E EFFECT OF NANO-TiO₂ ON THE DURABILITY OF ULTRA-HIGH PERFORMANCE CONCRETE WITH AND WITHOUT A FLEXURAL LOAD

In this study, the durability of nano-TiO 2 modified ultra-high performance concrete (UHPC) with and without a flexural load was experimentally investigated. Firstly, the mechanical properties of UHPC with various nano-TiO 2 contents were tested, and the results showed that UHPC with 1 wt. % nano-TiO 2 exhibited the best mechanical properties. Then, 1 wt. % nano-TiO 2 was added into UHPC to evaluate its effects on dry shrinkage, chloride ingress resistance, freeze-thaw resistance and carbonation resistance of UHPC. The effect of the flexural load on the durability of UHPC was also studied. The dry shrinkage of nano-TiO 2 modified UHPC was reduced compared with the control UHPC. The flexural load accelerated the chloride penetration process in the tensile region of the UHPC specimens, and the addition of nano-TiO 2 mitigated the negative influence of flexural load on the chloride ingress resistance of UHPC. Moreover, the addition of nano-TiO 2 particles also improved the freeze-thaw resistance of the flexural loaded UHPC by reducing the mass loss after enduring 800 freeze-thaw cycles. Carbonation was not detected in all UHPC specimens after being exposed to 60 % CO 2 for 180 days. Furthermore, the MIP results indicated that the addition of nano-TiO 2 refined the pore structure of the UHPC, which improved the mechanical properties and durability of the UHPC.