ASTM C270-19ae1

Standard Specification for Mortar for Unit Masonry

ABSTRACT
This specification covers mortars for use in the construction of non-reinforced and reinforced unit masonry structures. Four types of mortar are covered in each of two alternative specifications: (1) proportion specifications and (2) property specifications. The property specification applies to mortar mixed to a specific flow in the laboratory. When neither proportion nor property specifications are specified, the proportion specifications shall govern, unless data are presented to and accepted by the specifier to show that mortar meets the requirements of the property specifications. This specification does not cover the determination of mortar strengths through field testing. The compressive strength values resulting from field tested mortars do not represent the compressive strength of mortar tested in the laboratory nor that of the mortar in the wall. Physical properties of field sampled mortar shall not be used to determine compliance to this specification and are not intended as criteria to determine the acceptance of rejection of the mortar. Compliance to this specification is verified by confirming that the materials used are as specified, meet the requirements as given, and added to the mixer in the proper proportions as described.
SCOPE
1.1 This specification covers mortars for use in the construction of non-reinforced and reinforced unit masonry structures. Four types of mortar are covered in each of two alternative specifications: (1) proportion specifications and (2) property specifications.
Note 1: When the property specification is used to qualify masonry mortars, the testing agency performing the test methods should be evaluated in accordance with Practice C1093.  
1.2 The proportion or property specifications shall govern as specified.  
1.3 When neither proportion or property specifications are specified, the proportion specifications shall govern, unless data are presented to and accepted by the specifier to show that mortar meets the requirements of the property specifications.  
1.4 This standard is not a specification to determine mortar strengths through field testing (see Section 3).  
1.5 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.  
1.6 The terms used in this specification are identified in Terminologies C1180 and C1232.  
1.7 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.8 The following safety hazards caveat pertains only to the test methods section of this specification:  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.  
1.9 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: 30-Apr-2019
• ICS: 91.100.10 - Cement. Gypsum. Lime. Mortar
• Technical Committee: C12 - Mortars and Grouts for Unit Masonry
• Drafting Committee: C12.03 - Specifications for Mortars

Relations

• Replaces: ASTM C270-19a - Standard Specification for Mortar for Unit Masonry
• Effective Date: 01-May-2019
• Refers: ASTM C109/C109M-23 - Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 50 mm [2 in.] Cube Specimens)
• Effective Date: 15-Dec-2023
• Refers: ASTM C1232-23 - Standard Terminology for Masonry
• Effective Date: 15-Dec-2023
• Refers: ASTM C1384-23 - Standard Specification for Admixtures for Masonry Mortars
• Effective Date: 01-Dec-2023
• Refers: ASTM C305-20 - Standard Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
• Effective Date: 15-Jul-2020
• Refers: ASTM C1717-19 - Standard Test Methods for Conducting Strength Tests of Masonry Wall Panels
• Effective Date: 01-May-2019
• Refers: ASTM C150/C150M-19 - Standard Specification for Portland Cement
• Effective Date: 01-Apr-2019
• Refers: ASTM C1717-18 - Standard Test Methods for Conducting Strength Tests of Masonry Wall Panels
• Effective Date: 15-Dec-2018
• Refers: ASTM C1586-18 - Standard Guide for Quality Assurance of Mortars
• Effective Date: 15-Dec-2018
• Refers: ASTM C1180-18 - Standard Terminology of Mortar and Grout for Unit Masonry
• Effective Date: 01-Dec-2018
• Refers: ASTM C780-18 - Standard Test Method for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry
• Effective Date: 01-Jul-2018
• Refers: ASTM C1384-18 - Standard Specification for Admixtures for Masonry Mortars
• Effective Date: 01-Jun-2018
• Refers: ASTM C1384-18e1 - Standard Specification for Admixtures for Masonry Mortars
• Effective Date: 01-Jun-2018
• Refers: ASTM C1586-17 - Standard Guide for Quality Assurance of Mortars
• Effective Date: 15-Dec-2017
• Refers: ASTM C144-17 - Standard Specification for Aggregate for Masonry Mortar
• Effective Date: 15-Dec-2017

Overview

ASTM C270-19ae1: Standard Specification for Mortar for Unit Masonry is a critical international standard developed by ASTM International. This specification covers mortars used in the construction of both non-reinforced and reinforced unit masonry structures. It establishes the requirements for four types of mortar, detailing both proportion specifications and property specifications to ensure quality and consistency in masonry construction. This standard does not include requirements for determining mortar strengths through field testing, emphasizing laboratory-based evaluations for compliance.

Key Topics

• Scope of ASTM C270-19ae1: The standard addresses mortars for unit masonry, encompassing both proportion-based and property-based specifications for Types M, S, N, and O mortars.
• Proportion and Property Specifications:
  • Proportion specifications outline the required ratios of cementitious materials, aggregates, and water.
  • Property specifications define performance characteristics such as compressive strength, water retention, and air content, but are applicable to mortar samples prepared in laboratory conditions.
• Quality Assurance: Compliance is verified by confirming that materials and mixing proportions meet the requirements, with laboratory tests prioritized over field sampling for determining compliance.
• Test Methods: The standard references numerous ASTM test methods and specifications for materials and testing, such as those for compressive strength, water retention, and physical properties of constituents.
• Unit Systems: The standard uses inch-pound units primarily, with SI conversions provided for reference.

Applications

ASTM C270-19ae1 is widely applied across the construction industry for:

• Design and Construction of Masonry Structures: Used by architects, engineers, contractors, and inspectors to ensure that mortar used in the assembly of masonry units meets minimum quality, strength, and durability requirements.
• Quality Control in Masonry Projects: Provides a basis for selecting the appropriate type of mortar for specific types of masonry work, whether reinforced or non-reinforced, interior or exterior, and according to expected loading and environmental conditions.
• Specification Development: Serves as a reference in project specifications and construction documents for defining acceptable mortar mixes and performance criteria.
• Material Selection: Ensures that cementitious materials, aggregates, and admixtures conform to referenced ASTM standards, contributing to the longevity and safety of masonry walls.

Related Standards

ASTM C270-19ae1 references and relates closely to several other standards, supporting comprehensive coverage of material and testing requirements:

• ASTM C91/C91M: Specification for Masonry Cement
• ASTM C144: Specification for Aggregate for Masonry Mortar
• ASTM C150/C150M: Specification for Portland Cement
• ASTM C207: Specification for Hydrated Lime for Masonry Purposes
• ASTM C595/C595M: Specification for Blended Hydraulic Cements
• ASTM C780: Test Method for Preconstruction and Construction Evaluation of Mortars
• ASTM C109/C109M: Test Method for Compressive Strength of Hydraulic Cement Mortars
• ASTM C1329/C1329M: Specification for Mortar Cement

Practical Value

Adhering to ASTM C270-19ae1 ensures that mortars utilized in masonry construction offer reliable performance, durability, and safety. By standardizing mortar proportions and required properties, the specification provides a clear framework for quality assurance and uniformity, minimizing risks associated with improper material selection or mixing practices. Its emphasis on laboratory-prepared samples for compliance testing aligns with best practices and promotes consistency in construction outcomes-an essential component for meeting the demands of modern building codes and project specifications.

Keywords

ASTM C270-19ae1, unit masonry, mortar specification, proportion specification, property specification, mortar compressive strength, masonry construction, quality assurance, ASTM mortar standards, masonry cement, Portland cement-lime mortar, aggregate, water retention, air content, laboratory testing.

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.
´1
Designation:C270 −19a
Standard Specification for
Mortar for Unit Masonry
This standard is issued under the fixed designation C270; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Editorially corrected 4.1.1.2 in July 2019.
1. Scope* mental practices and determine the applicability of regulatory
limitations prior to use.
1.1 Thisspecificationcoversmortarsforuseintheconstruc-
1.9 This international standard was developed in accor-
tion of non-reinforced and reinforced unit masonry structures.
dance with internationally recognized principles on standard-
Four types of mortar are covered in each of two alternative
ization established in the Decision on Principles for the
specifications: (1) proportion specifications and (2) property
Development of International Standards, Guides and Recom-
specifications.
mendations issued by the World Trade Organization Technical
NOTE 1—When the property specification is used to qualify masonry
Barriers to Trade (TBT) Committee.
mortars, the testing agency performing the test methods should be
evaluated in accordance with Practice C1093.
2. Referenced Documents
1.2 Theproportionorpropertyspecificationsshallgovernas
2.1 ASTM Standards:
specified.
C5 Specification for Quicklime for Structural Purposes
1.3 When neither proportion or property specifications are
C91/C91M Specification for Masonry Cement
specified, the proportion specifications shall govern, unless
C109/C109M Test Method for Compressive Strength of
data are presented to and accepted by the specifier to show that
Hydraulic Cement Mortars (Using 2-in. or [50-mm] Cube
mortar meets the requirements of the property specifications.
Specimens)
1.4 This standard is not a specification to determine mortar
C110 Test Methods for Physical Testing of Quicklime,
strengths through field testing (see Section 3).
Hydrated Lime, and Limestone
C128 Test Method for Relative Density (Specific Gravity)
1.5 The text of this specification references notes and
and Absorption of Fine Aggregate
footnotes which provide explanatory material. These notes and
C144 Specification for Aggregate for Masonry Mortar
footnotes (excluding those in tables and figures) shall not be
C150/C150M Specification for Portland Cement
considered as requirements of the standard.
C188 Test Method for Density of Hydraulic Cement
1.6 The terms used in this specification are identified in
C207 Specification for Hydrated Lime for Masonry Pur-
Terminologies C1180 and C1232.
poses
1.7 The values stated in inch-pound units are to be regarded
C305 Practice for Mechanical Mixing of Hydraulic Cement
as standard. The values given in parentheses are mathematical
Pastes and Mortars of Plastic Consistency
conversions to SI units that are provided for information only
C511 Specification for Mixing Rooms, Moist Cabinets,
and are not considered standard.
Moist Rooms, and Water Storage Tanks Used in the
Testing of Hydraulic Cements and Concretes
1.8 The following safety hazards caveat pertains only to the
C595/C595M Specification for Blended Hydraulic Cements
test methods section of this specification: This standard does
C780 Test Method for Preconstruction and Construction
not purport to address all of the safety concerns, if any,
Evaluation of Mortars for Plain and Reinforced Unit
associated with its use. It is the responsibility of the user of this
Masonry
standard to establish appropriate safety, health, and environ-
C952 Test Method for Bond Strength of Mortar to Masonry
This specification is under the jurisdiction of ASTM Committee C12 on
Mortars and Grouts for Unit Masonryand is the direct responsibility of Subcom-
mittee C12.03 on Specifications for Mortars. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2019. Published June 2019. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1951. Last previous edition approved in 2019 as C270 – 19. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0270-19AE01. 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
´1
C270−19a
Units (Withdrawn 2017) specification of this standard applies to mortar mixed to a
C979/C979M Specification for Pigments for Integrally Col- specific flow in the laboratory.
ored Concrete
3.2 Property specifications requirements in Table 1 shall not
C1072 Test Methods for Measurement of Masonry Flexural
be used to evaluate construction site-produced mortars.
Bond Strength
NOTE 2—Refer to X1.5.3.1 for further explanation.
C1093 Practice for Accreditation of Testing Agencies for
Masonry
3.3 Since the compressive strength values resulting from
C1157/C1157M Performance Specification for Hydraulic
field tested mortars do not represent the compressive strength
Cement
ofmortarastestedinthelaboratorynorthatofthemortarinthe
C1180 Terminology of Mortar and Grout for Unit Masonry
wall, physical properties of field sampled mortar shall not be
C1232 Terminology for Masonry
used to determine compliance to this specification and are not
C1324 Test Method for Examination and Analysis of Hard-
intended as criteria to determine the acceptance or rejection of
ened Masonry Mortar
the mortar (see Section 8 and Guide C1586).
C1329/C1329M Specification for Mortar Cement
C1384 Specification for Admixtures for Masonry Mortars
4. Materials
C1489 Specification for Lime Putty for Structural Purposes
4.1 Materials used as ingredients in the mortar shall con-
C1506 Test Method for Water Retention of Hydraulic
form to the requirements specified in 4.1.1 to 4.1.4.
Cement-Based Mortars and Plasters
4.1.1 Cementitious Materials—Cementitious materials shall
C1586 Guide for Quality Assurance of Mortars
conform to the following ASTM specifications:
C1717 Test Methods for Conducting Strength Tests of Ma-
4.1.1.1 Portland Cement—Types I, IA, II, IIA, III, IIIA, or
sonry Wall Panels
V of Specification C150/C150M.
E514/E514M Test Method for Water Penetration and Leak-
age Through Masonry 4.1.1.2 Blended Hydraulic Cements—Types IL, IL-A, IS,
E518/E518M Test Methods for Flexural Bond Strength of IS-A, IP, IP-A, IT, and IT-A of Specification C595/C595M.
Blended hydraulic cements with 70 % or more slag cement
Masonry
content are only permitted for use in property specifications.
2.2 Masonry Industry Council:
4.1.1.3 Hydraulic Cements—Types GU, HE, MS, and HS of
Hot and Cold Weather Masonry Construction Manual, Janu-
Specification C1157/C1157M. Types MH and LH are only
ary 1999
permitted for use in property specifications.
3. Specification Limitations
4.1.1.4 Masonry Cement—See Specification C91/C91M.
4.1.1.5 Mortar Cement—See Specification C1329/C1329M.
3.1 Laboratory testing of mortar to ensure compliance with
the property specification requirements of this specification 4.1.1.6 Quicklime—See Specification C5.
shall be performed in accordance with 5.3. The property 4.1.1.7 Hydrated Lime—Specification C207,Types S or SA.
Types N or NA limes are permitted if shown by test or
performance record to be not detrimental to the soundness of
the mortar.
The last approved version of this historical standard is referenced on
4.1.1.8 Lime Putty—See Specification C1489.
www.astm.org.
4 4.1.2 Aggregates—See Specification C144.
Available from the Mason Contractors Association of America, 1910 South
Highland Avenue, Suite 101, Lombard, IL 60148.
A
TABLE 1 Property Specification Requirements
B
Mortar Type Average Compressive Water Retention, min, % Air Content, max, % Aggregate Ratio
Strength at 28 days, min, (Measured in Damp,
psi (MPa) Loose Conditions)
Cement-Lime M 2500 (17.2) 75 12
S 1800 (12.4) 75 12
C
N 750 (5.2) 75 14
C
O 350 (2.4) 75 14
Mortar Cement M 2500 (17.2) 75 18 Not less than 2 ⁄4 and not
more than 3 ⁄2 times the
S 1800 (12.4) 75 18
D
N 750 (5.2) 75 20 sum of the separate
D
volumes of cementitious
O 350 (2.4) 75 20
materials
Masonry Cement M 2500 (17.2) 75 18
S 1800 (12.4) 75 18
D
N 750 (5.2) 75 20
D
O 350 (2.4) 75 20
A
Laboratory prepared mortar only (see Note 5).
B
See Note 6.
C
When structural reinforcement is incorporated in cement-lime, the maximum air content shall be 12 %.
D
When structural reinforcement is incorporated in masonry cement mortar or mortar cement mortar, the maximum air content shall be 18 %.
´1
C270−19a
4.1.3 Water—Water shall be clean and free of amounts of 5.2 Proportion Specifications—Mortar conforming to the
oils,acids,alkalies,salts,organicmaterials,orothersubstances proportion specifications shall consist of a mixture of cemen-
that are deleterious to mortar or any metal in the wall. titious material, aggregate, and water, all conforming to the
4.1.4 Admixtures—Admixtures shall not be added to mortar requirements of Section 4 and the proportion specifications’
unless specified. Admixtures shall not add more than 65 ppm requirements of Table 2. See Appendix X1 or Appendix X3 for
(0.0065 %) water soluble chloride or 90 ppm (0.0090 %) acid a guide for selecting masonry mortars.
soluble chloride to the mortar’s overall chloride content, unless
5.3 Property Specifications—Mortar conformance to the
explicitly provided for in the contract documents.
property specifications shall be established by tests of labora-
4.1.4.1 Classified Admixtures—Admixtures which are clas-
tory prepared mortar in accordance with Section 6 and 7.2.The
sified as bond enhancers, workability enhancers, set
laboratory prepared mortar shall consist of a mixture of
accelerators, set retarders, and water repellents shall be in
cementitious material, aggregate, and water, all conforming to
accordance with Specification C1384.
the requirements of Section 4 and the properties of the
4.1.4.2 Color Pigments—Coloring pigments shall be in
laboratory prepared mortar shall conform to the requirements
accordance with Specification C979/C979M.
of Table 1. See Appendix X1 for a guide for selecting masonry
4.1.4.3 Unclassified Admixtures—Mortars containing ad-
mortars.
mixtures outside the scopes of Specifications C1384 and
5.3.1 No change shall be made in the laboratory established
C979/C979M shall be in accordance with the property require-
proportions for mortar accepted under the property
ments of this specification and the admixture shall be shown to
specifications, except for the quantity of mixing water. Mate-
be non-deleterious to the mortar, embedded metals, and the
rials with different physical characteristics shall not be utilized
masonry units.
in the mortar used in the work unless compliance with the
4.1.4.4 Calcium Chloride—When explicitly provided for in
requirements of the property specifications is reestablished.
the contract documents, calcium chloride is permitted to be
used as an accelerator in amounts not to exceed 2 % by weight
NOTE 4—The physical properties of plastic and hardened mortar
of the portland cement content or 1 % of the masonry cement
complying with the proportion specification (5.1) may differ from the
physical properties of mortar of the same type complying with the
content, or both, of the mortar.
property specification (5.3). For example, laboratory prepared mortars
NOTE 3—If calcium chloride is allowed, it should be used with caution
batched to the proportions listed in Table 2 will, in many cases,
as it may have a detrimental effect on metals and on some wall finishes.
considerably exceed the compressive strength requirements of Table 1.
NOTE 5—The required properties of the mortar in Table 1 are for
5. Requirements
laboratory prepared mortar mixed with a quantity of water to produce a
flow of 110 6 5 %. This quantity of water is not sufficient to produce a
5.1 Unless otherwise stated, a cement/lime mortar, a mortar
mortar with a workable consistency suitable for laying masonry units in
cement mortar, or a masonry cement mortar is permitted. A
the field. Mortar for use in the field must be mixed with the maximum
mortar type of known higher strength shall not be indiscrimi-
amount of water, consistent with workability, in order to provide sufficient
nately substituted where a mortar type of anticipated lower
watertosatisfytheinitialrateofabsorption(suction)ofthemasonryunits.
strength is specified. The properties of laboratory prepared mortar at a flow of 110 6 5, as
TABLE 2 Proportion Specification Requirements
NOTE 1—Two air-entraining materials shall not be combined in mortar.
Proportions by Volume (Cementitious Materials)
A
Mortar Type Cement Aggregate Ratio
Hydrated Lime (Measured in
Mortar Cement Masonry Cement
or Lime Putty Damp, Loose Con-
ditions)
MS N M S N
Cement-Lime M 1 . . . . . . . . . . . . . . . . . . ⁄4
1 1
S 1 . . . . . . . . . . . . . . . . . . over ⁄4 to ⁄2
1 1
N 1 . . . . . . . . . . . . . . . . . . over ⁄2 to 1 ⁄4
1 1
O 1 . . . . . . . . . . . . . . . . . . over 1 ⁄4 to 2 ⁄2
Mortar Cement M 1 . . . . . . 1 . . . . . . . . . . . . Not less than 2 ⁄4
M . 1 . . . . . . and not more than
S ⁄2 . . 1 . . . . 3 times the sum of
the separate vol-
S . . 1 . . . . .
N . . . 1 . . . . umes of cementi-
tious materials
O . . . 1 . . . .
Masonry Cement M 1 . . . . . . . . . . . . . . . 1 . . .
M . . . . 1 . . .
S ⁄2 . . . . . 1 .
S . . . . . 1 . .
N . . . . . . 1 .
O . . . . . . 1 .
A
Includes Specification C150/C150M, C595/C595M, and C1157/C1157M cements as described in 4.1.1.
´1
C270−19a
required by this specification, are intended to approximate the flow and
mixed mortar shall be of the materials and proportions to be
properties of field prepared mortar after it has been placed in use and the
used in the construction.
suction of the masonry units has been satisfied. The properties of field
6.4 Air Content—Determine air content in accordance with
prepared mortar mixed with the greater quantity of water, prior to being
placed in contact with the masonry units, will differ from the property
Specification C91/C91M except that the laboratory mixed
requirements in Table 1. Therefore, the property requirements in Table 1
mortar is to be of the materials and proportions to be used in
cannot be used as requirements for quality control of field prepared
the construction. Calculate the air content to the nearest 0.1 %
mortar. Test Method C780 may be used for this purpose.
as follows:
NOTE 6—Air content of non-air-entrained portland cement-lime mortar
is generally less than 8 %.
W 1W 1W 1W 1V
~ !
1 2 3 4 w
D 5
W W W
6. Test Methods W
2 3 4
1 1 1 1V
w
P P P P
1 2 3 4
6.1 Proportions of Materials for Test Specimens—
Laboratory mixed mortar used for determining conformance to W
m
A 5 100 2 (3)
this property specification shall contain construction materials 4D
in proportions indicated in project specifications. Measure
where:
materials by weight for laboratory mixed batches. Convert
D = density of air-free mortar, g/cm ,
proportions, by volume, to proportions, by weight, using a
W = weight of portland cement, g,
batch factor calculated as follows:
W = weight of hydrated lime, g,
Batch factor 5 1440/ 80 times total sand volume proportion (1)
~ !
W = weight of mortar cement or masonry cement, g,
Determine weight of material as follows:
W = weight of oven-dry sand, g,
V = millilitres of water used,
Mat. Weight 5 Mat.Volume Proportion 3Bulk Density 3Batch Factor
w
P = density of portland cement, g/cm ,
(2)
P = density of hydrated lime, g/cm ,
NOTE 7—See Appendix X4 for examples of material proportioning.
P = density of mortar cement or masonry cement, g/cm ,
6.1.1 When converting volume proportions to batch
weights, use the following material bulk densities:
P = density of oven-dry sand, g/cm ,
Material Bulk Density
A = volume of air, %, and
Portland Cement Obtain from bag or supplier
W = weight of 400 mL of mortar, g.
m
Blended Cement Obtain from bag or supplier
Hydraulic Cement Obtain from bag or supplier
6.4.1 Determine the density of oven-dry sand, P , in accor-
Slag Cement Obtain from bag or supplier
dance with Test Method C128, except that an oven-dry
Masonry Cement Obtain from bag or supplier
specimen shall be evaluated rather than a saturated surface-dry
Mortar Cement Obtain from bag or supplier
Lime Putty 80 pcf (1280 kg/m )
specimen. If a pycnometer is used, calculate the oven-dry
Hydrated Lime 40 pcf (640 kg/m )
density of sand as follows:
Sand 80 pcf (1280 kg/m )
P 5 X / Y1X 2 Z (4)
~ !
4 1 1
NOTE 8—All quicklime should be slaked in accordance with the
manufacturer’s directions. All quicklime putty, except pulverized quick-
where:
lime putty, should be sieved through a No. 20 (850 µm) sieve and allowed
X = weight of oven-dry specimen (used in pycnometer) in
to cool until it has reached a temperature of 80°F (26.7°C). Quicklime
putty should weigh at least 80 pcf (1280 kg/m ). Putty that weighs less
air, g,
than this may be used in the proportion specifications, if the required
Y = weight of pycnometer filled with water, g, and
quantity of extra putty is added to meet the minimum weight requirement.
Z = weight of pycnometer with specimen and water to
NOTE 9—The sand is oven-dried for laboratory testing to reduce the
calibration mark, g.
potential of variability due to sand moisture content and to permit better
accounting of the materials used for purposes of air content calculations.
6.4.1.1 If the Le Chantelier flask method is used, calculate
Itisnotnecessaryforthepurposesofthisspecificationtomeasuretheunit
the oven-dry density of sand as follows:
weight of the dry sand.Although the unit weight of dry sand will typically
P 5 X / 0.9975 R 2 R (5)
be 85–100 pcf (1360–1760 kg/m ), experience has shown that the use of @ ~ !#
4 2 2 1
an assumed unit weight of 80 pcf (1280 kg/m ) for dry sand will result in
where:
a laboratory mortar ratio of aggregate to cementitious material that is
similar to that of the corresponding field mortar made using damp loose
X = weight of oven-dry specimen (used in Le Chantelier
sand. A weight of 80 lb (36 kg) of dry sand is, in most cases, equivalent
flask) in air, g,
3 3
to the sand weight in 1 ft (0.03 m ) of loose, damp sand.
R = initial reading of water level in Le Chantelier flask, and
6.1.2 Oven dry and cool to room temperature all sand for
R = final reading of water in Le Chantelier flask.
laboratorymixedmortars.Sandweightshallbe1440gforeach
6.4.2 Determine the density of portland cement, mortar
individual batch of mortar prepared. Add water to obtain flow
cement, and masonry cement in accordance with Test Method
of 110 6 5 %. A test batch provides sufficient mortar for
C188. Determine the density of hydrated lime in accordance
completing the water retention test and fabricating three 2-in.
with Test Methods C110.
cubes for the compressive strength test.
6.5 Compressive Strength:
6.2 Mixing of Mortars—Mix the mortar in accordance with
6.5.1 Determine compressive strength in accordance with
Practice C305.
Test Method C109/C109M. The mortar shall be composed of
6.3 Water Retention—Determine water retention in accor- materialsandproportionsthataretobeusedintheconstruction
dance with Specification C1506, except that the laboratory- with mixing water to produce a flow of 110 6 5.
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C270−19a
6.5.2 Alternative Molding Procedure—Immediately after 8. Quality Assurance
determining the flow and mass of 400 mL of mortar, return all
8.1 Compliance to this specification is verified by confirm-
of the mortar to the mixing bowl and remix for 15 s at the
ing that the materials used are as specified, meet the require-
medium speed. Then mold the test specimen in accordance
ments as given in 2.1, and added to the mixer in the proper
with Test Method C109/C109M, except that the elapsed time
proportions. Proportions of materials are verified by one of the
for mixing mortar, determining flow, determining air
following:
entrainment, and starting the molding of cubes shall be within
8.1.1 Implementation and observation of appropriate proce-
8 min.
dures for proportioning and mixing approved materials, as
6.5.3 Specimen Storage—Keep mortar cubes for compres-
described in Section 7.
sive strength tests in the molds on plane plates in a moist room
8.1.2 Test Method C780 Annex 4, Mortar Aggregate Ratio
or a cabinet meeting the requirements of Specification C511,
to determine the aggregate to cementitious material ratio of
from 48 to 52 h in such a manner that the upper surfaces shall
mortars while they are still in a plastic state.
be exposed to the moist air. Remove mortar specimens from
8.2 Guide C1586 is suitable for developing quality assur-
the molds and place in a moist cabinet or moist room until
ance procedures to determine compliance of mortars to this
tested.
standard.
6.5.4 Testing—Test specimens in accordance with Test
8.3 Test Method C780 is suitable for the evaluation of
Method C109/C109M.
masonry mortars in the field. However, due to the procedural
differences between Specification C270 and C780, the com-
7. Construction Practices
pressive strength values resulting from field sampled mortars
7.1 Storage of Materials—Cementitious materials and ag-
are not required nor expected to meet the compressive strength
gregates shall be stored in such a manner as to prevent
requirements of the property specification of Specification
deterioration or intrusion of foreign material.
C270, nor do they represent the compressive strength of the
7.2 Measurement of Materials—The method of measuring mortar in the wall.
materials for the mortar used in construction shall be such that
8.4 Test Method C1324 is available to determine the pro-
the specified proportions of the mortar materials are controlled
portions of materials in hardened masonry mortars.There is no
and accurately maintained.
ASTM method for determining the conformance of a mortar to
the property specifications of Specification C270 by testing
7.3 Mixing Mortars—All cementitious materials and aggre-
hardened mortar samples taken from a structure.
gate shall be mixed between 3 and 5 min in a mechanical batch
mixer with the maximum amount of water to produce a
NOTE 12—The results of tests using Test Methods C780 Annex 4 and
workable consistency. Hand mixing of the mortar is permitted
C1324canbecomparedwithSpecificationC270proportionrequirements;
however, precision and bias have not been determined for these test
withthewrittenapprovalofthespecifieroutlininghandmixing
methods.
procedures.
NOTE 13—The results of tests done using Test Method C1324 can be
compared with the Specification C270 proportion requirements, however,
NOTE 10—These mixing water requirements differ from those in test
precision and bias have not been determined for this test method.
methods in Section 6.
NOTE 14—Where necessary, testing of a wall or a masonry prism from
7.4 Tempering Mortars—Mortars that have stiffened shall
the wall is generally more desirable than attempting to test individual
be retempered by adding water as frequently as needed to components.
NOTE 15—The cost of tests to show initial compliance are typically
restore the required consistency. No mortars shall be used
borne by the seller. The party initiating a change of materials typically
beyond 2 ⁄2 h after mixing.
bear the cost for recompliance.
Unless otherwise specified, the cost of other tests are typically borne as
7.5 Climatic Conditions—Unless superseded by other con-
follows:
tractual relationships or the requirements of local building
If the results of the tests show that the mortar does not conform to the
codes, hot and cold weather masonry construction relating to
requirements of the specification, the costs are typically borne by the
mortar shall comply with the Masonry Industry Council’s “Hot
seller.
and Cold Weather Masonry Construction Manual.” If the results of the tests show that the mortar does conform to the
requirements of the specification, the costs are typically borne by the
NOTE 11—Limitations—Mortar type should be correlated with the
purchaser.
particular masonry unit to be used because certain mortars are more
compatible with certain masonry units. 9. Keywords
The specifier should evaluate the interaction of the mortar type and
9.1 air content; compressive strength; masonry; masonry
masonry unit specified, that is, masonry units having a high initial rate of
cement; mortar; portland cement-lime; water retention; water
absorption will have greater compatibility with mortar of high-water
retentivity. retentivity
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C270−19a
APPENDIXES
(Nonmandatory Information)
X1. SELECTION AND USE OF MORTAR FOR UNIT MASONRY
X1.1 Scope—Thisappendixprovidesinformationtoallowa standards wholly based upon performance, thus the continued
more knowledgeable decision in the selection of mortar for a use of the traditional prescription specification in most situa-
specific use. tions.
X1.4.3 It is recommended that Test Method C780 and
X1.2 Significance and Use—Masonry mortar is a versatile
assemblage testing be considered with proper interpretation to
material capable of satisfying a variety of diverse require-
aid in determining the field suitability of a given masonry
ments. The relatively small portion of mortar in masonry
mortar for an intended use.
significantly influences the total performance. There is no
single mortar mix that satisfies all situations. Only an under-
X1.5 Plastic Mortars:
standing of mortar materials and their properties, singly and
collectively, will enable selection of a mortar that will perform X1.5.1 Workability—Workability is the most important
property of plastic mortar. Workable mortar can be spread
satisfactorily for each specific endeavor.
easily with a trowel into the separations and crevices of the
X1.3 Function:
masonry unit. Workable mortar also supports the weight of
masonryunitswhenplacedandfacilitatesalignment.Itadheres
X1.3.1 Theprimarypurposeofmortarinmasonryistobond
to vertical masonry surfaces and readily extrudes from the
masonry units into an assemblage which acts as an integral
mortar joints when the mason applies pressure to bring the unit
element having desired functional performance characteristics.
into alignment. Workability is a combination of several
Mortar influences the structural properties of the assemblage
properties, including plasticity, consistency, cohesion, and
while adding to its water resistance.
adhesion, which have defied exact laboratory measurement.
X1.3.2 Because portland cement concretes and masonry
The mason can best assess workability by observing the
mortars contain some of the same principal ingredients, it is
response of the mortar to the trowel.
often erroneously assumed that good concrete practice is also
X1.5.2 Workability is the result of a ball bearing affect of
good mortar practice. Realistically, mortars differ from con-
aggregate particles lubricated by the cementing paste. Al-
crete in working consistencies, in methods of placement and in
though largely determined by aggregate grading, material
the curing environment. Masonry mortar is commonly used to
proportions and air content, the final adjustment to workability
bind masonry units into a single structural element, while
dependsonwatercontent.Thiscanbe,andusuallyis,regulated
concrete is usually a structural element in itself.
on the mortar board near the working face of the masonry. The
X1.3.3 A major distinction between the two materials is
capacity of a masonry mortar to retain satisfactory workability
illustrated by the manner in which they are handled during
under the influence of masonry unit suction and evaporation
construction. Concrete is usually placed in nonabsorbent metal
rate depends on the water retentivity and setting characteristics
or wooden forms or otherwise treated so that most of the water
ofthemortar.Goodworkabilityisessentialformaximumbond
will be retained. Mortar is usually placed between absorbent
with masonry units.
masonry units, and as soon as contact is made the mortar loses
X1.5.3 Flow—Initial flow is a laboratory measured property
water to the units. Compressive strength is a prime consider-
of mortar that indicates the percent increase in diameter of the
ation in concrete, but it is only one of several important factors
base of a truncated cone of mortar when it is placed on a flow
in mortar.
table and mechanically raised ⁄2 in. (12.7 mm) and dropped 25
times in 15 s. Flow after suction is another laboratory property
X1.4 Properties:
which is determined by the same test, but performed on a
X1.4.1 Masonrymortarshavetwodistinct,importantsetsof
mortar sample which has had some water removed by a
properties, those of plastic mortars and those of hardened
specific applied vacuum. Water retention is the ratio of flow
mortars. Plastic properties determine a mortar’s construction
after suction to initial flow, expressed in percent.
suitability,whichinturnrelatetothepropertiesofthehardened
X1.5.3.1 Construction mortar normally requires a greater
mortarand,hence,offinishedstructuralelements.Propertiesof
flow value than laboratory mortar, and consequently possesses
plasticmortarsthathelpdeterminetheirconstructionsuitability
a greater water content. Mortar standards commonly require a
include workability and water retentivity. Properties of hard-
minimum water retention of 75 %, based on an initial flow of
ened mortars that help determine the performance of the
only 105 to 115 %. Construction mortars normally have initial
finished masonry include bond, durability, elasticity, and com-
flows, although infrequently measured, in the range of 130 to
pressive strength.
150 % (50–60 mm by cone penetration, as outlined in the
X1.4.2 Many properties of mortar are not quantitatively annex of Test Method C780) in order to produce a workability
definable in precise terms because of a lack of measurement satisfactory to the mason. The lower initial flow requirements
standards. For this and other reasons there are no mortar for laboratory mortars were arbitrarily set because the low flow
´1
C270−19a
mortars more closely indicated the mortar compressive unit/mortar combinations obtained from existing masonry.Test
strength in the masonry. This is because most masonry units Method E518/E518M provides a method for testing a masonry
will remove some water from the mortar once contact is made. prism as a simply supported beam to determine flexural
While there may be some discernible relationship between strength. While individual joints are not loaded in the Test
bond and compressive strength of mortar, the relationship Method E518/E518M procedure, the resulting strength is
between mortar flow and tensile bond strength is apparent. For determined as the prism behaves in flexure. The flexural
most mortars, and with minor exceptions for all but very low strength of masonry walls is perhaps best indicated by testing
suction masonry units, bond strength increases as flow in- full-scale wall specimens with Test Method C1717 with lateral
5,6
creases to where detectable bleeding begins. Bleeding is uniform or point loading applied to the specimen. Research
defined as migration of free water through the mortar to its on concrete masonry indicates the flexural bond strength of
surface. concrete masonry walls, using Test Method C1717, may be
correlated with results of flexural bond strength of concrete
X1.5.4 Water Retention and Water Retentivity—Waterreten-
masonry prisms, tested in accordance with Test Method C1072
tion is a measure of the ability of a mortar under suction to
and Test Method E518/E518M.
retain its mixing water. This mortar property gives the mason
X1.6.1.2 Extent of bond may be observed under the micro-
time to place and adjust a masonry unit without the mortar
scope. Lack of extent of bond, where severe, may be measured
stiffening.Water retentivity is increased through higher lime or
indirectly by testing for relative movement of water through
air content, addition of sand fines within allowable gradation
the masonry at the unit-mortar interface, such as prescribed in
limits, or use of water retaining materials.
Test Method E514/E514M. This laboratory test method con-
X1.5.5 Stiffening Characteristics—Hardening of plastic
sists of subjecting a sample wall to a through-the-wall pressure
mortar relates to the setting characteristics of the mortar, as
differential and applying water to the high pressure side. Time,
indicated by resistance to deformation. Initial set as measured
location and rate of leakage must be observed and interpreted.
in the laboratory for cementitious materials indicates extent of
X1.6.1.3 The tensile and compressive strength of mortar far
hydration or setting characteristics of neat cement pastes. Too
exceeds the bond strength between the mortar and the masonry
rapid stiffening of the mortar before use is harmful. Mortar in
unit. Mortar joints, therefore, are subject to bond failures at
masonry stiffens through loss of water and hardens through
lower tensile or shear stress levels. A lack of bond at the
normal setting of cement. This transformation may be accel-
interface of mortar and masonry unit may lead to moisture
erated by heat or retarded by cold. A consistent rate of
penetration through those areas. Complete and intimate contact
stiffening assists the mason in tooling joints.
between mortar and masonry unit is essential for good bond.
This can best be achieved through use of mortar having proper
X1.6 Hardened Mortars:
composition and good workability, and being properly placed.
X1.6.1 Bond—Bond is probably the most important single
X1.6.1.4 In general, the tensile bond strength of laboratory
physical property of hardened mortar. It is also the most
mortars increase with an increase in cement content. Because
inconstant and unpredictable. Bond actually has three facets;
of mortar workability, it has been found that Type S mortar
strength, extent and durability. Because many variables affect
generally results with the maximum tensile bond strength that
bond, it is difficult to devise a single laboratory test for each of
can practically be achieved in the field.
thesecategoriesthatwillconsistentlyyieldreproducibleresults
X1.6.2 Extensibility and Plastic Flow—Extensibility is
and which will approximate construction results. These vari-
maximumunittensilestrainatrupture.Itreflectsthemaximum
ables include air content and cohesiveness of mortar, elapsed
elongation possible under tensile forces. Low strength mortars,
time between spreading mortar and laying masonry unit,
which have lower moduli of elasticity, exhibit greater plastic
suction of masonry unit, water retentivity of mortar, pressure
flow than their high moduli counterparts at equal paste to
applied to masonry joint during placement and tooling, texture
aggregate ratios. For this reason, mortars with higher strength
of masonry unit’s bedded surfaces, and curing conditions.
than necessary should not be used. Plastic flow or creep will
X1.6.1.1 Several test methods are available for testing bond
impart flexibility to the masonry, permitting slight movement
strength of mortar to masonry units, normal to the mortar
without apparent joint opening.
joints. These include Test Methods C1072, E518/E518M, and
X1.6.3 Compressive Strength—The compressive strength of
C1717. Test Method C1072 tests the flexural bond strength of
mortar is sometimes used as a principal criterion for selecting
hollow and solid units and mortar, constructed in prisms.
mortar type, since compressive strength is relatively easy to
Individual joints of the prisms are tested for tensile bond
measure, and it commonly relates to some other properties,
strength. Test Method C1072 is becoming more widely used to
such as tensile strength and absorption of the mortar.
test the flexural bond strength than the others, due to the large
X1.6.3.1 The compressive strength of mortar depends
amount of data produced by relatively small amounts of
largely upon the cement content and the water-cement ratio.
material. Test Method C1072 has three distinct methods. The
first method, for laboratory prepared specimens, is intended to
compare bond strengths of mortars using a standard solid
Thomas, R., Samblanet, P., and Hogan, M., “Research Evaluation of the
Flexural Tensile Strength of Concrete Masonry,” Seventh Canadian Masonry
concrete masonry unit constructed in a prism. The second
Symposium , June 1995 .
method, for field prepared specimens, is intended to evaluate
Melander, J. and Thomas, R., “Flexural Tensile Strength of Concrete Masonry
bond strength of a particular unit/mortar combination. The
Constructed with Type S Masonry Cement Mortar,”Eighth Canadian Masonry
third method describes procedures to evaluate bond strength of Symposium, June 1998.
´1
C270−19a
The accepted laboratory means for measuring compressive X1.7.2 Each of the principal constituents of mortar makes a
strength is to test 2 in. (50.8 mm) cubes of mortar. Because the definite contribution to its performance. Portland cement con-
referenced test in this specification is relatively simple, and tributes to strength and durability. Lime, in its hydroxide state,
because it gives consistent, reproducible results, compressive provides workability, water retentivity, and elasticity. Both
strength is considered a basis for assessing the compatibility of portland cement and lime contribute to bond strength. Instead
mortar ingredients. Field testing compressive strength of mor- of portland cement-lime combinations, masonry cement or
tar is accomplished with Test Method C780 using either 2 in. mortar cement is used. Sand acts as a filler and enables the
(50.8 mm) cubes or small cylindrical specimens of mortar. unset mortar to retain its shape and thickness under the weight
of subsequent courses of masonry. Water is the mixing agent
X1.6.3.2 Perhaps because of the previously noted confusion
regarding mortar and concrete, the importance of compressive which gives fluidity and causes cement hydration to take place.
strength of mortar is overemphasized. Compressive strength
X1.7.3 Mortar should be composed of materials which will
should not be the sole criterion for mortar selection. Bond
produce the best combination of mortar properties for the
strength is generally more important, as is good workability
intended service conditions.
and water retentivity, both of which are required for maximum
X1.7.4 Cementitious Materials Based on Hydration—
bond. Flexural strength is also important because it measures
Portland cement, a hydraulic cement, is the principal cemen-
the ability of a mortar to resist cracking. Often overlooked is
titious ingredient in most masonry mortars. Portland cement
the size/shape of mortar joints in that the ultimate compressive
contributes strength to masonry mortar, particularly early
load carrying capacity of a typical ⁄8 in. (9.5 mm) bed joint
strength, which is essential for speed of construction. Straight
will probably be well over twice the value obtained when the
portland cement mortars are not used because they lack
mortar is tested as a 2 in. (50.8 mm) cube. Mortars should
plasticity, have low water retentivity, and are harsh and less
typically be weaker than the masonry units, so that any cracks
workable than portland cement-lime or masonry cement mor-
will occur in the mortar joints where they can more easily be
tars.
repaired.
X1.7.4.1 Masonry cement is a proprietary product usually
X1.6.3.3 Compressive strength of mortar increases with an
containingportlandcementandfines,suchasgroundlimestone
increase in cement content and decreases with an increase in
orothermaterialsinvariousproportions,plusadditivessuchas
lime,sand,wateroraircontent.Retemperingisassociatedwith
air entraining and water repellency agents.
a decrease in mortar compressive strength. The amount of the
X1.7.4.2 Mortar cement is a hydraulic cement similar to
reduction increases with water addition and time between
masonry cement, but the specification for mortar cement
mixing and retempering. It is frequently desirable to sacrifice
requires lower air contents and includes a flexural bond
some compressive strength of the mortar in favor of improved
strength requirement.
bond, consequently retempering within reasonable time limits
is recommended to improve bond.
X1.7.5 Cementitious Materials Based on Carbonation—
Hydrated lime contributes to workability, water retentivity, and
X1.6.4 Durability—Thedurabilityofrelativelydrymasonry
elasticity. Lime mortars carbonate gradually under the influ-
which resists water penetration is not a serious problem. The
ence of carbon dioxide in the air, a process slowed by cold, wet
coupling of mortars with certain masonry units, and design
weather. Because of this, complete hardening occurs very
without exposure considerations, can lead to unit or mortar
slowly over a long period of time. This allows healing, the
durability problems. It is generally conceded that masonry
recementing of small hairline cracks.
walls, heated on one side, will stand many years before
X1.7.5.1 Lime goes into solution when water is present and
requiring maintenance, an indication of mortar’s potential
migrates through the masonry where it can be deposited in
longevity. Parapets, masonry paving, retaining walls, and other
cracks and crevices as water evaporates. This could also cause
masonry exposed to freezing while saturated represent extreme
some leaching, especially at early ages. Successive deposits
exposures and thus require a more durable mortar.
may eventually fill the cracks. Such autogenous healing will
X1.6.4.1 Mortar, when tested in the laboratory for
tend to reduce water permeance.
durability, is subjected to repeated cycles of freezing and
X1.7.5.2 Portland cement will produce approximately 25 %
thawing. Unless a masonry assemblage is allowed to become
of its weight in calcium hydroxide at complete hydration. This
nearly saturated, there is little danger of substantial damage
calcium hydroxide performs the same as lime during
due to freezing. Properly entrained air in masonry mortar
carbonation, solubilizing, and redepositing.
generally increases its resistance to freeze-thaw damage where
extreme exposure (such as repeated cycles of freezing and
X1.7.6 Aggregates—Aggregates for mortar consist of natu-
thawing while saturated with water) exists. Air content within
ralormanufacturedsandandarethelargestvolumeandweight
the specification limits for mortar, however, may be above the
constituent of the mortar. Sand acts as an inert filler, providing
amount required for resistance to freeze-thaw damage. Dura-
economy, workability and reduced shrinkage, while influenc-
bility is adversely affected by oversanded or overtempered
ingcompressivestrength.Anincreaseinsandcontentincreases
mortars as well as use of highly absorbent masonry units.
the setting time of a masonry mortar, but reduces potential
cracking due to shrinkage of the mortar joint. The special or
X1.7 Composition and Its Effect on Properties:
standard sand required for certain laboratory mortar tests may
X1.7.1 Essentially, mortars contain cementitious materials, produce quite different test results from sand that is used in the
aggregate and water. Sometimes admixtures are used also. construction mortar.
´1
C270−19a
X1.7.6.1 Well graded aggregate reduces separation of ma- established by laboratory test under conditions duplicating
terials in plastic mortar, which reduces bleeding and improves their intended use, and experience, that they improve the
workability. Sands deficient in fines produce harsh mortars, masonry.
while sands with excessive fines produce weak mortars and X1.7.8.2 Use of an air entraining admixture, along with the
increase shrinkage. High lime or high air content mortars can limits on air content in a field mortar, still continues to create
carry more sand, even with poorly graded aggregates, and still controversy. Most masonry cements, all Type “A” portland
provide adequate
...