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REPORT OF CANVASSING COMMITTEE OF VOTES
CAST BY LETTER BALLOT

Vote on the adoption of the proposed specifications for Asphalt Macadam Pavement as submitted to the 1925 convention: Yes, 99; noes, none; not voting, 1.

E. R. KINSEY,

W. W. HORNER,

C. L. HAWKINS.

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Chapter XII

BRICK PAVEMENTS

SPECIFICATIONS COMMITTEE-1925

GEO. F. FISK, Chairman..

E. A. FISHER.

ALDEN CHASE.

COMMITTEE REPORT

. Buffalo, N. Y. . Lakewood, Ohio .St. Louis, Mo.

The Brick Committee of the American Society for Municipal Improvements respectfully submits the following report:

The last conference on Elimination of Unnecessary Sizes and Types of Paving Brick held at Washington, D. C., on March 20th, 1925, recommended the elimination of one more size of paving brick, namely 3" x 32" x 8" wire cut lug brick (Dunn) leaving the following four sizes as the recognized sizes and types of paving brick:

Plain Wire Cut Brick (as usually laid)

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We recommend that the present specifications for brick paving be continued as standard, and also that the Society approve the recommendation of the Permanent Committee on Simplification of Varieties and Styles of Paving Brick of the United States Department of Commerce.

GEORGE F. FISK, Chairman.

MEMBER: I second the motion.

MR. FISK: I will make that as a motion.

CHAIRMAN POOLE: Is there any discussion on the motion? You have heard the motion. All those in favor make it known by signifying aye; contrary minded, no. The motion is carried.

Chapter XIII

CEMENT CONCRETE PAVEMENTS

SPECIFICATIONS COMMITTEE-1925

E. E. BUTTERFIELD, Chairman...

CLIFFORD OLDER.

GEO. D. FAIRTRACE.

H. E. BREED..

O. LAURGAARD.

.Long Island City, N. Y. ...Chicago, Ill.

COMMITTEE REPORT

Highland Park, Texas
New York City

. Portland, Ore.

The tentative specifications as printed in the 1924 Proceedings of the American Society for Municipal Improvements form the basis of the Proposed Specifications for Portland Cement Concrete Pavements, which are submitted herewith.

The committee has held two meetings since the Boston Convention, one at Washington in December, 1924, at the time of the meeting of the Highway Research Board of the National Research Council and another in January, 1925, in conjunction with the meeting of the American Road Builders' Association in Chicago.

A new section on "Recommendations on Design" has been added, and the text has been rearranged to conform to the relocation of matters pertaining to design. The section of joint fillers has been made more definite and specific as to requirements and methods of test.

Your Committee believes that the proposed specifications will serve as a safe guide to engineers in charge of the design and construction of concrete pavements, within the limits stated in the report on the tentative specifications:

"Realizing the practical difficulty, or impossibility in the preparation of a universal specification for concrete pavements to meet the varying conditions in different sections of the United States, your Committee has attempted to establish certain minimum requirements in design, proportions and reinforcement to meet average normal conditions. The engineers in charge of design may determine in each particular case just how far above

these minimum requirements it will be necessary to go in the matter of slab design, richness of mix, and quantity of reinforcement.

H. ELTINGE BREED,

GEORGE D. FAIRTRACE,
O. LAURGAARD,
CLIFFORD OLDER,

E. E. BUTTERFIELD, Chairman.

PROPOSED SPECIFICATIONS FOR PORTLAND CEMENT CONCRETE PAVEMENTS

Introduction. These specifications are intended to cover average conditions for concrete and reinforced concrete pavements. Throughout the speifications certain minimum requirements, which have been known to give satisfactory results for average conditions, are used. For other conditions of traffic and for unusual conditions of subgrade and drainage it will be necessary for the engineer to make provisions for such conditions by increasing the requirements for the thickness of pavement and the quantity of reinforcement.

I. RECOMMENDATIONS ON DESIGN

The principles of the design of concrete pavements as outlined herein have been evolved gradually from independent sources by observation, experiment and theoretical considerations, and are assembled in this section for the convenience and guidance of the engineer. While the equations are based on sound physical principles, they are in reality only reasonably safe approximations when applied to concrete slabs.

(1) Pavement Cross Section. It is recommended that the thickness of all pavement slabs for distance of at least two feet from any unsupported edge over which maximum wheel loads may pass, be not less than that determined by the following equation: 3P

f

in which t =thickness of slab in inches

(Equation 1.)

P-maximum wheel load in pounds
f=allowable fiber stress of concrete in tension,
pounds per square inch.

The maximum wheel load to be provided for is one-third (%) of the total weight of the loaded truck, on the assumption that two-thirds (%) of the total load is distributed over the rear axle and that the tread of each rear wheel bears one-half (2) of the rear axle load. The allowable fiber stress of the concrete should not be greater than one-half (%) of the modulus of rupture. The modulus of rupture should be determined on test specimens of the concrete as mixed for the work. For concrete complying with the minimum requirements of these specifications (Section V, paragraphs 16-19), a modulus of rupture not greater than 500 lbs. per sq. in. may be assumed, so that ƒ would be 250 lbs. per sq. in. The thickness of the slab at a distance of four (4) feet or more from an unsupported edge may be reduced to seventenths (7/10) of t, or the thickness may be represented by a double parabolic curve decreasing from t at the unsupported edge to 0.7t at the center.

(2) Width and Length of Pavement Slabs. The width of the pavement is necessarily determined by traffic and economic conditions. It is recommended that, when conditions do not justify the paving of the whole area of the street between curbs, the minimum width of pavement shall be twenty (20) feet. It is recommended that the maximum size of slabs of plain concrete. shall be twenty (20) feet in width by twenty-five (25) feet in length, and of reinforced concrete twenty (20) feet in width by sixty (60) feet in length.

(3) Reinforcement. It is recognized that one of the functions of steel in pavement slabs is to prevent the widening of contraction cracks, and it is believed that the steel may also aid in the prevention or diminution of cracks formed during the period of curing. The relief of the first condition may be accomplished by using sufficient steel so that, when contraction of the slab takes place, the steel across a crack or joint, located midway between the edges or joints, will not be over-stressed because of the friction developed between the pavement and subgrade. It is recommended, therefore, that the area of both transverse and longitudinal steel be proportional in accordance with the following equation,

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