Definition: A concrete block is one of several precast products (the word ” precast ” refers to the process in which the block is shaped and hardened, before being brought to the job site) and is commonly made with one or more cavities. hollow and on their sides they can be smooth or with a design.
Concrete blocks or also called concrete blocks or concrete masonry units (CMU) are mainly used as construction material in the manufacture of walls and walls.
What should we know about concrete blocks?
The Concrete Block (BH) is a masonry for walls and walls, manufactured from Vibro-compressed concrete. This means that they are subjected to a vibration and compression process inside a mold that ensures dimensional accuracy and uniform compaction of the material.
Concrete blocks are made from a mixture of cement, stone, sand, and other aggregates. This mixture is subjected to the Vibro-compaction process, which then undergoes controlled curing for optimum quality.
Since they come in a variety of sizes and styles, they provide a quick and inexpensive way to create the security, control, or storage you need.
History of Concrete block
The Romans began to use cement mortar in 200 BC. C. to join pieces of stone in the manufacture of their constructions and their architecture.
During the reign of the Roman emperor, Caligula (37 AD – 41 AD), small pieces of prefabricated concrete were used as construction material in the area that includes present-day Naples, in Italy.
Much of the particular technology that the Romans developed was lost during the fall of their empire in the fifth century.
And it was not until 1824 that the Englishman Joseph Aspdin developed and patented portland cement, which became one of the main materials of modern concrete.
According to history, the first hollow concrete block was designed by Harmon Sylvanus Palmer in 1890 in the United States. After 10 years of experimentation, Harmon managed to patent his design in 1900.
The blocks Harmon designed measured 8 inches (20.3 cm) by 10 inches (25.4 cm) by 30 inches (76.2 cm), and were so heavy that they had to be lifted into place with a small crane.
By 1905, more than 1,500 companies were already manufacturing concrete blocks in the United States alone.
At that time, the first blocks that were made were usually made by hand, and the average production capacity was 10 pieces/blocks per hour.
Currently, the production of concrete blocks is a highly automated process that is capable of producing up to 2,000 pieces per hour.
The raw material used to manufacture cement blocks
The concrete usually used in the manufacture of concrete blocks is a mixture of water, sand, portland cement, and gravel. These components combined to produce a light gray block with a fine surface texture and high compressive strength.
Generally, the cement mix used to make blocks has a higher amount of sand and a lower amount of water and gravel than the concrete mixes used for general construction.
On the contrary, lightweight concrete blocks are made by changing gravel and sand for expanded clay, shale, or slate. These last elements are generated by crushing some raw materials and subsequently subjecting them to high temperatures close to 1093 ° C. At this temperature level, the materials swell or expand due to the rapid generation of gases caused by the combustion of matter. organic that is trapped inside.
Commonly a light or lightened block weighs between 10 and 12.7 kilos and is used to build walls, walls, and partitions that do not resist much load.
Regardless of the basic materials, the concrete mix used to make blocks can also contain some chemicals, which are known as additives. These elements help modify the curing time, increase compressive strength or workability.
It is essential that the additives comply with the IS 2185-2 “Chemical additives for concrete”.
The compound may contain added pigments to give the cement blocks a uniform color across their entire surface, or the surface of the blocks may be coated with a baked enamel to create a decorative design or to protect against chemical attacks.
The formula for making cement blocks
We already know the raw materials that are used to make cement blocks, but now we must take into account another super important part, the amount of material to be used.
Here we present a table with information to manufacture different amounts of blocks:
|Quantity||Mix M3||Water in |
|Cement||Sand||Gravel||F + G|
|60 blocks||1||40||50 Kg||150 Kg||200 Kg||0.4|
|120 blocks||2||80||100 Kg||300 Kg||400 Kg||0.4|
|240 blocks||3||160||200 Kg||600 Kg||800 Kg||0.4|
|480 blocks||4||320||400 Kg||1200 Kg||1600 Kg||0.4|
|960 blocks||5||640||800 Kg||2400 Kg||3200 Kg||0.4|
Concrete block design
The sizes and shapes of the most used blocks in the world have become a standard to guarantee the uniform construction of buildings.
That is why here we present the characteristics of the standard or most used concrete blocks:
Size of Concrete Block
The measurements or dimensions of the most common concrete blocks are standardized at 10x20x40 cm, 15x20x40 cm and 20x20x40 cm .
Similarly, some block manufacturers make some modifications available to the basic block for unique visual effects or special structural features. An example of the latter can be a block specially designed to prevent water from leaking through the surface of the exterior walls.
In this case, the block must incorporate a waterproof mixture that is capable of repelling water to reduce the absorption of the concrete.
Types of Concrete blocks
The block, being a prefabricated material, can have so many models that it would be impossible to list each one, but what we can do is classify them in a general way according to the types of blocks:
- Glasses: They are the most common model. Sometimes it is used with the holes horizontally to allow a bit of vision and give way to the air from the outside.
- Multi-chamber: The internal holes of this model are compartmentalized. These types of blocks are usually used when you want to build a single sheet wall.
- Load-bearing: They are usually more solid and are used for walls that have structural functions.
In addition, here we show you a classification of the blocks according to their finish or design:
- Normal block for lining
- solid block
- column block
- Reinforced wall block
- H type block
- Visible face block
- smooth block
- split block
- diamond point block
- Multi-chamber anti-humidity blocks
A common question among people is: How are concrete blocks made?
We tell you that for any of the cement block manufacturing modalities the stages are basically the same, below we show you a list with the process steps:
Make the Mix
- Gravel and sand are stored outside and transported to storage bins at the plant via a conveyor belt.
- Once production begins, the necessary units of portland cement, gravel, and sand are transported to a weigh batcher where the required amounts of each material are measured.
- Mixing of the dry materials is carried out for several minutes.
- After the dry materials have been mixed, a small portion of water is added to the mixer.
- The concrete is mixed for a time of 6 to 8 minutes.
- Once the concrete load has been mixed, it is poured into a bucket conveyor and transported to an elevated hopper.
- From the hopper, the concrete moves to another hopper that is located in the upper part of the block-making machine. As the material is in the block machine, the concrete is pressed down to form the molds.
- With the mixture in the mold, the concrete compaction/vibration phase begins to start forming the blocks.
- The already compacted blocks are pushed down and out of the molds onto a flat steel platform. The blocks and platforms are transferred out of the block-making machine onto a chain conveyor.
- The block platforms are transported to an automatic stacker that places them on a curing rack. When the grid is complete, they are taken to the curing oven (the most common is a low-pressure steam oven).
- In the oven, the blocks are kept for 1 to 3 hours at room temperature so that the material hardens slightly. Subsequently, steam is gradually introduced to raise the temperature at a maximum rate of 16° C per hour.
- When the proper curing temperature (66 to 74°C) is reached, the steam is turned off and the blocks are allowed to soak in the hot, moist air for 12 to 18 hours.
- Subsequently, the blocks dry by consuming all the humid air and raising the temperature of the oven even more. The entire curing process takes approximately 24 hours.
- Stacks of cured blocks are removed from the kiln and pallets of blocks are de-stacked to be placed on a chain conveyor. The blocks are then pressed out of the steel pallets and the pallets are sent back to the block-making machine to be filled with a new group of molded blocks.
- The extracted blocks go through a bucket that lines each block and then they are taken out with a forklift and stored.
Advantages of Concrete Block
- Being large in size, construction time is greatly reduced.
- It requires a smaller amount of mix to stick the blocks together.
- The thick plaster is not necessary.
- The measurements are exact and uniform, which allows building in a modular way and being certain of the amount of material needed.
- They are very resistant and highly durable.
- In the face of fire, the blocks retain their structural characteristics.
- Excellent thermal insulation: because they are thick blocks, they take a long time to heat up and cool down.
- Excellent sound insulation, for the same reason.
Disadvantages of Concrete Block
- The blocks cannot be split but must be worked whole, which makes it difficult to use them when making pipes or openings with standard measurements.
- At the time of placement, they must be absolutely dry, which means that we must find a place to store them since they must be protected from rain and night dew before being placed.
- Its price varies a lot from time to time.