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Blocks from Mine and Industrial Wastes

Wednesday 16 January 2008, by Deepa

A lot of research and testing has happened to verify the concept of using industrial waste as raw material for making bricks or blocks to be used as a construction material especially as a walling material. The waste materials that would otherwise end up being disposed of unscientifically causing irreparable damage to environment, is converted into an inert component, whose performance is most times on par with mainstream building materials. It helps in the conservation non-renewable natural mineral wealth and agricultural soil(rich top soil) from being used for brick making. The technology to manufacture these building materials has low specific energy consumption.

Majority of the large-scale industries and thermal power plants generate solid wastes in bulk quantities. Red-mud, coal ash, slag, phosphogypsum etc. represent such wastes unutilized for several decades. For example, millions of tones of red-mud are stored near aluminium manufacturing units ( 20 × 106 tones of red-mud is heaped into hillocks at the aluminium manufacturing unit at Belgaum in Karnataka state). Such wastes can be utilized for the manufacture of bricks/blocks, substitute for fine aggregates in concrete, partial replacement of cement in concrete, lime–pozzolana cements, etc.

Huge quantities of solid wastes (generally known as mine tailings) are produced by the mining industries. Gold mines, Iron Ore mines, Coalmines, copper mines, etc. generate and store huge quantities of solid wastes. Generally, mine tailings are accumulated in heaps near the mines resulting into huge hillocks. For example Bharat Gold Mines Limited at Kolar Gold Fields (KGF) has created 33 × 106tonnes of tailings (which are non-toxic) heaped into 13hillocks.

There is a large scope for utilizing mine wastes for the manufacture of building materials and products. For example 33 × 106 tones of gold mine tailings at KGF can be converted into bricks/blocks, which can satisfy the demand for bricks at Bangalore city for the next 30 years or more. Similarly utilizing the 150 × 106 tones of iron ore tailings can meet the requirement of sand and bricks and blocks of Karnataka State for decades. Thus there is a great potential for utilizing industrial and mine wastes for the manufacture of building materials and products.

- Clay Red Mud Burnt Bricks

During aluminium production, bauxite ore is digested with caustic soda, when most the aluminium passes into a solution as Aluminate. The muddy red residue consists of Alumina, Iron Oxide, Titanium Oxide and small quantities of silica, Calcium Oxide and Alkali. It is now being used as a binder, as a cellular concrete additive, in making floor and wall tiles, coloured composition of concrete, heavy clay products, composite panels for door shutters and most importantly for making construction blocks.
It possesses all the physical properties of normal clay bricks and solves the problem of disposal of the waste product and environmental pollution. In addition, they have good architectural value as facing bricks due to their pleasing hues of colour. Red mud in addition improves the quality of bricks made from inferior soil deficient in clay content.

- Phosphogypsum Block

Phosphogypsum is generated as a by-product of the phosphoric acid based fertilizer industry. The interaction of ground phosphate rock with sulphuric acid produces 10-40% free moisture along with phosphogypsum. Nearly 4.5 million tonne’s is generated per year. Over 10 million tonne’s has accumulated at plant sites. The fluoride contents of phosphogypsum, causes land and water pollution. These blocks are ecofriendly, waste utilization and reduction of air, land and water pollution, energy efficient, cost effective, bulk density is 1000-1100 kg/m3, its compressive strength is 2.5-3.0 Mpa.

PERFORMANCE

Appearance
Structural Capability
Sound Insulation
Fire and Vermin Resistance
Durability and Moisture Resistance
Toxicity and Breath-ability
Sustainability (environmental impacts)
Buildability, Availability and Cost
Applicability

Appearance

These bricks have a uniform in shape and smooth in finish, also, most of the times they are used in exposed brick works. The bricks are of dense composition, uniformly shaped with/without a frog, free from visible cracks and warp-age. The colour of these bricks depends on the composition of the brick, but could be altered with the addition of admixtures during the process of brick making. They come in various sizes, but generally are similar to the sizes of clay bricks.

Structural Capability

These bricks can provide savings in mortar plastering because of its regular smooth finish, and giving smart looking brickwork. High compressive strength eliminates breakages/ wastages during transport and handling, the cracking of plaster is reduced due to lower thickness of joints and plaster and basic material of the bricks, which is more compatible with cement mortar. Due to its comparable density the bricks do not cause any extra load for design of structures and provides better resistance for earthquake loads due to panel action with high strength bricks. Compressive strength is ideal to be used as a walling material for load bearing structures up to 3 floors high.

Sound Insulation

It provides an acceptable degree of sound insulation.

Fire and Vermin Resistance

These bricks have a good fire rating. It has no problems of vermin attacks or infestation.

Durability and Moisture Resistance

These blocks are highly durable, after proper pointing of joints, the bricks can be directly painted in dry distemper and cement paints, without the backing coating of plaster. Rectangular faced with sharp corners, solid, compact and uniformly Water absorption is considerably lower than Clay burnt bricks which allows them to be used as external walls, exposed without plaster.

Toxicity and Breath-ability

There are no definite studies on the toxic fume emissions or the indoor air quality of structures built with these bricks, though the constituents maybe inherently a source of pollution.

Sustainability (environmental impacts)

There is a great potential for utilizing industrial and mine wastes for the manufacture of building materials and products. This takes care of a systematic and sustainable option for disposal of otherwise polluting wastes. This technology helps conserve precious natural resources.

Buildability, Availability and Cost

The bricks have an easy workability and high compressive strength eliminates breakages/wastage during handling giving a neat finish, with lower thickness of joints and plaster. The construction technique remains the same as regular bricks ensuring easy change of material, without requiring additional training for the masons. Though these bricks are manufactured closer to industrial plants and mines, it could be sourced from dealers in far off places due to its cost effectiveness over other materials.

Applicability

The bricks are suitable for use:
- Load bearing external walls, in low and medium size structures.
- Non-load bearing internal walls in low and medium size structures.
- Non-load bearing internal or external walls in high-rise buildings.