Vacuum Method for Carbonation of Cementitious Wasteforms
Bibliographic record
Abstract
The application of carbonation treatment to cement-based wasteforms as a means to reduce the leachability of entrained undesirable substances, both radioactive and nonradioactive, has been the subject of much study over the past decade. Upon carbonation, hydrated cement phases release their water of hydration and are converted into carbonate minerals. The carbonation process has been shown to reduce the pore size distribution and permeability of the cementitious materials since portions of the original pore network become sites for precipitation of secondary carbonate minerals. As a result, the leachability of entrained contaminants can be markedly reduced. Current methods to carbonate cement-based wasteforms after they have cured rely on exposure to high pressure or supercritical CO2 pressures. In this study, a new low-pressure technique is presented. The method provides more complete carbonation than high-pressure techniques. The principle is to remove the water of reaction as it is produced, thereby maintaining an open pore network to facilitate the transfer of CO2 into the specimen. This is accomplished by conducting the reaction at near-vaccum pressures in the presence of a desiccant. The near-vacuum conditions lower the impedance of water transport from the carbonating specimen to the desiccant due to the large mean free path of the water vapor molecules. The technique was applied to a series of wasteform samples with entrained cationic and anionic waste components. Carbonation penetration depths of up to 11 mm were attained within 45 h of reaction for cylindrical wasteform samples prepared with OPC at a water/cement ratio of 0.60. A carbonation penetration depth of 15 mm was attained in a 6 d reaction of blended cement (OPC and 30% Class 'F' fly ash). In standardized leach tests, cationic waste constituents showed lower leachabilities from carbonated samples than from uncarbonated samples. Anionic waste constituents, however, showed greater leachabilities, and anion leachability increased with the degree of carbonation.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 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) | 0.002 | 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".