35G STATE BOARD OF AGRICULTURE. 



title should thou be kept coustantly wet on the surface by spriukling 

 witli water for not less thau sevcu days, for case (a) aud fourteen days 

 for case (b), aud the teuiperature be uiaiutaiued uot lower than 70 

 degrees Fahrenheit in the hardening chamber. After removal from 

 the chamber the tile should be treated as described above for steam 

 hardening, except that the period of storage in the yard should be at 

 least fourteen days. 



Steam and Water Hardening: In cases where it is desired to use a 

 combination of steam and water in hardening the tile, they should be 

 hardened in the chamber under conditions described above for steam 

 hardening, until such time as they are sufficiently hard to permit piling 

 one on top of the other. They may then be removed to a sprinkling 

 chamber where they will be at all times protected from drafts of air. 

 Here they must be kept constantly wet on the surface by sprinkling 

 for a period of at least two days for case (a), and for at least seven 

 days for case (b). The temperature in the sprinkling chamber should 

 be maintained not lower than 70 degrees Fahrenheit for the periods 

 mentioned. After removal from the sprinkling chamber, the tile should 

 be treated as described for steam hardening, except that the period of 

 storage in the yard should be at least tweut3^-oue days. (In cold 

 weather this method of hardening permits handling a large output with 

 smaller facilities than does steam hardening alone, and is recommend- 

 ed.) 



It may appear that an unwarranted amount of space has been given 

 to a discussion of proper hardening methods, but this is a very import- 

 ant stage in the manufacture, since neglect of this final precaution or 

 slighting it in any way is quite likely' to nullify the effects of care taken 

 in other steps of the process of manufacture. 



Knowledge of what actually takes place in the hardening of cement 

 is still somewhat limited. More complete knowledge of these processes 

 will undoubtedly develop better methods in the manufacture of cement 

 drain tile. However, with the knowledge now at hand, there seems to 

 be no reason why sound tile which will withstand ordinary soil condi- 

 tions cannot be made; and one would expect that such tile, if properly 

 made aud hardened before placing, should become better rather than 

 poorer in the drain. But, unless the manufacturer has facilities for 

 bringing into use all of the best possible materials and methods, he 

 should not undertake tile manufacture, even for his individual use. 

 The investment of labor and material required to place a drain is 

 enough to warn one against the risk of using poor tile. The best are 

 none too good. 



In all of the foregoing discussion the recommended practice to be 

 followed in the manufacture of plain concrete pipe aud drain tile by 

 machine, as adopted by the American Concrete Institute, has been 

 kept in mind. These recommendations may seem rigid but serve to 

 show that in order to produce a satisfactory tile, considerable knowl- 

 edge of the processes of manufacture is necessary and that careful ob- 

 servance must be made of a number of important requirements. 



