THE INTEEPRETATION OF CEMENT ANALYSES. 267 



The INTERPRETATION op CEMENT ANALYSES, 

 Including a new Method of Recording Results. 



By W, M. Hamlet, f.c.s., f.i.c. 



[Read before the Royal Society of N. S. Wales, November 7, 1894.^\ 



During the past twenty years the value of cement testing by 

 chemical analysis has declined somewhat in the estimation of the 

 engineer and the practical man, owing partly to the ready means 

 afforded by improved appliances for measuring the amount of 

 strain any given cement-briquet be can be made to bear; and partly 

 owing to the difficulty encountered in the correct interpretation 

 of the results of the chemical analysis. 



Now, however, I venture to think there are signs of a revival 

 of interest in the chemistry of Portland cement, which will doubt- 

 less lead towards a better appreciation of the minute structure 

 and composition of this useful material. 



To those who had not utterly discarded cement analyses as 

 altogether useless, the good cements — that is, those cements that 

 were found to survive the Deval bath and other severe physical 

 tests — showed on analysis the following general results : — ■ 



58-62 per cent, of lime 



20 - 24 „ silica 



7J „ alumina 



3 J ,, iron oxide 



3 — 10 „ subsidiary constituents 



The bad or indifferent cements showed varying deflections from 

 this standard, and contained notable quantities of magnesia, 

 sulphates and other useless bodies. 



A fresh impetus is given to the subject by Le Chatelier,* who 

 proposes the equation now bearing his name, in which 



* Recherches Experimentales sur la constitution des mortiers Hydraul- 



iques. 



