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Quantities of Materials for 1 cu. yd. of 4000 lb. per sq. in. Concrete
The volume of cement is expressed in barrels and of aggregates in cubic yards. F = fine aggregate; C = coarse aggregate.
Quantities are net, no allowance being made for waste; for average conditions, the following additions are suggested: Cement, 2%; fine aggregate, 10%; coarse aggregate, 5%.
JOINT COMMITTEE ON SPECIFICATIONS FOR CONCRETE
JOB TUTHILL, Chairman; A. F. ROBINSON, Joint Committee.
The Joint Concrete Culvert Pipe Committee was formed to prepare
College, Ames, Iowa.
T. L. D. Hadwen, Masonry Engineer, C. M. & St. P. Ry., Chicago, Ill.
A. B. Cohen, Consulting Engineer, New York City.
C. F. Buente, Manager, Concrete Products Company, Pittsburgh, Pa.
Prof. T. R. Agg, Iowa State College, Ames, Iowa.
Bureau of Public Roads, U. S. Department of Agriculture:
Thos. H. MacDonald, Chief of Bureau.
A. T. Goldbeck, Engineer of Tests. American Railway Engineering Association: A. F. Robinson, Bridge Engineer, Atchison, Topeka & Santa Fe Rail
way. Job Tuthill, Assistant Chief Engineer, Pere Marquette Railway.
The first meeting of the Committee was held at Atlantic City, June 27, 1919, when Mr. H. T. Shelly, then representing the American Society for Testing Materials, was elected Chairman and the following sub-committees were appointed :
No. 1-Classification and Loading Requirements.
The representation at this meeting was but one member from each association and it was decided to ask that a second representative be appointed. This was subsequently done, bringing the membership to its present numbers,
Professor Agg advised the meeting that the Iowa State College would extend its experimental work in its investigation of pressures of earth on pipes to include larger sizes and greater height of fills, conforming to conditions of railroad and highway work and that the information obtained would be available to the Committee for determining the loading that should be considered in designing concrete pipe.
Several meetings of sub-committees and two of the general committee have been held since and more or less preliminary work done awaiting more definite information as to the actual pressures coming on pipes from fills. Last spring Mr. Shelly resigned and Dean Marston was appointed in his stead as representative for the American Society for Testing Materials and elected by the Committee as its chairman.
The investigation at the Engineering Experiment Station of the Iowa State College to determine the pressures of earth on pipes under conditions similar to those of railroad and highway work has been in progress and two experiments completed. The details of these and the results obtained will be published in a Bulletin at an early date by the Engineering Experiment Station. A pipe 42 inches in diameter was used and the embankment carried to a height of twenty feet. In a general way the results indicate considerably greater pressures than have heretofore been assumed or considered probable and that the pressure increases in proportion to the increase in the height of the fill above the pipe. The Engineering Experiment Station intends to continue this investigation, as it is not felt that the results so far obtained are sufficient to afford an authoritative answer to the question, and that considerable more experimental work is necessary.
The information gained has been made available for the immediate use of the Committee and will be a valuable help in its work.
OUTLINE OF WORK FOR THE ENSUING YEAR
C. C. Westfall, Chairman; R. ARMOUR, T. L. CONDRON, RICHARD L.
The following outline of work is recommended for next year's work: 1. Study the Manual and submit proposed revisions thereof.
2. Continue representation on Joint Committee on Standard Specifications for Concrete and Reinforced Concrete and report progress and recommendations thereon.
3. Continue representation on Joint Committee on Specifications for Concrete Pipe and report progress and recommendations thereon.
4. Study and report on factors causing deterioration of concrete structures.
5. Report on distribution of loads and impacts through ballast and embankments as affecting the design of masonry structures.
6. Study and report on the developments in the art of making concrete.
7. Recommend a carefully considered outline of work for the ensuing year.
COMMENTS ON TENTATIVE REPORT OF THE JOINT COMMITTEE ON CONCRETE AND REIN
Samuel T. Wagner, Chief Engineer, Philadelphia & Reading Railway
The Joint Committee on Standard Specifications for Concrete and Reinforced Concrete are to be congratulated upon the promptness with which they have presented their first progress report. When the efforts of the original Joint Committee on Concrete and Reinforced Concrete are considered, which was in 1904 and finished its labors in 1916, the promptness of the existing Committee is especially commendable.
The difficulty in the preparation of the present report it is believed lies in the fact that it is not as easy to prepare a specification as it is to set down items of recommended practice on which a specification could be based. In a general way what is now presented has very many commendable features and if all of the conclusions are accepted as facts, it will be comparatively easy for an Engineer to prepare a specification for any particular kind of work. It is believed that the present report bears the earmarks which characterized so many of the reports of the American Society for Testing Materials at the 1921 convention; that is, that the majority of the conclusions are based on research work rather than on the personal experience and opinions of the members of the Joint Committee.
The following are a few of the points which appear to deserve some comment. No attempt has been made to cover the section devoted to
(III) QUALITY OF CONCRETE.-A distinct innovation is introduced in this Section, in that the Engineer is to specify the strengths required for the concrete in the various parts of the work based either upon preliminary test or upon the view given in Table IV. From the theoretical and scientific standpoint, this is, of course, ideal, as it recognizes the various uses to which the method is applied. It contemplates much more testing and of a much more elaborate kind than has ever been used in general practice and particularly upon work of moderate size and how it will work out practically is an open question. The theoretical idea is sound.
The proposed use of the slump test for determining consistency is a decided step forward in the proposed specification. It is an easy test to make on the work and after the proper amount of slump is determined for any piece of work, it is a simple matter to test the consistency frequently, and thus keep check on it. This is a very difficult operation without such a test. The use of mortar tests of a fine aggregate, using either briquettes, cylinders or prisms, compared with similar tests of Ottawa sand is believed to be the only adequate manner of determining its quality and is sure to exclude from important work many grades of finé aggregate which should never be used and which could not otherwise be detected.