© 2017 Matthew L. Schafer

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UTILIZATION OF MUNICIPAL SOLID WASTE INCINERATOR BOTTOM ASH AS A SUSTAINABLE CONSTRUCTION MATERIAL: ISSUES CONCERNING MATERIAL

LEACHING AND DURABILITY

By

MATTHEW L. SCHAFER

A THESIS PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF ENGINEERING

UNIVERSITY OF FLORIDA

2017

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© 2017 Matthew L. Schafer

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ACKNOWLEDGMENTS

I would like to extend my genuine gratitude to the faculty members of my

graduate supervisory committee; Dr. Jean-Claude Bonzongo, Dr. Christopher Ferraro,

and Dr. Timothy Townsend, for allowing me the opportunity to perform this novel

research. The continuous support, direction, and technical guidance offered by these

individuals was vital to the successful and timely completion of this project. I’d like to

extend distinct appreciation to Dr. Tim Townsend for his professional mentorship, and

for the role he played in facilitating my personal and professional growth throughout

graduate school.

I would also like to thank the Solid Waste Authority of Palm Beach County,

Florida for providing me with the unique opportunity to perform this study, and supplying

the financial means required to accommodate such research. Furthermore, I would like

to acknowledge the innovation which was displayed by the Authority in their pursuit of

developing a waste-to-energy ash recycling program in Florida. The opportunity to work

in conjunction with the knowledgeable and experienced staff at the Authority was a true

pleasure. Additional thanks is extended to the Hinkley Center for Solid and Hazardous

Waste Management in Gainesville, FL for supplementary funding which accommodated

this research.

I would also like to recognize the numerous individuals who assisted me in a

variety of ways throughout the duration of this project; on matters ranging from technical

discussions and troubleshooting to heavy lifting and field sampling. Thank you to my

research colleagues Kyle Clavier, Justin Roessler, Linda Monroy Sarmiento, Chad

Spreadbury, and Stephen Townsend for all your help. Thank you to the graduate

students and faculty in the UF Civil Engineering department for helping me to better

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understand the fundamentals of concrete as a material: Danielle Kennedy, Taylor

Humbarger, Jerry Paris, Caitlin Tibbets, and Ben Watts. Thank you to the

undergraduate research assistants who assisted with the extensive field and laboratory

work involved in this study: Rachel Cohen, Sara Fox, Ryan Hundersmarck, and Jarrod

Petrohvich.

Finally, I’m most thankful for the constant love and support provided by my family

and friends throughout my years at the University of Florida, especially during graduate

school. I can’t thank you enough for the steady affirmation and motivational backing

you’ve all imparted on me, whether it came during the trivial times of my education, or

during the challenging ones. This effort would not have been possible without your

endless support. Thank you all so much.

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TABLE OF CONTENTS page

ACKNOWLEDGMENTS .................................................................................................. 3

LIST OF FIGURES .......................................................................................................... 9

LIST OF ABBREVIATIONS ........................................................................................... 11

ABSTRACT ................................................................................................................... 12

CHAPTER

1 INTRODUCTION .................................................................................................... 13

Background ............................................................................................................. 13 Motivation and Objective ......................................................................................... 14

Outline of Thesis ..................................................................................................... 15

2 LEACHING OF METALS FROM MUNICIPAL SOLID WASTE INCINERATOR BOTTOM ASH AND NATURAL AGGREGATE BLENDS: IMPLICATIONS FOR BENEFICIAL USE AS A GRANULAR ROAD BASE ............................................... 16

Background ............................................................................................................. 16

Methods .................................................................................................................. 19

Risk Assessment of Waste Materials ............................................................... 19

Experimental Approach .................................................................................... 20 Materials ................................................................................................................. 21

MSWI Bottom Ash ............................................................................................ 21

Natural and Recycled Aggregates .................................................................... 22 Leaching Procedures .............................................................................................. 23

Synthetic Precipitation Leaching Procedure ..................................................... 23 Leaching as a Function of Liquid-to-Solid Ratio ............................................... 23

Analytical Procedures ............................................................................................. 23

Results and Discussion........................................................................................... 24 Direct Exposure Pathway ................................................................................. 24

MSWI bottom ash ...................................................................................... 24

Natural and recycled aggregates ............................................................... 25

Blended products ....................................................................................... 25 Leaching to Groundwater Pathway .................................................................. 26

MSWI bottom ash ...................................................................................... 26 Natural and recycled aggregates ............................................................... 28 Blended products ....................................................................................... 28

Implications for Reuse as Road Base ..................................................................... 30 Summary of Findings .............................................................................................. 32 Figures and Tables ................................................................................................. 33

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3 CHARACTERIZATION AND MITIGATION OF ALKALI-AGGREGATE REACTIVITY IN MORTARS CONTAINING MUNICIPAL SOLID WASTE INCINERATION ASH AS AN AGGREGATE COMPONENT .................................. 41

Background ............................................................................................................. 41 Materials and Methods............................................................................................ 44

Bottom Ash Collection and Material Description ............................................... 44 Cementitious Materials ..................................................................................... 45 Experimental Approach .................................................................................... 45

Preparation of Mortar and Experimental Procedure ......................................... 46 Results and Discussion........................................................................................... 48

AMBT Expansion .............................................................................................. 48

Summary of Findings .............................................................................................. 49 Figures and Tables ................................................................................................. 50

4 CONCLUSIONS ..................................................................................................... 57

Summary of Research ............................................................................................ 57 Major Findings and Observations ........................................................................... 57

Recommendations for Future Work ........................................................................ 58

APPENDIX

A CHAPTER 2 SUPPLEMENTARY MATERIALS ...................................................... 59

B CHAPTER 3 SUPPLEMENTARY MATERIALS ...................................................... 63

LIST OF REFERENCES ............................................................................................... 66

BIOGRAPHICAL SKETCH ............................................................................................ 73

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LIST OF TABLES Table page 2-1 Total environmentally available concentrations (mg/kg-dry) of MSWI bottom

ash and natural/recycled aggregate materials. Total concentrations exceeding the residential Florida Soil Cleanup Target Levels are identified as COPC for the direct exposure risk pathway and have been shaded accordingly. ........................................................................................................ 33

2-2 Theoretical total environmentally available concentrations (mg/kg-dry) of blended products containing 15% MSWI bottom ash and 85% natural or recycled aggregates. Elemental concentrations exceeding the Florida Residential Soil Cleanup Target levels are identified as COPC and are shaded accordingly. ............................................................................................ 34

2-3 Average leachate concentrations of EPA Method 1312 (SPLP) performed in triplicate on MSWI bottom ashes and natural/recycled aggregates individually. Elemental concentrations exceeding the respective MCL are identified as COPC for the leaching to groundwater risk pathway and have been shaded accordingly. ................................................................................... 35

2-4 Average leachate concentrations of EPA Method 1312 (SPLP) performed in triplicate on blends of MSWI bottom ash and natural/recycled aggregates at a mass ratio of 15:85. Elemental concentrations of contaminants which exceed the respective MCL are identified as COPC for the leaching to groundwater risk pathway and have been shaded accordingly. .............................................. 36

3-1 Oxide composition (% weight) of materials obtained using X-ray fluorescence (XRF) spectroscopy. ........................................................................................... 50

3-2 Proportions of mortar materials for ASTM C160 mixes containing 15%, 30%, and 50% MSWI BA aggregate replacement. ...................................................... 51

3-3 Proportions of mortar materials for ASTM C1567 mixes containing portland cement, 20% pozzolan (ground glass or class F fly ash), and 30% MSWI BA aggregate replacement. ...................................................................................... 52

3-4 Length change data and performance classification of ASTM C160 and ASTM C1567 mortar mixes containing MSWI BA aggregate replacements. ...... 53

B-1 Aggregate properties of coarse fraction of MSWI bottom ash (3.5mm-19mm) used as aggregate replacements in accelerated mortar bar tests (ASTM C1260 and ASTM C1567) .................................................................................. 63

B-2 Individual length change measurements of ash-amended mortar bar specimens used in ASTM C1260 (portland cement only) ................................... 64

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B-3 Individual length change measurements of ash-amended mortar bar specimens used in ASTM C1567 (pozzolans included as portland cement replacement)....................................................................................................... 65

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LIST OF FIGURES

Figure page 2-1 Concentrations of aluminum in SPLP leachates for blends of Facility A MSWI

bottom ash and natural or recycled aggregates as a function of the bottom ash contained in the blended product. The risk-derived US EPA Regional Screening Level for aluminum (residential tap water) is displayed as dashed reference line. ..................................................................................................... 37

2-2 Ratio of aluminum leachate concentrations in the control bottom ashes to aluminum leachate concentrations in blended products containing lime rock and bottom ash at percentages of 0%, 15%, 30% and 50%, and 100% ash (SPLP batch leaching test). ................................................................................ 38

2-3 Concentrations of antimony in SPLP leachates for blends containing weathered MSWI bottom ash and four different aggregates. Antimony leachate concentrations are plotted as a function of bottom ash contained in the blended product. The US EPA National Primary Drinking Water Standard MCL for antimony is displayed as a dashed reference line. ............................... 39

2-4 Leaching of Antimony as a function of LS ratio (EPA Method 1316) in blended products containing 15% weathered MSWI bottom ash and 85% RCA and LR aggregates. ................................................................................... 40

3-1 ASTM C160 average length change of mortars containing 100% portland cement and 15%, 30%, and 50% aggregate replacement by MSWI BA1. ......... 54



3-4 ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash) and 30% aggregate replacement by MSWI BA1 .......... 55

3-5 ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash), and 30% aggregate replacement by MSWI BA2. ........ 56

3-6 ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash), and 30% aggregate replacement by MSWI BA3. ........ 56

A-1 ASTM C136 particle size distribution of weathered MSWI bottom ashes used for EPA Method 1312/1316 batch leaching tests and EPA Method 3015A total metals analysis. .......................................................................................... 59

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A-2 EPA LEAF Method 1313 lead leaching as a function of eluent pH performed on fresh MSWI bottom ashes. ............................................................................ 60

A-3 EPA LEAF Method 1313 antimony leaching as a function of eluent pH performed on fresh MSWI bottom ashes ............................................................ 61

A-4 EPA LEAF Method 1316 antimony leaching as a function of liquid-to-solid ratio performed on weathered MSWI bottom ashes ........................................... 62

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LIST OF ABBREVIATIONS

AAR Alkali-Aggregate Reaction

AMBT Accelerated Mortar Bar Test

ASR Alkali-Silica Reaction

ASTM American Society for Testing and Materials

BA Bottom Ash

COPC Contaminant of Potential Concern

LEAF Leaching Environmental Assessment Framework

MSW Municipal Solid Waste

MSWI Municipal Solid Waste Incineration

PC Portland Cement

PCC Portland Cement Concrete

RAP Reclaimed Asphalt Pavement

RCA Recycled Concrete Aggregate

RSL Regional Screening Level

SCM Supplementary Cementitious Material

SCTL Soil Cleanup Target Level

SPLP Synthetic Precipitation Leaching Procedure

TCLP Toxicity Characteristic Leaching Procedure

TEA Total Environmentally Available

US EPA United States Environmental Protection Agency

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the

Requirements for the Degree of Master of Engineering

UTILIZATION OF MUNICIPAL SOLID WASTE INCINERATOR BOTTOM ASH AS A SUSTAINABLE CONSTRUCTION MATERIAL: ISSUES CONCERNING MATERIAL

LEACHING AND DURABILITY

By

Matthew L. Schafer

May 2017

Chair: Timothy G. Townsend Major: Environmental Engineering Sciences

In this thesis, the beneficial reuse of municipal solid waste incinerator bottom ash

is explored with a focus on increasing the use of bottom ash as a construction material.

In Chapter 2, the environmental mobility of metal contaminants in a road base

reuse scenario is investigated using laboratory batch leaching tests. Blended products

containing bottom ash and natural aggregates are also considered for leaching.

Antimony and aluminum leachates exceeded risk-based thresholds by factors of

approximately 5-6, but blending of bottom ash with natural aggregates significantly

reduced the concentrations of leached aluminum. Antimony release from bottom ash

was found to be governed by solubility and pH.

In Chapter 3, the durability of concrete made with bottom ash as an aggregate

replacement is evaluated using an accelerated test method. The expansion of mortar

specimens is used as an indicator of the alkali-aggregate reactivity of bottom ash.

Mortars containing 15% bottom ash expanded beyond the innocuous limit of 0.1%. Two

pozzolans were found to reduce expansion in the mortars by up to 90%, and allowed for

increased amounts of bottom ash to be used (at least 30% replacement).

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CHAPTER 1

INTRODUCTION

Background

An expanding global population has resulted in an increase in the quantity of raw

materials and resources exhausted by consumers, and subsequent generation of

municipal solid waste. The strategic management of municipal solid waste (MSW) is of

growing importance as municipal resource consumption rates climb and spatial

availability for landfill disposal becomes increasingly limited, especially in developing

countries [1] . As a result, numerous strategies and processes have been developed to

more effectively manage MSW and decrease reliance on landfill disposal.

The incineration of MSW with energy recovery, or MSW incineration (MSWI) is a

popular strategy for solid waste management due to the volumetric reduction of waste

achieved by combustion (up to 90%), as well as the ability to simultaneously recover

heat and generate steam or electricity. While MSWI drastically reduces the initial

quantity of incoming waste, a large portion of residual bottom ash (BA) is produced as a

byproduct of the incineration process (in addition to fly ash). Bottom ashes represent the

non-combusted fraction of MSW which is discharged from the incinerator furnace

grating, and generally make up 15-20% of the original mass of MSW incinerated [2].

The high volume of bottom ash produced by MSW incinerators in addition to its

physical characteristics create the potential for the material to be beneficially reused,

primarily as a secondary building material in construction applications. While beneficial

reuse of MSWI BA has been highly successful in some areas [3]–[5], additional

research regarding the behavior of the material could promote higher recycling rates in

certain regions, such as the United States. The goal of the research presented in this

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thesis is to supplement the existing knowledge surrounding the beneficial reuse of

MSWI BA as an alternative construction material, and to provide a technical

investigation into two specific constraints which currently limit the reuse of bottom ash

as a construction aggregate.

Motivation and Objective

Recycling of MSWI BA as an alternative construction material is common

practice in many areas, primarily in Europe and parts of Asia, and numerous reuse

applications have been identified for BA produced in these regions [6], [7]. In the United

States, however, recycling of MSWI BA is highly underutilized and current practice is to

dispose of the vast majority of BA in lined ash monofills [8]. The lack of BA recycling in

the US can be attributed to a plethora of domestic factors, but two specific issues have

been identified which limit current BA recycling rates in the US:

1. The presence of trace amounts of inorganic contaminants (primarily metals and salts) contained in MSWI BA often hinders beneficial reuse as a construction aggregate, due to the potential risks these contaminants may pose to human or environmental health if they become mobile in the environment. These risks are particularly prohibitive in the scenario of MSWI BA being reused as a granular material in pavement base or subbase applications.

2. A gap in comprehensive research regarding the reuse of MSWI BA as an aggregate replacement in Portland cement concrete, particularly regarding a series of potential chemical reactions between MSWI BA and Portland cement, which may jeopardize the long-term durability and performance of concretes amended with MSWI BA.

The objective of this research is to investigate these two issues individually as

they relate to MSWI BA recycling, and to produce peer-reviewed data and

recommendations that can be used by decision makers and end users to facilitate an

increase in current MSWI BA recycling rates in the U.S.

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Outline of Thesis

Chapters 2 and 3 in this document address issues 1 and 2 listed in the Research

Motivation and Objectives section of this document, respectively. Chapter 2 examines

the leaching of select metals from MSWI BA intended for reuse as a granular material in

a road base, and presents an engineered approach to mitigate the environmental risk

presented by such contaminants. Chapter 3 investigates the durability of MSWI BA as a

prospective aggregate replacement concrete, with a focus on dimensional expansion

induced by reactivity of the ash. Chapter 4 provides conclusions, synthesis of the two

studies, and recommendations for future work. Each chapter is organized such that all

figures and tables appear at the end of each respective chapter. References to all cited

literature and methodology appear after the conclusion of Chapter 4.

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CHAPTER 2 LEACHING OF METALS FROM MUNICIPAL SOLID WASTE INCINERATOR BOTTOM ASH AND NATURAL AGGREGATE BLENDS: IMPLICATIONS FOR BENEFICIAL USE

AS A GRANULAR ROAD BASE

Background

Municipal solid waste incineration (MSWI) with energy recovery is an effective

solid waste management practice resulting in the production of significant amounts of

bottom ash (BA) as a residual byproduct (about 20% of the initial mass of MSW). In

2014, approximately 30 x 106 Mg of MSW was incinerated in the US (13% of the total

domestic MSW produced) at some 80 operational incineration facilities, generating over

5 x 106 Mg of residual BA. The vast majority of BA produced in the US is comingled with

fly ash (in order to create a nonhazardous waste product) and ultimately disposed of in

an ash monofill, with current recycling/reuse rates lower than 5% (US EPA, 2016a).

Comprehensive research has been performed to identify beneficial reuse options

for MSWI BA [6], [10]–[12]. The recycling of MSWI BA as a secondary aggregate

material in roadway applications has been carried out in Europe [13], Asia [14], and is

slowly gaining attention in the US [8]. MSWI bottom ashes exhibit similar mineralogy

and physical properties to some natural aggregates [15]–[17] and thus may prove

economically and environmentally advantageous if natural aggregates can be

supplemented or replaced in roadways (especially when factoring in the avoided cost of

landfilling the ash). Furthermore, a sustainable aggregate source used as granular road

base decreases reliance on naturally-mined minerals and offsets greenhouse gas

emissions from mining. In 2014, 59.2 x 106 Mg of crushed stone (primarily lime rock and

dolomite) was mined in the US with usage designation as a graded aggregate in road

base and subbase applications [18]. The mining of crushed stone could be reduced if

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the available tonnage of MSWI BA were utilized to help meet the aggregate demand for

granular road base.

One concern that must be addressed concerning the use of MSWI BA as a road

base material is the risk of human or environmental harm as a result of exposure to

contaminants of potential concern (COPC) present in the ash. While MSWI BA is

predominantly classified as a nonhazardous waste in the US by the Toxicity

Characteristic Leaching Procedure, research has demonstrated that BA contains small

amounts of metals and salts that may pose a risk to environmental and ecological

health [2], [19], [20]. While the risk posed by direct contact to COPC in MSWI BA is low

when the material is placed beneath a compacted pavement layer, the potential for

contaminant leaching to groundwater must still be considered. Much of the risk posed

by COPC in BA can be mitigated by use of certain engineering controls (e.g. natural

weathering, physical encapsulation, ash washing) and institutional controls (e.g.

scenario-specific approval, leaching criteria, etc.). Other engineering controls are still

being explored to reduce any risks posed by the use of MSWI BA. To date, little

laboratory or field research has been conducted to investigate road base products

containing a combination of MSWI BA and a more conventional aggregate source (e.g.,

lime rock). The idea of blending incinerator bottom ash with common granular materials

is one engineering control for risk reduction which has yet to be targeted in laboratory or

pilot studies. While blending the materials should reduce the total concentrations of

metals in the ash, leaching of certain species may not always be directly proportional to

the original mass of ash present. Other factors, including pH, solubility, redox, and

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surface complexation play a role in leaching [19], [21]–[23], thus materials-specific

testing is necessary to best assess risk.

Previous pilot studies conducted on bottom ashes assessed the leaching risk

posed by metals, but only when ash was the sole component in the base or subbase

material [4], [24]–[27]. Other research has investigated stabilizing bottom with cement

ash to enhance the mechanical properties of the material as a base, but the treatment

did not reduce heavy metals leachability [28]. In areas where reuse of MSWI BA is

approved by regulation, reuse as a road base may be hindered by a limited supply of

bottom ash. Road base and subbase projects require substantial amounts of aggregate,

often of such magnitude that MSWI bottom ash alone cannot sufficiently accommodate,

and thus diminish industry-wide acceptance. Combining MSWI BA with natural

aggregates may produce a blended aggregate product that provides some of the

economic and environmental benefits of materials recovery, but also offers contractors

a consistent and sustainable aggregate source. The practice of blending aggregates

may not only reduce dependency on natural resources, but could also reduce the

amount of environmental risk posed by the use of MSWI ash alone.

This research investigates the behavior of MSWI BA ash blended with a variety

of natural and recycled aggregates with a focus on leaching of trace metals (As, Mo, Pb,

Sb) and macro elements (Al). The study aims to assess the blending effect on bottom

ash leaching, and to examine if total metals and those leached can be reduced to an

acceptable level of risk for a road base. To examine this hypothesis, aggregate fractions

of two MSWI bottom ashes were blended with two natural aggregates and two recycled

aggregates in varying percentages, and a leaching analysis was performed using

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standard protocols. A total concentrations analysis of metals in the materials was also

performed.

Methods

Risk Assessment of Waste Materials

When assessing the risks to human health associated with the beneficial reuse of

a nonhazardous solid waste material, two exposure pathways are typically considered

[29]:

1. Leaching of aqueous COPC to water supplies (groundwater or surface water)

2. Direct exposure (DE) to COPC through direct human contact (e.g. inhalation, ingestion, dermal contact)

The risk of COPC leaching to water supplies is often measured using batch

leaching tests (concentration results in mg/L), while direct exposure (DE) risk is

relatable to the total metals content of the material (mg metal/kg material). COPC

concentrations obtained from batch leaching tests and total metals analyses are

typically compared to appropriate regulatory benchmarks or screening levels to assess

the potential risk posed to a specific exposure pathway. In the US, state regulatory

agencies set their own risk-based thresholds to characterize DE risk; these thresholds

vary depending on assumed exposure and risk criteria, as well as background soil

concentrations. For this analysis, we compare total metal concentration results to the

DE risk thresholds applicable to the location where the ash was generated (Florida Soil

Cleanup Target Levels (SCTLs; [30] and in some cases, the US EPA’s Regional

Screening Levels (RSLs) are compared to provide additional context [31]. Leach test

results were compared to the US EPA National Primary Drinking Water Standards

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(NPDWS) [32], and in some cases to residential tap water RSLs [31] (for constituents

with no health-based NPDWS).

Experimental Approach

Bottom ash samples collected from two MSW incinerators in Florida, US, were

characterized individually for total metals and leaching, and then blended with two

naturally-mined aggregates (lime rock, cemented coquina) and two recycled aggregates

(reclaimed asphalt pavement, recycled concrete) in different mass-based proportions.

Batch leaching concentrations for each ash and aggregate (derived using EPA

Method 1312, the Synthetic Precipitation Leaching Procedure (SPLP) [33] were used to

identify leaching COPC, and then blends of ash and aggregate were similarly leached.

COPC concentrations in the blended samples were compared to the predicted leachate

concentrations (mathematically weighting the leaching results on individual materials).

The leaching data were supplemented by conducting EPA Method 1316 [34] on the ash

samples and on select blends of ash and conventional aggregates. The data obtained

from Method 1316 were used to examine the release of metals over a range of liquid-to-

solid (LS) ratios, and to investigate the leaching behavior of solubility-controlled species

(As, Pb, Sb).

Total environmentally available (TEA) concentrations were used to identify

COPC which present a risk to the direct exposure pathway. After obtaining the TEA

concentrations of COPC in each material individually, concentrations in the blended

products were estimated empirically by multiplying the concentration of COPC in each

ash and aggregate by its prospective mass-based ratio in a blended product.

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Materials

MSWI Bottom Ash

Bottom ash generated at two Florida MSWI facilities (hereafter Facilities A and B)

was collected for this study. Facility A is a 62-megawatt refuse-derived fuel (RDF)

facility with a nominal bottom ash production of 400 Mg per day, and Facility B is a 95-

megawatt mass burn facility producing up to 700 Mg of bottom ash per day. Each

facility’s feedstock consists primarily of MSW along with small amounts of construction

and demolition debris. Following combustion and water quenching, bottom ash from

both facilities undergoes ferrous and nonferrous metal recovery as it exits the furnace.

Composite samples of bottom ash were collected from each facility during a 7-

day collection event following an EPA sampling protocol [35]. Approximately 10 Mg of

freshly quenched bottom ash was obtained daily from each facility’s ash bunker and

transferred to an on-site staging area over the course of one week. The samples were

obtained in a manner to ensure that only bottom ash was included. At the conclusion of

the 7-day sampling period, the seven individual piles of bottom ash were uniformly

mixed, and a 70 Mg composite stockpile was created for each facility. The stockpile was

representative of one week of routine ash production at each MSWI unit.

Each composite stockpile was left undisturbed for approximately 4 months to

allow for natural weathering (aging). Temporary weathering of MSWI BA has been

shown to immobilize various heavy metals by allowing for atmospheric carbonation and

the formation of insoluble metal hydroxides and carbonates, thus creating a more

environmentally inert material for reuse [19], [36]–[38]. After weathering, the stockpiles

were screened to obtain a desired particle size using an industrial aggregate vibratory

screen. The screening operation produced a bottom ash fraction containing particles 38

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mm in size and less (with many particles as small as 50 microns). A particle size

distribution of the two bottom ashes collected for this study can be found in the

supplemental materials accompanying this paper. The less than 38 mm in size fraction

of bottom ash was targeted under the assumption that it possesses the optimum

structural and geotechnical properties for reuse as a road base coarse (e.g., gradation,

optimum compaction, bearing strength). Several 20 kg composite samples of the

weathered, screened MSWI BA were collected from various locations on a circular

sampling pad in accordance with ASTM D75 [39] and sealed in 20L HDPE containers to

retain moisture and limit additional carbonation.

Natural and Recycled Aggregates

Two natural aggregate materials, Florida lime rock (LR) and cemented coquina (CC),

were used as components in blended products containing MSWI BA. CC aggregates

are naturally occurring deposits formed of broken mollusk shell, corals and the skeletal

remains of other marine invertebrates cemented together by carbonates or other natural

cementing agents [40]. LR aggregate consists of natural minerals, primarily calcium and

magnesium carbonates. Both materials have been approved by the Florida Department

of Transportation (FDOT) as graded aggregate road base and are produced at

aggregate mines in proximity to the MSWI facilities. Several 20 kg bagged samples of

the LR and CC aggregates were obtained directly from stockpiles at the aggregate

mines.

The recycled aggregates included reclaimed asphalt pavement (RAP) and recycled

concrete aggregate (RCA). Both materials were also collected in 20 kg bags from

aggregate stockpiles at a recycling facility in Florida. The RCA stockpile was pre-

approved as a graded aggregate road base material in Florida.

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Leaching Procedures

Synthetic Precipitation Leaching Procedure

For the SPLP, homogeneous samples of the weathered, screened MSWI BA

were size reduced to less than 9.5 mm using an industrial-grade blender, and mixed

with the natural and recycled aggregates in mass-based ratios of 0:100, 15:75, 30:70,

50:50, and 100:0 in a nonreactive HDPE vessel. The vessels were then filled with a

diluted 60:40 nitric and sulfuric acid extraction fluid (pH = 4.2 ± 0.05) at a LS ratio of

20:1. The solutions were placed on a standard rotary agitator at room temperature and

rotated for 18 hours. The resulting eluent was extracted by vacuum filtration through a

0.7-micron glass microfiber filter, and a 50-mL aliquot of the leachate was preserved for

elemental analysis. SPLP extractions were performed in triplicate for all materials and

blended proportions.

Leaching as a Function of Liquid-to-Solid Ratio

EPA Method 1316 was performed in duplicate on the two ash samples and on

blended samples containing 15% bottom ash and 85% of either RCA or LR. The

necessary mass of the size reduced (< 2 mm) materials was added to a volume of

reagent water to obtain 5 target LS ratios: 0.5, 1, 2, 5, and 10 L/kg. The samples were

agitated in an end-over-end fashion for 48 hours and the eluent was vacuum-filtered

through a 0.45-micron polypropylene filter and preserved for elemental analysis.

Analytical Procedures

For TEA characterization, several 2-g samples of MSWI BA and aggregate

samples were size reduced to < 2 mm, then digested using a microwave-assisted

HCl/HNO3 acid digestion following EPA Method 3051A [41]. Leachates obtained from

the batch leaching tests were prepared for elemental analysis using an automated hot

24

block HCl/HNO3 acid digestion in accordance with EPA Method 3010A [42]. Following

each digestion procedure, both the leachate and solid samples were analyzed for 23

inorganic elements (Al, As, B, Ba, Be, Ca, Cd, Cr (total), Cu, Fe, K, Mg, Mn, Mo, Na, Ni,

Pb, Sb, Se, Sn, Sr, V, and Z) using inductively coupled plasma atomic emission

spectrometry (ICP–AES) in accordance with EPA Method 6010D [43] . TEA

concentrations were reported as the average of five replicates analyzed for each

material. Concentrations were reported on a dry-mass basis. Leachate concentrations

were reported as averages of the triplicate SPLPs performed on each material and each

blend of materials. Standard quality control and quality assurance measures including

method blanks, blank spikes, matrix spikes (75% - 125% recovery), certified metal

standard solutions, and duplicate spectrometer exposures were applied during the

analysis.

Results and Discussion

Direct Exposure Pathway

MSWI bottom ash

The TEA concentrations results of the two bottom ashes found six inorganic

elements to exceed the residential SCTL: As, Ba, Cr, Cu, Pb, and Sb. The total

concentrations of these elements were above the SCTL in both of the ashes analyzed,

with the exception of Cr (only exceeded for facility A ash). These six elements are

considered COPC to DE in terms of the bottom ash itself. The measured total

concentrations of these elements were similar to the range of concentrations of other

incinerator bottom ashes [2], [8], [44]–[46]. Of the 6 metals that exceeded the residential

SCTL, none exceeded the corresponding commercial thresholds. Table 2-1 displays the

total concentrations of the six COPC in comparison to the residential and commercial

25

SCTLs. As, Ba, Cr, Pb and Sb marginally exceeded the residential limit (concentrations

of these elements were within three times of the benchmark). The total concentration of

Cu in both bottom ashes (3400 mg/kg and 1900 mg/kg) exceeded the residential SCTL

by an order of magnitude. Total Cu was well below the commercial SCTL of 89,000

mg/kg.

Natural and recycled aggregates

The four natural and recycled aggregates were found to be relatively low in total

metal concentrations in comparison with risk-based DE thresholds. Only As exceeded

the residential SCTL, with a total concentration of 3.5 mg/kg in the lime rock and 6.4

mg/kg in the RCA. Thus, As is considered a COPC to the DE pathway in limerock and

RCA. These concentrations were comparable to the total As concentrations in both

MSWI ashes (5.17 mg/kg and 7.68 mg/kg). Previous research has reported background

soil As concentrations in the same geological area to be above the residential SCTL

[47]. RAP and CC aggregates produced no elements with total concentrations above

the Florida residential SCTL.

Blended products

The TEA concentrations of metals calculated in the blended products suggests

that DE risk to bottom ash is reduced a with the addition of other aggregates.

Concentrations of all bottom ash COPC declined as ash was substituted with any of the

four other aggregates. At a mass-based ratio of 15:85 BA to aggregate, the estimated

total concentrations of four of the original six bottom ash COPC (Ba, Cr, Pb, Sb) fell

beneath the residential SCTL. The theoretically calculated TEA concentrations of the

blended products containing 15% bottom ash can be seen in Table 2-2. As and Cu were

estimated to exceed the residential SCTL at all of the blended proportions considered,

26

however, blends containing CC and RAP were within 10% of the residential SCTL for

these elements. Again, as the arsenic concentration in BA is similar to lime rock and

RCA, which are major construction materials of common use, this element was not

viewed as problematic to the DE risk pathway.

The estimated values of total Cu exceed the residential target level in all four

blended products, even at low ash percentages. This is partly due to the fact that the

Florida residential SCTL for Cu (150 mg/kg) is significantly more stringent than the

commercial limit (89,000 mg/kg), as compared to the limits for the other COPCs. The

larger discrepancy between the residential and commercial benchmarks for Cu can be

explained by the methodology in which they were developed, where an acute exposure

scenario rather than chronic exposure was assumed [48]. The use of acute toxicity data

as reference dose for Cu implied that a child might ingest a relatively large quantity of

soil (>10 g) at one time (this is unlikely for BA placed beneath a pavement). Additionally,

if the US EPA RSL for total Cu (residential setting) of 3,100 mg/kg were applied, Cu

would not be considered a residential COPC to DE in any of the reported blended

proportions, including BA itself. If it is assumed that the current SCTLs for Cu and As

are overly conservative, BA could be introduced to the blends at more than 30% by

mass until total concentrations of other COPC (primarily Pb) would approach their

respective SCTLs and begin to present a DE concern.

Leaching to Groundwater Pathway

MSWI bottom ash

The SPLP leaching tests conducted on the two bottom ashes identified four

COPC that might possibly present a leaching risk to water supplies: Al, As, Pb, and Sb.

In Table 2-3, the SPLP leachate concentrations from both bottom ashes are compared

27

to risked-based drinking water standards. Average leachate concentrations of Al, As,

Pb, and Sb were greater than or equal to the NPDWS in at least one of the two leached

bottom ashes. The elevated leaching of these four COPC is consistent with other batch

leaching tests performed on weathered bottom ashes under similar laboratory

conditions [46], [49]. Arsenic leached from Facility B ash at the same concentration as

the NPDWS, and below the method detection limit for Facility A ash. Pb leachate

concentrations narrowly exceeded the NPDWS by 5 ± 1 µg/L in one bottom ash, and

was below detection limit in the other. The low concentrations of Pb and As with respect

to the NPDWS suggests that these COPC do not pose a significant health risk at a

groundwater point of compliance, where leachate concentrations are expected to be

much lower after being reduced by natural dilution and attenuation factors in the

subsurface environment [50], [51]. Furthermore, the weathering of fresh MSWI BA is

effective in controlling the mobility of Pb by reducing the natural bottom ash pH to levels

at which amphoteric Pb species become insoluble [37], thus allowing the risk of Pb

leaching from road base to be accurately predicted and controlled.

Al and Sb leached to the greatest extent in both ashes, exceeding risk-based

MCL’s by factors of approximately five and six, respectively. Sb likely poses a greater

leaching risk than Al in an unencapsulated road base scenario, given its classification

as a primary drinking water contaminant in the US and its behavior as a blood irritant at

low reference doses [32]. The data provided in Table 2-3 suggests that Al and Sb are

the two primary metals in the MSWI BA leachates that should be monitored for a

reduction in the blended products.

28

Natural and recycled aggregates

The four natural and recycled aggregates investigated were relatively inert in

regard to metals leaching, as expected. Compared to the BA, these aggregates leached

much less in terms of COPC. Molybdenum, a natural lime rock impurity, appeared in the

lime rock aggregate (0.064mg/L) and RCA (0.049 mg/L) at concentrations higher than

both bottom ashes (0.024 mg/L), but below the EPA RSL of 0.1 mg/L. The presence of

Mo in the leachate of both of these materials is unsurprising, as lime rock is a commonly

used aggregate in the production of portland cement concrete, and in turn is likely to be

present in recycled concrete. Any risk posed by Mo leaching is considered marginal as

batch test concentrations are well below the EPA RSL of 0.1 mg/L, and concentrations

of Mo are known decrease with increasing time and L/S ratios [52].

In the RAP samples, the average Ni, and Pb leachate concentrations were

elevated in comparison to drinking water standards, however, the standard deviation of

Ni concentrations in the batch leaching test was greater than the arithmetic mean, and 2

of the 3 triplicate samples were below the method detection limit for Ni. Ni is not known

to be a leaching COPC in RAP according to data from other studies on the material [53].

Pb leached from the RAP in this study at a concentration equal to the NPDWS.

Elevated Pb leaching from RAP has been reported in column leaching experiments [54],

but the peak concentrations decreased sharply with elapsed time, and were below 0.1

µg/L at the end of the 40-day column extraction.

Blended products

The SPLP leaching tests performed on blended proportions of MSWI BA and the four

aggregates showed a reduction in leachate concentrations of some elements initially

identified as COPC in the ash itself. At all blended proportions tested, the introduction of

29

other aggregates to the MSWI BA showed a reduction in concentration of most COPCs.

Mixtures containing 15% MSWI BA and 85% aggregate were the most environmentally

inert products in respect to leaching. Table 2-4 presents the SPLP leaching data from

the blends containing 15% bottom ash. As can be seen in Table 2-4, several of the ash

COPC initially identified in Table 2-3 were no longer in exceedance of drinking water

standards when the ash was blended with other aggregates. Leaching of aluminum was

clearly dependent on the mass of bottom ash present in the blend. This can be seen in

Figure 2-1, where Al leached below the RSL of 20 mg/L for blends containing 15% and

30% bottom ash. In fact, leaching of Al displayed a near linear relationship between the

measured leachate concentration and the mass of bottom ash included in the blend.

This linear relationship for Al leaching can be observed in Figure 2-2.

Unlike Al, the leaching of Sb from the bottom ashes remained elevated above the

NPDWS, and was relatively unaffected by the addition of three of the four tested

aggregates (LR, RAP, CC). This suggests that leaching of Sb species is primarily

controlled by solubility and is unaffected by the mass of bottom ash contained in a

sample. Other research has found that solubility to be the primary mechanism affecting

the leaching behavior of oxyanion-forming elements such as Sb [55]. However, in

blends containing RCA, the observed leachates steadily decreased in Sb concentration

as ash was substituted with RCA. At a mixture of 15% ash and 85% RCA, leaching of

Sb was at or within 1 µg/L of the NPDWS. The pH-dependent leaching behavior of Sb

can be observed in data from a pH static leaching procedure (EPA Method 1313) [56]

performed on MSWI BA in the supplemental materials of this paper. MSWI BA displays

a leaching minima for Sb in the 10.8 -11.0 pH range of mildly weathered MSWI BA, and

30

dissolution increases at pH > 11, while over-carbonation of fresh bottom ash to pH < 9

increases leaching of Sb due to equilibrium with calcium antimonite [36]. The eluent pH

of the SPLP on the blend of 15% BA and 85% RCA (10.97) was in the leaching minima

range for Sb, thus these blends leached less Sb compared to the other three aggregate

blends. The leaching behavior of Sb in the SPLP on the 15% ash blends can be seen in

Figure 2-3, in which RCA clearly shows a lower Sb release as compared to the other

blends. In Method 1316, however, the 15/85 blends of ash and RCA leached below the

NPDWS for Sb at all LS ratios, even at equilibrium pH values > 11, where MSWI BA

should release more Sb according to the pH dependence observed from Method 1313.

The leaching of Sb in Method 1316 can be seen in Figure 2-4, where Sb leached much

less from RCA blends compared to lime rock blends containing the same percentage of

bottom ash.

Arsenic leaching was relatively unaffected by the addition of other aggregate

sources, and remained below the method detection limit or within 2 µg/L of the NPDWS.

Iron and nickel leaching was below target levels for all materials at all blended

percentages.

Implications for Reuse as Road Base

Two pathways of human health and environmental risk posed by MSWI bottom

ash used as road base were assessed: DE and leaching to groundwater. The DE risk

pathway for BA is not a major concern during the use phase of a road base due to a low

likelihood of direct human contact while the bottom is confined underneath an asphalt or

concrete pavement coarse of varying thickness. The total metals results demonstrated

that blending should reduce DE risk to a point where the blended product the complied

with most COPC regulated by residential SCTLs (the most stringent category of soil

31

benchmarks in Florida, and a conservative benchmark for a granular base or subbase

layer). Cu persisted in the blended products at levels higher than residential SCTL of

150 mg/kg, but below the EPA RSL for residential soils. The latter set of contaminant

benchmarks are developed using tools such as the EPA's Integrated Risk

Information System (IRIS) and The Agency for Toxic Substances and Disease

Registry (ATSDR) to provide the most up to date and accurate toxicity data inputs.

Total concentrations of Cu in US bottom ashes should decline in the future as

incinerator operators explore increased nonferrous metal recovery technologies [57].

From a DE perspective, the blending of aggregates with MSWI BA showed that the risk

posed by COPC is low and should not be prohibitive to the inclusion of bottom ash into

the stream of road construction aggregates.

When assessing the leaching pathway, the SPLP demonstrated that Al and Sb

were the most likely elements to exceed risked-based concentrations for groundwater.

For Al, leaching was reduced by the amount of bottom ash contained in the sample, but

the actual aggregate which was blended with the bottom ash did not compound an

additional reduction in metals leaching. Given the mass-dependent leaching

relationship, the anticipated increase of nonferrous metal recovery from incinerator

ashes should certainly reduce the environmental burden presented by Al leachates [58].

Sb presented to be the most prominent leaching risk, but immobilization of Sb seems to

achievable by blending ash with a calcium-bearing aggregate material such as RCA,

having an alkaline pH and mineralogy with an adsorption affinity for Sb. The reduced Sb

leachate concentrations in RCA blends at a high equilibrium pH suggests that other

interactions between with calcium-bearing minerals (portlandite and ettringite) could be

https://www.epa.gov/iris

http://www.atsdr.cdc.gov/

32

responsible for the Sb immobilization observed in the RCA blends, and pH is not the

sole mechanism controlling dissolution. The higher abundance of the portlandite and

ettringite mineral phases in RCA as compared to the other three aggregates and MSWI

BA itself may allow for a higher rate of adsorption and corresponding reduction in

leaching.

Summary of Findings

In this study, the blending of conventional road base aggregates with MSWI BA

reduced the relative direct exposure and groundwater contamination risks posed by

metals inherent to the bottom ash. For most of the blends of materials considered, the

total and leached concentrations of COPC declined as bottom ash was replaced with

the cleaner aggregates. Sb leached at elevated concentrations in blends containing

even small proportions of bottom ash, but RCA was found to mitigate Sb leaching in

these blends to levels comparable to drinking water standards. The analysis of the

leaching data suggests that the environmental risk posed by most bottom ash COPC

decreases when the ash is combined with a cleaner road base aggregate, and blending

of such aggregates presents a unique opportunity for the generation a sustainable

construction product to be used in road base infrastructure.

33

Figures and Tables

Table 2-1. Total environmentally available concentrations (mg/kg-dry material) of MSWI bottom ash and natural/recycled aggregate materials. Total concentrations exceeding the residential Florida Soil Cleanup Target Levels are identified as COPC for the direct exposure risk pathway and have been shaded accordingly.

MSWI Bottom Ash Natural Aggregates Recycled Aggregates Soil Benchmarks

Facility A

< 38 mm,

weathered

Facility B

< 38 mm,

weathered

LR CC RCA RAP Florida SCTL

(Residential)

Florida

SCTL

(Commercial)

US EPA

RSL

(Residential)

As 5.17 ± 2.99 7.68 ± 1.82 3.50 ± 0.268 1.37 ± 0.445 6.38 ± 0.693 1.27 ± 0.586 2.1 12 0.68

Ba 307 ± 69.7 245 ± 27.6 25.6 ± 2.94 4.73 ± 0.563 39.4 ± 3.30 10.2 ± 0.837 120 130,000 150,000

Cr (total) 305 ± 198 205 ± 87.7 40.8 ± 4.95 79.6 ± 38.7 55.1 ± 2.01 70.4 ± 9.35 210 470 -

Cu 3400 ± 1290 1920 ± 1780 2.43 ± 0.374 2.26 ± 1.11 45.1 ± 3.26 6.02 ± 0.619 150 89,000 3100

Pb 446 ± 111 981 ± 352 0.826 ± 0.00 0.816 ± 0.00 12.1 ± 1.54 7.90 ± 3.88 400 1,400 400

Sb 39.4 ± 14.5 39.6 ± 12.1 2.24 ± 0.541 1.98 ± 1.27 2.27 ± 0.560 2.15 ± 0.466 27 370 31

34

Table 2-2. Theoretical total environmentally available concentrations (mg/kg-dry) of blended products containing 15% MSWI bottom ash and 85% natural or recycled aggregates. Elemental concentrations exceeding the Florida Residential Soil Cleanup Target levels are identified as COPC and are shaded accordingly.

Facility A Blended Products 15%

MSWI Bottom Ash

< 38 mm, weathered

Facility B Blended Products 15% MSWI Bottom Ash

< 38 mm, weathered

Soil Benchmarks

85%

LR

85%

CC 85% RCA

85% RAP

85% LR

85% CC

85% RCA

85% RAP

Florida SCTL

(Residential)

Florida

SCTL

(Commercial)

US EPA

RSL

(Residential)

As 3.74 1.92 6.20 1.84 4.10 2.27 6.57 2.21 2.1 12 0.68

Ba 66.8 48.6 79.3 54.2 57.5 39.3 69.8 44.7 120 130,000 150,000

Cr (total) 79.5 112 92.4 105 64.6 97.6 77.2 90.0 210 470 -

Cu 500 495 545 507 281 287 322 287 150 89,000 3100

Pb 65.9 65.3 76.7 72.7 143 150 155 150 400 1,400 400

Sb 7.68 7.41 7.80 7.66 7.66 7.64 7.78 7.64 27 370 31

35

Table 2-3. Average leachate concentrations of EPA Method 1312 (SPLP) performed in triplicate on MSWI bottom ashes and natural/recycled aggregates individually. Elemental concentrations exceeding the respective MCL are identified as COPC for the leaching to groundwater risk pathway and have been shaded accordingly.

MSWI Bottom Ash Natural Aggregates Recycled Aggregates Groundwater Benchmark

Facility A < 38 mm,

Weathered

Facility B < 38 mm,

Weathered

Cemented Coquina

Florida Lime rock

Recycled Concrete

Aggregate

Reclaimed Asphalt

Pavement

Maximum Contaminant Level

Element mg/L ± std

dev mg/L ± std

dev mg/L ± std

dev mg/L ± std

dev mg/L ± std

dev mg/L ± std

dev mg/L

Al 112 ± 2.07 52.6 ± 8.75 0.116 ± 0.049

0.154 ± 0.061 2.86 ± 0.008 0.240 ± 0.077 20***

As < 0.004 0.010 ± 0.002 < 0.008 < 0.008 < 0.008 < 0.008 0.01*

Fe 0.009 ± 0.004 < 0.004 < 0.004 < 0.004 < 0.004 0.399 ± 0.684 14**

Mo 0.024 ± 0.000 0.024 ± 0.001 < 0.006 0.064 ± 0.009 0.049 ± 0.004 < 0.006 0.10**

Ni < 0.004 0.008 ± 0.006 < 0.002 < 0.002 < 0.002 0.326 ± 0.562 0.2**

Pb 0.020 ± 0.001 < 0.008 < 0.008 < 0.008 < 0.008 0.015 ± 0.012 0.015*

Sb 0.043 ± 0.006 0.037 ± 0.004 < 0.006 < 0.006 < 0.006 < 0.006 0.006*

Eluent pH

10.7 ± 0.04 10.2 ± 0.04 8.13 ± 0.40 8.64 ± 0.13 10.97 ± 0.44 7.83 ± 1.10 -

*US EPA National Primary Drinking Water Standard **US EPA Regional Screening levels (RSL) for residential tap water was applied in the absence of a NPDWS for a given pollutant. RSLs for carcinogens are based on a target cancer risk = 1 in 1,000,000. RSLs for non-carcinogens are based on a hazard quotient =1. ***The National Secondary Drinking Water Standard for aluminum of 0.2 mg/L was established to meet certain aesthetic conditions for drinking water and is not toxicity-based. The health-risk based RSL of 20 mg/L was substituted to accurately quantify the risk Al poses to human health.

36

Table 2-4. Average leachate concentrations of EPA Method 1312 (SPLP) performed in triplicate on blends of MSWI bottom ash and natural/recycled aggregates at a mass ratio of 15:85. Elemental concentrations of contaminants which exceed the respective MCL are identified as COPC for the leaching to groundwater risk pathway and have been shaded accordingly.

Facility A Blended Products

15% MSWI Bottom Ash, < 38 mm, weathered

Facility B Blended Products

15% MSWI Bottom Ash, < 38 mm, weathered

Groundwater

Benchmark

85%

LR

85%

CC

85%

RCA

85%

RAP

85%

LR

85%

CC

85%

RCA

85%

RAP

Maximum

Contaminant

Level

Element mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev

mg/L ± std

dev mg/L

Al 22.7 ± 0.77 23.6 ± 0.76 7.89 ± 0.79 12.6 ± 0.14 8.93 ± 0.24 10.8 ± 1.93 5.56 ± 1.00 8.34 ± 2.54 20***

As < 0.004 < 0.004 < 0.004 < 0.004 0.009 ± 0.002 0.010 ± 0.003 0.010 ± 0.002 0.012 ± 0.003 0.010*

Fe 0.009 ± 0.004 0.011 ± 0.006 0.018 ± 0.002 0.031 ± 0.014 < 0.004 < 0.004 < 0.004 < 0.004 14**

Mo 0.086 ± 0.002 < 0.006 0.063 ± 0.001 < 0.006 0.081 ± 0.002 < 0.006 0.057 ± 0.002 < 0.006 0.10**

Ni < 0.004 0.004 ± 0.003 0.005 ± 0.002 0.015 ± 0.012 < 0.002 < 0.002 < 0.002 < 0.002 0.2**

Pb < 0.004 < 0.004 0.017 ± 0.007 < 0.004 < 0.004 < 0.004 < 0.004 < 0.004 0.015*

Sb 0.036 ± 0.001 0.034 ± 0.002 0.006 ± 0.002 0.040 ± 0.003 0.029 ± 0.000 0.026 ± 0.000 0.007 ± 0.001 0.027 ± 0.002 0.006*

Eluent

pH 10.46 ± 0.03 10.67 ± 0.06 11.33 ± 0.03 10.32 ± 0.03 9.92 ± 0.02 9.90 ± 0.06 11.04 ± 0.16 9.88 ± 0.65 -

*US EPA National Primary Drinking Water Standard **US EPA Regional Screening levels (RSL) for residential tap water was applied in the absence of a NPDWS for a given pollutant. RSLs for carcinogens are based on a target cancer risk = 1 in 1,000,000. RSLs for non-carcinogens are based on a hazard quotient =1 ***The National Secondary Drinking Water Standard for aluminum of 0.2 mg/L was established to meet certain aesthetic conditions for drinking water and is not toxicity-based. The health-risk based RSL of 20 mg/L was substituted to accurately quantify the risk Al poses to human health.

37

Figure 2-1. Concentrations of aluminum in SPLP leachates for blends of Facility A

MSWI bottom ash and natural or recycled aggregates as a function of the bottom ash contained in the blended product. The risk-derived US EPA Regional Screening Level for aluminum (residential tap water) is displayed as dashed reference line.

38

Figure 2-2. Ratio of aluminum leachate concentrations in the control bottom ashes to

aluminum leachate concentrations in blended products containing lime rock and bottom ash at percentages of 0%, 15%, 30% and 50%, and 100% ash (SPLP batch leaching test).

39

Figure 2-3. Concentrations of antimony in SPLP leachates for blends containing

weathered MSWI bottom ash and four different aggregates. Antimony leachate concentrations are plotted as a function of bottom ash contained in the blended product. The US EPA National Primary Drinking Water Standard for antimony is displayed as a dashed reference line.

40

Figure 2-4. Leaching of Antimony as a function of LS ratio (EPA Method 1316) in

blended products containing 15% weathered MSWI bottom ash and 85% RCA and LR aggregates.

41

CHAPTER 3 CHARACTERIZATION AND MITIGATION OF ALKALI-AGGREGATE REACTIVITY IN MORTARS CONTAINING MUNICIPAL SOLID WASTE INCINERATION ASH AS AN

AGGREGATE COMPONENT

Background

The practice of incorporating solid waste products into the manufacture of

construction materials such as portland cement (PC) and PC concrete is gaining

popularity due to a growing awareness into the sustainable management of materials

[59]–[61]. Bottom ash (BA) residues produced from municipal solid waste incineration

(MSWI) possess physical properties similar to common natural aggregates [6], and

reuse of MSWI BA as a coarse aggregate in hardened concrete is a prospective second

life application for the waste material [11], [16], [49], [62]. In densely populated countries

where incineration is a common waste management technique [3], [63], [64] , thousands

of tons of MSWI BA are generated annually. The availability of such quantities of MSWI

BA could offset the mining of natural concrete aggregates if recycling rates of ash are

increased.

In portland cement concrete (PCC), a number of deleterious alkali-aggregate

reactions (AAR) can occur between interaction of the alkali hydroxides found in cement

paste and reactive minerals present in certain aggregates. One particular form of AAR,

the alkali-silica reaction (ASR), is a common reaction between the amorphous silica of

certain aggregates and the alkali species (KOH, NaOH) in cement paste [65] . ASR is

well known to produce deleterious effects to concrete when reactive, siliceous minerals

are used as aggregates [66]. The dimensional expansion produced by the swelling of

silica-based gels in the presence of moisture can propagate cracking and result in an

overall reduction in the integrity and serviceability of the affected concrete. It has also

42

been documented that fine particles of aluminum in MSWI BA may produce similar

expansive reactions [67]. The high content of amorphous silica and metallic aluminum in

MSWI BA present an AAR risk. It is critical that the potential for any AAR in MSWI BA is

evaluated in order to ensure that ash-amended concrete will maintain suitable durability

during its service life.

To date, the potential for AAR to occur in MSWI BA as an aggregate replacement

in concrete has not been comprehensively examined throughout research. Müller and

Rübner [68] identified three types of AAR in specimens of field and laboratory concretes

containing MSWI bottom ash as a partial aggregate replacement:

1. Alkali-silica reaction of bottle glass fragments and glassy compounds of other siliceous components of the bottom ash

2. Reaction of elemental aluminum to form aluminum hydroxide and calcium aluminate hydrate (CAH) and

3. Reaction of aluminate with calcium sulfate to form ettringite and monosulphate

Damage as a result of the aluminum hydroxide reaction was reported to be more

severe than that caused by ASR. Deleterious cracking, spalling, and longitudinal voids

were attributed to the reaction of aluminum and the evolution of hydrogen gas. It should

be noted that this study used petrographic techniques to characterize AAR; dimensional

length changes of the concrete specimens were not reported; information which is

pertinent to accurately quantify the presence of reactive aggregates and the magnitude

of relative degradation caused by AAR. Van den Heede et al., [69] observed the

expansion of concrete blocks made with bottom ash as a full aggregate replacement

(100% coarse and fine), and found expansion to be more than double that of the

reference concrete, indicating that an AAR had occurred. However, both the ash-

43

amended and reference concretes in the study expanded by more than 0.1% over 14

days; the industry expansion limit indicative of innocuous field performance per ASTM

C160 [70]. This anomaly indicates the possibility that a reactive material was present in

the reference concrete, or that the testing conditions were overly aggressive for proper

characterization of the MSWI BA under investigation. Chemical methods have been

utilized to provide a rapid indication of the AAR potential of aggregates [71]; Forteza et

al. [6] performed a chemical analysis as part of a geotechnical assessment of

incinerator ashes in Spain using the Spanish method UNE 146507-1:1999 [72]. This

study reported the BA as nonreactive after a granular fraction of ash was immersed in a

1N solution of NaOH at 80° C for 24 hours, and the corresponding leachate was

measured for levels of dissolved silica and alkalinity.

The conclusions on AAR in MSWI BA obtained from a small sample size of

research suggests the need for rapid and conclusive information on the issue of AAR in

concrete or mortar containing BA as an aggregate, and a quantification as to the

amount of damage that can be attributed to inclusion of the BA. The limited amount of

comprehensive data summarizing the expansion of bottom ash-amended specimens

was the main motivation in performing this study. Due to the significant amount of time

required to test the expansion induced by reactive aggregates in actual concrete

specimens (minimum of 64 weeks), the accelerated mortar bar test (AMBT) was

adopted for use in this study [70] . The AMBT can be used to rapidly quantify the AAR

of aggregates (in as little as 16 days) by immersing small mortar bars in a highly

alkaline solution at elevated temperatures and monitoring periodic length change of the

specimens. Expansion results obtained from the short term AMBT are known to

44

correlate well with those obtained in the 15-month concrete prism test, and yield an

accurate indication of reactivity. [73], [74].

In this study, three different sources of MSWI BA were used as partial aggregate

replacements in the AMBT to determine the maximum amount of BA that could be

introduced to mortars before deleterious expansion was observed. Furthermore, two

supplementary cementitious materials (class F coal fly ash and a ground glass powder)

were investigated as mineral admixtures to mitigate AAR in the ash-amended mortars,

as many SCM’s are known to reduce the deleterious reactions caused by reactive

aggregates [73], [75], [76].

Materials and Methods

Bottom Ash Collection and Material Description

Three bottom ashes (hereafter referred to as BA1, BA2, and BA3) were collected

from different municipal waste incinerators in the southeastern United States.

Composite samples of the freshly quenched ashes were obtained over a 7-day period,

and immediately transported to outdoor stockpiles where they were weathered or aged

for approximately 90 days to facilitate atmospheric carbonation and allow the formation

of stable metal hydroxides and carbonates. Research indicates that aging limits the

environmental mobility of select heavy metals contained in the ash [37], [77]. BA3 was

sampled as a combined ash stream (containing bottom and fly ash), then processed to

remove any material finer than 6 mm, effectively removing all fly ash content from the

sample. The weathered bottom ashes were sieved in the field using a large double-deck

vibratory screening conveyor to obtain an aggregate particle size range of 6.35 mm -19

45

mm. The stockpiles of screened bottom ash were then sampled in accordance with

ASTM D75 [39].

Physically, the weathered bottom ash samples comprised of a heterogeneous

mixture of mineral components (primarily silicates), ceramics, and some incompletely

combusted organics and deleterious materials (textiles, fibers, food scraps). Fragments

of ferrous and nonferrous metals (primarily aluminum, copper, and zinc) were visible in

the ash, which had not extracted by the ferrous magnets and eddy current separators

installed at each incinerator. A chemical composition of each bottom ash analyzed using

X-ray fluorescence spectroscopy is presented in Table 3-1. The high alkali content of

the MSWI BA (> 5%) in comparison to the cementitious components of the mortars is

noteworthy, as portland cement is typically the main source of alkalis in the material

system which contribute to AAR. As aggregates typically account for 50-70% of the total

volume of concrete, it is expected that the inclusion of MSWI BA will result in a higher

total alkali load to the system.

Cementitious Materials

The cement used in the AMBT was classified as a type I/II PC as per ASTM

C150 [78]. Two pozzolans were used in an attempt to mitigate the expected expansion

in the ash-amended mortars. A class F (low calcium) fly ash was obtained from an

electrostatic precipitator at a coal-fired power station in Jacksonville, FL and met the

specifications for class F fly ash per ASTM C618 [79]. A low-alkali ground glass powder

was obtained from a local glass recycling facility.

Experimental Approach

A total of 16 mortar mixes were created and used in two variations of the AMBT

to quantify length change of specimens containing BA as a partial aggregate. An initial

46

series of 10 mixes were cast based on ASTM C1260 [70], with each BA replacing a

nonreactive natural sand in mass-based percentages of 0% (control), 15%, 30%, and

50%. The mortar used in this series of bars contained only Type I/II PC as the binder.

Length change of these specimens was measured to quantify the maximum allowable

BA content that could be introduced while maintaining innocuous expansion. Then, an

additional set of 6 mixes were cast according to ASTM C1567 [80]. Each of these

mortars contained an aggregate content of 30% MSWI BA, and a binary cementitious

matrix comprised of 80% PC and 20% SCM (ground glass or class F fly ash). The

expansions of this set of bars was compared to the initial ASTM C1260 mortars to

identify any reduction in expansion achieved by the addition of a pozzolan. Scanning

electron microscopy (SEM) was performed on several post-mortem specimens to

observe the specific AAR products that had evolved in the ash-amended mortars.

Preparation of Mortar and Experimental Procedure

Specimens cast to measure the expansion of mortar containing MSWI BA

aggregates in the AMBT were prepared following the guidelines specified in ASTM

C1260 [70]. The three BA’s and a nonreactive sand were dried in an oven at 100°C,

then size reduced using a benchtop jaw crusher with tungsten carbide plates to produce

the fine aggregate gradation specified in ASTM C1260 [70]. All materials were

proportioned using a Mettler-Toledo PB3002-S scale with a 0.01 g precision. The

mixtures were batched with the prescribed fine aggregate:binder:water ratio of

2.25:1:0.47. In the event that the fine aggregates (bottom ash and sand) resulted in an

average weighted specific gravity of less than 2.45, the aggregates were proportioned

according to the equation denoted in ASTM C1260 Part 8.4.3 “Proportioning of Mortar”

47

[70]. Each aggregate replacement was proportioned as a percentage of the total

aggregate content. Mortar proportions for specimens containing only BA, cement, and

the nonreactive sand are presented in Table 3-2. The two pozzolans used were

introduced as a percentage of the total cementitious content. Mortar mixes containing

combinations of PC, fly ash, ground glass, BA, and natural sand were prepared in

accordance with ASTM C1567 [80]. The specific mortar proportions for the binary mixes

can be seen in Table 3-3.

Mortars were mixed using a stainless steel mixing bowl and paddle stirrer

following the mixing sequence listed in ASTM C305 [81]. After being mixed, the mortar

was placed into steel double-gang molds of dimension 25.4 mm x 25.4 mm x 254 mm

with steel gage studs embedded at a fixed length. The molded mortar specimens were

allowed to cure in air for 24 ± 2 hr (while preventing any loss of moisture), then

demolded, measured for initial dimensions, and placed in cylindrical HDPE containers,

where they were completely submerged in a tap water bath at 80°C for an additional 24

± 2 hr period. Following removal from the water bath, initial zero readings of the

specimens were taken using a dial gauge comparator with precision of 0.0025 mm and

a fixed-length invar calibration bar. After the zero reading, the bars were reintroduced to

the containers and immersed in a 1N NaOH solution at 80° C. The containers remained

in the NaOH bath for 14 days and expansion measurements were taken using the dial

gage comparator at ages of 4, 7, 10, and 14 days. The average 14-day length change

readings of the four replicate bars for each mortar mix was reported.

48

Results and Discussion

AMBT Expansion

The length change measurements of the ash-amended mortar specimens are

presented in Table 3-4. Mortars which expand more than 0.10% during the AMBT are

considered to be potentially deleterious, and those exceeding 0.20% are considered

deleterious, as per ASTM’s C1260 [70] and C1567 [80]. The 30% BA and 50% BA

mortars containing only portland cement expanded beyond the deleterious limit of

0.20%. At 15% aggregate replacement, BA1 and BA2 mortars exceeded 0.10%

expansion, but did not reach the deleterious threshold (Figures 3-1 and 3-2). BA3

performed innocuously at 15% aggregate replacement (Figure 3-3). The length change

data from this evaluation indicates that MSWI BA could replace 15% of the nonreactive

sand before deleterious effects would be expected in field concretes or mortars using

the same mix proportions (if Type I/II portland cement is the sole binder used).

For the binary mortars containing 20% pozzolan, all specimens were classified

as innocuous at an aggregate replacement of 30% BA (Figures 3-4, 3-5, and 3-6). Both

fly ash and ground glass were effective in reducing reactivity during the AMBT, and

limited total of expansion all specimens to under 0.05% - less than half of the innocuous

limit. Neither pozzolan appeared to outperform the other in terms of relative reduction in

expansion. Both pozzolans reduced the expansion of the ash-amended specimens by

approximately 90% for each of the three MSWI BA studied in the AMBT.

49

Summary of Findings

The following conclusions were made regarding mortars made with MSWI BA as

an aggregate replacement in the AMBT:

1. MSWI BA is abundant in amorphous silica, which facilitated the alkali-silica reaction and produced expansive reaction products when MSWI BA was in the presence of alkalis and water.

2. The alkali-silica reaction was the dominant expansive reaction observed in the ash-amended mortars, more so than the alkali-aluminum reaction. The latter of which was not correlated with expansive reactions, only instances of spalling and hydrogen gas evolution.

3. Inclusion of MSWI BA as an aggregate at replacements greater than 15% resulted in deleterious expansion of mortar specimens containing only portland cement.

4. The introduction of pozzolanic ground glass or class F fly ash to the cementitious matrix reduced the expansion associated with AAR of the MSWI BA by approximately 90%, and increased the achievable percentages of MSWI BA as an aggregate replacement to levels of at least 30%.

50

Figures and Tables

Table 3-1. Oxide composition (% weight) of materials obtained using X-ray fluorescence (XRF) spectroscopy.

Aggregates Cementitious Materials1

Analyte BA1 BA2 BA3 Type I/II

PC Class F Fly Ash

Ground Glass

SiO₂ 43.6 45.8 41.9 18.7 57.8 61.2

Al₂O₃ 10.1 6.75 9.28 5.36 21.4 14.0

Fe₂O₃ 11.7 11.2 10.8 4.44 11.8 0.28

CaO 14.5 15.9 16.1 63.5 1.29 17.2

MgO 1.58 1.78 1.68 0.94 1.32 2.6

SO₃ 2.15 1.69 2.78 3.27 0.24 <0.01

Na₂O 4.89 4.69 5.83 0.14 0.90 2.64

K₂O 1.02 0.87 0.98 0.40 2.52 0.05

TiO₂ 0.86 0.62 0.91 0.27 0.99 0.69

P₂O₅ 0.83 0.75 0.90 0.64 0.19 0.05

Mn₂O₃ 0.13 0.11 0.12 0.07 0.04 <0.01

SrO 0.04 0.11 0.04 0.07 0.05 0.07

Cr₂O₃ 0.18 0.18 0.17 0.07 0.02 0.02

ZnO 0.37 0.34 0.44 0.08 0.02 <0.01

BaO 0.11 0.16 0.12 <0.01 0.07 <0.01

L.O.I. (950°C) 7.18 8.19 6.09 1.78 0.90 0.27

Total 99.2 99.2 98.1 99.7 99.6 99.1

Alkali Eq. (Na₂O + 0.658K₂O)

5.57 5.26 6.47 0.41 2.56 2.68

1Adopted from Paris, et al., 2016 “Evaluation of Alternative Pozzolanic Materials for Partial Replacement of Portland Cement in Concrete”.

51

Table 3-2. Proportions of mortar materials for ASTM C160 mixes containing 15%, 30%, and 50% MSWI BA aggregate replacement.

Control 15BA1 15BA2 15BA3 30BA1 30BA2 30BA3 50BA1 50BA2 50BA3

Type I/II portland cement (g)

523 515 511 510 508 522 521 524 522 520

MSWI BA (g) 0 174 173 172 343 326 323 538 517 511

Natural sand (g) 1176 985 978 976 800 760 754 538 517 511

Water (g) 246 242 240 240 239 245 245 246 245 245

Water:binder 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47 0.47

Aggregate:binder 2.25 2.25 2.25 2.25 2.25 2.08 2.07 2.05 1.98 1.97

52

Table 3-3. Proportions of mortar materials for ASTM C1567 mixes containing portland cement, 20% pozzolan (ground glass or class F fly ash), and 30% MSWI BA aggregate replacement.

Control

30 BA1-F

30 BA1-G

30 BA2-F

30 BA2-G

30 BA3-F

30 BA3-G

Type I/II portland cement (g)

523 401 403 412 414 431 433

Class F fly ash (g) 0 100 0 103 0 108 0

Ground glass (g) 0 0 101 0 104 0 108

MSWI BA (g) 0 339 340 321 323 334 335

Natural sand (g) 1176 790 793 750 753 779 782

Water (g) 246 236 237 242 243 253 254

Water:Binder 0.47 0.47 0.47 0.47 0.47 0.47 0.47

Aggregate:Binder 2.25 2.25 2.25 2.08 2.08 2.07 2.07

Cementitious replacement (% mass)

0 20 20 20 20 20 20

53

Table 3-4. Length change data and performance classification of ASTM C160 and ASTM C1567 mortar mixes containing MSWI BA aggregate replacements.

Mix

Average 14-day Expansion1 (%)

Results Classification2

Portland Cement Mixes

Control (0 BA) 0.011 Innocuous

15BA1 0.171 Potentially Deleterious

15BA2 0.101 Potentially Deleterious

15BA3 0.077 Innocuous

30BA1 0.320 Deleterious






Binary Mixes

30BA1-F 0.021 Innocuous



30BA1-G 0.031 Innocuous



1Length changes reported as an average of four specimens created for each mix.

2Expansion classification limits for listed in ASTM C1260/C1567 as indication of innocuous or

deleterious field performance of aggregates.

54

Figure 3-1. ASTM C160 average length change of mortars containing 100% portland cement and 15%, 30%, and 50% aggregate replacement by MSWI BA1.


0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (days)

Control (0BA1) 15BA1 30BA1

50BA1 Innocuous Limit Deleterious Limit

BA1

0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (Days)



BA2

55


Figure 3-4. ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash) and 30% aggregate replacement by MSWI BA1.

0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (Days)



BA3

0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (Days)

Control (0BA1) 30BA1 30BA1-F

30BA1-G Innocuous Limit Deleterious Limit

BA1

56

Figure 3-5. ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash), and 30% aggregate replacement by MSWI BA2.

Figure 3-6. ASTM C1567 length change of mortars containing 20% pozzolan (ground glass or class F fly ash), and 30% aggregate replacement by MSWI BA3.

0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (Days)



BA2

0.00%

0.10%

0.20%

0.30%

0.40%

0.50%

0 2 4 6 8 10 12 14 16

Len

gth

Ch

an

ge (

%)

Elapsed Time (Days)



BA3

57

CHAPTER 4 CONCLUSIONS

Summary of Research

In this thesis, two studies were conducted on bottom ash, a residual byproduct

created from the incineration of municipal solid waste. Both studies aimed to address

matters associated with the beneficial reuse of bottom ash as a secondary construction

material in the US. In the first study, a risk assessment of heavy metals was performed

using laboratory batch leaching tests, with a focus on recycling bottom ash as a road

base aggregate. In the second study, the expansive reactivity of bottom ash used was

investigated to characterize the durability of ash a replacement to natural aggregates

typically used in concrete. Both studies produced findings that could aid in the

development of bottom ash recycling programs in the US.

Major Findings and Observations

The following conclusions were made concerning the risk assessment of MSWI

bottom ash as a prospective road base material:

1. Six inorganic contaminants (As, Ba, Cr, Cu, Pb, and Sb) were detected in bottom ash at total concentrations higher than residential soil benchmarks in the state of Florida.

2. Four inorganic contaminants (Al, As, Pb, and Sb) were detected in the leachates of bottom ash at concentrations higher than or equal to risk-based drinking water benchmarks in the U.S.

3. The relative health risks associated with exposure to bottom ash COPC (direct and leaching) were reduced when the material was blended with a virgin or recycled aggregate source.

4. The leaching of antimony from bottom ash was reduced when recycled concrete was

used as a blended aggregate. The reduction in antimony leaching did not follow a typical solubility-controlled leaching behavior displayed by oxyanions in a high pH environment, suggesting that other mechanisms (e.g. sorption, complexation) associated with the recycled concrete contributed to the observed decline in antimony leaching.

58

The following conclusions were made concerning the reactivity of bottom ash as

a prospective coarse aggregate replacement in concrete:

1. The alkali-silica reaction was the dominant expansive reaction in ash-amended mortars. The large quantity of amorphous silica present in bottom ash was reactive during the accelerated mortar bar test, resulting in deleterious effects and volumetric expansion in specimens containing replacements higher than 15%.

2. Aluminum particles in bottom ash were reactive in an alkaline environment, and resulted in minor cracking and spalling of ash-amended mortar specimens, however, expansive reaction products/gels were not observed.

3. The replacement of ordinary portland cement with supplementary cementitious materials (coal fly ash and ground glass powder) greatly reduced the observed expansion in the bottom ash-amended mortar specimens.

Recommendations for Future Work

Based on this research, the following recommendations are suggested

concerning the use of MSWI bottom ash as a construction material:

1. The environmental mobility of COPC (particularly in groundwater) should be measured in pilot-scale in which bottom ash is utilized as a blended or exclusive road base aggregate.

2. The leaching of COPC should continue to be investigated through batch or pilot scale testing in road base products containing a combination of bottom ash and natural/recycled aggregates.

3. Additional batch leaching tests should be performed to observe the effect of recycled concrete on the leaching mechanisms of antimony.

4. The alkali-aggregate reactivity of bottom ash should be further investigated using

long-term test methods which evaluate actual concrete specimens cast with bottom ash as a coarse aggregate component.

5. The feasibility of increased ferrous and non-ferrous metal recovery from bottom ash

should be considered due to the benefits that could be gained in terms of increased material durability and reduction in leachability of certain elements identified as leaching COPC (e.g. aluminum, lead).

59

APPENDIX A CHAPTER 2 SUPPLEMENTARY MATERIALS

Figure A-1. ASTM C136 particle size distribution of weathered MSWI bottom ashes

used for EPA Method 1312/1316 batch leaching tests and EPA Method 3015A total metals analysis.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.01 0.1 1 10 100

Pe

rce

nt M

ass P

assin

g

Nominal Sieve Opening (mm)

MSWI BA1

MSWI BA2

60

Eluent pH

0 2 4 6 8 10 12 14

Le

ach

ed

Co

nce

ntr

atio

n (

mg/L

)

0.001

0.01

0.1

1

10

100

US EPA Primary Drinking Water Standard

Method Detection Limit

MSWI BA1

MSWI BA2

Pb

Figure A-2. EPA LEAF Method 1313 lead leaching as a function of eluent pH performed on fresh MSWI bottom ashes.

61

Eluent pH

0 2 4 6 8 10 12 14

Le

ach

ed

Co

nce

ntr

atio

n (

mg/L

)

0.001

0.01

0.1

1



MSWI BA 1

MSWI BA 2

Sb

Figure A-3. EPA LEAF Method 1313 antimony leaching as a function of eluent pH performed on fresh MSWI bottom ashes

62

Figure A-4. EPA LEAF Method 1316 antimony leaching as a function of liquid-to-solid ratio performed on weathered MSWI bottom ashes

LS Ratio (L/kg-dry)

0 2 4 6 8 10 12

Le

ached

Con

cen

tration

(m

g/L

)

0.001

0.01

0.1



MSWI BA1

MSWI BA2

Sb

63

APPENDIX B CHAPTER 3 SUPPLEMENTARY MATERIALS

Table B-1. Aggregate properties of coarse fraction of MSWI bottom ash (3.5mm-19mm)

used as aggregate replacements in accelerated mortar bar tests (ASTM C1260 and ASTM C1567).

MSWI BA1 MSWI BA2 MSWI BA3

Bulk SG (oven dry) 2.22 2.05 2.05

Bulk SG (saturated surface dry) 2.32 2.25 2.24

Apparent SG 2.49 2.56 2.54

Water Absorption 8.6% 9.7% 9.3%

64

Table B-2. Individual length change measurements of ash-amended mortar bar specimens used in ASTM C1260 (portland cement only).

Mortar Mix Date Expansion

(%) Expansion

(%) Expansion

(%) Expansion

(%)

Average Expansion

(%)

Control Specimen 1 Specimen 2 Specimen 3 Specimen 4

Demold/Water Bath 8-Nov-16 -- -- -- -- --

NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 -0.0101 -0.0080 -0.0150 -0.0111 -0.0111

Day 6 15-Nov-16 0.0041 0.0050 -0.0020 0.0010 0.0020

Day 10 19-Nov-16 0.0051 0.0090 -0.0270 0.0484 0.0089

Day 14 23-Nov-16 0.0122 0.0151 0.0090 0.0091 0.0113

15 BA1

Demold – Water Bath 8-Nov-16 -- -- -- -- --

NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 -0.0061 -0.0051 0.0111 -- 0.0000

Day 6 15-Nov-16 0.0203 0.0192 0.0332 -- 0.0242

Day 10 19-Nov-16 0.0813 0.0628 0.0653 -- 0.0698

Day 14 23-Nov-16 0.1555 0.1539 0.2021 -- 0.1705

15 BA2


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 -0.0020 0.0050 0.0040 0.0030 0.0025

Day 6 15-Nov-16 0.0121 0.0252 0.1348 0.0151 0.0468

Day 10 19-Nov-16 0.0556 0.2969 -- 0.2231 0.0932

Day 14 23-Nov-16 0.1344 0.1510 -- 0.1171 0.1006

15 BA3


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0040 0.0051 0.0020 0.0010 0.0030

Day 6 15-Nov-16 0.0091 0.0081 0.0041 0.0111 0.0081

Day 10 19-Nov-16 0.0121 0.0670 0.0862 0.0755 0.0602

Day 14 23-Nov-16 0.0889 0.0792 0.0608 0.0785 0.0768

30 BA1


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 -0.0020 0.0081 0.0142 0.0010 0.0053

Day 6 15-Nov-16 0.0467 0.0333 0.0417 0.1606 0.0706

Day 10 19-Nov-16 0.1707 0.1546 0.2500 -- 0.1918

Day 14 23-Nov-16 0.3130 0.2748 0.3710 -- 0.3196

30 BA2


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0060 0.0060 0.0010 0.0050 0.0045

Day 6 15-Nov-16 0.0603 0.0869 0.0559 0.0687 0.0679

Day 10 19-Nov-16 0.1648 0.0410 0.2774 0.2222 0.1763

Day 14 23-Nov-16 0.2854 0.3578 0.2814 0.3100 0.3087

30 BA3


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0000 0.0000 0.0030 0.0020 0.0013

Day 6 15-Nov-16 0.0231 0.0243 0.0263 0.0173 0.0228

Day 10 19-Nov-16 0.1469 0.1449 0.2331 0.2182 0.1858

Day 14 23-Nov-16 0.2798 0.2604 0.2574 0.2101 0.2519

50 BA1


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0151 0.0427 0.0121 0.0041 0.0185

Day 6 15-Nov-16 0.1199 0.1504 0.1112 0.1388 0.1301

Day 10 19-Nov-16 0.2851 0.3190 0.2759 0.3141 0.2986

Day 14 23-Nov-16 0.3919 0.4298 0.3921 0.4256 0.4099

50 BA2


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0160 0.0111 0.0091 0.0183 0.0136

Day 6 15-Nov-16 0.2075 0.2101 0.1848 0.1778 0.1950

Day 10 19-Nov-16 0.1804 0.3317 0.3209 0.2946 0.2819

Day 14 23-Nov-16 0.5082 0.4945 0.4580 0.4338 0.4736

50 BA3


NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 0.0010 0.0121 -0.0130 0.0000 0.0000

Day 6 15-Nov-16 0.0836 0.1121 0.0773 0.1600 0.1083

Day 10 19-Nov-16 0.3181 0.2878 0.1556 0.3697 0.2828

Day 14 23-Nov-16 0.3589 0.4201 0.3885 0.4335 0.4002

65

Table B-3. Individual length change measurements of ash-amended mortar bar specimens used in ASTM C1567 (pozzolans included as portland cement replacement).

Mortar Mix Date Expansion

(%) Expansion

(%) Expansion

(%) Expansion

(%)

Average Expansion

(%)

Control Specimen 1 Specimen 2 Specimen 3 Specimen 4

Demold/Water Bath 8-Nov-16 -- -- -- -- --

NaOH Day 1 9-Nov-16 -- -- -- -- --

Day 2 11-Nov-16 -0.0101 -0.0080 -0.0150 -0.0111 -0.0111

Day 6 15-Nov-16 0.0041 0.0050 -0.0020 0.0010 0.0020

Day 10 19-Nov-16 0.0051 0.0090 -0.0270 0.0484 0.0089

Day 14 23-Nov-16 0.0122 0.0151 0.0090 0.0091 0.0113

30BA1 – 20F

Demold/Water Bath 18-Jan-17 -- -- -- -- --

NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0171 0.0111 0.0172 0.0201 0.0164

Day 7 26-Jan-17 0.0161 0.0111 0.0192 0.0221 0.0171

Day 10 29-Jan-17 0.0181 0.0131 0.0192 0.0201 0.0176

Day 14 2-Feb-17 0.0272 0.0131 0.0202 0.0241 0.0212

30BA1 – 20G

Demold – Water Bath 18-Jan-17 -- -- -- -- --

NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0110 0.0140 0.0091 0.0101 0.0110

Day 7 26-Jan-17 0.0170 0.0220 0.0201 0.0212 0.0201

Day 10 29-Jan-17 0.0190 0.0230 0.0342 0.0192 0.0239

Day 14 2-Feb-17 0.0251 0.0260 0.0483 0.0242 0.0309

30BA2 – 20F


NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0191 0.0101 0.0162 0.0122 0.0144

Day 7 26-Jan-17 0.0242 0.0161 0.0345 0.0172 0.0230

Day 10 29-Jan-17 0.0221 0.0141 0.0345 0.0162 0.0217

Day 14 2-Feb-17 0.0372 0.0272 0.0456 0.0426 0.0382

30BA2 – 20G


NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0091 0.0050 0.0091 0.0080 0.0078

Day 7 26-Jan-17 0.0152 0.0131 0.0193 0.0161 0.0159

Day 10 29-Jan-17 0.0142 0.0121 0.0152 0.0101 0.0129

Day 14 2-Feb-17 0.0243 0.0202 0.0253 0.0211 0.0227

30BA3 -20F


NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0232 0.0211 0.0223 0.0231 0.0224

Day 7 26-Jan-17 0.0242 0.0271 0.0304 0.0292 0.0277

Day 10 29-Jan-17 0.0303 0.0291 0.0406 0.0332 0.0333

Day 14 2-Feb-17 0.0343 0.0381 0.0527 0.0372 0.0406

30BA3 – 20G


NaOH Day 1 19-Jan-17 -- -- -- -- --

Day 2 21-Jan-17 0.0223 0.0272 0.0194 0.0201 0.0222

Day 7 26-Jan-17 0.0243 0.0282 0.0234 0.0211 0.0243

Day 10 29-Jan-17 0.0304 0.0352 0.2987 0.0241 0.0299

Day 14 2-Feb-17 0.0334 0.0362 0.0296 0.0281 0.0318

66

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BIOGRAPHICAL SKETCH

Matthew L. Schafer was born in 1992 to Joseph and Donna Schafer in Utica, NY,

a small town in the northern portion of the state. At the age of five, Matthew and his

family relocated to Ocala, Florida, where he spent the remainder of his childhood

adolescence. Matthew was the youngest of three siblings, with a brother Joe and a

sister Amanda whom he shares close relationships with. Upon graduating from Forest

High School, Matthew enrolled at the University of Florida in the fall of 2011.

In December of 2015, Matthew received a Bachelor of Science degree in

Environmental Engineering Sciences, graduating Cum Laude. He immediately began

graduate school at the University of Florida in January 2016 under the advising of Dr.

Timothy Townsend, with a research focus on the sustainable management of solid

waste materials. During his tenure as a graduate student, Matthew conducted several

studies related to the beneficial reuse of incineration residues in the state of Florida, and

published two journal articles. In May 2017, Matthew completed his research thesis and

was awarded a Master of Engineering degree in Environmental Engineering. Upon the

completion of his graduate education, Matthew intends to begin his career in the private

consulting industry with HDR Engineering, Inc. in the south Florida area.

In his leisure time, Matthew enjoys recreational fishing and diving along the

Florida coastline and offshore waters, as well as spending time with his family and

friends.

© 2017 Matthew L. Schafer

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