26 BULLETIN 555, U. S. DEPARTMENT OF AGRICULTURE. 



I. Chemical Properties. 



ii m it s . : (2) The following limits shall not be exceeded : 



Per cent. 



Loss on ignition 4. 00 



Insoluble residue .85 



Sulphuric anhydride (SO.) 2.00 



Magnesia (MgO) 5.00 



II. Physical Properties. 



Specific 

 ity. 



graf- 



Fineness. 



Soundness. 



Time of set- 



tins 



Ten 

 strength, 



s 1 1 e 



(3) The specific gravity of cement shall be not less than 3.10. 

 Should the test of cement as received fall below this requirement, 

 a second test may be made upon an ignited sample. The specific- 

 gravity test will not be made unless specifically ordered. 



(4) The residue on a standard 200-mesh sieve shall not exceed 

 22 per cent by weight.* 



(5) A pat of neat cement shall remain firm and hard, and show 

 no signs of distortion, cracking, checking, or disintegration in the 

 steam test for soundness. 



(6) The cement shall not develop initial set in less than 45 

 minutes when the Vicat needle is used, or 60 minutes when the 

 Gillmore needle is used. Final set shall be attained within 10 

 hours. 



(7) The average tensile strength in pounds per square inch of 

 not less than three standard mortar briquets composed of 1 part 

 cement and 3 parts standard sand, by weight, shall be equal to or 

 higher than the following: 



Age at 

 test 



Storage of briquets. 



Tensile 



strength 



per square 



inch. 



1 day in moist air, 6 days in water. . 

 1 day in moist air, 27 days in water. 



Pounds. 

 200 

 300 



(8) The average tensile strength of standard mortar at 28 

 days shall be higher than the strength at 7 days. 



III. Packages, Marking, and Storage. 



Packages and 

 marking. 



Storage. 



(9) The cement shall be delivered in suitable bags or barrels 

 with the brand and name of the manufacturer plainly marked 

 thereon, unless shipped in bulk. A bag shall contain 94 pounds 

 net. A barrel shall contain 376 pounds net. 



(10) The cement shall be stored in such a manner as to permit 

 easy access for proper inspection and identification of each ship- 

 ment, and in a suitable weather-tight building which will pro- 

 tect the cement from dampness. 



* The United States Government specification requires that on and 

 after July 1, 1918, the residue on the 200-mesh sieve shall not exceed 

 20 per cent by weight. 



