■NlAXUrACTURK OF CKMIvXT PipE 101 



satisfactory ; overlapped palm leaves are good. The shed should be 

 close to the pipe machine and on level ground. In moving the pipe 

 from the shed to the stackyard, each length is turned on its side 

 and rolled, care being taken to avoid striking any hard object. 



Nearly all hand-tamped pipe is made and cured in the open air. 

 Here is opportunity for reform. In a humid climate it may be pos- 

 sible to cure pipe in the open, but in Arizona a covering is needed 

 during most of the year. 



In a few cases farmers have rolled their new-made pipe into the 

 irrigation ditch or a creek when the pipe was about three days old. 

 In each case unusually good pipe has resulted. 



Steam curing, as practiced in the Middle West, is exceedingly 

 effective. The green tile are placed on the platforms of low cars 

 and run on tracks into tunnels. When a tunnel is full, the doors 

 are closed tight and saturated steam from a boiler is admitted. The 

 boiler pressure is kept at about 5 pounds. The hot, dripping atmos- 

 phere accelerates the setting and hardening, and makes the curing 

 independent of unfavorable weather conditions, especially freezing 

 temperatures. After 36 hours in a steam chamber the pipe can be 

 loaded and shipped immediately. 



In southern Arizona less difficulty is experienced from freezing 

 than from the extreme heat and dryness of the summer months. 

 One efYect of the dry heat is to make some cements set before the 

 mortar can be placed. During the construction of the Laguna dam, 

 a shipment of California cement persisted in setting in one minute. 

 It was necessary to dig the concrete out of the mixer with chisels 

 and drills. Another California brand gave the same trouble in 

 another locality. The author rejected two carloads of a Kansas 

 cement in 1908, because the cement took its initial set in three min- 

 utes. In this case the author's tests were confirmed by a commer- 

 cial testing firm in Philadelphia. This phenomenon of abrupt set- 

 ting is not well understood, but it is a safe conclusion that the stor- 

 age of cement in hot, dry places for long periods may be dangerous, 

 and furthermore the cement pile and sand pile should be kept as 

 cool as possible in midsummer, possibly by sprinkling the sand pile 

 with water. 



The importance of curing should be emphasized for it is the 

 feature of pipe manufacture that is most apt to be neglected. Un- 

 doubtedly much cement pipe, both hand-made and machine-made, 

 never attains the strength of which it is capable, because it is al- 

 lowed to become dry before the hardening process has progressed to 

 a proper point. 



