clay brick

Clay brick

           A solid masonry unit made of clay, usually formed into a rectangular unit while in the                     

plastic state and treated in a kiln at an elevated temperature to harden it.

Types of clay bricks

·         1)Common Brick

·         2)Facing Brick

 

Common Brick à used for general purposes, where appearance is not important. Usually they are used in walls where the surfaces are plastered.

Facing Brick à are bricks required to have good appearance and they are specially made with good quality control. In Malaysia there are a number of factories making these bricks of high quality. Facing bricks are classified according to the texture of their surfaces, with names like;

·         smooth face

·         rock face

·         sandblast

·         cobble

·         ledge brick

·         castle brick

Basic Advantages of Brick

1. Aesthetic Appeal
2. Thermal & Acoustic Insulation
3. Zero Maintenance Cost
4. Fire Resistance
5. Flexible in Application

1. Aesthetic Appeal

      Brick possesses natural and infinite pleasant colors of burnt clays. Its color formation is achieved through a complicated physio-chemical reaction during the firing process. Brick colour is permanent and will not fade. Brick colour will has many different colour due to different clay compositions, firing temperatures, or kiln atmosphere, If can control these effects, we can produce many different colours that we want

2. Thermal & Acoustic Insulation

Thermal Insulation: Brick provides better thermal insulation than other building materials like concrete. Perforation can improve the thermal insulation property of bricks to some extent. Besides, brick can absorbed the thermal mass and moisture and help to keep the temperature inside the house relatively constant. Bricks can absorb and release heat slowly. So it can keep the house cool during day-time and warm during night-time.

Acoustic Insulation: Brick wall provides good sound insulation due to its dense structure. The thickness and density of brick will slow down the noise transmission and deflect noise from outdoors.

3. Zero Maintenance Cost

Clay bricks do not require maintenance because it can prevent from rotting, denting, warping, rusting, spliting, peeling, fading, and termites. We only need use some money in painting. Clay brick has a special properties which is as your home gets older, it naturally becomes more beautiful.

4. Fire Resistance
         The fire resistance of a building material refers to the length of time a walling element is about to resist a fully developed fire.The walls which build by clay brick can obtain maximum fire ratings compare to other building materials. So, own a clay brick building, we can rest assured live in clay brick building. The table below show the Design of Clay Brickwork for Fire.

DESIGN OF CLAY BRICKWORK FOR FIRE
Fire resistance period, minutes	Required material thickness for insulation Mm	Maximum slenderness for structural adequacy
30	60	25.0
60	90	22.5
90	110	21.0
120	130	20.0
180	160	18.0
240	180	17.0

5. Flexible in Application
         The high compressive strength of fired clay bricks has been exploited to build structures ranging from single-storey huts to massive public buildings, enormous bridges and viaducts. Claybrick is has been exploited and become popular because it can be used for loadbearing structures. Besides that, brick can be made into convenient shape and size to facilitate the construction work.

Manufacture of Clay Bricks

Bricks are made from clays which composed of silica and alumina and various impurities including iron compounds, magnesia, potash, etc.

The main processes in the manufacture of clay bricks involve:

1) Preparation

2) Forming

3) Drying and firing

1) Preparation

This involves the removal of stones and other undesirable particles, and in some cases the addition of fuel or other organic compounds. The burning of the organic material during  firing contributes to the heat and thus save fuel. Also the burning out of these materials leave a more open, lower density structure in the bricks.

2) Forming

The wet clay must be formed to dimensions which allow for shrinkage in firing later. Forming can be done in 4 ways;

Soft mud process

The clay is blended with 25-30% water using mixers. The mud is formed into lumps of the size of one brick and the lumps dipped in sand to reduce the stickiness of the surface. The lumps are then manually or mechanically placed and formed in moulds, with excess mud cut off with a wire. Because of the high drying shrinkage of such wet mixes and the plasticity of the the green brick, the shape and size of such units are fairly variable. However the finished brick is fairly porous which improves its insulation properties and its effectiveness as a rain screen, but limits the strength.

Stiff plastic process

The clay is blended with 10-15% water to make a very stiff but plastic compound. This is then extruded from the mixer and cut into brick-shaped pieces and allowed to dry for a short period before being press in a mould. The clay, being very stiff, when ejected from the mould retains exactly the shape of the mould. The low moisture content in this process leads to the following advantages;

·         Shrinkage of brick after firing is low

·         Size of the brick is easier to control

·         The drying time is relatively short.

The process is used to produce engineering bricks, facing bricks and bricks where very accurate dimensions are required.

Wire cut process

In this process, clay of a softer consistency (with moisture content of 20-25%) is extruded from a rectangular die. The ‘column’ of clay is then cut into bricks by wires. The process is fully continuous.

Perforations are usually made along the length of the ‘column’ to produce perforated bricks. Perforations in bricks give the following advantages;

1. Reduction in the quantity of clay required per unit of brick, thus reducing costs of production and in transportation.

2. A reduction in environmental impact by reducing the rate of use of clay deposites.

3. Opening up of more surface area in the unit of brick, thus speeding up drying and firing.

4. Thermal insulation is improved with the existence of air voids in the brickwork.

5. The lighter units of bricks are less tiring to lay.

Pressing

In this process, stiff clay, without addition of water is formed into bricks by mechanical pressure (pressing). This obviates the need for drying the green bricks in a separate drier.

 3)Drying and firing

‘Green’ bricks must be dried before they are fired. Drying is usually done in separate drier or in the drying zone of a continuously fired kiln.

The great majority of bricks are fired in continuous kilns. A very efficient way of mass-producing bricks is to use tunnel kilns, in which the bricks, usually pre-dried, are moved through a stationary fire (see Fig 30.5).

how to make clay brick