# Portland cement
**Portland cement** is the binder used in most concrete and mortar, made by grinding clinker, a sintered material composed dominantly of hydraulic calcium silicates, together with a small amount of calcium sulfate, usually gypsum[1](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx). It is a hydraulic cement: it forms solid hydrates on reaction with water and can harden even under water[2](https://www.cement.org/cement-concrete/types-of-cement/). The name comes from the resemblance of the set product to [Portland stone](https://www.edgepedia.org/portland-stone), a building limestone from the [Isle of Portland](https://www.edgepedia.org/isle-of-portland) off the English coast[1](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx).
| Key fact | Detail |
|---|---|
| Definition | Product obtained by pulverizing clinker consisting of hydraulic calcium silicates, with calcium sulfate usually interground; specific gravity of the particles is about 3.15[1](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx) |
| Origin | Patented by Joseph Aspdin of Leeds, England, on 21 October 1824 (British Patent No. 5022)[3](https://todayinsci.com/A/Aspdin_Joseph/AspdinJoseph-Cement.htm) |
| Clinker phases | Four principal compounds, C\(_3\)S, C\(_2\)S, C\(_3\)A, and C\(_4\)AF, make up about 95% of clinker by weight[4](https://www.cement.org/wp-content/uploads/2024/08/eb071-02w.pdf) |
| Manufacture | Raw materials heated to the beginning of fusion, about 1480 °C, in rotary kilns that may exceed 210 m in length and 5 m in diameter; 2 to 5% gypsum by mass is added during grinding[5](https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=675) |
| Environmental load | About 1.7 tons of raw materials per ton of clinker, yielding about 1 ton of CO\(_2\), roughly half from limestone calcination and half from fuel combustion[6](https://www.usgs.gov/publications/cement-manufacture-and-environment-part-i-chemistry-and-technology) |
| Standard types | ASTM C150 covers ten types: I, IA, II, IIA, II(MH), II(MH)A, III, IIIA, IV, and V[7](https://store.astm.org/c0150_c0150m-21.html) |
## Origin and name
In 1824 Joseph Aspdin, a Leeds bricklayer and mason, received British Patent No. 5022, granted 21 October 1824, for "An Improvement in the Modes of Producing an Artificial Stone", a product he named Portland cement because the set cement resembled the oolitic limestone of Portland, England[3](https://todayinsci.com/A/Aspdin_Joseph/AspdinJoseph-Cement.htm). The patent's specifications were vague: a very pure limestone was burned to lime, mixed with a definite quantity of clay, pulverized wet, dried, crushed, calcined in a vertical kiln, and powdered; it stated neither the proportions of lime and clay nor the burning temperature[3](https://todayinsci.com/A/Aspdin_Joseph/AspdinJoseph-Cement.htm).
Aspdin was not working alone in the field. James Frost had produced "British Cement" from 1811, and the name "Portland cement" appears in a directory of 1823 associated with William Lockwood; Aspdin's patent nonetheless became the foundation document from which the industry traces a continuous thread of production and development[8](https://collections.soane.org/object-m626) • [9](https://cement.mineralproducts.org/MPACement/media/Cement/Publications/2024/Portland_Cement_200_Years_of_Building_for_the_Future.pdf). A debate persists over whether Aspdin's original product was a quick-setting hydraulic lime or a modern slow-setting, high-strength cement; no memorial to him was raised until 1924, the patent centenary, when the American Portland Cement Association installed a plaque in Leeds Town Hall[10](https://www.cementkilns.co.uk/cemkilndoc024.html).
## Manufacture
Cement is made from clinker, which is produced from a precise combination of calcareous, aluminous, ferrous, and siliceous materials transformed by pyroprocessing in a rotary kiln[11](https://www.usgs.gov/centers/national-minerals-information-center/cement-statistics-and-information). The finely ground raw materials are intimately mixed and heated to the beginning of fusion, about 1480 °C. The partially fused material that emerges is clinker in roughly round particles up to the size of golf balls; it is cooled and ground to a very fine powder, which is portland cement[5](https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=675).
During grinding, a small amount of calcium sulfate, about 2 to 5% by mass, is added to control setting properties; for air-entraining cements, the air-entraining addition is interground at this stage[5](https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=675). The process is resource-intensive: about 1.7 tons of raw materials are required per ton of clinker, and production yields about 1 ton of CO\(_2\), with calcination of limestone and fuel combustion each contributing about half[6](https://www.usgs.gov/publications/cement-manufacture-and-environment-part-i-chemistry-and-technology).
## Composition and hydration
Four principal compounds make up about 95% of clinker by weight: tricalcium silicate (C\(_3\)S, also called alite), [dicalcium silicate](https://www.edgepedia.org/dicalcium-silicate) (C\(_2\)S, belite), tricalcium aluminate (C\(_3\)A), and tetracalcium aluminoferrite (C\(_4\)AF)[4](https://www.cement.org/wp-content/uploads/2024/08/eb071-02w.pdf) • [1](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx). The strength and other properties of concrete derive mainly from the hydration of the tricalcium and dicalcium silicates[1](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx).
When water is added, a series of reactions follows. C\(_3\)A reacts with gypsum and water to form ettringite and heat, \( \mathrm{C_3A + 3CSH_2 + 26H \rightarrow C_6AS_3H_{32}} \), releasing 207 cal/g; ettringite consists of long crystals that do not contribute to strength[12](https://www.engr.psu.edu/ce/courses/ce584/concrete/library/construction/curing/Hydration.htm). The tricalcium silicate hydrates to calcium silicate hydrate (C-S-H) and lime, \( \mathrm{2C_3S + 6H \rightarrow C_3S_2H_3 + 3CH} \), releasing 120 cal/g; the short-networked fiber structure of C-S-H contributes greatly to the initial strength of the cement glue[12](https://www.engr.psu.edu/ce/courses/ce584/concrete/library/construction/curing/Hydration.htm). The dicalcium silicate reaction, \( \mathrm{C_2S + 4H \rightarrow C_3S_2H_3 + CH} \), releases less heat (62 cal/g) and proceeds more slowly, so C\(_2\)S is responsible for the long-term strength of portland cement concrete[12](https://www.engr.psu.edu/ce/courses/ce584/concrete/library/construction/curing/Hydration.htm). Gypsum added during final grinding slows the hydration rate of C\(_3\)A[4](https://www.cement.org/wp-content/uploads/2024/08/eb071-02w.pdf).
Sulfate attack is the practical consequence of the aluminate chemistry. Sulfates in soil or water can enter concrete and react with hydrated C\(_3\)A phases, causing expansion, scaling, and cracking; magnesium sulfate can directly attack calcium silicate hydrate[2](https://www.cement.org/cement-concrete/types-of-cement/).
## Types and specifications
In the United States, portland cements are manufactured to meet [ASTM C150](https://www.edgepedia.org/astm-c150), Standard Specification for Portland Cement, harmonized with AASHTO M 85[2](https://www.cement.org/cement-concrete/types-of-cement/). The current specification covers ten types[7](https://store.astm.org/c0150_c0150m-21.html):
- **Type I** for general use, when no special properties are required; **Type IA** is its air-entraining counterpart.
- **Type II** for general use, especially when moderate sulfate resistance is desired; **Type IIA** is air-entraining.
- **Type II(MH)** for general use with moderate heat of hydration and moderate sulfate resistance; **Type II(MH)A** is air-entraining.
- **Type III** for high early strength; **Type IIIA** is air-entraining.
- **Type IV** for low heat of hydration.
- **Type V** for high sulfate resistance.
Combined designations such as Type I/II indicate a cement meeting the requirements of both types[7](https://store.astm.org/c0150_c0150m-21.html). In recent years, Type I/II has been the most widely available portland cement in the United States[2](https://www.cement.org/cement-concrete/types-of-cement/). High early strength cement can reach design strength in days rather than the typical 28 days, useful for early form removal, rapid pavement repair, and shortening curing in cold weather[2](https://www.cement.org/cement-concrete/types-of-cement/).
**Blended cements** are a separate category under ASTM C595 (AASHTO M 240), produced by intergrinding or blending portland cement or clinker with limestone, slag cement, coal ash, silica fume, calcined clay, or other pozzolans[2](https://www.cement.org/cement-concrete/types-of-cement/). Substituting clinker with such materials lowers the clinker-to-cement ratio and hence the energy intensity and emissions of cement production[13](https://www.iea.org/articles/driving-energy-efficiency-in-heavy-industries).
## Environmental footprint
The cement industry is one of the top two manufacturing industry sources of greenhouse gases, though in many countries its contribution is a small fraction of that from fossil fuel combustion by power plants and motor vehicles[6](https://www.usgs.gov/publications/cement-manufacture-and-environment-part-i-chemistry-and-technology). According to the [International Energy Agency](https://www.edgepedia.org/international-energy-agency), the sector is not on track to meet net zero by mid-century: total CO\(_2\) emissions have been rising since 2015, and emissions intensity of cement production has risen by nearly 10% since 2015, largely due to an increase in the clinker-to-cement ratio in China[14](https://www.iea.org/reports/breakthrough-agenda-report-2023/cement). By 2030, total emissions need to fall by around 20%, enabled in part by carbon capture, utilization, and storage[14](https://www.iea.org/reports/breakthrough-agenda-report-2023/cement).
## References
1. [Definition of portland cement, ACI Technical Questions](https://www.concrete.org/frequentlyaskedquestions/faqid/671.aspx)
2. [Types of Cement, American Cement Association](https://www.cement.org/cement-concrete/types-of-cement/)
3. [Joseph Aspdin's Portland Cement, Today in Science History](https://todayinsci.com/A/Aspdin_Joseph/AspdinJoseph-Cement.htm)
4. [Portland Cement Chemistry, PCA EB071](https://www.cement.org/wp-content/uploads/2024/08/eb071-02w.pdf)
5. [The making of portland cement, ACI Technical Questions](https://www.concrete.org/frequentlyaskedquestions.aspx?faqid=675)
6. [Cement manufacture and the environment, Part I: Chemistry and technology, USGS](https://www.usgs.gov/publications/cement-manufacture-and-environment-part-i-chemistry-and-technology)
7. [ASTM C150/C150M-21, Standard Specification for Portland Cement](https://store.astm.org/c0150_c0150m-21.html)
8. [A sample of Lockwood's patent Portland Stone cement, Sir John Soane's Museum](https://collections.soane.org/object-m626)
9. [Joseph Aspdin and the Portland Cement Patent of 1824, E. A. R. Trout, Mineral Products Association](https://cement.mineralproducts.org/MPACement/media/Cement/Publications/2024/Portland_Cement_200_Years_of_Building_for_the_Future.pdf)
10. [Cement Kilns: Joseph Aspdin Memorial](https://www.cementkilns.co.uk/cemkilndoc024.html)
11. [Cement Statistics and Information, U.S. Geological Survey](https://www.usgs.gov/centers/national-minerals-information-center/cement-statistics-and-information)
12. [Hydration of Portland Cement, Penn State College of Engineering](https://www.engr.psu.edu/ce/courses/ce584/concrete/library/construction/curing/Hydration.htm)
13. [Driving Energy Efficiency in Heavy Industries, IEA](https://www.iea.org/articles/driving-energy-efficiency-in-heavy-industries)
14. [Cement, Breakthrough Agenda Report 2023, IEA](https://www.iea.org/reports/breakthrough-agenda-report-2023/cement)
---
*Topic: Encyclopedia › Technology and the built world › Engineering and manufacturing › Civil, structural, and geotechnical engineering*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license