PART IX 



PORTLAND-CEMENT CONCRETE 



THE following specifications for Portland-cement concrete 

 were adopted in 1904, as standard by the American Railway 

 Engineering and Maintenance of Way Association, see Pro- 

 ceedings, Vol. V. 



307. Cement. The cement shall be Portland, either American 

 or foreign, which will meet the requirements of the standard 

 specifications adopted by the American Society for Testing 

 Materials. (See Part VIII.) 



308. Sand. The sand shall be clean, sharp, coarse, and of 

 grains varying in size. It shall be free from sticks and other 

 foreign matter, but it may contain clay or loam not to exceed 

 5 per cent. Crusher dust, screened to reject all particles over 

 J in. in diameter, may be used instead of sand, if approved by 

 the Engineer. 



309. Stone. The stone shall be sound, hard, and durable, 

 crushed to sizes not exceeding 2 in. in any direction. For rein- 

 forced concrete, the sizes usually are not to exceed in. in any 

 direction, but may be varied to suit the character of the rein- 

 forcing material. 



310. Gravel. The gravel shall be composed of clean pebbles 

 of hard and durable stones of sizes not exceeding 2 in. in diam- 

 eter, free from clay and other impurities except sand. When 

 containing sand in any considerable quantity, the amount 

 per unit of volume of gravel shall be determined accurately to 

 admit of the proper proportion of sand being maintained in the 

 concrete mixture. 



311. Water. The water shall be clean and reasonably 

 clear, free from sulphuric acid and strong alkalies. 



312. Mixing by Hand : 



(a) Tight platforms shall be provided of sufficient size to 

 accommodate men and materials for the progressive 



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