Effects of nano-clay on the mechanical and microstructural properties of cement-based grouting material in sodium chloride solution

Abstract

The main objective of this study was to investigate the influence of nano-clay (NC) on the mechanical and microcosmic properties of sulfoaluminate cement grouting material in 5% sodium chloride (NaCl) solution. All specimens were prepared with a water/cement ratio (W/C) of 1.0. The setting time, bleeding ratio, flow time, mass change rate, and uniaxial compressive strength were obtained by various tests. Further, the resistance toward chloride ion penetration and the permeability of pastes were also evaluated. Hydration products and micro-morphology were investigated through X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, and energy dispersive spectroscopy. The test results revealed that with the addition of NC, both the setting time and flow time were significantly shortened and bleeding capacity and mass loss rate decreased; nonetheless, the uniaxial compressive strength increased significantly. Moreover, addition of NC reduced the chloride ion penetration and permeability. Furthermore, the theoretical model based on permeability and immersion time was established, and its correctness was successfully verified by experimental data. As a result, the grouting material with added 2% NC exhibited the best experimental performance, whereas 3% and more content of NC resulted in inferior performance; however, it was still better than that of the control group (NC = 0%). Moreover, microcosmic test results showed that ettringite is the main product of the dominant hydration reaction. It was thus proved that NC could promote the hydration process, and thus it weakens the chloride ion erosion due to the porosity reduction effect.