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Terra Cotta Construction

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TERRA COTTA CONSTRUCTION Structural Tiling.—Hollow tiling for use in building con struction is made in many different forms. It is employed either as the main structural material or as fireproof covering for other materials.

The materials of which the tiles are made are similar to those used in making bricks, but requiring usually higher grade and more refractory materials. Shales or seini-fire clays, similar to those used for paving bricks, are frequently employed for this purpose, or some times fire clays are mixed with plastic clays to prevent fluxing at moderate temperatures. Tiling for use in construction may be made either dense or porous according to the qualities desired.

Dense Tiling is made from materials which vitrify at high tem peratures (above 2000° F.) and is burned to the point of vitrifica tion like paving bricks. This material when of good quality pos sesses high strength and is practically It is used in outer walls of buildings, or for floor and wall construction when strength is needed.

Hollow blocks as made for ordinary wall construction are not usually vitrified, but are burned to a less degree than the hest dense tiling: They must be hard burned to be of value. In the rapid growth of the tile industry, attempts have been made to produce hollow tiling from inferior materials, and soft tiles lacking in strength and durability have sometimes been offered. Care must be exercised in selecting tiling to make sure of its quality.

Porous Tiling, or Terra Cotta Lumber, is made from refractory plastic clays by mixing sawdust with the clay in forming the blocks, and burning at high temperature. The sawdust burning out leaves the material light in weight and porous. These blocks may be cut with a saw, and nails or screws may be driven into them without difficulty. This tiling does not possess the strength of good dense tiling, but is tough and less brittle, and is largely used in fireproofing and for interior walls and partitions.

Tiling of less porosity but possessing somewhat the character of the terra cotta lumber is sometimes made by mixing ground coal with the clay before burning. It is claimed that this makes a better fireproofing than the dense tiling. These blocks are sometimes known as scmi-porous tiling.

The forms and sizes of hollow blocks depend upon the uses to be made of them. For walls or partitions, the blocks are usually in 12-inch lengths, and of rectangular or interlocking sections.

Rectangular blocks are iiiade in various sizes-12-inch widths may be had from 2 inches to 8 inches thick. Widths of 6 and S

inches are made in thicknesses from 2 to 5 inches. They are divided by webs into cells, as shown in Fig. 38. In the heavier tiling, intended for use where loads are to be carried, and in outside walls, the shells are at least 1 inch and the webs at least ;-inch in thickness, and the cells not more than or 4 inches in width. In lighter tiling, used as filler in concrete work or for light partitions, the webs are s to inch, and cell openings may be 5 or 6 inches.

Interlocking blocks are made in various shapes, with the object of improving the bond of the wall, and eliminating joints extending through the wall. These blocks are often used in outside walls to prevent moisture passing through the wall and provide air spaces in all parts of the wall. Fig. 39 shows one of the common forms of interlocking tile.

Hollow blocks for use in fire protection are made in many shapes to fit around structural members of other materials. They are also made to fit together in round or flat arches to support floors between steel beams.

Good tiling must be well burned, true in form and free front checks or cracks, and should give a ringing sound when struck with metal.

The following requirements for hollow tile are given in the Build ing Code of the city of St. Louis for 1917: All hollow tile used in the construction of walls or partitions shall be hollow shale or terra cotta, well manufactured and free from cheeks and cracks, each piece or block to be molded square and true and to be hard burned so as to give a good clear ring when struck, and not to absorb more than twelve (12) per cent of its own weight in moisture. Each of said blocks shall develop an ultimate crushing strength of not less than three thousand (3000) pounds per square inch of available section of web area, and shall not be loaded when in the wall more than eighty (SO) pounds per square inch of effective bearing area. Tiles shall have outer shells or walls not less than three-quarters (;) of an inch thick and shall be additionally reinforced by continuous interior walls or webs which shall not be less than one-half (z) inch thick, and so arranged that no void shall exceed four (4) inches in cross-section at any point. It is further provided that the building commissioner may require a test to be made of such blocks before allow ing the same to be placed in the wall, if, in his judgment, there be any doubt as to whether such blocks, proposed to he used, meet the requirements above specified.

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