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Research on the mechanical and electromagnetic properties of white Portland cement paste containing basalt fiber

Li Yue, Liu Yunze, Cheng Yaping, Jin Caiyun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e63, 2023

EN

The search for construction materials that contribute to 5G signal transmission is important for the development of modern communication technologies. In this paper, the mechanical properties of white Portland cement (WPC) paste mixed with basalt fiber (BF) were analyzed and its electromagnetic properties were fully investigated. First, the fluidity and strength of WPC pastes with different BF contents were tested. Subsequently, the electromagnetic parameters of WPC paste samples were tested in the frequency band of 3.94 GHz-5.99 GHz, and their electromagnetic transmission properties were calculated. Finally, the mechanism of BF affecting the strength and electromagnetic transmission performance of WPC pastes was profiled using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results show that BF can reduce the fluidity of WPC pastes. With the increase of BF doping, the strength of WPC paste rises and then decreases, and reaches the maximum strength when the volume content of BF is 0.6%. With the increase of BF content, the electromagnetic wave reflection rate of WPC paste decreases, but the absorption and transmission rate increases. The bridging effect of BF, etc. improves the strength of the paste. In WPC pastes, with the increase of BF doping, the increase of electromagnetic wave absorption rate is smaller than the decrease of reflection rate, which leads to the improvement of electromagnetic transmission performance.

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Electromagnetic properties of cement paste after microwave pretreatment

Li Yue, Liu Yunze, Jin Caiyun

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e185, 2023

EN

In this paper, the effect of microwave pretreatment on the electromagnetic properties of cement paste was investigated. Four different durations of microwave pretreatment were carried out after the standard conditioning of cement paste specimens for 3 days. Subsequently, the electromagnetic properties of the cement paste were tested, the electromagnetic losses of the specimens were calculated and the changes in the dielectric constants were analyzed. Finally, the mechanism by which microwave pretreatment affects the electromagnetic properties was analyzed based on the pore characteristics and hydration results. The results show that microwave pretreatment can improve the electromagnetic loss as well as the dielectric constant of cement paste specimens, but has no significant effect on the magnetic permeability. With the increase of microwave pretreatment time, the reflection loss, absorption loss, and total loss of electromagnetic waves increase significantly, and the multiple reflection loss decreases. The real part of the dielectric constant, imaginary part, and loss angle tangent all increased. There are two main reasons for the increase in electromagnetic loss and dielectric properties of the specimens after microwave pretreatment. One is the significant increase in the percentage of micropores less than 50 nm in the specimen, which increases the reflection loss and absorption loss of electromagnetic waves. On the other hand, microwave pretreatment significantly increased the degree of hydration of the specimen, making the specimen intermediate electrical properties of the larger proportion of the material phase (such as gel), which in turn increased the electromagnetic loss.In this paper, the effect of microwave pretreatment on the electromagnetic properties of cement paste was investigated. Four different durations of microwave pretreatment were carried out after the standard conditioning of cement paste specimens for 3 days. Subsequently, the electromagnetic properties of the cement paste were tested, the electromagnetic losses of the specimens were calculated and the changes in the dielectric constants were analyzed. Finally, the mechanism by which microwave pretreatment affects the electromagnetic properties was analyzed based on the pore characteristics and hydration results. The results show that microwave pretreatment can improve the electromagnetic loss as well as the dielectric constant of cement paste specimens, but has no significant effect on the magnetic permeability. With the increase of microwave pretreatment time, the reflection loss, absorption loss, and total loss of electromagnetic waves increase significantly, and the multiple reflection loss decreases. The real part of the dielectric constant, imaginary part, and loss angle tangent all increased. There are two main reasons for the increase in electromagnetic loss and dielectric properties of the specimens after microwave pretreatment. One is the significant increase in the percentage of micropores less than 50 nm in the specimen, which increases the reflection loss and absorption loss of electromagnetic waves. On the other hand, microwave pretreatment significantly increased the degree of hydration of the specimen, making the specimen intermediate electrical properties of the larger proportion of the material phase (such as gel), which in turn increased the electromagnetic loss.

3

Effect of water-cement ratio on the electromagnetic shielding performance of C3S paste cured long-term

Liu Yunze, Li Yue, Jin Caiyun, Mu Jinlei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 2

art. no. e83, 2023

EN

This paper investigated the electromagnetic shielding properties and the mechanisms of tricalcium silicate (C3S) paste with three water-cement (W/C) ratios after long-term curing. The C3S pastes with three W/C ratios were tested by XRD and other tests for the qualitative and quantitative analysis of the individual phases. The electromagnetic shielding properties and electromagnetic parameters of the specimens were obtained using the waveguide method. Finally, the microscopic mechanism of the variation of electromagnetic shielding properties of C3S paste affected by the W/C ratio was dissected based on the individual phases. The results show that the volume fraction of pore, calcium silicate hydrate (C-S-H) gel, calcium hydroxide (CH), and calcite (CaCO3) in the specimen increases with the rise of the W/C ratio, and the unhydrated C3S decreases; the electromagnetic shielding of the paste specimen increases; the complex relative permittivity gradually increases. The mechanism of the W/C ratio affecting the electromagnetic shielding performance of C3S paste is that, on the one hand, both the volume fraction of C-S-H and the relative permittivity in the solid phase, which have the greatest influence on the electromagnetic shielding performance, gradually increase with the increase of W/C ratio. On the other hand, as the W/C ratio increases, the volume fraction and area fraction of the mesopores in the specimen increase, which increases the internal loss of electromagnetic waves.