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Appendix C

PLANS AND SPECIFICATIONS FOR CONCRETE FENCE

POSTS

T. E. Rust, Chairman;

0. H. SESSIONS, ARTHUR ANDERSON, Vice-Chairman; W. C. SWARTOUT, L. B. Curtis,

Sub-Committee.

The Sub-Committee to which was assigned the preparation of plans and specifications for concrete fence posts has prepared and submits herewith plans of round and square concrete line posts and specifications sufficiently general to cover concrete fence posts of any size. The SubCommittee recommends that these plans and specifications be submitted to the Association for information and criticism. Plans for concrete end and corner posts have not yet been prepared.

SPECIFICATIONS.—The specifications herewith submitted follow, in general, the Tentative Specifications for Concrete and Reinforced Concrete of the Joint Committee of this Association, the American Society of Civil Engineers, the American Society for Testing Materials, the American Concrete Institute and the Portland Cement Association, which specifications were submitted to the constituent organizations on June 4, 1921. A great deal of matter not considered applicable to concrete fence posts has been omitted and other things have been added, but the spirit of these Tentative Specifications has been followed quite closely. The reason for following these Tentative Specifications rather than the specifications heretofore adopted by this Association is that the former presumably reflect the latest developments in the art of making concrete. We also considered that it was probable that this Association would, as soon as the Joint Committee submits its final report, adopt specifications very closely following such tentative specifications. The Sub-Committee does not believe that this Association should adopt any specifications for concrete posts at this time and perhaps not until revised specifications for concrete and reinforced concrete have been adopted. The accompanying specifications are submitted for information and for criticism as to their scope, arrangement and special features, so that the Association will have, when such revised specifications for concrete are adopted, a set of specifications for concrete fence posts which will require only minor revision.

PLANS.-- The plans and specifications for concrete fence posts must be considered as a unit. The plans herewith submitted were drawn with the assumption that the materials used and methods employed would be in accordance with the specifications. For this reason the Sub-Committee asks that the plans be not adopted separately, as they are, like the specifications, submitted for information and criticism.

Some information regarding the posts shown on the plans is given in the following table:

Square Post Round Post Average sectional area of post 7 ft. long.....13,915 sq. in. 14,333 sq. in. Sectional area of steel, wire reinforcing. .0984 sq. in. .1232 sq. in. Sectional area of steel, bar reinforcing. .1104 sq. in. .1656 sq. in. Volume of post 7 ft. long....

.676 cu. ft. .697 cu. ft. Approximate weight of post 7 ft. long. 101 lb.

104 1b. Weight of steel, wire reinforcing.

.2.34 lb. 2.94 lb. Weight of steel, bar reinforcing.

.2.63
1b.

3.94

lb. Approximate ultimate strength of post, wire reinforcing

219 lb.

192 1b. Approximate ultimate strength of post, bar reinforcing

219 lb.

224 lb. The "ultimate strength" shown above is the load which, applied at the small end of the post would cause the post to fail as a cantilever beam, the point of support being 60" from the load. The breaking load is calculated by the ordinary formulae for beams reinforced top and bottom, the ultimate strength of cold drawn steel wire being assumed to be 90,000 lb. per sq. in., and of hard steel bars 80,000 lb. per sq. in. In 1917 the Association adopted the conclusion that, “it is not economical to make posts that will have the strength to resist a force of over 200 lb. when the post is tested in the manner above described.” The use of the next smallest commercial size of reinforcing in the posts shown on the plans would reduce the force which the posts could resist to considerably less than 200 lb. and is not advocated. As to the reasonableness of the ultimate strengths of steel referred to above it may be stated that the average ultimate strength of the wire reinforcing in posts tested by Committee IX in 1914 was about 100,000 lb. per sq. in. At that time three round posts 1/2" larger in diameter than the post shown on the plans and reinforced with six No. 8 wires were tested and the average strength found to be considerably in excess of that given above, allowance being made for the difference in size.

In deciding on the size of posts and amount of reinforcing, as shown on the accompanying plans, the Sub-committee was guided by the conclusions already adopted by the Association, the tests made in 1914, theoretical calculations made this year as to the strength of posts of various sizes, and, more particularly, the record of posts now in service. There are nearly a half million round posts in use by railroads, of the size shown on the Committee's plans and reinforced with six No. 8 or No. 9 wires, which are giving satisfaction and the Committee could not justify the use of a larger section or heavier reinforcing. The size and reinforcing decided upon for square posts is such as to give them a strength substantially the same as that of the round posts. The Committce suggests that it might be well, during the coming season, to test posts made in accordance with the plans and specifications herewith submitted and using rods and wires whose ultimate strength and elastic limit have been previously tested. Possibly such tests might result in more definite specifications as to proportions of ingredients and amount of water used in mixing as well as confirming the theoretical calculations as to strength.

The Committee repeats its former conclusions as to the relative merits of round and square posts. Viewed as a beam the square section seems obviously superior. The above table shows a saving in both concrete and steel by the use of square posts. On the other hand the round post is perhaps superior in resisting fire and disintegration. The methods used in the manufacture of round posts have probably been better than those usually employed in the manufacture of square posts, but the Committee can see no reason why the same methods could not just as well be employed in both cases.

The Committee also believes that “U” shaped posts, if properly made and reinforced, will be entirely satisfactory. This type of post has lost favor with railroads more because of improper reinforcing than on account of any defect in the shape of the post, which differs very little from that of a square post. Most of these posts have been reinforced with flat bars, a shape which seems to cause longitudinal cracks in the concrete and which, also, does not give as good adhesion as a round or square bar.

The Sub-Committee is not yet prepared to submit plans for corner, end or gate posts, or methods of bracing end and corner panels. A few examples of such posts and methods of bracing are submitted for information. No two roads, apparently, use the same size of end posts or the same style of bracing.

RECOMMENDED SPECIFICATIONS FOR CONCRETE FENCE

POSTS

(1) MATERIALS 1. Intent. The intent of these specifications and the plans of which they form a part is to produce concrete fence posts having a uniform and sufficient strength and durability at a minimum of cost. On account of the thinness of the section, this can only be accomplished by intelligent and constant attention to securing proper proportions of all ingredients.

2. Cement. Cement shall conform to the present Stanlard Specifications and Tests for Portland Cement of the American Railway Engineering Association and subsequent revisions thereof.

3. Fine Aggregate. Fine aggregate shall consist of sand, stone screenings, or a combination thereof, having clean, hard, strong, durable, uncoated grains, and free from injurious amounts of dust, lumps, soft or flaky particles, shale, alkali, organic matter, loam or other deleterious substances. It shall range in size from fine to coarse, preferably within the following limits : Passing through a No. 4 sieve

not less than 95% Passing through a No. 50 sieve

.not more than 30% Weight removed by decantation

not more than 3%

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4. Coarse Aggregate. Coarse aggregate shall consist of crushed stone, gravel, or combination thereof, having clean, hard, strong, durable, uncoated particles free from injurious amounts of soft, friable, thin, elongated or laminated pieces, organic or other deleterious matter. shall range in size from fine to coarse within the following limits : Passing a 12" screen..

.not less than 95% Passing a No. 4 screen.

not more than 15% Passing a No. 8 screen

..not more than 5% 5. Bank Gravel. Natural combinations of fine and coarse aggregate, in the form of bank gravel, may be used providing its particles meet all the requirements in paragraphs 2 and 3 above, and provided such particles are properly graded from fine to coarse within the following limits : Passing a 1/2" screen.

.not less than 95% Passing a 14" screen.

from 35% to 55% Passing a No. 50 screen..

not more than 15% Weight removed by decantation....

. not more than 172% 6. Water. Water for concrete shall be clean and free from nil, acid, alkali, organic or other deleterious substance.

7. Metal Reinforcement. Steel reinforcement shall be hard steel and shall conform to the present Standard Specifications for Steel Reinforcement of the American Railway Engineering Association or, if wire is used, to the present Tentative Specifications for Cold-Drawn Steel Wire of the American Society for Testing Materials, or to such modifications of either of such specifications as may hereafter be adopted by the American Railway Engineering Association. Reinforcement shall be in the form of round or square bars, preferably deformed, or steel wires. Crimped, stranded or flat reinforcing shall not be used. Reinforcing, before being placed in the molds, shall be thoroughly cleaned of mill and rust scale, and of coating that will destroy or reduce the bond.

(II) PROPORTIONING AND MIXING CONCRETE

8. Proportioning. The unit of measure shall be the cubic foot, One bag of Portland cement shall be considered as one cubic foot. Each of the constituent materials shall be measured separately by volume, using a method which will secure the specified proportions. The water shall be measured by an automatic device that will secure the same quantity in successive batches.

9. Strength. The proportions of cement, water and aggregate shall be such as to produce a concrete having a compressive strength at 28 days of 2,000 lb. per sq. in. The proportions of fine and coarse aggregate to produce such a concrete shall be determined by making a screen analysis of the available aggregates and using such a mixture as will secure a maximum density. To such a mixture sufficient cement shall then be added to produce concrete of the desired strength. If bank gravel is used it shall be screened and remixed, if necessary in order to produce concrete of the desired strength, or if such screening and remixing will produce concrete of the desired strength with enougie less cement so that the saving in the cost of cement wiii ceed the cost of screening and remixing.

10. Consistency. No more water shall be used than is necessary to produce a concrete which can be worked thoroughly into the forms and around the reinforcing. The consistency shall be measured by the slump test in the method described in the 1921 report of the Committee on Masonry, American Railway Engineering Association. The maximum slump shall not exceed 6 inches. The consistency shall be checked up from time to time.

11. Mixing. Mixing shall be done in a batch mixer of approved type, equipped with a suitable charging hopper, water storage, and water measuring device. The entire contents of the drum shall be discharged before recharging. Each batch shall be mixed for not less than 115 minutes after all the materials are in the mixer, during which time the mixer shall rotate at a peripheral speed of about 200 feet per minute. The volume of the mixed batch shall not exceed the manufacturer's rated capacity. The retempering of concrete which has partially hardened shall not be permitted. In cold weather aggregate shall be heated, if necessary, to remove frost and frozen lumps.

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12. General. Before depositing concrete the molds shall be thoroughly cleaned and coated with non-staining mineral oil or other approved material. The mixer should be so located that the concrete can be discharged directly into the molds or conveyed to the molds in such a manner as to cause no separation of the ingredients. Each mold shall be completely filled in one continuous operation.

13. Molds. Molds shall be substantial, rigid, and true to plan. Metal molds are more satisfactory than wooden molds.

14. Placing Reinforcing. The reinforcing shall be securely and continuously held in its proper position in the post during the placing of the concrete and until the post is removed from the mold. Metal spacers that would cause distinct lines of cleavage in the post shall not be used. The reinforcing shall be supported as often as is necessary to prevent its sagging to any appreciable extent due to its own weight or to the weight of the wet concrete.

15. Compacting. Concrete shall be thoroughly compacted into the molds and around the reinforcing. This is best accomplished by giving the molds a jogging or vibratory motion during and after depositing.

16. Finish. All posts shall have a clean, smooth finish. If any pockets or holes are discovered upon removal from the molds, they shall be immediately filled with a mixture of one part cement to two parts fine aggregate. Pockets or holes more than 12 inch in depth or more than Yz-inch in diameter, or any exposure of the reinforcing shall cause the rejection of the post.

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