Micro Concrete Roof Tiles1.ppt

7/27/2019 Micro Concrete Roof Tiles1.ppt

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MICRO-CONCRETE ROOFING TILE PRODUCTION

Much attention has been paid to developing the small-scale

production of concrete roofing tiles as an affordable alternative

to both traditional roofing materials, such as thatch, and

modern, mass-produced, often inappropriate, galvanized iron

sheeting or asbestos cement.

These tiles are relatively low in cost, durable (with a life span

expected to exceed 50 years in most areas), aesthetically

acceptable, able to offer adequate security and comfort, and

provide protection from both the heavy rain and the hot sun.


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Concrete roofing tiles are now produced by small businesses

in a number of countries in Africa, South and Central America,

Asia and South-east Asia, and in the former Soviet Union. The

key to the success of this technology was the development of

equipment and techniques to produce the tiles on a small

scale.

It typically costs US$5000 (excluding land and buildings) to

set up a concrete roofing tile workshop, and can be less than

US$1000 in areas where the vibration equipment and the

moulds are made locally.


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When the technology was first developed it was decided

to make large roofing sheets similar in size and shape to

the corrugated asbestos or galvanized iron sheets usedon many buildings. These were reinforced with natural

fibres such as sisal or coir.


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Agave sisalana


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The fibre-cement mortar mix was simply spread out by hand

on a flexible plastic sheet in a large mould. Afterwards the

sides of the mould were taken away and the sheet with the

mortar on top was gently pulled over onto a corrugated mould

where it took its shape. Problems were experienced with

decay of the fibres and cracking of the sheets after only a few

years, and so the production of fibre-reinforced concrete

roofing sheets has been abandoned in many countries.


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A more recent development has been to make concrete tiles

without any fibre at all. These are the so-called micro-concrete

roofing (MCR) tiles. Greater care needs to be taken with MCR

tile production compared with FCR if the number of damaged

or sub-standard tiles is to be kept low.

MCR tiles are also more brittle than FCR tiles, and can be

damaged if dropped or handled carelessly when transporting

them or fixing them to the roof.


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To produce a good MCR tile, care needs to be taken in the

quality of the sand to make the mortar. This should have a

regular grain-size grading without too much material of one

size and, particularly, without too much fine silty material.

If the sand from one source contains too much material of any

one size it should be mixed with a sand of different grading from

another source. In addition, the batching of the quantities of

sand, cement, and water needs to be done accurately to

ensure that there is enough cement and that the mix is not too

wet.

Quality control


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The tile maker needs to mould the tile with care and skill, and

it is important that the tiles are properly cured.

With FCR tile production there is some capacity for these

quality aspects to be less rigorously exercised, but with MCR

production there is no margin to be lax on quality control if

large numbers of damaged or sub-standard tiles are not to

result.

If the potential producer cannot ensure good quality control at

all stages of production, then it probably is not a good idea to

produce MCR tiles.


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Equipment and Materials

The equipment and materials needed to produce MCR tiles are the same

as for FCR tiles, except that no fibre is used and the sand used needs to

be of good quality, as noted above. The essential equipment is:

a tile vibrator

moulds

plastic sheets

batching boxes

a water curing tank

a table to work on


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The use of a vibrator is essential for MCR tile production.

Vibration helps to consolidate the mortar mix and removes air

bubbles, which would otherwise cause weak spots in the

hardened tile. The vibrator unit itself consists of a flat metal

plate which is suspended on dampers and to which is

attached a rotating eccentric cam.

It is the rotation of this cam which translates into the up-and-

down motion of the plate. A hinged metal cover fits onto the

plate. This defines the sides of the tile. The vibrator may be

driven manually, electrically with a standard 12-volt truck

battery, or on mains electricity.


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Because cement mortar sets slowly and the tiles need to be left on themoulds at least overnight before they can be removed, the producer will

need enough moulds to cover a whole days production.

A single person should comfortably be able to make at least 200 tiles per

day, and probably considerably more. (Note: the cost of 200, or more,

moulds should not be underestimated they could cost more in total than

the vibrating unit itself.)


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Because it is important that MCR tiles cure in a damp

environment, the enveloping type of mould needs to be used.

These moulds are stacked one on top of the other and hence cover

the curing tiles and prevent them drying out too quickly.


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Tiles are moulded on top of a plastic sheet on the tile vibrator. After

vibration, the tile is removed carefully from the vibrator, still on its plastic

sheet, and positioned on the mould which forms its shape. The same

number of plastic sheets as moulds will be needed, but some additional

sheets should be kept in stock to replace those which wear out.

Accurate batching of sand and cement is essential. For this reason, it is

usual to have two batching boxes to measure out exactly the right amount

of sand and cement needed for one tile. A measuring jug for water, to

ensure that similar amounts of water are added for each tile, would also be

useful.


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A water tank is needed for curing the tiles. As the tiles are cured in water

for at least seven days, the tank should be large enough to hold 1000 or

more tiles. A single tank to accommodate this number of tiles would need

to be about 8 metres long, 0.8 metres wide and at least 0.6 metres high,

although it probably would be more convenient to use a number of smaller

tanks.


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The water used should be clean and free from significant quantities of

dissolved salts, particularly sulphates. If water of good enough quality

to drink is available, then this should be used. Pigments for colouring

the tiles are popular in some areas. Red is probably the most common

colour used for tiles.


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The Production Sequence

Place the plastic sheet onto the vibrator unit and clamp down the sides.

Transfer the mortar mix onto the vibrator, spreading it out with a trowel.

Switch on the vibrator unit and continue to spread the mix with the trowel.

A vibration time of 45-60 seconds will usually be sufficient. Vibration for

more than a minute is not recommended: it can cause the mix to

segregate.

Add the tile nib, to be used to fix the tile to the roof, manually.

Remove the sides of the unit and carefully slide the green tile, still on its

plastic sheet, onto the mould so that it takes the corrugated or ridge shape

of the mould.


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Stack the moulds and leave over night.

Next day remove the tiles from the moulds and place them in the

water curing tank, leaning the tiles against each other. Leave the

tiles in the tank for at least seven days.

Remove the tiles from the tank and leave them to cure in the air

for at least 20 days in a cool, shaded place. Sprinkle with water

at least twice a day.


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Dr. Ashok Khosla, Chairman of Development Alternative

Ashok Khosla is one of world's leading experts on the environment

and sustainable development. A former director of the United NationsEnvironment Programme, he was awarded the 2002 SasakawaEnvironment Prize - "the Nobel Prize of the environment world" - andhas been named in the UNEP's Global 500 Roll of Honour.

Born in Kashmir in 1940, the son of a university professor and a

college lecturer, Khosla gained a masters degree in natural sciencesfrom Cambridge University before going on to do a PhD inexperimental physics at Harvard.


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Development Alternatives believes that a technology will sustain itself

only if it is appropriated by a network of government bodies,

development organisations, research institutions, business groups,

industry, building material producers and consumers. So, with support

from the Swiss Agency for Development and Co-operation and incollaboration with the Swiss Centre for Development Co-operation in

Technology and Management (SKAT), DA set out to establish an Indian

MCR Business Network.

The last two years have seen a rapid spread of Micro Concrete Roofing

Technology in India. With over 80 MCR production units and approximately 4million MCR tiles on roofs throughout the country, MCR is poised to enter the

large-scale dissemination phase.

Micro Concrete Roofing and Development Alternatives


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There is a growing feeling in development circles that

"Appropriate technology" must reach levels of acceptance

similar to those of industrial products. It is perhaps the only

chance we have of moving towards a sustainable future.

Unfortunately not many of us have an idea of what it takes to

successfully develop, produce or market products and

processes that have the potential to improve standards of living

Development Alternatives (A Status Report on MCR Tiles)


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The last two decades have seen a vast array of alternative

technologies solutions being offered. Innumerable deliverymechanisms have been devised, discussed and tried out. Only ahandful have worked. These too, when compared for examplewith the spread of consumer durables, have been woefullyinadequate.

Almost everyone is struggling to find a dissemination strategy forwidespread acceptance of their product or technology. Somelimit themselves to publishing articles, other agencies manage toinstall them in their local areas of influence and many peddletheir wares in the hope of official sponsorship or subsidies. Very

rarely have multi-partner networks been used to effect rapidpropagation of a particular technology.


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It is with this background in mind that the Shelter Group atDevelopment Alternatives (DA) is closely monitoring the activities of

thirteen operational Micro-concrete roofing tile production centres in

India.

It seems likely that they will achieve a considerable degree of

success as the disseminating ends of an institutional chain that also

includes the Swiss Centre for Appropriate Technology (SKAT), DA

and Technology and Action for Rural Advancement (TARA) as theother links.


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Fibre based cement mortars have been used in a number of ways to

form a good roof cladding material. There have been significant

advances over the last twenty years in research on mortar mixes,

equipment and production methods.

SKAT has been coordinated the efforts of agencies all over the world

in the use of cement mortar tiles as an intermediate solution

(between thatch on one hand and asbestos cement or galvanised

iron on the other) to the roofing problem.


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Global feedback has confirmed that fibre concrete roofing tiles have a few distinct advantages. They are:

Global feedback has confirmed that micro concrete roofing tiles have a

few distinct advantages. They are:

Capable of being produced on a small scale in village workshops; an

aggregation of units can also supply a larger distribution system.

Cheaper in cost than most roofing systems of comparable performance. Easy to make. The skills for production and installation of these tiles can

be acquired by local masons.

Reusable and easy to replace.


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In India, SKAT has provided continuing support to the research programme at Development Alternatives. Theirs is in fact, the first level of colla

In India, SKAT has provided continuing support to the research

programme at Development Alternatives. Theirs is in fact, the first levelof collaboration in the institutional chain that we have talked of earlier.

Over the years of R&D work at DA, the Shelter Group has:

Designed production equipment that is more efficient and significantly

cheaper than otherwise available.

Undertaken extensive studies on the optimization of mortar mix for

tiles. Their experiments resulted in the replacement of coconut fibre inthe mix with fine stone chips.

Designed training packages for effective dissemination.


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As soon as DA had frozen (till the next interaction) its design of the

product, production equipment and process, TARA stepped in with

its manufacturing and marketing process to ensure the easy

availability of tile making kits.

Simultaneously, a nation wide search began for people or

agencies interested in working with Micro-concrete roofing tile

technology. Market surveys were conducted and enquiries were

sent out to agencies that had the potential to manufacture tiles and

make sure they got through to the people.


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The first few units were set up by voluntary agencies in

the southern state of Andhra Pradesh - one of them a

centre for rehabilitation of leprosy patients.

These units took on regular production but the tiles were

used largely in housing work controlled by the agencies

themselves. DA was still on the lookout for an

economically viable independent unit.


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The first real breakthrough came in the person of Mr. Devendra Sharma of

Etawah in Uttar Pradesh. He had come to Development Alternatives to attend a

training programme on low cost earth construction which included a session on

Micro-concrete roofing. All said and done the credit goes to Mr. Sharma for taking

the plunge and setting himself up as Indias private entrepreneur in the field of

MCR.

He offers villagers within a radius of approximately forty kilometres an installed

roof at the highly competitive price of only Rs. 6 6o Rs. 8 per square foot of area.

In just over one year of operation his team has put up more than seventy

thousand square feet of roofs. Mr. Sharma has of course already recovered his

capital investment of Rs. 25,000.


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The Etawah initiative is being replicated in north-east Bihar where M/s

Manju Micro-concrete products have set themselves up a manufacturers

and suppliers of MCR tiles.

In Fatehpur district of Uttar Pradesh, a voluntary agency Manava Kalyan

Pratisthan has launched a comprehensive project for the transfer of

MCR technology with financial assistance from the Council for

Advancement ofPeoples Action and Appropriate Technology (A Govt. of

India body).

They plan to set up a micro enterprise for tile production, the initial

production of which will be used to roof 46 low cost demonstration

houses.


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In Andhra Pradesh, things have also started happeningon a bigger scale, where m/s Nagarjuna Techtrans Pvt.

Ltd., have entered into agreement with DA and TARA for

equipment and technical assistance in setting uptwenty-four units in eight districts of the state. These

units will feed an already existing distribution network

for building materials.


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These examples may not yet qualify as success stores and are

probably inadequate if Micro-concrete roofing tiles are to make a

mark in the country.

They do however hint at the combination of institutions, each

playing its role, that may be required to bring about widespread use

of a technology that is accepted to be appropriate for our conditions.

The Shelter Group has in fact already started pinning down the

ingredients needed for a successful enterprise in tile making.


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Entrepreneurial skill; a person must have basic education, organizational capacity

and an instinct for business not many of us do).

Initial finance; about Rs. 40,000 which can be borrowed because returns are

substantial and quick.

Good cash flow; it helps if the tile making venture is linked to other sources of

income such as cement concrete flower pots, cement water tanks etc. or even a

poultry Farm.

Quality control and integrity in input of materials are very important.

The target group; aim for the very large segment of people who want a good over

one room but just cannot spend more that Rs. 999. Four figure sales are rare.

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