ASTM D8021-23

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8021 − 23
Standard Guide for
Blast Furnace and Steel Furnace Slag as Produced During
the Manufacture of Iron and Steel
This standard is issued under the fixed designation D8021; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This standard is intended to provide guidance as to the 2.1 ASTM Standards:
appropriate/typical mineralogy observed when iron and steel C125 Terminology Relating to Concrete and Concrete Ag-
slag, produced during the manufacture of iron and steel, is gregates
designated as a product. The included information covers the C595/C595M Specification for Blended Hydraulic Cements
mineral properties of blast furnace slag and steel slag when C702/C702M Practice for Reducing Samples of Aggregate
they are manufactured in conjunction with the production of to Testing Size
iron or steel, or both (Note 1). C989/C989M Specification for Slag Cement for Use in
Concrete and Mortars
NOTE 1—This guide is not intended to be used to determine the
C1252 Test Methods for Uncompacted Void Content of Fine
applicability of iron or steel slag, or both, for various applications.
Aggregate (as Influenced by Particle Shape, Surface
Terminology D8 designates steel slag as a product, while Terminology
C125 designates blast furnace slag as a product. Its sole intent is to
Texture, and Grading)
provide guidance as to the typical mineralogy when the iron or steel slag,
D8 Terminology Relating to Materials for Roads and Pave-
or both, is designated as a product.
ments
1.2 The values stated in SI units are to be regarded as
D75/D75M Practice for Sampling Aggregates
standard. No other units are utilized in this standard.
3. Terminology
1.3 The text of this standard references notes and footnotes
3.1 Definitions—For the definitions of terms used in this
that provide explanatory material. These notes and footnotes
standard, refer to Terminology D8.
(excluding those in tables and figures) should not be considered
as requirements of the specification.
3.2 Definitions of Terms Specific to This Standard:
1.4 This standard does not purport to address all of the 3.2.1 blast furnace slag, n—see Terminology C125.
3.2.1.1 Discussion—Slag, ferrous metal, blast furnace
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- (granulated, GBS or air-cooled, ABFS or ABF)—Blast furnace
slag is formed in a continuous process by the fusion of
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. limestone (or dolomite, or a combination thereof) and other
fluxes with the residues from the carbon source and the
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard- non-metallic components of the iron-bearing materials (for
example, iron ore, iron sinter). Blast furnace slag is generated
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- at temperatures above 1500 °C. Dependent on the manner of
cooling of the liquid slag, it can be distinguished between
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee. crystalline, air-cooled blast furnace slag and glassy, granulated
blast furnace slag. Various cooling processes are defined in
Terminology C125.
This guide is under the jurisdiction of ASTM Committee D04 on Road and
Paving Materials and is the direct responsibility of Subcommittee D04.99 on
Sustainable Asphalt Pavement Materials and Construction. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2023. Published December 2023. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2020. Last previous edition approved in 2020 as D8021 – 20. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D8021-23. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8021 − 23
3.2.2 slag, steelmaking, n—steelmaking slags (SMS) are recognition and characterization, powdered XRD-Rietveld
generated as products during the refining/modification of steel analysis, and SEM-PARC results, using this guide.
in the production process.
5. Classification
3.2.2.1 Discussion—Steelmaking slag is formed (for
5.1 Slag, ferrous metal, blast furnace (granulated, GBS or
example, from the conversion of hot metal to steel) from the
melting of scrap in an electric arc furnace or from the air-cooled, ABFS).
subsequent treatments of various refinements/modifications of
5.2 Slag, steelmaking, and converter—BOF.
the crude steel, or both. The composition of the slags varies
5.3 Slag, steelmaking, and electric arc furnace—EAF C
depending on the process step in which they are produced. The
(carbon steel production).
molten slag which has tapping temperatures of around 1600 °C
5.4 Slag, steelmaking, electric arc furnace—EAF S
is discharged into pots or pits where it cools and solidifies to
provide an artificial aggregate having a crystalline structure. (stainless/high-alloy steel production).
They are sometimes referred to as ladle modification or caster
5.5 Slag, steelmaking—SMS.
slags.
6. Properties
3.2.3 steel slag, BOF/converter, n—a product of the conver-
sion of liquid iron (hot metal) into steel during a batch process 6.1 Mineral Constituents:
in a basic oxygen furnace. 6.1.1 Granulated blast furnace slag (GBS) typically contains
up to 100 w ⁄w% of glassy (vitreous) material (Specification
3.2.3.1 Discussion—BOF/converter slag is generated by the
C989/C989M). In some cases where a minor mineral compo-
addition of fluxes, such as limestone, dolomite, or both, during
nent is detected, it is usually in the form of melilite (calcium-
the blowing of oxygen into the melt. Due to the oxidizing
magnesium-silicate). Since the mineral component is usually
conditions, some elements (like Fe and Mn) are partly oxidized
minor, no characteristic mineral constituents can be given.
and contribute to the formation of the slag. Furthermore, some
6.1.2 All other iron and steel slags exist predominantly in a
components are either oxidized to gas (like carbon) or are
crystalline form. Many are considered air cooled, although the
chemically bound in the slag (like silicon or phosphorus). The
process does allow for a water addition during cooling. The
liquid slag which has tapping temperatures of around 1600 °C
typical tables for ABFS, BOF, and EAF C include major
is air cooled under controlled conditions in pits forming
primary mineral constituents which are characteristic for the
crystalline slag.
fresh slag. The table for EAF S contains typical major mineral
3.2.4 steel slag, EAF C, n—electric arc furnace slag gener-
constituents (primary and secondary), and for SMS slags the
ated during carbon steel production is a product of melting
most common mineral constituents are listed. Other mineral
steel scrap in an electric arc furnace. 3
phases can occur, because the slags are UVCB substances.
3.2.4.1 Discussion—Steel slag, EAF C (carbon steel pro-
The XRD diagrams of all slags can show secondary mineral
duction) is generated by the addition of fluxes, such as
phases, for example hydroxides and carbonates, which are a
limestone, dolomite, or both. Furthermore, some elements of
result of weathering and aging of the slags. This is the case
the melt are oxidized and contribute to the formation of the
especially for EAF S slags and a large quantity of SMS slags,
slag. The liquid slag which has tapping temperatures of around
which are mostly soaked directly after the production.
1600 °C is typically air cooled (possibly applying small
6.1.3 Sometimes impurities, for example sand (quartz), can
amounts of water) under controlled conditions in pots or pits
occur due to sampling, processing, or loading. In that case the
forming crystalline slag.
quartz is not a fine-grained respirable crystalline silica, but
granules, and therefore is considered to have no adverse health
3.2.5 steel slag, EAF S, n—electric arc furnace slag gener-
effects. The slag itself generally does not include crystalline
ated during stainless steel or high-alloy steel production.
quartz.
3.2.5.1 Discussion—Steel slag, EAF S (stainless/high-alloy
6.1.4 Slag, ferrous metal, blast furnace (granulated)—GBS,
steel production) is generated by the addition of fluxes and
CAS No. 65996-69-2. Mineral constituents: glass (amor-
reducing agents, for example lime or dolomite (or a combina-
phous).
tion thereof), silicon compounds, or aluminum. The liquid slag
6.1.5 Slag, ferrous metal, blast furnace (air-cooled)—ABS,
which has tapping temperatures of around 1600 °C is con-
CAS No. 65996-69-2 (Table 1, Note 2).
trolled and treated, if necessary, to improve the properties of
the slag. Then, the slag is cooled under controlled conditions in
NOTE 2—Air-cooled blast furnace slag from some steel plants may also
pots or pits forming crystalline slag. contain a certain amount of glass.
6.1.6 Slag, steelmaking, converter—BOF, CAS No. 91722-
4. Significance and Use
09-7 (Table 2).
6.1.7 Slag, steelmaking, electric furnace (carbon steel
4.1 This guide provides guidance as to the appropriate/
production)—EAF C, CAS No. 91722-10-0 (Table 3).
typical mineralogy observed when iron and steel slag is
produced during a variety of processes in the manufacture of
iron and steel.
UVCB: unknown or variable composition, complex reaction products, and
biological materials.
4.2 Slag can be considered a product based on the mineral-
XRD: X-ray powder diffraction.
ogy of samples that are tested using X-ray diffraction, phase CAS: Chemical Abstracts Service.
D8021 − 23
TABLE 1 Slag, Ferrous Metal, Blast Furnace (Air-Cooled) TABLE 5 Slag, Steelmaking—SMS
Major Primary Mineral Constituents Molecular and Structural Formula Major Primary Mineral Constituents Molecular and Structural Formula
Melilite (solid solution between Ca MgSi O – Ca Al SiO Gamma-dicalcium-silicate gamma-Ca SiO
2 2 7 2 2 7 2 4
akermanite and gehlenite), calcium- Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
aluminum-magnesium-silicate Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32
Merwinite, calcium-magnesium-silicate Ca MgSi O Mayenite, calcium-aluminum-oxide Ca Al O
3 2 8
12 14 33
Pseudowollastonite, calcium-silicate CaSiO
Cuspidine, calcium-fluoride-silicate Ca F Si O
3 4 2 2 7
2+ 3+
Monticellite CaMgSiO Spinel Me Me O
4 2 4
Amorphous . . . Free lime, calcium-oxide CaO
Periclase, magnesium-oxide MgO
Gehlenite, calcium-aluminum-silicate Ca Al SiO
2 2 7
Merwinite, calcium-magnesium-silicate Ca MgSi O
3 2 8
TABLE 2 Slag, Steelmaking, Converter—BOF
Srebrodolskite, calcium-iron-oxide Ca Fe O
2 2 5
Brownmillerite, calcium-aluminum-iron Ca AlFeO
Major Primary Mineral Constituents Molecular and Structural Formula 2 5
oxide
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
Srebrodolskite, calcium-iron-oxide Ca Fe O
2 2 5
with MgO and MnO
Hatrurite, tricalcium-silicate Ca SiO
3 5
2+ 3+
Hatrurite, tricalcium-silicate Ca SiO
3 5
Spinel Me Me O
2 4
Portlandite, calcium hydroxide Ca(OH)
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O 2
1-x-y x y z
Calcite, calcium carbonate CaCO
with MgO and MnO
Brucite Mg(OH)
Free lime, calcium oxide CaO 2
Amorphous . . .
Amorphous . . .
TABLE 3 Slag, Steelmaking, Electric Furnace (Carbon Steel
7.1.2 Frequently found mineral components that are usually
Production)—EAF C
identified in iron and steel slags are given in Section 6. When
Major Primary Mineral Constituents Molecular and Structural Formula
samples are analyzed by the techniques discussed in 8.2.1, the
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Srebrodolskite, calcium-iron-oxide Ca Fe O major mineral constituents, items constituting greater than
2 2 5
Brownmillerite, calcium-aluminum-iron Ca AlFeO
2 5
10 % of the sample, should correspond with the appropriate
oxide
2+ 3+ table in 6.1 (Note 3).
Spinel Me Me O
2 4
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
NOTE 3—The amorphous portion of a slag XRD can exceed 10 % when
with MgO and MnO
air cooled.
Gehlenite, calcium-aluminum-silicate Ca Al SiO
2 2 7
Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32
7.1.3 Environmental—The material should meet all appli-
Amorphous . . .
cable environmental regulations of the local governmental
agencies in effect at the time of use.
TABLE 4 Slag, Steelmaking, Electric Furnace (Stainless/High-
8. Sampling and Testing
Alloy Steel Production)—EAF S
8.1 Sampling:
Major Primary Mineral Constituents Molecular and Structural Formula
Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32 8.1.1 Sample the material in accordance with Practice
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
D75/D75M. The slag sample can be obtained immediately
Gamma-dicalcium-silicate gamma-Ca SiO
2 4
after the material is removed from the cooling area or after/
Merwinite, calcium-magnesium-silicate Ca MgSi O
3 2 8
Cuspidine, calcium-fluoride-silicate Ca F Si O
4 2 2 7
during processing.
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
8.1.2 Samples should be reduced to the appropriate size for
with MgO and MnO
Periclase, magnesium oxide MgO testing in accordance with Practice C702/C702M.
2+ 3+
Spinel Me Me O
2 4
8.2 Testing:
Mayenite, calcium-aluminum-oxide Ca Al O
12 14 33
Portlandite, calcium hydroxide Ca(OH)
8.2.1 The combination of XRD (X-ray diffraction) (bulk
Calcite, calcium carbonate CaCO
analysis) and PARC (phase recognition and characterization)
Amorphous . . .
microanalysis can provide an accurate tool for mineralogical
characterization of steel slag. (See Note 4.)
8.2.1.1 Powdered XRD-Rietveld analysis is used for crys-
talline phase identification and corresponding phase amounts.
6.1.8 Slag, steelmaking, electric furnace (stainless/high-
8.2.1.2 SEM-PARC results in amounts and chemical com-
alloy steel production)—EAF S, CAS No. 91722-10-0 (Table
position of individual crystalline and amorphous phases.
4).
6.1.9 Slag, steelmaking—SMS, CAS No. 65996-71-6
NOTE
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