A novel approach to amplify the strengthening and toughening effect of nano-TiO2 to concrete

Significance 

The use of concrete has significantly increased globally due to the rapid growth of the building and construction industries. This can be attributed to their low costs, simple preparation methods and excellent compressive strengths. However, various materials used in construction must satisfy some specified environmental needs in compliance with the set mitigation measure aimed at protecting the environment and ecosystem in general. Unfortunately, concrete do not meet these demands due to low fracture toughness and tensile strain as well as poor functional/smart property. As such, researchers have been looking for alternative ways to improve the mechanical properties and durability as well as photocatalytic performances of concrete and have identified nano-TiO2 as a promising solution. Regardless of the remarkable improvements, the nano-TiO2 dispersivity and resulting defects at the concrete and nano-TiO2 interface still remain great challenges in enhancing the efficiency of concrete.

In previous published literatures, nano-TiO2 surface has been modified with SiO2 to improve the nano-TiO2 dispersivity. However, the effects of adding nano SiO2-coated TiO2 (NSCT) on the properties of concrete have not been fully explored. Alternatively, reactive powder concrete has attracted significant attention of researchers due to its excellent mechanical properties and durability. To this note, the contribution of nano SiO2-coated TiO2 in enhancing the mechanical properties of reactive powder concretes is also an area of interest.

Recently, scientists at the Dalian University of Technology: Professor Baoguo Han, Doctoral candidate Zhen Li, Dr. Liqing Zhang, Doctoral candidate Shuzhu Zeng, M.S. Bing Han and Professor Jinping Ou in collaboration with Professor Xun Yu from New York Institute of Technology assessed the contribution of NSCT in developing high-performance reactive powder concrete. Their work is currently published in the research journal, Construction and Building Materials.

The authors observed great improvements in compressive and flexural properties of NSCT reinforced reactive powder concrete. The compressive strength of reactive powder concrete at 28 days of curing ages can be increased by 12.26%/12.2 MPa due to the usage of NSCT. Especially, NSCT can improve the toughness of concrete significantly. The maximum flexural strength of NSCT reinforced reactive powder concrete achieve an increase of 87%/6.69 MPa with respect to control reactive powder concrete. Professor Han and colleagues designed a series of analyses such as thermogravimetry analysis, X-Ray powder diffraction analysis, elemental analysis and scanning electron microscope observation to research the reinforcing mechanisms of NSCT on the mechanical property of concrete, and the results showed that coating of SiO2 at surface of nano-TiO2 can bring more negative charges at the surface of nano-TiO2 which is beneficial for dispersion of nano-TiO2 in matrix. And the NSCT dispersed in the matrix can inhibit the expansion of micro cracks by making the cracks go through the crystal or occur deflection. In addition, the SiO2 coated at surface of nano-TiO2 has pozzolanic effect which can promote the cement hydration and make the matrix more compact. Furthermore, NSCT can limit Ca(OH)2 (CH) crystal size and reduce CH crystal orientation which is helpful to strength promotion.

In summary, NSCT proved a promising solution for modifying infrastructure and enhancing the mechanical properties and durability as well as photocatalytic performances of concrete due to its efficient dispersion, excellent nano-core effect, and high catalytic activity. Altogether, the study by Professor Baoguo Han and his colleagues will advance the development of these high-performance and multifunctional/smart concrete materials for various applications.

A novel approach to amplify the strengthening and toughening effect of nano-TiO2 to concrete : Coating TiO2 with SiO2 - Advances in Engineering

About the author

Baoguo Han received his PhD in the field of smart materials and structures from the Harbin Institute of Technology, China, in 2005. He is currently a professor of civil engineering in the Dalian University of Technology, China. His main research interests include cement and concrete materials, smart materials and structures, multifunctional composites, nanotechnology, sensing technology, and structural health monitoring and traffic detection. He is a member of the editorial board of five international journals and has published 3 books (Self-Sensing Concrete in Smart Structures, Elsevier 2014; Smart and Multifunctional Concrete toward Sustainable Infrastructures, Springer 2017; Nano-Engineered Cementitious Composites: Principles and Practices, Springer 2019), 12 book chapters and more than 150 technical papers.

He has hold more than 10 authorized national invention patents. He was invited to the University of Minnesota and has worked as a visiting research scholar there for 3 years. He was also awarded the New Century Excellent Talents in University and the First Prize of Natural Science by the Ministry of Education of China.

ResearchGate , Google Scholar

About the author

Zhen Li is a PhD candidate in the field of multifunctional concrete and structures in Dalian University of Technology, China. Her main research interests include high performance cement and concrete materials, multifunctional/smart concrete, nanotechnology, sensing technology and structural health monitoring. She has published 1 book chapter, 1 review article (Composites Part A: Applied Science and Manufacturing, 2018) and 13 technical papers in reputable journals such as Cement and Concrete Composites, Construction and Building Materials, Journal of Materials in Civil Engineering and Archives of Civil and Mechanical Engineering, and hold 2 authorized national invention patents. She was invited to the Northwestern University and has worked as a visiting research scholar there for 1 years. She was also invited to give oral presentation in prestigious international conferences such as Engineering Mechanics Institute Conference, Advances in Cement-Based Materials conference and International Workshop on Nano-Engineered Meta-materials for Civil Infrastructures.

ResearchGate

Reference

Han, B., Li, Z., Zhang, L., Zeng, S., Yu, X., Han, B., & Ou, J. (2017). Reactive powder concrete reinforced with nano SiO2-coated TiO2Construction and Building Materials148, 104-112.

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