Ion Concentration Distribution and Vickers Hardness Degradation of Fly Ash Cement Pastes in Complicated Environment

Abstract

Abstract: Reinforced concrete structures in subway engineering are often exposed to a combination of sulfate, chloride and stray current. In this study, the effect of the amount of fly ash on the distribution of sulfate ion concentration distribution, chloride ion concentration distribution and Vickers hardness of cement pastes under the coupling effect of sulfate, chloride and electric field were discussed. Moreover, the logistic function was applied to the prediction model of Vickers hardness. Finally, mechanism and deterioration of cement pastes were analyzed by XRD. The results show that as the erosion depth increases, the concentration of sulfate ion decreases continuously, while chloride ion concentration increases first and then declines gradually. With the increase of fly ash addition, the chloride ion and sulfate ion invading cement pastes decrease first and then increase. When the fly ash content increases to 10% (mass fraction), the content of chloride ion and sulfate ion invading specimen is the lowest. The Vickers hardness distribution of the eroded cement pastes is divided into three areas: degraded area, enhanced area and intact area. There is a good correlation between the prediction model and the experimental values of Vickers hardness. A suitable content of fly ash addition reduces the formation of ettringite and gypsum in the eroded cement pastes, and improves the stability of bound chloride ion.

Key words: fly ash, cement paste, sulfate ion, chloride ion, Vickers hardness, prediction model

CLC Number:

TU528.01

WANG Tao, CHU Hongqiang, DING Tianyun, ZHU Zhengyu, ZENG Youxu, XIE Jiaxuan, JIANG Linhua. Ion Concentration Distribution and Vickers Hardness Degradation of Fly Ash Cement Pastes in Complicated Environment[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(12): 4011-4019.

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