SEEPAGE |
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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