For the past couple of days we have worked with cardboard tubes to test both the strength of them as well as their resistance to the natural elements. We found that when the tube is standing vertically and weight is applied directly on top it has a very large strength ratio. Our first run of tests we found that the tube was able to hold over 200 pounds. In terms of the the strength of a tube when it is laid horizontally with two other tubes holding each end up, the weight it holds is dependent upon the span of the tube and it's diameter. For instance, a 36" tube with a 3" diameter has the ability to hold over 160 lbs while a 60" tube with a 1.5" diameter has the ability to hold 59 lbs (equivalent to one CMU block).
In terms of the resistance to the natural elements the cardboard tubes proved to be able to withstand exposure to water. When soaked for 5 minutes the tube resisted the water pretty well. We found that it is still able to support weight, while it is drying and when completely dried it returns back to its original state. When soaked for over 2 hours it begins to decompose and the tube fragments begin to unravel. The results from this test helped us to understand where it is best to apply loads and also that the amount of time that the tubes are exposed to water is a huge factor in their ability to perform.
-Nicole and Ryan
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