Standard Method of Test for

Air Content of Hydraulic

Cement Mortar

AASHTO Designation: T 137-12

ASTM Designation: C185-08

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Standard Method of Test for

Air Content of Hydraulic Cement Mortar

AASHTO Designation: T 137-12

ASTM Designation: C185-08

1. SCOPE
1.1. This test method covers the determination of the air content of hydraulic cement mortar under the
conditions hereinafter specified.

1.2. The values stated in SI units are to be regarded as the standard.

1.3. Values in SI shall be obtained by measurement in SI units or by appropriate conversion, using the
Rules for Conversion and Rounding in IEEE/ASTM SI10, of measurements made in other units.

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 and health
practices and determine the applicability of regulatory limitations prior to use.
Warning—Fresh hydraulic cementitious mixtures are caustic and may cause chemical burns to
skin and tissue upon prolonged exposure.

2. REFERENCED DOCUMENTS
2.1. AASHTO Standards:
 M 85, Portland Cement
 M 152M/M 152, Flow Table for Use in Tests of Hydraulic Cement
 M 240M/M 240, Blended Hydraulic Cement
 T 106M/T 106, Compressive Strength of Hydraulic Cement Mortar (Using 50-mm or 2-in.
Cube Specimens)
 T 127, Sampling and Amount of Testing of Hydraulic Cement
 T 162, Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency

2.2. ASTM Standards:

 C91/C91M, Standard Specification for Masonry Cement
 C778, Standard Specification for Standard Sand
 C1005, Standard Specification for Reference Masses and Devices for Determining Mass and
Volume for Use in the Physical Testing of Hydraulic Cements
 E438, Standard Specification for Glasses in Laboratory Apparatus
 E694, Standard Specification for Laboratory Glass Volumetric Apparatus

2.3. IEEE/ASTM Standard:

 SI10, American National Standard for Metric Practice

TS-3a T 137-1 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
3. SUMMARY OF TEST METHOD
3.1. Prepare a mortar with standard sand and the cement to be tested using a water content sufficient to
give a required flow. Compact the mortar into a measure of known volume and determine mass.
Calculate the air content from the measured density of the mortar, the known densities of the
constituents, and the mixture proportions.

4. SIGNIFICANCE AND USE

4.1. The purpose of this test method is to determine whether the hydraulic cement under test meets the
air-entraining or non–air-entraining requirements of the applicable hydraulic cement specification
for which the test is being made. The air content of concrete is influenced by many factors other
than the potential of the cement for air entrainment.

5. APPARATUS
5.1. Flow Table, Flow Mold, and Caliper—Conforming to the requirements of M 152M/M 152.

5.2. Measure—A cylindrical measure having an inside diameter of 76 ± 2 mm and a depth

(approximately 88 mm) adjusted by standardization with water to contain 400 ± 1 mL at 23.0 ±
2.0°C (see Note 1). For the purposes of this test, the capacity of the measure in milliliters is the
mass of the water content of the measure, in grams, divided by 0.9976, no correction in mass
being made for the buoyant effect of air. The measure shall have a uniform wall thickness. The
thickness of the wall and bottom shall not be less than 2.9 mm. The total mass of the empty
measure shall not be more than 900 g. The measure shall be made of a metal not attacked by the
cement mortar.
Note 1—The 400-mL measure can be calibrated readily by filling with distilled water at 23.0 ±
2.0°C to a point where the meniscus extends appreciably above the top of the measure, placing a
clean piece of plate glass on the top of the measure, and allowing the excess water to be squeezed
out. The absence of air bubbles as seen through the glass ensures the measure is completely full.
Care shall be taken that the excess water is wiped from the sides of the container before
determining the mass.

5.3. Mixer, Bowl, and Paddle—Conforming to the apparatus section of T 162.

5.4. Straightedge—A steel straightedge not less than 200 mm long and not less than 1.5 mm or more
than 3.5 mm in thickness.

5.5. Standard Masses and Balances—Conforming to the requirements of ASTM C1005. The balance
device shall be evaluated for precision and accuracy at a total load of 2 kg.

5.6. Glass Graduates—Glass graduates of 250-mL capacity, conforming to the requirements of

ASTM E438 and ASTM E694.

5.7. Tamper—In accordance with T 106M/T 106. The tamping face of the tamper shall be flat and at
right angles to the length of the tamper.

5.8. Tapping Stick—A piece of hard wood having a diameter of approximately 16 mm and a length of
approximately 152 mm.

5.9. Spoon—A metal restaurant-type serving spoon not less than 230 mm in length and with a bowl
approximately 100 mm in length.

TS-3a T 137-2 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
6. TEMPERATURE AND HUMIDITY
6.1. Maintain the temperature of the room and dry materials at 23.0 ± 4.0°C.

6.2. Condition the mixing water and the measure, if it is being calibrated at 23.0 ± 2.0°C.

6.3. The relative humidity of the laboratory shall not be less than 50 percent.

7. STANDARD SAND
7.1. Use sand conforming to the requirements of ASTM C778 for 20–30 sand.

8. SAMPLING
8.1. Sample the cement in accordance with T 127 (see Note 2).
Note 2—Polyvinyl chloride (PVC) sample containers, upon occasion, have been found to affect
the air-entraining potential of a cement sample. The same problem might be experienced with
containers made from other plastics.

9. PROCEDURE
9.1. Batch—Proportion the standard mortar using 350 g of cement to 1400 g of 20–30 standard sand
and sufficient water to give a flow of 87.5 ± 7.5 percent when determined in accordance with
Section 9.3.
Note 3—T 137 refers to hydraulic cements that comply under M 85 and M 240M/M 240.
Masonry cements, mortar cements, and plastic (stucco) cements require different sand, mass, and
flow. Refer to the applicable specification.

9.2. Mixing of Mortar—Mix the mortar in accordance with T 162.

9.3. Flow Determination—Carefully wipe dry the flow table top and place the flow mold at the center
of it. Using the spoon, place a layer of mortar about 25 mm in thickness in the mold and tamp
20 times with the tamper. The tamping pressure shall be just sufficient to ensure uniform filling of
the mold. Over fill the mold approximately 20 mm with mortar and tamp as specified for the first
layer. Then cut off the mortar to a plane surface, flush with the top of the mold, by drawing the
straightedge with a sawing motion across the top of the mold. Wipe the flow table top clean and
dry, being especially careful to remove any water from around the edge of the mold. Lift the mold
away from the mortar 60 s after completing the mixing operation. Immediately drop the table ten
times in accordance with M 152. The flow is the resulting increase in average diameter of the
mortar mass, as determined with the calipers, measured on at least four diameters at approximately
equispaced intervals and expressed as a percentage of the original diameter. Make trial mortars
with varying percentages of water until the specified flow is obtained. Make each trial with fresh
mortar.

9.4. Mass per 400 mL of Mortar—When the quantity of mixing water has been found that produces a
flow of 87.5 ± 7.5 percent, immediately determine the mass per 400 mL of mortar, using the
mortar remaining in the mixing bowl after the flow has been determined. In the determination of
the mass per 400 mL, do not use the portion of the mortar used in the flow determination.
Using the spoon, place the mortar gently into the 400-mL measure in three equal layers, tamping
each layer 20 times with the tamper around the inner surface of the measure. The position of the
tamper shall be that the broad side of the tamper is parallel to the radius and is perpendicular to the
inner surface of the measure. Each layer is tamped in on complete revolution (rotation) with only

TS-3a T 137-3 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
 sufficient pressure to adequately fill the measure and eliminate voids within the mortar. After the
measure has been filled and tamped in the above-prescribed manner, tap the sides of the measure
lightly with the side of the tapping stick, one each at five different points at approximately equal
spacing around the outside of the measure, to preclude entrapment of extraneous air (see Note 4).
No obvious space shall be left between the mortar and the inner surface of the measure 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 the straightedge with a sawing motion across the top of the measure, making
two passes over the entire surface, the second pass being made at right angles to the first. If, in the
striking-off operation, loose sand grains cause the straightedge to ride above the top surface of the
measure, these grains shall be removed and the operation repeated. Complete the entire operation
of filling and striking off the measure within 90 s. Wipe off all mortar and water adhering to the
outside of the measure. Determine the mass of the measure and its contents. Subtract the mass of
the container, and record the mass of the mortar in grams.
Note 4—This operation may be facilitated by placing the measure on a steady flat-surfaced
support of lesser diameter than the measure while filling and wiping.

10. CALCULATION
10.1. Calculate the air content of the mortar from the following formula (see Note 5), which is based on
batch proportions given in Section 9.1, taking the specific gravity of portland cement as 3.15 and
of 20–30 standard sand as 2.65. When the hydraulic cement is other than portland, the appropriate
value for its specific gravity shall be substituted for the value of 3.15 and the formula rederived
accordingly:
air content, volume, percent =100 − W [(182.7 + P)/(2000 + 4P)] (1)
where:
W = mass of 400 mL of mortar, g; and
P = percentage of mixing water, based on mass of cement used.

Note 5—This formula can be derived as follows:

air content, volume, percent
= 100[1 − (Wa / Wc )] (2)
where:
Wa = actual mass per unit of volume as determined by this test method;
= W/400 g/mL, where W is the mass in grams of the specified 400 mL of mortar (see
Section 9.4);
Wc = theoretical mass per unit of volume, calculated on an air-free basis as follows and
using the values for quantities of materials and specific gravities as given in Sections 9.1
and 10.1:
350 + 1400 + 350 × P × 0.01
=
350 1400 350 × P × 0.01
+ +
3.15 2.65 1
(5 + 0.01P)
=
(1.827 + 0.01P)
P = percentage of mixing water, based on mass of cement.
Substituting for Wa and Wc, we have:
Air Content, Volume, Percent:
 W 1.827 + 0.01P 
= 100 1 − × 
 400 5 + 0.01P 

TS-3a T 137-4 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
 W (1.827 + 0.01P)
= 100 − ×
4 (5 + 0.01P)
(182.7 + P)
= 100 − 2.5W
(5000 + 10 P)
(182.7 + P)
= 100 − W
(2000 + 4 P)

10.2. Make only one determination of air content on a batch. (See Note 6.)
Note 6—Difficulty has occasionally been experienced with this test by some persons. These
difficulties usually have taken the form of values for air content that are abnormally high and that
may be greater than the specified maxima in specifications for hydraulic cement. The air-
entraining potential of the sand may be reduced by washing in the laboratory with potable water
by decantation until a clear, colorless supernatant liquid is obtained. In case of dispute, such
freshly washed sand shall be used.

11. REPORT
11.1. When this test method is used for specific action in compliance testing, the value for air content
shall be reported to the nearest 1 percent.

12. PRECISION AND BIAS

12.1. The single operator, within-laboratory, standard deviation has been found to be 0.56 percent
air content throughout the range of 8 to 19 percent air. Therefore, results of two properly
conducted tests by the same operator on similar batches should not differ by more than
1.6 percent air.

12.2. The multilaboratory standard deviation has been found to be 1.0 percent air content throughout the
range from 8 to 19 percent air. Therefore, results of two different laboratories on similar batches
should not differ from each other by more than 2.8 percent air.

13. KEYWORDS
13.1. Air content; hydraulic cement; mortar.

TS-3a T 137-5 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.