Advantages of Fly Ash Bricks
Fly ash bricks are nowadays mostly used for construction and gaining its popularity overbuilders and engineers because of its high strength, uniformity and less consumption of mortar plastering.
Fly ash bricks are lightweight material compared to clay bricks, so it is suitable for multi-storey building, less weight means less stress on the building, safety assured.It’s a proven fact that Fly ash bricks which is made with the BIS standards are 100 % reliable and long-lasting than normal red clay bricks of any other conventional building material. Using fly ash is economical and environment-friendly. There is no emission of greenhouse gases during production. The required operational area is smaller than any other brick producing unit.
Using fly ash in concrete creates a denser mix that provides a smoother surface. Fly ash is the residue that is left from burning coal, and this is formed when the gaseous releases of the coal is efficiently cooled. It is somewhat like a glass powder that is fine in nature. However, the chemical constituents of this residue might vary from one other. Fly ash has several industrial applications and is widely found in power plant chimneys. The material is also used as substitute cement by mixing it with lime and water. The material is embedded with myriad beneficial features and so is being utilized as a significant building material for the construction purposes. This type of concrete is much dense and smooth. Below listed are few of the advantages and
Disadvantages of fly ash concrete
The significant benefits of using fly ash in concrete Fly ash in the concrete mix efficiently replaces Portland cement that in turn can aid in making big savings in concrete material prices.It is also an environmentally-friendly solution, which meets the performance specifications. It can also contribute to LEED points.It improves the strength over time and thus, it offers greater strength to the building.
Increased density and also the long-term strengthening action of flash that ties up with free lime and thus, results in lower bleed channels and also decreases the permeability.
The reduced permeability of concrete by using fly ash also aids to keep aggressive composites on the surface where the damaging action is reduced. It is also highly resistant to attack by mild acid, water and sulfate.It effectively combines with alkalis from cement, which thereby prevents the destructive expansion.It is also helpful in reducing the heat of hydration. The pozzolanic reaction in between lime and fly ash will significantly generate less heat and thus, prevents thermal cracking.
It chemically and effectively binds salts and free lime, which can create efflorescence. The lower permeability of fly ash concrete can efficiently reduce the effects of efflorescence. Fly ash is used in many countries because of its advantages. There are also some disadvantages of using fly ash in concrete. These pros and cons are described in brief below.
The advantages of using fly ash in concrete include the followings.
The bricks have the appearance which is very pleasant like cement; Due to smoothness and finish on their surface, they require no plastering for building work. These are compact, uniformly shaped and free from visible cracks. They are lighter in weight than ordinary clay bricks and are less porous. The colour of these bricks can be altered by the addition of admixtures during the process of brick making. The size of these bricks can vary but they are generally available in the same sizes of the normal clay bricks.
2. Structural Capability
These bricks do not cause any extra load on design of structures due to its comparable density and thus provide better resistance for earthquakes and other natural calamities. Compressive strength of fly ash sand lime bricks is av.9.00 N/mm2 (as against 3.50 N/mm2 for handmade clay bricks). The bricks possess high compressive strength which eliminates breakages/wastages during transport and handling. When a structure is formed using fly ash bricks the possibility of cracking of plaster is reduced due to a lower thickness of joints and plaster and basic material of the bricks, which is more compatible with cement mortar.
3. Thermal properties
These bricks have got thermal conductivity around 0.90-1.05 W/m2 ºC (20-30% less than those of concrete blocks). These bricks do not absorb heat; they reflect heat and gives maximum light reflection which causes less heating of huge structures.
4. Sound insulation
It provides an acceptable degree of sound insulation. The sound produced at one side of a wall made using fly ash bricks do not let the sound waves pass easily to the other side of the wall due to its compactness. Hence they may be considered for the abatement of noise pollution.
5. Fire and vermin resistance
Fly ash bricks have a good fire rating due to the absence of fire catching materials. It has no problems of vermin attacks or infestation.
6. Durability and moisture resistance
Fly ash blocks are highly durable. When their joints are properly joined, the bricks are ready to be directly painted with the paints available in the market or with the cement paint without plaster. The bricks, usually, are rectangular faced having sharp corners, solid, compact and uniformly shaped. The bricks are said to absorb the moisture approximately 6-12% than that of 20-25% for handmade clay bricks thus they help reducing dampness of the walls.
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7. Toxicity and Breath-ability
There are no positive evidence and studies that suggest about toxic fume emissions or the indoor air quality of structures built with fly ash bricks. Although scientists in some part of the world have claimed about the radioactive emissions by these blocks.
The raw material is very fine so care has to be taken while its handling and transport to avoid any kind of air pollution in the view of occupational safety.Once it is flue,it can remain airborne for long periods of time, causing serious health problems relating to the respiratory system. But block manufactured from fly ash has no such problems.
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We can conclude that fly ash is a cocktail of unhealthy and hazardous elements like silica, mercury, iron oxides, calcium, aluminium, magnesium, arsenic and cadmium. It poses serious environmental and health hazards for a large population who live in the nearby area of the plants. But the brick is better off, during the process of brick making the toxins associated with fly ash has no such problems.
We can conclude that fly ash is a cocktail of unhealthy and hazardous elements like silica, mercury, iron oxides, calcium, aluminium, magnesium, arsenic and cadmium. It poses serious environmental and health hazards for a large population who live in the nearby area of the plants. But the brick is better off, during the process of brick making the toxins associated with fly ash gets changed into a non-toxic product. The mixing of with lime at ordinary temperature leads to the hydration of calcium silicate and formation of a dense composite inert block. Thus it has the potential of being a good building material. In India, about 100 million tons of fly ash is produced annually by the numerous thermal power plants, which could cause serious contamination of land, groundwater and air but due to the practice of fly ash bricks now it is safe and sound.
9. Buildability, availability and cost
The compressive strength of blocks is so high that it eliminates breakages/wastage during handling and gives a neat finish, with a lower thickness of joints and plaster. The construction technique does not change in the case of bricks and remains as same as in the case of regular bricks which ensures an easy change of material.
Masons do not require additional training while construction. Though these bricks are abundantly and widely available closer to thermal power plants all over the country for obvious reasons, finding dealers in all major cities and towns wouldn’t be a problem.
The blocks are easily available in several load bearing grades which are suitable for use in various construction practices
• 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.