Comparative analysis of the effects of Nano-SiO2 and carbon nanotubes on mechanical properties of polyethylene fibre reinforced cementitious composites

To conduct a comparative analysis of the impacts of nanosilica (NS) and carbon nanotubes (CNTs) on the mechanical properties of polyethylene fiber-reinforced cementitious composites, seven groups of ECC specimens with different nanomaterial contents were prepared. The uniaxial compression and tensile tests were conducted, the mineral composition of the specimens was analyzed via X-ray diffraction, and the microstructure of the specimens was examined using a scanning electron microscope. The results show that both types of nanomaterials can effectively enhance the mechanical properties of ECC. Meanwhile, the mechanical characteristics of ECC exhibit a pattern of initial increase followed by a decrease as the nanomaterial content rises. NS exhibited superior performance in augmenting the compressive strength and early tensile crack strength of ECC; however, CNTs were more effective in enhancing the peak compressive strain and peak tensile strain of ECC. The difference between NS and CNTs in the enhancement of tensile strength was not significant. NS can consume more CH crystals to generate C-S-H gels to make the matrix material more dense, and can improve the properties of the transition zone at the fibre-gel interface to enhance the strength of ECC. While CNTs can bridge and inhibit crack extension on the micron scale, and can form a fibre mesh structure with PE fibres for more effective stress transfer, and can improve the deformation capacity of ECC on a macroscopic scale.