Bricks and Blocks

A brick is a block of ceramic material used in masonry construction, usually laid using 

various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.

"Bricks" for building may be made from clay, shale, soft slate, calcium silicate, concrete, or shaped from quarried stone. However, true bricks are ceramic, and therefore created by the action of heat and cooling. 

Clay is the most common material, with modern clay bricks formed in one of three processes - soft mud, dry press, or extruded. 


Normally, brick contains the following ingredient:

1.    Silica (sand) - 50% to 60% by weight

2.    Alumina (clay) - 20% to 30% by weight

3.    Lime - 2 to 5% by weight

4.    Iron oxide - 5 to 6% (not greater than 7%) by weight 
5.    Magnesia - less than 1% by weight

 

This is a building that is entirely made out of mud brick.

The soft mud method is the most common, as it is the most economical. It starts with the raw clay, preferably in a mix with 25-30% sand to reduce shrinkage. The clay is first ground and mixed with water to the desired consistency. The clay is then pressed into steel moulds with a hydraulic press. The shaped clay is then fired ("burned") at 900-1000 °C to achieve strength.

This Is the largest mud brick building in the world. 

     Bricks are used for building, block paving and pavement.  In the USA, brick pavement was found incapable of withstanding heavy traffic, but it is coming back into use as a method of traffic claiming or as a decorative surface in pedestrian precincts. For example, in the early 1900s, most of the streets in the city of Grand Rapids, Michigan were paved with brick. Today, there are only about 20 blocks of brick paved streets remaining (totalling less than 0.5 percent of all the streets in the city limits).

Bricks building
 

      
     Fired clay bricks remain one of the most enduring building materials known to the world wide building industry. Some might argue that it is also one of the most beautiful and that it adds character to any building with its color, strength and texture. Clay brick dates as far back as the Egyptian age and connects us with the history of our ancestors. 

     Being such a versatile building material and because of its very good climatic characteristics, it remains the material of choice for residential buildings in South Africa. Bricks have an excellent fire rating, it is weatherproof and has really good acoustic properties and is almost soundproof, and best of all it amount to only about 10 per cent of the total cost of a typical residential building. Homebuyers will almost always prefer to buy a house constructed out of clay brick as it does not deteriorate over time and has a higher resale value.

     Bricks vary quite significantly in because of the diverse manufacturing processes and types of clay used in their manufacture in various regions. Often potential home builders make the mistake in thinking that all bricks are the same and there is no need to shop around for different finishes and colours. This can be costly as the quality of different brick manufacturers vary considerably as will also be reflected in the price. A very cheap brick might be of un-even size or may warp making building with them a lot more difficult. 

 Clay brick

    

     Clay brick is the most commonly used building material in construction. Clay brick is mostly used to make nice looking homes and towers. Since clay brick does not burn, it is often used to make fireplaces. Clay bricks are made by putting clay in a furnace and then craft the bricks. It is a durable block and resists explosions well. It has better sound performance characteristics to outside noise. All sound leaks are important because sound will travel through any opening with little loss. A very small air hole in a brick wall can easily reduce insulation from 50 dB to as low as 20 dB.

     Besides,clay brick offers lower utility costs. Energy efficient homes not only save money for the homeowner, they also reduce the nation's energy needs and build a cleaner environment. Clay brick's thermal mass makes it an energy efficient material and recent studies have shown that brick homes can lower heating and cooling cost by up to eight percent over vinyl homes of a comparable size. Furthermore, clay brick offers a wide range of non-fade colors, is a load bearing material, features a lower rate of moisture absorption, is virtually maintenance-free and creates higher resale value for homeowners.

     Moreover,clay brick is flexible in applications. It is used for a wide range of applications in buildings and engineering structures. It can be used in loadbearing walls,non-loadbearing partition walls and decorative walls,earth retaining walls,manholes and drain sumps,furnaces,kilns,flues and fencings. Brick can be made into convenient shapes and sizes to make them handy and flexible in application.

Face brick 

    The use of face brick is often used in residential architecture for its low maintenance properties and often the aesthetics is overlooked completely. Face brick can be very aesthetically pleasing with its rustic look and a good architect might combine face brick with plastered areas to come to more a balanced aesthetic as face brick in its single form can be a bit overwhelming. When opting to build with face brick make sure you appoint a good builder with a good face brick portfolio as the jointing of a face brick wall can make or break the aesthetic of this type of construction. Also make sure you order sufficient bricks the first time as, because it being a natural material can vary noticeably per batch. 

Cement bricks 

    These bricks are similar to a clay stock (plaster) brick but are more often used in regions where clay might be in short supply. There is usually not a big price difference between cement and clay plaster bricks and cement brick is mostly used as a substitute. When ordering cement bricks make sure that they are properly cured and dry before using them. If more that 5 per cent breaks upon delivery, have a knowledgeable person check the quality of the bricks. 

 Plaster (Stock) bricks

    Cheaper than face bricks, a plaster brick still is manufactured to high standards to ensure uniformity of size and structure, but have to be plastered and painted thereby canceling out the cost saving and has to be maintained at fairly regular intervals. Often great aesthetics can be achieved by combining plastered walls with face brick walls. 

 Calcium Silicate Bricks

     The raw materials for calcium silicate bricks include lime mixed with quartz, crushed flint or crushed siliceous rock together with mineral colourants. The materials are mixed and left until the lime is completely hydrated; the mixture is then pressed into moulds and cured in an autoclave for two or three hours to speed the chemical hardening. The finished bricks are very accurate and uniform, although the sharp arrises need careful handling to avoid damage to brick (and bricklayer). The bricks can be made in a variety of colours, white is common but pastel shades can be achieved.

    The strength of calcium silicate brick is more uniform than clay brick but it cannot achieve the extremely high strength of engineering clay brick. The extent of reversible moisture movement of calcium silicate brick is greater than clay brick but lower than concrete brick. It tend to shrink during the first few weeks following manufacture. If the bricks are used too soon or if the bricks get very wet before laying the wall is likely to crack. Attention also needs to be paid to movement joints which should be approximately every  7.5 to 9 metres. Light bed-joint reinforcement in brickwork courses, above and below openings, can help reduce the risk of shrinkage cracking. To ensure the brick is dry before and during construction so that cracking will not occur. 

 Blocks

     Block permits rapid and economical construction,give better strength,finishes,densities and thermal properties. 

 Clay block

     Clay blocks are suitable for single and multi storey applications. Modern clay blocks are precision engineered walling units designed to be thermally and acoustically efficient. During manufacture clay is prepared with sand, straw or recycled materials, extruded, dried and fired. The addition of these other materials helps enhance their unique properties as they are burned off during firing leaving behind innumerable small holes and connecting pores. The air trapped within these pores helps retain heat and reduce sound transmission. Clay block construction projects are highly eco-friendly. The blocks themselves have less environmental impact during their manufacture than most other building materials, and the finished building offers very high insulation values. 

 

Concrete block

     Concrete blocks are primarily used as a building material in the construction of walls. Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design. In use, concrete blocks are stacked one at a time and held together with fresh concrete mortar to form the desired length and height of the wall. Concrete bricks can be reinforced with steel to help protect against high winds or earth tremors. Not only does this help protect you and your investment in the event of a tragedy, but it also may help reduce your homeowner's insurance. Concrete homes are not susceptible to dry rot and other long-term issues associated with wood construction. Concrete block homes create a tighter seal between each block when compared to traditional homes. This minimizes wall leaks that serve to reduce insulation. 

Manufacture of Concrete Blocks

The following steps are commonly used to manufacture concrete blocks.

Mixing

•1 The sand and gravel are stored outside in piles and are transferred into storage bins in the plant by a conveyor belt as they are needed. The portland cement is stored outside in large vertical silos to protect it from moisture.

•2 As a production run starts, the required amounts of sand, gravel, and cement are transferred by gravity or by mechanical means to a weigh batcher which measures the proper amounts of each material.

•3 The dry materials then flow into a stationary mixer where they are blended together for several minutes. There are two types of mixers commonly used. One type, called a planetary or pan mixer, resembles a shallow pan with a lid. Mixing blades are attached to a vertical rotating shaft inside the mixer. The other type is called a horizontal drum mixer. It resembles a coffee can turned on its side and has mixing blades attached to a horizontal rotating shaft inside the mixer.

•4 After the dry materials are blended, a small amount of water is added to the mixer. If the plant is located in a climate subject to temperature extremes, the water may first pass through a heater or chiller to regulate its temperature. Admixture chemicals and coloring pigments may also be added at this time. The concrete is then mixed for six to eight minutes.

Molding

•5 Once the load of concrete is thoroughly mixed, it is dumped into an inclined bucket conveyor and transported to an elevated hopper. The mixing cycle begins again for the next load. 

•6 From the hopper the concrete is conveyed to another hopper on top of the block machine at a measured flow rate. In the block machine, the concrete is forced downward into molds. The molds consist of an outer mold box containing several mold liners. The liners determine the outer shape of the block and the inner shape of the block cavities. As many as 15 blocks may be molded at one time.

•7 When the molds are full, the concrete is compacted by the weight of the upper mold head coming down on the mold cavities. This compaction may be supplemented by air or hydraulic pressure cylinders acting on the mold head. Most block machines also use a short burst of mechanical vibration to further aid compaction.

•8 The compacted blocks are pushed down and out of the molds onto a flat steel pallet. The pallet and blocks are pushed out of the machine and onto a chain conveyor. In some operations the blocks then pass under a rotating brush which removes loose material from the top of the blocks.

Curing

•9 The pallets of blocks are conveyed to an automated stacker or loader which places them in a curing rack. Each rack holds several hundred blocks. When a rack is full, it is rolled onto a set of rails and moved into a curing kiln.

•10 The kiln is an enclosed room with the capacity to hold several racks of blocks at a time. There are two basic types of curing kilns. The most common type is a low-pressure steam kiln. In this type, the blocks are held in the kiln for one to three hours at room temperature to allow them to harden slightly. Steam is then gradually introduced to raise the temperature at a controlled rate of not more than 60°F per hour (16°C per hour). Standard weight blocks are usually cured at a temperature of 150-165°F (66-74°C), while lightweight blocks are cured at 170-185°F (77-85°C). When the curing temperature has been reached, the steam is shut off, and the blocks are allowed to soak in the hot, moist air for 12-18 hours. After soaking, the blocks are dried by exhausting the moist air and further raising the temperature in the kiln. The whole curing cycle takes about 24 hours.

     Another type of kiln is the high-pressure steam kiln, sometimes called an autoclave. In this type, the temperature is raised to 300-375°F (149-191°C), and the pressure is raised to 80-185 psi (5.5-12.8 bar). The blocks are allowed to soak for five to 10 hours. The pressure is then rapidly vented, which causes the blocks to quickly release their trapped moisture. The autoclave curing process requires more energy and a more expensive kiln, but it can produce blocks in less time.

Cubing

•11 The racks of cured blocks are rolled out of the kiln, and the pallets of blocks are unstacked and placed on a chain conveyor. The blocks are pushed off the steel pallets, and the empty pallets are fed back into the block machine to receive a new set of molded blocks.

•12 If the blocks are to be made into split-face blocks, they are first molded as two blocks joined together. Once these double blocks are cured, they pass through a splitter, which strikes them with a heavy blade along the section between the two halves. This causes the double block to fracture and form a rough, stone-like texture on one face of each piece.

•13 The blocks pass through a cuber which aligns each block and then stacks them into a cube three blocks across by six blocks deep by three or four blocks high. These cubes are carried outside with a forklift and placed in storage.