Oh ,so much material I have to buy ?

Dear Readers ,

We are meeting after a long gap .

I was occupied in some different priorities during this time.

When one of the students ( who is also a  follower to this blog ) asked me about no new post for a long time , I thought I shall immediately post something interesting today.

In our previous articles, we have already covered the basic theory behind using the AAC blocks. [ Read the article here ]

As you know , these blocks , Autoclaved Aerated concrete blocks are quite light in weight.

When you compare the unit weight of AAC blocks @ 600 Kg/cum with that of the red bricks @1900 Kg/Cum, we find that these blocks reduce the dead weight of the building.

These are also faster to build . Whereas we need 510 bricks for 1 cum of brick work, we need only 42 Blocks for 1 CuM of AAC block masonry. Thus, the mason needs to handle only 42 AAC blocks as against 510 bricks.

The mortar quantity is also reduced from 25% in brick work to 4.5 % in AAC block masonry.

Now let us solve one practical example from the site.

Question :

Find out the total material needed to construct a wall using AAC blocks with the following details :

  1. Size of AAC block : 625 mm x 240 mm x 150 mm
  2. Cement mortar mix ; CM ( 1:4 )
  3. Thickness of the joint : 5 mm

4.Wall dimensions : 5.5 m x 2.9 m x 0.15 m

 

Solution :

Step 01 : Volume of the masonry wall : 5.5 m x 2.9 m x 0.15 m =  2.3925 Cum.

Step 02 : Materials needed for the Cement mortar CM 1:4 :

Cement : 1.52*28.8 /( 1+4 ) = 8.76 Bags

Sand : 1.52*4 /( 1+4 )   = 1.216 Cu M.* 0.3529 = 0.429 Brass

Step 03 :  Volume of 1 block of size  625 mm x 240 mm x 150 mm :

0.625 m x 0.240 m x 0.150 m = 0.0225 cum.

Step 04 : No of blocks in 1 Cum = 1/0.0225 = 44.44 Nos.

Step 05 :  Increased dimensions of  1 block due to 5 mm mortar  joint :

 ( 625 +5 ) mm x ( 240 +5 )mm x ( 150+5 ) mm :

= 630 mm x 245mm x 155 mm

Step 06 : Volume of block with mortar :

0.63  m x 0.245  m x 0.155 m = 0.0239 cum.

Step 07 : No of blocks in 1 Cum = 1/0.0239 = 41.84 Nos.= 42 blocks.

Step 08 : Difference in no of blocks due to mortar : 44 -42 = 2 blocks.

Step 09 : Volume of mortar in 1 Cum = volume of 2 blocks = 2 * 0.0225 = 0.045 Cum.

Note : this means 0.045 x 100 = 4.5 % mortar.

Step 10 : Calculate the materials needed for 1 Cum of block masonry :

Blocks : 42 Nos

Cement :  8.76 Bags * 0.045 Cum. = 0.39 bags.

Sand : = 0.429 Brass* 0.045 Cum. = 0.019 Brass

Step 11 :  Total material needed for 2.3925 Cum. of masonry :

Blocks :    42 Nos * 2.3925 Cum  = 100.485 Blocks = 105 Blocks

Cement :  0.39 bags. x   2.3925 Cum = 0.93 Bags = 1 bag

Sand :       0.019 Brass x 2.3925 Cum =0.045 Brass =0.046 Brass

With this much information , it is also easy to find out the cost of the materials .

Step 12 :

Blocks :    105 Blocks@ 72 per block = Rs.7560

Note :The cost of AAC block is considered @ Rs.3300 per Cum.

Cement :  1 bag@ 300 Rs/bag  =             Rs.300

Sand : 0.046 Brass@4200 Rs/Brass       Rs. 193

Total cost : Rs.7560 + Rs.300 + Rs. 193 = Rs.8053

Cost per Cum = 8053/2.3925 = Rs.3366

Cost per CFt : Rs.3366/35.29 = Rs.95

 

Hope you are able to follow these steps.

In case of any doubt , please let me know.

All the best !

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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