DA Sustainable Livelihoods  Technologies

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Building Technologies

Concrete Block Technology
Compressed Earth Block Technology
Micro Concrete Roofing Tiles
Ferrocement Roofing Technology

Concrete Block Technology

Concrete Block Technology offers a speedier, cost effective, environmentally sound alternative to conventional walling materials. It is based on the principle of densification of a lean concrete mix to make a regular shaped, uniform high performance masonry unit. Concrete Block Technology can be easily adapted to suit special needs of users by modifying design parameters such as mix proportion, water/cement ratio and type of production system. It is an effective means of utilizing wastes generated by stone crushers, quarrying and stone processing units. The technology has high potential in areas where raw materials are easily available.

Business

The Concrete Block Technology package is a highly profitable business for micro and small scale building material producers and construction companies. A total investment of about Rs.1,75,000/-* assures a net profit of approximately Rs. 60,000/- per annum. The market for concrete blocks is growing at a rapid rate, specially in the areas where burnt bricks are not easily available or are of poor quality.

* Typical cost of stationary semi-mechanised machine and working capital

Product

The specifications and the characteristics of a concrete block depend on the machine used to manufacture concrete blocks.

The most common size of solid concrete blocks is 300x200x150mm. The basic raw material is cement, fine aggregate and coarse aggregate. Very little water is used. This is possible only with mechanised compaction and vibration and gives the block high quality in spite of the lean mix, which uses very little cement. Weight of a concrete block is about 18-19 kgs. Concrete blocks can be surface engineered by using pieces of stone or ceramic waste on their face. Another common type are hollow concrete blocks. They are made with a richer mix, but offer a number of advantages, such as lighter weight, easier handling and facility for conduiting or reinforcement through the hollows.

Unique features of Concrete Block Technology:

  • Cost effective compared to other traditional walling systems
  • Maximum utilisation of wastes and local resources
  • Structural performance can be engineered
  • Decentralised local production
  • Offers business opportunities

Production process

Concrete blocks are usually produced using a semi-mechanised stationary type machine. The other production systems are - manual moulds which require hand tamping, a mobile semi-mechanised egg-laying machine and fully mechanized system which combines compression and vibration.

High quality machines provide optimum vibration in the mix so that the ratio of cement used can be reduced substantially without compromising on the strength of the blocks. The machine also compacts and consolidates the mix so that the blocks are uniform in size and attain desired physical properties. The blocks are cured for a minimum period of 14 days, before they are ready to use. On an average 600 - 800 blocks can be made in 8 hours by 1 skilled and 6-8 semi-skilled workers.

Building with Concrete Blocks

Concrete blocks can be used like any other masonry unit to build foundations, walls, arches and corbels, etc. A typical concrete block is equivalent to 4.5 bricks, thus construction is faster than with other masonry units. The mortar used is also less which results in cost saving. Concrete blocks have been extensively used in combination with conventional roofing systems like RCC, RBC, GI sheets, ACC sheets etc. They are also compatible with other materials like fired bricks, dressed stone and compressed earth blocks for composite wall construction.

Acceptability of concrete blocks is very high in urban areas for all types of buildings. They are very popular as a long lasting, low maintenance and investment for institutional and industrial buildings. The permanence of a cement based product is making concrete blocks a preferred choice in rural areas as well.

Technical specifications of Concrete Blocks

ParameterDescription
Typical size300 x 200 x 150 mm
Average compressive strength at 28 days50 - 110 kg/sq.cm
Mix Proportion1:12-14 (1 part cement : 12-14 parts sum graded aggregates)
Water absorption in 24 hoursLess than 10 % by weight of block

* BIS code IS:2185 Part I, 1979 defines the technical specifications of concrete blocks

The Concrete Block Technology package has been adapted by Development Alternatives with financial support from Swiss Agency for Development Cooperation.

Compressed Earth Block Technology

The Compressed Earth Block (CEB) technology offers a cost effective, environmentally sound masonry system. The product, a Stabilised Compressed Earth Block has wide application in construction for walling, roofing, arched openings, corbels etc. Stabilised Compressed Earth Blocks (SCEBs) are manufactured by compacting raw earth mixed with a stabiliser such as cement or lime under a pressure of 20-40 kg/cm2 using a manual or mechanised soil press.

Equipment

A number of manual and hydraulic machines are available in India. The basic principle of all the machines is the compaction of raw earth to attain dense, even sized masonry units.

Business

The Compressed Earth Block technology package is a profitable business for micro and small scale building material producers and construction companies. A total investment of approximately Rs. 1,00,000/- for a manual scale production unit yields a net profit of Rs. 70,000/- per annum; while an investment of Rs.6,50,000/- lakhs in a mechanised unit can yield up to Rs. 2,50,000/- per annum after the second year. The market for CEB technology is especially good in areas where soil of adequate quality is available and fired bricks are of poor quality.

Product

The Stabilised Compressed Earth Block is a masonry unit of cuboidal shape. This may be solid or hollow or interlocking. The shape and size of a block is defined by the equipment used in its manufacture. SCEBs can be used for load bearing construction up to 3 storeys. The cost of a block depends upon a variety of factors including quality and price of available soil, amount of stabilisation, labour productivity, equipment and overhead costs. The degree of stabilisation has the maximum influence on the cost of the product.

Technical Specifications

The performance specifications of SCEB are based on B.I.S code IS 1725, 1982 and tested in accordance with IS 3945 - 1992

Techno-economic Characteristics

Specifications
Dimensional Variation+/-2 mm
Wet compressive strength20 - 30 kg/cm2
Water absorption<15% by weight
Erosion< 5% by weight
Expansion on Saturation< 0.15% in block thickness
Surface characteristicsNo pitting on the surface

Production process

The production of SCEB is based on the principle of densification of raw earth mixed with stabiliser ( cement or lime ) in small quantities ranging from 5-10% by weight of the mix. The production process incorporates 3 main stages.

Mix Preparation
Compaction
Post Production
SievingFilling the mouldHumid and wet curing
BatchingMouldingFinal storage
MixingBlock ejection and stackingTransportation

Labour Inputs

6-10 persons are required to operate a manual machine. For hydraulic machines the manpower required is 6-8 persons. In both the systems 1 skilled worker is required while the rest are semiskilled. The workers can be trained to operate any machine in 10-12 days.

Raw Material

The primary raw material for the production of SCEB is raw earth or soil. OPC cement in small quantities and water are other constituents. Coarse sand or stone dust may be added depending on soil quality. Soil is made up of grains of various sizes. The grain size distribution of a soil determines its suitability for the manufacture of SCEB.

Soil composition for use in CEB

Grain typeGrain size (mm)Optimum(%)Acceptable range
Fine gravel2.0-4.070 - 10
Coarse sand0.2-2.03015 - 35
Fine sand0.02-0.22315 - 35
Silt0.002-0.022015 - 25
Claybelow 0.0022010 - 30

Building with CEB

Earthblock photo 1

The Compressed Earth Block building system can be used in a variety of ways to construct buildings that are aesthetic, efficient and easy to build.

The basic design principles of a good SCEB building are:

  • Strong foundation with sufficient plinth height
  • Sufficient roof overhang and a strong wall finish
  • Careful detailing of joints and use of concrete elements where tensile stresses are active

In India more than 5 million Stabilised Compressed Earth Blocks have been used to build residential and community buildings in both urban and rural areas. The benefits of this technology have been appreciated by the public sector and it is being promoted by HUDCO's network of building centres to build public sector housing and institutional projects.

Unique features of CEB:

  • Low energy and emissions
  • Uniform size
  • High strength
  • Thermal insulation
  • Versatile
  • Cost effective

The Compressed Earth block technology package has been developed with initial support from Department of Science and Technology, Govt. of India and financial support from the Swiss Agency for Development Cooperation.

Micro Concrete Roofing Tiles

Roofing photo

The Aesthetic, Durable and Inexpensive Sloping Roof Alternative. Classic styling with the latest in modern concrete technology

Product

Micro Concrete Roofing (MCR) tiles are made from a carefully controlled mix of cement, sand, fine stone aggregate and water.

The mix is vibrated at an optimum frequency for forty-five seconds on a precision engineered TARA TileMaker screeding table. It is then transferred to High Impact Polystyrene moulds that give MCR tiles their unique profile. After initial setting in an airtight environment for 24 hours, the tiles are cured in water for a period of 7 days. This process gives MCR tiles unmatched strength and durability.

MCR tiles undergo stringent quality control at every step. They are put through rigorous tests for water tightness, strength, shape and size.

MCR technology is a result of global research and development effort. The tiles are being marketed extensively in Latin America, East and West Africa and South-East Asia. Each year, over ten million tiles covering an area of 800,000 sqm of roofs are installed. In India, MCR technology is promoted by TARA, Development Alternatives in association with SKAT of Switzerland.

Competitive Advantages

Roofing photo 2

MCR tiles offer many advantages over other sloping roof materials such as G.I. sheets, Mangalore tiles, wooden shingles, slate and asbestos. MCR tiles are:

  • highly cost effective
  • durable - they have the life of concrete
  • lighter than other roofing tiles - they require less understructure
  • easily installed

In addition, MCR tiles:

  • can be coloured to specification
  • reduce heat gain
  • do not make noise during rains

Micro Concrete Roofing is available at these attractive prices:

Type of Tile Cost per tile (Rs)Cost of Roof with Wooden Understructure (Rs./sqft)Secondary WoodPrimary Wood
Plain pan tile5.0011-1315-20
Cement painted pan tile7.0015-1717-22
Synthetic painted pan tile9.0018-2019-25

Cost of roof varies according to span and roof form. Special Roman tile profile available on request.

Applications

A variety of roof designs for farm and country houses, bungalows, verandahs and pavilions are possible with MCR tiles. They have also been used on industrial sheds, workshops and restaurants. MCR tiles allow total creative freedom to designers, architects and engineers to create a variety of roof forms.

Roof Construction

MCR roofs are constructed in a conventional manner using rafters and purlins made from wood or steel. Rafters are typically spaced at 90 cm to 110 cm apart. The purlins are mailed at a distance of 40 cm from each other.

MCR tiles are secured to purlins by tying them to the purlins with G.I. wire. The angle of roof slope should be at least 22°. Greater inclination of up to 30° is preferred for more aesthetic appeal.

Standard architectural details for gable and hipped roof ridges, eaves, side over-hangs and valleys can be used for MCR roofs.

Design Data for MCR Roofs

Tiles per sqm............................. 13 nos. Wt. per sqm............................... 32 kg

Tiles along

10 m of roof length ............. 50 nos. 10 m of width ..................... 25 nos.

Technical Data

MCR Tile

  • Clear length of tile ........................ 488 mm
  • Length after overlap ..................... 400 mm
  • Clear width of tile ......................... 240 mm
  • Width after overlap ....................... 200 mm
  • Thickness ..................................... 8 mm
  • Corrugated depth ........................... 50 mm
  • Nominal weight .............................. 2.25 kg
  • Load bearing capacity of tile ............ 80 kg

Technology Validation

MCR technology has been validated and certified by:

Building Materials and Technology Promotion Council, Ministry of Urban Development, Govt. of India. Certificate No. 95/1

Ferrocement Roofing Technology

The Ferrocement technology package for roofing developed by Development Alternatives uses state-of-the-art design principles to manufacture reinforced shells, commonly called channels. They are produced on specially designed vibrating tables and profiled moulds. The production system is uniquely tailored to provide special end details, consistent shape and thickness; all crucial for high performance. The channels made with an optimised proportion of cement, sand and water, have a very high density, are impervious to penetration of water and provide high structural strength. Ferrocement roofing channels produced on mechanised equipment can be used for intermediate floor applications as well. Ferrocement roofing technology offers a viable alternative to conventional flat roofing systems such as reinforced cement concrete, reinforced brick cement, sand stone, etc. in both rural and urban areas of the country.

Business

Ferrocement technology is a highly profitable business for small scale building material producers or construction companies. A total investment of roughly Rs. 3,80,000/- for a mechanised production system assures a net profit of approximately Rs.1,50,000/- per annum.

Product

Ferrocement roofing channels have a uniform segmental profile; they are 2.5 cm thick and 83 cm. wide. Maximum length of mechanically produced channels can be 6 metres. Longer spans for roofing can be built with intermediate supports.

Ferrocement roofing channels are manufactured using a fixed proportion of cement, sand and water to give high strength mortar that is reinforced with a layer of galvanised iron chicken wire mesh of 22 gauge and Tor steel bars of 8-12 mm diameter provided in the bottom nibs of the channel.

Ferrocement roofing channels can be safely transported after a curing period of 14 days.

Unique Features of Ferrocement Roofing Channels:

  • Speedy installation; no shuttering required
  • 30% cost saving over RCC roofing
  • Lower dead load on the walls
  • Usable as an intermediate floor
  • High strength to weight ratio
  • Elegant profile and uniform sizes
  • Large spans possible with intermediate supports

Production process

Ferrocement roofing channels are prefabricated elements. The mechanised system of production uses a vibrating table and profiled steel shell moulds. The production yard consists of a vibrating table positioned under a gantry system 6.5mts. in width. The gantry is fitted with a chain and a pulley system for ease of handling of shell moulds. A production team consisting of 2 masons, 6 semi-skilled workers and a supervisor can produce up to 5 channels of 4.6 mts. length each in 8 hours operation.

The shell moulds are lifted with the cast channels in the green state. After 24 hours, the roofing channels are demoulded by using a specially designed mould lifting frame and demoulding tongs. The mechanised system does not require high skills but ensures high quality. Whereas, manual method needs highly trained masons and stringent quality control measures.

Installation

Ferrocement roofing channels are simply placed in a series, next to each other, resting on opposite walls of a structure. The valley between channels are then filled with a plain cement concrete, over which a layer of bitumen is spread to ensure water tightness. A lean concrete of 2.5 cm thickness or mud phuska with brick tiles can be laid to make a flat surface and provide thermal insulation.

Application

Ferrocement roofing channels, offer unmatched speed of construction and can be used for:

  • Residences
  • Primary schools, and other community buildings
  • Porticos, verandahs and garages
  • Industrial sheds, workshops and godowns
  • Farm houses and semi-covered structures

Technical specifications of Ferrocement Channels

ParameterDescription
Shape and size of roofing channelClear bay length 750 mm, total bay length 830 mm, rise of arch 290 mm, shell thickness 25 mm.
Weight of channel50 kg per meter length
Mortar composition1 part cement : 3 parts fine aggregates
Load carrying capacity350 kg/sqmt. for simple roof and 870 kg/sqmt. for intermediate floor
Water absorptionLess than 5% by weight of channel

Also:
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Building Technologies | Handlooms and Accessories | Hand Made Paper Technologies and Products

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