Alkali–aggregate reaction in concrete—history of the development of the Canadian concrete expansion test
Bibliographic record
Abstract
This paper is based on an invited address at the 17th International Conference on alkali–aggregate reaction held in Ottawa in May 2024. A previous conference, the 6th, was also held in Ottawa in 1986. Alkali–aggregate reaction in concrete was first discovered in California in the late 1930s and then discovered in Canada in the mid-1950s. This paper briefly describes the first major occurrence and the history of the development of the concrete prism expansion test to predict the reaction in dolomitic limestone concrete aggregates found in eastern Ontario. Subsequent developments and modifications have enabled the test to also identify alkali–silica reactive aggregates. The test was finalized in the 1990s and has not been substantially modified. The key to improving the test was the recognition of loss of alkalis from concrete by a process of alkali leaching during high-humidity storage of the concrete that often reduced the development of the reaction in the laboratory.
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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 | 0.004 | 0.007 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.004 | 0.004 |
| Science and technology studies | 0.003 | 0.004 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.003 | 0.002 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".