PACINI, METAMORPHISM OF PORTLAND CEMENT 



Table 26 

 Tensile Strength of 1:4 Mortars, stored in Rock Water 



217 



Water 



Strength, pounds per square inch 



Specimens 

 in average 



Stored in laboratory 



Stored in field 



7 days 



Gain 



28 days 



Gain 



3 mos. 



Gain 



6 mos. 



Gain 



Drinking.. 

 "A" 

 "B". ... 



"C" 



211 

 220 

 203 

 221 



+4% 

 -4% 



+4% 



297 

 312 



287 

 288 



5% 

 -3% 

 -3% 



320 

 323 

 313 

 340 



1% 



-2% 



6% 



324 



247 

 303 

 328 



-24% 



- 5% 



1% 



12,12,6,6 

 12,12,6,6 

 12,12,6,6 

 12,12,6,6 



Table 27 

 Analyses of Rock Waters in Previous Experiments 





Parts per million 



A 



B 



c 





44 

 20 



7 

 284 

 124 

 727 

 826 

 949 



15 

 5 

 399 

 118 

 353 

 546 

 459 



4 

 4 



87 



38 



31 



270 



317 



Si0 2 



Fe,Oo+ ALO, 



CaO 



MgO 



so 3 



CI 



Total solids 



3037 



1895 



751 



The drinking water used to store the blanks contained in neither case 

 more than 100 parts per million of total solids. 



The most consistent reduction of strength, although a slight one, is 

 observed in the case of water B, a fairly typical sulphato-chloride water 

 according to Clarke's classification (18, p. 190). A strikingly high and 

 sudden reduction occurs at six months in water A, a sulphate water 

 charged with hydrogen sulphide, while water C, a chloride water, shows 

 no marked reduction of the strength, which, however, may be due to a" 

 low salinity. 



The six-month briquettes stored in water A showed superficially much 

 minute pitting, due to the removal of the sand grains, presumably by 

 solution of the matrix of the cement. Two sections were cut from one 

 of these briquettes, one transverse and one longitudinal, in the hope of 

 discovering whether any replacement of the original material by sul- 



