Environment-Friendly, Energy Efficient, Cost-Effective Composite Materials/Products for Low Cost Housing

Sources of Flyash

72% of India's power plants are coal based. These power stations generate nearly 40 million tonnes of flyash annually. Sources of Flyash

Nature of Pollution

Flyash causes severe pollution of air and water, and its disposal gobbles up large tracts of land. Well planned programmes for proper management of flyash are therefore being undertaken to enhance the use of flyash in various applications, so that our already perilously imbalanced environment can be protected.

Recycling of Flash

Bricks, Portland pozzolana cement, blocks, tiles, light weight aggregates and hollow blocks are produced utilising flyash as raw material. Mechanised manufacture of flyash lime bricks is a major thrust area. The twofold aim is to utilise bulk quantities of flyash and help bridge the huge shortfall of bricks and other building materials required by the constantly rising construction activity.

Advantages of flyash bricks:

• Several loadbearing grades.
• Savings in mortar, plastering.
• Smart looking brickwork.

Material handling, storage, transportation equipment:

Material hoppers, vibratory feeders, weigh hoppers; silos, screw and belt conveyors; brick transfer cars; brick wagons for charging autoclaves.

Basic process equipment:

High speed batch mixer; double shaft mixer, hydraulic brick press with automatic lifting and stocking; Industrial autoclaves of boiler grade steel designed to specified operating steam pressure; Industrial steam boiler for continuous steam at pressure to the autoclaves.

Ancillary/auxillary equipment:

Crane: fork lifter, power supply, destination and control station; air compressor; weigh bridge for trucks; water tube well; piping for air and water; air conditioners; spares; work-shop and control laboratory equipment; electrical and light fittings etc. Diesel generator.

Sources of Phosphogypsum

Phosphogypsum is generated as a by-product of the phosphoric acid based fertiliser industry. The interaction of ground phosphate rock with sulphuric acid produces 10-40% free moisture along with phosphogypsym. 4.5 million tonnes is generated per year in India. Over 10 million tonnes has accumulated at plant sites.

Nature of Pollution

The fluoride content of phosphogypsum causes land and water pollution.

Recycling of Phosphogypsum

This pollutant by-product from the fertiliser industry can be used to make several building materials:

• Gypsum plaster, boards, tiles.
• As set controller in the manufacture of Portland cement.
• Non-shrinking cement, super sulphated/anhydride cement.
• As a hydraulic binder.
• As mineraliser.
• Simultaneous manufacture of cement and sulphuric acid.
• Artificial marble, fibre boards.

A plant has recently been set up in India to produce walling blocks, ceiling tiles and binder from Phosphogypsum.

The following steps convert phosphogypsum to commercially gypsum plaster boards:

• Grinding of calcined gypsum, and its storage
• Proportioning and mixing of gypsum plaster with water. Set controller and filler is-added to this slurry with a small quantity of glass fibre as reinforcement;
• Casting of board with the board forming machine.
• Carrying the 'green' board on a belt conveyor until the core sets and edges are stuck.
• Cutting boards with a rotary knife into lengths of 1m to 6m before the 'green' board reaches the end of the machine belt.
• Drying of boards by passing them through a tunnel kiln. Hot-air/steam allow recirculation of air. Natural drying is possible for small production. Drying is a very sensitive operation requiring careful attention.
• Transferring of dry boards on to portable platform and transportation to the warehouse.

BMTPC has produced a composite from red mud, polymer and natural fibres, called Red Mud Jute Fibre Polymer Composite (RFPC), to replace wood in the wood based panel products in the building industry. This product uses zero energy aided raw materials and conserves energy by room-temperature processing.

Known as Red Mud Jute Fibre Polymer Composite (RFPC), this composite contains ferric oxide, alumina and titanium oxide from red-mud, 82.5% cellulose and 11.3% lignin from its jute component (jute is 15% of the total volume of the shutter).

This newly developed material is particularly suitable for door shutters, ensuring significant savings in initial as well as maintenance costs. There is a huge market for composite doors and panels, with the potential waiting to be tapped both in developing and developed countries.

RFPC can also be used for furniture, flooring and panelling work, electrical switch boxed and insulating sheets for housing.

Sources of Red Mud:

During aluminium production, bauxite ore is digested with caustic soda, when most of the aluminium passes into solution as aluminate. The muddy red residue consists of alumina, iron oxide, titanium oxide and small quantities of silica, calcium oxide and alkali. India generates over 4 million tonnes of this by-product annually which is not otherwise put to any use.

Nature of Pollution

Red Mud is usually disposed off in ponds. During monsoons, the waste may carry by run-off to surface water courses and cause ground water contamination due to leaching.

Recycling of Red Mud

Red Mud can be used for making high quality exposable bricks, tiles, corrugated roofing sheets, and as binder for several useful products including composite doors, panels etc.

Source of plastic waste

In the latter half of the 20th century, the use of plastics has become wide-spread in all kinds of products and everyday objects. Not surprisingly, plastics constitute a large part of a city's garbage, and are nearly impossible to dispose of as plastic waste is not biodegradable.

Recycling of Plastics

Mixed & multilayer plastics containing several grades of plastic material can be made into pallets. Pallets can take the shape of tile flooring, waste containers, planks, profiles, railway sleepers etc.

Plastic Waste as Binder

Plastic that cannot be further recycled can be used with fillers for processing composites, useful for applications like fence posts, park benches, pallets, street furniture, as substitute to timber and concrete products.

Recycled PET

Unsaturated polyester resin from recycled PET can replace the conventional high cost resin for use in GRP products, polymer concrete/polymer mortar, and industrial floorings.

Agro waste as raw material

India is primarily an agricultural country. In the absence of organised data, exact estimates of the agricultural wastes such as bagasse, banana leaves and stalks, saw mill waste, sisal fibre, rice husk, jute stalk etc., are not available, but their availability in the country is more than 500 million tonnes per year.

Recycling Agro Waste

The building materials industry is gainfully utilising these wastes in a wide range of applications, many of which can serve as timber substitutes for wood-based products. By their very nature, fibrous wastes along with suitable binders under pressure are eminently suitable for making several kinds of insulation boards, panels and roofing sheets. These products can be strong, lightweight and also find aesthetic acceptance.

Tiles From Granite Slurry (New upcoming technology)

India has got best granite deposits in the world. It accounts for over 20% of total Granite reserve of the world. Total Granite reserve is in India is about 42,916 million cubic meters. Granite slurry is the waste generated during cutting and polishing of stone.

Physical and Chemical Properties of Granite Slurry:

Color = Grey Specific Gravity = 2.60 Fineness =< 100 micron

Details and cost of plant and machinery:

• Pan mixer motor & gear box
• Vibratory screen/table
• Rubber moulds
• Transfer trolleys