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 crushing 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 flushing 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. Crushing, 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.
The chemical laboratory is fully equipped with the necessary apparatus for carrying on special chemical research in silicate chemistry, including electrical resistance furnaces, shaking devices, etc. It is not the intention to do routine work in this laboratory. The office adjoins this laboratory, and near it is the physical laboratory, devoted to the study of the structure of raw materials. The latter contains n.o.bel and Schoene elutriators, together with viscosimeters of the flow and the Coulomb and Clark electrical types, sieves, voluminometers, colorimeters, vernier shrinkage gauges, micrometers, microscopes, and the necessary balances.
The room across the hall is devoted to the study of the specific gravity, absorption, porosity, permeability, hardness, translucency, etc., of burnt-clay products, all the necessary apparatus being provided. In the two remaining rooms, intended for research work, special apparatus adapted to the particular investigation may be set up.
All the rooms are piped for water, gas, compressed air, steam, and drainage, and wired for light and power.
In the kiln house there is a test kiln adapted for solid fuel and gas.
It is of the down-draft type, with an available burning s.p.a.ce of about 8 cu. ft. (Fig. 9). For heavier ware and the study of the fire behavior of clay products under conditions approaching those of practice, a round down-draft kiln, with an inside diameter of 6 ft., is installed. About 13 ft. above the floor level, and supported by iron beams, there is a flue parallel to the long side of the structure. This flue conducts the gases of the kilns to the stack, which is symmetrically located with reference to the kiln house. Natural gas is the princ.i.p.al fuel. In addition to these kilns, a small m.u.f.fle furnace, fired with petroleum, is provided for the determination of melting points, and an electric carbon resistance furnace, with an aluminum m.u.f.fle for high-temperature work. For crucible-fusion work, a gas-fired pot furnace is installed.
[Ill.u.s.tration: Fig. 7.
CLAY-DRYING OVEN]
Along the north wall, bins are provided for the storage of fuel, clay, sand, and other kiln supplies. There are two floor drainage sinks, and electric current, steam, water, and compressed air, are provided.
[Ill.u.s.tration: Fig. 8.
DRYING CLOSETS FOR CERAMICS]
_Results of the Work._--More than 39,300 separate test pieces have been made at the structural-materials testing laboratory. In connection with the study of these, 86,000 tests and nearly 14,000 chemical a.n.a.lyses have been made. Of these tests more than 13,600 have been of the const.i.tuent materials of concrete, including tensile tests of cement briquettes, compression tests of cylinders and cubes, and transverse tests of various specimens.
Nearly 1,200 beams of concrete or reinforced concrete, each 13 ft. long and 8 by 11 in. in cross-section, have been made, and, in connection with the investigation of the behavior of these beams, nearly 3,000 tests have been made. Nearly 900 of these beams, probably more than double the entire number made in other laboratories in the United States, during a period of more than 15 years, have been tested.
In the section of building blocks, 2,200 blocks have been tested, including, with auxiliary pieces, more than 4,500 tests; also, more than 900 pieces of concrete have been tested for permeability and shear. The physical tests have numbered 14,000; tests of steel for reinforcement, 3,800; and 550 tests to determine fire-resistive qualities of various building materials, have been made on 30 special panels, and on miscellaneous pieces.
[Ill.u.s.tration: Fig. 9.
DOWN-DRAFT KILN]
The tests of the permeability of cement mortars and concretes, and of water-proofing and damp-proofing materials, have numbered 3,470.
The results of the work of the Structural Materials Division have already appeared in preliminary bulletins, as follows: No. 324, "San Francisco Earthquake and Fire of April 18, 1906, and Their Effects on Structures and Structural Materials"; No. 329, "Organization, Equipment, and Operation of the Structural-Materials Testing Laboratories at St.
Louis, Mo."; No. 331, "Portland Cement Mortars and Their Const.i.tuent Materials" (based on nearly 25,000 tests); No. 344, "Strength of Concrete Beams" (based on tests of 108 beams); No. 370, "Fire-Resistive Properties of Various Building Materials"; No. 387, "The Colloid Matter of Clay and its Measurements." A bulletin on the results of tests of reinforced concrete beams, one on the manufacture and chemistry of lime, and one on drying tests of brick, are in course of publication.
FUEL INVESTIGATIONS.
The scope of the fuel investigations has been planned to conform to the provisions of the Act of Congress which provides for a.n.a.lyzing and testing coals, lignites, and other mineral fuel substances belonging to the United States, or for the use of the United States Government, and examinations for the purpose of increasing the general efficiency or available supply of the fuel resources in the United States.
In conformity with this plan, the investigations inaugurated at St.
Louis had for their initial object the a.n.a.lyzing and testing of the coals of the United States, using in this work samples of from 1 to 3 carloads, collected with great care from typical localities in the more important coal fields of the country, with a view to determining the relative values of those different fuels. In the work at Norfolk, during 1907, this purpose was modified to the extent of keeping in view relative fuel efficiencies for naval purposes. The tests at Denver have been on coal from Government land or from land contiguous thereto, and are conducted solely with a view to perfecting methods of c.o.king this coal by prior washing and by manipulation in the process of c.o.king.
Three general lines of inquiry are embodied in the plan of investigation undertaken and contemplated by the Technologic Branch, after conference and with the advice and approval of the Advisory Board: 1. The ascertainment of the best mode of utilizing any fuel deposit owned or to be used by the Government, or the fuel of any extensive deposit as a whole, by conducting a more thorough investigation into its combustion under steam boilers, conversion into producer gas, or into c.o.ke, briquettes, etc. 2. The prevention of waste, through the study of the possibility of improvement in the methods of mining, shipping, utilizing, etc. 3. The inspection and a.n.a.lysis of coal and lignite purchased under specification for the use of the Government, to ascertain its heating value, ash, contained moisture, etc.
The first general line of work concerns the investigation and testing of the fuel resources of the United States, and especially those belonging to the Federal Government, to determine a more efficient and more economical method of utilizing the same. This work has developed along the following lines:
The collection of representative samples for chemical a.n.a.lysis, and calorimeter tests by a corps of skilled mine samplers, from the mines selected as typical of extensive deposits of coal in a given field or from a given bed of coal; and the collection from the same mines of larger samples of from 1 to 3 carloads, shipped to the testing station for tests in boiler furnaces, gas producers, etc., as a check on the a.n.a.lysis and calorimeter tests;
The testing of each coal received to determine the most efficient and least wasteful method of use in different furnaces suitable for public buildings or power plants or ships of the Government;