126 
The Philippine Journal of Science 
1921 
The foregoing specification has been superseded by that pub- 
lished in the third edition of Circular 33, issued January 18, 
1917. The latter United States Government specification for 
the testing of Portland cement has been in force in the Philippine 
Islands since May 24, 1918, and is effective at the present time. 
For the purpose of comparison, the new requirements are here 
given. 
CHEMICAL LIMITS 
2. The following limits shall not be exceeded: 
Per cent. 
Loss on ignition 4.00 
Insoluble residue 0.85 
Sulphuric anhydride (SOa) 2.00 
Magnesia (MgO) 5.00 
SPECIFIC GRAVITY 
3. The specific gravity of cement shall be not less than 3.10 (3.07 for 
White Portland cement) .• 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. 
FINENESS 
4. The residue on a standard No. 200 sieve shall not exceed 22 per cent 
by weight. 
SOUNDNESS 
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. 
TIME OF SETTING 
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. 
TENSILE STRENGTH 
7. The average tensile strength in pounds per square inch of not less 
than three standard mortar briquettes composed of one part cement and 
three parts standard sand, by weight, shall be equal to or higher than the 
following : 
Age at 
test. 
Storage of briquettes. 
Tensile 
strength, 
pounds 
per 
square 
inch. 
Days. 
7 
28 
1 day in moist air, 6 days in water 
200 
300 
1 day in moist air, 27 days in water 
