ASTM C1531-22

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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: C1531 − 16 C1531 − 22
Standard Test Methods for
In Situ Measurement of Masonry Mortar Joint Shear
Strength Index
This standard is issued under the fixed designation C1531; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 These test methods cover procedures for the determination of the average in situ mortar joint shear strength index in existing
unreinforced solid-unit and ungrouted hollow-unit masonry built with clay or concrete units. Three methods are provided:
1.1.1 Method A (with Flatjacks Controlling Normal Compressive Stress)—For determining mortar joint shear strength index when
the state of normal compressive stress at the test site is controlled during the test using the flatjack method described in Test Method
C1197. Horizontal displacement of the test unit is monitored throughout the test. The test setup for Method A is shown in Fig. 1.
NOTE 1—A paper by Francesco Graziotti et. al of Univ. of Pavia included in ASTM STP 1612 discusses alternative methods for interpreting Method A
testing results.
1.1.2 Method B (without Flatjacks Controlling Normal Compressive Stress)—For determining mortar joint shear strength index
when using an estimate of the normal compressive stress at the location of the test site. Horizontal displacement of the test unit
is not monitored during this procedure. The test set up for Method B is shown in Fig. 2.
1.1.3 Method C (with Flatjack Applying Horizontal Load)—For determining mortar joint shear strength index using an estimate
of the normal compressive stress at the location of the test site, as shown in Fig. 3. Horizontal displacement of the test unit is
generally not measured during this procedure.
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 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 safety, health, and healthenvironmental 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.
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 June 1, 2016Dec. 1, 2022. Published July 2016December 2022. Originally approved in 2002. Last previous edition approved in 20152016 as
C1531 – 15.C1531 – 16. DOI: 10.1520/C1531-16.10.1520/C1531-22.
Graziotti, F., Guerrini, G., Rossi, A., Andreotti, G., and Magenes, G., “Proposal for an Improved Procedure and Interpretation of ASTM C1531 for the In Situ
Determination of Brick-Masonry Shear Strength,” Masonry 2018, ASTM STP 1612, ASTM International, 2018, pp. 13–33, http://dx.doi.org/10.1520/STP161220170181
*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
C1531 − 22
FIG. 1 Test Setup—Method A
FIG. 2 Test Setup—Method B
FIG. 3 Test Setup—Method C
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2. Referenced Documents
2.1 ASTM Standards:
C1180 Terminology of Mortar and Grout for Unit Masonry
C1196 Test Method for In Situ Compressive Stress Within Solid Unit Masonry Estimated Using Flatjack Measurements
C1197 Test Method for In Situ Measurement of Masonry Deformability Properties Using the Flatjack Method
C1232 Terminology for Masonry
E4 Practices for Force Calibration and Verification of Testing Machines
2.2 Other Document:
International Existing Building Code (Appendix A, Chapter A1, Seismic Strengthening Provisions for Unreinforced Masonry
Bearing Wall Buildings), 2014
ASCE/SEI 41 Seismic Evaluation and Retrofit of Existing Buildings, ASCE Standard ASCE/SEI 41 (Chapter 11, Masonry)
3. Terminology
3.1 Terminology defined in Terminologies C1180 and C1232 shall apply for these test methods.
4. Summary of Test Method
4.1 The in-place shear test is used to provide an index of the in situ, horizontal shear resistance of mortar joints in unreinforced
masonry. For Method A, a single masonry unit is removed from opposite ends of the chosen test unit as shown in Fig. 1. For
Method B, a single masonry unit and a head joint are removed from opposite ends of the chosen test unit, as shown in Fig. 2. For
Method C, head joints on both ends of the tested unit are removed as shown in Fig. 3. Ensure that the bed joints are not disturbed
in the unit to be tested. The test unit is then displaced horizontally relative to the surrounding masonry using a hydraulic jack or
specialized flatjacks. The horizontal force required to cause first movement of the test unit provides a measured index of the mortar
joint shear strength.
5. Significance and Use
5.1 This test method provides a means of evaluating the horizontal in-plane shear behavior of mortar joints in existing
unreinforced masonry assemblies (see Note 12).
NOTE 2—The masonry mortar joint shear strength index obtained by this test method can be related to the masonry wall shear strength by relationships
contained in referencing Codes and Standards. For example, formulas relating shear index to wall shear strength are found in Chapter A1 of the
International Existing Building Code and Chapter 11 of the Seismic Evaluation and Retrofit of Existing Buildings, ASCE Standard ASCE/SEI 41. The
user of this standard is cautioned that these shear strength relationships are typically empirical relationships based on tests of early 20th-century
unreinforced brick masonry. These relationships typically assume that wall shear strength is limited by shear of the mortar joints rather than shear through
the units
5.2 For hollow ungrouted or solid unit masonry construction the shear strength index is measured only for the mortar bed joints
vertically adjacent to the unit being tested. When testing hollow ungrouted masonry construction, the shear strength index is based
on the horizontal interface between the mortar and the test unit and the masonry above and below the test unit. In the case of
multi-wythe construction, the measured mortar joint shear strength index is applicable only to the wythe in which the test unit is
located; no headers shall exist immediately above or below the test unit. The contribution of any existing collar joint mortar to the
measured shear strength index is neglected, and this may lead to an overestimate of the shear strength index (see Note 23).
NOTE 3—Some documents that reference this test method, including ASCE/SEI 41, include a reduction factor to account for the contribution of a filled
collar joint to the measured shear strength index.
5.3 The test procedure listed for Method A may be conducted as an extension of Test Method C1197. The two-flatjack test,
conducted in accordance with Test Method C1197, provides half of the required test setup for Method A. At the completion of both
the C1197 and the C1531 Method A test, one would know the deformability of the masonry at the test and the relationship between
the expected joint shear strength index and the normal compressive stress.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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Available from American Society of Civil Engineers (ASCE), 1801 Alexander Bell Dr., Reston, VA 20191, http://www.asce.org.
C1531 − 22
6. Apparatus
6.1 The following equipment is required for both Method A and Method B:
6.1.1 Equipment to measure load; two options exist: (1) A hydraulic jack with an appropriate working pressure range to load the
test unit. The force output of the jack throughout its working pressure range shall be known, to facilitate conversion between
hydraulic pressure and force applied to the masonry; (2) For more precision, use a load cell to measure the force applied by the
hydraulic jack. Verify load in accordance with Practices E4. Place the load cell between the spherical seat and the bearing plate
nearest the test unit.
6.1.2 Steel bearing plates shall be provided at each end of the test jack to distribute the load uniformly across the ends of the test
unit and the reaction unit as shown in Fig. 1. The bearing plates shall have a minimum thickness equal to ⁄8 the vertical dimension
of the bearing plate. The bearing plates shall have a vertical dimension that is ⁄8 in. (3.2 mm) less than the height of the unit; the
plate shall be centered vertically on the end of the unit. The bearing plate shall have a horizontal dimension that equals or exceeds
the thickness of the unit. The bearing plate surface in contact with the loaded unit shall be faced with a neoprene pad ⁄16 in. (1.6
mm) thick; the pad shall have a durometer hardness in the range of 50 to 60.
6.1.3 An electrically or manually operated hydraulic pump with hydraulic hoses to pressurize the loading jack. Measure pressure
using gauges calibrated to a traceable standard having both an accuracy of 1 % of full hydraulic scale and an appropriate operating
range. The pressure gauge shall have a peak hold feature to indicate the maximum hydraulic pressure attained during specimen
loading. The hydraulic system shall be capable of maintaining constant pressure within 1 % of full scale for at least 5 min.
6.2 The following additional apparatus is required for Method A:
6.2.1 Flatjacks and associated equipment to measure the state of compressive stress as described in Test Method C1196. Test
Method C1197 describes apparatus necessary to apply a known state of normal compressive stress to the masonry at the test site
using flatjacks.
6.2.2 Use mechanical extensometers or electronic devices to measure horizontal displacement of the unit. The method or device
used to measure deformation shall be capable of deformation measurements up to ⁄4 in. (6 mm). Deformation measurements shall
have an accuracy of at least 0.005 % of gauge length. Fasten brackets or other attachment devices securely to the surface of the
masonry using a rigid adhesive.
6.3 The following equipment is required for Method C:
6.3.1 A small rectangular flatjack that is sized to fit in the head joint on one side of the test unit. The flatjack dimensions must
not exceed the dimensions of the end of the tested unit to prevent load application to the mortar joints.
6.3.2 If load-deformation data are required, use instrumentation as described in 6.2.2.
7. State of Normal Compressive Stress
7.1 The magnitude of normal compressive stress will have a direct effect on the measured joint shear strength index and must be
determined beforehand.
7.2 Method A (with Flatjacks Controlling Normal Compressive Stress)—Apply normal compressive stress using flatjacks. Place
an upper flatjack two courses above and centered over the test unit to within a tolerance of 6 ⁄8 in. (3 mm). Place a lower flatjack
five courses below the upper flatjack, centered under the test unit to within a tolerance of 6 ⁄8 in. (3 mm). A single masonry unit,
located on the centerline midway between the two flatjacks, is the unit to be tested for measurement of joint shear strength. The
slots and flatjack installation shall be in accordance with Test Method C1197.
7.3 Method B (without Flatjacks Controlling Normal Compressive Stress)—Estimate and record the average normal compressive
stress on the unit based upon the location of the test unit in the structure and the estimated dead and acting live loads.
NOTE 4—Estimates of normal compressive stress typically assume uniform stress distributions that often result in overestimates of normal stress and
corresponding underestimates of shear index. The effects of inaccurate dead and acting live load estimation can be minimized by locating tests beneath
windows, beneath other wall openings, near the tops of walls, or in other areas with minimal load.
C1531 − 22
7.4 Method C (with Flatjack Applying Horizontal Load)—Estimate the average normal compressive stress using the method
described in 7.3.
8. Preparation of Test Site
8.1 The location at which the joint shear strength index is measured is dictated by engineering objectives. Avoid areas in which
the mortar joints appear to be nonparallel. The unit to be tested must be in the stretcher orientation. Locate the test site far enough
from wall openings or ends so that the loading jack bears against enough masonry to resist forces generated during loading of the
test unit. The basic arrangement is illustrated in Fig. 1 for Method A, in Fig. 2 for Method B, and in Fig. 3 for Method C. At the
desired location the following steps must be taken to prepare the site for testing:
8.1.1 For Method A or Method B, provide a space for the loading jack by removing a unit on one end of the test unit. Do not
remove a unit for Method C.
8.1.2 For Method A, if the joint shear strength index in opposite directions is to be determined, remove the unit at both ends of
the test unit to isolate the joints being investigated. Otherwise, follow the procedure of 8.1.3. The mortar in the joints above and
below the test specimen shall not extend beyond the vertical ends of the unit being tested.
8.1.3 For Method B, remove a masonry unit on one side of the test unit and the head joint on the opposite end of the test unit.
The mortar in the joints above and below the test specimen shall not extend beyond the vertical ends of the unit being tested.
8.1.4 For Method C, remove the head joints on both ends of the test unit. The mortar in the joints above and below the test unit
shall not extend beyond the vertical ends of the unit being tested.
8.2 For solid unit and solid grouted masonry construction, measure the width and length at the top and bottom of the test unit to
an accuracy of ⁄32 in. (0.8 mm). For hollow ungrouted masonry construction, measure the length at mid-height of each face to an
1 1
accuracy of ⁄32 in. (0.8 mm) and measure the minimum thickness of each face shell at a point ⁄2 in. (12.7 mm) above the
mortar-bed plane to an accuracy of ⁄32 in. (0.8 mm).
9. Procedure
9.1 Method A
...