Engineering properties and microstructure of expansive soil treated with nanographite powder

To reduce geological disasters caused by expansive soil, it is crucial to use a new type of modified material to rapidly improve soil strength instead of traditional soil improvement materials such as lime and cement. Nanographite powder (NGP) has excellent properties, such as high adsorption, conductivity, and lubrication, since it has the characteristics of small size, large specific surface area, and high surface energy. However, previous studies on the improvement of expansive soil with NGP are not processed enough. To study the improvement effect of NGP on expansive soil, non-load swelling ratio tests, consolidation tests, unconfined compressive strength tests, mercury injection tests, and micro-CT tests on expansive soil mixed with different NGP contents were performed. The results show that the non-load swelling ratio, mechanical properties, and porosity of expansive soil show some increasement after adding NGP. The strength of expansive soil reaches the maximum when the NGP content is 1.450%. The cumulative mercury volume and compressive strain of expansive soil reach the maximum with the 2.0% NGP content. Finally, the modification mechanism of swelling, compressibility, microstructure, and compressive strength of expansive soil by NGP is revealed.