Concrete + rubber bands

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By Josh Thornton, Brandon Pawloske, Marc Hopkins and Eric Meyers

Initiating the concrete + rubber band project, the group decided to look at concrete flexibility based on changes to the mix; such as replacing water with liquid latex, and casting rubber bands within the concrete. After allowing the concrete to cure, the casts were subjected to bending stress tests and while the idea of replacing water with latex made the cured casts very brittle, the rubbers bands added a degree of flexibility that lead the group into different, smaller tests regarding rubber band layouts and their relative strengths when keeping the broken concrete in position. After finding a grid pattern of bands that worked, the team began to question the typical ways that concrete is used, and developed a rubber band grid that allowed ample flexibility. From there, the group worked on creating a mold that would allow easy and quick reproduction of modules by creating a tool to quickly apply concrete to the new surface by spraying onto it.

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Integral to the manufacturing process was the idea of casting a module with rubber bands in it, breaking those casts on specific break lines, and finally using those new modules to form our wall. Due to this process, a sizeable amount of time was used in the development of a mold that was reusable, and allowed for quick and easy setting up of the casts with strung rubber bands and placed inserts for our pre-determined break lines. After quite a few iterations, a final mold was developed that allowed over 8 casts to be produced per day, and reset within a reasonable time even with only one or two people working the molds.

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The second major task that was decided as a necessity to the project was the development of a shotcrete gun. After researching the available commercial stucco sprayers, an initial design was agreed on and prototyped using a garden hose handle and PVC piping with minimal success, but was quickly iterated with a second design that also held marginal success. The final iteration, which ended up being very similar to the first, ended up working very well and sped up the application process of the concrete to our test modules quite significantly, while remaining extremely inexpensive adding a high design value.

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Assembling the wall was quite the task. While the first course of the wall was easy to lay out and support, the remaining courses to lay down were troublesome. The development of a framework was not completely thought out, and looking back, a processes of using the CNC machine to cut out an exact form that acts as support for the wall would have been a much better route to take. The framework that was created was attempted to be used, but did not end up helping the process in any way, and a make-shift supporting element was used to help support the 3rd, 4th, and 5th courses of the wall during construction.  Success thorough failure was the lesson of our formwork.

The design of the wall was conceived in a way that could display the strengths of the concrete modules, allowing them to curve in multiple directions (without a series of complex molds), and also remaining thin, strong, and freestanding. Construction went relatively quickly when supporting elements were determined, as well as the use of pre-combined modules that improved the strength and stability of the wall during construction. Finally, spraying the wall with concrete throughout the construction process increased the strength further, and allowed for one side to have a relatively smooth finish, while the other displayed the modules and broken grid patterns.

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