Adding Magic Dust to Concrete: Cementing Ties with Graphene

–By Girish Linganna

The cement industry contributes majorly to global greenhouse gas emissions, accounting for at least 8% of the total. This makes it a significant polluter, even when compared to other industries known for their high emissions, such as iron and steel or oil and gas manufacturing.

The construction of modern buildings and urban infrastructure consumes vast amounts of raw materials globally. Cement and concrete production, in particular, accounts for roughly 8% of the carbon dioxide (CO₂) emissions generated by human activities worldwide. This significant environmental impact calls for rapid development, and widespread use, of concrete with a lower carbon footprint in the construction industry.

As the world population grows, cities are expanding and living standards are improving, with the global demand for concrete products increasing at an ever-faster pace. The use of concrete has skyrocketed over the past three decades due to its versatility, affordability and the long-lasting nature of concrete buildings and structures. Globally, we use about 30 billion tons of concrete every year—a 300% increase compared to just 40 years ago. The demand for concrete now far exceeds demand for other construction materials, such steel or wood.

Per Capita Cement Consumption

India’s per capita cement consumption is significantly lower than the global average, at between 250 kg and 270 kg per person, compared to 500kg and 550 kg per person globally. China, on the other hand, leads the world in per capita cement consumption, in the range of 1,750 kg-1,850 kg per person, ahead of Korea which has a per capita consumption of 850 kg.

India’s cement production currently sits at 370 million metric tons, (approx 0.4 billion tons), while China produces a much larger amount of 2,100 million metric tons, according to Statista. Crisil ratings predict that India’s cement industry will increase its production capacity by 80 million tons by FY 2024. In terms of actual consumption, India used 355.46 million tons of cement in FY 2022. This is projected to rise to 450 million tons by end-FY 2027.

Procedure for Making Concrete

To make concrete, one starts by mixing sand, gravel, cement and water. This mixture is then poured into molds where it hardens into the final structure. However, producing the cement, itself, involves a complex process. It begins with such raw materials as limestone and clay, which are crushed and then subjected to extremely high temperatures (over 1,400°C) in a special furnace, or kiln. The intense heat is typically generated by burning fossil fuels, and this, unfortunately, leads to significant pollution.

As these materials are heated, they undergo a series of chemical reactions that transform them into a substance, called ‘clinker’. Clinker consists of small, hard, spherical particles. Once it cools, the clinker is ground down to a fine powder and mixed with gypsum and other additives to create cement. This cement is the crucial binding agent used in concrete, providing the necessary durability and strength for construction projects.

Additionally, a significant chemical reaction takes place during the formation of clinker. Limestone, or calcium carbonate (CaCO₃), is transformed into calcium silicate (Ca₂SiO₄). This reaction is not only crucial for producing clinker, but also releases about 600 kilograms of CO₂ for every ton of cement produced, contributing to environmental concerns. Clinker is indispensable in cement, acting as the key adhesive that ensures concrete’s structural integrity and strength.

To reduce the environmental impact of concrete production, cement manufacturers have joined forces with researchers and engineers. They are exploring ways to use less clinker in cement, which is the main source of CO₂ emissions. This involves replacing some of the clinker with alternative materials, called supplementary cementitious materials (SCMs).

These SCMs include byproducts from other industries, such as fly ash and blast furnace slag. Using these materials can help lessen the overall environmental impact of cement production. But the main challenge in using SCMs in concrete is that they lack the strong binding properties of clinker. As a result, concrete made with low-clinker cement often falls short in terms of performance for many applications.

Bolstering Strength of Cement

A spin-off from the University of Exeter and University of Manchester’s Graphene Engineering Innovation Centre, Concrene Limited, in recent years, has achieved a breakthrough and discovered a way to add graphene to concrete. This innovation enhances the material’s strength and its ability to resist water. Even more significantly, this graphene addition allows for a reduction in the cement content of concrete by as much as 50%, even eliminating the need for steel reinforcement.

What is Graphene?

Imagine a sheet of paper so thin that it is only one atom thick! That is grapheme—a super-strong material made entirely of carbon atoms arranged in a honeycomb pattern. Think of it like a giant sheet of graphite, the stuff in your pencil, but stretched out to be incredibly thin and strong

Graphene is incredibly light, but intensely powerful. It is an amazing conductor of electricity and heat and is stronger than steel by a factor of 200! Besides, it is flexible, meaning it can bend and move without breaking. These incredible properties make graphene a promising material for many exciting applications

Graphene to Solve Clinker Issue?

Ever since graphene was discovered, scientists have been busy exploring how adding it to cement can improve the properties of concrete. Back in 2014, University of Exeter researchers had a big “Aha!” moment. They figured out how to mix tiny bits of graphene with water—a tricky thing to do because graphene usually does not like water. This was a big deal because it opened the doors to using graphene in concrete!

Think of it like trying to mix oil and water—they do not usually get along. But, by finding a way to make graphene happy in water, scientists could then add it to cement, creating a new kind of concrete with super-strength and other amazing properties. Exeter scientists did a test where they added a tiny amount of graphene (just 0.03%) to concrete.

The results were amazing! The concrete became much stronger—both in terms of how much weight it could hold (compressive strength) and how well it could bend without breaking (flexural strength). It is like adding a little bit of magic dust to your concrete! Even a tiny amount of graphene made a big difference to concrete’s strength.

Pooram Srikanth, managing partner and technical head of Bangalore-based company Pooram & Pooram, who has vast experience in the field of tribology and has formulated innumerable export-substitutes, achieved a breakthrough in the Indian construction industry by successfully incorporating graphene into concrete, says, “Graphene-reinforced concrete has been tested at numerous ready-mix concrete (RMC) plants across India under various climatic conditions. There’s potential for graphene in EV batteries manufacture and a host of other industries. Our company can now manufacture graphene in bulk. We’ve recently been awarded a patent for our lead-free X-ray block tiles.”

The author of this article is a Defence, Aerospace & Political Analyst based in Bengaluru.

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