20 BULLETIN 704, U. S. DEPARTMENT OF AGRICULTURE. 



SPECIFICATION Ct-1. 



Portlomd Cement. 



Definition. d) Portland cement is the product obtained by finely pulverizing 



clinker produced by calcining to incipient fusion an intimate and prop- 

 erly proportioned mixture of argillaceous and calcareous materials, with 

 no additions subsequent to calcination except water and calcined or un- 

 calcined gypsum. 



I. CHEMICAL PROPERTIES. 



Chemical 

 Limits. 



(2) The following limits shall not be exceeded : 



Per cent. 



Loss on ignition 4.00 



Insoluble residue . 85 



Sulphuric anhydride (SO3) 2.00 



Magnesia (MgO) 5. 00 



II. PHYSICAL PROPERTIES. 



SpeeilSc Gravity, 



Fineness. 



Soandness. 



Time of 

 Setting. 



Tensile 

 Strength. 



(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 : 



at 

 test. 



Storage of briquets. 



Tensile 

 strength 



per 

 square 

 inch. 



Days. 



7 

 28 



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

 1 day in moist air, 27 days in water . 



Pounds. 

 200 

 300 



Packages and 

 Marking. 



Storage. 



(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. 



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

 brand and namp 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 proppr inspection and identification of each shipment, and in a 

 suitable weather-tight building which will protect the cement from 

 dampness. 



IV. INSPECTION. 



Inspection. (11) Every facility .shall be provided the purchaser for careful sam- 



pling and inspection either at the mill or at the site of the work, as may 



