Direct Shear Behavior of Nanometer Magnesia Reinforced Cement Soil with 28d Age

ABSTRACT

In order to properly understand the modification effects of nanometer magnesia additive on cement soil’s mechanical performance, a consolidated quick shear laboratory test on nano-magnesium-modified cement-soil (NmCS) sample with different mixing ratio at 28-day age was conducted. Eight kinds’ of nanometer magnesia additives with mixing ratios ranging from 0% to 3% were designed to be used in the test. The result shows that: (1) shear stressdisplacement curves of all samples consisted of three distinct stages with brittle failure. Moreover, (2) as the nanometer magnesia mixing ratio increased, the NmCS shear strength also showed an increase at first, followed by a decrease, and the shear strength reached the maximum with the mixing ratio of 1%. (3)In addition, both the friction angle and cohesive force were fluctuating and had a concave and convex shape respectively and (4) with greater deformation resistance, the shear displacement of NmCS was significantly less than the ordinary cement soil in the shear failure process. Finally, according to the test results, the micro-mechanism of NmCS mechanical performance was analyzed from the perspective of cement hydration and particle interaction.

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