PHYSICAL PROPERTIES OF PORTLAND CEMENT. 



603 



contact with carbon dioxide. The mass was then dried, reground, mixed 

 with half its weight of calcium sulphate and 33 per cent of water, and 

 made up into rods, which were kept moist and protected from carbon 

 dioxide by storage on moistened filter paper under a glass bell. At 

 the end of three weeks the increase in length of the rods was measured, 

 with the following results: 



TABLE 233. 

 EFFECT OF ALUMINA. 



It will be noted that the percentage of elongation of the rods, varied 

 directly with the percentage of alumina in the cements tested, proving 

 conclusively that the swelling was due to the action of the calcium 

 sulphaluminate formed during the operation. 



STANDARD METHODS OF TESTING, AM. SOC. C.E. 



A Committee appointed by the American Society of Civil Engineers 

 to examine methods of making cement tests, offered a progress report 

 early in 1903, and a brief supplementary report in 1904. These reports 

 have been combined and are presented below. 



Standard Methods of Cement Testing. 



SAMPLING. 



1. Selection of sample. The selection of the sample for testing is 

 a detail that must be left to the discretion of the engineer; the number 

 and the quantity to be taken from each package will depend largely 

 on the importance of the work, the number of tests to be made and the 

 facilities for making them. 



2. The sample shall be a fair average of the contents of the packing; 

 it is recommended that, where conditions permit, one barrel in every 

 ten be sampled. 



3. All samples should be passed through a sieve having 20 meshes 

 per linear inch in order to break up lumps and remove foreign material; 



