Back in the 1960s to early 1970s the term “rap” meant to talk freely and honestly. There were rap sessions and “getting together with your old lady (or man) to rap about life.”
A decade later, rap became a genre of music spawned from various urban centers throughout the United States. The name allegedly derived from people saying, “That’s a rap!” after performing with a DJ. A rap can usually consist of rhymes and a beat, although sometimes done a cappella. Often accused of being about nothing but sex and drugs, it usually depicts daily life in the black ghettos or other assorted issues faced by the poorest.
Today, in the paving industry, RAP stands for reclaimed asphalt pavement. RAP comes from the millings of old asphalt surfaces removed during resurfacing, rehabilitation or reconstruction operations. These removed and/or reprocessed pavement materials containing asphalt and aggregates are recycled.
The use of RAP in asphalt paving actually predates M.C. Hammer’s first pair of baggie pants and became 2 legit 2 quit during the 1970s due to the high cost of crude oil during the Arab oil embargo. The 1973 OPEC oil embargo acutely strained a U.S. economy that had grown increasingly dependent on foreign oil. American ingenuity was needed.
At that time, the Federal Highway Administration (FHWA) provided partial funding to State transportation departments, through Demonstration Project 39, to construct paving projects using recycled asphalt and to document any effective use of recycled resources in light of asphalt shortages and increased material costs. The result of the positive report: Paving practices and technologies quickly evolved to include RAP.
Amazingly today, according to the FHWA, asphalt pavement is America’s most recycled and reused material, which makes the asphalt industry the country’s number one recycler. The aluminum, glass, plastic, and paper markets have some catching up to do.
For the paving contractor, using RAP makes total sense.
It’s Good to Be Green
RAP is an environmentally sound practice. Recycling asphalt pavement creates a cycle of reusing materials that optimizes the use of natural resources. It is a useful alternative to virgin materials, because it reduces the need for virgin aggregate, which is an already scarce commodity in some areas of the country. In a sense, RAP constitutes a “treasure trove” of pre-processed road-building materials.
As early as 1993, the Environmental Protection Agency and FHWA identified asphalt pavement as America’s No. 1 recycled product in a report to Congress. It continues to be reclaimed and reused at a greater rate than any other product in the United States. All sorts of waste materials are now incorporated into asphalt pavements, including ground tire rubber, glass, foundry sand, slag and even pig manure, but the most widely used are reclaimed asphalt pavement and recycled asphalt shingles (RAS).
The use of recycled materials in asphalt pavements saves hundreds of millions of cubic yards of landfill space each year. Recycling asphalt pavement keeps this oil-covered aggregate from landfills and waste facilities all over the country.
Using RAP greatly reduces the amount of construction debris going into landfills, and it does not deplete nonrenewable natural resources such as virgin aggregate and asphalt binder do.
Makes Good Economic Sense
As a useful alternative to virgin materials, RAP reduces the need to use the more expensive virgin aggregate and new more costly asphalt binder required in the production of asphalt paving mixtures.
Considering that more than 90 percent of U.S. highways and roads are constructed with hot mix asphalt (HMA), the same materials used to build the original highway and road system can be re-used to repair, reconstruct, and maintain them. As the FHWA recycled materials policy states: “Where appropriate, recycling of aggregates and other highway construction materials makes sound economic, environmental, and engineering sense.”
There are four major asphalt production cost categories: materials, plant production, trucking, and lay down paving.
Materials are the most expensive production cost category, comprising about 70 percent of the cost to produce HMA. Add to that the most expensive and economically variable material in an asphalt mixture is the asphalt binder. Binder is needed in the intermediate and surface layers of flexible pavement to provide tensile strength to resist distortion, protect the asphalt pavement structure and subgrade from moisture, and provide a smooth, skid-resistant riding surface that withstands wear from traffic. As a result, the most economical use of RAP is in the intermediate and surface layers of flexible pavements where the less expensive binder from RAP can replace a portion of the more expensive virgin binder.
The use of RAP also conserves energy, lowers transportation costs required to obtain quality virgin aggregate and preserves resources. Additionally, using RAP decreases the amount of construction debris placed into landfills and does not deplete nonrenewable natural resources such as virgin aggregate and asphalt binder. Ultimately, recycling asphalt creates a cycle that optimizes the use of natural resources and sustains the asphalt pavement industry.
With using RAP, contractors can avoid tipping fees, In many areas of the country, tipping fees for waste RAP are becoming the norm. Some are as high as $20 per ton. By recycling, a contractor keeps that money in their pocket.
Highway agencies and taxpayers benefit because recycling stretches tax dollars, allowing more roads to be kept in better condition.
Good Quality Results
Contractors won’t risk their reputations on RAP if it doesn’t perform. Fortunately, it does appear to work as well, and in some cases better than the use of virgin materials.
Based on an evaluation of pavements containing 30 percent RAP through the FHWA’s long-term pavement performance (LTPP) program, it has been determined that the performance of pavements containing up to 30 percent RAP is similar to that of roadways constructed from virgin materials with no RAP. This report is of interest to engineers, contractors and others involved in the specification and design of asphalt mixtures for flexible pavements, as well as those involved in promoting the optimal use of RAP.
The LTPP report concludes that: “The use of recycled material in the construction of highways to the maximum economical and practical extent possible shows equal or improved performance.”
So, to wrap things up on RAP…the benefits are apparent.
For the asphalt paving contractor, RAP can increase profitability, eliminate RAP disposal costs, reduce reliance on the hot-mix plant, provide the ability to produce hot mix material 24/7, provide the ability to produce virgin asphalt (with certain asphalt recyclers) and increased opportunity benefits.
For cities, county and state highway departments, RAP provides many benefits which include reduced hot-mix costs through recycling, eliminating RAP disposal costs, reduced reliance on the hot-mix plant, ability to produce hot mix material 24/7, ability to produce virgin asphalt (with certain asphalt recyclers) and the ability to eliminate wasted labor costs required when using cold patch for pothole repairs.
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