Concrete Ideas

This was a very frustrating, but very beneficial exercise. Although I thought I had thought of everything ahead of time, clearly I had not. . .




I constructed a tapered spandex tube with a galvanized ring at either end. The galvanized ring at the base is meant to be left in place as a third mediating material between the concrete column and the floor; the concrete will bulge over the ring, and slightly obscure it. 4 acrylic dowels bisect the plan of the column at 3" intervals.












The revised acrylic dowel - washer detail.

I changed this detail from the previous experiment by adding a piece of plastic tubing and a secondary washer to allow for the zip ties to be removed even if the concrete bulges a lot.









The acrylic rods bisecting the spandex form work














Salvaging wood from a skid, I constructed a wooden scaffold to support the from work until the concrete set.
















After much cursing. . .


Not at all what I had hoped for. Gravity is a force that is difficult to overcome when working with a liquid contained in a flexible membrane. The spandex stretched more than I had accounted for; the concrete kept flowing downwards and the bottom kept stretching outward.














Some parts were successful though


















Notice the fabric texture





























The DETAIL















What I have learned from this test:

I have switched from a 100% spandex fabric to a 10% spandex microfibre fabric which is less stretchy.

Stitching in the form work reduces the stretch of the material and can be used to add reinforcement to counteract the stress of the liquid concrete.

Massaging the concrete through the form work gets rid of "honeycombing" in the concrete; the breathability of the fabric allows air bubbles to escape.

The fabric is easiest removed 24 hours after pouring when the fabric is still damp.