Concrete Block as a Building Material: Uses | Types | Pros & Cons!
Janvi Desai is a Civil Engineer (BE). She graduated from Government Engineering College – Bharuch in 2017. She is an Engineer (Civil) at SDCPL – Gharpedia. She is passionate about research and study of latest developments. You can easily reach her via LinkedIn, Facebook, Twitter, Instagram, Pinterest. Besides being blogger, she also participates in quantity survey, site management, design & detailing.
For centuries, people have transformed and adapted many god-given structures, such as caves to their homes, long before they embarked on a journey to create abode for themselves.
With the onset of civilisation, people began to settle & build their own residences. These differed drastically based not only on people’s origin, taste or culture but also on the easily available materials and environment around them.
Similarly, a building is just NOT a house for people living in. It is much more than that. It has many components which gives the building its character, strength, safety & identity, like its foundation, wall, floor, stair, roof, etc.
The space thus created in a building gets divided into different categories based on its end usage, like living room, bedroom, kitchen, bathroom, washroom, etc., accomplished by various kind of masonry work.
The term masonry primarily refers to construction of walls with the use of bricks or stones & mortar. A masonry structure thus gets erected either in varying combination of blocks, bricks, stones, etc. or sometimes with some exclusive preferred stock as its building material. Not that these are the ONLY materials that contributes in creating a long lasting structure. Sometimes wood, steel or concrete is also used extensively for fabricating a building.
Some major masonry unit types are:
- Natural Stones
- Clay Bricks
- Fly Ash Bricks
- Concrete Blocks
The concrete blocks are used extensively now a days as the normal clay bricks are not environment friendly. Let us check out everything we can about Concrete Blocks.
What is a Concrete Block?
As per the definition given by ‘David Blockley’ (Author of New Dictionary of Civil Engineering), a Concrete Block is a ‘Building Block’ made entirely of concrete, which is then bonded together with Mortar to form an imposing long-lasting structure. These building blocks may be ‘Hollow’ or ‘Solid’ constructed either of ordinary or lightweight concrete in various standardised sizes, depending on specific requirement/s.
Such Concrete Blocks can be used as a masonry unit for load-bearing walls, partitions or panel walls. These are used in an area where brick or stones of suitable quality & strength necessary for masonry are not readily available, but required aggregates are that much easily accessible.
Types of Concrete Blocks
These Concrete Blocks are further categorised as:
01. Solid Concrete Blocks
02. Hollow Concrete Blocks
Hollow Concrete Blocks are more frequently used than the solid ones because:
- They reduce overall weight and thus are easier to handle
- They can be grouted and reinforced, yet meets demanding structural requirements easily
Solid Concrete Blocks are rare in its day-to-day usage because of its added mass. It calls for special needs, wants & requirements, such as Higher Fire Resistance, where Sound Absorption is a criteria or where being impenetrable is of paramount importance.
Let us know a bit more about each category in detail:
01. Solid Concrete Blocks
A block which has more than 75% of the total mass filled up with concrete, of the overall dimensions is categorised as Solid Concrete Block. It is also known as Concrete Brick.
02. Hollow Concrete Blocks
A Concrete Block having solid material only between 50-70% of the total volume, calculated from the overall dimensions is categorised as a Hollow Concrete Block. Hollow Concrete Blocks have one or more large ‘Holes’ or ‘Cavities’, which either passes through the Block (open cavity) or just might been made to reduce the mass but not at the cost of its strength (closed cavity).
Hollow Concrete Blocks are further classified into two categories, viz Grade A & Grade B. This Grade B category is sometimes referred to as Cinder Block, as the Cinder is the aggregate more often used in its material base.
The Hollow Concrete Blocks presently available in the market varies greatly in shape & size. These are often used according to its location or position in the wall. These are Concrete Stretcher Blocks, Lintel Blocks, Partition Concrete Blocks, Concrete Pillar Blocks, Corner Concrete Blocks, Jamb Concrete Blocks, Bullnose Concrete Blocks, Frogged Brick Blocks, etc.
Advantages of Concrete Blocks:
- Makes the room larger by increasing the carpet area because of the reduced wall thickness due to narrower Concrete Blocks than the conventional brick masonry wall. [6” (150 mm) or 8” (200 mm) as against 9” (230 mm)
- Provides better thermal insulation
- Protects the interiors against noise pollution, as it absorbs the sound better
- Gives added protection against fire
- Protects invaluable agricultural land, which otherwise would have been excavated extensively for manufacturing clay bricks
- Construction with Concrete Block is more systematic, faster & stronger, as compared to the brick masonry due to the large size of blocks.
- Individual units can be made to larger custom size & shape, ensuring quick turnaround in construction cycle With fewer joints mortar consumption rate reduces, as compared to standard masonry construction, yet enhances the overall strength of the building
- Unlike conventional bricks, Concrete Blocks’ uniform size cuts down on plaster usage, hence becomes economically viable alternative
Of course, other than these obvious ones, there are some more advantages & disadvantages of Concrete Blocks, which are as given below.
Advantages of Solid Concrete Blocks:
- Comparatively easier to design Solid Concrete Blocks
- These Blocks are highly resistive to extreme weather conditions, like high winds, storms, floods, etc.
Advantages of Hollow Concrete Blocks:
- Hollow Concrete Blocks requires no additional formwork or any special construction machinery for reinforcement
- Semi-skilled labour can do just fine
Disadvantages of Concrete Blocks:
- If the required raw materials are not readily available then this becomes an expensive proposition
- For fast & steady production of Concrete Blocks, labour needs to be experienced & skilled
Disadvantages of Solid Concrete Blocks:
- Concealed wiring, plumbing becomes a tad difficult to make
Disadvantages of Hollow Concrete Blocks:
- During earthquakes, a structure built using Hollow Concrete Blocks without any internal reinforcement is more likely to sustain damage
Uses of Concrete Blocks
With these set of advantages, the Concrete Blocks are ideal for mass housing and various civil engineering projects. Some of the few applications where Concrete Blocks excel are:
01. Concrete Blocks for Building Walls
Partition walls benefit hugely by adopting usage of Concrete Blocks, for quick and easy installation. With steel reinforcement this provides additional strength to the structure.
Solid Concrete Blocks are ideal for construction of Chimney & Fireplaces, yet they equally excel at Non-load Bearing Walls & Garden Walls.
Hollow Concrete Blocks are widely used for Exterior & Interior Load-bearing Walls, Partition Walls, Panel Walls, Boundary Walls, etc.
02. Concrete Blocks Used for the Formation of Material Bin
Concrete Blocks can protect the stored materials from different climatic conditions. No wonder, it remains engineers’ choice for the formation of Material Bins. It helps in keeping the materials isolated from one another, which is just the reason why construction companies choose to employ this. They use these Concrete Blocks to store material for long-term – like rock, aggregate, etc.
03. Concrete Blocks Used in Landscape Projects
The Concrete Blocks are also used in many small Landscape Projects. For example, in Outdoor Seating, Decorative Screen, Outdoor Bar, Flower Bed, many Outdoor Furniture & Patio designs.
Properties of Concrete Blocks
The various properties of Concrete Blocks are:
The dimension is the size of Blocks in terms of Length, Width & Height. Concrete Blocks are referred by its nominal dimensions. The term ‘nominal’ means dimensions that include the thickness of mortar joints. Actual dimensions (Length and Height only) have to be 10 mm short of the nominal dimensions.
For example, a 400 mm X 200 mm X 200 mm Block has an actual Length, Width and Height proportion of 390 mm, 200 mm and 190mm respectively.
As per the Indian Standard Code 2185 – Part 1, The nominal dimensions of Concrete Block are:
Length: 400, 500 or 600 mm
Width: 50, 75, 100, 150, 200, 250 or 300 mm
Height: 100 or 200 mm
Other than the above mentioned Concrete Block sizes, they tend to differ vastly based on the mutual agreement between the purchaser and the supplier.
Density is the mass per unit volume of a substance. It is a parameter for describing the material and form of a mass in the presence of gravity. The density of Concrete Blocks is:
Solid Concrete Blocks -1,800 kg/m3 (Minimum)
Hollow Concrete Blocks
Grade A – 1,500 kg/m3 (Minimum)
Grade B – 1,100 kg/m3 and 1,500 kg/m3
03. Compressive Strength
Compressive strength is the ability of a material to withstand compression. The minimum average compressive strength of Concrete Blocks is:
Solid Concrete Blocks– 4.0 and 5.0 N/mm2 respectively at 28 days
Hollow Concrete Blocks
Grade A – 3.5, 4.5, 5.5, 7.0, 8.5, 10.0, 12.5 and 15.0 N/mm2 respectively at 28 days
Grade B – 3.5 and 5.0 N/mm2 respectively at 28 days
04. Water Absorption
Water Absorption is the ability of material to absorb and retain water. The water absorption of Concrete Blocks should be less than 10% by mass.
05. Drying Shrinkage
The drying shrinkage of Concrete Blocks should be less than 0.06%.
06. Moisture Movement
The moisture movement occurs because materials often expand or contract due to the effect of swelling and shrinkage. The moisture movement of Concrete Blocks should be less than 0.09%.
Raw Materials for Concrete Blocks Manufacturing
The basic materials required for the production of Concrete Blocks are:
The types of cement used for manufacturing Concrete Blocks are Portland Cement, Portland Slag Cement, Portland Pozzolana Cement, etc. It should conform to its respective standard codes.
For more detail about cement you can read our blog: Cement Widely Used Building Material | All the Basic Info You Need to Know!
The aggregate of various types have been used with varying degree of success, and they include gravel, cinder, clinker, crushed stones, etc. The aggregates are selected on virtue of its weight, texture or composition of a unit designed.
The strength, texture and price of Concrete Block depends on the careful grading of the aggregate. The classification of the combined aggregate shall conform to the requirements of Indian Standard Code 383. The locally available aggregate is but naturally economical.
The potable water is the basic necessity in the manufacturing process of Concrete Blocks.
Additives or Admixtures
Additives or admixtures may be added either as admixtures to the concrete mix or as additives to the cement during its manufacturing process. Additives or admixtures used in the production of Concrete Masonry Units are:
- Water reducing, accelerating, air-entraining and super plasticizers conforming to Indian Standard Code 9103
- Waterproofing agents conforming to Indian Standard Code 2645
Where no applicable Indian Standards are available, the additives or admixtures shall be used based on ASTM or British Standard.
Manufacturing Process of Concrete Blocks
The production of Concrete Blocks consists of following basic stages,
The proportion of the material is taken as per the Indian Standard Code 2185 – Part 1 or as per the strength needed.
Batching of the ingredients should be done accurately and mixing shall be done in a mixture to achieve homogeneous mix. It shall be continued until there is a uniform distribution of the materials.
The Block should be compacted by vibro compaction and finished to the proper size without any broken edges.
The Blocks shall be cured in a curing water tank or curing yard and should be kept continuously moist for at least 14 days. When the Blocks are cured in an immersion tank, the water of the tank should be replaced at least every 4 days.
After curing, the Blocks are dried for 2/3 weeks and then only, they become fit to use for various purposes. If you do not follow its, shrinkage cracks are likely to appear in walls.
Manufacturing of Concrete Blocks
The fully automatic plants are available for the production of high strength Concrete Blocks. These automatic machines produce superior quality of Concrete Blocks, but they involve significant capital investment.
The manually operated machines are also available and can even be installed at the project site. This will reduce the transportation cost of the Concrete Blocks from the place of production to the place of actual use.
As mentioned earlier, there are a large variety of masonry units from which an architect, owner or engineer can choose the most suited for a particular situation. According to Handbook on Masonry Design and Construction – SP 20, the primary consideration in choosing particular unit are Availability, Strength Requirement, Durability, Dimensional Stability, Resistance to Rain Penetration, Fire Rating, Thermal Properties, Style of Architecture and of course – Economy in Cost.
Concrete Blocks are extensively used in building construction throughout the country. Its properties such as Durability, Strength & Structural Stability, Fire Resistance, Insulation and Sound Absorption make it suitable for various types of applications.
Concrete Blocks are suitable in areas where brick or stone of adequate quality for masonry are not available at a reasonable cost. If proper variety of aggregates are available for manufacturing, they are used for masonry unit for Blocks which can be used for load-bearing or even non load-bearing walls, partitions and panel walls.
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