Freeze-thaw-induced microstructural damage in polyester fiber-reinforced cementitious composites revealed by X-ray microtomography
Bibliographic record
Abstract
Fiber-reinforced cementitious composites are increasingly used in cold-region infrastructure because of their robustness, rapid installation, and sustainability. However, their long-term behavior under freeze-thaw cycles (FTCs) is still poorly understood at the microstructural scale. This study investigates frost-induced damage in a polyester fiber-reinforced cementitious composite using a fully saturated, closed-system protocol over 100 laboratory FTCs. High-resolution X-ray micro-computed tomography (11 µm voxel) performed at nine time points on a single specimen, combined with deep-learning segmentation, yields fiber-resolved pore and crack evolution and a mechanism-informed interpretation. The combined pore-plus-crack volume fraction rose from 10.0 % to 21.0 %, with local maxima up to 24.8 % in fiber-sparse zones. Thermomechanical modeling of a 185 µm cylindrical pore shows that differential thermal expansion between ice and matrix generates hoop stresses far exceeding those from crystallization pressure, identifying thermal-dilation mismatch as the dominant cracking mechanism under full saturation. Although polyester fibers usually toughen the composite under mechanical loading, freeze–thaw induces internal pore expansion that produces tensile hoop stresses in the matrix and concentrates them at fiber-matrix interfaces. These results provide new microstructural insight into durability limits and underscore the need to optimize pore structure and fiber-matrix interfaces to enhance freeze–thaw resistance. • Polyester reinforcement fibers were found to locally amplify freeze–thaw cracking by concentrating stresses around fiber–matrix interfaces in the cementitious composite. • The geometry and connectivity of the pore network were shown to control the initiation and growth of freeze–thaw damage, with local porosity rising from 10 % to 24.8 % after 100 cycles. • A deep-learning segmentation approach enabled reliable phase separation in three-dimensional tomographic images of the heterogeneous composite despite overlapping grey levels. • Thermo-mechanical analysis revealed that thermal expansion mismatch between ice and the cement matrix generates hoop stresses exceeding 120 MPa, identifying it as the dominant cracking mechanism under full saturation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 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) | 0.006 | 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 teacher head, 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".