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        Problems encountered due to:

Seepage through Roofs

1. Structural distress
                            - Alkali aggregate reaction
                            - Corrosion in reinforcement
2. Aesthetics
                            -Paint gets stripped off
3. Seepage through cracks
                            - water droplets start falling into the room from the roof

Seepage through Walls(beams & columns)

1. Structural distress
                              - Alkali aggregate reaction
                              - Corrosion in reinforcement
2. Aesthetics
                              - Efflorescence in brickwork
                              - Paints get stripped off
 

In order to avoid the seepage through walls waterproofing coatings are done on it.

  Water proofing coatings on walls:-

The process and the types of coatings are as follows.
1. Primer:- This coat is used to close the pores so that less amount of top coat is consumed. Actually waterproofing is expected from topcoat alone. This coat may be either cement paint or may be the same material as that used for topcoat.
2. Top coat:-This is of two types
a)Water based:-
+points: More compatible with brick or concrete surface. This has a very good grip on the surface of the brick or cement concrete.
-points: This has very slow drying.
This is again of 3 types:
 i) Epoxy water based:- This has good tensile & compressive strength. Also it forms an impermeable layer for the gases as well as moisture. But the permeability is so less that in order for the vapourised water to get out it gets punctured.

 ii) Acrylic:- It has better compatibility to the brick particularly. Also it is U-V stabilised. So, it has more life.
 iii) Silicon:- It has good water repellant characteristics but the film deposition is so thin that the layer degrades gradually.
b) Solvent based:- This has three types
 i) PU(polyurethene) coatings
 ii) Acrylic coatings
 iii) Epoxy coatings
PU, acrylic coatings have good flexibility. So, they suit well, as concrete also expands and contracts. But epoxy has less flexibility.
        Apart from these there are also some admixtures to UV stabilise the coating material. Also UV stabilisation can be done by pigmentation. UV absorption reduces inherently as it is opaque.
 

                                    Experiment conducted on the coatings

Aim: - To estimate the percentage reduction in the absorption of water for the brick after the application of the coat on it.

Coat applied: - Acrylic coating

Procedure: - Six bricks of the same frog mark are taken, oven dried for 24 hours and cleaned using a wire brush. Three bricks are taken from them and two coatings are applied on them at interval of four hours. Now the coated and the uncoated bricks are taken and weighed. After that they are immersed in water for 24 hours. Then they are removed and weighed again. The average percent increase in the absorption for the coated and the uncoated bricks are found out and then compared.

Observation and Result: -

For uncoated bricks
 

Dry weight(kg) Wt after 5min of submersion %absorption after 5 min Wt after 24 hrs of submersion %absorption after 24 hrs
Brick 1 2.78 3.11 11.87 3.17 14.0
Brick 2 2.89 3.15 9.0 3.22 11.4
Brick 3  2.895 3.08 6.39 3.19 10.2
Average 9.08 11.87

For the coated bricks
 

Dry weight(kg) Wt after 5 min of submersion %absorption after 5 min Wt after 24 hrs of submersion %absorption after 24 hrs of submersion
Brick 1 2.805 2.835 1.06 3.22 14.79
Brick 2 2.685 2.725 1.49 3.02 12.47
Brick 3 2.94 2.965 0.85 3.12 6.12
Average 1.133 11.12

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