Benefits of TiO2 photocatalyst on mechanical properties and nitrogen oxide removal of ultra-high-performance concrete

This study aims to develop a novel type of ultra-high-performance fiber-reinforced concrete (UHPFRC) with excellent mechanical properties and nitrogen oxide (NOx) removal capability. To achieve this, an inert filler, silica flour, was replaced with titanium dioxide (TiO2), which is known as a photocatalyst. The test results indicated that the average bond strength of a straight steel fiber embedded in ultrahigh-performance concrete (UHPC) increased by replacing the silica flour with TiO2 powder up to 75% in general. Approximately 53% and 63% higher bond strengths and pullout energies, respectively, were thus achieved at 50% replacement rate. The tensile properties of UHPFRC were improved by TiO2, and its tensile strength slightly increased, while the strain capacity and g-value substantially increased. The energy absorbing capacity increased by as much as 78% due to the addition of TiO2 powder. Furthermore, the plain sample exhibited almost zero NOx removal efficiency, but increased with the replacement ratio of TiO2 powder up to 75%. The best NOx removal capability in the UHPC sample containing 75% TiO2 powder was thus 7.7 times higher than that of the plain sample. (C) 2021 Elsevier Ltd. All rights reserved.