Use of oxygen-rich environment to test concrete containing sulphide-bearing aggregate and evaluate the effect of mitigative measures
Bibliographic record
Abstract
Oxygen plays a key role in the oxidation of sulphide minerals in concrete aggregates. This study developed an accelerated test using high oxygen concentrations to evaluate the potential for sulphide oxidation and internal sulphate attack in concrete. Two methods were used: drying of water-saturated samples in an oxygen-filled environment, referred to as oxygen-drying, and wetting of semi-dried samples in oxygen chambers at 100 % relative humidity , referred to as oxygen-wetting. The idea beyond the two methods was to maintain the samples at levels of saturation and access to oxygen that accelerates oxidation. The oxygen-wetting method produced higher expansion. In this method, different approaches of pre-drying the samples before exposure to oxygen and 100 % RH were attempted, and the optimized approach – drying the samples at 40 °C for 24 hours – was selected. The method was used to evaluate the efficacy of possible mitigation methods. The acceleration of the proposed method was validated by comparing its expansion to that of outdoor samples, revealing that the lab samples exhibited 7–10 times greater expansion Using metakaolin and slag increases the expansion, likely due to the higher reactive alumina content in the mixture. Type-F fly ash reduces the expansion since the alumina in fly ash is less reactive. High silica fume cement combined with slag reduces the deterioration, partly because it decreases permeability. Crystalline coatings applied after cracking reduced the ongoing expansion; however, the reduction was not significant. The sodium silicate-based coating was more effective when applied before cracking than when applied after cracking.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 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 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".