ASTM C1761/C1761M-23

Standard Specification for Lightweight Aggregate for Internal Curing of Concrete

SCOPE
1.1 This specification covers lightweight aggregate intended to provide water for internal curing of concrete. It includes test methods for determining the absorption and desorption properties of lightweight aggregate.
Note 1: Internal curing provides an additional source of water to sustain hydration and substantially reduce the early-age autogenous shrinkage and self-desiccation that can be significant contributors to early-age cracking. Appendix X1 provides guidance on calculating the quantity of lightweight aggregate for internal curing.  
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. Some values have only SI units because the inch-pound equivalents are not used in practice.
Note 2: 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 that 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 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.

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 C1608-23 - Standard Test Method for Chemical Shrinkage of Hydraulic Cement Paste
• Effective Date: 01-Dec-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 C29/C29M-23 - Standard Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
• 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 C1698-19 - Standard Test Method for Autogenous Strain of Cement Paste and Mortar
• Effective Date: 01-Oct-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 C125-18a - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jul-2018
• Refers: ASTM C125-18 - Standard Terminology Relating to Concrete and Concrete Aggregates
• Effective Date: 01-Jan-2018
• Refers: ASTM C1608-17 - Standard Test Method for Chemical Shrinkage of Hydraulic Cement Paste
• Effective Date: 01-Aug-2017
• Refers: ASTM C330/C330M-17 - Standard Specification for Lightweight Aggregates for Structural Concrete
• Effective Date: 01-May-2017
• Refers: ASTM D2172/D2172M-17 - Standard Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures
• Effective Date: 01-Apr-2017
• Refers: ASTM D2172/D2172M-17e1 - Standard Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures
• Effective Date: 01-Apr-2017

Overview

ASTM C1761/C1761M-23 is the international standard specification for lightweight aggregate used for internal curing of concrete. Published by ASTM International, this standard defines the requirements, test methods, and application guidelines for lightweight aggregate materials that supply additional water within concrete mixes to promote optimal hydration and reduce early-age cracking.

Internal curing is a proven technique in concrete technology that mitigates autogenous shrinkage and self-desiccation, common causes of early-age cracking. The standard provides a framework for evaluating the absorption and desorption properties of lightweight aggregates to ensure sufficient water is available to support cement hydration during curing.

Key Topics

• Scope & Purpose: Specifies properties and requirements for lightweight aggregate intended for internal curing applications in concrete.
• Types of Lightweight Aggregates: Covers manufactured aggregates (e.g., expanded clay, shale, slate, pelletized products) and processed natural materials (e.g., pumice, scoria, tuff).
• Absorption and Desorption Testing: Includes methods for determining the 72-hour water absorption and the ability of pre-wetted aggregates to release water at relative humidity levels similar to curing environments.
• Chemical and Physical Requirements:
  • Limits on organic impurities, iron staining, and loss on ignition to ensure aggregate quality.
  • Restrictions on clay lumps, friable particles, and specific grading requirements for fine, coarse, and combined aggregates.
  • Maximum dry loose bulk density specifications for different aggregate classes.
• Measurement Units: Stipulates the use of SI and inch-pound units independently; values in each system are not directly interchangeable.
• Safety and Compliance: Outlines the user’s responsibility for safety, health, environmental practices, and compliance with relevant regulations.

Applications

The standard is directly applicable to:

• Concrete Production: Selection and qualification of lightweight aggregate for integration into concrete mixes, particularly where reduced cracking and sustained hydration are desired.
• Quality Assurance: Laboratory and field use of the outlined test methods for verifying aggregate absorption and desorption, ensuring adequate internal curing performance.
• Infrastructure Projects: Infrastructure, bridges, slabs, and mass concrete applications where internal curing enhances durability, reduces thermal gradients, and minimizes shrinkage-induced cracks.
• Preconstruction and Procurement: Guidance for specifying agencies, concrete producers, and contractors in ordering, certifying, and documenting compliance of aggregates used for internal curing.

Related Standards

Standards commonly referenced in conjunction with ASTM C1761/C1761M-23 include:

• ASTM C330/C330M: Specification for lightweight aggregates for structural concrete.
• ASTM C29/C29M: Test method for bulk density and voids in aggregates.
• ASTM C128: Test method for relative density and absorption of fine aggregate.
• ASTM C136/C136M: Sieve analysis of fine and coarse aggregates.
• ASTM C40/C40M & C87/C87M: Methods for assessing the effect of organic impurities on aggregate.
• ASTM C142/C142M: Test for clay lumps and friable particles in aggregates.
• ASTM E11: Standard for test sieve designations.
• ASTM D75/D75M: Practice for sampling aggregates.

Practical Value

ASTM C1761/C1761M-23 provides essential guidelines for ensuring that lightweight aggregates used in internal curing meet rigorous quality and performance criteria. This ensures:

• Enhanced crack resistance and long-term durability in concrete structures.
• Improved predictability and reliability in concrete curing and strength development.
• Standardized sampling, testing, and reporting procedures that benefit producers, contractors, and project owners alike.

Keywords: lightweight aggregate, internal curing, concrete hydration, ASTM C1761, absorption, desorption, concrete aggregate standards, shrinkage reduction.

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: C1761/C1761M − 23
Standard Specification for
Lightweight Aggregate for Internal Curing of Concrete
This standard is issued under the fixed designation C1761/C1761M; 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
2.1 ASTM Standards:
1.1 This specification covers lightweight aggregate intended
C29/C29M Test Method for Bulk Density (“Unit Weight”)
to provide water for internal curing of concrete. It includes test
and Voids in Aggregate
methods for determining the absorption and desorption prop-
C40/C40M Test Method for Organic Impurities in Fine
erties of lightweight aggregate.
Aggregates for Concrete
NOTE 1—Internal curing provides an additional source of water to
C87/C87M Test Method for Effect of Organic Impurities in
sustain hydration and substantially reduce the early-age autogenous
Fine Aggregate on Strength of Mortar
shrinkage and self-desiccation that can be significant contributors to
early-age cracking. Appendix X1 provides guidance on calculating the
C114 Test Methods for Chemical Analysis of Hydraulic
quantity of lightweight aggregate for internal curing.
Cement
C125 Terminology Relating to Concrete and Concrete Ag-
1.2 The values stated in either SI units or inch-pound units
gregates
are to be regarded separately as standard. The values stated in
C128 Test Method for Relative Density (Specific Gravity)
each system may not be exact equivalents; therefore, each
and Absorption of Fine Aggregate
system shall be used independently of the other. Combining
C136/C136M Test Method for Sieve Analysis of Fine and
values from the two systems may result in non-conformance.
Coarse Aggregates
Some values have only SI units because the inch-pound
C142/C142M Test Method for Clay Lumps and Friable
equivalents are not used in practice.
Particles in Aggregates
NOTE 2—Sieve size is identified by its standard designation in Speci-
C330/C330M Specification for Lightweight Aggregates for
fication E11. The alternative designation given in parentheses is for
Structural Concrete
information only and does not represent a different standard sieve size.
C641 Test Method for Iron Staining Materials in Light-
1.3 The text of this specification references notes and
weight Concrete Aggregates
footnotes that provide explanatory material. These notes and
C702/C702M Practice for Reducing Samples of Aggregate
footnotes (excluding those in tables and figures) shall not be
to Testing Size
considered as requirements of the standard.
C1498 Test Method for Hygroscopic Sorption Isotherms of
Building Materials
1.4 This standard does not purport to address all of the
C1608 Test Method for Chemical Shrinkage of Hydraulic
safety concerns, if any, associated with its use. It is the
Cement Paste
responsibility of the user of this standard to establish appro-
C1698 Test Method for Autogenous Strain of Cement Paste
priate safety, health, and environmental practices and deter-
and Mortar
mine the applicability of regulatory limitations prior to use.
D75/D75M Practice for Sampling Aggregates
1.5 This international standard was developed in accor-
D2172/D2172M Test Methods for Quantitative Extraction of
dance with internationally recognized principles on standard-
Asphalt Binder from Asphalt Mixtures
ization established in the Decision on Principles for the
E11 Specification for Woven Wire Test Sieve Cloth and Test
Development of International Standards, Guides and Recom-
Sieves
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions:
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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2023. Published August 2023. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2012. Last previous edition approved in 2017 as C1761/C1761M – 17. Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/C1761_C1761M-23. 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
C1761/C1761M − 23
3.1.1 For definitions of terms used in this practice, refer to 3.2.10 self-desiccation, n—reduction in the internal relative
Terminology C125. humidity of a sealed cementitious mixture, due to chemical
3.2 Definitions of Terms Specific to This Standard: shrinkage, that may reduce the rate of hydration or stop
hydration.
3.2.1 absorption, A , n—of lightweight aggregate, the in-
crease in mass of a specimen of oven-dry lightweight aggregate
3.3 Symbols: A = the 72-h absorption, expressed as a
due to water penetrating into the permeable pores of the
percentage of the oven-dry mass.
particles after being submerged for 72 h, expressed as percent-
D = the desorption, expressed as a percentage of the A
age of oven-dry mass.
absorption.
3.2.2 autogenous shrinkage, n—reduction in volume due to
G = relative density (oven-dry) of lightweight aggregate.
OD
chemical shrinkage of a sealed cementitious mixture, not
G = relative density (oven-dry) of normal weight aggre-
ODN
subjected to external forces and under constant temperature,
gate.
measured from the time of final setting.
M = calculated mass of oven-dry lightweight aggregate
LWA
3.2.2.1 Discussion—The chemical shrinkage leads to emp-
needed for internal curing per unit volume of concrete,
3 3
tying of the internal pores (see self-desiccation) that causes the
kg/m [lb ⁄yd ].
formation of menisci in the partially water-filled pores. The
M = mass of normal weight aggregate in oven-dry con-
NWA
3 3
menisci in turn give rise to internal tensile stresses that cause
dition to be removed, kg/m [lb ⁄yd ].
bulk shrinkage. While autogenous shrinkage is due to the
M = mass of lightweight aggregate specimen in oven-dry
OD
chemical shrinkage, the magnitude of autogenous shrinkage is
condition, g.
less than the chemical shrinkage after setting occurs, because
M = mass of pycnometer containing lightweight aggregate
PS
the aggregate particles and the hydrated cement paste network
specimen and filled with water, g.
restrain the shrinkage. The restraint may in turn lead to
M = mass of pycnometer filled with water, g.
PW
cracking.
M = mass of lightweight aggregate specimen in wetted
SD
3.2.3 chemical shrinkage, n—the reduction in volume of
surface-dry condition, g.
cementitious paste that occurs during hydration because the
M = equilibrium mass of aggregate originally in wetted
hydration products occupy less volume than the volume
surface-dry condition and subsequently stored at 94 % relative
occupied originally by the water and unhydrated cementitious
humidity, g.
materials.
C = cementitious materials content of concrete mixture,
f
3 3
kg/m [lb ⁄yd ].
3.2.4 density (OD), n—of lightweight aggregate, the mass of
oven-dry lightweight aggregate particles per unit volume of CS = chemical shrinkage of cementitious material, expressed
aggregate particles, where the volume includes the permeable as kg water/kg of cement [lb/lb] (see Note 3).
and impermeable pores within the particles but does not S = degree of saturation of lightweight aggregate relative to
include the voids between the particles.
wetted surface-dry condition (0 to 1.0).
w/cm = water-cementitious materials ratio, kg/kg [lb/lb].
3.2.5 desorption (D), n—of lightweight aggregate, the de-
α = maximum potential degree of hydration of cementi-
crease in mass of lightweight aggregate originally containing max
tious materials expressed as a decimal fraction (0 to 1.0).
absorbed water due to water leaving the permeable pores as the
W = mass of water released by lightweight aggregate in
aggregate attains moisture equilibrium with the surrounding
LWA
going from the wetted surface-dry condition to the equilibrium
environment maintained at constant temperature and a relative
mass at a relative humidity of 94 %, expressed as a fraction of
humidity less than 100 %, and expressed as a percentage of the
the oven-dry mass.
72-h absorption.
3.2.6 internal curing, n—supplying water within a cemen-
NOTE 3—Chemical shrinkage is measured in units of volume of water
per unit mass of cement. In using the value of chemical shrinkage to
titious mixture using pre-wetted lightweight aggregate, or other
calculate the required amount of lightweight aggregate for internal curing,
materials that readily release water from within the particles,
the volume of water is converted to the mass of water. Hence chemical
thereby mitigating self-desiccation and sustaining hydration.
shrinkage is expressed as mass of water per unit mass of cement.
3.2.7 oven-dry (OD), adj—related to lightweight aggregate
particles, the condition in which the specimen of lightweight 4. Ordering Information
aggregate has been dried by heating in an oven at 110 °C 6 5
4.1 The direct purchaser of lightweight aggregate for inter-
°C [230 °F 6 10 °F] for sufficient time to reach a constant
nal curing shall include the following information in the
mass.
purchase order as applicable.
3.2.8 relative density, (OD), n—of lightweight aggregate,
4.1.1 Reference to this specification, as Specification
the ratio of the density (OD) of the lightweight aggregate to the
C1761/C1761M.
density of water at a stated temperature.
4.1.2 Whether the order is for fine aggregate, coarse
aggregate, or combined fine and coarse aggregate.
3.2.9 wetted surface-dry (WSD), adj—related to lightweight
4.1.3 Quantity in metric tons [tons] or cubic meters [cubic
aggregate particles, the condition in which the permeable
yards].
pores of lightweight aggregate particles are filled with water, to
the extent achieved by submerging an oven-dry specimen for 4.1.4 If the order is for coarse aggregate or combined fine
72 h, and the surfaces of the particles are dry. and coarse aggregate, provide the nominal size designation as
C1761/C1761M − 23
given in Table 1 or alternative grading as agreed between the 7. Physical Properties
TABLE 1 Grading Requirements
Percentages (Mass) Passing Sieves Having Square Openings
A
Nominal Size Designation
25.0 mm 19.0 mm 12.5 mm 9.5 mm 4.75 mm 2.36 mm 1.18 mm 300 μm 150 μm
75 μm
3 1 3
(No. 200)
(1 in.) ( ⁄4 in.) ( ⁄2 in.) ( ⁄8 in.) (No. 4) (No. 8) (No. 16) (No. 50) (No. 100)
Fine aggregate:
4.75 mm to 0 (No. 4 to 0) . . . . . . . . . 100 65–100 . . . 15–80 0–35 0–25 . . .
Coarse aggregate:
25.0 to 4.75 mm (1 in. to No. 4) 95–100 . . . 25–60 . . . 0–10 . . . . . . . . . . . . 0–10
19.0 to 4.75 mm ( ⁄4 in. to No.4) 100 90–100 . . . 10–50 0–15 . . . . . . . . . . . . 0–10
12.5 to 4.75 mm ( ⁄2 in. to No. 4) . . . 100 90–100 40–80 5–40 0–20 0–10 . . . . . . 0–10
9.5 to 2.36 mm ( ⁄8 in. to No. 8) . . . . . . 100 80–100 5–40 0–20 0–10 . . . . . . 0–10
Combined fine and coarse aggregate:
12.5 mm to 0 ( ⁄2 in. to 0) . . . 100 95–100 . . . 50–80 . . . . . . 5–20 2–15 0–10
9.5 mm to 0 ( ⁄8 in. to 0) . . . . . . 100 90–100 65–90 35–65 . . . 10–25 5–15 0–10
A
The surfaces of pyro-processed lightweight aggregate particles finer than the 75 μm (No. 200) sieve are not deleterious and may be moderately pozzolanic.
purchaser and aggregate supplier. 7.1 Clay Lumps and Friable Particles—Test Method C142/
4.1.5 Whether certification shall be furnished indicating that C142M. The total amount of clay lumps and friable particles
the material was sampled and tested in accordance with this shall not exceed 2 % by dry mass.
specification and found to meet the requirements.
7.2 Grading—Test Method C136/C136M as modified in
4.1.6 Whether a report of the results of aggregate tests shall
Specification C330/C330M. The grading shall conform to the
be furnished.
requirements shown in Table 1 or established by mutual
4.1.7 Whether the results of tests of concrete properties are
agreement between interested parties.
required.
NOTE 5—In general, a volume of lightweight aggregate (fine or a
4.1.8 Any exceptions or additions to this specification.
combination of coarse and fine) for internal curing will replace an equal
volume of normal weight aggregate in an existing conventional concrete
5. Materials and Manufacture
mixture. The grading of the lightweight aggregate can be chosen to closely
match the existing grading of the normal weight aggregates, or to fill in a
5.1 Two general types of lightweight aggregate are covered
gap in the existing normal weight aggregate grading, such as using a
by this specification, as follows:
mid-range size lightweight aggregate to enhance the gradation of a
5.1.1 Aggregates produced by expanding, pelletizing, or
gap-graded mixture (1).
sintering products such as blast-furnace slag, clay, diatomite,
7.2.1 Uniformity of Grading—For continuing shipments of
fly ash, shale, or slate, and
fine aggregate from a given source, the fineness modulus shall
5.1.2 Aggregate prepared by processing natural materials,
not vary more than 7 % from the base fineness modulus. The
such as pumice, scoria, and tuff.
base fineness modulus shall be that value that is typical of the
5.2 The aggregate shall be composed predominately of
source. The purchaser has the authority to approve a change in
lightweight-cellular and granular inorganic materials.
the base fineness modulus. For coarse aggregate and combined
fine and coarse aggregate, the uniformity of grading require-
6. Chemical Requirements
ments of Specification C330/C330M shall apply.
6.1 Organic Impurities—Test Method C40/C40M. Light-
weight aggregate shall not produce a color darker than the
standard color solution, unless it is demonstrated that when the
TABLE 2 Maximum Dry Loose Bulk Density
aggregate is tested for the effect of organic impurities on
Maximum Density
Size Designation
3 3
strength of mortar, the relative strength at 7 days, determined in
kg/m [lb ⁄ft ]
accordance with Test Method C87/C87M, is not less than Fine aggregate 1120 [70]
Coarse aggregate 880 [55]
95 %.
Combined fine and coarse 1040 [65]
aggregate
6.2 Staining—Test Method C641. Lightweight aggregate
shall produce a stain index of less than 60. Lightweight
aggregate producing a stain index of 60 or higher shall be
subject to rejection if the deposited stain is found upon
chemical analysis to contain an iron content, expressed as
7.3 Bulk Density—Test Method C29/C29M. The dry bulk
Fe O , equal to or greater than 1.5 mg/200 g of sample.
2 3 density using the shoveling method of compaction shall
6.2.1 Loss on Ignition—Test Method C114. The loss on
conform to the requirements of Table 2 using a 14 L [ ⁄2 ft ]
ignition of lightweight aggregates shall not exceed 5 %.
measure.
NOTE 4—Some aggregate 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 The boldface numbers in parentheses refer to the list of references at the end of
given to the material characteristics that cause the ignition loss. this standard.
C1761/C1761M − 23
7.4 Water Absorption—The lightweight aggregate shall 10.2.4 The relative density (oven-dry) is used to calculate
have a 72-h absorption not less than 5 % when tested in the mass of the normal weight aggregate that is to be replaced
accordance with Section 10. by an equal volume of lightweight aggregate.
10.3 Apparatus:
7.5 Desorption Properties—The lightweight aggregate shall
10.3.1 Balance—Having a capacity of at least 4 kg and
release at least 85 % of its absorbed water at 94 % relative
humidity when tested in accordance with Section 11. accurate to at least 0.1 g.
10.3.2 Wide-mouth jars—Glass jars with nominal capacities
of 1 L [1 qt] and 2 L [2 qt].
8. Sampling
NOTE 7—Ordinary canning jars are suitable for this purpose.
8.1 Sample lightweight aggregates in accordance with Prac-
tice D75/D75M.
10.3.3 Pycnometer top—For filling the 1 L [1 qt] or 2 L [2
qt] jars with water to a repeatable level.
8.2 Reduce sample to test sizes in accordance with Practice
10.3.4 Paper towels—Commercial grade, either folded type
C702/C702M.
or roll type.
9. Number of Tests and Retests
NOTE 8—Brown paper towels make it easier to determine whether
aggregate particles contain surface water during the drying procedure for
9.1 Tests on Aggregates—One representative sample is re-
bringing aggregate to the wetted surface-dry condition.
quired of sufficient size to prepare specimens for the following
10.3.5 Centrifuge extractor—An apparatus similar to that
tests: organic impurities, staining, loss on ignition, grading,
shown in Fig. 1, including a 241 mm [9.5 in.] diameter
clay lumps and friable particles, bulk density, absorption and
centrifuge bowl and an apparatus in which the bowl can be
relative density (OD), and desorption from WSD to 94 %
revolved at controlled variable 72 speeds up to 377 rad/s [3600
relative humidity.
revolutions per minute] (see Note 9). The speed shall be
9.2 Tests on Internally Cured Concrete—When specified by
controlled either manually or using a preset speed control. The
the purchaser, at least three specimens are required for each of
apparatus shall be provided with a container for catching the
the following tests of concrete: compressive strength,
surface water thrown from the aggregate particles and a drain
shrinkage, resistance to freezing and thawing, and presence of
for removing the water.
popout materials. At least eight specimens are required for
NOTE 9—A standard 1500 g (3.3 lb) capacity centrifuge extractor
splitting tensile strength tests. Tests shall be performed in
meeting the requirements of Test Methods D2172/D2172M meets these
accordance with Specification C330/C330M and test results
requirements. The specified 241 mm [9.5 in.] bowl diameter (outside
shall comply with Specification C330/C330M.
diameter of the rim) relates to the centrifuge speed to produce the desired
result of removing surface water without removing absorbed water.
TEST METHODS
10.3.5.1 Filter rings—Low-ash paper filter rings approxi-
mately 1.3 mm [0.05 in.] thick. The ash content of the paper
10. Absorption and Relative Density
shall not exceed 0.2 % (approximately 0.034 g per ring).
10.1 Scope:
10.3.6 Drying oven—Of sufficient size and capable of main-
10.1.1 This test method uses the pycnometer method to
taining a uniform temperature of 110 °C 6 5 °C [230 °F 6
determine the 72-h absorption and relative density (oven-dry)
10 °F].
of lightweight aggregate for internal curing.
10.3.7 Metal pans—For soaking aggregate under water and
for drying aggregate in drying oven.
10.2 Significance and Use:
10.3.8 Water storage container—Approximate capacity of
10.2.1 It is difficult to obtain complete saturation of the
20 L [5 gal] for maintaining a supply of water at the laboratory
permeable pores in some lightweight aggregate particles. In
temperature of 23.0 °C 6 2 °C [73.5 °F 6 3.5 °F].
this test method, a 72-h soaking period of essentially dry
aggregate is used to define the absorption. 10.4 Procedure:
10.4.1 Fill the wide-mouth jar with pycnometer top with
10.2.2 After the prescribed soaking period and the removal
water at a temperature of 23.0 °C 6 2 °C [73.5 °F 6 3.5 °F].
of surface moisture, the aggregate is in the wetted surface-dry
For tests of coarse aggregate or combined coarse and fine
condition, which is analogous to the saturated surface-dry
aggregate, use the 2-L [2-qt] jar. Use the 1-L [1-qt] jar for tests
condition applicable to normal weight aggregate. The former
of fine aggregate. Ensure that no air bubbles are present on the
term is used because the permeable pores in some lightweight
wall of the jar and the pycnometer top is filled to capacity.
aggregate particles are not filled completely by soaking for
Wipe the surface of the jar to remove any surface water and
72-h (2).
weigh the filled jar to the nearest 0.1 g. Record this mass as
10.2.3 The absorption is used to determine the mass of
M .
lightweight aggregate needed to provide the required quantity PW
10.4.2 Obtain a representative sample of lightweight aggre-
of water for internal curing.
gate as specified in 8.2. For coarse aggregate and for combined
NOTE 6—The higher the absorption of the lightweight aggregate, the
coarse and fine aggregate, the test size shall be in the range of
less of it will be needed to provide a given quantity of water for internal
2.0 kg to 2.5 kg [4.5 lb to 5.5 lb]. For fine aggregate, the test
curing. For a lower absorption aggregate, more aggregate will be needed,
size shall be in the range of 500 g to 750 g [1 lb to 1.5 lb]. Place
which will result in a better distribution of water for internal curing within
the cementitious mixture, assuming the grading is the same. aggregate in the drying pan and dry for 24 h 61 h in the drying
C1761/C1761M − 23
FIG. 1 Example of Centrifuge Extractor
oven. Allow the aggregate to cool to about 50 °C [120 °F] or and bowl cover. Remove filter ring with caution as aggregate
less. Cover aggregate with water and permit to stand for 72 h may be pressed into the filter. Transfer the aggregate to a vessel
6 4 h at a temperature of 23.0 °C 6 2 °C [73.5 °F 6 3.5 °F].
appropriate for oven-drying. It may be necessary to use a
10.4.3 Remove surface moisture from aggregate using spatula to scrape aggregate particles from the walls of the
10.4.3.1 or, for fine aggregate, either 10.4.3.1 or 10.4.3.2.
centrifuge bowl into the vessel. If aggregate particles are on the
10.4.3.1 Paper Towel Method—Decant the excess water filter ring, use a brush to transfer the aggregate from the filter
while avoiding loss of fine material. Measure the mass of the
to the vessel. The aggregate is now in the wetted surface-dry
aggregate to the nearest 0.1 g and record the mass as M . condition. Measure the specimen mass to the nearest 0.1 g and
S
Spread the aggregate on a flat nonabsorbent surface covered
record the mass as M .
SD
with brown paper towels. Expose the aggregate to a gently
NOTE 10—If sample is improperly balanced, excessive vibrations may
moving current of air. Pat the surface of the aggregate with
occur during spinning and results may be inaccurate.
paper towels, and stir frequently to secure homogeneous
NOTE 11—Some centrifuge extractors are equipped with a speed
drying. Replace the bottom towels when they become too
controller with a digital readout that can be adjusted to the specified 209
damp to absorb additional moisture. Continue patting and
rad/s (2000 rpm). Extractors may have presets that can be selected before
stirring the aggregate, replacing the towels as they become too powering on to produce the specified speed of 209 rad/s (2000 rpm).
NOTE 12—Research (3) indicates no significant change in results if
damp or dirty to absorb additional moisture. Repeat the patting
sample is spun for at least 3 minutes up to 15 minutes at 209 rad/s (2000
and spreading until no moisture appears on clean paper towels.
rpm).
The aggregate is now in the wetted surface-dry condition.
Measure the aggregate mass to the nearest 0.1 g and record the 10.4.3.3 Centrifuge Method—Decant the excess water while
mass as M . avoiding loss of fine material. Measure the mass of the
SD
10.4.3.2 Centrifuge Method—
...

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: C1761/C1761M − 17 C1761/C1761M − 23
Standard Specification for
Lightweight Aggregate for Internal Curing of Concrete
This standard is issued under the fixed designation C1761/C1761M; 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 aggregate intended to provide water for internal curing of concrete. It includes test
methods for determining the absorption and desorption properties of lightweight aggregate.
NOTE 1—Internal curing provides an additional source of water to sustain hydration and substantially reduce the early-age autogenous shrinkage and
self-desiccation that can be significant contributors to early-age cracking. Appendix X1 provides guidance on calculating the quantity of lightweight
aggregate for internal curing.
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. Some values have only SI units because the inch-pound equivalents are not used in
practice.
NOTE 2—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 that 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 specificationstandard 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 and healthsafety, 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:
C29/C29M Test Method for Bulk Density (“Unit Weight”) and Voids in Aggregate
C40/C40M Test Method for Organic Impurities in Fine Aggregates for Concrete
C87/C87M Test Method for Effect of Organic Impurities in Fine Aggregate on Strength of Mortar
C114 Test Methods for Chemical Analysis of Hydraulic Cement
C125 Terminology Relating to Concrete and Concrete Aggregates
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 2017August 2023. Originally approved in 2012. Last previous edition approved in 20152017 as
C1761/C1761M – 15.C1761/C1761M – 17. DOI: 10.1520/C1761_C1761M-17.10.1520/C1761_C1761M-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
C1761/C1761M − 23
C128 Test Method for Relative Density (Specific Gravity) and Absorption of Fine Aggregate
C136/C136M Test Method for Sieve Analysis of Fine and Coarse Aggregates
C142/C142M Test Method for Clay Lumps and Friable Particles in Aggregates
C330/C330M Specification for Lightweight Aggregates for Structural Concrete
C641 Test Method for Iron Staining Materials in Lightweight Concrete Aggregates
C702/C702M Practice for Reducing Samples of Aggregate to Testing Size
C1498 Test Method for Hygroscopic Sorption Isotherms of Building Materials
C1608 Test Method for Chemical Shrinkage of Hydraulic Cement Paste
C1698 Test Method for Autogenous Strain of Cement Paste and Mortar
D75/D75M Practice for Sampling Aggregates
D2172/D2172M Test Methods for Quantitative Extraction of Asphalt Binder from Asphalt Mixtures
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 practice, refer to Terminology C125.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorption, A , n—of lightweight aggregate, the increase in mass of a specimen of oven-dry lightweight aggregate due to
water penetrating into the permeable pores of the particles after being submerged for 72 h, expressed as percentage of oven-dry
mass.
3.2.2 autogenous shrinkage, n—reduction in volume due to chemical shrinkage of a sealed cementitious mixture, not subjected
to external forces and under constant temperature, measured from the time of final setting.
3.2.2.1 Discussion—
The chemical shrinkage leads to emptying of the internal pores (see self-desiccation) that causes the formation of menisci in the
partially water-filled pores. The menisci in turn give rise to internal tensile stresses that cause bulk shrinkage. While autogenous
shrinkage is due to the chemical shrinkage, the magnitude of autogenous shrinkage is less than the chemical shrinkage after setting
occurs, because the aggregate particles and the hydrated cement paste network restrain the shrinkage. The restraint may in turn lead
to cracking.
3.2.3 chemical shrinkage, n—the reduction in volume of cementitious paste that occurs during hydration because the hydration
products occupy less volume than the volume occupied originally by the water and unhydrated cementitious materials.
3.2.4 density (OD), n—of lightweight aggregate, the mass of oven-dry lightweight aggregate particles per unit volume of aggregate
particles, where the volume includes the permeable and impermeable pores within the particles but does not include the voids
between the particles.
3.2.5 desorption (D), n—of lightweight aggregate, the decrease in mass of lightweight aggregate originally containing absorbed
water due to water leaving the permeable pores as the aggregate attains moisture equilibrium with the surrounding environment
maintained at constant temperature and a relative humidity less than 100 %, and expressed as a percentage of the 72-h absorption.
3.2.6 internal curing, n—supplying water within a cementitious mixture using pre-wetted lightweight aggregate, or other materials
that readily release water from within the particles, thereby mitigating self-desiccation and sustaining hydration.
3.2.7 oven-dry (OD), adj—related to lightweight aggregate particles, the condition in which the specimen of lightweight aggregate
has been dried by heating in an oven at 110110 °C 6 5 °C [230[230 °F 6 10 °F] for sufficient time to reach a constant mass.
3.2.8 relative density, (OD), n—of lightweight aggregate, the ratio of the density (OD) of the lightweight aggregate to the density
of water at a stated temperature.
3.2.9 wetted surface-dry (WSD), adj—related to lightweight aggregate particles, the condition in which the permeable pores of
lightweight aggregate particles are filled with water, to the extent achieved by submerging an oven-dry specimen for 72 h, and the
surfaces of the particles are dry.
C1761/C1761M − 23
3.2.10 self-desiccation, n—reduction in the internal relative humidity of a sealed cementitious mixture, due to chemical shrinkage,
that may reduce the rate of hydration or stop hydration.
3.3 Symbols: A = the 72-h absorption, expressed as a percentage of the oven-dry mass.
D = the desorption, expressed as a percentage of the A absorption.
G = relative density (oven-dry) of lightweight aggregate.
OD
G = relative density (oven-dry) of normal weight aggregate.
ODN
M = calculated mass of oven-dry lightweight aggregate needed for internal curing per unit volume of concrete,
LWA
3 3
kg/m [lb ⁄yd ].
3 3
M = mass of normal weight aggregate in oven-dry condition to be removed, kg/m [lb ⁄yd ].
NWA
M = mass of lightweight aggregate specimen in oven-dry condition, g.
OD
M = mass of pycnometer containing lightweight aggregate specimen and filled with water, g.
PS
M = mass of pycnometer filled with water, g.
PW
M = mass of lightweight aggregate specimen in wetted surface-dry condition, g.
SD
M = equilibrium mass of aggregate originally in wetted surface-dry condition and subsequently stored at 94 % relative
humidity, g.
3 3
C = cementitious materials content of concrete mixture, kg/m [lb ⁄yd ].
f
CS = chemical shrinkage of cementitious material, expressed as kg water/kg of cement [lb/lb] (see Note 3).
S = degree of saturation of lightweight aggregate relative to wetted surface-dry condition (0 to 1.0).
w/cm = water-cementitious materials ratio, kg/kg [lb/lb].
α = maximum potential degree of hydration of cementitious materials expressed as a decimal fraction (0 to 1.0).
max
W = mass of water released by lightweight aggregate in going from the wetted surface-dry condition to the equilibrium mass
LWA
at a relative humidity of 94 %, expressed as a fraction of the oven-dry mass.
NOTE 3—Chemical shrinkage is measured in units of volume of water per unit mass of cement. In using the value of chemical shrinkage to calculate the
required amount of lightweight aggregate for internal curing, the volume of water is converted to the mass of water. Hence chemical shrinkage is
expressed as mass of water per unit mass of cement.
4. Ordering Information
4.1 The direct purchaser of lightweight aggregate for internal curing shall include the following information in the purchase order
as applicable.
4.1.1 Reference to this specification, as Specification C1761C1761/C1761M.
4.1.2 Whether the order is for fine aggregate, coarse aggregate, or combined fine and coarse aggregate.
4.1.3 Quantity in metric tons [tons] or cubic meters [cubic yards].
4.1.4 If the order is for coarse aggregate or combined fine and coarse aggregate, provide the nominal size designation as given
in Table 1 or alternative grading as agreed between the purchaser and aggregate supplier.
TABLE 1 Grading Requirements
Percentages (Mass) Passing Sieves Having Square Openings
A
Nominal Size Designation
25.0 mm 19.0 mm 12.5 mm 9.5 mm 4.75 mm 2.36 mm 1.18 mm 300 μm 150 μm
75 μm
3 1 3
(No. 200)
(1 in.) ( ⁄4 in.) ( ⁄2 in.) ( ⁄8 in.) (No. 4) (No. 8) (No. 16) (No. 50) (No. 100)
Fine aggregate:
4.75 mm to 0 (No. 4 to 0) . . . . . . . . . 100 65–100 . . . 15–80 0–35 0–25 . . .
Coarse aggregate:
25.0 to 4.75 mm (1 in. to No. 4) 95–100 . . . 25–60 . . . 0–10 . . . . . . . . . . . . 0–10
19.0 to 4.75 mm ( ⁄4 in. to No.4) 100 90–100 . . . 10–50 0–15 . . . . . . . . . . . . 0–10
12.5 to 4.75 mm ( ⁄2 in. to No. 4) . . . 100 90–100 40–80 5–40 0–20 0–10 . . . . . . 0–10
9.5 to 2.36 mm ( ⁄8 in. to No. 8) . . . . . . 100 80–100 5–40 0–20 0–10 . . . . . . 0–10
Combined fine and coarse aggregate:
12.5 mm to 0 ( ⁄2 in. to 0) . . . 100 95–100 . . . 50–80 . . . . . . 5–20 2–15 0–10
9.5 mm to 0 ( ⁄8 in. to 0) . . . . . . 100 90–100 65–90 35–65 . . . 10–25 5–15 0–10
A
The surfaces of pyro-processed lightweight aggregate particles finer than the 75 μm (No. 200) sieve are not deleterious and may be moderately pozzolanic.
C1761/C1761M − 23
4.1.5 Whether certification shall be furnished indicating that the material was sampled and tested in accordance with this
specification and found to meet the requirements.
4.1.6 Whether a report of the results of aggregate tests shall be furnished.
4.1.7 Whether the results of tests of concrete properties are required.
4.1.8 Any exceptions or additions to this specification.
5. Materials and Manufacture
5.1 Two general types of lightweight aggregate are covered by this specification, as follows:
5.1.1 Aggregates produced by expanding, pelletizing, or sintering products such as blast-furnace slag, clay, diatomite, fly ash,
shale, or slate, and
5.1.2 Aggregate prepared by processing natural materials, such as pumice, scoria, and tuff.
5.2 The aggregate shall be composed predominately of lightweight-cellular and granular inorganic materials.
6. Chemical Requirements
6.1 Organic Impurities—Test Method C40/C40M. Lightweight aggregate shall not produce a color darker than the standard color
solution, unless it is demonstrated that when the aggregate is tested for the effect of organic impurities on strength of mortar, the
relative strength at 7 days, determined in accordance with Test Method C87/C87M, is not less than 95 %.
6.2 Staining—Test Method C641. Lightweight aggregate shall produce a stain index of less than 60. Lightweight aggregate
producing a stain index of 60 or higher shall be subject to rejection if 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 sample.
2 3
6.2.1 Loss on Ignition—Test Method C114. The loss on ignition of lightweight aggregates shall not exceed 5 %.
NOTE 4—Some aggregate 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.
7. Physical Properties
7.1 Clay Lumps and Friable Particles—Test Method C142/C142M. The total amount of clay lumps and friable particles shall not
exceed 2 % by dry mass.
7.2 Grading—Test Method C136/C136M as modified in Specification C330/C330M. The grading shall conform to the
requirements shown in Table 1 or established by mutual agreement between interested parties.
NOTE 5—In general, a volume of lightweight aggregate (fine or a combination of coarse and fine) for internal curing will replace an equal volume of
normal weight aggregate in an existing conventional concrete mixture. The grading of the lightweight aggregate can be chosen to closely match the
existing grading of the normal weight aggregates, or to fill in a gap in the existing normal weight aggregate grading, such as using a mid-range size
lightweight aggregate to enhance the gradation of a gap-graded mixture (1).
7.2.1 Uniformity of Grading—For continuing shipments of fine aggregate from a given source, the fineness modulus shall not vary
more than 7 % from the base fineness modulus. The base fineness modulus shall be that value that is typical of the source. The
purchaser has the authority to approve a change in the base fineness modulus. For coarse aggregate and combined fine and coarse
aggregate, the uniformity of grading requirements of Specification C330/C330M shall apply.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
C1761/C1761M − 23
TABLE 2 Maximum Dry Loose Bulk Density
Maximum Density
Size Designation
3 3
kg/m [lb ⁄ft ]
Fine aggregate 1120 [70]
Coarse aggregate 880 [55]
Combined fine and coarse 1040 [65]
aggregate
7.3 Bulk Density—Test Method C29/C29M. The dry bulk density using the shoveling method of compaction shall conform to the
requirements of Table 2 using a 14 L [ ⁄2 ft ] measure.
7.4 Water Absorption—The lightweight aggregate shall have a 72-h absorption not less than 5 % when tested in accordance with
Section 10.
7.5 Desorption Properties—The lightweight aggregate shall release at least 85 % of its absorbed water at 94 % relative humidity
when tested in accordance with Section 11.
8. Sampling
8.1 Sample lightweight aggregates in accordance with Practice D75/D75M.
8.2 Reduce sample to test sizes in accordance with Practice C702/C702M.
9. Number of Tests and Retests
9.1 Tests on Aggregates—One representative sample is required of sufficient size to prepare specimens for the following tests:
organic impurities, staining, loss on ignition, grading, clay lumps and friable particles, bulk density, absorption and relative density
(OD), and desorption from WSD to 94 % relative humidity.
9.2 Tests on Internally Cured Concrete—When specified by the purchaser, at least three specimens are required for each of the
following tests of concrete: compressive strength, shrinkage, resistance to freezing and thawing, and presence of popout materials.
At least eight specimens are required for splitting tensile strength tests. Tests shall be performed in accordance with Specification
C330/C330M and test results shall comply with Specification C330/C330M.
TEST METHODS
10. Absorption and Relative Density
10.1 Scope:
10.1.1 This test method uses the pycnometer method to determine the 72-h absorption and relative density (oven-dry) of
lightweight aggregate for internal curing.
10.2 Significance and Use:
10.2.1 It is difficult to obtain complete saturation of the permeable pores in some lightweight aggregate particles. In this test
method, a 72-h soaking period of essentially dry aggregate is used to define the absorption.
10.2.2 After the prescribed soaking period and the removal of surface moisture, the aggregate is in the wetted surface-dry
condition, which is analogous to the saturated surface-dry condition applicable to normal weight aggregate. The former term is
used because the permeable pores in some lightweight aggregate particles are not filled completely by soaking for 72-h (2).
10.2.3 The absorption is used to determine the mass of lightweight aggregate needed to provide the required quantity of water for
internal curing.
C1761/C1761M − 23
NOTE 6—The higher the absorption of the lightweight aggregate, the less of it will be needed to provide a given quantity of water for internal curing.
For a lower absorption aggregate, more aggregate will be needed, which will result in a better distribution of water for internal curing within the
cementitious mixture, assuming the grading is the same.
10.2.4 The relative density (oven-dry) is used to calculate the mass of the normal weight aggregate that is to be replaced by an
equal volume of lightweight aggregate.
10.3 Apparatus:
10.3.1 Balance—Having a capacity of at least 4 kg and accurate to at least 0.1 g.
10.3.2 Wide-mouth jars—Glass jars with nominal capacities of 1 L [1 qt] and 2 L [2 qt].
NOTE 7—Ordinary canning jars are suitable for this purpose.
10.3.3 Pycnometer top—For filling the 1 L [1 qt] or 2 L [2 qt] jars with water to a repeatable level.
10.3.4 Paper towels—Commercial grade, either folded type or roll type.
NOTE 8—Brown paper towels make it easier to determine whether aggregate particles contain surface water during the drying procedure for bringing
aggregate to the wetted surface-dry condition.
10.3.5 Centrifuge extractor—An apparatus similar to that shown in Fig. 1, including a 241 mm [9.5 in.] diameter centrifuge bowl
and an apparatus in which the bowl can be revolved at controlled variable 72 speeds up to 377 rad/s [3600 revolutions per minute]
(see Note 9). The speed shall be controlled either manually or using a preset speed control. The apparatus shall be provided with
a container for catching the surface water thrown from the aggregate particles and a drain for removing the water.
NOTE 9—A standard 1500 g (3.3 lb) capacity centrifuge extractor meeting the requirements of Test Methods D2172/D2172M meets these requirements.
The specified 241 mm [9.5 in.] bowl diameter (outside diameter of the rim) relates to the centrifuge speed to produce the desired result of removing
surface water without removing absorbed water.
10.3.5.1 Filter rings—Low-ash paper filter rings approximately 1.3 mm [0.05 in.] thick. The ash content of the paper shall not
exceed 0.2 % (approximately 0.034 g per ring).
10.3.6 Drying oven—Of sufficient size and capable of maintaining a uniform temperature of 110 6 5 ºC [230 6 10 ºF].110 °C
6 5 °C [230 °F 6 10 °F].
FIG. 1 Example of Centrifuge Extractor
C1761/C1761M − 23
10.3.7 Metal pans—For soaking aggregate under water and for drying aggregate in drying oven.
10.3.8 Water storage container—Approximate capacity of 20 L [5 gal] for maintaining a supply of water at the laboratory
temperature of 23.0 6 2 ºC [73.5 6 3.5 ºF]. 23.0 °C 6 2 °C [73.5 °F 6 3.5 °F].
10.4 Procedure:
10.4.1 Fill the wide-mouth jar with pycnometer top with water at a temperature of 23.0 6 2 ºC [73.5 6 3.5 ºF]. 23.0 °C 6 2 °C
[73.5 °F 6 3.5 °F]. For tests of coarse aggregate or combined coarse and fine aggregate, use the 2-L [2-qt] jar. Use the 1-L [1-qt]
jar for tests of fine aggregate. Ensure that no air bubbles are present on the wall of the jar and the pycnometer top is filled to
capacity. Wipe the surface of the jar to remove any surface water and weigh the filled jar to the nearest 0.1 g. Record this mass
as M .
PW
10.4.2 Obtain a representative sample of lightweight aggregate as specified in 8.2. For coarse aggregate and for combined coarse
and fine aggregate, the test size shall be in the range of 2.02.0 kg to 2.5 kg [4.5[4.5 lb to 5.5 lb]. For fine aggregate, the test size
shall be in the range of 500500 g to 750 g [1[1 lb to 1.5 lb]. Place aggregate in the drying pan and dry for 24 h 61 h in the drying
oven. Allow the aggregate to cool to about 50 ºC [120 ºF]°C [120 °F] or less. Cover aggregate with water and permit to stand for
7272 h 6 4 h at a temperature of 23.0 6 2 ºC [73.5 6 3.5 ºF]. 23.0 °C 6 2 °C [73.5 °F 6 3.5 °F].
10.4.3 Decant the excess water while avoiding loss of fine material. Spread the aggregate on a flat nonabsorbent surface covered
with brown paper towels. Expose the aggregate to a gently moving current of air. Pat the surface of the aggregate with paper towels,
and stir frequently to secure homogeneous drying. Replace the bottom towels when they become too damp to absorb additional
moisture. Continue patting and stirring the aggregate, replacing the towels as they become too damp or dirty to absorb additional
moisture. Repeat the patting and spreading until no moisture appears on clean paper towels. The aggregate is nowRemove surface
moisture from aggregate using 10.4.3.1 in the wetted surface-dry condition.or, for fine aggregate, either 10.4.3.1 or 10.4.3.2.
10.4.3.1 Paper Towel Method—Decant the excess water while avoiding loss of fine material. Measure the mass of the aggregate
to the nearest 0.1 g and record the mass as M . Spread the aggregate on a flat nonabsorbent surface covered with brown paper
S
towels. Expose the aggregate to a gently moving current of air. Pat the surface of the aggregate with paper towels, and stir
frequently to secure homogeneous drying. Replace the bottom towels when they become too damp to absorb additional moisture.
Continue patting and stirring the aggregate, replacing the towels as they become too damp or dirty to absorb additional moisture.
Repeat the patting and spreading until no moisture appears on clean paper towels. The aggregate is now in the wetted surface-dry
condition. Measure the aggregate mass to the nearest 0.1 g and record the mass as M .
SD
10.4.3.2 Centrifuge Method—Decant the excess water while avoiding loss of fine material. Measure the mass of the specimen of
600 g 6 10 g to the nearest 0.1 g and record the mass as M . Place the specimen in the centrifuge bowl. Distribute aggregate evenly
S
inside of centrifuge bowl to ensure proper balance (see Note 10). Place centrifuge bowl in centrifuge. Place filter ring on top of
centrifuge bowl and secure centrifuge bowl cover with cover nut. Place upper housing on top of centrifuge and secure with clamps.
Power centrifuge on. Set centrifuge speed control to 209 rad/s 6 2 rad/s (2000 6 20 rpm) (see Note 11). Testing time of 4 minutes
6 1 minute shall begin when centrifuge speed reaches 209 rad/s 6 2 rad ⁄s (2000 rpm 6 20 rpm). If centrifuge does not have a
digital readout of speed, time shall begin when centrifuge reaches a steady speed. After specimen has been spun for 4 minutes 6
1 minute at 209 rad/s 6 2 rad/s (2000 rpm 6 20 rpm), turn centrifuge power off (see Note 12). When the centrifuge has come to
rest, open the upper housing. Remove bowl cover nut and bowl cover. Remove filter ring with caution as aggregate may be pressed
into the filter. Transfer the aggregate to a vessel appropriate for oven-drying. It may be necessary to use a spatula to scrape
aggregate particles from the walls of the centrifuge bowl into the vessel. If aggregate part
...