A hollow brick is a type of building material that is commonly used in construction. It is made from a mixture of clay, sand, and other materials, and is molded into the desired shape and size.
Unlike solid bricks, hollow bricks have a hollow center that makes them lighter and less expensive. They are also easier to work with because they can be cut and drilled more easily than solid bricks.
In addition, hollow bricks have better insulation properties, making them more energy-efficient. Despite these benefits, hollow bricks are not as strong as solid bricks and are therefore not recommended for use in load-bearing walls.
What Are Hollow Brick?
Hollow Bricks can be defined as the block with one or more than one hole of cavities passing through the block having 50 to 75 percent of solid material of its total volume calculated from the overall dimension of the block.
In Simple Words, it can be explained as the brick with holes purposefully made to make the brick light in weight subsequently adding characteristics like strength, durability, fire resistance, etc.
One of the properties making hollow blocks popular in construction is eco-friendly, made of recycled materials, and remains of the construction materials.
Hollow Brick Price
Hollow brick price is different from location to location which may depend on brick strength and material used for manufacturing.
Hollow brick price in India varies between Rs. 21 to Rs. 55 per block depending quality of bricks and size.
Hollow bricks price in the USA is 1$ to 3 $ per block depending on the brick’s quality and size.
Advantages of Hollow Bricks
Hollow bricks advantage as follows,
- The use of Hollow Brick reduces the mortar consumption in subsequent amount hence reducing the use of cement which in turn affect the cost of the project.
- These bricks have superior thermal insulation material, which reduces the heat transfer through the wall of the structure.
- These bricks are economical as compared to solid blocks.
- Hollow blocks have a cavity inside which reduces the weight of bricks hence when placed, transfer a small dead load.
- It has a good sound insulation property.
- The material used in the construction of hollow brick is totally environment friendly which makes hollow brick an eco-friendly material considering its construction does not cause pollution.
- Hollow bricks have adequate strength which makes them usable for load-bearing structures.
- Hollow Bricks are highly durable and require less maintenance around the time period of their design life.
Other advantages of hollow bricks,
- Bricks are good fire-resistant
- Easy as well as fast construction system
- Have better Architectural features
- Good Compressive strength
- A cavity of bricks provides passage for electrical wires
- Passage for plumbing fixtures through the wall
Disadvantages of Hollow Bricks
Hollow brick’s Disadvantages are as follows,
- Even though they are environment-friendly, hollow bricks have disadvantages in themselves. They have a low bearing capacity compared to other bricks.
- Considering their load-bearing capacity hollow bricks cannot be used in very heavy load-bearing structures.
- Once the wall is constructed of hollow bricks it should not be used to hang heavy objects from the perspective of safety.
- Hollow bricks are not suitable for foundation purposes or any base construction from the point of view of their density.
- In research, it was found that hollow bricks are prone to salt attacks and may lose their strength once exposed to salt.
- Hollow bricks are avoided in earthquake zones.
Sizes of Hollow Bricks
Hollow bricks are used at various stages during construction serving different purposes such as partition walls, compound walls, etc. For such purposes, different sizes of hollow bricks could be used depending on the requirement.
Even for the partition wall itself the different sizes of Hollow Bricks could be used as the thickness of the partition wall may differ for every component of the structure.
Hollow bricks are available with different no. of cavities in the market with different sizes. Their standard sizes are mentioned below for Hollow Brick with two cavities and Half Blocks:
- 400 mm x 200 mm x 200 mm
- 400 mm x 200 mm x 150 mm
- 400 mm x 200 mm x 100 mm
Manufacturing Process of Hollow Clay Bricks
- Hollow bricks are made of different sizes and designs. The blocks are made in different sizes with hollow spaces may be cores, cells, deep frogs, or combinations of these.
- In the manufacturing process firstly cement, stone chips, sand, etc. are mixed in a ratio of 1:6 or 1:12 and this mixture is poured into a vibrator machine. Molds are kept ready of specific sizes and designs for the mix frequently to be poured into it.
- After completing 24 hours of drying, the blocks are put in for curing in a water tank.
- The process of curing lasts for two to three weeks to give the blocks acceptable compression strength as per the requirement of structures.
- After carrying out specific tests on bricks and eliminating the damaged ones, bricks are made ready for sale.
- Even though it is easy to make a concrete block, the successful brickyard must however make blocks of uniform quality and sell them at a price high enough to cover costs and earn a reasonable profit.
Hollow Bricks Properties
Hollow Bricks Properties are as follows,
1. Hollow Brick Compressive Strength
The compressive strength of hollow brick is about 3.5N/mm2. Where 1st class clay brick has compressive strength is around 10 N/mm2.
there is a big difference in the compressive strength of normal brick and hollow bricks. It is clear that hollow bricks possess lower compressive strength compared to normal bricks.
Therefore, try to avoid the use of hollow brick in heavily loaded structures. You can utilize it for light load or single stories load-bearing construction.
- The compressive strength of the hollow bricks is around 3.5N/mm2.
- The hollow bricks have a dry density of about 694-788kg/m3.
- Its thermal conductivity is around 0.28-0.31W/mk.
- Water absorption is about 15% of the total weight of a brick.
2. Flexural Strength
The Hollow Brick’s Flexural strength is impacted by the mix of mortar and its unit arrangements when placed in masonry. The flexural strength of hollow brick is also well impacted by the reinforcement steel used in construction.
Recent studies shows that hollow bricks bedded with face shell gives less flexural strength compared to hollow bricks with solid layers with use of similar mortar mix proportion.
Also, there is a study show are hollow bricks with a 20-35% void ratio do not have a significant effect on hollow brick’s flexural strength.
3. Fire Resistance
Hollow bricks possess very good fire resistance properties compared to normal bricks. There are various tests performed on hollow brick to check its fire resistance properties and it shows good resistance than any other clay brick used for construction.
Fire Resistance Rating Calculation of Hollow Bricks
- Industrial standards or actual testing can be used for calculating the fire resistance ratings for hollow bricks.
- However, an alternative way of determining the fire resistance of a hollow brick with respect to wall assembly is by calculating the equivalent thickness of the brick.
- This approach has been approved by the model building codes to determine fire resistance ratings of walls that could not be tested physically.
- The imperviousness to fire rating of hollow brick masonry work is controlled by its identical strong thickness.
- The same thickness is determined by taking away the volume of center or cell spaces from the complete gross volume of brick and partitioning by the uncovered face space of the unit.
- The subsequent thicknesses can measure up to the prerequisites given inside the construction standards of structures.
4. Water Resistance
Water resistance of hollow bricks is majorly affected by the quality of hollow bricks and the material used for manufacturing them.
These defects can be strengthened by providing a well-designed drainage system to drain water penetrate through it.
These provide good water resistance by delaying and lowering the dampness in a brick wall. The empty space left between hollow brick is provided to colled the dampness from outside and collect it for a longer time.
5. Sound Resistance
The sound insulation property of hollow bricks is quite complex. Because of the cavity provided and brick design structure hollow brick exhibit strong anisotropy.
Hollow brick walls are often provided with Plaster–render layers to seal the face of the brick. This will increase the total mass of the wall and increase the airflow resistance which in turn improves sound insulation properties.
It has been tested that the design dimension and layout of webs and holes within hollow bricks can influence the overall sound insulation property. Cross webs within the hollow bricks are average better for sound insulation than staggered webs but poorer than straight webs.
Some hollow brick designs also have the possibility to insert insulation material within the block’s larger holes, such as jacket blocks for increasing sound resistance.
Design And Detailing of Hollow Bricks
1. Mortar Bedding
Hollow Bricks larger in size used in structural walls requires mortar to be applied to the full thickness of the face shell (face-shell bedding). Whereas for smaller hollow brick units that are used in veneer applications, mortar should be applied to the full width of the brick veneer (full bedding) to maintain proper anchor embedment and cover.
Reinforcement in hollow brick masonry is not always used. Although if used the large cells of hollow bricks allow the units to be easily reinforced and grouted. One of the precautions to be taken is that the reinforcing must be embedded in grout, not mortar.
Read More: 7 Brick Test to Decide Quality of Bricks
3. Corbelling and Other Design Details
Certain construction of structures requires the use of solidly filled hollow units. The use of hollow brick is restricted by the model building codes as follows;
Corbelling: For corbelling, solidly filled hollow bricks are used with the approval of the building official.
Masonry Piers: The height of masonry piers constructed of unfilled hollow bricks is limited to four times their least dimension.
Parapet Walls: An unreinforced hollow unit masonry parapet must be no less than 8 in. (203 mm) thick, and its height must not exceed three times its thickness.
Fireboxes and Chimneys: Fireboxes and chimneys constructed of hollow units are required to be grouted solid.
Uses of Hollow Bricks
Following are some of the uses of hollow bricks;
- Hollow Bricks are used in constructions where the dead load imposed on the foundation is to be reduced.
- The use of hollow brick in boundary fences is cost-efficient.
- Huge structures demand the building materials have less weight so as to reduce the superimposed load of the structure on soil, hollow brick is a common engineer’s choice in such circumstances.
- Hollow bricks are used to reduce the cost of construction by reducing the amount of mortar used.
- The manufacturing process of hollow brick is environment friendly, hence used in areas prone to pollution.
- Used when steel is to be reinforced within the masonry wall or similarly when electrical wires and plumbing fittings are to be passed through constructed walls.
In conclusion, hollow bricks are a versatile and cost-effective building material that has many uses in construction.
Despite their lighter weight and better insulation properties, they are not as strong as solid bricks and are best used in non-load-bearing walls.
However, their ease of workability and affordability make them a popular choice for many builders. Overall, hollow bricks are an important building material that plays an important role in the construction industry.
Bricks with holes in the cavity made for making brick light in weight and adding properties to it can be termed as Hollow Bricks. Hollow bricks have 50 to 75 percent of solid material of their total volume while the rest is a cavity within.
Uses of Hollow Bricks
Hollow Bricks are used in partition walls, boundary fences, huge structures, etc. It is also likely to be used in areas prone to pollution for construction, in the masonry walls to be reinforced, and to reduce the use of mortar.
Size of Bricks Blocks
Hollow bricks are available with different no. of cavities in the market with different sizes. Their standard sizes are mentioned below for Hollow Brick with two cavities and Half Blocks
Are hollow bricks cheaper than solid bricks?
Yes, hollow bricks are generally less expensive than solid bricks because they require less material and are lighter.
What are the advantages of using hollow bricks in construction?
The advantages of using hollow bricks in construction include lower cost, better insulation, and easier workability.
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