is send to primary settling tank by gravity flow through a 6 inch pipe. Here the flocs get settled at the inclined base.

3.2.6 Aeration Tank

The water from the primary settling tank overflows in to the aeration tank. Aeration is done in this tank by making use of twin blowers and slotted PVC/MS pipes for bubbling air through the water collected in the tank. This prevents foul smell.

3.2.7 Secondary Settling Tank

The finer suspended particles present in the clear overflow from the aeration tank is allowed to settle in the secondary settling tank. It is cleaned once in a month.

3.2.8 Sludge Recirculation Sump

Sludge from secondary settling tank is to be fed to sludge recirculation sump by gravity. Sludge will be partially recycled back to the aeration tank. Balance portion will be send to sludge drying bed. It is cleaned once in a month.

3.2.9 Chemoxidation Tank

Overflow from secondary settling tank is fed to Chemoxidation tank. Diluted sodium hypochlorite solution is dosed for 24 hours (20 litre NaHOCl in 180 litre of water). General flow rate is maintained as 1400-200ml/min. Addition of NaHOCl oxidizes residual biodegradable organics. pH after dosing is maintained at 7-8.

3.2.10 Pressure Sand Filter

The clear overflow from the chemoxidation tank is pumped through two Pressure Sand Filters operated in parallel for removing any precipitated solids during Chemoxidation. Filter feed pumps are used for feeding the effluent to the pressure sand filter. The filter is backwashed every 20 minutes.

3.2.11 Treated effluent water collection tank

Overflow from sand filter fed to final effluent water collection tank through a cascade. The overflow from the final treated water is discharged through the final outlet. pH of treated water is maintained at the range of 6-8 and recycled on hourly basis. The flow rate through final outlet is noted using V notch. Calculation using V notch

Q=H5/2 X 1.4 X 60 X 60 X 24

Height of water flow through V notch is maintained in the range of 6.5-12.5 cm.

3.2.12 Recycling of treated effluent water

40% of treated water is used for gardening, toilet flushing, floor cleaning, ETP cleaning works etc. In addition to the above, treated water is supplied in tankers for gardening at Golf Club, Trivandrum.

3.2.13 Sludge Drying Beds

Solid cake from the filter press will be transferred to sludge drying beds. Sludge from the other tanks during cleaning operation will also be transferred to sludge drying beds. There are 6 cells in sludge drying beds. After filling each cell, sludge will be taken to the next cells. This process is separated till the sludge covers the entire cells in drying cells. Filtrate from the bed is allowed to enter aeration tank for further treatment.

3.3.Characteristics of treated water

Test Item Unit Amount Limit

pH ... 7 6 to 8

COD mg/l 54 250 max

Oil & Grease mg/l 5 10 max

Suspended Solids mg/l 34 100 max

Kjeldahl’s Nitrogen mg/l 34 100 max

Sulphide mg/l Nil 2 max

BOD mg/l 18 30 max

Total dissolved solids mg/l 111 2100 max

Ammoniacal Nitrogen

mg/l 8 50 max

4.BRICKS

Brick is one of the oldest building materials and it is extensively used even at present

because of its durability, strength, reliability, low cost, easy availability etc. Bricks are obtained

by moulding clay in rectangular blocks of uniform size then by drying and burning these blocks

in brick kilns.

4.1.Composition of good brick earth

A good brick should contain clay and sand in such a way that when water is added, it can be

easily moulded and dried without cracking or warping. Following are the main constituents of

good brick earth:

1. Silica-50% to 60% by weight. Presence of this constituent prevents cracking, shrinking

and warping of raw bricks. It imparts uniform shape to bricks. If silica is in excess, it

makes the brick brittle.

2. Alumina-20% to 30% by weight. It imparts plasticity to earth so that it can be moulded

easily. If alumina is present in excess, raw bricks shrink and warp during drying and

burning.

3. Lime-2% to 5% by weight. Lime causes the grains of sand to melt and bind the particles

of clay together. It prevents shrinkage of raw bricks. If lime is excess, it will cause the

brick to melt and hence shape is lost.

4. Iron oxide-5% to 6% by weight. Iron oxide act as a flux to cause the grains of sand to

melt and this helps to bind the particles together. It imparts red colour to brick on

burning. Excess amount of iron oxide makes the brick dark blue.

5. Magnesia-less than 1% by weight. It imparts yellow colour to brick and it decreases

shrinkage. Excess magnesia leads to decay of bricks.

4.2.Properties of good bricks

A good brick should have the following properties:

Bricks should have perfect edges, well burnt in kilns, copper coloured, free from

cracks with sharp and square edges.

It should be uniform in shape and of standard size.

Colour should be uniform and bright.

The brick when broken should show a bright homogeneous and uniform compact

structure free from voids.

It should produce clear ringing sound when struck with each other.

Water absorption should not be greater than 20% for first class bricks and 22% for

second class bricks when soaked in water for 24 hours.

Bricks should be sufficiently hard, i.e. no nail impression must be present when

scratched.

It should not break when dropped from a height of one metre.

It should have low thermal conductivity and should be sound proof.

Good brick should not show any white or grey deposits of salts when immersed in

water and dried. i.e. it should not have any efflorescence.

Good brick should have crushing strength above 5.5N/mm2.

4.3.Standard Size and weight of bricks:

Size of standard bricks is 19 X 9 X 9cm. Such brick is known as Modular Bricks. The size of bricks

including mortar thickness is 20 X 10 X 10cm. Average weight of brick is about 3 to 3.5kg.

4.4.Manufacture of Bricks

4.4.1.Raw materials

Bricks for building may be made from clay, shale, soft slate, calcium silicate, concrete etc. True

bricks are ceramic and are created by the action of heat followed by cooling. Clay is the most

commonly used material for the manufacture of bricks. Natural clay minerals,

including kaolin and shale, make up the main body of brick. Many additives have been used in

brick, including byproducts from papermaking, ammonium compounds, wetting

agents, flocculents (which cause particles to form loose clusters)

and deflocculents (which disperse such clusters). Some clays require the addition of sand. A wide

variety of coating materials and methods are used to produce brick of a certain color or surface

texture. To create a typical coating, sand is mechanically mixed with some type of colorant.

Sometimes a flux or frit (a glass containing colorants) is added to produce surface textures. The

flux lowers the melting temperature of the sand so it can bond to the brick surface.

4.4.2.Manufacturing Process

1. Grinding, sizing & combining raw materials

First, each of the ingredients is conveyed to a separator that removes oversized materials. A

jaw crusher then crushes the particles in order to render finer particles. After the raw materials

for each batch of bricks have been selected, a scalping screen is often used to separate the

different sizes of material. Material of the correct size is sent to storage silos, and over-sized

material goes to a hammermill, which pulverizes it with rapidly moving steel hammers. The

hammermill uses another screen to control the maximum size of particle leaving the mill, and

discharge goes to a number of vibrating screens that separate out material of improper size

before it is sent on to the next phase of production.

2. Extrusion

Pulverized material and water are fed into one end of a pug mill, which uses knives on a

rotating shaft to cut through and fold together material in a shallow chamber. The blend is then

fed into an extruder at the far end of the mill. The extruder usually consists of two chambers.

The first removes air from the ground clay with a vacuum, thereby preventing cracking and

other defects. The second chamber, a high-pressure cylinder, compacts the material so the

auger can extrude it through the die. After it is compressed, the plastic material is forced out of

the chamber though a specially shaped die orifice. The cross-section of the extruded column,

called the "pug," is formed into the shape of the die.

In moulding, soft, wet clay is shaped in a mould, usually a wooden box. The interior of the box is

often coated with sand, which provides the desired texture and facilitates removing the formed

brick from the mold. Water can also be used to assist release.

3. Chamfering the brick

Chamfering machines were developed to produce a furrow in brick for such applications as

paving. These machines use rollers to indent the brick as it is being extruded. They are

sometimes equipped with wire cutters to do the chamfering and cutting in one step. Such

machines can produce as many as 20,000 units per hour.

4. Coating

The choice of sand coating, also applied as the brick is extruded, depends on how soft or hard

the extruded material is. A continuous, vibrating feeder is used to coat soft material, whereas

for textured material the coating may have to be brushed or rolled on. For harder materials a

pressure roller or compressed air is used, and, for extremely hard materials, sand blasting is

required.

5. Drying

Before the brick is fired, it must be dried to remove excess moisture. If this moisture is not

removed, the water will burn off too quickly during firing, causing cracking.

6. Firing

After drying, the bricks are fired to high temperatures in furnaces called kilns at 900-1000 °C

4.5.Tests on Burnt Clay Building Bricks

4.5.1.Test for Compressive Strength of Bricks [Ref: IS 3495 (Part 1):1992]

Apparatus

A compression testing machine, the compression plate of which shall have a ball seating in the

form of apportion of a sphere the center of which coincides with the center of the plate shall be

used.

Specimens

Six numbers of bricks from the sample to be tested are to be taken. The dimensions shall be

measured to the nearest 1mm.

Preconditioning

Remove the unevenness observed in the bed faces of the bricks to provide two smooth and

parallel faces by grinding. Immerse in water at room temperature for 24 hours. Remove the

specimen from water and drain out any surplus moisture at room temperature. Fill the frog(if

provided) and all voids in the bed and flush with cement mortar (1 cement, clean coarse sand of

grade 3mm and down).Store under damp jute bags for 24 hours followed by immersion in

clean.

Procedure

Place the specimen with flat faces horizontal, and mortar filled face facing upwards between

two 3-ply plywood sheets each of thickness 3mm and carefully centered between the plates of

the testing machine. Apply load axially at a uniform rate of 14N/mm2 (140 kgf/cm2) per minute

till failure occurs and note the maximum load at failure. The load at failure shall be the

maximum load at which the specimen fails to produce any further increase in the indicator

reading of the testing machine.

Compressive strength in N/mm2= Maximum load at failure in NAverage area of bed faces in mm2

The average of results shall be reported as the compressive strength of bricks in N/mm2.

Observations & Calculations

Specimen NoDimensions

(mm)

Failure load

(N)

Compressive Strength

(N/mm2)

Result

Average Compressive Strength of the given building brick sample=................. N/mm2

IS Specification

As per IS 1077:1992, the bricks when tested in accordance with the procedure laid down in IS

3495 (Part 1): 1992 shall have a minimum average compressive strength for various classes as

given in the following table.

Class DesignationAverage Compressive Strength not less than

N/mm2 Kgf/cm2

35 35.0 350

30 30.0 300

25 25.0 250

20 20.0 200

17.5 17.5 175

15 15.0 150

12.5 12.5 125

10 10.0 100

7.5 7.5 75

5 5.0 50

3.5 3.5 35

The compressive strength of any individual brick tested shall not fall below the minimum

compressive strength specified for the corresponding class of brick. The lot shall then be

checked for the next lower class of brick.

4.5.2.Water Absorption test of Building Bricks (Ref: IS 3495 (Part 2)-1992

Apparatus

A sensitive balance capable of weighing within 0.1 percent of the mass of the specimen and a

ventilated oven.

Test Specimen

Five numbers of bricks from the sample to be tested are to be taken. The dimensions shall be

measured to the nearest 1mm.

Preconditioning

Dry specimen in a ventilated oven at a temperature of 105 to 115°C till it attains substantially

constant mass. Cool the specimen to room temperature and obtain its weight(W 1). Specimen

warm to touch shall not be used for the purpose.

Procedure

Immerse completely the dried specimen in clean water at a temperature of 27±2°C for 24

hours. Remove the specimen from water and wipe out any traces of water with a damp cloth

and weigh the specimen. Complete the weighing within 3 minutes after the specimen has been

removed from the water (W2). Water absorption, percentage by weight, after 24 hour

immersion in cold water is given by the following formula:

Percentage water absorption = (W2-W1) X 100

W1

Observations & Calculations

Specimen N0.Weight of dry brick

(W1)

Weight of wet brick

(W2)

Percentage Water

absorption

Result

Water absorption of the given burnt clay building brick sample, percentage by weight, after 24

hour immersion in cold water=...........%

Is Specification

As per IS 1077:1992, the bricks when tested in accordance with the procedure laid down in IS

3495 (Part 2):1992 after immersion in cold water for 24 hours, water absorption shall not be

more than 20% by weight upto class 12.5 and 15% by weight for higher classes.

4.6.Types of bricks

1. Common Burnt Clay Bricks: Clay bricks are fired bricks. These are formed by pressing in

moulds or by an extrusion and wire cutting process. Then these bricks are dried and

fired in a kiln.

2. Sand Lime Bricks (Calcium Silicate Bricks): These bricks are mixtures of sand and

hydrated lime pressed in moulds and cured in a high-pressure steam autoclave.

3. Concrete Bricks: Concrete bricks are mixtures of cement, sand and aggregates vibrated

in moulds and steam cured.

4. Fly ash Clay Bricks: Fly ash is used along with clay in these bricks. Fly ash is obtained

from boilers of thermal power stations.

5. Fire Clay Bricks: Fire clay exists at much depth below the surface and is usually mined.

Generally, Fire clays contain metallic oxides less than surface clays and have more

uniform chemical and physical properties.

Special types of bricks

1. Face bricks: Special bricks having uniform colour, texture, size, etc are used for face

works, sometimes it may contain some face design. It is used for garden walls, steps,

side walls, and other exposed works where good appearance is desired.

2. Fire bricks: They are made up of special fire clay. And it is used for lining furnaces, fire-

places, etc, where high temperature are prevalent and where ordinary bricks get

decomposed.

3. Glazed and coloured bricks: Glazed and coloured bricks have one surface glazed in

colour. They are used for exterior surfaces of walls in hospitals, dairies, etc where

cleanliness is important.

4. Imitation bricks: Bricks made of Portland cement and sand are known as imitation

bricks. They are used for the construction of compound wall, partition wall, etc. these

bricks have same qualities as good mortar.

5. Channel bricks: These bricks are moulded to the shape of a gutter or a channel and they

are glazed to prevent sediment deposition. These bricks are used to function as drains.

6. Coping bricks: These bricks are made to suit the thickness of walls on which coping is to

be provided. It take various forms such as chamfered, half-round or saddle-back.\

7. Hollow bricks: These bricks are also known as cellular or cavity bricks. Such bricks have

wall thickness of about 20 to 25mm. they are light in weight hence transportation cost is

less. These bricks reduce the transmission of heat, sound and damp. They are used in

the construction of brick positioning.

8. Paving bricks: These bricks are prepared from clay containing a higher percentage of

iron. Excess iron vitrifies the bricks at a low temperature; such bricks resist the abrasive

action of traffic effectively. Thus they can be used for the construction of foot paths,

garden walks, stable floor, etc

9. Perforated bricks: These bricks contain cylindrical holes through out their thickness.

These bricks are light in weight and they require less quantity of clay for their

preparation. Bricks with perforations of about 30-40% of the total area of the

corresponding face of the brick would offer adequate thermal insulation property. The

distance between the side of brick and edge of perforation should not be less than

15mm. Water absorption should not exceed 20% by weight. The compressive strength

of perforated bricks should not be less than 7N/mm². These bricks are used for brick

wall where thermal insulation is important.

5.MATERIALS AND METHODS USED

The sludge used in this study was collected from the HLL Lifecare Limited, Peroorkada. Before collection the sludge had been subjected to drying in the sludge drying bed for a period of two weeks. The objective of this study is to identify the possibilities of using sludge obtained from effluent treatment plant (HLL) as a brick material. The different engineering properties studied are as follows:

5.1.Moisture Content

Moisture content is the ratio of weight of water present in the sludge to the weight of dry sludge.

Procedure for determining moisture content:

Weigh a dry container & note down its weight(w1) Place some amount of wet sludge in the container and weigh it(w2) Keep the container in the oven & allow it to dry for 24 hours at105-110°C Remove the container from the oven & weigh it(w3) Moisture Content=(w2-w3)/(w3-w1)

Obtained value of moisture content=162.31%. This indicates that more than 50% of the

total mass of the sludge is that of water.

5.2.Specific Gravity

Specific gravity of sludge is the ratio of weight in air of the given volume of dried sludge

to the weight of equal volume of water at 4°C.

Procedure for determining moisture content:

Dry & weigh a pycnometer(w1)

Oven dried sludge is filled in the pycnometer up to one-third of its volume &

weighed(w2)

Add sufficient water to cover the sludge and shake it well. Note down its weight(w3)

Fill the pycnometer completely with water & weigh(w4)

Specific Gravity of sludge=(w2-w1)/((w4-w1)-(w3-w2))

Obtained value of specific gravity= 1.53. The value obtained corresponds to the specific

gravity of organic soil, which generally falls below 2.00

5.3.Preparation of bricks

Sludge and clay were first dried and powdered. Clay having very high plasticity when

subjected to sun drying became rock hard.

5.3.1. Sieving

Clay was used after sieving through IS Sieve 1.18mm . Sand used was also sieved

through IS Sieve 600micron.

5.3.2.Mixing

Sludge and additives were mixed together in different proportions. Different quantity of

water was added for different proportions till a workable mix is obtained. Hand mixing was

done to mix the sludge and additives uniformly. Brick moulds were properly oiled using furnace

oil. The mixed sludge was then filled in brick moulds in 3 layers. Each layer was compacted with

the compaction rod and the surface was finished with a trowel.

5.3.3.Drying

The bricks were removed from the mould immediately and were kept aside at room

temperature for drying.

5.3.4.Burning

After 1 day the bricks were subjected to burning in a muffle furnace. The bricks were

burned at a temperature of 1000°C for 2 days.

5.3.5.Testing

Standard tests as per IS Specification were conducted on bricks. The tests were

conducted in the strength of materials lab in the college. The following tests were conducted:

1. Compression test

2. Water absorption test

3. Efflorescence test

6.Results and discussions

6.1.Proportioning

Sand:Sludge:clay 1:1:3 1:2:2Total volume(cm³) 1.2x19x9x9x4 = 7387.2 1.2x19x9x9x4 = 7387.2Yield 1/2.6 + 1/5.3 + 3/1.6 = 2.913 1/2.6 + 2/1.53 + 2/1.6 = 2.94Weight of sand required(kg) 7387.2/2.913 = 2.54 7387.2/2.94 = 2.51Weight of sludge required(kg) 2.54 5.03Weight of clay required(kg) 7.6 5.03