BRICKS

BRICK

         Brick is a important building material used in the construction of structures. Brick is the oldest building material replacing stone. The brick is obtained by molding the clay into block and burning it. The manufacturing of brick is started by hand moulding, drying in the sun and burning in the clamps. Later with increased technology, knowledge of raw materials, improved machineries and burning techniques, the quality of brick has been improved than earlier.

      The size of the bricks are of 190mm × 90mm × 90mm and 190mm × 90mm × 40mm. With

mortar joints, the size of these bricks are taken as 200mm × 100mm × 100mm and 200mm × 100mm × 50mm.

Types of Bricks

        Bricks may be broadly classified as:

                    (i) Building bricks

                    (ii) Paving bricks

                    (iii) Fire bricks

                    (iv) Special bricks.

(i) Building Bricks:These bricks are used for the construction of buildings ie walls etc.

(ii) Paving Bricks: These are vitrified bricks and are used as pavers.

(iii) Fire Bricks: These bricks are specially made to withstand furnace temperature. Silica bricks belong to this category.

(iv) Special Bricks:  These bricks are different from the commonly used building bricks with respect to their shape and the purpose for which they are made.

                                            (a) Specially shaped bricks

                                            (b) Facing bricks

                                            (c) Perforated building bricks

                                            (d) Burnt clay hollow bricks

                                            (e) Sewer bricks

                                            ( f ) Acid resistant bricks.

Properties of Bricks

        The following are the required properties of good bricks:

(i) Colour: Colour should be uniform and bright.

(ii) Shape: Bricks should have plane faces. They should have sharp and true right angled corners.

(iii) Size: Bricks should be of standard sizes as prescribed by codes.

(iv) Texture: They should possess fine, dense and uniform texture. They should not possess fissures, cavities, loose grit and unburnt lime.

(v) Soundness: When struck with hammer or with another brick, it should produce metallic sound.

(vi) Hardness: Finger scratching should not produce any impression on the brick.

(vii) Strength: Crushing strength of brick should not be less than 3.5 N/mm2. A field test for

strength is that when dropped from a height of 0.9 m to 1.0 mm on a hard ground, the brick should not break into pieces.

(viii) Water Absorption: After immersing the brick in water for 24 hours, water absorption should

not be more than 20 per cent by weight. For class-I works this limit is 15 per cent.

(ix) Efflorescence: Bricks should not show white patches when soaked in water for 24 hours and then allowed to dry in shade. White patches are due to the presence of sulphate of calcium, magnesium and potassium. They keep the masonry permanently in damp and wet conditions.

(x) Thermal Conductivity: Bricks should have low thermal conductivity, so that buildings

built with them are cool in summer and warm in winter.

(xi) Sound Insulation: Heavier bricks are poor insulators of sound while light weight and hollow

bricks provide good sound insulation.

(xii) Fire Resistance: Fire resistance of bricks is usually good. In fact bricks are used to encase

steel columns to protect them from fire.

Tests on Bricks

          The following laboratory tests may be conducted on the bricks to find their suitability:

                          (i) Crushing strength

                          (ii) Absorption

                          (iii) Shape and size and

                          (iv) Efflorescence.

Classification of Bricks Based on their Quality

          The bricks used in construction are classified as:

                  (i) First class bricks

                  (ii) Second class bricks

                  (iii) Third class bricks and

                  (iv) Fourth class bricks

(i) First Class Bricks: These bricks are of standard shape and size. They are burnt in kilns.They fulfill all desirable properties of bricks.

(ii) Second Class Bricks: These bricks are ground moulded and burnt in kilns. The edges may

not be sharp and uniform. The surface may be somewhat rough. Such bricks are commonly used for the construction of walls which are going to be plastered.

(iii) Third Class Bricks: These bricks are ground moulded and burnt in clamps. Their edges are

somewhat distorted. They produce dull sound when struck together. They are used for temporary and

unimportant structures.

(iv) Fourth Class Bricks: These are the over burnt bricks. They are dark in colour. The shape is

irregular. They are used as aggregates for concrete in foundations, floors and roads.

Uses of Bricks

      Bricks are used in the following civil works:

                   (i) As building blocks.

                   (ii) For lining of ovens, furnaces and chimneys.

                   (iii) For protecting steel columns from fire.

                   (iv) As aggregates in providing water proofing to R.C.C. roofs.

                   (v) For pavers for footpaths and cycle tracks.

                  (vi) For lining sewer lines.