Cement industry

“ The cement so made possessed extraordinary strength and hardness, and it has been a matter of surprise that iron masters and others have not adopted such a means of converting a waste material—which at the present time entails upon its producers constant heavy outlay for its removal—into a remunerative branch of industry by the expenditure of a comparatively small amount of capital. ”

“ Here, and above Rochester Bridge, the pleasant Medway valley is scarred and seamed with the chalk-quarrying and the mud-dredging that go towards the making of Portland cement, this neighbourhood being one of the chief centres of that industry. The chalk and the river-mud are mixed roughly in the proportion of three parts of chalk to one of mud, and are then burnt in kilns and ground into a flour-like powder. Portland cement, invented about 1826, is an important industry, with an output of over 3,000,000 tons a year in this country. ”

“ With the exception of satisfactory fuels, the raw materials required for the manufacture of cement are found quite generally throughout the world. While practically all countries produce some cement, much of it of natural grade, only the largest producers make enough for their own requirements and as a result there is a large world movement of this commodity. The world trade is chiefly in Portland cement. ”

“ Some authorities advocate this method of securing light colored blocks as always cheaper and usually superior to the use of special cements. The choice between the two methods will be governed by the results sought; where as nearly as possible a pure white is desired it stands to reason that a white or nearly white cement will give the better results.
In the matter of sand and aggregate for ornamental work, the kinds used will ordinarily be the kinds that are available. They must conform in quality to the standard requirements of such materials for concrete work. ”

“ All this expansion of an old art has been stimulated by a steady reduction in the price of Portland cement, and by constant improvement in its quality. As the manufacture has expanded, its standards have risen, its machinery has become more economical and trustworthy in results. While the cost of concrete has thus been lowered by a fall in the price of cement, the wages of bricklayers and stone-masons have advanced, adding a new reason for building in concrete, since it requires in execution but little skilled labor. The good points of concrete are manifold ”

“ So strongly did the railroads’ idea of economy (the dollar argument) appeal to him that the farmer of the West is now building practically everything about the farm of concrete. At first, and quite naturally, land-owners in the rock and gravel regions began using this new form of construction; but, since its cheapness in first cost and value in lasting qualities have become generally known, a wave of enthusiasm for farm structures of concrete has swept the entire country. A gravel pit is now more valuable than many a gold mine. ”

“ With the growth of engineering in the early part of the 19th century arose a great demand for hydraulic cement. The supply of materials containing naturally suitable proportions of calcium carbonate and clay being limited, attempts were made to produce artificial mixtures which would serve a similar end. Among those who experimented in this direction was Joseph Aspdin, of Leeds, who added clay to finely ground limestone, calcined the mixture, and ground the product, which he called Portland cement. ”

“ In the past they have not been used freely because wooden buildings have been so much cheaper; but cement, concrete and brick are now manufactured much more cheaply, on account of improved methods, while the price of lumber has been increasing rapidly. Within the last ten years, the value of cement manufactures has increased nearly six times. In 1900 we used seventy pounds of cement for each person ”

“ But, generally speaking, in steel concrete the cost of the cement is but a small item of the whole expense, and it is worth while to be generous with it. If It is used in piles or structures where it is likely to be bruised the proportion of cement should be increased. The mixing and laying should all be done very thoroughly; the concrete should be rammed in position, and any old surface of concrete which has to be covered should be cleaned and coated with fresh cement. ”

“ In the manufacture of natural cement the raw material generally used is some stone in which the carbonate of lime, silica, and alumina are present in more or less correct proportions, while in the manufacture of the artificial cement the raw material used consists of the essential ingredients, each in a comparatively pure state, thoroughly mixed in theoretically the correct proportions. It is due to this fact that artificial or Portland cement is not only much superior to natural cements, but that it is much more uniform in its quality. ”

“ These impurities that are inherent in the nature of the materials from which the natural cement is made and also in the process of manufacture that is of necessity followed, result in a cement that can be made and sold at a less price than Portland cement and that is inferior to it for many purposes, while, on the other hand, for a great many purposes natural cements have been found to answer every requirement and are made and used in enormous quantities. ”

“ Has there ever been an instance in which cement was used for a purpose other than to plaster over the Land? Whether it is made into buildings, fences, wharves, Hume pipe, or to make channels, its ultimate role is inevitably to block off the Land. So for every bag of cement that is produced, that much more of the Land will be covered over. ”

“ To-day the manufacture of cement constitutes one of the twelve most important industries in the United States, and the greater part of this material is made from what a few years ago was accepted as sheer waste—residue from the iron-works which, having no further ostensible use, was dumped in huge piles to the disfigurement of the landscape. ”

“ It can be transported on a belt conveyor, elevated by bucket conveyer, mixed with sand and cement and delivered to the work all with very little manual labor when the installation of a very efficient plant is justified by the magnitude of the job. Large rubble stones cannot be handled so cheaply or with so great rapidity as crushed stone; the work may be so expensive, due to repeated handlings, as to offset the cost of crushing as well as the extra cost of cement in plain concrete. ”

“ At Concrete, a town of 1,200 people in Skagit county, two factories, employing 500 men, are daily turning out 1,400 barrels of Portland cement of fine quality, which is finding ready market in all the large cities. ”

“ This is true not merely in the general way that it is true of all engineering construction—it is true in a special way peculiar to the material. Except for the reinforcing steel, the contractor for concrete building work has no guarantee of the quality of any element of his work except his own faithful care in performing every task that combines to produce that element. The quality of his concrete depends upon the care with which he has chosen his cement, sand and stone, and on the perfection with which he has incorporated them into a homogeneous mixture. ”

“ Improvements in the manufacture of hydraulic cements have given an impetus to the use of concrete, but its use is by no means of recent date. It is no uncommon thing in the taking down of heavy walls several centuries old to find that the method of building was to carry up face and back with rubble and stiff mortar, and to fill the interior with bowlders and gravel, the interstices of which were filled by grouting—the whole mass becoming virtually a monolith. Modern quick-setting cement accomplishes this object within a time consistent with the requirements of modern engineering works ”

“ It is my opinion, founded on what I have seen and know, that Portland cement concrete is grand stuff when properly made; but you can't make the 'extra' profit on it you could, unless you can forget to rightly proportion the material. I mean leave out anything on the quiet you find is more profitable when it is absent; and now mixing machines are always used on works of importance where concrete is made in any considerable quantity, that is the only way you get a chance of a bit 'extra,' at least so runs my experience. ”

“ The demand for Portland cement has increased and is still increasing at a rapid ratio. It is being manufactured upon a gigantic scale.
Great interests are involved; large sums of money are being expended in the erection and maintenance of expensive plant for its production; and the author submits that the development of any method which will improve the quality and at the same time reduce the cost of manufacture of this valuable material will tend to increase the prosperity of one of our great national industries, and stimulate commercial enterprise. ”

“ The factory cost of concrete blocks varies according to the cost of materials. Let us assume cement to be $1.50 per barrel of 380 pounds, and sand and gravel 25 cents per ton. With a 1 to 4 mixture, 1 barrel cement will make 1,900 pounds of solid concrete, or at 130 pounds per cubic foot, 14.6 cubic feet. ”

“ Safety in this respect calls for a much greater degree of hardness than would be needed to bear the weight of the building. Again, strength and hardness, with a given proportion of cement, depend greatly on the character of the other materials used; blocks made of cement and sand, 1 to 3, will not be so strong or so impermeable to water as those made from a good mixed sand and gravel, 1 to 5. On the whole, it is doubtful whether blocks of satisfactory quality can be made, by hand mixing and tamping, under ordinary factory conditions, from a poorer mixture than 1 to 5. ”

“ The principal causes of scaling or crumbling surfaces are improper mixing, drying out before the cement has thoroughly hardened and the use of bad materials.
Cement needs water not only when mixed, but after being placed and tamped, and until it has entirely hardened. If concrete is not kept continually wet until hard, it is weakened, and the surface of such a walk scales or becomes soft and chalky. ”

“ I did not trouble myself about it then, but I do now, for I had a month or two in and about the testing places when there was no other job for me that suited, and I firmly believe almost all the failures of Portland cement concrete occur because the men that used it do not understand it, or the specification is not carried out, or is wrong somewhere. The best goods in the world want proper treatment, and, after all, the abuse of a thing is no argument against its use. Some quarry owners and stone merchants don't like cement concrete; it is poison to them, because it hurts their trade. ”

“ Where a very strong cement is needed for stone-work, it can be prepared by mixing a fine cement powder—e.g., Portland cement—with liquid silicate of soda. As it dries almost at once, it must be promptly applied. It is particularly well adapted for building under water, since it then becomes extremely hard. ”

“ Probably few materials have been found more generally useful to the civil engineer, in works which are not of metal, than has been Portland cement. It should be noticed that during the last twenty-two years great improvements have been made in the grinding and in the quality of the cement. ”

“ But although people see the operation constantly performed254 and buy liberally of the cement, it will be found that in nine cases out of ten, the cement proves worthless in the hands of the purchasers, simply because they do not know how to use it. They are afraid to heat a delicate glass or porcelain vessel to a sufficient degree, and they are apt to use too much of the material, and the result is a failure. ”

“ The concrete blocks made with 1 to 3 mortar disintegrated in nearly every case, while the stronger ones remained in fairly good condition. The best results were given by concrete containing an excess of very fine sand. Mixing very finely-ground silica, or trass, with the cement proved an advantage where a weak mixture was employed, but in the other cases no benefit was observed. ”

“ The burning drives off the small amount of combined water and all the carbon dioxide from the stone, leaving the lime and magnesia as oxides, while the grinding to a powder puts it into the best possible condition for mixing with sand and gravel, and moistening to form a mortar. Artificial cement consists of about sixty-two per cent of lime mixed with silica and silicate of alumina in nearly the same proportions as those found in the cement stone, and it is free from magnesia. ”

“ Cars are now being built of steel, and of combinations of metal with asbestos. These are not yet entirely satisfactory, but it is hoped that they can be perfected soon. Cement and concrete are taking the place of wood to a great extent in building, and their use will doubtless increase rapidly. ”

“ I found that the slag coming from the furnaces, which in many great manufacturing sections of the country we see piled up in great, unsightly masses, is all being converted into cement, and that cement is being used by the people of this country. And so we find an interesting situation—that the steel being manufactured by that plant is likely soon to be a by-product, and not the main product for which the plant is operated. ”