Thursday, 1 December 2011

December 1, 2011

I'm stuck on pushing translucent concrete sculpture, so I ordered some Rocalite cement additive from Mexico (which I picked up in Nogales last week), and some 2.0 mm Eska plastic fiber optic cable from Circuit Specialists in Mesa, Arizona. The Rocalite retards the cement, so that one can push the fiber optic strands through it before the form hardens.

Ariel and I decided to make a test translucent concrete cube. 2 parts Rocalite to 1 part Portland Cement by weight, to make a dry mix. Then add 4 parts dry mix to one part water, or acrylic medium, by volume:


We cut down a small carton of cream to 2.75 x 2.75 inches:


We zeroed out the scale with an empty measuring cup on top:


300 ml of Rocalite weighed 1 pound:


125 ml of Portland Cement weighed a half a pound:


Ariel blended the Rocalite with the Portland Cement to make 1.5 pounds of dry mix, which filled the carton cube (with very little left over):


Ariel then added acrylic medium to the dry mix:


1 part acrylic medium, to 4 parts dry mix by volume --115 ml of arcylic medium, to 460 ml of dry mix:


However, after adding the arcylic medium in, the mix was far too dry. Therefore we added enough water to make it more pastey (did we add too much water? The instructions say no more than 4: 1.25, dry mix to water by volume):


The resulting cement was wetter than clay, but only stood on its own in small forms. And it broke like dryish bread dough (maybe if one added more acrylic medium, instead of water, he would have a better chance of sculpting with the cement):


The carton swelled after we added the cement, and lost its form. Therefore we put rubber bands around the carton to make the cube more rigid:


I cut the fiber optic cable in small pieces, which Ariel then pushed through the cement cube:


We spent a half hour pushing the plastic fiber optic strands into the cement cube (larger), and they went through easily.

3 hours later I could press my thumb and fingers into the tiny cube (to the right), but it was getting pretty hard. 6 hours later the tiny cube was pretty firm and cold, but not strong.


Ten meters of fiber optic cable did not fill the whole cube, when placed in a dense pattern. That cable probably cost about $30, so this translucent cement is expensive.

One might push cheaper translucent materials through the cement to save money and arrive at different effects.

The next day we demolded the cement cube. It was hard, but I wondered if it would crumble under some pressure. I thought it might need a few more days to cure.

The plastic fiber optic strands did not reach all the way through to the bottom of the cube. Ariel said that he pressed the strands all the way to the bottom, but only the pattern of the carton shows on the bottom:


5 days later we cut the cement cube, to expose the fiber optic strands on the bottom (Dec 5):


Finally! Light passing through the cement block:

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