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

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.