A concrete block is a building material that is used to build walls. It is a pre-cast concrete product that is used in the construction industry. Pre cast means that the blocks are made and hardened before they are brought into the construction site. Concrete blocks are standard sized regular blocks that are used to make walls. They are also known as “Concrete Masonry Unit (CMU).” These blocks usually have one or more cavities and their sides may be smooth or may have a certain design. There are different types of concrete blocks available in the market.
Concrete blocks are made in plants that specializes in the manufacture of such blocks. Some of these plants are automatic while others are manual. Manually operated concrete block making machines can be installed at the project site itself. With manual machines at site, the transportation charges for the concrete blocks. Concrete blocks are manufactured in four steps:
- Selection and proportion
Concrete blocks are made up of fine and coarse aggregates, cement and water. The ingredients are firstly selected according to the requirement which will give the desired strength to the concrete blocks. The careful grading of aggregates will depend upon the strength, texture and economy of concrete blocks. Aggregates used in the making of concrete blocks includes crushed stones, gravel, furnace clinker, etc. which are selected depending on the weight, texture and composition of the unit desired. The cement that is used for making such blocks is ordinary Portland cement and the water Is normal potable water.
Once the selection and carefully matched proportion of the material is done, the second step is to mix all these materials together. The mixture of water, cement and aggregates should be done in a proper way and it is better to mix these ingredients in a mechanical mixer. If mixed using hand, one should be extremely careful while doing so.
After the mixture is made properly, the concrete mix is poured into the mold box up to the top level. Filling the box up to the top level is compulsory. Vibration of concrete is done inside the mold box until the concrete has finally settled in the box uniformly. The excess concrete is removed from the face of the mold box and levelled by using plywood. For general construction purposes, concrete mixture for concrete blocks contains higher percentage of sand and lower percentage of gravel and water. This produces a very dry, hard and stiff mixture that has no problem in holding its shape when it is removed from the mold block.
After the block is casted, it is watered for about one day. The curing process is done for minimum seven days and maximum twenty eight days. The longer the concrete blocks are cured, better will be the quality of the block.
Different types of concrete blocks
There are different types of concrete blocks available in the market today. Concrete blocks are generally divided into seven categories which are as follows:
- Solid concrete blocks
These concrete blocks are heavy in weight and have a solid appearance. These blocks are made using dense aggregates, are very strong and help make the structure very stable. Hence they are preferably used in load bearing walls. The sizes of these blocks are also much larger than the sizes of bricks and hence construction using such blocks takes very less time. Solid concrete blocks are very similar to concrete brick but are costlier and heavier in comparison to bricks. That is why they can withstand more forces that bricks.
- Hollow concrete blocks
These concrete blocks contain voids that are greater than 25% of its entire area. The solid area of the brick should be more than 50. They are made using light weight aggregates and hence are very light weight. They are also very easy to install and the voids are filled with light weight mortar as well while making a structure.
There are a total of eight types of hollow concrete blocks which are:
- Stretcher Block
- Corner Block
- Pillar Block
- Jamb Block
- Partition Block
- Lintel Block
- Frogged Brick Block
- Bull Nose Block
- Aerated auto claved concrete block (AAC)
These type of concrete blocks are usually compared with bricks and are very different in a lot of ways. These concrete blocks are larger and lighter version of bricks. They are usually made using the same ingredients as that of bricks but with a different composition. Due to this, these blocks are way cheaper than bricks. According to recent studies, these blocks have helped reduce the overall steel and concrete consumption by 15% and 10%. These blocks also, take less construction time in comparison to bricks, are fire resistant, and can adapt to various surfaces well.
- Concrete bricks
Concrete bricks are mainly small blocks that are rectangular in shape and are arranged together to create a rigid wall. These bricks are usually made of cooked clay or concrete. Some use only concrete to manufacture such bricks while others play with the cement and aggregate ratio for cost cutting purposes. These bricks are usually used in facades, fencing as they are light weight and give a very slick look.
- Paving blocks
These blocks are just rectangular or square blocks that are manufactured using reinforced concrete. They are mostly used for paving purposes, and must be painted with high visibility concrete paints so that people using vehicles can easily notice the blocks. Also, these blocks must be strong and rigid enough as they must be able to withstand vehicular and passenger weight.
These were the different types of concrete blocks that are usually used today.
Advantages and disadvantages of using concrete blocks:
- Concrete blocks are more fire resistant, provide better thermal insulation and sound absorption in comparison to bricks.
- Concrete blocks saves land of farmers that are usually used for brick manufacturing plants.
- The making of concrete blocks takes less time, is easier, faster and is stronger in comparison to bricks.
- The perfect shape of the concrete blocks makes the masonry work very simpler.
- Plastering is not needed really in concrete blocks.
- Concrete blocks are very much environmentally friendly in comparison to bricks.
- Wider and larger cracks occur in structures made using concrete blocks in comparison to bricks.
- Sometimes shrinkage occurs due to the movement of moisture in concrete blocks.
- Plumbing issues arise in concrete blocks in comparison to bricks.
Concrete blocks are slowly being used heavily and they are in fact replacing bricks and steel structures. Once we can overcome the disadvantages, it is not very far that concrete bricks will be used everywhere as they are cheaper and more environmentally friendly option.