Does the use of fly-ash helps in civil works?

Fly ash can be used as a substitute for cement upto some extent thereby reducing the cost of concrete.

Fly ash is much reasonable than cement and it also helps in making concrete more durable.

Which brick is stronger among these concrete block, concrete brick or fly ash brick?

Concrete blocks typically have holes that make them easier to handle.  They’re very strong in the vertical direction, i.e., in line with the axis of the holes. 

They’re also used for foundation walls. Fly ash brick is light weighted; however it still has good strength in compression. 

It is not used for walls that are subjected to the greatest loads, like foundation walls or interior load-bearing walls.  It is appropriate for light-duty applications. Concrete bricks are solid concrete. 

They’ve huge compressive and impact strength.  But they’re much more expensive to work with, as it takes many more of them to build a wall than when using concrete blocks.

 The labor cost is much greater too.  Concrete bricks are used when one needs greater strength without much thickness, such as a patio floor or a driveway.

What should be the specific gravity of Fly ash?

Specific gravity of fly ash ranges from 2.2 to 2.8, depending on fly ash composition.

Is there any way in which we can add roughness to fly ash bricks?

The bricks come with threaded outer walls. All sides of a brick are marked with threads or slots so that neither gripping of mortar with bricks would’ve doubts nor gripping of plastering.

That is a personalised idea. Perhaps you would not find such bricks with most of fly ash bricks supplier.

Sometimes a rough finish will add to the appearance of the finished wall. It is done by forming the bricks double width and then splitting them in the middle.

It is done so that you have a "broken finish" on the one face.  When built, it gives the wall a very nice random roughness.

All the other faces are smooth from the mould and there should be no problem with the bonding of the mortar to these surfaces.

What’re the pros and cons of fly ash bricks?

Advantages:-

·         Fly ash by mixing efficiently with the concrete mix will replace Portland cement, which in turn aid in making big savings in concrete material prices.

·         It’s an environmentally-friendly solution.

·         It improves the strength over time and also offers greater strength to the building.

·         Increased density and the long-term strengthening action of flash results in lower bleed channels. It decreases the permeability.

·         It is also highly resistant to attack by sulfate, mild acid, and water.

·         It effectively combines with alkalis from cement and 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 produce less heat and thus, prevents thermal cracking.

·         It binds salts and free lime that creates efflorescence. The lower permeability of fly ash concrete will reduce the effects of efflorescence.

·         Fly ash bricks are environmentally very beneficial. They replace clay which has all nutrients for good agriculture.

·         Top soil erosion is an environmental hazard and Fly ash bricks may prevent this.

Disadvantages:-

·         Poor quality often has a negative impact on the concrete. It increases the permeability and can damage the building.

·         Some fly ash is produced in the power plant. They’re usually compatible with concrete, while some needs beneficiation.

·         Thus, it’s very much important to use only high quality fly ash to prevent negative effects on the structure of the building.

How fly ash can be used for making concrete if it contains heavy metals?

The important chemical requirements that fly ash have to conform to for use in concrete is given by ASTM C618, which does’nt has any restrictions on heavy metal ion content.

So legally speaking, you may use fly ash with heavy metal ions in concrete.  It wouldn’t significantly affect since the size of these ions are a bit larger and thus may not have any impact on hydration.

These ions would end up in the pore solution of concrete rather than affecting the hydration products.

If you indeed ask about fly ash use in cement (blended cement), then I don’t know how the behaviour would be.

About Author:

Garg Brothers and Plasters industry is one of the most reputed fly ash bricks manufacturers in Rajasthan.

We deal in all grades of plaster of paris, selling premium quality plaster of paris under brand name Gypsona.