39    A FEASIBILITY STUDY TO USE COAL TAR
CONTAMINATED SOIL IN ASPHALT CEMENT
MIXTURE PRODUCTION
Chandra S. Dulam, Graduate Student
George E. Hoag, Director and Associate
Amine Dahmani, Laboratory Manager
Farhad Nadim, Graduate Student
Environmental Research Institute
University of Connecticut
Storrs, Connecticut 06268
INTRODUCTION
Coal gasification process was widely used by utility companies from 1850s to 1950s. Coal tars
are the residues produced during the gasification of coal. Traditionally, coal tars were buried on- -
site at the power plants or left as residuals in the bottom of gas holders. Currently, there are more
than 1500 such historic sites which will undergo site assessment in the near future. Most of these
sites contain both Non Aqueous Phase Liquids (NAPLs), and residuals contaminating soil and
groundwater.
Coal tar is primarily composed of polycyclic aromatic hydrocarbons (PAHs), such as pyrene,
benzo[a]pyrene, naphthalene, and phenanthrene.1-2 Coal tar also consists of phenolic compounds
and volatile organic compounds (e.g., benzene, toluene, and xylenes). The physical characteristics and the composition of coal tar depend on the type of coal and catalyst used, and the operating conditions of the gasification process. While coal tar residues are not classified as a toxic
waste, the material is subject to being a characteristic waste due to its composition. Studies have
shown the carcinogenicity of coal tar in rats, primarily due to PAHs.3
Yan4 formulated AC-10 asphalt from a mixture of used tires, coal tar pitch, and asphalt bottoms and discussed the similarities in the physical properties of coal tar pitch and asphalt. The
use of coal tar residuals in asphalt-based products could result in greatly reduced disposal costs,
in comparison to current methods of disposal. Present disposal practice of coal tar contaminated
residuals includes disposal in hazardous waste landfills or incineration. Treatment and disposal
costs are reported to be as much as $l,000/ton for current coal tar contaminated residuals disposal options. This feasibility study was performed to determine the use of coal tar contaminated
soil (CTCS) in bituminous materials to produce hot asphalt mix. Mixtures of varying composition of CTCS and bituminous material were produced to perform TCLP. The air emissions during
the mixing process were captured and analyzed. In this study, a bench scale investigation was
performed to identify and quantify the emissions from heating the CTCS at the mixer temperature. The pilot scale investigations were performed by replacing reclaimable asphalt pavement
(RAP) with CTCS during the hot asphalt mix production. The investigations were performed on
two types of mixtures; using CTCS as the direct additive in the first type, and using SS-1 (slow
setting asphalt emulsion) stabilized CTCS as an additive in the second type.
EXPERIMENTAL PROCEDURE
Preliminary Test
The physical and chemical properties of CTCS were determined prior to performing the feasibility studies. ASTM methods D421-58 and D422-63 were followed to obtain the grain size distri-
50th Purdue Industrial Waste Conference Proceedings, 1995, Ann Arbor Press, Inc., Chelsea. Michigan 48118.
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