When was cement discovered

Around BC, the ancient Egyptians used mud mixed with straw to form bricks. Mud with straw is more similar to adobe than concrete. However, they also used gypsum and lime mortars in building the pyramids, although most of us think of mortar and concrete as two different materials.

The Great Pyramid at Giza required about , tons of mortar, which was used as a bedding material for the casing stones that formed the visible surface of the finished pyramid. About this same time, the northern Chinese used a form of cement in boat-building and in building the Great Wall. Spectrometer testing has confirmed that a key ingredient in the mortar used in the Great Wall and other ancient Chinese structures was glutenous, sticky rice.

Some of these structures have withstood the test of time and have resisted even modern efforts at demolition. By BC, the Greeks had discovered a natural pozzolan material that developed hydraulic properties when mixed with lime, but the Greeks were nowhere near as prolific in building with concrete as the Romans. It was not a plastic, flowing material poured into forms, but more like cemented rubble.

The Romans built most of their structures by stacking stones of different sizes and hand-filling the spaces between the stones with mortar. Above ground, walls were clad both inside and out with clay bricks that also served as forms for the concrete.

The brick had little or no structural value and their use was mainly cosmetic. True chemical hydration did not take place. These mortars were weak. For marine structures and those exposed to fresh water, such as bridges, docks, storm drains and aqueducts, they used a volcanic sand called pozzuolana.

These two materials probably represent the first large-scale use of a truly cementicious binding agent. Pozzuolana and harena fossicia react chemically with lime and water to hydrate and solidify into a rock-like mass that can be used underwater. The Romans also used these materials to build large structures, such as the Roman Baths, the Pantheon, and the Colosseum, and these structures still stand today.

As admixtures, they used animal fat, milk and blood -- materials that reflect very rudimentary methods. On the other hand, in addition to using natural pozzolans, the Romans learned to manufacture two types of artificial pozzolans -- calcined kaolinitic clay and calcined volcanic stones -- which, along with the Romans' spectacular building accomplishments, are evidence of a high level of technical sophistication for that time.

Built by Rome's Emperor Hadrian and completed in AD, the Pantheon has the largest un-reinforced concrete dome ever built. The dome is feet in diameter and has a foot hole, called an oculus, at its peak, which is feet above the floor. It was built in place, probably by starting above the outside walls and building up increasingly thin layers while working toward the center. The Pantheon has exterior foundation walls that are 26 feet wide and 15 feet deep and made of pozzolana cement lime, reactive volcanic sand and water tamped down over a layer of dense stone aggregate.

That the dome still exists is something of a fluke. Settling and movement over almost 2, years, along with occasional earthquakes, have created cracks that would normally have weakened the structure enough that, by now, it should have fallen. The exterior walls that support the dome contain seven evenly spaced niches with chambers between them that extend to the outside.

These niches and chambers, originally designed only to minimize the weight of the structure, are thinner than the main portions of the walls and act as control joints that control crack locations. Stresses caused by movement are relieved by cracking in the niches and chambers.

This means that the dome is essentially supported by 16 thick, structurally sound concrete pillars formed by the portions of the exterior walls between the niches and chambers. Another method to save weight was the use of very heavy aggregates low in the structure, and the use of lighter, less dense aggregates, such as pumice, high in the walls and in the dome. The walls also taper in thickness to reduce the weight higher up.

Another secret to the success of the Romans was their use of trade guilds. Each trade had a guild whose members were responsible for passing their knowledge of materials, techniques and tools to apprentices and to the Roman Legions. In addition to fighting, the legions were trained to be self-sufficient, so they were also trained in construction methods and engineering.

During the Middle Ages, concrete technology crept backward. After the fall of the Roman Empire in AD, the techniques for making pozzolan cement were lost until the discovery in of manuscripts describing those techniques rekindled interest in building with concrete.

He used limestone containing clay that was fired until it turned into clinker, which was then ground it into powder. He used this material in the historic rebuilding of the Eddystone Lighthouse in Cornwall, England. Finally, in , an Englishman named Joseph Aspdin invented Portland cement by burning finely ground chalk and clay in a kiln until the carbon dioxide was removed.

During vitrification, materials become glass-like. Aspdin refined his method by carefully proportioning limestone and clay, pulverizing them, and then burning the mixture into clinker, which was then ground into finished cement.

Before Portland cement was discovered, and for some years afterward, large quantities of natural cement were used, which were produced by burning a naturally occurring mixture of lime and clay.

Because the ingredients of natural cement are mixed by nature, its properties vary widely. Modern Portland cement is manufactured to detailed standards. Some of the many compounds found in it are important to the hydration process and the chemical characteristics of cement. Eventually, the mix forms a clinker, which is then ground into powder. A small proportion of gypsum is added to slow the rate of hydration and keep the concrete workable longer.

Between and , systematic tests to determine the compressive and tensile strength of cement were first performed, along with the first accurate chemical analyses. In the early days of Portland cement production, kilns were vertical and stationary. In , an English engineer developed a more efficient kiln that was horizontal, slightly tilted, and could rotate.

The rotary kiln provided better temperature control and did a better job of mixing materials. By , rotary kilns dominated the market. In , Thomas Edison received a patent for the first long kiln.

This was about 70 feet longer than the kilns in use at the time. From , 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 s 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 , 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 s, rotary kilns replaced the original vertical shaft kilns, as they use radiative heat transfer, more efficient at higher temperatures.

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.

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.

Vitruvius reported a 2 parts pozzolana to 1 part lime. Animal fat, milk, and blood were used as admixtures substances added to cement to increase the properties. These structures still exist today! The quality of cementing materials deteriorated. The use of burning lime and pozzolan admixture was lost, but reintroduced in the 's.

John Smeaton found that the calcination of limestone containing clay gave a lime which hardened under water hydraulic lime. He used hydraulic lime to rebuild Eddystone Lighthouse in Cornwall, England which he had been commissioned to build in , but had to first invent a material that would not be affected by water. He wrote a book about his work.

James Parker from England patented a natural hydraulic cement by calcining nodules of impure limestone containing clay, called Parker's Cement or Roman Cement. Edgar Dobbs received a patent for hydraulic mortars, stucco, and plaster, although they were of poor quality due to lack of kiln precautions.

Louis Vicat of France prepared artificial hydraulic lime by calcining synthetic mixtures of limestone and clay. Maurice St. Leger was issued patents for hydraulic cement.

Natural Cement was produced in the USA. Natural cement is limestone that naturally has the appropriate amounts of clay to make the same type of concrete as John Smeaton discovered.

Joseph Aspdin of England invented portland cement by burning finely ground chalk with finely divided clay in a lime kiln until carbon dioxide was driven off. The sintered product was then ground and he called it portland cement named after the high quality building stones quarried at Portland, England. Brunel is credited with the first engineering application of portland cement, which was used to fill a breach in the Thames Tunnel.

Isaac Johnson claims to have burned the raw materials of portland cement to clinkering temperatures. David Saylor was issued the first American patent for portland cement.

He showed the importance of true clinkering.