# 039. Supplementary binder usage

**Question:** How do observed supplementary-binder fractions compare in 28-day samples?

## Result

The largest computed metric is 51.02 for (0.0, 0.2]; the smallest is 28.43 for (0.4, 0.6]. Metric: median_strength (MPa).

No emissions or costs are supplied; a replacement fraction cannot establish a sustainability benefit.

![Supplementary binder usage](outputs/chart.png)

| fraction_band | samples | median_strength | p10 |
| --- | --- | --- | --- |
| (-0.001, 0.0] | 80 | 32.01 | 19.69 |
| (0.0, 0.2] | 13 | 51.02 | 37.82 |
| (0.2, 0.4] | 141 | 40.93 | 26.91 |
| (0.4, 0.6] | 120 | 28.43 | 13.28 |
| (0.6, 1.0] | 71 | 31.03 | 24.58 |

The chart shows 5 of 5 result rows; the table previews the first 5 in the analysis-defined order. [Download the full result table](outputs/results.csv). Numerical values are computed from the source; missing results stay unavailable.

## Method

Restrict to 28-day tests, then summarize strength by slag-plus-fly-ash share.

The study uses shared source preparation and reusable statistical routines. Its specific transformations are in [analysis.py](analysis.py), and common model/evaluation code is in [portfolio/methods.py](../../portfolio/methods.py). The [notebook](analysis.ipynb) executes the study and displays the saved results.

## Decision and limitations

Investigate comparable alternatives using additional durability, cost and embodied-carbon evidence.

Laboratory observations do not certify a construction mix. Composition and curing conditions are confounded. Models require independent engineering validation and cannot replace strength testing. 

Related studies may share observations or holdouts. These are focused analytical studies, not independent replications or deployed business systems. Any model refinements informed by these results need new untouched evaluation data. No commercial impact is inferred from an association or backtest.

## Reproduce

From the repository root, after installing `requirements.txt`:

```powershell
python projects/039-supplementary-binder-usage/analysis.py
```

Source data are downloaded automatically if absent. Original archives are retained unchanged and checked by SHA-256. The cleaned cache normalizes column names; field-specific changes are visible in [data preparation](../../portfolio/data.py). Runtime evidence is in [receipt.json](outputs/receipt.json).

## Source

[Concrete Compressive Strength](https://archive.ics.uci.edu/dataset/165/concrete+compressive+strength), Yeh (1998). [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). Source data are transformed and aggregated in this study. [Source provenance](../../data/provenance/concrete.json) and [prepared-data audit](../../data/provenance/concrete_prepared.json) record the downloaded files, field coverage and hashes.