Carbonation of cementitious wasteforms under supercritical and high pressure subcritical conditions
Bibliographic record
Abstract
A comparison of cement wasteform carbonation under subcritical and supercritical CO2 conditions has been conducted, as well as leach tests on the carbonated products. Cement samples were prepared with water containing As, Cs, Sr, Ni and Cl, and dried under vacuum prior to exposure to CO2 gas at sub and supercritical conditions. Carbonation under supercritical conditions (50 degrees C, 1200 psi) showed similar CO2 mass uptake as subcritical carbonation (25 degrees C, 800 psi). The apparent depth of carbonation from microscopic examination, however, appeared greater with the supercritical treatment. Microscopic examination also revealed a dark intermediate zone, likely a chemical transition area, between the uncarbonated and carbonated material. Results from experiments where the initial water to cement ratio (w/c) and curing time were varied indicate that high w/c ratios and short curing times promote greater carbonation. In addition, the pore network in specimens with low w/c ratios (0.45) completely filled with water during carbonation. This caused pore water containing soluble contaminants to exude from the specimens. This does not occur at a w/c of 0.60 because the larger pore network after the drying step easily accommodates all the water produced during the reaction. No measurable arsenic or nickel were released in leach tests conducted on both carbonated and uncarbonated specimens. Calcium, cesium and strontium leachability were reduced by carbonation while the leachability of chloride and nitrate were increased with carbonation. Samples carbonated under supercritical pressure conditions showed similar leaching characteristics as samples carbonated under subcritical conditions.
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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 | 0.000 | 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) | 0.001 | 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 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".