Slag - FEhS

// A product with exceptional variety.
Slag is ideally suitable for a surprisingly wide
variety of applications. //
Slag: A sound choice in favour of ecology.
Slag : A sound choice in favour of ecology.
A publication by the steel industry in North Rhine-Westphalia, Germany
FEhS – Institut für Baustoff-Forschung e. V.,
Duisburg
DSU
Gesellschaft für Dienstleistungen und
Umwelttechnik mbH & Co. KG, Duisburg
HKM Hüttenwerke Krupp Mannesmann GmbH,
Duisburg-Huckingen
ArcelorMittal Ruhrort GmbH,
Duisburg
ThyssenKrupp Steel AG,
Duisburg
01
Foreword //
Slag a valuable raw material
Dr. Karl-Ulrich Köhler
Chairman of the board at
ThyssenKrupp Steel AG and
member of the executive
board at ThyssenKrupp AG
Ecology and Intelligence
Sustainability is one of the major themes of the future in our society. The German
steel industry meets this challenge: we want to use our resources sparingly, we
want to contribute to economic prosperity and we want to take responsibility for
the social balance.
Whether environmentally, economically or socially – the German steel industry is
working actively in all areas to ensure that sustainability becomes a reality for
ourselves and for coming generations.
Today we want to introduce you to an issue closely linked with the responsible use
of our resources. Producing iron and steel automatically generates slag. Steel can be
found in almost every facet of life: architecture, transport, in the home etc. But what
happens to the other product, where is the slag and the valuable materials made
from it used?
We would like to show you in how many areas the “lava from the blast furnace and
the converter” is utilised. We would like to explain to you the lengths to which the
German steel industry and its service providers have gone to, to make slag usable as
a high-grade product for very varied fields of application – a significant contribution
to saving natural resources and reducing CO2 emissions.
Slag products are extremely versatile. They are used to fertilise crops and to build
houses and bridges. They make roads stable, safe and quiet, and they help to protect
the landscape. We would like to inform you about the manufacture and use of slag
products. We hope we can capture your interest.
From Nature. For
Slag in hydraulic engineering. Slag products are also used in hydraulic
engineering to stabilise the natural course of riverbanks.
02 03
Content //
Nature.
04
Valuable materials
06
Ores, iron, steel & slag
10
Slag for a sound natural environment
14
Safe driving with OPA
18
Granulated blast furnace slag binds
20
Constructing with blast furnace cement
24
Lower CO2 emissions
26
Fertilising with slag
30
Glossary
32
Addresses / Contacts
Valuable
raw materials
Origin of the Earth. Slag is one of the most ancient and
natural products. The slag that runs out of the blast furnace is
red-hot liquid rock. The history of life on Earth began with the
same material around 4 billion years ago: red-hot liquid lava,
cooling slowly, decayed to fertile soil and formed the basis for the
development of life on our planet.
04 05
Slag a valuable raw material //
A sustainable product
Slag. We want to introduce to you an interesting, perhaps even
extraordinary product and a fascinating production process.
Plants. Slag is cooled, previously liquid rock – the original material of
our planet. In some parts of our Earth, for example on the island of
Hawaii, it is possible to watch the history of the Earth in fast-forward
motion. Liquid magma, red-hot streams of lava cool down, decay and
soon become home to plants.
Earth. There is virtually nothing more closely related to the original
state of our Earth than slag. But slag is also the product of one of the
oldest and most developed production processes: manufacturing iron.
A decisive invention for the development of mankind, right up to the
present day.
Environmental protection is particulary emphasised
in all German steel works.
Ores, iron, steel and slag
What are ores? How is iron extracted from the ore? Why are
slags from iron smelting excellent products? During the
smelting of iron ore, valuable materials are produced with
an extraordinarily broad range of applications.
06 07
Slag as a product //
Ores, iron, steel & slag
Ores. For those who are not familiar with ores, these materials
represent just small lumps of rock that are mined from Nature. They
are especially interesting because they contain, for example, iron
(depending on where they are mined from, this can be up to 70 %).
Iron. To extract the iron from the ore, people invented the blast
furnace. In the blast furnace a mixture of iron ore and coke is “melted
down” at over 1500 degrees. Three products are generated: hot metal
(molten iron), flammable gas and molten rock, the blast furnace slag.
Steel. Still in a hot, molten state the iron is refined to steel. This is done
for example by top-blowing with oxygen (BOF-process). During topblowing with oxygen, the remaining carbon contained in the molten
iron is burnt. Instead of brittle iron, steel is created that can be forged or
rolled. The steelworks also produces steel slag respectively BOF-slag,
used for example in road construction.
Slag. Whilst still in a molten state, the chemical composition of the slag
can be altered, for example by adding lime, sand or oxygen, thereby
generating different types of slags. The manner of cooling the slag will
alter the physical composition.
Catchword: Iron Ore
Generation of iron and steel slags
Nature supplies us with iron ore. It consists of iron
Blast furnace
BOF-converter
oxide and adhering rock, gangue, as the miner calls it.
“Over 3000 years
ago, people started
the systematic
production of iron in
so-called ‘bloomery
hearths’. When the
right temperature
was reached, ore and
charcoal caused the
iron to ‘bloom’, to
emerge.”
Dr. Michael Peters
Senior Vice
President – Hot
Metal Production,
Division Metallurgy,
ThyssenKrupp
Steel AG
What slag consists of:
The chemical composition
varies between blast furnace
To obtain the iron from the ore, the metallurgist
slag, basic oxygen furnace slag
needs high temperatures and coke. When the coke is
and electric arc furnace slag.
“burned”, the iron oxide becomes iron and the gangue
10 – 40 % silicon oxide
becomes slag.
What are rocks, really? We know many different kinds:
20 – 55 % calcium oxide
the white sand by the sea consists almost solely of
silicon oxide; limestone and marble are rocks made of
1 – 15 % magnesium oxide
calcium carbonate. Many structures and monuments
are built of these. Calcium and silicon oxides are
important components of slag.
Blast furnace
slag
Hot metal
(molten iron)
BOF-slag
Crude steel for
further processing
1 – 40 % iron oxide
Slag products ...
... proven over centuries. From the beginning of the Iron Age,
800 B.C., through the invention of the blast furnace process in the
18th Century, they have been put to advantageous use, and still are
to this day.
... ecological and intelligent. With various techniques for further
processing, they are prepared for a wide range of applications as
building materials or fertilisers. By recycling, a portion of the steel slag
is reused in the blast furnace as a secondary lime and iron burden.
... for roads. They are exceptionally well suited for road construction
“In nature, rocks also
have very varied
features: hard or
soft, crystalline or
glassy, rough or
smooth. We are able
to specifically
determine some
typical characteristics of slag and thus
prepare them for
various applications.”
Dr. Nicola Hirsch
Managing Director
HR,
ArcelorMittal Germany
GmbH
as “open porous asphalt” helping to reduce traffic noise. Further
positive characteristics are durability and high skid resistance.
... for bridges. They are used for demanding construction projects
such as bridges and skyscrapers.
... for waterways. In hydraulic engineering – such as in building locks,
river bottoms and bank reinforcements – they are proven materials.
... as fertiliser. Slag products have been successfully used as fertilisers
for generations.
Use slag!
A smart solution on both counts: Ecology and economy.
Porous as sponge and hard as glass
Slag and slag are not alike. They can be extremely hard or “moist/granu-
crystalline air-cooled blast furnace slag (ACBFS) is produced. This slag is
lar”. They can be transparent like glass or have the form of a sponge
porous and, amongst other applications, is used as a water-permeable layer
made of rock. These qualities can be influenced through a variety of
in road construction.
process measures, for example by rapid or slow cooling or by the addi-
Steel slag is produced in basic oxygen furnace- and electric arc furnace
tion of sand, oxygen or lime when in a molten state. Generally, three
processes.
kinds of slag are produced for different fields of application:
Basic oxygen furnace slag (BOFS) is produced when refining hot metal to
Blast furnace slag is produced when “melting down” iron ore and coke to
make steel. It is used in road construction, for example, for surface layers.
make hot metal (molten iron). The blast furnace produces hot metal , gas
Generations of farmers would swear by fertiliser made from steel slag.
and blast furnace slag. The red-hot blast furnace slag that flows out is
Electric arc furnace slag (EAFS) is produced in the electric arc furnace. Here,
rapidly cooled with water in a special process, and granulated. Granu-
scrap is melted down by the electric arc at temperatures of up to 3500 degrees
lated blast furnace slag (GBS) is produced and prized in the cement
Celsius . New steel is created from scrap. Slag from the electric arc furnace has
industry. If the “lava of the blast furnace” is left to cool slowly in the air,
proved itself particularly suitable for “porous asphalt” on motorways.
08 09
Slag as a product //
Ores, iron, steel & slag
Iron/steel slags, annual production 2006, Germany
53% Proportion of blast
furnace slag
17
%
30% Proportion of basic
oxygen furnace slag
17%
53%
Proportion of electric
arc furnace slag
%
30
Quantity of blast furnace slag:
Quantity of basic oxygen furnace slag:
Quantity of electric arc furnace slag:
7.7 million tonnes
4.3 million tonnes
2.5 million tonnes
Use of blast furnace slag 2006, Germany
Steel works in Germany
0.2%
1.2%
72.2% Granulated blast furnace
slag as cement raw material
26.4% Crystalline blast furnace slag
for road construction etc.
26
.4%
1.2%
Granulated blast furnace
slag for road construction
0.2% Fertiliser
72
.2
%
Production:
Stockpile reduction:
Total:
7.7 million tonnes
1.2 million tonnes
8.9 million tonnes
Use of steel slag 2006, Germany
(Basic oxygen furnace slag and electric arc furnace slag)
68.3% Construction material
5.5%
8.8
17.4% Internal Recycling
8.8% Landfill
%
17.4
%
5.5%
Fertiliser
68.3%
Blast furnaces
Of construction material:
Road construction:
24.2%
Construction country
lanes/rural ways:
14.0%
Earthworks:
25.6%
Hydraulic engineering: 4.5%
Production:
Stockpile reduction:
Total:
6.8 million tonnes
0.1 million tonnes
6.9 million tonnes
Locations of:
BOF converters
Electric arc
furnaces
Using natural stone means quarrying it from natural sources. Natural stone
can be replaced by slag products – a contribution to protecting the landscape.
10 11
Protecting the landscape using slag //
Intact nature
Slag – contributing to keeping Nature intact
Natural stone – that sounds very natural. But using natural stone
does not automatically mean protecting nature or the landscape.
Natural stone has to be exploited. In quarries.
They blast there with dynamite. Bulldozers, big vehicles and powerful processing machines are used for quarrying natural stone.
Slag products instead of natural stone! Natural stone – that
“Saving natural
resources is one of
the genuinely
important tasks of
the future. If products from the iron
and steel industry
for example can
help, this should be
promoted.
The steel works have
gone to enormous
lengths to sustainably guarantee the
quality of slag products at a high level.
This must also be
supported in the
political arena.”
sounds very ecological, very natural. Basalt, granite, diabase – these are
all natural varieties of stone that have useful characteristics.
But – to use them, they have to be quarried. This means quarries,
blasting, bulldozers and a degree of non-reusable waste. In many fields
of application natural stone can be replaced with slag products.
A mountain as tall as the Zugspitze, the tallest in Germany.
Since 1945, around a billion tonnes of slag have been used in Germany
for the broadest range of applications. With this quantity, a gigantic
tower could be heaped up, 600 metres in diameter and 2900 metres
tall, as tall as the Zugspitze. Slag products contribute to less natural
stone being quarried and fewer quarries being exploited. The use of
slag products is a contribution to the protection of our environment.
Karl Heinz Florenz
MEP, Chairman of
the Environment
Committee in the
European Parliament
Replacing or supplementing natural stone
Natural stone diabase
replaced in road construction with
Slag
Natural stone basalt
replaced in hydraulic engineering with Slag
12 13
Protecting the landscape using slag //
Intact nature
Testing by the FEhS-Institute
Slag products are regularly tested. Whether environmental
questions or the quality of building materials – the “FEhS –
Building Materials Institute” in Duisburg tests and evaluates
every aspect of slag and other building materials. The
abbreviation FEhS means Forschungsgemeinschaft Eisenhüttenschlacken (Research Association for Iron and Steel Slags),
which was founded in 1968 through the merger of two earlier
organisations, the “Arbeitsgemeinschaft Thomasphosphat”
(Basic Slag Trade Association) and the “Arbeitsgemeinschaft
Hochofenschlackenforschung” (Blast Furnace Slag Research
Association). In order to meet new requirements and survive in
competition, every product has to be accompanied by research.
The tasks of the FEhS-Institute are common research on the
utilisation of iron and steel slag, representation of interests in
national and international bodies, and general research,
testing, monitoring and certification of building materials.
Replacing natural stones
with slag products
There are fields of application in which natural
FEhS research areas:
– Environmental compatibility
– Road construction
– Binding agents
– Cement / concrete
– Slag metallurgy
– Fertilisers
– etc.
Utilisation of slag products and natural aggregates
(in millions of tonnes per year)
400
stone is the right choice. The edges of garden
paths look absolutely great with pale grey
granite bordering. But in many other fields of
300
application, natural stone can be replaced.
Slag products are just as hard, last just as long
and are generally significantly more cost-
200
effective. It does not always have to be natural
stone.
In the construction of roads, for example,
100
the traditional natural stone fine aggregates
are increasingly being replaced with slag
products. For the paving of paths, too, slag
products are being used ever more frequently.
0
Slag products
Natural Stone
Gravel / sand
Drive safely on “OPA” – Roads made of slag
Safe, quiet and long-lasting – that is typical “OPA”. Open-porous asphalt
(OPA) combines many good characteristics. “OPA” is therefore the future
of road construction. Steel slag has proved to be excellent for openporous asphalt surfaces.
The “polished stone value” (PSV) decides
How high is the PSV? This question is asked ever more frequently
High-quality asphalt surface layers require PSVs of up to 55. In steel
when discussing road surfaces properties. Put differently, the question
slag aggregates, PSVs of over 60 are verified! With a significantly bet-
is, what happens to the road surface when thousands of cars “polish”
ter proportion of voids. Steel slag is as hard as cooled lava, but has
it with their tyres? Does the surface become smooth? And hence
many finely-distributed voids that open up when “polished” by the
dangerously slippery? Or does the surface retain its grip?
tyres, and hence guarantees a constantly gripping and rough surface.
Over decades, mixtures predominantly of bitumen and natural stone
Steel slag offers extraordinarily good characteristics for the use in
(processed into fine aggregates) were used for the construction
road construction. During the production process at high tempera-
of road surfaces. The “polished stone value” especially was a convinc-
tures, stable voids are created. It is extremely suitable for surface
ing argument for the use of this natural stone. A high PSV shows that
layers in modern road constructions.
a material can only very slowly be driven smooth by the rolling tyres.
14 15
Road construction //
Safe and environmentally friendly
The future of roads belongs to OPA
Safe. Roads must not be slippery. Neither on dry nor
on rainy days. Dry roads generally have sufficient grip.
To keep as much grip as possible in the rain, the
modern road is especially required to direct water
away as quickly as possible. “How well a road surface
copes with water can be seen for example from the
“spray effect” created by the car in front when it is
raining. Modern, “open porous” asphalt surfaces based
on slag hardly permit spray effects to form and reduce
the risk of aquaplaning.
Quiet. The voids of these new asphalts not only let
water through, a proportion of the noise generated by
the rolling tyres also disappears into these voids.
For this reason they are significantly quieter than
conventional asphalt layers.
“The characteristics
of blast furnace and
steel slags have been
steadily improved in
recent years in order
to fulfil the high
requirements placed
on modern building
materials for the
construction of
roads, paths and
waterways.
Factory production
control and external
monitoring by
neutral testing,
inspection and
certification bodies
guarantee the
lasting performance
of slag products.”
Dr. Carl-Heinz
Schütz
Senior Vice
President –
Steel Production,
Division Metallurgy,
ThyssenKrupp
Steel AG
Slag as an export commodity
In Duisburg, slag
is loaded directly
onto vessels “ex
works”. The slag
goes down the
Rhine, for example to the Netherlands and is used
there for road
construction.
Slag products
are increasingly
establishing
themselves as
very economical materials
for road
construction.
During the day it is one of the most travelled roads in Europe,
the A 40 in the Ruhr region, in the middle of Essen. Every day,
hundreds of thousands of vehicles roll over a surface layer
constructed with steel slag.
"Through a variety of procedures
during the processing, it is ensured that the requirements
of the market and the applicable
standards are adhered to.
A certified quality management
system ensures that the users
keep the slag products at a
consistently high quality.”
Jörg Schürmann
Member of Managing Board
(CEO)
DSU – Gesellschaft für Dienstleistungen und Umwelttechnik
mbH & Co. KG
Slag for all road layers
Layer by layer with slag
Roads consist of a number of layers.
Water-permeable layers especially
ensure that the road is not ruptured
by frost in winter. The base course has
to withstand the main load, after all,
heavy lorries “press down” on the road
structure about 100 tonnes per square
metre. The binding layer “passes the
pressure on down from top to
bottom”. The top surface layer has to
have “grip”, direct water away and
should muffle the rolling noise. In all
layers, slag products are used as the
“active elements” in modern roads.
The voids in slag aggregates
and porous asphalt as surface
layers take up:
Asphalt surface layer
Asphalt binder course
Asphalt base course
Unbound base course
Frost protection layer
Foundation
Sub-grade
Noise
Water
Economic efficency
The requirements placed on modern roads are high: traffic safety and
noise reduction! The answer to the many requirements is “open porous
asphalt” (OPA). Safe and quiet, but still economical. How long does an OPA
road last? 6 to 8 years, say the experts. An OPA test road made of BSN steel
slag formed part of the A 5 near Baden-Baden for ten years (1995 to 2005).
After ten years, the road engineers certified that it was still in extraordinarily good condition.
16 17
Road construction //
Safe and environmentally friendly
Listen for yourself
This is where the BSN open porous asphalt surfaces with
steel slag have been constructed.
A5
Ispringen
51
A8
Airport
Baden-Baden
43
43 Pforzheim-Zentrum
51 Baden-Baden
Schönbühl
A 8, Pforzheim Nord – Pfhm. West A 5, Rastatt / Baden-Baden
42
Palmbach
Mutschelbach
42 Karlsbad
A8
A 8, Karlsbad
When building the A 5 and A 8, steel slag from BSW-Stahl-Nebenprodukte GmbH, Kehl, was used.
Load-bearing capacity of roads
400%
360*
300%
290*
270*
200%
175*
100%
100*
60*
Assumed
value
T1
T2
T3
T4
T5
T6
* CBR value in percent. The higher the CBR value, the higher the load-bearing capacity of a road (comparison after 180 days setting).
Composition of the slag mixtures
T1 = 100% granulated blast furnace slag (GBS)
T2 = 100% crystalline blast furnace slag (ACBFS)
T3 = 70% GBS + 20% ACBFS + 10% BOF slag (BOFS)
T4 = 80% ACBFS + 20% GBS
T5 = 75% ACBFS + 10% BOFS + 15% GBS
T6 = 95% GBS + 5% calcium hydrate
The load-bearing capacity depends on what slag mixture is used in road construction. The stability required by the authorities
in road construction is regularly exceeded through the use of slag mixtures.
Granulated blast furnace slag
creates strong bonds
Portland blast furnace cement and regular blast furnace
cement for especially high-value and long-lasting concrete is
manufactured from a mixture of granulated blast furnace
slag and Portland cement clinker. Structures built with blast
furnace cement are particularly stable and long-lasting.
The use of granulated blast furnace slag causes lower CO2
emissions, than when producing Portland cement.
18 19
Blast furnace sand //
Powerful adhesive
Granulated blast furnace slag is created during hot metal
production in the blast furnace. The molten blast furnace slag is
granulated by using water at high pressure.
Granulated blast furnace slag grains are glassy, have a very dense
structure and a high strength. Granulated blast furnace slag is a
main component of Portland blast furnace cement and Blast
furnace cement which have been manufactured for around 100
years by the cement industry.
"Good products are a
prerequisite for high
job security. The
constant training of
our employees is an
important instrument, for example,
in adapting the high
quality of our steel
and slag products to
the changing
market conditions.”
Strength. Blast furnace cement is particularly suitable for
“high-performance concrete”. The hardening – the hydration – of
concrete with blast furnace cement is generally slower than with
Portland cements. More granulated blast furnace slag, however,
means fewer stresses and a lower tendency to crack – a big
advantage with concrete structures such as bridge pillars, dams,
large-scale foundations or locks.
Blast furnace cement: Powerful adhesive
directly taken from the blast furnace
In 2006, around 5.9 million tonnes of granulated blast
furnace slag were produced in Germany. Over 90 %
was used in the cement industry. Granulated blast
Peter Gasse
Member of the
board of
management,
HKM Hüttenwerke
Krupp Mannesmann GmbH
Production of blast furnace slag since 1972
Million tonnes per year
14
Granulated blast furnace slag
Crystalline blast furnace slag
12
furnace slag and Portland cement clinker are the main
components of blast furnace cement. With water,
10
aggregates and other components, concrete is made
from blast furnace cement whose strength comes
8
very close to that of natural rock.
6
4
2
0
1972
1976
1980
1984
1988
1992
1996
2000
2004
Resists wind and weather.
Concrete made from blast furnace cement with
a high proportion of granulated blast furnace
slag ensures the stability and durability of the
telecommunications tower in Düsseldorf.
Rising high thanks to blast furnace cement
Portland blast furnace cements and blast furnace cements
make structures especially stable and weather-resistant.
Concrete with a high proportion of granulated blast furnace
slag is the right material for particularly demanding
architecture.
20 21
Rising high thanks to blast furnace cement //
Stable and safe
Massive pillars support the Rheinkniebrücke (Rhine Knee Bridge) in Düsseldorf. Water
from below, sun, wind and weather from all sides and traffic with the high frequency of
a metropolis. The engineers decided on concrete with a high proportion of granulated
blast furnace slag for good reason.
Blast furnace cements. These cements have some special features.
The cement mostly sets more slowly than with normal Portland
cements. This means that the energy released during the setting
process is lower. Especially in massive concrete structures such as the
pillars of bridges, for example, crack formation through temperature
variations can thus be prevented. Fewer pores or fewer cracks in the
surface means a significantly better resistance to chemicals and road
salt. This is also a reason why blast furnace cements are used in road
construction.
“German cements
consist, on average,
of around 20 %
granulated blast furnace slag, and this is
an increasing tendency. This makes
clear that granulated
blast furnace slag
nowadays constitutes an important
basis for the economical, resourcesaving and low-CO2
manufacture of
cement. It should
also not be ignored,
that blast furnace
cement additionally
has special structural qualities that
make building with
it very durable.”
Dr. Hans Andreas
Brodersen
Managing Director
CEMEX HüttenZement
GmbH
Senior Director
CEMEX Deutschland
AG
Television towers and protection against floods
Concrete made from blast furnace cement differentiates itself from concrete
the mouth of the Emscher, are made of concrete with blast furnace
made from Portland cement without granulated blast furnace slag by its
high resistance to chemical attack and abrasion, as well as by its high den-
cement.
–
Structures with special requirements, such as the television towers
sity, especially for the following construction types:
in Düsseldorf and Dortmund, the locks in the Rhine and the Ooster-
–
Industrial structures such as the blast furnace foundation and the new
schelde flood barrier to protect against storm flooding in the Nether-
coke oven plant of ThyssenKrupp Steel AG have been built exclusively
lands were manufactured with blast furnace cement, because of the
using blast furnace cement. All the sewage works in Duisburg, including
exceptionally high stresses that occur there.
Size. In 1994, the south lock of the Rhine-Herne Canal in Wanne-Eickel went operational, suitable even for ships of the large “European ship class II”. The requirement was
for water-impermeable concrete with high frost resistance. Blast furnace cement with a
high proportion of granulated blast furnace slag was used.
Profile. For the construction of the new Norddeutsche Landesbank in Hannover, the
building sponsor decided on particularly extravagant architecture. Such buildings
require foundations that can support extreme loads in the long term. Therefore blast
furnace cement with a high proportion of granulated blast furnace slag was used.
194 foundation pillars made of concrete now support the
headquarters of the Norddeutsche Landesbank in Hannover.
In order to guarantee this supporting role in the long term,
blast furnace cement was used.
Altering the properties of the concrete
slower hardening
Increasing
proportion of
granulated blast
furnace slag
lower initial strength
greater subsequent
hardening
denser structure
higher resistance to
chemical attack
22 23
Rising high thanks to blast furnace cement //
Stable and safe
How much pressure can concrete withstand?
How porous is the surface?
What stresses can concrete take?
The FEhS – Building Materials Institute tests concrete and many other materials for all areas of application.
Protecting the environment
Less CO2 – the topic of climate and carbon dioxide is being
discussed intensively world-wide. Carbon dioxide is also
released during the production of cement.
These CO2 emissions can however be significantly reduced
if granulated blast furnace slag is added to the cement.
24 25
Protecting the environment //
Fewer CO2 emissions – Slag helps
Fewer CO2 emissions –
Slag products help
Is the climate changing?
If yes, is climate change caused or accelerated by
CO2 emissions? The debate over these questions is
as intensive as ever. Fewer CO2 emissions! That is
certainly one aim of environmental policy. The use
of slag products advances this aim.
The production of cement takes place in large
rotary kilns. In the process, one tonne of carbon
dioxide is released per tonne of Portland cement
produced.
CO2 emissions generated during production of one tonne of cement
The higher the proportion of granulated blast furnace slag , the lower the CO2 emissions
>>>
1 tonne CO2
>>>
0.7 tonne CO2
50% GBS
>>>
0.5 tonne CO2
75% granulated blast furnace slag (GBS)
>>>
0.25 tonne CO2
100% Portland cement (PC)
70% Portland cement
30% GBS
50% Portland cement
25% PC
Carbon dioxide / CO2
Generation of CO2 emissions
Carbon dioxide has no smell and no taste. It cannot really be seen, either, except for example
When manufacturing Portland ce-
as bubbles in beer, lemonade or mineral water – what bubbles is carbon dioxide (CO2). The CO2
ment, a great deal of carbon dioxide
either comes from fermentation (beer and champagne) or it is forced into the drinks from pres-
(CO2) is released. Around one tonne
surised tanks (lemonade). CO2 is created by the combustion of substances that contain carbon.
of carbon dioxide per tonne of ce-
Petrol, coal, fuel oil – all burn with the oxygen from air to make carbon dioxide. Critical voices
ment. This CO2 escapes into the air.
describe CO2 as a greenhouse gas, because it is blamed for the increase in the temperature of
Cement with a higher proportion of
the Earth.
granulated blast furnace slag means
The debate over the causes continues. But the fact remains that most industrialised countries
lower carbon dioxide emissions.
have committed to “less CO2”. “Less CO2” – the use of granulated blast furnace slag makes a
perceptible contribution to this goal.
Higher yield, healthy growth. On a test field in Rösrath, near Cologne,
the effects of fertiliser made from slag are regularly tested. The cows seem
to enjoy grass fertilised with slag as well!
Fertilisers made from iron and steel slags
Basic slag is the number one for many farmers when it
comes to fertilising their fields. Crops grow better with
fertiliser made from slag, and the soil stays healthy and
fertile.
26 27
Fertilisers made from iron and steel slags //
Better growth
Basic slag – recognised quality
Fertilisers made from iron and steel slags can look
back on over 100 years of tradition. Basic slag – also a
slag product – has an excellent reputation among
farmers and gardeners because of its quality. For
decades, the effects of fertilisers made from slag have
been scientifically investigated.
Ecological. Crops grow better with fertiliser that is
ecologically unobjectionable. The converter lime manufactured from steel slags is ecologically unobjectionable. That is why sieved converter lime was
approved by the European Community for use in
organic farming. This fertiliser is also approved for
organic farming by the association “Bioland”.
The minerals of our Earth
Virtually no other fertiliser offers as many natural
components as converter lime. This fertiliser contains
the most important building blocks on our Earth.
Through a variety of processing procedures, it is possible
to produce a fertiliser that disintegrates quickly,
releases no carbon dioxide (CO2), supports stable plant
growth and simultaneously helps to keep the soil loose
and aerated. Various plant growth experiments consistently show that crops grow faster and more steadily
with fertiliser made from iron and steel slags.
Strengthens the immune system
Converter lime (slag fertiliser) combines many positive characteristics.
Because of its specific mineral content,
it promotes plant growth.
This has been proven in numerous
series of experiments over decades.
The experiments have also shown
that converter lime helps crops defend
themselves against damage by
mildew. The immune system of the
crops is especially strengthened by
the high proportion of silicate in the
converter lime.
The livestock like it
Field test from the year 1930: the pasture areas marked
with “P”and “KP” were treated with slag fertiliser.
Trust your taste. If that is what counts,
livestock have long been approving of
slag fertilisers. This photo from 1930
shows a fertiliser experiment in a
pasture. On the parts of the pasture
marked with “P” and “KP”, fertilisers
were used that came from the iron
and steel making process..
The same result is still produced
today: whether cattle or sheep – after
a short taste test, the livestock consistently choose the pasture fertilised
with slag products.
28 29
Fertilisers made from iron and steel slags //
Better growth
Less CO2
Other fertilisers contain
minerals that are “carbonically” bound (as CO2
bonds). Fertilising releases
CO2. Per tonne of fertiliser,
around 400 kilogrammes of
CO2. With converter lime,
no carbon dioxide is
released – a contribution to
protecting the climate.
No compaction of the soil
Slag has a similar mineral
composition to our Earth.
For the plants, that means
good growth. The soil also
remains loose and aerated,
and not just for one growth
cycle.
Special effects of silicic acid on soil and plants
Improved storage
of SO2 leads to a
better resistance
Damage from fungus
is reduced: glume
spot, mildew, eyespot
Silicic acid from
Thomas fertilisers
Regulated
lime effect
Fertilised P
in soil more
available
Effects on the
soil structure
Cohesion of clay
particles to form
larger clumps,
formation of grains
SO2 absorption
by the roots
No reaction surges,
more available trace
nutrients
Improved nutrient
absorption due to
better root growth
Better pore
volumes, better
distribution of air
and water
Slag lime – better yields from silty soil
Annual yield increase (in 100 kg yield / ha)
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0.0
Hard clayey silt
Clayey silt
Blast furnace lime
Soft clayey silt
Non-siliceous control lime
Sandy silt
Glossary
Explanations of some terms connected
with the product slag
Iron. Iron is a chemical element (Fe = Ferrum).
Blast furnace. Iron ore and coke are “melted
Our planet consists of 32 % oxygen and 28 %
iron. The iron is very unevenly distributed. The
Earth's core consists almost 80 % of iron. It is
hypothesised that the iron core of the Earth is
the source of the Earth's magnetic field. Iron is
rarer in the Earth's crust. Higher proportions of
iron can be found in the Earth's crust where
magma flows in prehistoric times “brought
the iron up from within” the Earth.
down” in the blast furnace. During this process the coke gets the oxygen it needs from
the iron oxide. Viewed chemically, the iron
oxide is reduced to iron and the carbon is
oxidised to carbon dioxide. Predominantly,
the blast furnace at over 1500 degrees Celsius
produces three products: blast furnace gas,
hot metal (molten iron) and molten blast
furnace slag.
The electric arc furnace process is a process
for manufacturing steel. Hot metal (molten
iron) from the blast furnace is not used in the
electric arc furnace, instead it is loaded with
scrap. Thus steel and electric furnace arc slag
(EAF-Slag) are generated.
Blast furnace cement consists of Portland
cement and 36 to 95 % granulated blast
furnace slag.
Ores. Iron ore is mined from nature, around
a billion tonnes annually (main suppliers are
Brazil and Australia). Iron ore contains up to
70 % iron.
30 31
Glossary //
Granulated blast furnace slag. The
granulated blast furnace slag is created by
cooling molten blast furnace slag with jets of
pressurized water. It is a fine-grained, glassy
product of the hot metal production process in
the blast furnace, with a grain size of up to
5 millimetres.
LD/BOF process. The hot metal from the blast
furnace is refined to steel while still in a hot,
molten state. This takes place by top-blowing
with oxygen. It is called the LD process (engl.
BOF – basic oxygen furnace) after the Austrian
towns of Linz and Donawitz, where it was
developed in 1952. Steel and BOF slag (BOFS )
are thus produced.
OPA. Open-porous asphalts (OPA) for road
construction combine many positive
characteristics: they are safe, quiet and longlasting. Steel slag is increasingly used for this
purpose.
Portland blast furnace cement consists
(Mg) are likewise indispensable for humans,
animals and plants. The World Health Organisation recommends that a person consume
half a gramme of calcium every day with
their food.
of Portland cement clinker and 6 to 35 %
granulated blast furnace slag.
Steel can be forged, bent, rolled, drawn to
Slag. During iron and steel making, slag is
produced. Viewed chemically, slags are rock,
mostly consisting of the oxides of silicon,
calcium and magnesium. Silicon (Si) is familiar from the beach. White sand is virtually
pure silicon dioxide. The human skeleton also
needs silicon. Calcium (Ca) and magnesium
make wire or welded. In many fields of application, steel is the most important material.
Iron contains more carbon than steel, is
hence brittle and as a material is therefore
not suitable for many fields of application.
Steel is produced from hot metal (molten
iron), for example in the BOF process, and
from scrap in the electric arc furnace process.
Slag: A sound choice in favour of ecology.
Published jointly by the FEhS-Institute, steel companies
and co-operating service providers in North Rhine-Westphalia, Germany
FEhS-Institut
FEhS – Institut für
Baustoff-Forschung e. V.
Bliersheimer Straße 62
47229 Duisburg
Telephone: +49 (0)2065 / 9945-0
Fax: +49 (0)2065 / 9945-10
E-Mail: fehs@fehs.de
DSU
Gesellschaft für Dienstleistungen
und Umwelttechnik mbH & Co. KG
Vinckeufer 3
47119 Duisburg
Telephone: +49 (0)203 / 469 02-0
Fax: +49 (0)203 / 469 02-84
E-Mail: info@dsu.eu
HKM Hüttenwerke Krupp
Mannesmann GmbH
Ehinger Straße 200
47259 Duisburg-Huckingen
Telephone: +49 (0)203 / 999-01
Fax: +49 (0)203 / 999-44 11
E-Mail: post@hkm.de
ArcelorMittal Ruhrort GmbH
Vohwinkelstr. 107
47137 Duisburg
Telephone: +49 (0)203 / 52-67353
Fax: +49 (0)203 / 52-66332
E-Mail: ArcelorMittalDuisburg@
ArcelorMittal.com
ThyssenKrupp Steel AG
Kaiser-Wilhelm-Straße 100
47166 Duisburg
Telephone: +49 (0)203 / 52-28212
Fax: +49 (0)203 / 52-28488
E-Mail:
georg.don@thyssenkrupp.com
Copyright
Publisher: FEhS-Institut, Duisburg
Conception/realisation: Medienpool Köln GmbH
Editing assistance, FEhS-Institut:
Dr. Heribert Motz, Dr. Thomas Merkel
Photos (page): Medienpool Köln, FEhS-Institut, Corbis (2/3),
Bildagentur online (10, 11), CEMEX Hüttenzement (19),
Reinecke (22), HeidelbergCement (25)
Slag products undergo constant testing
Safety through inspections and
certifications
FEhS-Institute. The FEhS – Institut
für Baustoff-Forschung e. V. (Building
Materials Institute ) in Duisburg has
the following responsibilities:
• common research on the utilisation
of blast furnace and steel slags (iron
and steel slags) and residues from
steel making
• representation of interests in
national and international bodies
• general building materials research
as well as Testing Laboratory,
Inspection Body and Certification
Body
• consultancy on the manufacture
and utilisation of building materials, and examination of structures
Kamperhof – experiment
facility for fertilisers
in Mülheim an der Ruhr
Kamperhof. Depending on
the request, fertilisers are
tested in every detail of their
yield and quality effects as
well as their profitability,
whether in the “microfield”
of a small pot at the Kamperhof experiment facility or in
major field tests in practical
agriculture.
A publication by the steel industry in North Rhine-Westphalia, Germany
Lava – Origin of our Earth
No product is so closely related
to this origin as slag