Effects of MgO nanoparticles on dynamic shear modulus of loess subjected to freeze-thaw cycles

This study evaluated the utilization of nano-MgO in problematic loess to enhance the dynamic performance and freeze-thaw resistance. To address these issues, samples of different blend ratios, with or without freezing-thawing, were prepared, and their dynamic modulus were examined by a series of dynamic triaxial tests. The results indicate that an addition of 2.5% nano-MgO improved the maximum shear modulus of pre- and post-freezing-thawing samples by 75.26% and 184.9% on average. Significant detrimental effects of freezing-thawing and water content were also observed. While it is found these detrimental effects could be alleviated with the addition of nano-MgO. Novel models for dynamic modulus of nano-MgO treated loess were accordingly proposed towards infrastructure design in cold regions. Additionally, the stabilizing mechanism of nano-MgO was explored by nuclear magnetic resonance tests. The results indicate that the water-absorbing effect of nano-MgO turns free water into bound water, therefore, resulting in significant improvements of dynamic performance and freeze-thaw resistance. This study provides conclusive evidence that nano-MgO is a high-function additive for the stabilization of loess soil subjected to freezing-thawing environment.