Concrete Blocks | Construction Materials | By Ashutosh Nautiyal

Concrete Blocks

Concrete Blocks

Introduction Of Concrete Blocks:-

• Concrete block is also called a Concrete Masonry Unit (CMU).

• A Concrete block is primarily used as a building material in the construction of walls.

• A concrete masonry unit (CMU) is a standard size rectangular block used in building construction.

• A Concrete block is one of the precast concrete products used in construction.

• CMUs are some of the most versatile building products available because of the wide variety of appearances that can be achieved using them.

• Concrete blocks are produced in a large variety of shapes and sizes.

• The first hollow concrete block was designed in 1890 by Harmon S. Palmer in the United States.

• The concrete commonly used to make concrete blocks is a mixture of powdered portland cement, water, sand and gravel. 

• Concrete block construction has gained importance and has become a valid alternative to fire clay bricks.

• They can be produced manually or with the help of machines.

• Concrete blocks may be produced with hollow centres to reduce weight or improve insulation.

• The common size of concrete blocks is 39 cm * 19 cm * (30 cm or 20 cm or 10 cm) or 2 inch, 4 inch, 6 inch, 8 inch, 10 inch and 12-inch unit confirmation. 

• Most concrete blocks have one or more hollow cavities, and their sides may be cast smooth or with a design.

• In use, concrete blocks are stacked one at a time and held together with fresh concrete mortar to form the desired length and height of the wall.

• Today, concrete block manufacturing is a highly automated process that can produce up to 2000 blocks per hour.

• Most commonly used concrete blocks are sized:-

• Length- 40 cm (half blocks: 20 cm)

• Height- 20 cm 

• Width - 8/10/15/20 cm 

Concrete Blocks

• Solid concrete blocks have no cavities or according to the US standards have no voids amounting to not more than 25% of the gross cross-sectional area.

• Hollow concrete blocks are the most common type of concrete blocks which are having one or more holes that are open at both sides.

• The total void area for hollow blocks can amount to 50% of the gross cross-sectional area.

Advantages Of Concrete Blocks:-

Technical Advantages:-

Solid Blocks:-

• They have high compressive strength, resistance to weathering, impact and abrasion.

• They have the capability of being moulded into components of any shape and size.

• They have good fire resistance up to about 400°C.

• They facilitate rapid construction. 

• They are having very good stability.

Hollow Blocks:- 

• They can be made larger than the solid blocks.

• They are lighter in weight.

• They facilitate easy and quick construction of walls.

• Their voids can be filled with steel bars and concrete because of which they acquire high earthquake resistance.

• The air space in them provides good thermal insulation.

• The cavities in them can be used for electrical installation for pumping.

Economic Advantages:-

• The production of concrete blocks can be started with little capital.

• With concrete blocks, less working time is required for bricklaying work.

• There is less mortar consumption with concrete blocks.

• Generally, the production cost of concrete blocks is slightly lower than that of fire bricks.

Limits Of Applications Of Concrete Blocks:-

• Raw materials of good quality and economically feasible must be locally available.

• A relatively large amount of cement is needed, which can be expensive and difficult to obtain.

• Special knowledge and experience of the production process are needed.

Raw Materials For Concrete Blocks:- 

Cement:- 

• Ordinary Portland Cement 

• Special cements

Aggregate:-

• Sand or gravel

• The maximum particle size of the coarser aggregate is 10 mm.

• Suitable aggregates are usually obtained from natural sources(river bed, gravel pits, volcanic deposits) or from industrial by-processes(granulated blast furnace slag, sintered fly ash).

Cement-Aggregate Ratio:-

• A suitable proportion of aggregate to cement must be found by testing.

• Common ratios are 1:6 and 1:8.

• Test the quality of blocks produced.

Water-Cement Ratio:-

• Only drinking quality water should be used to mix the concrete.

• Recommended water-cement ratio is 0.5.

Equipment Used For Production Process Of Concrete Blocks:-

• Masonry tools

• Mixers: Pan mixers; Trough mixers

• Blockmaking machine: Hand-operated; "Egg-laying" mobile machines; fully mechanised stationary machines.

Production Process Of Concrete Blocks:-

Batching And Mixing:-

• Batch aggregates and cement by weight.

• Mix cement and aggregates using mattock, shovel or mixer until it reaches homogeneous condition.

• Add some water.

• In hot climates, the fresh mix must be shaded from the sun.

Moulding:-

• Put the mixture into wooden or steel mould boxes or moulding machine.

• Demould blocks immediately after compaction.

Curing:- 

• Cover the demoulded bricks with plastic sheets for 24 hours.

• Keep the concrete blocks moist by keeping underwater in tanks or by regularly spraying with water for 7 days.

Storing:- 

• Don't expose to direct sunlight; keep the blocks in a dry and covered area.

• Store for 2 weeks before using.

Skills Required For Production Process:-

• Concrete making and masonry skills. 

Lightweight Concrete Blocks

• Lightweight concrete block is a concrete masonry unit(CMU) made of expanded aggregate to reduce the density and weight compared to standard concrete blocks.

• Lightweight concrete blocks are made by replacing the sand and gravel with expanded clay, shale, or slate. 

• The light weight concrete blocks can help reduce heavy lifting and carrying by minimizing the weight of the concrete blocks that must be lifted and carried during brick-laying tasks.

• Using lightweight concrete block reduces strain and loading on mason's backs.

*Self Typed
*Source- Internet, Books, Self-Analysis