The effect of carbon nanotubes on the mechanical and damping properties of macro-defect-free cements

Zhang Wenhua,Yang Fenghao,Zhang Yunsheng,Zeng Weizhao,Wu Peipei

doi:10.1515/secm-2020-0005

Abstract

Abstract The effect of CNTs on the mechanical and damping properties of macro-defect-free (MDF) cements was studied, and polyvinyl alcohol (PVA) fibers were also studied as a contrast. It was found that the compressive strength of MDF cements was not significantly affected by the two types of fibers. The CNTs enhanced the flexural strength of MDF, while PVA fibers made negative contribution. The strengthening mechanism of flexural strength of MDF cements by CNTs can be summarized as fiber bridging, crack deflection and fiber slippage. For the damping properties, the proper contents of CNTs and PVA fibers improved the loss factor significantly. The interface transition zone (ITZ) between the PVA fibers and matrix was large, which was favorable for fiber slippage. The damping property of MDF cements with CNTs was mainly due to the slippage between the inner tubes of the CNTs rather than the slippage between the CNTs and matrix.

Highlights

Macro-defect free (MDF) cements are ultra-high performance cement-based materials developed by Birchall [1] in the early 1980s
It was found that the significant increases in flexural strength achieved in MDF cements were attributed to a reduction in the density of defects in the materials as well as to chemical reactions occurring between the organic constituent and inorganic ions coming from the hydration products of the cement
Because of the transverse expansion and cracking during compression, most of the CNTs and polyvinyl alcohol (PVA) fibers were in the compressive state and could not play a bridging role in the crack

Summary

Introduction

Macro-defect free (MDF) cements are ultra-high performance cement-based materials developed by Birchall [1] in the early 1980s. The flexural strength of MDF cements can reach up to 300MPa. MDF cements are composite materials obtained by mixing, high shear and hot pressing. The high shear stress produced by the open mill can break the C-C bond in the polymer chain into two active macromolecular functional groups with equal molecular weight. The addition of silica fume can effectively improve the strength of ordinary cement-based materials, but it had an adverse effect on MDF cements. It was found that the addition of fiber could improve the flexural strength and fracture toughness of MDF cements. The fibers formed a network structure in the MDF cements that limited the volume change of the material and improved the mechanical properties. The surface-modified fiber could strengthen the bonding with the matrix to further enhance the bending strength [9]

Methods

Results

Conclusion