SAND-LIME BRICK. 331 
burning, while the presence of moisture or steam lowers the 
temperature at which limestone is decarbonated. Wood is the 
fuel which is best suited technically for burning limestone. Coal, 
to give the best results, should be high in volatile constituents, 
hydrogen, and calorific value, and low in fixed carbon, sul- 
phur, and ash. 
LABORATORY METHODS. 
In testing the siliceous materials, the following general method 
of making sand-lime brick was used. When necessary, the sand 
or crushed stone was dried in the air and ground to almost its 
final degree of pulverization. Then 10 per cent by weight of 
dry, pulverized, hydrated Montalban lime was ground with part 
of the siliceous material, and the whole thoroughly mixed before 
and after the addition of water. The mixture was then molded 
into bricks under pressure as indicated in the tables, and finally 
the bricks were subjected to the action of live steam at a pressure 
of 125 pounds per square inch (8.79 kilograms per square centi- 
meter) for five and one-half to eight hours, as specified. 
The first experiments were made to ascertain only the general 
adaptability of the available raw materials, and no attempt was 
made to secure better conditions and results than would have 
been obtained had the material been subjected to an ordinary 
commercial process for the manufacture of common brick. In 
fact, it was our desire to make the test a severe one, and for this 
reason the bricks were molded at the low pressure of 4,600 pounds 
per square inch or less, steamed only five and one-half hours, and 
no attempt was made to secure the greatest density or most 
desirable fineness. After this, the materials were tested under 
more favorable conditions in order to ascertain their fitness for 
the manufacture of face brick, tiles, ornamental stonework, fire 
brick, etc. We have not had sufficient time to make a detailed 
study of each material such as would enable us to subject each to 
ideal conditions of manufacture, and the results obtained and 
recorded throughout this paper can be, and in many instances 
have been, improved by more thorough mixing, better granu- 
larimetric composition, and a higher molding pressure. 
P. L. Simson has pointed out that the ordinary American 
method of testing the strength of bricks on their largest flat 
surface gives about 30 per cent higher results than the German 
method of dividing the brick in two and placing one-half above 
* Cem. & Eng. News (1912), 24, 160. 
PPE SONGS 
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