LIME AXD CEMENT IXDUSTKIES 



703 



No. 



Kesults of Candlot in 1S91. 1 



MORTAR 



Xeat cem. briq. 



Days 



( 28 

 1 ceni. to 3 sand briq . . . i 



Per cent of 



plaster paris 



added 



Strength of sand briq 

 per sq. in. 

 8 days 7 days 



[. 1-3 lb. 

 28 days 



• • • 



• • • 



160 



240 



1 



• • • 



212 



298 



2 



• • • 



167 



254 



• • • 



174 



285 



307 



.5 



225 



305 



344 



1 



227 



320 



408 



1.5 



230 



381 



399 



2 



182 



290 



400 



2.5 



184 



295 



390 



3 



115 



235 



360 



SULFATE LIMB 







0% lb 1* 



2% 



u 



4 



485 645 



533 



435 



264 



673 738 



674 



790 



483 



223 252 



263 



185 



126 



333 377 



377 



367 



201 



Lewis considers these results remarkable as regards strength 

 and not explained. 



Cements high in alumina have a tendency to expand and to 

 blow or to check. Magnesia is also supposed to cause expansion 

 after a lapse of a considerable interval, while sulfates are looked 

 on as causes of disintegration of Portland cement when exposed 

 to sea water. Cements low in lime and without an excess of 

 alumina but high in silica are simply of low strength like under- 

 burned cements. If the alumina goes above Sfc, it is considered 

 high, if below 5$, it is considered very low. Mr Richardson 

 considers that over 3$ of magnesia is an excessive and undesirable 

 quantity, and the proper limit for sulfuric acid is \\i. The fol- 

 lowing are the percentages of magnesia and sulfuric acid in Port- 

 land cements which have been placed on American markets dur- 

 ing the past few years. 



1 Ciments et chaux hydrauliques. Paris 1891. p. 254. 



