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damp-proofing of a building is done by interposing a layer of damp-proofing material between
source of dampness and building and this layer is known as damp-proofing course (D.P.C.). The
principle of damp-proofing is to provide D.P.C. horizontally or vertically without any break
and thought the thickness of wall.
A good water-proofing material should be impervious, durable and should be able to resist
loads to which it will be subjected. It should be in position to accommodate some structural
movement without fracture. The materials commonly used to check dampness can be divided
into the following four categories:
- Flexible materials the examples are bitumen felts, plastic sheeting (Polythene sheet) etc.
- Semi-rigid materials the examples are mastic asphalt or a combination of materials or
layers. - Rigid materials the examples are first class bricks, stones, slates, cement concrete etc.
- Grout consists of cement slurry and acrylic based chemicals/polymers.
The choice of a material to function as an effective damp-proof course requires a judicious
selection. It depends upon the climatic and atmospheric conditions, nature of structure and the
situation where D.P.C. is to be provided.
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Fiber is a class of materials that are continuous filaments or are discrete elongated pieces,
similar to lengths of thread. Fibers are of great importance in the biology of both plants and
animals, for holding tissues together. Fibers used by man can be classified as follows.
Natural fibers include those produced by plants, animals, and geological processes. They
can be classified according to their origin and are described as follows:
Vegetable fibers are generally based on arrangements of cellulose, often with lignin: examples
include cotton, linen, hemp jute, flax, ramie, and sisal. Plant fibers serve in the manufacture of
paper and cloth.
Wood fiber, distinguished from vegetable fiber, is from tree sources. Forms include groundwood,
thermomechanical pulp (TMP) and bleached or unbleached kraft or sulfite pulps. Kraft and
sulfite, also called sulphite, refer to the type of pulping process used to remove the lignin
bonding the original wood structure, thus freeing the fibers.
Animal fibers consist largely of particular proteins. Instances are spider silk, sinew, catgut and
hair (including wool). Polar bear fibers are noted for being hollow.
Mineral fibers comprise asbestos. Asbestos is the only naturally occurring long mineral fiber.
Short, fiber-like minerals include wollastinite, attapulgite and halloysite.
Man-made fibersmay be from natural raw materials or from synthetic chemicals.
Many types of fiber are manufactured from natural cellulose, including rayon, modal, and the
more recently developed Lyocell. Cellulose-based fibers are of two types, regenerated or pure
cellulose such as from the cupro-ammonium process and modified or derivitized cellulose
such as the cellulose acetates. Fiberglass made from specific glass formulas and optical fiber