An elementary course of civil engineering for the use of cadets of the United States military academy

Front matter

TTUi rroo jt

AN C/

ELEMENTARY COURSE

Part I. Building Materials

1. The materials in general use for civil constructions may be arranged in three classes :

1st. Those which constitute the more solid components of structures, ;is Stone, Brick, Wood, and the Metals;

2d. The cements in general, as Mortar, Mastics, Glue, etc., which are used to unite the more solid parts ; and

3d. The various mixtures and chemical preparations, as solutions of Salts, Paints, Bituminous Substances, etc., employed to coat the more solid parts and protect them from the action of the weather and other causes of destructibility.

Chapter I. Stone

2. The qualities required in stone for building purposes are so various ili.it no very precise directions can be given thai would exactly meei any particular case. Whai would be required for a sea-wall would not answer for ;• dwelling-house. In most cases the choice is limited by the cost. 'II: iii"i e Bential properties of stone as a building-material are strength, fiardness, durability, ami ease of working. These properties are determined by experience or actual experiment.

;:. The term Stone <>r Bock is applied to any aggregation o\' several

mineral lib tances, and For the convenience of description may be ar-

d under three general heads— the 8Uieiou8 t the argillaceous, and the

I. — SILICIOUS STONES.

4. Silicious stones are those in which silica is the principal constituent. With a few exceptions, their structure is crystalline-granular, the grains in them being hard and durable. They emit sparks when struck with a steel , and generally do not effervesce with acids.

5. Some of the principal silicious stones used in building are Syenite, Granite, Gneiss, Mica Slate, Hornblende Slate, Steatite, and the Sandstones. For their composition, particular description, etc. , see any of the manuals of mineralogy.

G. Syenite, Granite, and Gneiss.— These stones differ but little in the essential qualities for a good building material, and from the great resemblance of their external characters and physical properties are generally known to builders by the common term granite.

Granite (Syenite, Granite, and Gneiss).— This stone ranks high as a building material, in consequence of its superior strength, hardness, and durability, furnishing a material particularly suitable for structures which require great strength. It does not resist well very high temperatures, and its great hardness requires practised stone-cutters to be employed to work it into proper shapes. It is principally used in works of magnitude and importance, as light-houses, sea-walls, revetment-walls of fortifications, large public buildings, etc. It is only in districts where it abounds that it is used for ordinary dwelling-houses. It was much used by the ancients, especially by the Egyptians, some of whose structures are still remaining in good condition, so far as the stone is concerned, after 3,000 years' exposure. Granite occurs in extensive beds, and may be obtained from the quarries in blocks of almost any size that may be required. Gneiss, in particular, from the mica being more in layers, which gives it a stratified appearance, admits of being broken out into thin slabs or blocks. A granite selected for building purposes should have a fine grain, even texture, and the constituents of which it is composed uniformly disseminated through the mass. It should be free from pyrites or any iron ore, which on exposure to the weather will rust and deface, if not destroy, the stone. The feldspathic varieties are the best, and the syenitic are the most durable. An examination of the rock in and around the quarry may give some idea of its durability.

7. Mica Slate has the same materials in its composition as gneiss, and breaks with a glistening or shining surface. The compact varieties are much used for flagging, for door and hearth stones, and often for lining furnaces, as it can be broken out in thin, even slabs. In districts where it abounds it is often used in ordinary masonry work.

8. Hornblende Shite resembles mica slate, but is tougher, and is an excellent material for flagging.

9. 8U utile or Soapstone is a soft stone, easily cut by a knife, and greasy to the touch. From the ease with which it is worked, and its refractory nature, it is used for tire-stones in furnaces and stoves, and for jambs in fire-places. Being soft, it is not suitable for ordinary building purposes.

10. Sandstone is a stratified rock consisting of grains of silicious sand arising from the disintegration of silicious stones cemented together by some material, generally a compound of silica, alumina, and lime. It has a harsh feel, and every dull shade of color from white through yellow, red, and brown to nearly black. Its strength, hardness, and durability vary between very wide limits ; some varieties being little inferior to good granite as a building-stone, others being very soft, friable, and disintegrating rapidly when exposed to the weather. The least durable sandstones are those which contain the most argillaceous matter; those of a feldspathic character are also found not to withstand well the action of the weather. The best sandstone lies in thick strata, from which it can be cut in blocks that show very faint traces of stratification ; that which is easily split into thin layers is weaker. It should be firm in texture, not liable to peel off on exposure, and be free from pyrites or iron-sand, as these rust and disfigure the blocks. It is generally porous and capable of absorbing much water, hut it is comparatively little injured by moisture, unless when built with iis layers set on edge. In this case the expansion of water in fre >zing between the layer-; makes them split or "scale" off. It should be built with the strata in a horizontal position, so that any water which may penetrate between the layers lias room to expand or escape. It is used very extensively as a building-stone, for flagging, for road materials, ami

s ■ of it- varieties furnish an excellent tire-stone. Most of the varieties

of sandstone yield readily under the ehisel and saw, and split evenly, and, from these properties, have received from workmen the name of lr, , slum .

1 1. other varieties of silicious stones besides those named, as porphyry, trap or greenttone, basalt, quartz-rock (cobble-stone), buhr-stone, etc., are " ed for building ami engineering purposes, and are eminently tit, either

Qe or rubble, bo far a- strength and durability are concerned.

ARGILLACEOUS STONES.

12. Argillaceous or Clayey Stones are those in which alumina exists in sufficient quantity to give the stone its characteristic properties.

Roofing Slate is the most important variety of building-stone of this class. It is a stratified rock of great hardness and density, commonly of a dark dull blue or purplish color. To be a good material for roofing it should split easily into even slates, and admit of being pierced for nails without fracturing. It should be free from everything that can undergo decomposition on exposure. The signs of good quality in slate are compactness, smoothness, and uniformity of texture, clear dark color, give a ringing sound when struck, and absorb but little water.

Being nearly impervious to water, it is principally used to cover roofs, line water-tanks, and for similar purposes.

CALCAREOUS STONES.

13. Calcareous Stones are those in which calcium monoxide or lime is the principal constituent. It enters as a sulphate or carbonate.

14. Calcium Sulphate, known as gypsum in its natural state, when burnt and ground up forms a white powder known as plaster-of-Paris. This powder, being mixed with a little water, becomes, on drying, hard and compact. Gypsum is not used as a building-stone, being too soft. The plaster, owing to its snowy whiteness, translucency, and fine texture, is used for taking casts, making models, and for giving a hard finish to walls. Care must be taken to use it only in dry and protected situations, as it absorbs moisture freely, then swells, cracks, and exfoliates rapidly.

15. Calcium Carbonates, or lime-stones, furnish a large amount of ordinary building-stone, ornamental stones, and the principal ingredient in the cements and mortars.

They' are distinguished by being easily scratched with a knife, and by effervescing with an acid. In texture they are either compact or granular ; in the former the fracture is smooth, often conchoidal ; in the latter a crystalline-granular surface, the fine varieties resembling loaf-sugar.

The lime-stones are generally impure carbonates, and we are indebted to these impurities for some of the most beautiful as well as the most in. valuable materials used for constructions. Those which are colored by metallic oxides, or by the presence of other minerals, furnish the large number of colored and variegated marbles, while those which contain a certain proportion of impurities, as silica, alumina, etc., yield, on calcination, those cements which, from their possessing the property of hardening under water, have received the names of hydraulic lime, hydraulic cement, etc. As a building material, they are classed into two divisions — those that receive a polish, and those that do not — which are known as marbles and common limestones.

16. Marbles. — Owing to the cost of preparing them, and the high polish of which they are susceptible, the marbles are mostly reserved for ornamental buildings and purposes.

They present great variety, both in color and appearance, and have generally received some appropriate name descriptive of these accidents.

Statuary Marble is of the purest white, finest grain, and free from all foreign minerals. It receives that delicate polish without glare which admirably adapts it to the purposes of the sculptor, for whose uses it is mostly reserved.

Conglomerate Marble. — This consists of two varieties ; the one termed pudding stone, which is composed of rounded pebbles embedded in compact lime-stone ; the other termed breccia, consisting of angular fragments united in a similar manner. The colors of these marbles are generally variegated, forming a very handsome ornamental material.

Bird's-eye Marble. — The name of this stone is descriptive of its appearance, which arises from the cross-sections of a peculiar fossil (fucoides demissus) contained in the mass, made in sawing or splitting it.

Lumachtlla Marble. — This is obtained from a lime-stone having shells embedded in it, and takes its name from this circumstance.

Verd Anil [tie. — This is a rare and costly variety, of a beautiful green color, caused by veins and blotches of serpentine diffused through the lime-stone.

There are many other varieties that receive their name either from their appearance or the localities from which they are obtained.

Many of these are imitated by dealers, who Btain the common marbles, by processes known to themselves, so successfully as to require a close examination t<> distinguish them from the real.

i; Common Linn Stones. — These furnish a great variety of building-

which present -rem diversityin their physical properties. Some

(•f them s.cm us durable as the best silicious stones, and are but little

Inferior to them in strength and hardness; others decompose rapidly on

exposure I" the Weather; and some kinds are so soft that, when firs!

V quarried, they can be scratched with the nail and broken between the fingers. Their durability is materially affected by the foreign minerals they may contain ; the presence of clay injures the stone, particularly when, as sometimes happens, it runs through the bed in very minute veins ; blocks of stone having this imperfection soon separate along these veins on exposure to moisture. Ferrous oxide, sulphate, and carbonate of iron, when present, are also very destructive in their effects, frequently causing by their chemical changes rapid disintegration.

Among the varieties of impure carbonates of lime are the magnesia n lime-stones, called dolomites. They are regarded in Europe as a superior building material ; those being considered the best which are most crystalline, and are composed of nearly equal proportions of the carbonates of lime and magnesia. Some of the quarries of this stone which have been opened in New York and Massachusetts have given a different result ; the stone obtained from them being, in some cases, extremely friable.

ARTIFICIAL STONES.

18. The term Artificial Stone is applied to any composition to which, by an artificial process, the general properties of natural stone are imparted. Yarious attempts from time to time have been made to make an imitation which, possessing all the merits, and being free from the defects, of the most useful building-stones, would supplement, if not supersede, them.

For a brief description of some of them and their mode of manufacture see paragraphs 116 to 120.

GENERAL OBSERVATIONS ON THE PROPERTIES OF STONE AS A BUILDING

r

MATERIAL.

19. Strength, hardness, durability, and ease of working have already been mentioned as essential properties to be considered in stone to be selected for building purposes.

It is not easy to judge of the qualities from external appearances. In most cases stone which has one of the three properties first named will have also the other two. In general, when the texture is uniform and compact, the grain fine, the color dark, and the specific gravity great, the stone is of good quality. If there are cracks, cavities, presence of iron, etc.. even though it belong to a good class of stone, it will be deficient in some of these essential qualities, and should be rejected. A coarse stone is ordinarily brittle, and is difficult to work ; it is also more liable to disintegrate than those of a finer grain.

20. Strength. — Among stones of the same kind, that which has the greatesl heat iness is almost always the strongest.

As stone is ordinarily to be subjected only to a crushing force, it will only be in particular cases that the resistance to this force need be considered, as the strength of stone in this respect is ordinarily greater than is generally required of it. If its durability is satisfactorily proved, as a rule, its strength may be assumed as sufficient.

21. Hardness. — This property is easily ascertained by actual experiment and a comparison made with other stones wliose qualities have been tested. It is an essential quality in stone exposed to wear from attrition. Stones selected for paving, flagging, and steps for stairs should be hard and of a grain sufficiently coarse not to admit of becoming very smooth under the action to which they are submitted.

By the absorption of water stones become softer and more friable. The materials for road coverings should be % selected from those stones which absorb least water, and are also hard and not brittle. Granite and varieties, lime-stone, and common sand-stone do not make the best materials for roads of broken stone. All the hornblende rocks, porphyry, compact feldspar, and the quartzose rock associated with graywacke, furnish good, durable road coverings. The fine-grained granites which contain hut a small proportion of mica, and the fine-grained silicious sand-stones which arc free from clay, form a durable material when used in blocks for paving. Mica slate, talcose slate, hornblende slate, some varieties of gneiss, some varieties <>r sand-stone of a slaty structure, and graywacke slate, yield excellent materials for flag-stone.

22. Durability. — By this term is meant the power to resist the wear and Prom atmospheric causes when exposed to their influence, the capacity to sustain high temperature, and the resistance to the destructive action of fresh and salt water.

The appearances which indicate probable durability are often deceptive.

genera] rule, those stones of the same Hnd which are fineted, absorb least water, and are of greatest specific gravity, an

| durable under ordinary exposures. The weight of a stone, how.

may arise from a large proportion of metallic oxide - a circumstai

linfai oiaUe In il durahilil v.

The various chemical combinations of iron, potash, and clay, when found in considerable quantities, both in the primary and sedimentary silicious rocks, greatly affect their durability. The potash contained in feldspar dissolves, and, carrying off a considerable proportion of the silica, leaves nothing but aluminous matter behind. The clay, on the other hand, absorbs water, becomes soft, and causes the stone to crumble to pieces.

24. Frost, or rather the alternate actions of freezing and thawing, is the most destructive agent of nature with which the engineer has to contend. Its effects vary with the texture of stones ; those of a fissile nature usually splitting, while the more porous kinds disintegrate, or exfoliate at the surface. When stone from a new quarry is to be tried, the best indication of its resistance to frost may be obtained from an examination of any rocks of the same kind, within its vicinity, which are known to have been exposed for a long period. Submitting the stone fresh from the quarry to the direct action of freezing would seem to be the best test, if it were not that some stones, which are much affected by frost when first quarried, splitting under its action, become impervious to it aftei fchey have lost the moisture of the quarry, as they do not reabsorb near so large an amount as they bring from the quarry.

25. A test for ascertaining the probable effects of frost on stone was invented by M. Brard, a French chemist, which can be used for determining the probable comparative durabilities of specimens. It is to imitate the disintegrating action of frost by means of crystallization of sodium sulphate. The process may be stated briefly as follows : Let a cubical block, about two inches on the edge, be carefully sawed from the stone to be tested. A cold saturated solution of the sodium sulphate is prepared, placed over a fire, and brought to the boiling-point. The stone, having been weighed, is suspended from a string, and immersed in the boiling liquid for thirty minutes. It is then carefully withdrawn, the liquid is decanted free from sediment into a flat vessel, and the stone is suspended over it in a cool cellar. An efflorescence of the salt soon makes its appearance on the stone, when it must be again dipped in the liquid. This should be done once or more frequently during the day, and the process be continued in this way for about a week. The earthy sediment found at the end of this period in the vessel is carefully weighed, and' its quantity will give an indication of the like effect of frost. This process is given in detail in Vol. XXXVIII. Annates cle Chemie et de Physique.

This test, having corresponded closely with their experience, has received the approval of man}' French architects and engineers. Experiment, however, made on some of the more porous stones, by exposing them to the alternate action of freezing and thawing, gave results very different from those obtained by Brard's method.,

26. The wear of stone from ordinary exposure is very variable, depending not only upon the t3xture and constituent elements of the stone, but also upon the locality and the position it may occupy in a structure with respect to the prevailing driving rains. This influence of locality on the durability of stone is very marked. Stone is observed to wear more rapidly in cities than in the country, and the stone in those parts of edifices exposed to the prevailing rains and winds soonest exhibits signs of decay. The disintegration of the stratified stones placed in a wall is mainly affected by the position which the strata or laniinoe receive with respect to the exposed surface ; proceeding faster when the faces of the strata are exposed, which is the case when the error is committed of not 1 mill ling in the stones with their laminae lying horizontally.

27. The only sure test, however, of the durability of any kind of stone, is experience.

28. Stones are often exposed to the action of high temperatures, as in the case of great conflagrations. This quality should be looked for in using stone for building purposes under such circumstances. They are also used to protect portions of a building from great heat, and sometimes to line furnaces. Those that resist a high degree of heat are termed. ///v- Btoiws. A good (ire-stone should not only be infusible, but also not liable to crack or exfoliate from heat. Stones that contain lime or magnesia, excepl in the form of silicates, are usually unsuitable. There are several varieties of sandstone which, from their being free from feldspar, uncrystallized, BOmewhal porous, hard, and gritty, are suitable. Talcose slate i- often a good fire-stone.

29. Expansion of Stone f nun fftat. — Experiments have been made in this country and Great Britain to ascertain the expansion for even degree "i Fahrenheit, and tabulated. Within the ordinary ranges of temperature the -tone is loo slightly affected by expansion or contraction to cause am perceptible change. Professor Bartlett's experiments, however, showed that in a long line of coping it was sufficiently great to crush mortar between the blocks.

80 I'r Mention of Stone.— To add to their durability, especially those naturally perishable or„ showing signs of decay, various processes have been tried or proposed. All have the same end in view, which is to fill the pores of the stone when exposed with some substance which shall exclude the air and moisture. Paints and oils have been used. Great hopes have been expected from the use of soluble glass (silicate of potash), and also of silicate of lime. The former, being applied in a state of solution in water, gradually hardens, partly through the evaporation of its water, and partly through the removal of the potash by the carbonic acid in the air. The latter is used by filling the pores with a solution of silicate of potash, and then introducing a solution of calcium chloride or lime nitrate. The chemical action produces silicate of lime, filling the pores of the natural stone. Time and experience will show if the hopes expected from their use will be realized.

31. Ease of Working the Stone. — This property is to a certain extent the inverse of the others. The ease with which stone can be cut or hammered into shape implies either softness or a Jow degree of cohesiveness between its particles. Independent of the cost, which is largely affected by this property, it often happens that the qualities in a stone in every other way suitable prevent it from being wrought to a true surface and receiving a smooth edge at the angles.

It requires experience and good judgment to strike a medium between these conflicting qualities.

32. Quarrying. — If the engineer should be obliged to get out his own stone and open a new quarry, he should pay particular attention to the best and cheapest method of getting it out and hauling it to the point where it is to be used. In all cases he will, if possible, open the quarry on the side of a hill, and arrange the roads leading to and in it with gentle slopes to assist the draught of the animals employed. The stone near the surface, not being so good as that beneath, is generally discarded. The mass or bed of stone being exposed, a close inspection will discover the natural joints or fissures along which the blocks will easily part from each other. When natural fissures do not exist, or smaller blocks are required than those indicated by them, a line of holes is drilled at regular short intervals, or grooves are cut in the upper surface of a bed. Then blunt steel wedges or pins, slightly larger than the holes, are inserted, which are struck sharply and simultaneously with hammers until the block splits off from the layer.

If large masses of stone be required, resort is made to blasting. This operation consists in boring the requisite number of holes, loading them with an explosive compound, and firing them. The success of blasting will depend upon a judicious selection of the position and depth of the holes and the proper charges used. It is well to ascertain, by actual experiments on the particular rock to be quarried, the effect of the charges, so as to determine the amount required to produce a good effect, instead of trusting, as too often is the case, to an empirical rule or no rule at all.

Chapter II. Limes And Cements

LIMES.

33. If a lime-stone be calcined, the carbonic acid will be driven off in the process, and the substance obtained is generally known as lime.

This product will vary in its qualities, depending on the degree of purity and impurity of the lime-stone. As a building material, the products are divided into three principal classes :

1. Common or fat lime.

2. Hydraulic i:me.

3. Hydraulic cement.

Common lime is sometimes called air-lime, because a paste with water or mortar made from it will harden only in the air.

Hydraulic lime and cement are also called water-limes and cement*, because a paste made from them has the valuable property of hardening under water.

( OMMON LIME.

84. Lime, common lime, air-lime, quick-lime, and caustic lime (synony mous terms) is a calcium monoxide, produced whenever any variety of pure <>r nearly pure lime-stone is calcined with a heat of sufficient

Intensity and duration to expel the carbon dioxide or carbonic acid. It i-

amorphous, Infusible, somewhat spongy, highly caustic, a specific gravity

'-••■'iid po real avidity for water. On being mixed with an

equlvalenl Of water, the water is rapidly absorbed with evolution of great heal | Hi-' linn- swells, bursts Into pieces, and finally crumbles into a tin.

white powder, of which the volume is from two and a half to three and a half times that of its original bulk. In this condition the lime is said to be sliked and ready for use in making mortar.

85. White chalk and statuary marble are specimens of pure carbonates of lime. Those which furnish the lime of commerce are seldom pure. The impurities are silica, alumina, magnesia, oxides of iron, manganese, etc., amounting sometimes to nearly ten per cent. The purer the lime-stone, the larger is the increase of volume or growth of the lime made from it in slaking, and the paste made from this lime is unctuous to the sight and touch. For which reason they are often called/«£ or rich limes, as distinguished from others not having these qualities, known as poor or meagre limes.

The latter are seldom reduced to an impalpable, homogeneous powder by slaking, and are characterized by less growth. They yield a thin paste, and are principally used as fertilizers. If it be necessary to use them for building purposes, they should be reduced to a fine powder by grinding, although they should never be used if it be possible to avoid it.

HYDRAULIC LIMES.

36. These occupy an intermediate place between the common limes and the hydraulic cements. They are obtained by calcining lime-stones in which the impurities, silica, alumina, magnesia, etc. , range from ten to twenty per cent. When they contain from ten to twenty per cent, of clay homogeneously mixed with carbonate of lime, they are known as argillaceous hydraulic lime-stones ; and when this proportion (nearly) is of silica, they are called silicious hydraulic lime-stones.

37. Hydraulic lime sfekes upon being mixed with water more slowly than the meagre limes, with slight elevation of temperature, accompanied by little or no vapor, and with an increase of volume rarely exceeding one-third of its original bulk. This lime after slaking, being mixed into a stiff paste, hardens under water.

38. It is not manufactured in the United States, nor is it known if there be any deposits of the argillaceous hydraulic lime-stones in the United States capable of furnishing good hydraulic lime.

39. That made from the argillaceous lime-stone is manufactured in several localities in France, notably at Seilley, about seventy miles from Paris. The best type of hydraulic lime from the silicious lime-stone is thai known as the hydraulic lime of Teil, from the quarries at Teil on the Rhone, Department of Ardeche, France.

HYDRAULIC CEMENT.

40. If the lime-stone contain more than 20 per cent, and less than 60 of the impurities before named, the product obtained by calcination is an hydraulic cement.

It will not slake, and when made into a paste will harden or set under water. The rapidity of setting and the degree of hardness will vary with the homogeneous character of the stone, the proportions into w r hich the clay and lime enter, and the intensity and duration of the burning.

41. There are two general classes, the slow and the quick setting.

1 1 t he stone contain at least 20, and not more than 22, per cent, of clay, and burned at high heat, the product is a heavy, slow T -setting cement. The natural Portland cement is an example.

If there be from 27 to 30 per cent, of clay, and even as high as 35 in aome cases, and a moderate burning, the result is a light, quick-setting cement.

The stone that might, with proper burning, have yielded a slow-setting cement, burned at a moderate heat, will produce a light, quick-setting cement. The Roman cement, that of Vassy, and the hydraulic cements ordinarily made in the United States, are examples of the quick-setting class.

42. The proportion existing between the clay and the lime exercises a controlling influence on the properties of the hydraulic cements, and, when lie proportion of lime is less than 40 per cent., the stone will, upon calcination, produce neither lime, hydraulic lime, nor hydraulic cement. If clay he present in excess, the product is known as calcareous pozzuolana : and when tlcre is 10 per cent, of lime or less, simply pozzuolana.

POZZUOLANAS.

i:;. Pozzuolana, which gives the name to this class, is a volcanic material, :i bind of tufa, containing about i) percent, of lime, 16 of silica, L5 of alumina, and the real other impurities, and is found near Home, Itah.