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Comparison of the mechanical property and microstructures of cementitious composites with nano- and micro-rutile phase TiO2

Li Zhen, Han Baoguo, Yu Xun, Zheng Qiaofeng, Wang Yanlei

Archives of Civil and Mechanical Engineering

2019

Vol. 19, no. 3

615--626

Rutile phase TiO2 with the diameter of 50 nm and 500 nm were used to fabricate TiO2 modified cementitious composites (RTMCC) in this paper. The mechanical property and microstructures of RTMCC were compared. Research results showed both types of TiO2 can improve the flexural and compressive strengths of cementitious composites. The addition of 2.32 vol.% 50 nm and 500 nm TiO2 increased the 28 days flexural strength/compressive strength by 27.7%/10.78% and 53.71%/18.58%, respectively. In addition, the fracture tough-ness of cementitious composites can be enhanced by the inclusion of TiO2. The microstruc-ture analysis demonstrated that the strengthening effect of TiO2 to cementitious composites results from the nucleation effect, filling effect, pinning effect and self-curing effect. However, the reinforcing effect of 500 nm TiO2 is superior to that of 50 nm TiO2. Nuclear magnetic resonance and energy dispersive spectrum analyses suggested that 50 nm TiO2 can make the decalcification of the C–S–H (i.e., calcium is removed from the interlayer) and cause defect sites in the silicate chains, which lead to the less-density C–S–H. In addition, zeta potential and scanning electron microscope analyses manifested that 50 nm TiO2 is easier to reunite, therefore generating more defects in cementitious composites.