In the terminology of environmental experts, recycling is good but reusing is better.
“Recycling” means incorporating a reclaimed material into another form. That’s how soda bottles turn into fleece jackets and park benches.
“Reusing” a product like steel puts it back into use in the same way that it was originally used; when an old bridge is demolished, the reclaimed steel can be fed into a foundry oven and come out as new girders for a new bridge. Similarly, the glass you put into your recycling bin goes back into new glass.
That’s what the asphalt industry does with roads when we mill off a couple of inches of the surface and apply a new pavement layer. The old asphalt is reused in the new surface. The asphalt cement is reactivated and it behaves as it originally did, becoming part of the glue that holds the pavement together. The new surface, which contains reclaimed materials, is smooth, durable, safe and quiet. These perpetual pavements are the epitome of sustainability.
The latest numbers show that asphalt pavement is still No. 1 in the U.S. for both recycling and reusing. A survey that NAPA just completed on behalf of the Federal Highway Administration found that the amount of reclaimed asphalt pavement (RAP) used in asphalt mixtures in 2011 was 66.3 million tons, a 7% increase over 2010.
These tonnages dwarf recycling efforts in post-consumer waste. For example, the glass industry is extremely proud of recycling 3 million tons annually. The aluminum can people are very pleased to report that they recycle 1.5 million to 2 million tons a year. Nearly 45 million tons of paper and paperboard were recovered in 2010, a recycling rate of better than 63%.
So, the asphalt industry recycled more tonnage than glass, paper and aluminum combined. We also did better percentage-wise: We recycled or reused 99% of what we reclaimed, sending only 1% to landfills.
Asphalt-pavement recycling saved the American public at least $1.5 billion in 2011. It also conserved more than 3.3 million tons (19 million barrels) of asphalt binder and more than 310 million tons of aggregate.
The numbers get even better when we add materials from other industries that asphalt incorporates into pavements. The FHWA-NAPA survey showed that 2.89 million tons of asphalt shingles were used in asphalt pavements in 2011, up from 1.1 million tons in 2010. This represents 578,000 additional tons (3.2 million barrels) of asphalt binder conserved.
Looking at greenhouse gases, we see that the reuse of 20% RAP in asphalt pavement can offset close to 50% of the CO2 emissions associated with a pavement’s life cycle.
So just in the course of ordinary business, the asphalt industry saves landfill space; constructively reuses materials that otherwise would be wasted; conserves precious natural resources including asphalt cement and aggregates; saves billions of dollars a year; and reduces greenhouse gases.
In comparison, the portland cement in reclaimed concrete can’t be reactivated. Concrete can only be recycled as aggregate. According to the Portland Cement Association’s website, it can be used as general bulk fill, bank protection, base or fill for drainage structures, noise barriers and embankments. If the recycled material is further processed, it can be used for new concrete for pavements, shoulders, median barriers, sidewalks, curbs and gutters, and bridge foundations; structural-grade concrete; soil-cement pavement bases; and lean-concrete or econo-crete bases.
Crushed concrete is rarely used as aggregate in asphalt pavement because the crushed concrete is absorptive. This leads to higher design asphalt cement contents, which is not economic.
In our opinion, the best use for a concrete pavement that has reached the end of its useful life is to be rubblized and overlaid with asphalt. Rubblized concrete forms an exceptional road base, as the pieces of broken-up pavement are interlocked. Capping this rubblized base with infinitely reusable asphalt is a win-win-win for the traveling public (a great ride), the taxpayer (significantly lower cost) and the environment (conservation of natural resources plus reduced emissions).
In today’s world, where the highway system is mature and the emphasis for agencies is on preserving the existing system, it is absolutely imperative to choose the best material for the road user, the taxpayer and the environment. All signs point to asphalt.
Let the recycling, reuse and rubblization begin! AT