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HISTORY

Cement has been around for at least 12 million years. When the earth itself was undergoing intense geologic changes natural, cement was being created. It was this natural cement that humans first put to use. Eventually, they discovered how to make cement from other materials.

Concrete is a compound material made from sand, gravel and cement. The cement is a mixture of various minerals which when mixed with water, hydrate and rapidly become hard binding the sand and gravel into a solid mass. The oldest known surviving concrete is to be found in the former Yugoslavia and was thought to have been laid in 5,600 BC using red lime as the cement.

The Assyrians and Babylonians used clay as the bonding substance or cement. The Egyptians used lime and gypsum cement. In 1756, British engineer, John Smeaton made the first modern concrete (hydraulic cement) by adding pebbles as a coarse aggregate and mixing powered brick into the cement. In 1824, English inventor, Joseph Aspdin invented Portland Cement, which has remained the dominant cement used in concrete production. Joseph Aspdin created the first true artificial cement by burning ground limestone and clay together. The burning process changed the chemical properties of the materials and Joseph Aspdin created a stronger cement than what using plain crushed limestone would produce.

The first major concrete users were the Egyptians in around 2,500 BC and the Romans from 300 BC The Romans found that by mixing a pink sand-like material which they obtained from Pozzuoli with their normal lime-based concretes they obtained a far stronger material. The pink sand turned out to be fine volcanic ash and they had inadvertently produced the first 'pozzolanic' cement. Pozzolana is any siliceous or siliceous and aluminous material which possesses little or no cementitious value in itself but will, if finely divided and mixed with water, chemically react with calcium hydroxide to form compounds with cementitious properties.

The Romans made many developments in concrete technology including the use of lightweight aggregates as in the roof of the Pantheon, and embedded reinforcement in the form of bronze bars, although the difference in thermal expansion between the two materials produced problems of spalling. It is from the Roman words 'caementum' meaning a rough stone or chipping and 'concretus' meaning grown together or compounded, that we have obtained the names for these two now common materials.

Building a Dam using steel reinforced concrete

Portland Cement

Lime and Pozzolana concretes continued to be used intermittently for nearly two millennia before the next major development occurred in 1824 when Joseph Aspdin of Leeds took out a patent for the manufacture of Portland cement, so named because of its close resemblance to Portland stone. Aspdin's cement, made from a mixture of clay and limestone, which had been crushed and fired in a kiln, was an immediate success. Although many developments have since been made, the basic ingredients and processes of manufacture are the same today.

Reinforcement

In 1830, a publication entitled, "The Encyclopaedia of Cottage, Farm and Village Architecture" suggested that a lattice of iron rods could be embedded in concrete to form a roof. Eighteen years later, a French lawyer created a sensation by building a boat from a frame of iron rods covered by a fine concrete which he exhibited at the Paris Exhibition of 1855. Steel reinforced concrete was now born. The man normally credited with its introduction as a building material is William Wilkinson of Newcastle who applied for a patent in 1854 for "improvement in the construction of fireproof dwellings, warehouses, other buildings and parts of the same".

It is not only fire resistance that is improved by the inclusion of steel in the concrete matrix. Concrete, although excellent in compression, performs poorly when in tension or flexure. By introducing a network of connected steel bars, the strength under tension is dramatically increased allowing long, unsupported runs of concrete to be produced.

Steel and concrete complement each other in many ways. For example, they have similar coefficients of thermal expansion so preventing the problems the Romans had with bronze. Concrete also protects the steel, both physically and chemically.

Composition of Portland Cement

Portland cement is a complex mix of many compounds, some of which play a major part in the hydration or chemical characteristics of the cement. It is manufactured commercially by heating together a mixture of limestone and clay up to a temperature of 1300 to 1500°C. Although twenty to thirty percent of the mix becomes molten during the process the majority of the reactions which take place are solid-state in nature and therefore liable to be slow. Once cooled, the resulting clinker is ground to a fine powder and a small amount of gypsum (calcium sulphate dihydrate) is added to slow down the rate at which the cement hydrates to a workable level.

The work of early investigators using optical and X-ray techniques, starting in 1882 with Le Chatelier, has shown that most Portland cement clinkers contain four principal compounds. These are tricalcium silicate (3CaO.SiO2), aluminate (3CaO.Al2O3) and a ferrite phase from the (2CaO.Fe2O3 - 6CaO.2Al2O3.Fe2O3) solid solution series that at one time was considered to have the fixed composition (4CaO.Al2O3.Fe2O3). These phases were named alite, belite, celite and felite respectively by Tornebohm in 1897.

Hydration of Portland Cement

When water is mixed with Portland cement a complicated set of reactions is initiated. The main strength giving compounds are the calcium silicates which react with water to produce a calcium silicate hydrate gel (C-S-H gel) which provides the strength, and calcium hydroxide which contributes to the alkalinity of the cement. Tricalcium silicate reacts quickly to provide high, early strengths while the reaction of dicalcium silicate is far slower, continuing, in some cases, for many years. The other cement compound of particular relevance to steel reinforced concrete is tricalcium aluminate. It reacts rapidly with water to produce calcium aluminate hydrates.

The amount of tricalcium aluminate present may well be limited as in the case of sulphate resisting Portland cement, to prevent adverse reactions between the hydrate and sulphates from the environment which can result in swelling and cracking of the cement matrix.

The great advantage of tricalcium aluminate is its ability to combine with chlorides, so removing them from the liquid phase of the cement. Chloride ions, as will be seen, are one of the major causes of corrosion of embedded steel.

12,000,000 BC	Reactions between limestone and oil shale during spontaneous combustion occurred in Israel to form a natural deposit of cement compounds. The deposits were characterized by Israeli geologists in the 1960's and 70's.
3000 BC Egyptians	Used mud mixed with straw to bind dried bricks. They also used gypsum mortars and mortars of lime in the pyramids.
Chinese	Used cementitious materials to hold bamboo together in their boats and in the Great Wall.
800 BC Greeks, Crete & Cyprus	Used lime mortars which were much harder than later Roman mortars.
300 BC Babylonians & As Syrians	Used bitumen to bind stones and bricks.
300 BC - 476 AD Romans	Used pozzolana cement from Pozzuoli, Italy near Mt. Vesuvius to build the Appian Way, Roman baths, the Coliseum and Pantheon in Rome, and the Pont du Gard aqueduct in south France. They used lime as a cementitious material. Pliny reported a mortar mixture of 1 part lime to 4 parts sand. 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!
1200 - 1500 The Middle Ages	The quality of cementing materials deteriorated. The use of burning lime and pozzolan (admixture) was lost, but reintroduced in the 1300's.
1678	Joseph Moxon wrote about a hidden fire in heated lime that appears upon the addition of water.
1779	Bry Higgins was issued a patent for hydraulic cement (stucco) for exterior plastering use.
1780	Bry Higgins published "Experiments and Observations Made With the View of Improving the Art of Composing and Applying Calcereous Cements and of Preparing Quicklime."
1793	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 1756, but had to first invent a material that would not be affected by water. He wrote a book about his work.
1796	James Parker from England patented a natural hydraulic cement by calcining nodules of impure limestone containing clay, called Parker's Cement or Roman Cement.
1802	In France, a similar Roman Cement process was used.
1810	Edgar Dobbs received a patent for hydraulic mortars, stucco, and plaster, although they were of poor quality due to lack of kiln precautions.
1812 -1813	Louis Vicat of France prepared artificial hydraulic lime by calcining synthetic mixtures of limestone and clay.
1818	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.
1820 - 1821	John Tickell and Abraham Chambers were issued more hydraulic cement patents.
1822	James Frost of England prepared artificial hydraulic lime like Vicat's and called it British Cement.
1824	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.
1828	I. K. Brunel is credited with the first engineering application of portland cement, which was used to fill a breach in the Thames Tunnel.
1830	The first production of lime and hydraulic cement took place in Canada.
1836	The first systematic tests of tensile and compressive strength took place in Germany.
1843	J. M. Mauder, Son & Co. were licensed to produce patented portland cement.
1845	Isaac Johnson claims to have burned the raw materials of portland cement to clinkering temperatures.
1849	Pettenkofer & Fuches performed the first accurate chemical analysis of portland cement.
1860	The beginning of the era of portland cements of modern composition.
1862	Blake Stonebreaker of England introduced the jaw breakers to crush clinkers.
1867	Joseph Monier of France reinforced William Wand's (USA) flower pots with wire ushering in the idea of iron reinforcing bars (re-bar).
1871	David Saylor was issued the first American patent for portland cement. He showed the importance of true clinkering.
1880	J. Grant of England show the importance of using the hardest and densest portions of the clinker. Key ingredients were being chemically analyzed.
1886	The first rotary kiln was introduced in England to replace the vertical shaft kilns.
1887	Henri Le Chatelier of France established oxide ratios to prepare the proper amount of lime to produce portland cement. He named the components: Alite (tricalcium silicate), Belite (dicalcium silicate), and Celite (tetracalcium aluminoferrite). He proposed that hardening is caused by the formation of crystalline products of the reaction between cement and water.
1889	The first concrete reinforced bridge is built.
1890	The addition of gypsum when grinding clinker to act as a retardant to the setting of concrete was introduced in the USA. Vertical shaft kilns were replaced with rotary kilns and ball mills were used for grinding cement.
1891	George Bartholomew placed the first concrete street in the USA in Bellefontaine, OH. It still exists today!
1893	William Michaelis claimed that hydrated metasilicates form a gelatinous mass (gel) that dehydrates over time to harden.
1900	Basic cement tests were standardized.
1903	The first concrete high rise was built in Cincinnati, OH.
1908	Thomas Edison built cheap, cozy concrete houses in Union, NJ. They still exist today!
1909	Thomas Edison was issued a patent for rotary kilns.
1929	Dr. Linus Pauling of the USA formulated a set of principles for the structures of complex silicates.
1930	Air entraining agents were introduced to improve concrete's resistance to freeze/thaw damage.
1936	The first major concrete dams, Hoover Dam and Grand Coulee Dam, were built. They still exist today!
1956	U.S. Congress annexed the Federal Interstate Highway Act.
1967	First concrete domed sport structure, the Assembly Hall, was constructed at The University of Illinois, at Urbana-Champaign.
1970's	Fiber reinforcement in concrete was introduced.
1975	CN Tower in Toronto, Canada, the tallest slip-form building, was constructed. Water Tower Place in Chicago, Illinois, the tallest building was constructed.
1980's	Superplasticizers were introduced as admixtures.
1985	Silica fume was introduced as a pozzolanic additive. The "highest strength" concrete was used in building the Union Plaza constructed in Seattle, Washington.
1992	The tallest reinforced concrete building in the world was constructed at 311 S. Wacker Dr., Chicago, Illinois.

Concrete that includes imbedded metal (usually steel) is called reinforced concrete or ferroconcrete. Reinforced concrete was invented (1849) by Joseph Monier, who received a patent in 1867. Joseph Monier was a Parisian gardener who made garden pots and tubs of concrete reinforced with an iron mesh. Reinforced concrete combines the tensile or bendable strength of metal and the compressional strength of concrete to withstand heavy loads. Joseph Monier exhibited his invention at the Paris Exposition of 1867. Besides his pots and tubs, Joseph Monier promoted reinforced concrete for use in railway ties, pipes, floors, arches, and bridges.

History of Structural Concrete Case Studies

Buildings that were significant to the development of the architectonic language of reinforced concrete. Each one was a proving ground, in one way or another, for design techniques, construction methods or spatial delineation.

Related Information

Skyscrapers
Sea-cretion

Wolf Hilbertz, German architect and inventor is the father of sea-cretion, the electrolytic deposition of sea-shell-like minerals from seawater that creates a construction material. Patented on January the 20th, 1981.

COMMENT

It is essential to provide housing at affordable prices for every person in the United Kingdom. At present houses are kept artificially high. For this reason life is harder for young couples starting out.

Part of the reason houses are so expensive, is that the planning officers employed by town councils are not accountable to the ratepayer. MANY ARE ON THE TAKE and in property themselves. In addition, councillors are usually retired or well off, or perhaps do not need to work.

Instead of worrying about providing housing for the man in the street, they simply want to make their plot worth more. It stands to reason. If you had the chance to make your porperty worth more, what would you do? Whatever the reason, councillors do not argue against some planning applications, but will argue against other identical proposals. The opposite is also true. Some planning applications are approved before they hit the committee room. While other applications more in line with good planning policy, get a rough ride - delays - questions and requests for more details.

It really all depends on who is making the application. If you are not on the list of friends and associates, you stand much less of a chance of obtaining planning permission.

THIS SITE CONTAINS MANY EXAMPLES OF COUNCIL'S UNREASONABLE BEHAVIOUR - With thanks to Action Groups across the country for the supply of real case history and supporting documents. *THAT THE PUBLIC MAY KNOW*

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