540 



CEMENTS, LIMES, AND PLASTERS. 



In the experiments * of Nihoul and Dufossez a commercial Portland 

 cement of the following composition was used: 



Silica (Si0 2 ) 22.80 



Alumina (AlgO^ 7 . 79 



Iron oxide (Fe 2 O 3 ) l - 27 



Lime (CaO) 65.80 



Magnesia (MgO) 0.59 



Carbon dioxide (CO 2 ) 1 .36 



Water 0.20 



It is to be noted that this cement, though probably made in a sta- 

 tionary kiln, is very high-limed and correspondingly quick-setting. 

 It can therefore be considered as closely similar to the average rotary 

 clinker. 



03/0 



FIG. 136. t Effect of plaster on setting-time. (Sabin.) 



TABLE 198. 



EFFECT OF ADDING VARIOUS PERCENTAGES OF CALCINED PLASTER. 

 (NlHOUL AND DUFOSSEZ.) 



Composition. 



Pure cement 



Cement with 1 per cent plaster. 



" 2 



" 3 



" 4 



" 5 



Initial Set. 

 Hours. Minutes 



10 

 40 



7 

 51 





 33 



Final Set. 

 Hours. Minutes. 



13 

 20 

 

 32 

 50 

 10 

 12 



* Journ. Soc. Chem. Industry, vol. 21, pp. 859-860. 1902. 

 t From Johnson's "Materials of Construction", p. 187. 



