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According to foreign media reports, since we started producing infrastructure, the power of nature has always surpassed the materials we use to build infrastructure. Every year, ice and snow turn the main roads into gravel, although the foundations of sturdy houses still have cracks. In addition to the tons of waste generated from cement fragments, the United States also spends approximately $24000 annually on road maintenance.
To solve this problem, engineers usually enhance the functionality of materials by increasing the carbon content, but doing so will cause the material to lose some mechanical properties. Now, researchers from Northwestern University in the United States are introducing nanoparticles into ordinary cement to form a smarter, more durable, and more functional cement.
This study was published on June 21, 2021 in Philosophical Transactions of the Royal Society A.
Cement is a widely consumed material globally, and the material industry accounts for 8% of greenhouse gas emissions caused by human activities. To this end, Professor of Civil and Environmental Engineering, Angel Therese Akono, turned to nanoreinforced cement for solutions. Akono, the first author of the study and assistant professor at the McCormick School of Engineering, stated that although nanomaterials reduce the carbon footprint of cement composites, so far, few people know their impact on fracture behavior.
Akono said, quot;Prior to this, people had not yet understood the role of nanoparticles in this application, so this was a major breakthrough. As a trained fracture mechanics expert, I want to understand how to change cement production to improve crack response.quot;
Traditional fracture testing involves projecting a beam of light onto a large piece of material, which requires a significant amount of time and material, and rarely discovers new materials.
However, Akonos laboratory effectively predicted the properties of materials in a very short period of time by using an innovative method called scratch testing. This method tests crack response by applying a conical probe that increases vertical force to the surface of a micro cement drill bit. Akono developed this new method during her doctoral work, stating that it requires fewer materials and accelerates the discovery of new materials.
Akono said, quot;I can observe many different materials simultaneously. My method is directly applied at the micrometer and nanometer scales, saving a considerable amount of time. Based on this, we can understand the behavior of materials, how they crack, and ultimately predict their fracture resistance.quot;
In addition, the predictions formed through scratch testing also allow engineers to make changes to the material to improve its performance on a larger scale. In the paper, graphene nanosheets were used to improve the fracture resistance of ordinary cement, and this material quickly gained popularity in the formation of intelligent materials. The addition of a small amount of nanomaterials also improved water transport performance, including pore structure and water permeability resistance, which were relatively reduced by 76% and 78%.
This study involves many fields, including construction, road maintenance, sensor and generator optimization, and structural health monitoring.
The United Nations predicts that by 2050, two-thirds of the worlds population will be concentrated in cities. Considering the trend of urbanization, cement production is expected to soar. The use of lighter and better performing cement in green concrete will reduce the overall carbon footprint by extending maintenance time and reducing waste.
On the other hand, smart materials enable cities to meet the connectivity, energy, and multifunctional needs of the growing population. Carbon based nanomaterials, including graphene nanosheets, have been considered in the design of smart cement sensors for structural health monitoring.
Akono expressed her excitement about the follow-up research of the paper in her own laboratory and the ways in which her research will influence others. She is already researching proposals to use construction waste to form new concrete, and is also considering further developing this paper by increasing the proportion of nanomaterials in cement.
Akono said, quot;I want to look at other assets to understand long-term performance. For example, if you have a building made of carbon based nanomaterials, how can you predict resistance for 10, 20, or even 40 years?quot;
It is reported that Akono will give a speech on the paper quot;A Cracking Approach to Inventing Tough New Materials: Frature Stranger That Frictionquot; at the October meeting of the Royal Society of England. The speech will highlight the significant progress in fracture mechanics over the past century.
