Commentary on concrete

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Journal of the American Concrete Institute, 30, 9, pp. 925-933, 1959-04-01

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Commentary on concrete

Legget, R. F.

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BI.DG

NATIONAT RESEARCH

COUNCIT

C A N A D A

DIVISION OF BUITDING

RESEARCH

COMMENTARY

ON CONCRETE

By

R. F. LEGGET

ilg'yp"Xul$1'n

A N A L Y Z E D

_MAY'

_{t2 1959}

Authorized reprinl from copyrighted

JOURNAL OF THE AMERICAN CONCRETE INSTITUTE Vol. 3Q No. 9, Morch 1959, pp.995-933

TECHNICAL

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1959

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T i t l e N o . 5 5 - 5 9

M i l e s t o n e s o f t e c h n o l o g y o s

reviewed ot the dedicqtion of

the ACI Heodquorters Building

Commentory

on Concrele

Bv ROBERT

F. LEGGET

I Trus rNrEnNArrolt,tr, gathering and the official opening of the new ACI building surely mark a milestone in the long history of the technology of con-crete. The building that has now been well and truly dedicated, for the use of the American Concrete Institute in its wide-spread services, is of unusual interest in the architectural sense, unique indeed in some of its features. Is it not the first building ever to be erected by a professional and independent society whose aim is the advancement of the state of the art of concrete technology? In many countries, including the United States, there exist splendid organizations devoted to the promotion of the proper production and use of portland cement and concrete that are supported financially (at least in part) by the manufacturers of cement. Their work is of great value. The American Concrete Institute is, however, to the best of my knowledge, unique in this field in that it is supported entirely by its individual members who work together not only for the advancement of the art but also for the promulgation of codes of good practice-in design and construction-which they make freely available for voluntary use.

This is a fine thing, one of the great characteristics of the engineering scene in North America, now symbolized for this society by the new building, itself paid for in large part by the members themselves. The very freedom of enter-prise rvhich it betokens is a continuing responsibility, but of this there is no need for me to speak. The address of your President is in itself warrant, enough for full confidence that the American Concrete Institute is going for-ward to still finer work, fully conscious of these responsibilities, well aware of the international leadership that is its heritage and its challenge.

9e6 JOURNAL OF THE AMERTCAN CONCRETE |NST|TUTE Morch 1959

MITESTONES OF CONCRETE TECHNOLOGY

Milestones are markers of a quieter age than ours. Is it not significant that the great new superhighways of today rarely includd such useful markers of the passing miles? We can, however, still speak of milestones metaphoric-ally, and this is certainly an occasion for using this happy simile. Do you recall the old rhyme about the milestone .

"It tells two things well worth the knowing; Where we are and where we're going; More candid than that other stone, Which only says that we have gone."

May we, together, spend a few minutes in seeing where we are and where we're going with this wonder material concrete?

Concrete, as we know it today, has a history of about a century-a century of remarkable advance in its use, as in all branches of technology. It is easy to become so enthusiastic about the things now done with concrete that it may be salutary to remind ourselves first that although we, as engineers, know what we are talking about when we discuss concrete, the man in the street generally does not-even after a century of such splendid technical progress.

How often do we hear, and even read, of an operation described as "pouring cement." In a fine bookwhich I have just finished reading, a stimulating dis-cussion of work and contemplation by one of your eminent philosophers,l I c&me across this expression twice-and this in the writing of a learned student of manual work. How often do we hear of "cement sidewalks"? Why is it, I wonder, that the editors of even our greatest newspapers and of our leading journals of opinion, expert as they are, have not yet discovered that cement is but one of the ingredients of concrete? And even as engineers, we need not be too complacent. How many engineers still invariably talk of "pour-ing" concrete when they know quite well that, if the concrete they use is good concrete, it can not be poured but must be placed? Even so eminent a journal as Engineerin,g News-Record, which tries to follow a rule of using "place" or "cast," still misses sometimes and lets "pour" slip in.

Tomorrow's lesson from yeslerdoy

There is still a tremendous educational job to be done-a fact of which I am reminded almost every day, as I pass on my way to work a concrete side-walk which failed miserably, mainly because it was not properly cured in the

COMMENTARY ON CONCRETE 997

heat of high summer. And you will know, as f know, that the necessity of curing fresh concrete, and the use of damp sand for this purpose, was recog-nized (by Wilkinson) at least 100 years ago. But these are small things; let us look at the other side of the picture.

What a versatile material is concrete! Has it ever occurred to you that there is no other building material which can be used throughout the wide range from the placing of a few cubic inches around a pole in a garden to the use of over 10,000,000 cu yd in a single man-made structure such as the Grand Coulee Dam. It can be made by a child; it can be produced by the ton. It can be mixed on a shovel; it can be manufactured in majestic fully-automatic plants. It can be placed in tropical climes, cooled if necessary as it'sets; I have personally supervised the placing of concrete when the air temperature was -40 F, and concrete was heated, instead of being cooled, until it gained its full stability. It is man's equivalent of nature's conglomerates, with the added advantage that man can choose his constituent materials and so even get the better of nature-provided that he selects his materials carefully.

AESTHETIC POSSIBITITIES

More than this, of all the more common structural materials, concrete is the only one which is completely susceptible in form and size to the molding hand of the designer. Despite all that is sometimes said to the contrary, engineers in general are appreciative of true aesthetics. What possibilities concrete places in the hands of the master designer for combining beauty with utility! _{rt has been well said that "beauty is a refinement on function which} induces visual comfort or stimulates visual delight or visual excitement." With how little extra effort can concrete structures be charged with delight? And how good it is to think that more and more the aesthetic possibilities of concrete structures are being appreciated by designers-engineers, and engineers working together with architects in happy combinations that can remind us of the master builders of another age. We can think together of the clean-cut lines of some of your TVA dams and power houses, the gaunt outlines of Canadian grain elevators-bastions of the great plains, the slender arched bridges of Robert Maillart in the remote mountain valleys of Switzer-land, the splendid symmetry of some of the more recent works of Nervi in Italy with their almost unbelievable weblike structures. These and count-less more examples from almost every country testify to the skill which the engineer has acquired in molding this most natural of all artificial materials to his designs, for the use and for the delight of his fellow men.

PROGRESS ABROAD

I speak of countries overseas. You know well the concrete works of your country and of mine. Would you care to glance briefly at some concrete struc-tures in the far places of the world, places which it has been my great privilege

998 JOURNAL OF THE AMERICAN CONCRETE INSTITUTE Morch 1959 to visit in recent years on official duty? Your imaginations are vivid; let them provide you with a magic carpet to circle the globe from this pleasant room in the busy heart of Detroit. Flying off to the west, and spanning the broad Pacific, we can recall the vast quantities of concrete made in lecent years using coral for aggregate, now to be seen on many a tropical atoll. Right at the other side of the world, we come to New Zealand-a small country with a population of not much more than 2,000,000, but with truly significant engineering works worthy of a population several times as large. As we fly in over Auckland, at the extremity of the North Island, we shall see one of the pioneer reinforced concrete bridges of the world, the Grafton Bridge which, when built in 1910, was the longest single span reinforced concrete bridge in the world.2 Although the main arch with its span of 320 ft has long since been exceeded in size by other structures, this pioneer structure yet serves its city well and has a long life still ahead of it. It does not take long for a visitor to New Zealand to find that this is a country where earthquake shocks are an ever present danger. As engineers, we shall notice how Satis-factorily structures of reinforced concrete have performed eYen when sub-ject to such severe loading, the monolithic character of concrete structures giving them particular advantage for all such critical locations.

Down under

Crossing the Tasman Sea, we come to the Island continent of Australia. There are concrete structures aplenty to be seen in Sydney but its skyline is still dominated by its famous steel arch bridge. If present plans are carried out, however, a rival will soon appear in the form of an opera house, the architecture of which will be even mole "functional" than that of the ACI building, the architect having attempted to reproduce in a concrete structure the appearance of sails in the wind, so widespread and lovely a sight on the blue waters of the harbor. It is in Melbourne, however, that we shall find the most notable concrete structure of Australia, this being the great dome of the public library. When built, it was the largest reinforced concrete dome in the world; those older members who recall the 1914 war may find interest in the fact that it was designed by Sir John Monash who achieved international fame as the leader of the Australian forces in that first world conflict.3

we shall have to cross to the quiet island of Tasmania, however, to see quite the most unusual concrete structure of Australasia, the arched bridge across the harbor of the beautiful capital city in Hobart. This is a rein-forced concrete bridge arched in plan, and not in profile, for it is also a float-ing bridge. Designed by a good friend of mine, David Isaacs, it was con-structed in 1936. Foundation conditions dictated the unusual nature of the structure which is 3156 ft long, and which weighs about 25,000 tons. The tidal range is 9 ft and strong ocean swells add to the complications of the site rvith the result that the bridge sometimes acts as an arch in compression, sometimes as a catenary in tension, depending on winds and tides'a

COMMENTARY ON CONCRETE 999

Singopore

Singapore must be our next stop, that amazing little island almost exactly on the equator. Its area is only 224sq miles and yet about 1,500,000 people live on this famous island, most of them in such crowded quarters that these have to be seen to be believed. But for almost 30 years the Singapore Im-provement Trust has been making steady progress at improving housing conditions. Its most recent housing developments constitute some of the finest reinforced concrete structures which it has been my privilege to see anywhere. Can you visualize clean-cut 14-story blocks of simple flats, con-structed entirely of reinforced concrete, with flat roofs, open balconies, a judicious use of bright colors, and pure white precast concrete grillages over all open wells? These are exciting buildings, exciting aesthetically, and exciting to watch under construction, for the "jungle" scaffolding which is used right up to the top of the full 14 stories consists of slender sticks of bamboo merely lashed together.s

lndio

On to India, that amazing sub-continent with its population of almost 400,000,000, a population increasing at the rate of 5,000,000 every year. These fantastic numbers will make you think of the traditional type of Indian building, seen in typical pictures of Indian villages. Simple brick and soil structures still dominate the national scene but India is awakening. The fine pioneer engineering work of the British is now being continued at an ever increasing rate by the engineers of the new nation. Would it surprise you to know that the first prestressed concrete bridges in the world, designed for railway use, were constructed in India? Exceptions these may have been but they were built for the Assam Railway in 1949.6 As early as 1934,

Old ond new-A piece of Romon "con-crele" with the new ACI Heodquorlers Building in the bockground. The Romon "concrele" wos presenled to ACI by ihe Division of Building Reseorch, Notionol Reseorch Council of Conodo ot the dedi-cotion of rhe ACI building. The inscriptions reod:

ROMAN 'CONCRETE' FROM NEAR ONE OF NERO'S AQUEDUCTS: VIA VERGINE

A. D. 60

A TOKEN OF WELL-WISHING: 29.X.1958 DBR. NRC, CANADA, TO ACI

930 JOURNAL OF THE AMERICAN CONCRETE INSTITUTE Morch 1959

a mass concrete dam (the Methur Dam in south India) 5300 ft long and 200 ft high had been built across the Cauvery River. And today there is being constructed of mass concrete, with much American assistance and with modern construction methods, the great Bhakra Dam 680 ft high and 1700 ft long, across the Sutlej River, for what will be one of the largest multi-purpose projects of the world.

Not all Indian concrete structures follow the lead of the West, however. In New Delhi one can see a beautiful temple in the ancient Hindu style of architecture. One can admire it, and then be surprised to find that it was built as recently as 1939 in reinforced concrete-a truly adaptable material. And most of the dams being built in India are still constructed by hand, of masonry hand-placed in cement mortar, up to heights far exceeding 100 ft. The great manpower problem of India is vividly shown by the fact that this type of construction is. still, in 1958, about two thirds of the cost of ma,ss concrete placed with the aid of all the most modern equipment.T If time permitted, we could inquire about the ancient use on the Malabar Coast of mortars made of lime mixed with molasses (a clue for modern research work-ers?). Would, too, that we had time to fly across the Indian Ocean to the west to visit South Africa, another country which uses concrete well. Our travel must, however, be to Europe.

Europe

Many of you will know the countries of western Europe whefe so. much splendid concrete work is to be seen. How pleasant it would be to wander in Flance, to visit the sites of some of the early pioneer reinforced concrete structures, certainly to make pilgrimage to le Pont d'Ivry where in 1903-55 years ago, Consider6 tested a large reinforced concrete bowstring arched bridge to destruction.8 We could find much of interest in Belgium, in Holland, and in West Germany. So much fine work has been done in all these coun-tries, especially in recent years, that it would be almost invidious to select any for individual mention apart, perhaps, from Professor Paduart's superb "arrow" at the Brussels Exhibition. Research into concrete problems has also been actively pursued, notably at the fine Materialprufungsamt der Technische Hochschule in Munich. In Switzerland, we would be aston-ished by the audacity of some Swiss concrete bridges, even as we would be enthralled by the beauty of many of them in their superb natural settings. In Denmark we could walk over a small reinforced concrete bridge that was built in the year 1894 and which still gives good service, crossing a main road r'vith a span of just over 70 ft.

Scondinovio

Flying north into Scandina-via, we come to another area where modern reinforced concrete work is indeed challenging. We would see precast concrete units in use on a scale equalled only, perhaps, in the USSB,, and possibly in Britain and France. In Stockholm I have .visited a.real concrete "factory" u'hich made and distributed precast, prestressed concrete-units not just in

COMMENTARY ON CONCRETE 931 that city but to all parts of sweden. In that same lovely city, so well called the "venice of the north," we would see reinforced concrete arched bridges that are masterpieces of design, with spans amongst the longest in the world. (I hesitate to mention which swedish bridge has the greatest span since I found this still to be a matter of argument among swedish friends.) \ve would find, too, another of the great concrete research centers of the rvorld, the Swedish Cement and Concrete Research Laboratorv.

For north

I must ask you, however, to travel still further north with me, over first to Finland-that _{valiant tittle land-self-sufficient for many years in its} cement needs, and using concrete with vigor and vision. on still to the north, however, right into Lapland, to rvalo and to Karasgniemi at the far northern tip of Finnish Lapland. concrete in Lapland? Yes,.here too. Just over a year ago, I stood by a concrete mixer in Ivalo operated by a f,ap-lander and saw most excellent concreie being placed for building foundations in this land of the midnight sun. But even I was not prepared for what I found when I went further north still, across the border into Norway, and on up to Hammerfest-the _{most northern town in the world, located beyond the} 70th parallel, only a thousand miles from the North Pole. This ancient fishing port with a hardy population of about 5000, was one of the Scandinavian towns to be devastated in the shocking waste of war, every single building razed. to the ground by fire in 1944. rts rebuilding was virtually complete last year, the new town hall being one of the last of the new buildings to be completed. And the town hall, as also many of the larger buildings of the town, was a first class piece of reinforced concrete construction.

WHERE ARE WE GOING?

From the Antipodes to the Equator, from the Equator to far north of the Arctic circle, concrete well and truly used all the way. where better, in imagination, could we ask our second question-"where _{are we going?"} with concrete already used in such a variety of ways, it would not be reason-able to suggest that any major changes in concrete technology or in the use of concrete will occur in the foreseeable future. The variability of concrete ingredients can never be forgotten, requiring ceaseless vigilance for the de-teetion of any new and previously unknown reactions, constant research into the problems raised by the use of new and untried materials. The suc-cess of air-entraining agents suggests, in an almost tantulizing rvey, thet there may yet be found an admixture which really would influence the be-havior of concrete (this statement having no relation to, nor reflection on admixtures now on the market).

Design

Turning to design, surely the time has come when the problem of designing satisfactorily for shear stresses must be solved? Working stresses must be continually under review, as efforts are made to raise them effectively,

per-939 JOURNAL OF THE AMERICAN CONCRETE INSTITUTE Morch 1959 haps some logic introduced into their determination. Even more important, possibly, will be the more mundane task of really designing "concrete for permanence." In this, careful reviews of experience with concrete structures irr practice will always be valuable, such as American studies of the per-formance of concrete in dams, and the B1ifi,sh report on the durability of concrete buildings.l0 Recent British practice supports one further predic-tion-that we shall see a considerable increase in the use of precast concrete units. In London, there was recently finished a l0-story concrete office building, completely precast, typical of recent European advances in this direction.rr

But with this briefest of references to British practice, we should head to the rvest again, to complete our imaginary journey. As our magic carpet carries us away from England's green and pleasant land, we may catch sight of a solitary llghthouse, seemingly rising out of the sea, south of Plymouth. This is the Eddystone Lighthouse. John smeaton was entrusted with its reconstruction in 1756, just two centuries ago. This first of civil engineers was a true research worker; his investigations for the final mixture of blue lias lime and, pozzolan from Civita Vecchia laying the foundations for all modern cement and concrete research. And where did Smeaton get his in-spiration? From the Romans, and from the records of their works of 1700 years before, works which were so strangely forgotten throughout the middle ages. Let us, also take a quick glance back in time across the centuries for was it not Edmund Burke who said "people will not look forward to pos-terity who never look backward to their ancestors."

Eorly uses

What interest can we find. Here, for example, is Pliny writing in his ltrar-ural History: "Cisterns should be made of five parts of pure gravelly sand, two of the very strongest quicklime, and fragments of silex (lava) . when thus incorporated, the bottom and sides should be well beaten with iron rammers." And then we think that vibrated concrete is something new! Admittedly, the Romans did not use portland cement but their mixtures of aggregate, lime, and pozzolan gave a material that is the direct ancestol of good concrete of today. They even used lightweight aggregate' the mag-nificent dome of the Pantheon, with a clear span of I42 fL 6 in., being possible only because of the use of pumice as aggregate. They used wooden molds just as we do today. And we know that they really did "pour'l some of their "concrete" instead of placing it, as they should have done, by what we can see of its appearance today, 2000 years later. Sad to relate, they did not always clean out their formwork as they should have done, sometimes leaving chips of wood from the forms to be mixed in with the "concrete."

You will think that I exaggerate. But if we could go together to the Flavian Palace on the Palatine in Rome, built more than 2000 years ago, we could see in the foundation walls the marks of the boards then used for formwork, clear indication of too much water in.the mix. And the chips of wood in the forms? These must be seen to be believed. So much do we owe to the Romans,

COMMENTARY ON CONCRETE l / 5 3 and so useful is it to be reminded occasionally that all engineering is not the work of the twentieth century that I would like to conclude this brief com-mentary by presenting to the President of the Institute as a small token a piece of Roman "concrete," almost 2000 years old, fairly well graded but containing a small chip of wood still clearly to be seen.

If, therefore, Mr. President, this small specimen can find a place in the new building, will you please accept it not only as a token of well-wishing to your fnstitute from Canadian engineers and research workers, coming to you across the borders of space, but coming also across the borders of time, as a reminder of our debt to the past, a symbolic token of all that has been done down the ages in developing the concrete technology of today, challenge indeed that we must never forget the ancient words:

"That which our Fathers bequeathed to us, we must earn to possess.tt

SPECIAT ACKNOWTEDGMENT

The specimen of Roman "concrete" was kindly obtained through the Canadian Embassy in Rome (N. F. H. Berlis, Charg6 d'Affaires) with the expert and interested assistance of Professor Maurizo Borda, vice-director. Museo Nazionale Romano, Rome, Italy,.

REFERENCES

1. Steere, D. Y., Worh and Contemplation, Harper and Brothers, New york, 1gb7, 148 pp. 2. Personal communication from H. L. flume, Wellington, New Zealand.

3. Personal cornmunication from David Isaacs, Sydney, N.S.W., Australia.

4. "Floating Concrete Arch Bridge," Engineering News-Recoril, V. 13b, Aug.9, 1g4S, pp. 181-183.

5. Legget, R. F., "Singapore's Progressive Public Ilousing," Engineering News-Becoril, V. 159, July 11, 1957, pp.7&83.

6. Personal communication from Lt. Gen. sir Harold williams, Roorkee, u.p., India. 7, Rao, K. L., "Engineering Problems in Recent River Valley projects in India," V. 11, Proceedings, fnstitution of Civil Engineers (London), Sept. 1958, pp. 1-40.

8. March, C.F., Reinlorced Concretc, p.507. (This interesting book of 845 pp. with 512 illustrations was published by D. van Nostrand co., New York, in 1904; it was printed in England by Butler and Tanner.)

9. Plum; N. M., "concrete in Denmarkr" concrete anil constructional Engineering (Lon-don), V.51, Jan. 1956, pp. 1-19.

10. Elamilton, s. B., "A Note on the History of Reinforced concrete in Buildings," -lfo-tional Buikl;ing stud'ies special Report No. 24, IJer Majesty's stationary office, London, 19b6, 3o pp.

11. Derrington, J. A., "Multistory Construction in Concrete," Proceeilings, Institution of Civil Engineers (London), V. 9, Apr. 1gb8, pp. 4gB-482.

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