b EFFECT OF WATER ON ROCK POWDERS. 



rock powders when mixed with water to the consistency of a stiff 

 dough and allowed to stand, gradually increase in binding power up 

 to a maximum constant value which is generally reached at the end of 

 twenty-four hours. If, however, this same wet mass is worked or 

 kneaded by hand the binding power rises to a much higher value. 

 These results are easily explainable if we suppose that the action of 

 the water takes place upon the surface of the particles, which soon 

 becomes clogged with the product of the hydrolytic decomposition. 

 A similar case is presented by finely divided metallic lead, which is 

 readily attacked by water at first, the reaction slowing down as the 

 particles film over with hydroxid and carbonate. 



Following up these results, Mr. L. W. Page conducted a series of 

 experiments in which kilogram charges of rock dust were ground 

 with approximately 20 per cent by weight of water in the ball mill for 

 about three hours. At the end of this time the binding power was 

 determined by test and compared with the binding power as obtained 

 in the ordinary way, where the rock dust was ground dry for three 

 hours, mixed with water to a stiff dough, and allowed to stand for 

 twenty -four hours. Almost without exception the binding power has 

 been increased very much by this method of procedure, as is shown in 

 Table I. It has also been found that, having once been developed by 

 wet grinding, the higher cementing value is not destroyed by subse- 

 quent air drying a most important point from the road- building point 

 of view. 



TABLE I. The relative cementing value of various rock samples when ground wet and dry. 



