96 



Bulletin 86 



PIPE MAKING 



THE MORTAR 



The materials for making cement pipe must be of good quality. 

 The cement must pass the standard specifications of the American 

 Society for Testing Materials. A comparatively quick setting ce- 

 ment is desirable. Riverside (California) cement was used at Con- 

 tinental. Four carloads were sampled and tested for strength and 

 fineness. The normal consistency was obtained with 25^^ percent 

 water in 1917 and 24 percent in 1918. 



TABLE III. TENSILE STRENGTH OE RIVERSIDE CEMENT 



TABLE IV. FINENESS OE RIVERSIDE CEMENT, OCTOBER 2, 1916 



The percentage of magnesia (MgO) was 4.1, as determined in 

 June, 1917, and again in June, 1918. 



Users of cement should take samples occasionally and have stan- 

 dard tests made for soundness, strength, fineness, and percentage of 

 magnesia. In every large city there are commercial testing engi- 

 neers, and in Arizona the University offers to make these tests for 

 a moderate charge to cover the cost. 



The sand for cement pipe must be clean, and should be composed 

 of sharp quartz particles. If it comes from gravel beds and is for 

 use on a McCracken or other trowel machine, it should be screened 

 through a half-inch mesh screen, for larger pieces are apt to roll 

 under the action of the packer-head. For tamped pipe, whether 

 made by hand or on one of the tamping machines, a considerable 

 percentage of coarse gravel or broken stone is desirable, for the 

 strength of the pipe is enhanced thereby. All the better class of 

 pipe contractors who tamp are coming to use coarse aggregate with 



