Wiki: Bitumen

This has been hanging around a while... input welcome, though I may be slow in dealing with it this time
NT
==Properties== Bitumen is the black solid in tarmac roads. Its slight flexibility enables roads to handle vibration from traffic, and enables roofing felts to bend, as long as they're not too cold.
It melts when heated with a torch, at a temperature high enough to make molten bitumen a definite risk to handle.
Bitumen sticks to almost anything, even polythene, but few things stick to it once its dry.
==Uses== ===Sealant=== Bitumen is totally waterproof, and sticks to most things. The slow drying time of solvent bitumen can be an issue, and most things won't stick to bitumen unless its blinded with sand.
===Glue=== Bitumen is an effective glue, and unlike most glues its 100% waterproof. However there are stronger glues. The slow drying time of solvent bitumen is an issue, as is its tendency to slowly ooze out of joints making a mess. Hot bitumen was widely used for parquet floors, and is still good for the job.
Bitumen used as glue can be removed from non-porous surfaces with solvent or heat. When bitumen remains and regluing is wanted, most glues won't stick to it, but more bitumen will.
===Paint=== Bitumen used as paint isn't prone to peeling off, and it sticks the surface of the substrate together. It lasts extremely well out of the sun, and well in the sun when on a firm porous surface such as masonry. When it has no hard immovable substrate under it it tends to crack & split over time.
The black colour isn't the most popular. Adding red pigment (iron oxide) can make bitumen brown or a very dull red. Iron oxide is sold as red cement colouring powder.
===Roofing felt, with fibres=== Many roofing felts are simply bitumen and fibres. When a small patch is wanted it can be easier to use bitumen in sovlent & synthetic fibre cloth than travel out for a new roll of felt.
===DPC/Tanking=== Bitumen paint has long been used as a DPC in floors & walls. Its also used for tanking basements etc.
===Tarmac=== There are 2 types of tarmac, hot lay and cold lay. The difference is that cold lay has added paraffin, diesel or white spirit to soften it, so it doesn't need heating to apply it. Tarmac must be rolled to compact it, and needs to be laid on a good solid surface for it to last, eg hardcore and gravel rolled firm.
Tarmac is much cheaper bought as tarmac than mixing on site. Scalpings (used road surface), can be had for around 200 per 20 ton truck load in 2010.
===Roof sheet=== Rigid roofing sheets such as corruline and onduline are fibres stuck together with bitumen.
==Forms== Bitumen comes in various forms
# Just bitumen. Heat to melt it and apply. # Bitumen in solvent. Pour/brush on and let dry # Bitumen emulsion. Emulsified in water # Roof repair gloop. Bitumen with fibres & solvent # Tarmac. Bitumen with stone & chalk/clay. Cold lay also contains a little solvent. # Roofing felt. Bitumen and fibres, sometimes capped with stone waste # Roofing sheet. Bitumen and fibres
==Techniques== ===Blinding=== Where its wanted for something to stick to bitumen, sand is sprinkled on while its wet. Cement, paints etc then stick to the sand.
===Roof repair gloop=== Bitumen is used to repair cracks and splits on roofs, both felt roofs and permanent roofs. The result doesn't last forever, but it has its uses.
Mixing chopped fibres into bitumen enables it to last better on a roof. The fibres reduce its tendency to crack. Synthetic fibres last much better than rottable natural fibres, and glass fibre lasts even better.
===Solvents=== Petrochemical solvents are used with bitumen. Choice of solvent affects drying times. From slowest to fastest: * Diesel - when you want it to stay soft as long as possible * Paraffin - paint dries out in a couple of days in summer * heating oil & lamp oil - as paraffin * White spirit - a much used solvent with bitumen * Petrol - not safe to use * Lighter gas - evaporates in seconds, usable for removing small spots of bitumen, but other solvents are preferable.
===Roofing felt=== Applied with any of the following: # Blow torch to melt the underside, then apply, pressing it down # Stick it down with bitumen in solvent # Nail it
Most better quality roofing felts use modified bitumen, which stays flexible in cold weather. The longer life of good felts comes primarily from the synthetic fibre content, whereas cheap felt uses mixed rag, which contains a high percentage of rottable natural fibres.
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