This article will answer the question “Why is concrete not sustainable?” and will ponder on topics such as its manufacturing process, its contribution to different types of environmental pollution, and the future of construction using green building materials.
Why is concrete not sustainable?
Concrete is not sustainable because its production emits large amounts of anthropogenic carbon dioxide (CO2). Approximately 2.8 billion tonnes of CO2 is released each year as a by-product of making cement, the key material in concrete. Concrete industry is the third ranking producer of CO2 in the world next to transport and energy generation.
There are also adverse effects of continuous use of concrete in land and water. Concrete contributes to land degradation by covering the fertile soil with hard surfaces which alter the healthy ecosystem. Moreover, most concrete cannot absorb a big volume of stormwater leading to surface runoff that can cause flooding, soil erosion, and eventually, water pollution.
Cement as Key Component of Concrete
The terms cement and concrete are often used interchangeably, pertaining to the heavy, rough construction material in buildings, roads, bridges, etc. However, they are not quite the same. Cement is a gray powder made from calcined lime and clay. In contrast, concrete is a mixture of gravel, sand, water and cement. Cement is the key component in concrete that makes the materials hard and adhere to each other, also known as curing.
Concrete for Industrial Construction
Concrete is one of the most famous building materials in the world. In fact, it is the second most consumed material on earth next to water. As the world advances with technology, infrastructural development also aims to fortify structures for industry, energy, transport, healthcare and education, thus, the use of concrete.
There are many good qualities of concrete that make it the foundation of industrialization. It is strong, affordable, long-lasting and easily adaptable to many designs. It does not easily burn, rot or rust. It is an excellent thermal sink that absorbs and retains heat for hot and cold weather. Raw materials of concrete are also abundant around the world making it accessible to many countries.
Cement Production
Cement is only one of the components of concrete. To manufacture cement, limestone, clay and sand are the raw materials ground into powder and heated in a 1500°C kiln to form pellets, also known as clinkers. The clinker is then mixed with gypsum and ground into fine powder forming cement. The most common type of cement is the portland cement with more than 95% of the cement market.
Greenhouse Gases
The greenhouse gas CO2 is one of the undesirable by-products of cement production. It is produced at two points in the process. First point of CO2 release is during the burning of fossil fuels to achieve the very high temperature in the kiln. Second point is during thermal decomposition of calcium carbonate in producing clinker. Majority of CO2 output comes from the second point of production, the decarbonation, which accounts for 70% of the total CO2.
Production of CO2 is directly proportional to the production of cement. Almost one tonne of CO2 is released into the atmosphere in every tonne of cement produced. If countries will continue to pursue industrial development through concrete, world concrete production is expected to increase to 5 billion tonnes in a year. As per the Global Commission on the Economy and Climate, this may lead to 470 gigatonne of carbon dioxide by 2050.
Global Warming
Global warming is considered as the battle of the 21st century. The rise of the industrial sector may have increased the quality of human life through the creation of innovative technologies, products, and services; but the level of anthropogenic carbon dioxide in the atmosphere has drastically increased as well. In terms of environmental repercussions, the world is at a disadvantage.
Clearly, the manufacturing of cement is linked to the demand of concrete. More concrete entails more cement requirement, resulting in the lethal increase of greenhouse gases in the atmosphere. If this continues, the world may face an irreversible damage to the extent of species extinction.
Concrete is not Sustainable in the Long Run
Despite the many good attributes of concrete as a building material, one cannot deny the fact that it is one of the main contributors of CO2 production in the world. Cement production aids global warming by releasing tonnes of CO2 into the atmosphere every time it is manufactured. By this reason alone, use of cement or concrete in the long run is not environmentally sustainable.
Sustainability, in simple terms, means meeting the needs of the present generation without completely harming the ability of future generations to satisfy their own needs. For instance, the good and favorable conditions of the present environment must be maintained for the future generations to still benefit from it.
Cement or concrete production is not environmentally sustainable because it does not only contribute to air pollution, but also worsen the land and water pollution.
- Air pollution
As previously mentioned, concrete production emits massive volume of the greenhouse gas CO2. In fact, if concrete industry were a country, it would be the third largest producer of CO2 in the world after China and the USA. Dust brought by the cement itself also contributes to the air pollution by increasing the particulate matter in the air which is harmful in the respiratory system.
- Land pollution
Concrete is slowly turning the earth’s fertile soil into hard pavement. The once healthy ecosystem where life flourishes is now covered with roads and bridges. One source even says that concrete may have already outweighed the plant matter on the planet. Moreover, continuous quarrying of minerals destroys the land and will eventually bring ecological imbalance in the area.
- Water pollution
Impervious surfaces, like in most concrete structures, can block water infiltration into the soil. This may result in flash floods, soil erosion and water pollution during heavy rain.
Indeed, the traditional method and use of concrete are not sustainable. However, it is also undeniable that the discovery of concrete has largely contributed to modern development. Thus, many studies have been done to look for an alternative method and materials that are more sustainable but equally excellent in performing its function.
The Future: Green Building Materials
Concrete is a versatile construction material, but its adverse effects in the environment must not be overlooked. As per Paris agreement, annual emissions of concrete industry need to fall by 16% before 2030 to meet with the standards. This is highly unlikely with the current rates.
One excellent alternative of concrete is cross-laminated timber. Timber captures CO2 instead of producing it making it more sustainable. Another low-carbon alternative material is CEM II which uses fly ash as a substitute for clinker. Ground Granulated Blastfurnace Slag (GGBS) is also a good material that involves no quarrying and does not require high energy to process.
A company known as Solidia aims to produce cement and concrete with a more sustainable method. It uses the same raw materials but is able to design a process in which they use less energy and emit less CO2. This is just one of the many examples that through innovation, use of concrete may later be sustainable.
Conclusion
This article answered the question “Why is concrete not sustainable?” It was explained on this blog post that the manufacturing of cement (component of concrete) releases an appreciable amount of greenhouse gases into the atmosphere. Apart from air pollution, the production of this material also contributes to water and land pollution, establishing its unsustainable use. Fortunately, efforts have been made to develop a more sustainable usage and production.
For any questions and suggestions about this article, please feel free to submit your thoughts in the comment section below.
Frequently Asked Questions (FAQs): Why is concrete not sustainable?
Why is concrete not environmentally friendly?
Large amount of energy as well as appreciable volume of water is required to manufacture the key component of concrete. Furthermore, the acquisition of its raw materials requires extensive quarrying resulting in pollution and at worse, irreversible environmental destruction.
How can concrete be made more sustainable?
To make concrete more sustainable, it is necessary to develop a more sustainable raw material that will replace cement. This could be done by replacing it with a higher fraction of supplementary cementing material (SCM) or by replacing it with different types of SCM’s resulting in a reaction with synergistic effects.
Is Concrete bad for the environment?
Yes, it is bad for the environment since its main component, cement, is produced together with the release of a large volume of greenhouse gases. Moreover, concrete has the ability to degrade the topsoil layer of the earth which is considered fertile and important to agriculture. Surface runoff that results in water pollution and soil erosion can also be related to concrete as it is used to create hard surfaces.
Which cement is more environmentally friendly?
As a replacement to conventional cement, fly ash may be utilized together with lime and water to make it a more reliable construction material. Replacement of cement for concrete building consequently reduces the release of greenhouse gases into the atmosphere.
Can I use pure cement?
If you require strong structure, no, pure cement is not an option. Pure cement is weaker compared to concrete in the context of structural strength. It results in a structural entity with less compressive strength, so it is prone to shrinkage and volume deformation.
Is cement the same as concrete?
No, cement is not the same as concrete. While some people use the term interchangeably, cement is just a component of concrete. In fact, concrete is composed of water, sand aggregates, and cement.
BIBLIOGRAPHY
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Global Cement and Concrete Association. (2020). Sustainability value of concrete. https://gccassociation.org/sustainability-innovation/sustainability-value-of-concrete
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