A BONUS SYSTEM FOR THE PURCHASE OF PORTLAND CEMENT 



By W. C. Reibling 



(From the Division of General, Inorganic, and Physical Chemistry, Bureau 

 of Science, Manila, P. I.) 



INTRODUCTION 



In the first paper from this Bureau on the subject of Portland 

 cement, 1 the efficiency of modern cement specifications and 

 standard methods of testing were discussed. It was made evi- 

 dent that the ability of a cement to pass even the most approved 

 specifications did not prove either its real or relative value in 

 construction work, and that no tests had been devised which 

 would give definite information about the behavior of cement 

 both before and after induration. Since then information con- 

 cerning the physical and chemical properties of Portland cement 

 has increased, and standard specifications have shown a corre- 

 sponding improvement; but they still leave much to be desired, 

 and both the accuracy of standard methods of testing and the 

 efficiency of standard specifications must undergo considerable 

 change before they will secure the manufacture and purchase 

 of Portland cement having the desired constancy in volume, 

 strength, setting properties, and sand-carrying capacity. 



The weakness of all cement specifications is due largely to the 

 lack of definite knowledge concerning the chemical and physi- 

 cal properties of Portland cement. In fact, the results obtained 

 from standard tests are so little understood that they do not 

 enable us to arrange the various products in their true order of 

 merit. Consequently : 



(1) The chief object of testing is defeated, and it is necessary 

 to specify minimum requirements which are intended only to 

 cover the lowest limits which can be allowed on the work and 

 to provide for lack of uniformity in tests as well as in real 

 quality. 



(2) There is practically no difference between the qualities 

 and properties of a rejected and of an accepted cement in the 

 immediate vicinity of the limit set by specifications; and it is 

 often impossible to avoid the use of inferior material. 



(3) As quality is specified, the enforcement of cement speci- 

 fications usually makes it compulsory to award contracts to the 



Reibling, W. C, and Salinger, L. A., This Journal, Sec. A (1908), 3, 

 137-185. 



107 



