ASTM D8021-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D8021 − 20 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
1.1 This standard is intended to provide guidance as to the appropriate/typical mineralogy observed when iron and steel slag,
produced during the manufacture of iron and steel, is designated as a product. The included information covers the mineral
properties of blast furnace slag and steel slag when they are manufactured in conjunction with the production of iron or steel, or
both (Note 1).
NOTE 1—This guide is not intended to be used to determine the applicability of iron or steel slag, or both, for various applications. Terminology D8
designates steel slag as a product, while Terminology C125 designates blast furnace slag as a product. Its sole intent is to provide guidance as to the typical
mineralogy when the iron or steel slag, or both, is designated as a product.
1.2 The values stated in SI units are to be regarded as standard. No other units are utilized in this standard.
1.3 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes
(excluding those in tables and figures) should not be considered as requirements of the specification.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
C125 Terminology Relating to Concrete and Concrete Aggregates
C595/C595M Specification for Blended Hydraulic Cements
C702/C702M Practice for Reducing Samples of Aggregate to Testing Size
C989/C989M Specification for Slag Cement for Use in Concrete and Mortars
C1252 Test Methods for Uncompacted Void Content of Fine Aggregate (as Influenced by Particle Shape, Surface Texture, and
Grading)
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.
Current edition approved Nov. 1, 2020Nov. 1, 2023. Published November 2020December 2023. Originally approved in 2020. Last previous edition approved in 2020 as
D8021 – 20. DOI: 10.1520/D8021-20.10.1520/D8021-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8021 − 23
D8 Terminology Relating to Materials for Roads and Pavements
D75/D75M Practice for Sampling Aggregates
3. Terminology
3.1 Definitions—For the definitions of terms used in this standard, refer to Terminology D8.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 blast furnace slag, n—see Terminology C125.
3.2.1.1 Discussion—
Slag, ferrous metal, blast furnace (granulated, GBS or air-cooled, ABFS or ABF)—Blast furnace slag is formed in a continuous
process by the fusion of limestone (or dolomite, or a combination thereof) and other fluxes with the residues from the carbon source
and the non-metallic components of the iron-bearing materials (for example, iron ore, iron sinter). Blast furnace slag is generated
at temperatures above 1500 °C. Dependent on the manner of cooling of the liquid slag, it can be distinguished between crystalline,
air-cooled blast furnace slag and glassy, granulated blast furnace slag. Various cooling processes are defined in Terminology C125.
3.2.2 slag, steelmaking, n—steelmaking slags (SMS) are generated as products during the refining/modification of steel in the
production process.
3.2.2.1 Discussion—
Steelmaking slag is formed (for example, from the conversion of hot metal to steel) from the melting of scrap in an electric arc
furnace or from the subsequent treatments of various refinements/modifications of the crude steel, or both. The composition of the
slags varies depending on the process step in which they are produced. The molten slag which has tapping temperatures of around
1600 °C is discharged into pots or pits where it cools and solidifies to provide an artificial aggregate having a crystalline structure.
They are sometimes referred to as ladle modification or caster slags.
3.2.3 steel slag, BOF/converter, n—a product of the conversion of liquid iron (hot metal) into steel during a batch process in a
basic oxygen furnace.
3.2.3.1 Discussion—
BOF/converter slag is generated by the addition of fluxes, such as limestone, dolomite, or both, during the blowing of oxygen into
the melt. Due to the oxidizing conditions, some elements (like Fe and Mn) are partly oxidized and contribute to the formation of
the slag. Furthermore, some components are either oxidized to gas (like carbon) or are chemically bound in the slag (like silicon
or phosphorus). The liquid slag which has tapping temperatures of around 1600 °C is air cooled under controlled conditions in pits
forming crystalline slag.
3.2.4 steel slag, EAF C, n—electric arc furnace slag generated during carbon steel production is a product of melting steel scrap
in an electric arc furnace.
3.2.4.1 Discussion—
Steel slag, EAF C (carbon steel production) is generated by the addition of fluxes, such as limestone, dolomite, or both.
Furthermore, some elements of the melt are oxidized and contribute to the formation of the slag. The liquid slag which has tapping
temperatures of around 1600 °C is typically air cooled (possibly applying small amounts of water) under controlled conditions in
pots or pits forming crystalline slag.
3.2.5 steel slag, EAF S, n—electric arc furnace slag generated during stainless steel or high-alloy steel production.
3.2.5.1 Discussion—
Steel slag, EAF S (stainless/high-alloy steel production) is generated by the addition of fluxes and reducing agents, for example
lime or dolomite (or a combination thereof), silicon compounds, or aluminum. The liquid slag which has tapping temperatures of
around 1600 °C is controlled and treated, if necessary, to improve the properties of the slag. Then, the slag is cooled under
controlled conditions in pots or pits forming crystalline slag.
4. Significance and Use
4.1 This guide provides guidance as to the appropriate/typical mineralogy observed when iron and steel slag is produced during
a variety of processes in the manufacture of iron and steel.
4.2 Slag can be considered a product based on the mineralogy of samples that are tested using X-ray diffraction, phase recognition
and characterization, powdered XRD-Rietveld analysis, and SEM-PARC results, using this guide.
D8021 − 23
5. Classification
5.1 Slag, ferrous metal, blast furnace (granulated, GBS or air-cooled, ABFS).
5.2 Slag, steelmaking, and converter—BOF.
5.3 Slag, steelmaking, and electric arc furnace—EAF C (carbon steel production).
5.4 Slag, steelmaking, electric arc furnace—EAF S (stainless/high-alloy steel production).
5.5 Slag, steelmaking—SMS.
6. Properties
6.1 Mineral Constituents:
6.1.1 Granulated blast furnace slag (GBS) typically contains up to 100 w ⁄w% of glassy (vitreous) material (Specification
C989/C989M). In some cases where a minor mineral component is detected, it is usually in the form of melilite (calcium-
magnesium-silicate). Since the mineral component is usually minor, no characteristic mineral constituents can be given.
6.1.2 All other iron and steel slags exist predominantly in a crystalline form. Many are considered air cooled, although the process
does allow for a water addition during cooling. The typical tables for ABFS, BOF, and EAF C include major primary mineral
constituents which are characteristic for the fresh slag. The table for EAF S contains typical major mineral constituents (primary
and secondary), and for SMS slags the most common mineral constituents are listed. Other mineral phases can occur, because the
3 4
slags are UVCB substances. The XRD diagrams of all slags can show secondary mineral phases, for example hydroxides and
carbonates, which are a result of weathering and aging of the slags. This is the case especially for EAF S slags and a large quantity
of SMS slags, which are mostly soaked directly after the production.
6.1.3 Sometimes impurities, for example sand (quartz), can occur due to sampling, processing, or loading. In that case the quartz
is not a fine-grained respirable crystalline silica, but granules, and therefore is considered to have no adverse health effects. The
slag itself generally does not include crystalline quartz.
6.1.4 Slag, ferrous metal, blast furnace (granulated)—GBS, CAS No. 65996-69-2. Mineral constituents: glass (amorphous).
6.1.5 Slag, ferrous metal, blast furnace (air-cooled)—ABS, CAS No. 65996-69-2 (Table 1, Note 2).
NOTE 2—Air-cooled blast furnace slag from some steel plants may also contain a certain amount of glass.
6.1.6 Slag, steelmaking, converter—BOF, CAS No. 91722-09-7 (Table 2).
6.1.7 Slag, steelmaking, electric furnace (carbon steel production)—EAF C, CAS No. 91722-10-0 (Table 3).
6.1.8 Slag, steelmaking, electric furnace (stainless/high-alloy steel production)—EAF S, CAS No. 91722-10-0 (Table 4).
TABLE 1 Slag, Ferrous Metal, Blast Furnace (Air-Cooled)
Major Primary Mineral Constituents Molecular and Structural Formula
Melilite (solid solution between Ca MgSi O – Ca Al SiO
2 2 7 2 2 7
akermanite and gehlenite), calcium-
aluminum-magnesium-silicate
Merwinite, calcium-magnesium-silicate Ca MgSi O
3 2 8
Pseudowollastonite, calcium-silicate CaSiO
Monticellite CaMgSiO
Amorphous . . .
UVCB: unknown or variable composition, complex reaction products, and biological materials.
XRD: X-ray powder diffraction.
CAS: Chemical Abstracts Service.
D8021 − 23
TABLE 2 Slag, Steelmaking, Converter—BOF
Major Primary Mineral Constituents Molecular and Structural Formula
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Srebrodolskite, calcium-iron-oxide Ca Fe O
2 2 5
Hatrurite, tricalcium-silicate Ca SiO
3 5
2+ 3+
Spinel Me Me O
2 4
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
with MgO and MnO
Free lime, calcium oxide CaO
Amorphous . . .
TABLE 3 Slag, Steelmaking, Electric Furnace (Carbon Steel
Production)—EAF C
Major Primary Mineral Constituents Molecular and Structural Formula
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Srebrodolskite, calcium-iron-oxide Ca Fe O
2 2 5
Brownmillerite, calcium-aluminum-iron Ca AlFeO
2 5
oxide
2+ 3+
Spinel Me Me O
2 4
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
with MgO and MnO
Gehlenite, calcium-aluminum-silicate Ca Al SiO
2 2 7
Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32
Amorphous . . .
TABLE 4 Slag, Steelmaking, Electric Furnace (Stainless/High-
Alloy Steel Production)—EAF S
Major Primary Mineral Constituents Molecular and Structural Formula
Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Gamma-dicalcium-silicate gamma-Ca SiO
2 4
Merwinite, calcium-magnesium-silicate Ca MgSi O
3 2 8
Cuspidine, calcium-fluoride-silicate Ca F Si O
4 2 2 7
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
with MgO and MnO
Periclase, magnesium oxide MgO
2+ 3+
Spinel Me Me O
2 4
Mayenite, calcium-aluminum-oxide Ca Al O
12 14 33
Portlandite, calcium hydroxide Ca(OH)
Calcite, calcium carbonate CaCO
Amorphous . . .
6.1.9 Slag, steelmaking—SMS, CAS No. 65996-71-6 (Table 5).
TABLE 5 Slag, Steelmaking—SMS
Major Primary Mineral Constituents Molecular and Structural Formula
Gamma-dicalcium-silicate gamma-Ca SiO
2 4
Larnite, beta-dicalcium-silicate beta-Ca SiO
2 4
Bredigite, calcium-magnesium-silicate Ca Mg Si O
14 2 8 32
Mayenite, calcium-aluminum-oxide Ca Al O
12 14 33
Cuspidine, calcium-fluoride-silicate Ca F Si O
4 2 2 7
2+ 3+
Spinel Me Me O
2 4
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
Srebrodolskite, calcium-iron-oxide Ca Fe O
2 2 5
Brownmillerite, calcium-aluminum-iron Ca AlFeO
2 5
oxide
Wuestite, solid solution of iron(II)-oxide (Fe , Mg , Mn )O
1-x-y x y z
with MgO and MnO
Hatrurite, tricalcium-silicate Ca SiO
3 5
Portlandite, calcium hydroxide Ca(OH)
Calcite, calcium carbonate CaCO
Brucite Mg(OH)
Amorphous . . .
D8021 − 23
7. Criteria
7.1 The slag should meet the following criteria in order to be designated as a product:
7.1.1 Definition—The production of the molten material should be similar to the one of those outlined in Section 5 for the type
of slag being addressed.
7.1.2 Frequently found mineral components that are usually identified in iron and steel slags are given in Section 6. When samples
are analyzed by the techniques discussed in 8.2.1, the major mineral constituents, items constituting greater than 10 % of the
sample, should correspond with the appropriate table in 6.1 (Note 3).
NOTE 3—The amorphous portion of a slag XRD can exceed 10 % when air cooled.
7.1.3 Environmental—The material should meet all applicable environmental regulations of the local governmental agencies in
effect at the time of use.
8. Sampling and Testing
8.1 Sampling:
8.1.1 Sample the material in accordance with Practice D75/D75M. The slag sample can be obtained immediately after the material
is removed from the cooling area or after/during processing.
8.1.2 Samples should be reduced to the appropriate size for testing in accordance with Practice C702/C702M.
8.2 Testing:
6 7
8.2.1 The combination of XRD (X-ray diffraction) (bulk analysis) and PARC (phase recognition and characterization)
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 crystalline phase identification and corresponding phase amounts.
8.2.1.2 SEM-PARC results in amounts and chemical composition of individual crystalline and amorphous phases.
NOTE 4—The XRD, Rietveld, and PARC techniques are utilized for determining quantitative values of the mineral components for the characterization
of slag in the European Reach program. The data presented in this guide was determined using these techniques as well as ICP (inductively coupled
plasma) and XRF (X-ray fluorescence).
9. Keywords
9.1 ACBF slag; blast furnace; BOF slag; EAF slag; electric furnace; slag; slag composition; steel furnace
APPENDIX
(Nonmandatory Information)
X1. TERMINOLOGY (DESCRIPTIONS)
(for reference purposes only)
X1.1 International Glossary of Terms – World of Iron and Steel Network 2020
Methods and Practices in X-Ray Powder Diffraction, 3rd ed., International Centre for Diffraction Data, Newtown Square, PA, 1989.
Van Hoek, C., Small, J., and Van der Laan, S., “Large-Area Phase Mapping Using PhAse Recognition and Characterization (PARC) Software,” Microscopy Today, Vol
24, No. 5, 2016, pp. 12–21.
The Rietveld Method, Young, R. A., Ed., Oxford University Press, 1993.
D8021 − 23
X1.1.1 This glossary contains terms and phrases that are commonly used by those who are involved with the production, handling,
management, storage, value add applications, and use of iron and steel slags (ISS) across the globe.
X1.1.2 Stakeholders within the iron and steel slags value chain have used these terms for many years, with other modern terms,
for example, co-product, have been included over time which better define the essential role of slag production to the primary
products of iron and steel.
X1.1.3 The acronym ISS was first used in 2010 and subsequently globally adopted and encouraged through the World of Iron and
Steel Slag Network (WoISS).
X1.1.4 This glossary of terms is an attempt to aid in future standardization, and reflect these terms in common usage across the
industry. Additionally, some ASTM, allied products, environmental, and regulatory terms associated with ISS are included for
comparison purposes. The ASTM terms and definitions utilized are related to Terminologies C125 and D8.
X1.1.5 Contributions, suggestions, corrections, and/or improvements to this living document are welcome. Please submit these to
the Australasian (Iron & Steel) Slag Association (asa-inc.org.au), the National Slag Association (nationalslag.org), or EuroSlag
(euroslag.com).
X1.2 Terminology
X1.2.1 Definitions:
X1.2.1.1 aggregate—material complying with the specified grading requirements for fine and coarse aggregates. It may be
produced from rock, gravel, metallurgical slag, or artificial stone.
X1.2.1.2 aggregate—a granular material used as a construction material, meeting the requirements of road and paving
applications. D8
X1.2.1.2.1 Discussion—
Examples of aggregate include sand, gravel, shell, slag, and crushed stone. See coarse aggregate and fine aggregate for more
information.
X1.2.1.3 aggregate—granular material such as sand, gravel, crushed stone, or iron blast-furnace slag, used with a cementing
medium to form hydraulic-cement concrete or mortar. C125
X1.2.1.4 air-cooled blast furnace slag (ABS)—after separating from the heavier iron, the slag is typically tapped or poured onto
ground bays to air cool to form a crystalline aggregate.
X1.2.1.5 air cooling—process where the slag is allowed to cool down slowly by leaving it in contact with ambient temperature
air.
X1.2.1.6 AOD process—AOD stands for Argon Oxygen Decarburization, a refining process associated with the production of
stainless steel. Most stainless steel is initially produced in an electric arc furnace before being transferred to a separate ladle furnace
for refining to achieve the precise metallurgical content required, a process known as secondary metallurgy. In the AOD process,
a mixture of argon and oxygen is blown through the molten steel in the ladle furnace, and the oxygen achieves the main objective
D8021 − 23
of oxidizing unwanted carbon in the steel melt. But because the vital and expensive chromium contained in all stainless steels is
also prone to oxidation and subsequent loss with the process slag, the argon is introduced to inhibit this reaction.
X1.2.1.7 ash—the solid residue from combustion processes. Industrial combustion processes mostly aim to extract energy from
coal, oil, or even domestic waste. The primary aim is therefore not to obtain valuable materials, as it is in metallurgical processes,
where the focus is on obtaining a metal.
X1.2.1.8 basic oxygen furnace (BOF)—also known as LD converter or Basic Oxygen System (BOS), is a steel making furnace
in which hot metal from the blast furnace, with some amounts of steel scrap, is converted into steel. High-purity oxygen is blown
through the molten bath to lower the carbon content. Fluxes are used to reduce other unwanted elements. Those fluxes combine
with silicates and oxides to form liquid slag that floats on the surface of the hot metal. Also see Guide D8021 for further
information.
X1.2.1.9 basic oxygen furnace slag (BOF slag)—also known as LD converter slag or Basic Oxygen System Slag (BOS) are slags
from a steel making furnace which are defined as co-products. The slag is removed from the vessel after the exothermic refinement
of molten iron and recycled steel in the presence of fluxes and oxygen. The slag is typically dark gray in color and characteristically
harder than blast furnace slag (BFS) with a density approximately 20 to 25 % greater than natural quarried aggregates or BFS. Also
see Guide D8021 for further information.
X1.2.1.10 blast furnace (BF)—a furnace used in the integrated metallurgical process in which iron ore, sinter, or pellets are melted
down under a hot air flow (enriched with oxygen), using carbon in the form of coal and coke as a heating and reducing agent in
the chemical process. As a result, as well a liquid hot metal (“pig iron”) as a liquid slag are produced. Also see Guide D8021 for
further information.
X1.2.1.11 blast furnace lime (BFL)—product from blast furnace slag obtained by milling the slag. As essential ingredients it
contains calcium and magnesium silicates as well as oxides and is used as fertilizer.
X1.2.1.12 blast furnace slag (BFS)—a co-product of the iron-making process. Formed within a blast furnace with molten iron
from iron ore in the reducing presence of heated air, coke/coal, and additions like limestone. The resulting molten slag and iron,
once removed from the furnace, are subjected to further processing to form a crystalline aggregate (air-cooled blast furnace slag,
ABS) or a glassy granulate (granulated blast furnace slag, GBS). See Guide D8021 for additional information on the process.
X1.2.1.13 blast furnace slag—the nonmetallic product, consisting essentially of silicates and alumino-
...