Before understanding fly ash Bricks, we must know about What is fly ash?
Introduction of Fly Ash Bricks
In thermal power Stations, a lump of coal is burned to produce heat energy, heat energy is converted to electric power. The residue which is formed due to the compression of coal comprises fine particles and rises with few gases that are called fly ash.
Fly ash contains very low amounts of toxic metals such as Mercuric, Arsenic, Chromium, Selenium, Lead, Cadmium, Nickel, and Zinc.
These metals can create a negative effect on human health, plants, and land. When fly ash settles on the leaves of plants it lowers the yield. When fly ash gets decomposed on lad then it becomes infertile.
Fly ash is a very fine powder and tends to travel in the air, when not properly disposed of it pollutes air, water and causes respiratory problems when inhaled.
Fly ash is one of the numerous substances that cause air, water & Soil Pollution. It disturbs the ecological and cycles and set of hazards.
To overcome these problems many new uses of fly ash have been found through research. One of its uses is as fly ash bricks.
Fly ash is a building material used for construction works containing fly ash and water.
The main composition of fly ash bricks are:
- Fly ash
Also Read: Hydration of Cement
Properties of Fly Ash Bricks
- The density of fly ash bricks is 1700-1850kg/m3 which means it has a higher load-bearing capacity.
- The compressive strength of fly ash bricks is (10-12 N/mm²) 90-100 kg/cm2
- Water absorption of fly ash bricks is 10-14% that helps in less dampness.
- Wastage during transit is less than 2%.
- It has a high tolerance.
- Plastering in fly ash bricks saves up to 15%.
Advantages and Disadvantages of Fly Ash Bricks
Advantages of Fly Ash Bricks
- They are an eco-friendly option that takes care of the environment from being polluted.
- Fly ash bricks have high fire insulation.
- Fly ash bricks are very strong and sturdy, and hence there is almost no breakage during their transportation.
- Due to the uniform size of fly ash bricks, it reduces the requirement of mortar for joints and plaster.
- Fly ash bricks provide good thermal insulation.
- Different sizes of fly ash bricks are not required for lintel, sill, and jamb.
Disadvantages of Fly Ash Bricks
- The mechanical strength of fly ash bricks is less, but it can be enhanced by doing marble waste or mortar between blocks.
- There is a limitation to its size only modular size can be manufactured because if size increases then the chances of breaking also increases.
- It is recommended for the subtropical regions or particularly for the region where there is a warm climate.
- They are heavy in weight.
- Only concealed wiring is possible in this masonry work.
- It is not possible to use steel fly ash brick masonry work.
Manufacturing Process of Fly Ash Bricks
Now here we are going to know about the making process of fly ash bricks. Before this, we need to know the materials required for manufacturing fly ash bricks.
Raw materials used for making fly ash bricks are:
- Fly ash
- Hydrated lime
After that, we must manage a quality machine for manufacturing fly ash bricks. We must know about the quantity used. The proportion of raw materials vary from place to place, after calculating the average we came to know.
Also Read: Manufacturing of Red Bricks
Fly Ash Bricks Mixing Ratio
The quantity of fly ash should be 55-60%, 20-25% should be sand (River sand is preferred), and 15% should be cement or gypsum lime in the normal method. Please see the given table for both methods.
|Normal Method||Profitable Method|
|Ingredients||Percentage (Ratio)||Percentage (Ratio)|
Fly ash bricks are made of two types:
- Normal fly ash brick is composed of stone dust, fly ash, and cement.
- FLAG (Fly ash lime gypsum) is composed of stone dust, fly ash, cement, limestone, and Gypsum.
Steps involved in Fly Ash bricks
- Firstly all raw materials such as Fly ash, cement, stone dust, are mixed with water in a mixture machine and after that, all ingredients are transferred to the hopper through a conveyor belt, Machine has 100-ton power pressure through which mixture is compressed.
- There is a wooden base in the machine through which bricks are cut into shapes through machine mould.
- After cutting these are collected in one place that is called staging. After staging all bricks these are exposed to nature for 2-3 days and after that curing with water is done for 14 days. In this way fly ash bricks are manufactured in 30days.
- According to customer’s needs, it can be manufactured in different shapes and sizes with the help of machine mould.
- It only requires 12-18 manpower for the manufacturing of fly ash bricks.
- The shape and size of fly ash bricks depend upon the customer’s requirement. Although the shape of fly ash bricks is rectangular solid it is the medium and lightweight used in construction work, their minimum, regular or nominal size is 230mm*110mm*75mm.
There are two most BIS standards (IS 3495 and IS 10077)is available for testing the fly ash bricks.
Comparison between Fly Ash Bricks and Red Bricks (Clay Bricks)
|Fly ash bricks||Red bricks|
|These bricks are composed of cement, slag, fly ash||Red bricks are composed of clay soil|
|Fly ash bricks have a cement grey colour.||Red brick has colour red to light brown.|
|These bricks have a uniform shape as they are cast in machine mould.||Red brick does not have a uniform shape as they are hand mould-made|
|The compressive strength of fly ash brick is 75-100 kg/cm²||The compressive strength of red brick is 30-35 kg/cm²|
|The density of fly ash brick is about 1700-1850 Kg/m³||The density of red brick is about 1600-1750kg/m³|
|Wastage of these bricks is around 2-5% on-site||Wastage on the site of red brick is more than 10%|
|The weight of fly ash bricks is 2.6kg||The weight of red brick is about 3.5kg|
|The cost of fly ash brick is less in comparison to red brick||The cost of red brick is more than fly ash brick|
Now here a question arises,
Can fly ash brick create any harmful effect on human health?
The research was conducted by the National Science Foundation in the USA and it was concluded that fly ash bricks do not emit any mercury at all.
Fly ash brick does emit radon gas but only at about 50% of that emitted from concrete.
The leaching of pollutants from fly ash bricks caused by rain is negligible. Fly ash bricks are nonhazardous for landing or handling.
Fly Ash Brick Compressive Strength Test Procedure
- The bricks are chosen randomly from each mix proportion.
- The average of three bricks is considered.
- Uniform load is applied at the rate of 2.9 KN/min.
- The maximum load at which the specimen fails will be the maximum compressive strength of brick.
Fly Ash Bricks Video
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