BUILDING MATERIALS: Bricks

BRICKS

A brick is a block of ceramic material used in masonry construction, usually bonded by mortar. It has been regarded as one of the longest lasting and strongest building material used throughout history.

The requirements of bricks:

· Be of sufficient strength, at least to be able to support the self-imposed load
· Durable, able to withstand weathering and exposure to elements
· Aesthetic appeal-should be good appearance if used in facing brickworks
· Regular shape and size to facilitate bonding

Common bricks used in Malaysia:

CALSUIM SILICATE BRICKS CLAY BRICKS

CONCRETE BRICKS

Properties of bricks:

strength & durability
water absorption
moisture movement
appearance
fire resistance
thermal & sound insulation
efflorenscence
flexibility in application

Comparison of Properties of Clay Bricks, Calcium Silicate Brick and Concrete Bricks

Compressive strength---- Clay bricks fired to sufficiently high temperature and can withstand compressive strength exceeding 28N/mm². Because of it, they are suitable for load bearing wall. Strength of calcium silicate bricks and concrete brick is comparable to clay bricks. However, Calcium silicate cannot achieve the extremely high strength of engineering clay bricks (around 50 N/mm²)

Fire resistance-----Clay bricks, calcium silicate bricks and concrete bricks have similar excellent fire resistance by retaining its stability, integrity and insulating properties, with 100mm brickwork giving 2 hours of fire resistance and 200mm brickwork giving 6 hours of fire resistance.

Thermal insulation-----Thermal conductivity of brickwork is depended on density and moisture content. Clay bricks are similar poor thermal insulators. Brick manufacturers quote thermal conductivities at standard 5% moisture content for exposed brickwork, may also give the 1% moisture content for protected brickwork.

The manufacturing process of bricks:

Manufacture of calcium silicate bricks

The raw materials are silica sand, hydrated lime, and crushed flint, coloring pigment and water. A mixture of sand, lime and water is used to manufacture the natural white sand lime brick. Pigments may be added for color.

The approximately proportioned blended is pressed into brick unit under high pressure. The brick move to autoclave and subjected to steam at pressure up to 1.7 n/mm^2 for 4-15 hours. The hydrated lime reacted chemically with the surface of the silica particles to form hydrated calcium silicate. Carbon dioxide from atmosphere will react slowly with calcium silicate and form calcium carbonate, thus increase the strength and hardness of bricks.

Manufacture of concrete bricks

Concrete bricks are manufactured from blended dense aggregates such as crushed limestone and sand together with cement under high pressure in steel moulds. Up to 8% of controlled blended iron oxide pigments, depending on the tone and depth of color required, is added to coat the cement particles which will form the solid matrix with the aggregate. The use of colored aggregate also increase color range.

Manufacture of clay brick

Clay brick are made in a process than starts with a suitable blend of clay that have to mined, aged and mixed. The clay is then extruded through a special pressed and sliced to size. These unburned brick are dried out before being placed into a kiln that heated between 700c and 1100c. After the firing process, the brick need to be cooled and classified as to color and strength. There are several types of clay bricks: