Reinforcing effects of carbon nanotubes on cement-based grouting materials under dynamic impact loading

Abstract

Carbon nanotubes (CNTs) are reasonable materials to modify the property of cement-based grouting materials to improve their strength and durability, optimize their pore structure, and reduce their carbon emissions. However, dynamic impact loading frequently occurs in underground engineering, while there is very limited research concerning the reinforcing effects of CNTs on cement-based materials under dynamic impact loading. Hence, in this work, we applied the split Hopkinson pressure bar to investigate the dynamic mechanical behaviors of CNTs cement-based grouting materials. The results exhibited that CNTs cement-based grouting materials presented superior impact resistance, with a maximum peak stress of 59.33 MPa. Compared with plain cement grouting materials, mixing CNTs and fly ash into cementitious composites could reinforce the dynamic compressive properties by 10.25%–31.86%. The impact resistance of CNTs cement-based grouting materials was more significant under high dynamic loading, enhancing the dynamic properties by up to 31.86%, which indicates that CNTs reinforcement is more efficient in impacting engineering. The strain nephogram and fractal dimension further suggested that the excellent capacity of the CNTs in cement-based grouting materials could be achieved after ultrasonic treatment. A mathematical physical model was then established for CNTs reinforcing cement-based materials, revealing the whole process of CNTs extraction from the cement-based and giving a factor that can measure reinforcement performance. The findings of this study not only promote that the CNTs cement-based grouting materials can enhance the dynamic loading properties and reduce cement usage, but also provide a theoretical basis for the subsequent research on the mechanism of the microscopic reinforcement of CNTs.