Sustainable Use of Steel Slag in North America

Workshop: Sustainability of Brazilian Steel Sector

Steel Slag – From Generation in Steelworks to Environmentally Sustainable Utilization

Agenda

Sustainable plan for steel slag in Canada

Agricultural liming standard & certification

Risk assessment from US steel slag coalition

Properties and sustainable uses of SS in US

Phosphorus removal

Conclusion

Environmental Authority in Quebec, Canada

Ministry of Sustainable Development,

Environment & Park

Adopt the Rio declaration from 1992 UN

conference in Rio

• Urgency of reconciling economic and social development

• Environmental protection

• Conservation of natural resources

Residual material in Quebec

Non-hazardous material generated in Quebec = 20 Tonnes per minutes.

Quebec Residual Materials Management Policy 1998-2008 has goal to reclaim 65% of them by year 2008.

For helping, use of laws, regulations, guidelines, R&D, directives, fact sheets, guides and standards.

For steel slag tool was:

• R&D :Bioavailability Evaluation of Heavy Metal Inbound in Industrial Inorganic Residual Materials

• Guide to reclaim Industrial Residual Material, non-hazardous and inorganic as construction material

Evaluation of the material

Description of the process generating

Representative sampling

Checking if it is non-hazardous

Gradation (Sieve analysis)

Physical properties

Organic matter

Capability to neutralize the acid

Sulfur contents = acidic generator

Total component

Leaching tests, neutral and acid

Reclaim Agreement for Steel Slag

Agreement between Minister of Environment and the steel Mill which generate the steel slag (SS)

Minister facilitate and encourage such value added while ensuring that it is done in a manner that does not harm the quality of the environment

SS is not consider soil in the meaning of Soil Protection and Sites Rehabilitation Policy

The use of SS is associated with structures and not mingling with soils

Contract to set out the terms and conditions governing the interventions, actions, and activities with respect to the recycling

Obligation for marketing Steel Slag

Inform purchaser of the potential uses and restriction

Proceed periodically to the analysis of SS

Present a report specifies the quantity of SS received and the quantity processed and for each category of aggregate, specifies the quantities marketed, stored or disposed

Invest part of the benefit from SS sales for R&D

Produce & distribute a brochure (approved) intended to

• Inform customers of the nature of SS

• Promote the use of SS for authorized uses

• Subsequent to a dismantling of the work at the end of its useful life, reuse possible (same as permit)

Decision-making diagram for aggregate categorization

Usage authorized according to category

UsageCategory of materials

I II III IV V

1. Construction or repair of roadways, roads and streets (including those in residential, municipal and agricultural sectors)

Sub-base x x x x

Base – paved roads x x x x

Paved road shoulder x x x x

Base – unpaved roads x x x

Unpaved road shoulder x x x

Backfill x x x x

Mineral filler x x x x

Manufactured sand x x x x

Surface treatment x x x x x

Hot and cold mix asphalt x x x x x

Aggregate for slurry seal x x x x x

Filling concrete x x x x x

Usage authorized according to category

UsageCategory of materials

I II III IV V

2.Winter anti-skid for roads x

3.Residential driveway for automobile x x

4.Other residential uses x

5.Construction on municipal land x x x

6.Construction on commercial or industrial land x x x x

7.Coating for landfill sites x x x x x

8.Sandblast aggregate x x x x x

9.Railroad Ballast x x x

The reuse of SS dismantled from a structure shall be done in accordance with those one

Slag sales scale ticket

Usage permitted

Slag uses

Slag uses

Slag uses

Slag uses

Slag uses

Liming material for agricultural use

BNQ is a standards development body accredited by the Standards Council of Canada (SCC) Authorized to develop consensual normative documents (Standards) up to the national level and to participate into regional and international standardization activities In 1998, a committee of 20 persons from different industries and government agencies elaborate the specification: #NQ 0419-910/1998 Liming Materials from Industrial Processes The certification to have recognized, on an ongoing basis, the conformity of ladle furnace slag according to this specification Certification bring : authenticity, safety of the product and technical info

Requirement for certification

BNQ 2 visits and sampling per year

Production and sales report to submit

Size 100% < 14mm

Size 95% < 12,5mm

Water content > 1% (CaO)

Neutralizing value (CCE) > 25% (our value 85%)

Causticity (Ca+Mg)/(Na+K) > 2,5

Marking of the product should be on the scale ticket

Efficiency is obtained by comparing the effect of pH

increase with pure ACS grade CaCO3

Metal content depend of CCE

Metal limit in lime material

Metal (ppm)Dry basis

CCE25%

CCE50%

CCE75%

CCE100%

As 37 75 75 75

Cd 10 20 30 30

Co 75 150 225 300

Cr 530 1 060 1 590 2 120

Cu 378 757 1 135 1 500

Hg 2,5 5,0 7,5 10

Mn 6 250 12 500 18 750 25 000

Mo 10 20 30 40

Ni 90 180 270 360

Pb 250 500 500 500

Se 7,0 14 21 28

Zn 926 1 850 2 778 2800

US Geological Survey-2005

Ferrous slags are valuable co-products of ironmaking and

steelmaking.

In 2005 about 21 million tons of domestic iron and steel

slag, valued at about $326 million (f.o.b.) was consumed.

There were 29 slag-processing companies servicing iron

and/or steel companies or reprocessing old slag piles at

about 130 locations: iron slag at about 40 sites in 14

States and steel slag at about 90 sites in 32 States.

Risk assessment from US Slag Coalition

In 1998, group of 63 US Steel producers and/or Slag processor companies commissioned ChemRisk for:

Comprehensive study of chemical composition of 3 slag types; BF, BOF, EAF : potential human health & ecological risk associated with possible exposure to such slag

Study utilized worse-case exposure assumptions in risk calculations

Conclusion:

• “Slag pose no meaningful threat to human health or the environment when used in a variety of residential, agricultural, industrial and construction applications”

• Steelmaking slag: A safe and valuable product

Steelmaking slag composition

Chemically, steelmaking slag is a complex matrix structure consisting primarily of oxides of calcium, iron, silicates, aluminum, magnesium, and manganese in complexes of calcium silicates, aluminosilicates and aluminoferite. These compounds are similar to those found in the natural environment.Typical furnace temperatures of about 1600oC fuses the oxidized components captured in slag.The matrix tightly binds metals found in slag and they are not readily liberated from the particles. Metals in slag are not easily leached.

Matrix

Physical properties

Cubical, vesicular surface

Excellent frictional properties

High stability

Interlocking

High angle of repose

Major uses of steelmaking slag aggregates

Bituminous applications: pavement surfaces, surface treatments, asphalt, seal coats, slurry coats and cold patchConcrete aggregateRaw feed for Portland Cement manufacturingAnti-skid (snow and ice control)Stabilization: shoulders, banks, erosion control, gabions and riprapBase and sub-baseUnpaved driveways, surface roads, walkways, trailsNeutralization: acid mine drainageAgricultural applications: soil remineralization, liming agent, fertilizerControlled granular fill, structural fill, pipe and tank backfill, bermsFluxing agent for steel millsLandfill cover materialLandscapingTrench / drain fieldsSand blast gritRoofing granulesBulk filler (paint, plastics, adhesives)Soil stabilizationMineral woolAll purpose construction aggregate

Risk Assessment Process

To quantify potential threats to human health or the environmentThree phases• Dose-response assessment• Exposure assessment• Risk characterization

Results demonstrated BF, BOF and EAF slags are safe for use in a broad variety of applications and pose no significant risks to human health or the environment

Risk Assessment Conclusion

BF, BOF and EAF slags are a safe sustainable material

Steelmaking slag is an environmentally safe product

Unique physical structure out-performs natural aggregates

Superior construction, industrial and agricultural

aggregate

A safe, useful and valuable product – not a “solid waste”

Emphasis on State and Federal regulatory systems in

recognition of the value of steelmaking slag as a product

Conserves natural resources

Sustainable Utilization of Steel Slag in the US

Bituminous ApplicationsStone matrix asphaltSuperpaveAsphaltChip and SealSlurry SealCold patch• Advantages:

frictional properties hardness soundness angularity

Indianapolis Speedway

Sustainable Utilization of Steel Slag in the US

Slag as raw feed in Portland CementReduction in CO2 emissions and energy cost

• Slag has already undergone calcination (clinker)• Melts at a lower temperature

Improved clinker production• 100% yield of cement clinker vs. limestone as low as 60%

Chemically compatible• CaO• SiO2

• Al2O3

• Fe2O3

Reduce or replace:• Iron ore• Mill scale• Bauxite• Clay • Sand• Fly ash• Shale

Methods of introduction:• Inter-ground in existing raw mill• Feed directly into the back end of the kiln (a patented process in the

US)

Feed into the back end of kiln

Sustainable Utilization of Steel Slag in the US

Base ApplicationsUnpaved surfaces• Roads and road shoulders• Access roads for heavy equipment• Parking lots and lay-down yards• Driveways• Pathways / walkways • Equestrian rings / trails• Berms• Embankments

Advantages:• Durability• Compaction• Cementitious properties

Unpaved Applications in Arkansas, Mississippi and Utah

Sustainable Utilization of Steel Slag in the US

StabilizationBank stabilization• Erosion control• High angle of repose• Durability

Gabions and riprapDikes and barriersSoil stabilization• Current research being performed by the School

of Civil Engineering, Purdue University– joint cost sharing between MultiServ and Levy as industry, and the Indiana Department of Transportation

Oyster beds in Maryland (2), Wildlife Bird Refuse in Utah and Soil Stabilization in Michigan

Gabion basket with steel slag

Rectangular wire mesh basket filled with coarse size (50 to 100mm) Steel Slag

To shore up creek bank and control water flow

Angular shape and high density provide stability

Protection against erosion

Sustainable Utilization of Steel Slag in the US

Other ApplicationsRail ballastAnti-skid for snow and ice control• Dark color – absorbs heat from the sun• Stays in place

Landscape rockDaily Landfill coverAggregate for septic systemsAcid mine drainage Agricultural soil re-mineralization, liming agent, fertilizer

Ag-lime in North Carolina

Acid mine drainage treatment

SS generate exceptionally high levels of alkalinity over extended periods (several hundred times more than limestone)

SS has a high neutralization potential

Design and sizing can provide a low-to-zero maintenance

No leaching even in acidic condition

Requirements vary by State

State regulationsEPA regulationsTest Methods for materials• ASTM• AASHTO

Environmental testing• TCLP• Total metals• Chemical analysis

General testing• Sieve analysis (gradation)• Specific gravity• Absorption• Unit weight• Moisture density (proctor)• LA abrasion• Soundness• Calcium carbonate Equivalent (CCE) for agricultural applications

Analytical Test Methods

U.S. Environmental Protection (EPA) approved test methodsTotal metalsToxicity Characteristic Leachate Potential (TCLP)pH parametersAmerican Society of Testing Materials (ASTM) distilled water leachate tests for certain metalsBioaccessibility of certain metalsParticle size distribution

Comparisons

TCLP and ASTM leaching tests to determine if any metals in slag would potentially affect groundwater and surface water.

Results compared to appropriate TCLP drinking water quality standards and EPA Ambient Water Quality Criteria.

EAF Slag for phosphorus removal

Phosphorus = Phosphate (P), a nutrient that may cause

lake eutrophication and toxic blue green algae

Tests on dairy farm waste water and fish farm

Conclusion proved that phosphorus filter with EAF

significantly reduced dissolve reactive P (DRP)

Removed over 70% of DRP during the first 269 days

Need to use wetland pre-treatment to remove suspended

solid and prevent clogging

EAF can be reuse after treatment as aggregate for farm

road.

Phosphorus retention mechanism

Scories

Phase aqueuse

Dissolution

Adsorption

Ca Al Fe

HPO4 PO4 PO4

OH OH OH

KH2PO4

HPO42-

H+

PO43-

H2PO4-

K+ H+

H+

CaO FeO

Ca2+ Fe2+

KH2PO4

HPO42-

H+

PO43-

H2PO4-

K+ H+

H+

OH-

HDPHAP

OH-H+

H2O

Strengite

OH-

H+

H2O

Al2O3

Al3+

Variscite

Précipitation (cristallisation)

H2O H2O H2O

Fe3+

CO2atm

CaCO3

NB: Précipités formés:HDP = Ca2HPO4(OH)2HAP = Ca10

(PO4)6(OH)2Strengite = FePO4.2H2OVariscite = AlPO4.2H2O

Scories

Phase aqueuse

Dissolution

Adsorption

Ca Al Fe

HPO4 PO4 PO4

OH OH OH

KH2PO4

HPO42-

H+

PO43-

H2PO4-

K+ H+

H+

CaO FeO

Ca2+ Fe2+

KH2PO4

HPO42-

H+

PO43-

H2PO4-

K+ H+

H+

OH-

HDPHAP

OH-H+

H2O

Strengite

OH-

H+

H2O

Al2O3

Al3+

Variscite

Précipitation (cristallisation)

H2O H2O H2O

Fe3+

CO2atm

CaCO3

NB: Précipités formés:HDP = Ca2HPO4(OH)2HAP = Ca10

(PO4)6(OH)2Strengite = FePO4.2H2OVariscite = AlPO4.2H2O

Steel slag

University of Waterloo research

BOF Slag: sorption and co-precipitation removal of phosphate and arsenic and selenium

Excellent removal of arsenic to very low levels

Effective removal of E-Coli

• Elevated pH provides environment that eliminates bacteria

Elevated pH is buffered by soils and sediments upon release to subsurface

North Bay System: Phosphate Versus Time

Days of Operation0 200 400 60

0800 1000 1200 1400 1600

Ph

osp

ha

te-P

(m

g/L

)

0

5

10

15

20Raw PhosphateSand Filter PhosphateBOF Chamber Phosphate

Phosphate removal with BOF

From: David Smyth Department of earth sciences, University of Waterloo, Waterloo, CanadaFrom: David Smyth Department of earth sciences, University of Waterloo, Waterloo, Canada

Batch Removal Rates with BOF

Time (h)

00 22 44 66 88

00

200200

400400

600600

800800

10001000As(III) + As(V)As(III) + As(V)

Time (h)

00 22 44 66 88

00

200200

400400

600600

800800

10001000Se(VI)Se(VI)

Se(

VI)

(S

e(V

I) (

mg

/Lm

g/L))

As

tota

l (

As

tota

l (

g/L

)g

/L)

From: David Smyth Department of earth sciences, University of Waterloo, Waterloo, CanadaFrom: David Smyth Department of earth sciences, University of Waterloo, Waterloo, Canada

Time (h) Time (h)

Montreal Biodome research project

Closed marine system 3000 m3 (large marine aquarium)

Home to about 100 seabirds, 600 fishes, 2000

invertebrates from gulf of St-Lawrence

Contained 20 mg P/L (60 kg P)

Pilot unit of 9.5T remove 7 kg P (0.75 g P/kg slag) lasted

93 days, the flow rate = 3 to 9 L/min

During test some animals breed, that showed the good

quality of the water

Efficiency limited by the formation of a bacterial biofilm

Conclusion

Reputation

Co-product

Quality control of this resource is important

Slag processor = aggregate processor

SS has more advantage than disadvantage

Sustainability = conservation of natural resource