Investigation of the low-temperature cracking performance of field-produced asphalt mixture in the state of Iowa
Bibliographic record
Abstract
Low-temperature cracking, also known as thermal cracking, is the most common pavement distress found in asphalt pavements in regions experiencing cold climates such as the Northern United States and Canada. Low-temperature cracking manifests as surface-initiated transverse cracks of various lengths and widths on the pavement. Low-temperature cracking occurs because of high thermal-induced tensile stresses buildup, which causes cracking when they exceed pavement tensile strength. These cracks may lead to water infiltration into the underlying pavement layers and air permeability, thus oxidation of the binder and therefore loss of pavement integrity and reduced pavement life. The loss of pavement integrity leads to decreased ride quality for road users and increased rehabilitation and maintenance costs. The federal government has encouraged the use of recycled material during pavement construction. Thus, specifications have been developed to accommodate the use of recycled materials. For low-temperature cracking, most departments of transportation (DOT) have established low-temperature cracking tests to be carried out where recycled asphalt pavement (RAP) binder exceeds 25% of the total asphalt in an asphalt mix design to characterize mixtures for long-term pavement performance. 400 J/m2 , Disk-Shaped Compact Tension (DCT) test and Semicircular Bend tests (SCB), fracture energies have been set as the minimum fracture energy values in the specifications. DCT and SCB fracture energy is the parameter that is often used to show the fracture resistance or low temperature cracking performance of asphalt mixtures. The test specimens for SCB are easy to fabricate and reproduce using either 150mm diameter field-cored asphalt concrete or 150mm diameter standard laboratory compacted samples. SCB has been used to evaluate the factors that affect fracture energy, estimate fatigue cracking using the fracture toughness, and determine testing configuration effect in SCB fracture of asphalt mixtures. The Iowa DOT uses the DCT test as a criterion for the low-temperature cracking performance of asphalt mixtures. The minimum Gf values for these criteria are 400J/m2, 460J/m2, and 690J/m2 for traffic levels of Standard Traffic (ST), Heavy Traffic (HT), and Very Heavy Traffic (VT), respectively. However, the DCT test is only carried out when binder replacement exceeds 30% for mixtures containing only RAP or 25% for mixtures containing asphalt binder from recycled asphalt shingles. Good fracture properties of pavement for long-term performance can be achieved by understanding the current mixtures' fracture properties and relating to the performance. Characterizing the mixture can help produce a durable mix and prediction of the performance for cracking prevention and developing maintenance measures. This research aims to evaluate low-temperature cracking of the field-produced asphalt mixture in the State of Iowa, with the intention to understand these mixtures' resistance to low-temperature cracking. Ten different field-produced asphalt mixtures from projects paved between 2013 and 2018 were evaluated. These mixtures were reheated for two hours and were laboratory compacted using a gyratory compactor to produce specimens with 150 mm diameter and a height of approximately 50 mm. DCT testing was carried out following ASTM D7313-13, and SCB tests were carried out as specified by AASHTO TP 105-13 to determine the fracture energies of the compacted samples. The I-FIT Illinois test procedure 405 was used for testing at intermediate temperatures to obtain the flexibility index (FI). Fracture energies were used to rank the laboratory cracking resistance of the mixtures and correlation to the field performance of the mixtures. Effect of percent binder replaced on the mixtures fracture energies and the flexibility index was evaluated. The ten mixes have fracture energy values ranging from 265.25j/m2 to 470j/m2 for the DCT, with most of them not meeting the fracture energies for the designed level of traffic. Additionally, the mixtures had average SCB fracture energy ranging from 485 J/m2 to 905 J/m2. The flexibility index obtained for the mixtures ranged from 8.36 to 23.32. The fracture energy and the flexibility index indicate a good overall crack resistance. The correlation between binder replaced and the fracture energies showed a negative correlation. However, only 12.3% of the variability is explained. The specification on the need for a DCT test should be revised to state that the test is required when the asphalt binder replacement exceeds 15% for mixtures with RAP and RAS, rather than the current value of 30% and 25% binder replacement.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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".