SAND-LIME BRICK. 319 
aggregate makes such work expensive, but in spite of this and 
the great need of a cheap and durable building stone the sand- 
lime brick industry has not been introduced into these Islands 
in any form. 
The latest and best methods for the manufacture of artificial 
sandstone place the process midway between a quicklime and a 
cement industry, and important technical considerations are in- 
‘volved. The most efficient methods of quarrying and burning 
limestone, of slaking lime, of mining and grinding the raw ma- 
terials, and of molding and hardening the products have not yet 
been determined. Also, the effect of impurities such as clay, 
feldspar, and dehydrated kaolin have not been thoroughly inves- 
tigated. However, sufficient information is available to insure 
the commercial value and feasibility of this industry in the 
Philippines if it is carefully and conservatively managed after a 
proper selection of a factory site, raw materials, process of 
manufacture, and machinery. On the other hand, if the cost 
of production includes large items for “promotion,” “secret 
formulas,” etc., the stability and success of the enterprise are 
questionable. 
This laboratory is carrying on a thorough investigation to 
ascertain the suitability and relative efficiency of available raw 
materials for the manufacture of sand-lime bricks and to study 
some of the most important technical considerations involved. 
This work is far from complete, but owing to numerous requests 
for data on the subject the publication of these preliminary notes 
seems advisable. The information herein contained is not in- 
tended to cover all the possibilities and processes of the industry 
nor the technical conditions involved. A discussion of these 
points may be found elsewhere.® 
CARBONATE BINDER. 
Previous to 1880 lime-mortar bricks were manufactured simply 
by molding a stiff mixture of sand and slaked lime by hand 
and then exposing it to the sun and air. The hardening process 
involved depends primarily upon the conversion of calcium hy- 
droxide into calcium carbonate. It is slow and comparatively 
expensive, as several months’ time and a very large percentage 
*Peppel, S. V., Bull. Geol. Surv. Ohio (1906), 5. Hssais sur le Silico 
Caleaire, by E. Leduc, current numbers of Cem. & Eng. News, and the 
Tonnd.-Ztg. 
= 
SNL es 
