Owner-Built Home & Homestead
(Page 11 of 15)
An interesting use of sawdust as an aggregate was developed not long ago by Carl Fabritz, in Germany. He uses a formula (full details available from me upon request) that gives a product with a lightweight-granular composition, using readily accessible raw materials. A proportion of sawdust and cement is first mixed, and to this is added a froth-forming agent (soapy water), with a small proportion of waterglass before agitation. Although somewhat involved, a multicellular composition is produced as follows. Moisture is withdrawn from the mixture by the frothing action; in fact, so much is withdrawn that the walls of the froth globules are not supported by the binder (cement). As a result, the binder coats the grains of sawdust. The waterglass functions to support the froth globule walls, holding the grains in suspension until all moisture is evaporated. When evaporation is complete the binder sets, and the froth globules gradually burst. The result is a low cost, lightweight, strong and well-insulating composite product.
RELATED CONTENT
Fabritz's technique for producing a lightweight concrete product is but one of a number of air-entraining developments of the past forty years. Air-entraining was first employed to improve the resistance of concrete to weathering, especially to freezing and thawing conditions. The cellular composition of air-entrained concrete creates a greater resistance to the passage of capillary water. The minute air bubbles act as a sponge, providing spaces where the factors that generally cause concrete disintegration can be dissipated. Air-entrained concrete is not significantly lower in strength, less water and cement are needed, and the workability is improved. The major advantage of air-entrained concrete, however, is that it is lightweight, and has a corresponding high insulation value.
Some air-entraining agents require special mixers, as, for instance the English "Aerocem" and John Rice's "Bubblestone." The Rice apparatus for making a cellular concrete product was first patented in 1937. It consists of a series of perforated cylinders, one within another, which revolve about a horizontal axis inside a cylindrical tank. As the perforated inner cylinders revolve, air is introduced directly into the slurry, and this air is "trapped" by a froth composition of phenols and aldehydes dissolved in water. Vinsol resin is another commonly used air-entraining agent.
A somewhat less involved procedure for achieving cellular concrete is to mix a suitable lightweight aggregate directly into a mixture. There are a number of such aggregates on the market, and natural deposits can be found. Several years ago a Texan built a complete house—walls, roof, and floor—with diatomaceous earth as the sole aggregate (diatomaceous earth is formed from the decayed skeletons of tiny marine life, and deposits are scattered over wide sections of this country). In 1952 an experimental building using this aggregate was built at the University of Idaho. The 24 by 48 structure cost $2.85 a square foot (as contrasted with estimates of $5 to $8 a square foot using conventional materials). Proportions were 1 cement, 1 1/2 diatomaceous earth, and 6 to 8 parts wood shavings from a planer mill.
Page:
<< Previous 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 | 11 |
12 |
13 |
14 |
15 |
Next >>
