Durability of a Metakaolin-Incorporated Cement-Based Grouting Material in High Geothermal Tunnels
Bibliographic record
Abstract
To improve the durability of cement-based grout in high geothermal tunnel grouting projects, metakaolin was incorporated to replace 8% of the cement. The permeability, chloride penetration, and sulfate and carbonate erosion tests were carried out on the grout cured at varying temperatures (20, 30, 40, 50, and 60 °C). It was shown that with the increase in curing temperature, the impermeability and resistance to chloride penetration initially increased and then decreased, reaching the highest values at 40 °C. Furthermore, the incorporation of metakaolin into grout enhanced the impermeability by 11.11-38.91% and resistance to chloride penetration by 12.23-12.77%. As attacked by sulfate, the surface spalling of the specimen was more obvious with the increase in the curing temperature and immersion time. Conversely, the appearance remained almost unchanged under carbonate erosion. As immersion time increased, both the antisulfate and anticarbonate erosion coefficients declined. The effect of curing temperature on erosion resistance was assessed via the relative antierosion coefficient. When immersed in sulfate, the coefficient achieved the highest value of 1.08 as cured at 30 °C, and in carbonate, the coefficient reached a maximum of 0.99 as cured at 40 °C. Through scanning electron microscopy and binarized images, it was verified that gypsum and ettringite were formed during sulfate attack, leading to volume expansion and cracking, consequently reducing the strength. Meanwhile, in the case of carbonate erosion, calcium hydroxide (CH) and calcium silicate hydrate gel (C-S-H) were dissolved and degraded, resulting in a large number and size of pores in the grout. The research results have certain theoretical significances and reference values for the application of cement-based grouting materials in high geothermal environments.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".