

NEW rORK si MUSEUM 



PORTI.AXD CEMENT 



A Ground to ordi 

 nary fineness 

 A N finely 



.ud 



B 



* •••• 



D 



I ••• 



F 



U 



HARDENED IN AIR 



it cement 



Normal mixture 

 1 to a 



HARDENED IN WATER 



it cement 



Normal mixture 

 1 to 3 



Time of hardening, in days 



-.555 



-.ii.V, 

 -.101 

 -.075 



-.117 

 -.125 



28 00 



-.121 



-.134 



-.106 



-.16 





-.26 



-.lis 



-.OTf) 



— .125 



-.195 



-.12 



-.175 





-.321 



— .234 





-.019 



-.01 



-.025 



—.015 



—.015 



—.ON 



23 90 



-.034 



-.043 

 —.074 

 -.02 

 -.073 



-.07.-. 



-.032— .072 

 — .015— .058 



-.086 



-.06 



-.123 



—.068 



-.09 



— .11 



-.12 



+ .021 



+ .027 

 + .008 

 +.005 

 + .005 

 + .027 

 + .035 

 +.025 



28 90 



+.037 



+ .027 +, 

 +.013 + 

 + .02 + 



+ .012 + 

 + .048 + 



+ .048 +.006 



+ .03 1 ) 

 + .035 



-i 



008 



01 

 01 



019 

 086 



053 



+ .018 

 + .005 

 + .03 

 + .005 

 + .007 

 + .015 



28 90 



+ .012 +.088 



005 



01 

 086 



02 

 + .013I+.02 



017|+.O2 



033 +.035 



+ .08 



+ .005 



+ .043 



+.019 



Fineness 



An the qualitv of a cement is improved by grinding, it is com- 

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

 it improves the quality 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 is seldom carried 

 to this point. 



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

 lue 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. Johnson states 1 that u The proportion 

 of the cement wliieli passes ft neve of less than about 100 meshes 

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

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



termimng the fineness now generally used on the continent of 



1 M <>i construction, p. 410. 



