lime a:nd cement indtjstkies 727 



very slow setting cements for 48 hours. Hydraulic limes and 

 all cements that have not set after 48 hours will be allowed 72 

 hours for previous hardening. 



4 Treatment in the water bath. The previously hardened test 

 samples are placed in a water bath at the ordinary temperature, 

 which is then gradually — in not less than 30 minutes — heated 

 to the prescribed temperature and kept there. After three hours 

 at this temperature the test is interrupted, the test pieces are 

 taken out of the bath, and, after having cooled sufficiently, ex- 

 amined as to their condition. They must not be chilled suddenly 

 by means of cold water. 



For each warm bath test the water must be renewed. The 

 temperature of the bath will be: for Roman cements and hy- 

 draulic limes, 50° C. Portland, slag and pozzuolana cements, 

 100° C. 



5 In order to be considered of absolutely constant volume, 

 the sample must, during the test, remain perfectly sound and 

 entirely free from cracks and warping. If the ball cracks slightly 

 in this test or disintegrates somewhat, it should be considered at 

 least as doubtful, though it might not fail in actual practice. 



This test is not good for natural cements, as they will not 

 stand it in most cases. 



Abrasion test 



This is sometimes applied to neat cement and also to mixtures 

 of cement and sand when they are to be used for flooring. It 

 depends on hardness of cement itself and also on its cementing 

 qualities. 



Jameson states that the grinding machines are of two kinds. 

 A Berlin form is a cast iron disk that rotates 22 times a minute. 

 The cube after seven days' immersion and drying is held on the 

 disk with a clamp weighted to 56 pounds. 308 grains of Napus 

 quartz is put on the plate at the start and at the end of the 15th 

 revolution. After 30 revolutions the cube is weighed and the 

 loss noted. Jameson uses a cube 3 inches on edge, and a coarse 



