How to Make Clay Bricks - All You Need to Know About Them
We live in a world where buildings are a work of art. Each aspect and the functionality of that aspect depend on a separate space, which is pretty understandable. We encounter heavy rains and storms, which were previously disastrous to us. Now, they merely cause any harm due to the durable and sturdy structures we have constructed. The basis of these structures are bricks; clay bricks to be specific.
Brick is a term that refers to a small unit used as building material. These are often made with fired clay and are secured in places with mortar, which is a mixture of water, cement, and sand. This acts as a bonding agent to achieve maximum durability. The properties of bricks are that they retain heat; they fight against corrosion and also resist fire. Bricks are the best possible material for structures in confined spaces, buildings, as well as curved designs, with very little upkeep, and which generally lasts a long time. Being 4-inches wide and 8-inches long, bricks are made twice as long as the width. As these are small units, there really aren't many limitations; you can easily build an array of structures using bricks.
Most of us have seen the appearance of bricks. These are rectangular in shape and are solid masonry units when in their plastic states. These are then treated in a kiln at extremely high temperatures to harden them. The bricks usually found in general work, which does not have any significant traits in their appearance, are common burnt clay bricks. These bricks can't be used alone to build walls, as they will require plastering and rendering. The reason why fired bricks are so hard and durable is that they are fired in a kiln until they reach this state. We cannot specify one single process in which bricks are made since, in modern times, three processes are mainly used: dry press, extruded or soft mud.
The Several Processes of Making Clay Bricks
Soft Mud Process
Firstly, relatively moist clay is taken, which has about 30% water in it’s weight. It is then placed into a mould, either by hand or with a moulding machine and is pressed in the moulds. The main concern here is to keep the clay from sticking to the moulds, the moulds may be dipped in water immediately before being filled producing bricks with a relatively smooth, dense surface that are known as water struck bricks. You can use this same process to create sand-moulded or sand-struck bricks by dusting the wet mould with sand right before forming the brick. These bricks have a textured and matted surface.
Dry Press Process
The dry press process is the most commonly used process when making refractory bricks. Unlike the soft mud process, the clay in this has minimal water content, which is about 10% of the total weight only. The clay is placed in the moulds and the hydraulic press is used to give extremely high-pressure conditions for the bricks. After they are exposed to high pressure, the bricks are then dried and fired. While they are still moist you can engrave them with different designs, grooves, functional grooves or different kinds of textures.
These bricks are known as wire cut bricks and this process is most commonly used in today's time. These bricks are relatively new however, over the past decade, these have gained a lot of popularity. Wire cut bricks, which are formally called extruded bricks, are made using a relatively modern method of brick manufacturing, which is very different compared to the above-mentioned processes. The bricks used in this have less moisture than the two mentioned above which is then extruded (as the name suggests) through a die and then are cut using a wire.
Classes of Bricks
Like everything else in this world, there are several qualities available when it comes to bricks. These are sold in four classes. The first class includes the most strong and high-quality bricks. High-quality bricks such as these do not have any apparent flaws but they do cost more than the lower grade bricks. If you want to use these bricks for walls then they will require plastering and rendering with mortar.
As there are four classes of bricks available, it can be a pretty hard choice to make. Most people do not even know the difference between those classes but worry no more because we can help you with that. The best thing you can do is to judge the type of bricks you want according to what you need them for.
- These bricks are burned very thoroughly and their colours range from dark red, copper, and cherry.
- The exterior should be rectangular and smooth; the edges should be sharp and parallel and the corners should be square with all edges straight.
- There should be no visible flaws such as cracks and/or stones.
- The texture should be consistent.
- If a scratch is made into the brick there should be no impression left.
- Lumps or lime should not be present on the fractured exterior of the brick.
- When you strike two of these bricks together you should hear a ringing or metallic sound.
- It has specific water content as well. The water absorption, when placed in cold water for twenty-four hours, should be 12-15%.
The crushing strength should also be no less than 10N/mm², although, this limit will vary according to every country's government organizations.
Uses: The use of these bricks is great for exposed face work or pointing in masonry structures, reinforced brickwork and flooring. The other three classes also have their set of characteristics. So, you can easily determine the difference between the four.
Second Class Bricks
Should have the same requirements as the first-class bricks except:
- Small distortions and cracks are allowed.
- Water absorption of around 16-20% of its dry weight is allowed.
- Crushing strength shouldn’t be less than 7.0 N/mm2
Uses: Second class bricks are recommended for hidden masonry works.
Third Class Bricks
- Are under burnt.
- They’re light-coloured and soft, producing a “dull” sound whenstriking against each other.
- Water absorption is about 25% of dry weight.
Uses: Temporary structures use this class of brick.
Fourth Class Bricks
- Are overburnt, the shapes and sizes are not consistent and are fragile in nature.
Uses: Floors and foundation in lime concrete as well as road metal will use this class of brick.
Types of Brick Pigment
Brown Brick Oxide - Manganese Umber
This is basically a brick pigment that comes from Africa and is brown and ceramic. Manganese umber, when mixed with red firing clay, can produce an array of gorgeous browns such as nutmeg, speckled, chocolate, and so depending on the percentage and contents of your mixture and also the sizing. This material is referred to as a brown brick oxide or a brown brick pigment. This beautiful brown clay can then be used for bricks which produces consistent and high-quality texture and colour in the end product. The colour finish of the product is also great. The best part is that manganese dioxide can take temperatures as high as 1280° Celsius. Not all bricks can withstand such high temperatures and end up being unstable and vitreous.
The main use of manganese dioxide in bricks is used as a brown brick oxide to either change the background colour or used as an additive manufacturing speckled brick or even both. It's important to note that even though the same basic material is used for both the processes, the determining factor between the two things is basically the particle size. Enquire with us now to find your perfect brown brick pigment.
Black Brick Oxide – K37
Black brick oxide or K37, forming the black colour in ceramics or brick. K37 is a custom-designed, black brick stain for your ceramic surfaces. Colour can range from a dark brown to a rich black, depending on your requirements for a black brick pigment.
This beautiful black clay can then be used for bricks, pavers, roof tiles, and other ceramics. Black bricks are becoming increasingly popular, because architects and designers can use contrasting colours of white and stainless steel to great effect. Contact us today for your black brick oxide
Grey Brick Oxide - Chrome Flour
Naturally white firing clay or ivory clay is used with chrome flour to form different shades of grey colour in your ceramic bricks. Often concrete or cement is used to achieve these colours however concrete is very limited in the shades of grey used. Iron chromite is used as a grey brick oxide and can create a vast range of grey colours as well as the benefits of having a fired ceramic rather than a concrete or cement brick. This is a very effective grey brick pigment
Different shades and shapes can be made according to your preference. Although not as in demand as black brick oxide, these grey brick oxides add a unique touch to your building.
Chrome flour is also used in the production of chrome magnesite refractory bricks, which are used in the construction of certain furnaces and kilns.
Due to its highly corrosion-resistant nature, chrome flour is also used to produce magnesia chrome refractories that are used in non-ferrous metals like copper, lead, and zinc. These bricks are suitable for the following:
- Open earth furnaces
- Electric arc furnaces
- Metallurgy furnaces
- Cement rotary kilns
- Glass kilns
- High-temp industrial furnaces
As you can see there are a few brick pigments available which can offer an array of shades to create unique effects and colors to your clay brick. Many brick manufacturers use brick pigments to give their bricks a unique look which so many architects are in search of.
The Initial Step
The first thing that is done when manufacturing clay bricks is basically crushing and grinding all the raw materials in a jaw crusher and a separator. This is done to ensure all minerals are mixed evenly. These ingredients include material like clay and the colour for the clay, it can range from brown brick oxide, black brick oxide or even grey brick oxide. Then, the mixture of ingredients desired for each particular batch is filtered and selected before being sent to one of the three brick shaping processes which are: extrusion, moulding, or pressing.
Extrusion, out of these three is the most common and is also found to be the most acceptable process. Now that the bricks are finally formed and have gone through any following procedures, they then have to be dried so that they are free from any extra moisture. This is highly important as they are then dried to remove any excess moisture that might result in cracking during the firing process. Once this is done, they are taken to the ovens ready to be fired, after which they are cooled. Lastly, they are de-hacked, automatically stacked, steel bands are used to wrap them, and plastic corner protectors are used for padding.
Keeping these four procedures and types of bricks in mind, making a choice can be quite challenging to a person with no experience in this field. The best option is to judge them according to their characteristics and then decide which type of brick would suit you and your building. All these bricks are sturdy, but the best quality ones are the strongest. If you want to go for certain coloured bricks then you should go for the ones, which have manganese umber in them and decide the best colour you prefer. Even plain brick building without any plastering have this unique feel and look to them. If you will not be exposing the bricks then the colours aren't that important and the quality and durability should be what matters most to you.