Why Fly Ash?
The Main ingredient in Fly Ash Bricks is “Fly Ash” – Pulverized fuel ash is a by-product of Coal based Thermal Power Stations. 50-60 % of Fly Ash is used in manufacturing of Fly Ash Bricks. With increasing requirement for power companies, the production of Fly Ash is being accumulated as waste material in huge quantities near thermal power plants. The disposable of the increasing amounts of solid waste from coal-based thermal plants is becoming serious concern to environment due to lack of adequate facilities. To overcome this problem the construction industry came up with the idea of formulating concrete out of Fly Ash and utilizing it for making Fly Ash Bricks. Coal is responsible for large amount of greenhouse gas emission and pollutes the environment, while on the other hand Fly Ash (by-product of coal) helps curb carbon emission in the construction industry. Also production of Fly Ash Bricks saves agricultural land which is destroyed and unfertilized by making clay or Red Bricks. At the same time, Fly ash bricks have favourable characteristics such as high compressive strength, no emission of green house gases during production, durability, and a solution to prevent environmental pollution.
Advantages of Fly Ash
- Flyash bricks are light weight material compared to clay bricks, so it is suitable for multi storey building, Less weight means Less stress on building , safety assured.
- Low absorption of heat, FAB (fly ash bricks) absorbs less heat than normal bricks, it keeps your building cool even in summer, hence most suitable for Indian conditions.
- Thermal conductivity is 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 without glare.
- Uniform shape – hence no plastering required if used for compound wall or godowns.
- Less mortar required in construction and saves 20% morar, because all bricks are machine made and even in shape.
- High compressive strength compared to normal bricks which is [70-150kg/cm2].
- Less porous, absorbs very little water, whereas burnt clay bricks absorbs more water during construction. Saves money on water and 20% water usage during construction and even keeps your building strong during rainy seasons.
- Fly ash by mixing efficiently with the concrete mix can replace Portland cement that in turn can aid in making big savings in concrete material prices.
- It is an environmentally-friendly solution.
- It improves the strength over time and offering 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.
- The cost of these brick will come down significantly if Ash producers like power plants start making them with automated systems ensuring highest quality and consistency and gaining from economies of scale.
Eco Friendly Bricks
Fly Ash is a By-Product of coal based thermal power stations. With the increasing number of thermal power stations, the disposal of Fly Ash is becoming serious concern for environmentalists. To overcome this problem the construction industry came up with the idea of formulating concrete out of Fly Ash and utilising it for making Fly Ash Bricks. Also production of Fly Ash Bricks saves agricultural land which is destroyed by making clay or Red Bricks. At the same time Fly ash Bricks have favourable characteristics such as high compressive strength, no emission of green house gases during production, durability, and a solution to prevent environmental pollution.
Market Drivers & Raw Material Proposition
Proportioning of raw materials is an important aspect of ensuring quality of ash bricks, pavers and blocks. The proportioning will depend on the quality of the raw materials and the class of brick required. The following mix proportion is being adopted.
- For Fly Ash, Sand/Stone dust, Sludge Lime and Gypsum bricks:Fly ash55-60%Sand/Stone dust20-25%Sludge lime15-20%Gypsum5%
- For Fly Ash, Sand/Stone dust, Hydrated Lime and Gypsum bricks:Fly ash60-65%Sand/Stone dust18-27%Hydrated lime8-12%Gypsum5%
- For Fly Ash, Sand/Stone dust and Cement bricks:Fly ash50-60%Sand/Stone dust32-40%Cement8-10%The strength of bricks manufactured with the above proportion is generally of the order 7.5 to 10.0 N/sq.mm after 28 days.
Note: Mix proportion as suggested above can be used as guide lines.
Mix proportion largely depends upon characteristics and quality of raw materials used. Based on the qualities of raw materials, the exact mix proportion may be finalized by trial mixes to produce good quality bricks of required compressive strength.