vin, a, 2 Reibling: Portland Cement 111 



and kilns become minimized when several hundred tons of cement 

 become mixed in the same bin. The skill of the workmen, the 

 kind of kilns and fuel used, the efficiency of grinders and mixers 

 employed, as well as the hardness, purity, uniformity, and chem- 

 ical composition of the raw materials are essential factors which 

 vary more or less at different plants. However, a gradual falling 

 off in quality is usually the result of deliberate intention. The 

 manufacturer can control the quality of his product within 

 reasonable limits ; and, as he knows the character of his cement, 

 no manufacturer unknowingly sends out whole shipments of poor 

 material. 



Manufacturers as a rule are anxious to supply satisfactory 

 material, but they claim that the policy of purchasing from the 

 lowest bidder compels them to direct their main efforts toward 

 cutting down operating expenses rather than toward perfecting 

 their cement. The manager at one plant made this point very 

 clear. When asked if he did not think that better burning and 

 finer grinding would improve his product, he replied : "Certainly, 

 I could increase its efficiency about 20 per cent, and it would 

 cost only about 8 cents per barrel to do so, but the Philippine 

 Government will not pay to have it improved. Our cement passes 

 the specifications as it is, and in order to get the contract we 

 have to figure close to the quality specified. At first we bid 

 only as low as good practice permitted, but, after losing several 

 contracts because cement inferior to ours sold at a few cen- 

 tavos, or even one centavo, less, we had to change our policy." 

 Our own extensive investigations on the physical and chemical 

 properties of Portland cement made the truth of this statement 

 very apparent. For best results, the raw materials must be 

 carefully proportioned, finely ground, thoroughly mixed, and 

 hard burned, and the finished product must be ground to extreme 

 fineness. Therefore, efficiency is obtained only at a correspond- 

 ing expense to the manufacturer, and the practice of awarding 

 contracts to the lowest bidder has tended to limit the quality of 

 the cement and discourage the best manufacturing practices. It 

 also has failed to obtain the best results from the standpoint of 

 relative cost and efficiency. 



Some time ago the Philippine Division of the United States 

 Army advertised for bids on 75,000 barrels of Portland cement to 

 be used for fortification work at Corregidor. The three lowest 

 bids were as follows: 



(a) A Belgian cement at 4.36 pesos per barrel. 

 (&) An American cement at 4.38 pesos per barrel, 

 (c) An English cement at 4.38 pesos per barrel. 



