Cement plant

“ On the whole, however, ferric cements are much less frequently found in hardpans than in sandstones formed above ground.
Clay substance washed from the surface into the subsoil by rains (chapter 10, p. 161) always helps materially to render the hardpan impervious when afterwards cemented, a much smaller proportion of the cementing material sufficing in that case to form a solid layer. In such cases however the cement is rarely of a calcareous nature, since lime prevents the diffusion and washing-down of the clay. It is mostly siliceous or zeolitic ”

“ The treatment is descriptive and statistical rather than scientific, and the work is hence mainly one of reference for the use of engineers.
'The Cement Industry,' published by the 'Engineering Record,' is an octavo volume of 235 pages which gives detailed descriptions of numerous cement plants in Europe and America. The production of natural cement in the United States has been somewhat checked during the last decade by the rapid improvements in the manufacture of the Portland product, particularly by the introduction of rotary kilns. ”

“ 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. ”

“ 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. ”

“ Cement is more expensive than brick. The surface to be covered should, first, be levelled, then saturated with water; after which is laid a three-inch bed of cement concrete, made of gravel, sand, and cement in proper proportions. Upon this is placed a three-fourth-inch layer of cement mortar. Ordinary American, hydraulic cement may be used for concrete, but for the three-fourth-inch layer nothing but best Portland cement should be considered. Sometimes the cement work in the cellar is done by the plasterer. Outside cement work for walks requires special skill. ”

“ At times a lean mixture, 1 cement, 3 sand, 5 gravel, might be advantageously adopted. Where gravel or broken stone is not used, the proportion of cement to sand should be as 1 to 4. A fat mixture has greater tensile strength than a lean mixture, but resistance to compression depends upon a thorough filling of voids. A lean mixture thoroughly worked, proves more satisfactory than a fat mixture with hasty and indifferent handling. With any mixture success is attained only by completely coating every grain of sand with cement, and every piece of stone or gravel with the sand-cement mortar. ”

“ 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. ”

“ It should be used on the surface only and not for the entire tile or pottery. If used without any sand or gravel, it is termed “too fat,” and has the fault of cracking sooner or later. Therefore neat cement is always backed up with a concrete mixture.
CONCRETE is a mixture of sand and cement, gravel and cement, or rock and cement. In all instances where such a mixture is made, the two parts should be mixed dry before any water is added. Only enough should be mixed to meet immediate needs as it is not best to use cement that has stood so long that it has commenced to harden. ”

“ 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. ”

“ The mass should be turned two or three times, or until it is of uniform color and there are no streaks of either sand or cement. A man with a hoe or rake may assist by raking the top over as the two men turn. When the sand-cement mixture is of a uniform color it should be spread out carefully in a layer and the gravel box placed on top. The box is filled with gravel and then removed, the gravel being spread over the sand-cement mixture. The mass is soaked with about one-half the quantity of water to be used, care being taken not to wash away any of the cement. ”

“ 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. ”

“ 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 ”

“ The materials then should be turned over in much the same manner as was the sand-cement, except that instead of shaking them off the end of the shovel the whole load should be dumped and dragged back toward the mixer with the square end of the shovel. The wet gravel picks up the sand and cement as it rolls over when dragged back. The mixing should be continued until the mass is uniform, water being added to the dry spots during the mixing until the desired consistency is obtained.
Experience counts considerably in mixing concrete with the least amount of labor ”

“ The transformation of wood into cement is proceeding relentlessly all over the country; to my infinite disgust. Those numerous wooden watertroughs for the use of householders and their cattle, which used to be quite a feature of the streets, are now all being manufactured out of this damnably durable material; there is a cement-factory near our station, and I wish somebody would drop a bomb on it. ”

“ 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. ”

“ 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. ”

“ It must be kept in a dry place. Once wet, it becomes hard and lumpy, and in such condition is useless. If, however, the lumps are caused by pressure in the store house, the cement may be used with safety. Lumps thus formed can be easily broken by a blow from the back of a shovel.
In storing cement, throw wooden blocks on the floor. Place boards over them and pile the cement on the boards, covering the pile with a canvas or a piece of roofing paper. Never, under any circumstances, keep cement on the bare ground, or pile it directly against the outside walls of buildings. ”

“ Fresh concrete will riot bond readily to concrete that has hardened and a seam may be formed that will permit water to trickle through. When bonding fresh concrete to that which has been in place for a short time it is usually sufficient to roughen the hardened surface with a pick or by other means so as to expose the gravel or stone, and to clean off all loose particles. The hardened concrete should be soaked with water, the excess water removed, and the surface then given a coat of grout (a mixture of cement and water) of the consistency of cream just before the new concrete is deposited. ”

“ The ideal mixture is one in which all the spaces or voids between the grains of sand are filled with the cement and all the voids in the gravel are filled with the cement-sand mortar. This perfection is seldom attained, because the voids in each lot of gravel and sand vary slightly, and in order to be absolutely safe a little more sand and cement than will just fill the voids are used.
The strongest concrete is not required in every structure, and, in many instances, the cost of it would be unwarranted. ”

“ Soft, spongy foundations of natural cement or Portland cement of inferior quality are not only an inadequate support for the yielding surface, but they are easily penetrated by water from below and act as conveyors of water, while a sound and firm foundation of the best Portland cement concrete not only presents an unyielding support to the surface, but also, when properly set and dried before the surface is laid, keeps the surface as free as is possible under the circumstances from ground water, and thus contributes to the longevity of the surface. ”

“ 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. ”

“ Inasmuch as the variation in sizes of the individual particles of rounded gravel is such that a dense concrete results naturally, it is quite reasonable both to increase the amount of stone and decrease the amount of cement if that variation in size seems to be one which will produce a dense mixture. Thus one cubic yard of stone, one-third cubic yard of sand, and four bags of cement may be used and will, under favorable conditions, result in a good concrete. ”

“ Under such circumstances the membrane treatment used in addition to a properly proportioned concrete, while the most expensive method of waterproofing, probably will give the most reliable results. This treatment consists of layers of burlap or tar paper cemented to the surface and together with tar or asphalt. Where the membrane is subject to injury it is sometimes protected by a coating of cement mortar or brick backing.
First-class workmanship and special attention to details are required to secure water-tightness. The essential requisite is that the voids be filled. ”

“ If a long nail or rod or strong stick is placed in the center of this mass, it can serve the purpose as an axis to a templet which will form the contour of the jardinière when moved around in a circular direction. The metal must be good and heavy and sometimes it is necessary to reinforce the templet with wood.
After the clay form is built, cases are made in several sections from the plaster the same as for small forms; and cement and concrete used in large quantities after the same method as for small forms. ”

“ To avoid such unhappy consequences, farmers have been accustomed to bank up the house outdoors in the fall with dry leaves, spruce-boughs, or manure, usually to a point on the woodwork. This, of course, closes the cellar windows for the winter for the sake of keeping out the wind. A concrete wall, at the present price of cement, using gravel for the mixture instead of stone, need cost but little more than the price of the cement and the labor involved, and a tight cellar wall may thereby be obtained. ”

“ Number of Men
For the above operation only two men are required, although more can be used to advantage. If three men are available, let two of them mix as described above and the third man supply the water, help mix the concrete by raking over the dry or unmixed spots as the two mixers turn the concrete, help load the wheelbarrows with sand and stone or gravel, etc. Fig. 5 shows a third man on the board. In this illustration, he is helping mix the sand and cement by raking it—a most effective practice. ”