PHYSICAL PROPERTIES OF PORTLAND CEMENT. 



591 



In practical use, it may be assumed that at the end of a year the 

 average Portland-cement mortar will have a compressive strength 

 about ten times as great as its tensile strength. 



In Table 225 are given the results of a series of tests carried out 

 at the Watertown Arsenal.* The tensile tests were made on the usual 

 briquettes, the compressive tests on 2-inch cubes, and each average 

 given is the result of ten tests. The cement used was the Peninsular 

 brand, giving the following results for fineness and specific gravity. 



Per cent of fineness : 



Retained on 98X 100 sieve 4.95 



Passed by 98X100 sieve; retained on 174X182 bolting-cloth 19.75 

 Passed by 174 X 182 bolting-cloth 75 . 30 



Specific gravity: 



As taken from barrel 3 . 20 



After mixing with 22 per cent water, setting 7 days in air, 



regrinding, and heating to a constant weight at 110 C . . 2.81 



A chemical analysis of the cement is also given, but is evidently 

 erroneous and therefore will not be quoted here. 



TABLE 225. 

 RELATION OF TENSILE TO COMPRESSIVE STRENGTH. (WATERTOWN ARSENAL.) 



Modulus of elasticity. The determinations of the modulus of elas- 

 ticity given in the following table were made at the Watertown Arsenal. 



* Report on Tests of Metals, etc., at Watertown Arsenal during 1902, p. 511. 

 1903. 



