186 



ANNALS NEW YORK ACADEMY OF SCIENCES 



TEMPEEATUEE OF THE WATEE AT FIBST ADDED 



Two standard cements were gaged with the requisite quantity of mix- 

 ing water for each at different temperatures. The effect upon the time 

 of initial and final set was noted, as follows : 



Table 1 

 Effect of Temperature of Gaging Water on Time of Initial and Final Set 



Per cent by weight 



Temperature of 



Initial set, 



Final set, 



of mixing water 



mixing water 



hours 



hours 



A 



B 



A and B 



A 



B 



A 



B 



22 



21 



70° F. 



4.25 



4.50 



6.75 



7.50 



22 



21 



100° F. 



1.50 



4.00 



4.00 



7.00 



22 



21 



150° F. 



0.33 



3.75 



0.50 



5.75 



22 



21 



212° F. 



1.00 



2.75 



2.75 



6.00 



The results seem to indicate that interference of hydrolytic decompo- 

 sition with the setting appears between 150° F. and the boiling point of 

 water. Below these limits, the effect of increase of tenrperature of the 

 mixing water, as is well known, is to increase the speed of setting (31). 

 The setting time at these temperatures is a resultant of two opposed 

 processes, — the formation of the water crystalline network, and the de- 

 structive hydrolytic action of water upon the original constituents of the 

 cement, resulting in a product which has no hydraulic qualities. 



Where the second process overbalances the first is the point at which 

 the speed of setting ceases to increase and begins to diminish. 



This is true of course of the stage known technically as the final set 

 (9). In the first few hours of setting, there is a period of relaxation, 

 which McKenna has aptly termed reverse set, and which he has been 

 able to detect with precision by means of an ingenious chronographic 

 apparatus of his invention (60). The phenomenon has been observed by 

 the writer and his associates in the laboratory of the Board of Water Sup- 

 ply, using the Vicat needle; but this apparatus does not lend itself to a 

 scientific study of the finer differences in rigidity which occur during the 

 setting period. McKenna's apparatus should throw a great deal of light 

 upon the initial metamorphism of cement. 



TEMPEEATUEE OF THE WATEE THAT MAY SUBSEQUENTLY COME INTO 

 CONTACT WITH THE SYSTEM 



High pressure steam. — Wig (109) has recently presented an account 

 of the excellent effects of high pressure steam when used in curing con- 



