The binders, and what distinguishes them
A "cement" is not one material. EN 197-1 recognizes five main types and some twenty-seven products, and the difference between them is how much of the clinker has been replaced, and by what. That single question decides the chemistry: which elements enter the paste, which hydrates can form, and which of this package's models the calculation needs.
This page is the map. The calculations themselves are on the pages it points to.
The families
| type | name | clinker | main other constituent |
|---|---|---|---|
| CEM I | Portland | 95–100 % | — |
| CEM II/A-S | Portland-slag | 80–94 % | blastfurnace slag 6–20 % |
| CEM II/B-S | Portland-slag | 65–79 % | blastfurnace slag 21–35 % |
| CEM II/A-D | Portland-silica fume | 90–94 % | silica fume 6–10 % |
| CEM II/A-P, /A-Q | Portland-pozzolana | 80–94 % | natural (P) or calcined (Q) pozzolana 6–20 % |
| CEM II/B-P, /B-Q | Portland-pozzolana | 65–79 % | pozzolana 21–35 % |
| CEM II/A-V, /A-W | Portland-fly ash | 80–94 % | siliceous (V) or calcareous (W) fly ash 6–20 % |
| CEM II/B-V, /B-W | Portland-fly ash | 65–79 % | fly ash 21–35 % |
| CEM II/A-T, /B-T | Portland-burnt shale | 80–94 / 65–79 % | burnt shale 6–20 / 21–35 % |
| CEM II/A-L, /A-LL | Portland-limestone | 80–94 % | limestone 6–20 % |
| CEM II/B-L, /B-LL | Portland-limestone | 65–79 % | limestone 21–35 % |
| CEM II/A-M, /B-M | Portland-composite | 80–94 / 65–79 % | a mixture of the above |
| CEM III/A | Blastfurnace | 35–64 % | slag 36–65 % |
| CEM III/B | Blastfurnace | 20–34 % | slag 66–80 % |
| CEM III/C | Blastfurnace | 5–19 % | slag 81–95 % |
| CEM IV/A | Pozzolanic | 65–89 % | D + P + Q + V + W, 11–35 % |
| CEM IV/B | Pozzolanic | 45–64 % | D + P + Q + V + W, 36–55 % |
| CEM V/A | Composite | 40–64 % | slag 18–30 % and pozzolana/fly ash 18–30 % |
| CEM V/B | Composite | 20–38 % | slag 31–49 % and pozzolana/fly ash 31–49 % |
The letters
EN 197-1 designates each constituent by a letter, and the composite families (CEM II/*-M, CEM IV, CEM V) use them without repeating the name. They are:
| letter | constituent |
|---|---|
| S | blastfurnace slag |
| D | silica fume — the letter is not a mnemonic in English; it is simply the code the standard assigns |
| P | natural pozzolana |
| Q | natural calcined pozzolana |
| V | siliceous fly ash (low calcium) |
| W | calcareous fly ash (high calcium) |
| T | burnt shale |
| L, LL | limestone — LL is the stricter grade, capped at 0.20 % total organic carbon against 0.50 % for L |
So a CEM V/A (S-V) is a composite of slag and siliceous fly ash, and a CEM IV/B (V) is pozzolanic with siliceous fly ash alone. The letter in parentheses is what the binder actually contains, which the calculation needs and the type alone does not give.
The standard is the authority, not this table
The ranges above summarize EN 197-1, Cement — Part 1: Composition, specifications and conformity criteria for common cements. They are given as context for choosing a composition to calculate; percentages are by mass of the main constituents, excluding calcium sulfate and minor additional constituents. Anything with consequences — a conformity claim, a specification — must be read from the standard itself, which this package does not ship and cannot substitute for.
EN 197-5 adds two families this table does not carry: CEM II/C-M and CEM VI, which push the replacement further than EN 197-1 allows.
What each constituent brings to the chemistry
The percentages matter because of what they do. Each constituent changes the element budget, and the element budget decides which hydrates the minimization can form.
| constituent | brings | consequence for the calculation |
|---|---|---|
| clinker | Ca, Si, Al, Fe, and all of the heat | the reference case; see CEM I from the clinker up |
| blastfurnace slag (S) | Ca, Si, Al, Mg, and sulfur as S(-II) | needs a redox treatment: the slag's sulfide meets the pore solution's sulfate, and both must be held at once. The Mg forms hydrotalcite |
| fly ash (V, W) | Si, Al, alkalis; W also Ca | the Al goes into the C-S-H, which then needs CNASH_ss rather than CSHQ |
| natural/calcined pozzolana (P, Q) | Si, Al, alkalis | as fly ash, and at high alkali the zeolites become stable |
| silica fume (D) | Si, and nothing else | lowers the Ca/Si of the C-S-H; no new phase family |
| limestone (L, LL) | CO₃ | changes the aluminate sequence: monocarboaluminate forms instead of monosulphate, which stabilizes the ettringite |
| burnt shale (T) | Ca, Si, Al, sulfate | behaves as a weak clinker plus a pozzolana |
Read the table as a list of model requirements, because that is what it is. A CEM I needs none of this package's later machinery; a CEM III needs the oxidation state to be a conserved quantity; a CEM IV or V needs a C-S-H that can take aluminum and alkalis.
Two things the table does not contain, and both belong to every row of it.
The alkalis of the clinker. A Bogue calculation returns four phases and no Na₂O or K₂O — they are minor oxides, outside the decomposition — and they are what sets the pH of the pore solution, the calcium being held at the portlandite floor near 12.5. A budget entered through Bogue and nothing else returns that floor on every binder alike, which is a signature worth recognizing; see trap 4.
How much of each constituent has reacted. The percentages above are what was put in, not what has dissolved. A Gibbs minimization reacts everything it is handed, so the reacted fraction is part of posing the problem: capped for every constituent alike by the water and space available (powers_alpha_max, and the water budget for why that cap is not thermodynamics), and for a glass capped far lower still by its own dissolution rate — measured, at 28 days, at 38–49 % for a slag and about 20 % for a siliceous fly ash (Durdziński et al., 2017).
What the heat says about all of it
Every joule of hydration heat comes from the clinker. Replacing clinker with anything lowers it, and the ordering of the measured records this package ships is exactly the ordering of the replacement:
| record | family | final Q |
|---|---|---|
122-cemI-52.5R-cizkovice | CEM I | 376 J/g |
116-cemI-52.5R-ladce | CEM I | 355 J/g |
165-cemII-A-LL-42.5R-hranice | CEM II/A-LL | 329 J/g |
149-cemII-B-S-32.5R-mokra | CEM II/B-S | 296 J/g |
184-cemIII-A-42.5N-hranice | CEM III/A | 261 J/g |
200-cemV-A-S-V-32.5R-prachovice | CEM V-A (S-V) | 259 J/g |
121-cemIII-B-32.5N-mokra | CEM III/B | 234 J/g |
Measured on one instrument at 20 °C, from the CC-BY-4.0 deposit of Šmilauer and Reiterman (Šmilauer and Reiterman, 2025); see data/experimental/README.md for the full provenance and for one inconsistency found in the source metadata.
What these records do not report
The deposit gives the calorimetry, the Blaine fineness and the water/binder ratio. It gives neither the clinker phase composition nor the actual replacement level of any blend.
So a calculation of one of these cements has to assume a composition inside the EN 197-1 range of its family. Every page that does so says which number is measured and which is assumed, at the point of use. A page that presented "40 % clinker" as a property of the specimen would be inventing it, and the distinction matters most exactly where a reader is least able to check.
Before you compute: which species to declare
Each line of the table above is also a requirement on the species list, and a Gibbs minimization cannot form a phase it was not given — nor will it tell you that the one it needed was missing. It reports a poor element balance, or a pH of 7, or an assemblage that looks almost right.
Choosing the species list is the check-list, with the six traps that were met while writing this manual and what each looked like when it happened.
Where the calculations are
| page | what it does |
|---|---|
| Bogue Calculation | an oxide analysis to clinker phases — the entry point for a CEM I |
| CEM I from the clinker up | the reference paste, hydrated and certified |
| A CEM I at equilibrium, with every solid solution declared | the phase list as a modeling decision |
| The full Portland cement, through its pore solution | the coupled run, and its calorimetry |
| Calibrating hydration kinetics | the inverse problem, against measured calorimetry |
And one page per blended family, each on the same shape — element budget in, certified assemblage out, measured calorimetry beside it:
| page | family | what it is about |
|---|---|---|
| Two CEM II, and the two different things a replacement can do | CEM II | a carbonate that rewrites the aluminate sequence, against a glass that brings magnesium |
| A blastfurnace cement, and the oxidation state it needs | CEM III | the glass entry route, hydrotalcite, and sulfur at two oxidation states |
| A pozzolanic binder, and the C-S-H that has to carry the aluminum | CEM IV | CSHQ against CNASH_ss, and portlandite as the limiting reagent |
| A composite binder: two glasses at once | CEM V | all four difficulties simultaneously, on one additive budget |
The CEM IV page is the one without a measured specimen behind it — the deposit carries no record of that family — and it says so at its head rather than in a footnote.