142 



CEMENTS, LIMES, AND PLASTERS. 



1.75 

 0.50 

 1.00 



85-95 per cent 

 9- 



6 ~ 2 ' 



A third, slightly more detailed, gave the following figures for a plant 

 of 15.000 capacity. 



Sand and lime $} ^ 



Labor 



Fuel and repairs 



Fixed charges 



Total cost per thousand S4 . 35 



Composition of lime-sand bricks. Lime-sand bricks will usually 

 range in composition between the following limits: 

 Silica (SiO 2 ), alumina (A1 2 O 3 ), and iron oxide (Fe 2 O 3 ) . . 



Lime (CaO) and magnesia (MgO) 



Water 



The bulk composition of the product is therefore a fairly definite 

 matter and not subject to discussion. The point concerning which 

 there is a definite disagreement is as to the manner in which the above 

 constituents are combined in the brick. The more ardent advocates 

 of lime-sand brick claim that most of the lime is combined with part 

 of the silica as a calcium silicate, and support this contention by pre_ 

 senting analyses showing the presence of noticeable percentages of 

 soluble silica. In the opinion of the present writer this contention is 

 not proven. All that we know concerning the character and formation 

 of the various silicates of lime seems to point in the opposite direction. 

 So far as known no lime silicate can be formed except at very high tem- 

 peratures, 900 C. or thereabouts. 



Physical properties of lime-sand bricks. Lime-sand bricks are 

 sufficiently strong, when subjected to direct compressive strains, for 

 all ordinary structural purposes. Many of them, however, are very 

 fragile and require careful handling both in transportation and on 

 the work. 



The following comparison has been made * by Peppel between 

 lime-sand bricks and a series of natural sandstones tested by the Wis- 

 consin Geological Survey. 



TABLE 52. 

 LIME-SAND BRICKS vs. NATURAL SANDSTONE. (PEPPEL.) 



* Trans. Amer. Ceramic Society, vol. 5, p. 31 of pamphlet edition. 



