Ancient Binding Materiais, Mortars and Concrete Technoiogy: History and Durability Aspects

Ancient binding materiaIs, mortars and concrete technoIogy: history and durability aspects

6. Klrca ÇimSA Cement Produclion and Trading Company. Mersin, Turkey

ABSTRACT: This paper deals with the history of technology related with binding materiais. Lime, gypsum, and hydraulic binders, i.e. lime-pozzolan mixture have been the major types of binding materiais survived in different regions ofthe world for 8000 years. Whatever type ofbinding materiais the ancient civilizations used, it can be seen that those structures built by ancient binders, particularly !ime-pozzolan mixture have survived for several hundred years. It can be claimed that even at that time architects were aware of the importance of the durability of binding materiais. However, those structures belonging to modem civilizations and made by using modem binders, i.e. portland cement have experienced significant deterioration throughout their service life, generally lesser than 100 years. In this research, the object of the study is to investigate the historical time!ine of binding materiais and to focus on their durability aspects by comparing the traditional technologies with modem ones.

rNTRODUCTION to make hydraulic binder, i.e. lime-pozzolan cement by adding materiais, such as volcanic ash or powdered Binding material or cementing material in the gen bricks, tiles and pottery to lime. eral sense of the world can be described as a material The modem cement, i.e. portland cement was with adhesive and cohesive properties, which make it invented by Joseph Aspdin in England in 1824. Afier capable ofbonding mineral fragments into a compact that time, modem Portland cement and concrete tech whole. For constructional purposes, the meaning of nology has proceeded till today by invention of new the term "cement" is restricted to the bonding materi chemical and mineral admixtures and additions. ais used with stones, sand, building blocks, etc (Neville Although radical advances in cement and concrete 1989). technology have been observed for two centuries, The use of cementing materiais is very old. The there are still problems related with lhe endurance of first evidence of its existence dates back to 12000 cement and concrete. Many modem structures expe BC in Israel. Reactions between limestone and oil rienced significant deterioration within their service shale during spontaneous combustion occurred in !ife, which is generally lesser than 100 years. Yet, many Israel to form a natural deposit of cement compounds. ancient Roman concrete buildings or slructures are still Another example of ancient binder from the history in use afier more than 2000 years. According to the of the human being is the use of naturally occurring Vitruvius's book De Architectura, the magnificent bitumen by the Babylonians and Assyrians in their quality of Roman concrete resulted from the exten brick and gypsum plaster construction. The Egyplians sive use of artificial pozzolanic mortars and concretes improved the technology of lime and gypsum mortar (Vitruvius 1960). In addition, placement, compaction, and builded the pyramids by the use of such mortars. workability properties of ancient Roman concrete The Greeks made furlher improvements and finally the contributed to its magnificent survivability. Romans developed a cement lhat produced structures of remarkable durability and that can sei and harden even under waler. 2 CHRONOLOGICAL SUMMARY OF Lime was known to the Greeks and was widely used BINDING MATERIALS AND MORTARS by the Romans. The Roman architect and engineer Vitruvius published the first specification for the use The nature and usefulness of cement as a kind of of lime in building in his celebrated work De Archi artificial stone was probably first understood by the tectura (Vitruvius 1960). The Romans also knew how Romans; but it seems likely that they copied the

87 technology from Etruscans and Greeks and improved in order to be used in construction it must be mixed it drastically. with water to form a lime paste, which is defined as Concrete and/or cement itself is actually a phe "hydration" or "slaki ng". nomenon of nature, with the first evidence of its To produce dry powdered hydrated lime just suf existence in Israel dating back to 12 000 BC, when nat ficient water is added for the quicklime lumps to ural deposits of cement compounds were said to have break down to a fine powder. This material would formed due to reactions between limestone and oi l have a "shelflife" of only a number ofweeks, depend shale, employing spontaneous combustion. However, ing on storage conditions. "Old" hydrated lime would the earliest known concrete produced intentionally by have partially carbonated and become a less effective human beings was discovered in th e fl oor of a crude binder. Iftoo little or toa much water is added, the prop shelter built about 5600 BC on the banks of the river erties ofthe slaked lime will be spoil ed; the slaked lime Donube in Yugoslavia. The floor was made from mix will not harden and the paste will not be as plastic as ture of sand, gravei and red lime. That concrete was it should be (Erdogan 2002). manufactured deliberately, rather than w1intentionally However, if qui cklime is hydrated with a proper by util izing the red lime from a site 320 km away. For amount of water and well agitated, it forms a milky some reason, it appears that the technique for using suspension known as milk oflime, which can be easily lime-based cements was lost for at least 2500 years, used in building applications. until indications of use by the ancient Assyrians and Limestone containing a proportion of clay is Babylonian civilizations around 3000 BC. They used ofien seen as an advantage in building as they pro bitumen to bind stones and bricks. About the same duce hydraulic limes. In fact, limes do not possess time Egyptians used mud bricks mixed wi th straw to hydraulicity, si nce it needs carbon dioxide for its hard bind dried bricks and also th is phenomenon furthered ening reaction (Erdogan 2002). However, in the case the discovery oflime and gypsum mortars as a binding of hydraulic limes, as the name implies, they can set agent for building the pyramids. Even at that time, th e and harden even under water and will produce stronger ancient Chinese people used cementitious materiais to mortars. hold bamboo together in their boats and in the Great In the construction industry, usually lime, in its Wall, one of the Wonders of the world. By 500 BC hydrated or putty fo rm, is mixed with aggregate and the art of making concrete had spread to the Mediter water to produce concrete or mortar for different ranean island of Crete, and from there to the ancient purposes such as plastering sand-lime brick produc Etruscans and Greeks. tion etc. Plai n lime-sand mortars are quite weak; Yet, it was the Romans who brought the manufacture any early adhesive strength results from drying out and use of li me-based cement to an art form o 300 BC whereas longer-term hardening occurs as a result of saw the Romans employing slaked lime and volcanic carbonation ofthe lime. ash called pozzolan, named afier the town of Pozzuoli, Traditionallime plasters were ofien mixed with ani near Mt Vesuvius. This was a hydrauli c cement that mal hair to improve cohesion and adhesion. Today can set harden when mixed with water in ai r as well addition of gypsum or portland cement and/or poz as under the water. Moreover, some natural additions zolans to increase durability and give faster setting such as animal fats, milk, and blood were also used times is more common. throughout this era. Afier the fali of the Roman Empire, knowledge of cement was lost till the 18th century. 3.2 Ancient lime technology The whole historical timeline of cement and con Quarrying: The first step of lime production required crete is summarised in Table I, where the develop finding a suitable raw material which was generally ments in modem era are also outlined. calcium carbonate based stones such as limestone and marble. Quarrying techniques had become well advanced during construction of the great Egypti an 3 TECHNOLOGY OF ANCIENT LIME pyramids and further advanced during the Roman AND LIME MORTARS building era. The determination of raw material involved trial and error, as well as ages of experi 3. 1 Properties o.flime mentai attempts. Once workable quarries and materiais There are two forms of lime: quicklime and hydrated were located, workmen acquired skills for identifying lime. and extracting suitable calcium carbonate raw mate Quicklime is produced by heating rock or stone con riais. Then such materiais had to be transported to taining calcium carbonate (limestone, marble, chalk, sites where they were prepared for calcination. The shell s, etc.) to a temperature of around 900°C for sev major technological factors surrounding acquisition eral hours in a process known as ' calcining'. It is an of the raw carbonate material, therefore, involved, unstable and slightly hazardous product. Therefore, identifi cation of suitable stone, workable extraction,

88 Table I. Historical timeline of binding materiaIs.

12000 BC Reactions between limestone and oil shale during spontaneous combustion occurred in Israel to form a natural deposit of cement compounds. 5600 BC Intentionally production of concrete from sand, graveI, and lime a natural concrete in Yugoslavia. 3000 BC Bitumen to bind bricks and stones was used by Babylonians and Assyrians. 3000 BC Egyptians used mud mixed with straw to bind dried bricks. They also used lime and gypsum mortars in the pyramids. 3000 BC Chinese used cementitious material to hold bamboo together in their boats and in the Great Wall. 500 BC The art of making concrete had spread to the Mediterranean island of Crete, and from there to the ancient Etruscans and Greeks. 300 BC-476 AD Used pozzolan cement from Pozzuoli, Italy near Mt. Vesuvius to build several structures. They used lime as a cementitious material also Animal fat, milk, and blood were used as admixtures. 400-1779 The art of concrete was lost after the fali of the Roman Empire. 1779 Bry Higgins was issued a patent for hydraulic cement (stucco) for exterior plastering use. 1793 John Smeaton found that the calcination of limestone containing clay gave a lime, which hardened under water (hydraulic lime). 1796 James Parker from England patented a natural hydraulic cement by calcining limestone-containing clay, called Parker's cement or Roman cement. 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 natl.lrally has the appropriate amounts of clay to make the same type of concrete as John Smeaton discovered. 1822 James Frost of England prepared artificial hydraulic lime likes 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 quarries at Portland, England. 1828 l.K. Brunel is credited with the first engineering application of portland cement, which was used to fill a breach in the Thames Tunnel. 1843 1M. Mauder, Son & Co. Were licensed to produce patented portland cement 1845 Isaac Johnson claims to have burned the raw materiaIs of portland cement to clinkering temperatures 1849 Pettenkofer & Fuches performed the first accurate chemical analysis ofportland cement. 1860 The beginning ofthe era ofportland cements ofmodern composition. 1862 Blake stone breaker of England introduced the jawbreakers to crush clinker. 1867 Joseph Monier of France reinforced William Wand 's (USA) flowerpots with wire ushering in the idea of iron reinforcing bars (re-bar). 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 pro per amount oflime to produce portland cement. 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 than 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. lt 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. 1909 Thomas Edison was issued a patent for rotary kilns.

(continued)

89 Table l. ( continued)

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. 1967 First concrete domed sport structure, the Assembly Hall, was constructed at the University of Illinois, at Urbana-Champaign. 1970's Fibre reinforced in concrete was introduced. 1980 's Superplasticizers were introduced as admixtures. 1985 Silica fume was introduced as pozzolanic additive. The highest strength concrete was used in building the Union Plaza constructed in Seattle, Washington.

quarrying methods, and suitable means oftransporta equal in weight to 1/3 of the quicklime was sprinkled tion to a site for further treatment (Krumnacher over it. Heat was given off, the material cracked open 2001). and became a powdereel, and increased in volume. This Calcination: In orderto convert the ca1cium carbon method was considered the best. (2) Immersion: the ate based raw material into quicklime, it was necessary quicklime, placed in a basket, was lowered into the to heat the mass of stone or shell up to required temper water for the proper length of time, and drawn up to atures. By ca1cining the raw materiais, the water and complete the slaking. The handling was tricky, at best, carbon dioxide was driven off from within the stone. and demanded considerable skill. (3) Air-slaking: the Ca1cining of raw materiais took place in either kilns quicklime was simply left exposeel, to pick up moisture or clamps customarily constructed of stone or brick from air (Krumnacher 2001, McKee 1971). with clamps sometimes representing an open heap of The slaking procedure, like ali other steps involving carbonate material and fuel (Krumnacher 200 I). the preparation of mortar had a great influence upon "When the charge of ca1cium carbonate undergoes the resultant properties and performance of finished firing it transforms to a ca1cium oxide known as quick mortar. lime. This transformation involves the release ofwater Mortar Mixing: In order to create a mortar for unit and carbon dioxide, which are driven off after being ing brick or stone, workers introduced slaked lime to heated through the ca1cining processo Through trial a sand aggregate. This practice involved proportion and error lime burners found that the raw limestone ing the amount of lime, sand and water. According to fired more completely if broken into pieces about the McKee, in Roman perioel, three primary methods of size of two closed fists. If the stones were toa large mortar mixing predominated: (1) mixing dry slaked there would remain unaltered clinkers, which would lime powder, sanei, and water; (2) mixing wet slaked be found during the subsequent processo These clinkers lime paste and sanei, adding water ifneeded; (3) mixing would jeopardize the consistency and effectiveness of pulverized dry quicklime, sand and water, using the a resulting lime. Since quicklime was difficult to store mortar while it was still hot (McKee 1971). and transport, clamps and kilns were set up near the Fat lime or high ca1cium lime could be mixed with site where lime was used and the raw material would the aggregate and allowed to age, provided it was be transported to the ki ln site" (Krumnacher 200 I). protected from exposure to the air. Exposure to the "Constant attention and responsive orchestration of air would act to recarbonate or solidify the mass. the firing were essential. Lime burners worked unusual Many ancient artisans practiced this custom of storing hours and were highly skilleel, although not always lime putty or lime mortar. Plasterers would keep their highly respected. In Roman times, inrnates and crim lime in sealed vats for considerable lengths of time. inais would often be sent to provide labour at the Nicholson describes the mixing and aging of mortar limekilns" (Krumnacher 2001). as follows (Nicholson 1850): "The mortar should be Slaking: Quicklime intended for use in construc made undergrounel, then covered up, and kept for a tion must first be mixed with water, to form a lime considerable length of time, the longer the better; and paste, by being slaked (Erdogan 2002). Ali calcin when it is to be useel, it should be beat up afresh. This ing process of ca1cium carbonate based stones had makes it set sooner, renders it less liable to crack and to be followed by slaking, which was necessary for harder when dry... How very different was the prac construction purposes. tice of the Roman! The lime which they employed Throughout the Roman perioel, there were three was perfectly burnt, the sand sharp, clean, and large different hydration methods for transformation of grained; when these ingredients were mixed in due quicklime into the hydrated (or slaked) lime by the con proportions, with a small quantity of water, the mass trolled addition ofwater. One ofthe three methods was was put into a wooden mortar pan, and beaten with followed: (1) sprinkling or 'drowning' : ideally, water a heavy wooden or iron pestle, till the composition

90 adhered to the morta r: being thus far prepared, they highly esteemed and respected, the techniques of kept it until it was at least three years old. The beating preparation and application of lime and lime mortars ofmortar is ofthe outmost consequence to its durabil have remained less than fully understood" (Krum ity, and it would appear that the effect produced by it, nacher 2001). is owing to something more than a mere mechanical Vitruvius, a 1st century S.C. Roman architect under mixture" (Krumnacher 2001, Nicholson 1850). Augustus, conveys the earliest comprehensive details regarding lime treatment and its use as a building material. Craft tradition was advanced by the Romans, 3.3 Ancient lime applications who developed a strong infrastructure of labour, raw material, technological order and transportation. This In order to understand the techniques associated with craft tradition and supportive infrastructure facili lime mortars it is necessary to review the lineage from tated a sophisticated building program (Krumnacher which they arose. While the actual techniques involv 2001). ing preparation and application of lime remains less than fully understood, examples of finished materiais still in existence testify on behalf of the early success acquired by those working with lime. According to 4 TECHNOLOGY OF ANCIENT HYDRAULIC Lazell, the picture of the early development of lime BINDER (LIME-POZZOLAN MIXTURE) technology is as follows (Lazell 1915): ''The art of AND ITS MORTAR using morta r in some from or other is as old as the art of building or as civilization itself. Evidences of Throughout the history of human beings, for the first the use of mortar are found not only in the older coun time, a hydraulic binder was used during the era of tries ofEurope, Asia, andAfrica, but also in the ruins of Roman Empire. This hydraulic binder has been called Mexico and Peru. The remains ofthe work ofthese arti as Roman cement or concrete, as well. The techniques sans are evidence to us ofthe enduring qualities oflime used by architects and artisans for the production of mortar as well as the skill and knowledge possessed binding materiais at the time of the Roman Empire by the user" (Krumnacher 2001 , Lazell 1915). were substantially based upon those described by Lazell additionally describes ancient era as fol Vitruvius in his splendid handbook De Architectura lows (Lazell 1915): "Plastering is one of the earliest (Vitruvius 1960). instances of man's power of inductive reasoning, for However, as Vitrllvills says, the Roman art ofbuild when men built they plastered; at first like the birds ing was the heritage ofthe Greek culture. On the other and beavers, with mud; but they soon found out a more hand, the construction technique know-how, includ lasting and more comfortable method, and the earli ing building materiais, carne from the Egyptians and est efforts of civilization were directed to plastering. Persians through a slow transmission process of the The inquiry into it takes us back to the dawn of social original culture (particularly from East Iran) through life until its origin becomes mythic and prehistoric. the Mesopotamian and the Mediterranean civilization In that dim, obscure period we cannot penetrate far (Collepardi 1997). enough to see clearly, but the most distant glimpses In the previous part, the primitive binder, lime, and we can obtain into it shows us that man had very early its history of technology were examined. However, attained almost to perfection in compounding material from now on, the technology of the Roman concrete, for plastering. In fact, so far as we yet know, some of which is very similar to the modem concrete are going the earliest plastering which remains to us excels, in to be investigated. In fact, the fact that ancient Roman its scientific composition, that which we use at the concrete has withstood the attack by elements for present day, telling of ages of experimental attempts. 2000 years, while the modem one undergoes prema The pyramids of Egypt contained plaster work exe ture deterioration within its service !ife lesser than 100 cuted at least 4000 years ago, and this, where wilful years, shows that the basic construction techniques violence has not disturbed it, still exist in perfection, of the Romans must be better than those of modem out vying in durability the very rock it covers, where practice as judged by comparing the products (Moore this is not protected by its shield of plaster". 1993). "Development of masonry construction technol Mortar consisting of lime and sand has been lIsed ogy emerged and spread through empirical trial and as an integral part of masonry structures for thousands error. Within the 1st century S.c. Romans borrowed of years. It also was applied to protect the earthen and applied Greek and Etruscan techniques of lime walls of ancient houses. When mixed with volcanic preparation and applications for creating their mor ash (pozzolan), it becomes a mortar that the Romans tar. Roman use of lime mortars reflected a keen used to build rock walls. The Romans later discovered insight into the material and its technological prepara how to mix this mortar with small stones, bricks, and tion and application toward their momentous building other materiais to produce concrete called as 'Roman accomplishnlent. Although these accomplishments are Concrete' (Moore J 993).

91 The constituents ofRoman Concrete, aggregate and shales possess pozzolanic properties when they are in pozzolan, are going to be described in the following a finely divided form (Erdogan 1997). parts, except the lime, which was discussed previously. In fact, the name pozzolan comes from the town of Pozzouli in the foothills of Mount Vesuvius, in Italy, where the ancient Romans had produced a hydraulic 4.1 Aggregates binder by mixing lime with volcanic soil more than 2000 years ago (Erdogan 1997). Stone aggregate is a necessary part of the concrete Likewise, Vitruvius describes pozzolan as a kind of because mortar by itself cannot sufficiently resist the powder, which from natural causes produces astonish crushing force of great weights. Aggregate gives con ing results. He says in his handbook De Architectura crete its necessary structural body by increasing the that this substance, when mixed with lime and rubble, density of mass. It ais o reduces the amount of lime not only gives strength to buildings of other kinds, but that must be burnt and slaked. The Romans used sev even when it is used in the sea, they can set and harden eral kinds of stone for aggregates, ranging in weight under water. from selce, a very heavy lava stone used in founda By the day the Romans had mastered the use of tion walls, to lightweight tufa (a local granular stone) pozzolan, which they added to the dry mix in lieu of and pumice, both used in vaults. Other kinds of stone, part of the sand. Pozzolan is a friable volcanic mate as well as broken bricks and tiles were also used. rial, found in thick beds of chunks and gravel-sized Ali of these materiais were found in and near Rome. pieces in Latium and Campania and easily reduced Architectural sculptures and other stone members of to usable formo It often has a distinct reddish or yel demolished buildings were sometimes broken up and lowish hue and has the property of forming hydraulic used as aggregate. In many structures different aggre silicates in combination with lime, quartz sand, and gates were used according to the loads to be carried. water. The importance ofpozzolan can be exaggerated, Certain vaults of the Flavian Amphitheatre contain for some large Roman concrete buildings were built pumice, and the five kinds of aggregate in the walls without it, but mortar made with it set readily under and dome of the Pantheon were separated into five water, an advantage Roman engineers made good use horizontal zones, each containing a lighter aggregate of. The architects and builders ofthe high empire must than the one below. In foundations the aggregate often have been convinced that pozzolan improved their con occupies two thirds of the total volume of the fabric crete, for it was used in almost ali buildings and rarely (Singer et aI. 1965). absent from high imperial construction in Rome and Aggregate was added to the morta r during the actual its environs (Singer et aI. 1965). construction ofthe wall or vault. Often the stones were spaced at random, having been dumped into the forms and left untouched, though sometimes they were raked 6 DURABILITY OF ANCIENT MORTARS out. In Trajanic and Hadrianic work they were fre ANO CONCRETE: COMPARISON WITH quently laid by hand in regular rows, spaced evenly in MODERN CONCRETE the mortar both horizontally and vertically in order to distribute evenly resistance to load. The stone is such Concrete experts talk today about how to make con cases is usually a yellowish tufa, roughly shaped into crete durable. Many ancient concrete and buildings loaf forms about half-foot in length. Such aggregate are still in use after more than 2000 years. For these takes up about halfthe volume ofthe concrete ofwalls modern concrete experts, the Romans were fortunate and vaults. lt is always completely surround by mor builders in that they apparently simply used natural tar, with the exception of the exposed irregular side pozzolan deposits, which were found to be suitable ofpieces laid against wooden shuttering or formwork for producing a hydraulic mortar. Contrary to this (Singer et aI. 1965). pronouncement, Vitruvius states in his book De Archi tectura that the magnificent quality ofRoman concrete resulted from the extensive use of artificial pozzolanic 5 POZZOLAN mortars and concretes. Two artificial pozzolans were intensively used: (1) calcined kaolinitic clay, in Latin Natural pozzolans are the naturally occurring siliceous testa; (2) calcined volcanic stones, in Latin carbuncu or siliceous and aluminous materiais which in them lus. In addition to artificial reactive ingredients, the selves possess little or no cementitious value but Romans used a natural reactive volcanic sand named will, in finely divided form and in the presence of harena fossicia. The ingredients testa, carbunculus moisture, chemically react with calcium hydroxide at and harena fossicia were intensively used in Roman ordinary temperatures to form compounds possess buildings (Vitruvius 1960). ing cementitious properties. Volcanic glasses, volcanic Dusty ancient history books taught us that Roman tuffs, trusses, diatomaceous earths and some clays and concrete consisted ofjust three parts: a pasty, hydrated

92 lime; artificial or natural pozzolan; and a few pieces concrete product called Roller Compacted Concrete offist-sized rock. Ifthese parts were mixed together in (RCC) had been crudely developed, U.S. Bureau of the manner of modem concrete and placed in a struc Reclamation 's refinements made it an economical can ture, the result certainly would not pass the test ofthe didate for dam construction. In the construction of a ages (Moore 1993). How did those Romans around dam in Utah, USA, a concrete consisting of a binding the time of Christ build such elaborate, ageless struc mixture of 40% Portland cement and 60% f1y ash. By tures in concrete is the question on which the durability coincidence, the f1y ash contained the same amorphous of ancient concrete and its comparison with modem silica compounds as the ash from explosive volcanoes. one will be discussed in the following part of this And the hydrated portland cement released the cal investigation. cium component recognized in the lime part of the "A most unusual Roman structure depicting their ancient concrete formula. When Reclamation mixed technical advancement is the Pantheon; a brick faced these two parts for their dam, a bonding gel was formed building that has withstood the ravages ofweathering to tie inert rock pieces of the hatch together. These in near perfect condition. Solving the riddle of ancient rocks were used as a strong filler material much in the concrete consisted oftwo studies: one was understand same manner as is used in standard concrete practices" ing the chemistry, and the other was determining the (Moore 1993). So, a close relationship between the placement ofancient concrete. To understand its chem calcium hydroxide molecules from Portland cement ical composition, going back in time much before and that of the ancient wet lime, and between the Moses is essential. People of the Middle East made amorphous silica of the pozzolanic f1y ash and the walls for their fortifications and homes by pound amorphous silica ofthe volcanic pozzolan can be con ing moist clay between forms, often called pise work. structed. As a result, such a reasonable relationship To protect the surfaces of the clay from erosion, the for the concrete components that make the gel for ancients discovered that a moist coating ofthin, white, both modem and ancient concrete can be useful for bumt limestone would chemically combine with the comparison purposes (Moore 1993). gases in the air to give a hard protecting shield. Although the similarity ofthe ingredients ofmodem As a guess, the event of discovering pseudo con and ancient concrete has been explained, there is more. crete occurred some 200 years before Christ when a Studies ofthe placement process are very important in lime coating was applied to a wall ma de of volcanic, making durable concrete. The Bureau of Reclamation pozzolanic ash near the town of Pozzuoli in Italy" mixed their components (cement, ash, and rock) with (Moore 1993). as little water as possi ble to give a stiff, 'no slump' A chemical reaction took place between the vol concrete; spread it in layers on the dam; and pounded it canic ash containing silica and small amounts of alu into place by large vibrating rollers to make a new class mina and iron oxide and the lime (calcium hydroxide). of concrete. The ancients had mixed their components Later Romans noticed that mixing finely ground vol (wet lime and volcanic ash) in a mortar box with very canic ash with lime made a thicker coat, but it also pro little water to give a nearly dry composition; carried duced a durable product that could be set and harden it to the jobsite in baskets placing it over pre-placed even under water. In order to understand the di fference layer of rock pieces; and then proceeded to pound the between lime and lime-pozzolan mixtures, the chem morta r into the rock layer. Vitruvius mentioned this ical reaction have to be examined separately. When process in his history formulas for his concrete, plus only lime is used as a binding agent within lime-sand the fact that special tamping tools were used to build a water mixture, the strength development of the mix cistem wall. Close packing ofthe molecular structure occurs as a result of carbonation, whereas in the case of by tamping reduced the need of excess water, which lime-pozzolan mixture strength development is based is a source of voids and weakness. But also packing upon the reaction between hydrated lime and finely produces more bonding gel than might be normally ground amorphous silica. There is no need to carbon expected (Vitruvius 1960, Moore 1993). dioxide in the case of lime-pozzolan mixture, which Throughout the above paragraphs, the ancient con means that it possess hydraulicity. It is also found that crete was compared with one type ofmodem concrete, parts of the complex chemistry of the lime-pozzolan RCC, which was invented few years ago and whose bonding gel matching the same chemical formula of applications are restricted overall the world. The other modem concrete bonding gel, which is called as C-S-H modem concrete applications generally suffer from or tobermoritte gel in modem concrete world. And this premature deterioration within their service or design is so; the pozzolan-wet lime gel gave the high perfor life. Some of the reasons for that are as follows: mance to the ancient concrete. The placement technic (I) modem cement is too active, thus the rate of used in ancient concrete was the other important point hydration reaction, which is exothermic, is too high; causing high performance (Moore 1993). and thus modem concrete becomes more prone to "Chemistry alone will not make good concrete; thermal cracking and thus more permeable. (2) Expec ratherpeople will make good concrete. Although a new tation of high strength performance from concrete

93 induces use ofhigher dosage of cement or use offiner "www.portcement.org/cern/cementindustry_ cement, which causes same result of (I). (3) Speed history.asp" of construction induces use of high early strength "realtytimes. com/rtnews/rtcpages/20000 128_ cement and concrete or use of speeded curing methods concrete. htm" (e.g. heat curing), and thus causes again the same .. www.romanconcrete.com.. result of (1). .. www.qcl.com.au .. This is sincerely appreciated by the author of this article. 7 CONCLUSION

The history ofPortland cement, modem binding mate REFERENCES rial invented in 1824 is too short, when the whole history ofbi nding materiaIs utilized by ancient people Collepardi, M. 1997. A Historical Review ofDevelopment of throughout several centuries is considered. Through Chemical and Mineral Admixtures for Use in Stucco and the long history of human bei ngs, severa I types of Terrazzo Floor. Proceedings of the Fiflh CA NMET/ACI International Conference on "Superplasticizers and Other binding material have been invented sometimes inten Chemical Admixtures in Concrete ", SP 173, pp. 673-694. tionally, sometimes unintentionally. Mud, gypsum, Erdogan, T.y. I 997.Admixturesfor Con crete. Ankara: METU lime, and lime-pozzolan mixture are some examples Press. of ancient binding materiaIs. Erdogan, T.y. 2002. Materiais of Construction. Ankara: Whatever type ofbinding materiaIs the ancient civ METU Press. ilizations used, it can be seen that those structures built Krumnacher, P.J. 200 I. Lime and Cement Technology: Transi by ancient binders, particularly lime-pozzolan mix tion form Traditional to Standardized Treatm ent Meth ods, ture have survived for several hundred years. lt can MSc's Thesis in Virginia Polytechni c Institute and State be claimed that even at that time architects were aware University, USA. Lazell , E.W. 1915. Hydrated Lime: History, Manufacture and of the importance of the durability of binding materi Uses in Plaster-Mortar-Concrele. aIs and their mortars. For instance, th e Romans built McKee, H.J. 197 1. Early American Masonry Materiais in many beautifu l, massive structures such as the famous Walls, Floors and Ceiling: Notes on Prolotypes, Sources, Pantheon lasting through several hundred years till Preparation and Manner of Use. NY. today. However, those structures belonging to modem Moore, D. 1993. The Riddle of Ancient Roman Con civi!izations and made by using modem binders, i.e. crete. "Spil/way" a newsletter of lhe US Dept. of the portland cement have experienced significant deterio Inlerior. Bureau ofReclamation. Upper Colorado Region. ration throughout their service !ife, generally lesser Neville, A.M. 1998. Properlies of Concrete. New Jersey: than 100 years. As a result, it can be sai d that the Prentice Hall lnc . 4th Edition. Nicholson, P 1850. Encyc/opaedia ofArchitecture: A Diclio whole process of modem binding materiaIs, mortars nary of the Science and Practice of Architecture, Building, and concrete should be re-examined beginning from Carpentry, ele. From lhe EarlieslAges to lhe Presenl Time. raw materiaIs, production processes of bi nding mate Vol.2. NY: Johnson Fry Co. riaIs up to mixing, placing, compaction, finishing and Singer, c. , Holmyard, E.J., Hall , A.R. , Wi ll iams, T. 1. 1965. curing processes of mortars and concrete. At that History ofTechnology. Vo l. 1- 5. Oxford: Clarendon Press. point, it is imperative to examine many good examples Vitruvius, P 1960. Vitruvius: Ten Book on Architectura. New throughout the ancient centuries. York: Dover Publications.

ACKNOWLEDGEMENT

Throughout this study some informations are quoted from several web sites i.e. "www.aubum.edu/academic/architecture/bsc/ classes/bsc314/timeline/time!ine.htm" "matse I.mse.uiuc.edu/ ~ tw/ concre te/hist. htm I" "www.oneworld.org/itdg"