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: C780 − 20

Standard Test Method for

Preconstruction and Construction Evaluation of Mortars for
Plain and Reinforced Unit Masonry1
This standard is issued under the fixed designation C780; 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.

INTRODUCTION

This test method provides a standard procedure for sampling and testing mortars for composition
and plastic and hardened properties, either before or during actual construction. The procedures
outlined in the Annexes are considered applicable for evaluating various combinations of portland
cement, lime, and masonry cement for mortars common to plain and reinforced unit masonry
construction.
The test procedures describe methods for the measurement of mortar composition and mortar
properties. No attempt is made to claim or substantiate specific correlations between the measured
properties and mortar performance in the masonry. However, data from these test methods can be
combined with other information to formulate judgments about the quality of the masonry.
Testing using these procedures is limited to the preconstruction evaluation of masonry mortars
within the laboratory, to the evaluation of masonry mortars at the construction site, and in establishing
the degree of quality control exercised during mortar production at the construction site.

1. Scope* proportions, comparing test results for field mortars to precon-

1.1 This test method covers procedures for the sampling and struction testing, and determining batch-to-batch uniformity of
testing of mortars for composition and for their plastic and the mortar.
hardened properties, either before or during their actual use in 1.4 The test results obtained under this test method are not
construction. required to meet the minimum compressive values in accor-
dance with the property specifications in Specification C270.
NOTE 1—Guide C1586 provides guidance on evaluating mortar and
clarifies the purpose of both this test method and Specification C270. 1.5 The values stated in inch-pound units are to be regarded
NOTE 2—The testing agency performing this test method should be as standard. The values given in parentheses are mathematical
evaluated in accordance with Practice C1093. conversions to SI units that are provided for information only
1.2 Preconstruction Evaluation—This test method permits and are not considered standard.
comparisons of mortars made from different materials under 1.6 The text of this standard references notes and footnotes
simulated field conditions. It is also used to establish baseline that provide explanatory material. These notes and footnotes
values for comparative evaluation of field mortars. (excluding those in tables and figures) shall not be considered
1.3 Construction Evaluation—Use of this method in the as requirements of the standard.
field provides a means for quality assurance of field-mixed 1.7 This standard does not purport to address all of the
mortar. It includes methods for verifying the mortar mix safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
1
This test method is under the jurisdiction of ASTM Committee C12 on Mortars mine the applicability of regulatory limitations prior to use.
and Grouts for Unit Masonry and is the direct responsibility of Subcommittee For specific hazards statements, see Section 8.
C12.02 on Research and Methods of Test.
1.8 This international standard was developed in accor-
Current edition approved June 15, 2020. Published July 2020. Originally
approved in 1974. Last previous edition approved in 2019 as C780 – 19. DOI: dance with internationally recognized principles on standard-
10.1520/C0780-20. ization established in the Decision on Principles for the

*A Summary of Changes section appears at the end of this standard

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 C780 − 20
Development of International Standards, Guides and Recom- 3.2.3 as-mixed samples, n—mortar samples that are ob-
mendations issued by the World Trade Organization Technical tained after mixing and prior to use of the mortar in construc-
Barriers to Trade (TBT) Committee. tion.
3.2.4 mortar board samples, n—mortar samples that are
2. Referenced Documents obtained from the mortar board after some established time
2.1 ASTM Standards:2 period from the end of mixing, and before retempering.
C39/C39M Test Method for Compressive Strength of Cylin- 3.2.4.1 Discussion—Retempered mortar board samples are
drical Concrete Specimens those obtained from the mortar board after retempering. Since
C109/C109M Test Method for Compressive Strength of mortar on a mason’s mortar board is disturbed by the activity
Hydraulic Cement Mortars (Using 2-in. or [50 mm] Cube of the mason, samples from a mason’s mortar board shall be so
Specimens) identified to differentiate them from samples taken from a
C128 Test Method for Relative Density (Specific Gravity) mortar board used exclusively for test purposes.
and Absorption of Fine Aggregate
C173/C173M Test Method for Air Content of Freshly Mixed 4. Summary of Test Method
Concrete by the Volumetric Method 4.1 Preconstruction evaluation of mortar systems involves
C185 Test Method for Air Content of Hydraulic Cement the preparation of one or more trial batches which are mixed in
Mortar the laboratory using mechanical batch mixers. These trial
C187 Test Method for Amount of Water Required for Nor- batches are sampled and used in establishing the plastic and
mal Consistency of Hydraulic Cement Paste hardened properties of the mixtures. Because all the trial
C231/C231M Test Method for Air Content of Freshly Mixed mixtures are prebatched by weight, additional characteristics of
Concrete by the Pressure Method the mortars may be calculated and used in an analysis of mortar
C270 Specification for Mortar for Unit Masonry performance.
C470/C470M Specification for Molds for Forming Concrete
4.2 During actual construction, evaluation of masonry mor-
Test Cylinders Vertically
tars is possible by sampling the mortar at various stages of
C511 Specification for Mixing Rooms, Moist Cabinets,
construction, and performing tests on both its plastic and
Moist Rooms, and Water Storage Tanks Used in the
hardened properties. The test results permit further verification
Testing of Hydraulic Cements and Concretes
of preconstruction testing, and reflect batch-to-batch variations
C617/C617M Practice for Capping Cylindrical Concrete
introduced during mortar production and use at the construc-
Specimens
tion site. More immediate corrective action for the mixing
C1093 Practice for Accreditation of Testing Agencies for
procedure is thereby attainable.
Masonry
C1180 Terminology of Mortar and Grout for Unit Masonry 4.3 The following test methods may be singly or collec-
C1231/C1231M Practice for Use of Unbonded Caps in tively incorporated into the testing to establish mortar
Determination of Compressive Strength of Hardened Cy- composition, and mortar plastic and hardened properties:
lindrical Concrete Specimens 4.3.1 Annex A1—Test Method for Consistency by Cone
C1324 Test Method for Examination and Analysis of Hard- Penetration,
ened Masonry Mortar 4.3.2 Annex A2—Test Method for Consistency Retention
C1586 Guide for Quality Assurance of Mortars (Board Life) of Mortars for Unit Masonry Using a Cone
E11 Specification for Woven Wire Test Sieve Cloth and Test Penetrometer,
Sieves 4.3.3 Annex A3—Test Method for Initial Consistency and
Consistency Retention (Board Life) of Masonry Mortars Using
3. Terminology a Modified Concrete Penetrometer,
3.1 Terminology defined in Terminology C1180 shall apply 4.3.4 Annex A4—Test Method for Mortar Aggregate Ratio,
for this test method. 4.3.5 Annex A5—Test Method for Mortar Air Content, and
4.3.6 Annex A6—Test Method for Compressive Strength of
3.2 Definitions of Terms Specific to This Standard: Molded Masonry Mortar Cylinders and Cubes.
3.2.1 disturbed sample, n—any plastic mortar test sample
which is taken at some time after mixing and bulk sampling, 5. Significance and Use
that is further remixed or molded immediately prior to test, or
5.1 During preconstruction and construction evaluations,
both.
use of these test methods establishes specific and overall
3.2.2 undisturbed sample, n—any plastic mortar test sample performance characteristics for the mortar system.
molded immediately after mixing and sampling that sits on a
vibration-free surface until tested. 5.2 Preconstruction testing of mortars prebatched by weight
provides information for the selection of the individual mortar
system best suited for the masonry to be constructed. The
2
recommended tests and their significance are as follows:
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2.1 Consistency determinations by cone penetration (An-
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 nex A1) allow gaging the water additions for all mortars
the ASTM website. included in the preconstruction test series. Even if the mortar

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 C780 − 20
consistency as measured at the construction site is at a different to be compared, the cylinder compressive strength is approximately 85 %
penetration value than those measured during the preconstruc- of the cube compressive strength.
tion tests, the cone preparation test serves to standardize water 5.3 Testing during the actual construction may employ one
additions for mortars being considered as alternatives before or more of the test methods described in 4.2. Repetitive testing
construction. Additional testing of mortar water content- using these test methods on consecutive or intermittent batches
consistency relationships (Annex A4) will allow relating these provides a method for measurement of batch-to-batch varia-
two factors to batch-to-batch variations at the construction site. tions in the mortar production. Testing during actual construc-
5.2.2 Consistency retention by cone penetration (Annex A2) tion may be referenced to laboratory testing and used to predict
using disturbed or undisturbed mortar samples provides a later age mortar characteristics. In addition to the comments in
means of establishing the early-age setting and stiffening 5.2, the following test meanings may be obtained from
characteristics of the mortars. Because laboratory testing is construction project testing:
conducted under static climatic conditions, consistency reten- 5.3.1 Consistency by cone penetration (Annex A1) is used
tion test results reflect the relative performance of the mortar as a quick reference for indicating batch-to-batch variations in
systems under test. The same general relationships are ex- mix ingredients and mixing time. Erratic consistency readings
pected to hold during testing at the construction project, except indicate poor control during batching and mixing, but they do
as they are influenced by jobsite weather conditions. not indicate if cement, sand, or water additions are improper.
5.2.3 Mortar water-content determinations (Annex A4) al- Other test methods must be used to isolate and identify the
low measurement of the water content of the mortar mixture. unsatisfactory proportioning or mixing procedure, for example,
Mortars prebatched using moist masonry sand may be math- cement to aggregate, mortar water, or air content tests.
ematically analyzed for mortar water content; however, this 5.3.2 Consistency retention by cone penetration (Annex A2)
test, when used for preconstruction evaluation, establishes the tests establishes the early-age setting and stiffening character-
effectiveness of the test method and serves as the control or istics of the mortar. These properties are influenced by mix
base for tests performed at the construction site. proportions and ingredients, weather conditions, effects of
5.2.4 Mortar aggregate ratio testing (Annex A4) provides a chemical additives, and mixing time.
method for determining the ratio of aggregate-to-cementitious 5.3.3 Individual and repeated evaluations of mortar water
materials. The sieving operation employed during this test is content (Annex A4) show the ability of the mixer operator to
incapable of separating an individual cementitious material properly and consistently add water to the mixer.
when more than one such material is used, but can accurately 5.3.4 Individual and repeated tests for mortar aggregate
establish the aggregate-to-cementitious materials ratio of the ratio (Annex A4) show the ability of the mixer operator to
mixture. properly and consistently add the cementitious material and
5.2.5 Mortar air-content testing (Annex A5) is useful in sand to the mixer, and will establish batch-to-batch variations
establishing the value of this component of the mortar. This test in the composition of the mortar.
is of particular importance in evaluating mortars that contain 5.3.5 Individual and repetitive tests for mortar air content
air-entraining portland cement, air-entraining lime, masonry (Annex A5) show the changes caused by variations in mixing
cement or any combination thereof. time, mixing efficiency and other factors.
5.2.6 Compressive strength testing (Annex A6) of molded 5.3.6 Comparison of compressive strength tests (Annex A6)
mortar cylinders and cubes establishes one of the characteris- of field batched mortars to preconstruction mortar compression
tics of hardened mortar. Mortar compressive strength test tests, each conducted in accordance with this test method, can
values are not representative of the actual compressive strength be used to identify variations in mortar mix constituents and/or
of mortar in the assembly and are not appropriate for use in proportions. Variations in compressive strength values typi-
predicting the compressive strength that would be attained by cally indicate changes in mix water content, mixing
the mortar in the masonry assembly. The measured compres- procedures, mix materials, material proportions, and environ-
sive strength of a molded mortar specimen is almost always mental conditions.
lower than the strength of the same mortar in the wall, NOTE 4—Variations in the measured compressive strengths of field-
primarily as a result of differences in mortar water content and sampled mortar and between the measured compressive strengths of
specimen shape. Mortar compressive strength is influenced by construction and pre-construction mortar samples should be expected.
Many of these variations result from sampling mortar from the mixer or
mortar water content at the time of set. Because molded mortar mortarboard and do not necessarily translate into significant mortar
specimens are not in contact with absorptive masonry units and strength variations in the wall. Unit suction will remove water from the
are not subjected to other mechanisms of water loss, they have mortar in the wall and the curing conditions are different. However,
higher water contents than mortar in the wall. Higher water significant variation between measured compression strength values
contents almost always result in lower strengths. Specimen size should prompt evaluation of probable causes of this variation. Conducting
companion mortar aggregate ratio tests would assist in determining if
and shape also affect compressive strength. Cylinders and changes in mix constituents and proportions are the likely cause. (See
cubes exhibit different strengths even when made from the 5.2.6 for additional information).
same mortar mix. Both of these specimen configurations yield
lower strengths than what would be attained if a specimen 6. Test Method Limitations
having the same size and configuration of a typical mortar joint
6.1 During mortar aggregate ratio testing, no attempt has
could be reliably tested.
been made to establish the proportions of either portland
NOTE 3—When cube and cylinder test specimens from like mixtures are cement to lime or portland cement to masonry cement in the

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 C780 − 20
mixture. Additional testing could establish this proportioning, is performed, the sampling method used in construction testing
however, batching operations should be supervised to ensure shall be the same as that used during preconstruction testing.
the correct proportioning of these ingredients.
NOTE 5—Many factors, including sampling, can affect the characteris-
6.2 Due to the greater ability to weigh materials accurately, tics of fresh mortar. Sampling should be done in a consistent manner. Care
mix on a precise schedule, and control other factors relating to should be taken to ensure that the same sampling procedure is used when
comparing test results throughout the course of a project. Unless specific
the production and testing of mortar under laboratory condi-
time-dependent properties of the mortar are being evaluated, sampling
tions as compared to field conditions, the principal purpose of should be done in accordance with 9.3.1.
this test method is to provide a means to identify, measure,
evaluate, and control differences that exist between laboratory 9.3.1 Take as-mixed samples as follows: When mixing is
and jobsite mortars. performed in a mixer, obtain samples either during the dis-
charge of the mixer or after the mortar has been discharged into
6.3 Test Method C1324 is available for examination and the mortar receptacle. If samples are taken during the discharge
analysis of hardened masonry mortars. There is no ASTM of the mixer, they shall be taken at any time except for the first
method for determining compressive strength of hardened and last 10 % of the batch. Samples of the mortar taken after
mortar from samples taken from a structure. discharge from the mixer shall be representative of the entire
batch. When mixing is not performed in a mixer, obtain
7. Apparatus samples following the procedure in 9.3.
7.1 The apparatus required for this test, along with the 9.3.2 Take mortar for mortar board tests in accordance with
apparatus for sampling (see Section 9) are given in the 9.3.1, and place upon mortar boards typical of those used or to
individual tests included in the annexes. be used at the project. For construction site testing, expose the
test mortar on the board(s) to climatic conditions typical of
8. Hazards those on the jobsite. When mortar from a mason’s mortar board
is used for test purposes, identify it further to reflect this
8.1 During any period that the alcohol used in the mortar
exception for proper data interpretation. Thoroughly hand-mix
aggregate ratio test is exposed to the atmosphere, and particu-
mortar selected for testing with a trowel immediately before
larly when the test sample is being dried, the tester should be
sampling for tests or specimens. Record the lapsed time from
aware that alcohol is a very flammable material. Prior to drying
the end of mixing as part of the test data.
the sample in an oven, place the sample in a shallow pan and
9.3.3 Take retempered mortar board samples from the
flash off the alcohol by intentional ignition in an open,
mason’s mortar board at recorded time periods after mixing
well-ventilated area.
and retempering. Thoroughly hand-mix all mortar on the board
with a trowel before sampling.
9. Sampling
9.1 This section deals with the sampling of individual 9.4 Time to Test:
mortar ingredients and of the mortar itself for preconstruction 9.4.1 The test for cone penetration (Annex A1) shall be
evaluation in the laboratory and construction evaluation at the started within five minutes after obtaining the final portion of
jobsite. the sample.
9.4.2 The initial readings for consistency retention (Annex
9.2 Complete the sampling of materials as follows: A2 and Annex A3) shall be started within five minutes after
9.2.1 Bagged material, such as portland cement, lime, and obtaining the final portion of the sample.
masonry cement, shall be of the type and brand that will be 9.4.3 The mortar samples for mortar-aggregate ratio (Annex
used or is being considered for use in the actual construction. A4) shall be introduced into the containers with alcohol within
Obtain full-bag lots in sufficient quantity for completing the five minutes after obtaining the final portion of the sample.
desired tests.
9.4.4 The test for air content (Annex A5) shall be started
9.2.2 Aggregate for test purposes shall be from the same
within five minutes after obtaining the final portion of the
source and of the same description as will be used or is being
sample.
considered for use in the actual construction. Obtain a repre-
9.4.5 Molding of specimens for compressive strength (An-
sentative sample of sufficient quantity to complete the desired
nex A6) shall be started within 15 minutes after obtaining the
tests.
final portion of the sample.
9.2.3 Water for test purposes need not be the same as that to
be used in construction, except when it is known or suspected 9.5 Record sampling procedures to include the date, time,
that the properties of the water available for mortar production place, and method of sampling. When applicable, note and
at the construction site will have a measurable effect upon the record the climatic conditions.
mortar properties. In normal testing, clean, potable water shall
be acceptable for test purposes. 10. Test Specimens
9.3 Obtain plastic mortar samples both in the laboratory and 10.1 During preconstruction evaluation of masonry mortars,
at the construction project by taking uniformly distributed measure plastic mortar properties using a single test specimen
incremental samples, and mixing them to form a bulk sample for each part of the tests. For determining hardened mortar
from which the quantity of mortar required for a specific test or properties, prepare three test specimens for each test age and
specimen can be randomly taken. When preconstruction testing property.

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 C780 − 20
10.2 During construction evaluation of masonry mortars, NOTE 7—There is some disagreement regarding the relative values of
measure plastic mortar properties using a single test specimen the cone penetration test versus the flow table test. The cone penetration
test is selected for this procedure since a flow table mounted in accordance
for each part of the method of test. For determining hardened with applicable ASTM specifications is not practically portable, and
mortar properties, prepare three test specimens for each test correlation between laboratory and field would be lost if one procedure
age and property. used the flow table and the other the cone penetrometer.
10.3 During actual construction evaluation of masonry 11.2 Complete the preconstruction and construction evalu-
mortars, and when batch-to-batch variations are to be ation in accordance with the test methods appended, Annex A1
established, sample three consecutive batches and test for – Annex A6.
plastic and hardened properties.
11. Procedure 12. Report

11.1 Mortar Preparation—Prepare and mix the mortar for 12.1 A complete report shall include the following informa-
preconstruction evaluation in the laboratory using the materials tion:
(see 9.2.3, regarding water) and proportions intended for use in 12.1.1 Name and address of the testing laboratory,
construction. Use a mechanical batch mixer similar to that 12.1.2 Identification of the report and the date of issue,
intended for use in construction. 12.1.3 Name and address of the client and the identification
11.1.1 Use masonry sand in the damp, as-received of the project,
condition, and handle in such a manner as to prevent segrega- 12.1.4 Description and identification of the test sample,
tion. Correct the water added to the mortar as free water in including:
sands above the saturated, surface-dry condition, in accordance 12.1.4.1 Description of constituent mortar materials,
with Test Method C128. Report the total water used in the mix.
12.1.4.2 Identification of mixing procedures,
11.1.2 Prebatch the mortar materials, by weight, to meet the
desired volume proportions. 12.1.4.3 For field-batched mortar, material proportions, and
11.1.3 Mixing—Mix the mortar following this sequence: 12.1.4.4 For preblended dry mortar materials, reference to
11.1.3.1 For each batch, mix mortar in accordance with lot number, run number, or other marking provided by the
mixing instructions provided. If no instructions are provided, manufacturer.
mix in accordance with the method below. Charge the mixer 12.1.5 Date of receipt of the test sample,
for preconstruction evaluation tests as follows: 12.1.6 Date(s) of sampling and identification of sampling
(1) approximately 1⁄2 to 3⁄4 of the estimated mixing water method used,
required, 12.1.7 Date(s) of test performance,
(2) 1⁄2 to all of the sand, 12.1.8 Identification of the standard test method used and a
(3) all the cementitious materials and mix briefly, and notation of any known deviation from the test method,
(4) add the remainder of the sand, if any, and the balance of 12.1.9 Name of the person(s) accepting technical responsi-
the mixing water required to produce the desired consistency. bility for the test report,
Inasmuch as laboratory procedures permit a more rapid com-
12.1.10 Identification of subcontractor test results, if appli-
bination of materials than is generally achieved under actual
cable.
construction conditions, time delays between the various mix-
ing sequences must be made to approximate jobsite situations. 12.2 A complete report shall also include the test results and
(5) Mix the mortar at normal speed for 3 to 5 min after the all pertinent data relating to the conduct and conditions of the
completion of the charging sequence. Mortar shall be mixed tests in the test report, as required by the applicable Annex. The
for a minimum of one minute after subsequent water additions. data sheet in Appendix X1 is suggested as a general format for
the development of report forms.
NOTE 6—For best results, mix mortar in the same way each time it is
sampled. Alternative mixing equipment may require shorter mixing times
than traditional paddle mixers. 13. Keywords
11.1.3.2 Determine the cone penetration value of the mortar 13.1 aggregate ratio; air content; compressive strength;
for preconstruction evaluation tests in accordance with Annex concrete penetrometer; cone penetrometer; consistency; con-
A1. sistency retention; mortar

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 C780 − 20
ANNEXES

(Mandatory Information)

A1. TEST METHOD FOR CONSISTENCY BY CONE PENETRATION

A1.1 Scope A1.3.2 Using the spoon, place the mortar gently into the
A1.1.1 This test method covers a procedure for determining measure in three layers of equal volume, tamping each layer 20
the consistency of mortars for unit masonry by measuring the times with the tamper in one complete revolution around the
penetration of a conical plunger into a mortar sample. inner surface of the measure. Consider one complete up-and-
down motion of the tamper held in a vertical position as one
A1.2 Apparatus tamping. In tamping the first layer, do not strike the tamper
A1.2.1 Unit Measure—A cylindrical measure conforming to forcibly against the bottom of the measure. In tamping the
the physical requirements of Test Method C185. second and third layers, each layer is tamped in one complete
revolution (rotation) with only sufficient pressure to adequately
A1.2.2 Straightedge—A steel straightedge not less than 4 in. fill the measure and eliminate voids within the mortar. After the
(101.6 mm) long and not less than 1⁄16 in. (1.59 mm) nor more measure has been filled and tamped in the above prescribed
than 1⁄8 in. (3.2 mm) in thickness. manner, tap the sides of the measure lightly with the side of the
A1.2.3 Tamper—In accordance with Test Method C109/ tapping stick once each at five different points at approximately
C109M. The tamping face shall be flat and at right angles to the equal spacing around the outside of the measure in order to
length of the tamper. preclude entrapment of extraneous air. Take care that no space
A1.2.4 Tapping Stick—A maple wood rod, having a diam- is left between the mortar and the inner surface of the measure
eter of 5⁄8 in. (15.9 mm) and a length of 6 in. (152.4 mm). as a result of the tamping operation. Then cut the mortar off to
a plane surface flush with the top of the measure, by drawing
A1.2.5 Spoon, metal, kitchen-type, with the handle cut off to
the straightedge with a sawing motion across the top of the
make the overall length approximately 9 in. (228.6 mm) and
measure, making two passes over the entire surface, the second
with the bowl of the spoon being approximately 4 in. (101.6
pass being made at right angles to the first. Take care in the
mm) long, 21⁄2 in. (63.5 mm) in width at the widest portion, and
1⁄2 to 3⁄4 in. (12.7 to 19.05 mm) deep.
striking-off operation that no loose sand grains cause the
straightedge to ride above the top surface of the measure.
A1.2.6 Cone Penetrometer—A Vicat apparatus, conforming Complete the entire operation of filling and striking off the
to the physical requirements of Test Method C187, shall be measure within 11⁄2 min. Wipe off all mortar and water
modified to allow reading cone penetrations to a depth of adhering to the outside of the measure.
89 mm. The frame shall be raised 2 in. (50.8 mm) to accom-
modate the unit measure and the plunger in the raised position. A1.3.3 Raise the penetration plunger and slide the unit
The indicator scale shall be extended to allow measuring a full measure underneath the plunger until the point of the plunger
drop of 89 mm. The plunger shall be an aluminum cone, 15⁄8 in. rests on the edge of the container. Tighten the set screw just
(41.3 mm) in diameter by 35⁄8-in. (92.08-mm) long, blunted to enough to hold the plunger and move the indicator opposite the
a hemisphere a distance of 1⁄8 in. (3.2 mm) making the overall zero point of the scale.
length 31⁄2 in. (88.9 mm). The base of the cone shall be drilled A1.3.4 Center the container under the plunger and release
and tapped on the centerline for threading to a stainless steel the plunger with a swift, definite turn of the set screw while
tube of proper size and able to slide freely in the guides of the holding the entire apparatus firmly with the other hand.
apparatus. The weight of the tube shall be adjusted so that the
combined weight of the cone, tube and index pointer is 200 6 A1.3.5 Read the depth of penetration in millimetres at the
2 g. end of 30 seconds.

A1.3 Procedure A1.4 Report

A1.3.1 Begin filling the unit measure within five minutes of A1.4.1 Report the depth of cone penetration to the nearest 1
obtaining the final portion of the sample. mm.

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 C780 − 20

A2. TEST METHOD FOR CONSISTENCY RETENTION (BOARD LIFE) OF MORTARS FOR UNIT MASONRY USING A
CONE PENETROMETER

A2.1 Scope Prepare one test specimen in accordance with Annex A1 for
A2.1.1 This method describes a procedure for determining each test age. One test container will be required for each test.
the consistency retention of mortars after various time intervals Immediately after filling the test container, cover the sample
by the cone penetration test method. Both disturbed and with a cover plate and invert the entire assemblage and place
undisturbed sample testing are included in the method. Unless upon a firm, level surface. Immediately prior to testing, turn the
otherwise stipulated, only the disturbed sample testing will be assemblage upright and remove the cover plate. The normal
required. interval between tests is 15 min. Two options are available
under this test procedure. The method given for undisturbed
A2.2 Apparatus samples in A2.3.3 minimizes, by the use of the cover plate, the
A2.2.1 In addition to the apparatus required for completing effects of surface moisture evaporation on the consistency of
the cone penetration test in Annex A1, extra unit measures and the mortar. Although a mason seldom uses a board of mortar
glass cover plates are required when using the undisturbed which has sat undisturbed for some time without mixing it with
sample test procedure for each test time to be included in the his trowel first, some mortar study programs may wish to
determination of consistency retention. No additional equip- include determinations of these surface effects. If this is
ment is necessary using the disturbed mortar sample test desired, vary the procedure by not covering and not inverting
procedure. the test molds for the interval between their preparation and
testing. The test report must note the use of this alternate
A2.3 Procedure procedure when it is employed.
A2.3.1 Begin filling the unit measure(s) within five minutes A2.3.4 Determine the penetration of the cone into the
of obtaining the final portion of the sample. mortar sample as described in Annex A1.
A2.3.2 Disturbed Samples—When testing disturbed mortar A2.3.5 Record the first measured penetration as Po.
samples, sample and use the mortar in filling the mortar test A2.3.6 Except when required by another standard, repeat
container immediately prior to conducting the test. Sample the the procedure in A2.3.4 at 15 minute intervals until the
mortar as it is discharged from the mixer, and place on a mortar measured penetration is less than 70 % of Po. See Note A2.1.
board reserved for test purposes. This mortar shall not be used
by the mason, or disturbed until immediately prior to testing. NOTE A2.1—Some specifications and test methods may reference the
consistency by cone penetration test and provide reading intervals and test
Just before the test, remix the mortar sample with a trowel until
duration. When this information is provided in the standard that references
it is of uniform consistency. Then agitate or handle the mortar ASTM C780, those test details should be used.
just enough to allow proper consolidation of the mortar in the
test container. After the mortar sample has been consolidated in A2.4 Report
the mold as described in Annex A1, immediately complete the A2.4.1 The report shall include the following:
test. The normal interval between tests is 15 min. A2.4.1.1 Depth of penetration to the nearest 1 mm,
A2.3.3 Undisturbed Samples—When testing undisturbed A2.4.1.2 Notation as to whether the data refers to disturbed
mortar samples, prepare the test specimens for all test ages or undisturbed samples, and
immediately after the mortar is discharged from the mixer. A2.4.1.3 Test time.

A3. TEST METHOD FOR INITIAL CONSISTENCY AND CONSISTENCY RETENTION (BOARD LIFE) OF MASONRY MOR-
TARS USING A MODIFIED CONCRETE PENETROMETER

A3.1 Scope A3.2.1.1 board life—the time period during which penetra-
A3.1.1 This method allows determination of initial consis- tion resistance stays below a given value (Pf).
tency and board life of masonry mortars. The method is A3.2.1.2 Po—the initial penetration resistance or consis-
sufficiently restrictive to be used as a basis for acceptance of tency of a masonry mortar as measured, using this method.
mortars. Results correspond to pounds per square inch of A3.2.1.3 Pf—the penetration resistance or consistency of a
pressure required to penetrate a sample of mortar 1 in. with a masonry mortar when the mortar is too stiff for use.
disk of a given size and weight. English units of measure will
A3.2.1.4 rate of stiffening—the ratio of the difference be-
be used throughout the method.
tween Po and Pf per time interval.
A3.2 Terminology A3.2.1.5 To—the time when the initial penetration resis-
A3.2.1 Definitions: tance measurement was made.

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 C780 − 20
A3.2.1.6 Tf—the time when Pf was reached, obtained by for three seconds. Read and record penetrometer scale pres-
interpolation. sure. Repeat applications of downward force in increments of
1 lb from 1 to 30 lb and record each incremental penetrometer
A3.3 Significance and Use scale reading. Divide the total applied load plus the weight of
A3.3.1 Data obtained from this method are used to deter- the penetrometer by the cross sectional area of the disk. These
mine consistency of a mortar, as well as board life of a mortar. values represent pressure at the face of disk. Prepare a
The method is also useful for determining when a mortar is or calibration chart to allow converting penetrometer scale read-
is not acceptable for use due to stiffness. When penetration ing to penetration resistance, in psi. See Table A3.1.
resistance is outside the desired range (Po to Pf) the mortar is
retempered or discarded. A3.7 Procedure
A3.7.1 Mortar to be tested for board life shall be prepared so
A3.4 Apparatus the initial penetration resistance (Po) is either 0.94 6 0.05 psi
A3.4.1 Concrete Penetrometer, spring activated with cali- for mortar to be used with brick sized units or 1.24 6 0.05 psi
bration markings from 20 to 700 psi. The penetrometer shall be for mortar to be used with heavier units requiring less plastic
modified as required by A3.4.1.1. The modification of the mortars for proper bedment. Water additions to the mortar
penetrometer prevents direct use of the scale on the penetrom- decrease penetration resistance. Prepare comparison mortars
eter. Therefore, the penetrometer shall be calibrated in accor- with varied composition and proportions controlling equip-
dance with A3.6. ment and procedures.
A3.4.1.1 Disk Modification—The penetrometer shall be A3.7.2 Begin filling the circular ring within five minutes of
modified by securely attaching a disk perpendicular to the obtaining the final portion of the sample.
bottom of the penetrometer shaft. The disk shall be 1 6 1⁄16 in.
A3.7.3 Place the mortar in the circular ring, previously
thick with a diameter of 2.65 to 3.05 in. The disk material shall
centered on the damp mortar board. Spade the mortar with the
be rigid and non-absorbent. See Note A3.1.
square-nosed shovel. Screed the top surface of the specimen to
NOTE A3.1—Pocket-sized concrete penetrometers are available in the surface of the ring using either the straightedge or trowel.
different configurations. Satisfactory results have been achieved with a Remove mold within three min after mortar mixing was
disk made of either (1) machined steel secured to the penetrometer shaft
with a retaining sleeve and thumbscrew, or (2) vulcanized rubber (such as
a regulation National Hockey League puck) secured to the penetrometer
shaft by epoxying the shaft to a hole drilled into the center of the disk. TABLE A3.1 Penetrometer Calibration
Other materials and securing methods can be used as long as they meet the (5.67 in.2 Disk, 2.47 lb of Penetrometer and Disk)
requirements of A3.4.1.1. It is recommended that the disk also be abrasion
resistant and resistant to chemical attack by mortar. NOTE 1—The pressure exerted on the specimen is the measured weight
plus the weight of the penetrometer and disk divided by the area of the
A3.4.2 Trowel—A mason’s trowel. disk. For example, the disk weighs 2.47 lb and the area of the disk is
5.67 in.2; 1 lb of measured weight + 2.47 lb weight of penetrometer and
A3.4.3 Shovel—A square nosed shovel. disk (tare)/5.67 in.2 = 0.61 psi.
A3.4.4 Ring—A 16-in. inside diameter ring made of steel or Measured Weight, lb Scale Readings psi
other rigid, chemical and abrasive resistant material, 3 in. high 1 20 0.61
with exterior, opposing handles. 2 40 0.79
3 60 0.96
A3.4.5 Mortar Board—A nominal 2 ft by 2 ft by 3⁄4 in. 4 80 1.14
5 100 1.32
mortar board of exterior grade plywood. 6 120 1.49
7 140 1.67
A3.4.6 Straightedge—A wooden straightedge of nominal 8 160 1.85
dimensions, 2 in. by 4 in. and 24 in. in length (optional). 9 180 2.02
10 200 2.20
A3.5 Sampling, Test Specimens, and Test Units 11 220 2.38
12 240 2.55
A3.5.1 At least one specimen shall be prepared for each 13 260 2.73
mortar. 14 280 2.90
15 300 3.08
A3.5.2 Test condition shall be either actual climatic condi- 16 320 3.26
17 340 3.43
tions and construction practices at the construction site or 18 360 3.61
simulated conditions considering temperature, humidity, wind, 19 380 3.79
sand, water, mixing equipment, handling, mixing procedure, 20 400 3.96
21 420 4.14
etc. 22 440 4.32
23 460 4.49
A3.6 Calibration and Standardization 24 480 4.67
25 500 4.84
A3.6.1 Calibrate the penetrometer by placing it on a weigh 26 520 5.02
scale with a capacity of 30 lb and accurate to 0.05 lb. Place the 27 540 5.20
penetrometer on the weigh scale platform and tare to zero. 28 560 5.37
29 580 5.55
Push downward on the handhold of the penetrometer until the 30 600 5.73
weigh scale registers 1 lb. This pressure shall be applied within

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 C780 − 20
completed. Immediately take three penetration readings. Posi- Rate of stiffening 5 ~ P f 2 P o ! /T f , psi permin (A3.1)
tion the disk of the penetrometer on the surface of the mortar where:
at least one disk diameter from both the edge and previous test Pf and Po are as indicated:
areas. Apply uniform pressure within three seconds so the disk
Mortar for Brick Sized UnitsA Mortar for Heavier Units
penetrates the mortar a distance of 1 in., the disk thickness. Pf = 1.74 Pf = 2.44
Read the penetrometer scale to the nearest 5 psi and record Po = 0.94 Po = 1.24
penetrometer scale reading and time of readings. Reset scale —————

marker to zero. Average the three readings and convert to A

The size, weight and bedding area of the unit should be considered in selecting
applied pressure, in psi, using the calibration curve. Record this the appropriate values of Pf and Po.
result as Po, psi, and the time as To, min. T f 5 interpolated time when P f obtained. (A3.2)
A3.7.4 Within two minutes after completing the three initial (see Note A3.3)
penetration readings, thoroughly remix the mortar using ma-
NOTE A3.3—For graphic illustration, see Fig. A3.1.
son’s trowel. Position ring, screed, and remove ring. Allow
mortar to remain undisturbed for 15 min since To. Read and A3.8.2 Report Tf as board life, in minutes. Pf is approxi-
record three additional penetrations and time, using the proce- mately equal to the consistency when mortars are judged too
dures of A3.7.3. Repeat this procedure every 15 min till the stiff to be used properly.
average penetration resistance is either 1.74 psi for mortars to A3.8.3 Report all penetration resistance data in psi and
be used with brick sized units or 2.44 psi for mortars to be used associated times in minutes.
with heavier units. (Note A3.2)
A3.9 Precision and Bias
NOTE A3.2—Uniformly spaced measurements other than 15 min may
be desirable for research and other testing needs. A3.9.1 The precision of the procedure in Test Method C780,
Annex A3, for measuring consistency and board life is being
A3.8 Report determined.
A3.8.1 Report the following information: A3.9.2 The procedure in Test Method C780, Annex A3, for
A3.8.1.1 Plot data of penetration resistance, in psi, with measuring the consistency and board life of masonry mortars
elapsed time until Pf is reached. has no bias because the value of consistency and board life can
A3.8.1.2 Calculate and report the rate of stiffening as: be defined only in terms of a test method.

FIG. A3.1 Penetration Resistance Versus Elapsed Time

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 C780 − 20

A4. TEST METHOD FOR MORTAR AGGREGATE RATIO

A4.1 Scope A4.3.2 Use as-mixed samples for this test. Introduce the
mortar samples into the sample containers within five minutes
A4.1.1 This test method describes a procedure for determin-
of obtaining the final portion of the sample.
ing the aggregate-to-cementitious materials ratio of mortars for
unit masonry by determining the mortar fraction coarser than a A4.3.3 At the construction site, place 1.1 to 1.2 lb (500 to
150-µm (No. 100) sieve and correcting for the sand finer than 550 g) of mortar into each mortar sample container with the
the 150-µm (No. 100) sieve. This test method also includes a alcohol, as rapidly as is practical. Tightly reseal the lids to
procedure for determining the water content of mortar. minimize evaporation, then agitate the containers until no
lumps are visible. Take care to minimize any loss of alcohol
NOTE A4.1—Previous editions of this standard included a stand-alone
method for determining water content of mortars. That method and the
during mortar sampling and agitation. Record and report the
mortar aggregate method were so interrelated that they have been time the mortar is mixed and the time the sample is placed in
combined into one method. This method retains methods for calculating alcohol. Identify where that mortar is being installed on the
and reporting mortar water contents and can be performed with a single project.
sample of mortar without determination of the ratio of aggregate to
cementitious materials. A4.3.4 At the construction site, obtain a representative sand
sample in excess of 1.1 lb (500 g). Place the sand sample in the
A4.1.2 This test method determines the aggregate-to-
sand sample container.
cementitious materials ratio by weight. For mortars specified
by volume proportions, guidance for converting the ratio by A4.3.5 Mortar Water Content—Upon returning to the
weight to a ratio by volume is located in Note A4.3. laboratory, determine and record the combined weight of the
mortar sample, alcohol, and container (b) to the nearest 0.002
A4.2 Apparatus lb (1 g). Then, using water or isopropyl alcohol, transfer the
A4.2.1 Sand Sample Container—A clean wide-mouth clear entire mortar sample to a weighing pan. Ignite the alcohol
glass or plastic watertight container or waterproof sand bag of within the sample following the safety precautions of Section
sufficient size to contain the sample. 8 of this test method, and then bring the partially dried sample
in the oven at 230 6 9°F (110 6 5°C) to constant weight. The
A4.2.2 Mortar Sample Container—Two clean wide-mouth sample is at constant weigh when drying for an additional 15
clear glass or plastic watertight containers of sufficient size to min results in a change of less than 0.1 %. Determine and
contain the samples and with sealable lids. record the oven-dry weight of the mortar (d) to the nearest
NOTE A4.2—A container with a volume of approximately 1 qt or 1 L is 0.002 lb (1 g). Calculate the mortar water content in accor-
typically sufficient for containing the samples.
dance with A4.4.1.
A4.2.3 Spoon—A stainless steel tea or soup spoon.
A4.3.6 Return the samples to the laboratory as soon as
A4.2.4 Sieves: possible following sampling.
A4.2.4.1 Wash Sieve—A 150-µm (No. 100) sieve conform- A4.3.7 Aggregate-to-Cementitious Materials Ratio—Upon
ing to the requirements of Specification E11. returning to the laboratory, determine and record the combined
A4.2.4.2 Protection Sieve—If used, a 1.18-mm (No. 16) weight of the mortar sample, alcohol, and container (I) to the
sieve conforming to the requirements of Specification E11. nearest 0.002 lb (1 g). Then, using water, transfer the entire
A4.2.5 Oven—An oven capable of maintaining a constant mortar sample to the 150-µm (No. 100) sieve for wet sieving.
temperature of 230 6 9°F (110 6 5°C). If a protection sieve is used, nest protection sieve on top of
wash sieve, and place entire mortar sample onto the protection
A4.2.6 Alcohol—Isopropyl or methyl alcohol, minimum sieve. Wash the mortar with a gentle flow of water accompa-
concentration 70 %. nied by a slight tilting of the screen in various positions until
the wash water is clear and contains no visible particles of sand
A4.3 Procedure
or cementitious material when viewed against a background of
A4.3.1 Prior to going to the construction site, uniquely label contrasting color such as a white sink basin. Complete the
each of the mortar sample containers—one for the mortar water washing of the sample as soon as possible after sampling, and
content test and the other for the aggregate-to-cementitious in no case shall the time between sampling and washing exceed
materials ratios test. Add 8.5 oz (250 mL) of isopropyl or 24 hours. Dry the + 100-mesh fraction in the oven to constant
methyl alcohol to each mortar sample container. Tightly seal weight without removing the material from the screen(s) at 230
the containers to prevent evaporation. Determine and record 6 9°F (110 6 5°C). The sample is at constant weight when
the combined weight of each container with alcohol (for the drying for an additional 15 min results in a weight change of
mortar water content test (a) and for the aggregate-to- less than 0.1 %. Determine the oven-dry weight of the + 100
cementitious materials ratio test (H)) to the nearest 0.002 lb fraction (Y) (including any material retained on the protection
(1 g). sieve) and record to the nearest 0.002 lb (1 g).

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 C780 − 20
A4.3.7.1 Weigh the sand sample, dry in the oven to constant Cementitious Material Bulk Density
weight at 230 6 9°F (110 6 5°C), and record the weight (R)
Portland Cement 94 lb/ft3 (1505 kg/m3)
to the nearest 0.002 lb (1 g). Wet-sieve as described in A4.3.7, Blended Cement Obtain from bag or supplier
dry in the oven to constant weight at 230 6 9°F (110 6 5°C), Masonry Cement Obtain from bag or supplier
weigh, and record the + 100 sand fraction (W) to the nearest Mortar Cement Obtain from bag or supplier
Lime Putty 80 lb/ft3 (1280 kg/m3)
0.002 lb (1 g). Hydrated Lime 40 lb/ft3 (640 kg/m3)
A4.3.7.2 Calculate the aggregate-to-cementitious materials
Aggregate Bulk Density
ratio in accordance with A4.4.2.
Sand 80 lb/ft3 (1280 kg/m3)
A4.4 Calculation
A4.4.1 Calculate the mortar water content, expressed on the Example 1—To convert a cement and lime mortar specified to contain
1 part by volume of portland cement, 11⁄4 parts by volume of hydrated lime
wet and dry basis as follows: and 63⁄4 parts by volume of damp, loose sand (this represents a volume
Mortar water content, wet basis, % 5 @ ~ b 2 a 2 d ! / ~ b 2 a ! # 3 100 ratio of aggregate-to-cementitious material of 3 to 1) to a weight ratio,
perform the following:
(A4.1)
Aggregate 2 to 2 Cementitious Ratio ~ by wt! *
Mortar water content, dry basis, % 5 G 5 @ ~ b 2 a 2 d ! /d # 3 100 6.75 parts aggregate ~ by vol! 3 80 lb/ft3
5
where: @ 1 part portland cement ~ by vol! 3 94 lb/ft3 # 1
a = weight of the mortar sample container and alcohol, lb (g) @ 1.25 parts hydrated lime ~ by vol! 3 40 lb/ft3 #
540
(per A4.3.1), 5
94150
b = weight of the container, alcohol, and mortar, lb (g) (per
540
A4.3.5), and 5
144
d = weight of the oven-dry mortar sample following
53.75 or 3.75 to 1
ignition, lb (g) (per A4.3.5).
A4.4.2 Calculate the ratio of the aggregate-to-cementitious
Example 2 (convert weight ratio as tested to volume ratio)—This
materials ratio as follows: conversion can only be performed on mortars in which the bulk density of
Weight of dry mortar 5 K 5 J/ @ 11 ~ G/100! # (A4.2) the combined cementitious material is known. Consider a sample mortar
in which the measured weight ratio using this method was determined to
Weight of wet mortar 5 J 5 I 2 H be 3.4 parts aggregate to 1 part cementitious material. Inspection of the
mortar materials at the time of sampling shows a masonry cement (with a
Weight of1100 mortar, dry, corrected 5 Q 5 ~ Y 3 R/W ! bulk density of 70 lb/ft3 as shown on the bag) was the only cementitious
material used. To convert this weight ratio to a volume ratio, perform the
Weight of 2 100 mortar, dry, corrected 5 P 5 K 2 Q following:
Aggregate 2 to 2 Cementitious Ratio ~ by vol! *
Aggregate 2 to 2 Cementitious Materials ratio 5 Q/P to 1 3.4 parts aggregate
where: 80 lb/ft3
5
1 part masonry cement
H = weight of container and alcohol, lb (g), (per A4.3.1),
70 lb/ft3
I = weight of container, alcohol and mortar, lb (g), (per
3.4 parts aggregate 70 lb/ft3
A4.3.7), 5 3 3
80 lb/ft 1 part cement
G = mortar water content, dry basis, %, (per A4.4.1),
238
Y = weight of + 100 mortar fraction, dry, lb (g), (per 5
80
A4.3.7)
52.98 or 2.98 to 1
R = weight of sand, oven dry, lb (g), (per A4.3.7.1), and
*Values shown in examples use English units. If English units are
W = weight of the + 100 sand, dry, lb (g), (per A4.3.7.1). replaced with SI units, the resulting calculated proportions by weight
NOTE A4.3—This test method does not differentiate between multiple would be identical to those shown here.
cementitious materials, simply the total cementitious content as compared
to the aggregate content. This method yields the aggregate-to- A4.5 Report
cementitious materials ratio by weight, yet aggregate-to-cementitious
material ratios are typically specified by volume. A4.5.1 Report the following information:
If the specified volume ratio is known, it can be converted to a weight A4.5.1.1 The measured weights of all sample containers,
ratio, which can then be compared with the result of this test method. mortar samples, sand samples, and oven-dried sample fractions
Alternatively, if only one cementitious material is used in the mortar, the to the nearest 0.002 lb (1 g).
results of this method can be converted to a volume ratio, which can then A4.5.1.2 The mortar water content (on both a dry and wet
be compared to the specified ratio. This method cannot be reliably used to
convert the test result of mortar with multiple cementitious materials into basis) as determined in A4.4.1 to the nearest 0.1 %.
a volume ratio. A4.5.1.3 The aggregate-to-cementitious materials ratio as
When converting ratios, use the following material bulk densities: determined in A4.4.2 to the nearest 0.1 %.

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 C780 − 20

A5. TEST METHOD FOR MORTAR AIR CONTENT

A5.1 Scope A5.3.2 When determining the air content of the mortar by
A5.1.1 This test method covers a procedure for determining the pressure method, use the test procedures and calculations
the air content of mortars for unit masonry using either the contained in Test Method C231/C231M.
pressure meter method or the volumetric method.
A5.4 Volumetric Method Procedure (Test Method C173/
A5.2 Apparatus C173M)
A5.2.1 For the pressure method (Section A5.3), the appara- A5.4.1 Begin the air content test within five minutes of
tus requirements and calibration procedures shall be in accor- obtaining the final portion of the sample.
dance with Test Method C231/C231M.
A5.4.2 When determining the air content of the mortar by
A5.2.2 For the volumetric method (Section A5.4), the
apparatus requirements and calibration procedures shall be in the volumetric method, use the test procedures and calculations
accordance with Test Method C173/C173M. contained in Test Method C173/C173M.

A5.3 Pressure Method Procedure (Test Method C231/ A5.5 Report

C231M) A5.5.1 Report the air content, test method used, and type of
A5.3.1 Begin the air content test within five minutes of air meter.
obtaining the final portion of the sample.

A6. TEST METHOD FOR COMPRESSIVE STRENGTH OF MOLDED MASONRY MORTAR CYLINDERS AND CUBES

A6.1 Scope A6.2.1.2 Straightedge—A steel straightedge not less than

A6.1.1 This test method establishes sampling and testing 7 in. (178 mm) long, and not less than 1⁄16 in. (1.59 mm) nor
procedures for determining compressive strength of precon- more than 1⁄8 in. (3.18 mm) in thickness.
struction and construction mortars. Strength values for mortars A6.2.1.3 Spoon—A stainless steel tea or soup spoon.
obtained through these testing procedures are not required, nor A6.2.1.4 Maximum-Minimum Thermometer.
expected, to meet strength requirements of laboratory Specifi- A6.2.1.5 Tamper, in accordance with Test Method C109/
cation C270 mortars or necessarily represent the strength of the C109M. The tamping face shall be flat and at right angles to the
mortar in the wall. The values obtained from construction length of the tamper.
testing are to be correlated only with those of preconstruction A6.2.1.6 Trowel, with blade 4 to 6 in. (101.2 to 152 mm) in
mortars made with the same materials, in the same proportions, length, with straight edges.
mixed to a similar consistency, cured under similar conditions, A6.2.1.7 Nonabsorbent Container—A metal or plastic bowl
and tested at the same age. or bucket suitable for collecting field mortar samples.
A6.2.1.8 Testing Machine—The testing machine shall con-
A6.1.2 This method covers the procedure for determining
form to the requirements of Test Method C39/C39M when
the compressive strength of mortars for unit masonry using any
testing cylindrical specimens and Test Method C109/C109M
of the following: 2 by 4-in. (50.8 by 101.6-mm) cylinders, 3 by
when testing cube specimens.
6-in. (76.2 by 152.4-mm) cylinders, or 2-in. (50.8-mm) cubes.
A6.2.1.9 Scoop—A stainless steel or aluminum scoop.
Any of the listed specimen sizes can be used, but specimen size
A6.2.1.10 Moist Storage Facilities—The moist cabinets and
and shape affects the measured strengths and the results from
rooms shall conform to the requirements of Specification C511.
different sized specimens are not the same.
A6.1.3 Tests of Hardened Mortar Compressive Strengths— A6.3 Procedure
There is no accepted standard for measuring individual hard- A6.3.1 Sample the mortar immediately after initial mixing
ened mortar joint compressive strengths. has been completed using the procedures in Section 9 and test
the mortar for consistency using the procedures in Annex A1.
A6.2 Preparation of Specimens
A6.2.1 Apparatus: A6.3.2 Begin fabricating test specimens within 15 minutes
A6.2.1.1 Molds—Cylinder molds for 2 by 4 in. (50.8 by of obtaining the final portion of the sample.
101.6 mm) cylinders, or 3 by 6 in. (76.2 by 152.4 mm) A6.3.3 Fabricate the test specimens immediately after the
cylinders, shall be single-use or reusable molds and shall mortar has been sampled using either the procedures in either
comply with Specification C470/C470M. Molds for 2 in. A6.3.3.1 (cube specimens) or A6.3.3.2 (cylindrical specimens).
(50.8 mm) cubic specimens shall comply with Test Method Select the specimen casting area in close proximity to the area
C109/C109M. where the specimens will be stored for the first 24 to 48 h. Coat

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 C780 − 20
reusable metal molds with a light coating of mineral oil or The specimens shall be maintained in a moist storage facility
other acceptable form release to minimize mortar sticking to up to the testing age. The test age of preconstruction and
the molds. A minimum of three specimens shall be made for construction test sets must match. Unless specified otherwise,
each mortar sample and test age. tests shall be conducted at 7 days 6 3 h or 28 days 6 12 h after
A6.3.3.1 Fabricate cube specimens using the procedures molding.
described in Test Method C109/C109M. To minimize
A6.4.3 Remove the cylindrical specimens from storage and
evaporation, after fabrication, cover the top surface of the mold
cap using neat cement paste, sulfur mortar, or high strength
using either a cap, plastic bag, or other non-absorbent, non-
gypsum paste following the the procedures in Practice C617/
permeable material.
C617M or use unbonded caps using the procedures in Practice
A6.3.3.2 Cylindrical specimens shall be fabricated using the C1231/C1231M. Different methods of capping shall not be
following procedures. Using the spoon or scoop, place the used on specimens from the same project. When unbonded
mortar gently into the cylinder mold in three layers of caps are used on cylindrical specimens expected to test lower
approximately equal volume, tamping each layer 20 times with than 1500 psi (10.3 MPa), the user or supplier of the pad caps
the tamper in one complete revolution around the inner surface shall qualify the caps and retainers using Sections 8 and 9 of
of the mold. Consider one complete up-and-down motion of Practice C1231/C1231M for the lower strength requirements.
the tamper, held in a vertical position, as one tamping. In
tamping the first layer, do not strike the tamper forcibly against A6.4.4 Maintain moist-cured cylindrical specimens in a
the bottom of the mold. In tamping the second and final layers, moist condition between capping and testing by returning them
each layer is tamped in one complete revolution (rotation) with to moist storage or wrapping them with a double layer of wet
only sufficient pressure to adequately fill the measure and burlap. Do not immerse specimens in water. Do not store
eliminate voids within the mortar. Slightly overfill the top layer specimens with gypsum plaster caps in a moist room for more
of the mold prior to and during the period the top layer is than 4 h. If stored in a moist room, protect the plaster cap
tamped. After the mold has been filled and the mortar tamped, surfaces from dripping water.
tap the sides of the mold lightly five to ten times with an open A6.4.5 Keep cube and cylindrical specimens moist after
hand to release any large air bubbles that may have been their removal from the moist storage facility and prior to
trapped. Strike off the top surface of the specimen using the testing using a wet burlap or towel covering.
straightedge, so it is level with the top of the mold. To
minimize evaporation, after fabrication, cover the top surface A6.4.6 Prior to testing the cube specimens, determine the
of the mold, using either a cap or a plastic bag. size of the specimens using procedures described in Test
Method C109/C109M. Prior to testing the cylindrical
A6.4 Storing the Test Specimens specimens, determine the size of the specimens using the
A6.4.1 Immediately after completion of the molding, place procedures described in Test Method C39/C39M.
the specimens in job site storage facility. Minimum job site A6.4.7 Test cube specimens using procedures described in
facilities shall include an insulated container, in a vibration- Test Method C109/C109M. Test cylindrical specimens using
free location, with a maximum-minimum thermometer placed procedures described in Test Method C39/C39M.
beside the specimens to record the maximum and minimum
temperatures until they are taken to the laboratory. When a 6- A6.5 Calculation
by 12-in. (152.4 by 304.8-mm) concrete cylinder mold is used
A6.5.1 Calculate the compressive strength of the specimen
for storing cube test specimens, it must comply with the
by dividing the maximum load carried by the specimen during
following:
the test by the average cross-sectional area, determined as
A6.4.1.1 The cylinder used for storage shall contain several
described in Test Method C109/C109M or Test Method C39/
thicknesses of wet paper towels underneath the molded speci-
C39M, as appropriate, and express the result to the nearest
mens. The wet towels shall not touch the mortar specimen.
10 psi (0.07 MPa).
A6.4.1.2 The storage cylinder must be maintained so that
the cube specimens are maintained in a horizontal upright A6.6 Report
position at all times and the cylinder must be sealed and
covered with insulating material. A6.6.1 In addition to the general reporting requirements of
Section 12, the report shall include the following:
A6.4.1.3 The storage temperatures shall be maintained at
not less than 40°F (4.4°C) nor greater than 90°F (32.2°C) as A6.6.1.1 A description of the specimen by size and type
measured by a maximum-minimum thermometer placed beside (cube or cylinder),
the specimens. If temperatures exceed these limits, the speci- A6.6.1.2 The test mold material,
mens shall be discarded. A6.6.1.3 The mortar consistency, curing procedure and
A6.4.2 Remove the specimens from their stored position at duration, and
the end of 24 to 48 h and carefully transport them to the A6.6.1.4 For cylindrical specimens, the capping method
laboratory. Place the test specimens in a moist closet or moist used (bonded or unbonded), and
room for the next 20 to 24 h with their upper surfaces exposed A6.6.1.5 Dimensions, total load, and compressive strength
to the moist air but protected from dripping water. Following of the individual specimens for each test age and the specimen
the 20 to 24-h period, remove the specimens from the molds. set average.

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 C780 − 20
A6.6.2 Report any deviations from the test method, includ-
ing storage temperature or relative humidity.

APPENDIX

(Nonmandatory Information)

X1. SAMPLE REPORT FOR PRECONSTRUCTION AND CONSTRUCTION EVALUATION OF MORTARS FOR PLAIN AND
REINFORCED UNIT MASONRY

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 C780 − 20

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 C780 − 20

SUMMARY OF CHANGES

Committee C12 has identified the location of selected changes to this standard since the last issue (C780 – 19)
that may impact the use of this standard. (June 15, 2020)

(1) Changed Section 3 to make definitions conform with Form (2) Modified 6.3 to reference ASTM C1324.
and Style requirements.

Committee C12 has identified the location of selected changes to this standard since the last issue (C780 – 18a)
that may impact the use of this standard. (December 15, 2019)

(1) Added 1.6. (3) Revised titles of annexes for consistency.

(2) Removed the term ‘batch mixer sample’ and changed
wording to address sampling of mortar not mixed in a mixer in
9.3.1.

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 C780 − 20
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