Bricks may be one of the oldest building materials in the industry. Building construction continues to evolve with the discovery of new materials to combat current issues like the environment crisis and rapidly growing population. Paired with 21st century innovation in technology, this humble building material of brick, has given rise to many modern alternatives and variations, like the porous brick.
Porous bricks are bricks with voids or holes. They can be made of clay, concrete, or hollow ceramic blocks that are made from a mixture of sand, clay and special raw natural admixtures. This building material is widely used in private and commercial construction and it is produced via thermal methods. Porous blocks are desirable for being a material lighter in weight, therefore easier, faster and cheaper to construct.
First.. The Available Types of Bricks
Bricks can be made with clay, stone, concrete, or a mixture. Your present climate, building type and availability of raw material will determine the best type of brick suitable to your structure.
Clay bricks for example, have better thermal insulation, meaning they keep heat or cool better indoors. This can lead to savings in energy costs.
Concrete bricks on the other hand have better acoustic insulation and when reinforced with steel are far stronger than a clay brick wall.
There are various colors of brick available, however limited to the natural tones of the earth and rocks used. Red bricks were just preferred in England to make the buildings out in the fog. (1)
Studies show that bricks with a numerous amount of pores (total diameters smaller than 1 µm) are subject to frost damage, resulting in zero freezing resistance.
Currently, dampness is a common problem in brickwork due to damaged roof leaks, faulty mortar pointing or lack of water proofing finishes. Having satisfied those concerns, chances are water will still find a way to creep into your blocks to escape. Therefore, with porous bricks, you can purposefully control where water or air flows. (2)
Next,… What is Porosity?
Porosity defines the voids of pores in different types of material. They can be noticed on the surface of the materials or in its inner structure. The porosity of the inner structure is highly related to the density of the materials as well as the nature of its composition, explaining the empty areas among the compounds,
In other words, “Porous” means the presence of microscopic pores in the masses, which are given by blocks and bricks of their unique properties. This allows liquids of water or air to easily pass through.
How are they Made?
The production process includes several basic steps: (3)
In this first stage, the mass of clay and sand is cleaned, and grinding them happens with a special equipment that leads them to merge into a single state. In addition, raw materials are added with specialized quickly-acting admixtures. These admixtures can provide special properties such as water resistance, quick drying, and most importantly, an air-entraining agent to insert those air bubbles making the brick lighter with the same amount of mass. The quality of preparation of raw materials will largely determine the technical characteristics of the finished product.
The prepared mass undergoes vacuum presses. As a result of this effect, blocks of certain specified dimensions are obtained at the end.
Materials are sent to drying chambers to remove excess moisture from them.
Firing is also done with special furnace equipment. In the furnaces, depending on the raw materials that are being used, we can notice the forming of straws, sawdust, and most importantly their “pores.” Their microscopic hermetic air cavities make up a volume that reaches 50 percent of the total volume of the future blocks. These closed pores and cracks prevent heat loss through the walls of buildings and increase heat transfer resistance. (3)
Why Use Porous Bricks?
Bricks need to improve their environmental performance to compete with (or stand relevant with) other building materials. (4)
There are several industrial standard sizes for porous brick blocks. All of them are as large as regular bricks, yet its volume can replace around 15 standard bricks. This greatly reduces the amount of construction materials needed for building walls as well as reduces overall transport costs. Advantages of porous bricks are:
- High strength material.
- A small mass.
- Possibility to choose the optimal size for any construction.
- Environmental acceptability.
- Excellent heat and sound insulation.
- Good sanitary and hygiene indicators
- The presence of a pen-wide system on side parts of the brick, providing their reliable connection without the use of cement mortar.
- Resistance to fire.
- Great solution for energy savings (depending on climatic context)(3)
A regular brick of standard dimension, typically weighs about 4-6 kilograms each. Imagine having to stack several a day to build a wall. A lighter brick would make the job faster, statistically 2-2.5x less construction time spent versus ordinary bricks. In other words, they are easier to transport, carry and construct brick masonry structures.
The construction of a porous brick wall would also mean reducing the amount of cement mortar, because of their little to zero requirement of it. They create an additional air barrier in areas with the highest heat loss – on its seams.
Block Sizes & Form Variations
Modern manufacturers produce porous bricks in several standard sizes of existing bricks, with the intention for construction of facilities with various indications of the wall thickness.
Insulation and finishing will depend on the manufacturer you buy your bricks from and whether you’ll employ a single layer or double layer of brick wall.
In addition to the standard brick size, manufacturers are also producing bricks in the form of half of the standard size, for screens or simply as light cladding for a brick look on a concrete wall.
Additional construction materials are used to lay the corners, and can also be used for the most appropriate connecting external and internal walls
Resistant & Adaptive Material
These engineered blocks are made more resilient to external factors such as fire, freezing, mold and weather. Giving a lessened fear in the long term effects of “atmospheric deposit” in bricks that lead to its deterioration.
The blocks are able to withstand the same number of defrost and freezing cycles as conventional bricks do. Among other things, porous material is inert in biological terms, which is why mold or mushrooms do not form on their surface. Exceptions are putrefactive processes. Buildings made of porous brick can create a favorable microclimate inside the building in creating a more breathable atmosphere.
Experts claim that such buildings can be compared to those made of carbonated concrete or wood. These buildings have excellent sanitary and hygienic characteristics.
People also prefer porous bricks because of their resistance to fire. This material can be compared to clay or silicate bricks, which not only contain the fire, (to not leave the room and spread), but are also able to withstand the effect of open flames for a few hours.
The term “resistance” can also be connected with both sound and thermal insulation.
Thanks to the internal cavities and pores, these bricks provide ideal protection and resistance. The resulting air barrier prevents sound wave penetration and in the same time reduces heat transfer three times in relation to gas blocks.
If a masonry worker uses a full brick, in his daily shift time he can set about 4 m3 wall surface. On the other hand If he were using porous blocks, then with the specified parameter, he’d already be reaching 8 m3.
Consumption solutions are reduced by reducing the number of layers and since load of the foundation can be reduced, we also reduce the costs of its construction. It is a consequence of the already mentioned slight volumetric weight of the brick, which is 800 kg / m 3.
Force & Strength
This is probably the most important factor that needs to be taken into account when choosing the right construction materials. This special material with internal cavities allows you to take enough high pressure on both sides of the brick – up to 150 kg / cm2. In this case, the internal pores serve as additional local hotspots that resist pressure on the material.
As we previously mentioned, porous bricks are made of clay and organic impurities. After baking them at 1800 ° C, all fine particles combine and form the “desired” pores in the mass of materials. This means that they are 100% environmentally friendly since apart from natural ingredients, there are zero chemicals, toxins, or poisonous materials used in them.
Having reduced the volume of material per block, there are tremendous savings in the amount of concrete, sand or clay to construct the same size structure. In using less raw material, less is extracted from the earth to construct more buildings.
Due to the reduced brick volume, the building load on the foundations of the building are significantly reduced. Therefore there is no need to place as strong a mass on the foundation (saving costs on foundation work).
Being lighter in weight, more bricks can be transported via truck, resulting in fewer trips or a lower carbon footprint overall.
Like all other building materials, porous bricks have their own disadvantages too, mainly:
- Building Height up to 9 floors/storey
- Special Construction
The main drawback is a fairly high price, being 2 times higher than the blocks of other materials. (3)
Another disadvantage is difficulty in calculating the volume of solution. During the construction process, it should not be forgotten that it is necessary to use elements for reinforcement. In addition, blocks should be handled carefully because they have quite fragile walls. This shortcoming can cause problems in installing elements, such as furniture, in the future inside the premises.
An additional shortcoming is that only vapor resistant materials should be selected for finishing. The blocks themselves must be laid by the use of a special masonry mortar only.
Another important consideration and disadvantage when choosing porous bricks is ensuring your workers are equipped with the know-how and skills of handling these bricks. Different suppliers may have different connection methods, sizes, finishes and may pose changes affecting your building design.
Building Blocks of the Future
Weighing it all up, we can say by using a porous brick to build a house, you can reduce the costs of the building while being more environmentally friendly overall. However, since all sites pose their own unique challenges and contexts, always check to see if it is the most sustainable choice for you.
Is it made in your area? Do the workers there know how to build with porous brick?
If the answer to both are no, perhaps the cost of shipping them over and finding someone to construct and repair them are not worth the innovation just yet.
However, there are many ways to be creative with brick. Porous bricks are just the beginning. There are low-tech solutions like “perforated brick”, which is staggering regular bricks at a pattern, creating a nice breeze wall barrier, naturally cooling a home. (5)
There’s also highly engineered porous bricks of loofah and charcoal, aimed at promoting biodiversity. Being 20 x more porous for organic matter to grow within those pores. The charcoal will clean the air by absorbing nitrates for the plants to feed on. The loofah acts as a natural substitute to metal reinforcement. (6)
Other new bricks are byproducts of factories, made of mushrooms, or with bigger holes to encourage bees to nestle and thrive.
What new bricks will this age bring?
- Mcdonald, L. (2019, May 3). The many types of bricks. The American Ceramic Society. Retrieved March 2022, from https://ceramics.org/ceramic-tech-today/construction/the-many-types-of-bricks
- Steve. (2018, October 18). Penetrating damp causes. Safeguard Europe. Retrieved March 2022, from https://www.safeguardeurope.com/penetrating-damp/causes
- Admin. (2022, March). Brique Poreuse (poreuse): Caractéristiques et application, conductivité thermique de la brique de 510 mm et avis: Une maison privée 2022. Building counsels. Retrieved March 2022, from https://fr.buildingcounsels.com/11357258-porous-porous-brick-characteristics-and-application-thermal-conductivity-of-510-mm-brick-and-reviews
- Bories, C., Borredon, M. E., Vedrenne, E., & Vilarem, G. (2014). Development of eco-friendly porous fired clay bricks using pore-forming agents: a review. Journal of environmental management, 143, 186–196. https://doi.org/10.1016/j.jenvman.2014.05.006
- Wang, L. (2019, July 11). Porous brick walls keep this bold Vietnamese home naturally cool. Inhabitat. Retrieved March 2022, from https://inhabitat.com/porous-brick-walls-keep-this-bold-vietnamese-home-naturally-cool/
- Aouf, R. S. (2019, July 14). Bricks made from Loofah and charcoal could promote biodiversity in cities. Dezeen. Retrieved March 2022, from https://www.dezeen.com/2019/07/14/green-charcoal-bricks-loofah-technology-materials/