Stone, Ar-ti-fi′cial.
Many kinds of material have been used for the production of artificial stone.
That which has been used on the largest scale, and, until a comparatively recent period, exclusively, was cemented by a calcareous substance, as
Roman, or, still better,
Portland cement, which hardens after being mixed with water.
Ordinary
concrete and Beton (which see) are of this class.
Terra-cotta, employed for architectural ornaments, statuary, etc., is in the nature of a fine brick.
Cement stones have been largely employed for constructions in the sea, especially for harbor dams, breakwaters, and quay walling.
We may cite the moles of
Dover and Alderney, in
England, of Port Vendre, Cette, La Ciotat,
Marseilles, and
Cherbourg in
France,
Carthagena in
Spain,
Pola in the
Adriatic, of
Algiers and
Port Said in
Africa, and
Cape Henlopen at the mouth of the
Delaware.
For the break water at
Cherbourg artificial stone blocks of 712 cubic feet each were immersed
The fortifications before
Copenhagen are made of a concrete of broken stone and hydraulic mortar.
The sluice of
Francis Joseph on the
Danube, in
Hungary, is built entirely of concrete.
This work forms a reservoir, the bottom and the sides of which consist of one piece.
Its length is 360 feet, and width 30 feet. Its construction, begun in 1854, was completed within 90 days, the work being pushed forward both night and day.
M. Coignet's beton agglomere was used in the erection of the aqueduct of La Vanne, which now carries pure water from the river of La Vanne in the department of the Aube and of the Yonne to the city of Paris The distance from
Paris to La Vanne is over 135 miles. The section which traverses the forest of
Fontainebleau comprises three miles of arches, some of them as much as 50 feet in hight, and 11 miles of tunnels, nearly all constructed of the material excavated on the spot.
The monolithic test-arch at St. Denis,
Paris, has a span of 196 feet, and an elevation of 19 feet. See
Fig. 666.
Coignet's beton is compounded of sand 5, lime 1, and say 25 of
hydraulic cement, mixed with an unusually small quantity of water, considerable mechanical exertion, followed by heavy ramming when the concrete is placed in the mold.
The reduction of the volume by the ramming is 1.7 to 1, and the weight of a cubic foot becomes 140 pounds. The blocks soon harden in the air, and the resistance to compression is 5,000 pounds to the square inch.
An ordinary mortar of the same material will be crushed by a pressure of 500 pounds. See Beton.
Recent French inventions in this line embrace: compacting the particles of which the stone is formed together by the action of a rammer upon successive layers while in a plastic state; forming monolithic buildings of a stone paste, the heating and ventilating flues and also the gas and water pipes being formed within the mass by the introduction of cores, which are afterward withdrawn; a modification of this for wharves, dams, abutment walls, etc., consists in making the walls hollow or honeycombed, and filling in the spaces or cells with earth or other cheap material; iron scraps may be incorporated with the material to bind it together, or a skeleton metallic framework may be imbedded in the walls while being made.
Orsi's
artificial lava consists of
| Stone or gravel | 48 |
| Pulverized chalk | 32 |
| Tar | 16 |
| Wax | 1 |
The solid ingredients are added to the melted tar and wax, and the mixture poured into molds.
Metallic lava consists of
| Ground flint | 2 |
| Broken marble | 3 |
| Resin | 1 |
with small quantities of wax and coloring matter to imitate stone.
It is used for tesselated pavements, the slabs being backed with concrete.
Artificial stone, having silica as the cementing material, was first introduced by
Ransome.
He originally made this stone by boiling flints, under a pressure of about 60 pounds to the inch, in a solution of soda, to which lime was added to render it caustic.
The soluble glass thus obtained, about the consistency of treacle, was mixed in the proportion of about 1 part to 10 of sand, 1 powdered flint, 1 clay; forming a paste which was molded into blocks, afterward dried in a steam-bath, to prevent the formation of a coating of silicate on the outside, which would prevent the escape of the vapor from the interior, and afterward burned in a kiln.
As at present made, the stone consists of clean sand and silicate of lime.
It resists boiling, roasting, freezing, pickling in acids, fumigating with gases, soaking and freezing, heating to redness, and then plunging into ice-water.
Flints are digested by boiling in a caustic solution of soda under pressure, giving a silicate of soda (see soluble glass). This is added at the rate of one gallon to each bushel of well-dried sand, whose interstices are partially filled with dust of carbonate of lime.
After careful mixing, the plastic mass is rammed and molded.
The block is immersed in a solution of chloride of calcium A reaction takes place; the silicate of soda and the chloride of calcium mutually decompose each other and reunite as silicate of lime and chloride of sodium, the former practically indestructible in air, the latter, common salt, perfectly deliquescent and removable by washing, although the stone,
after the washing, is impermeable to water.
The tensile strength of this, by experiment, was, for a piece 2 1/4 bore, from 870 to 1,200 pounds. Crushing strength, cubes of 4 inches square, 44 to 48 tons.
It has been used for grindstones with excellent effect.
The same process forms the basis of several
United States patents.
A “silicious varnish” (so called by the narrator) was used to give sharpness and permanency to the tri-lingual cruciform inscriptions on the scarp of a limestone mountain at Besitun, on the
Tigris.
It has been partially detached by the action of the elements during 23 centuries, and lies in scales at the foot of the precipice.
It was cut by the orders of
Darius Hytaspes, about 516 B. C., to celebrate a victory over the Magians.
We are indebted to
Rawlinson for the deciphering of the inscription.
In
Sorel's process, natural magnesite—carbonate of magnesia —is first calcined, which reduces it to the oxide of magnesium.
In this state it is mixed dry in the proper proportion, by weight, with the powdered marble, quartz, sand, or whatever material forms the basis of the stone.
It is then wetted with bittern water, which converts the oxide of magnesium into the oxychloride.
The now semi-plastic mixture is rammed into molds, where it speedily hardens, sufficiently to be taken out and laid on skids.
In two hours time the stone will resist rain, and in two weeks the stones may be used.
See also scagliola.
Patent 163,676, May 25, 1875, proposes to render artificial stone impervious to moisture and to prevent efflorescence thereon by mixing with the ordinary constituents in the process of manufacture soluble earthy or metallic sulphates in the form of a powder, and then a solution of the fatty acids.
McMurtie and
Chambers, May 25, 1875, treat the surface of the stone with a solution of earthy or metallic sulphates, and then with a solution of the fatty acids.
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