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Portland and Other Cements.*
Mineral resources have fixed Pennsylvania's position with reference to the other Commonwealths forming our greater country. Coal, iron, steel, limestone and clays are among the principal elements of industry growing from the wealth which God has concealed in the hills and valleys of our great State.
Within the past decade another industry has been making giant strides in this country, but more especially in our own State. This is the production of Portland cement, which for many years had been considered an exotic plant and one incapable of establishment in the United States. This industry, which owes its successful de. velopment to the perseverance, patience and energy of a Pennsylvanian, finds its principal habitation and source in the State of Pennsylvania, and more than one-half of the total amount produced in the United States last year of this important building material was produced within the confines of this Commonwealth. In writing, therefore, of the growth, development and future of the Portland cement industry in the United States, it is impossible to write it without reference to what has been done in our own State, for the growth of the American manufacture is synonymous with that of Pennsylvania.
History.–From the earliest days of the ancients the desirability of a cementitious material that would set under water was recognized, and in the books of Vitruvius, who wrote of the structural material of the ancients, much stress is laid on the necessity in some of his coffer-dam constructions of allowing the material in the coffer-dam to remain exposed for at least two months, in order that the cementing material used in his foundations might have time to set. This difficulty was one that was met by him, as well as by many of the other builders of that time, and goes to show that what is known at this time as "Roman" cement, and what we, of this period, are prone to talk of as the all-enduring “Roman cement,” was not a cement at all, but merely a mixture of lime and argillaceous material, which, after considerable time, set under water.
The mortars of the ancients which we find to-day still standing
** Pennsylvania Production for 1901, will be found on the closing pages of this book.
are mostly mortars which have been used in air, and by analysis are shown to have been formed of combinations of slaked lime and powders made by crushing and pounding up the volcanic deposits found in the vicinity of Naples and other points in Southern Italy. These mortars, by reason of the silicious character of the volcanic sand used, had the power of ultimately hardening under water, and the mortar which we see at this day and which seems to have such great strength, was nothing but a form of our old lime mortar, but made with a material a little more suitable in character than the sharp sand we use at this day.
Pliny, also, in describing in one of his works some of the buildings he ran across in olden Rome, finds cases where the walls of the city had fallen and which he says were frequently composed of lime lacking in adhesiveness. His experience only corroborates that of Vitruvius, and shows that the ancient Romans, notwithstanding all the credit we give their Roman cement, really were no better off than those who, in the early part of this century, were using lime mortar as the safest and only material for the binding together of brick and stone.
From the time of the Romans away down until the end of the fifteenth century, there was little improvement in the making of mortar for building purposes, and it was a recognized thing in most of the structural work of the middle ages, that a stone and brick construction had to be gone over every few years and repointed with new mortar, and chimneys had constantly to be rebuilt. At the end of that century a petition was presented to the then King of France by a builder, who claimed he had discovered a method of making good mortar, and what he claims to have found was that in all the years gone by, the blunder had been made of allowing the sand and lime to slake together for months at a time in open pits in order that there should be a homogeneous mixture, whereas the real way was to take the lime hot from the kiln and then incorporate with it sand and water. This discovery, however, was but a "flash in the pan,” and nothing came of it. In consequence,
, the history of binding material for structural work remains almost a closed book until we come to about the beginning of the nineteenth century, when the first real progress in the direction of finding a good mortar was made.
To Smeaton, the constructor of the Eddystone light house, is due the credit of the discovery of hydraulic mortars. His problem was the construction of foundations under water in a difficult place, and it was imperative that mortar to set under water should be had. Out of this necessity grew the first introduction of hydraulic cement or hydraulic limestone mortar. In the course of his work he stones for the purpose of procuring lime for his construction, and the result of these tests showed that the theories of the ancients were incorrect, and that the burning of the hard limestones did not give the hardest mortar, as they had supposed. He discovered that the softer limestones, namely, those limestones which contained by analysis, a fair amount of argillaceous substances or clay, would give excellent results in hydraulic construction, and he laid down, as a result of his discovery, the principle that a limestone yielding one-fifth to one-fourth per cent. residue when dissolved in hydrochloric acid, would set under water. To these limestones he gave the definition of hydraulic limestones, and from the principle laid down by him come the two great definitions of what we know as the "natural" and the "artificial,” or “Portland” cement of commerce.
While Smeaton had discovered the scientific application of the principle, he reaped no financial reward and it remained for James Parker, of Christ Church, Surrey county, England, to invent and patent a cement in 1796. To this cement he gave the name of Roman cement, claiming it to be the same material as the Romans used. His material was prepared from argillaceous limestone pebbles found in the septaria on the Island of Heppy, Whitstable and Harwich, in England, and he put the article on the market in quite an extensive way. Investigations were going on in France about the same period. Experiments were made under the auspices of government engineers at Metz, Viviers and Nismes, France, with the puzzolan of Italy and the tarras of Germany, and also with well-burned tiles ground to powder, for the production, by the addition of lime, of hydraulic mortar, and in 1812 Vicat, one of the leading engineers in France, started his investigations towards the formulation of a doctrine of calcareous cements, and in collaboration with Messrs. John and Berthier and M. Bruyere, Inspector General of Roads and Bridges, Messrs. Avril and Girard de Caudemberg and Lacordaire, succeeding in arriving at the secret of the production of hydraulic mortar, and actually in an experimental way produced an artificial cement similar to the present Portland cement of commerce.
Concurrent with these scientific researches in France, General Pasley, the leading English engineer, was working in the same direction and discovered in that country the value of burning a mixiure of lime and clay to a point of incipient vitrifaction, but it remained for another than the scientific engineer to succeed on the commercial side of the subject in manufacturing a commercial product.
This was done in 1813 by Jos. Aspdin, a bricklayer of Leeds, Eng. “My method of making a cement or artificial stone for stuccoing buildings, water works, cisterns, or any other purpose to which it may be applicable (and which I call Portland cement) is as follows: I take a specified quantity of limestone, such as that generally used for making or repairing roads, after it is reduced to a puddle or powder; but if I cannot procure a sufficient quantity of the above from the roads, I obtain the limestone itself, and I cause the puddle or powder, or the limestone, as the case may be, to be calcined. I then take a specific quantity of argillaceous earth or clay and mix them with water to a state approaching impalpable, either by manual (sic) labour or machinery. After this proceeding I put the above mixture into a slip pan for evaporation by the heat or by the sun or by submitting it to the action of fire or steam conveyed in flues or pipes under or near the pan, until the water is entirely evaporated. Then I break the said mixture into suitable lumps and calcine it then in a furnace similar to a lime kiln, till the carbonic acid is entirely expelled. The mixture so calcined is to be ground, beat or rolled to a fine powder and is then in a fit state for making cement or artificial stone. This powder is to be mixed with a sufficient quantity of water to bring it into the consistency of mortar and thus applied to the purpose wanted.”
This product he called Portland cement because of its resemblance when set to Portland stone, a well-known building stone of England, and he produced it in a small way in competition with the Roman cement, or Parker's cement, which was then ruling the English market.
He was followed in 1925 by James Frost, a builder of Finchley, who established a cement works at Swanscombe, Kent, which is now the site of one of the principal cement works in England.
In 1847, according to General Pasley's book, there were three Portland cement works then in existence, though in that book Aspdin's Wakefield factory is omitted. By 1843 the competition between the Roman cement made under Parker's process and the Portland cement made under Aspdin's process was very close and many experiments were made to determine which of the two was the better, and as the concensus of opinion at that time was rather in favor of the Roman cement, and as railroad building was at its height in England, Sir Robert Peel, fearing an exhaustion of the septaria out of which Roman cement was made, proposed putting a tax upon it, and it was only upon the assurance of Mr. Aspdin that if the supply of stone failed from which the Roman cement was made, that he could offer an equally good material, that the proposed legislation was abandoned.
The London Exhibition of 1851 again gave occasion for competi