Figure 1. mor- tar work in ancient Egypt in 1950 B.C. as seen on a mural at Thebes. At the top, workmen fill earth- enware jars with water, which is then mixed with to create . Be- low, a masonry-faced concrete wall is under construction.

The history of concrete

Part 1: lthough the Romans are gener- , , and water to form the earliest ally credited as being the first concrete yet discovered in Europe. From concrete engineers, a form of Archaeologists have also discovered con- prehistoric A concrete dating to 6500 B.C. crete in Gansu Province in northwest China has been discovered by archaeologists in that dates to about 3000 B.C. Greenish- rubble Syria. From the Middle East, concrete tech- black in color, it was used for floors and nology spread and evolved, primarily in contained a mixed with sand, bro- mixes to Europe. In 1871, the first ken pottery, bones, and water. was produced in the United States at There is no further proof of the art of Roman Coplay, Penn. making rudimentary concrete until about cement Stone Age Syrians built permanent fire 2500 B.C. in Egypt. Sources are in some pits for heating and cooking. This led to a disagreement, but it has been reported that By Richard W. primitive calcining of surrounding rock and a cementing material produced from either Steiger the accidental discovery of lime as a build- a lime concrete or burnt was used ing material. There is evidence that the in the Great Pyramid at Giza. The earliest newly discovered technology gained wide- known illustration (dating to about 1950 spread use. Central lime-burning were B.C.) of concrete being used in Egypt is constructed to supply mortar for rubble- shown in a mural on a wall in Thebes wall house construction, concrete floors, (Figure 1). and waterproofing cisterns. The evolution The use of lime-based mortars and con- of concrete technology had begun. cretes continued in the lands around the eastern Mediterranean Sea. About 600 B.C. Yugoslavia and China the Greeks discovered a natural Another form of early concrete was dis- on Santorini Island that developed hy- covered along the banks of the Danube draulic properties when mixed with lime. River in Yugoslavia. Stone Age hunters/fish- This made it possible to produce concrete ermen used it to make floors in huts about that would harden under water, as well as 5600 B.C. The floors consisted of 10 inches in the air. The chemical reaction between of concrete over a chalk base. Analysis indi- the lime and the silica-alumina in the poz- cates that a red lime was brought to the site zolan made this possible. The Greeks used from 200 miles upstream and mixed with these lime-based compositions as protec- tive coverings for walls of un- burned bricks. The Greeks also mixed a pseudo- concrete that preceded real con- crete and consisted of roughly bro- ken stone held together with a mortar of lime and sand. This mix- ture, however, was too weak to bind the whole together into a compact mass for serious building purposes.

Roman concrete The first examples of Roman con- crete date to 300 B.C. The Romans not only improved concrete techni- cally, they also gave it a name. The word “concrete” comes from the concretus, meaning grown to- gether or compounded. A concrete Figure 2. Completed in A.D. 128, the Pantheon of had unreinforced concrete lower made with pozzolanic, hydraulic walls that were 20-feet-thick. Brick rubble and volcanic stone were used as . The ce- cement, developed by the Romans ment was made from pozzolanic powder which was produced from . The lightest in 75 B.C. was used in building the of this was used in the dome which is 142 feet in diameter. The Pantheon is 1,867 theater at and the Roman years old, and still in fine condition. baths. The cement was a ground mix of lime and volcanic ash con- prove successful because the Normans who brought more so- taining silica and aluminum, found bronze had a higher rate of thermal phisticated concrete technology to near , Italy, hence the expansion than the concrete and Britain when they landed in 1066. name, pozzolanic cement. caused spalling and cracking. Reading Abbey in Berkshire (dating , although unrein- Unfortunately, although the Ro- to 1130) has been stripped of its forced, still stands today and was mans used concrete in many struc- stone facade revealing a concrete used on a large scale. Both the tures built across their far-flung em- core which still stands today. (completed in A.D. 82) pire, it was impractical to transport Concrete was widely used in cas- and the Pantheon (completed in volcanic ash from Italy. Therefore, tles, including the White Tower in A.D. 128, Figure 2) contain large the pozzolan technology used so the Tower of London. Salisbury amounts of concrete. The successfully in Rome, did not sur- Cathedral (completed in 1265), with of Constantine and the foundations vive the fall of the the tallest spire in Britain, has a of the buildings also were in A.D. 476. All concrete construc- concrete foundation that is still in constructed of concrete. tion for the next 1,300 years used excellent condition. Some cathe- In the Pantheon, aggregate in the lime mortars and . drals founded on less durable mate- concrete ranged from heavy basalt rials have recently required major in the foundations and 20-foot-thick British concrete technology underpinning operations to save lower walls, through brick and Originally it was thought the Nor- them from collapse. (a stone formed from volcanic dust) mans had reintroduced the art of in the upper walls, to the lightest of making concrete into Britain, but ’s breakthrough pumice toward the top of the 142- recent excavations in Northampton In 1756, engineer John Smeaton foot diameter dome. The entire have brought to light three Saxon was commissioned to build a new structure is in good condition and concrete mixers dating from A.D. on the Eddystone rocks stands today in its original form. It 700 (Figure 3). They were in the in the English Channel 14 miles is an amazing feat considering that form of shallow bowls cut into southwest of . Two previ- the builders did not understand the bedrock, with a central post hole. A ous on the site had chemistry of . beam rotated around a central axis been destroyed. The first, made of There was an attempt by Roman with paddles attached to it and did wood, burned down, and the sec- engineers to use bronze strips and the mixing. Labor was supplied by ond, also of timber, blew away in a rods to reinforce concrete in their either humans or animals. gale. Smeaton determined that quest for lighter weight and thinner Saxon concrete work was rela- blocks of stone were the only prac- wall sections. However, it did not tively limited and it really was the tical . The problem Figure 3. Remains of a Saxon discovered in Britain show that shallow bowls were cut into bedrock, with a central post of tim- ber. A wooden beam with paddles rotated about the central axis to mix the concrete. Labor was supplied by humans, as shown here, or by ani- mals such as oxen or horses. was how to bind them together to Smeaton’s original lighthouse was middle of the 19th century. create a solid monolithic structure dismantled and re-erected as a The first major use of Parker’s ce- that could withstand the constant monument on Plymouth Hoe ment was in mortar for the first tun- soaking of seawater. The only ce- where it stands to this day. The nel under a navigable river, the ments available in 1756 were weak original stump of Smeaton’s tower 1,200-foot-long brick tunnel under and slow-setting. He undertook a is still in evidence, resisting the ele- the Thames River. During construc- program of trial and error, combin- ments on the same rock on which tion from 1825 to 1845 there were ing all of the known materials used Smeaton built it over 200 years ago. some breaks in the tunnel roof. to produce mortar from various Tons of portland cement, which parts of England and the Continent. patented was available after 1828, were re- Finally he made a real break- Rev. James Parker of portedly dumped into the river to through when he combined burnt patented what he called Roman ce- seal the roof. Eventually the tunnel Aberthaw , a ment in 1796. Attracted to some was completed and is still in use to- from South Wales, and an Italian beach stones on the Isle of Shep- day, carrying trains between White- pozzolan from Civitavecchia. With pey, Parker collected some of the chapel and New Cross. ✥ this combination Smeaton pro- stones and when he got home duced the first high-quality cement threw one into the fireplace. It Richard W. Steiger is an industrial de- since the fall of the Roman Empire. rolled out later thoroughly calcined. signer, photographer, and writer based Smeaton used this hydraulic ce- Undertaking some experiments, he in Farmington Hills, Mich. ment in the mortar to key and ce- was able to develop a natural ce- Next month in Concrete Journal, ment stone blocks together to cre- ment he believed to be the reincar- read “The history of concrete, Part ate the first nation of the Roman cement of an- 2: From portland cement to struc- in 1759. Smeaton’s lighthouse en- cient times. Large quantities of the tural concrete.” dured for more than a century. By stones, which were actually nod- 1876 the structure began to weaken ules of septaria from the London and was replaced by a new, much , were collected from the PUBLICATION #J950584 larger concrete lighthouse. At the Thames Estuary to make a cement Copyright © 1995, The Group request of the people of Plymouth, which remained popular until the All rights reserved