What is Green Concrete? 7 Important Point

Green concrete is an eco-friendly sustainable concrete that can act as a substitution for traditional concrete by using recycled materials to produce similar properties to traditional concrete with less production of carbon dioxide during the process.

Who Invented Green Concrete?

In 1998, Dr WG from Denmark invented this concept of green concrete and it gains popularity over time as it has various environmental benefits. The increased demand for cement production on a global level is accountable for more than 6% (1)of CO2 emissions around the world. Green concrete helps in reducing CO2 emissions to a greater extent.

What is Green Concrete Made of?

All the materials that are used to produce green concrete should be eco-friendly and releases less energy during the manufacturing process. The rationale behind selecting the materials for green concrete involves the following aspects:

Local abundance:

The materials that are used for green concrete should be locally available in significantly higher quantities so that the overall lead and lift for the materials can be reduced.

Reused/Recycled:

The selected materials should be reused or recycled materials so that overall production cost will be reduced, and the amount of energy produced also can be significantly put down. The selected materials should have all the cementitious properties which traditional concrete consists of within a similar cost.

The materials that are used for the manufacturing process are listed below.

Recycled waste aggregate
Recycled concrete aggregate.
Blast furnace slag.
Manufactured sand
Glass aggregate
Fly ash

How to make Green Concrete?

The process of manufacturing green concrete is similar to traditional concrete only but some proportion of ordinary Portland cement can be replaced by various cementitious materials with varying percentage shares. They are discussed in detail in the below sections.

The methodology adopted for the manufacturing of green concrete is depicted below.

Flow Diagram for Green concrete

Flow Diagram for Green concrete

Process for Green concrete:

The entire process for green concrete starts with the production of traditional concrete. By using the various cementitious materials, coarse aggregate, sand, and water in the required proportions concrete will be manufactured.
This produced concrete is used for various purposes like bridges, buildings, highways based on the requirement.
When these structures are exposed to demolition, the waste materials are collected and used as recycled concrete.
From the collected waste material, the aggregate can be separated as per the size requirements and can be used along with various other recycled materials to produce green concrete.
Based on the availability of various cementitious materials like ground granulated blast furnace slag (GGBS), fly ash, silica fume/micro silica, fibreglass etc., can be added as per the required proportions (Percentage V/V) to form the green concrete.

Why is Green Concrete used?

Green concrete is having various environmental benefits which increase its usage in modern times. Following are the various benefits of using green concrete:

Increases the life of concrete structures/ elements when equated to traditional concrete.
Increases the compressive strength of concrete for a min of 20% after 90 days of casting.
As it is sustainable concrete it has better resistance to salts or sulphates than traditional concrete.
Green concrete has better workability equated to traditional concrete and reduces the rate of cracking effectively.
Reduces the moisture & water permeability in concrete, therefore, reducing the rusting of reinforcement.
Improves the degree of thermal insulation & fire resistance of concrete to a greater extent.
Reduces the amount of CO2 emission by around 80% as contrasted to traditional concrete.
Usage of less cement leads to the generation of less heat of hydration contrasted to traditional concrete.
It has a higher modulus of elasticity as equated to traditional concrete.

What are the other forms of eco-friendly concrete?

There are various other forms of Eco-friendly concrete in which some portion of the ordinary Portland cement is replaced by other cementitious materials and are listed below.

Ashcrete:

Ashcrete can be utilized as a substitute for traditional concrete in which large quantities of fly ash are treated as a cementitious material. This is the by-product of burning coal in electric power generating plants. It is generally used as a partial substitute for 25 to 55% of the normal Portland cement.

Fly ash is mixed with water and a certain amount of lime to make strong and eco-friendly concrete that has similar properties as traditional concrete. By applying the fly ash in Ashcrete makes it further resistant to alkali-silica reactivity, increases the strength of concrete, reduced the bleeding, and reduces shrinkage when contrasted to traditional concrete.

Ground granulated blast furnace slag (GGBS):

Ground granulated blast furnace slag is also called slag cement and it is a by-product of the steel industry. It can be commonly used as a partial substitute for ordinary Portland cement up to 80% of concrete. This produces less amount of heat of hydration during its production.

Micro silica/Silica fume:

Micro silica can also be called Silica fume which is the by-product that comes from the electric furnace which is used in the production of silicon alloy. It can be applied up to 5 to 10 % as a replacement for normal Portland cement. Micro silica enhances the durability of concrete by increasing the compressive strength of concrete plus making it less preamble for moisture content.

Concrete made using micro silica are mainly used for structures that will be exposed to highly concentrated chemicals.

Fibrous Concrete/Fiber Glass:

Very fine materials of fibres of glass will make up fibreglass which can act as a substitute for ordinary Portland cement but to a very minimal extent up to 0.1 to 3%. By the implementation of fibrous material in concrete the flexural strength could be increased significantly as contrasted to the traditional concrete.

All these percentage shares by which they can be utilized as a replacement for OPC are mentioned in table A.6 of the British standard BS 8500 part1, 2006.

Applications of Green concrete?

Green concrete has a wide range of applications and some of them are listed below.

It can be widely used in Highways (mainly bridges)
It can be used in the construction of structural columns.
It can be used in building construction.

I hope the blog provides you with adequate knowledge of Green Concrete and its associated features. Please feel free to like, share and comment.

P. Dinesh Kumar
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Please see our Pillar Post to know why we founded gcelab.com.

References:

(1) https://www.ijert.org/research/green-concrete-for-the-future-a-review-IJERTCONV4IS08011.pdf

(2) https://www.specifyconcrete.org/blog/eco-friendly-alternatives-to-traditional-concrete

(3)https://www.sciencedirect.com/science/article/pii/

(4) http://data.conferenceworld.in/IIMT2017/P270-274.pdf

(5) https://madhavuniversity.edu.in/green-concrete.html

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What is Green Concrete? 7 Important Point