Introduction
Asphalt pavements often are being cold planed to correct surface irregularities, maintain curb lines and remove poor quality pavement prior to asphalt overlay. This has created large quantities of stockpiled reclaimed asphalt pavement (RAP).

Although RAP is used for a variety of pavement maintenance applications, a very effective use is for the production of maintenance mixes. The RAP is cold central plant recycled (CCPR) with an asphalt emulsion. These mixes can be produced for immediate use or for stockpiling and later placement. Besides being very high quality and salvaging pavement materials, RAP mixes result in good cost savings as can be from 25 to 50 percent less expensive than new mixes.

Collecting and Stockpiling RAP
Cold planing is recommended for pavement removal as individual layers of different types of mixes can be obtained and placed in separate stockpiles, if desired. Also, the size of the RAP will be smaller than if the pavement is obtained by ripping with sizing by screening and crushing much easier. A very important part of the removal process is preventing contamination of the RAP.

The location chosen for stockpiling the RAP, if possible, should be where the mix can be both produced and stored for maintenance uses to keep material handling to a minimum. This is important to keeping the cost of the final product well below that of new maintenance mixes.

Proper stockpile management is essential to having a successful cold central plant recycling operation. RAP of varying quality and uniformity can be separated to create more uniform stockpiles. Dumping of concrete, soil, wood and trash into RAP stockpiles should not be permitted. RAP tends to compact and so the lowest stockpile height that the space will permit should be used with a maximum height of about 10 feet (3 meters) preferred. A large bucket loader is recommended with the bucket having teeth to loosen the RAP. Also, if the RAP has a high asphalt content or the asphalt is not old/hardened so tacky, a bulldozer may be necessary to loosen and mix the material.

Asphalt Emulsions
Asphalt emulsions are used as the asphalt binder for RAP maintenance mixes with the type dependent on how the mix is to be used. When the mix is to be stockpiled and extended workability is needed, an emulsion containing a petroleum distillate is used, such as a high float emulsion. For immediate placement after mixing, slow setting emulsions also may be used. RAP can be sampled from stockpiles and a mix design completed to determine an emulsion percentage.