Effects of Silica, Alumina, and Lime on Brick Clay

Excess of silica makes the brick ______ and weak on burning.

If alumina is present in excess of the specified quantity, it produces ______ in brick on drying.

Lime normally constitutes less than 10 per cent of ______.

Lime in brick clay has the effect of reducing the ______ on drying.

Excess of lime causes the brick to ______ and the brick loses its shape.

Magnesia rarely exceeding 1 percent affects the ______ and makes the brick yellow.

Iron oxide constituting less than 7 percent of clay, imparts ______ colour on burning when excess of oxygen is available.

Improved kiln designs and more advanced ______ have all contributed to advancing the brick industry.

Clay is one of the most abundant natural ______ materials on earth.

After pugging, the tempered clay goes through a de airing chamber that maintains a vacuum of 15 to 29 in.(375 to 725 mm) of ______.

The soft-mud or molded process is particularly suitable for clays containing too much ______ to be extruded by the stiff-mud process.

Clays are mixed to contain 20 to 30 percent ______ and then formed into brick in molds.

To prevent clay from sticking, the molds are lubricated with either ______ or water to produce “sand-struck” or “water-struck” brick.

This process is particularly suited to clays of very low ______.

Clay is mixed with a minimal amount of ______ (up to 10 percent), then pressed into steel molds under pressures.

Wet brick from molding or cutting machines contain 7 to 30 percent ______, depending upon the forming method.

The brick are typically placed by ______ or mechanical means.

Fuel may be ______ gas, coal, sawdust, methane gas from landfills or a combination of these fuels.

The manufacturing process has six general phases, including _______________ of raw materials.

Surface clays, shales and some fire clays are mined in open pits with _______________ equipment.

To break up large clay lumps and stones, the material is processed through _______________ machines.

The material is processed through _______________ vibrating screens to control particle size.

Tempering produces a _______________, plastic clay mass.

Water is added to the clay in a _______________ to achieve tempering.

There are three principal processes for forming brick: _______________-mud, soft-mud and dry-press.

In the stiff-mud or extrusion process, water in the range of 10 to 15 percent is mixed into the clay to produce _______________.

The final phase of the manufacturing process is _______________ and storing finished products.

In a tunnel kiln, bricks are loaded onto ______ cars, which pass through various temperature zones as they travel through the tunnel.

Firing may be divided into five general stages: 1) final drying (evaporating free water); 2) dehydration; 3) oxidation; 4) ______; and 5) flashing or reduction firing.

Although the actual temperatures will differ with ______ or shale, final drying takes place at temperatures up to about 204 ºC.

De-hacking is the process of unloading a ______ or kiln car after the brick have cooled, a job often performed by robots or machines.

When a desirable amount of lime is present in the ______, it results in good bricks, but if in excess, it changes the colour of the brick from red to yellow.

Pebbles, Gravels, Grits : do not allow the ______ to be mixed thoroughly and spoil the appearance of the brick.

On burning green bricks, the organic matter gets charred and leave pores making the bricks ______; the water absorption is increased and the strength is reduced.

Alkalis (Alkaline Salts) : forming less than 10 per cent of the raw ______, are of great value as fluxes, especially when combined with silicates of alumina.

Cooling is an important stage in brick manufacturing because the rate of cooling has a direct effect on ______.

When bricks come in contact with ______, water is absorbed and the alkalis crystallise.

On drying, the ______ evaporates, leaving behind grey or white powder deposits on the brick.

Efflorescence should always be ______ brushed away before rendering or plastering a wall.

Sulphur is usually found in clay as the sulphate of ______, magnesium, sodium, potassium or iron.

If there is ______ in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur, the latter will cause the formation of a spongy, swollen structure in the brick.

A large proportion of ______ water generally causes clay to shrink considerably during drying.

The use of water containing small quantities of magnesium or calcium carbonates, together with a ______ fuel often causes similar effects as those by sulphur.

The brick will be decoloured by white ______ if there is carbon in the clay and insufficient time is given during burning for proper oxidation of carbon and sulphur.

Efflorescence is a phenomenon that spoils the ______ of the brick.