History of Portland Cement

The invention of Portland cement is credited to the Englishman Joseph Aspdin, who was granted a patent for its production in 1824. The name originates from the color of the resulting cement, which reminded Aspdin of Portland limestone—then considered one of the finest and most expensive building materials in Great Britain. Today, Portland cement is available in various shades, from dark gray to white (the latter being free of iron compounds).

Cement, used in the production of concrete, enabled the construction of impressive structures during the Industrial Revolution, including bridges, viaducts, and factories. Its production began in Great Britain and later spread to Germany and France, becoming widely used by the end of the 19th century.

Composition of Portland Cement

Portland cement is produced by combining finely ground cement clinker with gypsum. Cement clinker is obtained by firing a mixture of finely ground raw materials containing limestone and aluminosilicates at a temperature of 1450°C. The chemical composition of clinker includes:

• Alite (tricalcium silicate, 50–65% of clinker mass),
• Belite (dicalcium silicate, approximately 20% of clinker mass),
• Brownmillerite (a compound of calcium oxide, aluminum oxide, and iron(III) oxide, approximately 10% of clinker mass),
• Tricalcium aluminate (approximately 10% of clinker mass),
• Other compounds of aluminum, calcium, and magnesium.

To the clinker produced from this mixture, gypsum or a mixture of gypsum and anhydrite is added as a setting time regulator, along with up to 5% of other ingredients (such as limestone, slag, or pozzolana). The final step involves grinding the entire mixture in a specialized cement mill.

As a fine powder, Portland cement requires careful handling. It is caustic and can cause burns, while inhalation of fine particles poses serious health risks, including severe lung diseases (and even cancer), which were historically common among cement plant workers.

Types of Portland Cement

• Ordinary Cement (Fun fact: its strength after 7 days is equivalent to the strength achieved by rapid-hardening Portland cement after 24 hours).
• Rapid-hardening Cement
• Very Rapid-hardening  Cement
• Ultra-high Early Strength Cement
• Sulfate-resistant  Cement
• White Cement
• Pozzolanic Cement

It is important to note that the labeling of cement is related to its composition. If the cement contains additives such as slag or fly ash, it is classified as composite cement and is designated with the symbol CEM II.

In addition to slag and fly ash Portland cements, silica cements are also recognized. On the other hand, cement without additives is referred to as CEM I.