srd Project Doc Final

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ROLE OF FLY- ASH IN BRICK CONSTRUCTION

C.S.I.T DEORI Page 1

CHAPTER 1INTRODUCTION

1.1 GENERAL

Fly ash brick First invented in 2007.....

American civil engineer Henry liu announced the invention of a new type of fly ash brick in 2007.

Liuss brick is compressed of at 4,ooo psi and cured for 24 hrs in a 150 F(66 C) steam bath, then

toughened with air entrainment agent , so that it lasts for more than 100freeze thaw cycles. Owing to

high concentration of calcium in class c fly ash , the brick can be described as self cementing. Since

method contains no clay and uses pressure instead of heat ,it saves energy, reduces mercury pollution, costs 20% less than traditional manufacturing techniques. This type of brick is now

manufactured under license in USA.

Fly ash bricks are constructed at least partially from the residue of burnt coal. Depending on the

type of coal that is burned, the resulting fly ash can take a number of different forms. Some kinds of

fly ash require a cementing agent, such as quicklime or Portland cement. Other types contain a large

enough percentage of lime that they are self setting, requiring only the addition of water to be turned

into fly ash bricks.

These bricks have been utilized in construction since the 1950s in some parts of the world, and in

certain configurations are able to meet or exceed specifications for clay or cement bricks.

When coal is burned, one of the results is a fine powder known as fly ash. While other ashes might

settle at the base of the furnace where the coal is being burned, fly ash is light and fine enough that

flue gases often are able to carry it up through the chimney.

In the past, this ash was typically allowed to escape into the atmosphere, though in many locations

environmental regulations the fly ash must be captured for safe disposal or reuse. Since toxic

materials like mercury and lead may be highly concentrated in fly ash, this can lead to environmental

or health concerns.

Since the 1950s in places like the United Kingdom (UK) and the 1970s in parts of Africa, houses and

other structures have been build with fly ash bricks.


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1.2 UTILISATION OF FLY ASH IN CEMENT AND BRICKS

It has been above 70 years to research and use fly ash. With its application, the action

mechanism of fly ash had been recognized. During the initial stage, only its pozzolanic activity is paid attention [8 and 9]. Many researchers devoted themselves to the research of the potential

activity of fly ash and the hydration process of fly ash cement. With the deepening of the

cognition for fly ash properties, some people found that the particles of fly ash have the

morphology that is different to other pozzolanic materials. It is the unique particle morphology to

make it have the ability reducing water, which other pozzolanic materials do not have [10, 11, 12

and 13]. and In 1981, Yinji [15] and Danshen [16] summarized the previous research results and

put forward the hypothesis of "fly ash effects." They considered that fly ash has three effects in

concrete, i.e., morphological, activated and micro aggregate effects. The three effects are relative

each other. This shows that the morphological effect is the important aspect of fly ash effects.

1.3 Fly Ash Production

In each country utilization of fly ash depends on the local condition and has much to do

with the fact that fly ash is multifunctional material and can be used for various purposes. In the

building industry fly ash can be used in different ways for different products. In concrete fly ash

can be used as partially replacement of cement and/or sand to enhance workability of fresh concrete,to reduce heat of hydration and to improve concrete impermeability and resistance to sulfate attack.


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.

FIG 1.1 COAL ASH PRODUCTION

The properties of fly ash are varying depending on the coal kind and origin and on the power

plant mode of operation. In certain uses some kind of beneficiation is required, either to improve its

properties for the specific use or to achieve homogeneity. In concrete, fly ash can actually be usedalso "as is" when its properties fall within certain limits, but classification by particle size and/or

control of the unburned coal greatly enhance the beneficial effects of the fly ash and of course its

commercial value.

Utilization of fly ash ranged between 3-5% in the late 1980s and early 1990s. There was no

large-scale concerted effort for promoting fly ash utilization. Technologies and research were

generally isolated with little emphasis on commercialization.

Although attempts were made to use of fly ash in manufacturing bricks, cellular concrete, prefab

items, and cement as well as for reclamation of low lying areas and construction of roads, the desired

impact could not be achieved.

Fly Ash Mission (FAM) was created to help with confidence building in fly ash based

technologies. Fifty-five technology demonstration projects have been completed, as a result of which


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fly ash utilization has increased to 13% of the total generation. Broad estimates of ash production and

utilization in different parts of India (Utility Thermal Power Stations) are given in Table 1.

TABLE NO. 1 FLY ASH PRODUCTION & UTILIZATION

The BIS standards related to fly ash and its utilization is being revised through drafting a

second second revision of IS: 3812, i.e., Specification for fly ash for use as pozzolan and admixture.

The minimum and maximum percentages of fly ash in PPC, specified by IS 456, have risen from

10% to 15% and from 25% to 35% respectively. The government of India has issued a notification

that makes it mandatory to use at least 25% ash in the manufacture of clay bricks, blocks, or tiles

within a radius of 50 km from coal or lignite based thermal power plants.

There are some fiscal incentives to encourage the production and use of fly ash based products,

the government of India has withdrawn the 8% excise duty previously imposed on such products. Now, no excise duty shall be levied on the manufacture of a good in which a minimum of 25% fly

ash is used

1.4 SCOPE AND OBJECTIVE OF STUDY

The study covers the following aspects, which are based on the following Terms of

Reference:

The relationship of fly ash bricks to construction sector, in the context of fly ash generation

by coal based thermal power plants. The present status of fly ash brick manufacture in India,

availability of fly ash, and potential of utilization of fly ash bricks.

Status of fly ash brick technologies in India by way of research work being done by

various institutions, and technologies being used for manufacture of these bricks.

Sr.No Zone Name FA generation Utilization(million tones)

Utilization(%)

1 Southern 13.5 0.8 6.0

2 Western 16.5 0.8 5.0

3 Central 18.0 2.84 15.8

4 Eastern 10.21 2.94 28.8

5 Northern 15.5 2.3 14.8

Total(All India) 73.71 9.96 13.1


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Keeping in view, the technological status for fly ash brick manufacture, assessment of the

technologies for its relevance and suitability, keeping in view material inputs required, energy

requirements, costs, infrastructure requirements etc.

It may also be noted that various cements and mixes which can be made using fly ash, have the

potential become raw materials for fly ash bricks and blocks of various specifications. Therefore, this

aspect has also been discussed. Utilization of fly ash can result not only in reducing the magnitude of

the environmental problems, but it is also to exploit fly ash as raw material for value added products

(and conserve traditional materials), and for extraction of valuable materials.

Amongst many uses that fly ash can be put to, that in building materials is particularly suitable.

It is also anticipated, that there would be considerable short-fall in production of various building

materials. According to a study, there would be a large short-fall in the production of bricks to the

tune of 25 billion bricks on an estimated demand of 100 billion bricks per year in India by the turn ofthe century.

Considerable work has been done in various research institutions in India for utilization of fly

ash. In spite of the recognition of the size of fly ash utilization / disposal problem and availability of

technologies appropriate for Indian fly ashes and applications, India utilizes hardly about 3% of the

total fly ash generated.


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CHAPTER 2

LITERATURE REVIEW

2.1 GENERAL

Fly ashes from Vijayawada thermal power plants were used in the experiments of the present

study. A brief review of literature about the physical and chemical properties; mineralogy and

morphology behavior of fly ashes is presented. Literatures regarding concrete applications of fly

ashes have been used in construction are also discussed.

Fly ash is produced from burning of pulverized coal in thermal power plants. The pulverized

coal is fed into the boilers and burnt with the supply of additional air. The temperature in the boiler

exceeds 1600 C and the most of the mineral matter present in the coal are fused and altered physically and chemically. The resulting residue is called coal combustion by-products namely

bottom ash, economizer ash, air pre-heater ash, and electrostatic precipitator ash (fly ash). These

ashes are handled and disposed off separately owing to their differing qualities by mechanical,

hydraulic and pneumatic conveying systems.

The quality of ash produced is dependent on various factors like source coal and its degree of

pulverization, design of furnace, changes in coal supply, changes in boiler load, and firing condition.

Because of this inherent variability of the material, it is necessary to study the characteristics and

engineering behavior of fly ash in detail before its use in an application.

Fly ash is a promising and economical alternative material to construction engineering

applications. Review of literature shows that fly ash has been utilized in the construction of pavement

construction, in high strength concrete, high performance concrete and in other applications.

2.2 CHARACTERISTICS OF FLY ASH

As per ASTM C 618 1993, there are two classes of fly ash namely class F and class C. Class

F fly ash is produced from burning anthracite or bituminous coal and is pozzolanic in nature and

class C is obtained from lignite or sub-bituminous coal. Class C fly ash possesses both pozzolanic

and self-hardening property. Hence, it is necessary to characterize the material scientifically to utilize

it in different applications.


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2.2.1 Physical Properties Of Fly Ash

The specific gravity, loss on ignition ( LOI ) and specific surface area are the prominent physical

properties of fly ashes. The specific gravity of fly ash may vary from 1.3 to 4.8. The iron oxide

content plays a decisive role in the specific gravity of the material. The specific gravity is more for

fly ashes containing more iron oxide and vice versa.

The presence of opaque spherical magnetite and hematite particles in sufficient quantity will increase

the value of specific gravity to about 3.6 to 4.8. On the other hand, as the amount of quartz and

mullite increases, the specific gravity decreases.

However, coal particles with some minerallic impurities will have lower specific gravity in the range

1.3 to 1.6. The range of specific gravity of Canadian fly ashes is reported to be in the range of 1.91 to

2.94 and that of American fly ashes in the range of 2.14 to 2.69.

Dayal and Sinha (1999) , have reported the specific gravity of Indian coal ashes to range between

1.94 and 2.34 with a mean value of 2.16 and standard deviation of 0.21. The specific gravity of fly

ash decreases as the particle size increases. The specific gravity increases when the fly ash particles

were crushed. Typical values of the specific surface of Indian fly ashes (3267 to 6842 cm 2/g) were

comparable with that of the foreign ashes (2007 to 6073 cm 2/g).

2.2.2 Chemical Compositions Of Fly Ash

The main chemical compounds of class F fly ash are silica, alumina and iron oxide.

Other minor constituents include oxides of calcium, magnesium, titanium, sulphur, sodium and

potassium. Class C fly ash contains relatively higher proportion of calcium oxide and lesser

proportion of silica, alumina and iron oxide than class F fly ash. Typical chemical compositions of

various Indian fly ashes are summarized in

Table 2.1.

2.2.3 Morphology Of Fly Ash

Fly ash is a heterogeneous material; with the degree of heterogeneity persisting at all levels viz

macro, micro and nano structural levels (Sun Wei at al 2003). By using scanning electron

microscopy and energy dispersive X-ray analysis (EDXA) technique the particle shape and surface

characteristics of fly ash can be studied. Some of the particles are hollow and spherical, which are

termed as cenospheres


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[Fig2.1 (a)]. These cenospheres are also called floaters, as they are light in weight.

Fly ashes contain small spherical particles within a large glassy sphere, called plerospheres [Fig. 2.1

(b)]. In some particles, where regions of a spherical particle melted or eroded away are known as

clathrosphere [Fig. 2.1 (c)].

This indicates the intense chemical activity having occurred within the particles in the furnace

zone during the short residence time. The exterior surfaces of solid and hollow spherical particles of

low calcium oxide fly ashes are generally smoother than the high calcium oxide fly ashes, which may

have surface coatings of materials rich in calcium1. In some fly ashes small sub-micron size particles

may be sticking to the large spherical particles, due to the convexity of the surfaces. The studies

conducted by Mehta (1998) on low calcium fly ashes (CaO


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Presence of heterogeneous structure of particles contained within a plerosphere Was also identified. Plate like structures that constitute the surface of a sphere was also present Occasionally. These structures may represent the magnetic plate.

Garg (1995) , studied the morphology of Indian fly ashes. The fly ashes contained angular as well as

rounded black particles, spheroid glass, and minute silica grains. Sharma (1993 ), has classified Indian

fly ashes based on the shape of particles as one of the parameters. According to him group- fly

ashes contained mainly spherical particles with the size range between 2-25 m. The surfaces of

glassy spheres in this group are predominantly smooth without any deposit, only some adherence was

observed.

Group- fly ashes contained a wide range of particles (2-35 m). Most of the particles were

spherical in shape, but some sintering and surface depositions were also observed.

Where as group- fly ashes which were of low reactive type contained mostly irregularly

shaped and relatively coarser particles, which have undergone probably little or no fusion in the

combustion process.

2.2.4 Mineralogy of Fly Ash

Fly ash consists of both crystalline and amorphous phases. The crystalline phases could be

quartz, mullite, silimanite, crystallite, cristobalite, sulphates of iron, magnetite etc. The amorphous

phases could be of silica and silicates predominantly of aluminium but containing calcium,

magnesium, and iron in varying concentration with and without traces of sodium and potassium.

The reactivity of fly ashes depends on the non crystalline or glass content in it. The chemical

composition of the glass in the high calcium fly ash is different from the low calcium fly ash and

hence the reactivity of both the ashes are different. The high calcium fly ashes are more reactive than

low calcium fly ashes. Diamond (1986) and Mehta (1998),pointed out that the composition of glassin low calcium fly ashes is different from high calcium fly ashes. Typically low calcium fly ashes

show a diffused halo with maxima at 2 = 21-25 and high calcium fly ashes at 30-34 .Garg

(1999) conducted XRD studies of Indian fly ashes and the crystalline constituents identified were

quartz (SiO 2), mullite (3 Al 2O3. 2SiO 2), hematite (Fe 2 O3) and magnetite (Fe 3 O4).


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The minerals present in fly ash obtained from Koradi thermal power plant (Nagpur) were quartz

low (syn) most predominant, mullite- predominant, brookite, sillimanite and ferroselite

(Gangadhara Rao et al. 1998)

As reported by Garg (1999) , mentioned that quartz and mullite were the main crystalline constituents

in British fly ashes and the American fly ashes contained magnetite and hematite in large

proportions. The range of quantitative measurement in British fly ashes was quartz (1-6.5%); mullite

(9 35%); magnetite and hematite (5% or less). For American fly ashes the proportions were quartz (0

- 4%); mullite (0 16%); magnetite (0 30%); and hematite (1 8%). The glass proportions in these fly

ashes were found to range from 50 to 90%.

2.2.4.1 Reactivity

It is generally agreed that the glass or non-crystalline constituent of Class F fly ash goes into

reaction with Ca(OH)2,which is added as lime or released from the hydration of portland cement.

However, there are many other factors that influence there activity and relative rates of hydration

such as fineness, particle shape, particle size distribution. Fly ash is generally judged for its quality in

terms of strength behaviour. This is studied for pozzolanic characteristics in two approaches; lime

reactivity strength (LRS) and pozzolanic activity index (PAI). IS:3812-1981,accords two grades to

fly ash based on LRS2. Grade I is identified with a minimum 4 MPa

LRS whereas fly ash with lower strength at 3 MPa is categorised as Grade II. The same code has also

specified replacement compressive strength(PAI) at 80 percent as another yardstick. The LRS given

forthese grades generally does not correlate with pozzolanic activity index. It is observed that certain

fly ashes registering low LRS prove better for PAI and certain other fly ashes recording good LRS

have shown lower PAI. Hence to as certain the suitability of fly ash as supplement to cement,the

reactivity study in terms of PAI is desirable


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2.3CLASSIFICATION OF FLY ASHFLY ASH: THE MODERN POZZOLON

FIG.2.2 THE MODERN POZZOLON

Fly ash is comprised of the non-combustible mineral portion of coal consumed in a coalfueled power plant. Fly ash particles are glassy, spherical shaped ball bearings typically finer

than cement particles that are collected from the combustion airstream exiting the power plant.

There are two basic types of fly ash:

A) Class F

B) Class C.

Both types react in concrete in similar ways. Both Class F and Class C fly ashes undergo a

pozzolanic reaction with the lime (calcium hydroxide) created by the hydration (chemical reaction)of cement and water, to create the same binder (calcium silicate hydrate) as cement. In addition,

some Class C fly ashes may possess enough lime to be self- cementing, in addition to the pozzolanic

reaction with lime from cement hydration.

The main benefit of fly ash in bricks is that it not only reduces the amount of nondurable

calcium hydroxide (lime), but in the process converts it into calcium silicate hydrate (CSH), which is

the strongest and most durable portion of the paste in concrete. Fly ash also makes substantial

contributions to workability, chemical resistance and the environment.

2.4 FLY ASH UTILIZATION

Several factors have impeded fly ash utilization in India, while it is being extensively used

globally. Coal-based thermal power stations have been operational for more than 50 years but the

concept of developing environment-friendly solutions for fly ash utilization is only about 15 years


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old. Overall fly ash utilization in India stands at a fairly low level of about 15 per cent of the quantity

generated. Various possibilities for its use are under research.

Among numerous factors that account for the low level of utilization, the chief factors are:

Poor understanding of the chemistry of fly ash and its derivatives for proper end applications Absence of standards and specifications for fly ash products Lack of reliable quality assurance for fly ash products Poor public awareness about the products and their performance

Non-availability of dry fly ash collection facilities Easy availability of land with top soil at cheap

rates for manufacturing conventional bricks

Lack of proper coordination between thermal plants and ash users.Fly ash utilization in the country is gaining momentum owing to the stringent regulations that the

MoEF has stipulated, as also to increased awareness about the benefits of using fly ash for various

products.

Fly ash from coal-fired thermal power stations is an excellent potential raw material for the

manufacture of construction material like blended cement, fly ash bricks, mosaic tiles and hollow

blocks. It also has other, high volume applications and can be used for paving roads, building

embankments, and mine fills.

Fly ash products have several advantages over conventional products. The use of cement in themanufacture of construction products can be reduced by substitution with fly ash. While the use of

cement cannot be completely avoided, for certain products like tiles, the substitution can go up to 50

per cent. These products are known to be stronger and more cost-effective because of substantial

savings on raw material.

2.4 Technological scenario:

Generally fly ash-lime bricks are classified into high densityand low density (aerated auto claved

concrete-AAC) bricks.Fly ash-lime reactions are known for their slow chemistry resulting in feeble =

strengths at early age. Hence, autoclave is an indispensable production unit wherein, at a high

temperature of around 180 oC and pressure of about 8-12bar, the chemistry is augmented. The

reactions between flyash and lime effectively progress under induced hydrothermal conditions to

form calcium silicate hydrates, which impart strength to the matrix.


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While AAC is extensively marketed in other parts of the world, it could not makeenough

penetration in Indian market due to the tendency to compare the price of the bricks with that of clay

bricks regardless of technical virtues.

By integrating the principles of FaL-G technology withparameters of age-old aeration process, the authors have developed alternate technology called non-autoclaved aerated concrete

that dispenses away autoclaving. By doing so, the energy consumption could be slashed down

from 250 kcal/kg to 75 kcal/kg, simultaneously bringing down the plantcost by about 25 percent.

FaL-G is the product name given to a cementitious mixture composed of fly ash (Fa), lime

(L) and gypsum (G). FaL-G technology, developed by the authors, is based on two principles

namely, that the fly ash-lime pozzolanic reactiondoes not need external heat under tropical

temperature condition, and that the rheology and strength of fly ash-lime mixtures can be greatly

augmented in the presence of gypsum.

This has dispensed with the need for heavy-duty press and auto clave, and also made the process

energy efficient, bringing the activity within the reach of tiny sector entrepreneurs.

FaL-G is the extension of work based on the theory of crystallo-mineral combination of

setting behaviour, postulated and presented by the authors in 1986, which says3.A weak crystal

formation of the hydrated reactions of a cementitious material can be made good for attaining

healthy cohesive bond if compensatory mineralogical formation isinitiated through conducive

stoichiometry..FaL-G technology has been successfully used with even low quality of lime and gypsum

that are obtained as by products from other industries. In the modified version of FaL-G

technology, OPC is used as a substitute for lime at parallel cost. It was observed that, for FaL-G

production, LT fly ash proves good in lime route and HT fly ash proves good in OPC route.

By disregarding the standard chemical and physical requirements for use of fly ash in the

cement and concrete industries, it is found that tailor-made blends of even non standardly ashes

with lime and gypsum or with Portland cement produced adequate strength on normal curing..

Such opening up of Application Avenue creates market for hundreds of billions of bricks

summoning for additional production capacities in huge quantities, not withstanding its demand

in the housing sector.


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CHAPTER 3FLY ASH BUILDING BLOCKS/BRICKS

3.1 General

Fly Ash bricks are alternative to burnt clay bricks in the construction sector in India. At this

time India is witnessing a new phase in development. With rapid economic growth and high rate

of urbanisation. Construction provides the direct means for the development, expansion,

improvement and maintenance of human settlements is particular and economic growth in

general. Construction activity accounts for more than 50% of the development outlays in India.

Building construction costs are increasing at rates which are so per cent over inflation.

This is primarily due to the increase in the cost of basic building materials like burnt brick,steel, cement, timber, etc. As a result, the cost of construction using conventional building

materials and construction forms range from As. 40001- to As. 6000/- per sqm even for normal

housing. Construction costs of this order is beyond the affordable capacity of the economically

Weaker Section and Low Income Group and a large cross section of the Middle Income Groups,

whose income levels have not increased commensurately. This has become all the more relevant

in the macro context. due to the large volume of housing to be done in both rural and urban areas

and the limited resource of building materials and finance available.

According to the projections for the Ninth Five Year Plan, there will be a shortage of 6.6

million houses in urban areas and 12.76 million houses in the rural areas at the end of year 2001,

inspite of all the Governmental efforts and resources.

However, it also needs to be recognized that construction also adversely affect the

environment, through physical disruption. the depletion of key renewable resources like fertile

top soil, forest cover and excessive consumption of energy. Therefore, there Is a strong need to

adopt cost-effective, environmentally appropriate technologies by upgradation of the traditional

technologies and also using local materials as well as using appropriate and intermediate

technologies using modem construction materials with efficient, effective technology inputs.

Building materials is an area where enormous amount of innovation for cost reduction, can

be achieved. May bricks being the most important area for innovation as the total demand of clay


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bricks, as an challenged walling material in India, is estimated at 180 billion per annum causing

the depletion 540.000 metric tonnes of fertile soil.

In the above background, Flyash, basically a waste material, has a dear edge over the other

construction material as it can be converted to a resource with minimum amount of investments.Further, it can help to increase the speed and quality of construction and thereby helping in

enhancing the efficiency of housing delivery mechanism.

3.1.1 Availability of Fly Ash

Total flyash generation in India from Thermal Power Plants is estimated at aboot 60 million

tonnes per year, which may increase to about 110 million tonnes per year by 2010 AD. India

utilise only 3-4% of the flyash generated as compared to more than 40% utilisation in Europe,

China and America etc. The Government has indicated a clear willingness to achieve 50% fIyash

utilisation by the turn of the century at its enlarged level of 90 million tonnes per annum. A

variety of experiences are now available to us on the scenario at different levels of

manufacturing of flyash bricks

3.2 Raw Materials Required

Fly Ash bricks are made of fly ash, lime, gypsum and sand and water . These can be

extensively used in all building constructional activities similar to that of common burnt clay bricks. The fly ash bricks are comparatively lighter in weight and stronger than common clay

bricks. Since fly ash is being accumulated as waste material in large quantity near thermal power

plants and creating serious environmental pollution problems, its utilisation as main raw material

in the manufacture of bricks will not only create ample opportunities for its proper and useful

disposal but also help in environmental pollution control to a greater extent in the surrounding

areas of power plants.


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3.2.1 Fly Ash(pulverized fuel ash):

FIG 3.1 FLYASH DUST

Fly ash is the dust removed from the smoke of coal-fired power plants by using air pollution

abatement equipment. Flyash an industrial waste from thermal power stations as a useful

building material. Use of flyashhas been incorporated in a number of experimental projects

Flyash is a waste material from thermal power stations. About30 million tonnes of flyash is

produced annually from as many as 63 thermal power stations in the country.

This very fine industrial waste not only causes environmental pollution butalso poses problem of

disposal. The need for scientific and pollution free disposal of flyash has become a compelling

necessity.

Research and development efforts undertaken inmany countries in the west over the past few

decades have ledto the development of appropriate technology which could help in converting

this industrial waste into useful building material. As a result of this development, flyash could

beutilised in the production of pozzolana cement, cellular concrete in combination with lime,

flyash lime bricks and sintered flyash lightweight aggregate. The level of utilisation of flyash indeveloped countries like the USA, West Germany and France is about 70 percent. Unfortunately,

the level of utilization of flyash is not encouraging in India, which is a poor 3 percent.

Large variations in the grading of flyash from different thermal power plants, no availability

of flyash in dry form, absence of any organized building industry in the


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country, high initial investment in setting up flyash based building material units, no availability

of indigenous plants and machinery for commercial production of building materials from flyash

are among the major hurdles in the production of different building products from Indian flyash.

The work done on VTPS-fly ash has shown low reactivity and very less lime content.The Vijayawada thermal Power station at Vijayawada has facilities of collecting fly ash from

hoppers in dry state with the help of electrostatic precipitator. Fly ash collected from Vijayawada

Thermal Power Plant at Vijayawada was a Class F fly ash. It may also be noted that until very

recent time, there has not been much efforts in India to classify the dry-collected fly ash or to

process the bulk collected dry fly ash through separation of cenoshere, removal of carbon or

further size reduction.

Fly ash was collected directly from hoppers in dry state with the help of electrostatic

precipitator are being used. From the previous study done on the same source of fly ash [8,48],

the following observations can be made. Fly ash fulfil the criteria for lime reactivity specified in IS 3812-1981. It was found that fly ash particles retained on 45 m sieve was very small (1.0-

1.5 percent) and 90 percent of particles have diameter between 17 and 20 m

3.2.2 Lime

Lime is truly a versatile material in building construction projects. Lime can be used to

prepare the construction site by stabilizing the soil or remediating brownfield sites. Lime can be

used in the construction of masonry systems as a component of mortar or the masonry unit.

Exterior (stucco) and interior plaster systems can also contain lime.

Finally, the decorative finishes can be created with lime washes.

Lime has been used in building construction for thousands of years to create durable mortar

and plaster. Though lime putty was originally used for these applications, most modern

applications utilize hydrated lime. Dolomitic Type S hydrated lime is preferred for applicationsin the United States due to its exceptional water retention capability and proven performance.

Lime provides benefits in the plastic and hardened state to mortars and plasters. In the plastic

state, lime can enhance the workability and water retention of plasters and mortars. In the

hardened state, lime products react with carbon dioxide to regenerate calcium carbonate or

limestone. This is a slow, gradual process which increases the hardness of the finished surface


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and allows for the healing of hairline cracks by a process called autogenous healing. Since initial

strength is needed in most applications, additives such as gypsum, cement or pozzollans are

mixed with lime in construction applications. Lime can react with pozzolanic materials in the

mortar or plaster to produce a cement-like product.The strength of lime-based mixes can be modified based on the application. This is beneficial

in restoration applications where low strengths and high vapor permeability are needed.

3.2.3 Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the

chemical formula CaSO42H2O . It is found in alabaster, a decorative stone used in Ancient

Egypt. It is the second softest mineral on the Mohs scale of mineral hardness. It forms as an

evaporite mineral and as a hydration product of anhydrite.

Gypsum is a common mineral, with thick and extensive evaporite beds in association with

sedimentary rocks. Deposits are known to occur in strata from as far back as the

Archaean eon. Gypsum is deposited from lake and sea water, as well as in hot springs, from

volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly

hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the

minerals halite and sulfur.

Gypsum is also formed as a by-product of sulfide oxidation, amongst others by pyriteoxidation, when the sulfuric acid generated reacts with calcium carbonate. Its presence indicates

oxidizing conditions. Under reducing conditions, the sulfates it contains can be reduced back to

sulfide by sulfate reducing bacteria. Electric power stations burning coal with flue gas

desulfurization produce large quantities of gypsum as a byproduct from the scrubbers. Calcium

sulfate, commonly known as natural gypsum, is found in nature in different forms, mainly as the

dihydrate (CaSO4 2H2O) and anhydrite (CaSO4). They are products of partial or total

evaporation of inland seas and lakes. Both the dihydrate and the anhydrite occur in nature in a

variety of forms.

The origin of gypsum, its genesis, varieties and properties are discussed, and the focus is then

on the most common binding material produced from it, plaster of Paris ( - hemihydrate), known

in France as pltre de Paris , in the USA as calcined gypsum, and in Germany as Stuckgips.

Details are given of the properties of gypsum paste (setting, expansion, and adhesion) and of


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hardened gypsum (strength, bulk weight, thermal expansion, volume and linear changes under

humidity fluctuations, moisture absorption, paintability, corrosivity, thermal and acoustic

insulation behaviour, and fire resistance).

3.2.4 Sand(Fine Aggregate)

Natural River Sand was used which is locally available in Hyderabad region. The specific

gravity was found 2.57. Fineness Modulus is also determined using 10mm to 150 m and is

found 2.972 . The fineness modulus gives the idea about average size of particles in the fine

aggregates. The value 2.972 indicates medium size sand. The details of sieve analysis are

presented in Table 3.1, and the grading curve is shown in

Figure 3.1. With sieve analysis data and fineness modulus value, sand is considered as zone II

grading sand of IS: 383 1970 , which is considered as good fine aggregate for concrete

production. The grading limits of zone II sand for fine aggregates as per IS: 383-1970 is also

presented in Table 3.2.1for reference only.

Sieve Size mm WeightRetained(gm)

%Weight Retained Cumal;ative %Weight Retained

% Passing

40 0 0 0 100

20 0 0 0 100

10 0 0 0 100

4.75 36 1.80 1.80 98.20

2.36 150 7.50 9.30 90.70

1.18 560 28.0 37.30 62.70

600 476 23.80 61.10 38.90

300 554 27.70 88.80 11.20

150 202 10.10 98.90 1.10

L.P 22 1.10 100 0

Table3.1: Sieve Analysis of Fine Aggregate

Weight Of sample: 2000gm


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Modulus = cumlative % weight retained/100 = 2972/100=2.972

Grading zone 11

SIEVE ANALYSIS OF FINE AGGREGATE WEIGHT OS SAMPLE: 2000gm

TABLE NO. 3.1 GRADING CURVE FOR FINE AGGREGATE

TABLE NO.3.1 GRADING LIMITS OF FINE AGGREGATE IS: 383-1970

Sand is an extremely needful material for the construction but this important material must be

purchased with all care and vigilance. Sand which is used in the construction purpose must be

clean, free from waste stones and impurities.

It is important to know what type of sand is beneficial for construction purpose as sand is also

classified into three different forms that make it suitable for specific type of construction.


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Sand is classified as: Fine Sand (0.075 to 0.425 mm), Medium Sand (0.425 to 2 mm) and

Coarse Sand (2.0 to4.75 mm). However this classification of sand is further has types of sand in

particular and on that basis only they are being incorporated in the construction.

Read out the detailing of the types of sand :

i) Pit Sand (Coarse sand)

Pit sand is classified under coarse sand which is also called badarpur in common language.

This type of coarse sand is procured from deep pits of abundant supply and it is generally in red-

orange colour. The coarse grain is sharp, angular and certainly free from salts etc which is mostly

employed in concreting.

ii) River Sand

River sand is procured from river streams and banks and is fine in quality unlike pit sand.

This type of sand has rounded grains generally in white-grey colour. River sand has many uses in

the construction purpose such as plastering.

iii) Sea Sand

As the name suggest, sea sand is taken from seas shores and it is generally in distinct brown

colour with fine circular grains. Sea sand is avoided for the purpose construction of concretestructure and in engineering techniques because it contains salt which tends to absorb moisture

from atmosphere and brings dampness.

Eventually cement also loses its action when mixed with sea sand that is why it is only used for

the local purpose instead of structural construction.

There are different standards for the construction purpose which must be checked and

considered for the better construction. The requirement according to which sand is chosen should

be like:

For plastering purpose the overall fine sand used must not be less than 1.5 while silt is

preferred to not less than 4 percent. For brick work fine sand used must not be less than 1.2 to

1.5 and silt is preferred is 4 percent generally.

Concreting work require coarse sand in modulus of 2.5 to 3.5 with not less than 4 percent silt

content.


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3.2.5 Water

Ordinary tap water was used in the production of bricks. water is one of the most important

elements in construction but people still ignore quality aspect of this element. The water is

required for preparation of mortar, mixing of cement concrete and for curing work etc duringconstruction work. The quality and quantity of water has much effect on the strength of mortar

and cement in construction work.

Quality of Water

The water used for mixing and curing should be clean and free from injurious quantities of

alkalis, acid, oils, salt, sugar, organic materials, vegetable growth and ther substances that may

be deleterious to bricks, stone, concrete or steel. Potable water is generally considered

satisfactory for mixing. The pH value of water should be not less than 6.

Water Reducing Admixtures

The water reducer admixture improves workability of concrete/mortar for the same water

cement ratio. The determination of workability is an important factor in testing concrete

admixture. Rapid loss of workability occurs during first few minutes after mixing concrete and

gradual loss of workability takes place over a period from 15 to 60 minutes after mixing. Thus

relative advantages of water reducing admixture decrease with time after mixing. Theseadmixtures increase setting time by about 2 to 6 hours during which concrete can be vibrated.

This is particularly important in hot weather conditions or where the nature of construction

demands a time gap between the placements of successive layers of concrete.

3.3 Procurement of Raw materials

Fly ash is mixed with the three other ingredients available as industrial by -products:

i) Lime from the acetylene industry, and

ii) Gypsum from chemical plants.

iii) stone dust from stone crusher (or)

iv) sand from local river areas

v) water


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This is proving to be a revolutionary invention that produces bricks without the sintering

process and consequently no greenhouse gases are emitted. The ultimate product is none other

than FaL G Brick which is well qualified as emission-abating project to receive the benefits

of carbon credits.

.

FIG NO.3.2 TYPES OF RAW MATERIAL

3.4 Types of Flyash Bricks

Fly ash bricks can be divided into the following types :

i)FAL-G (fly ash-lime-gypsum) Bricks:Fly ash-lime-gypsum bricks/blocks technology has been developed successfully by

National Thermal PowerCorporation (NTPC), Bhanu International and

Ahmadabad Electricity Company (AEC) for manufacturing bricks/blocks which can replace

burnt clay bricks as walling material. It is also known as Fly Ash-Lime-

Gypsum (FaL-G)bricks. It is not a brand name but it is duct name,christened to the mix for easy

identification of its ingredients.

Fal-G bricks and blocks are manufactured without using thermal energy, in contrast to the

sintering involved in the production of clay bricks.

Fal-G bricks are made of a mixture of fly ash-limegypsum or fly ash-cement-gypsum.

In either combination, Fal-G is a hydraulic cement, which means it sets and hardens in the

presence of moisture, on the lines of ordinary portland cement, gaining strength progressively

over ageing. Nearly 200 tonnes of coal is used to sinter one million clay bricks, a process that


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generates over 350 tonnes of carbon dioxide (CO2). The production process ofWorld Bank has

offered to buy 800,000 tonnes of CO2reductions from utilisation of Fly ash. Fal-G bricks

eliminates harmful emissionsof this scale.

FIG 3.3 TYPES OF BRICKS & TILES

ii) Clay- Flyash Bricks :

Manufacturing process of clay flyash bricks by manual or extrusion process involves mixing

of flyash (60 %) with clay of moderate plasticity. The green bricks are dried under ambient

atmospheric conditions or in shed to equilibrium moisture level of below 3 percent. Dried bricks

are fired in traditional brick kilns at 1000 30 C with a soaking period of 5 7 hoursat

maturing temperature. This technology has great potential to reduce not only precious topsoil and

consumption of coal in making conventional clay bricks, but also requires minimumcharges in

existing set up at kiln sites and not very much susceptible to quality of ash.

FIG 3.4 CLAY FLY ASH BLOCK


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iii) Flyash Sand Lime Bricks :

In presence of moisture, fly ash reacts with lime at ordinary temperature and forms a

compound possessing cementations properties. After reactions between lime and flyash,calciumsilicate hydrates are produced which are responsible for the high strength of thecompound.

This processes involves homogeneous mixing of raw materials (generally fly ash,sand and

lime), moulding of bricks and then curing of the green bricks. Some technologies call forusage of

chemical accelerator like gypsum. These processes are almost similar and varyslightly from

water curing to steam curing at low pressure or autoclaving at 10-14 kg/cm2.Bricks made by

mixing lime and flyash are, therefore, chemically bonded bricks.

These bricks are suitable for use in masonry just like common burnt clay bricks. These bricks

posses adequate crushing strength as a load-bearing member and are lighter in weight than

ordinary clay bricks.

FIG 3.5 FLYASH & SAND LIME BRICK

Generally, dry fly ash available from power plants meets the properties specified in

IS: 3812and is suitable for manufacture of Fly Ash lime bricks in accordance with

the requirementsof IS: 12894.

iv) Cold Bonded Lightweight Flyash Bricks, Blocks and Tiles:

The material can be produced in a variety of building blocks, bricks and tiles, depending

onlocal markets and regulations. Keraton consists of cheap and ubiquitous raw materials such

asfly ash and / or other waste materials. These materials are mixed and a cold bonding agent


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isadded. The mixed raw material is cast in moulds, after which the moulds are processed in

amicrowave oven for transportation to the building site.

The products can be applied as a lightweight material in the house building industry and

utility building, such as stables, barns, garages, etc. A surface treatment or coating for coloring is possible. Strong points are theability to use fly ash, the insulation properties and the production

flexibility.

FIG 3.6 BLOCK & TILES

v) Flux Bonded Flyash Bricks Blocks and Tiles:

The process is similar to the one in the conventional tile industry: fly ash is mixed with less

than 10 % plastic clay and a few additives and tiles, bricks or blocks are pressed. Theseshapes

are fired in the range of 900C to 1000C to make the final product. More than 85% of flyash is

used in the process.

The process is based on the formation of low melting fluxes at the firing temperature,

which partly react with the fly ash and form a high temperaturereactive glass binder phase. The

bricks, tiles and blocks are brick red in colour, but changing the initial composition can make a

variety of colours


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3.5 Market Demand

180 billion tones of common burnt clay bricks are consumed annually approximately 340

billion tones of clay- about 5000 acres of top layer of soil dug out for bricks manufacture, soil

erosion, emission from coal burning or fire woods which causes deforestation are the serious problems posed by brick industry. The above problems can be reduced some extent by using fly

ash bricks in dwelling units.

Demand for dwelling units likely to raise to 80 million units by year 2015 for lower middle

and low income groups, involving an estimated investment 0f $670 billion, according to the

Associated chamber of commerce and industry. Demand for dwelling units will further grow to

90 million by 2020,which would requires a minimum investment of $890billion. The Indian

housing sector at present faces a shortage of

20million dwelling units for its lower middle and low income groups which will witness a spurt

of about 22.5million dwelling units by the end of Tenth plan period.

There is ample scope for fly ash brick and block units.

In Chennai alone 1 crore bricks are required for constructional activities in every day.

But good quality of bricks as well as required quantity are not available moreover during the

rainey seasons supply of clay bricks are very difficult. Therefore, in order

to fulfill the required demand there will be a great chance to start more units in the

field of fly ash bricks. 4At present 20nos units are engaged and 40 lakhs nos of bricks per month are manufactured in

our state. And there will be scope to start near about 100 units , which will be produced more

than 2 cores no of bricks per month in future.

Thus marketing of these product are well shinning.

1) India ranks as one of the largest generators of fly ash in the world, mainly from its

80 plus thermal power stations (TPS) widely distributed within the country. The low utilisation

levels of fly ash in civil engineering purposes & building components, currently is at 15% (2002-

03) of the total fly ash generated annually in India.

2) Research both in India and abroad has amply proved that the building components produced

using fly ash are competitive, both in quality and cost, as compared to traditional building


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materials. A techno-feasible study on utilisation of fly ash as building material in major cities of

India, beginning with Hyderabad, initiative taken by BMTPC is laudable.

3) The scope of the study can be broadly divided into two major aspects. Estimating the currentconsumption of bricks, blocks, pavers and the market potential to replace the traditional material

with cement-based fly ash bricks, blocks and pavers

Preparation of techno-economic feasibility outline for establishing a unit to manufacture

cement based fly ash bricks, blocks, pavers at Hyderabad.

4) The data inputs for the study were generated from

(i) review of secondary data,

(ii) meetings& discussions with manufacturers & users for collective opinion,

(iii) visits to TPS, brick/blockmanufacturing plants and

(iv) sampled primary survey of individual manufacturers and users

A. Fly Ash Products: An Overview

1. The various applications to which fly ash can be used as a replacement material in the

building component industry are

Bricks (clay ash, fly ash sand lime, fly ash lime gypsum),Blocks (hollow, solid, pavers),

Others (fly ash cellular concrete, flux & cold bonded fly ash blocks & tiles, wall tiles, fly ash

refractories, extraction of cenospheres) and

Extensively in manufacture of cement.

2. Specific codes have been issued by BIS for utilization of fly ash as building components.

The technical & economical benefits of using fly ash in building components, savings in raw

materials, clay, energy, etc. and reduction in ecological damage has been documented.

3. The survey of manufacturers of bricks & blocks at Hyderabad was conducted to study various

issues concerning this industry and perceptions on the fly ash products. Majority of the

manufacturers are small-scale operators, operating in the last 5 years. The manufacturing units

are mostly located on leased land of average size of 2 acres. This industry in Hyderabad provides

employment to around 19,200 persons with nine out of ten persons employed in traditional brick


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manufacturing units. Survey of 17 fly ash and 10 cement block manufacturers revealed the

manufacture of 31 different types fly ash and 16 cement based products in Hyderabad. Bricks

manufactured are of 9 X4 X3 size. Blocks manufactured commonly are 11.5 , 12 or 16

length, with varied breadth & depth.

4. Four out of 5 bricks manufactured in Hyderabad are traditional clay bricks. Estimated total

annual production of bricks in and around Hyderabad is approx. 131 crore, i.e. 4 lakh fly ash

bricks, 5.1 lakh cement bricks and 43 lakh traditional bricks per day. The share of fly ash bricks

in the brick industry is around 9%.

B. Adoption of IS standards by manufacturers is scanty, evident from poor

quality of bricks available in Hyderabad.

1. Perceptions of brick & block manufacturers on fly ash products Fly ash is available

continuously and of satisfactory quality. It is perceived that technical support initially was

provided by INSWAREB of Vizag, but technology transfer & support from Government is non-

existent.

The current prices of fly ash bricks & blocks are in the same range of cement blocks &

traditional bricks. The manufacturers are equally divided on the pricing of fly ash bricks &

blocks as against traditional bricks & blocks. High preference for fly ash products is observedamong those customers contacting manufacturers. Increased media coverage & favourable

policies are considered key to increasing utilization of fly ash bricks & blocks.

Very high willingness is observed among traditional manufacturers regarding use of fly ash in

their products. Technical assistance & increased product awareness among the public are

considered important for promoting the shift in the manufacturing practices.

C. Current Market Scenario:1. Manufacturing technologies for utilizing fly ash in building components have been developed

various research agencies in India like CFRI, CBRI, NCBM, AEC,

INSWAREB etc.

2. The survey of users in Hyderabad was conducted to study the utilization pattern and

perceptions on the fly ash products.


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Most of the bricks & blocks used are light in weight and used chiefly for construction of

buildings, and procured directly from manufacturers & suppliers alike within Hyderabad.

Users are of the opinion that strength, durability, finish, availability, price are the important

qualities in bricks or blocks. The number of users satisfied and dis-satisfied with traditional products are equally divided. Awareness level among users regarding fly ash products and

willingness to adopt them in their projects is high. Despite their low availability, 35% of the

users desire to use fly ash bricks & block

D. COMMODITY FUTURE : Market Potential

1. The growth of households in Hyderabad Urban Agglomeration in the last decade has increased

by 32%, while the population increased by 27%, indicative of increased household formation

rate, and consequently increase demand for housing.

2. The housing stock in Hyderabad UA in 2001 is around 10,22,106. The housing stock between

1991-2001 has increased by 33%.

3. At current growth rates, the total housing stock to be added by 2010 including replacement for

ageing & dilapidation is approx. 3,77,400. The proportion of permanent structures in the total

housing stock is likely to increase from 87% in 2001 to more than 90% in this decade, thus

necessitating increased building components into the construction industry.

4. It is perceived that current production levels of manufacturers are able to meet 70% of themarket demand. Both manufacturers and users agree an increase in the annual requirements

(between 10 to 15% current manufacturing levels) in the next 5 years. The demand is perceived

to be higher for fly ash bricks & blocks than traditional bricks or blocks.

E. Scope for New Entrant:

5. The annual demand of bricks by 2010 studied under different scenarios is expected to vary

between 1275 million to 1495 million, while demand for fly ash bricks would be around 318

million to 373 million.


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CHAPTER 4

EXPERIMENTAL WORK

4.1 General

As discussed in previous chapters, the selection of materials, judicious mix proportioning

and proper workmanship (quality control) leads to high performance bricks, which is required

exhibit enhance strength and durability. In establishing these requirements, careful consideration

of properties of local available materials has to be accounted for. Hence in this chapter main

consideration is given to the planning

Fly ash bricks are nowadays mostly used for construction and gaining its popularity over

builders and engineers because of its high strength, uniformity and less consumption of mortar plastering. Above to this it is eco friendly bricks which saves environmental damage caused by

burnt clay bricks and saves top agricultural soil which was the main raw material in the burnt

clay bricks.

73% power generated in INDIA is from Thermal Power and 90% of it is coal based.

Ash content is 27% to 42% of the coal used. Increase in FLYASH generation has risen from 4

crore to 11crore ton in the last decade and will rise to 1100 crore ton in coming decade.

Approximately 10,000 hectares of top soil is being lost every year for brick manufacturing and

road construction.

If we continue in this format, very soon, we will not have sufficient soil to produce our

minimum required food.

Ministry of Environment & Forest (MoEF) Had issued a Gazette Notification on 14 Sep 1999,

Stipulating that no person shall be permitted to manufacture clay bricks or tiles or blocks for use

in construction activity without at least 25% of ash (fly ash, bottom ash, or pond ash on weight to

weight basis), within a radius of 50 Km from coal or lignite based thermal power plants in

INDIA

Ministry of Environment & Forest Had amended the Gazette Notification on 27 Aug 2003

making it compulsory to use fly ash for manufacturing building material by increasing the radius

from 50 Km to 100 Km


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Fly ash bricks are masonry units that are used in the construction of buildings. They are

considered to be a part of good and affordable building materials. They contain Class C fly ash

and water.

Fly ash bricks are made by compressing Class C fly ash and water at 4000psi and then curingis carried on for 24 hours at a temperature of 66 degrees Celsius steam bath. Air entrainment

agent is used to toughen the bricks.

FIG 4.1 FLY ASH BRICK

Since the concentration of calcium oxide is very high in class C fly ash, the brick is

described as self cementing.It is considered to be a good alternative to traditional mud bricks since the method of

manufacture of fly ash is energy efficient that is it helps save energy, brings about

reduction of mercury pollution and plus it is cost effective.


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4.2 MANUFACTURING OF FLY ASH BRICKS

FIG 4.2 MANUFACTURING OF FLY ASH BRICKS

For manufacturing Flyash bricks , most of the machine manufacturers suggest the following

two mixing ratio, you can choose profitable mixing ratio to survive in the market if you are

facing low availability of Flyash .At the same time you should maintain the quality too.

The fly ash bricks are comparatively lighter in weight and stronger than common clay bricks.

Since fly ash is being accumulated as waste material in large quantity near thermal power plants

and creating serious environmental pollution problems, its utilization as main raw material in the

manufacture of bricks will not only create ample opportunities for its proper and useful disposal

but also help in environmental pollution control to a greater extent in the surrounding areas of

power plants.

There are several techniques for manufacturing construction bricks from fly ash, producing a

wide variety of products.

1. One type of fly ash brick is manufactured by mixing fly ash with an equal amount of

clay, then firing in a kiln at about 1000 degrees C. This approach has the principal benefit

of reducing the amount of clay required.


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2. Another type of fly ash brick is made by mixing soil, plaster of paris, fly ash and water,

and allowing the mixture to dry. Because no heat is required, this technique reduces air

pollution. More modern manufacturing processes use a greater proportion of fly ash, and

a high pressure manufacturing technique, which produces high strength bricks withenvironmental benefits. In the United Kingdom, fly ash has been used for over fifty years

to make concrete building blocks. They are widely used for the inner skin of cavity walls.

They are naturally more thermally insulating than blocks made with other aggregates.

3. Ash bricks have been used in house construction in Windhoek, Namibia since the 1970s.

There is, however, a problem with the bricks in that they tend to fail or produce unsightly

pop-outs. This happens when the bricks come into contact with moisture and a chemical

reaction occurs, causing the bricks to expand. In India, fly ash bricks are used for

construction. Leading manufacturers use an industrial standard known as "Pulverized fuel

ash for lime-Pozzolana mixture" using over 75% postindustrial recycled waste, and a

compression process. This produces a strong product with good insulation properties and

environmental benefits.

A. NORMAL METHOD

Process of Manufacture:

Fly Ash bricks are made of fly ash, lime, gypsum and sand. Fly ash, lime sand and gypsum aremanually fed into a pan mixer where water is added in the required proportion for intimate

mixing. The proportion of the raw material is generally in the ratio 60-80% of fly ash 10-20%

lime, 10% Gypsum and 10% sand, depending upon the quality of raw materials. The mixture is

slow setting pozzalona cement mix. After mixing, the mixture is shifted to the

hydraulic/mechanical presses. The specially designed machine to give high pressure load at the

slow rate in mould designed for customer requirements in the order of

280 to 350 kg/ inch. Holding the pressure at specific time gives the more strength of the finished

product. The moulded the bricks then transfer to hydraulic operated wooden pellets manually and

store in covered space for three days (minimum) for setting.

Then the bricks taken to yard for water curing for 15 to 20 days. Then it sorted and tested before-

despatch. These can be extensively used in all building constructional activities similar to that of


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common burnt clay bricks. The fly ash bricks are comparatively lighter in weight and stronger

than common clay bricks.

TABLE NO. 4.1 PROCESS OF MANUFACTURE(NORMAL METHOD)

B. PROFITABLE METHOD

Fly ash, lime sand and gypsum are manually fed into a pan mixer where water is added in

the required proportion for intimate mixing. The proportion of the raw material is generally in

the ratio 60-80% of fly ash 10-20% lime, 10% Gypsum and 10% sand, depending upon the

quality of raw materials.After mixing, the mixture is shifted to the hydraulic/mechanical presses. The bricks are carried

on wooden pellets to the open area where they are dried and water cured for 21 days. The bricks

are tested and sorted before despatch.

TABLE NO.4.2 PROCESS OF MANUFACTURE(PROFITABLE METHOD)


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FLOW CHART NO 4.1

4.3 Characteristics of FlyAsh Bricks The standard size of the brick is 230x110x70.

The bricks are manufactured and tested as per IS 12894-2002.

Fly ash bricks are sound, compact and uniform in shape, size and colour. Smooth

rectangular faces of the bricks are accompanied with sharp and square corners.

FIG NO.4.3 FLY ASH BRICKS


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Fly ash Bricks are available in various colours and shapes. The above picture shows the

bricks in dark peach colour with three holes on it. These holes are used for grouting. The mortar

is poured into these holes for proper bonding in between the bricks .

They are free from visible cracks, warpage, flaws and organic matter. Economical & environment friendly. 28% lighter than ordinary clay bricks. Compressive strength: 7.5N/mm2 on an average. Water absorption:


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(i) Cement : Best Quality OPC 53 Grade Cement / Gypsum Powder,Lime Powder(ii) Thermal Station Fly Ash(iii) Crushed Sand / Stone Dust(iv) Chemicals

(9) Thermal Conductivity :0.90 1.05 W/m2 0 C( 0.75 0.90 K cal/m2 hr 0C )(10) Drying Shrinkage :Maximum Average drying test shrinkage 0.035-0.04 %(11) Brick Colour :-Gray / Dark Gray

4.4.1 Comparison of Normal Clay bricks and Fly Ash Bricks:

4.5 Quality standards:

Bureau of Indian Standards formulated specifications for clay fly ash bricks, lime fly ash

bricks, common burnt clay bricks and calcium silicate bricks which can be referred to as regards

to the quality of Fal-G bricks. IS: 12894:1990 Specification for Fly Ash Lime bricks. IS:13757:1976 Specification for Burnt clay fly ash buildingBricks. S:4137:1989 Specification for calcium silicate bricks. IS:3102:1976 Classification of burnt clay solid bricks.

The other relevant BIS specifications are : IS:3812:1981 Specification for Fly Ash for use as Pozzolana and admixture.


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IS:712:1984 Specification for Building limes. IS:3495(Pt.I)1976 Methods of tests of burnt clay building bricks.

For production of good quality fly ash bricks the quality of Fly Ash should be as follows :

i) Moisture content of fly ash should not exceed 5%.ii) Visual appearance of fly ash should be of light steel grey or smoky grey colour.

iii) Unburnt carbon content in the fly ash be around 5%.

The typical physical requirement of Fal- G bricks as per customers specifications

is as follows :

a) Compressive strength 60-250 kg/cm.2

b) Water absorption 5-12%

c) Density 1.5 gms./c.c.

4.5.1 Pollution control needs :

Workmen working with Fly Ash and at the mixing area are to be provided with protective

equipment like dust masks and safety goggles.

4.5.2 Energy Conservation Needs :

The management has to be vigilant in ensuring higher productivity by the best utilization of man

and machine hours. Periodic checks over working stages ,functioning of machinery and their preventive maintenance and timely repair etc. will help in energy conservation.

4.6 Preliminary laboratory tests:

Compressive strength AS/NZS 4456.4:

Fairly obviously, this is the ability of the masonry unit (brick or block) to resist crushing loads,

eg the weight of the roof that the wall is supporting, plus the weight of the wall itself. The

designer of the structure needs to be sure that the masonry unit will be able to carry the load

being placed upon it, including any live loads.

Salt attack resistance AS/NZS 4456.10:

In some situations, bricks can be attacked by salts from ground water, swimming pools ,

spas etc. How resistant a given brick is to the effects of salt crystallisation will depend on things


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like the porosity of the paver and the strength of the material the paver is made from, as well as

the concentration and type of salt, and moisture and temperature conditions.

Bricks and blocks may be classed as Exposure Grade if they either have a history of coping with

a salty environment, or have passed a laboratory test which simulates such conditions.Units are required to be exposure grade, according to AS 3700 Masonry Structures , wherever

they are in contact with aggressive soils (eg with high concentrations of salts in the ground-

water), or in a severe marine environment , i .e within 1 km of a surf coast or 100 m of a

bayside coast.

The lab test puts small segments of the masonry units through a series of 40 cycles of

alternate soaking in a salt solution, then drying in an oven. If the specimens survive the 40 cycles

with less than a specified loss in mass, theyve passed the test.

Moisture expansion AS/NZS 4456.11:

All fired clay bricks expand slowly after their manufacture, by taking up moisture out of the

atmosphere. The expansion continues for many years, and needs to be taken into account in

building design. To predict the long-term expansion, a brick length can be accurately measured

before and after a laboratory steam treatment and the change in length used to estimate how

much the brick will expand in 15 years.

Information on how far a used brick has already expanded ( past expansion ) can be gainedfrom re-firing the brick in a laboratory kiln, and measuring its shrinkage. How far the used bricks

still have to expand (residual expansion ) can be ass essed by the difference between these two

measurements.

These expansion characteristics depend on the clays used in making the bricks, and on the

manufacturing process itself.

Dimensions AS/NZS 4456.3:

AS/NZS 4455 Masonry units and segmental pavers calls for bricks and blocks to be

classified into dimensional categories based on their deviation from their work size , or the size

specified in manufacture. This is usually a standard size; it is important that deviations from this

be controlled to a low level so bricklayers are able to build the structure to the designers

specifications and with minimum joint thickness variation.


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Under this standard test, 20 units can be either measured individually for length, width and

thickness, or they can be placed side by side, end to end, etc and their cumulative dimensions

measured.

Potential to efflorescense AS/NZS 4456.6:Efflorescence is a deposit of salts, usually white, on the surface of bricks and blocks after

being laid. The salts usually come from ground water or out of the mortar, but may come from

within the masonry units themselves.

This test predicts the likelihood that the units will display such unsightly deposits from salts

that they already contain.

Water absorption AS/NZS 4456.14:

A standard soaking-in-water test can determine the porosity of bricks and blocks, which

can then be used as an indication of the potential for the development of problems related to the

penetration of salts and other materials into the units, such as salt attack and efflorescence.

Water absorption of brick is nothing but the % of water that the brick can absorbs when it is

placed in water. It should not be more that 15 to 20 % of its weight.

During the time of manufacturing bricks, mixture of minerals like silica, clay,ash,sand,etc

this propotionate should vary in all every production and also water content plays very major

role in the bricks as per IS CODE and it says that 15 TO 20 % is the max limit of water

absorption in brick in 24 hrs. water absorption in bricks depend only on void ratio of bricks andalso poor compaction.

WATER ABSORPTION IS CALCULATED BY THIS FORMULAE

[{(W2 -W1)/W2}/100] = ?? %

Where, W1 = Dry weight of Sample

W2 = Weight after 24 hrs in water.

Initial rate of absorption AS/NZS 4456.17:

As soon as the bricklayer puts the mortar on a brick, the brick starts to absorb water out of

the mortar. The microscopic pores in the brick soak up the water, which carries with it some of

the partly- dissolved cement and lime. Its the settin g of this cementitious material within the

brick pores that provides most of the bond between the brick and the mortar, and thus gives the

wall its strength.


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To get the best bond, its important to match the suction of the brick to the water retaining

properties of the mortar. If the initial rate of absorption of the brick is too high for the mortar

thats being used, the mortar may dry out too quic kly and stiffen before the next course can be

laid. If its too low, not enough cementations material is drawn up into the brick pores. In eithercase, the bond strength will suffer. The Initial Rate of Absorption test measures the amount of

water a dry brick can soak up during the first minute of contact with water

4.7 Brick Making Machines:

The technology consist of regular mechanical type and hydraulic version. The hydraulic

version is latest and gives higher production output with minimal inputs like in labour and

power. The strength of bricks in hydraulic version is better than the others. It gives the pressure

of 25 to 50 Ton in lieu of 15 ton in mechanical versions. Embossing the monogram of company

on the bricks is easy. Production is high. Continuous operation is possible.

FIG NO. 4.5 BRICK MAKING MACHINE


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The machine consist of following parts:

1.Fly ash Brick making machine, vibrator, hydraulic power pack motor and Control

panel

It is hydraulically operated automatic machine. The structure is capable of handling load up to100 bar. Different size of mould can be fitted with machine. Embossing on brick is easy.

It give high production at minimal power loads. Circulated water cooling ensure longer

operation.

2.Pan mixing machine with gear box and motor:

A mechanical sturdy constructed with heavy rollers to grind the raw materials efficiently.

Drive by worm reduction gear box. Easy unloading mechanism with proper door arrangements.

3.Belt conveyer system

A fabricated belt conveyer to take the raw materials of 1.5 tiem more than the capacity of

machines. The raw materials can regulated according to the requirements. Rubber with nylon

coated belts.

4.Hydraulic pallot trolley

The trolley capable of transporting maximum bricks to stocking area operated hydraulically,

which reduce the manpower and cracks of bricks. We in Agni Engg. & Industreis manufacturing

the following capacity machines

For production of 3000 mt per annum

FIG 4.6 FOR PRODUCTION OF 3000 mt PER ANNUM


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4.8 Advantages:

Technical advantages:o Energy Efficiento Fire resistanto Sound Resistanto Structurally soundo Strong Durable Versatileo Safe Secure Robust o Economical

o Will not Warp, Twist or Roto

Traditionalo 100% Recyclable- Huge saving in foundation and structure savings up to 30% on

beam costs.

o Good earth quake resistance properties.o Easy handling.

o Faster construction.o Huge saving of lab Reduced Air conditioning expenses.

o Bricks are fire resistant.o Non toxic fumes in case of fire.o Highly accurate and smooth walls reduction in plastering.

Other advantageso It is eco-friendly.o It is Aging materialo Full size and shep saving cement in mortar and plaster.o Less wastage and breakages

o Effloresce and termite freeo Full size and shep saving cement in mortar and plaster.

o Less wastage and breakageso Effloresce and termite free

o Reduce dead load on total Building Structure, thus saving steel and cement


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o It can reduce 10% of water consumption.o It can improve mixture of cement concrete for workability.o Compression strength improves by more than 15 %.

o It can reduce initial stage of cement heat hydration by large margin.o It has no function of corrosion reinforcing bars.

o It increases workability, density and strength without increasing the quantity of cement.o Due to high strength, practically no breakage during transport and use.

o Due to lower water penetration seepage of water through bricks is considerably reduced.

4.9 Disadvantages :

Actually, the disadvantages listed by some people about fly ash bricks are imaginary. But

the flyash bricks manufacturing process involves strong health hazard for the labors. The fly ash

is a very tiny particle and it penetrates in to lungs and cause serious health trouble to the labors

engaged in flyash bricks manufacturing process.

So many reports have proved this dangerous nature of fly ash, and still no awareness is created

among the labours in the thermal power plants, cement factories, Brick manufacturing units etc..

o Fly ash causes severe pollution of air and water, and its disposal gobbles up large tracts

of land. Well-planned programs for proper management of fly ash are therefore

undertaken to enhance the use of fly ash in various applications, so that our already perilously imbalanced environment can be protected

o Fly ash is one of the numerous substances that cause air, water and soil pollution,

disrupt ecological cycles and set off environmental hazards.

o The combustion of powdered coal in thermal power plants produces fly ash.

o The high temperature of burning coal turns the clay minerals present in the coal powder

into fused fine particles mainly comprising aluminium silicate. Fly ash

produced thus possesses both ceramic and pozzolanic properties.

o When pulverised coal is burnt to generate heat, the residue contains 80 per cent fly

ash and 20 per cent bottom ash. The ash is carried away by flue gas collected at

economiser, air pre-heater and ESP hoppers. Clinker type ash collected in the water

impounded hopper below the boilers is called bottom ash.


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Fly ash Hazard to Environment and Life:

FA contains trace amounts of toxic metals (U, Th, Cr, Pb, Hg, Cd etc.), which may have

negative effect on human health and on plants. Several studies have been carried out to assess

hazards caused by FA on environment and plants. SO2 and NO2 released from TPP cause acidrain, which corrodes structural surfaces and may affect agriculture by causing yellowing of green

leaves. Thermal pollution due to disposal in surface water sources disrupts aquatic life, whereas

toxic metals leached contaminate underground water resources. Light and continuous prolonged

inhalation causes pneumonitis, allergy, asthma, lung fibrosis, bronchitis, cancer, and silicosis.

Metal Content (ppm) Diseases

Nickel (Ni) 77.6 Respiratory problem, lungcancer

Cadmium(Cd) 3.4 Anaemia, hepatic disorder

Antimony(Sb) 4.5 Gastroenteritis

Arsenic(As) 43.4 Skin cancer, dermatitis

Chromium (Cr) 136 Cancer

Lead (Pb) 56 Anaemia

FIG 4.7 DISEASES DUE TO THE PRESENCE OF HEAVY METALS IN FLYASH

4.10 Uses :

Several factors have impeded fly ash utilization in India, while it is being extensively used

globally. Coal-based thermal power stations have been operational for more than 50 years but the

concept of developing environment-friendly solutions for fly ash utilization is only about 15

years old. Overall fly ash utilization in India stands at a fairly low level of about 15 per cent of

the quantity generated. Various possibilities for its use are under research.

Among numerous factors that account for the low level of utilization, the chief factors are:

Poor understanding of the chemistry of fly ash and its derivatives for proper end

applications

Absence of standards and specifications for fly ash products


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Lack of reliable quality assurance for fly ash products Poor public awareness about the

products and their performance

Non-availability of dry fly ash collection facilities Easy availability of land with top soil

at cheap rates for manufacturing conventional bricks Lack of proper coordination between thermal plants and ash users. Fly ash utilization in the country is gaining momentum owing to the stringent regulations

that the MoEF has stipulated, as also to increased awareness about the benefits of using

fly ash for various products.

Fly ash from coal-fired thermal power stations is an excellent potential raw material for

the manufacture ofconstruction material like blended cement, fly ash bricks, mosaic tiles

and hollow blocks. It also has other, high volume applications and can be used for paving

roads, building embankments, and mine fills.

Fly ash products have several advantages over conventional products. The use of cement

in the manufacture of construction products can be reduced by substitution with fly ash.

While the use of cement cannot be completely avoided, for certain products like tiles, the

substitution can go up to 50 percent. These products are known to be stronger and more

cost-effective because of substantial savings on raw materia l

Fly ash in bricks

Fly ash products are also environment-friendly. A case in point is fly ash bricks . The

manufacture of conventional clay bricks involves the consumption of large amounts of

clay. This depletes topsoil and degradation of agricultural land. Fly ash bricks do not

require clay and serve two purposes; preservation of topsoil and constructive utilization

of fly ash.

Agricultural uses of fly ash

Research on agricultural uses of fly ash has been going on in universities and research

institutes (see box) across the country for several years.The same fly ash that causes harm when it settles on leaves, can prove beneficial when

applied scientifically to agricultural fields. It can be a soil modifier and enhance its

moistur

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