SPECIAL REPORT 97-16

Increasing Cold Weather Masonry

Construction Productivity

Charles J. Korhonen, Robert D. Thomas, and Edel R. Cortez August 1997
Abstract: The thermal protection requirements for cold

weather masonry, as established in current industry

specifications, were evaluated. Experiments were

conducted to define the most relevant factors in the

process of freezing of newly placed mortar. The effect

of unit absorption on the moisture content of mortar

during the first hours after assembly was assessed.

Correlations of moisture content with time were developed for mortar in contact with masonry units. Frost

immunity thresholds in terms of mortar moisture content and in terms of maturity were determined. The test

results provided the basis for new proposed guidance

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on when fresh mortar can be safely exposed to freezing temperatures. Test methods for evaluation of the

freeze–thaw resistance of masonry units were evaluated. A new test was proposed and adopted by ASTM as

a new standard test for the freeze–thaw testing of masonry units. In addition, several chemicals were evaluated for their potential as antifreeze admixtures for

masonry mortar. Antifreeze admixtures were first developed for use in concrete, but the practicality of using antifreeze admixtures in masonry mortars was

demonstrated in a field application in Michigan during

the winter.
Special Report 97-16

Increasing Cold Weather Masonry

Construction Productivity

Charles J. Korhonen, Robert D. Thomas, and Edel R. Cortez August 1997

Prepared for

OFFICE OF THE CHIEF OF ENGINEERS

Approved for public release; distribution is unlimited.

US Army Corps

of Engineers®

Cold Regions Research &

Engineering Laboratory
PREFACE

This report was prepared by Charles J. Korhonen and Edel R. Cortez, Research Civil Engineers, Civil and Geotechnical Research Division, Research

and Engineering Directorate, U.S. Army Cold Regions Research and Engineering Laboratory, and Robert D. Thomas, Director of Research, National Concrete Masonry Association.

This research project was conducted under authority of the U.S. Army

Corps of Engineers Construction Productivity Advancement Research (CPAR)

initiative. The project, titled Increasing Cold Weather Masonry Construction Productivity, was approved in August 1993. It was conducted in partnership between the U.S. Army Cold Regions Research and Engineering Laboratory

(CRREL) and the National Concrete Masonry Association (NCMA). The research was conducted from May 1994 to July 1996.

Technical review of this report was provided by Albert W. Isberner, Consulting Materials Engineer, and Marshal Brown, General Manager, Research,

Lehigh Portland Cement Company. The authors acknowledge the support of

William Ring, NCMA, Albert W. Isberner, consultant, and Brian Charest and

Christopher Berini of CRREL. LaFarge is acknowledged for providing the cement used in this project.

The contents of this report are not to be used for advertising or promotional purposes. Citation of brand names does not constitute an official endorsement or approval of the use of such commercial products.

ii
iii

CONTENTS

Preface ................................................................................................................................................ ii

Introduction....................................................................................................................................... 1

Background................................................................................................................................... 1

Objectives ...................................................................................................................................... 1

Approach ...................................................................................................................................... 2

Laboratory experiments .................................................................................................................. 2

Absorption .................................................................................................................................... 2

Freezing strength ......................................................................................................................... 12

Antifreeze admixtures ................................................................................................................ 14

Freeze–thaw durability ............................................................................................................... 17

Field demonstration ......................................................................................................................... 23

Objective........................................................................................................................................ 23

Temporary enclosure................................................................................................................... 23

Constructing the wall.................................................................................................................. 23

Thermal history............................................................................................................................ 24

Mortar strength ............................................................................................................................ 25

Efflorescence ................................................................................................................................. 26

Cost comparison .......................................................................................................................... 26

Conclusions ....................................................................................................................................... 26

Recommendations ............................................................................................................................ 27

Commercialization and technology transfer ............................................................................... 28

Literature cited .................................................................................................................................. 28

Appendix A: Absorption test results ............................................................................................. 29

Appendix B: Bond strength of mortar joints ................................................................................ 31

Appendix C: ASTM C 1262, “Standard Test Method for Evaluating the Freeze–Thaw

Durability of Manufactured Concrete Masonry Units and Related Concrete Units” ...... 33

Appendix D: Masonry unit freeze-thaw durability test results ............................................... 37

Appendix E: Air-void analyses ...................................................................................................... 43

Appendix F: Proposal to the All-Weather Council ..................................................................... 47

ILLUSTRATIONS

Figure

1. Research plan........................................................................................................................... 2

2. Effect of unit moisture on water uptake ............................................................................. 5

3. Effect of water temperature on water uptake .................................................................... 5

4. Effect of unit manufacture on water uptake ...................................................................... 6

5. Effect of absorption surface on water uptake .................................................................... 6

6. Effect of unit moisture on mortar moisture loss ................................................................ 9

7. Effect of bagged test condition on test no. 14 ..................................................................... 9

8. Effect of air temperature on rate of moisture mortar loss ................................................ 10

9. Effect of mortar temperature ................................................................................................ 11

10. Effect of unit manufacture on rate of mortar moisture loss ............................................. 11

11. Critical moisture ..................................................................................................................... 12

12. Critical maturity ...................................................................................................................... 13

13. Setting times of admixture-free mortar and mortar containing the admixture KC1... 15
iv

Figure

14. Rapid freeze–thaw test results for specimens with and without KC1 ........................... 16

15. Joint test results of the experiments to assess the effect of KC1 on bond strength,

and the effect of mortar moisture content at the time of freezing on bond strength 16

16. Results of the modified ASTM C 666 freeze–thaw test on segmental retaining wall

units ...................................................................................................................................... 18

17. Freeze–thaw test results for median specimen from each set of segmental retaining

wall units ............................................................................................................................. 19

18. Pore size distributions before and after freezing and thawing ....................................... 21

19. Penetration of mortar with and without the antifreeze admixture ................................ 24

20. Building the wall ..................................................................................................................... 24

21. Thermal history of the masonry walls and surrounding air ........................................... 25

22. Strength of mortar cylinders cast during construction..................................................... 26

TABLES

Table

1. Mortar mixture volumetric proportions ............................................................................. 3

2. Specific gravity and density of mortar ingredients ........................................................... 3

3. Allowable absorption values for concrete masonry units ............................................... 4

4. Unit properties ........................................................................................................................ 4

5. Matrix of partial unit immersion tests................................................................................. 4

6. Matrix of mortar moisture loss tests .................................................................................... 8

7. Compressive strength of mortars containing various admixtures ................................. 14

8. Average tested properties of SRW units using ASTM C 1262 and C 141 ...................... 19

9. Test results from the microscopic examination of hardened mortar .............................. 20

10. Relative performance of specimens in each test ................................................................ 23
INTRODUCTION

Background

Since 1970, the International Masonry Industry All-Weather Council (IMIAWC) has provided

guidance for cold weather masonry construction

(IMIAWC 1988). Among other things, IMIAWC

recommends that fresh mortar not be placed on

snow- or ice-covered surfaces, and that it be

maintained above freezing for 16 to 24 hours after

placement. Low temperatures can slow the

strength gain of mortar, and sufficiently low temperatures can permanently damage it. Though

fresh mortar can develop apparent strength while

frozen, this strength dramatically degrades when

the mortar is thawed.

In its guide specifications, the Council requires

that the moisture content of newly placed mortar

be reduced to a maximum of 6% prior to discontinuing heating. The guide specification does not

provide guidance on the time needed for typical

masonry mortars to reach the required moisture

content. In addition, heating mortar ingredients,

especially water, up to 50°C (122°F) is recommended to assist in frost protection.

The recommendations contained in the guide

specification were based on the experience and

empirical data available at the time it was written. As a result of limited experimental data, the

guidance is quite conservative. It constitutes a

safe approach to uncertainty, but results in significant cost penalty. This research project has produced experimental data that can lead to a safe

reduction in thermal protection.

The minimum cold weather protection is no

thermal protection at all. This can only be

achieved with the help of antifreeze admixtures.

Antifreeze admixtures have been successfully

Increasing Cold-Weather Masonry Construction Productivity

CHARLES J. KORHONEN, ROBERT D. THOMAS, AND EDEL R. CORTEZ

used in concrete (Korhonen et al. 1994). Since masonry mortars are also portland-cement-based, it

seems reasonable to investigate the application of

antifreeze admixtures to masonry mortar as well.

However, there are significant differences between concrete and mortar that must be considered. As little water as possible is used in the

preparation of concrete. In contrast, high water

contents in mortar are not of concern during mixing because the concrete masonry units on which

the mortar is placed draw free water out of the

mortar. This suction of water from mortar results

in a rather open pore structure in the hardened

mortar. The aggregates used in concrete are also

much coarser than those used in mortar. For these

and other reasons, while positive experiences

with admixtures in concrete provide promise for

their use in masonry mortar, testing is certainly

required to demonstrate their effects on masonry

mortar.

Objectives

The intent of this project was to develop improved cold-weather masonry criteria, construction procedures, and guide specifications that

minimize excessive protection requirements for

newly installed masonry, thus resulting in improved long-term freeze–thaw durability and

economy. The specific objectives were:

1. Evaluate cold-weather performance of

masonry,

2. Evaluate antifreeze admixtures for masonry

mortars, and

3. Update guide specifications for coldweather masonry.

To evaluate the cold-weather performance of

conventional masonry systems, experiments
were planned to define the parameters that determine whether a newly placed masonry system

will be harmed by cold weather. The active ingredient in the mechanism of frost damage is water.

Therefore, the experimental work followed the

moisture content of mortar and masonry units

from the mixing operation to the masonry assembly stage through the curing period. The experiments also evaluated the practicality of using

antifreeze admixtures, originally designed for

cold-weather concrete, in masonry mortars. The

final objective was to transfer findings through reports, conference papers, and updates to masonry

construction manuals.

Approach

The experimental work in this project consisted of two major stages: a series of laboratory

experiments, and a field application. As shown in

Figure 1, the laboratory experiments were divided

into two sections. Section 1 evaluated the effect of

low temperatures on conventional masonry, and

section 2 evaluated the usefulness of antifreeze

admixtures. The laboratory experiments were a

series of tests, each designed to produce information useful to better define the minimum thermal

protection requirements for cold weather

masonry construction. The test results enhanced

our knowledge of the mechanisms of freezing

and the moisture regime of typical masonry built

in cold weather. The field application demonstrated the use of antifreeze admixtures in winter

masonry construction.

LABORATORY EXPERIMENTS

Absorption

Objective

Dry mortar is immune to frost damage; watersaturated mortar is susceptible to frost damage.

At the time of placing, mortar is water saturated,

and therefore frost susceptible. To define the transition between susceptibility and immunity, three

fundamental parameters needed to be defined: a)

the maximum water content that mortar can have

without frost damage, b) the time needed for

mortar to dry to any given moisture content, and

c) the major factors that determine the rate of

mortar moisture loss. One of these factors is the

absorption of mortar moisture by the masonry

units. The objective of this section of the report is

to develop correlations of mortar moisture content versus time for mortar placed between typical masonry units.

Mortar types and mixture proportions

ASTM C 270 lists four types of mortar (M, S, N,

and O) specified under each of two types of cement blending methods: on-the-job blending of

portland cement and lime (PCL), and factory preblended masonry cement (MC). Two mortar mix

design methods are in common use: the proportion method and the property method. The

proportion method specifies certain volumes of

portland cement, hydrated lime, and sand to be

mixed with water to achieve a certain degree of

workability. Alternatively, prebagged masonry

cement (MC) can be used together with sand and

water to achieve the same effect. The property

method allows for the use of alternative volume

combinations, provided laboratory test mortar

achieves the prescribed values for strength, water

retention, and air content. The proportion method was used for the mortar mix designs of this

project.

Hydration and strength development rates are

reduced as ambient temperatures drop. Generally, no specific rules are given for selecting a

mortar type for use at low temperatures. However, it is acknowledged that higher portland

cement contents promote higher strengths at low

temperatures compared with similar mortars

2

Figure 1. Research plan.

Conventional

Masonry

Section 1

Antifreeze

Admixtures

Section 2

Absorption Compressive

Strength

Bond

Strength

Field

Demonstration

Durability

Freezing

Strength

Technology

Transfer

Durability
containing low amounts of portland cement.

Thus, two of the four mortar types from the portland cement–lime (PCL-M and -N) and the

masonry cement (MC-M and -N) proportioning

methods were chosen for testing. The type M mortar contains more portland cement than does type

N.

The mixture proportions of the four mortars

studied are given in Table 1 based on bulk volumes as specified in ASTM C 270. Table 2 provides

the physical values used to determine batch

weights for each study.

Experimental approach

Lower water contents in mortar result in improved resistance to damage from freezing. Because concrete masonry units are porous in nature

and have an affinity for drawing moisture from

masonry mortar, the absorptive properties of the

masonry unit may play an important role in the

performance of masonry assemblies in cold

weather.

Immediately after fresh mortar is placed in contact with the masonry unit, the masonry begins to

draw free water from the mortar. Over time, water

loss in the mortar continues due to prolonged contact with the masonry unit, evaporation to the air,

and hydration of the cement within the mortar. We

evaluated the rate of water loss by the mortar as it

is affected by contact with the concrete masonry

unit. Several different unit types with a range of

unit properties, moisture contents, and temperatures were used to document this effect.

The rate of absorption of water by masonry

units was also compared with their rate of absorption of free water (determined through partial unit immersion in accordance with the initial

rate of absorption procedures of ASTM C 67) as

well as with the total absorption potential of the

unit (determined through full unit immersion in

accordance with the absorption procedures of

ASTM C 140). If there is a correlation between absorption of water from mortar to either of these

standardized procedures, the values of those

standard procedures can be used to predict the

rate of mortar water loss.

Full unit immersion tests

The absorption procedures within ASTM C

140 involve the full immersion of units in water

maintained at approximately 20°C (68°F) for a

period of 24 hours. After 24 hours, the assumption of the test method is that the unit has

absorbed as much water as it will ever absorb as a

result of the pressure created by the water in the

tank. While immersed, the unit is weighed suspended so that its buoyancy force can be evaluated to determine the volume of water it displaces.

Once removed from the tank, the unit is weighed

in air in a saturated, surface-dry condition and

then placed into an oven maintained at approximately 107°C (225°F) for not less than 24 hours.

The oven dry weight of the unit is then recorded.

The test method provides two methods of

expressing the total amount of water that the unit

could absorb. The first is absorption expressed as

the volume of water absorbed per net volume of

solid concrete material. The second method is

absorption expressed as the weight of water

absorbed per dry weight of material presented on

a percentage basis. For concrete masonry units,

the first method is preferred.

The absorption values for a concrete masonry

unit are affected by a number of production variables including gradation of the aggregates used,

mix water content, amount and types of cement,

admixtures and other materials used, production

machine type and settings, and even unit configuration. All of these variables affect how well a

unit can be compacted. However, the variable

that has the most influence on the absorption of

the unit is the type of aggregate(s) used in its

manufacture. Lighter-weight aggregates tend to

be more porous and therefore have more air

voids that can be filled with water. The industry

standards for concrete masonry units include

maximum absorption limits as a means of ensur3

Table 1. Mortar mixture volumetric proportions.

Portland

cement, Hydrated Masonry Masonry

Type type I lime cement sand

PCL-M 1.00 0.25 — 3.75

PCL-N 1.00 1.25 — 6.75

MC-M — — 1.00 3.00

MC-N — — 1.00 3.00

Table 2. Specific gravity and density of

mortar ingredients.

Specific Bulk density

Ingredient gravity (kg/m3 [lb/ft3])

Portland cement 3.15 1507 (94)

Masonry cement, type M 2.97 1271 (80)

Masonry cement, type N 2.95 1122 (70)

Lime 2.34 641 (40)

Masonry sand 2.67 1271 (80)
ing adequate compaction was achieved. The higher

absorptive properties of units made with lighterweight aggregates is reflected in the sliding-scale

requirements for absorption based on unit density.

ASTM C 90, “Standard Specification for Loadbearing Concrete Masonry Units,” includes the

absorption requirements given in Table 3.

For this research, three sets of concrete masonry

units, each having different absorption characteristics resulting from production differences, and

one set of concrete brick were used. Representative specimens from each set were tested in

accordance with the absorption procedures of

ASTM C 140. The results of those tests are shown

in Table 4 along with other tested parameters determined in accordance with ASTM C 140.

Partial unit immersion tests

A standard method of evaluating the water

uptake capabilities of a unit partially immersed

in water is included in ASTM C 67. The method

involves placing a unit within a container of water such that the immersion depth of the unit is

3.2 mm (1/8 in.) for a period of 1 min. The amount

of water absorbed by the unit over the 1-min period is determined by the difference in unit weight

before and after immersion.

The primary force that pulls water up into the

unit is capillary suction. The test method determines the effect of various parameters on water

absorption including unit moisture, unit manufacture, unit surface characteristics, and water

temperature (Table 5).

The units described as having “dry” moisture

content had been stored in the laboratory for several months, and their moisture content at the

time of testing averaged 15% of their total absorption, which is typically drier than most units used

in winter construction. Those units referred to as

having “normal” moisture content are perhaps

nearer in water content to units typically used in

winter construction. To obtain this moisture con4

Table 3. Allowable absorption values for concrete

masonry units.

Light Medium Normal

Unit weight weight weight weight

classification (kg/m3) (kg/m3) (kg/m3)

Unit oven-dry density < 1680 1680 to 2000 >2000

Max. allowable absorption 288 240 208

Table 4. Unit properties.

Unit property Concrete CMU CMU CMU

(average) brick A B C

Width, mm (in.) 91.4 (3.60) 194.1 (7.64) 193.8 (7.63) 193.5 (7.62)

Height, mm (in.) 69.1 (2.72) 193.8 (7.63) 193.5 (7.62) 192.8 (7.59)

Length, mm (in.) 188.5 (7.42) 396.5 (15.61) 396.2 (15.60) 396.5 (15.61)

Net area, top, mm2 (in.2) 17,226.0 (26.7) 37,548.0 (58.2) 37,548.0 (58.2) 37,548.0 (58.2)

Net area, bottom, mm2 (in.2) 17,226.0 (26.7) 42,774.0 (66.3) 42,774.0 (66.3) 42,774.0 (66.3)

Absorption, kg/m3 (pcf) 157.0 (9.8) 155.0 (9.7) 229.0 (14.3) 230.0 (14.4)

Density, kg/m3 (pcf) 2,110.0 (131.9) 2,096.0 (131.0) 1,642.0 (102.6) 1,490.0 (93.1)

Net strength, MPa (psi) — 21.9 (3,180) 16.1 (2,340) 21.2 (3,070)

Table 5. Matrix of partial unit immersion tests.

Unit Water Air

Test Unit Unit temperature Unit temperature temperature

no. type surface* (°C) (°F) moisture (°C) (°F) (°C) (°F)

1t CMU A Top 20 68 Dry 20 68 20 68

1b CMU A Bottom 20 68 Dry 20 68 20 68

2t CMU B Top 20 68 Dry 20 68 20 68

2b CMU B Bottom 20 68 Dry 20 68 20 68

3t CMU C Top 20 68 Dry 20 68 20 68

3b CMU C Bottom 20 68 Dry 20 68 20 68

4 Brick Side face 20 68 Dry 20 68 20 68

5 Brick Side face 20 68 Normal 20 68 20 68

6 Brick Side face 20 68 Wet 20 68 20 68

7 Brick Side face 5 41 Dry 5 41 5 41

8 Brick Side face 5 41 Dry 20 68 5 41

9 Brick Side face 5 41 Dry 30 86 5 41

* Unit surface described based on orientation of unit as made.
tent, units were fully immersed in water for 24

hours and then allowed to dry until they averaged 50% of their total absorption. The units

referred to as “wet” contained much more moisture than units typically used in winter construction. This condition was achieved by allowing

saturated units to air-dry only to the point that

there was little to no remaining free surface moisture present, although a large majority of the surface area was still observed to be damp. The resulting moisture content of these units averaged

85% of total absorption.

Appendix A summarizes the water uptake results. Figures 2 through 5 provide a discussion of

the most important findings from the partial immersion tests.

5

Time of Partial Immersion (min)

Weight of Water Absorbed (g)

Dry Units

Normal Units

Wet Units

70

60

50

40

30

20

10

0

0 2 4 6 8 10 12 14 16

Figure 2. Effect of unit moisture on water uptake. The brick, water, and

air temperatures are 20°C.

Time of Partial Immersion (min)

Weight of Water Absorbed (g)

 5°C Water

20°C Water

30°C Water

80

70

60

50

40

30

20

10

0

0 5 10 15 20 25 30

Figure 3. Effect of water temperature on water uptake. Brick and air

temperatures are 5°C.

Effect of unit moisture. The dry concrete brick

absorbed nearly twice the water weight in the

partial immersion test in comparison with the

normal and wet units (Fig. 2). The water uptakes

were nearly identical for the normal and the wet

units after 1 minute of immersion time, but after

15 minutes the wet units absorbed nearly 15%

more water than did the normal units.

Effect of water temperature. This comparison

used dry brick. Water temperature appeared to

have little effect on the ability of cold units to

absorb water in the partial immersion test. As

shown in Figure 3, cold units were able to absorb

slightly more 20°C (68°F) water than 5°C (41°F)

water and slightly more 5°C water than 30°C

(86°F) water. However, there was never more
than 7% difference between the absorption rates at

any time during the test.

Effect of unit manufacture. The difference in the

water uptake test results of CMU B in comparison

with the other units indicates that physical unit

characteristics can significantly influence capillary

suction (Fig. 4). While the absorption rates (top

and bottom surfaces averaged) of CMU A and

CMU C were very similar, CMU B had absorbed

nearly 50% more water than the other two CMUs

after 1 minute and nearly 100% more water after

15 minutes. The water uptake rates of the concrete

brick were more similar to those of CMUs A and C.

However, while the concrete brick absorbed more

water than either of these two CMUs after 1

minute, it absorbed very little additional water

over the next 14 minutes of immersion in comparison with CMUs A and C such that its total absorption was less than that of the two CMU types.

Effect of absorption surface. The top and bottom

surfaces of concrete masonry units can differ significantly in surface texture and appearance. The

bottom surface of the unit is molded against the

machine pallet during manufacture, resulting in a

smooth and fine texture. The top of the unit is not

molded, however, and therefore is typically

rougher and more open. In concrete masonry, the

mortar bed joint is in contact with both of these

unit surfaces from the units above and below it.

Water uptake tests were performed on both surfaces of the concrete masonry units to determine

surface effects.

As shown in Figure 5, surface characteristics

can have a significant influence on capillary suction. In the case of CMUs B and C, there was a dif6

Time of Partial Immersion (min)

Weight of Water Absorbed per Area (g/cm2) 1.0

0.8

0.6

0.4

0.2

0.0

0 2 4 6 8 10 12 14 16

CMU A

CMU B

CMU C

Brick

Figure 4. Effect of unit manufacture on water uptake. Unit, water, and

air temperatures are 20°C.

0.49 0.51

1.17

0.2

0.4

0.6

0.8

1.2

1.4

CMU A CMU B CMU C

Ratio of Top Water Uptake to Bottom Water Uptake 1.0

0.0

Figure 5. Effect of absorption surface

on water uptake.

ference in water absorptions of approximately

100% between the top and bottom surfaces of the

same unit, with the bottom manufactured surface

having the greater capillary suction. However,

the results of tests on CMU A prevent drawing

the conclusion that the bottom surface consistently results in increased water uptake. While the

water weight absorbed by the two surfaces of

CMU A were nearly identical, the smaller surface

area of the top of the unit as manufactured actually gave it a greater water absorption per unit

area than the bottom surface.
Mortar moisture loss tests

The rate of water loss from mortar can be affected by a number of different variables. Those variables investigated as part of this research include:

unit type, unit moisture content, unit temperature,

mortar type, mortar temperature, and air temperature. Among those properties not evaluated are the

relative humidity of the air surrounding the units

and the effects of wind. The testing was not structured to distinguish between mortar moisture loss

attributed to absorption from the units and moisture loss attributed to evaporation to the air. To reduce the number of tests required and to facilitate

laboratory constraints, most of the testing was performed using a single unit type (concrete brick)

and a single mortar type (type M masonry cement

mortar).

All mortar was proportioned using 2880 g of

masonry sand. Batch weights of other materials

(portland cement, masonry cement, and lime)

were determined based on the volume proportions included in Table 1. Mortar was mixed in the

laboratory using a Hobart mechanical mixer. With

the exception of the type of mixer used, mixing

was performed to simulate field conditions. In the

field, the mason is allowed to adjust the water content of the mortar by eye to achieve the necessary

mortar workability to accommodate the existing

conditions at the job site. For example, on hot,

windy days, the mason may use additional water

in mixing to prevent premature drying of the mortar. Less absorptive units may require the mason

to reduce the amount of water in the mix. Various

mortar admixtures may also require the mason to

adjust the mortar. Because some of the variables in

these tests may affect water demand, the mason

was allowed to adjust the water content as necessary to achieve the desired mortar consistency.

Tests were performed on the fresh mortar to document its air content, unit weight, and consistency

by cone penetration (ASTM C 780).

For all mixes involving the primary mortar type

in this program, type M masonry cement mortar,

no adjustments of water content were found to be

necessary despite variations in the temperature of

the mortar materials from 5 to 20°C (41 to 68°F).

The resulting tested moisture contents for these

mortars were therefore rather consistent (13.9 to

15.9%), as were the cone penetrations. It was

found that more water was required to obtain a

similar mortar consistency in the portland cement

and lime mortars—particularly for the PCL type

M mortar, which contains a greater proportion of

cementitious materials than the other mortars.

The mortar was used to fabricate two prisms

each with two units separated by a single full mortar bed joint. The mortar was placed on the top of

the bottom brick using a mortar template to

achieve a uniform joint thickness and to reduce

workmanship variations between prisms. The second brick was then carefully placed onto the mortar joint and the joint was compacted using a 1.8-kg

(4-lb) drop hammer to apply an impact force to the

top brick. Using the same mortar, the second prism

was then fabricated in the same manner. Prism fabrication was completed within 10 minutes after

mortar mixing.

Five minutes after the first prism was fabricated, the top unit was removed from the prism and

the exposed mortar joint was cut into a grid. One of

the grid segments was sampled using a spatula

and measured for moisture content. Approximately 30 g of mortar was sampled, placed on a ceramic

plate, and dried in a microwave oven. The moisture content was calculated based on the difference

between the initial weight of the mortar compared

with its final dry weight. The top brick was placed

back on the exposed mortar joint, and the prism

remained undisturbed until the next sampling

time. This procedure was repeated at 5, 15, 30, 45,

60, 120, 240, and 1440 min.

These procedures were used to evaluate the effects of unit temperature, unit moisture content,

mortar type, mortar temperature, and air temperature on the rate of mortar water loss. Similar procedures were used with several different concrete

masonry units to investigate the effects of unit

manufacturing. The matrix of combinations used

to achieve this information is listed in Table 6. Two

prisms were fabricated for each of the combinations shown.

Different mortar temperatures were achieved

by heating or cooling the mortar materials (cement, sand, water) before the mortar was mixed.

Unit temperatures were achieved by the same

method. Two different air temperatures were used,

5 and 20°C (41 and 68°F). Those prisms that were

kept at 20°C (68°F) were stored in the open lab air

for the duration of the test. Those prisms kept at

5°C (41°F) were placed within an environmental

chamber maintained at that temperature. Because

the chamber requires air circulation to maintain

specified temperatures, the prisms were sealed in

plastic bags to prevent wind effects from influencing the loss of moisture from the mortar. At the

specified sampling times, the prisms were removed from the chambers, the bags were opened,

the mortar sample was taken, and the prisms were

7
placed back into the bags and returned to the cooling chamber.

Appendix A summarizes the results of the mortar moisture loss tests. Figures 6 through 10

present the significant findings from the tests.

Effect of unit moisture. The effect of masonry unit

moisture content on mortar moisture loss was

measured using six different combinations of mortar and unit temperature. In all six cases, mortar in

contact with the dry units exhibited a much

greater rate of moisture loss than with either the

normal or the wet units. In addition, in all six cases, as expected, the wet units resulted in the lowest

rate of mortar moisture loss. While the moisture

loss of the mortar in contact with normal units was

always greater than that in contact with wet units

and lower than that in contact with dry units, the

relationships between them were not always consistent. In two of the six cases, the mortar moisture

loss was approximately equal to the average of

that with the dry and wet units, as exemplified in

Figure 6a. In the other four cases, there was essentially no difference in mortar moisture loss between the normal and the wet units, as shown in

Figure 6b.

The tests plotted in Figure 6 were all cured in

sealed bags in the cooling chamber, as were all

tests conducted at 5°C (41°F) air temperatures. It is

reasonable to assume that throughout the test the

mortar was losing moisture not only to the units in

which it was in direct contact, but also to the air

within the bag. The wetter the unit, the quicker the

buildup of relative humidity within the bag,

which reduced subsequent moisture loss from the

mortar to the humid air. Condensation within the

plastic bags during the tests supports this contention. The effect of bagging the prisms can be seen

in Figure 7. Due to handling, the bag surrounding

one prism developed a hole that permitted moisture within the bag to escape. The effect of the

vented bag resulted in a significant reduction in

mortar moisture content in comparison with the

mortar in the other prism. At the conclusion of the

24-hr test, both prisms were removed from their

bags and returned to the cooling chamber. The rate

of moisture loss from the mortar in the unvented

prism then increased significantly, but the rate of

moisture loss from the mortar in the vented prism

was virtually unaffected. Within several hours, the

moisture contents of both prisms stabilized at an

8

Table 6. Matrix of mortar moisture loss tests.

Unit Mortar Air

Test Unit temperature Unit Mortar temperature temperature

no.* type† (°C) (°F) moisture type (°C) (°F) (°C) (°F)

1 Brick 20 68 Dry MC-M 20 68 20 68

3 Brick 20 68 Dry MC-N 20 68 20 68

4 Brick 20 68 Dry PCL-M 20 68 20 68

6 Brick 20 68 Dry PCL-N 20 68 20 68

7 Brick 20 68 Dry MC-M 5 41 5 41

8 Brick 20 68 Dry MC-M 20 68 5 41

9 Brick 20 68 Dry MC-M 30 86 5 41

10 Brick 5 41 Dry MC-M 5 41 5 41

11 Brick 5 41 Dry MC-M 20 68 5 41

12 Brick 5 41 Dry MC-M 30 86 5 41

13 Brick 20 68 Normal MC-M 5 41 5 41

14 Brick 20 68 Normal MC-M 20 68 5 41

15 Brick 20 68 Normal MC-M 30 86 5 41

16 Brick 5 41 Normal MC-M 5 41 5 41

17 Brick 5 41 Normal MC-M 20 68 5 41

18 Brick 5 41 Normal MC-M 30 86 5 41

19 Brick 20 68 Wet MC-M 5 41 5 41

20 Brick 20 68 Wet MC-M 20 68 5 41

21 Brick 20 68 Wet MC-M 30 86 5 41

22 Brick 5 41 Wet MC-M 5 41 5 41

23 Brick 5 41 Wet MC-M 20 68 5 41

24 Brick 5 41 Wet MC-M 30 86 5 41

28 CMU A 20 68 Dry MC-M 20 68 20 68

29 CMU B 20 68 Dry MC-M 20 68 20 68

30 CMU C 20 68 Dry MC-M 20 68 20 68

* Several of the initially planned tests were not performed (2, 5, 25, 26, 27).

† Unit properties are listed in Table 4.
9

Time After Mortar Placed on Brick (min)

Moisture Content (%)

0

4

8

12

16

0 50 100 150 200 250

Dry

Normal

Wet

Time After Mortar Placed on Brick (min)

Moisture Content (%)

0

4

8

12

16

0 50 100 150 200 250

Dry

Normal

Wet

Figure 6. Effect of unit moisture on mortar moisture loss using 20°C and

5°C units. Mortar (MC-M) and air temperatures are 5°C.

a. 20°C units.

b. 5°C units

Time After Mortar Placed on Brick (min)

Moisture Content (%)

Prism A (in sealed bag)

Prism B (in vented bag)

16

12

8

4

0

0 400 800 1200 1600 2000

Cured in

Bag

Cured out of

Bag

Figure 7. Effect of bagged test condition on test no. 14. Units and mortar

(MC-M) at 20°C, air temperature of 5°C.
approximately equal value. The removal of the

unvented prism from its bag and the venting of

the bag around the other prism resulted in a lower

relative air humidity around the prisms, which increased the rate of water loss to the air by both the

mortar and the units. The air circulation would

also contribute to increased evaporation. As the

units continued to dry due to these two factors, the

units were also then capable of absorbing more

water from the mortar.

Effect of air temperature. While air temperature

obviously influences many aspects of masonry

construction, air temperature by itself does not

appear to have a significant direct effect on the rate

of moisture loss in the masonry mortar (as long as

those temperatures are above the freezing point of

the water). The effect of reducing air temperature

from 20 to 5°C (68 to 41°F) using warm units and

warm mortar is shown in Figure 8.

Effect of mortar temperature. Mortar temperatures of 5, 20, and 30°C (41, 68, and 86°F) were

used with units of different moisture contents and

different unit temperatures in different air temperatures. Based on the results of these tests, there

appears to be little effect of mortar temperature on

rate of mortar moisture water loss (Fig. 9). A

slightly increased rate of water loss in the 30°C

(86°F) mortar was observed in comparison with

the other mortar temperatures when used with the

warm units. However, when cold units were used,

the mortar with a temperature approximately

equal to that of the units appeared to have the

slightly greater rate of water loss.

The effects of mortar temperature were evident

in the results of tests performed on fresh mortars.

Cone penetrations were consistently lower for

higher-temperature mortars and, correspondingly,

air contents decreased with increases in temperature (mortar water contents were maintained equal).

Effect of unit manufacture. The results of the full

immersion tests and the partial immersion tests as

well as other individual tests on the various units

considered confirmed that each unit has very different unit properties. The results of the absorption

from mortar tests, as shown in Figure 10, demonstrate that these different properties also affect the

rate of mortar moisture loss. The results correspond rather well to those of the partial immersion

test results. The partial immersion test demonstrated the wicking or suction potential for the

units. CMU B demonstrated the greatest such

potential in those tests, and the effect of that potential is shown in Figure 10 by working to reduce the

moisture content in the mortar at a faster rate than

the other unit types.

Effect of unit temperature. In nearly all of the nine

cases in which the effect of unit temperature could

be evaluated, the units with the higher unit temperature resulted in the greater rate of unit moisture loss. However, for the majority of those cases,

the increased rate of mortar moisture loss was negligible. The only cases in which there appeared to

be a real benefit to the warmer units was when

they were used with 30°C (86°F) mortar. This research did not address the effects of unit temperatures below the freezing point of water, 0°C (32°F).

10

Time After Mortar Placed on Brick (min)

Moisture Content (%)

16

12

8

4

0

0 400 800 1200 1600

20°C Air Temperature

5°C Air Temperature

Figure 8. Effect of air temperature on rate of moisture mortar loss. Dry units

and mortar (MC-M) at 20°C.
Comparison of water absorption test methods

While there does not appear to be a good relationship between the results of the full immersion

absorption test and the results of either of the two

other absorption test methods performed, there

does appear to be a rather promising relationship

between the results of the partial immersion tests

and the mortar moisture loss tests. These results

could support the use of the partial immersion

tests to predict the effects of concrete masonry

units on the rate of moisture loss by a masonry

mortar. For the partial immersion tests performed, the following conclusions about the mortar moisture loss tests could have been accurately

estimated:

• The relative relationship between the rate of

mortar moisture loss to the different units

evaluated

• The relative relationship between the effect of

unit moisture content on mortar moisture

loss

• The lack of significant influence of mortar

temperature on mortar moisture loss.

11

64.4

61.0

67.4

55

60

65

70

Mortar Temperature (°C)

Cone Penetration (mm)

5 20 30

9.0

9.5

10.0

10.5

Mortar Temperature (°C)

Air Content (%)

5 20 30

10.4

9.7

9.6

Figure 9. Effect of mortar temperature.

a. Initial cone penetrations b. Air contents.

Time After Mortar Placed on Brick (min)

Moisture Content (%)

16

12

8

4

0

0 400 800 1200 1600

CMU B

Concrete Brick

CMU A

CMU C

Figure 10. Effect of unit manufacture on rate of mortar moisture loss. Unit

and mortar (MC-M) temperatures are 20°C.
Freezing strength

Objective

Mortar is most susceptible to frost damage at

early age because: a) its pore structure is underdeveloped, and b) its moisture content is high.

Based on these two conditions, two experiments

were devised to establish thresholds of when

mortar can withstand one cycle of freezing and

thawing. The objective was to determine these

thresholds in terms of moisture content or in

terms of maturity.

Critical moisture

As stated above, the moisture content of mortar is a critical factor during early-age freezing.

Mortar is typically mixed to a moisture content of

between 13 to 16%, but due to evaporation, absorption into masonry units, and cement hydration, its moisture content declines. Current guidance is based on the premise that mortars that are

frozen while they contain more than 6% moisture

will be frost damaged and subsequently never

develop full strength. Conversely, it is believed

that mortars with moisture contents below 6% are

frost resistant. This section evaluated the effect of

freezing on fresh mortar in an attempt to identify

the maximum moisture content that mortar may

have and still be immune to one event of freezing.

The four mortar types described earlier were

made into several batches, each containing a different moisture content. Once mixed, the mortars

were cast into 50- × 100-mm (2- × 4-in.) plastic cylindrical molds. The mortar was placed into the

12

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Compressive Strength (MPa)

AA

% Moisture 

40

30

20

10

0

6 8 10 12 14 6 8 10 12 14 6 8 10 12 14 6 8 10 12 14

Portland

Cement/Lime–M

Portland

Cement/Lime–N

Masonry

Cement–M

Masonry

Cement–N

No Freeze AFreeze

Figure 11. Critical moisture.

cylinders in three equal lifts and was consolidated using a vibration table. This method of cylinder consolidation overcame many of the difficulties of dealing with the different moisture levels

between the mortar batches. Once consolidated,

the filled cylinder molds were capped with plastic lids and placed into a –20°C (–4°F) room overnight. The next morning the cylinders were

moved into a 20°C (68°F) room. After 28 days, not

including the time in the cold room, the mortar

cylinders were stripped from the plastic molds

and tested for compressive strength. Control cylinders from each batch that were not subjected to

freezing temperatures were tested at an equivalent age.

Figure 11 presents the compressive strength

test results from the four mortars made with five

different moisture contents. As can be seen, all

mortars were unaffected by being frozen at moisture contents of 6 and 8%, and each had a 28-day

strength that was equal to or greater than that of

the control mortar. In fact, the mortars performed

better, compared with the control, when frozen at

8% moisture contents than when frozen at 6%.

The effects of frost damage started to become evident at a moisture content of 10%. At that level,

the portland cement–lime mortars suffered a 9 to

12% loss of strength, but the masonry cement

mortars were largely unaffected. (Microscopic examination showed the masonry cement mortars

contained entrained air bubbles. The portland

cement–lime mortars did not contain entrained

air.) At moisture contents of 12% and above, all

mortars showed some, though not significant,
damage from early-age freezing. Interestingly,

the strongest portland cement–lime mortars

resulted from a moisture content of 12%, and the

strongest masonry cement mortar came from a

moisture content of 10%. Moisture contents

above and below these levels weakened the mortar. Despite efforts to mix and consolidate all of

the batches equally regardless of the mixing

water content, difficulties in working with drier

mortar batches may account for some of the

reductions in strength of the mortars with lower

water-to-cement ratios.

Critical maturity

The development of pore structure in mortar is

another mechanism that produces frost resistance. As a mortar matures, its water chemically

combines with cement, with the result that the

mortar increases in strength and decreases in free

water. At some age the quantity of freezable

water falls below a critical level and creates

empty pore space within the mortar that enables

the mortar to accommodate water–ice expansion

without damage. The objective of this experiment

was to determine the age at which mortar first

becomes resistant to a single cycle of freezing and

thawing.

A type M masonry cement mortar was utilized

for this test series. It was mixed to a 16% moisture

content at room temperature according to existing standards and cast into cylindrical samples

measuring 50 × 100 mm (2 × 4 in.) using vibration

as the method of consolidation. All of the mortar

cylinders cast for this phase of the testing were

made from a single mortar batch. The test consisted of periodically bringing one set of three cylinders into a –20°C (–4°F) room for at least 24 hr followed by room temperature curing for a total of 7

days, excluding the time in the cold room. The

cylinders were then stripped from their plastic

molds and tested in compression. Strengths were

compared with those of control samples that

were never frozen. The first set of cylinders went

into the cold room immediately after the samples

were cast. Additional cylinders were brought to

the cold room at 1-hr intervals through the first 12

hr, as well as a final set of cylinders at 48 hr. The

cylinders were kept in the cold room overnight,

and returned to a warm room the following afternoon.

Figure 12 shows the 7-day compressive

strengths for these cylinders. The dotted line in

the figure represents the 7-day strength of the

control mortar that was never frozen. As can be

seen, if a mortar is frozen at too early an age the

mortar loses strength. However, it is also clear

that once a mortar attains a certain maturity it can

resist frost damage. In this case, keeping the mortar at room temperature for a minimum of 5 3/4

 hr

before freezing enabled the mortar not only to resist frost damage but to begin to gain strength in

excess of the control. In fact, curing the mortar for

12 hr at room temperature before exposing it to

freezing temperatures produced a 10% increase

in strength. To confirm that there is a benefit to

freezing mortar, similar testing was done with the

other mortar types frozen at times between 8 and

60 hr and then cured at room temperature for 28

13

Time (hr) 

Compressive Strength (MPa)

14

12

10

8

0 8 16 24 32 40 48

7-Day Control (never frozen)

Figure 12. Critical maturity.
days. The optimum curing time was between 12

and 16 hr. Thus, early-age freezing is not always

harmful. One explanation for greater strengths of

mortar subjected to freezing temperatures is that

these low temperatures slow the hydration of the

cement, resulting in a more controlled (less violent) chemical reaction rate.

Antifreeze admixtures

Objective

The primary objective of the following tests

was to assess the practicality of using antifreeze

admixtures developed for concrete with masonry

mortars. In addition, some alcohols were evaluated for their ability to perform as antifreeze

admixtures for mortar.

Antifreeze admixtures are chemicals that protect mortar from freezing without the use of heaters. Currently, antifreeze admixtures are not recommended for use in mortar. The concern is that

such chemicals will harm compressive and bond

strengths or corrode embedded metals within the

mortar. A similar concern existed for concrete a

few years ago. Since then, certain chemicals have

been shown to protect concrete from freezing

without causing detrimental side effects (Korhonen et al. 1994). The objective of this section

was to evaluate whether a similar result was possible for mortar. This study evaluated chemicals

for their effect on low-temperature strength gain,

bond strength, and the freeze–thaw durability of

mortar.

14

Table 7. Compressive strength of mortars containing various admixtures. Strengths are

expressed as percentage relative to admixture-free mortar cured at 20°C (68°F).

Curing temp. (20°C) Curing temp. (–5°C) Curing temp. (–1°C)

Day Day Day Day Day Day Day Day Day Day Day Day

Admixture* 7 14 28 56 7 14 28 56 7 14 28 56

11.6% meth 79 90 94 100 8 36 63 103 0 5 29 96

17.4% meth 68 80 91 94 3 16 44 97 0 5 20 109

23.3% meth 47 63 78 92 0 6 23 91 0 0 8 105

2% CaCl2 , 11.6% meth 76 85 92 99 18 44 68 93 5 14 34 76

2% CaCl2 , 17.4% meth 67 72 87 91 12 29 51 101 4 10 22 96

2% CaCl2 , 23.3% meth 68 73 84 95 7 19 36 93 1 4 11 91

4% CaCl2 , 11.6% meth 72 80 87 91 7 33 52 95 0 4 22 88

4% CaCl2 , 17.4% meth 65 73 86 93 3 24 43 97 0 0 10 91

4% CaCl2 , 23.3% meth 55 62 79 86 2 14 34 93 0 0 5 87

1% CaCl2 , 23.3% IPA 68 80 94 103 5 18 37 102 0 4 17 104

17.4% IPA 83 93 100 104 2 0 31 104 0 0 2 90

6% KC1† 105 97 97 98 67 87 88 112 26 49 56 77

Control 100 100 100 100 5 10 13 NA NA NA NA NA

* meth = methanol; CaCl2 = calcium chloride; IPA = isopropyl alcohol; NA = not available.

† KC1 = U.S.-Army-patented admixture made of 3 weights of sodium nitrate + 1 weight of sodium sulfate.

Effect of temperature on strength

Experiments were conducted in the laboratory

to develop data that relate strength gain to curing

temperature. Strength tests were done on 50- ×

100-mm (2- × 4-in.) cylinders of admixture-free

mortar and mortar that contained the chemicals

shown in Table 7. The calcium chloride and KC1

chemicals were dosed by weight of cement, and

the two alcohols were dosed by weight as a percent replacement of water so as to maintain constant plasticity of the mortar. The mortars were

mixed to a moisture content of 16%, and cylinders

were cast at room temperature and brought into a

given coldroom a few minutes after being cast. At

the prescribed testing age, the cylinders were

brought back to room temperature and compression-tested as soon as the temperature at their

center of mass reached 5°C (41°F). (A dummy cylinder instrumented with a thermocouple served

as the temperature reference.) Some of the test

samples were kept in their respective coldrooms

for as long as 28 days, then returned to room temperature for an additional 28 days (56 days curing

time) to test for strength recovery.

Table 7 presents a summary of the strength test

results expressed as a percentage of the same-age

strength of a control, admixture-free mortar

made with a type M masonry cement cured at

20°C (68°F). As seen in the 20°C results, methanol

retarded strength gain, especially at higher dosages. At 7 days, methanol produced strengths

that were only 47 to 79.4% strong relative to the

control. At –5 and –10°C (23 and 14°F) the metha-
nol performed even more poorly. However, the

methanol protected the mortar from permanent

frost damage, allowing full recovery of strength

at 56 days. Since methanol retarded strength gain,

calcium chloride, a well-known strength-accelerator, was added to see if the results would

dramatically improve. They did not. The 2% dosage of calcium chloride produced strengths that

were somewhat less than those achieved with the

methanol alone, and the 4% dosage produced

even lower strengths. Isopropyl alcohol produced results similar to methanol. The strength

development of the KC1 mix outperformed the

other chemicals. It did not retard strength gain,

and it promoted significant strength gain at –5°C

and –10°C. None of the chemicals evaluated outperformed the admixture KC1. Therefore, KC1

was used in the subsequent tests to demonstrate

the feasibility of using in masonry mortars antifreeze admixtures that were originally developed

for concrete.

Setting times

Low temperatures delay the setting times of

mortar. This section evaluated the effect of temperature and KC1 on the setting time of mortar.

The experiment was conducted on a type M

masonry cement mortar according to ASTM C

403, “Test Method for Time of Setting of Concrete

Mixtures by Penetration Resistance.” Two mortars were tested: a normal, admixture-free mortar

and one that contained 6% KC1 based on cement

weight. Both mortars had a moisture content of

16%. Figure 13 presents the setting times as defined in the referenced ASTM standard.

The effect of KC1 on initial and final set of mortar held at room temperature was insignificant.

At 5°C (41°F) the KC1 worked better than the

control mortar where both initial and final set

times were shortened by 4.5 hr. At –5°C (23°F) the

initial and final set times for the KC1 mortar were

increased by 10 and 18 hr, respectively, compared

with the normal mortar held at 5°C. Normal mortar at –5°C froze and could not be measured for

set time.

Effect of KC1 on freeze–thaw resistance

Beam specimens made with type M masonry

cement mortar were freeze–thaw tested according to ASTM C 666, procedure B. Two mortars

were tested: a conventional, admixture-free mortar and one that contained 6% KC1 based on

cement weight. Both mortars had a moisture content of 16%. (Though an air-entraining admixture

was not used, a quick examination of the hardened mortar with a microscope showed that both

mortars contained entrained air bubbles.) The

mechanical condition of each beam prior to and

at intervals during the test was monitored by

measuring its relative dynamic modulus of elasticity (RDME) according to ASTM C 215. ASTM C

666 considers concrete to be durable if it maintains an RDME above 60% through 300 cycles of

freezing and thawing. Since mortar is quite simi15

Time (hr)

Penetration Resistance (MPa)

Final 

70

60

50

40

30

20

10

0

0 12 24 36 48

Initial 

Cont+20

Cont+5

KC+20

KC+5

KC–5

Figure 13. Setting times of admixture-free mortar and mortar containing the admixture KC1.
lar to concrete, these ASTM guides were used to

evaluate the mortar beams. Figure 14 shows the

test results. As can be seen, both mortars performed well. They had RDMEs at or above 96% at

the end of the test. The differences in performance were small enough that it can be concluded

that the admixture KC1 did not have a significant

effect on the freeze–thaw durability of this mortar.

Effect of KC1 on bond strength

Bond strength of mortar to masonry units is

one of the most important engineering properties

for unreinforced masonry. The bond strength

tests were conducted according to ASTM C 1072,

commonly referred to as “the bond wrench test.”

The test specimens were assemblies of two solid

concrete bricks and one mortar joint. The masonry

assemblies were tested at an age of 28 days by

applying an eccentric compressive load to the

assembly resulting in flexural tension across the

width of the mortar joint.

These tests evaluated the effect of the admixture KC1 on bond strength. These tests and those

16

Number of Freeze-Thaw Cycles

Relative Dynamic Modulus of Elasticity (%)

100

98

96

94

92

90

0 270 300 330 30 60 90 120 150 180 210 240

Control Beam 1

Control Beam 2

Control Beam 3

KC1 Beam 1

KC1 Beam 2

KC1 Beam 3

Figure 14. Rapid freeze–thaw (ASTM C 666) test results for specimens with and

without KC1.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

16%

No

Freeze

16%

Freeze

10%

Freeze

8%

Freeze

6%

Freeze

KC1

No

Freeze

KC1

–5°C

Freeze

KC1

–10°C

Freeze

Flexural Tensile Strength (MPa)

Figure 15. Joint test results of the experiments to assess the effect of KC1

on bond strength, and the effect of mortar moisture content at the time of

freezing on bond strength
on the effect of mortar moisture content on bond

were conducted together, and their results are

presented jointly in Figure 15. The results in Figure 15 represent the average of five specimens.

Appendix B shows the individual test results. The

mortars were made with a type M masonry

cement. The KC1 mortars were made with 16%

water content, which was the same initial water

content as the admixture-free mortars included in

Figure 15. The primary finding is that KC1 mortar

developed a stronger bond to the masonry units

than did normal mortar. This could be due to an

increase in the plasticity of the mix, which could

have resulted in better mechanical anchoring into

the pores of the bricks.

Effect of mortar moisture content at

time of freezing on bond strength

This experiment was designed to define the

effect of mortar moisture content at the time of

freezing (a function of absorption, age, and temperature) on the bond strength of a masonry

assembly. The initial moisture content of all mortars was 16%. The moisture content of the mortar

at time of freezing was regulated by allowing the

masonry assemblies to stand at room temperature

until curves like those in Figure 6 indicated that a

prescribed moisture content had been achieved.

At the prescribed moisture content, the specimens

were brought into a –10°C (14°F) room. Twentyfour hours later, the specimens were returned to a

20°C (68°F) room for 28 days. The “bond wrench

test” followed. The results presented in Figure 15

represent the average of five specimens (individual test specimen results are included in Appendix B).

Of the sets tested using the control mortar (no

admixture), the one with the highest tested bond

strength had the highest moisture content: 16%.

These prisms were placed into the cold room immediately after construction. These results may be

explained by the fact that the mortar in these

prisms was in a plastic state when water expansion within the mortar occurred and thus was able

to accommodate volume changes. Bond strengths

decreased with decreases in mortar moisture content (achieved by longer delay periods between

prism construction and placement in the cold

room) until a rebound in strength is observed

with the estimated 6% mortar moisture. This

rebound effect is consistent with mortar compressive strength development as discussed under

Critical Maturity in the Freezing Strength section of

this report.

17

At first glance, these results seem to support

current guideline recommendations that mortar

be allowed to fall to 6% moisture before it is subjected to freezing. However, it is clear that the

10% moisture content shows the same bond

strength as the 6% does. We conclude, from both

compression and bond strengths, that mortar can

be allowed to freeze at an earlier age than now

allowed in current guidelines. The admixtures

can lessen cold-weather constraints.

Freeze–thaw durability

Objective

Masonry has historically been viewed as a durable construction material. Long-term performance of concrete masonry structures exposed to

the weather in cold regions requires the use of

units that can resist the potentially destructive

forces imposed on the units by cyclical freezing

and thawing. The severity of the exposure and

the properties of the masonry unit control the

long-term performance of the units.

The objective was to evaluate several test

methods that could be used as indicators of the

freeze–thaw durability of concrete masonry

units. Two freeze–thaw test methods that subject

water-saturated specimens to cyclical freezing

and thawing were considered: ASTM C 666, “Resistance of Concrete to Rapid Freezing and Thawing,” and ASTM C 1262, “Method for Evaluating

the Freeze–Thaw Durability of Manufactured

Concrete Masonry Units and Related Units.” The

first of the two methods was originally developed for structural concrete, and the second is a

new method that was developed specifically to

evaluate dry mix, no-slump concrete products

such as concrete masonry units.

Knowledge about the air void structures of

other related materials has provided insight into

freeze–thaw durability performance. Therefore,

two other test methods were also considered to

determine if they might provide similar insights

into concrete masonry unit durability: ASTM C

457, “Microscopic Determination of Air-Void

Content and Parameters of the Air-Void System in

Hardened Concrete,” and ASTM D 4404, “Determination of Pore Volume Distribution of Rock

and Soil by Mercury Intrusion Porosimetry.”

To evaluate these methods, six different sets of

concrete segmental retaining wall units were

used. The units are manufactured using the same

materials and methods as conventional concrete

masonry units.
Rapid freeze–thaw test for concrete, ASTM C 666

At the time this project was initiated, there was

no standard method designed specifically to

evaluate the freeze–thaw resistance of concrete

masonry units (Method C 1262 was not approved

by ASTM until late 1994). Before then, ASTM C

666 was often used for this purpose when needed. The ASTM C 666 test method includes two

different procedures: procedure A, Rapid Freezing and Thawing in Water, and procedure B,

Rapid Freezing in Air and Thawing in Water.

Both procedures are considered to be more severe

than field conditions, primarily due to the rapid

freezing rates in the test of roughly 5 to 15°C (9 to

27°F)/hr as compared with common field rates of

less than 3°C (5.4°F)/hr. As with all laboratory

freeze–thaw test methods, the test is not intended

to simulate field conditions, but instead it produces an indication of relative freeze–thaw resistance between different specimens.

Test specimens were saw-cut from units representing each of the six different sets of segmental

retaining wall units. Due to the size limitations of

the full-size units, the saw-cut test specimens

were much smaller than required by C 666. The

specimens were subjected to cyclical freezing and

thawing using procedure B. Prior to testing and

at regular intervals, the specimens were removed

from the test chamber to evaluate their condition

using ASTM C 215, “Test Method for Fundamental Transverse, Longitudinal, and Torsional Frequencies of Concrete Specimens.” The results of

this method are expressed as a percentage of the

original relative dynamic modulus of elasticity

(RDME). Each specimen starts with an RDME of

100, but this value decreases throughout the duration of the C 666 test as the internal structure of the

specimen is damaged by the expansive forces of

the water within its pores.

The conventional criterion used with structural

concrete is that specimens must retain at least 60%

of the original RDME at the end of 300 freeze–thaw

cycles. If this criterion were used to evaluate the

six sets of segmental retaining wall units, all

would be considered to fail. However, it is important to note that the criterion used to evaluate performance of structural concrete used in horizontal

highway applications would not be appropriate

for use in evaluating concrete masonry units.

Freeze–thaw damage requires saturation of the

concrete. Vertical, free-draining concrete masonry

walls are rarely saturated. Therefore, their exposure conditions are much less severe than those of

horizontal structural concrete, and the criteria for

evaluating satisfactory performance in the test

method should not be consistent for the two materials. While retaining walls may have a somewhat

greater saturation potential than most concrete

masonry walls, their exposure is still much less

severe than most highway concrete.

The results of the tests cannot be compared to

standard pass–fail criteria, since none exists for

concrete masonry units. However, the results

(shown in Figure 16) do provide useful information by demonstrating the relative performance

between the specimens.

18

Number of Freeze-Thaw Cycles

Relative Dynamic Modulus of Elasticity

100

80

60

40

20

0

0 40 80 120 160 200

SRW-K

SRW-G

SRW-A

SRW-H

SRW-J

SRW-I

Figure 16. Results of the modified ASTM C 666 freeze–thaw test on segmental

retaining wall (SRW) units.
New freeze–thaw test method for

concrete masonry units, ASTM C 1262

As part of this research effort, a new test method was developed specifically to evaluate the

freeze–thaw durability of concrete masonry units.

This method was presented to the American Society of Testing and Materials (ASTM) and was first

published in 1994 as ASTM C 1262. Test specimens

are partially submerged in water and sealed in

flexible containers. Air temperatures around the

containers are controlled for thaw cycles at 20°C

(68°F) and for freeze cycles at –15°C (5°F). The

method was written specifically to accommodate

automatically cycling freeze–thaw chambers to

perform up to three cycles per day as well as for

conventional freezers. Performance of specimens

throughout the test is determined by weight loss.

Residue within the containers, the result of surface

scaling and general breakdown of the test specimen, is collected and reported as a percentage of

19

Table 8. Average tested properties of SRW units using ASTM C

1262 and C 141.

Compressive Unit

Specimen No. of cycles at strength weight Absorption

SRW* 1% wt loss (MPa [psi]) (kg/m3 [lb/ft3]) (kg/m3 [lb/ft3])

A 1500† 43.8 (6351) 2138 (133.5) 98 (6.1)

G 90 52.9 (7669) 2233 (139.4) 87 (5.4)

H 180 68.9 (10,283) 2310 (144.2) 69 (4.3)

I 55 26.6 (3860) 1757 (109.7) 170 (10.6)

J 50 30.9 (4474) 1720 (107.4) 232 (14.5)

K 60 29.4 (4268) 1607 (100.3) 157 (9.8)

* SRW = Segmental retaining wall unit.

† Estimated value. Test was terminated at 875 cycles with average

weight loss of less than 0.5%.

Figure 17. Freeze–thaw test results for median specimen from each set of

segmental retaining wall units (ASTM C 1262).

the original weight of the specimen. A copy of the

method is included in Appendix C.

Due to the limited experience with this method, there are no standard freeze–thaw durability

requirements for concrete masonry units using

this method as well. Once again, however, the

method permits a comparison between the performance of the different sets of units evaluated.

For reference purposes, the compressive strength,

absorption, and unit weight of the concrete used

in these units were also determined. These values, measured in accordance with ASTM C 140,

have often been used in the past, with mixed results, to ensure field performance in freeze–thaw

environments.

Table 8 summarizes the data gathered during

this test. As can be seen, SRW A was clearly most

durable. It withstood an estimated 1500 cycles of

freezing and thawing compared with less than

200 cycles for all the others. Figure 17 presents the

Number of Freeze-Thaw Cycles

Weight Loss (%)

14

12

10

8

6

4

2

0

0 200 400 600 800 1000

SRW-A

SRW-G

SRW-H

SRW-I

SRW-J

SRW-K
results in graphical form. Appendix D presents

individual results from each sample tested.

Microscopic examination of the air void system

A test method used to assess the susceptibility

of porous materials to freezing and thawing is

ASTM C 457, “Standard Practice for Microscopical

Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete.” Although this test method was developed

for concrete, its principles may be used for other

concrete-like materials. The specimens are saw-cut

slabs that are ground and polished and then

observed through a stereo microscope. The main

parameters of the test are the air content and the

spacing factor, an indication of the distance within

the cement paste that moisture must travel to

reach an unsaturated void to release hydraulic

pressure during freezing. The test examines the

air-void parameters of the cement paste but fails to

include the characteristics of the aggregate. The

test is carried out under the assumption that the

aggregate is freeze–thaw-durable. Experience

gained with structural concrete indicates that this

test can reasonably predict freeze–thaw susceptibility if the aggregate phase is freeze–thaw resistant.

The most significant parameters shown in Table

9 are the spacing factor and the air content. (Detailed information is provided in Appendix E.) A

small spacing factor is an indicator of durable material. Spacing factors of less than 200 μm indicate

good freeze–thaw resistance in concrete, spacing

factors above 250 μm indicate frost susceptibility,

and values in between constitute a gray area. As

explained above, this test method is concerned

with the cement paste only. It ignores the characteristics of the aggregate. Although not included in

the standard test method, a brief description of the

aggregates used in the manufacture of each set of

specimens is included in Table 9 for reference.

Mercury intrusion porosimetry

Mercury intrusion porosimetry (MIP) is a newer technique that determines the pore size distribution in porous materials such as rock, concrete,

and mortar. Its use with masonry is still a subject

of research. Samples from the specimens that

were freeze–thaw-tested as described above were

also tested by mercury intrusion porosimetry.

Small samples were enclosed in a small test

chamber capable of withstanding high pressures.

Mercury was injected into the chamber to fill the

air space available. Higher pressures are needed

to intrude mercury into smaller pores. The pressure was increased gradually and the amount of

mercury that went into the chamber was recorded. The pressure needed to intrude mercury was

correlated to the pore size by means of the Washburn equation (Washburn 1921). The amount of

mercury intruded at a given pressure range was

correlated to the total pore volume of a given

pore size. The procedure for this test is described

in ASTM D 4404, “Standard Test Method for Determination of Pore Volume and Pore Volume

Distribution of Rock and Soil by Mercury Intrusion Porosimetry.”

Based on the documented mechanisms of

freezing of moisture in the pores of cement paste,

pore sizes can be classified in three ranges:

1) Protective pores, larger than 5 μm

2) Capillary pores, from about 0.1 μm to 5 μm

3) Subcapillary pores smaller than 0.1 μm.

Protective pores are usually benign because

they provide reservoirs for excess moisture to

migrate to during freezing, thereby relieving

hydraulic pressure. Moisture in these voids can

freeze, but the voids are usually water-free because neighboring capillary pores draw their

moisture away by suction. Capillary pores are

small enough to generate high suction, which fills

them up, and large enough that the moisture in

20

Table 9. Test results from the microscopic examination of hardened mortar.

Spacing

Specimen Volume fractions (%) factor

SRW* Aggregate Paste Air (μm) Aggregate description

A 52.6 31.0 16.4 143 Quartzite, sound

G 67.8 22.6 9.6 137 Sound, well graded, angular

H 67.3 28.2 4.5 212 Sound, well graded, angular

I 54.6 32.2 13.2 133 Coarse pores

J 60.2 32.2 7.6 271 Mostly porous and soft

K 51.9 35.2 12.9 106 Pumice with coarse vesicles

* SRW = Segmented retaining wall unit.
them freezes at common low temperatures. Subcapillary pores also have very high suction properties that keep them filled with moisture, but

due to the small sizes of these pores the moisture

within them is maintained in a supercooled condition without freezing.

Figure 18 shows the test results from the mer21

Figure 18. Pore size distributions before

and after freezing and thawing.

a. SRW A.

b. SRW G.

c. SRW H.

cury intrusion porosimetry (MIP) test. The tests

were conducted in replicate specimens before

and after 300 ASTM C 666 freeze–thaw cycles.

There were two objectives in using this MIP test.

The first was to see if there may be a reasonable

correlation between pore size distribution in concrete masonry units and freeze–thaw test results.

Diameter (μm)

Incremental Intrusion (mL/g)

0.010

0.008

0.006

0.004

0.000

0.001

0.002

0.01 0.1 1 10 100 1000

Before

After

Diameter (μm)

Incremental Intrusion (mL/g)

0.004

0.003

0.002

0.001

0.000

0.001 0.01 0.1 1 10 100 1000

Before

After

Diameter (μm)

Incremental Intrusion (mL/g)

0.005

0.004

0.003

0.002

0.000

0.001

0.001

0.01 0.1 1 10 100 1000

Before

After
The second objective was to determine if this

method would detect changes in the pore size

distribution of the test specimen due to freezing

and thawing action.

Based on these results, MIP tests performed

before and after freeze–thaw cycling do not show

the expected increases in pore size. Comparisons

22

d. SRW I.

e. SRW J.

f. SRW K.

Figure 18 (cont’d). Pore size distributions before and after freezing and

thawing.

between the results of these tests and the other

test methods are summarized in the next section

of this report.

Comparison of test results

Table 10 compares the results of the different

test methods for six sets of test specimens classiDiameter (μm)

Incremental Intrusion (mL/g)

0.010

0.008

0.006

0.004

0.000

0.001

0.002

0.01 0.1 1 10 100 1000

Before

After

Diameter (μm)

Incremental Intrusion (mL/g)

0.010

0.008

0.006

0.004

0.000

0.001

0.002

0.01 0.1 1 10 100 1000

Before

After

Before

After

Diameter (μm)

Incremental Intrusion (mL/g)

0.006

0.005

0.004

0.003

0.000

0.001

0.002

0.01 0.1 1 10 100 1000

0.001
fied in one of four categories: excellent, good, fair,

and poor. These ratings are not defined in any of

the referenced methods. They are used simply for

the purposes of this report to evaluate potential

correlation between the results.

In general, the two freeze–thaw test methods

used, C 666 and C 1262, provided fairly similar

results in identifying the relative performance of

the sets of units, with several notable exceptions.

For example, both methods indicated that set A

was clearly the most durable of all sets evaluated,

and both methods demonstrated similarly poor

performances for sets I and J. However, the results

contrasted regarding the remaining sets G, H, and

K. Method C 666 indicated that sets G and H performed worse than sets I and J and that set K performed well. These results are nearly opposite to

those of Method C 1262, which showed G and H

to be good performers and set K to be a poor performer similar to that of I and J.

The microscopic examination and MIP (C 457

and D 4404, respectively) results for sets A, G, and

H demonstrated some promise as a method of

predicting freeze–thaw performance using one of

the test methods. The same was not the case for

sets I, J, and K. However, the less durable aggregates used in each of these last three sets may

have resulted in the poor correlation between test

methods, since the microscopic examination and

MIP can only evaluate the paste structure. The

microscopic examinations can often give indications of the soundness of the aggregate, however.

Potentially frost-susceptible aggregates were

identified in examinations of specimens from sets

I, J, and K.

With the limited data available here, it appears

that Method C 1262 may be a better method for

evaluating freeze–thaw durability of these concrete masonry related units. The C 1262 results

show better differentiation between sets of units.

The C 1262 test results compare better with the

results of microscopic evaluations and mercury

intrusion porosimetry. Both methods are time23

Table 10. Relative performance of specimens

in each test.

SRW ASTM ASTM ASTM ASTM

set C 666 C 1262 C 457 D 4414

A Excellent Excellent Good Good

G Poor Fair Good Fair

H Poor Good Fair Fair

I Poor Poor Good Poor

J Poor Poor Poor Good

K Good Poor Excellent Poor

consuming and expensive to perform, but equipment costs are less for the C 1262 method, and

some laboratories are equipped to perform it. Due

to the cost and time needed to perform these tests,

additional future consideration should be given to

the use of microscopic evaluations, MIP, and other

methods of providing indicators of potential unit

durability.

FIELD DEMONSTRATION

Objective

A concrete masonry wall consisting of 251/2

blocks per row that was five blocks high was constructed in northern Michigan at the U.S. Army

Corps of Engineers Soo Locks, Sault Ste. Marie, in

March 1995. Each block was nominally 203 × 203 ×

406 mm (8 × 8 × 16 in.). The objectives of this

experiment were to demonstrate the practicality of

using antifreeze admixtures in masonry mortar

and to compare it with conventional cold-weather

masonry practices.

Temporary enclosure

A temporary enclosure was erected in which

the wall was constructed. Half of the shelter was

heated and half was unheated. A canvas separated

the two halves. Conventional type M masonry

cement mortar was used to build the section of

wall within the heated portion of the shelter, while

the same type of mortar with the addition of an

antifreeze admixture was used to build the section

of wall within the unheated section of the shelter.

The mortar

All mortar used for building the wall was handmixed with hoes in a mixing trough in the heated

side of the shelter. The ingredients, which were all

preheated to the temperature of the enclosure,

were preweighed and combined in the proportions shown in Table 1. The antifreeze admixture

KC1 was dissolved in a portion of mixing water.

The sand and cement were thoroughly combined

before water was added. The amount of water

added was estimated by eye by the mason until a

desired consistency was achieved. The mortar was

retempered as needed. The average water contents of the as-mixed mortars were 12.9 and 13.4%

for the conventional and the antifreeze mortar,

respectively.

Constructing the wall

Both wall sections were laid in running bond

with faceshell mortar bedding using conventional
masonry construction techniques. The mortar

was tooled concave when it was thumbprint

hard. The masons found that the admixtured

mortar adhered very well to the masonry units

and that it remained workable much longer than

did the conventional mortar; this was probably

due to the differences in air temperature. Figure

19 compares the average penetration of the three

conventional mortars (on the warm side) to the

average penetration of the three admixtured mortars (on the cold side) over time. Due to the lowerthan-average initial mixing moisture content, the

cone penetrations for the fresh mortar averaged

about 38 mm (1.5 in.). The masons retempered the

mortar when its penetration dropped to about 28

mm (1.1 in.). The three batches of conventional

mortar were each retempered once, but the two

24

38

36

34

32

30

28

26

0 10 20 30 40 50

AA

AAAA

AA

AAAA

AAA

AAA AAA

AAA

AAAA

AAAA

AA

AA

AA

AAAAAA

AAAAA

AAA

AAA

AAA

AAA AAA

Time (min)

Penetration (mm)

KC1

Control

Figure 19. Penetration of mortar with and without the antifreeze admixture.

Figure 20. Building the wall.

antifreeze mortar batches were not retempered.

For construction of the wall section (Fig. 20) on

the cold side, masonry units were transferred

from the heated enclosure and used immediately.

The mortar made with KC1, once mixed, was

placed in the cold side and used within about 50

min.

Thermal history

Mortar and air temperatures were recorded

every 5 minutes for seven days. Thermocouples

in each side of the shelter monitored temperatures in the mortar beds between masonry units,

in 5 × 10 cm (2 × 4 in.) mortar cylinders, and in the

air next to the walls. The temperature of the mortar cylinders, which were stored adjacent to the

wall sections, was nearly identical to that in the
25

mortar joints. Figure 21 shows the 7-day temperature history of the cylinders and air in each side of

the shelter. The initial mortar mixture temperatures were approximately 17°C (62°F) for both

conventional and antifreeze mortars. While typical protection methods for newly constructed

concrete masonry may include overnight heated

enclosures, the heated wall section for this project

was protected for a full 7 days. The mortar on the

unheated side of the shelter had a 7-day average

temperature of 3.9°C (39°F), a maximum temperature of 9.5°C (49°F) at 3:30 p.m. on the 26th, and

a minimum of –0.6°C (31°F) at 7:30 a.m. on the

23rd. In contrast, the mortar on the heated side of

the shelter had a 7-day average temperature of

15.3°C (60°F), a maximum of 22°C (71.6°F) at 5:15

p.m. on the 27th, and a minimum of 10.1°C (50°F)

at 5:15 p.m. on the 21st.

Mortar strength

Two sets of 50- × 100-mm (2- × 4-in.) cylindrical

samples were cast from each type of mortar. The

samples made from the conventional mortar

were stored in the warm side of the shelter, and

those from the antifreeze mortar were stored in

the cold side. The cylinders were allowed to cure

in their respective environments for 7 days. Then

they were shipped to CRREL, stored at room temperature, and tested at a maturity of 28 days. The

strength results are presented in Figure 22. The

March 1995

Temperature (°C)

KC1

Air

20

15

10

5

0

–5

20 22 24 26 28 30

March 1995

Temperature (°C)

25

20

15

10

5

0

20 22 24 26 28 30

Air

Control

Figure 21. Thermal history of the masonry walls and surrounding air.

a. An unheated shelter.

b. A heated shelter.
antifreeze mortar, cured in the unheated side of

the shelter for 7 days, is as strong as the conventional mortar.

Efflorescence

Efflorescence is of concern whenever anything

is added to the mortar, and it appears to occur

with greater frequency in cold-weather construction projects. It was reported that the wall exhibited some white discoloring at the joints on the half

of the wall containing the KC1 admixture during

the spring time. However, after the first rain the

white coloring had disappeared. During a summertime inspection, both halves of the wall

appeared identical.

Cost comparison

The primary difference between conventional

winter masonry construction and masonry construction done with antifreeze admixtures is with

the type of freeze protection provided in each

case. The conventional practice is to provide heat

to keep the masonry above freezing until it gains

sufficient strength. With antifreeze admixtures,

the mortar is placed and cured in the cold without heaters or insulation. However, since the

work environment must not be too cold for the

workers, most winter masonry construction

projects would require a temporary shelter regardless of which construction method is employed. The primary difference between the two

methods is that with the antifreeze method the

shelter would not have to be heated after the

work stopped. In this case, the weather was mild

enough that the antifreeze side of the shelter did

not have to be heated for the comfort of the masons.

The workers were able to stay warm just by wearing jackets but no gloves. There was no significant difference in the production rate between the

two walls. Other labor and materials are considered common to both construction methods.

A heater produced 34,000 Btu/hr for each day

it was in operation. Two heaters were used. A

commonly used heat source on construction sites

is liquid propane. At $0.94/gal and 91,000 Btu/

gal, the cost to keep the conventional mortar

above freezing was about $15/day. On the other

hand, based on costs for other admixtures sold on

the market today, the antifreeze admixture is estimated to cost about $15.00 for the total amount of

admixture used on this project. Since the mortar

only had to be heated for 1 day, the antifreeze admixture produced no cost saving—it cost as

much as the heat. Keep in mind that the average

daily outdoor temperature was roughly 3°C

(37°F). Colder temperatures would increase heating demand. The saving in this case, however, is

that no fuel had to be burned to protect the antifreeze mortar.

Although the cost comparison and productivity of the two walls in this demonstration did not

yield significant differences, antifreeze admixtures may cause significant savings for masonry

built with large, prefabricated units. In this type

of construction, cranes are used to lift and place

the heavy units into the assembly, and the ability

to do this work in the open, without a shelter,

opens new opportunities for cost-effective winter

masonry construction.

CONCLUSIONS

1. The frost susceptibility of newly placed mortar is directly related to its moisture content.

Fresh mortar is frost-susceptible because it is

water-saturated. Dry mortar is frost-immune.

After mortar is placed, its moisture content

decreases. There is a critical moisture content at which the mortar becomes frost-resistant. The experiments in this project showed

that the moisture content of the masonry

units at the time of assembly and the absorptive characteristics of the unit are the preFigure 22. Strength of mortar cylinders

cast during construction.

26

KC1 Site Control Site

30

25

20

15

5

0

Compressive Strength (MPa)
dominant factors that determine the rate of

mortar moisture loss. The air temperature

and the temperatures of the masonry units

and the mortar had only a minor effect on the

rate of moisture loss from mortar.

2. Mortar becomes immune to a single cycle of

freezing at a moisture content between 8 and

10%.

3. The time for mortar to reach a moisture content of 8% is typically about 4 hours.

4. Mortar cured at or above 5°C (41°F) reaches

critical maturity within 6 hours. Critical

maturity is the minimum maturity needed

for mortar to withstand one event of freezing

without damage.

5. Freezing does not always harm early-age

mortar. The 7-day strength of mortar can be

increased by around 10% when it is frozen

after about 10 to 16 hours of curing at or

above 5°C, provided that the time in freezing

temperatures is discounted from the computation of the 7 days.

6. Current guidance allows mortar to be heated

up to 50°C (120°F). This study showed that

40°C (104°F) mortar placed in the cold does

not stay above freezing appreciably longer

than 5°C (41°F) mortar. Therefore, there is

minimal benefit from heating mortar above

20°C (68°F). Thin mortar joints will not

remain above freezing significantly longer

when higher temperatures are used.

7. Current guidance requires that mortar be

thermally protected for a minimum of 16

hours. Based on critical moisture contents

and critical maturities, thermal protection

could be realistically reduced to 4 to 6 hours.

A conservative change to current practice

would be to relax the time of thermal protection from the current 16 hours to 8 hours.

8. Antifreeze admixtures are a viable alternative

to thermal protection. A major drawback is

that, at the present time, no antifreeze admixture commercially available is labeled for use

with concrete or with masonry. However, the

ingredients of the U.S.-Army-patented antifreeze admixture KC1 are available as generic

chemicals from various sources. The recommended dosage is 4.5% of sodium nitrate and

1.5% of sodium sulfate by weight of portland

cement. These chemical compounds are usually supplied in powder form and dissolve

easily into the mix water. Other antifreeze admixtures for concrete or masonry may become commercially available in the future.

9. The laboratory tests showed that the antifreeze admixture KC1 had a negligible effect

on the freeze–thaw durability of mortar. This

admixture decreased the setting times at low

temperature and substantially increased the

bond between mortar and the units.

10. Although parameters such as spacing factor,

specific surface, number of air voids per 25

mm (1 in.), total air content, and pore size

distribution are used frequently to predict

freeze–thaw durability of slumpable concrete, these parameters are less reliable when

it comes to dry-cast concrete performance as

measured by ASTM C 666 (procedure B) or

ASTM C 1262.

11. Although C 666 uses change in relative

dynamic modulus of elasticity (RDME) to

measure freeze–thaw durability performance, cumulative percent weight loss per

surface area as used in C 1262 may be a more

appropriate measure of performance for

dry-cast concrete specimens. More study is

needed.

12. No physical property measured in this

study, including compressive strength, density, or absorption, consistently predicted

the same freeze–thaw resistance of dry-cast

concrete products as that measured using C

666 or C 1262.

13. The cost comparison and productivity of the

two walls built as a demonstration in this

project did not yield significant cost differences when the outdoor air temperature

averaged 3°C (37°F). Colder weather will

increase heating demand. However, in all cases where some heating is required, use of antifreeze admixtures will reduce the amount of

fuel burned for thermal protection.

RECOMMENDATIONS

1. The laboratory experiments in this project

showed that the time of thermal protection

for masonry may safely be reduced from the

current 16 hours to 8 hours if the following

conditions are met:

a) The masonry units are not extremely

damp. If this is suspected, the units must be

allowed to dry at room temperature until all

visible signs of moisture disappear.

27
28

b) The masonry units are cold. However, if

units are below 5°C (41°F), they must be

allowed to warm up in a heated shelter.

2. Increased thermal protection is required for

masonry constructed using wet masonry

units. Therefore, it is recommended that

masonry units delivered to the job site be protected from moisture as much as possible.

Units that are visibly damp should not be

laid. It is generally not considered necessary

to dry wet units by heat. Air drying is typically

sufficient, provided units are unstacked and

separated to permit air flow between them.

3. The practice of heating the mortar ingredients prior to mixing to temperatures greater

than 5°C does not provide significant thermal

protection. In addition, very high water temperatures may cause flash set. Therefore, it is

recommended that the mortar mix be produced at temperatures of 5 to 20°C (41 to 68°F).

4. Antifreeze admixtures originally developed

for concrete provide enhanced performance

to masonry mortar. The experiments conducted in this project support a recommendation for their use in masonry mortars as soon

as they become commercially available.

COMMERCIALIZATION AND

TECHNOLOGY TRANSFER

The knowledge derived from this research is

being shared with the engineering community

through conference papers, technical reports, updates to guide specifications, and new testing

methods:

• A conference paper was presented at the

American Society of Civil Engineers 8th International Specialty Conference on Cold Regions Engineering in Fairbanks, Alaska, in

August of 1996. The paper was published in

the proceedings of this conference.

• A proposal (Appendix F) was submitted to

the International Masonry Industry All Weather Council to update the minimum thermal

protection requirements included in the

Council’s guide specifications. The proposal

was submitted through NCMA, which is a

member of that council.

• A new standard test method was developed

and adopted by ASTM under specification C

1262, “Standard Test Method for Evaluating

the Freeze–Thaw Durability of Manufactured

Concrete Masonry Units and Related Concrete Units.” This new standard has been

published in the ASTM Annual Book of Standards.

This study showed that antifreeze admixtures

can promote appreciable strength in mortar when

its internal temperature is below 0°C (32°F). However, these products are yet to become commercially available.

LITERATURE CITED

Korhonen, C.J., E.R. Cortez, and R.D. Thomas

(1996) Minimum thermal protection requirements

for cold weather masonry. In Proceedings of the 8th

International Cold Regions Engineering Specialty

Conference. American Society of Civil Engineers,

New York.

IMIAWC (1988) Recommended Practices and Guide

Specifications for Masonry Construction. International Masonry Industry All Weather Council. Washington, D.C.: International Masonry Institute.

Korhonen, C.J., E.R. Cortez, B.A. Charest, and C.E.

Smith, Jr. (1994) Low-temperature admixtures for

concrete. In Proceedings of the 7th International Cold

Regions Engineering Specialty Conference. American

Society of Civil Engineers, New York.

Sneck, T. (1972) The interaction between mortar

and masonry units as a basis for standards for masonry mortars. In Joint RILEM-ASTM-CIB Symposium Proceedings, NBS Special Publication 361, vol.

1. Washington, D.C.: U.S. Department of Commerce, National Bureau of Standards.

Washburn, E.W. (1921) Note on a method of determining the distribution of pore sizes in a porous

material. In Proceedings of the National Academy of

Sciences, U.S., vol. 7, p. 115–116.
29

Unit Water Air

Test Unit Unit Unit temp. Unit temp. temp. Weight increase (g) of unit (at specified time in min.)

no. type no. surface (°C) moisture (°C) (°C) 0 1 2 5 10 15 30 60

1 CMU A 1 Top 20 Dry 20 20 0 159 186 209 227 231 245 254

1 Bottom 0 163 191 213 231 245 259 272

2 Top 0 73 86 109 132 141 159 177

2 Bottom 0 68 82 95 113 122 141 163

Surface area

 Top = 375 cm2 Average of top surfaces from both units... 0 116 136 159 179 186 202 215

 Bottom = 428 cm2 Average of bottom surfaces from both units ... 0 116 136 154 172 184 200 218

Average of all surfaces from both units ... 0 116 136 156 176 185 201 217

2 CMU B 1 Top 20 Dry 20 20 0 91 122 168 222 254 327 390

1 Bottom 0 240 304 386 435 458 494 531

2 Top 0 91 127 177 227 259 322 395

2 Bottom 0 268 331 417 472 503 558 617

Surface area

 Top = 375 cm2 Average of top surfaces from both units... 0 91 125 172 225 256 324 392

 Bottom = 428 cm2 Average of bottom surfaces from both units ... 0 254 318 401 454 481 526 574

Average of all surfaces from both units ... 0 172 221 287 339 369 425 483

3 CMU C 1 Top 20 Dry 20 20 0 77 91 109 127 141 163 191

1 Bottom 0 150 168 195 213 227 254 277

2 Top 0 45 54 73 86 95 118 141

2 Bottom 0 168 181 209 222 236 259 281

Surface area

 Top = 375 cm2 Average of top surfaces from both units... 0 61 73 91 107 118 141 166

 Bottom = 428 cm2 Average of bottom surfaces from both units ... 0 159 175 202 218 231 256 279

Average of all surfaces from both units ... 0 110 124 146 162 175 198 222

4 Brick 1 Side 20 Dry 20 20 0 62 66 67 69 70 74 76

2 Side 0 51 53 55 57 58 61 64

3 Side 0 56 58 60 62 64 66 68

Surface area = 172 cm2 Average of all three units ... 0 56 59 61 63 64 67 69

5 Brick 1 Side 20 Normal 20 20 0 29 30 31 32 33 — —

2 Side 0 30 32 33 34 34 — —

3 Side 0 34 34 37 37 38 — —

Average of all three units ... 0 31 32 33 34 35 — —

6 Brick 1 Side 20 Wet 20 20 0 35 40 43 46 46 — —

2 Side 0 26 28 30 31 32 — —

3 Side 0 30 34 37 38 40 — —

Average of all three units ... 0 30 34 37 38 39 — —

7 Brick 1 Side 5 Dry 5 5 0 65 67 70 71 73 76 —

2 Side 0 52 55 57 60 60 62 —

3 Side 0 57 62 64 67 68 68 —

Average of all three units ... 0 58 62 64 66 67 69 —

8 Brick 1 Side 5 Dry 20 5 0 70 75 76 78 79 81 —

2 Side 0 60 64 66 68 69 71 —

3 Side 0 53 56 58 61 61 64 —

Average of all three units ... 0 61 65 67 69 70 72 —

9 Brick 1 Side 5 Dry 30 5 0 52 55 57 58 60 62 —

2 Side 0 47 51 53 55 57 61 —

3 Side 0 70 71 73 75 76 80 —

Average of all three units ... 0 57 59 61 63 64 68 —

APPENDIX A: ABSORPTION TEST RESULTS

Table A1. Summary of water uptake test results.
Table A2. Summary of mortar absorption test results.

Unit Mortar Air Mortar Mix Min.

Test Unit temp Unit Mortar temp. temp. properties water Mortar moisture content (at specified time in min.) to

no. type (°C) moisture type (°C) (°C) Air Unit wt. Flow Penetr. (%) 0 5 15 30 45 60 120 240 1440 6%

1 Brick 20 Dry MC-M 20 20 9.3 125.5 131.0 65.0 14.8 15.4 12.3 11.3 9.6 9.2 7.8 6.5 3.4 1.7 1402 Brick 20 Dry MC-S 20 203 Brick 20 Dry MC-N 20 20 8.6 125.9 131.0 62.0 15.1 15.1 11.8 11.5 9.6 8.4 7.5 6.3 3.4 1.0 1334 Brick 20 Dry PCL-M 20 20 3.1 133.6 131.0 59.0 21.0 15.2 14.0 11.3 9.7 8.8 8.1 5.2 3.7 0.6 1055 Brick 20 Dry PCL-S 20 206 Brick 20 Dry PCL-N 20 20 1.9 128.7 126.0 56.0 24.3 19.0 16.0 14.3 12.9 11.1 10.1 7.8 5.0 1.7 1987 Brick 20 Dry MC-M 5 5 10.6 123.7 134.0 69.0 14.8 14.8 12.1 10.8 9.1 8.6 7.5 6.5 4.8 2.0 1608 Brick 20 Dry MC-M 20 5 10.2 124.3 133.0 66.0 14.8 15.9 11.8 10.4 8.6 8.0 7.4 6.1 3.5 1.2 1259 Brick 20 Dry MC-M 30 5 10.0 124.6 131.0 63.0 14.8 13.9 10.5 9.8 7.9 7.5 5.3 5.1 3.7 1.5 55

10 Brick 5 Dry MC-M 5 5 10.8 123.5 133.0 69.0 14.8 14.6 11.9 11.5 10.0 9.0 8.1 6.0 5.0 1.1 120

11 Brick 5 Dry MC-M 20 5 10.0 124.6 131.0 66.0 14.8 14.5 12.4 10.9 9.5 9.2 8.0 6.2 4.6 0.8 136

12 Brick 5 Dry MC-M 30 5 9.7 125.0 131.0 59.0 14.8 14.1 12.2 10.9 10.2 9.9 8.9 7.3 5.0 1.3 18813 Brick 20 Normal MC-M 5 5 10.6 123.8 135.0 66.0 14.8 15.4 13.0 11.5 10.8 10.7 9.9 8.8 6.9 3.0 51614 Brick 20 Normal MC-M 20 5 9.9 124.7 133.0 63.0 14.8 14.4 13.0 11.9 11.7 10.7 10.4 10.1 9.1 7.6 144015 Brick 20 Normal MC-M 30 5 9.8 124.8 131.0 59.0 14.8 15.2 11.9 11.2 10.4 9.6 9.1 7.4 6.6 3.4 46516 Brick 5 Normal MC-M 5 5 10.3 124.1 136.0 68.0 14.8 15.9 12.7 12.0 11.3 11.0 10.5 10.1 9.7 9.5 144017 Brick 5 Normal MC-M 20 5 10.0 124.6 130.0 63.0 14.8 15.8 12.5 12.5 11.3 11.5 10.9 10.7 9.6 8.6 144018 Brick 5 Normal MC-M 30 5 9.9 124.7 125.0 60.0 14.8 14.7 12.3 12.1 11.7 11.5 10.7 11.0 10.7 9.8 144019 Brick 20 Wet MC-M 5 5 10.3 124.3 134.0 68.0 14.7 14.3 13.2 12.4 11.8 11.3 11.3 10.7 9.6 7.9 144020 Brick 20 Wet MC-M 20 5 9.4 125.4 135.0 66.0 14.8 14.8 13.0 12.0 11.1 10.8 10.8 10.4 10.8 9.2 144021 Brick 20 Wet MC-M 30 5 9.4 125.3 131.0 61.0 14.8 14.0 12.8 11.7 10.9 10.9 10.5 10.6 10.8 10.3 144022 Brick 5 Wet MC-M 5 5 10.8 123.5 137.0 69.0 14.8 14.4 12.4 11.6 11.3 11.3 11.0 10.1 10.0 10.0 144023 Brick 5 Wet MC-M 20 5 9.2 125.7 128.0 62.0 14.8 14.6 13.1 12.6 12.1 11.6 11.8 11.1 10.9 10.1 144024 Brick 5 Wet MC-M 30 5 10.1 124.4 133.0 65.0 14.8 14.9 13.2 12.2 11.1 11.2 10.7 10.7 10.3 8.4 144025 Brick 20 Dry MC-M 20 2026 Brick 20 Normal MC-M 20 2027 Brick 20 Wet MC-M 20 2028 CMU A 20 Dry MC-M 20 20 9.5 125.3 128.0 63.0 14.8 14.9 12.1 10.6 9.4 8.4 7.4 4.6 2.1 0.0 9029 CMU B 20 Dry MC-M 20 20 9.1 125.8 129.0 65.0 14.8 14.9 11.2 9.6 7.4 6.1 5.8 2.8 1.5 0.0 8030 CMU C 20 Dry MC-M 20 20 8.5 126.6 131.0 60.0 14.8 14.5 11.7 11.6 9.8 8.2 8.2 5.4 2.2 0.0 57

30
31

NCMA CPAR Project Sections 1.2.4 & 2.2. September 1995

Mortar bond strength according to ASTM

Comp. Tens. Comp. Tens.

Resisting bond bond bond bond

moment strength strength strength strength

Moist % (kgf-m) (MPa) (MPa) (psi) (psi)

16%, no freeze 12.49 2.39 0.23 346.7 34.0

16%, freeze 13.86 2.65 0.26 384.6 37.8

10%, freeze 11.08 2.12 0.21 307.6 30.1

8%, freeze 8.27 1.58 0.15 229.7 22.3

6%, freeze 10.79 2.07 0.20 299.6 29.3

KC1, no freeze 31.57 6.04 0.60 875.3 86.9

KC1, –5°C freeze 27.93 5.34 0.53 774.5 76.8

KC1, –10°C freeze 22.82 4.36 0.43 632.9 62.6

Note: The 16% no freeze and 16% freeze were retested because of

excessive spread of test results.

Mortar bond strength according to ASTM Set Avg (ASTM)

Comp. Tens. Comp. Tens.

Resisting bond bond bond bond

moment strength strength strength strength

Moist % (kgf-m) (MPa) (MPa) (psi) (psi)

16%, no freeze 18.71 3.58 0.35 519.0 51.2

16%, no freeze 14.6 2.79 0.27 405.1 39.9

16%, no freeze 9.71 1.86 0.18 269.6 26.3

16%, no freeze 9.71 1.86 0.18 269.6 26.3

16%, no freeze 9.71 1.86 0.18 269.6 26.3

16%, freeze 18.71 3.58 0.35 519.0 51.2

16%, freeze 12.2 2.33 0.23 338.6 33.2

16%, freeze 12.2 2.33 0.23 338.6 33.2

16%, freeze 13.4 2.56 0.25 371.9 36.5

16%, freeze 12.8 2.45 0.24 355.2 34.9

10%, freeze 4.98 0.96 0.09 138.6 13.2

10%, freeze 13.88 2.66 0.26 385.2 37.9

10%, freeze 13.4 2.56 0.25 371.9 36.5

10%, freeze 14.48 2.77 0.27 401.8 39.5

10%, freeze 8.67 1.66 0.16 240.8 23.4

8%, freeze 6.18 1.18 0.11 171.8 16.5

8%, freeze 8.97 1.72 0.17 249.1 24.3

8%, freeze 10.74 2.06 0.20 298.2 29.2

8%, freeze 6.78 1.30 0.13 188.5 18.2

8%, freeze 8.67 1.66 0.16 240.8 23.4

6%, freeze 6.78 1.30 0.13 188.5 18.2

6%, freeze 6.78 1.30 0.13 188.5 18.2

6%, freeze 15.47 2.96 0.29 429.2 42.3

6%, freeze 16.67 3.19 0.31 462.5 45.6

6%, freeze 8.25 1.58 0.15 229.2 22.3

KC1, no freeze 33.03 6.31 0.63 915.8 90.9

KC1, no freeze 33.1 6.33 0.63 917.7 91.1

KC1, no freeze 34.7 6.63 0.66 962.0 95.5

KC1, no freeze 30.11 5.76 0.57 834.9 82.8

KC1, no freeze 26.92 5.15 0.51 746.5 74.0

KC1, –5°C freeze 26.92 5.15 0.51 746.5 74.0

KC1, –5°C freeze 29.34 5.61 0.56 813.5 80.7

KC1, –5°C freeze 26.92 5.15 0.51 746.5 74.0

KC1, –5°C freeze 31.85 6.09 0.60 883.1 87.6

KC1, –5°C freeze 24.6 4.70 0.47 682.2 67.6

KC1, –10°C freeze 23.45 4.48 0.44 650.3 64.4

KC1, –10°C freeze 20.18 3.86 0.38 559.7 55.3

KC1, –10°C freeze 20.18 3.86 0.38 559.7 55.3

KC1, –10°C freeze 28.25 5.40 0.54 783.3 77.7

KC1, –10°C freeze 22.03 4.21 0.42 611.0 60.4

APPENDIX B: BOND STRENGTH OF MORTAR JOINTS
33

APPENDIX C: ASTM C 1262, “STANDARD TEST METHOD FOR

EVALUATING THE FREEZE–THAW DURABILITY OF

MANUFACTURED CONCRETE MASONRY UNITS AND RELATED CONCRETE UNITS”
34
35
37

APPENDIX D: MASONRY UNIT FREEZE–THAW DURABILITY TEST RESULTS

NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (A)

Cycle 145 Cycle 283 Cycle 373 Cycle 448 Cycle 542 Cycle 818 Cycle 875

Acc.* % Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

SSD† res. loss res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from wt. from wt. from

 no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (A)-1 2.9514 0.0040 0.1 0.0066 0.2 0.0106 0.4 0.0124 0.4 0.0148 0.5 0.0222 0.8 0.0236 0.8

SRW (A)-2 3.0012 0.0032 0.1 0.0048 0.2 0.0060 0.2 0.0072 0.2 0.0084 0.3 0.0136 0.5 0.0222 0.7

SRW (A)-3 3.0584 0.0032 0.1 0.0048 0.2 0.0058 0.2 0.0068 0.2 0.0074 0.2 0.0104 0.3 0.0118 0.4

SRW (A)-4 3.0882 0.0032 0.1 0.0048 0.2 0.0058 0.2 0.0070 0.2 0.0080 0.3 0.0118 0.4 0.0138 0.4

SRW (A)-5 3.0884 0.0018 0.1 0.0028 0.1 0.0032 0.1 0.0036 0.1 0.0042 0.1 0.0062 0.2 0.0066 0.2

SRW (A)-6 3.1062 0.0012 0.0 0.0022 0.1 0.0024 0.1 0.0030 0.1 0.0034 0.1 0.0052 0.2 0.0058 0.2

SRW (A)-7 3.1480 0.0028 0.1 0.0042 0.1 0.0050 0.2 0.0056 0.2 0.0062 0.2 0.0094 0.3 0.0098 0.3

SRW (A)-8 3.1530 0.0040 0.1 0.0070 0.2 0.0080 0.3 0.0094 0.3 0.0102 0.3 0.0144 0.5 0.0162 0.5

SRW (A)-9 3.0760 0.0044 0.1 0.0062 0.2 0.0070 0.2 0.0080 0.3 0.0082 0.3 0.0120 0.4 0.0130 0.4

SRW (A)-10 3.2016 0.0044 0.1 0.0064 0.2 0.0078 0.2 0.0086 0.3 0.0094 0.3 0.0132 0.4 0.0142 0.4

Avg. 3.0872 0.1 0.2 0.2 0.2 0.3

SD 0.0695

COV 2.2504

* Accumulated residual weight.

† Saturated, surface dry.
NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (G)

Cycle 76 Cycle 102 Cycle 172 Cycle 216 Cycle 246 Cycle 266

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

SSD res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from wt. from

 no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (G2)-1 3.1252 0.0318 1.0 0.0448 1.4 0.0664 2.1 0.0808 2.6 0.0894 2.9

SRW (G2)-2 3.0604 0.0246 0.8 0.0348 1.1 0.0584 1.9 0.0914 3.0 0.1860 6.1 0.2632 8.6

SRW (G2)-3 3.2350 0.0156 0.5 0.0186 0.6 0.0272 0.8 0.0348 1.1 0.0384 1.2

SRW (G2)-4 3.1022 0.0352 1.1 0.0496 1.6 0.0650 2.1 0.0730 2.4 0.0788 2.5

SRW (G2)-5 3.2304 0.0240 0.7 0.0306 0.9 0.0396 1.2 0.0460 1.4 0.0494 1.5

SRW (G2)-6 3.2456 0.0362 1.1 0.0454 1.4 0.0582 1.8 0.0704 2.2 0.0786 2.4

SRW (G2)-7 3.2744 0.0314 1.0 0.0392 1.2 0.0528 1.6 0.0618 1.9 0.0652 2.0

SRW (G2)-8 3.1954 0.0248 0.8 0.0336 1.1 0.0508 1.6 0.0580 1.8 0.0646 2.0

SRW (G2)-9 3.2566 0.0160 0.5 0.0200 0.6 0.0314 1.0 0.0396 1.2 0.0468 1.4

SRW (G2)-10 3.2800 0.0354 1.1 0.0450 1.4 0.0584 1.8 0.0698 2.1 0.0818 2.5

Avg. 3.2005

SD 0.0735

COV 2.2967

Cycle 274 Cycle 286 Cycle 307 Cycle 333 Cycle 362 Cycle 397 Cycle 436

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

res. loss res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. from wt. from wt. from wt. from wt. from wt. from wt. from

 no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (G2)-1 0.0964 3.1 0.1026 3.3 0.1102 3.5 0.1180 3.8 0.1338 4.3 0.1532 4.9

SRW (G2)-2 0.3288 10.7

SRW (G2)-3 0.0484 1.5 0.0510 1.6 0.0580 1.8 0.0614 1.9 0.0684 2.1 0.0812 2.5

SRW (G2)-4 0.0846 2.7 0.0898 2.9 0.0964 3.1 0.1048 3.4 0.1234 4.0 0.1440 4.6

SRW (G2)-5 0.0560 1.7 0.0596 1.8 0.0676 2.1 0.0712 2.2 0.0786 2.4 0.0944 2.9

SRW (G2)-6 0.0902 2.8 0.0954 2.9 0.1056 3.3 0.1144 3.5 0.1288 4.0 0.1482 4.6

SRW (G2)-7 0.0738 2.3 0.0756 2.3 0.0794 2.4 0.0848 2.6 0.0910 2.8 0.1074 3.3

SRW (G2)-8 0.0728 2.3 0.0792 2.5 0.0846 2.6 0.0950 3.0 0.1096 3.4 0.1284 4.0

SRW (G2)-9 0.0534 1.6 0.0560 1.7 0.0606 1.9 0.0642 2.0 0.0718 2.2 0.0850 2.6

SRW (G2)-10 0.1014 3.1 0.1116 3.4 0.1240 3.8 0.1324 4.0 0.1422 4.3 0.1584 4.8

Cycle 490 Cycle 525 Cycle 590 Cycle 669 Cycle 798 Cycle 907

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. from wt. from wt. from wt. from wt. from wt. from

 no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (G2)-1 0.1696 5.4 0.1852 5.9 0.2090 6.7 0.2386 7.6 0.2770 8.9 0.3206 10.3

SRW (G2)-2

SRW (G2)-3 0.0954 2.9 0.1082 3.3 0.1248 3.9 0.1650 5.1 0.2208 6.8 0.2718 8.4

SRW (G2)-4 0.1674 5.4 0.1818 5.9 0.2028 6.5 0.2322 7.5 0.2682 8.6 0.2990 9.6

SRW (G2)-5 0.1046 3.2 0.1102 3.4 0.1300 4.0 0.1476 4.6 0.1690 5.2 0.1764 5.5

SRW (G2)-6 0.1652 5.1 0.1792 5.5 0.2002 6.2 0.2300 7.1 0.2668 8.2 0.2946 9.1

SRW (G2)-7 0.1260 3.8 0.1412 4.3 0.1564 4.8 0.1888 5.8 0.2274 6.9 0.2472 7.5

SRW (G2)-8 0.1480 4.6 0.1654 5.2 0.1838 5.8 0.2044 6.4 0.2498 7.8 0.2794 8.7

SRW (G2)-9 0.0920 2.8 0.0966 3.0 0.1096 3.4 0.1246 3.8 0.1548 4.8 0.1874 5.8

SRW (G2)-10 0.1732 5.3 0.1932 5.9 0.2080 6.3 0.2496 7.6 0.2820 8.6 0.3158 9.6

38
39

NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (H)

Cycle 73 Cycle 140 Cycle 184 Cycle 244 Cycle 305 Cycle 360

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

SSD res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from wt. from

no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (H)-1 3.0894 0.0150 0.5 0.0350 1.1 0.0440 1.4 0.0566 1.8 0.0666 2.2 0.0768 2.5

SRW (H)-2 3.2062 0.0072 0.2 0.0136 0.4 0.0172 0.5 0.0230 0.7 0.0284 0.9 0.0342 1.1

SRW (H)-3 3.1532 0.0058 0.2 0.0154 0.5 0.0208 0.7 0.0268 0.8 0.0358 1.1 0.0430 1.4

SRW (H)-4 3.1920 0.0114 0.4 0.0216 0.7 0.0260 0.8 0.0320 1.0 0.0384 0.0440 1.4

SRW (H)-5 2.9938 0.0148 0.5 0.0280 0.9 0.0348 1.2 0.0412 1.4 0.0536 1.8 0.0654 2.2

SRW (H)-6 3.0822 0.0224 0.7 0.0332 1.1 0.0426 1.4 0.0514 1.7 0.0586 1.9 0.0728 2.4

SRW (H)-7 3.0982 0.0080 0.3 0.0132 0.4 0.0188 0.6 0.0242 0.8 0.0306 1.0 0.0380 1.2

SRW (H)-8 3.1036 0.0068 0.2 0.0154 0.5 0.0210 0.7 0.0254 0.8 0.0322 1.0 0.0410 1.3

SRW (H)-9 3.0942 0.0176 0.6 0.0316 1.0 0.0418 1.4 0.0524 1.7 0.0656 2.1 0.0786 2.5

SRW (H)-10 3.0892 0.0234 0.8 0.0426 1.4 0.0540 1.7 0.0676 2.2 0.0834 2.7 0.0972 3.1

Avg. 3.1102

SD 0.0578

COV 1.8583

Cycle 395 Cycle 434 Cycle 481 Cycle 605 Cycle 729 Cycle 920 Cycle 938

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

res. loss res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. from wt. from wt. from wt. from wt. from wt. from wt. from

no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (H)-1 0.0814 2.6 0.0896 2.9 0.0976 3.2 0.1116 3.6 0.1352 4.4 0.1570 5.1 0.1594 5.2

SRW (H)-2 0.0366 1.1 0.0412 1.3 0.0448 1.4 0.0536 1.7 0.0600 1.9 0.0770 2.4 0.0780 2.4

SRW (H)-3 0.0458 1.5 0.0514 1.6 0.0554 1.8 0.0700 2.2 0.0792 2.5 0.0968 3.1 0.0982 3.1

SRW (H)-4 0.0484 1.5 0.0548 1.7 0.0590 1.8 0.0742 2.3 0.0894 2.8 0.1080 3.4 0.1088 3.4

SRW (H)-5 0.0720 2.4 0.0866 2.9 0.0932 3.1 0.1144 3.8 0.1290 4.3 0.1548 5.2 0.1564 5.2

SRW (H)-6 0.0774 2.5 0.0914 3.0 0.0994 3.2 0.1178 3.8 0.1618 5.2 0.1944 6.3 0.1996 6.5

SRW (H)-7 0.0426 1.4 0.0498 1.6 0.0538 1.7 0.0710 2.3 0.0842 2.7 0.0968 3.1 0.0978 3.2

SRW (H)-8 0.0460 1.5 0.0530 1.7 0.0596 1.9 0.0698 2.2 0.0822 2.6 0.0958 3.1 0.0968 3.1

SRW (H)-9 0.0854 2.8 0.0946 3.1 0.1028 3.3 0.1194 3.9 0.1364 4.4 0.1674 5.4 0.1704 5.5

SRW (H)-10 0.1042 3.4 0.1146 3.7 0.1200 3.9 0.1344 4.4 0.1482 4.8 0.1656 5.4 0.1678 5.4
40

NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (I)

Cycle 41 Cycle 56 Cycle 64 Cycle 73 Cycle 81

Acc. % Acc. % Acc. % Acc. % Acc. %

SSD res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from

no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (I)-1 2.7876 0.0188 0.7 0.0676 2.4 0.1680 6.0 0.3872 13.9 —

SRW (I)-2 2.8026 0.0106 0.4 0.0396 1.4 0.0850 3.0 0.1686 6.0 0.3852 13.7

SRW (I)-3 2.8506 0.0058 0.2 0.0096 0.3 0.0148 0.5 0.0287 1.0 0.0470 1.6

SRW (I)-4 2.8772 0.0140 0.5 0.0490 1.7 0.0682 2.4 0.2234 7.8 0.4028 14.0

SRW (I)-5 2.8054 0.0058 0.2 0.0084 0.3 0.0160 0.6 0.0314 1.1 0.2270 8.1

SRW (I)-6 2.8338 0.0084 0.3 0.0126 0.4 0.0164 0.6 0.0254 0.9 0.0414 1.5

SRW (I)-7 2.7914 0.0064 0.2 0.0134 0.5 0.0240 0.9 0.0394 1.4 0.0736 2.6

SRW (I)-8 2.7344 0.0066 0.2 0.0190 0.7 0.0536 2.0 0.2324 8.5 0.3820 14.0

SRW (I)-9 2.8206 0.0086 0.3 0.0268 1.0 0.0374 1.3 0.1618 5.7 0.2886 10.2

SRW (I)-10 2.7540 0.0156 0.6 0.0644 2.3 0.2246 8.2 0.3840 13.9 —

Avg. 2.8058

SD 0.0405

COV 1.4450

Cycle 89 Cycle 94 Cycle 100 Totals

Acc. % Acc. % Acc. % %

res. loss res. loss res. loss Failure loss

Unit wt. from wt. from wt. from cycle from

 no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (I)-1 — — — 73 13.9

SRW (I)-2 — — — 81 13.7

SRW (I)-3 0.0610 2.1 0.2430 8.5 0.3092 10.8 100 10.8

SRW (I)-4 — — — 81 14.0

SRW (I)-5 0.3010 10.7 — — 89 10.7

SRW (I)-6 0.0654 2.3 0.1414 5.0 0.2946 10.4 100 10.4

SRW (I)-7 0.2282 8.2 0.2944 10.5 — 94 10.5

SRW (I)-8 — — — 81 14.0

SRW (I)-9 — — — 81 10.2

SRW (I)-10 — — — 73 13.9
41

NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (J)

Cycle 52 Cycle 57 Cycle 61 Cycle 67 Cycle 69

Acc. % Acc. % Acc. % Acc. % Acc. %

SSD res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from

no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (J)-1 2.7968 0.0148 0.5 0.0210 0.8 0.0284 1.0 0.1292 4.6 0.1722 6.2

SRW (J)-2 2.7424 0.0234 0.9 0.0320 1.2 0.0492 1.8 0.2436 8.9 0.4044 14.7

SRW (J)-3 2.8282 0.0214 0.8 0.0328 1.2 0.0464 1.6 0.0932 3.3 0.1660 5.9

SRW (J)-4 2.7922 0.0168 0.6 0.0286 1.0 0.0394 1.4 0.1066 3.8 0.1424 5.1

SRW (J)-5 2.7830 0.0188 0.7 0.0340 1.2 0.0434 1.6 0.1366 4.9 0.2814 10.1

SRW (J)-6 2.9644 0.0612 2.1 0.1052 3.5 0.1318 4.4 0.2750 9.3 0.3272 11.0

SRW (J)-7 2.8082 0.0632 2.3 0.1328 4.7 0.1906 6.8 0.7478 26.6 —

SRW (J)-8 2.7942 0.0080 0.3 0.0130 0.5 0.0202 0.7 0.1342 4.8 0.2312 8.3

SRW (J)-9 2.8408 0.0122 0.4 0.0302 1.1 0.0498 1.8 0.1912 6.7 0.3018 10.6

SRW (J)-10 2.9749 0.0986 3.3 0.1294 4.3 0.1484 5.0 0.3662 12.3 —

Avg. 2.8325

SD 0.0730

COV 2.5771

Cycle 72 Totals

Acc. % %

res. loss Failure loss

Unit wt. from cycle from

no. (lb) SSD (lb) SSD

SRW (J)-1 0.2832 10.1 72 10.1

SRW (J)-2 — 69 14.7

SRW (J)-3 0.2994 10.6 72 10.6

SRW (J)-4 0.2832 10.1 72 10.1

SRW (J)-5 — 69 10.1

SRW (J)-6 — 69 11.0

SRW (J)-7 — 67 26.6

SRW (J)-8 0.3120 11.2 72 11.2

SRW (J)-9 — 69 10.6

SRW (J)-10 — 67 12.3
NCMA Research Lab: ASTM C 1262 Freeze–Thaw Data Sheet

Specimens: SRW (K)

Cycle 47 Cycle 55 Cycle 63 Cycle 72 Cycle 80 Cycle 88

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

SSD res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. wt. from wt. from wt. from wt. from wt. from wt. from

no. (lb) (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (K)-1 2.6226 0.0064 0.2 nsl 0.0152 0.6 nsl 0.1330 5.1 0.3090 11.8

SRW (K)-2 2.6386 0.0060 0.2 nsl 0.0080 0.3 nsl 0.0152 0.6 0.2174 8.2

SRW (K)-3 2.5718 0.0626 2.4 0.4228 16.4 — — — —

SRW (K)-4 2.6870 0.0104 0.4 nsl 0.0354 1.3 0.1282 4.8 0.3352 12.5 —

SRW (K)-5 2.5896 0.0054 0.2 nsl 0.0074 0.3 nsl 0.0144 0.6 0.0140 0.5

SRW (K)-6 2.5741 0.3870 15.0 — — — — —

SRW (K)-7 2.6140 0.0150 0.6 nsl 0.0296 1.1 0.0414 1.6 0.0492 1.9 0.0768 2.9

SRW (K)-8 2.6050 0.0088 0.3 nsl 0.0190 0.7 0.0320 1.2 0.0706 2.7 0.1390 5.3

SRW (K)-9 2.6880 0.0066 0.2 nsl 0.0090 0.3 nsl 0.0146 0.5 0.0172 0.6

SRW (K)-10 2.6486 0.0082 0.3 nsl 0.0270 1.0 0.0606 2.3 0.2828 10.7 —

Avg. 2.6239

SD 0.0397

COV 1.5122

Cycle 93 Cycle 99 Cycle 108 Cycle 118 Cycle 127 Cycle 133

Acc. % Acc. % Acc. % Acc. % Acc. % Acc. %

res. loss res. loss res. loss res. loss res. loss res. loss

Unit wt. from wt. from wt. from wt. from wt. from wt. from

no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (K)-1 — — — — — —

SRW (K)-2 0.2964 11.2 — — — — —

SRW (K)-3 — — — — — —

SRW (K)-4 — — — — — —

SRW (K)-5 nsl 0.0236 0.9 0.0676 2.6 0.1028 4.0 0.2228 8.6 0.3142 12.1

SRW (K)-6 — — — — — —

SRW (K)-7 0.0890 3.4 0.1252 4.8 0.3008 11.5 — — —

SRW (K)-8 0.1848 7.1 0.2278 8.7 0.2700 10.4 — — —

SRW (K)-9 nsl 0.0186 0.7 0.0246 0.9 0.0306 1.1 0.0398 1.5 0.0528 2.0

SRW (K)-10 — — — — — —

Cycle 138 Cycle 147 Cycle 156 Cycle 167 Cycle 179 Totals

Acc. % Acc. % Acc. % Acc. % Acc. % %

res. loss res. loss res. loss res. loss res. loss Failure loss

Unit wt. from wt. from wt. from wt. from wt. from cycle from

no. (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD (lb) SSD

SRW (K)-1 — 88 11.8

SRW (K)-2 — 93 11.2

SRW (K)-3 — 55 16.4

SRW (K)-4 — 80 12.5

SRW (K)-5 — 133 12.1

SRW (K)-6 — 47 15.0

SRW (K)-7 — 108 11.5

SRW (K)-8 — 108 10.4

SRW (K)-9 0.0598 2.2 0.0720 2.7 0.1038 3.9 0.1530 5.7 0.3232 12.0 179 12.0

SRW (K)-10 — 80 10.7

42
43

NCMA-SRW-A10

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 27 26 6 59 45.8 44.1 10.2 27

2 53 42 22 117 45.3 35.9 18.8 49

3 85 57 35 177 48.0 32.2 19.8 71

4 113 77 46 236 47.9 32.6 19.5 91

5 147 94 54 295 49.8 31.9 18.3 114

6 177 117 61 355 49.9 33.0 17.2 132

7 212 134 69 415 51.1 32.3 16.6 146

8 245 151 77 473 51.8 31.9 16.3 162

9 279 167 88 534 52.2 31.3 16.5 178

10 314 185 98 597 52.6 31.0 16.4 202

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 372.2 mm

Voids/mm = n = N/T = 0.54

Specific surface in mm2/mm3 = 4/l = 13.21

Average chord intercept (l) in mm = A/100 n = 0.30

Paste/air ratio (p/A) = 1.888 <4.342

If p/A >4.342, then spacing factor (L) = 226 μm

If p/A <4.342, then spacing factor (L) = 143 μm

Conclusion: Air content is high. Spacing factor is small (good). Most of the aggregate is quartzite, well graded,

and apparently sound. The air void system in the cement paste is good and aggregate is of good quality. Good

F-T resistance is expected.

NCMA-SRW-G1

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 36 7 1 44 81.8 15.9 2.3 6

2 60 18 9 87 69.0 20.7 10.3 18

3 90 25 13 128 70.3 19.5 10.2 31

4 118 36 18 172 68.6 20.9 10.5 42

5 151 46 19 216 69.9 21.3 8.8 51

6 178 56 23 257 69.3 21.8 8.9 64

7 207 64 29 300 69.0 21.3 9.7 75

8 238 71 32 341 69.8 20.8 9.4 85

9 264 80 38 382 69.1 20.9 9.9 97

10 288 96 41 425 67.8 22.6 9.6 109

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 263.5 mm

Voids/mm = n = N/T = 0.41

Specific surface in mm2/mm3 = 4/l = 17.15

Average chord intercept (l) in mm = A/100 n = 0.23

Paste/air ratio (p/A) = 2.341 <4.342

If p/A >4.342, then spacing factor (L) = 191 μm

If p/A <4.342, then spacing factor (L) = 137 μm

Conclusion: Air content is low. Spacing factor is low (good). Based on air voids in the paste alone, adequate FT resistance is expected. The aggregate appears to be sound, well graded, well packed, and angular. Paste/air

ratio is low.

APPENDIX E: AIR-VOID ANALYSES

ASTM C 457, Modified Point Count Method
NCMA-SRW-H1

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 28 14 1 43 65.1 32.6 2.3 6

2 57 27 3 87 65.5 31.0 3.4 14

3 85 39 4 128 66.4 30.5 3.1 21

4 111 52 6 169 65.7 30.8 3.6 27

5 141 60 9 210 67.1 28.6 4.3 36

6 174 67 13 254 68.5 26.4 5.1 48

7 198 82 15 295 67.1 27.8 5.1 56

8 229 92 15 336 68.2 27.4 4.5 60

9 255 105 17 377 67.6 27.9 4.5 66

10 282 118 19 419 67.3 28.2 4.5 71

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 259.7 mm

Voids/mm = n = N/T = 0.27

Specific surface in mm2/mm3 = 4/l = 24.11

Average chord intercept (l) in mm = A/100 n = 0.17

Paste/air ratio (p/A) = 6.211 >4.342

If p/A >4.342, then spacing factor (L) = 212 μm

If p/A <4.342, then spacing factor (L) = 258 μm

Conclusion: Air content is low. Spacing factor is low (good). Based on air voids in the paste alone,

adequate F-T resistance is expected. The aggregate appears to be sound, well graded, well packed, and

angular. Paste/air ratio is low.

NCMA-SRW-I10

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 29 8 4 41 70.7 19.5 9.8 11

2 54 19 9 82 65.9 23.2 11.0 30

3 70 37 17 124 56.5 29.8 13.7 47

4 93 49 23 165 56.4 29.7 13.9 67

5 116 63 27 206 56.3 30.6 13.1 77

6 138 78 31 247 55.9 31.6 12.6 88

7 155 87 45 287 54.0 30.3 15.7 110

8 175 106 47 328 53.4 32.3 14.3 126

9 196 121 52 369 53.1 32.8 14.1 140

10 224 132 54 410 54.6 32.2 13.2 154

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 254 mm

Voids/mm = n = N/T = 0.61

Specific surface in mm2/mm3 = 4/l = 18.41

Average chord intercept (l) in mm = A/100 n = 0.22

Paste/air ratio (p/A) = 2.444 <4.342

If p/A >4.342, then spacing factor (L) = 182 μm

If p/A <4.342, then spacing factor (L) = 133 μm

Conclusion: Air content is low. Spacing factor is low (good). Based on air voids in the paste alone,

adequate F-T resistance is expected. However, abundance of very porous (large-pored) aggregates

may indicate questionable performance. Paste/air ratio is very low.

44
45

NCMA-SRW-J10

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 51 27 5 83 61.4 32.5 6.0 12

2 106 52 8 166 63.9 31.3 4.8 24

3 152 80 15 247 61.5 32.4 6.1 40

4 206 104 18 328 62.8 31.7 5.5 49

5 257 132 24 413 62.2 32.0 5.8 65

6 303 158 33 494 61.3 32.0 6.7 84

7 354 181 40 575 61.6 31.5 7.0 99

8 405 204 48 657 61.6 31.1 7.3 117

9 447 234 57 738 60.6 31.7 7.7 138

10 493 264 62 819 60.2 32.2 7.6 153

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 513.7 mm

Voids/mm = n = N/T = 0.30

Specific surface in mm2/mm3 = 4/l = 15.74

Average chord intercept (l) in mm = A/100 n = 0.25

Paste/air ratio (p/A) = 4.258 <4.342

If p/A >4.342, then spacing factor (L) = 273 μm

If p/A <4.342, then spacing factor (L) = 271 μm

Conclusion: Air content is very low. Spacing factor is larger than wanted. About 80% of the aggregate is

white, relatively porous, and soft (Moh’s hardness is 4). Questionable F-T resistance is expected.

NCMA-SRW-K

Cum. no. of points landing on Cumulative Volume fractions (%) No. of interTraverse Fine Cement Total total no. Fine Cement Total connected

no. aggregate paste air of points aggregate paste air air voids

1 21 14 7 42 50.0 33.3 16.7 16

2 46 28 11 85 54.1 32.9 12.9 35

3 73 36 17 126 57.9 28.6 13.5 51

4 97 51 19 167 58.1 30.5 11.4 74

5 118 67 24 209 56.5 32.1 11.5 95

6 136 85 31 252 54.0 33.7 12.3 122

7 156 98 39 293 53.2 33.4 13.3 141

8 174 118 41 333 52.3 35.4 12.3 166

9 197 130 48 375 52.5 34.7 12.8 192

10 217 147 54 418 51.9 35.2 12.9 215

Total length of traverse (T) = (Total no. of points – No. of traverse lines) * Grid interval = 259.1 mm

Voids/mm = n = N/T = 0.83

Specific surface in mm2/mm3 = 4/l = 25.69

Average chord intercept (l) in mm = A/100 n = 0.16

Paste/air ratio (p/A) = 2.722 <4.342

If p/A >4.342, then spacing factor (L) = 137 μm

If p/A <4.342, then spacing factor (L) = 106 μm

Conclusion: Air content is low. Spacing factor is low (good). Based on air voids in the paste alone,

adequate F-T resistance is expected. However, almost all aggregate is pumice (large vesicles). This may

indicate questionable F-T performance. Paste/air ratio is low.
47

APPENDIX F: PROPOSAL TO THE ALL-WEATHER COUNCIL

Proposal for an Update

to

Recommended Practices and Guide Specifications for

Cold Weather Masonry Construction

April 1996

Background

The following recommendations for updating

the April 1, 1988, 11th printing of the subject document are the product of a cooperative research

project conducted in partnership between the

U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) and the National Concrete Masonry Association (NCMA). This work

was done from 1992 to 1995 under the authority

of the U.S. Army Corps of Engineers Construction

Productivity Advancement Research (CPAR) initiative, which is a cost-shared program between the

Corps and the construction industry for the purpose of enhancing construction productivity. Its

primary purpose is to develop improved guidance on thermal protection requirements for coldweather masonry construction. In addition, the

feasibility of using antifreeze admixtures in

masonry mortar was studied. The existing guide

specifications do not recommend antifreeze

admixtures primarily because little is known

about them. However, the findings from this and

other recent studies on antifreeze admixtures

have shown significant potential that merits further consideration.

Recommendations

The following recommendations are referenced to the subject document by page, section,

and paragraph. Items we recommend be deleted

from the document are crossed out. Items in bold

italics are recommended to be added to the document. A general comment, but one not incorporated into the recommendations below, is to produce a parallel document with SI units (formerly

referred to as a “metric” document). ACI 318 and

ACI 318M are an example.
Recommended Practices for

Cold-Weather Masonry Construction

Page Section Para. Recommendation

7 General 2 It is acknowledged that As the ambient temperature falls

below freezing, more of the construction materials must be

are preconditioned in the effort to permit foster satisfactory

masonry strength development. To successfully ... is

essential.

3 The times, temperatures, moisture contents, and strengths

provided in this booklet do not apply to any one circumstance in the field. They do, however, suggest expected

trends. Good judgment is required to apply the guidance

herein to particular situations.

8 Mortar Performance at Temperatures Below Normal

General 1 As the ambient ... involved. The heat-liberating reaction

between portland cement and water is slowed or stopped

when the cement paste is subjected to temperatures cools

below 40°F (5°C). Hydration and strength development

proceed only at temperatures when the cement paste is

above freezing and only when sufficient water is available.

However, cold weather masonry construction may proceed

at air temperatures below freezing, ... construction.

9 Effects of Freezing 2 The water content ... characteristics. Mortars possessing

water contents in excess of 6 to 8% 8 to 10% expand on

freezing do not attain full potential strength on freezing.

Expansion Strength loss increases as the water content

increases, ... to some value below 6% 8% to avoid the

disruptive expansive forces frost-weakened mortar.

3 Through the combined effects of evaporation, hydration

and absorption, the moisture content of masonry mortar

will drop below 8% within 4 to 8 hours. By maintaining a

masonry assembly at or above 40°F (5°C) for at least 8

hours, the mortar will become immune to one cycle of

freezing and thawing. (It is unknown whether mortar in

this moisture condition can resist multiple freeze–thaw

cycles.)

9 4 In a situation where evaporation and absorption are held

to a minimum, such as when mortar is placed on glass

blocks and the masonry assembly is covered by plastic

sheets, the primary mechanism of moisture loss is that due

to cement hydration. In this situation, mortar that is

maintained at or above 40°F (5°C) for at least 6 hours

becomes immune to one cycle of freezing and thawing. (It is

unknown whether mortar at this maturity can resist

multiple freeze–thaw cycles.)

5 Therefore, based on both moisture content and maturity

considerations, it is necessary to maintain fresh mortar at

or above 40°F (5°C) for only 8 hours before it is allowed to

freeze. Beyond 8 hours, a single freezing will not have a

detrimental effect on the strength properties of masonry

mortar.

48
49

Loss of Water 1 The early freezing of mortars does not significantly reduce

either transverse or compressive strength. Mortar that is

frozen at a moisture content above 8% can lose nearly half

its potential compressive strength. The effect of ... unknown. Masonry once frozen and dried may be expected to

suffer a strength reduction because it may not contain

water sufficient to complete cement hydration. Consequently, ... development.

Note: Mortar develops maximum strength when it is cured

at a moisture content of 12%. Strength decreases if the

initial water content is changed in either direction. For

example, mortar mixed with only a 6% water content

(impractically dry) may produce only 20% of the strength

attained by the equivalent mortar with 12% water. Conversely, mortar mixed with 14% water (a typical field

mortar) attains only half the strength of its 14% counterpart.

Summary 1 The performance characteristics of masonry mortars are

influenced by temperatures below normal. Early-age

freezing can lead to irreparable strength loss. The changes

... materials. Heated mortars, which prolong the period

before freezing, Mortars heated and maintained at 40°F

(5°C) possess hardened properties equal to or more desirable than their unfrozen highly heated or early-frozen

counterparts.

9 Performance of Masonry Units at Below-Normal Temperatures

Basis of Selection 1 The architect’s ... construction. An absorptive ... freezing.

Conversely, a ... expansion. From maturity considerations,

auxiliary dry heat to promote mortar strength and drying

may be is not required for even very low absorptive units

such as glass blocks, provided the mortar can be maintained

at or above 40°F (5°C) by other means for at least 8 hours.

Performance of Masonry at Low Temperatures

10 General 3 When masonry freezes, two conditions are identifiable:

Masonry mortar becomes immune to one cycle of freezing

when either of two conditions is met:

(1) masonry frozen while the mortar is in the wet (greater

than 6% moisture) condition, and the moisture content of

the mortar is reduced by evaporation and/or absorption to

less than 8%, or

(2) masonry frozen while the mortar is in the dry (less than

6% moisture) condition the mortar has attained a maturity

equivalent to an 8-hour cure at 40°F (5°C) with no external

water to the mortar.

4 Masonry mortar frozen while the mortar is in the wet

condition (greater contains more than 6% 8% moisture)

contains has enough ... ice.

5 Masonry mortar frozen while the mortar is in the dry

condition ( contains less than 6% 8% moisture would ...

forces.

Page Section Para. Recommendation
6 Masonry mortar frozen after it has cured 8 hours is able to

resist a single freezing cycle. When moisture transfer

between the mortar and the surrounding environment is

completely prohibited, which is conservative compared

with field conditions, the amount of freezable water in

fresh mortar decreases as the mortar ages. Some of the

water chemically combines with cement during hydration,

and some becomes entrapped within the extremely fine

pore structure of the hardening cement gel. This water is

practically unfreezable. By an age of 8 hours, the freezable

water content diminishes to where one cycle of freezing

and thawing will not be disruptive.

7 Although a few ... conclusions. Mortar of sufficient

maturity and exposed to the cold at an early age can

attain more late-age strength than their warm-cured

counterparts. For example, mortar that is cured for 12 to

16 hours at or above 40°F (5°C), then exposed to sub-0°C

temperatures for about 12 hours, and then returned to 40°F

(5°C) or above can attain about 10% more late-age

strength than mortar that is continuously cured at 70°F

(20°C).

Summary 8 The consensus of the Council regarding the performance

of masonry at low temperature is that masonry should be

constructed in such a manner that it will develop sufficient

strength maturity and or that the mortar will lose sufficient water to prevent freezing. Further, all masonry frozen

dried during the early periods after construction should be

moistened either naturally or artificially to reactivate

ensure continuing the cement hydration process, which in

turn will promote further strength development of the

masonry.

Materials

Masonry Units 1 All masonry units ... construction. No change or ... masonry. Low absorption units ... freezing. The effect of the ...

if freezing occurs after the moisture within the mortar has

been decreased sufficiently low or the mortar has attained

sufficient maturity to prevent expansion on freezing. Units

with ... instances. Units with ... freezing.

11 Admixtures

Antifreeze 1 Most of the ... misidentified. They are ... depressants.

Antifreeze admixtures are chemical compounds that both

depress the freezing point of water and accelerate strength

gain of mortar at low temperatures. Some actual antifreeze admixtures freeze-point depressants are available ...

alcohol. If used in quantities ... rapidly. Since antifreeze ...

recommended.

11 2 Recent work1 has shown that antifreeze admixtures can

protect mortar from freezing when the internal temperature of the mortar is below 0°C with no detrimental sideeffects to the mortar. The main drawback is that there are

no commercially available antifreeze admixtures today.

50

Page Section Para. Recommendation
51

Page Section Para. Recommendation

Note: Expectations are that antifreeze admixtures will

eventually become available. Before they are used in

masonry mortar, test data should be produced to show

that they do not adversely affect mortar compressive

strength, bond strength, or freeze–thaw durability and

that they do not cause ferrous metals to corrode.

Air-Entraining 1 Air-entraining admixtures ... workability. There are some

Admixtures data that indicate that Laboratory air-entrained mortar

specimens are less subject to disintegration due more

resistant to freezing and thawing deterioration in the

presence of moisture. Excessive ... masonry. Therefore, airentraining admixtures should not be used are appropriate

in cold weather masonry construction provided excessive

amounts are not used. This recommendation ... materials.

Some masonry cements already contain an air-entraining

agent.

12 Materials Heating

General 1 The mixing water ... heated. Heating only ... unfrozen

Water ... probes. Any method ... acceptable. The mixing

water should be heated sufficiently to produce mortar

temperatures between 40°F (5°C) and 120°F 70°F (20°C).

There is minimal benefit to heating the mortar above 70°F

(20°C). The mortar in thin joints does not remain above

freezing significantly long nor does it achieve improved

strengths. Once a mortar ... batches.

1 C. Korhonen, B. Charest, and K. Romisch (1995) Developing new low-temperature admixtures for

concrete: A field evaluation. Corps of Engineers Structural Engineering Conference 95, San Antonio, Texas,

August.
COLD-WEATHER MASONRY CONSTRUCTION

AND PROTECTION RECOMMENDATIONS

Page Para. Recommendation

14 1 1. The cold weather ... followed.

2. Construction materials ... materials.

3. If climatic conditions ... overheating.

4. Sufficient mortar ... temperatures between 40°F (5°C) and 120°F 70°F (20°C). Every

effort ... range. The mortar ... batches. Heated mortar ... (greater than 120 F 70°F (20°C)).

5. During below-normal ... foundations. Masonry should ... surface.

6. At the end ... masonry. This protection ... masonry.

WORK DAY CONSTRUCTION

TEMPERATURE REQUIREMENT PROTECTION

Above 40°F Normal ... Procedures Cover walls ... masonry.

40°F–32°F Heat ... between 40°F Cover walls ... canvas.

(5°C) and 70°F (20°C)

32°F–25°F Heat ... between 40°F With wind velocities ... freezing. Maintain masonry ...

(5°C) and 70°F (20°C) for 16 8 hours using auxiliary heat or insulated blankets.

25°F–20°F Mortar on ... 40°F. With wind velocities ... freezing. Maintain masonry ...

for 16 8 hours using auxiliary heat or insulated blankets.

20°F–0°F Heat mixing ... between Provide enclosures ... above 32° 40°F (5°C).... 24 8 hours.

40°F (5°C)... 120° 70°F

(20°C)

52
Guide Specifications for

Cold-Weather Masonry Construction

Section Suggested Change

1.1 All materials shall be delivered in usable condition and stored to prevent

wetting by capillary action, rain and snow. Masonry units received at the

construction site must not be excessively wet. If visual inspection of the units

reveals surface moisture, some air drying must be allowed.

Note: Units in an intermediate moisture condition are most desirable. Very wet

units are prone to frost damage. Very dry units may excessively dry the mortar,

causing a weak layer.2

1.3 note Some clay brick units require ... bond. For cold weather ... construction. When

sprinkling ... brick. Water shall ... when units are below 32 degrees F 0°C (32°F),

and water ... below 32 degrees F 0°C (32°F).

Concrete masonry units ... sprinkling.

2 PRODUCTS MATERIALS

2.1 note ... No changes in ... for Materials (products) are required ... construction. However, it is ... masonry.

1. Change to a higher ... 270. (Example: If ... M.)

2. omit

3. Without changing ... and maintaining 24 8 hr. thermal protection in Section

3.3, replace type I portland cement in the mortar with type III, ASTM C 150.

3.2.1 Use dry masonry units that are free of observable surface moisture. Wet or ...

laid.

3.2.2 Air temperatures ... between 40°F (5°C) and 120°F 70°F (20°C).

3.2.3 Air temperatures ... between 40°F (5°C) and 120°F 70°F (20°C). Maintain mortar

... above freezing at or above 40°F (5°C).

3.2.4 Air temperatures ... between 40°F (5°C) and 120°F 70°F (20°C). Maintain mortar

... above freezing at or above 40°F (5°C). Salamanders or ... construction. Windbreaks shall ... 15 mph.

3.2.5 Air temperatures ... between 40°F (5°C) and 120°F 70°F (20°C). Enclosure and

auxiliary ... above 32 degrees F 40°F (5°C). Temperature of units ... 20 degrees F

20°F (–7°C).

3.3.1 Mean Daily ... for 24 hr. 8 hr. by ... membrane.

3.3.2 Mean Daily ... for 24 hr. 8 hr.

3.3.3 Mean Daily ... for 24 hr. 8 hr.

3.3.4 Mean Daily ... above 32 degrees F for 24 hr. 40°F (5°C) for 8 hr. by ... methods.

COLD WEATHER

PROTECTION

1.2 The Contractor ... above 32 degrees F 40°F (5°C) within ... areas.

2 T. Sneck (1972) The interaction between mortar and masonry units as a basis for standards for

masonry mortars. Joint RILEM-ASTM-CIB Symposium Proceedings, NBS Special Publication 361, vol. 1,

U.S. Department of Commerce, National Bureau of Standards, Washington, D.C.

53
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August 1997

Increasing Cold Weather Masonry Construction Productivity

Charles J. Korhonen, Robert D. Thomas, and Edel R. Cortez

U.S. Army Cold Regions Research and Engineering Laboratory

72 Lyme Road Special Report 97-16

Hanover, New Hampshire 03755-1290

Office of the Chief of Engineers

Washington, D.C. 20314-1000

58

UNCLASSIFIED UNCLASSIFIED UNCLASSIFIED UL

The thermal protection requirements for cold weather masonry, as established in current industry specifications, were evaluated. Experiments were conducted to define the most relevant factors in the process of

freezing of newly placed mortar. The effect of unit absorption on the moisture content of mortar during the

first hours after assembly was assessed. Correlations of moisture content with time were developed for

mortar in contact with masonry units. Frost immunity thresholds in terms of mortar moisture content and

in terms of maturity were determined. The test results provided the basis for new proposed guidance on

when fresh mortar can be safely exposed to freezing temperatures. Test methods for evaluation of the

freeze–thaw resistance of masonry units were evaluated. A new test was proposed and adopted by ASTM

as a new standard test for the freeze–thaw testing of masonry units. In addition, several chemicals were

evaluated for their potential as antifreeze admixtures for masonry mortar. Antifreeze admixtures were first

developed for use in concrete, but the practicality of using antifreeze admixtures in masonry mortars was

demonstrated in a field application in Michigan during the winter.

Antifreeze admixture Thermal protection

Cold-weather masonry Winter construction

Freeze–thaw