76 STANDARD SPECIFICATIONS 



grease. All mil] scale shall be removed by hammering the metal, 

 or preferably by pickling the same in a weak solution of muriatic 

 acid. 



328. Placing of Reinforcement. The metal reinforcement 

 shall be placed and kept during the deposition and tamping of 

 the concrete in the proper position. Whenever it is practicable 

 it shall be placed in position first. This can usually be done 

 where the metal occurs in the bottom of the forms, by supporting 

 it on transverse wires or otherwise. 



329. Ingredients. The contract covering any reinforced 

 concrete work shall specifically state the quality of the cement 

 and the aggregates and, if possible, the particular brands of 

 cement, sand, gravel, or broken stone to be used; shall state the 

 exact proportions of cement and aggregates and the approxi- 

 mate proportion of water to be mixed, and the required strength 

 in compression to be attained in 28 days by test cylinders 8 

 in. in diameter and 16 in. long. 



Methods of measurements of the proportions of the various 

 ingredients, including the water, shall be used, which will secure 

 separate uniform measurements at all times, preferably by 

 weight. 



330. Mixing by Hand. (See Par. 312.) 



331. Mixing by Machine. (See Par. 313.) 



332. Consistency. The materials should be mixed wet 

 enough to produce a concrete of such a consistency as will flow 

 into the forms and about the metal reinforcement, and, at the 

 same time, can be conveyed from the mixer to the forms without 

 separation of the coarse aggregates from the mortar. 



333. Placing of Concrete: 



(a) Before placing the concrete care shall be taken to see 



that the forms are thoroughly wetted and the space 

 to be occupied by the concrete is free from debris. 



(b) Great care must also be taken to insure the coating of 



the metal with cement mortar and the thorough flushing 

 of the bottoms of the forms with same; after which the 

 concrete must be deposited rapidly, thoroughly com- 

 pacting it around the metal. 



(c) Concrete, after the addition of water to the mix, shall 



be handled rapidly, in as small masses as is practicable, 

 from the place of mixing to the place of final deposit. 



