732 



N^EW YOIiK STATE MUSEUM 



PORTLAND CEMENT 

 BRAND 



A Ground to orili 

 nary fineness 



A No so finely 

 ground 



B 



C 



D r 



E 



F 



G 



HARDENED IN AIR 



Neat cement 



Normal mixture 

 1 to a 



HARDENED IN WATER 



Neat cement 



N ormal mixture 

 lto3 



Time of hardening, in days 



-.555 



-.056 

 -. 01 

 -.075 

 -.0 5 

 -.045 

 -.117 

 -.13. 



28 



—.121 



-.106 



—.168 



—.118 



—.125 



-.12 



—.252 



—.234 



90 



—.134 



-.16 



-.26 

 —.075 



— .195 



— .175 



— .321 



.019 



.01 



.025 



.015 



.015 



.028 



.032 



.015 



23 90 



.034 



.043 

 .074 

 .02 

 .073 



-.086 



— .06 

 -.123 

 —.068 



— .09 

 075'— .11 

 072— .12 

 058 



+.021 



027 

 003 

 005 

 €05 

 027 

 035 



28 



+ .(37 



90 



+ .048 +.006 



027 +, 

 013 +, 

 02 |+, 

 012 +, 



+ . 



025|+ 



048 

 03 i 

 035 



-f 



C03 



01 



01 



019 



035 



053 



012 



005 



03 



OOi 



007 



015 



013 



28 90 



+.012 



+.017 



+ .033 



+.005 



+.01 



+.035 



+.02 



+ .02 



+.033 

 I 



+.02 

 + .035 

 + .03 

 +.005 

 + .043 

 +.019 



Fineness 



As tlie quality of a cement is improved by grinding, it is com- 

 mon to test the degree of fineness. Fineness of grinding, while 

 it improves the qnality of the material, also increases the cost 

 of manufacture, up to a point where the increase in cost is more 

 rapid than the increase in quality; but grinding i's seldom carried 

 to this point. 



The test is to pass it through a 100 mesh linear sieve, the 

 residue remaining on the sieve and also the amount that passes 

 through being noted. 



Jameson states that a cement which will pass through a sieve 

 of 625 meshes per square inch and only leave 4-5^ residue on a 

 2500 mesh per square inch sieve is fine enough. 



The degree of fineness is of great importance, for the setting 

 is due to the chemical action that takes place between the finest 

 particles of the cement. eTohnson states^ that ^' The proportion 

 of the cement which passes a sieve of less tham about 100 mesiies 

 to the linear inch does not give any intelligent idea of the sig- 

 nificant fineness of the grinding. In fact, the standard sieve for 

 determining the fineness now generally used on the continent of 



1 Materials of construction, p. 410, 



