Frost Resistance of Nano-TiO2 Concrete Based on Nuclear Magnetic Resonance Method.

The evolution of pore structure is very important to the frost resistance of concrete. In order to study the effect of nano-TiO₂ on pore structure and frost resistance of concrete, the nano-TiO₂ concrete with substitution rates of 0%, 1%, 3%, 5% (mass fraction, the same below) were selected as research object, and the quick freezing test, compressive strength test, nuclear magnetic resonance test and scanning electron microscope test were carried out. The changes of mass, dynamic elastic modulus, compressive strength, pore structure and micro-morphology of nano-TiO₂ concrete before and after freeze-thaw cycle were analyzed to evaluate the freeze-thaw damage at - 18 ~ 5 °C and to analyze the improvement mechanism of nano-TiO₂ on concrete properties. At the same time, the response models of compressive strength, relative dynamic modulus, free water saturation and crack ratio were established to determine the optimum content of nano-TiO₂. The results show that an appropriate content of nano-TiO₂ effectively improves the micro-morphology of concrete, increases the proportion of micropores and medium pores of concrete, and reduces the proportion of macropores and cracks, while excessive nano-TiO₂ increases the proportion of macropores and cracks in concrete, which is not conducive to the improvement of frost resistance of concrete. When the content of nano-TiO₂ is 1%, the frost resistance of concrete is the best. Based on the frost resistance performance index and pore test results, the response model is established, and the optimal content of nano-TiO₂ is close to 1%, which is consistent with the test results. [ABSTRACT FROM AUTHOR]