IX, A, 2 Reibllng and Reyes: Portland Cement Materials 137 



Table VII. — Physical properties of plastered and seasoned cements 5, la, 



2a, and 3a. 



Teat. 



Fineness: 



Per cent through the 100-mesh sieve 



Per cent through the 200-mesh sieve— 



Specific gravity (dried at 100° C.) 



Per cent water required for normal consistency - 



Soundness in air, water, and steam 



Time of setting in hours: 



Initial set 



Final set 



Tensile strength in pounds per square inch: 



1-day, neat mortar 



7-day, neat mortar 



28-day, neat mortar 



7-day, 1 : 3, Ottawa-sand mortar 



28 -day, 1:3, Ottawa-sand mortar 



No. 5. 



97.4 

 88.7 

 3.13 

 21 

 « sound 



4 

 6 



505 

 650 

 695 

 310 

 340 



I 

 No. la. No. 2a. 



98.7 

 78.4 

 3.13 

 21 

 » sound 



3.4 

 6.5 



395 



675 

 795 

 268 

 320 



98.8 

 77.2 

 3.19 

 21 

 » sound 



3.2 

 5.4 



393 

 540 

 640 

 232 

 390 



No. 3a. 



96 



77 



3.16 



21 



» sound 



2.7 

 5.9 



477 

 735 

 765 

 300 

 355 



" The perfect soundness of the steamed pats is shown in Plate I. 



The results obtained with No. 5 are as satisfactory in general 

 as those obtained with the first four mixtures. The modified 

 mixtures also produced cements which passed all of the require- 

 ments of our standard specifications for Portland cement. 



The principal object in testing these modified mixtures was to 

 ascertain the effects of the changes in the hydraulic moduli, 

 and therefore the other conditions of manufacture and testing 

 were maintained as nearly constant as possible. Slight devia- 

 tions might be expected on account of the unavoidable variations 

 in mixing, burning, and grinding and the personal equation in 

 testing. However, the results showed only slight differences 

 between the physical properties of cements 1 and la or between 

 3 and 3a, and as these were all very good cements the four 

 experiments show that the raw materials used are capable of 

 producing good Portland cement regardless of considerable 

 variation in the hydraulic moduli and unavoidable changes in 

 the conditions of manufacture. 



On the other hand, there is a very marked difference between 

 the setting properties of cement 2, which was very satisfactory, 

 and cement 2a, which required 3 per cent of plaster and 

 considerable seasoning. Additional experiments showed that 

 cement 2a, containing 2 per cent of plaster, failed to become 

 desirably slow setting while undergoing thorough aeration for 

 a period of seven days, although the specific gravity fell to 3.09. 



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