EP A/600/A-94/221
DEVELOPMENT OF CRITERIA FOR UTILIZATION OF
MWC RESIDUES IN CONSTRUCTION APPLICATIONS
David S. Kosson, Teresa T. Kosson, Frances E. Hoffman, Barbara Clay
Rutgers, The Stale University of New Jersey
Department of Chemical and Biochemical Engineering
P.O. Box 909
Piscataway, NJ 08855-0909
Hans van der Sloot
The Netherlands Energy Research Foundation
WestenJuinweg 3, P.O. Box I
Petten NM.
The Netherlands 17 55 ZG
ABSTRACT
Technical recommendations for the utilization of municipal waste combustion (MWC) residues in
construction applications are under development Technical criteria must consider the entire life cycle of
ash utilization from ash generation through use and ultimate disposal. Initial priorities focus on the use of
bottom ash without grate sittings (grate ash) as a replacement for aggregate in asphalt for paving, or, as an
aggregate replacement in portland cement based concrete used in shoreline protection and artificial reefs.

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INTRODUCTION
Management of residues generated from the combustion of municipal waste is one of the items
under consideration in RCRA reauthorization. Currently, since there are no federal guidelines, each state
determines under what conditions, if at all, municipal waste combustion (MWC) residue may be utilized as
a secondary product, rather than disposed of in landfills. RCRA reauthorization or other legislation may
require the USEPA to promulgate rules and guidelines for the utilization of MWC residues. In anticipation
of this, the USEPA Risk Reduction Engineering Laboratory (RREL) is conducting research through a
cooperative agreement with Rutgers University on technical requirements for environmentally sound
utilization of MWC residues. This research will provide recommendations to support the USEPA Office
of Solid Waste in developing guidelines for MWC residue utilization. The focus of this paper is to
considerations and various approaches to utilization criteria.
Municipal waste combustors generate two principal types of residues: (i) bottom ash, including ash
or slag retained on the combustion grates (referred to in this paper as "grate ash") and grate siftings
collected from the primary combustion chamber, and (ii) air pollution control (APC) residues, including fly
ash and add gas scrubber residue, collected from air pollution control devices. Relatively small quantities
of residues produced by the periodic cleaning of boiler and economizer tubes may be mixed either with the
APC residues or bottom ash. These residues from deposits on boiler and economizer tubes can be
considerably enriched in more volatile metals such as cadmium, zinc and lead. Bottom ash and APC
residues typically are generated at nominal mass ratios of 9:1, respectively. Grate ash typically represents
greater than 85 percent of the total bottom ash generated. APC residues typically contain higher
concentrations of soluble salts and specific metals, such as cadmium, lead, mercury, and zinc, than bottom
ash. In addition, the physical properties of bottom ash and APC residues are significantly different.
Currently, most MWC facilities in the United States mix bottom ash with APC residues for collection and
disposal. This mixed residue stream is referred to as "combined ash". Separate management of bottom
ash and APC residues may be appropriate for certain utilization scenarios. This is most frequently
considered to examine the potential for utilization or reduced disposal requirements for bottom ash.
Bottom ash constitutes the majority of the residue stream but contains substantially lower concentrations of
regulated metals and soluble salts. Separate management of bottom ash may result in the requirement of
revising or developing new management strategies for the APC residues.
Utilization of MWC residues is being considered for a variety of applications. Interest in utilization
principally is motivated by (i) the potential for extending existing ash landfill capacity, (ii) the potential for
reduced disposal costs, and (iii) replacement of the diminishing supply of natural materials in some regions
for which MWC residuals potentially could be substituted. Secondary effects of ash utilization may be (i)
reduced environmental impact, (ii) improved ash quality, and, (iii) improved product quality where ash is
substituted for natural aggregate. Reduced environmental impact may result because utilization scenarios
may have more stringent requirements than disposal. For example, increased contaminant immobilization
may occur because of ash encapsulation in either portland cement or asphalt for utilization. Improved ash
quality may result because motivation would exist for reducing contaminant concentrations in ash and
maintaining ash quality control to facilitate utilization. This may be achieved through combustion facility
operation or separation of specific components from the waste stream. Under the current disposal scenario,
no motivation exists to control or improve ash quality.
Primary applications under consideration is use of the MWC residues as (i) an aggregate substitute
in bituminous pavement, (ii) an aggregate substitute in portland cement based marine applications such as
artificial reefs and shoreline protection, (iii) as daily cover for municipal waste landfills, or, (iv) granular fill
material for embankments. Almost all of these applications, except use as daily landfill cover, would
involve some degree of ash treatment, either physical or chemical, either in preparation for or as a
consequence of utilization. For example, most applications would require screening of ash to achieve
desired particle size gradation or would result in ash encapsulation in another matrix. This paper focuses
on considerations for ash utilization in pavement and marine applications.
A typical pavement consists of the following layers or a subset combinations of layers
depending on design (listed from the top driving surface down): a shim/leveling course, a wearing/surface
course, a binder course, a base course, a sub-base course, a compacted subgrade, and a natural subgrade.
The shim/leveling course is placed cm the surface to level ruts and depression and typically consists of a
fine grain sand. The wearing/surface course is the top 0.5 to 1.5 inch and the binder course is below the
binder course. The binder course serves as the bottom portion of the roadbed if the wearing course is less
than four inches thick.. Otherwise it will be placed between the wearing course and the base course. The
base course is normally the lower portion of the pavement. However, a sub-base may be required and is
placed directly below the base. The pavement is built from the bottom to the top on a subgrade that has
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been prepared by compaction. The entire roadbed is placed on natural subgrade. Applications in die marine
environment include shoreline protection and artificial reefs. These involve the use of the MWC residues
mixed with portland cement to form concrete structures. Shoreline protection is the process of creating
physical resistance to storm disruptions, such as storm events, natural erosion, and boat wakes. Examples
of shoreline protection are bulkheads, sea walls, breakwaters, jetties, and piers. Artificial reefs are
constructed to provide structures for the growth of marine organism while additionally serving as shoreline
protection.
Utilization criteria also must consider potential impacts in addition to those during actual use and
competition from other residue sources. Potential impacts include evaluation of the entire residue
utilization life cycle, from ash generation, to actual use and through post-use deposition. Criteria developed
for MWC residues should be consistent with criteria for utilization of other waste residues, such as coal
ash, in similar applications. This will permit common market and environmental factors to decide the
appropriate application and extent of utilization of various potential materials.
UTILIZATION LIFE CYCLE CONSIDERATIONS
The typical projected life cycle of MWC residues during utilization includes the following stages:
1.	Ash generation (production at the MWC facility);
2.	Physical processing;
3.	Stockpiling;
4.	Manufacture;
5.	Use in designated application; and,
6.	Post-utilization management and disposal.
Potential ash impacts and considerations are essentially common independent of utilization
application from the time of ash generation to the point of manufacturing. Subsequent stages in the life
cycle arc significantly more application dependent because of the nature of the material in which the ash
will be used and exposure scenario during use. For example, utilization in portland cement applications
will have different effects on contaminant release than utilization in bituminous pavement. The following
sections discuss to potential impacts and approaches for criteria for each stage.
Ash Type Selection and Elements of Concern
Bottom ash without grate s if tings or boiler ash currently is considered to have the greatest potential
for utilization and therefore has the highest priority development of criteria. This ash type is considered to
have the greatest potential for utilization because it typically has the lowest content of leachable metals of
concern (e.g., lead, cadmium, mercury, etc.) and soluble salts. In addition, this ash fraction has physical
properties similar to natural aggregates and represents approximately 80 volume percent (ca. 70 wt %) of
the total residues generated. Grate siftings are excluded because of the content of fine particulates and
relatively high contents of lead and aluminum. Boiler ash is excluded because of the potential for relatively
high content of more volatile metals such as cadmium and zinc. A PC residues are excluded because of
high soluble salt content (ca. 40-60 wt %) and relatively high contents of metals of concern such as
cadmium, lead, zinc and mercury.
Table 1 presents the chemical elements and species concern which have been identified to be
present in bottom ash in significant concentrations. These elements and species were selected based on
either current regulatory guidelines for drinking water or solid waste management, potential aquatic life
toxicity or potential engineering effects.
Ash Generation
Ash generation is defined as the production of the residues to be utilized at the MWC facility. This
stage is the most critical for quality control. The intent at this stage should be to produce as uniform a
product (ash) as possible that will permit utilization after subsequent processing. This will minimize the
amount of processed ash that would be rejected as unacceptable at later stages or require disposal. Critical
testing parameters during this stage would be loss on ignition (LOI), alkalinity, total leachable salts,
leaching potential or availability of key elements, and moisture. LOI serves as an indicator of combustion
completeness and residual organic matter. Alkalinity or acid neutralization capacity provides a measure of
the material behavior in the environment because of leaching of potentially toxic metals is strongly a
function of pH. Development of a pH titration curve also would permit estimation of the contributions of
hydroxide, bicarbonate and carbonate buffer systems.
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Total teachable salts is an important parameter because total salt loadings can adversely effect soil
and potable water resources. Total salt content also can adversely effect the durability of portland cement
based products. The leaching potential, or availability, of key elements is important as threshold values for
acceptance based on projected impact at the utilization scenario. Here, availability is recommended rate
than total concentration because fractions of each element of concern may be bound in mineral forms that
would make it unleachable or biologically unavailable under the normal extremes of environmental
conditions. An example of this would be lead or chromium bound in a silicate matrix. Furthermore,
current methods (SW-846) recommended for total analysis do not provide true total concentrations and
revised methods to do so are significantly more cumbersome and costly. Moisture content is important to
insure that excessive freely draining water does not exist while moisture is high enough to prevent fugitive
dust problems and allow proper aging of residues to proceed (see "stockpiling").
The frequency of testing to be carried out needs to be developed based on a statistical evaluation of
the acceptable range and variation of critical parameters. Acceptance criteria should establish not only die
mean but also the acceptable variance of analytical results that limit quantity of material beyond die
threshold limits that would render an entire lot of material unacceptable. Thus, testing at this stage would
be for screening and quality control purposes and would be based on prior knowledge and detailed
characterization of the class of residue to be evaluated. Specific thresholds should be based on projected
impacts for each utilization scenario. Different utilization scenarios may have different acceptance
thresholds.
Physical Processing
Physical processing of ash is defined as mechanical processing such as ferrous and non-ferrous
metal removal, and, crushing and screening to control die particle size gradation of the material to be
utilized. Removal of oversized material is necessary to facilitate subsequent processing into appropriate
products (e.g., asphalt paving material or concrete forms) and would be based on the specific utilization
scenario. Removal of fines may be necessary to minimize fugitive dust, and attendant controls, during
subsequent stages. These operations may occur either at die MWC facility or at the stockpiling location.
The principal environmental and occupational health impact concerns during this stage would be a
consequence of fugitive dust Recommendations to minimize these effects are that physical processing
operations be carried out in enclosed facilities and that an occupational health assessment be carried out to
insure worker safety.
Stockpiling
Stockpiling of ash is carried out for several reasons. First, during stockpiling, aging reactions occur
within the ash which further stabilize the material. These reactions include oxidation, hydration and
carbonation (fixation or uptake of atmospheric carbon dioxide) reactions. Oxidation of reduced metals
typically result in less leach able forms. Carbon dioxide uptake results in a pH shift of the material from
typically greater than eleven to more neutral pH, e.g., less than 9. This process also results in respeciation
of some elements from hydroxides to carbonates. The net result of this process is a shift in the pH domain
and speciation of the material to a less leachable regime for metals such as lead and cadmium. Hydration
reactions typically result in swelling of the material. These swelling reactions must be allowed to progress
prior to utilization to avoid detrimental effects on the structural durability of the final products. Exact
intervals required for sufficient ash aging have yet to be defined, but preliminary finding indicate a period
between three and six months.
A second reason for ash stockpiling is to allow for storage of the material because of seasonal
demand For example, most paving applications will able to utilize the material only six to eight months out
of the year depending on loci climate.
Potential environmental or health impacts from stockpiling can be a consequence of fugitive dust,
precipitation runoff, leachate or site access. Fugitive dust can be controlled by limiting the fraction of fine
material (less than 200 mesh) permitted in the stockpile and maintaining a minimum moisture content
(greater than approximately 10 percent). Minimum moisture content also will facilitate ash aging
processes. All runoff and leachate from the stockpile should be collected and treated if necessary.
Applicable storm water and local regulations may be sufficient to address these concerns. Site access
should be controlled to avoid unwanted exposure by trespassers such as playing children.
Minimum ash stockpiling intervals should be established based on ash aging requirements.
Maximum storage intervals should be based on the local annual climatic cycle. Consideration must be
given if the aging process period and the seasonal demand period are mismatched. For example, in the
northeast U.S. ash generated in July may have to be stockpiled until the following April for paving
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applications. Maximum ash stockpile quantities can be based either on annual use or demonstrated prior
agreements for use with the entity receiving die ash after stockpiling.
Manufacturing
Manufacturing is defined as the processing of the ash into the final product form. This stage for
paving applications would include ash drying and blending with asphalt at the asphalt plant, and placement
of the pavement This stage for portland cement applications would include mixing with portland cement,
water and natural aggregate and forming into final structures such as blocks. Ash handling requirements at
this stage, and during subsequent stages, should conform with standard handling procedures for materials
which the ash is replacing to the greatest extent possible.
Potential environmental or health impacts during the manufacturing stage could result either from
fugitive dust or drying process emissions. Asphalt production will require drying of the ash prior to
blending with other aggregates and asphalt Aggregate drying typically is earned out at approximately
200°F. This temperature is not high enough to volatilize metals of concern, but may cause some
entrainment of fine particles in die drying air stream potentially increasing air emissions. Fugitive dust and
air emissions impacts most likely can be minimized by limiting the fraction of lines in the ash stream.
Use Applications
General Approach. A general approach for selection of acceptable utilization applications and
overall control of utilization can be classified by die following steps:
i.	Detailed ash characterization
ii	Detailed evaluation of impacts from proposed application
iii.	Ash screening and quality control
iv.	Verification of Ash characterization
v.	Categorically approved utilization for certain applications with limited restrictions.
Detailed ash characterization would require determination of the statistical variation of the ash to be utilized,
including composition, leaching and physical characteristics. Acceptance limits for key parameters and
statistical evaluation methods would be established. These key parameters would have to be indicative the
materials performance during use. After the variability of key characteristics has been determined, only a
reduced set of analyses for quality control would be required at the time of ash generation. Ash
characteristics and behavior would be verified prior to use. An initial set of potential quality control
parameters has been presented in the section entitled "Ash Generation." This approach is possible because
it has been demonstrated that combustion residues from similar types of MWC facilities exhibit common
characteristics. Thus, only quality control and screening for non-characteristic properties is required.
Evaluation of impacts from proposed applications and potential approaches to criteria are presented
in the sections that follow. For utilization to be practical, extensive permitting should not be required for
categorically approved applications which meet predefined restrictions. Predefined restrictions may include
restrictions on location of ash utilization and maximum quantities allowable. Record keeping should be
required with regard to the location, quantity and nature of each utilization application.
Two primary routes for environmental impact require consideration for most applications. The first
route is through particle transport followed by either incorporation into soil or sediment, or food chain
uptake. Food chain uptake is a much greater concern for marine applications. The principal controls over
panicle transport are through limiting direct abrasion on surfaces containing ash and through requiring
specific product durability.
The second exposure route is through leaching followed by impact either on groundwater, surface
water or soil resources. Contaminant release through leaching can be viewed as being comprised of two
components, contaminant release potential and contaminant release rate. Establishing limits on cumulative
contaminant release over a fixed time interval is a potential approach for limiting environmental impacts for
applications which have a finite use period. The cumulative contaminant release could be projected based
on integration of release rate and release potential data for defined geometries. This projection could
include application specific information such as mean temperatures and precipitation to provide translation
of laboratory data to field scenarios. Cumulative contaminant release would be the most important
parameter for elements or species of concern that accumulation in the surrounding environment Release
rate or flux would be the most important parameter for non-accumulating elements or species (e.g., sodium,
chloride). Release potential would be the limiting parameter when the utilization scenario is a permanent
placement of the ash. This would be the case for marine applications.
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Paving Applications. Tabic 2 presents a summary of utilization priorities developed in cooperation
with an advisory committee selected to assist in the development of criteria. The primary paving
applications considered were use of MWC residues in the wearing course (roadway surface), binder
course, base and embankments. Options were to use ash which has been physically processed and aged (i)
as a granular material (ii) directly incorporated in asphalt, (iii) further solidified or chemically stabilized and
used as a granular material, or, (iv) further solidified or chemically stabilized and incorporated in asphalt.
Applications using ash without further treatment as an aggregate replacement in asphalt used for
binder or base courses were given the highest priority. It was considered that significant reductions in
potential contaminant release would be realized as a consequence of ash incorporation into asphalt. Further
emphasis was given to these applications because both would have at least an impermeable asphalt layer
above the utilized material, if not both above and below. Lower priority was given to use of ash in the
wearing course because of potential abrasion and direct environmental exposure. Concern also was
expressed about dust generated during milling of the wearing course during maintenance and repaying
operations. Use of granular material in the wearing course was considered unacceptable. Use of granular
material in embankments was considered to be of lowest potential because it represented the greatest
potential environmental impact from release of salts. Use of ash incorporated into asphalt for
embankments was not considered a practical option because asphalt based materials are not typically used
in that application. Use of treated ash (e.g., ash which had been further solidified or chemically treated)
generally was ranked lower than use of untreated ash because additional processing requirements and
economic concerns.
Marine Applications. The two primary marine applications under consideration are ash utilization
in shoreline protection and artificial reefs. The principal purpose of shoreline protection is to minimize
coastal erosion while the principal purpose of artificial reefs is to enhance the quantity and diversity of
marine biota at the reef location. Both applications would utilize ash through replacement of natural
aggregate in defined portland cement based structures (e.g., blocks or other defined geometries).
The marine environment can be considered more environmentally sensitive than the paving
applications because of direct contact of marine biota with the application structure and the sediment and
water column in the immediate vicinity of the application. The principal mechanisms for environmental
impact in the marine environment would be through leaching and particle transport. Particle transport is
much more important in the marine environment than in the paving applications because it may be
manifested through (i) erosion and biota uptake from the water column, (ii) erosion and biota uptake in
local sediments or (iii) direct particle uptake by surface attached biota. In all cases, food chain
magnification of specific contaminants must be considered. Emphasis on particle transport also increases
requirements for structural durability of ash containing materials.
Definition of priority utilization scenarios for the marine environment is complex because of the
variety of marine environments and ecologically sensitive areas that exist. Primary variables arc the salinity,
intensity of wave energy, and the degree of water circulation or flushing. Lowest potential impact areas
would be areas of high salinity and a high degree of water circulation. Sensitive areas such as coral reefs or
highly productive estuaries should be avoided. Table 3 summarizes some environmental considerations for
selection of application scenarios.
Application Restrictions. This type of potential restriction would limit the type of ash to be utilized
and the specific utilization application. An example would be restriction of grate ash use to binder and base
course layers in paving applications. For marine applications, an analogous limitation would be for use in
defined structures either for shoreline protection or artificial reefs. The goal of this type of restriction is to
facilitate development of criteria for highest priority applications first and to allow for revisions to criteria as
more performance data becomes available.
Location Restrictions. This type of potential restriction would exclude ash utilization in
environmentally sensitive areas. It also could be used to control site accessibility or provide for safety
margins based on projected impacts. Examples for protection of sensitive areas include prohibiting ash
utilization in wetlands areas or near coral reefs. Examples for control of site access or provide for
additional safety margins are limiting use to applications on landfills or in industrially zoned area, or,
requiring a minimum distance from paving applications to groundwater supplies.
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Quantity Restrictions. This type nf pntwirial mstricrinn could be used to limit the maximum
quantity of ash to be used in a single location before more extensive review or permitting would be
required
Record Keeping and Monitoring Requirements. Records should be required to be maintained
detailing each utilization application. Information required should include ash characteristics, type of use
and location of application. This would allow for future investigation of application performance. Routine
environmental monitoring should be required only during pilot-scale evaluations of potential applications or
for applications which exceed certain quantity restrictions. Extensive monitoring of every point of use
would be impractical and prohibitive.
Reuse and Disposal
Paving Applications. Roads, parking lots and other paving applications are considered to have a
finite application period. This period may be defined in terms of years or decades depending on the
specific scenario. Asphalt pavement frequently is recycled into new paving material. Controls should be
established that limit use of recycled ash containing materials to applications approved for initial utilization.
Disposal of ash containing materials should be in conformance with applicable guideline for similar
materials not containing ash.
Marine Applications. Shoreline protection installations and artificial reefs are considered
permanent structures. Therefore, criteria for environmental acceptability should consider the utilization
scenario as the ultimate disposition of the material.
CONCLUSIONS
Development of technical recommendations for criteria for utilization of MWC residues is in
progress. Initial recommendations will focus on application scenarios of highest potential use with
minimum negative environmental impact Current applications being considered arc use of ash in binder
and base courses for paving, and, in portland cement structures for shoreline protection and artificial reefs.
Initial recommendations will focus on utilization of grate ash (bottom ash without grate siftings) only.
ACKNOWLEDGEMENT AND DISCLAIMER
This work was funded by the USEPA, Risk Reduction and Engineering Laboratory under
Cooperative Agreement# CR 818178-01-0. Carlton Wiles is the project officer. The views expressed
in this paper are those of the authors and do not necessarily express views or policies of the USEPA.
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Table 1. Chemical Parameters of Concern in Bottom Ash.
Pb 1.7
CdU
Ha 1.7
K3
Cu 2
Ho 1.7
Aa 1.7
Na 3.5
Zn 2
At 1.7
Cr 1.7
Ca 3
A|3
Sa 7
Mo?
Ma 3
SO4 *>5»6
C!«
TDS *
B r
Expansive
Oxides 5
LOI 2.3.5
NO3
pH and
alkalinity 2.3
1 Primary Drinking Water Standards
^Aquatic life effects
^Geochemical Parameters (effects on surrounding environment)
^Secondary Drinking Water Standards
^Engineering swelling and other effects
6SO4 Attachment on other materials (e.g. concrete) - Total (as delivered to asphalt plant)
^RCRA regulated
Table 2. Utilization Priorities for Grate Ash in Paving Applications.
Road
Application
Untreated in
Asphalt
Untreated in
Granular
Treated in
Asphalt
Treated in
Granular '
Wearing
Course
5
NO
4
NO
Binder
Course
1 A
NO
1 C
NO
Base Course
1 B
3
NO
2
Embankment
(Granular)
NO
7
NO
6
KEY
1A - 1C is the highest priority use, while 7 is the lowest priority for utilization
A "NO" indicates a decision not to utilize ash in the application.
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Table 3. Environmental Considerations for Marine Applications.
Location Conditions
Rationale
Biological Impact
potential for application to impact marine species
Circulation/Flushing of
Water Body
dispersal of leachate
Climate
influence on distribution of marine organisms
Coral Reefs
biologically sensitive area
Estuaries
biologically sensitive, vital area for reproductive
cycle of all marine organisms
High Physical Energy
potential for Increased erosion
High salinity
high salinity may effect durability of structure
Proximity to Biota
any structure placed in the water will attract
organisms
Recoverability
must be able to retrieve the test structure
Remediation and
Reversibility
design of experiment should include a contingency
plan that specifically states what will be done if the
experiment fails
Sensitive Areas
need to define which areas too biologically sensitive
for marine ash utilization
Shoreline or Open Marine
easier access for testing and remediation
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TECHNICAL REPORT DATA
(Please read Instruction* on the reverie before completing)
1. REPORT NO.
EPA/600/A-94/221
2.

4, title and subtitle Development of Criteria for Utilization of
MWC Residues in Construction Applications
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7.author{S) Teresa T. Kosson, David S. Kosson, and Ben Stuart
at Rutgers and Hans van der Sloot at The Netherlands Energy
Research Foundation
8. PERFORMING ORGANIZATION REPORT NO.
9. performing organization name and address Rutgers, The State
University of New Jersey, Department of Chemical and
Biochemical Engineering, P.O. Box 909,
Piscataway, NJ 08855-0909
The Netherlands Energy Research Foundation, Westerdiunweg
3, P.O. Box 1, Petten N.H., The Netherlands 17 55 ZG
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
CR818178-01-0
12. SPONSORING AGENCY NAME AND ADDRESS
US EPA, Risk Reduction Engineering Laboratory
26 W. Majjtin Luther King Drive
PinninnaVi . OH
13. TYPE OF REPORT AND PERIOD COVERED
Published Paper
14, SPONSORING AGEgp^)^
is. supplementary notes Project Officer: Carlton C. Wiles, 513-569-7795
1993 International MWC Conference Research Triangle Park, NC? May 1993; pg 1-9
is.abstract Technical recommendations for the utilization of municipal waste combustion (MWC)
residues in construction applications are under development. Technical criteria must
consider the entire life cycle of ash utilization from ash generation through use and
ultimate disposal. Initial priorities focus on the use of bottom ash without grate siftings
(grate ash) as a replacement for aggregate in asphalt paving, or, as an aggregate
replacement in portland cement based concrete used in shoreline protection and artificial
reefs.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.iOewriFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Municipal Waste Combustion Residues
Bottom ash
Ash utilization


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