Unit:3 Tiles ( Engineering materials Second year first parts)

Unit:8 Paints and Varnishes ( Engineering materials Second year first parts)

Introduction

• Tiles are the thin slab, made of fine brick earth and burnt in kiln. Tiles are thinner than bricks.
• Crack and warping effect may be more in drying and burning.
• These are most often made of ceramic, typically glazed for internal use and unglazed for roofing but other materials are also used such as glass, concrete. 
• Tiling stone is typically marbles granite and slate etc.

3.2 Types of tiles

• Roofing Tiles

• Wall Tiles

• Clay pipes or Drain Tiles

Roofing Tiles:

Roofing tiles are manufactured using clay, so they are also called as clay tiles. Roofing tiles give good aesthetic appearance and properties to the building.

• Roofing tiles are designed mainly to keep out rain.

• These may be flat like slates or may be made to different shapes.

• Modem materials such as concrete and plastic are also used and some clay tiles have a waterproof glaze.

• Roofing tiles are 'hung' from the framework of a roof by fixing them with nails.

• The tiles are usually hung in parallel rows, with each row overlapping the row below it to exclude rainwater and to cover the nails that hold the row below.

• These can either be bedded or pointed in cement mortar or clay mortar,

Roofing types tiles are:

Plain tiles

• Size of this tiles about 25 cm x 15 cm to 28 cm x 18 cm and from 10 mm to 17 mm thick. These may have a continuous projection at one end or two small projecting nibs (as shown).

• These nibs should not be less than 2 cm wide cm and 1 cm deep. 

• Camber should be between 5 mm and 10 mm for hand-made tiles.

• The camber could be reduced for machine-made tiles.

Pan tiles

These are 33 cm to 38 cm long and 23 cm to 28 cm wide. Implements needed for its moulding are a mould, a horse, a bow and a strike for moulding pan tiles a ball of prepared clay is pressed well to fill all corners of the mould.

• All surplus earth is cut with the bow and removed. 

• Strike is then passed over the wet top of tile in mould.

• It is done so many times as to render the top surface of tiles smooth.

• The tile is then carefully removed and placed over an already burnt tile to dry. 

• After the tile has dried a little it is then placed on the curved top of horse and pressed with hand to make it curved.

• After another five to six hours the raw tile is once again shaped on the horse and its edges trimmed with a sharp knife.

To stop the clay from sticking to the mould or horse their top is sprinkled over with ash every time before use.

Pot tiles

• It is ordinary but common class of boluig tiles.

• These are semicircular in section and tapering diameter 15 cm at one end 10 cm other end (Fig 3.7). 

• Diameter at larger end is about 23 cm and at the smaller end it is about 20cm.

• The length of such tiles are 20-25 cm and thickness 1.5-2 cm.

• Rows of these tiles are laid with the concave side up.

• Then rows of same tiles with convex sides up are laid to cover the adjoining edges of every pair of the previously laid tiles.

Allahabad tiles

• These are better class of roofing tiles generally made of superior quality of clay and machine pressing.

• The essential parts of this tile is flat provided with interlocking arrangement at the sides.

• These consist of two sets of tiles.

• The lower ones are flat tiles with upturned sides.

• These tiles tapering dimensions with bigger end 16.5 cm and smaller end 12 cm, width and length is 40 cm.

• The over tile is half round in section and tapers from 16.5 cm to 12 cm in diameter.

Mangalore tiles

• They are very popular class of roofing tiles.

• These are flat pattern tiles with suitable key projection.

• Dimensions of these tiles are 410x235mm, 420x250mm, 425x260mm and weight not less than 2 kg and not more than 3 kg. and about 16 tiles are required to cover one square meter of roof.

• Arrangement of Mangalore tiles on a slopping roof.

Concrete roofing tiles

Tiles of any shape, size or color could be made with cement concrete. These are more strong, durable and weather resistant.

Wall Tiles

• Tiles used to construct the wall surface are called wall tiles.

• These are available in a rectangular and square shape or various geometrical shapes are adopted.

• These are flat tiles available in varying thickness from 1.5 to 2.5 cm.

• These are available in any desirable colors. These are available in following sizes.

• 15x15x1.8 to2.5 cm

• 20x20x1.8 to 2.5 cm

• 25x25x1.8 to 2.5 cm

• 30x30x1.8 to 2.5 cm.

Clay pipes or Drain Tiles

These tiles are curved or circular in shape and made in various size to suit the work in which they are be used. These types of tile used in the construction of sewage system.

3.3 Manufacturing of tiles

Following four operations are involved in the general process of manufacturing the common tiles.

1. Preparation of clay

2. Moulding

3. Drying

4. Burning

1.Preparation of clay

• The selected clay is made free from harmful impurity such as pebbles, grit and any vegetarian matter etc. and converted into fine powder. Then large amount of pure water is added and mixed in a tank.

• The course heavy particles settle at the bottom of tank then fine particles are taken into the tank and water is allowed to dry off. 

• The fine clay used for the manufacturing of tiles.

2. Moulding

• The clay is placed in mould which the tiles is to be formed.

• The moulding may be done either with the help of wooden mould (prepared from well seasoned timber) or potter's wheel or machine.

• The clay is pressed into mould and tiles are ready for drying.

• The care should be taken to preserve the shape of tiles during the removal of mould.

3. Drying

• The tiles remove of moulds are placed flat on the ground.

• After 2 days, they are stacked on edges under a shade to dry for about 2 days and surface are cleaned.

• The drying under shade to prevents warping and cracking of tiles.

4. Burning          www.bibek00.com

• The dried tiles are placed in kiln on edges layer by layer for burning.

• A typical kiln, for about accommodating 30000-40000 tiles is shown in fig.

• It is circular in shape and is protected by a shed.

• A layer of bricks is laid flat on the rows of long narrow fuels.

• Then the firing wood placed in these fuels.

• The top of kiln covered with a layer of old tiles in a loose condition.

• The doorways is closing by brickwork in mud.

• Temp. raised about 800°C for 8 hrs and again temp. raised being 1300°C for a period 3 hrs.

• About 72 hrs to complete the process of burning tiles.

3.4 Uses of clay tiles

• They are used for small buildings of low cost.

• They are used to improve the aesthetic appearance of a building.

• They are widely used for Buddha temples in China or northern India. 

• These tiles are one of the main attractions of that temples.

3.5 Properties of tiles

• It should be free from any cracks, bends, etc.

• It should be regular in shape and size.

• It should be sound, hard and durable.     

• It should be well burnt.

• It should be give clear sound when struck each other two tile or light hammer.

• It should fit in properly when placed in position.

• It should possess uniform color.

• It should have compact structure when seen on its broken structure. 

Must Read: Unit:8 Paints and Varnishes ( Engineering materials Second year first parts)