Compact Tension Testing of Asphalt Binders at Low Temperatures
Bibliographic record
Abstract
This paper documents and discusses the development of a compact tension (CT) test for the grading of asphalt binders. The geometry was chosen because it provides an easy way to obtain the plane-strain fracture toughness (KIc), fracture energy (Gf), and crack tip opening displacement (δt) in brittle failure on a small sample. It is believed that the method will allow for a better ranking of binders in regard to their low-temperature fracture resistance. CT specimens were prepared in different sizes with varying notch depths. KIc was found to be constant, regardless of the notch depth or specimen width for both straight and modified binders. Gf was found to decrease with notch depth; this is thought to be the result of energy-absorbing mechanisms away from the crack tip. Deeper notches or an energy correction is able to account for that issue. A slightly different fracture energy, Jf, was obtained in a more direct fashion from the slope of a plot of the normalized failure energy (Uf/B) versus notch depth (a). Jf provided results close to those obtained with an energy correction from a single notch depth. Reproducibility of the fracture test was found to be good with pooled standard deviations of 5% to 10% for KIc and 15% to 20% for Gf, which is typical for such tests. Given the fact that brittle fracture properties can vary by orders of magnitude for binders of the same Superpave® grade, it is concluded that the test method has a high ability to reveal statistically significant differences in toughness.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".