Coal Combustion Products in

Constructed Landfills Characteristics, Beneficial Use, Disposal, &

Impact on Geocomposite Leachate Collection

Systems

Dr. Tarunjit S. Butalia, PE

Research Scientist

Department of Civil, Environmental, and Geodetic Engineering

The Ohio State University

ccp.osu.edu

What are Coal Combustion Products

(CCPs)?

• CCPs are solid minerals that remain after

coal is burned to generate electricity or

steam

• Types: • Fly Ash

• Boiler Slag

• Bottom Ash

• Flue Gas Desulfurization (FGD) Materials

• Dry FGD Materials (FBC, CFBC, SD)

• Wet FGD Materials (sulfite & sulfate)

How are CCPs generated? Flue Gas

Desulfurization (wet/dry)

Coal Boiler

Baghouse/ESP

Economizer

Coal Feed

SCR for

removing

NOx

BOTTOM ASH BOILER SLAG (dry bottom boilers) (wet bottom boilers)

FLY ASH FGD MATERIALS

Smokestack

Fly Ash

• Fine powdery mineral collected by ESP or

baghouse

• Consists mainly of non-combustible

matter but also some unburned carbon

• Mostly silt size particles (with some fine

sand sized), mostly spherical (and

sometimes hollow)

• Types:

• Class F (non self-cementing)

• Class C (self-cementing)

• Handled dry or wet

Bottom Ash

• Fine to coarse material collected from

dry bottom boilers

• Consists of dark agglomerated ash

particles

• Sand size particles typ. angular

• Handled dry or wet

Boiler Slag

• Glassy material collected from wet

bottom boilers

• Black, dense, hard angular particles

Flue Gas Desulfurization (FGD) Materials

• Solid / semi-solid material obtained from

flue gas scrubbers (for SO2 control)

• Predominantly silt size particles

• Wet or dry

• Types:

• Dry FGD Materials (CFBC, PFBC, SD)

• Wet FGD Materials

• Sulfite (Stabilized FGD material)

• Sulfate (FGD Gypsum)

Stabilized

FGD material

FGD

Gypsum

CCPs

CCP

Type

Characteristics

Texture Amount

Generated

Per Ton of

Coal Burned

(lbs)

Major

Constituents

Areas of Major Use

Fly Ash Non-combustible

particulate matter

carried in stack

gases

Powdery,

silt like

160 Si, Al, Fe, Ca Cement/Concrete/Grout, Structural

Fill, Flowable Fill, Waste Stabilization,

Surface Mine Reclamation, Soil

Stabilization, Road Base, Mineral Filler,

Agriculture Bottom

Ash Material collected in

dry bottom boilers,

heavier than fly ash

Sand like 40 Si, Al, Fe, Ca Concrete Block, Road Subbase, Snow

and Ice Control, Structural Fill, Waste

Stabilization, Agriculture, Pipe

Bedding, Cement Manufacture

Boiler

Slag Material collected in

wet bottom boilers

or cyclone units

Glassy

angular

particles

100 Si, Al, Fe, Ca Blasting Grit, Roofing Granules, Snow

and Ice Control, Mineral Filler,

Construction Backfill, Water Filtration,

Agriculture, Drainage Media

FGD

Material Solid/semi-solid

material obtained

from flue gas

scrubbers

Fine to

Coarse

(Dry or

Wet)

700 Ca, S, Si, Fe, Al Wallboard, Road Base/Subbase,

Structural Fill, Surface Mine

Reclamation, Underground Mine

Injection, Livestock Pad, Agricultural

Liming Substitute

Typical Engineering Characteristics of

CCPs

Typical Characteristics Fly Ash

Bottom

Ash /

Boiler Slag

FGD Material

Wet Dry

Particle Size (mm) 0.001-0.1 0.1-10.0 0.001-0.05 0.002-0.075

Compressibility (%) 1.8 1.4

Dry Density (lb/ft3) 40-90 40-100 50-110 65-90

Permeability (cm/sec) 10-6-10-4 10-3-10-1 10-6-10-4 10-7-10-6

Shear Strength Cohesion (psi) 0-175 0

Angle of Internal Friction (degree) 25-45 25-45

Unconfined Compressive Strength (psi) 0-1,600 40-2,250

Typical Engineering Properties of

Bottom Ash & Boiler Slag

Property Bottom Ash Boiler Slag

Specific Gravity 2.1 - 2.7 2.3 - 2.9

Dry Unit Weight 45 - 100 lb/ft3 60 - 90 lb/ft3

Plasticity NP NP

Absorption 0.8 - 2.0% 0.3 - 1.1%

(FHWA-RD-97-148)

Maximum Dry Density, lb/ft3 75 – 100 82 – 102

Optimum Moisture Content, % 12 – 24 8 – 20

LA Abrasion Loss, % 30 - 50 24 – 48

Sodium Sulfate Soundness Loss, % 1.5 – 10 1 – 9

Friction Angle, degrees 32 – 45 36 – 46

California Bearing Ratio, % 40 - 70 40 – 70

Permeability Coefficient, cm/sec 10-2 - 10-3 10-2 - 10-3

Typical Engineering Properties of

FGD Materials

Property Stabilized FGD FGD Gypsum

(Calcium Sulfite) (Calcium Sulfate)

Particle Sizing (%)

Sand Size 1 17

Silt Size 90 80

Clay Size 9 3

Specific Gravity 2.57 2.36

(FHWA-RD-97-148)

Property Stabilized FGD

Solids Content, % 55-80

Specific Gravity 2.25 – 2.60

Dry Density, lb/ft3 75 – 95

Friction Angle, degree 35 – 45

Permeability, cm/sec 10-6 – 10-7

UCS (28 days), psi 25 - 50

Composition of Fly Ash & Cement

(CBRC, 2003)

Trace Elemental Composition Element Fly Ash Bottom Ash/Boiler Slag Dry FGD Material

(mg/kg) Mechanical ESP/Baghouse

Range Median Range Median Range Median Range Median

Arsenic 3.3-160 25.2 2.3-279 56.7 0.50-168 4.45 44.1-186 86.5

Boron 205-714 258 10-1300 371 41.9-513 161 145-418 318

Barium 52-1152 872 110-5400 991 300-5789 1600 100-300 235

Cadmium 0.40-14.3 4.27 0.10-18.0 1.60 0.1-4.7 0.86 1.7-4.9 2.9

Cobalt 6.22-76.9 48.3 4.90-79.0 35.9 7.1-60.4 24 8.9-45.6 26.7

Chromium 83.3-305 172 3.6-437 136 3.4-350 120 16.9-76.6 43.2

Copper 42.0-326 130 33.0-349 116 3.7-250 68.1 30.8-251 80.8

Fluorine 2.50-83.3 41.8 0.4-320 29.0 2.5-104 50.0 --- ---

Mercury 0.008-3.0 0.073 0.005-2.5 0.10 0.005-4.2 0.023 --- ---

Manganese 123-430 191 24.5-750 250 56.7-769 297 127-207 167

Lead 5.2-101 13.0 3.10-252 66.5 0.4-90.6 7.1 11.3-59.2 36.9

Selenium 0.13-11.8 5.52 0.6-19.0 9.97 0.08-14 0.601 3.6-15.2 10.0

Silver 0.08-4.0 0.70 0.04-8.0 0.501 0.1-0.51 0.20 --- ---

Strontium 396-2430 931 30-3855 775 170-1800 800 308-565 432

Vanadium 100-377 251 11.9-570 248 12.0-377 141 --- ---

Zinc 56.7-215 155 14-2300 210 4.0-798 99.6 108-208 141

Leachate (TCLP) – Dry FGD and Fly Ash

Chemical

Constituent

(mg/L)

Dry FGD Fly Ash

pH 9.58-12.01 ---

TDS 11,840-

13,790 ---

Ag <0.024 0.0-0.05

Al 0.12-0.20 ---

As <0.005 0.026-0.4

B 0.543-2.17 0.5-92

Ba <0.002 0.30-2.0

Be 0.141-0.348 <0.0001-0.015

Ca 1,380-3,860 ---

Cd <0.003 0.0-0.3

Co <0.014-0.026 0.0-0.22

Cr <0.005-0.028 0.023-1.4

Cu <0.013 0.0-0.43

Fe <0.029 0.0-10.0

Hg <0.0002 0.0-0.003

K 1.3-22.1 ---

Chemical

Constituent

(mg/L)

Dry FGD Fly Ash

Li 0.04-0.18 ---

Mg <0.04-1,360 ---

Mn <0.001 0.0-1.9

Mo 0.025-0.088 0.19-0.23

Na 1.32-9.82 ---

Ni <0.01 0.0-0.12

P <0.12 ---

Pb <0.001-0.017 0.0-0.15

S 132-979 ---

Sb <0.24 0.03-0.28

Se <0.001-0.005 0.011-0.869

Si 0.10-0.33 ---

Sr 0.83-3.38 ---

V <0.019-0.024 ---

Zn <0.006 0.045-3.21

Cl- 19.6-67.8 ---

Leachate (Kosson Tier I, SPLP, TCLP)

FGD Gypsum

Element Tier I SPLP TCLP

(mg/mL) (mg/mL) (mg/mL)

As <0.006 <0.006 <0.006

B 0.227 0.130 0.137

Ba 0.161 0.101 0.37

Cd 0.0017 0.002 0.0017

Cr 0.0056 0.0044 0.0059

Cu <0.001 <0.001 <0.001

Hg 7.9E-06 3.60E-06 1.8E-05

K 0.646 <0.4 2.01

Pb <0.003 <0.003 <0.003

Se <0.011 <0.011 0.012

Historical CCP Production & Beneficial Use

(American Coal Ash Association)

2010 CCP Production & Beneficial Use

(American Coal Ash Association)

Each Ton of Fly Ash in Concrete Equals...

Some Past OSU Demonstration Projects

• Highway Embankment Stabilization (1993, 1994)

• Stabilized FGD Material as Pond Liner (1997)

• Accelerated Loading of Newly Constructed Full-Scale

Pavements (2003)

• Full Depth Reclamation of Failing Asphalt Pavements (2006)

Use of Clean Coal Technology By-Products in

Construction of Low Permeability Liners

• Constructed at OSU-OARDC Western Branch in

South Charleston, Ohio in Summer of 1997

• Holding Capacity of 1 million gallons (6 months

storage capacity)

• Primary Liner = 18” Compacted, Stabilized FGD

• Leachate Collection System

Current

Filling of Pond with

water - 1997 During construction

Use of Clean Coal Technology By-Products in

Construction of Low Permeability Liners

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

0 365 730 1095 1460 1825 2190

Curing Time (days)

Co

eff

icie

nt

of

Perm

eab

ilit

y (

cm

/sec)

Full Scale Test

Laboratory Test on Laboratory Compacted SampleBoutw ell(TP1)

Boutw ell(TP2)

Boutw ell(TP3)

Cored(TP1)Cored(TP2)

Cored(TP3)

Addition of swine

manure initiated

1998

Ongoing OSU Projects

• Reclamation of Ohio Coal Mine Sites Using

FGD Byproducts

• Role of Remining in Mitigating Impacts of

Legacy Mining in Ohio

• Stability of Fly Ash During Cyclic Loading

• Effectiveness of Geocomposites as Drainage

Layer for CCPs

2009-10 Research: Investigation of various CCP materials using non-woven

fabric (Alexis Semach MS Thesis)

Current Research: Study of various CCP materials using woven fabric

geocomposite drainage layer

Effectiveness of Geocomposites

as Drainage Layer for CCP Landfills

• Geocomposite leachate collection systems as possible

replacements for conventional graded sand filters in CCP

landfills

• Geocomposite drainage systems are attractive - not as

thick as graded sand filters

• Geocomposite must

• not restrict flow of leachate to collection system

• prevent migration of CCP material to be retained through the

filter and into leachate collection system

Background

• To evaluate effectiveness of using geocomposites as primary drainage layer for CCP landfills to study potential

• clogging of leachate collection system, and

• migration of material into leachate collection system

Research Objective

2009-10 Research – Fill and Geocomposite

2009-10 Research – % Solids in Leachate

2009-10 Research – Fly Ash and Geocomposite

• Measured permeabilities of the CCPs tested ranged from a high of slightly less than 1x10-4 cm/sec (silt) for FGD gypsum & Class F fly ash to 7x10-6 cm/sec (silt or clay) for stabilized FGD.

• When CCPs were underlain by the geocomposite, effective permeability decreased, typically by a factor of 5.

• Quantity of material recovered in leachate was small and decreased after only one to two pore volumes for FGD gypsum and stabilized FGD.

• Quantity of fly ash recovered in leachate increased during tests until it was more than the system could accommodate and testing had to be terminated.

• Fly ash appears to not be adequately retained by sample non-woven geocomposite. Even though initial permeabilities of fly ash and FGD gypsum were similar, the fly ash particles went into the leachate at a much higher rate than did FGD gypsum. The quantity of fly ash increased until laboratory tests on fly ash/geocomposite samples had to be terminated.

2009-10 Research – Laboratory Testing Summary

• Laboratory Experiments • Permeability of CCP fill material with & without geocomposite

• Percent solids in leachate of CCP fill with & without geocomposite

• Field Testing • Permeability and leachate quality of as installed CCP fills with geocomposite

Current Research

Focus: Study of Fly Ash (silo and ponded), FGD gypsum, and stabilized FGD material underlain by woven fabric geocomposite system

• Geocomposite with top woven geotextile layer

• CCP Materials Class F Fly Ash (silo and ponded) FGD Gypsum Stabilized FGD (sulfite) material

• Tests conducted Falling head permeability tests on CCP fill materials

only (porous stone at top and bottom of sample) Falling head permeability tests on drainage system

(bottom porous stone replaced by geocomposite)

• Test results Permeability and percent solids in leachate as a

function of pore volume

Laboratory Testing

Sample

Geotextile Fabric

Geo-Grid

Geotextile Fabric PVC Layer

Hole in PVC for Drainage

Sample

Geotextile Fabric

Geo-Grid

Geotextile Fabric PVC Layer

Hole in PVC for Drainage

CCP Fill and Geocomposite Test System

Silo Fly Ash M

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

porous stone (dry density=79.97pcf)

geocomposite (dry density=83.16pcf)

0

2

4

6

8

10

12

0 2 4 6 8

Pe

rce

nt

Solid

s (%

)

Pore Volume Fraction

porous stone (dry density=79.97pcf)

geocomposite (dry density=83.16pcf)

Ponded Fly Ash C

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

porous stone (dry density=95.37pcf)

geocomposite (dry density=95.15pcf)

0

2

4

6

8

10

12

0 2 4 6 8

Pe

rce

nt

Solid

s (%

)

Pore Volume Fraction

porous stone (dry density=95.37pcf)

geocomposite (dry density=95.15pcf)

FGD Gypsum M

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

geocomposite (dry density=85.03pcf)

porous stone (dry density=84.47pcf)

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7

Pe

rce

nt

Solid

s (%

)

Pore Volume Fraction

porous stone (dry density=84.47pcf)

geocomposite (dry density=85.03pcf)

FGD Gypsum C

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

porous stone (dry density=77.97pcf)

geocomposite (dry density=77.70pcf)

0

2

4

6

8

10

12

0 2 4 6 8

Pe

rce

nt

Solid

s (%

)

Pore Volume Fraction

porous stone (dry density=77.97pcf)

geocomposite (dry density=77.70pcf)

Sample

Top Geotextile Fabric

Geo-Grid

Bottom Geotextile Fabric PVC Layer

Hole in PVC for Drainage

Post-test Geocomposite Inspection

Top of “top geotextile fabric” Top of “geo-grid” Bottom of “top geotextile” fabric Top of “top geotextile fabric”

Typical

field

basin

constructed

at OSU

Olentangy

River

Wetland

Research

Park

CCP

CCP

Plan View

of Field

Test

Basins

Field Construction

Field Construction

Stabilized FGD C Silo Fly Ash M FGD Gypsum M Ponded Fly Ash C

Field Testing

Permeability - Silo Fly Ash M

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

porous stone (dry density=79.97pcf)

geocomposite (dry density=83.16pcf)

Laboratory Measured Permeability

Field Basin Permeability* = 4 x 10-4 cm/sec

Permeability - Ponded Fly Ash C

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

porous stone (dry density=95.37pcf)

geocomposite (dry density=95.15pcf)

Laboratory Measured Permeability

Field Basin Permeability* = 2 x 10-3 cm/sec

Permeability - FGD Gypsum M

1.00E-05

1.00E-04

1.00E-03

1.00E-02

0 2 4 6 8

Hyd

rau

lic C

on

du

ctiv

ity

(cm

/s)

Pore Volume Fraction

geocomposite (dry density=85.03pcf)

porous stone (dry density=84.47pcf)

Laboratory Measured Permeability

Field Basin Permeability* = 2 x 10-2 cm/sec

Total Suspended Solids - Field

Total Dissolved Solids - Field

Turbidity - Field

• Laboratory testing to date indicates that the new

geocomposite woven fabric:

• retains fly ash and other CCP fill particles

• does not restrict the flow of leachate to collection system

• prevents migration of CCP material into leachate collection

system

• Field test basin verifies laboratory observations

Current Research – Preliminary Conclusions

Our online library collection has been subdivided into the following categories:

Material Characterization

Applications

Economics of Beneficial Use

Our library listing of journal articles, conference papers and published information

sources is related to Coal Combustion Products research. Many of our documents

can be downloaded (typ. as pdf files). For references not available online and not

subject to copyright restrictions, a paper copy can be provided by contacting Carol

Scott at scott.30@osu.edu.

You are welcome to submit articles for inclusion in our reference library. Contact

Dr. Tarunjit S. Butalia at butalia.1@osu.edu.

Resources Available to You

M.S. Thesis

Dorothy Adams, Swelling characteristics of dry sulfur dioxide removal waste products

Jeffreys Chapman, Stress Model Verification with Reclaimed Asphalt Pavement

Malcolm Hargraves, The effect of freeze-thaw cycles on the strength of stabilized flue gas desulfurization sludge

James Howdyshell, Strain compatibility analysis in slope stability modeling

Jun Huang, Degradation of resilient modulus of saturated clay due to pore water pressure buildup under cyclic loading

Na Jin, Fly Ash Applicability in Pervious Concrete

James Kirch, Potential Use of Flue Gas Desulfurization Gypsum (FGD) in a Flowable Grout for Re-mining of Abandoned Coal Mines

Jangguen Lee, The Behavior of Pore Water Pressure in Cohesive Subgrade Soils

Jung Woo Lee, Beneficial reuse of FGD by-products as flowable fill

Yong-Woong Lee, Measurement and Prediction of Resilient Modulus of Lime-Fly Ash Stabilized Cohesive Subgrade Soils

Aleia Long, Evaluating material properties of fly ash modified concrete plates under low velocity impact

Ryan Mackos, Environmental Analysis of Full Depth Reclamation Using Coal Combustion By-Products

Deepa Modi, Potential Utilization of FGD Gypsum for Reclamation of Abandoned Highwalls

Jennifer Myers, Stabilization of sludge using spray dryer absorber ash

Salman Nodjomian, Clean-coal technology by-products used in a highway embankment stabilization demonstration project

Xueling Pan, The Effect of Freeze Thaw Cycling on the Permeability of Stabilized Flue Gas Desulfurization (FGD) Materials

Rachel Pasini, An Evaluation Of FGD Gypsum For Abandoned Mine Land Reclamation

Renee Payette, Landslide Remediation Using Clean Burning Coal Technology By- Products

Gloria Rodgers, Resilient modulus predictions using engineering properties and neural networks

Alexis Semach, Geotextiles for Use in Drainage Systems in Coal Combustion Product Landfills

Sharon Studer, Seepage analysis of a highway embankment constructed from the Flue Gas Desulfurization by-product

Wei Tu, Evaluation of Full-Scale CCP Pavement Performance Using Accelerated Loading Facility

Michael Nuhfer, Use of flue gas desulfurization by-product as a lake-bed liner

Ph.D. Dissertations

Dong-Gyou Kim, Development of a Constitutive Model for Resilient Modulus of Cohesive Soils

Sung Hwan Kim, A decision support system for highway embankment design using FGD by-products

J.W. Lee, Real-Time Monitoring of Landslide Using Wireless Sensor Network

Panuwat Taerakul, Characterization of trace elements in dry flue gas desulfurization (FGD) by-products

Wei Tu, Response Modeling of Pavement Subjected to Dynamic Surface Loading Based on Stress-Based Multi-layered Plate Theory

Chin-Min Cheng, Leaching of coal combustion products: field and laboratory studies

Graduate Student Research

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