8. Shearing strength with cement, material sifted to one size.

9. Modulus of elasticity in compression of different mixtures as to proportion and size of aggregate.

10. Modulus of elasticity in tension of different mixtures as to proportion and size of aggregate.

19. Effect of oil: (a) On hardening mortar; (b) on hardened mortar. 20. Effect of sea water.

III. TESTS AND CLASSIFICATION OF CONCRETE MADE WITH TYPICAL PORTLAND CEMENT AND STONE, STONE AND GRAVEL SCREENINGS, GRAVEL, SAND, CINDER, SLAG, ETC. A. Proportions and conditions.-Proportions to be stated by weight and volume. Unit of volume for cement, 100 pounds per cubic foot.

B. Physical tests in laboratory.—The laboratory tests include the following determinations, those designated as items 1 to 6 being each made at the ages of 30, 90, 180, and 360 days:

C. Full-size tests. The laboratory tests of full-size beams, building blocks, and

bricks include the following:

1. Beams of various spans, sections, and compositions.

2. Building blocks and bricks, as to (a) compressive strength, wet and dry mixtures; (b) transverse strength, wet and dry mixtures; (c) shearing strength, wet and dry mixtures; (d) absorption, wet and dry mixtures; (e) permeability; (ƒ) methods of waterproofing; (g) effect of accelerating the hardening of concrete blocks by means of live steam, etc.; (h) fire-resisting qualities; (i) efflorescence.

IV. TESTS OF REINFORCED CONCRETE.

A. Beams. Tests of beams to include determinations of

1. Effect of amount of reinforcement.
2. Effect of character of reinforcement.

3. Effect of form, size, and position of
reinforcing bars.

4. Effect of initial stress in reinforcement.

5. Effect of different manners of loading. 6. Methods of providing for diagonal

stresses.

7. Effect of variation in section, such as trapezoidal, T-shaped, etc.

8. Effect of variation in length and depth.

9. Effect of restraining the ends. 10. Effect of repetitive loading.

B. Columns.-Tests of columns to include determinations of

1. Effect of amount of reinforcement.

2. Effect of disposition of reinforcement:

4. Effect of character and eccentricity of

loading.

(a) Longitudinal; (b) hooped; (c) 5. Effect of variation in section, such as

combination of (a) and (b).

3. Effect of form, size, and position of reinforcement.

C. Slabs.-Tests to be made of slabs1. Supported at two or four edges. 2. Fixed at two or four edges.

3. Use of expanded metal, wires, etc.

4. Effect of concentration of load.

5. Variation in per cent of reinforcement. 6. Variation in span and thickness.

D. Arches.-Tests to be made of forms and features of arches as follows: 1. Continuous ring.

2. Hinged.

4. Shape.

5. Span and rise.

3. Voussoirs.

WORK AT TECHNOLOGICAL INSTITUTIONS.

In connection with the work at the laboratories it has been deemed desirable by the national advisory board and the joint committee on concrete and reinforced concrete to invite the cooperation of those technological institutions possessing proper facilities for carrying on investigations comprising, in part, tests in which the methods of execution are still open to formulation and which involve general phenomena. In addition to this, it was thought desirable for this laboratory to act in an advisory capacity to any laboratory desiring to conduct investigations along these lines. Among the topics which are available for such investigations may be mentioned

1. Shearing: Comparison of methods.

2. Modulus of elasticity: Comparison of methods.

3. Protective influence of concrete against corrosion.

4. Fire-resisting qualities of concrete.

5. Methods of waterproofing.

6. Coefficient of expansion.

7. Effect of vibration and applied stress.

8. Adhesion of concrete to metal.

9. Reinforced-concrete beams: (a) Effect of different manners of loading; (b) methods of providing for diagonal stresses; (c) effect of variation in section; (d) effect of restraining ends; (e) amount and character of reinforcement.

10. Reinforced-concrete columns: Method of testing.

SEQUENCE OF TESTS.

It is evident that the investigations embraced in the foregoing programme will cover a number of years, and it is therefore the aim of the United States Geological Survey to investigate first those questions which will yield information most urgently needed in constructive work by the different branches of the Government, the policy being to work continuously upon as many of the problems as the facilities and appropriation will permit.

As the investigation progresses it may be found necessary to do considerable experimental work in determining the proper methods to be followed, the sources of error to be guarded against, and the probable causes of given phenomena, and the programme may therefore be varied according to conditions.

SUMMARY.

In the following pages the character of the investigations being conducted at the laboratories is presented, together with a description of the apparatus and methods of testing, methods of computing, and forms used for recording the results, the work of each section being separately described..

The methods of testing are given in some detail without, however, any reference to the investigations which led up to their adoption. These investigations often entailed a series of comparative tests between a number of different methods. No change of method is made without a thorough series of tests on identical material by both the old and the proposed method, not only to determine the relative advantages and disadvantages of the two methods, but also to have an equation between the results obtained by both methods by which, should the new method be adopted, the results obtained by the old method would be comparable with those obtained by the new.

The theories underlying the methods of testing are not touched upon except in one instance. The methods used in testing beams are somewhat different from those used by other investigators, hence the theories underlying the methods used at these laboratories are explained.

The methods used in transforming the data obtained at the testing machines into form for publication are not treated in detail, an outline only being given.

a

a See Form B (p. 24) and footnote relating thereto (p. 23).