Using Roof Shingle for Asphalt Pavement - Research Paper Example

In addition it contains between 32% and 42% of a coating filler such as limestone followed by some 28% to 42% of granules. The remaining portion of asphalt shingles is composed of fiberglass, cotton rags, paper and adhesives (Carter, 2008). The use of asphalt is pervasive throughout shingle manufacturing and asphalt constitutes a major part of shingles. The large amount of asphalt present in roofing shingles make these shingles suitable for recycling applications such as for constructing roads.

It is estimated that the United States alone manufactures around 12.5 billion square feet of asphalt shingles in a single year (Asphalt Roofing Manufacturer's Association, 2012). In recent years there has been a renewed emphasis to recycle asphalt shingles for road based applications since the shingles contain a large amount of asphalt that can be reused. The Environmental Protection Agency estimates that around 11 million tons of waste is created each year from asphalt shingles in the United States.

This waste is comprised of around one million tons of scrap generated by various asphalt shingle manufacturers while around ten million tons of waste is generated from construction sites (Environmental Protection Agency, 2005). This indicates that asphalt shingle supply can be considered as a reliable source for use in road construction given its continuous supply. Another notable aspect is that asphalt shingles and their related waste comprises around 8% of building related waste. Also, asphalt shingles represent around 10% of the waste created from demolition debris.

Recycling one ton of asphalt shingles is estimated to conserve one barrel of crude oil (Owens Corning, 2011). Asphalt shingles can be recycled for use in a number of different road based applications including aggregate for road construction, creating pavements, to control dust content on gravel roads etc. It is typical to use asphalt shingles to form the hot aggregate mixture used for manufacturing and paving roads. The amount of asphalt shingles is kept constant at 5% in the aggregate mixture for desirable properties.

It has been researched that increasing the amount of asphalt shingles to 7.5% in the aggregate mixtures renders the mixture soft and compromises pavement performance. In addition, using asphalt shingles from construction projects may also result in brittle pavements that might crack especially at low temperatures. For this reason asphalt shingles are typically used where stone mastic asphalt mixtures are required (Newcomb, Stroup-Gardiner, Weikle, & Drescher, 1993). Waste asphalt shingles are recycled by shredding them to half an inch size for batch plants and shredding them to a quarter inch size for continuous feed plants.

These materials are added to the overall aggregate mixture before the virgin asphalt is added for binding. The waste shingles that are typically used for creating HMA contain hard asphalt. The combination of this hard asphalt and the soft virgin asphalt tend to provide highly desirable properties to the overall aggregate mixture. Generally the resulting mixture of waste hard asphalt and soft virgin asphalt provides better stability as well as better resistance to rutting which make it desirable for use in pavements.

The departments of transport of a number of states have approved the use of asphalt shingles for constructing roads and pavements. Asphalt shingles have mostly been approved for use in hot mix asphalt (HMA) pavements. While the use of asphal