This mortar is prepared by adding materials such as saw dust, wood powder, etc. This mortar is fire-resistant and it is therefore used with fire-bricks for lining furnaces, fire places, ovens, etc. The usual proportion is 1 part of aluminous cement to 2 parts of powder of fire-bricks. This mortar is prepared by adding aluminous cement to the finely crushed powder of fire-bricks. For decorative finishing, the mortars are composed of suitable materials with due consideration of mobility, water retention, resistance to atmospheric actions, etc.įollowing are the various types of special mortars which are used for certain conditions: The cement or lime is generally used as binding material for ordinary plastering mortar. These mortars include common plastering work and mortars for developing architectural or ornamental effects. Depending upon the working conditions and type of construction, the composition of masonry mortars with respect to the kind of binding material is decided. The mortars for bricklaying are intended to be used for brickwork and walls. These mortars are prepared from gypsum binding materials such as building gypsum and anhydrite binding materials.Īccording to the nature of application, the mortars are classified into two categories: This mortar may be used for bedding and for thick brick walls. It is also known as the composite mortar or lime-cement mortar and it can also be formed by the combination of cement and clay. The usual proportion of cement to lime by volume is about 1:6 to 1:8. It makes lime mortar economical, strong and dense. To improve the quality of lime mortar and to achieve early strength, the cement is sometimes added to it. The cement mortar is used where a mortar of high strength and water-resisting properties is required such as underground constructions, water saturated soils, etc. The proportion of cement with respect to sand should be determined with due regard to the specified durability and working conditions. Thus the sand only can be used to form cement mortar. It should be noted that surkhi and cinder are not chemically inert substances and hence they cannot be used as adulterants with matrix as cement. Depending upon the strength required and importance of work, the proportion of cement to sand by volume varies from 1:2 to 1:6 or more. In this type of mortar, the cement is used as binding material. But it cannot be used for plastering or pointing since surkhi is likely to disintegrate after some time. The surkhi mortar is used for ordinary masonry work of all kinds in foundation and superstructure. 9 sieve and the residue should not be more than 10% by weight. The powder of surkhi should be fine enough to pass BIS No. This type of mortar is prepared by using fully surkhi instead of sand or by replacing half of sand in case of fat lime mortar. It is generally used for lightly loaded above-ground parts of buildings. It is sufficiently durable, but it hardens slowly. It possesses good cohesiveness with other surfaces and shrinks very little. The lime mortar has a high plasticity and it can be placed easily. It possesses more strength and can be used in damp situations.
This mortar should be consumed within one hour after mixing. For hydraulic lime, the proportion of lime to sand by volume is about 1:2 or so. This mortar is unsuitable for water-logged areas or in damp situations.
The fat lime shrinks to a great extent and hence it requires about 2 to 3 times its volume of sand. The lime may be fat lime or hydraulic lime. In this type of mortar, the lime is used as binding material.
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