green-concrete

Everything About Green Concrete

Green Concrete is an alternative for conservative or typical concrete. So what is this green concrete? More importantly, why do we need it?

As the construction industry grows rapidly, new construction technologies emerge. Since the millennials are very much concerned about concepts like green constructions, these technologies tend to lean towards sustainability. Thus, most of the modern architectural trends are aiming towards sustainable concepts. In the setting of that, comes green concrete.

In simple terms, green concrete is the composite material that is made with concrete waste that is eco-friendly. Does this mean conventional concrete is not eco-friendly? In order to produce conventional concrete, we need to have new cement and aggregates. This creates a huge environmental impact, along with the increasing demand for concrete. Replacing cement and aggregate (conventional constituents of concrete) can help in minimizing the environmental impact caused during their manufacturing process.

What are the environmental benefits of green concrete?

Reduced carbon emission

In the process of making Portland cement, the main ingredients (limestone, clay, and sand) are heated to 1450°C. This process is responsible for 5% to 8% of all CO₂ emissions worldwide. In contrast, manufacturing green concrete has up to 80% lesser CO₂ emission. This is a big step people have to take if they want to protect the environment.

Reduced energy consumption

In the process of manufacturing Portland cement, it requires a huge amount of coal or natural gases to heat it up. But using less cement and more fly ash when mixing concrete, use less energy. (this will be discussed further in next chapters).

Using industrial waste

Instead of a 100% Portland cement mixture, green concrete uses anywhere from 25% to 100% fly ash. Fly ash is a byproduct of coal combustion. It is gathered from the chimneys of industrial plants (such as power plants) which use coal as a power source. This industrial waste product is available in abundance. Hundreds of thousands of acres of land are used to dispose of fly ash. A large increment in using green concrete will introduce new ways to use fly ash, and hopefully free many acres of land.

Conservation of water resources and natural habitats

As stated by Winfield and Taylor (2005), the excavations of minerals for the cement manufacturing and aggregates for the concrete changes the slope of the land and vegetation. This changes the drainage system. Furthermore, aggregate deposits behave as underground water reservoirs. Well, excavating them? You can imagine the rest. It obviously makes a major impact on the water table.

Related article: What is Low Impact Development

As mentioned earlier, the materials that are used to manufacture green concrete are different from those of conventional concrete. The three main ingredients that are used in conventional concrete are replaced as follows.

Traditional ingredientsReplacement material for concrete
01CementSolid fly ash, sludge ash, recycled glass, silica fumes
02Coarse Aggregates (Metal)Recycle wastes, waste ready mix concrete, waste glass
03Fine Aggregates (Sand)Fine recycled aggregates, demolished brick waste, Quarry dust, marble powder waste

As you see here almost every ingredient used in the process of manufacturing this industrial material is cheap and also eco-friendly. But how does it bode well for the construction industry?

What are the economic benefits of green concrete?

Durability

When compared with Portland cement, green concrete gains the strength faster and lowers the shrinking rate. Hence its structural durability is higher than in the normal concrete. Furthermore, when it comes to corrosion, it can withstand corrosion better than traditional concrete would.

Fire resistance

Concrete made using an industrial by-product or in a simple manner, green concrete has shown better fire endurance than traditional concrete when exposed to fires of nearly 1000°C. In a fire emergency, it is important that the structure does not collapse.

Minimum rebuilt or reconstruct cost

Since the structures or buildings that are made with green concrete has high durability and because of that, the occurrences of repairing is considerably low.

So, if everything is perfect with this material, why aren’t people using it everywhere? That is simply because even Superman has a weakness. So what is the catch of using green concrete? What are its limitations?

Limitations of green concrete

  • The main limitation or disadvantage of using green concrete is that the structures which are constructed using green concrete have less life than the structures constructed by conventional concrete. As they have less life span they cannot be used for important structures like dams, bridges, etc. For the use in dams and bridges, special air-entraining agents are mixed in the concrete which increases the overall cost of the structures.
  • The split tensile strength of the green concrete is less than in the conventional concrete. Thus more reinforcements are needed, which increases the construction cost of the structure.
  • Water absorption to green concrete is slightly higher than the conventional concrete. Hence the structures that are built with green concrete need to have proper protection from water.

With the current situation of our world, we are in desperate need of a healthy environment. But living in a naturalistic environment should not mean that we need to live like cavemen. We can move along with nature as well as technical advancement if we make eco-friendly decisions. And when considering the construction industry, green concrete is one of those major trends that we should follow. Start choosing green concepts, and help to make this world sustainable.

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S. Herath
Landscape Architect Department, University of Moratuwa
Articles: 7

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