The structural materials investigations are being conducted for the
purpose of determining the nature and extent of the materials available
for use in the building and construction work of the Government, and how
these materials may be used most efficiently.
These investigations include:
(1).--Inquiries into the distribution and local availability, near each
of the building centers in the United States, of such materials as are
needed by the Government.
(2).--How these materials may be used most efficiently.
(3).--Their fire-resisting qualities and strength at different
temperatures.
(4).--The best and most economic methods of protecting steel by
fire-resistant covering.
(5).--The most efficient methods of proportioning and mixing the
aggregate, locally available, for different purposes.
(6).--The character and value of protective coatings, or of various
mixes, to prevent deterioration by sea water, alkali, and other
destructive agencies.
(7).--The kinds and forms of reinforcement for concrete necessary to
secure the greatest strength in beams, columns, floor slabs, etc.
(8).--Investigation of the clays and of the products of clays needed in
Government works, as to their strength, durability, suitability as
fire-resisting materials, and the methods of analyzing and testing clay
products.
(9).--Tests of building stones, and investigations as to their
availability near the various building centers throughout the United
States.
The operations of the Structural Materials Division include
investigations into cement-making materials, constituent materials of
concrete, building stones, clays, clay products, iron, steel, and
miscellaneous materials of construction, for the use of the Government.
The organization comprises a number of sections, including those for the
chemical and physical examination of Departmental purchases; field
sampling and laboratory examination of constituent materials of concrete
collected by skilled field inspectors in the neighborhood of the larger
commercial and building centers; similar field sampling of building
stones and of clays and clay products, offered for use in Government
buildings or engineering construction; and the forwarding of such
samples to the testing laboratories at St. Louis or Pittsburg for
investigation and test. The investigative tests include experiments
regarding destructive agencies, such as electrolysis, alkaline earths
and waters, salt water, fire, and weathering; also experiments with
protective and water-proofing agencies, including the various washes or
patented mixtures on the market, and the methods of washing, and mixing
mortars and concrete, which are likely to result in rendering such
materials less pervious to water.
Investigations are also being conducted to determine the nature and
extent of materials available for use in the building-construction work
of the Government, and how these materials may be used most efficiently
and safely. While the act authorizing this work does not permit
investigations or tests for private parties, it is believed that these
tests for the Government cannot fail to be of great general value. The
aggregate expenditure by the Federal Government in building and
engineering construction is about $40,000,000 annually. This work is
being executed under so many different conditions, at points so widely
separated geographically, and requires so great a variety of materials,
that the problems to be solved for the Government can hardly fail to
cover a large share of the needs of the Engineering Profession, State
and municipal governments, and the general public.
_Character of the Work._--The tests and analyses, of the materials of
construction purchased by the various bureaus and departments for the
use of the Government, are to determine the character, quality,
suitability, and availability of the materials submitted, and to
ascertain data leading to more accurate working values as a basis for
better working specifications, so as to enable Government officials to
use such materials with more economy and increased efficiency.
Investigative tests of materials entering into Government construction,
relative to the larger problems involved in the use of materials
purchased by the Government, include exhaustive study of the suitability
for use, in concrete construction on the Isthmian Canal, of the sand and
stone, and of the cementing value of pozzuolanic material, found on the
Isthmus; the strength, elasticity, and chemical properties of structural
steel for canal lock-gates; of wire rope and cables for use in hoisting
and haulage; and the most suitable sand and stone available for concrete
and reinforced concrete for under-water construction, such as the
retaining walls being built by the Quartermaster’s Department of the
Army, in San Francisco Harbor.
These tests also include investigations into the disintegrating effect
of alkaline soil and water on the concrete and reinforced concrete
structures of the Reclamation Service, with a view to preventing such
disintegration; investigations into the proper proportions and
dimensions of concrete and reinforced concrete structural columns,
beams, and piers, and of walls of brick and of building stone, and of
the various types of metal used for reinforcement by the Supervising
Architect in the construction of public buildings; investigations into
the sand, gravel, and broken stone available for local use in concrete
construction, such as columns, piers, arches, floor slabs, etc., as a
guide to the more economical design of public structures, and to
determine the proper method of mixing the materials to render the
concrete most impervious to water and resistant to weather and other
destructive agencies.
Other lines of research may be stated briefly as follows:
The extent to which concrete made from cement and local materials can be
most safely and efficiently used for different purposes under different
conditions;
The best methods for mixing and utilizing the various constituent
materials locally available for use in Government construction;
The materials suitable for the manufacture of cement on the public
lands, or where the Government has planned extensive building or
engineering construction work, where no cement plants now exist;
The kinds and forms of reinforcement for concrete, and the best methods
of applying them in order to secure the greatest strength in
compression, tension, shear, etc., in reinforced concrete beams,
columns, floor slabs, etc.;
The influence of acids, oils, salts, and other foreign materials,
long-continued strain, or electric currents, on the permanence of the
steel in reinforced concrete;
The value of protective coatings as preventives of deterioration of
structural materials by destructive agencies; and
The establishment of working stresses for various structural materials
needed by the Government in its buildings.
Investigations are being made into the effects of fire and the rate of
conductivity of heat on concrete and reinforced concrete, brick, tile,
building stone, etc., as a guide to the use of the most suitable
materials for fire-proof building construction and the proper
dimensioning of fire-resistive coverings.
Investigations and tests are being made, with a view to the preparation
of working specifications for use in Government construction, of bricks,
tile, sand-lime brick, paving brick, sewer pipe, roofing slates,
flooring tiles, cable conduits, electric insulators, architectural terra
cotta, fire-brick, and all shapes of refractories and other clay
products, regarding which no satisfactory data for the preparation of
specifications of working values now exist.
Investigations of the clay deposits throughout the United States are in
progress, to determine proper methods of converting them into building
brick, tile, etc., at the most reasonable cost, and the suitability of
the resulting material for erection in structural forms and to meet
building requirements.
Investigations are being made in the field, of building stones locally
available, and physical and chemical tests of these building stones to
determine their bearing or crushing strength; the most suitable mortars
for use with them; their resistance to weathering; their fire-resistive
and fire-proof qualities, etc., regarding which practically no adequate
information is available as a guide to Government engineering and
building design.
_Results Accomplished._--During one period of six months alone, more
than 2,500 samples, taken from Government purchases of structural
materials, were examined, of which more than 300 failed to meet the
specified requirements, representing many thousands of dollars worth of
inferior material rejected, which otherwise would have been paid for by
the Government. These tests were the means of detecting the inferior
quality of large quantities of materials delivered on contracts, and the
moral effect on bidders has proven as important a factor in the
maintenance of a high quality of purchases, as in the saving of money.
The examination of sands, gravels, and crushed stones, as constituent
materials for concrete and reinforced concrete construction, has
developed data showing that certain materials, locally available near
large building centers and previously regarded as inferior in quality,
were, in fact, superior to other and more expensive materials which it
had been proposed to use.
These investigations have represented an actual saving in the cost of
construction on the work of the Isthmian Canal Commission, of the
Supervising Architect, and of certain States and cities which have
benefited by the information disseminated regarding these constituent
materials.
Investigations of clay products, only recently inaugurated, have already
resulted in the ascertainment of important facts relative to the colloid
matter of clay and its measurement, and the bearing thereof on the
plasticity and working values of various clays. The study of the
preliminary treatment of clays difficult to handle dry, has furnished
useful information regarding the drying of such clays, and concerning
the fire resistance of bricks made of soft, stiff, or dried clay of
various densities.
The field collection and investigation of building-stone samples have
developed some important facts which had not been considered previously,
relative to the effect of quarrying, in relation to the strike and dip
of the bedding planes of building stone, and the strength and durability
of the same material when erected in building construction. These
investigations have also developed certain fundamental facts relative to
the effects of blasting (as compared with channeling or cutting) on the
strength and durability of quarried building stone.
_Mineral Chemistry Laboratories._--Investigations and analyses of the
materials of engineering and building construction are carried on at
Pittsburg in four of the larger rooms of Building No. 21. In this
laboratory, are conducted research investigations into the effect of
alkaline waters and soils on the constituent materials of concrete
available in arid regions, as related to the life and permanency of the
concrete and reinforced concrete construction of the Reclamation
Service. These investigations include a study of individual salts found
in particular alkalis, and a study of the results of allowing solutions
of various alkalis to percolate through cylinders of cement mortar and
concrete. Other research analyses have to do with the investigation of
destructive and preservative agencies for concrete, reinforced concrete,
and similar materials, and with the chemistry of the effects of salt
water on concrete, etc. The routine chemical analyses of the constituent
materials of concrete and cement-making materials, are made in this
laboratory, as are also a large number of miscellaneous chemical
analyses and investigations of reinforcement metal, the composition of
building stones, and allied work.
A heat laboratory, in charge of Dr. J. K. Clement, occupies three rooms
on the ground floor of Building No. 21, and is concerned chiefly with
the measurement of temperatures in gas producers, in the furnaces of
steam boilers, kilns, etc. The work includes determinations of the
thermal conductivity of fire clays, concrete, and other building
materials, and of their fire-resisting properties; measurements of the
thermal expansion and specific heats of fire-bricks, porcelain, and
glazes; and investigations of the effect of temperature variations on
the various chemical processes which take place in the fuel bed of the
gas producer, boiler furnace, etc.
The heat laboratory is equipped for the calibration of the thermometers
and pyrometers, and electrical and other physical apparatus used by the
various sections of the Technologic Branch.
For convenience in analyzing materials received from the various
purchasing officers attached to the Government bureaus, this work is
housed in a laboratory on the fourth floor of the Geological Survey
Building in Washington.
Large quantities and many varieties of building materials for use in
public buildings under contract with the Supervising Architect’s office,
are submitted to the laboratory by contractors to determine whether or
not they meet the specified requirements. Further examinations are made
of samples submitted by superintendents of construction, representing
material actually furnished by contractors. It is frequently found that
the sample of material submitted by the contractor is of far better
quality than that sent by the superintendent to represent deliveries.
The needed constant check on deliveries is thus provided.
In addition to this work for the office of the Supervising Architect,
similar work on purchases and supplies is carried on for the Isthmian
Canal Commission, the Quartermaster-General’s Department of the Army,
the Life Saving Service, the Reclamation Service, and other branches of
the Government. About 300 samples are examined each month, requiring an
average of 12 determinations per sample, or about 3,600 determinations
per month.
The chemical laboratory for testing Government purchases of structural
materials is equipped with the necessary apparatus for making the
requisite physical and chemical tests. For the physical tests of cement,
there are a tensile test machine, briquette moulds, a pat tank for
boiling tests to determine soundness, water tanks for the storage of
briquettes, a moist oven, apparatus to determine specific gravity,
fineness of grinding, etc.
The chemical laboratory at Washington is equipped with the necessary
analytical balances, steam ovens, baths, blast lamps, stills, etc.,
required in the routine chemical analysis of cement, plaster, clay,
bricks and terra cotta, mineral paints and pigments, roofing material,
tern plate and asphaltic compounds, water-proofing materials, iron and
steel alloys, etc.
At present, materials which require investigative tests as a basis for
the preparation of suitable specifications, tests not connected with the
immediate determination as to whether or not the purchases are in
accordance with the specifications, are referred to the chemical
laboratories attached to the Structural Materials Division, at
Pittsburg.
The inspection and tests of cement purchased in large quantities, such
as the larger purchases on behalf of public-building construction under
the Supervising Architect, or the great 4,500,000-bbl. contract of the
Isthmian Canal Commission, are made in the cement-testing laboratory of
the Survey, in the Lehigh Portland cement district, at Northampton, Pa.
_Testing Machines._--The various structural forms into which concrete
and reinforced concrete may be assembled for use in public-building
construction, are undergoing investigative tests as to their compressive
and tensile strength, resistance to shearing, modulus of elasticity,
coefficient of expansion, fire-resistive qualities, etc. Similar tests
are being conducted on building stone, clay products, and the structural
forms in which steel and iron are used for building construction.
The compressive, tensile, and other large testing machines, for all
kinds of structural materials reaching the testing stations, are under
the general supervision of Richard L. Humphrey, M. Am. Soc. C. E. The
immediate direction of the physical tests on the larger testing machines
is in charge of Mr. H. H. Kaplan.
Most of this testing apparatus, prior to 1909, was housed in buildings
loaned by the City of St. Louis, in Forest Park, St. Louis, Mo., and the
arrangement of these buildings, details of equipment, organization, and
methods of conducting the tests, are fully set forth in Bulletin No. 329
of the U.S. Geological Survey. In brief, this equipment included
motor-driven, universal, four-screw testing machines, as follows: One
600,000-lb., vertical automatic, four-screw machine; one 200,000-lb.,
automatic, four-screw machine; and one 200,000-lb. and one 100,000-lb.
machine of the same type, but with three screws. There are a number of
smaller machines of 50,000, 40,000, 10,000, and 2,000 lb., respectively.
These machines are equipped so that all are available for making tensile
and compressive tests (Fig. 1, Plate XIII). The 600,000-lb. machine is
capable of testing columns up to 30-ft. lengths, and of making
transverse tests of beams up to 25-ft. span, and tension tests for
specimens up to 24 ft. in length. The smaller machines are capable of
making tension and compressive tests up to 4 ft. in length and
transverse beam tests up to 12 ft. span. In addition, there are ample
subsidiary apparatus, including concrete mixers with capacities of ½ and
1 cu. yd., five hollow concrete block machines, automatic sifting
machines, briquette moulds, storage tanks, etc.
At the Atlantic City sub-station, there is also a 200,000-lb.,
universal, four-screw testing machine, with miscellaneous equipment for
testing cement and moulding concrete, etc.; and at the Northampton
sub-station, there is a complete equipment of apparatus for cement
testing, capable of handling 10,000 bbl. per day.
At the Pittsburg testing station, a 10,000,000-lb., vertical,
compression testing machine (Plate XIV), made by Tinius Olsen and
Company, is being erected for making a complete series of comparative
tests of various building stones of 2, 4, and 12-in. cube, of stone
prisms, 12 in. base and 24 in. high, of concrete and reinforced concrete
columns up to 65 ft. in height, and of brick piers and structural-steel
columns up to the the limits of the capacity and height of the machine.
[Illustration: PLATE XIII.
Fig. 1.--Testing Beam in 200,000-Lb. Machine.