140 The Philippine Journal of Science 1917 



Tensile strength. — When 1.50 to 2.00 per cent sulphuric an- 

 hydride has been added, the strength both in neat and mortar 

 decreases with increase of the substance. Four of the cements 

 show a maximum strength with approximately 1.50 per cent 

 sulphuric anhydride, while two show a maximum with about 

 2 per cent. The 90-day briquettes develop maximum strength 

 with a higher percentage of sulphuric anhydride than do the 

 briquettes for the shorter periods. Additional neat and mortar 

 briquettes have been made for periods ranging from six months 

 to five years. No final conclusions can be drawn until the 

 long-time tests are available. In making the calculations, the 

 strengths of briquettes made with the cements as received were 

 taken as 100 per cent/ 4 and the comparison of results were made 

 on the basis of the percentage loss in tensile strength. The per- 

 centage loss in strength caused by placing plaster equivalent 

 to about 10 per cent of sulphuric anhydride in each cement was 

 then studied. The following points become apparent: 



1. With one exception, the percentage loss is greater with 

 mortar briquettes than with the corresponding neat briquettes. 



2. As the age of the neat briquettes increases from seven 

 days, the percentage loss decreases. No definite conclusions can 

 be drawn from the results of the mortar briquettes at present. 



3. No relationship between the chemical composition of the 

 cements and the effect of sulphate is apparent. 



INFLUENCE ON STORAGE FACTORS 



It often happens that a cement is satisfactory at the time of 

 manufacture, but becomes quick-setting or develops some other 

 fault during storage. These alterations may take place grad- 

 ually over a period of several weeks, or in as many days. Some 

 writers are of the opinion that there is some relation between 

 these changes and the sulphuric anhydride content. Accelera- 

 tion tests have been devised to determine in advance some of the 

 changes that may take place in cement during storage. One 

 such test is to spread the cement in thin layers exposed to the 

 moisture and carbon dioxide of the air and test from time to 

 time for soundness and setting time. 15 A test recommended 

 by Hentschel 1C is as follows : Two hundred grams of cement 



11 Brand F was quick-setting as received; so a sample containing 1.46 per 

 cent sulphuric anhydride was taken as the standard. 

 "This Journal, Sec. A (1911), 6, 207. 

 "Hentschel, G., Tonind.-Zeitg. (1912), 36, 557. 



