THE 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-TiO2 modified ultm-high performance concrete (UHPC) with and without a flexural load was experimentally investigated. Firstly, the mechanical properties of UHPC with various nano-TiO2 contents were tested, and the results showed that UHPC with 1 wt. % nano-710, exhibited the best mechanical properties. Then, 1 wt. % nano-TiO2 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-TiO2 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-TO2 mitigated the negative influence of flexural load on the chloride ingress resistance of UHPC. Moreover, the addition of nano-TiO2 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 % CO2 for 180 days. Furthermore, the MIP results indicated that the addition of nano-TO2 refined the pore structure of the UHPC, which improved the mechanical properties and durability of the UHPC.