CHAPTER XXXIX. 

 PHYSICAL PROPERTIES: TESTING METHODS. 



THE utilization of Portland cement does not properly come within 

 the province of this volume, as it is already covered by several excellent 

 books. An extensive and readily accessible literature has been created 

 on the subject of testing methods and testing results; but most of this 

 literature is more important to the professional cement-tester than to 

 the cement-manufacturer or cement-user. In the present chapter the 

 subject of testing will necessarily be considered, but merely incidentally. 

 Stress will be laid, on the other hand, on the general properties which 

 Portland cement develops in use, and attention will be directed to the 

 chemical and physical agencies which operate to disintegrate, or weaken, 

 or destroy the cement, or the structures in which it is used. 



Physical Properties of Portland Cement. 



Portland cement is at present used for many different purposes, 

 and the use to which it is applied seems to be rapidly increasing. Under 

 such circumstances it is necessary to supply a product well-fitted to 

 withstand the various disintegrating agencies to which it may be sub- 

 jected. 



In its ordinary uses, in heavy masonry for example, the cement 

 will be subjected to compressive stresses, but rarely to tensile. When 

 used as a paving material it will encounter transverse stresses and 

 severe abrasion. As a lining material its imperviousness will be tested. 

 In other places, as in gun emplacements for example, it may be sub- 

 jected to severe and often-repeated shocks. 



To these physical agencies of disintegration or destruction, are added 

 chemical agents, which are at times of paramount importance. Works 

 exposed to sea-water, for example, are subject to purely chemical attack 

 which must be guarded against so far as possible. 



The situation might be summed up by stating that cement may 

 fail through defects in its manufacture (internal agencies), or through 



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