Compressive strength and maturity of UHPC cubes and cylinders: new conversion factors and recommendations for early-age quality control
Bibliographic record
Abstract
Ultra-high-performance concrete (UHPC) is a robust cementitious material with high compressive strength exceeding 125 MPa. UHPC can reach up to 80 MPa after one day of casting, which expands the material application domain and makes it appealing for accelerated construction. The appropriate on-site quality control methods should be implemented to guarantee that desired UHPC design has been achieved. The cylinder specimens of 75 mm diameter are used in the United States for quality control purposes. However, cylinders require surface preparation and grinding using special equipment, which consumes more time and affects the strength results at very early ages. Thus, this research aims to establish the conversion factors to use cubes confidently for UHPC quality control. To provide comprehensive and generalized results and allow for immediate implementation, this research considers, for the first time, five UHPC types and a total of eight mixtures with variable steel fiber (SFs) ratios, different cube sizes, and examines the compressive behavior at both early and late ages. The study provides results from about 900 specimens with different curing conditions sets and covers a wide range of strength from 7 to 140 MPa. The experimental results assist in understanding the shape and size effect and revisit the cubes-to-cylinders strength conversion factors. A detailed application for strength maturity was also conducted to further validate the newly proposed conversion factors and extend the use of cubes for early age quality control. To summarize, this study presents new conversion factors for the cube compressive strength at an early age, in addition to recommendations for adopting the strength maturity method for quality control. The dataset of all tested specimens is also summarized and presented in the Appendices.
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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 | 0.008 | 0.010 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.005 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.003 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".