402 REIBLING AND REYES. 



Table XIII. — The influence of aeration on the rapidity of absorption. 



Material. 



Per cent of increase in weight at different ages. 



3 

 days. 



5 

 days. 



15 



days. 



1 

 month. 



2 



months 



3 

 months 



4 

 months 



5 

 months 



6 

 months 



Hard-burned rotary clinker 

 cement (brand 0)_ 



1.3 



1.8 



3.2 



4.6 



6.3 



7.3 



7.6 



7.8 



8.0 



The influence of a difference in the size of the particles is shown by 

 Table XIV (brand G-). The characteristic properties of absorption as 

 related to the fine and coarse particles in commercial Portland cement, 

 are also illustrated by the figures recorded for brand X. 



Table XIV. — The influence of fineness on the rate and amount of absorption. 



i> 



c; 



o a 



•dS 







m 



Fineness. 



w 



O . 



-" a 



t*-i o 



+J> -r-> 

 « P 



P* 



Per cent of increase in weight at different ages. 



w 



03 

 « 

 eo 



■d 



W 



03 



-a 



.-H 



J5 



a 



o 



a 



a 



o 



a 



K 

 rCJ 



+-> 



a 

 o 



a 



CO 



00 



S3 



a 

 o 



a 



CO 



.c 



+^ 

 

 c 



a 



to 



a 

 o 



a 



CO 



G 



N 



(As received commercially.. 

 <Reground to pass a 200- 



l mesh sieve 



(Fine material passing a 



I 200-mesh sieve 



[Coarse material retained 

 1 on a 200-mesh sieve 



3.29 



3.50 

 2.70 

 0.55 



0.5 

 1.2 

 1.5 

 0.8 



0.8 

 1.8 

 2.5 

 1.4 



1.9 



3.9 

 4.6 

 3.0 



3.2 

 6.0 

 6.9 

 4.2 



5.4 



9.0 



10.5 



5.5 



7.0 

 11.4 

 13.1 



6.0 



8.0 

 13.3 

 15.0 



6.3 



8.8 

 15.0 

 16.5 



6.4 



9.6 

 16.6 

 18.0 



6.4 



The great differences shown by the last column of Table XIV indicate 

 that the seasoning of cement is more or less confined to the surface of the 

 particles. 



The finer particles of commercial Portland cement usually show a 

 higher, and often a very much higher loss by ignition than the coarser 

 ones. This may be due to greater surface exposure, as well as to the fact 

 that the softest clinker grinds to the finest powder. Consequently, con- 

 clusions on the effects of fine grinding, drawn from experiments in which 

 the fine and coarse material used are separated from the same cement, and 

 where such conclusions are based upon the physical properties of the 

 two cements thus obtained, are apt to be erroneous. Failure to consider 

 the fact that the finer grinding, or regrinding, often increases the per- 

 centage of active lime has also caused confusion and error. 



The effect of the degree of burning upon the absortion of moisture and 

 carbon-dioxide by Portland cement Is a more complicated consideration. 

 It is almost an impossibility to grind two cements exactly to the same 

 fineness; there also is no accurate method for measuring the degree of 



