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Advantages of fly ash bricks:-

1. Due to Perfect size saving in cement mortar making the walls and plastering by 20-40%
2. Plaster of supplied is similar
3. Plaster of Paris and Putty can be applied directly without a backing coat of plaster
4. Lower water penetration to clay bricks
5. High Strength:- can be used for load-bearing walls.
6. Eco-Friendly

Disadvantages of fly ash bricks:-

1. Bonding is lower due to Smooth finish; This can be easily corrected by using cement, sand mortar of 1:4 and proper curing. Also, the quality of sand needs to be checked

Disadvantages of Clay bricks:-

• Uneven Shape
• Labour intensive
• Inefficient kilns coal Fired – Pollution
• Cutting of agricultural land and hills – pollution and against World food security.

Manufacturing Process of fly ash Bricks:-

1. Fly Ash Bricks manufactured by hydraulic or vibratory press
2. Raw Material required Are fly ash, shall conform to Grade 1 or Grade 2 of IS 3812 (60-65%), Bottom ash used as replacement of shall not have more than 12 percent loss on ignition when tested according to IS 1227, lime shall conform to class C hydrated lime of IS 712 (8-12%), gypsum(5%), locally available sand /Stone dust (18-27%) and water.
3. Ordinary Portland cement and also be used in place of hydrated lime and gypsum.
4. Raw material in the required proportion are mixed in the pan mixer to have a semi-dry uniform mix
5. The semi-dry mixture is placed in the molds of hydraulic/vibration press.
6. Molded bricks are air-dried for one /two days in a shed depending upon the weather conditions and then, submerged in the water for 48 hrs then after water cured for 14-21 days.
7. The bricks thus produced are sound, compact and uniform in shape.

Technical specification:-

Technical Specification of fly ash Bricks as per IS:12894-2002 is as Under

1. Compressive Strength

    The minimum average wet compressive strength of pulverized fuel ash-lime brick shall not be less than the one specified for each class in IS 12894 when tested as described in Is 3495 (Part 1). The wet compressive strength of any individual bricks shall not fall below the minimum average wet compressive strength specified for the corresponding class of bricks by more than 20 percent.

2. Drying Shrinkage

The average drying shrinkage of the brick, when tested by the method described in IS 4139, is the average of three units, shall not more than moderate up to class 12.5 and slight for higher classes

3. Water Absorption

The bricks, when tested in accordance with the procedure laid down in 3495 (part 3) shall have the rating of efflorescence not more than moderate up to class 12.5 and slight for higher classes.

4. Efflorescence Test

The bricks, when tested in accordance with the procedure laid down in IS 3495 (Part 2) after immersion in cold water for 24 hours, shall have average water absorption not more than 20 percent by mass up to class 12.5 percent by mass for higher classes.