Full
HE Bei (1993-), male, Doctoral candidate. E-mail: beihe@tongji.edu.cn
Outline
In order to prevent and control the corrosion damage of concrete structure caused by the stray current generated of metro operation, a high-impedance and ultra-high performance concrete (HI-UHPC) with 28-day resistivity of greater than 3 kΩ/m and compressive strength of greater than 120 MPa was prepared for subway engineering. The parameter influences on the alternating current (AC) impedance performance of HI-UHPC were investigated by AC impedance spectroscopy. An equivalent circuit model suitable for HI-UHPC was proposed. The results show that the compressive strength of HI-UHPC can be improved by adding steel fiber and PVA emulsion powder. The high-frequency arc of ordinary cement-based materials appears at 10-h hydration, while that of HI-UHPC appears at 1-h hydration. The addition of steel fiber can form the conductive channels via overlapping steel fiber in HI-UHPC, increase a possibility of free electron transfer and reduce the volume resistance of the matrix. When PVA emulsion powder is added into HI-UHPC, the interface between the matrix and PVA emulsion powder film is formed, changing the pore structure, reducing the effective conductive path in the interior of HI-UHPC, and ultimately improving the impedance performance. The equivalent circuit model of HI-UHPC consists of connected conductive path, disconnected conductive path and insulated path as well. As the ages increase, the hydration products and polymer films gradually form, the free water in the matrix consumes, and the pore structure becomes dense, leading to the blocking of the carrier transport channels in the pores. The resistance of connected conductive channel and the resistance of unconnected conductive channel increase, while the capacitance of unconnected conductive channel and the capacitance of insulating conductive matrix decrease.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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