ASTM C1072-22

Standard Test Methods for Measurement of Masonry Flexural Bond Strength

SIGNIFICANCE AND USE
5.1 This test method is intended for use in comparing the bond strengths (under the given conditions) of masonry mortars.  
5.2 This test method could be used, for example, to check one aspect of the quality of mortar products after production, or to indicate the bond potential of a mortar product without requiring the product to be tested in combination with many different units.  
5.3 This test method uses controlled conditions of fabrication and curing that are not intended to represent field conditions.  
5.4 This test method uses standard concrete masonry units. Mortars are batched by weight equivalents of volume proportions and are mixed to a prescribed flow. Prisms are constructed using a jig and are bag-cured.  
5.5 Flexural bond strength determined by this test method shall not be interpreted as the flexural bond strength of a wall (because standard units are not used for wall construction), nor shall it be interpreted as an indication of extent of bond for purposes of water permeability evaluation.
SCOPE
1.1 These test methods evaluate the flexural bond strength, normal to the bed joints, of masonry built of manufactured masonry units. Sampling and testing procedures are referenced, and terms are defined. Three different specimen fabrication methods are specified, each for a different purpose:  
1.1.1 The first method is the “Test Method for Laboratory-Prepared Specimens.” Its purpose is to compare the bond strengths (under the given conditions) of masonry mortars. It could be used, for example, to check the quality of mortar products after production, or to indicate the bond strength (under the given conditions) of a mortar product without requiring the product to be tested in combination with many different units. It is not intended to represent field conditions. It uses standard concrete masonry units. Mortars are batched by weight equivalents of volume proportions and are mixed to a prescribed flow. Prisms are constructed using a jig and are bag-cured.  
1.1.2 The second method is the “Test Method for Field-Prepared Specimens.” Its purpose is to evaluate the bond strength (under the given conditions) of a particular unit-mortar combination, either for preconstruction evaluation of materials or for quality control purposes during construction. Mortars are batched conventionally, and the flow is not prescribed. Prisms are constructed conventionally (no jig) and are bag-cured.  
1.1.3 The third method is the “Test Method for Prisms Removed from Existing Masonry.” Its purpose is to evaluate the bond strength of unit-mortar combinations of prisms cut from existing walls.  
1.1.4 The three methods are not consistent, nor are they intended to be. They are intended to be used for three different purposes. To make this clear, the three methods are presented separately.  
1.1.5 Appendix X1 suggests two possible criteria for assessing the bond strength values obtained using these test methods. These possible evaluation criteria are given for illustration only and are not mandatory.  
1.2 The text of this standard refers to 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.  
1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered 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 Princip...

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 91.060.10 - Walls. Partitions. Facades
• Technical Committee: C15 - Masonry – Manufactured Masonry Units, Mortars and Grouts
• Drafting Committee: C15.04 - Research for Masonry Units and Assemblies

Relations

• Replaces: ASTM C952-12 - Standard Test Method for Bond Strength of Mortar to Masonry Units (Withdrawn 2018)
• Effective Date: 12-Jan-2018
• Replaces: ASTM C1357-09 - Standard Test Methods for Evaluating Masonry Bond Strength (Withdrawn 2016)
• Effective Date: 06-Jun-2016
• Refers: ASTM C1232-23 - Standard Terminology for Masonry
• Effective Date: 15-Dec-2023
• Refers: ASTM C140/C140M-23a - Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units
• Effective Date: 01-Dec-2023
• Refers: ASTM C1532/C1532M-19a - Standard Practice for Selection, Removal, and Shipment of Manufactured Masonry Units and Masonry Specimens from Existing Construction
• Effective Date: 01-Dec-2019
• Refers: ASTM C67/C67M-19 - Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile
• Effective Date: 01-Jul-2019
• Refers: ASTM C270-19ae1 - Standard Specification for Mortar for Unit Masonry
• Effective Date: 01-May-2019
• Refers: ASTM C1532/C1532M-19 - Standard Practice for Selection, Removal, and Shipment of Manufactured Masonry Units and Masonry Specimens from Existing Construction
• Effective Date: 01-May-2019
• Refers: ASTM C270-19a - Standard Specification for Mortar for Unit Masonry
• Effective Date: 01-May-2019
• Refers: ASTM C270-19 - Standard Specification for Mortar for Unit Masonry
• Effective Date: 01-Feb-2019
• Refers: ASTM C140/C140M-18 - Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units
• Effective Date: 15-Jul-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 C67/C67M-18 - Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile
• Effective Date: 01-Feb-2018
• Refers: ASTM C140/C140M-17b - Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units
• Effective Date: 15-Dec-2017
• Refers: ASTM C780-17 - Standard Test Method for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry
• Effective Date: 01-Jun-2017

Overview

ASTM C1072-22: Standard Test Methods for Measurement of Masonry Flexural Bond Strength provides standardized procedures for determining the flexural bond strength of masonry assemblies. This standard is developed by ASTM International and is widely referenced for the assessment and comparison of bond strength between masonry units and mortar. The test methods outlined in ASTM C1072-22 are crucial for quality control, preconstruction evaluation, and analysis of existing masonry, enabling stakeholders to make informed decisions based on standardized data.

Key Topics

• Flexural Bond Strength: The standard defines methods to measure the tensile strength at the mortar-unit interface under flexural loading, perpendicular to the bed joints.
• Three Distinct Test Methods:
  • Laboratory-Prepared Specimens: Used for comparing the bond strengths of different mortars under controlled conditions, employing standard concrete masonry units and prescribed fabrication, mixing, and curing procedures.
  • Field-Prepared Specimens: Evaluates the bond strength of specific unit-mortar combinations, intended for preconstruction evaluations or on-site quality control, with conventional batching and curing practices closer to field conditions.
  • Prisms Removed from Existing Masonry: Allows assessment of bond strength from samples cut from existing structures, providing insights into the in-situ performance of masonry assemblies.
• Controlled vs. Field Conditions: The test methods highlight the difference between lab-based controlled testing and field-representative sampling, underscoring the impact of material selection, construction practices, and curing on bond performance.
• Reporting and Precision: Detailed guidance is provided for documenting results, including material identification, specimen dimensions, failure modes, and calculation of mean values and standard deviations.

Applications

ASTM C1072-22 is widely used in both research and practice for the following applications:

• Mortar Product Evaluation: Manufacturers and quality assurance professionals use the laboratory-prepared specimen method to assess the bond strength properties of different mortar types, supporting claims of product performance and compliance.
• Preconstruction Material Selection: Designers and contractors employ field-prepared specimen testing to determine the optimal mortar-unit combination before actual construction, helping minimize risks associated with poor bonding.
• Quality Control During Construction: Regular testing of field-prepared specimens ensures that the specified materials and workmanship achieve the desired bond strength, supporting the durability and safety of newly constructed structures.
• Assessment of Existing Structures: Engineering consultants and inspectors utilize the method for prisms removed from existing masonry to evaluate the in-service performance of walls, enabling informed decisions on repair, maintenance, or upgrade needs.
• Regulatory and Specification Compliance: Specifiers, code officials, and regulatory bodies reference ASTM C1072-22 to set minimum requirements for masonry flexural bond strength in project documentation.

Keywords: masonry flexural bond strength, bond wrench, mortar evaluation, standard test method, concrete masonry, field-prepared specimens, laboratory testing, ASTM masonry standards.

Related Standards

Astute use of ASTM C1072-22 may require reference to or integration with related ASTM and industry standards, including:

• ASTM C67/C67M: Test Methods for Sampling and Testing Brick and Structural Clay Tile
• ASTM C140/C140M: Sampling and Testing Concrete Masonry Units
• ASTM C270: Specification for Mortar for Unit Masonry
• ASTM C780: Preconstruction and Construction Evaluation of Mortars
• ASTM C1232: Terminology for Masonry
• ASTM C1437: Flow of Hydraulic Cement Mortar
• ASTM C1532/C1532M: Selection, Removal, and Shipment of Manufactured Masonry Units and Specimens
• TMS 402 / ACI 530 / ASCE 5: Building Code Requirements for Masonry Structures

Familiarity with these standards ensures comprehensive compliance and robust interpretation of test results conducted under ASTM C1072-22.

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Adhering to ASTM C1072-22 empowers construction professionals, engineers, and quality assurance teams to reliably assess and compare masonry bond performance, supporting durable, safe, and code-compliant masonry structures.

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: C1072 − 22
Standard Test Methods for
Measurement of Masonry Flexural Bond Strength
This standard is issued under the fixed designation C1072; 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* Thesepossibleevaluationcriteriaaregivenforillustrationonly
and are not mandatory.
1.1 These test methods evaluate the flexural bond strength,
1.2 The text of this standard refers to notes and footnotes
normal to the bed joints, of masonry built of manufactured
that provide explanatory material. These notes and footnotes
masonryunits.Samplingandtestingproceduresarereferenced,
(excluding those in tables and figures) shall not be considered
and terms are defined. Three different specimen fabrication
as requirements of the standard.
methods are specified, each for a different purpose:
1.1.1 The first method is the “Test Method for Laboratory-
1.3 The values stated in inch-pound units are to be regarded
Prepared Specimens.” Its purpose is to compare the bond
asthestandard.Thevaluesgiveninparenthesesaremathemati-
strengths (under the given conditions) of masonry mortars. It
cal conversions to SI units that are provided for information
could be used, for example, to check the quality of mortar
only and are not considered standard.
products after production, or to indicate the bond strength
1.4 This standard does not purport to address all of the
(under the given conditions) of a mortar product without
safety concerns, if any, associated with its use. It is the
requiring the product to be tested in combination with many
responsibility of the user of this standard to establish appro-
different units. It is not intended to represent field conditions.
priate safety, health, and environmental practices and deter-
It uses standard concrete masonry units. Mortars are batched
mine the applicability of regulatory limitations prior to use.
by weight equivalents of volume proportions and are mixed to
1.5 This international standard was developed in accor-
a prescribed flow. Prisms are constructed using a jig and are
dance with internationally recognized principles on standard-
bag-cured.
ization established in the Decision on Principles for the
1.1.2 The second method is the “Test Method for Field-
Development of International Standards, Guides and Recom-
Prepared Specimens.” Its purpose is to evaluate the bond
mendations issued by the World Trade Organization Technical
strength(underthegivenconditions)ofaparticularunit-mortar
Barriers to Trade (TBT) Committee.
combination, either for preconstruction evaluation of materials
orforqualitycontrolpurposesduringconstruction.Mortarsare
2. Referenced Documents
batched conventionally, and the flow is not prescribed. Prisms
2.1 ASTM Standards:
are constructed conventionally (no jig) and are bag-cured.
C67/C67M Test Methods for Sampling and Testing Brick
1.1.3 The third method is the “Test Method for Prisms
and Structural Clay Tile
Removed from Existing Masonry.” Its purpose is to evaluate
C140/C140M Test Methods for Sampling and Testing Con-
the bond strength of unit-mortar combinations of prisms cut
crete Masonry Units and Related Units
from existing walls.
C230/C230M Specification for Flow Table for Use in Tests
1.1.4 The three methods are not consistent, nor are they
of Hydraulic Cement
intended to be. They are intended to be used for three different
C270 Specification for Mortar for Unit Masonry
purposes. To make this clear, the three methods are presented
C780 Test Method for Preconstruction and Construction
separately.
Evaluation of Mortars for Plain and Reinforced Unit
1.1.5 AppendixX1suggeststwopossiblecriteriaforassess-
Masonry
ing the bond strength values obtained using these test methods.
C1232 Terminology for Masonry
C1437 Test Method for Flow of Hydraulic Cement Mortar
These test methods are under the jurisdiction of ASTM Committee C15 on
Manufactured Masonry Units and are the direct responsibility of Subcommittee
C15.04 on Research. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2022. Published December 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1993. Last previous edition approved in 2019 as C1072 – 19. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C1072-22. 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
C1072 − 22
C1532/C1532M Practice for Selection, Removal, and Ship- 3. Terminology
mentofManufacturedMasonryUnitsandMasonrySpeci-
3.1 Definitions:
mens from Existing Construction
3.1.1 lot, n—material of a given quantity of a single type,
2.2 Other Documents:
grade, class, and brand and practically of the same nominal
TMS 402⁄ACI 530⁄ASCE 5 Building Code Requirements
size, color range, texture, and composition produced by a
for Masonry Structures
single source by virtually the same process and under essen-
NBS Handbook 91
tially the same conditions.
3.2 For additional terms used in this test method, refer to
Available from the Masonry Standards Joint Committee, http://
Terminology C1232.
www.masonrystandards.org.
Natrella, M. G.,Experimental Statistics, National Bureau of Standards Hand-
book 91, U.S. Government Printing Office, Aug. 1, 1963, pp. 2–14.
TEST METHOD FOR LABORATORY-PREPARED SPECIMENS
4. Summary of Test Method
4.1 This test method is for evaluating the flexural bond 6.4 Mechanical Paddle-Type Mortar Mixer, of no less than
strength (under the given conditions) of masonry built of 0.6 ft (18 L) capacity.
standard masonry units. It uses standard concrete masonry
6.5 Flow Table, Flow Mold, and Caliper, conforming to the
units. Mortars are batched by weight equivalents of volume
requirements of Specification C230/C230M.
proportions and are mixed to a prescribed flow. Prisms are
constructed using a jig and are bag-cured. 6.6 Cone Penetrometer, Unit Measure, Straightedge,
Spatula, Tapping Stick, and Spoon, conforming to the require-
NOTE 1—Standard fired clay masonry units are under development but
are not now available. When their development is complete, they will be
ments of Test Method C780.
incorporated into these test methods.
6.7 Bond Strength Test Apparatus, conforming to the re-
quirements of Annex A3.
5. Significance and Use
5.1 This test method is intended for use in comparing the
7. Materials
bond strengths (under the given conditions) of masonry mor-
7.1 Select representative samples of each lot of mortar
tars.
materials. Each sample of material shall be of sufficient
5.2 This test method could be used, for example, to check
quantity to build a set of test prisms. Use standard concrete
oneaspectofthequalityofmortarproductsafterproduction,or
masonry units meeting the requirements of Annex A1.
to indicate the bond potential of a mortar product without
requiring the product to be tested in combination with many 7.2 Mortar materials (including water) shall be at an equi-
different units. librium temperature with laboratory air (see Section 8).
5.3 This test method uses controlled conditions of fabrica-
8. Temperature and Humidity
tion and curing that are not intended to represent field
conditions.
8.1 Maintainthetemperatureoflaboratoryairinthevicinity
of mixing of mortar, fabrication of specimens, curing, and
5.4 This test method uses standard concrete masonry units.
testing of specimens at 75 6 15°F (24 6 8°C).
Mortars are batched by weight equivalents of volume propor-
tions and are mixed to a prescribed flow. Prisms are con-
8.2 Maintain the relative humidity of laboratory air in the
structed using a jig and are bag-cured.
vicinity of mixing of mortar, fabrication of specimens, and
testing of specimens between 30 and 80 %.
5.5 Flexural bond strength determined by this test method
shall not be interpreted as the flexural bond strength of a wall
9. Procedure
(because standard units are not used for wall construction), nor
shall it be interpreted as an indication of extent of bond for
9.1 Fabricate a set of stack-bonded test prisms (any conve-
purposes of water permeability evaluation.
nient number of prisms) containing a total of not less than 15
mortar joints. Each prism shall have no more than 5 joints.
6. Apparatus
9.1.1 Proportion mortar materials by weights equivalent to
volume proportions to be used in prism construction. Use unit
6.1 Prism Alignment Jig, as described in Annex A2 and
weights for individual materials as given in Specification
shown in Fig. A2.1.
C270. Sand shall be permitted to be used in a damp loose
6.2 Mortar Joint Template, as described in Annex A2 and
condition,providedthatmoisturecontentofsandisdetermined
shown in Fig. A2.2.
with reference to the oven-dried condition and batch propor-
6.3 Drop Hammer, as described in Annex A2 and shown in tions are adjusted accordingly. Record weight of ingredients
Fig. A2.3. (including water) added to the batch of mortar.
C1072 − 22
9.1.2 Mix mortar in a mechanical paddle-type mortar mixer. 10.1.3 Include the following in the report:
Time periods referenced below are measured from when water 10.1.3.1 Weight of ingredients (including water) added to
and cementitious materials are combined. the batch of mortar.
9.1.2.1 For standard concrete masonry units, add an esti- 10.1.3.2 Flow or cone penetrometer reading of mortar used
mated amount of water to the mortar to achieve a flow of 127 to construct prisms.
6 3 determined in accordance with Test Method C1437. Mix 10.1.3.3 Flexural bond strength test results for each joint of
mortar for 3 min and determine flow. Once flow is recorded, the test specimens. Mean, standard deviation, and test age for
return the material used to measure flow to the mixer. If the each set of test specimens to the nearest psi.
flow is 127 6 3, continue mixing the batch for an additional 2 10.1.3.4 If one or more mortar joints break during the
min.Iftheflowislessthan124,addwatertothebatch,mixfor handling of the specimen and tightening of the loading clamps
1 min, and determine flow. Once flow is recorded, return the but before additional load is applied by the testing apparatus,
material used to measure flow to the mixer. If the flow is 127 report which joints broke prematurely but do not include them
6 3, continue mixing the batch for 1 min. in the calculation of the flexural tensile strength average and
9.1.2.2 If after the one-time addition of water the flow is not standard deviation. The top mortar joint shall be designated
127 6 3, discard the batch. joint Number 1, the second, Number 2, etc. Measured loads
9.1.2.3 If the measured flow exceeds 130 at any time, and calculations shall also be included.
discard the batch. 10.1.3.5 Description of failure, especially indicating
9.1.3 Immediately after mixing the mortar, determine its whether failure occurred at the top or bottom of the mortar
initial cone penetration in accordance with Test Method C780. joint, or both.
Determine the cone penetration of the mortar every 15 6 5
11. Precision and Bias
min. If the cone penetration is less than 80 % of its initial
value, discard the remaining portion of the mortar without
11.1 Precision—Published data are not available for within-
constructing additional mortar joints. laboratory variability of this test method. Published data
5 6
9.1.4 Use standard concrete masonry units as defined in
(Hedstrom, Melander ) obtained under conditions almost
AnnexA1. Clean the bed surface of units of dirt, loose sand, or identical with those of this test method show within-batch
other contaminants.
coefficients of variation varying between 10 % and 25 % for
9.1.5 Fabricate prism specimens as described in Annex A2. 30-joint samples of selected portland cement-lime mortars and
9.1.6 Cure prism specimens in accordance with Annex A2.
masonry cement mortars. Because only one sample of each
mortar was tested in each laboratory, sufficient data are not
9.2 Conduct bond-wrench tests on prism specimens.
available to establish repeatability for this test method. Inter-
9.2.1 Test the prisms in the same facility where they were
laboratory testing is now planned to determine the reproduc-
built.
ibility of this test method. It is the intent of this committee to
9.2.2 Test masonry prisms in accordance with Annex A3.
develop precision values within five years from the date of
Determine the flexural tensile strength of each mortar joint
issuance of this test method.
tested, as described in Annex A3.
11.2 Bias—No information can be presented on the bias of
NOTE 2—When test ages other than 28 days are specified, the general
this test method because no test having an accepted reference
relationship between the strength at the specified test age and that at 28
days is generally established by test. That relationship may vary with value is available.
different materials and curing conditions.
10. Report
10.1 Report the following information:
Hedstrom, E. G., Tarhini, K. M., Thomas, R. D., Dubovoy, V. S., Klingner, R.
10.1.1 Identify mortar materials and units tested, including
E., and Cook, R. A., “Flexural Bond Strength of Concrete Masonry Prisms Using
as applicable the manufacturer’s name, brand name, type,
PortlandCementandHydratedLimeMortars,” Masonry Society Journal,Vol9,No.
2, February 1991.
grade, source of sample, date sampled, and date tested.
Melander, J. M., Ghosh, S. K., Dubovoy, V. S., Hedstrom, E. G., and Klingner,
10.1.2 List unit and prism dimensions to the nearest 0.05 in.
R.E.,“FlexuralBondStrengthofConcreteMasonryPrismsUsingMasonryCement
(1.0 mm), number of joints per prism, and number of prisms
Mortars,” Masonry: Design and Construction, Problems and Repair, ASTM STP
per set of specimens and prism weight. 1180, ASTM, 1993.
TEST METHOD FOR FIELD-PREPARED SPECIMENS
12. Summary of Test Method
12.1 This test method is for evaluating the flexural bond conventionally, and their flow is not prescribed. Prisms are
strength (under the given conditions) of masonry built of constructed conventionally (no jig) and are bag-cured.
conventional masonry units. Mortars are batched
C1072 − 22
reading of 65 6 5 mm or a flow of 135 6 5 %. Optimum consistency for
13. Significance and Use
a specific mortar-unit combination may differ from these values.
13.1 This test method is intended for evaluation of flexural
16.2 Fabricate a set of any convenient number of stack-
bond strength (under the given conditions) between mortar and
bonded prisms, containing a total of at least 15 mortar joints.
units.
Each prism shall have no more than 5 joints and a minimum
13.2 The purpose of this test method is to evaluate the bond
width (b) of 3.5 in. (see Note 4). Do not fabricate more prism
strength(underthegivenconditions)ofaparticularunit-mortar
specimens than can be constructed within 30 min.
combination, either for preconstruction evaluation of materials
NOTE 4—It is recommended that a width (b) of 1 full masonry unit be
or for quality control purposes during construction. Precon-
used. When conducting construction field tests for quality control, one set
struction field tests may be used to provide information on the
of test prisms for each 5000 ft of masonry in the structure has been
potential performance of a mortar-unit combination under field
traditionally specified.
conditions of fabrication and workmanship (but not curing).
16.2.1 Sample and test mortar in accordance with Test
Construction field tests may be used as a quality control
Method C780 to determine initial consistency by cone pen-
measure to ensure that performance criteria established in
etrometer or flow table and air content.
preconstruction tests are being met.
16.2.2 Clean the bed surface of the units of dirt, loose sand,
13.3 Flexural bond strength determined by this test method
orothercontaminants.Sampleandtestclayunitsinaccordance
shall not be interpreted as the flexural bond strength of a wall
with Test Methods C67/C67M to determine initial rate of
constructed of the same material, nor shall it be interpreted as
absorption (Field Test).
an indication of extent of bond for purposes of water perme-
16.2.3 Keep handling of the prisms to a minimum and
ability evaluation. However, if effects of construction
handle in such a way that the joints will not be subjected to
conditions,specimensize,workmanship,andcuringconditions
detrimental tensile stresses.
are taken into account, the results may be used to estimate the
16.2.4 Set the first unit of each prism on a firm, horizontal
flexural strength of a wall.
surface without the use of mortar.
14. Apparatus
NOTE 5—An alignment device may be used to ensure plumbness and
14.1 Mechanical Paddle-Type Mortar Mixer, of no less than joint thickness uniformity.
0.6 ft (18 L) capacity.
16.2.5 Place a full or face shell mortar bed on all units
14.2 Cone Penetrometer, Unit Measure, Straightedge, without furrowing unless the effect of furrowing is being
Spatula, Tapping Stick, and Spoon, conforming to the require- studied.
ments of Test Method C780.
16.2.6 Immediately place the next unit on the mortar bed
and tap it to proper level and joint thickness. One face of each
14.3 Bond Strength Test Apparatus, conforming to the
prism shall be in a nearly true plane.
requirements of Annex A3.
16.2.7 Repeat 16.2.5 and 16.2.6 until the prisms are the
15. Sampling
desired height. Identify all specimens using a water-resistant
marker.
15.1 Select representative samples of each lot of masonry
16.2.8 Depending upon the desired test conditions, strike
materials intended for use in construction. Each sample of
flush or tool the mortar joints. If tooling is required, tool only
material shall be of sufficient quantity to build a set of test
the joints on one face of each prism.
prisms.Alot of each material shall consist of not less than the
following quantities: 16.2.9 Unless specified otherwise, construct specimens in
an open moisture-tight bag large enough to contain the com-
15.1.1 4000 of each type of masonry unit,
15.1.2 15 bags of each type of cement (or the equivalent pleted prism (see Annex A2). After fabrication, draw and seal
the bag around the specimen and cure for 28 days. Record and
bulk quantity),
15.1.3 15 bags of lime (or the equivalent bulk quantity), report the daily high and low temperatures in the area where
specimens are stored for curing. If other curing conditions (for
15.1.4 3 yd of sand, and
15.1.5 If mortar is delivered in bulk, 3 yd of mortar. example, no moisture-tight bag) are specified, record and
report all details of the curing.
16. Procedure
NOTE 6—Workmanship during fabrication, temperature of the materials
16.1 Prepare and mix mortar in accordance with the con-
during fabrication, curing conditions, time between removal from moist
struction contract specifications. If no construction contract
curing test, and other factors may affect the bond strengths measured by
thistest.Standardizedspecimenfabricationcuringproceduresthatattempt
specifications exist, use the mortar preparation procedures of
to control these variables are prescribed in the Test Method for
Test Method C780, modifying them as appropriate when
Laboratory-Prepared Specimens, above.
proprietary materials are added to the mortar or when pre-
16.2.10 Do not disturb or move specimens for the first 48 h
batched materials are used. Use sufficient water to achieve
after construction. Unless specified otherwise, keep specimens
optimum workability.
in the moisture-tight bags. Keep specimens at essentially the
NOTE 3—Workable consistency of mortar for concrete masonry con-
same temperatures as those experienced by the masonry that
struction generally requires an initial cone penetration reading of 55 6 5
the specimens are intended to represent. At 24 6 4 h prior to
mm or a flow of 125 6 5 %. Workable consistency of mortar for clay
masonry construction generally requires an initial cone penetration testage,removebagandplacespecimensinlaboratoryairwith
C1072 − 22
atemperatureof75 6 15°F(24 68°C)andarelativehumidity 17.1.7 Sketch or photo of masonry unit showing core
between 20 % and 80 %. configuration and mortar bedded area, full or face shell.
17.1.8 Description of bonding pattern, joint tooling, loca-
NOTE 7—Carefully package prisms and transport them to a laboratory
tion of tooled joint during test, and joint thickness.
in accordance with Practice C1532/C1532M for testing.
17.2 Include the following in the report of preconstruction
16.2.11 If specimens are transported for testing, strap them
evaluation and construction field test results:
tightly first. Prepare plywood boards at least ⁄4-in. thick, cut to
17.2.1 Volumeproportionsofmortaringredientsusedintest
thesizeofthebedareaoftheunit.Placetheseboardsunderthe
mortar batch. Note whether mortar was prepared under the
bottom unit and on the top unit of the prism prior to strapping.
proportion or the property specification requirements of Speci-
During transport, cushion the specimens from vibration and
fication C270.
from direct contact with each other.
17.2.2 Whether report is of preconstruction evaluation test
16.2.12 Test specimens at an age of 28 days unless other-
or construction field tests. If field tests, identify building area
wise specified. Do not test specimens at an age of less than 3
represented by set of specimens.
days.
17.2.3 Length of mixing time, time at which mixing was
16.3 Testing Specimens—Test masonry prisms in accor- completed, and time at which specimen fabrication was com-
dance with the requirements of Annex A3 except as otherwise pleted.
provided in this test method. Determine the flexural tensile 17.2.4 Initial consistency as determined by flow or cone
strength of each mortar joint tested, as described in AnnexA3. penetration, mortar water content, mortar aggregate ratio, air
content and compressive strength determined in accordance
NOTE 8—When test ages other than 28 days are specified, the general
with Test Method C780.
relationship between the strength at the specified test age and that at 28
17.2.5 Initial rate of absorption (Field Test) of fired clay
days is generally established by test. That relationship may vary with
different materials and curing conditions. masonry units, as determined in accordance withTest Methods
C67/C67M.
17. Report 17.2.6 Ambient temperature and humidity at time speci-
mens were fabricated.
17.1 Report the following information:
17.2.7 Daily high and low temperatures in area where
17.1.1 Identify mortar materials and units tested, including
specimens were stored for curing.
as applicable the manufacturer’s name, brand name, type,
17.2.8 Date and time when curing bags were removed from
grade, source of sample, date sampled, and date tested.
specimens.
17.1.2 List number of prisms per set of specimens, number
17.2.9 Description of strapping procedure, if applicable.
of joints per prism, unit dimensions, and joint thicknesses.
17.2.10 Date and time specimens were delivered to
17.1.3 Average prism dimensions to the nearest 0.05 in. (1.0
laboratory, if applicable.
mm) including width, depth, and height.
17.2.11 Condition of specimens as received from transport,
17.1.4 Weight of specimen, lbf (N).
if applicable.
17.1.5 Individual and average gross or net area flexural 17.2.12 Length of time specimens were exposed to labora-
tensile stress calculated to the nearest psi (MPa), standard
tory air prior to testing.
deviation, and position of the joint tested within the specimen.
18. Precision and Bias
If one or more mortar joints break during the handling of the
18.1 Precision—Because this test method can be applied to
specimen and tightening of the loading clamps but before
many different combinations of units and mortar, and because
additionalloadisappliedbythetestingapparatus,reportwhich
workmanship is not controlled in fabricating field-prepared
joints broke prematurely but do not include them in the
specimens, it is not possible to establish repeatability and
calculation of the flexural tensile strength average and standard
reproducibility values that would be universally correct.
deviation. The top mortar joint shall be designated joint
Number 1, the second, Number 2, etc. Measured loads and
18.2 Bias—No information can be presented on the bias of
calculation shall also be included.
this test method because no test having an accepted reference
17.1.6 Description of failure, especially indicating whether value is available.
failure occurred at the top or bottom of the mortar joint, or
both.
C1072 − 22
TEST METHOD FOR SAMPLES OBTAINED FROM EXISTING MASONRY
19. Summary of Test Method
19.1 This test method is for evaluating the flexural bond 23. Procedure
strength of masonry assemblies removed from existing ma-
23.1 Test masonry assemblies in accordance with the re-
sonry.
quirements o
...

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: C1072 − 19 C1072 − 22
Standard Test Methods for
Measurement of Masonry Flexural Bond Strength
This standard is issued under the fixed designation C1072; 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*
1.1 These test methods evaluate the flexural bond strength, normal to the bed joints, of masonry built of manufactured masonry
units. Sampling and testing procedures are referenced, and terms are defined. Three different specimen fabrication methods are
specified, each for a different purpose:
1.1.1 The first method is the “Test Method for Laboratory-Prepared Specimens.” Its purpose is to compare the bond strengths
(under the given conditions) of masonry mortars. It could be used, for example, to check the quality of mortar products after
production, or to indicate the bond strength (under the given conditions) of a mortar product without requiring the product to be
tested in combination with many different units. It is not intended to represent field conditions. It uses standard concrete masonry
units. Mortars are batched by weight equivalents of volume proportions and are mixed to a prescribed flow. Prisms are constructed
using a jig and are bag-cured.
1.1.2 The second method is the “Test Method for Field-Prepared Specimens.” Its purpose is to evaluate the bond strength (under
the given conditions) of a particular unit-mortar combination, either for preconstruction evaluation of materials or for quality
control purposes during construction. Mortars are batched conventionally, and the flow is not prescribed. Prisms are constructed
conventionally (no jig) and are bag-cured.
1.1.3 The third method is the “Test Method for Prisms Removed from Existing Masonry.” Its purpose is to evaluate the bond
strength of unit-mortar combinations of prisms cut from existing walls.
1.1.4 The three methods are not consistent, nor are they intended to be. They are intended to be used for three different purposes.
To make this clear, the three methods are presented separately.
1.1.5 Appendix X1 suggests two possible criteria for assessing the bond strength values obtained using these test methods. These
possible evaluation criteria are given for illustration only and are not mandatory.
1.2 The text of this standard refers to 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.
1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
These test methods are under the jurisdiction of ASTM Committee C15 on Manufactured Masonry Units and are the direct responsibility of Subcommittee C15.04 on
Research.
Current edition approved Dec. 1, 2019Dec. 1, 2022. Published December 2019December 2022. Originally approved in 1993. Last previous edition approved in 20132019
ɛ1
as C1072 – 13C1072 . – 19. DOI: 10.1520/C1072-19.10.1520/C1072-22.
*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
C1072 − 22
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C67/C67M Test Methods for Sampling and Testing Brick and Structural Clay Tile
C140/C140M Test Methods for Sampling and Testing Concrete Masonry Units and Related Units
C230/C230M Specification for Flow Table for Use in Tests of Hydraulic Cement
C270 Specification for Mortar for Unit Masonry
C780 Test Method for Preconstruction and Construction Evaluation of Mortars for Plain and Reinforced Unit Masonry
C1232 Terminology for Masonry
C1437 Test Method for Flow of Hydraulic Cement Mortar
C1532/C1532M Practice for Selection, Removal, and Shipment of Manufactured Masonry Units and Masonry Specimens from
Existing Construction
2.2 Other Documents:
TMS 402 ⁄ACI 530 ⁄ASCE 5 Building Code Requirements for Masonry Structures
NBS Handbook 91
3. Terminology
3.1 Definitions:
3.1.1 lot, n—material of a given quantity of a single type, grade, class, and brand and practically of the same nominal size, color
range, texture, and composition produced by a single source by virtually the same process and under essentially the same
conditions.
3.2 For additional terms used in this test method, refer to Terminology C1232.
TEST METHOD FOR LABORATORY-PREPARED SPECIMENS
4. Summary of Test Method
4.1 This test method is for evaluating the flexural bond strength (under the given conditions) of masonry built of standard masonry
units. It uses standard concrete masonry units. Mortars are batched by weight equivalents of volume proportions and are mixed
to a prescribed flow. Prisms are constructed using a jig and are bag-cured.
NOTE 1—Standard fired clay masonry units are under development but are not now available. When their development is complete, they will be
incorporated into these test methods.
5. Significance and Use
5.1 This test method is intended for use in comparing the bond strengths (under the given conditions) of masonry mortars.
5.2 This test method could be used, for example, to check one aspect of the quality of mortar products after production, or to
indicate the bond potential of a mortar product without requiring the product to be tested in combination with many different units.
5.3 This test method uses controlled conditions of fabrication and curing that are not intended to represent field conditions.
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.
Available from the Masonry Standards Joint Committee, http://www.masonrystandards.org.
Natrella, M. G.,Experimental Statistics, National Bureau of Standards Handbook 91, U.S. Government Printing Office, Aug. 1, 1963, pp. 2–14.
C1072 − 22
5.4 This test method uses standard concrete masonry units. Mortars are batched by weight equivalents of volume proportions and
are mixed to a prescribed flow. Prisms are constructed using a jig and are bag-cured.
5.5 Flexural bond strength determined by this test method shall not be interpreted as the flexural bond strength of a wall (because
standard units are not used for wall construction), nor shall it be interpreted as an indication of extent of bond for purposes of water
permeability evaluation.
6. Apparatus
6.1 Prism Alignment Jig, as described in Annex A2 and shown in Fig. A2.1.
6.2 Mortar Joint Template, as described in Annex A2 and shown in Fig. A2.2.
6.3 Drop Hammer, as described in Annex A2 and shown in Fig. A2.3.
6.4 Mechanical Paddle-Type Mortar Mixer, of no less than 0.6 ft (18 L) capacity.
6.5 Flow Table, Flow Mold, and Caliper, conforming to the requirements of Specification C230/C230M.
6.6 Cone Penetrometer, Unit Measure, Straightedge, Spatula, Tapping Stick, and Spoon, conforming to the requirements of Test
Method C780.
6.7 Bond Strength Test Apparatus, conforming to the requirements of Annex A3.
7. Materials
7.1 Select representative samples of each lot of mortar materials. Each sample of material shall be of sufficient quantity to build
a set of test prisms. Use standard concrete masonry units meeting the requirements of Annex A1.
7.2 Mortar materials (including water) shall be at an equilibrium temperature with laboratory air (see Section 8).
8. Temperature and Humidity
8.1 Maintain the temperature of laboratory air in the vicinity of mixing of mortar, fabrication of specimens, curing, and testing
of specimens at 75 6 15°F (24 6 8°C).
8.2 Maintain the relative humidity of laboratory air in the vicinity of mixing of mortar, fabrication of specimens, and testing of
specimens between 30 and 80 %.
9. Procedure
9.1 Fabricate a set of stack-bonded test prisms (any convenient number of prisms) containing a total of not less than 15 mortar
joints. Each prism shall have no more than 5 joints.
9.1.1 Proportion mortar materials by weights equivalent to volume proportions to be used in prism construction. Use unit weights
for individual materials as given in Specification C270. Sand shall be permitted to be used in a damp loose condition, provided
that moisture content of sand is determined with reference to the oven-dried condition and batch proportions are adjusted
accordingly. Record weight of ingredients (including water) added to the batch of mortar.
9.1.2 Mix mortar in a mechanical paddle-type mortar mixer. Time periods referenced below are measured from when water and
cementitious materials are combined.
9.1.2.1 For standard concrete masonry units, add an estimated amount of water to the mortar to achieve a flow of 127 6 3
determined in accordance with Test Method C1437. Mix mortar for 3 min and determine flow. Once flow is recorded, return the
C1072 − 22
material used to measure flow to the mixer. If the flow is 127 6 3, continue mixing the batch for an additional 2 min. If the flow
is less than 124, add water to the batch, mix for 1 min, and determine flow. Once flow is recorded, return the material used to
measure flow to the mixer. If the flow is 127 6 3, continue mixing the batch for 1 min.
9.1.2.2 If after the one-time addition of water the flow is not 127 6 3, discard the batch.
9.1.2.3 If the measured flow exceeds 130 at any time, discard the batch.
9.1.3 Immediately after mixing the mortar, determine its initial cone penetration in accordance with Test Method C780. Determine
the cone penetration of the mortar every 15 6 5 min. If the cone penetration is less than 80 % of its initial value, discard the
remaining portion of the mortar without constructing additional mortar joints.
9.1.4 Use standard concrete masonry units as defined in Annex A1. Clean the bed surface of units of dirt, loose sand, or other
contaminants.
9.1.5 Fabricate prism specimens as described in Annex A2.
9.1.6 Cure prism specimens in accordance with Annex A2.
9.2 Conduct bond-wrench tests on prism specimens.
9.2.1 Test the prisms in the same facility where they were built.
9.2.2 Test masonry prisms in accordance with Annex A3. Determine the flexural tensile strength of each mortar joint tested, as
described in Annex A3.
NOTE 2—When test ages other than 28 days are specified, the general relationship between the strength at the specified test age and that at 28 days is
generally established by test. That relationship may vary with different materials and curing conditions.
10. Report
10.1 Report the following information:
10.1.1 Identify mortar materials and units tested, including as applicable the manufacturer’s name, brand name, type, grade, source
of sample, date sampled, and date tested.
10.1.2 List unit and prism dimensions to the nearest 0.05 in. (1.0 mm), number of joints per prism, and number of prisms per set
of specimens and prism weight.
10.1.3 Include the following in the report:
10.1.3.1 Weight of ingredients (including water) added to the batch of mortar.
10.1.3.2 Flow or cone penetrometer reading of mortar used to construct prisms.
10.1.3.3 Flexural bond strength test results for each joint of the test specimens. Mean, standard deviation, and test age for each
set of test specimens to the nearest psi.
10.1.3.4 If one or more mortar joints break during the handling of the specimen and tightening of the loading clamps but before
additional load is applied by the testing apparatus, report which joints broke prematurely but do not include them in the calculation
of the flexural tensile strength average and standard deviation. The top mortar joint shall be designated joint Number 1, the second,
Number 2, etc. Measured loads and calculations shall also be included.
10.1.3.5 Description of failure, especially indicating whether failure occurred at the top or bottom of the mortar joint, or both.
C1072 − 22
11. Precision and Bias
11.1 Precision—Published data are not available for within-laboratory variability of this test method. Published data (Hedstrom,
Melander ) obtained under conditions almost identical with those of this test method show within-batch coefficients of variation
varying between 10 % and 25 % for 30-joint samples of selected portland cement-lime mortars and masonry cement mortars.
Because only one sample of each mortar was tested in each laboratory, sufficient data are not available to establish repeatability
for this test method. Inter-laboratory testing is now planned to determine the reproducibility of this test method. It is the intent of
this committee to develop precision values within five years from the date of issuance of this test method.
11.2 Bias—No information can be presented on the bias of this test method because no test having an accepted reference value
is available.
TEST METHOD FOR FIELD-PREPARED SPECIMENS
12. Summary of Test Method
12.1 This test method is for evaluating the flexural bond strength (under the given conditions) of masonry built of conventional
masonry units. Mortars are batched conventionally, and their flow is not prescribed. Prisms are constructed conventionally (no jig)
and are bag-cured.
13. Significance and Use
13.1 This test method is intended for evaluation of flexural bond strength (under the given conditions) between mortar and units.
13.2 The purpose of this test method is to evaluate the bond strength (under the given conditions) of a particular unit-mortar
combination, either for preconstruction evaluation of materials or for quality control purposes during construction. Preconstruction
field tests may be used to provide information on the potential performance of a mortar-unit combination under field conditions
of fabrication and workmanship (but not curing). Construction field tests may be used as a quality control measure to ensure that
performance criteria established in preconstruction tests are being met.
13.3 Flexural bond strength determined by this test method shall not be interpreted as the flexural bond strength of a wall
constructed of the same material, nor shall it be interpreted as an indication of extent of bond for purposes of water permeability
evaluation. However, if effects of construction conditions, specimen size, workmanship, and curing conditions are taken into
account, the results may be used to estimate the flexural strength of a wall.
14. Apparatus
14.1 Mechanical Paddle-Type Mortar Mixer, of no less than 0.6 ft (18 L) capacity.
14.2 Cone Penetrometer, Unit Measure, Straightedge, Spatula, Tapping Stick, and Spoon, conforming to the requirements of Test
Method C780.
14.3 Bond Strength Test Apparatus, conforming to the requirements of Annex A3.
15. Sampling
15.1 Select representative samples of each lot of masonry materials intended for use in construction. Each sample of material shall
be of sufficient quantity to build a set of test prisms. A lot of each material shall consist of not less than the following quantities:
15.1.1 4000 of each type of masonry unit,
Hedstrom, E. G., Tarhini, K. M., Thomas, R. D., Dubovoy, V. S., Klingner, R. E., and Cook, R. A., “Flexural“Flexural Bond Strength of Concrete Masonry Prisms Using
Portland Cement and Hydrated Lime Mortars Bond Strength of Concrete Masonry Prisms Using Portland Cement and Hydrated Lime Mortars,” ,” Masonry Society Journal,
Vol 9, No. 2, February 1991.
Melander, J. M., Ghosh, S. K., Dubovoy, V. S., Hedstrom, E. G., and Klingner, R. E., “Flexural“Flexural Bond Strength of Concrete Masonry Prisms Using Masonry
Cement Mortars Bond Strength of Concrete Masonry Prisms Using Masonry Cement Mortars,” ,” Masonry: Design and Construction, Problems and Repair, ASTM STP 1180,
ASTM, 1993.
C1072 − 22
15.1.2 15 bags of each type of cement (or the equivalent bulk quantity),
15.1.3 15 bags of lime (or the equivalent bulk quantity),
15.1.4 3 yd of sand, and
15.1.5 If mortar is delivered in bulk, 3 yd of mortar.
16. Procedure
16.1 Prepare and mix mortar in accordance with the construction contract specifications. If no construction contract specifications
exist, use the mortar preparation procedures of Test Method C780, modifying them as appropriate when proprietary materials are
added to the mortar or when pre-batched materials are used. Use sufficient water to achieve optimum workability.
NOTE 3—Workable consistency of mortar for concrete masonry construction generally requires an initial cone penetration reading of 55 6 5 mm or a
flow of 125 6 5 %. Workable consistency of mortar for clay masonry construction generally requires an initial cone penetration reading of 65 6 5 mm
or a flow of 135 6 5 %. Optimum consistency for a specific mortar-unit combination may differ from these values.
16.2 Fabricate a set of any convenient number of stack-bonded prisms, containing a total of at least 15 mortar joints. Each prism
shall have no more than 5 joints and a minimum width (b) of 3.5 in. (see Note 4). Do not fabricate more prism specimens than
can be constructed within 30 min.
NOTE 4—It is recommended that a width (b) of 1 full masonry unit be used. When conducting construction field tests for quality control, one set of test
prisms for each 5000 ft of masonry in the structure has been traditionally specified.
16.2.1 Sample and test mortar in accordance with Test Method C780 to determine initial consistency by cone penetrometer or flow
table and air content.
16.2.2 Clean the bed surface of the units of dirt, loose sand, or other contaminants. Sample and test clay units in accordance with
Test Methods C67/C67M to determine initial rate of absorption (Field Test).
16.2.3 Keep handling of the prisms to a minimum and handle in such a way that the joints will not be subjected to detrimental
tensile stresses.
16.2.4 Set the first unit of each prism on a firm, horizontal surface without the use of mortar.
NOTE 5—An alignment device may be used to ensure plumbness and joint thickness uniformity.
NOTE 5—An alignment device may be used to ensure plumbness and joint thickness uniformity.
16.2.5 Place a full or face shell mortar bed on all units without furrowing unless the effect of furrowing is being studied.
16.2.6 Immediately place the next unit on the mortar bed and tap it to proper level and joint thickness. One face of each prism
shall be in a nearly true plane.
16.2.7 Repeat 16.2.5 and 16.2.6 until the prisms are the desired height. Identify all specimens using a water-resistant marker.
16.2.8 Depending upon the desired test conditions, strike flush or tool the mortar joints. If tooling is required, tool only the joints
on one face of each prism.
16.2.9 Unless specified otherwise, construct specimens in an open moisture-tight bag large enough to contain the completed prism
(see Annex A2). After fabrication, draw and seal the bag around the specimen and cure for 28 days. Record and report the daily
high and low temperatures in the area where specimens are stored for curing. If other curing conditions (for example, no
moisture-tight bag) are specified, record and report all details of the curing.
NOTE 6—Workmanship during fabrication, temperature of the materials during fabrication, curing conditions, time between removal from moist curing
C1072 − 22
test, and other factors may affect the bond strengths measured by this test. Standardized specimen fabrication curing procedures that attempt to control
these variables are prescribed in the Test Method for Laboratory-Prepared Specimens, above.
NOTE 6—Workmanship during fabrication, temperature of the materials during fabrication, curing conditions, time between removal from moist curing
test, and other factors may affect the bond strengths measured by this test. Standardized specimen fabrication curing procedures that attempt to control
these variables are prescribed in the Test Method for Laboratory-Prepared Specimens, above.
16.2.10 Do not disturb or move specimens for the first 48 h after construction. Unless specified otherwise, keep specimens in the
moisture-tight bags. Keep specimens at essentially the same temperatures as those experienced by the masonry that the specimens
are intended to represent. At 24 6 4 h prior to test age, remove bag and place specimens in laboratory air with a temperature of
75 6 15°F 6 15°F (24 6 8°C) and a relative humidity between 20 % and 80 %.
NOTE 7—Carefully package prisms and transport them to a laboratory in accordance with Practice C1532/C1532M for testing.
NOTE 7—Carefully package prisms and transport them to a laboratory in accordance with Practice C1532/C1532M for testing.
16.2.11 If specimens are transported for testing, strap them tightly first. Prepare plywood boards at least ⁄4-in. thick, cut to the
size of the bed area of the unit. Place these boards under the bottom unit and on the top unit of the prism prior to strapping. During
transport, cushion the specimens from vibration and from direct contact with each other.
16.2.12 Test specimens at an age of 28 days unless otherwise specified. Do not test specimens at an age of less than 3 days.
16.3 Testing Specimens—Test masonry prisms in accordance with the requirements of Annex A3 except as otherwise provided in
this test method. Determine the flexural tensile strength of each mortar joint tested, as described in Annex A3.
NOTE 8—When test ages other than 28 days are specified, the general relationship between the strength at the specified test age and that at 28 days is
generally established by test. That relationship may vary with different materials and curing conditions.
NOTE 8—When test ages other than 28 days are specified, the general relationship between the strength at the specified test age and that at 28 days is
generally established by test. That relationship may vary with different materials and curing conditions.
17. Report
17.1 Report the following information:
17.1.1 Identify mortar materials and units tested, including as applicable the manufacturer’s name, brand name, type, grade, source
of sample, date sampled, and date tested.
17.1.2 List number of prisms per set of specimens, number of joints per prism, unit dimensions, and joint thicknesses.
17.1.3 Average prism dimensions to the nearest 0.05 in. (1.0 mm) including width, depth, and height.
17.1.4 Weight of specimen, lbf (N).
17.1.5 Individual and average gross or net area flexural tensile stress calculated to the nearest psi (MPa), standard deviation, and
position of the joint tested within the specimen. If one or more mortar joints break during the handling of the specimen and
tightening of the loading clamps but before additional load is applied by the testing apparatus, report which joints broke
prematurely but do not include them in the calculation of the flexural tensile strength average and standard deviation. The top
mortar joint shall be designated joint Number 1, the second, Number 2, etc. Measured loads and calculation shall also be included.
17.1.6 Description of failure, especially indicating whether failure occurred at the top or bottom of the mortar joint, or both.
17.1.7 Sketch or photo of masonry unit showing core configuration and mortar bedded area, full or face shell.
17.1.8 Description of bonding pattern, joint tooling, location of tooled joint during test, and joint thickness.
17.2 Include the following in the report of preconstruction evaluation and construction field test results:
C1072 − 22
17.2.1 Volume proportions of mortar ingredients used in test mortar batch. Note whether mortar was prepared under the proportion
or the property specification requirements of Specification C270.
17.2.2 Whether report is of preconstruction evaluation test or construction field tests. If field tests, identify building area
represented by set of specimens.
17.2.3 Length of mixing time, time at which mixing was completed, and time at which specimen fabrication was completed.
17.2.4 Initial consistency as determined by flow or cone penetration, mortar water content, mortar aggregate ratio, air content and
compressive strength determined in accordance with Test Method C780.
17.2.5 Initial rate of absorption (Field Test) of fired clay masonry units, as determined in accordance with Test Methods
C67/C67M.
17.2.6 Ambient temperature and humidity at time specimens were fabricated.
17.2.7 Daily high and low temperatures in area where specimens were stored for curing.
17.2.8 Date and time when curing bags were removed from specimens.
17.2.9 Description of strapping procedure, if applicable.
17.2.10 Date and time specimens were delivered to laboratory, if applicable.
17.2.11 Condition of specimens as received from transport, if applicable.
17.2.12 Length of time specimens were exposed to laboratory air prior to testing.
18. Precision and Bias
18.1 Precision—Because this test method can be applied to many different combinations of units and mortar, and because
workmanship is not controlled in fabricating field-prepared specimens, it is not possible to establish repeatability and
reproducibility values that would be universally correct.
18.2 Bias—No information can be presented on the bias of this test method because no test having an accepted reference value
is available.
TEST METHOD FOR SAMPLES OBTAINED FROM EXISTING MASONRY
19. Summary of Test Method
19.1 This test method is for evaluating the flexural bond strength of masonry assemblies removed from existing masonry.
20. Significance and Use
20.1 This test method is intended to provide a simple and economical means to evaluate the bond strength of unit-mortar
combinations of prisms cut from existing walls.
20.2 The flexural bond strengths determined by this method are influenced by such factors as masonry
...