ETL 1110-3-503
15 Sept 99
facility can satisfy all air, solid waste, liquid effluents, and health requirements (FHWA
1993 and Emery 1995).
i. Waste paper. Waste paper accounts for approximately 40 percent of the solid
domestic wastes produced each year. The paper, including: cardboard boxes,
newspapers, office paper, etc., that is not recycled into more paper can be used as a
mulching material. A few state DOT's have used waste paper as a mulch (Collins and
Ciesielski 1994).
B-4. Types and Pavement Applications of Industrial Waste. Industrial wastes, as a
group, are probably the most widely reused of the waste materials generated. The
amount of industrial wastes generated in the U.S. exceeds 400 million tons annually. Of
this amount, approximately 100 million tons are recycled pavement and 70 million tons
are coal ash. These materials are recycled at approximately 50 and 25 percent,
respectively (Shelburne and DeGroot 1998).
a. Asphalt Plant Baghouse fines. The majority of asphalt plants in the U.S. use a
dry dust collection system. These dusts, which are finely graded, are typically
immediately added back into the aggregate stream of the hot-mix asphalt (Collins and
Ciesielski 1994). Depending on the aggregate and the mixture being produced, excess
baghouse fines can be produced. These can be added to other hot-mix asphalt mixtures,
when additional fines are required.
superheated in a blast furnace to produce pig iron. A waste product of this procedure is
blast-furnace slag, which essentially consists mainly of silicates and alumino-silicates o f
lime (Ahmed 1991 and Collins and Ciesielski 1994). Variations in the cooling process
results in 4 types of blast-furnace slag: air cooled (under ambient conditions), expanded
(with controlled quantities of water), granulated (quick water quenched to a vitrified
state), and pelletized (water and air quenching in conjunction with a spinning drum). In
1989, 15.5 million tons of blast-furnace slag were sold, mainly for construc tion purposes;
about 90 percent of this was air-cooled blast-furnace slag and e xpanded slag made up the
next largest portion. In 1994, this had risen to more than 13 million tons and almost all
the blast-furnace slag produced in the U.S. was reused for construction purposes
(Schriefer 1997). This slag is fairly porous with a low unit weight that can range from
1,200 to 1,450 kg/m3 (62 to 75 pcf). Blast-furnace slag is available in numerous states,
generally in the northeast and midwestern states of the U.S. Blast-furnace slag is
classified as a mineral waste and is therefore not considered a hazardous waste (FHWA
1993).
Some slag bases and embankment applications have experienced problems with the
leading to increased maintenance requirements (Gupta et al. 1994). The tufa is formed by
carbon dioxide (CO2) in the water combining with free lime (CaO) in the slag. Steel slag
and blast-furnace slag from open-hearth and basic-oxygen furnaces have been shown to
be susceptible to the formation of tufa (Gupta et al. 1994). Only air-cooled blast furnace
slag does not have the potential for the formation of tufa, other slags should be evaluated
B-10
Previous Page
