Improvement of the Salinized Soil Properties of Fly Ash by Freeze-Thaw Cycles: An Impact Test Study

Zhuo Cheng, Gaohang Cui, Zheng Yang, Haohang Gang, Zening Gao, Daili Zhang and Chen Xi
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Zhuo Cheng: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China
Gaohang Cui: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China
Zheng Yang: School of Automobile, Chang’an University, Xi’an 710064, China
Haohang Gang: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China
Zening Gao: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China
Daili Zhang: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China
Chen Xi: College of Civil Engineering, Northeast Forestry University, Harbin 150040, China

Sustainability, 2021, vol. 13, issue 5, 1-24

Abstract: To explore the mechanism of the microstructural change in salinized soil under freeze-thaw cycles and the strength characteristics of subgrade salinized soil improved by fly ash, an unconfined compressive test, a triaxial shear test, and a scanning electron microscopy test were carried out using salinized soil samples with different fly ash contents along the Suihua to Daqing expressway in China. The results showed that after several freeze-thaw cycles, the unconfined compressive strength, triaxial shear strength, cohesion, and internal friction angle of saline soil showed a decreasing trend. With an increase in the fly ash content, the internal friction angle, cohesion, unconfined compressive strength, and shear strength of the improved saline soil first increased and then decreased. When the fly ash content was 15%, the mechanical indexes, such as cohesion and the internal friction angle, reached the maximum value. Microscopic test results showed that the freeze-thaw cycle will lead to an increase in the proportion of pores and cracks, an increase in the average pore size, and a loosening of the soil structure. The addition of fly ash can fill the soil pores, improve the microstructure of the soil, increase the cohesive force of the soil particles, and improve the overall strength of the soil. Fly ash (15%) can be added to subgrade soil in the process of subgrade construction in the Suihua-Daqing expressway area to improve the shear strength and the resistance to freezing and thawing cycles. These research results are conducive to promoting the comprehensive utilization of fly ash, improving the utilization rate of resources, and promoting sustainable development, thus providing a reference for the design and construction of saline soil roadbed engineering in seasonal frozen areas and the development and construction of saline land belts in seasonal and winter areas.

Keywords: fly ash; saline soil; seasonally frozen area; unconfined compressive strength; shear strength; microscopic pore structure (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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