Penny bridges

I first saw coin structures like the ones atcoinstacking.com a couple of years ago, but it’s still a fascination for me. Like an arch, these only things holding the structure together is gravity and friction. But unlike that most ancient architectural element, there is no strategically placed keystone. These coin structures are also much more easy to build because the structure is relatively stable during construction.

I like the way this guy kept stacking more columns of coins on a bridge spanning three coin diameters. It’s amazing when you think about how the load is carried to the ground. Notice that in the picture before collapse, the bottom-most penny at midspan doesn’t appear to be carrying any of the load above it.

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New cement conducts electricity like metal

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A new type of cement mixes Titanium with the usual lime / alumina compound and heats it up to 1100 degrees Celsius. The resulting compound conducts electricity about as well as other metals at room temperature.

With Titanium in the mix, don’t expect to see this mix in your every day concrete pour. The article mentions a possible application as a substitute material for Indium which is used in plasma TVs and the like. This material is going to find a home inside of an iPod or cell phone probably.

All in all, it reminds me of electrically conducting clay polymers but with the novelty of being made with portland cement.

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