TESTS ON CEMENT 229 



Inspection. All cement must be inspected, and may be 

 reinspected at any time. The contractor must submit the 

 cement, and afford every facility for inspection and testing, 

 at least 12 da. before desiring to use it. The chief engineer 

 shall be notified at once on receipt of each shipment at the 

 work. No cement will be inspected or allowed to be used 

 unless delivered in suitable packages properly branded. 

 Rejected cement must be immediately removed from the 

 work. 



Protection. The cement must be protected in a suitable 

 building having a wooden floor raised from the ground, or 

 on a wooden platform properly protected with canvas. It 

 shall be stored so that each shipment will be separate, and 

 each lot shall be tagged with identifying number and date 

 of receipt. 



Quality. The acceptance or rejection of a cement to be 

 used will be based on the following requirements: 



Specific gravity: Not less than 3.1. 



Ultimate tensile strength per square inch: POUNDS 



7 da. (1 da. in air, 6 da. in water) 500 



28 da. (1 da. in air, 27 da. in water) 600 



7 da. (1 da. in air, 6 da. in water), 1 part 



cement to 3 parts of standard quartz sand 170 

 28 da. (1 da. in air, 27 da. in water), 1 part of 



cement to 3 parts of standard quartz sand 240 



Fineness: Residue on No. 100 sieve not over 8%, by 

 weight; residue on No. 200 sieve not over 25%, by weight. 



Set: It shall require at least 20 min. to develop initial 

 set, and shall develop hard set in not less than 1 hr. nor more 

 than 10 hr. These requirements may be modified where the 

 conditions of use make it desirable. 



Constancy of Volume: Pats of cement 3 in. in diameter, 

 i in. thick at center, tapering to thin edge, immersed in water 

 after 24 hr. in moist air, shall show no signs of cracking, dis- 

 tortion, or disintegration. Similar pats in air shall also 

 remain sound and hard. The cement shall pass such accel- 

 erated tests as the chief engineer may determine. 



Analysis: Sulphuric anhydride, SO 3 , not more than 

 1.75%; magnesia, MgO, not more than 4%. 



