Special mortars: Following are tile various types of special mortars which are used for certain conditions:
1. Fire-resistant mortar
2. Lightweight mortar
3. Packing mortar
4. Sound-absorbing mortar
5. X-ray shielding mortar
1. Fire-resistant mortar: This mortar is prepared by adding aluminous cement to the finely crushed powder of fire-bricks. The usual proportion is 1 part of aluminous cement to 2 parts of powder of fire-bricks. This mortar is fire-resistant and it is therefore used with fire-bricks for lining furnaces, fire places, ovens, etc.
2. Lightweight mortar: This mortar is prepared by adding materials such as saw dust, wood powder, etc. to the lime mortar or cement mortar. Other materials which may be added are asbestos fibres, jute fibres, coir, etc. This mortar is used in the sound-proof and heat-proof constructions.
3. Packing mortar: To pack oil wells, special mortars possessing the properties of high homogeneity, water resistance, predetermined setting time, ability to form solid water-proof plugs in cracks and voids of rocks, resistance to subsoil water pressure, etc. have to be formed.
4. Sound-absorbing mortar: To reduce the noise level, the sound-absorbing plaster is formed with the help of sound-absorbing mortar. The bulk density of such a mortar varies from 6 to 12 kN/m3 and the binding materials employed in its composition may be Portland cement, lime, gypsum, slag, etc. The aggregates are selected from lightweight porous materials such as pumice, cinders, etc.
5. X-ray shielding mortar: This type of mortar is used for providing the plastering coat to walls and ceiling of X-ray cabinets. It is a heavy type of mortar with bulk density over 22 kN/m3. The aggregates are obtained from heavy rock and suitable admixtures are added to enhance the protective property of such a mortar.
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