ALTERANTIVE BUILDING MATERIALS

ALTERANTIVE BUILDING MATERIALS

INTRODUCTIONUNIT-I

Why Alternatives? 4 to 5 million houses have to be built every year in India to wipe out the housing shortage Majority of these houses would have to be build either in rural areas or for the rehabilitation of slum dwellers The gradual increase in the fuel prices

For instance a brick house of 50sq-m plinth area will consumes 5 to 6 tons of firewood for the burning operation To meet the demand without environmental degradation and over exploitation of natural resources, alternative building materials are needed SMB , hollow clay blocks, stone masonry blocks etc. are the alternative blocks which substitute for the conventional blocks Adoption of the alternate building blocks walling technology of construction results in considerable amount of saving in walling cost of any type of building against conventional blocks

Hence, this adoption of alternative building technology and alternative building materials is best suited for developing countries.

Characteristics of alternative building materials:

A good construction material would display the following characteristics:

Be strong enough for the required purpose

Tolerable in appearance Be locally available

Be easily manufactured (require little skill) and sophisticated machinery

Be easy to use , energy efficient, durable, cheap, thermal efficient, resistant to moisture, environmental friendly

Provide safety.

ENERGY IN BUILDING MATERIAL AND BUILDING

Construction activities of all types involve expenditures of energy in one form or the other. In traditional construction, the source of energy was either animate energy which used the muscle power of human beings and animals or biomass energy which was used as a source of thermal energy. Modern construction employs significant amounts of energy whether it is thermal energy or energy for transport. It is useful to recognize different categories of energy consumption in a building and his may be listed as,a) Energy consumption during building construction: Energy spent in transporting materials to site, energy spent in hoisting materials/water and energy spent in concrete mixing, floor polishing etc.b) Energy utilized for Maintenance during the life span of a building: The energy spent to meet the needs of the occupant of a building. Very often, this is mostly electrical energy. The electrical energy may be used in lighting, air condition gm water pumping and operation of elevators. In residential buildings, there are other types of energy expenditure. Use of ovens, water heaters, and TV and entertainment electronics are the other uses in such build8ings. In recent times use of computers represents another source of energy use in buildings.c) Energy spent in demolition of the building at the end of its life.d) Embodied energy in building materials: The embodied energy in typical building materials, in the Indian context is discussed below.

Energy in building material: The primary use of energy in building materials I in the production of the building material. For instance, bricks and tiles are produced by brining coal or firewood in kilns. Cement and lime are again produced by heating clay and limestone using coal. Steel is also produced by using coking coal as the fuel. In all these cases, the basic energy use in the form of thermal energy. However, many materials also need mechanical processing through electrical energy. For instance, pugging of clay bricks may use electricity. Grinding of raw materials and clinker in the case of cement needs electricity.

Some materials like sand, essentially need transportation energy for procurement at site

Energy in Building Blocks

Building blocks used for wall construction constitute a significant component of embodied energy in a building. This is due to the fact that walls represent the largest volume component in a building. The stabilized mud Block (SMB) is produced by pressing a mixture of soil, sand and cement in a machine. The example uses 6% cement stabilization. The Hollow Concrete Block had 7% cement in the mixture. The steam cured block is made by pressing lime, soil and fly ash mixture and curing in a steam chamber. Lime percentage is 10% of soil and fly ash.

Energy in Building

The total embodied energy in a building depends on the type of technologies used like RC framed structure construction with brick in-fill walls, RC roof, Load bearing walls, Mosaic floors etc.ENVIRONMENTAL ISSUES RELATED TO BUILDING MATERIALS

The production of building materials often leads to two types of environment/health related problems. Firstly, a particular building material can lead to a local environmental impact either in the form of pollution/health or in the depletion of natural resources. Secondly, building materials production using fossil fuel energies can cause global environmental problems like global warming. 1. Stone Stone, especially granite, is extensively used in building construction. Size stone is often used for foundations and walls. Crushed stone aggregate is widely used for concrete manufacture. Considerable amount of fine granite dust is generated at the site of stone extraction whether it is manual shaping of stone or mechanized crushing. The stone workers often inhale the fine dust and succumb to silicosis or tuberculosis after several years of such work.

2. Top soil for Brick

The top soil is often used for brick making, especially in the Indogangetic plains. It is well known that the top soil is a rich source of nutrients for trees and crops and this nutrient base is depleted by large scale brick manufacture near metropolitan cities. 3. Pollution by marble Dust

The marble processing industry in Rajasthan produces large quantities of fine marble dust which can affect the usability of agricultural land.

a. Additive to cement to make masonry cement.

b. Source of calcium carbonate for lime/cement industry.

c. Building products like Stabilized mud Blocks, marble dust + resin for wash basin.4. Mangalore Tile The extensive use of firewood for making Mangalore tiles in Coastal India has led to deforestation in the Coastal regions. It is possible to use natural gas or coal for tile burning.

5. The Question of Timber Good quality timber is in short supply in India. Many a time, attempts are made to replace timber by concrete or Ferro cement. Cement based materials cause depletion of fossil fuels and excessive carbon emissions leading to global warming. Use of timber also alleviates global warming since the carbon in timber is stored for a long period. Thus, timber is a very environment friendly material, provided it can be procured without disturbing natural forests.Global Warming

The utilization of fossil fuels like coal and petroleum has been increasing steadily for more than 200 years, carbon-di-oxide in the atmosphere which was about 280 ppm at the beginning of the Industrial Revolution, has now reached levels like 354 ppm. The importance of buildings in the energy scenario can be understood by the fact that in the European Union 40% of the total energy consumption is accounted for by buildings sector.

It is hence essential to explore Energy Efficient Building Alternatives. Here again, two categories of energy efficiency need to be recognized. Firstly, the embodied energy in a building needs to be reduced. Secondly, the energy used during the operational life of a building should be reduced. A building consumes far more energy during its life time than what is spent during its construction. Recent trends in air conditioning buildings in India can exacerbate the situation since most of the buildings are poorly insulated and guzzle lot of energy to maintain thermal comfort. Use of Solar Passive cooling concepts and improved thermal insulation are needed to mitigate these problems. A brick vaulted building with simple Solar Passive Cooling concepts was built in a village near Bangalore showed significant improvements in indoor climate with marginal cost. It is perfectly feasible to build 4 to 6 storeyed than masonry buildings using bricks/blocks with strengths in the range of 8.0 to 20.0 MPa. Hollow-Concrete Blocks or Stabilized Mud Blocks of 8.0 MPa strength can be easily obtained with technologies available in India. Thus a switch over to masonry of moderate rise (4 to 6 storeys) can save 30.0 to 40% of the embodied energy.ENVIRNOMENTAL FRIENDLY AND COST EFFECTIVE BUILDING TECHNOLOGIES

Role of Transportation in Buildings

Transportation of building materials to the construction site contributes to the cost and embodied energy of a building. Greater the distance of transportation, greater is the consumption of energy and money. An example, one can explore the issue of sand for building mortars. The city of Bangalore has exhausted nearby sources of sand and it has to be imported from distances of more than 100 km. Extraction of san from remote villages is also leading to rapid deterioration of roads and erosion of river banks due to loss of protective sand cover. In this context, if sandy soils are available locally, stabilization of the soil by lime and cement can easily produce a mortar with a short term strength of 2.0 MPa.

Efficient Foundations and walls

Use of stones (size stones or random rubble) is quite common in South India for foundations of walls. Wall construction can be cost effective, if the finish of the masonry unit is so good as to eliminate plastering. There is often a tendency to reduce the thickness of the wall, especially in framed structures, to achieve cost reduction. It must be noted that a wall thickness which is less than 225 mm can lead to penetration of heat, especially from East and West facing walls. The marginal reduction in cost is then accompanied by significant thermal discomfort in the interior. Increased use of fans and coolers will also lead to greater energy consumption throughout the lie of the building.Costs and Energy Efficient Roofing Systems

A number of efficient roofing alternatives can be considered. Use of partial or complete prefabrication can lead to efficient use of materials. This will also permit combination of two or three different materials for cost and energy economy. For instance, in a Jack Arch Roofing, expensive concrete is partially replaced by brick masonry. Use of filler slabs, where the tension zone concrete is partly replaced by SMB or brick is also cost and energy efficient. Use of brick domes and vaults can lead to roofing systems which reduce penetration of solar heat into the building.BUILDINGS IN DIFFERENT CLIMATE REGIONS

The Indian subcontinent has widely varied climatic conditions. Some of the major categories of climate can be listed as:

a. Hot Summer and Cold Winter

b. Hot Summer and Moderate Winter

c. Hot and Humid

d. Moderate Summer and Cold Winter

e. Cool Summer and very Cold Winter

The choice of building technologies/materials depends on the climate context. For instance, hot summer and cold winter occurs in most of North India and the buildings should use cooling techniques in summer while retaking the heat in Winter.

Well insulated buildings are needed here. In the case of hot and Humid environment, air circulation becomes important to eliminate the discomfort due to humidity. In situations like cool summer and very cold winter, where the Winter is very Cold (like in Ladakh and Sub-Himalayan Regions), use of Winter heating using Solar Energy becomes important. Concepts like Trombe Walls which use double glazing on the Southern Walls to capture Solar heat are useful.Traditional and Vernacular Architecture:

Use of stone, soil in place of cement mortar going for roofs out of Mangalore tiles instead of using concrete are the basic materials of construction. The use of conventional methods consumes energy less as the locally available material is used so it saves on the time and energy on transportation. Lime used to be final coat of paint unlike todays chemical constituent matrix in the paint.BUILDING BLOCKS

UNIT-IIINTRODUCTION

Walls of buildings are, most often, constructed using masonry. Masonry may be defined as a well element made by holding strong blocks together with the help of mortar. The blocks are usually strong in compression. Such blocks may also be referred to as masonry units. A wide variety of materials have been used for masonry. Use of sun dried mud, stone and burnt brick have been known since ancient times. Laterite has also been used for wall construction in specific locations where it is available. New materials have merged in recent times for use as masonry units. Concrete block, Hollow bunt clay block, Stabilization mud block and stone masonry block are some of the new alternatives. CHARACTERISTICS OF BUILDING BLOCKS FOR WALLS:

STONES AND LATERITE BLOCKS

They are igneous, sedimentary and metamorphic stones. Examples for igneous stones are granite and basalt, examples for sedimentary stones are limestone and sandstone and examples for metamorphic stones are marble and gneiss.

Granite has highest strength, fine grained stones are stronger than the coarse grained stones. Metamorphic rocks like gneiss shows lower strength if the loading is perpendicular.

Strength of the granite is known for its durability. Sand stone and basalt are less durable they do not deteriorate in time spans of the order a couple of centuries. Laterite which is found in coastal Karnataka is an interesting building material. It is used in Bidar region extensively. However, when Laterite blocks of more than 190mm is used, it is possible to use blocks of strength 2.0 2.5 MPa.

Generally, blocks of strength much lower than 2.0 MPa is desirable to avoid. TYPESTRENGTH OF STONES (MPa)

Granite65-228

Gneiss70-180

Limestone70-100

Sandstone60-150

Basalt80-160

Quarzite100-145

THE BURNT BRICK

Three types of burnt bricks may be mentioned in todays Indian context: namely the country brick, the table moulded brick and the wire cut brick. Country bricks are made using a simple four sided mould. Bricks are moulded by the soft mud process where soil has a high moisture content facilitating easier pressing. The moulding is done on level ground and the wet bricks are left on the ground to dry. After drying the bricks are stacked in clamp and burnt using firewood or paddy husk. In the case of table moulded bricks, a five side mould is used to shape a relatively stiffer mud into a brick. The use of lesser moisture at the time of moulding leads to an improved shape and strength for the brick. The wet brick is released by turning the mould upside down on a level platform. These bricks generally have a frog on one of the bedding faces. These bricks are then dried in shade and then burnt in a continuous kiln known as the Bulls Trench Kiln. The table moulded brick is generally much stronger than the country brick. Strengths ranging from 3.5 MPa to 7.0 MPa is quite common for such bricks. .The wire cut brick is produced by a more mechanized operation. The selected soil is pugged adequately and then extrude into a continuous slab of clay. This slab is then sliced by a wire frame into a number of bricks. After drying, the bricks are burnt in a Hoffmanns kiln. A good wire cut brick retains a good shape and often has strengths in the range of 10.0 MPa to 20.00 MPa. It is also a very expensive brick and is not used a widely as the table moulded brick. It must be pointed out that a wire cut brick masonry going up to 5 storeys without using RC frames. This can be quite cost effective compared to framed construction. CONCRETE BLOCK: HOLLOW/SOLID

The concrete block offers flexibility in production which is not there in brick manufacture. Brick manufacture comes to a grinding halt during the monsoon while concrete block making can be carried out throughout the year. The investment needed by way of land and capital is much less for concrete block manufacture compared to brick making. The presence of excessive fine and use of low percentage of cement leads to lower strength. The hollow concrete block can be deceptive in that it may look good but can have low strengths.

Hence, it must always be carefully evaluated for strength before using it in load bearing masonry.

Sl.No.BLOCK SIZECOMPRESSIVE STRENGTH (MPa)

1400 X 200 X 2002.20

2400 X 200 X 2002.83

3395 X 100 X 1982.00

4400 X 200 X 1501.54

5400 X 200 X 1502.68

Use of hollow concrete block can be quite cost effective. The lower the bulk density of hollow concrete block is a distinct advantage in construction of 3 to 4 storeys. They can be useful as the dead weight is low. They will probably prove useful a t places close to the factories manufacturing them.BURNT CLAY HOLLOW BLOCKS

These are burnt high clay blocks made by a process of extrusion. The wall thickness of the hollow block is often as low as 1.5 to 2.0 cms. They come in various sizes. It can be seen that these give a relatively high strength when tested with load parallel to the holes. When the blocks are laid with the holes aligned horizontally the strength is substantially less.

These blocks usually have bulk densities in the range of 950.0 kg/m3 to 1200 kg/m3 It is interesting to note that these blocks have a rather favorable weight/strength ratio. They can be quite useful in planning a building with several storeys since the dead weight can be kept low. They also offer possibilities of improved thermal comfort when the wall thickness is 200 mm or more and then external walls are painted white (or some light colour).

Stabilized Mud Blocks (SMB)

The Concept

It is now well known that when soils are compacted using external energy, the density of the soil reaches a maximum value at a moisture content known as the optimum moisture content (OMC). The value of OMC and the maximum density depends on the energy input during compaction. It is also easy to recognize that the compressive strength of the soil, in the dry state, depends on the density. Thus the process of mechanical compaction can lead to densification ad strengthening of the soil.

A variety of materials can be used for stabilization namely: cement, lime and bitumen.The Raw materials Soil consisting of clay, slit and sand is the basic raw material. It is preferable that the clay should be non-expansive, although expansive clays can also be stabilized using a somewhat more complex procedure. In general soils containing 10 to 15% clay and 65.0 to 70.0% sand are satisfactory for making cement stabilized mud blocks. Cement may be added to the tune of 6.0 to 8.0% by weight of the appropriate soil. In case the soil has high clay content, sand or a sandy additive like quarry dust may be added to correct the grading of the soil. A combination of cement and lime can be used. For non-expansive soil and with clay content around 15% a cement proportion of 5% and lime proportion 2% can be added for stabilization.

Lime has the advantage of combining with the clay in the soil and enhancing the long term durability and strength. The ProcessThe entire process of making a stabilized mud block may be summarized as under.

Sieve the soil in a 4 mm sieve to remove stones and lumps of clay.

Mix sad or quarry dust to correct the clay-sand percentages in the soil.

Add cement or cement and lime in appropriate proportions and mix thoroughly in the dry condition.

Sprinkle moisture onto the mixture and further mix thoroughly till the mixture is homogenous. Test for optimum moisture by trying to make a ball of soil in the hand. If a ball can be made without the soil sticking to the hand the moisture content is right.

Weight the correct amount o moist soil such that a fresh block density of 2.05 gm/cc can be achieved. The weight depends on the volume of the finished block. In case the soil contains too much sand and silt a density of 2.05 gm/cc may not feasible. Densities like 2.0 gm/cc or 1.95 gm/cc may be attempted.

The weighed soil is now poured into a soil compaction press like the Mardini.

The block is now pressed by operating the toggle lever, after closing the lid, the lid may then be opened and the block ejected by again using the lever.

The ejected block is then stacked in a five or six block high stack for curing.

Sprinkling of moisture may be pursued up to 21 days to complete the block making process.

Typical Block Sizes

In general, it is desirable to have a block size, which is somewhat larger than the size of a brick to achieve economy in the production of the material. Usual sizes are 230x190z100 mm or 305x143x100mm. Blocks of thickness less than 100m can be easily made, if necessary, by introducing thicker plates inside the mould. A half block size of 230 x 108 x 100mm is also sometimes useful for corner joint, door and window jambs, partition walls and so on.

Influence of Density and Cement Content on Block Strength

Density and the proportion of cement added are two important parameters, which control the strength and durability of stabilized mud blocks. The strength is very sensitive to the dry density. As the dry density increases from 1.75 gm/cc to 1.9 g/cc the strength increases from 12.0 MPa to 2.0 Mpa. Thus, a 9% increase in dry density leads to doubling of the compressive strength.

Strength of Blocks

The SMB technology is well suited to produce a range of block strengths at the site. As a rule a minimum wet compressive strength of 3.0 MPa is desirable for two storeyed house constructions. A cement percentage of 6 to 7% and a sand content of 65% and a clay content of 15% is usually sufficient to achieve a minimum strength of 3.0 MPa. Using higher percentages of cement, wet compressive strength in the range of 4.0 to 7.0 MPa can be easily achieved. A block with 7.0 MPa strength can be comfortably recommended for four storeyed load bearing masonry.THE STONE MASONRY BLOCK This BIS specification IS: 12440 give details of the technique. It is a very simple technology involving using odd sized stones, which are shaped by a layer of concrete surrounding the stone. Steel moulds resting on level ground can be used to place the odd shaped stone in the centre of the mould. Lean concrete is now poured in the space between the stone and the mould. Block sizes of 300x200x150mm and 300x150x150mm are quite common, compressive strength in the range of 5.0 to 10.0 MPa can be easily achieved. This technology has been implemented in a large number of locations in India, whenever stone is readily available.

SELECTION OF BUILDING BLOCKS

The selection of a suitable building block in any location will depend on the following requirements.

a. Local availability of the building material.

b. Strength and Performance requirements for the building in question.

c. Cost considerations.

In general, it is desirable to procure the building block at as short o distance as is feasible. Procurement from a location, which is hundreds of kilometers away, will often lead to expensive wall construction. For instance, procuring hollow clay blocks from Kerala for building in Bangalore will lead to significant transport costs. It is ideal if the building blocks can be obtained at distances less than 30 kms. Bricks or Stabilized Mud Blocks which depend on soil as a resource will generally be feasible in most locations since soils are more abundant than stones in nature.

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