ted Co its LOTTE; Be , be ‘ T= FE BOE eM f + oh A rN ¥ 7 . po AE i Nees eX . Oo © ge The Contribution of Scientific Research to the Development of the Portland Cement Industry in the United States By Durr A. ABRAMS Professor in Charge, Structural Materials Research Laboratory, Lewis Institute, Chicago HISTORICAL ~ CENTURY ago, Joseph Aspdin, an obscure mason of Leeds,! Eng- land, was granted a patent by Kiyg George IV on an artificial stone which he called “Portland”? cement, because of its resemblance to the well-known building stone quarried on the Isle of Portland,—the stone of which West- minster Abbey was constructed. According to the fragmentary his- tory of Joseph Aspdin, his patent fol- lowed years of experimenting, so that the present cement industry, which has developed from Aspdin’s factory of 1825, was founded upon research. His plan of combining two powdered raw materials in certain proportions, burn- ing them and then pulverizing the re- sulting clinker produced a cement much superior to the older hydraulic cements which were made from a single material that was lightly burned and then ground. The industry’s surpris- ing growth since Aspdin’s time has been based largely on that same factor; today scientific research into the con- stitution and manufacture of Portland cement and its use in making concrete is going forward on a still more exten- sive scale. PoRTLAND CEMENT IN THE U. S. The Portland cement industry in this country dates from 1872, when 1The writer was present at the Town Hall Leeds, England, September, 1924, upon the oc- casion of the unveiling of a table in memory of Aspdin, at the joint centennial celebration of the discovery of Portland cement, held by British and American cement manufacturers. 1 David O. Saylor made the first cement of this type in eastern Pennsylvania. Here again success followed a period of experimenting, and while the equip- ment was crude, the work was based upon sound ideas. It was not practi- cal for the American manufacturers to draw extensively upon the store of in- formation then existing in Europe, and for many years development was slow. When a marked stimulus did come, it was through the introduction of new types of kilns and grinding mills which, particularly in the case of the kilns, followed a long period of often disap- pointing research. Through further investigation, it was discovered how to utilize pulverized ‘coal in burning the clinker, in place of the more expensive and less widely distributed petroleum. Natural ce- ments have been made in the United States since the construction of the Erie Canal in 1820. In 1890, the produc- tion of natural cement was over 7,000,- 000 barrels, in comparison with a third of a million barrels of Portland cement. In 1900 the country’s output of Port- land cement exceeded that of the older natural cement for the first time. There are now 134 operating Port- land cement plants in this country, lo- cated in 29 states scattered from the Atlantic coast to the Pacific, and from the Canadian border to Mexico. The latest figures available from the U. 8. Geological Survey show an output of nearly 150,000,000 barrels for 1924. A better product, discovered and de- veloped through research, has strongly entrenched itself, while the once firmly aa Tur ANNALS OF THE AMERICAN ACADEMY established natural cement has _ al- most disappeared from the market. Some writers have attributed the de- cline of the natural cement industry to the lack of an aggressive educational and promotional policy, based upon re- search, as much as to anything else. COMPETITION WITH FoREIGN CEMENTS An understanding of present condi- tions in the Portland cement industry and the part research has played in its development will be best secured by going back some three decades. In 1895 the domestic Portland cement industry, then 23 years old, was pro- ducing less than 1,000,000 barrels a year, whereas imports were about 3,000,000 barrels. ‘T'wo years later the United States production had grown to 2,700,000 barrels, which for the first time was greater than imports. ‘Three years later the annual output had more than tripled, and by 1902 had reached more than 17,000,000 barrels. MANUFACTURE OF PoRTLAND CEMENT The manufacture of cement is fairly complicated because of the large quan- tities of materials that must be han- dled, and the close control of the ingre- dients that must be maintained at all times. The essential constituents of cement are lime, silica and alumina. These ingredients may be secured from a number of sources, the most common of which are limestone, marl and oyster shells for the lime; and clay, shale and blast furnace slag for the clayey mate- rials. In the case of blast furnace slag, considerable lime is also secured. Scientific research has made possible the utilization of deposits which once would have been considered unsatis- factory and has extended the possible locations of plants with a resulting saving to users of cement in various localities. Since cement is such a heavy, low-priced commodity, freight rates make up an important part of the cost where the shipping distance is considerable. The raw materials are quarried or excavated by powerful machinery and taken to the plant usually in cars. There the rock is put through crushers followed by various types of grinding apparatus until a materia] finer than flour is secured. Following crushing, the materials are weighed out in pro- portions determined by the chemist’s frequent tests so that in grinding a very intimate mixture of the ingredients is secured. The finely pulverized “‘raw mix”’ is now ready for the kilns, which are great steel cylinders, 6 to 10 feet in diameter and 100 to 250 feet long, lined with firebrick. The mixture is fed into one end of the kiln, which is slightly higher than the other so that as the kiln rotates the material slowly passes toward the lower end. The pulverized coal, fuel oil, or gas is blown into the lower end and burns in a great tongue of flame 30 to 40 feet in length, pro- ducing a heat greater than that re- quired to melt steel. It is in this high- temperature zone that entirely new physical and chemical compounds are formed, called cement clinker. ‘This is white-hot as it leaves the kiln, but upon emerging from rotary coolers it is ready for the storage pile or for the grinding mills. | Clinker, which consists of particles ranging from the size of a pea to that of a walnut, is glass-hard and is not affected by weather and needs only to be finely pulverized to produce cement. A little gypsum is added to control the rate of hardening of the cement. Although a variety of machinery is utilized in grinding clinker, final grind- ing is commonly done in rotating steel cylinders partly filled with a charge of many tons of small steel balls. As the cylinder rotates, these balls are carried Screntiric Resfarch AND THE Porttanp CEMENT INDUSTRY 3 part way up the side and then are thrown outward and down, resulting in pulverization of the clinker. PROPERTIES OF PoRTLAND CEMENT No matter what raw materials are utilized, the resulting cement must have certain well-defined characteris- tics and must meet standard specifica- tions which have been adopted jointly by the American Society for Testing - Materials and the U. S. Government. The standard specifications require that at least 78 per cent of the finished cement be fine enough to shake through a sieve having 40,000 holes to the square inch. This sieve is made from bronze wire, but is woven much more finely than a silk handkerchief. At the present time the quality stand- ards of the cement industry are well established and all cement must meet these specifications. In the early days _ of the industry, a great deal of atten- tion was paid to securing a product that would equal or exceed the imported brands and careful investigation was absolutely necessary in order to de- velop methods of quality control. In fact, it was only after the quality of the domestic product had been fully dem- onstrated that engineers adopted it. Without research the industry would never have reached a firm basis for its extensive later growth. Quatity CONTROL IN CEMENT PLANTS Chemical and physical laboratories are essential parts of every cement plant, and are jointly responsible for the control of the quality of the cement. . The first tests of the chemist are made on samples secured from the drill holes in the quarry, so that he knows what to expect from different parts of the quarry after the material is blasted loose. This control continues through the manufacturing process. It is the chemist’s duty to set and lock the scales which govern the proportioning of the raw materials, and to change the set- ting as the materials change. The physical laboratory makes tests during the process of manufacture, but it is concerned chiefly with testing the finished cement to see that it conforms to the standard specifications. Raw MarTeriAts IN CEMENT Perhaps some idea may be given by the following facts as to what it means for an industry to take some 48,000,000 tons of raw materials in the course of a year, put it through varied manufac- turing processes involving more than 80 operations and from it secure 28,- 000,000 tons of finished cement. It is estimated that 11,000,000 tons of coal were burned during the year, in addi- tion to large quantities of fuel oil and gas. In fact, the Portland cement in- . dustry is the fourth largest manufac- turing user of coal and the largest user of pulverized coal. _ Again, in breaking up the rock re- quired as raw material, more than 17,000,000 pounds of explosives were set off in cement mill quarries during 1924. Cement is shipped chiefly in return- able cloth sacks, four to the barrel. To replace the sacks lost and worn out in one year, a strip of cloth more than 37,000 miles long and 30 inches wide was needed. In addition to this, 50,000,000 heavy paper bags were used during the year. The most recent figures available from the Interstate Commerce Commission place the ce- ment industry fourth among shippers of manufactured articles. PoRTLAND CEMENT ASSOCIATION Here then was a rapidly developing industry, until a few. years previous greatly handicapped by a marked preference on the part of the users for A Tur ANNALS OF THE AMERICAN ACADEMY the product of foreign competitors, but fortified with recent improvements in manufacturing methods that had made the rapid expansion possible. Yet the industry was without any well-devel- oped plan or means of broadening its field of usefulness. In fact, many puzzling questions were before the manufacturers, and accordingly in 1902 a meeting of the producers in the east- ern states, where more than half of the entire output was then made, was held in New York for a discussion of matters of interest. This first meeting was devoted largely to the troublesome question of containers for the product, but it opened up such possibilities of co-operative effort in solving common problems of manufacturing and market development that before adjourn- ment a permanent organization was formed. Within a year other manufacturers from the West had joined and national representation was secured. ‘That or- ganization is still in existence as the Portland Cement Association, which has as members nearly 90 per cent of the companies manufacturing Portland cement in the United States, and in addition, several companies operating plants in Canada, Mexico, Cuba and South America. The one paid secretary of the first organization has now been replaced by some 425 employes of the pres- ent Association. Jn order that Asso- ciation activities might be carried on with great efficiency and in the light of local conditions, 28 district offices have been established in all parts of the United States, and one in Western Canada. General headquarters are maintained in Chicago, where there is also a research laboratory maintained jointly by the Portland Cement Asso- ciation and the Lewis Institute under the name of the Structural Materials Research Laboratory. An EpucATIONAL PROGRAM In effect, the Portland Cement Asso- ciation is the educational-promotional- research foundation of the cement industry. It is not engaged in the man- ufacture or sale of cement, but carries on for the entire industry educational and promotional work “to improve and extend the use of concrete,”’ all of which is based upon facts established by pains- taking research within the industry and by other organizations such as the U.S. Bureau of Standards and various university laboratories. The Association is a “Service’’ or- ganization for the user of cement as well as for the manufacturer. Princi- pal attention is given the educational and promotional work which has as its objective the extension of the use of cement. A secondary field of endeavor is the increased efficiency in manufac- turing methods. CoNCRETE RESEARCH In considering the major field of the Association’s activity, that devoted to extending the use of concrete, the leaders early saw that increasing the use of cement through education and promotion presented some peculiar problems. Cement is practically never used alone, but is mixed with other ma- terials such as sand and stone in making concrete and mortar. Because of the ease of transforming these various materials into concrete, a great number of people—some of them with very little practical knowledge of construc- tion—soon began to make things of concrete. Contrary to earlier accepted views, the way in which concrete is made has a great deal to do with the service it will give. ‘Therefore, no matter how careful the manufacturers were in turn- ing out a cement, it quite frequently happened that their product would be ScrENTIFIC RESEARCH AND THE PortTLAND CEMENT INDUSTRY 5 incorrectly used and consequently dis- satisfaction resulted which might strongly influence the builder and others against future use of concrete. The amount of mixing water added to the cement and aggregates—the sand and stone—in making concrete, the thoroughness of mixing, and the curing of the concrete, are some of the factors that govern the strength and quality of the final structure. Realizing that the knowledge of concrete making had not kept pace with the development of cement mak- ing, the manufacturers recognized that the biggest problem before them was the education of the user in the best ways of making concrete. In order that they might tell the user these important facts about concrete, the Association leaders knew that they must be sure of the basic principles and that led to one of the most important factors in the success of the Associa- tion’s work, namely, the establishment of a department primarily for research on concrete. Of course, a great deal of valuable investigation in that field had already been carried on. Many governmental bureaus, university laboratories, and others had conducted investigations; the difficulty was that the results lacked co-ordination, and in many instances were conflicting. STRUCTURAL MATERIALS RESEARCH LABORATORY In 1916, the Portland Cement Asso- ciation joined with Lewis Institute, a polytechnic school in Chicago, in es- _tablishing the Structural Materials Research Laboratory, where research into matters pertaining to concrete making had already been under way for about two years. Only eight members made up the staff at the time the co-operative work was begun, and the contribution of the Cement Association during the first year was about $15,000. From the first, the value of this work was recognized, although it was four years before the first bulletin describing the results of some of the investigation- al work was issued. The Laboratory developed steadily and additions were made from time to time both to equip- ment and personnel. Space on three floors is now required, and a staff of about 40 is employed by the Labora- tory. Tests are being made at the rate of about 45,000 per year. Inevitably more problems in such a broad field as concrete construction would present themselves for consider- ation than could be given adequate attention. Therefore, the selection of the problems to be investigated has re- ceived most careful consideration. An Advisory Committee, consisting of representatives of Lewis Institute and > the Portland Cement Association, de- termine the general policy and program of work for the Laboratory. Attention is focused upon one group of problems until satisfactory results have been secured, rather than dissipating the energies of the staff on unco-ordinated minor problems. FUNDAMENTAL PRINCIPLES OF CONCRETE The first important work of the Lab- oratory was to establish definitely the vital part that the water content of the mixture plays in determining the strength of concrete. It was found that the use of a pint too much mixing water in a batch of concrete was equivalent in its weakening effect to leaving out two pounds of cement. Therefore, this matter of maintaining a uniform and desirable consistency is extremely important. Important studies have been carried out which gave a better understanding of the effect of size and grading of ag- 6 Tur ANNALS OF THE AMERICAN ACADEMY gregate, the changes in quality of con- crete resulting from variations in ce- ment content, effect of different foreign materials in concrete, and many other factors. Co-OPERATION WITH OTHER - ORGANIZATIONS Much has been done in co-operation with other testing laboratories and technical societies, such as the Ameri- can Society for Testing Materials, the American Concrete Institute, the Bu- reau of Standards, the Bureau of Public Roads, the Associated General Con- tractors, and the California Highway Commission. Dissemination of the findings is given as complete attention as the in- vestigational work itself; until this in- formation is in the hands of the user of concrete, it has failed to accomplish the purpose of the cement industry in se- curing it. These results are frequently first given in papers before technical societies; later these papers are dis- tributed in printed form. Other data are issued directly by the Laboratory as bulletins and circulars. Facts from the Laboratory are given prominence in the literature of the Asso- ciation and in some instances form the entire basis of the publication. Through articles in the leading technical jour- nals, prepared both by the Laboratory and the Association, the facts are kept before those most interested. CoNCRETE Roaps One or two instances will show what this research has meant to the users of concrete, and consequently to the cement industry, through the broaden- ing of the market for its product be- cause of the satisfaction and economy secured through the proper use of cement. The concrete road is a comparatively modern development. As with any- thing new, the first examples left much to be desired. It was only through careful study and research into better methods of building concrete pave- ments—first on the part of individual cement companies and later on the part of the Portland Cement Association engineers in co-operation with this Laboratory, all of whom worked with the governmental agencies most inter- ested—that modern methods of high- way construction have been developed. In the five-year period, 1909 to 1913, which comprises the early days of con- crete roads, less than 114 per cent of the cement produced in the United States was used in pavements. In the five-year period, 1920 to 1924, this was increased to nearly 20 percent. Atthe present time, about 25 per cent of the cement made is being used in pave- ments of various classes. CONCRETE AGGREGATES In some parts of the country, it has been difficult to secure satisfactory aggregates at a reasonable cost for use in building concrete highways. In one instance in a western state, it was nec- essary to open a quarry and set up a crushing plant near the job. But the rock was of such a nature that crushing produced too much of the smaller pieces. In making concrete in accord- ance with the usually accepted specifi- cations it was necessary to throw away more than one-third of this crushed rock. One of the fieldmen of the Associa- tion suggested to the engineers in charge that the Laboratory might find means of utilizing some of the wasted material. Accordingly, the problem was submitted to the Laboratory with samples of the crushed rock. These samples were carefully examined and the usual concrete tests made. To the results, we applied the systematized knowledge gained in thousands of ScIENTIFIC RESEARCH AND THE PorTLAND CEMENT INDUSTRY 7 earlier tests and were able to recom- mend a mixture of fine and coarse ag- gregates so that nearly all the material could be utilized without sacrificing any of the strength of the resulting con- crete. These recommendations were put into effect; on this job alone the saving amounted to $30,000, or more than enough to build another mile of concrete road. ReEsEARCH APPLIED TO FIELD CONTROL There are always those who contend that the results of laboratory research may be theoretically correct, but are not practical in the field. But this ob- jection cannot be raised in this case, because many prominent engineers and contractors have applied the results on important jobs, and the principles an- nounced from time to time are now ac- cepted by the construction world. One interesting example of the appli- cation of laboratory principles to con- crete construction is found in the bridge built by the Big Four Railroad over the Miami River at Sidney, Ohio. T'wenty- eight thousand cubic yards of concrete went into this bridge, all of which was placed under scientific control. In- stead of using arbitrary proportions of the aggregates, guessing at the consis- tency of the concrete, and trusting to luck for curing, the mixture was de- signed for the desired strength on the basis of the aggregates used. ‘Tests were frequently made to control the consistency and modern methods of curing were employed. This research is not confined to the laboratory. Whenever desirable, tests ‘have actually been made on the job in studying the efficiency of various field methods. During 1923, important field investigations were made in the vicinity of New York City and Phila- delphia during the construction of seven large reinforced concrete build- ings. ‘These tests were made for the purpose of determining the uniformity of concrete under job conditions by the usual methods of proportioning an control. In 1924, tests on curing of concrete roads were carried out in California in| co-operation with the State Highway Commission. CONSERVATION OF POWER Through the Portland Cement Asso- ciation it has been possible for the manufacturers to co-operate in effective research into many subjects involved in the making of cement. This work has been carried on chiefly through a Con- servation Engineer working under the direction of a Committee on Conserva- tion, the membership of which in- cludes representative cement company officials. An outstanding example of this re- search is found in the utilization of the hot gases from the kiln in generating steam for power. Because of the high temperature (2,500° to 3,000° Fahren- heit) required near the lower end of the kiln in order that the raw mixture may be changed into cement clinker, the gases emerging from the kilnstaek have a temperature of 1,000° to /16,000° F. The volume of these hot gases_is-véry great, hence it has been found entirely practical to utilize them in heating boilers which generate from 50 per cent up to all of the steam required to furnish power for the plant. Since the power demands in cement making are ex- tremely heavy, this is an important matter. Of course, large expenditure is required for the installation of a “waste heat”’ system, but the eventual saving is considerable. The adoption of waste heat boilers has been rapid, and approx- imately 50 plants either have them in operation or in the course of installa- tion. Other matters recently investigated are the factors influencing the ease of 8 Tur ANNALS OF THE AMERICAN ACADEMY grinding cement clinker and the effi- ciency of different grinding media, the fineness of grinding of the pulverized coal so widely used as fuel in the kilns, and the various types of refractories for lining kilns have also been studied. PREVENTION OF PLANT ACCIDENTS Through theco-operation of the Asso- ciation with the individual companies, the number of accidents in proportion to the man-hours worked in the plants has been much reduced. Statistics for 1923 show a reduction of 17 per cent in accidents in the cement industry, whereas an increase occurred in acci- dents throughout industry in general. STUDIES OF CONSTITUTION OF PoRTLAND CEMENT At the present time a most thorough investigation into the constitution of Portland cement is being carried on in co-operation with the U. S. Bureau of Standards. Although methodsof man- ufacturing cement have been carefully worked out and considerable study given the chemistry involved, investi- gation has not thus far given positive information concerning the real con- stitution of Portland cement as dis- tinguished from its composition and has failed to explain the hardening process of the ground clinker. Here the latest developments in the chemical and physical sciences are being employed in a study of these obscure questions. While several years may be required to complete these investigations, it is anticipated that the work can be car- ried to a successful conclusion and will provide basic information of much value in the future development of the use of Portland cement as well as in its manufacture. No better grounds for the promotion of concrete for use in any particular structure can be found than the strength, economy, permanence, and satisfactory service of similar structures already in use. Such examples can be secured only if the ingredients of con- crete are good and, furthermore, if the concrete itself is properly designed, mixed and cured. The discovery of the basic principles underlying success in concrete making has called for exten- sive research, and it is only after the results of this research have been adopted that the foundation for the future success of the cement industry has been made more secure. e By