Fig. 73.—Standard Clay Pipe Specials.
Courtesy, Blackmer and Post Manufacturing Co.

In Fig. 73 are shown the various forms of vitrified pipe and specials which are ordinarily available on the market.

The life of vitrified clay sewers and some observations on the results of the inspection of the sewers in Manhattan are discussed in Chapter XII. The strength of vitrified sewer pipes is shown in Table 37.

TABLE 37
Strength of Sewer Pipe
Strength in pounds per linear foot to carry loads from ditch filling material such as ordinary sand and thoroughly wet clay, with the under side of the pipe bedded 60° to 90° by ordinary good methods. From Proc. Am. Society for Testing Materials, Vol. 20, 1920, page 604.
Height of Fill Above Top of Pipe, FeetBreadth of the Ditch a Little Below the Top of the Pipe
1 Foot2 Feet3 Feet4 Feet5 Feet
Ditch Filling Material
sandclaysandclaysandclaysandclaysandclay
226528061563597099013301,3501,6901,710
4400450105511251745182524552,5353,1653,250
6470545137015002370252534053,5754,4604,740
8505605160017902875311542154,4955,5955,890
10525640176520153275361049005,2956,5907,020
12535660188021853600403054856,0007,4608,035
14540675196523203855438059756,6208,2258,950
16545680202524254065467563957,1658,8909,775
18545685207025054230492067507,6309,48010,520
20545690210025654365513070508,0609,99511,190
22545690212526104470530573058,42510,44511,795
24545690214026454560544575258,75010,84012,340
26545690215026754630557577059,03511,18512,830
28545690216026954685568078609,28011,49013,270
30545690216527154725576579909,50011,75513,670
Very great5456902180277049106230872511,07513,63517,305

92. Cement and Concrete Pipe.—Although there is no general recognition of a difference between cement and concrete pipe, there is a tendency to term manufactured pipe of small diameter cement pipe, and large pipes or pipes constructed in place, concrete pipe. Cement, unlike clay, is used in the manufacture of pipe in the field or by more or less unskilled operators in “one man” plants. Great care should be used in the selection of cement, aggregate, and reinforcement for precast cement pipe since the shocks to which it is subjected in transit are more liable to rupture it than the heavier but steadier loads imposed on it in the trench.

The United States Government, various scientific and engineering societies, and other interested organizations have collaborated in the preparation of specifications for cement and cement tests. These specifications can be found in Trans. Am. Soc. Civil Engineers, Vol. 82, 1918, p. 166, and in other publications.

The following abstracts have been taken from the proposed tentative specifications for Concrete Aggregates, of the Am. Society for Testing Materials, issued June 21, 1921:

1. Fine aggregate shall consist of sand, stone screenings, or other inert materials with similar characteristics, or a combination thereof, having clean, hard, strong, durable uncoated grains, free from injurious amounts of dust, lumps, soft or flaky particles, shale, alkali, organic matter, loam or other deleterious substances.

2. Fine aggregates shall preferably be graded from fine to coarse, with the coarser particles predominating, within the following limits:

Passing No. 4 sieve100 per cent
Passing No. 50 sieve, not more than50 per cent
Weight removed by elutriation test, not more than3 per cent