Thin sheets of carbon, one atom thick, called graphene dramatically improve the strength of cement and concrete. A pinch or two of graphene can also improve the properties of other materials — from batteries to tires. But adding graphene to cement could be the “killer application” for this form of pure carbon since the world makes so much cement and concrete each year.
This is important because 5 billion tons of cement are made each year by the traditional process (known even to the Romans) which is responsible for 8% of world-wide carbon dioxide emissions. It has been calculated that if the production of cement were a country, it “would be the world’s third largest emitter of greenhouse gas emissions.” So, making cement stronger with a simple additive means less of it would be needed in a typical construction job and less energy derived from burning coal or natural gas would be required to make it in the first place.
Cement is typically made by heating a mixture of limestone, sand and clay by burning coal or natural gas. When limestone is heated, CO2 is dumped into the air from both the limestone itself and from the fossil fuel used to do the heating. Concrete is a mixture of cement, gravel, sand and water. Worldwide we pour 30 billion tons of it annually. Several companies and laboratories now know that with the addition of only 0.1% of graphene, the concrete becomes 30% stronger so less of it is needed, leading to a reduction in CO2.
James Tour, Ph. D., at Rice University in Houston is studying concrete made with graphene. He suggests that a trace of graphene acts somewhat like a molecular glue that binds cement components to one another, resulting in greater strength as the concrete cures. Greater strength means not only that less concrete is needed for a given application but that the final structure should last longer.
Graphene-enhanced concrete is expected to reduce corrosion of steel rebar in the concrete by reducing water infiltration and thus preventing crumbling. Perhaps such improved concrete might have prevented the collapse of the Surfside Condo building in Miami-Dade County, Florida, that killed 98 people in October 2020. A British construction company recently used graphene-enhanced concrete for the floor of a new gymnasium in Southern England without any rebar, saving one third on the cost of the materials and a similar amount in CO2 emissions.
Graphene is one of the basic forms of pure carbon like diamond and graphite that have different crystal structures with different physical properties. At the atomic scale, graphene is a flat sheet of six carbon atoms arranged in a regular pattern, like chicken wire or honeycomb. Each carbon atom is attached to three others. Graphite consists of many graphene sheets stacked together.
Other current applications of graphene include water filters, types of armor, or improved batteries that may have higher capacities and faster recharging times. Small amounts of graphene may also improve asphalt (fewer cracks), tires (better resistance to abrasion), and other composite materials.
But if we start adding it to all concrete, how will it be made since 0.1% of 30 billion tons is 30 million tons?
Happily, making graphene could become an enabling technique for other decarbonization processes. Graphene can be made by vapor deposition from methane (the main component of natural gas, having one carbon atom and four hydrogen atoms) released from landfills, farms, sewage treatment plants, oil wells and refineries. By this method, graphene comes out as a fluffy black powder while the hydrogen can be captured and resold.
A water-based method is currently being used by Canadian and Chinese companies to make graphene from graphite, although the graphite must be mined. Dr. Tour and team have shown they can make graphene by the “flash process,” in which a short, intense electrical discharge liberates graphene from almost anything: coal, petroleum coke, discarded food, old tires and mixed plastic waste.
Graphene can be made from a variety of sources and if the electricity is from renewable sources, it is green. Several of these processes could be scaled up to the levels needed for cement manufacturing.
Richard Gelinas, Ph. D., whose early work earned a Nobel prize, is a senior research scientist at the Institute for Systems Biology. He lives in Lakebay.
For more on graphene, see wikipedia.org/graphene
“Pouring graphene’s bright future.” The Economist, May 21, 2022, p. 75.
“Researchers have created emissions-free cement.” David Chandler, MIT News, Sept. 19, 2019.
Companies working on graphene include Levidian Nanosystems (UK), ZeroCarbonVentures (UAE), NanoXplore (Canada), Sixth Element Materials Technology (China), Nationwide Engineering (UK), Universal Matter (Canada), Applied Graphene Materials (UK). Many U.S. companies are also working on graphene.
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