15 Sept 99
USE OF WASTE MATERIALS IN
a. The safe disposal of waste materials is increasingly a major concern in the
United States and around the world. Even with heightened awareness of the importance
of recycling, the volume of waste materials continues to grow (Ciesielski and Collins
1993 and Ciesielski 1995). Between 1980 and 1988 the annual amount of waste recycled
grew by 9 million tons; however, the amount of waste generated increased by 30 millio n
tons per year (NSWMA 1990). In 1994, the total amount of waste produced in the U.S.
reached 4,500 million tons per year (Shelburne and DeGroot 1998). At the same time
that existing disposal facilities are reaching capacity, approval of additional facilities for
waste disposal or treatment are becoming more difficult to obtain. Increasingly
restrictive environmental regulations have made waste disposal more difficult. Together,
these factors have significantly increased the cost of disposal of waste materials
(Ciesielski and Collins 1993).
b. The use of waste materials (recycling) in the construction of pavements has
benefits in not only reducing the amount of waste materials requiring disposal but can
provide construction materials with significant savings over new materials. The use of
these materials can actually provide value to what was once a costly disposal problem.
Historically, because of the large volume of materials required for construction,
pavements have been favorable structures for the recycling of a wide range of waste
materials. Initially, this recycling was limited to the reuse of materials removed from
previous pavement structures such as: recyclable asphalt pavement, recyclable portland
cement concrete, and various base course materials. Recently, various other materials,
not originating or historically associated with pavements, have come into use, for
example various latex materials added to the asphalt cement. This ETL will discuss the
origin and use of various types of waste materials available and the design, construction,
and environmental considerations required with their use.
c. The majority of wastes discussed in this paper could be used to form a structural
component of the pavement. Some have uses as replacements for conventional
aggregates and some form part or all of the binder in the particular mixture. Existing hot-
mix asphalt design and analysis procedures are often inappropriate for mixtures
containing waste materials; therefore, procedures must be developed to provide for their
consistently successful application (Terrel et al. 1994). Other materials such as animal
manure, crop wastes, sewage sludge, and compost, unless they are incinerated or
reconditioned, are used for treatment of soils and landscaping along pavement edges and
rights of way. Some materials such as: carpet waste, slate waste, lime waste, used sand
blasting grit, etc., are not included in this ETL because they have only minor applications
or are limited in quantity.