624 CEMENTS, LIMES, AND PLASTERS. 



Concrete-steel Engineering Company.* 



No cement will be allowed to be used except established brands of 

 high-grade Portland cement which has been in successful use under 

 similar conditions to the work proposed for at least three years, and 

 has been seasoned or subjected to aeration for at least thirty days before 

 leaving the factory. All cement shall be dry and free from lumps, 

 and immediately upon receipt shall be stored in a dry, well-covered, 

 and ventilated place thoroughly protected from the weather. If 

 required the contractor shall furnish a certified statement of the chem- 

 ical composition of the cement and of the raw material from which it is 

 manufactured. 



The fineness of the cement shall be such that at least 90 per cent 

 will pass through a sieve of No. 40 wire, Stubbs gauge, having 10,000 

 openings per square inch, and at least 75 per cent will pass through a 

 sieve of No. 45 wire, Stubbs gauge, having 40,000 openings per square 

 inch. 



Samples for testing may be taken from every bag or barrel, but 

 usually for tests of 100 barrels a sample will be taken from every tenth 

 barrel. The samples will be mixed thoroughly together while dry, 

 and the mixture be taken as the sample for test. 



Tensile tests will be made on specimens prepared and maintained 

 until tested at a temperature not less than 60 F. Each specimen will 

 have an area of 1 square inch at the breaking section and after being 

 allowed to harden in moist air for twenty-four hours will be immersed 

 and maintained under water until tested. 



The sand used in preparing test specimens shall be clean, sharp, 

 crushed quartz retained on a sieve of 30 meshes per lineal inch, and 

 passing through a sieve of 20 meshes per lineal inch. In test speci- 

 mens of one cement and three sand, no more than 12 per cent of water 

 by weight shall be used. Specimens prepared from a mixture of one 

 part cement and three parts sand, parts by weight, shall after seven 

 days develop a tensile strength of not less than 170 Ibs. per square inch, 

 and not less than 240 Ibs. per square inch after twenty-eight days. 

 Cement mixed neat from 20 per cent to 25 per cent of water to form 

 a stiff paste shall, after 30 minutes, be appreciably indented by the end 

 of a wire inch T V in diameter loaded to weigh \ Ib. Cement made into 



* The specifications from which this section is taken were published in Cement, 

 vol. 4, pp. 105-108, May, 1903. They are for concrete-steel structures on the 

 Melan, Thacher, and Von Emperger patents. 



