Asbestos is a naturally available mineral substance. It is fire-proof, acid-proof. It is a good insulator of heat and electricity. It is used with cement to produce asbestos cement sheets for roofing, wall panelling, to cover fuse and electric boxes, for making downtake pipes, etc.
In these glass fibres provide stiffness and strength while resin provides a matrix to transfer load to fibres. GFRP is used for door and window frames, partition walls, roofing sheets, skylights, water tanks, for making chairs and tables.
These are called bituminous materials and their main constituent is hydrocarbon. (a) Bitumen: It is obtained by fractional distillation of crude petroleum. It is specified by term penetration, say 80/100 means penetration of standard needle is 80 to 100 mm at a temperature of 25°C. It is used for damp proof course, roofing felt. (b) Asphalt: It is bitumen mixed with inert material like sand, gravel and crushed stone. It is found in natural form. It is artificially manufactured also. It is used for waterproofing floors and roofs, lining reservoirs and swimming pools, for grouting expansion joints. (c) Tar: It is obtained by destructive distillation of coal, wood or mineral tar. It is used for road work, anti-termite treatment and waterproofing.
Sealants are the substances used to seal cracks or joints between wall and window frames, glazing and window frame or between roofing sheets. Elastomeric sealants are most efficient. They are based on silicon, acrylic or polysulphide
An adhesive is a material used to join two or more surfaces. Asphalt, shellac and cresin are natural adhesives which are used to glue papers. Rubber is another natural adhesive used to join plastic, glass and rubber. There are many synthetic varieties of adhesives like melamine resin, phenoil resin, urea resin and polyvinyl resin. They are used for joining plywood and laminated products. Starch glue, animal glue, casein glue (glue from skimmed milk), sodium silicate glue are also available for joining various materials.
It is a by-product in coal based thermal plants. Its particles can fly in ordinary air. At one time it was considered a nuisance but now it is used as a useful material in manufacturing bricks, for stabilizing soil and to improve workability of concrete.
What are different types of NBC in india
Needs to know difference between both.
(A) Not neededd (B) Provided equally on inner and front faces (C) Provided more on inner face than on front face (D) Provided more on front face than on inner face