History of Cement

The Long Road to Today's Portland Cement

 

Ancient History:

Cement has been in use by humans throughout history; variations of the material were used up to 12,000 years ago, with the earliest archaeological discovery of consolidated whitewashed floor made from burned limestone and clay found in modern-day Turkey. 

The first fired clay bricks were developed in the so-called Fertile Crescent, where it was discovered that lime could be produced from burnt limestone to prepare mortar. Around 800BC, the Phoenicians used the knowledge that a mixture of burnt lime and volcanic ash, today called 'pozzolana', could be used to produce hydraulic lime, that was not only stronger than anything previously used, but also hardened under water.

The Romans developed new masonry techniques, with which they could erect grand buildings with heavy foundations. One such development was "opus caementitium", a type of concrete made of lime with aggregates of sand and crushed rock. This was mostly used between masonry stones or bricks, serving as formwork. Other cements used crushed brick, tiles and ceramic pottery as aggregates. The Roman architect and engineer Marcus Vitruvius Polllio comprehensively described the knowledge and construction techniques of the time, which went on to to serve as the basis of building methods for hundreds of years.  

Famous historical buildings made from concrete, still standing today, are the Colosseum and Pantheon in Rome, and the Hagia Sophia in Istanbul.

The Middle Ages

The Middle Ages were a quiet time in the history of cement; any discoveries made during this era remain unknown, although masons are known to have used hydraulic cements to build structures such as fortresses and canals.

In the guilds of the Middle Ages, knowledge was a secret and was pased on to students orally, not written down, whilst alchemists researched properties and reactivity of substances, often using coded language. Typical mortars from this time consisted of lime and sand - concrete as we know it did not yet exist. 

The Industrial Revolution in Europe in the late 18th century saw a flurry of new developments in cement and concrete, with important contributions made by John Smeaton, who discovered that the hydraulicity of lime was directly related to the limestone’s clay content, James Parker, Louis Vicat and Egor Cheliev.

The Birth of Portland Cement:

The precursor to modern-day cement was created in 1824 by Joseph Aspdin, a British bricklayer and builder, who experimented with heating limestone and clay until the mixture calcined, grinding it and then mixing it with water. Aspdin named this Portland Cement, after the famously strong building stone from the Isle of Portland in Dorset, UK. His son, William Aspdin, made the first cement containing alite (an impure form of tricalcium silicate).

In 1845, Isaac Johnson fired chalk and clay at much higher temperatures than the Aspdins, at around 1400-1500oC, which led to the mixture clinkering, and produced what is essentially modern-day cement.

From 1850, the use of concrete made from Portland cement increased considerably. Projects such as sculptures, small bridges and concrete pipes were typical applications at the time and helped to increase its prominence. Then followed large scale sewage systems, such as in London and Paris, and the construction of metros and subways boosted demand. By the end of the 19th century, hollow concrete blocks for housing construction became mainstream. 

The advent of reinforced concretes began in the 1840s in France, starting a period of innovation, using reinforced columns, girders and so on to allow the construction of larger bridges, taller and larger buildings etc, and significantly decreased the dominance of steel construction. 

The first cement standard for Portland cement was approved in Germany in 1878, defining the first test methods and minimum properties, with many other countries following suit. 

Cement production and applications surged globally at the turn of the century. Since the 1900s, rotary kilns replaced the original vertical shaft kilns, as they use radiative heat transfer, more efficient at higher temperatures. achieving a uniform clinkering temperature and produces stronger cement. Gypsum is now also added to the resulting mixture to control setting and ball mills are used to grind clinker.

Other developments in the last century include calcium aluminate cements for better sulphate resistance, the blending of Rosendale (a natural hydraulic cement produced in New York) and Portland cements to make a durable and fast-setting cement in the USA, and the increased usage of cementitious materials to store nuclear waste.

The Future of Cement and Concrete

New technologies and innovations are constantly emerging to improve the sustainability, strength and applications of cement and concrete. Some advanced products incorporate fibres and special aggregates to create roof tiles and countertops, for example, whilst offsite manufacture is also gaining prominence with the rise of digitalisation and AI, which could reduce waste and improve efficiency and on-site working conditions. Cements and concretes are also being developed which can absorb CO2 over their lifetimes, reducing the carbon footprint of the building material.

 

Text contributions by Rainer Nobis, author of "Illustrated History of Cement and Concrete", available to buy online.