LAO ANNUAL REPORT 
Crushing Strength Tests, in Pounds Per Square Inch. 
A B C 
Cement ie af a no 2 
mixture. eS 3 2 ; 2 
Hy 3 tH as} u as} 
3 B 3 5 3S 5 
f f c G g E 
Neat 2.724 ies | ois | aa | Bes” | BONG 
il 2 il 2.168 2153 | 2,445 | 2314 | 6468 || 28116 
Ib ic} | 667 553 748 317 810 CE 
Addition of Portland Cement to Slag.—It has become quite a 
practice in Europe to add Portland cement to granulated slag in place of 
the slaked lime; since this addition produces a much better product, less 
sensitive to rapid drying conditions in setting and of a much higher all 
around strength, besides eliminating the troublesome slaking and handling 
of the lime. The Portland cement is either bought or made from the 
slag at hand, mixed and ground together with limestone in the proper 
Portland cement proportion. Such a mixture of granulated slag is called 
by the Portland cement manufacturers an adulterated Portland cement 
and not without justice. It must be evident that such a cement should 
never be sold under the name of Portland cement, but should be given a 
distinctive name, clearly indicating its character. If the cement cannot 
stand upon its own merits, it should not attempt to borrow credit from 
the Portland cement. In Europe this product is called “Iron Portland 
@enrentam 
Dr. Passow has investigated the effect of adding Portland cement 
to the granulated slag and has obtained the following results. All tests 
are 1:3 standard sand mixtures and have been made after 28 days. 
; a Tensile strength 
Mixture. in pounds per 
square inch. 
Portland cements (iiee3) tren eaere ase eis nerf ope auern ire oper a en aeae 327.1 
77% Portland cement -+ 23% granulated slag (1:3)......... 448 .0 
54% Portland cement + 46% granulated slag (1 :3)......... 484.9 
Portland cement -++ 30% fine ground sand(1:3)............. 301.5 
‘These tests all show plainly that the granulated slag does not play the 
role of a mere inert substance like sand, but effects a decided increase in 
tensile strength. | 
It cannot be questioned that the addition of Portland cement furnishes 
an ideal substitute for the slaked lime, and there enters into consideration 
