Concrete is the most widely used construction material in the world. It is second only to water in terms of commodity use, and the world produces more than 25 billion tonnes of it each year, which is close to 4 tonnes per human on earth. That’s a lot of concrete, and there are a lot of opportunities to adapt sustainable cement as part of an environmental solution.
Concrete is made of 4 simple ingredients, namely cement, aggregates, sand, and water. However, this simple construction material is one of the major contributors to the large environmental degradation. Among these four simple ingredients, cement is a serious player in CO2 emissions.
Cement is the “glue” in concrete that binds all the other ingredients together. It creates a durable, waterproof, and ubiquitous material upon which modern civilization is built.
“Concrete is beautiful and versatile but, unfortunately, it ticks all the boxes in terms of environmental degradation, and all of us have a responsibility to think about all the materials we are using and their wider impact on the environment.”
A report from the Guardian post… “Portland cement that came around 200 years ago is now has changed the natural environment that existed for millions of years”. There is no place on earth that concrete did not penetrate. All this is done in the name of development and urbanization. It is estimated that by 2050, around 80% of the world’s population will be living in cities.
However, the ability to construct engineering marvels around the world comes with a significantly high environmental and social cost. Focusing on environmental impact; cement production alone contributes almost 10% of global CO2 emissions, and more than half of it results from chemical reactions inherent in the production process. Other major industries such as automotive, manufacturing, power, and agriculture reduce their emission contributions; eventually, cement production may contribute almost one-third of all the CO2 emissions. On top of that, if the whole process of concrete activities is included, the emission rate could be close to 40%.
A recent study shows that by shifting the concrete making with sustainable cement; a saving between 1.7 and 2.7 billion tonnes of CO2 emissions annually could be achieved, thus moving the Earth Overshoot Day back by approximately ten days. By 2050 the emission savings could potentially move Earth Overshoot Day back by almost 40 days.
Sustainable cement could be made with the use of various technologies during production and alternative materials during the stage of making the concrete. This reduction in carbon footprint can be achieved by changing the type of cement we use to build cities and infrastructure. Further savings are achievable with more efficient design and the use of sustainable cement with enhanced performance so that less cement (and hence less carbon) is required to achieve the same outcome.
The Sustainable Cement Solution
In the last 20+ years, many low-CO2 emitting types of cement have emerged as attractive, most sustainable, and most importantly commercially viable alternatives to traditional Portland cement. Traditionally, ordinary Portland cement is produced by firing and heating a mixture of limestone and other secret ingredients to a temperature around 1,450°C. This is the stage where a large amount of CO2 is released because of the chemical reactions.
In the quest of making cement more sustainable, many large and ethical cement manufacturers are opting for cleaner and greener fuel for the firing and heating processes. This is one way to make sustainable cement during the manufacturing stage.
However, there are other ways too to make cement more sustainable. Many of those materials are the industrial waste and/or by-products of other industries, such as fly-ash from the coal power plants, blast furnace slag from steel industries, calcined clays, silica fume. These materials are generally added during concrete mixing. However, these materials also can be added to the cement during the manufacturing stage; thus, resulting in blended cement which can also be called sustainable cement.
The more we blend these substitute materials into the concrete or cement; the requirement for pure ordinary Portland cement will reduce. Then this will indirectly reduce the CO2 emission by an equal amount of the replacement.
Despite being waste material, the above-mentioned alternative cement substitutes do provide enhanced strength and durability, apart from providing improved sustainability by reducing associated CO₂ emissions and recycling industrial wastes. Therefore, it is in fact a win-win solution for the cement/concrete industry and well as for the environment.
However, even with the proven technical and environmental benefits; it is sad to see that many industry players are very reluctant (or slow) in adapting sustainable cement. One reason for this could be that in many countries the price for cement is still relatively cheaper compared to the cost of acquiring and incorporating the waste/by-product materials to make sustainable cement.
The government agencies of those countries can take some proactive role in promoting the use of sustainable cement. They can look into giving tax incentive for the companies that invest in producing and/or using sustainable cement. They also can impose environmental tax/carbon tax on the companies that are reluctant/refuse to move towards adapting sustainable cement. This is just a carrot-stick method – Reward the good ones, Punish the bad ones.
With all said and discussed; if we are really concerned about our environment, we must come together to mitigate the crisis that we all created.
In the year 2015, The Paris Agreement gets the leaders of 196 countries to commit to its goal of limiting global warming to well below 2 degrees Celsius, preferably to 1.5 degrees Celsius, compared to pre-industrial levels.
To achieve this goal, it is essential that the whole construction industry need to undergo a total overhaul. We must re-think the way we build and develop our cities, and a simple shift towards adapting sustainable cement technology could contribute greatly to the environment. The solutions are at our doorstep; it’s up to us to bring them in…
Our future generation is betting on our actions today
