Durability Properties of Blended Portland Limestone Cement Containing Calcium Carbonate Nanoparticles
Bibliographic record
Abstract
The use of Portland Limestone Cement (PLC) as a greener alternative to Portland Cement (PC) dates back to 1960s. In Canada, PLC was first introduced in 2008 with the limestone content limit of 15%. While the use of PLC alone in sulfate exposure is prohibited according to CSA A23.1, the limit of 15% is mainly to ensure a suitable level of mechanical and durability performance. Improving the performance of PLC and decreasing its clinker content is very appealing since it can contribute to reducing the carbon and energy footprint of cement industry. Calcium carbonate nanoparticles (NC) have been shown to be effective in accelerating cement hydration in ultra high performance concretes and concretes with high levels of supplementary cementing materials, but their effect on durability has been rarely studied. \nIn this research, limestone cement was made by blending micro limestone powder with general use cement at 15%, 20%, and 25% content levels. NC was used as an additive at 1%, 2%, 3%, and 4% and heat of hydration using isothermal calorimetry technic was evaluated. Based on the results of this test, 2% addition of NC was selected as the most favorable addition level and was used in mortar samples for further durability investigations. Additionally, the same mixtures were made with the addition of 2% nano silica (NS), which is a one of the most widely-used nanoparticles in cement, in order to put the efficacy of NC in perspective. Several mechanical and durability measures such as compressive strength, volume of permeable voids, sorptivity, bulk electrical conductivity, bulk electrical resistivity, and expansion due to ettringite and thaumasite sulfate attack were studied on mortar samples. \nThe results showed that 2% NC addition was significantly effective in improving durability of mortar samples. Also, 2% NC addition was found to be more effective than 2% NS addition in improving all of the measures except for compressive strength. Moreover, considering durability performance, it was concluded that, with the 2% NC addition, limestone content limit of 15% can be safely increased to 20% and even to 25% if sulfate resistance is not required.
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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) | 0.001 | 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".