1. Field of the Invention
Embodiments of the invention relate to methods and compositions for mixture of zeolite with reclaimed asphalt pavement (“RAP”) and/or recycled asphalt shingles (“RAS”) prior to use of the RAP or RAS in asphalt mixtures.
2. Description of the Related Art
RAP is a removed or reprocessed pavement material that contains asphalt cement and aggregates. RAP may be incorporated into asphalt paving using hot or cold recycling. It may also be used as an aggregate when constructing a base or sub base.
Asphalt shingles make up a significant portion of the residential roofing market in the United States. RAS can be made up of either virgin off-spec shingles from the manufacturer or from tear-offs (used shingles removed from service on roofs). Whether virgin or used the shingles are typically ground (milled) to a small particle for use in an asphalt mix plant. When removed and used as RAS, these shingles may be ground and mixed with both hot-mix asphalt and cold-patch asphalt. RAS and RAP mixtures provided to asphalt mix plants may have some disadvantages. For example, they may present storage issues because of their tendency to absorb water. The water absorption process may lead to the formation of clumps or agglomerates, resulting in poor mixing with raw aggregates and asphalt cement. There is also a weight percentage of the total mix limit that the mix plant can add RAP or RAS into their process, either determined by the temperature of raw aggregate or the stiffness of the mix caused by the recycled asphalt cement.