184 



REIBLING AND SALINGER. 



exposure to air." Sample number 8 contained 2.38 times as much silica 

 as alumina, and its actions supports Meade's conclusion. 



Cements which contain less alumina and more silica than sample 

 number 8 withstand exposure much better. All of the five different 

 cements recorded in Table XXVI below, failed in setting time and 

 tensile strength when their seasoning had progressed as indicated by 

 the "loss on ignition" column. However, number 5 withstood aeration 

 the best. It was only after it had stood exposed to the air for .a very 

 long time and had united with 6.36 per cent of water and carbonic acid 

 that it failed. 



Table XXVI. 



Constituent. 



Cement 1. 



Cement 2. 



Cement 3. 



Cement 4. 



Cement 5. 



Cement 5, 

 ignited. 



Silica (SiO.) 



Alumina (ALO3) 



Iron oxide (FeiOa) 



Lime (CaO) 



Magnesia (MgO) 



Moisture (110°) 



Loss on ignition (water and 

 carbonic acid). 



Sulphuric acid (SOj) 



Carbonic acid (00^) 



!■ cent. 



20.65 

 S.57 

 3.07 



61. 8S 

 2.26 

 0.41 

 2.47 



0.51 

 0.78 



Per cent. 

 20.70 

 8.42 

 3.01 

 61.60 

 1.94 

 0.34 

 2.76 



0.59 

 0.43 



Per cent. 



22.0 

 8.9 

 3.0 



59.9 

 1.55 



Per cent. 



20.52 

 8.71 

 2.65 



61.30 

 1.96 

 0.88 

 4.33 



0.46 

 3.04 



Per cent. 



21.28 

 6.95 

 2.29 



61. 08 

 0.21 

 0.72 

 6.36 



L17 

 4.36 



Per cent. 



22.9 



7. 5 



2.5 



65.7 



0.2 



1.26 



Seven and 28 day mortar briquettes (1 to 3), as the seasoning of the 

 cement progressed, gave the following tests of tensile strength: 



7-day. 



28-das'. 



Loss on 

 ignition. 



236 

 187 

 172 



320 

 247 

 211 



Per cent. 

 2.97 

 4.53 

 6.36 



Contrary to this behavior, number 4 gave the worst results and a very 

 plastic paste made from it set in fifteen minutes with a rise in temperature 

 from 29° to 38°. 5 C. Cements numbered 1 and 3 showed only 2.47 

 and 2.76 per cent loss on ignition resj^ectively and yet they were quick 

 setting. 



By further investigations of this nature we hope to prove what brands 

 of Portland cement in particular are best suited to withstand tropical 

 climatic influences best. At present we feel justified in drawing the 

 following conclusions as being conducive to the best results and practice 

 for all cement operations in this and similar regions. 



