ASTM C91/C91M-23

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C91/C91M − 18 C91/C91M − 23
Standard Specification for
Masonry Cement
This standard is issued under the fixed designation C91/C91M; 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.
1. Scope Scope*
1.1 This specification covers three types of masonry cement for use where mortar for masonry is required.
1.2 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in
each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from
the two systems may result in non-conformance with the standard. Values in SI units shall be obtained by measurement in SI units
or by appropriate conversion, using the Rules for Conversion and Rounding given in Standard IEEE/ASTM SI 10, of
measurements made in other units. Values are stated in only SI units when inch-pound units are not used in practice.
1.3 The text of this standard refers to notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of the standard.
1.4 The following safety hazards caveat pertains only to Sections 1615 and 1716 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. (Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue upon
prolonged exposure.Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to skin and tissue
upon prolonged exposure.))
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:
C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube Specimens)
C151 Test Method for Autoclave Expansion of Hydraulic Cement
C183C183/C183M Practice for Sampling and the Amount of Testing of Hydraulic Cement
C185 Test Method for Air Content of Hydraulic Cement Mortar
C187 Test Method for Amount of Water Required for Normal Consistency of Hydraulic Cement Paste
C188 Test Method for Density of Hydraulic Cement
This specification is under the jurisdiction of ASTM Committee C01 on Cement and is the direct responsibility of Subcommittee C01.11 on Masonry Cement.
Current edition approved March 1, 2018Jan. 1, 2023. Published April 2018January 2023. Originally approved in 1932. Last previous edition approved in 20122018 as
C91/C91M – 12.C91/C91M – 18. DOI: 10.1520/C0091_C0091M-18.10.1520/C0091_C0091M-23.
Annual Book of ASTM Standards, Vol 04.01. See the section on Safety Precautions in the Manual of Cement Testing.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
C91/C91M − 23
C219 Terminology Relating to Hydraulic and Other Inorganic Cements
C266 Test Method for Time of Setting of Hydraulic-Cement Paste by Gillmore Needles
C270 Specification for Mortar for Unit Masonry
C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
C430 Test Method for Fineness of Hydraulic Cement by the 45-μm (No. 325) Sieve
C511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic
Cements and Concretes
C778 Specification for Standard Sand
C1506 Test Method for Water Retention of Hydraulic Cement-Based Mortars and Plasters
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI): The Modern Metric System
3. Terminology
3.1 Definitions:
3.1.1 masonry cement, n—a hydraulic cement, primarily used in masonry and plastering construction, consisting of a mixture of
portland or blended hydraulic cement and plasticizing materials (such as limestone, hydrated or hydraulic lime) together with other
materials introduced to enhance one or more properties such as setting time, workability, water retention, and durability.
3.1.2 Other terms used in this specification are defined in Terminology C219.
4. Classification
4.1 Type N—For use in preparation of Specification C270 Type N mortar without further addition of cements or hydrated lime,
and for use in preparation of Specification C270 Type S or Type M mortar when cement is added in accordance with the
requirements of C270.
4.2 Type S—For use in preparation of Specification C270 Type S mortar without further addition of cements or hydrated lime.
4.3 Type M—For use in preparation of Specification C270 Type M mortar without further addition of cements or hydrated lime.
5. Physical Properties
5.1 Masonry cement shall conform to the applicable requirements prescribed in Table 1 for its classification.
6. Sampling
6.1 The masonry cement shall be sampled in accordance with Practice C183C183/C183M.
TABLE 1 Physical Requirements
Masonry Cement Type N S M
Fineness, residue on a 45-μm (No. 325) sieve, max, % 24 24 24
Fineness, residue on a 45 μm (No. 325) sieve, max, % 24 24 24
Autoclave expansion, max, % 1.0 1.0 1.0
Time of setting, Gillmore method:
Initial set, minutes, not less than 120 90 90
Initial set, minutes, not more than 1000 1000 1000
Compressive strength (average of 3 cubes):
The compressive strength of mortar cubes, composed of 1
part cement and 3 parts blended sand (half graded standard
sand, and half standard 20–30 sand) by volume, prepared and
tested in accordance with this specification shall be equal to or
higher than the values specified for the ages indicated below:
7 days, MPa (psi) 3.4 [500] 9.0 [1300] 12.4 [1800]
28 days, MPa (psi) 6.2 [900] 14.5 [2100] 20.0 [2900]
Air content of mortar, prepared and tested in accordance with
requirements of this specification:
Min, volume % 8 8 8
Max, volume % 21 19 19
Water retention value, min, % of original flow 70 70 70
C91/C91M − 23
7. Temperature and Humidity
7.1 The temperature and relative humidity of the air in the vicinity of the mixing slab and dry materials, molds, base plates, and
mixing bowl shall conform to the requirements of Test Method C109/C109M.
7.2 The moist cabinet or moist room shall conform to the requirements of Specification C511.
8. Fineness
8.1 Determine the residue on the 45-μm45 μm (No. 325) sieve in accordance with Test
...