Study on reinforcing mechanism of carbon nanotubes on tensile behavior of gangue cemented rockfill

Abstract

Gangue cemented rockfill (GCR) plays a key role in underground reinforcement projects and construction waste recycling. However, the tensile performance restricted by cementitious materials limits its wider application. Hence, in this study, carbon nanotubes (CNTs) was adopted to reinforce the tensile behavior of GCR samples, since CNTs own excellent mechanical properties and promising microstructure modification in cement-based materials. The test results demonstrate that only 0.007 wt% CNTs could significantly improve tensile strength up to 47.7% and ductility failure property. Through the characterization of acoustic emission (AE), digital image correlation (DIC) and SEM techniques, we found that the microscopic improvement of CNTs could reduce the intensity of failure events, promote the distribution of strain field, and weaken the stress concentration. AE counts of single failure events dropped over 80% and cumulative energy decreased up to 76.4%. Besides, the fractal dimension of macro strain field rose by 7.45∼15.5%, which further indicates the more complex strain distribution. The established CNTs pull-out model, based on above results, further revealed that bridging CNTs provided resistance, consumed fatal work during the pull-out process and slowed down the development of microcracks. This research broadens our understanding of the improvement mechanism of CNTs on the failure mode of GCR materials, which is of great significance for CNTs application and the production of eco-friendly construction materials.