PORTLAND CEMENT TESTING. 



143 



TABlii: III. — ^'ariaiious in the same hrand of cement received in paper tags. 



[Mortar, 1 to 3.] 



Sample 

 No. 



Highest. 



Sample 

 No. 



Average. . 



Sample 

 No. 



Lowest. 



7-aay. 



28-day. 



7-day. 



28-day. 



7-day. 



1 

 2S-day. 



Dl-1 



187 



2C9 



C5-1 



168 



260 



B9-1 



126 



194 



Dl-2 



179 



2.59 



C5-2 



141 



214 



■ B9-2 



166 



240 



Dl-3 



191 



259 



C5-3 



141 



210 



B9-3 



140 



181 



Dl-4 



ISO 



228 



C5-4 



139 



232 



B9-4 



143 



171 



Dl-5 



169 



234 



C.5-5 



144 



202 



B9-5 



106 



125 



Dl-6 



176 



245 



C5-6 



195 



257 



B9-6 



138 



193 



Dl-7 



168 



221 



C5-7 



ISO 



238 



B9-7 



135 



186 



Dl-8 



184 



257 



C5-8 



145 



224 



B9-8 



175 



178 



Dl-9 



174 



234 



C5-9 



168 



204 



B9-9 



103 



181 



Dl-10 



182 



234 



C5-10 



145 



210 



B9-10 



148 



185 



Table IV. — Time of setting. 



Sample No. 



Initial 

 set. 



Final 

 set. 



Sample No. 



Initial 



set. 



Final 

 set. 



B9-1 . . _. 



k. m. 



1 00 



1 30 



50 



48 



35 



k. m. 

 2 00 

 2 30 

 2 10 

 1 33 

 1 10 



B9-6 .. 



ll. V}. 



23 

 50 



ll. m. 

 2 30 

 1 35 



B9-2 



B9-3 



B9-7 _ 



B9-8 



B9-4 



B9-9 . 



48 

 31 



1 27 

 1 38 



B9-5 .. _ 



B9-10 _ _ 









Tlie above results led us to investigate inoie specifically the effect of 

 air exposure on this class of cement. In Talile V the depreciating effect 

 upon the mortar of freely exposing a small amount of cement (about 

 400 grams) to the air in open jars for ten days is clearly shown. All 

 mortar mixtures made from cement fresh from the sample jDackage, 

 dried or undried, and exposed to the air not longer than eighteen hours, 

 did not set before the molding was completed and passed in tensile 

 strength. All mortar mixtures made from cement exposed to the air 

 for ten days, set Ijefore the molding was completed and tlierefore failed 

 in tensile strength. 



