Sand is one of the most important ingredients in concrete, the second most consumed material in the world after water. However, the global demand for sand is exceeding the natural supply, leading to environmental and social problems. Sand mining, which is often unregulated and illegal, causes erosion, pollution, biodiversity loss, and conflicts.
A team of researchers from Rice University has found a potential solution to this problem, by using graphene derived from coal as a substitute for sand in concrete. Graphene is a form of carbon that consists of a single layer of atoms arranged in a honeycomb pattern. It has remarkable properties, such as high strength, flexibility, and conductivity.
The researchers used a technique called flash Joule heating, which involves passing a high electric current through coal to convert it into graphene. The resulting graphene has a similar size and shape to sand, and can be mixed with cement and water to form concrete. The researchers compared the properties of conventional concrete and graphene-based concrete, and found that the latter is 25% lighter but just as tough.
Graphene-based concrete has multiple benefits for the environment and the industry
The use of graphene derived from coal as a substitute for sand in concrete has several advantages, both for the environment and the industry. First, it reduces the need for sand mining, which has negative impacts on the ecosystems and the communities. Second, it reduces the carbon footprint of concrete production, which accounts for 8% of the global carbon dioxide emissions. Third, it improves the performance and durability of concrete, which can reduce the maintenance and repair costs.
The researchers used metallurgical coke, a type of coal that is widely available and cheap, as the source of graphene. Metallurgical coke is mainly used in the steel industry, but its demand has declined due to the shift to electric arc furnaces. The researchers said that using metallurgical coke for graphene production could create a new market and value for the coal industry, which is facing challenges from the transition to renewable energy sources.
The researchers also said that their technique of flash Joule heating is fast, scalable, and versatile, and can be applied to other types of coal and carbon materials. They have used the same technique for various applications, such as recycling battery parts, removing heavy metals from coal fly ash, and synthesizing hybrid carbon nanomaterials.
The potential and challenges of graphene-based concrete for the future
The researchers said that their discovery could have a major impact on one of the biggest industries in the world, and could help address the looming sand crisis. According to a 2022 report by the United Nations, the global demand for sand is expected to increase by 5.5% annually, reaching 60 billion tons by 2030. However, the natural supply of sand is limited and finite, and cannot keep up with the growing consumption.
The researchers said that their graphene-based concrete could be a viable alternative to conventional concrete, and could be used for various construction projects, such as buildings, roads, bridges, and dams. They said that their graphene-based concrete is compatible with the existing equipment and methods of concrete production, and does not require any special modifications or adaptations.
However, the researchers also acknowledged that there are some challenges and limitations to their innovation, such as the cost, availability, and quality of the coal, the safety and regulation of the flash Joule heating process, and the acceptance and adoption of the graphene-based concrete by the industry and the consumers. They said that they are working on addressing these issues, and collaborating with other researchers and stakeholders to test and optimize their product.
The researchers said that they hope that their work will inspire and influence other initiatives and policies that aim to improve the sustainability and efficiency of concrete production, and to protect the environment and the society from the harmful effects of sand mining.