122 The Philippine Journal of Science ms 



Good packing is insisted upon in order to prevent properly 

 stored cement from serious deterioration. Perfect soundness 

 (no warping, checking, cracking, or disintegrating after the 

 hot test) is also essential, and it might be advisable, as recom- 

 mended by H. J. Farce, 10 even to substitute the more severe auto- 

 clave test for steaming or boiling under ordinary pressure. 



It is useless to insist upon soundness unless we also take into 

 consideration the specific gravity (or the loss by ignition). We 

 can season an underburned cement, or a cement made from 

 poorly mixed or coarsely ground raw materials, until it passes 

 the accelerated tests for soundness ; not, however, without a cor- 

 responding reduction in the specific gravity and increase in the 

 loss by ignition. Likewise, we can not rely upon the specific 

 gravity or loss by ignition without taking into consideration the 

 soundness. A nonseasoned Portland cement usually has a high 

 specific gravity regardless of whether it is underburned or hard 

 burned and regardless of the amount of free lime present. 

 Therefore, a bonus is provided for perfect soundness in conjunc- 

 tion with a high specific gravity (or a low loss by ignition) 

 for the purpose of securing a well-burned product. 



Another bonus is provided for superiority in strength in order 

 to induce a careful selection and regulation of the raw materials. 

 Ordinarily it would not be advisable to base a bonus on the 

 strength developed in twenty-eight days. If a cement contains 

 more than a very small quantity of hard-burned free lime, then 

 no reliance can be placed on the results of the early tests for 

 strength. However, well-burned cements show little or no de- 

 crease in strength with age; and, since it is specified that no 

 bonus will be awarded unless the cement is well burned ; that is, 

 unless it has a high gravity (or low volatile constituents) and 

 is perfectly sound, no bonus would be granted except for superior 

 permanent strength. 



In conclusion, it may be stated that certain manufacturers, to 

 whom the proposed bonus system has been submitted, have ex- 

 pressed their willingness to cooperate on such a basis. The 

 agent of one company has written as follows : 



The advantages to be secured from such a system as suggested are of 

 so pronounced a nature to both the purchaser and to the contractor that it 

 is not necessary to enlarge on them. The. manufacturers would have every 

 inducement to produce cement above the minimum requirements set by the 

 specifications, and the bonus would undoubtedly cover the extra cost in- 

 curred for special care in packing, burning, and grinding. In the majority 



10 Eng. News (1911), 67, 1111. 



