off Late we are observing lots of projects coming up where the AAC blocks are being used. the Red clay bricks are now getting replaced with these AAC blocks , also known as Siporex blocks.This article explains the various aspects which strongly favor this choice of the builder.
In this context , author also sought expert’s opinion on these blocks.
The author is doing some fundamental thinking on Auto-claved aerated concrete blocks by Socrates’ method of questions and answers :
1. As a builder what is better choice for me ; bricks or AAC blocks ?
To answer this question , we need to ask :
What are the basic advantages of using Auto-claved aerated blocks ?
1.1 Multiple choice :
The length of block is 625 mm ,height is 240 mm and user has multiple options in thickness such as : 75 mm , 100 mm , 125 mm , 150 mm and 300 mm.
Whereas ,the bricks are produced in 2 sizes :
200 mm x 100 mm x 75 mm [ used for internal walls ]
200 mm x 150 mm x 100 mm [ used for external walls ].
1.2 Can AAC blocks bear more load ?
Most important thing to remember is that whereas Red clay bricks can certainly be used for load bearing wall , the AAC blocks are only for Non load bearing applications . So these can only be used as partition walls.
This must be due to the fact that AAC blocks have low crushing strength as compared to red clay bricks . [ First class red clay bricks would have a crushing strength of 75 Kg /Sqcm , the AAC blocks do have a crushing strength of only 40 Kg /sq.cm
1.3 A Happy Mason :
A mason is ought to be more comfortable in using the AAC blocks due to these reasons :
1.3.1 : Easy to handle :
The AAC weigh only 31 % as compared to Red clay bricks.
[ The dry density of AAC blocks is 600 Kg/ CuM as compared to red clay bricks @ 1900 Kg / CuM.]
1.3.2 : Lesser blocks to be handled per CuM of masonry :
A mason need to work only on 44 blocks for getting an output of 1 CuM whereas with red clay bricks at least 514 bricks need to be laid.
1.4.What is the raw material used ?
The Red clay bricks are made using the fertile clay from the farms or green fields whereas the AAC blocks use only cement and/or calcined lime, fly ash , sand quartz and some alumina & ferrous oxide.
Thus AAC blocks are more environment friendly since the fertile land is not damaged
1.5. What about the cost ?
1.5.1 AAC blocks appear to be costlier than Red clay bricks :
AAC blocks are priced around INR 3300 per CuM.
A red brick of size 200 mm x 150 mm x 100 mm would cost INR 7000 per thousand bricks.
Volume of one brick : 0.2 x 0.15 x 0.10 = 0 .003 CuM is costing INR 7=00
Thus , per cubic Metre cost for red clay bricks = 7/0.003 = INR 2333
so as a material , AAC blocks are costlier by 41 % than red clay bricks.
1.6 Why to use AAC blocks if these are costlier ?
1.6.1 : Reduced mortar quantity :
a. 44 AAC blocks make 1 CuM of masonry whereas we need to use 514 Bricks .
b. Thinner mortar joint : AAC blocks have a size variation of ( +/-) 1 mm as compared to Red clay bricks which have a dimensional variation of ( +/-) 5 mm.
1.6.2 : Reduced sizes of the RCC beams and columns and footings ( Not slab ):
The dead weight of walls is reduced from 1900 Kg / CuM in red clay bricks to 600 Kg / CuM.
Suggestions to the builder :
From the preceding discussions, it is clear that AAC blocks are advisable to be adapted . However, would like to make a few suggestions :
1. Make a firm decision on using AAC blocks and communicate to your RCC designer much before the designing is taken up . This is the only way of economizing on the RCC sections and reinforcement weight.This decision if made after completion of RCC works at site , there would not be any structural advantage.
2. Use chemical bonding for AAC blocks as this does not require any curing later on.
3.While negotiating the rates for Masonry work , do explain the features to the sub contractor and seek a discount on conventional rates. [ This would not be easy. ]
Given the larger dimensions higher productivity , the light weight and thinner mortar joints , the work of a mason is much more comfortable with AAC blocks.
Authors Note :
Dear reader ,
Need to add some photographs .
Just bear with me for time being.
Happy reading !