FAILURE MECHANISM OF CEMENTITIOUS NANOCOMPOSITES REINFORCED BY MULTI-WALLED AND SINGLE-WALLED CARBON NANOTUBES UNDER SPLITTING TENSILE TEST

摘要

Sudden concrete failure is due to inelastic deformations of concrete subjected to tension. However, synthesizing nanomaterials reinforcements has significant impact on cement-based composites failure mechanism. Nanomaterials morphology bridges cement crystals as homogeneous and ductile matrix. In this experiment, cement matrix with water to cement ratio of 0.5 reinforced by 0.2-0.6 wt% of functionalized (COOH group) multi-walled and single-walled carbon nanotubes were used. After sonication of carbon nanotubes in water solution for an hour, the cementitious nanocomposites were casted in cylindrical molds (25 mm diameter and 50 mm height). Failure mechanism of cementitious nanocomposite showed considerable ductility throughout splitting tensile test compared to cement mortar. Additionally, the failure pattern after developing the initial crack provided additional time before ultimate failure occurred in cement-based nanocomposites. The evolution of crack propagation was assessed until ultimate specimen failure during splitting-tensile test on cementitious nanocomposite surface. The deformation of cross section from circle to oval shape augmented tensile strength by 50% in cementitious nanocomposite compared to conventional cement mortar.