March 12, 2013

Self Healing Roads

Self-healing roads may one day become a reality, after a university engineering professor invented an asphalt that can last twice as long as the traditional porous variety.
Delft University of Technology professor Erik Schlangen said the key is to add steel wool fibers to close the cracks that may form in porous asphalt.
"We add a very small amount of steel wool fibers, less than one percent of the volume, and then apply an induction plate to heat up the steel wool. When the wool heats up it melts the bitumen around it and closes the micro cracks,” he said, according to a report on HumansInvent.
HumansInvent noted a porous asphalt road will last about eight years before the top layer will replacement.
Schlangen said that while porous asphalt has very good properties, it has "durability problems."
With many pores, he said oxidation is faster than with usual asphalt, and the bitumen becomes very brittle due to this oxidation and cracks easily.
"You get these small micro cracks in the bitumen and so, when a car drives over the road, the stones at the surface come off," he said.
Such small cracks may grow until they become large potholes that can damage vehicles and eventually cause accidents, HumansInvent said.
Schlangen said they have tested the steel-infused asphalt on a 400-meter section of road in the Netherlands, and the initial results appear encouraging.
“We’ve tested a 400 meter section of road in the southern Netherlands that we laid down two years ago. There we applied induction heat and it works perfectly. We took a lot of samples from the road and aged them in the lab by putting them in the oven and spraying them with water etc and then applied induction heat and the tests have proved that we can double the surface life of asphalt, maybe even more,” he said.
Induction heating
Under Schlangen's solution, when cracks start to appear every couple of years, induction heat can be applied to the roads and they would heal themselves.
“You have to do that before they turn into potholes. You go on the road with an induction machine, it can be on a truck say and you drive over it, it heats up the wool and melts the bitumen and then the stones are fixed again,” Schlangen said.
High cost
HumansInvent said that while the steel-infused asphalt costs more, it may bring savings in the long run.
“The cost of material is increased somewhat because you have to add steel fibres but that’s not more than a 25-percent increase of the cost of the material and then there is the induction machine – you need some investment to build that and you have to drive over the roads with it. However, if you have double the surface life of your road, and no maintenance in between except driving over it with an induction machine, that saves a lot of money – the government will be able to make new savings this way,” Schlangen said.
Source - TJD, GMA News
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