Part 10 (1/2)

1.--Determination of the failing elements and the nature of the failure;

2.--Determination of the value of the theories advanced at the present time; and,

3.--Determination of a method of eliminating or chemically recombining the injurious elements.

Preliminary tests are in progress, including a study of the effect of salt water on mortars and concretes of various mixtures and ages. The proportions of these mixtures and the methods of mixing will be varied from time to time, as suggested by the progress of the tests.

_Fire-Proofing Tests._--Tests of the fire-proofing and fire-resistive properties of various structural materials are carried on in the laboratories in Building No. 10, at Pittsburg, and in co-operation with the Board or Fire Underwriters at its Chicago laboratory (Fig. 2, Plate XIII). These tests include three essential cla.s.ses of material: (_a_), clay products, protective coverings representative of numerous varieties of brick and fire-proofing tiles, including those on the market and those especially manufactured for these tests in the laboratory at Pittsburg; (_b_), characteristic granites of New England, with subsequent tests of the various building stones found throughout the United States; and (_c_), cement and concrete covering material, building blocks, and concrete reinforced by steel bars embedded at different depths for the purpose of studying the effect of expansion on the protective covering.

In co-operation with the physical laboratory, these tests include a study of the relative rates of conductivity of cement mortars and concretes. By embedding thermo-couples in cylinders composed of the materials under test, obtaining a given temperature by an electric coil, and noting the time required to raise the temperature at the various embedded couples to a given degree, the rate of conductivity may be determined. Other tests include those in m.u.f.fles to determine the rate of expansion and the effect of heat and compressive stresses combined on the compressive strength of the various structural materials. The methods of making the panel tests, and the equipment used, are described and ill.u.s.trated in Bulletin No. 329, and the results of the tests have been published in detail.[10]

_Building Stones Investigations._--The field investigations of building stones are conducted by Mr. E. F. Burchard, and include the examination of the various deposits found throughout the United States. A study of the granites of New England has been commenced, which includes the collection of type specimens of fine, medium, and coa.r.s.e-grained granites, and of dark, medium, and light-gray or white granites. A comparative series of these granites, consisting of prisms and cubes of 4 and 2 in., respectively, has been prepared.

[Ill.u.s.tration: Fig. 6.

PLAN OF LABORATORY FOR SALT-WATER TESTS AT ATLANTIC CITY, N.J.]

The standard adopted for compressive test pieces in the 10,000,000-lb.

machine is a prism, having a base of 12 in. and being 24 in. high. The tests include not only those for compression or crus.h.i.+ng strength, but also those for resistance to compressive strains of the prisms and cubes, when raised to high temperatures in m.u.f.fles or kilns; resistance to weathering, freezing, and thawing; porosity; fire-resisting qualities, etc.

In collecting field samples, special attention is paid to the occurrence of the stone, extent of the deposit, strike, dip, etc., and specimens are procured having their faces cut with reference to the bedding planes, in order that compressive and weathering tests may be made, not only in relation to these planes but at those angles thereto in which the material is most frequently used commercially. Attention is also paid to the results of blasting, in its relation to compressive strains, as blasting is believed to have a material effect on stones, especially on those which may occur in the foundations of great masonry dams, and type specimens of stone quarried by channeling, as well as by blasting, are collected and tested.

_Clay and Clay Products Investigations._--These investigations are in charge of Mr. A. V. Bleininger, and include the study of the occurrence of clay beds in various parts of the United States, and the adaptability of each clay to the manufacture of the various clay products.

Experiments on grinding, drying, and burning the materials are conducted at the Pittsburg testing station, to ascertain the most favorable conditions for preparing and burning each clay, and to determine the most suitable economic use to which it may be put, such as the manufacture of building or paving bricks, architectural tiles, sewer tiles, etc.

The laboratory is equipped with various grinding and drying devices, m.u.f.fles, kilns, and apparatus for chemical investigations, physical tests, and the manufacture and subsequent investigative tests of clay products.

This section occupies the east end of Building No. 10, and rooms on the first and second floors have been allotted for this work. In addition, a brick structure, 46 by 30 ft., provided with a 60-ft. iron stack, has been erected for housing the necessary kilns and furnaces.

[Ill.u.s.tration: PLATE XVI.

Fig. 1.--Brick Machine and Universal Cutter.

Fig. 2.--House-Heating Boilers, Building No. 21.]

On the ground floor of Building No. 10, adjoining the cement and concrete section, is a storage room for raw materials and product under investigation. Adjoining this room, and connecting with it by wide doors, is the grinding room, containing a 5-ft. wet pan, with 2,000-lb.

rollers, to be used for both dry and wet grinding. Later, a heavy dry pan is to be installed. With these machines, even the hardest material can be easily disintegrated and prepared. In this room there is also a jaw crusher for reducing smaller quant.i.ties of very hard material, as well as a 30 by 16-in. iron ball mill, for fine grinding. These machines are belted to a line shaft along the wall across the building. Ample sink drainage is provided for flus.h.i.+ng and cleaning the wet pan, when changing from one clay to another.

A large room adjoining is for the operation of all moulding and shaping machines, representing the usual commercial processes. At present these include an auger machine, with a rotary universal brick and tile cutter, Fig. 1, Plate XVI, and a set of brick and special dies, a hand repress for paving brick, and a hand screw press for dry pressing. The brick machine is operated from the main shaft which crosses the building in this room and is driven from a 50-h.p. motor. It is possible thus to study the power consumption under different loads and with different clays, as well as with varying degrees of water content in the clay. As the needs of the work demand it, other types of machines are to be installed. For special tests in which pressure is an important factor it is intended to fit up one of the compression testing machines of the cement section with the necessary dies, thus enabling the pressing to be carried on under known pressures. Crus.h.i.+ng, transverse, and other tests of clay products are made on the testing machines of the cement and concrete laboratories.

Outside of the building, in a lean-to, there is a double-chamber rattler for the testing of paving brick according to the specifications of the National Brick Manufacturers' a.s.sociation.

In the smaller room adjoining the machine laboratory there are two small wet-grinding ball mills, of two and four jars, respectively, and also a 9-leaf laboratory filter press.

The remaining room on the first floor is devoted to the drying of clays and clay wares. The equipment consists of a large sheet-iron drying oven of special construction, which permits of close regulation of the temperature (Fig. 7). It is heated by gas burners, and is used for the preliminary heat treatment of raw clays, in connection with the study of the drying problems of certain raw materials. It is intended to work with temperatures as high as 250 cent.

Another drying closet, heated by steam coils (Fig. 8), intended for drying various clay products, has been designed with special reference to the exact regulation of the temperature, humidity, and velocity of the air flowing through it. Both dryers connect by flues with an iron stack outside the building. This stack is provided with a suction fan, driven by a belt from an electric motor.

On the second floor are the chemical, physical, and research laboratories, dealing with the precise manipulations of the tests and investigations.