Can You Use AAC Broken Blocks for Brickbat COBA Waterproofing?

AAC Blocks in Two Minutes

We all have been using brickbats for Terrace Waterproofing for a long time.

Now with everyone using AAC blocks in place of red clay bricks, the question comes up whether we can use the broken ACC blocks for the terrace waterproofing in the same way that we were using brickbats.

First, we will look at why we were using clay brickbats for terrace waterproofing.

Following are the 3 reasons which enabled us to use brickbats for the waterproofing COBA.

1.??????Providing Slop: One of the important roles of the terrace coba is to provide an excellent slope so that any rainwater falling on the terrace immediately drains away and does not get accumulated and seep into the concrete slab.

The clay bricks have a much lower density compared to the mortar which is used for waterproofing. Hence the clay brick pieces help us to provide good slop for this COBA without increasing too much of the dead load over our slab.

AAC blocks have a density much lower than even clay bricks, almost 2 and a half times less. This property of AAC blocks helps us to use them in place of clay brickbats in this waterproofing COBA treatment.

??

2.??????Thermal Insulation: The roof slab receives the maximum heat of the Sun. This leads to a high level of discomfort for the top-floor occupants. Clay bricks have better thermal resistivity than concrete. Hence using brickbats helps thermal insulation for the roof slab and slightly improves the comfort of the top-floor residents. AAC blocks have three times higher thermal insulation than clay bricks. Hence they fulfill this purpose of the brickbat coba waterproofing.

?

3.??????Absorbing Moisture: The third reason why brickbats were used inside this COBA treatment was that brickbats absorb the moisture rapidly in case there is any water ingress through the coba. Bricks can absorb moisture as there is capillary action inside them. However, AAC blocks do not have capillary action in them. This advantage of AAC blocks becomes a disadvantage in the case of this coba treatment, therefore, if we wish to use the AAC block broken pieces in this COBA treatment, we will have to ensure that no moisture ingress takes place through this COBA.

The way to achieve that is after completing the coba treatment, we can apply a layer of water-resistant coating which is readily available from many reputed companies today.

This is a tricky point. Because you might ask me that if we anyway have to apply the water-resistant coating, why should we do the brickbat Coba itself? My answer to this question is Brickbat Coba has a unique property - that it does not allow the accumulation of water on our slab. As mentioned in the point number one above, the slope provided through brickbat Coba helps to drain away the water quickly without allowing any seepage.

?

4.??????Resisting the shrinkage: The 3rd advantage of using a brickbat in the waterproofing COBA was that it helped in resisting the shrinkage of the coba. As the bricks are manufactured from clay, they have a completely different coefficient of shrinkage, and they prohibit the shrinkage of Cementitious Coba.

However, with AAC blocks this is not true. Because ACC blocks are also a cementitious product, it is going to shrink in a similar way as our Coba. Therefore, if you want to avoid the shrinkage of waterproofing COBA then you need to use a non-shrink additive in the coba mix. Then you will be able to use AAC broken blocks.

To summarise, we have seen 4 reasons why brickbats were used in the waterproofing COBA:

1.??????To provide a proper slope without increasing the dead load on the roof slab.

2. To improve the thermal insulation of the roof slab.

3.??????To absorb any ingress of moisture taking place in the Coba.

4.??????To avoid any shrinkage of the cementitious COBA.

We mentioned 2 solutions to enable us to use AAC broken blocks in place of brickbats in the waterproofing COBA.

1.??????Apply water-resistant admixture on top of the COBA - To avoid any seepage of moisture.

2.??????To use non-shrink admixture inside the COBA to avoid shrinkage of the COBA.

Happy Waterproofing!