Tensile Performance of GFRP Bars after Being Sprayed with Shotcrete
Bibliographic record
Abstract
Shotcreting involves pneumatically spraying concrete at high velocities of approximately 100 km/h, yielding efficient construction, but raises concerns that the high-velocity spray can damage glass fiber–reinforced polymer (GFRP) rebars. This study is the first to investigate shotcrete’s potential to harm the tensile performance of GFRP bars by subjecting 48 bars to wet-mix shotcrete, using conventional industry practices and equipment, for spray durations of 5, 15, or 25 s. Two common types of 15.9 mm diameter GFRP rebar with different surface profiles were used, comprising ribbed or sand-coated bars. Two shotcrete mixes were used with either round (pea gravel) or angular (crushed limestone) aggregate. After shotcreting, all 48 abraded and 16 control bars were 3D-scanned to quantify the damage, if any, and measure their minimum cross-sectional area before tension testing the bars. Shotcrete damage to the bars was caused primarily by abrasion rather than impact damage from high-velocity aggregate impacts. Varying abrasion severity was observed. Common observations include removed sand-coating and local fiber erosion in one bar type and partially worn-away ribs in the other. Prismatic sand-coated bars were more susceptible to shotcrete abrasion than ribbed bars and showed nonlinearly increasing abrasion with spray duration. The average and maximum cross-sectional area losses were approximately 7% and 18% for sand-coated bars sprayed for 25 s with angular aggregate shotcrete. This area loss resulted in average and maximum reductions in tensile capacities of 11% and 22%, respectively; however, the bars still exceeded their guaranteed tensile capacity. The damage to ribbed rebars from shotcrete abrasion was negligible, with the ribs seeming to act as a sacrificial layer. The round aggregate mix produced negligible damage to both bar types. A model is developed to predict bar abrasion duration during construction based on member geometry and nozzle parameters, which is then used to predict cross-sectional area loss and force reduction. The model was verified against another experimental study and predicted exposure time within an 11% difference. While this study offers a first look at shotcrete abrasion of GFRP bars, further research is needed to predict abrasion damage conservatively.
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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 | 0.000 | 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) | 0.002 | 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".