A PROJECT REPORTONFLYASH

In Partial Fulfillment for the Award ofBachelor of TechnologyDegree OfRajasthan Technical University, KOTA

2014-2015

Submitted by: -

ABHIJEET PARASHARRAVI PRAKASH SWAMIBHARAT BHUSHAN PIPLIWAL ACKNOWLEDGEMENT

We thank the Head of the Department of CIVIL ENGINEERING(CE),Prof. Dr .D.K SHARMA for cooperating us for making this project.Our special thanks go to the Principal, GRIET, Prof., for giving us such a wonderful opportunity to do this project.Without these people, it wouldnt have been possible to do this project on ROLEOF FLY-ASH BRICKS IN CONSTRUCTION.

ABHIJEET PARASHAR RAVI PRAKASH SWAMI BHARAT BHUSHAN

ABSTRACT Fly ash is a fused residue of clay minerals present in coal. The high temperature generated when coal burns in thermal power plants, transforms the clay minerals in coal powder into a variety of fused fine particles of mainly aluminium silicate composition. Pulverized fuel ash commonly known as fly ash. It is a useful by-product from thermal power stations using pulverized coal as fuel and has considerable pozzolonic activity. This national resource has been gainfully utilized for manufacture of fly ash-lime bricks as a supplement to common burnt clay buildings bricks leading to the conservation of natural resources and improvement in environment quality. Fly ash-lime bricks are obtained from materials consisting of pulverized fly ash in major quantity, lime and an accelerator acting as a catalyst. Fly ash-lime bricks are generally manufactured by intergrading blending various raw materials are then moulded into bricks and subjected to curing cycles at different temperatures and pressures. On occasion as and when required, crushed bottom fuel ash or sand is also used in the composition of the raw material. Crushed bottom fuel ash or sand is also used in the composition as a coarser material to control water absorption in the final product. Fly ash reacts with lime in presence of moisture from a calcium hydrate which is a binder material. Thus fly ash lime in presence of moisture form a calcium silicate hydrate which is binder material. Thus fly ash lime brick is a chemically ended bricks. These bricks are suitable for use in masonry construction just like common burnt clay bricks.

CONTENTS 1. INTRODUCTION 1.1 General 1.2 Utilization of fly ash in cement and bricks 1.3 Fly ash production 1.4 scope and objectives 2. LITERATURE REVIEW 2.1 General2.2 Characteristics of fly ash 2.2.1 Physical Properties Of Fly Ash 2.2.2 Chemical Compositions Of Fly Ash 2.2.3 Mineralogy of Fly Ash 2.2.4 Reactivity 2.3 Classification of Fly Ash 2.4 Fly Ash utilization 3. FLY ASH BUILDING BLOCKS/BRICKS 3.1 Raw Materials Required 3.1.1 Fly Ash (pulverized fuel ash) 3.1.2 Lime 3.1.3 Gypsum 3.1.4 Sand 3.1.5 Water 3.2 Types of Fly Ash Bricks 3.3 Market Demand 4. METHODOLOGY 4.1 Manufacturing process of bricks 4.2 Characteristics of Fly Ash Bricks 4.3 Technical Specifications 4.4 Comparison of normal clay bricks and Fly ash bricks 4.6 Fly Ash Brick Site Visit 4.7 Brick making machines 4.8 Advantages & Disadvantages4.9 Uses5. TEST RESULTS AND DISCUSSION

5.1 General 5.2 Test results 5.2.1 WATER ABSORBTION TEST 5.2.2 COMPRESSIVE STRENGTH TEST 6. CONCLUSION 7. BIBILOGRAPH

INTRODUCTION 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.

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. 1.2 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.

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. ~ 10 ~ 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 used also "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.

Table 1 Fly ash production and utilizationS.NO ZONE NAME FA GENERATION(Million tones)UTILIZATIONS(Million tones)

UTILIZATIONS(%)

1.2.3.4.SOUTHERNWESTERNEASTERNNORTHERN13.516.510.2115.5 0.8 0.8 2.94 2.3 6 5 28.8 14.8

TORAL (ALL INDIA)55.71 6.84 54.6

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.

1.4 SCOPE AND OBJECTIVE OF STUDY

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. 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 of the century.

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.

2.2 CHARACTERISTICS OF FLY ASH

As per ASTM C 618 1993[17], 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. 2.2.1 Physical Properties Of Fly Ash The specific gravity, loss on ignition 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. 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 flyash.

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)[20] and Mehta (1998)[19] pointed out that the composition of glass in low calcium fly ashes is different from high calcium fly ashes. 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 (935%); magnetite and hematite (5% or less). For American fly ashes the proportions were quartz (0 - 4%); mullite (016%); magnetite (030%); and hematite (18%). The glass proportions in these fly ashes were found to range from 50 to 90%.The range of quantitative measurement in British fly ashes was quartz (1-6.5%); mullite (935%); magnetite and hematite (5% or less). For American fly ashes the proportions were quartz (0 - 4%); mullite (016%); magnetite (030%); and hematite (18%). 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.

2.3 CLASSIFICATION OF FLY ASH FLY ASH: THE MODERN POZZOLON

Fly ash is comprised of the non-combustible mineral portion of coal consumed in a coal fueled power plant. Fly ash particles are glassy, spherical shaped ball bearings typically finer than cement particles that are collected from the combustion air-stream 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.

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 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.

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

3. FLY 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 economicgrowth and high rate of urbanisation. Construction provides the direct means for thedevelopment, expansion, improvement and maintenance of human settlements isparticular and economic growth in general. Construction activity accounts for morethan 50% of the development outlays in India. Building construction costs areincreasing at rates which are So per cent over inflation.

This is primarily due to the increase in the cost of basic building materials like burntbrick, steel, cement, timber, etc. As a result, the cost of construction usingconventional building materials and construction forms range from As. 40001- to As.6000/- per sqm even for normal housing. Construction costs of this order is beyondthe affordable capacity of the economically Weaker Section and Low Income Groupand a large cross section of the Middle Income Groups, whose income levels have notincreased commensurately. This has become all the more relevant in the macrocontext. due to the large volume of housing to be done in both rural and urban areasand the limited resource of building materials and finance available.According to the projections for the Ninth Five Year Plan, there will be a shortage of6.6 million houses in urban areas and 12.76 million houses in the rural areas at the endof year 2001, inspite of all the Governmental efforts and resources.

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 utilize 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 utilization by the turn of the century at its enlarged level of 90 million tonnes per annum. In India, from Rajasthan fly ash will be available from Kota Thermal Power Plant that is 15 years old.It can also be obtained from the cities like Ahmadabad , Bikaner , Barmer etc.

3.2 Raw Materials Required

Fly Ash bricks are made of fly ash, lime, gypsum and sand stone 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 pollutionproblems, 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.

3.2.1 Fly Ash(pulverized fuel ash):

Flyash is a waste material from thermal power stations. About30 million tonnes of flyash is produced annually from as manyas 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 andpollution free disposal of flyash has become a compelling necessity.

Large variations in thegrading of flyash from different thermal power plants, non- availability of flyash in dry form, absence of any organisedbuilding industry in the country, high initial investment insetting up flyash based building material units, nonavailabilityof indigenous plants and machinery for commercialproduction of building materials from flyash are amongthe major hurdles in the production of different building products from Indian flyash.

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 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 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.

CRUSHER DUST : 0 6 mm

3.2.3 Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate , with the chemical formula CaSO 42H 2O . 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 pyrite oxidation , 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 (CaSO 4 2H 2O) and anhydrite (CaSO 4). 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 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).

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 ~ 29 ~ 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 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.

Table 3.2.1: Grading limits of Fine Aggregates IS: 383-1970IS SIEVE DESIGNATION

Percentage passing by weight for

Grading - I

Grading - II

Grading - III

Grading - IV

10 mm100100100100

4.75 mm90-10090-10090-10095-100

2.36 mm60-9575-10085-10095-100

1.18 mm30-7055-9075-10090-100

600 micron15-3435-5960-7980-100

300 micron5-208-3012-4015-50

150 micron0-100-100-100-15

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.

SAND:

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 during construction 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 other 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.

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.

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.iii) Flyash Sand Lime Bricks : In presence of moisture, fly ash reacts with lime at ordinary temperature and forms a compound possessing cementitious properties. After reactions between lime and flyash,calcium silicate hydrates are produced which are responsible for the high strength of thecompound. This processes involves homogeneous mixing of raw materials (generally fly ash,sand andlime), moulding of bricks and then curing of the green bricks. Some technologies call forusage of chemical accelerator like gypsum.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 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.

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 lessthan 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.

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. 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 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.4. METHODOLOGY

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.

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. 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. 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 with environmental benefits.

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. 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: