CEMENT BASED WATER PROOFING TREATMENT WITH BRICK BAT COBA
Preparation of the Surface
The surface of the slab should be roughened by scrapping when the slab concrete is still green, however, the surface need not be hacked. In case the slab is already cast and surface fairly finished, the same shall be cleaned neatly of all mortar droppings, loose materials etc with brooms/cloth.
Providing and Laying of Slurry under Base Coat
The required quantity of slurry should be prepared using 2.75 kg. blended cement + water per sqm. area to be covered, taking particular care to see that only that much quantity of slurry shall be prepared which can be used within half an hour of preparation i.e. before the initial setting time of cement.
The prepared slurry shall be applied over the dampened surface with brushes very carefully,
including the joints between the floor slab and the parapet wall, holes on the surfaces, joints of pipes, masonry/concrete etc.
The application of the slurry should continue upto a height of 300 mm on the parapet wall and also the groove. The slurry should also be applied upto a height of 150 mm over pipe
projections etc.
including the joints between the floor slab and the parapet wall, holes on the surfaces, joints of pipes, masonry/concrete etc.
The application of the slurry should continue upto a height of 300 mm on the parapet wall and also the groove. The slurry should also be applied upto a height of 150 mm over pipe
projections etc.
Laying Base Coat 20 mm thick
Immediately after the application of slurry and when the application is still green, 20 mm thick cement plaster as base coat with cement mortar 1:5 (1 blended cement : 5 coarse sand) shall be evenly applied over the concrete surface taking particular care to see that all the corners and joints are properly packed and the application of the base coat shall be continued upto a height of 300 mm over the parapet wall.
Laying Brick Bat Coba
Brick bat of size 25 mm to 115 mm out of well burnt bricks shall be used for the purpose of brick bat coba.
The brick bats shall be properly dampened for six hours before laying.
Brick bats shall be laid to required slope/gradient over the base coat of mortar leaving 15-25 mm gap between two bats. Cement mortar 1:5 (1 blended cement: 5 coarse sand) shall be poured over the brick bats and joints filled properly. Under no circumstances dry brick bats should be laid over the base coat.
The haunches/gola at the junction of parapet wall and the roof shall be formed only with brick bat coba.
In case the brick bat coba is laid on the base coat immediately on initial set there will be no necessity of applying cement slurry over the base coat before laying the brick bat coba. However, if the brick bat coba is to be laid on the subsequent day, cement slurry prepared and applied over the top surface of the base coat, then only the brick bat coba shall be laid.
The brick bats shall be properly dampened for six hours before laying.
Brick bats shall be laid to required slope/gradient over the base coat of mortar leaving 15-25 mm gap between two bats. Cement mortar 1:5 (1 blended cement: 5 coarse sand) shall be poured over the brick bats and joints filled properly. Under no circumstances dry brick bats should be laid over the base coat.
The haunches/gola at the junction of parapet wall and the roof shall be formed only with brick bat coba.
In case the brick bat coba is laid on the base coat immediately on initial set there will be no necessity of applying cement slurry over the base coat before laying the brick bat coba. However, if the brick bat coba is to be laid on the subsequent day, cement slurry prepared and applied over the top surface of the base coat, then only the brick bat coba shall be laid.
Application of Slurry over Brick Bat Coba
After two days of curing of brick bat coba cement slurry prepared and shall be applied on the surface of brick bat coba. The application of slurry shall be the same as described above which should cover the haunches/gola, and the remaining small portion of parapet wall and also inside the groove.
Laying Finishing Layer (Protective Coat)
Immediately on applying the cement slurry over the surface of the brick bat coba and when the slurry applied is still green, the fibre glass cloth shall be spread evenly on the surface without any kink & pressed to see that no air spaces exist. The fibre glass cloth shall be taken up to a height of 300 mm on parapet walls & tucked in the groove specially prepared at that height. 20 mm thick layer of cement plaster, without leaving any joints shall be applied with cement mortar 1:4 (1 blended cement: 4 coarse sand) over the entire fibre glass cloth including the haunches/gola and the small portion on the parapet wall. The groove in the parapet wall over the haunches shall also be filled neatly packing the mortar firmly in the groove.
The surface of the finishing layer (protective coat) shall be neatly finished with cement slurry
prepared as above. The finished surface shall be allowed to dry for a while and then pattern of 300 mm x 300 mm groove, 8 mm deep shall be made over the entire surface.
The surface of the finishing layer (protective coat) shall be neatly finished with cement slurry
prepared as above. The finished surface shall be allowed to dry for a while and then pattern of 300 mm x 300 mm groove, 8 mm deep shall be made over the entire surface.
The entire surface thus treated shall be flooded with water by making kiaries with weak cement mortar, for a minimum period of two weeks.
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