Graphene for Carbon-Neutral Concrete

Graphene technology promises carbon-neutral ready mixed concrete.

Those seeking to aggressively push a transition to carbon neutrality should look to Adam Smith, known as the father of capitalism, for guidance. According to the 18th-century Scottish philosopher and economist, “By pursuing his own interest [the individual] frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good.”

With Smith’s wise counsel in mind, let’s take a look at a new technology that could put self-interest and carbon-neutrality for concrete on the same path.

The top carbon dioxide (CO2) emitters in the world are China at 32.88 percent, the United States at 12.6 percent and India at 6.99 percent. The worldwide annual manufacture of portland cement alone emits 8 percent CO2.

Regardless of anyone’s opinion on the science involved with global warming, the economic reality is that a rapidly growing number of construction opportunities incentivize using concrete with low and even no carbon footprint. In fact, entire countries are officially moving toward carbon neutrality, as evidenced by laws in many nations including the U.S.

What’s holding us back?
The problem is chemistry. Calcinating limestone (calcium carbonate), silica-bearing clay and a few other “spices” requires a rotating kiln at 1,400º C (2,552º F). This removes the carbon from the limestone, which is combined with oxygen to produce about half of portland cement’s CO2 footprint. The remaining footprint is from transport, quarrying plus energy for the kiln and cement finishing.

Many solutions abound, including reducing the energy footprint for the kiln, quarrying and transport. However, the big enchilada is reducing the footprint of calcination. The only way, at present, is to use less portland cement.

Enter das wunderkind: graphene
German researcher Hanns-Peter Boehm led the experimental discovery of graphene in 1962. Graphene is a single layer of carbon atoms arranged in a hexagonal lattice. It is incredibly strong, lightweight, flexible and highly conductive. First produced in 2004, it is now commercially available.

For more than a decade, concrete researchers have been using carbon in general, and graphene specifically, to increase concrete strength and durability while reducing the use of portland cement. Two big problems remain: inconsistent disbursement throughout the mix and the huge amount of energy needed to manufacture graphene.

Game changers
New manufacturing processes that require less energy are now being deployed for graphene. In some cases, they actually use waste products and consequently create biochar, which absorbs CO2 and can be safely “buried” in carbon deposits.

Further, to address disbursement, some companies are now combining graphene with other ingredients to effectively “coat” those constituents with graphene. Naturally occurring types of calcium carbonate, such as aragonite, can be included to improve strength. When introduced to the mix, either during the batching process or onsite, these ingredients provide a much better disbursement while maintaining the target strengths. Most importantly, with the right ingredients (such as titanium oxide) graphene-based admixes not only substantially reduce the need for portand cement but also can aggressively absorb CO2 after curing when exposed to sunlight.

Crunching the numbers
The U.S. Department of Energy (DOE) has tested finished carbon-absorbing, graphene-based concrete. Published results from one supplier of graphene admix indicate it is possible to sequester up to 900 kilograms of CO2 per cubic meter (690 kilograms per cubic yard).

For qualified infrastructure owners, IRS Code § 45Q – Credit for carbon oxide sequestration awards a tax credit of $26 per metric ton. Thus, for those qualified infrastructure owners, they have $17.86 per cubic yard ($26/metric ton x 0.69 metric ton/cubic yard) as an additional cost offset.

A typical 3,500-psi mix has around 533 pounds of portland cement. Replacing 90 percent of the portland cement (-$28.78 at $120/ST) with the graphene blend (price to be determined) and sands to make up the volume (+$3.60 at $15/ST) provides $25.18 per cubic yard to spend on the graphene admixture. For those who qualify, the IRS throws in an additional $17.86 per cubic yard, resulting in a total offset of $43.05 per cubic yard that could be used to purchase graphene admixtures without increasing the concrete price!

Money talks
The absolute truth is concrete will remain essential for modern society. However, portland cement need not be the only matrix binder material used. Given the incentive of at least $25 and up to $43 per cubic yard plus a low-carbon bidding advantage, portland cement-reducing graphene admixes with CO2 sequestration can deliver an economic advantage.

In Adam Smith’s world, money talks—and individual ambition serves the common good. Harnessing ambition is the key to reducing the carbon footprint. The best way to do this is to innovate forward.

Craig Yeack has held leadership positions with both construction materials producers and software providers. He is co-founder of BCMI Corp. (the Bulk Construction Materials Initiative), which is dedicated to reinventing the construction materials business with modern mobile and cloud-based tools. His Tech Talk column—named best column by the Construction Media Alliance in 2018—focuses on concise, actionable ideas to improve financial performance for ready-mix producers. He can be reached at [email protected].