308 



MASONRY 



sewers, unimportant work in damp or wet situations, or in 

 heavy work in which the working loads will not be applied 

 until long after completion, natural cement may be employed 

 to advantage. Slag cement is best adapted to heavy founda- 

 tion work that is immersed in water or at least continually 



REQUIREMENTS FOR HIGH-GRADE CEMENTS 



damp. This kind of cement should never be exposed directly 

 to dry air, nor should it be subjected either to attrition or 

 impact. 



The preceding tables give the average weights of hydraulic 

 cements and the various requirements for high-grade cements. 



