Concrete

“ Another method, called Concrete, is to make cases of boards, and to form a solid wall by pouring in the mixture, or ramming it down, according to its hardness. Thus a house is made entirely in one piece; but its excellence depends entirely on the quality of the cement employed, and on the care taken in building. ”

“ Concrete is fireproof, waterproof, sanitary, and resists frost when properly used. Our timber supply is decreasing, the supply of iron ore for structural steel is limited, and stone is expensive; so concrete, reinforced with steel, and used by engineers who understand their business, will be the greatest building material of the future. ”

“ T THE successful and economical use of concrete involves the selection of suitable materials, the correct proportioning of mixtures in the development of qualities to meet specific requirements, the proper placing and the care of the green concrete.
A concrete of great strength is uneconomical if a weaker mixture will serve and a cheap or weak concrete is costly if it does not fulfill all requirements. ”

“ Concrete is an artificial stone produced by mixing cement mortar with broken stone, gravel, broken slag, cinders or other similar fragmentary materials. The component parts are therefore hydraulic cement, sand and the broken stone or other coarse material commonly designated as the aggregate. ”

“ The subject of cement and concrete has been so well treated of in engineering literature, that to give an extended paper on the subject would be but the collection and reiteration of platitudes familiar to every engineer who has been engaged on foundation works of any magnitude. It shall therefore be the object of this communication to place before the society several notes, stated briefly and to the point, rather as a basis for discussion than as an attempt at an exhaustive treatment of the subject.
Concrete is simply a low grade of masonry. ”

“ As the task of proportioning concrete consists in so proportioning the several materials that all void spaces are filled with finer material the conditions influencing the proportion of voids in sand and aggregates must be known. ”

“ Everything of value to the concrete user is given including kinds of cement employed in construction, concrete architecture, inspection and testing, waterproofing, coloring and painting, rules, tables, working, and cost data. ”

“ The most extreme example of this form of degeneracy is found in the suggestion of a certain great inventor, that the age of concrete construction, now at hand, means that we are to have concrete houses poured into a standard mould, hardened in twenty-four hours, and finished for occupancy in a day or two. ”

“ Concrete being a plastic material when deposited requires molds or forms to give it the shape required and to maintain it in that shape until it has hardened to sufficient strength to require no exterior support. ”

“ Radical Stress, where force is applied to the opening of the concrete. (It should be said that a slight degree of radical stress is given even in the equable concrete, producing its full, clear opening.)
(2) Loud Concrete, where force is applied throughout the whole concrete, the proportion of the radical to the vanish remaining unaltered.
(3) Median Stress, where force is applied to the middle of the concrete, producing a swell, or impressive fulness.
[xvii] (4) Compound Stress, where force is applied in an unusual degree to each extremity of the concrete. ”

“ Good design in concrete as well as in steel, masonry and wood, requires that the structure shall be good to look at. This means that the proportions must be good and that the surface finish must be pleasing. Good proportions are a matter of design but a pleasing surface finish is a matter of construction. Many, perhaps the majority of, concrete structures do not have a pleasing surface finish ”

“ The proportion will of necessity vary with each particular material and the discussion of the various considerations involved may be obtained from various standard works on concrete and concrete materials. ”

“ Almost any material which will hold the concrete in place will do for a Form. Concrete foundations for farm buildings require shallow trenches, and usually the earth walls are firm enough to act as a Form. ”

“ Showing Street-Cleaning under the 'Orderly System.' The concrete surface, having been laid as nearly as possible of the proper contour, and having been thoroughly set, dried out and swept clean, is covered with a binder course to fill the inequalities of the concrete and form a bond between the concrete and surface that will not only attach the surface to the concrete, but will bold the surface in place and keep it from sliding from the center towards the gutters. ”

“ Concrete, covering the whole ground-area of the future building with a layer four inches thick, forms the most thoroughly sanitary foundation. Well-puddled clay is also good and inexpensive, but is not effective in old buildings. ”

“ Then, too, some engineers cast parts of their buildings separately and put them in place after they have set, while others run the concrete for beams, floors, and walls into moulds, built right where those parts are to be in the finished structure. ”

“ Because a plain concrete bow between solid abutments deflected in an elastic curve, reinforced concrete arches between settling abutments are designed with fixed ends. The theorist has departed about as far as possible from his premise in this case. On an exceedingly slender thread he has hung an elaborate and important theory of design, with assumptions which can never be realized outside of the schoolroom or the designer's office. ”

“ Mixing and Placing Concrete.—The placing of the concrete in the excavated wells is done by means of tremies, or, which is more usual, by simply dumping it in from the top, workmen going down to distribute it. The manner of mixing the concrete and of handling it to the caisson varies of course with almost every job. ”

“ Curing the Concrete.—The setting action of cement is a chemical process, not merely a drying out of the water introduced in mixing the concrete. The chemical action is progressive for a long time, but is more rapid during the first few hours than during the later periods, and the concrete reaches about three-fourths of its maximum strength at the end of seven days. ”

“ One of the essential features in good concrete is cleanliness and an entire absence of dirt, dust, greasy matter, and impurities of any description. The material will preferably be sharp and angular, with a rough, porous surface, to which the matrix will more readily adhere than to smooth, vitreous substances. The specific gravity of the aggregate will depend upon the purpose for which the concrete is to be used. ”

“ A broad-minded engineer will use reinforced concrete where it is most appropriate, and structural steel or cast iron where these are most appropriate, instead of using his clients' funds to carry out some cherished ideas. ”

“ Concrete, a composition of broken rock, gravel, broken bricks, sand, etc., usually cemented into solid form by the use of hydraulic cement. The proportions of the various ingredients differ according to the use to which the artificial stone called concrete is to be put, but the principle to be kept in mind in the mixing is that there should be enough of the mortar to a little more than fill the space between the fragments of broken rock, etc. A typical concrete is made of one part of cement, three parts of sand and five parts of broken rock. ”

“ Until the engineer pays more attention to checking his complicated theories with facts as determined by tests of actual construction, the view, now quite general among the workers in reinforced concrete regarding him will continue to grow stronger, and their respect for him correspondingly less, until such time as he demonstrates the applicability of his theories to ordinary every-day problems. ”

“ One of the places where we know concrete best is in pavements and sidewalks, and several of the booths exhibited samples of such work. To show its strength the men in charge piled on weights, struck the slabs with hammers, or subjected them to any kind of hard usage suggested by the crowd. ”

“ What appears to be the underlying principle of reinforced concrete design is the adhesion, or bond, between the steel and the concrete, and it is that which tends to make the two materials act in unison. ”

“ American engineers proportion concrete mixtures by measure, thus a 1-3-5 concrete is one composed of 1 volume of cement, 3 volumes of sand and 5 volumes of aggregate. In Continental Europe concrete is commonly proportioned by weight and there have been prominent advocates of this practice among American engineers. ”

“ Mixing the Surface Course.—See that the cement sand and stone are proportioned accurately and that the quantity of water used with each batch is measured, so as to make the concrete of uniform consistency. Do not permit any defective batches of concrete to be used in the surface-course—if suitable for the bottom course they may be used in it. Care in this respect is particularly necessary with machine-mixed concrete where the machine is not working normally or the men operating it are careless or unskillful. ”

“ Sums of two or three lines can thus be set out on the horizontal bars, and in processes of addition the answer can be on the bottom line. It is very easy, by this concrete means, to see the process in subtraction, and indeed the whole difficulty of dealing with ten is made concrete. ”

“ Some soils are liable to change in form, expanding and contracting under meteorological influences; such are clays which swell when wetted and shrink when dried. Concrete foundations are commonly interposed upon such soils to protect the building from derangement from this Foundations.cause; or walls of the cheaper material, concrete, instead of the more expensive brick or stone structure, are brought up from a level sufficiently below the ordinary surface of the ground. ”

“ The construction problem in building concrete structures of massive form and volume is chiefly a problem of plant arrangement and organization of plant operations. In most such work form construction is simple and of such character that it offers no delay to placing the concrete as rapidly as it can be produced. ”

“ When concrete is used to obviate the tendency of the soil to yield to pressure, expanse or extent of base is required, and the concrete being widely spread should therefore be deep or thick as a layer, only with reference to its own power of transmitting to the ground the weight of the wall to be built upon it, without breaking across or being crushed. ”

“ In short, we seem to be on the eve of a revolution in textiles that is the same as that taking place in building materials. Our concrete structures, however great, are all one stone. They are not built up out of blocks, but cast as a whole. ”

“ Therefore, if the beams be considered as plain concrete beams, and an average value be assumed for the modulus or coefficient of elasticity, a deflection may be found by a simple calculation which is an average of that which may be expected. Here again, simple theory is better than complex, because of the ease with which it may be applied, and because it gives results which are just as reliable. ”

“ The reinforcing rods are placed in these moulds and the concrete run in, and so on, a story at a time, or a small section at a time, until the structure reaches the height called for in the plans, and it stands completed. As the building progresses and the concrete on the lower floor sets, the moulds can be taken down and used on higher stories. Concrete is even used for the roofs of buildings, as it can be moulded right in place or set up in slabs that can be later cemented together. ”

“ We worked raptly, even through the hard, dull labour of levelling, setting the frames and laying [Pg 228] the concrete foundation. The finishing was the absorbing part. The idea was not for a fine-grained sand walk, but a mixture of all sizes from a penny large down to the finest sand. The cement makes the most lasting bond in a mixture of this kind; moreover, the pebbly finish was effective and darker for the insets. ”

“ Thorough mixing of concrete materials is essential, to increase the density and give the cement used a chance to produce its full strength. The cement, sand, and gravel should be intimately mixed dry, then the water added and the mixing continued. ”

“ I saw one remarkable looking old man, with a long flowing white beard, sitting on a fallen fragment of wall in the sunshine,{154} and never taking his eyes from the workmen who were tumbling down the great masses of concrete as fast as their excessive hardness would permit of their being detached. ”

“ With little help other than looking and listening, the farmer grasped the idea of a concrete walk, and being a natural inventor and jack-of-all-trades, improved on the method by adding a small curb next to his flower bed to keep the dirt from washing on the white walk. ”

“ Many large contractors mold a cube of concrete for each day's work and leave it standing on the finished floor exposed to the same conditions as the concrete in the forms; examination of this sample block gives a line on the condition of the concrete in the work and on the probable safety of removing the forms at any time. In all cases it should be the superintendent's duty to determine when to remove forms, and he should satisfy himself by personal inspection that the concrete is in condition to stand without support. ”

“ It is important that concrete be hard, as weak concrete is but a slight obstacle to the sharp rodent incisors. The mixture approved for ordinary building construction, however, is sufficiently hard to be entirely rat proof, and it is essential that approved practices of mixing and placing concrete be followed. Directions for using concrete and for building concrete floors are given in Farmers' Bulletin 1279, Plain Concrete for Farm Use, and in Farmers' Bulletin 1480, Small Concrete Construction on the Farm. ”

“ Nearby we see a few more skilled workmen mixing the concrete in great vats. When the mould and the material are ready we see the concrete taken to a tank on the roof and poured into troughs which carry the stuff to a number of different holes through 307 which it flows into the mould. ”