18, 2 King: Philippine Concrete and its Aggregates 125 
In Table 5 are recorded typical results of physical tests of 
eight brands of Portland cement that have been used in concrete 
construction in the Philippine Islands. These tests were made 
in the materials testing laboratory of the Bureau of Science in 
accordance with the United States Government specification 
for Portland cement.‘ The requirements of the older specifica- 
tion were in force in the Philippine Islands until May 24, 1918, 
and are abstracted here for convenience in studying the results 
given in Table 5, 
2. In the finished cement, the following limits shall not be exceeded: 
Per cent. 
Loss on ignition for 15 minutes See 4.00 
Insoluble residue och! 00 
Sulphuric anhydride (SO;) 1.75 
Magnesia (MgO) ... 4.00 
SPECIFIC GRAVITY 
3. The specific gravity of the cement shall be not less than 3.10. Should 
the cement as received fall below this requirement, a second test may be 
made upon a sample heated for 30 minutes at a very dull red heat. 
FINENESS 
4. Ninety-two per cent of the cement, by weight, shall pass through the 
No. 100 sieve, and 75 per cent shall pass through the No. 200 sieve. 
SOUNDNESS : 
5. Pats of neat cement prepared and treated as hereinafter prescribed 
shall remain firm and hard and show no sign of distortion, checking, 
cracking, or disintegrating. If the cement fails to meet the prescribed 
steaming test, the cement may be rejected or the steaming test repeated 
after seven or more days at the option of the engineer. 
TIME OF SETTING 
6. The cement shall not acquire its initial set in less than 45 minutes 
and must have acquired its final set within 10 hours. 
TENSILE STRENGTH 
7. Briquettes made of neat cement, after being kept in moist air for 
24 hours and the rest of the time in water, shall develop tensile strength 
per square inch as follows: 
Pounds. 
After 7 days 500 
After 28 days ; ‘ 600 
8. Briquettes made up of 1 part cement and 8 parts of standard Ot- 
_ tawa sand, by weight, shall develop tensile strength per square inch as 
follows: 
Pounds. 
After 7 days ... scant pee 200 
After 28 days 275 
‘United States Government Specification for Portland Cement, Circular 
Bur. Standards 33 (May 1, 1912, and January 18, 1917). 
