Let's Be Honest, Episode 33: Concrete

Let’s be honest is a Food Circle project to open up the conversation about the challenges when being or becoming a member of the SC (Sustainability Club). This series will shine a light on the different approaches to making life more sustainable and the step-backs and difficulties that arise. Being more kind and understanding, instead of critical, will hopefully help to encourage us to try instead of giving up when facing a step-back or failure. This is made possible thanks to Sapient, the mother company of Food Circle, which every year offers internships to students from all around the world, creating a uniquely multicultural environment.



Let’s celebrate the achievements and give room for honesty and struggles!

Concrete: the Backbone of Man-made Construction

It may be that you cannot even imagine just how vast the utilisation of concrete is. Currently the second most consumed material in the world (after water) and the most used man-made material overall, concrete is heavily relied upon in construction of individual and commercial buildings [1]. Each year, 30 billion tonnes of concrete are utilised globally. That is three times as much per capita as it was forty years ago, and the demand for concrete continues to rise more quickly than that for steel or wood [2].

This material is the cornerstone of contemporary civilisation, a vital building block of infrastructure, giving billions of people roofs over their heads, bolstering our natural disaster defences, and serving as structure for industries like healthcare, education, transportation, and energy [3]. And that is not the gist of all the concrete uses: it also staves off extreme weather conditions, it is used for construction of sewers and culverts, overpasses and so on. All in all, concrete is extremely durable, cost-efficient and versatile.


The right type of concrete must be chosen before beginning any concrete application [4]. Reinforced concrete, for instance, is appropriate for building components like columns and beams that require a high tensile strength. Building light concrete blocks for home construction is best done with lightweight concrete, however. Buildings made of concrete are more sturdy, need less maintenance, and have improved indoor air quality. Resistance to hurricanes, wind, and fire are further advantages of the material.


Concrete is one of the easiest and most affordable materials for building bridges, the material is widely used for bridge superstructures (the upper portions of bridges). These consist of sidewalks, decks, curbs, and side traffic barrier walls. One of the most difficult and massive concrete structures is a dam. In a dam water is pumped through pipes within the concrete to prevent cracking. For the design of the dam, concrete mix must be carefully chosen, together with the appropriate aggregates. And these are only a few of the plethora of applications of concrete.


Concrete's Clash with Environment

The thing about concrete is that in many ways the material can mask itself as environmentally friendly and that is due to multiple factors. We already established that the resilience and durability of concrete is its main selling point. It guarantees that the product will be long-lasting, hence sustainable. This adds to the next factor - there are seemingly no leftover traces of concrete visible in our everyday surroundings. Unlike plastic, concrete waste is not that much detected in seabed, in our bodies and in the bodies of other living creatures, creating an illusion that concrete waste does not exist, or that its imprint remains minimal. But in the grand scheme of things the environmental impact of concrete is not so clear cut. As it turns out, the expansive concrete industry is responsible for a number of predicaments regarding environment. Let’s talk about the main three:

1. A monster with a huge appetite, concrete consumes roughly 10% of the industrial water used worldwide. If current manufacturing practices remain the same, 590-710 cubic kilometres of water will be needed to produce concrete during the next 35 years. This basically equates to the entire amount of water that the river of Nile receives over an eight-year period [5]. Since most of this consumption occurs in dry and water-stressed areas, it often puts a pressure on resources for drinking water and irrigation.


2. Sand and gravel are added to cement, which is the main component of concrete, water is whisked into the mixture, and the slurry is then poured into moulds before it dries to create concrete. The most carbon-intensive step is producing the cement, which requires heating a mixture of clay and limestone to over 1,400 °C in a kiln using fossil fuels. Combining all production phases, concrete contributes to up to 8 percent of global CO2 emissions. Clinker, the key component of cement and the substance that holds all the components of concrete together, generates half of the CO2 emissions related to concrete production. For every tonne of cement made, about 600 kilos of carbon dioxide are generated when limestone (calcium carbonate) and clays are heated.


3. One of the primary ingredients of concrete is sand, but not all kinds of sand are appropriate for concrete manufacturing. Because of the surface texture that the water creates, we typically employ sand from river beds and oceans. Sand is becoming a more valuable resource as a result of the increase in concrete use over the past century, which has begun to leave a negative impact on the environment. Sand extraction without supervision has the potential to destroy local species and habitats. Throughout Southeast Asia, China, and other regions of the world where there is rapid population increase, sand extraction from rivers and lakes results in standing pools of water that serves as a breeding ground for mosquitoes, spreading diseases like malaria and other ones. Rural people who rely substantially on natural ecosystems for their livelihoods are likewise threatened by their degradation.

What do the Alternatives Look Like?

In some more developed countries, cement manufacturers are working to lessen the environmental impact of their product. The concrete industry has advanced with a number of initiatives, particularly in the UK over the past ten years. These initiatives include, on the one hand, technical advancements to reduce greenhouse gas emissions and, on the other hand, an educational program targeted at engineers and building designers that promotes concrete's sustainable credentials [6]. In order to utilise less energy throughout the cement-making process, researchers are experimenting with lowering the temperatures of cement making process.

Slag, the byproduct of the production of iron and steel, and unused fly ash, a byproduct of coal power plants, are two alternatives to concrete. Both are cementitious materials. In addition to increasing the capacity of cement plants, reducing fuel consumption, lowering greenhouse gas emissions, and improving durability, these cementitious materials have other benefits as well [7]. Seeing that both of these are byproducts of massive manufacturing processes, there are millions of tons of them produced annually. Naturally, it is highly beneficial to find more uses for these byproducts.


Already in 1990s efforts have been made to find sustainable concrete alternatives, and as a result a new, more sustainably structured product has emerged, namely, green concrete. Green concrete is made from concrete wastes [8]. Its formula ensures long life cycle with low maintenance surface, and has scored appeal with its redeeming qualities, such as saving energy, minimising CO2 emissions and use of wastewater. As a matter of fact, green concrete can reduce concrete industry’s CO2 emissions by up to 30 percent, making it one of the material’s biggest advantages. On top of that, less maintenance and better workability are two of many factors that weighs out green concrete in comparison to the standard one.

Concluding Point

Reflecting on the effects and the alternatives of concrete, it is worth mentioning that it is indeed the magnitude of concrete’s employment that may just be its most significant shortcoming. Concrete’s ever-persisting role as a tool for taming nature owes the material its absolute universality and wide use. Even dating back to the ancient world concrete-like structures have been in use [9], proving that all throughout the history of civilisation concrete has demonstrated advantages: from providing a structure of home and a shelter from weather to becoming an instrument of taming nature and gaining control over it. It is more so the fact that utilisation of concrete has not halted expanding that its growing negative influence comes into discussion and better alternatives are required. Fortunately, the concrete industry is already on its way to a greener future.



Author: Liva Puka


 
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References

  1. Is Concrete Sustainable? Here's Why We Need To Talk About Green Building & Sustainable Design | Ethical Unicorn

  2. Concrete Needs to Lose its Colossal Footprint | Nature

  3. Concrete: The Most Destructive Material on Earth | The Guardian

  4. Concrete Production and Applications | Reliance Foundry

  5. Rethinking Concrete to Build More Sustainable Cities | Metabolic

  6. Concrete and Sustainability | Greenspec

  7. Use of Alternative Cementitious Materials

  8. What is Green Concrete? Its Applications and Advantages in Constructions | The Constructor

  9. The History of Concrete | InterNachi

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