Asphalt Recycling Should Get as Much Attention as Electric Cars
The methods and equipment already exist to improve asphalt recycling by up to 95 percent. It's time to include roads in the electricle vehicle discussion.
Unless you're in the road-building business, you may not have heard of Cold-In-Place asphalt recycling. But it's a term you should know. According to Healthy Building Network, Cold-in-place recycling, the rarest form of asphalt pavement recycling, can reduce carbon dioxide emissions by as much as 95 percent per lane mile and save a lot of money ---- as much as 40 percent compared to conventional techniques. More common warm mix asphalt can reduce carbon dioxide emissions by 15 percent compared to conventional paving, and increase proportions of RAP used. In our report, we provide sources for these figures, as well as recommendations to greatly increase the recycling of asphalt."
The topic of road building and maintenance is rarely mentioned in the breathy excitement about electric vehicles and charging stations, but it should be. Not only are asphalt prices rising--resurfacing a mile of 4-lane road costs about $1.25 million--Also, the contribution to global warming is huge. A study of a 20 km stretch of road in China estimated total CO2e emission of the asphalt pavement part of the road project at 52,000 tons. There are more than 4 million miles of roads in the U.S. New technologies for road construction are on the way, including rubber roads, solar roads and roads made of recycled plastic, but they're still in their infancy. Cold-In-Place resurfacing of asphalt roads is here now, and needs to become a household word among regional and local road planners.
Here's an article from Cornell University describing the Cold-In-Place process:
Cold-in-Place (CIR) recycling is a method of removing and reusing the existing asphalt surface. It involves grinding off the top 2 to 5 inches of the existing asphalt surface and mixing the crushed asphalt with an asphalt recycling agent, and placing it back down with a paver. Sometimes an additional module is included crushing this material and screening it to a specific size. Often specific sized aggregate is added to correct the deficiencies found in the existing asphalt material. Asphalt deficiencies are determined by sampling and testing the existing asphalt material prior to beginning the process.
The cold-in-place process is typically performed using a “train” of equipment which includes an emulsion tanker, milling machine, sometimes a crusher and a screen, and an asphalt paver and a combination of pneumatic and vibratory rollers. Because of the length of the train this process can be difficult on tight, windy and narrow streets.
The milling depth is determined largely on the existing depth of the asphalt material. Only the asphalt layer is to be milled in this process. Milling depth can be done up to a depth of 5 inches, however, depths greater than 4 inches tend to present compaction problems when the improved material is re-placed onto the road surface with the paver.
Cold-in-place recycling is used to restore and reuse the existing material reducing the amount of outside material required to be hauled to the site. This efficiently improves the road surface and strength while minimizing expenses typically incurred during the paving process. In addition, CIP can correct deep asphalt defects such as rutting, fatigue (alligator) cracking, and utility cuts that cannot be addressed by a surface treatment or an overlay, and allows minor corrections to the profile of a road surface, reduces reflective cracking, and results in a minor inconvenience to traffic. As its name implies, this is a cold process that requires minimal additional heat during the rejuvenation of the asphalt material, resulting in a decrease in the amount of energy required to produce the final material.
Success when using this process includes taking multiple samples along the road surface to identify any changes in the existing asphalt material which may require an adjustment to the added materials. This will allow for a more consistent and structurally sound asphalt base when the material is placed back onto the road surface. Because this is a “cold” process the material is slightly more porous than one would have from a hot mix material; it is therefore highly recommended that a surface treatment or an asphalt overlay be applied to the CIR material to protect it from water intrusion and to extend the life of the material. According to an FHWA study findings for New York State, a “CIR (4”) with a 1.5 inch overlay is expected tolast 10-15 years with little maintenance as compared to a 5-8 year life of atraditional 1.5 inch overlay”.
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