Diffusivity of CO<sub>2</sub> in Bitumen: Pressure–Decay Measurements Coupled with Rheometry
Bibliographic record
Abstract
The combined pressure-decay technique with rheometry is developed to measure the diffusivity of carbon dioxide (CO 2 ) in bitumen at temperatures of 30, 50, and 70 °C and pressures of 2 and 4 MPa. Mixing due to shear imposed by a rheometer allows rapid direct measurement of the equilibrium pressure in CO 2 –bitumen systems accurately. The comparison of the measured equilibrium pressures with the values obtained from the data regression demonstrates significant discrepancies, which can lead to a great deviation in the diffusivity, up to 5-fold different than the true values. The measured values for the diffusivity of CO 2 into the bitumen increase with temperature, following the Arrhenius equation. By changing the temperature from 30 °C to 70 °C, the diffusivity increases by 88% at 2 MPa and 54% at 4 MPa. The diffusivity also increases with the pressure, suggesting the ease of diffusion at the presence of the CO 2 molecules in the liquid phase. The effect of pressure is more dominant at lower temperatures while the diffusivity increase is 53% at 30 °C, compared to 25% at 70 °C. Furthermore, the findings demonstrate that the CO 2 –bitumen system does not follow any constant pattern in the diffusivity–viscosity–temperature relationships, which is due to the ongoing phase change at the studied temperature range.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".