Owner-Built Home & Homestead
(Page 10 of 15)
The term "composite" has been chosen here to categorize the wide variety of building products made up of two or more materials. For the most part, either common cement or emulsified asphalt is used as a structural base, weatherproofing element or binding agent. A "filler" element is used to provide body and insulation.
RELATED CONTENT
Practically any readily available waste material can be simply processed for composite padding to serve as a composite filler, or aggregate. For example, in the Midwest section of our country, ground-up corn cobs have been successfully used as a filler for concrete; in the South, rice hulls have proved advantageous as a concrete filler; in the Northwest, sawdust has long been used as a concrete aggregate. The use of these and other materials will be discussed below, in demonstrating the practical value of composite construction practices.
"Cobcrete" samples made and tested at a Michigan agricultural college were found to have a relatively low thermal conductivity (3.0 k) and a sufficient compressive strength for average building requirements (1000 lbs. p.s.i., where 600 lbs. p.s.i. is the generally required minimum). Either cast-in-place or pre-cast blocks of this stuff can be fabricated. Fresh, dry cobs are first ground into pellet form by a farm hammer mill. After screening to the desired range of 1/8 to 1/4 inch, the cob-pellets are placed in burlap bags and soaked in water for at least 6 hours. Following a 4 hour draining period, Cobcrete is made by a mixture (in these proportions) of 1 cement, 2 sand, 3 cob-pellets, and 1/4 lime.
A cement and rice hull block house (the first in this country) built in 1923, at Payne, La., still stands in excellent condition. Experiments at Louisiana State University have proved that rice hulls have sufficient strength in compression and tension to meet ordinary structural requirements. Furthermore, cement and rice hull blocks have high insulating properties (being lightweight) and good weathering qualities, so that expansion and contraction of exposed blocks do not cause excessive cracking. A proportion of 1 cement, 4 rice hull ash, and 2 rice hulls was first used to make up these blocks, but later (in 1953) it was found that the addition of clay gave still better results, and then, instead of cement, emulsified asphalt was used as a waterproofing agent in a soil and rice ash mixture. The proportion used was 1 cu. ft. of soil (containing not more than 85% clay, nor less than 40%), 1 cu. ft. of rice hull ash, 3/4 gal. emulsified asphalt, and 2-1/2 gal. water. One-half of the total water and the total emulsified asphalt required is first placed in a mixer and allowed to mix for 3 minutes. The soil is then added, followed by the rice hull ash and the remaining water. The average density of this composite is 70 lbs. per cu. ft . which compares very favorably with adobe (100-120 lbs. per cu. ft.) and concrete (115-150 lbs. per cu. ft.)
Research in the use of a sawdust-cement composite for building construction started in 1930 at Oregon State College. It was found that the admixture of 1% diatomaceous earth resulted in a far superior product. Like the cob-pellets in Coberete, sawdust should be previously soaked. A proportion of 1 cement, 1 sand, 3 sawdust and 1/2 clay or lime has proven satisfactory for either block or poured-in-place walls.
Page:
<< Previous 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 | 10 |
11 |
12 |
13 |
14 |
15 |
Next >>
