PSI - Issue 64

Shaofeng Qin et al. / Procedia Structural Integrity 64 (2024) 168–174 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

169

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of these materials by controlling the fiber length, volume fraction, and bonding capacity [Zollo (1997); Li (2019)]. These fiber-reinforced cementitious composites can exhibit strain-softening or strain-hardening characteristics [Li (2003)]. In addition, controlling the fiber dispersion and alignment can enhance the flexural strength of FRCC [Rutzen et al. (2021); Hambach et al. (2019)]. Recent research has shown that the specific alignment of fibers in carbon fiber-reinforced cementitious composites (c-FRCC) using extrusion-based 3D printing can significantly improve their flexural strength [Rutzen et al. (2021); Hambach et al. (2016)]. This material is highly interesting for additive manufacturing, and it can partially replace conventional reinforced concrete, reducing the need for continuous steel bars and avoiding steel corrosion and degradation under atmospheric or marine conditions [Hambach et al. (2019)]. Additionally, the use of CFs as reinforcement grants the material electrical conductivity, making it suitable for heating elements and structural health monitoring. The mechanical and electrical properties of FRCC (including steel fiber and CF) have been investigated by Dong et al. (2019) and Li (2019) in the last several decades which are heavily affected by material tailoring like types, volume fraction, shape, and aspect ratio, hydrophilicity and hydrophobicity of the added fibers as well as the utilization of the cement or supplementary cementitious material. However, the electrical properties of aligned fibers particularly such as chopped polyacrylonitrile (PAN)-based CFs in cement-based materials, have rarely been studied due to limited control methods for fiber alignment. As additive manufacturing is developing, such as extrusion-based 3D printing techniques, the alignment of fibers with a larger aspect ratio can be achieved. In this study, the specific alignment of chopped PAN-based CFs was successfully controlled using an extrusion-based 3D printing technique, and the electrical properties were investigated under mechanical flexural loading. The findings of this exploratory study may enable the design of novel 3D printing multifunctional composites with conductive channels for heating and self sensing applications under different conditions.

Nomenclature c-FRCC carbon fiber-reinforcement cementitious composites CF carbon fiber PAN polyacrylonitrile

2. Material and methods 2.1. Materials

CEM I 52.5 Portland Cement was procured from Green Island Cement Co., Ltd (Hong Kong, China). Fly ash was generated by a local power plant in Castle Peak (Hong Kong, China). The physical characteristics of chopped polyacrylonitrile (PAN)-based CF (Toho Tenax Co., Ltd. Tokyo, Japan) are listed in Table 1. Besides, a kind of polycarboxylate-type polymer superplasticizer (ADVA® 189, Grace Co., Ltd, America) was used in this study.

Table 1. Physical properties of CFs used in this study. Properties

PAN carbon fiber

Length (mm) Diameter (μm)

12

7

Tensile strength (MPa) Young’s modulus (GPa) Conductivity (kS/m)

4900

230

64.6±2.1

Density (specific gravity, g/cm3)

1.75