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Experimental Study on Carbonation of Cement-Based Materials in Underground Engineering
Jun Zheng1,2, Gang Zeng3,4, Hui Zhou1,2
1China Railway 11th Bureau Group Co., Ltd., Wuhan 430061, China.
Materials (Basel, Switzerland)
|August 12, 2022
Summary
Carbonation significantly impacts cement durability in tunnels. Water-immersion environments cause greater material degradation and pore expansion than saturated-humidity conditions, affecting tunnel lining safety.
Area of Science:
- Civil Engineering
- Materials Science
- Corrosion Science
Background:
- Diversion tunnel linings face durability challenges due to corrosive water environments.
- Understanding carbonation effects on cement-based materials is crucial for infrastructure longevity.
Purpose of the Study:
- To investigate the impact of carbonation on cement-based materials under water-immersion and saturated-humidity conditions.
- To quantify carbonation depth and material property changes in different corrosive environments.
Main Methods:
- Exposure of cement mortar samples to varying CO2 concentrations in water-immersion and saturated-humidity environments.
- Visual inspection for color changes and measurement of carbonation depth over time.
- Analysis of calcium-silicon (Ca/Si) ratio and pore structure characteristics.
Main Results:
- Water-immersion environments show a distinct visual boundary of carbonation, unlike atmospheric conditions.
- Carbonation depth increases significantly over time in saturated-humidity (16.71 mm at 200 days) but minimally in water-immersion (2.31 mm).
- Water-immersion leads to a substantial decrease in Ca/Si ratio (0.11) and increased pore volume, accelerating material degradation.
Conclusions:
- Saturated-humidity environments primarily affect pore solution pH, while water-immersion severely degrades cement-based material structure.
- The carbonation coefficient is over nine times higher in saturated-humidity than in water-immersion environments.
- Findings offer critical insights for designing and maintaining durable diversion tunnel linings in corrosive conditions.
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