ASTM C331/C331M-23

Standard Specification for Lightweight Aggregates for Concrete Masonry Units

ABSTRACT
This specification covers lightweight aggregates intended for use in concrete masonry units when a prime consideration is to reduce the density of the units. Three general types of lightweight aggregates are covered by this specification: aggregates prepared by expanding, palletizing, or sintering products such as blast-furnace slag, clay, diatomite, fly ash, shale, or slate; aggregates prepared by processing natural materials such as pumice, scoria, or tuff; and aggregates consisting of end products of coal or coke combustion. The aggregates shall be composed predominately of lightweight-cellular and granular inorganic material. The aggregates shall not contain excessive amounts of deleterious substances, as determined by organic impurities, staining, and loss on ignition tests. Lightweight aggregate under test shall meet requirements for clay lumps and friable particles, uniformity of grading, loose bulk density, uniformity of loose bulk density, popouts, resistance to freezing and thawing, and drying shrinkage.
SCOPE
1.1 This specification covers lightweight aggregates intended for use in concrete masonry units when a prime consideration is to reduce the density of the units.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. Some values have only SI units because the inch-pound equivalents are not used in practice.
Note 1: Sieve size is identified by its standard designation in Specification E11. The alternative designation given in parentheses is for information only and does not represent a different standard sieve size.  
1.3 The text of this specification references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard.  
1.4 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.

General Information

• Status: Published
• Publication Date: 31-May-2023
• ICS: 91.100.30 - Concrete and concrete products
• Technical Committee: C09 - Concrete and Concrete Aggregates
• Drafting Committee: C09.21 - Lightweight Aggregates and Concrete

Relations

• Refers: ASTM C151/C151M-23 - Standard Test Method for Autoclave Expansion of Hydraulic Cement
• Effective Date: 01-Dec-2023
• Refers: ASTM C29/C29M-23 - Standard Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
• Effective Date: 01-Oct-2023
• Refers: ASTM C142/C142M-17(2023) - Standard Test Method for Clay Lumps and Friable Particles in Aggregates
• Effective Date: 01-Oct-2023
• Refers: ASTM C114-23 - Standard Test Methods for Chemical Analysis of Hydraulic Cement
• Effective Date: 01-Oct-2023
• Refers: ASTM C125-19a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 15-Dec-2019
• Refers: ASTM D75/D75M-19 - Standard Practice for Sampling Aggregates
• Effective Date: 01-Nov-2019
• Refers: ASTM C125-19 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2019
• Refers: ASTM C125-18b - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Oct-2018
• Refers: ASTM C1262/C1262M-18 - Standard Test Method for Evaluating the Freeze-Thaw Durability of Dry-Cast Segmental Retaining Wall Units and Related Concrete Units
• Effective Date: 15-Jul-2018
• Refers: ASTM C125-18a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jul-2018
• Refers: ASTM C151/C151M-18 - Standard Test Method for Autoclave Expansion of Hydraulic Cement
• Effective Date: 01-Apr-2018
• Refers: ASTM C125-18 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2018
• Refers: ASTM C157/C157M-17 - Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete
• Effective Date: 15-Aug-2017
• Refers: ASTM C142/C142M-17 - Standard Test Method for Clay Lumps and Friable Particles in Aggregates
• Effective Date: 15-Mar-2017
• Refers: ASTM C29/C29M-17 - Standard Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
• Effective Date: 01-Jan-2017

Overview

ASTM C331/C331M-23: Standard Specification for Lightweight Aggregates for Concrete Masonry Units defines the requirements for lightweight aggregates specifically used in producing concrete masonry units (CMUs) where reduced unit density is a primary consideration. Issued by ASTM International, this standard supports safer, more energy-efficient masonry structures by enabling the production of lighter, easily handled CMUs without compromising essential physical characteristics. ASTM C331/C331M addresses the composition, properties, and quality assurance of these lightweight aggregates, contributing to sustainable construction and innovative building design.

Key Topics

• Aggregate Types:

  • Expanded, pelletized, or sintered materials such as blast-furnace slag, clay, diatomite, fly ash, shale, or slate
  • Processed natural materials, including pumice, scoria, or tuff
  • End products of coal or coke combustion

• Material Requirements:

  • Aggregates must be predominantly lightweight-cellular and granular inorganic materials
  • Strict limits on deleterious substances such as organic impurities and iron-related stains

• Physical Properties:

  • Bulk density must not exceed specified maximums for different aggregate fractions
  • Uniformity in grading and bulk density across shipments is required
  • Performance tests for clay lumps, friable particles, popouts, freeze-thaw resistance, and drying shrinkage

• Testing and Sampling:

  • Sampling conducted according to ASTM D75/D75M
  • Additional test methods referenced for bulk density, impurities, grading, and durability

• Quality Assurance:

  • Certification and reporting are mandated as part of purchase agreements
  • Deficient material identified through testing must be rejected and reported to the supplier

Applications

ASTM C331/C331M-23 is crucial for:

• Concrete Masonry Unit (CMU) Manufacturing:
  By reducing unit weight through the use of compliant lightweight aggregates, manufacturers can produce blocks that are easier to transport and install, with better fire resistance and thermal insulation properties.

• Energy-Efficient and Seismic-Resistant Construction:
  Lightweight CMUs contribute to lower building mass, resulting in enhanced energy efficiency and improved structural performance in seismic regions.

• Sustainable Building Projects:
  Utilizing industrial by-products like fly ash and slag as lightweight aggregates supports sustainable construction practices and resource conservation.

• Custom Blends for Design Flexibility:
  The standard supports aggregates sourced and blended for specific project requirements, adjusting physical properties for optimal compaction, strength, and surface finish.

Related Standards

The following standards are referenced within ASTM C331/C331M-23 and are integral to its implementation:

• ASTM C29/C29M: Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
• ASTM C40/C40M: Test Method for Organic Impurities in Fine Aggregates for Concrete
• ASTM C114: Test Methods for Chemical Analysis of Hydraulic Cement
• ASTM C125: Terminology relating to concrete and aggregates
• ASTM C136/C136M: Test Method for Sieve Analysis of Fine and Coarse Aggregates
• ASTM C142/C142M: Test Method for Clay Lumps and Friable Particles in Aggregates
• ASTM C151/C151M: Test Method for Autoclave Expansion of Hydraulic Cement
• ASTM C157/C157M: Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete (drying shrinkage)
• ASTM C641: Test Method for Iron Staining in Lightweight Aggregates
• ASTM C702/C702M: Reducing Aggregate Samples to Testing Size
• ASTM C1262/C1262M: Test Method for Freeze-Thaw Durability in Concrete Units
• ASTM D75/D75M: Practice for Sampling Aggregates
• ASTM E11: Specification for Woven Wire Test Sieve Cloth and Sieves

Conclusion

Adhering to ASTM C331/C331M-23 ensures the reliable performance of lightweight aggregates in concrete masonry units, supporting innovation and efficiency in modern building and infrastructure projects. Proper implementation promotes higher quality CMUs, optimized construction processes, and compliance with global best practices in materials specification.

Standards Content (Sample)

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: C331/C331M − 23
Standard Specification for
Lightweight Aggregates for Concrete Masonry Units
This standard is issued under the fixed designation C331/C331M; 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* C125 Terminology Relating to Concrete and Concrete Ag-
gregates
1.1 This specification covers lightweight aggregates in-
C136/C136M Test Method for Sieve Analysis of Fine and
tended for use in concrete masonry units when a prime
Coarse Aggregates
consideration is to reduce the density of the units.
C142/C142M Test Method for Clay Lumps and Friable
1.2 The values stated in either SI units or inch-pound units
Particles in Aggregates
are to be regarded separately as standard. The values stated in
C151/C151M Test Method for Autoclave Expansion of Hy-
each system may not be exact equivalents; therefore, each
draulic Cement
system shall be used independently of the other. Combining
C157/C157M Test Method for Length Change of Hardened
values from the two systems may result in non-conformance
Hydraulic-Cement Mortar and Concrete
with the standard. Some values have only SI units because the
C641 Test Method for Iron Staining Materials in Light-
inch-pound equivalents are not used in practice.
weight Concrete Aggregates
NOTE 1—Sieve size is identified by its standard designation in Speci-
C702/C702M Practice for Reducing Samples of Aggregate
fication E11. The alternative designation given in parentheses is for
to Testing Size
information only and does not represent a different standard sieve size.
C1262/C1262M Test Method for Evaluating the Freeze-
1.3 The text of this specification references notes and
Thaw Durability of Dry-Cast Segmental Retaining Wall
footnotes which provide explanatory material. These notes and
Units and Related Concrete Units
footnotes (excluding those in tables and figures) shall not be
D75/D75M Practice for Sampling Aggregates
considered as requirements of the standard.
E11 Specification for Woven Wire Test Sieve Cloth and Test
1.4 This international standard was developed in accor-
Sieves
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
3. Terminology
Development of International Standards, Guides and Recom-
3.1 Definitions:
mendations issued by the World Trade Organization Technical
3.1.1 For definitions of terms used in this specification, refer
Barriers to Trade (TBT) Committee.
to Terminology C125.
2. Referenced Documents
4. Aggregate Types
2.1 ASTM Standards:
4.1 Three general types of lightweight aggregates are cov-
C29/C29M Test Method for Bulk Density (“Unit Weight”)
ered by this specification, as follows:
and Voids in Aggregate
4.1.1 Aggregates prepared by expanding, pelletizing, or
C40/C40M Test Method for Organic Impurities in Fine
sintering products such as blast-furnace slag, clay, diatomite,
Aggregates for Concrete
fly ash, shale, or slate, and
C114 Test Methods for Chemical Analysis of Hydraulic
4.1.2 Aggregates prepared by processing natural materials,
Cement
such as pumice, scoria, or tuff, and
4.1.3 Aggregates consisting of end products of coal or coke
combustion.
This specification is under the jurisdiction of ASTM Committee C09 on
Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee 4.2 The aggregates shall be composed predominately of
C09.21 on Lightweight Aggregates and Concrete.
lightweight-cellular and granular inorganic material.
Current edition approved June 1, 2023. Published July 2023. Originally approved
in 1953. Last previous edition approved in 2017 as C331/C331M – 17. DOI:
5. Chemical Composition
10.1520/C0331_C0331M-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.1 Lightweight aggregates shall not contain excessive
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
amounts of deleterious substances, as determined by the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. following limits:
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C331/C331M − 23
5.1.1 Organic Impurities (Test Method C40/C40M)— 6.2.1 Popouts—Concrete specimens prepared and tested in
Lightweight aggregates subjected to the test for organic impu- accordance with 9.1 shall show no surface popouts.
rities that produce a color darker than the standard shall be 6.2.2 Resistance to Freezing and Thawing—When required,
rejected, unless it is demonstrated that the discoloration is due the aggregate supplier shall demonstrate by test or proven field
to small quantities of materials not harmful to the concrete. performance that the lightweight aggregate when used in
5.1.2 Staining (Test Method C641)—An aggregate produc- manufactured concrete masonry units and related concrete
ing a stain index of 60 or higher shall be rejected when the units has the necessary resistance to freezing and thawing to
deposited stain is found upon chemical analysis to contain an perform satisfactorily in its intended use.
iron content, expressed as Fe O equal to or greater than 1.5
2 3
NOTE 3—Methods are available to evaluate the performance of manu-
mg/200 g of sample.
factured concrete masonry products made with lightweight aggregates.
5.1.3 Loss on Ignition (Test Methods C114)—Loss on igni-
For example, Test Method C1262/C1262M includes procedures for
evaluating manufactured concrete masonry units and related concrete
tion of aggregates, consisting of end products of coal or coke
units, but does not include criteria for determining compliance. Care
combustion, shall not exceed 12 %. Loss on ignition of other
should be used in evaluating the results of Test Method C1262/C1262M or
aggregates shall not exceed 5 %.
any other method since the results are affected by other characteristics of
the concrete mixture in addition to the characteristics of the lightweight
NOTE 2—Some aggregates may contain carbonates or water of hydra-
aggregate, including, but not limited to the following: cement content,
tion that contribute to loss on ignition but may not affect the quality of the
cement type, admixtures, and water content.
product. Therefore, when evaluating an aggregate, consideration should be
given to the material characteristics that cause the ignition loss.
6.2.3 Drying Shrinkage—Drying shrinkage of concrete
specimens prepared and tested in accordance with 9.6 shall not
6. Physical Properties
exceed 0.10 %.
6.1 Lightweight aggregate under test shall meet the follow-
ing requirements:
7. Sampling
6.1.1 Clay Lumps and Friable Particles—The amount of
7.1 Sample lightweight aggregates in accordance with Prac-
clay lumps and friable particles shall not exceed 2 % by dry
tice D75/D75M.
mass.
7.2 Reduce sample to test sizes in accordance with Practice
6.1.2 Grading—Aggregate grading shall be by mutual
C702/C702M.
agreement between interested parties. See Appendix X1 for
aggregate grading guidance.
8. Number of Tests
6.1.3 Uniformity of Grading—To ensure reasonable unifor-
mity in the gradation of successive shipments of lightweight
8.1 Tests on Aggregate—One representative sample is re-
aggregate, fineness modulus shall be determined on samples
quired for each test for organic impurities, staining, clay lumps,
taken from shipments at intervals stipulated by the purchaser. If
loss on ignition, grading, and bulk density.
the fineness modulus of the aggregate in any shipment differs
8.2 Tests on Concrete Masonry Units—Three specimens are
by more than 7 % from that of the sample submitted for
required for the test for popout materials.
acceptance tests, the aggregate in the shipment shall be
rejected, unless the supplier demonstrated that it will produce
9. Test Methods
concrete of the required characteristics.
6.1.4 Loose Bulk Density (Test Method C29/C29M)—The 9.1 Test for Popout Materials—Obtain test specimens by
loose bul
...

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: C331/C331M − 17 C331/C331M − 23
Standard Specification for
Lightweight Aggregates for Concrete Masonry Units
This standard is issued under the fixed designation C331/C331M; 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 specification covers lightweight aggregates intended for use in concrete masonry units when a prime consideration is to
reduce the density of the units.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each
system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the
two systems may result in non-conformance with the standard. Some values have only SI units because the inch-pound equivalents
are not used in practice.
NOTE 1—Sieve size is identified by its standard designation in Specification E11. The alternative designation given in parentheses is for information only
and does not represent a different standard sieve size.
1.3 The text of this specification references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of the standard.
1.4 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:
C29/C29M Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
C40C40/C40M Test Method for Organic Impurities in Fine Aggregates for Concrete
C114 Test Methods for Chemical Analysis of Hydraulic Cement
C125 Terminology Relating to Concrete and Concrete Aggregates
C136C136/C136M Test Method for Sieve Analysis of Fine and Coarse Aggregates
C142C142/C142M Test Method for Clay Lumps and Friable Particles in Aggregates
C151C151/C151M Test Method for Autoclave Expansion of Hydraulic Cement
C157/C157M Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete
C641 Test Method for Iron Staining Materials in Lightweight Concrete Aggregates
C702C702/C702M Practice for Reducing Samples of Aggregate to Testing Size
This specification is under the jurisdiction of ASTM Committee C09 on Concrete and Concrete Aggregates and is the direct responsibility of Subcommittee C09.21 on
Lightweight Aggregates and Concrete.
Current edition approved June 15, 2017June 1, 2023. Published July 2017July 2023. Originally approved in 1953. Last previous edition approved in 20142017 as
C331/C331M – 14. DOI: 10.1520/C0331_C0331M-17.17. DOI: 10.1520/C0331_C0331M-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C331/C331M − 23
C1262C1262/C1262M Test Method for Evaluating the Freeze-Thaw Durability of Dry-Cast Segmental Retaining Wall Units and
Related Concrete Units
D75D75/D75M Practice for Sampling Aggregates
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this specification, refer to Terminology C125.
4. Aggregate Types
4.1 Three general types of lightweight aggregates are covered by this specification, as follows:
4.1.1 Aggregates prepared by expanding, pelletizing, or sintering products such as blast-furnace slag, clay, diatomite, fly ash,
shale, or slate, and
4.1.2 Aggregates prepared by processing natural materials, such as pumice, scoria, or tuff, and
4.1.3 Aggregates consisting of end products of coal or coke combustion.
4.2 The aggregates shall be composed predominately of lightweight-cellular and granular inorganic material.
5. Chemical Composition
5.1 Lightweight aggregates shall not contain excessive amounts of deleterious substances, as determined by the following limits:
5.1.1 Organic Impurities (Test Method C40C40/C40M)—Lightweight aggregates subjected to the test for organic impurities that
produce a color darker than the standard shall be rejected, unless it is demonstrated that the discoloration is due to small quantities
of materials not harmful to the concrete.
5.1.2 Staining (Test Method C641)—An aggregate producing a stain index of 60 or higher shall be rejected when the deposited
stain is found upon chemical analysis to contain an iron content, expressed as Fe O equal to or greater than 1.5 mg/200 g of
2 3
sample.
5.1.3 Loss on Ignition (Test Methods C114)—Loss on ignition of aggregates, consisting of end products of coal or coke
combustion, shall not exceed 12 %. Loss on ignition of other aggregates shall not exceed 5 %.
NOTE 2—Some aggregates may contain carbonates or water of hydration that contribute to loss on ignition but may not affect the quality of the product.
Therefore, when evaluating an aggregate, consideration should be given to the material characteristics that cause the ignition loss.
6. Physical Properties
6.1 Lightweight aggregate under test shall meet the following requirements:
6.1.1 Clay Lumps and Friable Particles—The amount of clay lumps and friable particles shall not exceed 2 % by dry mass.
6.1.2 Grading—Aggregate grading shall be by mutual agreement between interested parties. See Appendix X1 for aggregate
grading guidance.
6.1.3 Uniformity of Grading—To ensure reasonable uniformity in the gradation of successive shipments of lightweight aggregate,
fineness modulus shall be determined on samples taken from shipments at intervals stipulated by the purchaser. If the fineness
modulus of the aggregate in any shipment differs by more than 7 % from that of the sample submitted for acceptance tests, the
aggregate in the shipment shall be rejected, unless the supplier demonstrated that it will produce concrete of the required
characteristics.
C331/C331M − 23
6.1.4 Loose Bulk Density (Test Method C29/C29M)—The loose bulk density of lightweight aggregates shall conform to the
requirements in Table 1 using a 14 L [ ⁄2 ft ] measure.
6.1.5 Uniformity of Loose Bulk Density—The dry loose bulk density of lightweight aggregate shipments sampled and tested shall
3 3
not differ by more than 650 kg/m [3 lb/ft ] or 7 %, whichever is greater, from that of the sample submitted for acceptance tests,
and shall not exceed the limits in Table 1.
6.2 Concrete specimens containing lightweight aggregate under test shall meet the following requirements:
6.2.1 Popouts—Concrete specimens prepared and tested in accordance with 9.1 shall show no surface popouts.
6.2.2 Resistance to Freezing and Thawing—When required, the aggregate supplier shall demonstrate by test or proven field
performance that the lightweight aggregate when used in manufactured concrete masonry units and related concrete units has the
necessary resistance to freezing and thawing to perform satisfactorily in its intended use.
NOTE 3—Methods are available to evaluate the performance of manufactured concrete masonry products made with lightweight aggregates. For example,
Test Method C1262C1262/C1262M includes procedures for evaluating manufactured concrete masonry units and related concrete units, but does not
include criteria for determining compliance. Care should be used in evaluating the results of Test Method C1262C1262/C1262M or any other method
since the results are affected by other characteristics of the concrete mixture in addition to the characteristics of the lightweight aggregate, including, but
not limited to the following: cement content, cement type, admixtures, and water content.
6.2.3 Drying Shrinkage—Drying shrinkage of concrete specimens prepared and tested in accordance with 9.6 shall not exceed
0.10 %.
7. Sampling
7.1
...