Mechanical Behavior of RC and SFRC Precast Tunnel Lining Segments under Chloride Ions Exposure
Bibliographic record
Abstract
The structural integrity of precast concrete tunnel lining (PCTL) segments largely depends on its durability performance. The ingress of chloride ions into PCTL segments can induce reinforcement corrosion, which has been the primary cause that jeopardizes the structural safety of PCTL. This study explores the mechanical behavior of specimens extracted from full-scale PCTL segments made with conventional steel-rebar-reinforced concrete (RC) and steel-fiber-reinforced concrete (SFRC) for a subway tunnel in Canada and subjected to chloride ions exposure. Test specimens were subjected to chloride ion (Cl−) solutions with various concentrations (3.5 and 10.0%) for up to 16 months, combined with weekly wetting and drying cycles. The mechanical degradation of RC and SFRC specimens was assessed after every 4 months of chloride ions exposure. Initially, an increase in concrete mass by 0.84 and 0.35% was observed for RC and SFRC PCTL segments, respectively, after 4 months of 3.5% Cl− exposure. However, after 8 months of Cl− exposure, a decreasing trend in mass was observed for both the RC and SRFC specimens. Furthermore, results indicated that the mechanical properties of conventional RC PCTL segments were more vulnerable to chloride-induced damage compared to that of SFRC PCTL segments. For instance, 19 and 47% decreases in compressive and flexural strengths, respectively, were observed in RC specimens after 12 months of exposure to 3.5% Cl− solution. Exposure to 10% Cl− solution led to a greater reduction in the mechanical properties of RC specimens compared to that of 3.5% exposure. No significant decrease in compressive and flexural strengths was observed in SFRC specimens due to Cl− exposure. Interestingly, the mechanical performance of SFRC specimens improved when subjected to chloride ions. Experimental results for both the RC and SFRC segments point to the potential of SFRC as a strong contender in the construction of precast concrete tunnel linings.
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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".