Decalcification kinetics of calcium silicate hydrates: role of Al content, crystallinity, and initial pH
Bibliographic record
Abstract
Calcium silicate hydrate (C-S-H) and calcium aluminum silicate hydrate (C-A-S-H) are the primary binding phases in Portland and blended cementitious systems, commonly retaining an amorphous to semi-crystalline structure. The longevity as well as the mechanical performance of such cementitious composites largely rely on the characteristics of C-S-H. On the other hand, ancient Roman concrete contains the crystalline analog of this phase – tobermorite, which is often attributed as the primary source of the extraordinary durability of this cementitious composite. With a goal of understanding the root cause of the enhanced durability of ancient and modern cementitious composites, this study investigated how amorphous and crystalline forms of C-S-H/C-A-S-H phases are affected by decalcification-induced degradation. Two different decalcifying environments were evaluated – using accelerated carbonation and NH 4 NO 3. In-situ Fourier-Transform Infrared (FTIR) spectroscopy was utilized to evaluate the decalcification of these phases for 18 h. The findings indicate that during this period, C-S-H was completely decalcified under accelerated carbonation, as reflected by the decrease in Q 2 silicate species in the network and the formation of silicate species with a higher degree of polymerization (Q 3 and Q 4 ). Conversely, the crystalline version of these phases (i.e., tobermorite) showed minimal impact from decalcification, with only a 10-15% decrease in Q 2 under the same exposure condition. This decalcification observation was corroborated using NH 4 NO 3 , yielding similar results. Optimization of low-carbon alternative binders can facilitate favorable conditions for the crystallization of C-S-H and C-A-S-H, thereby fostering the development of a sustainable and durable cementitious composite.
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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) | 0.000 | 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 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".