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
- 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:-
- 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.
- 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.
- 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:-
- Ordinary Portland Cement
- Special cements
- 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).
- 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.
- 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.
- Put the mixture into wooden or steel mould boxes or moulding machine.
- Demould blocks immediately after compaction.
- 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.
- 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.
*Source- Internet, Books, Self-Analysis