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3 uses and types of masonry mortar contd contd

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Unformatted text preview: ’d) Contains various amounts of Portland cement, masonry cement, Contains hydrated lime and sand - M-type contains 1:1:0.21/4 to 3 or M-type 1:0:1/4:21/4 to 3 - S-type contains 1/2:1:0:21/4 to 3 or 1:0:1/2:21/4 to S-type 3 - N-type contains 0:1:0:21/4 to 3 or 1/2:21/4 to 3 - O-type contains N-type O-type 0:1:0:21/4 to 3 or 1:0:11/4 to 11/2:21/4 to 3 0:1:0:21/4 9.4 MANUFACTURE OF BRICKS FROM CLAY 9.4 Bricks have greater fire resistance than stone or concrete masonry - Its size enables easy handling and placement in walls; it can be easily adapted to small-scale and large-scale structures to give pleasing appearance and texture small-scale Constituents: Brick clays are produced by blending together various clays (surface clays, shales, and fire clays) to produce the desired chemical composition and physical properties - Clays can be divided into calcareous clays (containing 15% Calcium Carbonate, which gives yellow color when burnt) or noncalcareous clays (containing silicate of alumina, feldspar, and iron oxide) - Iron oxide gives buff, red or salmon color, when burnt Molding of Brick: The raw material is dug from pits, crushed, ground, and screened to reduce it to a fine constituency - Then it is tempered with water to produce a plastic clay for forming into brick water 9.4 MANUFACTURE OF BRICKS FROM CLAY (Cont’d) (Cont’d) Methods of forming : Three different processes are used for brick forming (i) Soft Mud Process: A relatively moist clay (containing 20% to 30% of water) Soft is pressed into molds, either by hand or machine - The mold may be dipped in water (water-struck bricks) or dusted with fine sand (sand-struck bricks) before filling it with clay - (ii) Dry press bricks are formed with clays that shrink Dry excessively during drying - Is mixed with minimum amount of water(10%) - (iii) Stiff mud Process: Most widely used process nowadays - contains 12 % to 15% Stiff of water - passed through vacuum to remove any pocket of air, and then extruded through a rectangular die to form bricks through The rectangular column of moist clay extruded through the die is cut by automatic The wire cutters to form individual bricks - After molding and cutting, the bricks are wire dried for one or two days in low-temperature kilns - Then they are ready for firing or burning or 9.4 MANUFACTURE OF BRICKS FROM CLAY (Cont’d) (Cont’d) Fi...
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