88 STANDARD SPECIFICATIONS 



short steel rods embedded with one end in the concrete, and 

 free to slide with the other in embedded gaspipe. 



MATERIALS AND WORKMANSHIP 



364. 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.) 



365. Fine Aggregates. Fine aggregates are sand and screen- 

 ings of either gravel or crushed stone. They shall be graded 

 in size up to such grain which, when dry, will pass a screen hav- 

 ing J-in. meshes. 



366. Coarse Aggregates. Coarse aggregates most suitable 

 for reinforced concrete structures are gravel, broken stone, and 

 hard-burned cinders. They shall be screened and of such size 

 as will be retained on a screen having J-in. meshes, but will 

 pass a J- or 1-in. mesh, the smaller aggregate being used in 

 the fire-retarding coating covering the reinforcement. (Par. 

 359.) 



367. Sand. The sand shall be clean, coarse, and of grains 

 varying in size. It shall not contain clay or loam to the extent 

 of more than one-half (i%) per cent and shall be free from any 

 other foreign matter. 



368. Gravel. The gravel shall be composed of reasonably 

 clean pebbles of hard and durable stones of sizes not exceeding 

 J in. in diameter, free from clay and other impurities. To main- 

 tain the proper proportions in the concrete mixture it shall be 

 screened and divided into fine and coarse aggregate. (Pars. 365, 

 366.) 



369. Stone. The stone shall be clean, sound, hard, durable, 

 and free from all foreign matters, crushed or broken to sizes 

 not exceeding 1 in. in diameter. Only such stones as will break 

 in approximately cubical pieces shall be used; those, like slate 

 or shale, which break in thin flat pieces, shall be rejected. To 

 maintain the proper proportions in the concrete mixture it 

 shall be screened and divided into fine and coarse aggregate. 

 (Pars. 365, 366.) 



370. Cinders. Hard-burned cinders may be used as the coarse 

 aggregate of a fire-resisting coating. (Par. 359.) They shall be 



