To Recycle or Not to Recycle Asbestos-containing Recycled Asphalt Pavement (RAP): That is the Question
Bibliographic record
Abstract
In August 2008, as part of the City of Calgary's commitment to providing a safe work environment for its workers and contractors, The City requested that Golder Associates Ltd. (Golder) conduct an occupational hygiene assessment to determine the potential for worker exposure to asbestos during the various processes of The City Roads Business Unit that impact asbestos-containing asphalt and the use of recycled asphalt pavement (RAP). The final report, Asbestos in Asphalt, Calgary, Alberta, was submitted to the City of Calgary Roads Business Unit on November 27, 2008. Similar to other municipalities in North America, The City of Calgary incorporated chrysotile asbestos fibres (1-2 percent by weight) into their asphalt pavement to improve both durability and lifespan. From the mid-1960s to the mid-1980s, the asbestos-containing asphalt pavement installed by The City was primarily used as a surfacing material on major arterial roads. Since the mid-1980s, as part of pavement resurfacing, these roadways have been planed and recycled asphalt pavement (RAP) has been incorporated into new asphalt to pave various roadways around Calgary. Respecting The City of Calgary's triple bottom line of social, environmental and economic sustainability, the Roads business unit is committed to environmental protection and providing a safe workplace for employees, contractors and the citizens of Calgary. The City of Calgary's Roads Business Unit approached Golder in July 2008 to reassess the potential for asbestos exposure to workers during paving-related activities. The City also temporarily stopped using RAP until the outcome of this study was known.
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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 | 0.014 | 0.025 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.002 | 0.010 |
| Scholarly communication | 0.007 | 0.006 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.007 | 0.005 |
| Insufficient payload (model declined to judge) | 0.008 | 0.004 |
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".