OUTLINE

1. What is Steel Slag?

2. Recycling of Steel Slag

3. Properties of Steel Slag

4. Sustainable Development

5. Steel Slag Road Pavement

6. Conclusions 2

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1. WHAT IS STEEL SLAG ?

Steel slag is a co-product from the steelmaking process.

There are two types of steel slag:

EAF slag (from mini mills; Singapore)

BOS slag (from integrated mills)

Steel slag is a ceramic material formed from the reaction

of flux such as calcium oxide with the inorganic non-

metallic components present in the steel scrap.

The chemical composition of steel slag depends on the

quality of the feed material, the steelmaking process and

the grade of steel produced. 3

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1. WHAT IS STEEL SLAG ?

TREATED STEEL SCRAP

ElectricArc

MELTING

SCRAP CHARGING BUCKET SLAG TAPPING

Slag Pit

Slag

Steel slag floats on top of the molten steel.

The hot slag is processed into steel slag aggregates.

In-house treatment method ensures that the aggregate is

suitable for use as road construction material.

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Flux

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2. RECYCLING OF STEEL SLAG

In many countries, steel slag is typically landfilled or dumped onsite. Reuse of steel slag conserves landfill site and promotessustainable development.

NSL Chemicals, together with the local universities have jointlyconducted research projects on the use of steel slag since 1991.

In 1993, a successful public road trial conducted with the LandTransport Authority of Singapore (Public Works Dept.) led to theapproval of steel slag for use on Singapore roads.

Over the last 19 years, more than 1.3 million tons of steel slag hasbeen paved on Singapore roads.

NSL Chemicals practice on steel slag reutilization has beenestimated to save over 520,000 m3 of landfill site in Singapore.

Now 100% of the steel slag generated in Singapore is recycled intoroad-making materials. 5

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not use, divulge or reproduce the said information in any way without a written consent from NSL Chemicals Ltd.

3. PROPERTIES OF STEEL SLAG Typical comparative chemical compositions of steel slag

and granite:

Steel slag contains significantly higher calcium and ferrouscontent compared to granite rock.

Granite rock contains high silica and alumina content.

Steel slag is hydrophobic in nature (better adhesion withbitumen) while natural rock is generally hydrophilic (higheraffinity to water than to organic materials, e.g. bitumen).

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Components Steel Slag (wt%) Granite Rock (wt%)

SiO2CaOFeOMgOMnOAl2O3

Properties Granite Slag Remarks

pH 7 11 Steel slag is alkaline and bonds better with bitumen.

Polished Stone Value 49 60-61 Steel slag has better resistance to skidding.

LA Abrasion Value (%) 35 20-25 Steel slag has less abrasion loss.

Aggregate Impact Value (%)

21-31 14 Steel slag is harder than granite.

Magnesium SulphateSoundness (%)

2.1 0.6-2.4 Steel slag is more resistant to freeze-thaw weathering.

Flakiness Index 22 3-16 Lower flakiness index indicates higher structural stability.

3. PROPERTIES OF STEEL SLAG

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Typical comparative physical properties of steel slag and

granite aggregates:

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3. PROPERTIES OF STEEL SLAG

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Granite Steel Slag

Comparative physical properties of steel slag and granites:

The good resistance to stripping and high Polished Stone Valueexhibited by the steel slag aggregates show that steel slag issuperior to natural granite as a road surfacing material.

The superior adhesion between steel slag and bitumen reducestypical moisture damage problems affecting granite pavement.

Steel slag pavement performs better in wet climate. Suchpavement surfaces tend to stay intact over longer period of time.

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Road pavement mixes with steel slag formulation have

better rut resistance and mechanical stability.

This indicates a more durable wearing course for the

road.

Parameter Comparative Pavement

Mixes

LTA

Specs

Remarks

Steel slag Granite

Marshall Stability, kN

20.6 11.0 9 kN Steel slag mix displays better Marshall stability.

Flow, mm 3.60 3.85 2 4 Within specified range.

Void in Mix 4.93% 4.00 % 3 5% Within specified range.

Wheeltrack(mm/hr) 60oC

3.68 9.90 Steel slag mix has less deformation and wear.

3. PROPERTIES OF STEEL SLAG

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not use, divulge or reproduce the said information in any way without a written consent from NSL Chemicals Ltd.

4. SUSTAINABILTY

Environmentally friendly

Steel slag is classified as a non-hazardous waste.

Leaching test result shows compliance with

environmental regulation.

Element Steel Slag (ppm) Limit (ppm) Element Steel Slag (ppm) Limit (ppm)

As

4. SUSTAINABILITY

The use of steel slag

Reduces the reliance on natural resources.

Reutilizes waste material and conserves land.

Helps to reduce greenhouse gases emission.

0.00

0.01

0.02

0.03

0.04

0.05

Steel Slag Granite

k

g

C

O

2

e

Transportation

Electricity

Diesel

Explosives

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Life Cycle Analysis of Steel Slag and

Granite Aggregate

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5. STEEL SLAG ROAD PAVEMENT

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not use, divulge or reproduce the said information in any way without a written consent from NSL Chemicals Ltd.

6. CONCLUSIONS

Steel slag aggregate can be beneficially used as a road

surfacing material when it is properly treated, processed

and engineered for the application.

The physical and chemical characteristics are superior to

granite in road pavement application, particularly in its

Marshall stability and resistance to rutting, skid, and

bitumen stripping.

Use of steel slag aggregates mitigates the reliance on

quarry material extraction and assists in sustainable

development.

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not use, divulge or reproduce the said information in any way without a written consent from NSL Chemicals Ltd.

Thank You!

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The contents of these slides are private, confidential and proprietary to NSL Chemicals Ltd. The recipient / viewer of these slides shall

not use, divulge or reproduce the said information in any way without a written consent from NSL Chemicals Ltd.

NSL Chemicals Ltd

26 Tanjong Kling Road, Singapore 628051

Phone: (+65) 6513 6900

Email: Sales@nslchemicals.com.sg

Website: http://www.nslchemicals.com.sg/