PUZZOLANIC MATERIALS IN GENERAL. 



637 



Arenes, etc. The materials called "arenes" by early French writers 

 on cement technology are sands and residual material derived from 

 the decay of various igneous rocks, and particularly from the decay of 

 the more basic rocks, such as trap, basalt, etc. Such materials will 

 naturally vary greatly in composition and properties, but all of them 

 agree in possessing feeble hydraulicity. For present-day commercial 

 purposes they are practically worthless. 



TABLE 239. 



ANALYSES OF ARENES, FRANCE. 



1 Lime carbonate (CaCOs). 



1. Saint Astier, Department Dordogne. Vicat, analyst. 



2. Brest. Vicat, analyst. 



3. Saint Servan. Vicat, analyst. 



5. Chateaulin. 



As might be inferred from the examples given, natural materials 

 showing slightly hydraulic properties are not of rare occurrence. With 

 the exception of trass, santorin and pozzuolana proper, these materials 

 are rarely sufficiently hydraulic to be of service as bases for puzzo- 

 lan cements or mortars. The feebly hydraulic materials have, how- 

 ever, a practical value which may be noted briefly here. It is that, 

 owing to the fact that they are hydraulic, they can be profitably sub- 

 stituted in places where they occur for common sand in mortar. 



Chelius has tested * the fine material remaining after the crushing 

 of basalt in an ordinary stone-crusher. This fine material (dust and 

 screenings) gave the following results as compared with normal sand: 



TABLE 240. 

 STRENGTH OF BASALTIC DUST. 



* Journ. Soc. Chem. Ind., vol. 19, p. 826. 



