RETRACTED: The Effects of TiO2 Nanoparticles on Flexural Damage of Self-compacting Concrete

In the present study, flexural strength, thermal properties, and micro- structure of self-compacting concrete with different amount of TiO2 nanoparticles have been investigated. TiO2 nanoparticles with the average particle size of 15 nm were partially added to self-compacting concrete and various behaviors of the speci- mens have been measured. The results indicate that TiO2 nanoparticles are able to improve the flexural strength of self-compacting concrete and recover the negative effects of superplasticizer on flexural strength of the specimens. TiO2 nanoparticle as a partial replacement of cement up to 4 wt% could accelerate C-S-H gel formation as a result of the increased crystalline Ca(OH)2 amount at the early ages of hydration. The increase in the TiO2 nanoparticles' content by more than 4 wt%, reduces the flexural strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis, and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, also indicate that TiO2 nanoparticles up to 4 wt% could improve the mechanical and physical properties of the specimens. Finally, TiO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.