CONCRETE SEWER PIPE In the draining of marsh land and for sewer age purposes, pipe made of concrete—if prop erly made—is not surpassed by any other ma terial. Pipe of this kind has been made for many years in Germany, the matrix being Port land cement. Rudolph Hering, a New York engineer, who has investigated the subject, says: "Cement sewer pipe has a competitor in the United States perhaps to a greater extent than elsewhere, in vitri fied clay pipe, which is very extensively made in our country, and is still almost exclusively used for small sewers. As cement pipe can be made cheaper than clay pipe, it is naturally forcing itself into use." Mr. Hering claims the following advantages for concrete sewer pipe over the clay variety: A sectional form can be given them which is more conducive to stability and efficiency than the round form customary in clay pipes.
As vitrified pipe warp in burning, the section is not finished truly circular, and slight projec tions are formed at every joint when the pipes are laid to form a sewer.
As cement pipes have a truer sectional shape than vitrified pipes, they can be given a slant ing butt joint, as is customary in Europe, in stead of the more costly bell and spigot joint common for vitrified pipe, which are made in imitation of cast-iron pipe used under high pressures.
Concrete pipes are tougher and less brittle than vitrified pipes.
Concrete pipes, if well made of proper ma terials, have a strength to resist compressive, tensile, and bursting strains which is amply suf ficient for all purposes for a sewer in a large city. If the materials are carefully selected, the con crete pipe should be as permanent as the vitri fied pipe. Concrete work in the sewers of Paris several hundred years old is as sound to-day as when it was laid.
For the manufacture of concrete sewer pipes, a number of machines are on the market; and when the aggregate used is carefully selected and cleaned, the mixture being of 1 part Port land cement, of sharp, coarse sand, and 4 parts crushed stone not over half an inch in size, a good pipe should be turned out.
Circular forms of steel should be used, and the tamping should be done in the same manner as for concrete blocks.