It is being called a ticking time bomb. Because, despite the acres of sand on beaches, riverbeds, and the ocean floor, industry is rapidly using up this vital raw material.
While it is often taken for granted, sand is in fact a precious industrial and ecological resource. After water, sand is the second highest consumed raw material on Earth, with analysis by the UN finding that, “50 billion tonnes of sand [is] thought to be extracted for construction every year - enough to build a nine-storey wall around the planet.”
In fact, global sand consumption has tripled in the last twenty years and shows no sign of easing up.
To solve this problem, a study conducted at Rice University, has found that the nanomaterial graphene has the potential to replace sand in concrete as well as act as a reinforcing ingredient in cement. Furthermore, the application of nanomaterials in concrete can even added desired properties.
“We compared concrete made using the graphene aggregate substitute with concrete made using suitable sand aggregates, and we found our concrete is 25% lighter but just as tough,” says James Tour, a professor of nanoengineering at Rice University in Houston. “This could have a major impact on one of the biggest industries in the world.”
The discovery was made when the nanomaterial research team applied their patented Flash Joule-heating method to metallurgical coke – a treated form of coal – and found that it produced a kind of graphene that could replace sand in concrete.
“Initial experiments where metallurgical coke was converted into graphene resulted in a material that appeared similar in size to sand,” recounts Paul Advincula, the study’s lead author. “We decided to explore the use of metallurgical coke-derived graphene as a total replacement for sand in concrete, and our findings show that it would work really well.”
The discovery of the Flash Joule process to produce graphene from carbon feedstocks is itself a major breakthrough as, according to Advincula, it “produces graphene faster and at a larger scale than previous methods.”
It has also been used in applications such as the production of hybrid carbon nanomaterials, the recycling of battery parts, and the extraction of heavy metals from coal fly ash.
“It will take some time for the price of graphene to get low enough to make this viable,” admits Tour. “But this just shows there are alternatives we can pursue.”
So, while nanomaterials will not be replacing sand as a construction material tomorrow, it does seem that the team may have found a way for nanotechnology to solve the sand shortage in the long-term.
“30% of concrete is composed of sand,” notes Prof. Satish Nagarajaiah, one of the studies co-authors. “The fact that we’re on the brink of a ‘sand crisis’ motivates us to look for alternatives, and metallurgical coke, which costs about the same as sand at about 10% of the cost of concrete, could help not only make better-quality concrete, but also eventually translate into significant savings.”
This is no small achievement, as the Rice University press release outlines, “Concrete, a mixture of aggregates like sand and gravel bonded with cement and water, is essential for urban development. With 68% of the global population expected to live in urban areas by 2050, demand for concrete and hence sand mining is projected to grow significantly.” Adding that, “Cement production, a key component of concrete, accounts for 8% of worldwide carbon dioxide emissions. Moreover, sand mining, largely unregulated, poses severe threats to river and coastal ecosystems.”
Like so many other raw materials, humankind’s consumption of sand is rapidly outstripping replenishment rates, meaning that a replacement raw material is desperately needed.
Fortunately, nanotechnology research is providing answers and substitute products for the construction industry, much as it is doing in providing nanomaterial solutions for the polymer, cosmetic, medical, and electronics sectors.
Industry is standing at a crossroads, where the old industrial practices of the 19th and 20th centuries are being forced to change for the more modern and innovative use of raw materials in the 21st century. And nowhere is this more evident than in the construction industry and humankind’s consumption of sand. As Beatrice Kariuki, a spokesperson for the UN Environment Program, explains, “Without new thinking, the sands of time will run out.”
Perhaps nanomaterials are the new thinking that industry needs.