Replacement Of Coarse Aggregate In Concrete

Every material usage by the urban population affects nature and makes scarcity. 

For example, take petroleum. It takes quite a long time to get crude oil likely 50 million years. In just 50 years we are going to run out of it. So humanity is moving to another energy resource.

Like this, every construction material used in the construction industry has a significant impact on the environmental condition and will run out soon. 

What is coarse aggregate?

Aggregates are classified into two broad categories.

• Fine aggregate
• Coarse aggregate

When the aggregate particle is not passed through the 4.75mm sieve as per IS standard is called coarse aggregate. The size of fine aggregate particles is less than 4.75mm. 

Why is the replacement material required instead of coarse aggregate?

The cement, sand & coarse aggregates are the vital material in construction.

At present, a structure can not be constructed without those materials. In concrete, the aggregate occupies 75% to 80% of its total volume due to its strength.

As you all know from our previous topic classification of aggregates, Aggregates are derived from river banks, and nature formed rocks. Do you know how many years it would take a rock to be developed? Millions of Years…

So experts are desperately looking for a suitable alternative for coarse aggregate—the low cost and lightweight, which does not affect nature much.

• We have already started using M sand instead of river sand.
• The natural or synthetic lightweight aggregates make lightweight concrete. It is a low cost along with excellent durability.

When we use alternative material in construction, it may speed up the progress at a low cost.

What Are The Materials That Can Be Replaced As Coarse Aggregate In Concrete?

Possibilities are endless; many researchers have already found a handful for replacing the coarse aggregate.

• Coconut Shell
• E-waste Partial Replacement 
• Construction waste material
• Plastic waste Partial Replacement 
• Quarry dust For Partial Replacement 

Coconut Shell

The coconut shell can be used as a coarse aggregate in concrete. It has functional resistance capacity against crushing, impact & abrasion.

There is no special treatment required for coconut shells when used as coarse aggregate in concrete. The coconut shell can be easily crushed into particles, and it is economically best to transport the material.

The chemical composition of coconut shells is listed in the below table.

E-waste For Partial Replacement 

E-Waste, another major threat to the world with its large volume of dump to dispose of. 

We are running out of land to dispose of them. Experts are trying hard to get rid of it.

What is E-waste? – Simple, all electronic items have a lifetime after that we have thrown that away, so that is called E-Waste (TV, laptop, CD, Pen drive, etc.)

Using the E-waste as a partial replacement of coarse aggregate in concrete is the best solution. 

• We can not fully replace material in concrete because it impacts the workability of concrete.
• The electronic waste is crushed as required particle size and can be mixed with other aggregates in concrete which will not affect the quality & durability of the concrete.

The partial e-waste concrete also named E-crete concrete. 

Construction Waste Material

The construction waste material is also very suitable for replacing the coarse aggregate in concrete.

It contains mostly the demolished building pieces like a portion of slab, beam, column & masonry elements.

Moreover, some materials are wasted while construction works like bricks pieces, stone pieces, etc., those materials will perform well with concrete. 

We are already using broken bricks as brickbat coba (weatherproof) on the terrace.

Plastic Waste For Partial Replacement 

Like E-Waste, plastic waste is also a significant threat to humanity & the environment. Dumping it into the sea makes the seawater too contaminated. Plastic waste severely affects the environment. 

So recycling plastic waste into construction is the best technique to get rid of it. 

• The plastic material should be clean & free from dust or other impurities to use in concrete.  
• The workability of concrete is excellent when using plastic waste. 
• Mostly the plastic aggregates were used in road construction work. It is mixed with the asphalt to make the road.

Already so many projects have been done in this method.

Quarry dust For Partial Replacement 

The bricks, tile & other lightweight materials are made from the quarry dust.

• The chemical composition of quarry dust is mostly the same as granite rock. So the strength and durability of quarry dust are good to use in concrete. 
• The concrete will have high compressive strength when using quarry dust in concrete, the compressive strength also increases.

We have already started using quarry dust in our construction process, such as sand beds.

Glass Particles

• The crushed glass particles may be used in concrete partially instead of granite rock. 
• The workability & compressive strength will reduce when using waste glass particles. So the glass concrete may be used in filler areas like deck slabs.

Tests To Be Conducted To Find Successful Coarse Aggregate Replacement

We cannot merely replace the coarse aggregate with any other materials. To get a successful replacement of coarse aggregate, it must satisfy the below points

• It should have the characteristics of coarse aggregate
• It should withstand all the coarse aggregate tests
• It should not be harmful to nature

As per the Indian standard IS Code, we have to make sure the new product passes all the below tests. Once satisfied then it can be used as a replacement.

Advantages & Disadvantages of the Replacement

Advantages

• Eco-friendly
• Reduces Waste Material
• Usage of Natural Resources will be reduced
• Economical Products will be available for construction

Disadvantages

• More material tests are required.
• The strength of the structure may reduce.
• More maintenance work required to increase the life of a structure.

Happy Learning 🙂