226 



TESTS ON CEMENT 



monly used. It is also the one adopted by the technical 

 societies as standard. It consists of a glass flask about 

 30 cm. high. The lower part up to mark a contains 120 

 cu. cm., and the bulb between the marks a and b contains 

 exactly 20 cu. cm. The neck of the flask above the mark b 

 is graduated into A cu. cm. The funnel c inserted in the 

 neck is to facilitate the introduction of 

 the cement. 



Method of Making the Specific-Gravity 

 Test. The method of conducting the 



r specific-gravity test is as follows: 64 g. 



of cement is carefully weighed on scales 

 that should have a sensibility of at least 

 .005 g. The flask, Fig. 7, is filled to the 

 lower mark a with benzine or kerosene, 

 which has no action on the cement, and 

 carefully adjusted precisely to the mark 

 by adding the liquid a drop at a time. 

 | The funnel is then placed in the neck of 

 the flask and the weighed cement intro- 

 duced slowly through it, the last traces 

 of the cement being brushed through 

 with a camel's-hair brush. The funnel 

 is then removed and the height of the 

 benzine read from the graduations, esti- 

 mating to .01 cu. cm. The displaced 

 volume is then 20 plus the reading in 

 cubic centimeters, and the specific gravity 

 of the cement is 64 divided by that quan- 

 tity. For example, suppose that the 

 reading on the flask is .54, then the dis- 

 placed volume will be 20 + .54 = 20.54 and 

 the specific gravity will be 64 -=-20.54 = 3. 116. 



The apparatus must be protected from changes in tem- 

 perature while in use; even touching the flask with the 

 fingers will change the volume of the liquid noticeably. The 

 flask is sometimes immersed in water during tfye tests to 

 prevent these changes of temperature, but this precaution is 

 unnecessary if proper care is exercised. 



FIG. 



