PROPERTIES OF PORTLAND CEMENT. 



403 



fineness. Consequently, no conclusions can be drawn from slight dif- 

 ferences in results. 



The results recorded in Table XV were gained with cements ground in a 

 ball-mill until they gave about the same residue on the 100 and 200-mesh standard 

 sieves ; the well-burned material required the longer grinding. A microscopic 

 examination then indicated little difference in the relative amounts of impalpable 

 powder. Each cement was sieved and divided into two parts, that which passed 

 the 200-mesh sieve being separated from that which passed the 100, but remained 

 on the 200. 



Table XV. — The influence of the degree of burning on the rate of absorption. 



[Figures show percentages.] 



a 



tU 



s 



o 



O 



•a 

 a 



« 



• 



Sample. 



Fineness. 



a 

 o 



'3 



•5P 



>> 

 .a 

 co 

 to 

 o 



Increase in weight at different 

 ages. 



Total increase plus 

 the loss by igni- 

 tion. 



Through a 

 200-mesh 

 sieve. 



Through a 

 100-mesh 

 sieve - 



■o 



tO 



S' 

 ■a 



CO 



to 

 OS 



to 



>> 



CtJ 



-a 



oj 



■a 



00 

 tM 



to* 



Si 



a 

 o 



a 



0» 



Cement ground from un- 

 aerated clinker: 

























Underburned ce- 























ment — 

























Coarse particles.. 



0.0 



100 



0.42 



0.19 



0.53 



1.16 



2.10 



3.39 



3.98 



4.40 





Fine particles 



100.0 



100 



0.52 



0.26 



0.62 



1.48 



2.46 



3.52 



6.19 



6.71 





Well-burned cement- 

























Coarse particles.. 



0.0 



100 



0.30 



0.18 



0.44 



1.05 



2.00 



3.16 



3.60 



3.90 





Fine particles 



100.0 



100 



0.33 



0.35 



0.85 



1.74 



2.83 



4.15 



7.63 



7.98 







Cement ground from 

 clinker which was ae- 

 rated 3 months in the 

 laboratory: 

 Underburned ce- 

























ment- 























Coarse particles.. 



0.0 



100 











0.49 







1.46 



1.91 



"2.09 







Fine particles 



100.0 



100 



2.20 







0.73 







1.83 



3.25 



6.09 



8.29 





Well-burned cement- 

























Coarse particles 



0.0 



100 







0.69 





1.91 



2.89 



3.21 







Fine particles 



100.0 



100 



0.59 







1.33 







3.14 



4.72 



7.89 



8.48 





Underburned ce- 



84.0 



100 



200 







0.89 







2.09 



3.41 



5.95 



7.95 





ment not sieved, 

























+2. 5 per cent 

























plaster. 























a Similar results were obtained with cement ground from brand L clinker. 

 b 64 days old. 



The figures given in Table XV do not show the differences in results we had 

 anticipated. Making all allowance for the possible variations in fineness, the 

 well-burned cement absorbed carbon dioxide and water as readily as the under- 

 burned material. However, when these cements were later subjected to White's 

 free lime test, they all demonstrated the presence of unhydrated lime in consider- 

 able quantity. Three of the four cements also disintegrated during the steam 

 test. 



