Cement chemist notation
Encyclopedia
Cement chemist notation was developed to simplify the formula
s cement
chemists use on a daily basis. It is a "short hand" way of writing the chemical formula
of oxide
s of calcium
, silicon
, and various metal
s.
, Ca(OH)2, must first be converted in oxide and water.
To better understand the conversion process of hydroxide anions in oxide and water, it is necessary to consider the autoprotolysis of the hydroxyl
anions; it implies a proton
exchange between two OH–, like in a classical acid-base reaction:
or also,
For portlandite
this gives thus the following mass balance:
Thus portandite can be written as CaO • H2O or CH.
and in the non-hydrated Portland cement
.
They are formed at high temperature (1 450 °C) in the cement kiln
and are the following:
The four compounds referred as C3S, C2S, C3A and C4AF are known as the main crystalline phases of Portland cement. The phase composition of a particular cement can be quantified through a complex set of calculation known as the Bogue Formula.
products formed in hardened cement pastes (HCP) are more complicated, because many of these products have nearly the same formula and some are solid-solutions with overlapping formula. Some examples are given below:
The hyphens in C-S-H indicate a calcium silicate hydrate phase of variable composition, whilst CSH indicates a calcium silicate phase CaH2SiO4.
For instance, in ceramics applications, the kaolinite
formula can also be written in terms of oxides, thus the corresponding formula for kaolinite,
is
or in CCN
An example could be the formal comparison of belite hydration and forsterite
serpentinisation dealing both with the hydration of two structurally similar earth -alkaline silicates, Ca2SiO4 and Mg2SiO4, respectively.
Calcium system: belite hydration:
Magnesium system: forsterite
serpentinisation:
The ratio Ca/Si (C/S) and Mg/Si (M/S) decrease from 2 for the di-calcium and di-magnesium silicate reagents to 1.5 for the hydrated silicate products of the hydration reaction. In other term, the C-S-H or the serpentine are less rich in Ca and Mg respectively. This is why the reaction leads to the elimination of the excess of portlandite
(Ca(OH)2) and brucite
(Mg(OH)2), respectively, out of the silicate system, giving rise to the crystallization of both hydroxides as separate phases.
The rapid reaction of belite
hydration in the setting of cement
is formally "chemically analogue" to the slow natural hydration of forsterite
(the magnesium end-member of olivine
) leading to the formation of serpentine
and brucite
in nature. However, the kinetic of hydration of poorly crystallized artificial belite is much swifter than the slow conversion/weathering of well crystallized Mg-olivine
under natural conditions.
This comparison suggests that mineralogists could probably also benefit from the concise formalism of the cement chemist notation in their works.
Formula
In mathematics, a formula is an entity constructed using the symbols and formation rules of a given logical language....
s cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
chemists use on a daily basis. It is a "short hand" way of writing the chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
of oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
s of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
, silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, and various metal
Metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...
s.
Abbreviations of oxides
The main oxides present in cement (or in glass and ceramics) are abbreviated in the following way:| CCN | Actual Formula | Name |
|---|---|---|
| C | CaO | Calcium oxide Calcium oxide Calcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature.... , or lime |
| S | SiO2 | Silicon dioxide Silicon dioxide The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity... , or silica |
| A | Al2O3 | Aluminium oxide Aluminium oxide Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry... , or alumina |
| F | Fe2O3 | Iron oxide Iron oxide Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,... |
| T | TiO2 | Titanium dioxide Titanium dioxide Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of... |
| M | MgO | Magnesium oxide Magnesium oxide Magnesium oxide , or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds... |
| K | K2O | Potassium oxide Potassium oxide Potassium oxide is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound... |
| N | Na2O | Sodium oxide Sodium oxide Sodium oxide is a chemical compound with the formula Na2O. It is used in ceramics and glasses, though not in a raw form. Treatment with water affords sodium hydroxide.... |
| H | H2O | Water Water Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a... |
| C | CO2 | Carbon dioxide Carbon dioxide Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom... |
| S | SO3 | Sulfur trioxide Sulfur trioxide Sulfur trioxide is the chemical compound with the formula SO3. In the gaseous form, this species is a significant pollutant, being the primary agent in acid rain. It is prepared on massive scales as a precursor to sulfuric acid.-Structure and bonding:Gaseous SO3 is a trigonal planar molecule of... |
| P | P2O5 | Phosphorus hemi-pentoxide Phosphorus pentoxide Phosphorus pentoxide is a chemical compound with molecular formula P4O10 . This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant.-Structure:... |
Conversion of hydroxides in oxide and free water
For the sake of mass balance calculations, hydroxides present in hydrated phases found in hardened cement paste such as, in portlanditePortlandite
Portlandite is a rare oxide mineral, the naturally occurring form of calcium hydroxide . It is the calcium analogue of brucite .-Occurrence:...
, Ca(OH)2, must first be converted in oxide and water.
To better understand the conversion process of hydroxide anions in oxide and water, it is necessary to consider the autoprotolysis of the hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
anions; it implies a proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
exchange between two OH–, like in a classical acid-base reaction:
- OH– + OH– → O2– + H2O
- acid 1 + base 2 → base 1 + acid 2
or also,
- 2 OH– → O2– + H2O
For portlandite
Portlandite
Portlandite is a rare oxide mineral, the naturally occurring form of calcium hydroxide . It is the calcium analogue of brucite .-Occurrence:...
this gives thus the following mass balance:
- Ca(OH)2 → CaO + H2O
Thus portandite can be written as CaO • H2O or CH.
Main phases in Portland cement before and after hydration
These oxides are used to build more complex compounds. The main crystalline phases described hereafter are related respectively to the composition of:- Clinker and non-hydrated Portland cement, and;
- Hardened cement pastes obtained after hydration and cement setting.
Clinker and non-hydrated Portland cement
Four main phases are present in the clinkerClinker (cement)
thumb|200px|right|Typical clinker nodulesthumb|200px|right|Hot clinkerIn the manufacture of Portland cement, clinker is lumps or nodules, usually 3-25 mm in diameter, produced by sintering limestone and alumino-silicate during the cement kiln stage.-Uses:...
and in the non-hydrated Portland cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
.
They are formed at high temperature (1 450 °C) in the cement kiln
Cement kiln
Cement kilns are used for the pyroprocessing stage of manufacture of Portland and other types of hydraulic cement, in which calcium carbonate reacts with silica-bearing minerals to form a mixture of calcium silicates...
and are the following:
| CCN | Actual Formula | Name | Mineral Phase |
|---|---|---|---|
| C3S | 3 CaO • SiO2 | Tricalcium silicate | Alite Alite Alite is a name for tricalcium silicate, Ca3SiO5, sometimes formulated as 3CaO·SiO2 . It is the major, and characteristic, mineral phase in Portland cement. The name was given by Törneborn in 1897 to a crystal identified in microscopic investigation of Portland cement... |
| C2S | 2 CaO • SiO2 | Dicalcium silicate Calcium silicate Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and sometimes formulated 2CaO.SiO2. It is one of group of compounds obtained by reacting calcium oxide and silica in various ratios e.g. 3CaO.SiO2, Ca3SiO5; 2CaO.SiO2, Ca2SiO4; 3CaO.2SiO2, Ca3Si2O7 and... |
Belite Belite Belite is an industrial mineral important in Portland cement manufacture, a name for dicalcium silicate, Ca2SiO4, sometimes formulated as 2 CaO · SiO2 .... |
| C3A | 3 CaO • Al2O3 | Tricalcium aluminate Tricalcium aluminate Tricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates... |
Aluminate Tricalcium aluminate Tricalcium aluminate Ca3Al2O6, often formulated as 3CaO·Al2O3 to highlight the proportions of the oxides from which it is made, is the most basic of the calcium aluminates... or Celite |
| C4AF | 4 CaO • Al2O3 • Fe2O3 | Tetracalcium alumino ferrite | Ferrite Calcium aluminoferrite Calcium aluminoferrite is a dark brown crystalline phase commonly found in cements. In the cement industry it is termed ferrite... |
The four compounds referred as C3S, C2S, C3A and C4AF are known as the main crystalline phases of Portland cement. The phase composition of a particular cement can be quantified through a complex set of calculation known as the Bogue Formula.
Hydrated cement paste
HydrationHydration reaction
In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group and a hydrogen cation are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group. The reaction usually runs in a strong acidic, aqueous...
products formed in hardened cement pastes (HCP) are more complicated, because many of these products have nearly the same formula and some are solid-solutions with overlapping formula. Some examples are given below:
| CCN | Actual Formula | Name or Mineral Phase |
|---|---|---|
| CH Portlandite Portlandite is a rare oxide mineral, the naturally occurring form of calcium hydroxide . It is the calcium analogue of brucite .-Occurrence:... |
Ca(OH)2 or CaO • H2O | Calcium hydroxide Calcium hydroxide Calcium hydroxide, traditionally called slaked lime, is an inorganic compound with the chemical formula Ca2. It is a colourless crystal or white powder and is obtained when calcium oxide is mixed, or "slaked" with water. It has many names including hydrated lime, builders lime, slack lime, cal, or... |
| C-S-H Calcium silicate hydrate Calcium Silicate Hydrate is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials.-Preparation:... |
2(CaO) • SiO2 • 0.9-1.25(H2O), and/or; CaO • SiO2 • 1.1(H2O), and/or; 0.8-1.5(CaO) • SiO2 • 1.0-2.5(H2O) |
Calcium Silicate Hydrate Calcium silicate hydrate Calcium Silicate Hydrate is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials.-Preparation:... |
| C-A-H | This is even more complex than C-S-H | Calcium Aluminate Hydrate |
| AFt | C3AS3H30-32 | Aluminate Ferrite trisulfate, or ettringite Ettringite Ettringite is a hydrous calcium aluminium sulfate mineral with formula: Ca6Al2312·26H2O. It is a colorless to yellow mineral crystallizing in the trigonal system... |
| AFm AFm phase An AFm phase is an "alumina, ferric oxide, monosulfate" phase. AFm phases are important in the hydration of hydraulic cements.They are crystalline hydrates with general, simplified formula 3 CaO·2O3·CaSO4·nH2O.... |
C2ASH12 | Aluminate Ferrite monosulfate |
| C3AH6 | 3CaO • Al2O3 • 6 H2O | Hydrogarnet |
The hyphens in C-S-H indicate a calcium silicate hydrate phase of variable composition, whilst CSH indicates a calcium silicate phase CaH2SiO4.
Use in ceramics, glass, and oxide chemistry
The cement chemist notation is not restricted to cement applications but is in fact a more general notation of oxide chemistry applicable to other domains than cement chemistry sensu stricto.For instance, in ceramics applications, the kaolinite
Kaolinite
Kaolinite is a clay mineral, part of the group of industrial minerals, with the chemical composition Al2Si2O54. It is a layered silicate mineral, with one tetrahedral sheet linked through oxygen atoms to one octahedral sheet of alumina octahedra...
formula can also be written in terms of oxides, thus the corresponding formula for kaolinite,
- Al2Si2O5(OH)4,
is
- Al2O3 • 2SiO2 • 2H2O
or in CCN
- AS2H2.
Possible use of CCN in mineralogy
Although not a very developed practice in mineralogy, some chemical reactions involving silicate and oxide in the melt or in hydrothermal systems, and silicate weathering processes could also be successfully described by applying the cement chemist notation to silicate mineralogy.An example could be the formal comparison of belite hydration and forsterite
Forsterite
Forsterite is the magnesium rich end-member of the olivine solid solution series. Forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å , b 10.20 Å and c 5.98 Å .Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites...
serpentinisation dealing both with the hydration of two structurally similar earth -alkaline silicates, Ca2SiO4 and Mg2SiO4, respectively.
Calcium system: belite hydration:
- Belite + water → C-S-H phase + portlandite
- 2 Ca2SiO4 + 4 H2O → 3 CaO · 2 SiO2 · 3 H2O + Ca(OH)2
- 2 C2S + 4 H → C3S2H3 + CH
Magnesium system: forsterite
Forsterite
Forsterite is the magnesium rich end-member of the olivine solid solution series. Forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å , b 10.20 Å and c 5.98 Å .Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites...
serpentinisation:
- Forsterite + water → serpentine + brucite
- 2 Mg2SiO4 + 3 H2O → Mg3Si2O5(OH)4 + Mg(OH)2
- 2 M2S + 3 H → M3S2H2 + MH
The ratio Ca/Si (C/S) and Mg/Si (M/S) decrease from 2 for the di-calcium and di-magnesium silicate reagents to 1.5 for the hydrated silicate products of the hydration reaction. In other term, the C-S-H or the serpentine are less rich in Ca and Mg respectively. This is why the reaction leads to the elimination of the excess of portlandite
Portlandite
Portlandite is a rare oxide mineral, the naturally occurring form of calcium hydroxide . It is the calcium analogue of brucite .-Occurrence:...
(Ca(OH)2) and brucite
Brucite
Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites...
(Mg(OH)2), respectively, out of the silicate system, giving rise to the crystallization of both hydroxides as separate phases.
The rapid reaction of belite
Belite
Belite is an industrial mineral important in Portland cement manufacture, a name for dicalcium silicate, Ca2SiO4, sometimes formulated as 2 CaO · SiO2 ....
hydration in the setting of cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
is formally "chemically analogue" to the slow natural hydration of forsterite
Forsterite
Forsterite is the magnesium rich end-member of the olivine solid solution series. Forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å , b 10.20 Å and c 5.98 Å .Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites...
(the magnesium end-member of olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
) leading to the formation of serpentine
Serpentinite
Serpentinite is a rock composed of one or more serpentine group minerals. Minerals in this group are formed by serpentinization, a hydration and metamorphic transformation of ultramafic rock from the Earth's mantle...
and brucite
Brucite
Brucite is the mineral form of magnesium hydroxide, with the chemical formula Mg2. It is a common alteration product of periclase in marble; a low-temperature hydrothermal vein mineral in metamorphosed limestones and chlorite schists; and formed during serpentinization of dunites...
in nature. However, the kinetic of hydration of poorly crystallized artificial belite is much swifter than the slow conversion/weathering of well crystallized Mg-olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
under natural conditions.
This comparison suggests that mineralogists could probably also benefit from the concise formalism of the cement chemist notation in their works.
See also
- Hydration of belite in cement (analogous to forsterite hydration)
- Hydration reaction of forsterite (olivine) in serpentinisation