SPECIFICATIONS FOR PORTLAND CEMENT. 621 



time may be required. The contractor shall keep in storage, in sacks 

 or barrels, such stocks of cement as the engineer shall require, free of 

 expense to the United States, for sampling and testing during a period 

 of twenty-eight days. 



8. Shipment. The engineer shall give notice in writing to the con- 

 tractor of the approximate requirements for cement shipments and of 

 dates for sampling. In all cases the contractor shall be responsible for 

 the delivery of the cement in good condition at the place of consignment. 



9. Factory inspection. The Government engineer, or his author- 

 ized agent, shall at all times have liberty to inspect the materials, 

 process of manufacture, and daily laboratory records of analyses and 

 tests at the cement works. 



10. Fineness. Ninety-five per cent by weight must pass through 

 a No. 100 sieve having 10,000 meshes per square inch, the wire to be 

 No. 40 Stubbs wire gauge; and 75 per cent by weight must pass through 

 a No. 200 sieve having 40,000 meshes per square inch, the wire to be 

 No. 48 Stubbs wire gauge. 



11. Specific gravity. The specific gravity of the cement shall not 

 be less than 3. 



12. Soundness. Pats are to be made of neat mortar of normal 

 consistency. The pats are to be molded on glass plates. They are to be 

 circular in shape, 3 inches in diameter, inch thick in the center, and 

 drawn to a thin edge at their circumference, and are to be kept under 

 a wet coth, or in a moist atmosphere, until finally set. One pat is to 

 be put in water, the temperature of which is to be raised to the boiling- 

 point and kept at that point for six hours. If the pat softens, cracks, 

 warps, or disintegrates, the cement is unsound. 



13. Time of setting. The cement shall not acquire its initial set in 

 less than forty-five minutes, and must acquire its final set within twelve 

 hours. The pats made to test the soundness may be used in determin- 

 ing the time of setting. The cement is considered to have acquired 

 its initial set when the pat will bear, without being appreciably indented, 

 a wire -% inch in diameter loaded to weigh one fourth pound. The 

 final set has been acquired when the pat will bear, without being appre- 

 ciably indented, a needle V mcn m diameter loaded to weigh one pound. 



14. Making briquettes. In making briquettes, neat cement mortar 

 of normal consistency will be used. The mortar will be thoroughly 

 mixed with a trowel and kneaded into the molds with the thumbs, a 

 blunt stick, or a plunger. Six briquettes will be made from each sample. 

 In making sand briquettes, the proportions shall be one part by weight 

 of cement to three parts of standard crushed quartz sand and about 



