Energy Literacy Series:
Green Concrete Jungle
According to the United States Geological Survey cement statistics, China has used more cement in the past three years than the United States of America used in the entire 20th century.
As important as cement is, the manufacturing process is also a major cause of industrial air pollution. The production of clinker, a key ingredient in cement, is a chief source of emission of noxious gases, especially carbon dioxide.
In the cement manufacturing process, a mixture of limestone and clayey materials is fed to a kiln operating at 1400⁰C. After the thermal process, the processed material is ground, forming a lumpy and solid substance known as clinker. Finally, gypsum is mixed with clinker, forming cement.
The clinker production process is highly energy-intensive and releases gaseous effluents. For 1 tonne of cement produced, 0.6 to 1 tonne of carbon dioxide is released. In addition to clinker production, there are other processes in cement manufacture that give off CO2. But cement is so indispensable in all walks of life; it is hard to imagine a world without cement production.
Can there be a viable substitute for cement?
ENTER GREEN CEMENT
With the world having agreed in Paris to try and limit global warming to no more than 2℃, every sector of industry needs to do its part.
As an initiative to bring down the threats produced by emission, the manufacturing process of cement can be suitably altered to bring down the emission levels significantly. Green cement is a form of cement produced with the help of a “carbon-negative manufacturing process.”
In other words, cement produced as the final product of a technologically advanced process, such that emissions during unit operations (like clinker production) are minimized, is referred to as green cement. Green cement is an eco-friendly product which resolves serious environmental issues and minimizes the carbon footprint of cement production.
The prefix green before green cement represents anything that is environment-friendly or contributes to making the environment greener.
PROS OF GREEN CEMENT
Makes Use of Industrial Waste
Fly ash, a by-product of coal combustion, is produced in large quantities in industrial plants. Typically, several acres of land are used to dispose of it. Green cement not only makes use of the fly ash waste, but also protects land from becoming a dumping ground and ultimately being destroyed. Apart from fly ash, green cement also uses blast furnace slag (a by-product of iron manufacturing), which can produce harmful environmental effects if it is simply discarded.
Requires Less Energy
The materials used in the traditional cement manufacturing process require large amounts of natural gas / coal for heating purposes. Because green cement already contains industrial by-products, the energy needed in production is greatly reduced. Also, unlike Portland cement, green cement is more resistant to changes in temperature, therefore reducing the costs associated with both heating and cooling.
Lowers Carbon Dioxide Emission
Clay, sand, and pulverized limestone are some of the key ingredients used in traditional cement. These ingredients require heat, releasing approximately 5% – 8% of the total global carbon dioxide. Green cement, on the other hand, does not require as much heat during its production, releasing up to 80% less carbon dioxide.
Beneficial For/To Contractors
From a commercial standpoint, green cement tends to be more beneficial for contractors than traditional cement. This is because green cement does not require extra tools or equipment and eliminates the risk of cement burns. Also, since green concrete is self-drying, a coating can be applied as early as 72-96 hours.
This allows contractors to save time and prevent the loss of other projects. Further, green cement has an enhanced curing rate and strengthens very quickly, facilitating faster vertical construction, thus reducing construction time and increasing the rate of return when it comes to industrial assets.
Green concrete has a lower shrinkage rate and also becomes stronger far more quickly than concrete made with traditional cement. And since green concrete can withstand temperatures as high as 2400oF, it makes buildings significantly more fire-resistant. Green concrete can also withstand acid rain, thereby reducing the risk of corrosion.
CONS OF GREEN CEMENT
Lack of Trust
The major obstacle to the production and use of Green Cement is history. Portland cement works. People trust that. They can look around at all the buildings that have survived hundreds of years. So for Green Cement, the proof of durability will take time.
Varying Production Methods
Many companies are still working with different blends of Portland cement to try and create a sustainable alternative.
Since the realisation that it is difficult to modify traditional Portland cement to be eco-friendly, many new companies have sprung up, trying to rewrite the rule book on cement production.
Given the modernity of the green cement sector, it is difficult to judge which, if indeed any, of these new methods of cement production will be successful. All have benefits to the environment relative to Portland cement, but all equally have other issues, such as production costs or material integrity.
In addition to this, not enough research has yet been undertaken to understand what the potential environmental issues with these new production methods could be.
High Cost of Production
Manufacturers and consumers often consider it a financially risky venture to invest in an innovative product or production technology. Significant changes in industrial set-ups also lead to raised financial expenses.
The national governments need to support green cement production for meeting construction requirements. Manufacturing companies and investors must be given incentives for adopting green cement manufacturing processes.
Impact of Technological Change on Labour
The use of the machine increases the efficiency and performance by eliminating human errors and risk factor. This destroys jobs for unskilled labour.
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