BITUMEN WATER PROOFING

BITUMEN.... ???
Binding material present in asphalt.
Hydrocarbon obtained from distillation of crude petroleum.
Black or brown in colour & obtained in solid n semi solid state.
Contains 87%-carbon,11%-hydrogen,2%oxygen.

USES.... !!!
Damp proof course
Water proofing of roof, tanks,basements,swimming pools,etc...
Preparing paints & roofing felts
Filling cracks in masonry structures,for stopping leakages

DIFFERENT FORMS OF BITUMEN....
Bitumen emulsion:
Liquid containing bitumen to a great extent in aqueous medium.
Blown bitumen:
Used as roofing &damp-proofing felts,manufacture of pipe asphalt &joint fillers,as heat insulating material.
Cut-back bitumen:
Can be applied cold as a bitumen paint.
Plastic bitumen:
Used for filling cracks in masonry structures,for stopping leakages etc.

DIFFERENT TYPES OF BITUMEN FELT....
Fibre-based bitumen felt
Asbestos-fibre-based bitumen felt
Glass-fibre-based felt
High performance bitumen felt

FIBRE-BASED BITUMEN FELT:-
Traditional bitumen felt roofing is manufactured from cellulose fibers that are woven and compacted into a that is saturated in bitumen to protect the felt base and than coated on both sides with bitumen to provide a waterproof finish.
In time the fibre-based felt will rot,due to absorption of moisture,and lose so much of its strength as a reinforcement to the bitumen that will no longer hold the bitumen together and the covering will fail as a weather protection.
With improvements in felted bases and modifications of bitumen to improve the performance of felted roof coverings,the original fibre based felt is used much less than it was.
Its main uses are for short life coverings to sheds as the middle layer with other felt bases for economy

ASBESTOS-FIBRE-BASED BITUMEN FELT:-
Although it is more resistant to loss of strength by the absorption of moisture than fibre-based felt it will in time lose strength and no longer act as a reinforcement for the bitumen coating.
Because of the asbestos fibre base this felt maintains its integrity during fibres for a longer period than other felts and it has been used either as one layer of built up felt roofing or as a multi-layer system to improve the performance of coverings during fires.
This felt is sometimes used on sloping roofs as the material can be nailed more successfully to sloping surfaces to the covering than other felt bases.
More expensive.
Less used since the introduction of glass-fibre-based felts.

GLASS-FIBRE-BASED FELT:-
First introduced in the 1950s.
The glass tissue reinforcement of this felt is composed of glass fibres held together with an adhesive.
The insoluble glass fibres do not lose strength as a reinforcement to the bitumen coating.
Glass-fibre-based felt built up roofing is the cheapest and most durable of the 3 felts included in BS 747.
Three layers of glass-fibre based bitumen felt roofing should have a useful life up to 20 years.

HIGH PERFORMANCE BITUMEN FELT:-
This has a felt base with improved strength to resist elongation and provide a non rotting base, together with modifications of bitumen to improve the ageing characteristics of ordinary bitumen which hardens and loses elasticity during the first three to five years of exposure to ultraviolet light, ozone and oxygen, with resulting loss of flexibility, strength and fatigue resistance.

LAYING BUILT-UP BITUMEN FELT ROOFING:
Bitumen felt roofing is laid by pouring hot bitumen in front of the felt as it is unrolled across the roof so that the felt spreads the bitumen the full width of the roll.
This traditional ‘pour and roll method is used for each layer of felt, underlays, vapour checks and vapour barriers.
The rolls of bitumen felt roofing are laid with 50 side laps and 100 end laps with laps staggered a third of a roll width between layers of built-up roofing for the sake of water proofing and to avoid an excessive build-up of thickness of material.
The top layer of built up felt bitumen roofing is usually surfaced with a range of coloured mineral aggregates which adhere to the bitumen coating and are used for the sake of appearance.
To reduce the effects of temperature change, a reflective surface coating of mineral chippings is applied to the roof.
Bitumen felt roofing with layers of felt, is usually laid as three layers for built-up roofing.


SPECIFICATION FOR BITUMEN WATERPROOFING
GENERAL:- the item pertains to the provision and applying of a bitumen layer over the terrace structural slab for waterproofing.
MATERIALS:-
the bitumen felts shall conform to I.S. 1322-1970 and shall be of the fabric specified in the special provisions. in the absence of such mention, it shall be as specified in either paragraph 3.1.1. or 3.1.2. of I.S. 1322-1970.
Primer shall be bituminous solution of suitable viscosity to be applied to the wall or floor surface to assist adhesion of the binding material.
Bitumen binder shall conform to I.S.702-1961.the penetration of bitumen shall be limited to 40 when tested in accordance with I.S. 1203-1958.

APPLICATION:-
The exposed slab surface shall be thoroughly cleaned, bitumen shall then be applied at the rate 2kg. Per sq. m. at a temperature of not less than 121 C evenly throughout and allowed to set before laying brickbat coba and flooring of china mosaic or other types.

ITEM TO INCLUDE:-
1. bitumen, cleaning the terrace and applying bitumen.
2. all necessary labour, materials and use of tools.

MODE OF MEASURMENT AND PAYMENT:-
The contract rate shall be for one sq. m.

the length and breadth shall be on the inside of the parapets and measured correct to a cm. and the area calculated correct up tp two places of decimals of a sq. m. when parapet at the junction of the slab is also treated, the area so ordered and treated shall be measured for payment.

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