alternative walling material

7/30/2019 alternative walling material

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New ALTERNATIVE WALLING MATERIAL.

1. INTRODUCTION

About 80 million tones of fly ash is being produced

and thrown out as a waste, from about 60 Thermal Power stations

functioning in our country. This fine material not only creates pollution

but also poses serious disposal problem. One of the best ways of

utilizing this hazardous pollutant is to convert it into a building material

like brick. Brick is considered to be the most common walling material,

used by the man from pre-Vedic period. The conventional burnt clay

brick has been causing severe depletion of fertile land, directly affecting

the countrys green revolution campaign. Production of fly ash sand

lime bricks can, to a certain extent, help to solve the above mentioned

problems.


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2. MATERIALS

Fly ash is a siliceous material with association of

amorphous/Glassy mass. The constituent particles of fly ash react with

lime at elevated temperature and pressure of steam to form calcium

silicate hydrate and calcium aluminates hydrate. The nature and extent

of formation of calcium silicate hydrate depends upon many factors like

physics-chemical and mineralogical characteristics of raw materials,

molar ratio of calcium oxide and silica, and proportioning and curing

conditions. In the present study, three fly ash samples containing un

burnt carbon 0.5, 4.3, 7.9 percent have been taken. Different mixes

having Fly ash, sand and lime in 70: 20: 10, 60: 30: 10, 50: 40: 10 by

weight were prepared for producing Bricks.

TABLE 1

Raw materials Requirement

(a) Fly Ash

(b) Sand

(c) Lime

(d) Ordinary Portland cement

(e) Gypsum

Accelerator

CBRI

50-60%

30-40%

8-10%

--

0.5-2.0%

NIL


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3. PROCESS DETAILS

The CBRI has developed four technological options to

produce fly ash sand lime bricks are as under:

i) Shaping of bricks at high pressure and steam curing at high

pressure known as Autoclaved Fly ash sand lime bricks.

ii) Shaping of bricks at high pressure and steam curing at atmospheric

pressure.

iii) Shaping by vibro-compaction and steam curing at high pressure.

iv) Shaping by vibro-compaction and steam curing at atmospheric

pressure called C Bricks.

Option No.1:-

Shaping of bricks at high pressure and steam curing at

high pressure.

This option involves four major operations namely

proportioning of raw materials using screw feeds or box feeder, dry and

wet mixing by means of pair of double shaft mixer, shaping by suitable

press, enabling to impart a pressure of 200-240 Kg/Cm2 and steam curing

at 10 14 Kg/cm2 in autoclaves.


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1. Proportioning Unit

2. Bucket Elevator

3. Double Shaft Mixer

4. Water Spraying


6. Belt Conveyor

7. Hydraulic Press

8. Off- Take Belt Conveyor

9. Trolley with Bricks

10. Autoclave

SCHEMATIC DIAGRAM FOR PRODUCTION OF BRICKS BY HIGH PRESSURE

SHAPING AND HIGH PRESSURE STEAM CURING


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VARIATION OF COMPRESSIVE STRENGTH WITH LOSS ON

IGNITION


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Inference:

This option has a potential handle a fly ash with

unburnt carbon as high as 8% to produce bricks of compressive strength

more than 100 Kg/Cm2. In other words with this option even pond ash

can directly be used for brick production.

Brief Project Profile :

Capacity of plant : 40,000 bricks per day in 3 shifts

Total capital investment : Rs. 350 lacks.

Cost of Purchased Equipment : Rs 200 lacks.

Man power requirement : 100 persons.

Land Required : 0.6 Hectares

Installed power : 300 KW

Estimated cost of Production : Rs 1400 per 1000 bricks.


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Option No 2:

Shaping of bricks at high pressure and steam curing at

atmospheric pressure

In this option proportioning and shaping operations are done exactly as

in option no.(1). The steam curing of green bricks is done in ordinary

chambers at 1 Kg/Cm2 pressure instead of autoclaves.

Inference:

This option has a potential to handle a fly ash having

unburnt carbon upto 5% to produce bricks of compressive strength more

than 80 Kg/Cm2.

Brief Project Profile.

Capacity of Plant : 40,000 bricks per day in shifts.

Total capital investment : Rs.300 lacs.

Cost of purchased equipment : Rs. 130 lacs.

Manpower Requirement : 100 persons.

Land Requirement : 0.6 Hecters.

Installed Power : 300 K W.


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1. Proportioning Unit

2. Bucket Elevator


4. Water Spraying


6. Belt Conveyor

7. Hydraulic Press

8. Off- Take Belt Conveyor

9. Trolley with Bricks

10. Steam curing chamber

SCHEMATIC DIAGRAM FOR PRODUCTION OF BRICKS BY HIGH

PRESSURE SHAPING AND ATMOSPHERIC PRESSURE STEAM CURING


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VARIATION OF COMPRESSIVE STRENGHT WITH LOSS ON


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Option No 3:-Shaping by Vibro-compaction and steam curing at high

pressure.

Under this option, mixing of raw materials is done in

a pan mixer and shaping is done in a vibro-compaction machine which

produces a low moulding pressure. The green bricks are dried before

subjecting to steam curing at high pressure in autoclaves.

Inference

The fly ash having higher unburnt carbon can be used

for producing bricks of adequate strength by adopting this option i.e.

vibro-compaction moulding and high pressure steam curing.

Brief Project profile :

Capacity of Plant : 3000 bricks per shift.

Total capital investment : Rs. 8 lacs.

Cost of purchased equipment : Rs. 6 lacs.

Man Power Requirement : 14 persons.

Land requirement : 800 Sq. metres.

Installed power : 10 KW.

Estimated cost of production : Rs.1100/- per 1000 bricks.


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1. Flyash2. Sand

3. Lime

4. Pan Mill

5. Shaping Machine6. Autoclave

7. Ready Bricks

SCHEMATIC DIAGRAM FOR PRODUCTION OF BRICKS BY VIBRO-

COMPACTION SHAPING AND HIGH PRESSURE STEAM CURING


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VARIATION OF COMPRESSIVE STRENGTH WITH LOSS

ON IGNITION


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Option No 4

Shaping by vibro-compaction and steam curing at

atmospheric pressure. Under this option, proportioning, mixing and

shaping operations are done exactly as in option No 3 excepts for the

steam curing of green bricks at 1 Kg/Cm2 in ordinary chambers.

It is worth while to mention here that if cement is added as binder in this

option wet curing of 28 days can replace the steam curing.

Inference : In this option, fly ash with higher percentage of unburnt

carbon is not found to be suitable for producing good quality of bricks.

Therefore, it is necessary to go in for a fly ash with lower percentage of unburnt

carbon, obviously hopper ash can directly be used. With such fly ash being light

in colour, use of an appropriate pigment can also be made to produce

red/chocolate coloured bricks.

Brief Project Profiles:

Capacity of plant : 3000 bricks per shift.

Total capital investment : Rs. 3 lacks.

Cost of purchased equipment : Rs.1.25 lacks.

Manpower : 10 persons.

Installed power : 10 KW

Estimated cost of production : Rs. 1000/- per 1000 bricks.


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1. Fly ash2. Sand

3. Lime

4. Pan Mill

5. Shaping Machine

6. Chamber

7. Ready Bricks

SCHIMATIC DIAGRAM FOR PRODUCTION OF BRICKS BY VIBRO-

CPOMECTION SHAPING AND ATMOSPHERIC PRESSURE STEAM


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VARIATION OF COMPRESSIVE STRENGTH WITH

LOSS ON IGNITION


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4. PROPERTIES

A) ENGINEERING PROPERTIES :

i) Shrinkage : Depending on the characteristics properties of raw

materials and the process adopted for production, these bricks

show a drying shrinkage of the order of 0.02 to 0.04 %.

ii) Absorption Properties : The saturation coefficient tends to one,

indicating openness in the pore structure. This facilitated easier

evaporation of the water absorbed by the external face in wet

season. The initial rate of absorption ranges between25 to 35,

which is comparable to conventional bricks thus imparting similar

bonding characteristics.

iii) Prism strength : Masonry prisms with different mortars and having

a height to base ratio of 2 were tested in compression to assess

masonry strength. Observed prism strengths with 1: 1: 6, 1:1:9

(cement: Lime : Sand ) and 1:6 (Cements : Sand) mortars were

between 0.40 to 0.43 to the unit strength. This value is certainly

better than that of conventional bricks, which ranges between 0.3to

0.35.


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B) PHYSICAL PROPERTIES :

i) Compressive strength - 40 80(Wet comp. Strength) Kg/Cm2

ii) Water absorption - 15 20 %

iii) Durability - Good

iv) Efflorescence - Free from Efflorescence.

v) Bulk Density - 1400 1600

Kg/Cm2

vi) Shape - Uniform

vii) Finish - Smooth

5. ADVANTAGES


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In presence of moisture, fly ash reacts with lime at

ordinary temperature and forms a compound possessing cementations

properties. After reactions between lime and fly ash, calcium silicate

hydrates are produced which are responsible for the high strength of the

compound. Bricks made by mixing lime and fly ash are, therefore,

chemically bonded bricks. These bricks are suitable for use in masonry

just like common burnt clay bricks. These bricks have the following

advantages over the clay bricks.

1) Possess crushing strength more than that of good quality clay bricks

and can therefore be used as a load bearing member.

2) Have cement colour in appearance, are uniform in shape and smooth

in finish and require no plastering for building work.

3) Are lighter in weight than ordinary clay bricks. Are less porous than

the ordinary clay bricks.

4) Have more Durability than the ordinary clay bricks.

6. CONCLUSION


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Good quality building bricks can be produced from fly

ash by adopting an appropriate technology from the four technological

options described above. One can pick up the best suitable option in the

given set of conditions governed by characteristic properties of available

raw materials, desired Engineering properties of the end product and

financial investments.

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alternative walling material