178 



RBIBLING AND SALINGER. 



is also higher; these are all factors conducive to the development of high 

 earl}' strength.^'' Comparative tests of lioth sand and neat hriquettes 

 made and preserved in the cold-storage room (17° to 21° C.) and also 

 in the laboratory (26° to 30° C.) gave almost without exception lower 

 results, from 3 to 10 per cent, at the lower temperature. The briquettes 

 broke more uniformly when made at the colder temperature. The differ- 

 ence between the strength developed under both conditions was always 

 slight and within the limits of personal error. 



However, the relatively high temperature of this climate will seriously 

 effect the setting properties of some Portland cements. This is illustrated 

 by Tables XV and XVI (pp. 152 and 153). Fortunatelj^, the setting 

 properties of the majority of cements are only slightly influ.enced by this 

 difference in temperature (Tables XIV and XVII). It is the experience 

 of this laboratory that high alumina cements develop setting qualities 

 characteristic of class 2 (Tables XV and XVI) ; further experimented 

 work is necessary to determine whether this phenomenon holds true only 

 with this class. Wien comparatively fresh, high-alumina cements set 

 slowly at both temperatures (Table XIV), additional seasoning renders 

 them slow setting at first at 17° to 21°, but quick setting at 29° to 31°, 

 and finally quick setting at both temperatures. 



The development of quick setting is marked b}' other peculiar char- 

 acteristics. "\^Tien the absorption of carbonic acid and combined water 

 has progressed sufficiently, no practical amount of water which can be 

 added will retard the rapidity of setting or eliminate the early generation 

 of much heat, but in the earlier stages of seasoning a variation of as 

 little as 0.5 per cent of water in mixing may i^roduce a most remarkable 

 difference in the time of the initial and final sets. This is shown by 

 the following table: ''"^ 



Table XXV. — Showing the effect of varying amounts of water on the time of 



setting. 



Sample No. 



Water. 



Condition. 



Initial 

 set. 



Final 

 set. 



F5-1 



Per cent. 

 21 

 22 

 23 

 22 

 23 



22.5 

 23 



Becomes dry and noncohesive; lieats up 6° in 4 minutes. 



h. VI. 



(•) 



1.5 



1 10 

 20 



1 .30 



15 



1 16 



/(. m. 

 C) 



1 10 



2 25 



1 10 



2 25 

 30 



2 20 



rs-i 



F5-1 



Plastic 



F5-3 





F5-3 . 





F5-5 



do _ - - 



F5-5 



do 







•Impossible. 



.'^Annual Report Chief of Engineers, V. 8. A. (1894), 234. Sabiii, Louis 

 Carlton: Cement and Concrete, New York (1905), 119-120. Alexandre, Paul: 

 Eeoherches Experimentales sur les Mortiers Hj'drauliques. 

 "■See also Table XVII of this paper. 



