HOW TO KNIT A ROAD

How to knit a road sounds like an in-house joke of some sort, or some form of crochet that most of us have never heard of. The reality is even more bizarre, and fascinating. It’s a possible method of building real roads that have a much lower environmental impact than current methods, using materials that are environmentally friendly….and cheaper.

     Building roads has always been a dirty, messy, and labor-intensive business. The Romans and the Incas built them by hand, often with thousands of slaves. Today’s methods are just as dirty and messy. The only difference is that most of the labor is now provided by machines rather than slaves. In fact, today’s methods are much messier and dirtier because all the earth and rock movement required is exacerbated by layers of tarmacadam or concrete.

     Enter some researchers from the Swiss Federal Laboratories for Materials Science and Technology. They have used a robotic arm to produce an elaborate pattern using string, and then added layers of stones, crushing the mixture together. The result is a surprisingly strong structure that can support heavy weights without hardly any movement of the stones. The string “captures” the stone and holds it in place. There is almost no environmental impact and all the materials can be recycled.

     The Swiss researchers got the idea of “how to knit a road” from an architectural research group in Zurich who developed the technique to build a replica of Stonehenge. They used a robot to lay down 120 kilometers of string in geometric patterns, and then added 30 tons of crushed stones. The result was a series of three-meter high columns that comfortably supported a nine-ton capstone, just like Stonehenge.

     There is another advantage of using this technique to build roads. Concrete and asphalt are non-porous, and have to be designed so that water (rain) runs off. When cracks do appears, they are subject to freeze/thaw issues, and potholes (remember my blog about a man taking a bath in a pothole in Trinidad). The knitting of string and stone results in a porous material. The water drains straight through, thus avoiding those destructive issues. The road surface is always dry, and thus much safer for drivers.

     Many years ago, an Italian company produced a tarmac road surface that had little pockets in the surface. It virtually eliminated spray, especially from large trucks. However, it was not porous, so the water still had to run off the surface into gutters. This new technique would eliminate the need for gutters, and would allow water to pass through the road into the water table below – less environmental impact again.

     The Swiss researchers are now working on the best material to use as the string. They currently use polyester, which can be recycled, but they are looking for a biological material that will do the same thing.

     I read today that the U.K. is about to ban all halogen bulbs. Incandescent ones are already banned. The result of this mandatory restriction will significantly reduce the carbon footprint and the environmental impact on Britain by forcing the use of the more efficient LED bulbs. Maybe this new road-building technique, how to knit a road, will have the same environmental impact on a global level. We can only hope some traditional road making giant doesn’t buy the technology and kill it. Its happened too many times before.