PHYSICS, CHEMISTRY AND ENGINEERING 



159 



consistency, termed "standard consistency," required that the 

 percentage of water used in gaging the mixtures be from 37 

 to 39 per cent by weight of the total weight of the water and 

 gypsum used in the specimen. 



All the compression specimens tested were cylinders hav- 

 ing a height of twice the diameter. These were used be- 

 cause it has been found 3 that with specimens of this form 

 slight variations in the dimensions of the specimen cause less 

 variation in the strength than with specimens whose height 

 is equal to the diameter. Also it is believed that the speci- 

 mens used give strengths more nearly representative of what 

 may be developed in a structural member than would a 

 shorter specimen. A specimen whose height is equal to its 



260O 



2400 



(5 400 



200 

 o 



3x6-in. Cy//nJerj-ft//riDri<2(//<X?7: 



... 6x/2-/r>. " 



3X6- In •' Ail* •' 70'F 



£&concf &otf/G Gypsum 

 OJ% retarjar- 



5 /O /5 ZO 25 30 35 40 45 50 55 60 



Age at Test in D<?y5. _. _ 



9 y r /a. 2:. 



•See Journal of American Concrete Institute, Vol. 11, No. 6, October-November 

 1914, p. 424. 



