Technical Notes on Brick ConstructionBrick Industry Association
11490 Commerce Park Drive, Reston, Virginia 20191
1 REVISEDMarch 1992
ALL-WEATHER CONSTRUCTIONAbstract: This Technical Notes describes
how extremes of cold and hot weather can influence brick masonry
construction. Information on weather prediction necessary for
construction planning is provided. Cold and hot weather are
defined, and the reaction of clay brick masonry materials to these
extreme conditions is described. Recommendations are provided for
continuing construction in these severe exposure conditions.
Key Words: absorption, brick, climatology, cold weather,
evaporation, freezing, grout, hot weather,meteorology, mortar.
INTRODUCTION Periods of cold and hot weather have a tremendous
impact on the construction industry and the national economy. This
is reflected in several ways. Cold weather can cause temporary
delays and work stoppages on construction sites. Productivity and
the quality of construction on job sites may be reduced if workers
become too attentive to personal comfort during extremes in
temperature. Proper material protection and handling can increase
construction costs, although contractors and owners alike may
benefit in the long run. Completed work not properly constructed
during, or protected from, cold and sometimes hot weather may have
to be removed and rebuilt. Investigations to evaluate the
performance of suspect construction are an added expense which may
be necessary. Owners and businessmen can suffer from lost rentals
and business revenue when buildings are not completed on time.
Furthermore, the seasonal influence on construction results in idle
production facilities, large material inventories and high rates of
unemployment during the winter months. Stopping work on a project
due to extremes in weather conditions is not economically
desirable. The purpose of this Technical Notes is to describe how
masonry materials react to cold and hot weather conditions. It also
describes provisions which should be made to ensure that
construction does not decrease in quality and can continue without
interruption. Although "normal", "cold", and "hot" are relative
terms, normal, used in this Technical Notes, will be considered to
be any temperature between 40 F and 90 F (4C and 32 C). Cold will
be considered to be any temperature below 40F (4C), and hot any
temperature above 90F (32C). WEATHER PREDICTION To successfully
build during periods of abnormal weather conditions, designers and
contractors must have advance knowledge of local meteorological
conditions as
Examples of Climatic Data Available FIG. 1
well as knowledge of historic climatological information for a
given area. Meteorology may be defined as current state atmospheric
conditions, while climatology may be defined as the historic record
of the averages and extremes of weather representative of an area.
When in the planning stages for a project, designers are usually
concerned with climatological data such as the average and extreme
daytime and nighttime temperatures or average wind velocity for use
in designing mechanical or
structural systems. Contractors, however, are more concerned
with meteorological conditions during construction, such as hourly
temperatures and mean daily temperature, as well as the predicted
temperatures and wind velocities for the next few days. Mean daily
temperature is determined by adding together the maximum
temperature for each day (24 hours, midnight to midnight) and the
minimum temperature for the same day and dividing by two. Ambient
temperature as used in this Technical Notes is the outdoor
temperature at the time considered. Meteorological information can
be obtained from the National Weather Service, a branch of the
National Oceanographic and Atmospheric Administration (NOAA). The
National Weather Service has information centers located at major
airports in cities throughout the country. These centers provide
current weather information and regularly scheduled weather
forecasts for the region under consideration. Climatological
information can be obtained from the National Climatic Data Center,
also a branch of NOAA. The National Climatic Data Center usually
provides climatic information in the form of maps as shown in
Figure 1. These maps contain daily, monthly and annual data for a
region and may be obtained for a nominal fee by contacting the
Center [5]. EFFECTS OF COLD WEATHER Cold weather during masonry
construction affects the materials and labor used. Successful
construction will consider both in the planning, scheduling and set
up of the masonry work. In addition to anticipating the specific
weather conditions, the contractor must determine what the probable
effects of the weather will be on the materials and the workers,
how to protect materials and workers, how to store the materials,
and what procedures should be used to meet the requirements
specified in the construction documents. In the United States, all
model building codes have requirements relating to the construction
of masonry during cold weather. While not identical, each of the
building codes have similar general requirements regarding material
protection, heating of materials, use of frozen materials and
protection of completed work. Masonry Units Masonry units are the
material in masonry construction least affected by below-normal
temperatures. The physical properties of masonry units are
essentially the same in cold weather except that a cold unit will
have a slightly smaller volume than one at normal temperatures.
However, the absorption characteristics of the masonry unit and its
temperature contribute to the rate of freezing of masonry during
cold weather. Under normal conditions of construction, using
masonry units with initial rates of absorption (IRA) less than or
equal to 30 g/min/30 in. (30 g/min/194 cm ) at the time of laying
improves the bond between the brick and mortar which leads to
increased moisture resistance of the wall assembly. In cold
weather, brick having an initial rate of absorption of 25 g to 30
g/min/30 in. (25 g to 30 g/min/194 cm ) may be desirable.22 2 2
2
Using brick with a higher IRA reduces the risk of freezing by
more rapidly absorbing water from the mortar or grout. If a brick
with a low IRA is used, then the water content of the mortar should
be the minimum necessary for workability. If suction or other
measures reduce the water content to less than 6 percent of the
total mortar volume prior to freezing, the mortar will not
experience disruptive expansive forces upon freezing. Further,
signifi cant reductions in transverse or compressive strength of
the masonry assemblage will not occur. The temperature of the
masonry unit also contributes to the rate of freezing of masonry. A
cold unit will more rapidly withdraw the heat of hydration from the
mortar and thus increase the rate of freezing. Masonry units
preheated prior to laying minimize cold weather effects on the
hydration process of the mortar by maintaining the heat within the
mortar. Masonry units should be heated to a temperature of
approximately 40F (4C) prior to laying when ambient temperatures
are below 20F ( -7C). Heating units to temperatures above 40F (4C)
is seldom necessary. It may be advantageous to heat units even when
ambient temperatures are above 20F ( -7C). Preheated units will
exhibit the same absorption characteristics as units laid during
normal weather conditions. Units which are frozen should be thawed
and dried completely before use. Frozen masonry should not be built
upon. Completed masonry which is frozen may be moistened after
thawing to reactivate the hydration process and continue to develop
strength [7,10]. Mortar Mortar mixed with cold materials have
properties quite different from those at normal temperatures. Cold
weather retards the hydration of the cement in the mortar mix.
Mortar mixed during cold weather often has lower water content,
increased air content, and reduced early strength compared with
those mixed during normal temperatures. For these reasons, mortar
is often mixed with heated materials to produce performance
characteristics associated with mortar mixed at normal
temperatures, or with admixtures which may improve the early
strength and plasticity of the mix. Water, sand, or both may be
heated for use in mortar. Heating prepackaged materials such as
portland cement and hydrated lime can be difficult. Specific
recommendations are a function of temperature and are found in
later sections of this Technical Notes. Mortar materials and the
proportion of ingredients, within the permissible ranges, can also
be modified for cold weather conditions. A higher sand content
provides a stiffer mortar which will better support the weight of
subsequently laid masonry. A lower lime content will allow the
water content of the mortar to decrease more rapidly, just as a
brick with a higher IRA. High-early-strength (Type III) portland
cement may be used to increase the rate of early strength gain.
Admixtures, although not recommended, may be used to accelerate the
rate of set. Freezing of the mortar should be avoided in all cases.
Mortar which freezes is not as weather-resistant or as watertight
as mortar that has not been frozen [6]. Furthermore, significant
reductions in compressive and
bond strength may occur. Mortar having a water content over 6 to
8 percent of the total volume will experience disruptive expansive
forces if frozen due to the increase in volume of water when it is
converted to ice. Thus, the bond between the unit and the mortar
may be damaged or destroyed. Mortar in newly completed masonry
should be protected from freezing. Specific requirements are found
in Table 1. Grout Grout, although made from similar materials,
should not be confused with concrete. Typically smaller aggregate
is used in grout for easier placement and consolidation. Concrete
uses a minimum amount of water, whereas the water-cement ratio for
grout is high, because grout is placed in absorptive molds of
brick. Furthermore, high water content is necessary in grout for
ease of flow, but it greatly increases the amount of volumetric
expansion which can occur upon freezing. Thus grout, like mortar,
should be mixed with heated materials to prevent the damaging
effects of freezing. High-early-strength (Type III) portland cement
may be used to increase the rate of early strength gain of the
grout. Admixtures may also be used, but protection of the grouted
masonry is still required. MATERIALS IN COLD WEATHER CONSTRUCTION
Protection Although the temperature of the materials used in
masonry construction is one of the factors which should be adjusted
for cold weather construction, adjustments in construction
practices may also be necessary. ACI 530.1/ ASCE 6/TMS 602 ,
Specifications for Masonry Structures, addresses material heating
as well as requirements for protection of masonry constructed in
cold weather [3]. Protection is one of the most necessary
adjustments to make in construction practices. Construction
materials should be carefully covered to remain dry. ACI 530.1/ASCE
6/TMS 602 requires protection such as the use of insulating
blankets and forced air heaters. However, protection may also
include special light-weight, warm work clothes worn by laborers or
standard construction equipment adapted to unique cold weather
protection uses. This approach is common in northern Europe where
cold weather may last up to six months. All masonry materials
should be kept dry and free from ice and snow by covering with
tarpaulins or clear polyethylene sheets. Sand and masonry units
should be covered and stored on raised platforms to avoid contact
with the ground. Careless material storage increases the cost of
laying masonry because removal of ice and snow and thawing of
masonry units are necessary before construction may begin.
Partially completed or exposed walls should be covered at the end
of each day's work with a weighted tarpaulin which extends a
minimum of 2 ft (1 m) down each side of the wall to prevent
contamination by water, ice, or snow (Fig. 2).
TABLE 1 Requirements for Brick Masonry Construction in Cold
Weather
Temperature (see note)
Construction Requirements
Protection Requirements
100F-40F (38C-4C)
Normal procedures.
Cover walls with plastic or canvas at end of work day to prevent
water from entering masonry.
40F-32F (4C-0C)
Heat mixing water or sand to produce mortar between 40F120F
(4C-49C).
Completely cover newly constructed masonry with a weather
resistant membrane for 48 hr after construction. Completely cover
newly constructed masonry with a weather resistant membrane for 48
hr after construction.
32F-25F (0C- -4C)
Heat mixing water and sand to produce mortar between 40F120F
(4F-49C). Heat grout materials so grout is placed at a temperature
between 40F-120F (4C49C). Maintain mortar and grout above freezing
until used in masonry. Heat mixing water and sand to produce mortar
between 40F120F (4C-49C). Heat grout materials so grout is placed
between 40F-120F (4C-49C). Maintain mortar and grout above
freezing. Heat masonry units to 40F (4C) if grouting. Use heat
sources on both sides of walls under construction.
25F-20F (-4C- -7C)
Completely cover newly constructed masonry with insulating
blankets or equal protection for 48 hr. to prevent freezing.
Install wind breaks when wind velocity exceeds 15 mph (6.7
m/s).
20F and Below Heat mixing water (-7C and Below) and sand to
produce
Provide enclosure and heat to maintain temper atures above 32F
(0C) mortar between within the enclosure for 40F-120F (4C48 hr
after construction. 49C). Heat grout materials so grout is Heat may
be provided by placed between 40F- electric heating blankets,
infrared heat lamps or 120F (4C-49C). Heat masonry units to other
approved methods. 40F (4C). Use heat sources on both sides of walls
under construction. Provide enclosure and heat to maintain
temperatures above 32F (0C) within the enclosure.
Note: Construction requirements, while work is in progress, are
based on ambient temperatures. Protection requirements, after
masonry is placed, are based on mean daily temperatures.
3
Brick Noise Barrier Wall with Cold Weather Protection FIG. 2
Enclosures in Place FIG. 3
Workers should also be protected from the cold weather to
maintain their productivity. Recommended protection will vary with
weather conditions from warmer clothes to complete enclosure of the
work site. Masons may work in the open with forced air heaters as a
heat source at mean daily temperatures no less than 20 F ( -7 C).
Heated enclosures should be provided at temperatures below 20F (
-7C). By providing wind breaks or temporary shelters, workers can
remain productive at outside temperatures well below freezing. If a
shelter or enclosure is used both the workers and the materials
benefit from a warmer environment. The masons' comfort and
productivity are improved, and the materials need less preparation
prior to laying (i.e. heating). There are many types of equipment
which are available as sources of heat for cold weather
construction. The type selected will depend upon availability of
equipment, fuel source and economics, size of project and severity
of exposure. Salamanders are widely used as a source of heat on
scaffolds. Commercial electric blankets may be used to cover walls
during the curing period. When complete enclosure of the work area
is provided, space heaters are recommended. The enclosure should
allow circulation of warm air on both sides of the masonry wall.
Contractors have used several different methods for complete and
partial enclosures of buildings. Large tents, temporary wood
structures covered with clear plastic, and shelters built of
prefabricated panels covered with clear plastic sheets are examples
of complete enclosures (Figs. 3 and 4). Partial enclosures often
consist of enclosed swinging scaffolds which may be moved from
floor to floor when necessary (Figs. 5 and 6). Mortar and Grout
Admixtures Accelerators. Accelerators are admixtures used to speed
the setting time of mortar and grout. By increasing the rate of
hydration of the cement, accelerators increase the rate of early
strength gain. The most common accelerators are inorganic salts
such as calcium chloride, calcium nitrate, soluble carbonates and
some organic compounds. Any accelerator should be evaluated for
deleterious effects on masonry strength and materials. Admixtures
must not contribute to staining or efflorescence or cause4
Interior of Enclosure FIG. 4
corrosion of metal accessories used in construction of the
masonry. Indiscriminate use of accelerators can adversely affect
the in-place performance of the completed masonry. Accelerators
alone are not suggested treatment for cold weather construction
problems. Mortar and grout containing accelerators must still be
protected from freezing. Calcium chloride, while highly effective
as an accelerator and widely used in the past, causes corrosion of
metals used in masonry due to the chloride content. For this
Antifreeze. An antifreeze lowers the freezing point of the
substance to which it is added. Most commercial mortar "antifreeze"
admixtures do not do this, but are instead accelerators. However,
some true antifreeze admixtures are available. These admixtures are
alcohols or combinations of salts. If used in the quantities
required to be effective, significant reductions in mortar
compressive and bond strengths usually result. For this reason, use
of antifreeze compounds is not recommended. Heating In freezing
weather, ice may be present in mixing water and moisture in the
sand may turn to ice. Ice in the mixing water must be melted before
it can be added to the mixer. Sand which contains frozen particles
or frost cannot be used. It must first be thawed by heating in an
appropriate manner. Further heating may also be beneficial. As
stated earlier, both water and sand used in the mortar and grout
may be heated to provide proper temperatures for construction.
Water is the easiest method to heat. It is also the best material
to heat because of its high specific heat. Sand may also be heated.
This may be done by placing an electric heating pad on top of the
sandpile and covering with a weather-resistant tarpaulin (Fig. 7).
The electric pad can safely heat the sand overnight without
exceeding a temperature of 100F (38 C). A more labor intensive
method of heating the sand is to place the sand over a heated pipe
or to pile the sand around a horizontal metal culvert or smoke
stack section, in which a slow fire is built (Fig. 8). Other
methods for heating sand involve the use of a steam lance or other
steam heaters. Careful attention to the fire or other heat source
and the sand is required. Sand should be heated slowly to avoid
scorching. In an alternate approach, an electric rod can be used to
heat mixing water and sand simultaneously. The electric heating rod
is placed in a drum of water in the center of a sandpile. The rod
heats the water over several hours. The sand surrounding the drum
slowly absorbs heat from the drum and insulates the drum from
further heat losses. Materials heated for use in mortar should have
a minimum temperature of 70F (21C) and a maximum temperature of
160F (71C) to avoid flash set. Scorched sand (with a reddish cast)
must not be used in mortar. In cold weather, mortar should be mixed
in smaller amounts so it can be used before it cools. In any case,
mortar must be used within 2 1/2 hours from the time of initial
mixing. After combining all ingredients, the temperature of the
mortar should be between 40F and 120F (4 C to 49C). Mortar
temperatures over 120F (49C) may lead to flash set, resulting in
lower compressive strength and reduced bond strength. Once a mortar
temperature is selected, steps should be taken to mix successive
batches to the same temperature. Mortar may be placed on
electrically heated mortar boards to help maintain proper
temperature. However, use caution to avoid excessive drying of the
mortar with the heater. Grout should be placed at a minimum
temperature of 40F (4C) and a maximum temperature of 120F
(49C)5
Scaffold Enclosure FIG. 5
Tubular Scaffold Enclosure FIG. 6
reason, chlorides should not be used in mortar or grout in
contact with metals (i.e. ties, anchors and reinforcement). Also,
the incidence of efflorescence may be increased when excessive
salts are present. If a chloride accelerator is used, it is
recommended that it be limited to amounts not to exceed two percent
of the weight of Portland used in the mortar mix or one percent of
the weight of masonry cement. Calcium nitrite and calcium nitrate
are inorganic nonchloride compounds also used as accelerators.
These compounds require higher dosage by weight and are more costly
than calcium chloride, but will not corrode metals or contribute to
efflorescence.
be incorporated in the specifications of the project where
applicable. 1. Protect masonry units, cementitious materials and
sand so that they are not contaminated by rain, snow or ground
water. 2. Cover tops of masonry at all times when work is not in
progress. Cover shall extend a minimum of 2 ft (1 m) down the
masonry, and shall be securely held in place. 3. Units with higher
initial rates of absorption (up to 40 g/min/30 in. (40 g/min/194 cm
)) may be used to resist mortar freezing. However, units with
suctions inHeating of a Sandpile with an Electric Blanket FIG. 72
2
within 1 1/2 hours of mixing. As with mortar, water or
Heating of a Sandpile with a Metal Pipe FIG. 8
aggregate may be heated to produce a heated mixture. Water
temperature should not exceed 160F (71C). The sand may be heated
following recommendations for heating sand used in mortar. Masonry
receiving grout should have a minimum temperature of 40F (4C). COLD
WEATHER CONSTRUCTION RECOMMENDATIONS Special Precautions There are
two reasons why masonry should never be placed on a snow or
ice-covered base or bed. There is danger of movement when the base
thaws, and bond cannot be developed between the mortar bed and
frozen supporting surfaces. If the walls are properly covered when
work is halted, ice or snow removal from walls should not be
necessary. However, in the event that the covering is displaced,
the top course may be thawed with steam or a portable blowtorch,
carefully applied. The heat should be sustained long enough to
thoroughly dry out the masonry. If portions of the masonry are
frozen or damaged, defective parts should be replaced before
progressing with new work. General Requirements--Cold Weather The
following items are suggested in addition to the construction and
protection requirements for cold weather masonry construction found
in Table 1. These items can6
excess of 30 g/min/30 in. (30 g/min/194 cm ) shall be sprinkled,
but not saturated, with heated water just prior to laying. Water
temperature shall be above 70F (21C) when units are above 32F (0
C). If units are 32F (0C) or below, water temperature shall be
above 120F (49C). 4. Use a mortar with a higher sand content and a
lower water retention, especially with brick units having a low
IRA. If Type III portland cement is used, the protection period
listed in Table 1 may be reduced from 48 to 24 hours. 5. Heat sand
and water used in mortar and grout mixtures to a minimum
temperature of 70F (21C) and a maximum temperature of 160F (71C).
Keep mortar temperature less than 120F (49C) to avoid flash set. 6.
Maintain temperature of masonry units above 20F (-7C) when laid. 7.
Place grout at a minimum temperature of 40F (4C) and a maximum
temperature of 120F (49C). Maintain masonry receiving grout above
40F (4C). Maintain grouted masonry above 32F (0C) for 48 hours
following placement of grout. EFFECTS OF HOT WEATHER Periods of hot
weather may also adversely affect the construction of masonry. The
contractor must take measures to ensure that the quality of masonry
construction does not suffer from high temperatures. While hot
weather has been defined to be temperatures above 90F (32C),
temperature, wind speed, relative humidity and solar radiation all
influence the absorption of masonry units, the rate of set, and the
drying rate of mortar. The primary concern in controlling these
properties in hot weather is evaporation of water from the mortar.
If sufficient water is not present, bond between the brick and
mortar will be sacrificed. The effects of high temperature and high
humidity are not as damaging to the performance of the masonry as
are low temperatures and low humidity. The increased rate of
hydration of the cement and favorable curing conditions in hot,
humid weather will help develop masonry strength if sufficient
water is present at the time of construction. Temperature of the
materials may be the easiest factor to adjust to produce
performance characteristics associated with construction at normal
temperatures. Adjustments in construction practices further aid the
con-
2
2
struction of quality masonry in hot weather conditions. ACI
530.1/ASCE 6/TMS 602 specifies construction methods to produce
quality masonry in hot weather conditions. Masonry Units Masonry
units are the material in masonry construction least affected by
hot weather. However, the interaction between the masonry units and
the mortar or grout is critical. Warmer units will absorb more
water from the mortar. In hot weather conditions this is usually
not a problem unless high suction brick are used (IRA over 30
g/min/30 in. (30 g/min/194 cm )). If high suction brick are used,
they should be properly wetted prior to laying. Wetting may take
place immediately before laying the units, but the preferred method
is to wet the whole pallet 3 to 24 hours before use. The brick must
be surface dry at the time of laying and should have an IRA less
than 30 g/min/30 in. (30 g/min/194 cm ). Lower bond strength
results if not enough water is present in the mortar when the units
are laid. Thus, lower absorption units may be desirable because
they allow more complete hydration of the mortar. Mortar Mortar in
hot weather will tend to lose its plasticity rapidly due to
evaporation of the water from the mix and the increased rate of
hydration of the cement. The use of admixtures to increase
plasticity is not recommended unless their full effect on the
mortar is known. Mortar with a high lime content and high water
retention should be used. Retempering of the mortar should be
permitted. Mortar mixed at high temperatures often has higher water
content, lower air content, and a shorter board life than those
mixed at normal temperatures. Temperature of the mortar should be
maintained between 70 F and 120F (21C and 49C). Temperatures above
120F (49C) may cause flash set of the cement. Cold water may be
used to help control the temperature of the mortar. Ice is highly
effective in reducing the temperature of the mix water. When used,
ice should be completely melted before combining the water with any
other ingredients. In any case, mortar should be used within two
hours of initial mixing. Grout Grout reacts to hot weather in a
manner similar to mortar. Water more easily evaporates and thereby
reduces the water-cement ratio. Grout requires a high slump, at
least 8 in. (203 mm), for placement into the absorptive brick
molds. Therefore, a high water-cement ratio should be maintained by
reducing evaporation and initially mixing grout with adequate
water. Furthermore, ACI 530.1/ASCE 6/TMS 602 specifies grout shall
be used within 1 1/2 hours of mixing. As with mortar, ice may be
used to lower the mix water temperature. HOT WEATHER CONSTRUCTION
RECOMMENDATIONS Special Precautions During periods of hot weather
the temperature of the materials should be controlled for best
results. Storing brick and sand under cover of shade will help
control heat72 2 2 2
gain of the materials. Sand should be stored on a raised
platform and not in contact with a cover during the hot part of the
day. This prevents ground moisture from rising, then condensing on
the cover after temperatures cool down, thus contaminating the
materials. When possible, shade should also be provided for
laborers, whose productivity decreases with increasing temperature
and humidity. Starting work earlier in the day and scheduling
masonry construction to avoid the hot, mid-day periods can reduce
the effects of high temperatures on laborers and materials.
Adjusting masonry construction practices may effectively control
hot weather problems. ACI 530.1/ASCE 6/TMS 602 limits the length
that mortar may be spread to 4 ft (1.2 m) and requires masonry
units to be placed within one minute of spreading the mortar. Wind
breaks may prevent rapid drying of mortar during and after
placement, and covering walls with a weather resistant membrane at
the end of the work day will prevent rapid loss of moisture from
the masonry assemblage. Wet curing or fog spraying may further
improve masonry strength development during periods of high
temperatures and low relative humidity. General Requirements--Hot
Weather The following items are suggested in addition to the
construction and protection requirements for hot weather masonry
construction found in Table 2. These items can be incorporated in
the specifications of the project where applicable. 1. Maintain
temperature of mortar and grout between 70F and 120F (21C and 49C).
2. Cold water may be used when mixing mortar and grout. Ice used to
lower the mix water temperature must be completely melted before
adding the water to the other ingredients. 3. Masonry units with
high suctions (IRA over 30 g/min/30 in. (30 g/min/194 cm )) should
be properly wetted prior to use. Units with lower rates of
absorption may be desirable. 4. Mortar with a high water retention
is desirable. 5. Limit the spread of mortar beds to 4 ft (1.2 m)
when temperatures are 100F (38C) or above, or 90F (32C) with a 8
mph (3.6 m/s) wind. 6. Place masonry units within one minute of
spreading mortar. 7. Partially completed walls may be fog sprayed
at the end of the work day to control moisture evaporation. SUMMARY
This Technical Notes describes how masonry materials react to
extremes in weather conditions. Construction requirements and
protection requirements are recommended for construction in both
cold and hot weather to ensure that construction can continue
without a decrease in quality. Performance characteristics
associated with materials mixed and constructed during normal
temperatures can be achieved by following the appropriate
construction and protection recommendations addressed in this
Technical Notes. Tables 1 and 2 summarize these recommendations for
coldNote: Construction requirements, while work is in progress, are
based on ambient temperatures. Protection requirements, after
masonry is placed, are based on2 2
TABLE 2 Requirements for Brick Masonry Construction in Hot
Weather
Temperature (see note) Above 100F or 90F with 8 mph wind (above
38C or 32C with 3.6 m/s wind)
Construction Requirements Maintain mortar and grout at a
temperature between 70F and 120F (21C-49C). Limit spread of mortar
bed to 4 ft. Place units within 1 minute of spreading mortar.
Protection Requirements Partially or newly completed walls may
be fog sprayed and/or covered with plastic or canvas to control
moisture evaporation.
1970. 8. Standard Specification for Cold Weather Concreting (ACI
306.1), American Concrete Institute, 1990. 9. Suprenant, B.A.,
"Laying Masonry in Cold Weather", The Magazine of Masonry
Construction, Vol. 1, No. 9, December 1988. 10. Van der Klugt,
L.J.A.R., "Frost Damage to the Pointing and Laying Mortar of Clay
Brick Masonry", TNO Building Construction and Research, Rijswijk,
The Netherlands, 9th International Brick/Block Masonry Conference,
October 1991.
100F-40F (38C-4C)
Normal procedures.
Cover walls with plastic or canvas at end of work day to prevent
water from entering masonry.
mean daily temperatures.
and hot weather construction. The information and suggestions
contained in this Technical Notes are based on the available data
and the experience of the engineering staff of the Brick Institute
of America. The information contained herein must be used in
conjunction with good technical judgment and a basic understanding
of the properties of brick masonry. Final decisions on the use of
the information contained in this Technical Notes are not within
the purview of the Brick Institute of America and must rest with
the project architect, engineer and owner. REFERENCES 1.
All-Weather Masonry Construction State of the Art Report, Technical
Task Committee, International Masonry All-Weather Council, December
1968. 2. Brown, M.L., "Speeding Mortar Setting in Cold Weather",
The Magazine of Masonry Construction, Vol. 2, No. 10 October 1989.
3. Building Code Requirements for Masonry Structures (ACI 530/ASCE
5/TMS 402) and Specifications for Masonry Structures (ACI
530.1/ASCE 6/TMS 602), American Concrete Institute, American
Society of Civil Engineers, and The Masonry Society, 1992. 4. Cold
Weather Concreting (ACI 306R), American Concrete Institute, 1988.
5. National Climatic Data Center, Federal Building, Asheville, NC
28801-2696, phone (704) 259-0682. 6. Randall, Jr., F.A., and
Panarese, W.C., Concrete Masonry Handbook, Portland Cement
Association, 1991. 7. Recommended Practices & Guide
Specifications for Cold Weather Masonry Construction, International
Masonry Industry All-Weather Council, December8
Technical Notes on Brick ConstructionBrick Industry Association
11490 Commerce Park Drive, Reston, Virginia 20191
2 REVISEDReissued* September 1988
GLOSSARY OF TERMS RELATING TO BRICK MASONRYABSORPTION: The
weight of water a brick unit absorbs, when immersed in either cold
or boiling water for a stated length of time. Expressed as a
percentage of the weight of the dry unit. See ASTM Specification C
67. ADMIXTURES: Materials added to mortar to impart special
properties to the mortar. ANCHOR: A piece or assemblage, usually
metal, used to attach building parts (e.g., plates, joists,
trusses, etc.) to masonry or masonry materials. ANSI: American
National Standards Institute. ARCH: A curved compressive structural
member, spanning openings or recesses; also built flat. Back Arch:
A concealed arch carrying the backing of a wall where the exterior
facing is carried by a lintel. Jack Arch: One having horizontal or
nearly horizontal upper and lower surfaces. Also called flat or
straight arch. Major Arch: Arch with spans greater than 6 ft and
equivalent to uniform loads greater than 1000 lb. per ft. Typically
known as Tudor arch, semicircular arch, Gothic arch or parabolic
arch. Has rise to span ratio greater than 0.15. Minor Arch: Arch
with maximum span of 6 ft and loads not exceeding 1000 lb. per ft.
Typically known as jack arch, segmental arch or multicentered arch.
Has rise to span ratio less than or equal to 0.15. Relieving Arch:
One built over a lintel, flat arch, or smaller arch to divert
loads, thus relieving the lower member from excessive loading. Also
known as discharging or safety arch. Trimmer Arch: An arch, usually
a low rise arch of brick, used for supporting a fireplace hearth.
ASHLAR MASONRY: Masonry composed of rectangular units of burned
clay or shale, or stone, generally larger in size than brick and
properly bonded, having sawed, dressed or squared beds, and joints
laid in mortar. Often the unit size varies to provide a random
pattern, random ashlar. ASHRAE: American Society of Heating,
Refrigerating and Air-Conditioning Engineers, Inc. ASTM: American
Society for Testing and Materials. BACK FILLING: 1. Rough masonry
built behind a facing or between two faces. 2. Filling over the
extrados of an arch. 3. Brickwork in spaces between structural
timbers, sometimes called brick nogging. BACKUP: That part of a
masonry wall behind the exterior facing. BAT: A piece of brick.
BATTER: Recessing or sloping masonry back in successive courses;
the opposite of corbel. BED JOINT: The horizontal layer of mortar
on which a masonry unit is laid. BELT COURSE: A narrow horizontal
course of masonry, sometimes slightly projected such as window
sills which are made continuous. Sometimes called string course or
sill course. BLOCKING: A method of bonding two adjoining or
intersecting walls, not built at the same time, by means of offsets
whose vertical dimensions are not less than 8 in. BOND: 1. Tying
various parts of a masonry wall by lapping units one over another
or by connecting with metal ties. 2. Patterns formed by exposed
faces of units. 3. Adhesion between mortar or grout and masonry
units or reinforcement. BOND BEAM: Course or courses of a masonry
wall grouted and usually reinforced in the horizontal direction.
Serves as horizontal tie of wall, bearing course for structural
members or as a flexural member itself. BOND COURSE: The course
consisting of units which overlap more than one wythe of masonry.
BONDER: A bonding unit. See Header.*Originally published in Jan/Feb
1975, this Technical Notes has been reviewed and reissued.
BREAKING JOINTS: Any arrangement of masonry units which prevents
continuous vertical joints from occurring in adjacent courses.
BRICK: A solid masonry unit of clay or shale, formed into a
rectangular prism while plastic and burned or fired in a kiln.
Acid-Resistant Brick: Brick suitable for use in contact with
chemicals, usually in conjunction with acid-resistant mortars.
Adobe Brick: Large roughly-molded, sun-dried clay brick of varying
size. Angle Brick: Any brick shaped to an oblique angle to fit a
salient corner. Arch Brick: 1. Wedge-shaped brick for special use
in an arch. 2. Extremely hardburned brick from an arch of a scove
kiln. Building Brick: Brick for building purposes not especially
treated for texture or color. Formerly called common brick. See
ASTM Specification C 62. Clinker Brick: A very hard-burned brick
whose shape is distorted or bloated due to nearly complete
vitrification. Common Brick: See Building Brick. Dry-Press Brick:
Brick formed in molds under high pressures from relatively dry clay
(5 to 7 percent moisture content). Economy Brick: Brick whose
nominal dimensions are 4 by 4 by 8 in. Engineered Brick: Brick
whose nominal dimensions are 4 by 3.2 by 8 in. Facing Brick: Brick
made especially for facing purposes, often treated to produce
surface texture. They are made of selected clays, or treated, to
produce desired color. See ASTM Specification C 216. Fire Brick:
Brick made of refractory ceramic material which will resist high
temperatures. Floor Brick: Smooth dense brick, highly resistant to
abrasion, used as finished floor surfaces. See ASTM Specification C
410. Gauged Brick: 1. Brick which have been ground or otherwise
produced to accurate dimensions. 2. A tapered arch brick. Hollow
Brick: A masonry unit of clay or shale whose net cross-sectional
area in any plane parallel to the bearing surface is not less than
60 percent of its gross crosssectional area measured in the same
plane. See ASTM Specification C 652.
Jumbo Brick: A generic term indicating a brick larger in size
than the standard. Some producers use this term to describe
oversize brick of specific dimensions manufactured by them. Norman
Brick: A brick whose nominal dimensions are 4 by 2 2/3 by 12 in.
Paving Brick: Vitrified brick especially suitable for use in
pavements where resistance to abrasion is important. See ASTM
Specification C 7. Roman Brick: Brick whose nominal dimensions are
4 by 2 by 12 in. Salmon Brick: Generic term for under-burned brick
which are more porous, slightly larger, and lighter colored than
hardburned brick. Usually pinkish-orange color. "SCR Brick (Reg
U.S. Pat Off., SCPI (BIA)): See SCR (Reg U.S. Pat. Off., SCPI
(BIA)). Sewer Brick: Low absorption, abrasive-resistant brick
intended for use in drainage structures. See ASTM Specification C
32. Soft-Mud Brick: Brick produced by molding relatively wet clay
(20 to 30 percent moisture). Often a hand process. When insides of
molds are sanded to prevent sticking of clay, the product is
sand-struck brick. When molds are wetted to prevent sticking, the
product is water-struck brick. Stiff-Mud Brick: Brick produced by
extruding a stiff but plastic clay (12 to 15 percent moisture)
through a die. BRICK AND BRICK: A method of laying brick so that
units touch each other with only enough mortar to fill surface
irregularities. BRICK GRADE: Designation for durability of the unit
expressed as SW for severe weathering, MW for moderate weathering,
or NW for negligible weathering. See ASTM Specifications C 216, C
62 and C 652. BRICK TYPE: Designation for facing brick which
controls tolerance, chippage and distortion. Expressed as FBS, FBX
and FBA for solid brick, and HBS, HBX, HBA and HBB for hollow
brick. See ASTM Specifications C 216 and C 652. BUTTERING: Placing
mortar on a masonry unit with a trowel. CAPACITY INSULATION: The
ability of masonry to store heat as a result of its mass, density
and specific heat. C/B RATIO: The ratio of the weight of water
absorbed by a masonry unit during immersion in cold water to weight
absorbed during immersion in boiling water. An indication of the
probable resistance of brick to freezing and thawing. Also called
saturation coefficient. See ASTM Specification C 67.
CENTERING: Temporary formwork for the support of masonry arches
or lintels during construction. Also called center(s). CERAMIC
COLOR GLAZE: An opaque colored glaze of satin or gloss finish
obtained by spraying the clay body with a compound of metallic
oxides, chemicals and clays. It is burned at high temperatures,
fusing glaze to body making them inseparable. See ASTM
Specification C 126. CHASE: A continuous recess built into a wall
to receive pipes, ducts, etc. CLAY: A natural, mineral aggregate
consist ing essentially of hydrous aluminum silicate; it is plastic
when sufficiently wetted, rigid when dried and vitrified when fired
to a sufficiently high temperature. CLAY MORTAR-MIX: Finely ground
clay used as a plasticizer for masonry mortars. CLEAR CERAMIC
GLAZE: Same as Ceramic Color Glaze except that it is translucent or
slightly tinted, with a gloss finish. CLIP: A portion of a brick
cut to length. CLOSER: The last masonry unit laid in a course. It
may be whole or a portion of a unit. CLOSURE: Supplementary or
short length units used at corners or jambs to maintain bond
patterns. COLLAR JOINT: The vertical, longitudinal joint between
wythes of masonry. COLUMN: A vertical member whose horizontal
dimension measured at right angles to the thickness does not exceed
three times its thickness. COPING: The material or masonry units
forming a cap or finish on top of a wall, pier, pilaster, chimney,
etc. It protects masonry below from penetration of water from
above. CORBEL: A shelf or ledge formed by projecting successive
courses of masonry out from the face of the wall. COURSE: One of
the continuous horizontal layers of units, bonded with mortar in
masonry. CULLS: Masonry units which do not meet the standards or
specifications and have been rejected. DAMP COURSE: A course or
layer of impervious material which prevents capillary entrance of
moisture from the ground or a lower course. Often called damp
check.2
DAMPPROOFING: Prevention of moisture penetration by capillary
action. DOG'S TOOTH: Brick laid with their cor ners projecting from
the wall face. DRIP: A projecting piece of material, shaped to
throw off water and prevent its running down the face of wall or
other surface. EBM: See Engineered Brick Masonry. ECCENTRICITY: The
normal distance between the centroidal axis of a member and the
parallel resultant load. e1/e2: Ratio of virtual eccentricities
occurring at the ends of a column or wall under design. The
absolute value is always less than or equal to 1.0. EFFECTIVE
HEIGHT: The height of a member to be assumed for calculating the
slenderness ratio. EFFECTIVE THICKNESS: The thickness of a member
to be assumed for calculating the slenderness ratio. EFFLORESCENCE:
A powder or stain sometimes found on the surface of masonry,
resulting from deposition of water-soluble salts. ENGINEERED BRICK
MASONRY: Masonry in which design is based on a rational structural
analysis. FACE: 1. The exposed surface of a wall or masonry unit.
2. The surface of a unit designed to be exposed in the finished
masonry. FACING: Any material, forming a part of a wall, used as a
finished surface. FIELD: The expanse of wall between openings,
corners, etc., principally composed of stretchers. FILTER BLOCK: A
hollow, vitrified clay masonry unit, sometimes salt-glazed,
designed for trickling filter floors in sewage disposal plants. See
ASTM Specification C 159. FIRE CLAY: A clay which is highly
resistant to heat without deforming and used for making brick. FIRE
RESISTIVE MATERIAL: See Noncombustible Material. FIREPROOFING: Any
material or combination protecting structural members to increase
their fire resistance.
FLASHING: 1. A thin impervious material placed in mortar joints
and through air spaces in masonry to prevent water penetration
and/or provide water drainage. 2. Manufacturing method to produce
specific color tones. FROG: A depression in the bed surface of a
brick. Sometimes called a panel. FURRING: A method of finishing the
interior face of a masonry wall to provide space for insulation,
prevent moisture transmit tance, or to provide a level surface for
finishing. GROUNDS: Nailing strips placed in masonry walls as a
means of attaching trim or furring. GROUT: Mixture of cementitious
material and aggregate to which sufficient water is added to
produce pouring consistency without segregation of the
constituents. High-Lift Grouting: The technique of grouting masonry
in lifts up to 12 ft. Low-Lift Grouting: The technique of grouting
as the wall is constructed. HACKING: 1. The procedure of stacking
brick in a kiln or on a kiln car. 2. Laying brick with the bottom
edge set in from the plane surface of the wall. HARD-BURNED: Nearly
vitrified clay products which have been fired at high temperatures.
They have relatively low absorptions and high compressive
strengths. HEAD JOINT: The vertical mortar joint between ends of
masonry units. Often called cross joint. HEADER: A masonry unit
which overlaps two or more adjacent wythes of masonry to tie them
together. Often called bonder. Blind Header: A concealed brick
header in the interior of a wall, not showing on the faces. Clipped
Header: A bat placed to look like a header for purposes of
establishing a pattern. Also called a false header. Flare Header: A
header of darker color than the field of the wall. HEADING COURSE:
A continuous bonding course of header brick. Also called header
course. INITIAL RATE OF ABSORPTlON: The weight of water absorbed
expressed in grams per 30 sq. in. of contact surface when a brick
is partially immersed for one minute. Also called suction. See ASTM
Specification C 67. IRA: See Initial Rate of Absorption.
KILN: A furnace oven or heated enclosure used for burning or
firing brick or other clay material. Kiln Run: Brick from one kiln
which have not been sorted or graded for size or color variation.
KING CLOSER: A brick cut diagonally to have one 2 in. end and one
full width end. LATERAL SUPPORT: Means whereby walls are braced
either vertically or horizontally by columns, pilasters, cross
walls, beams, floors, roofs, etc. LEAD: The section of a wall built
up and racked back on successive courses. A line is attached to
leads as a guide for constructing a wall between them. LIME,
HYDRATED: Quicklime to which sufficient water has been added to
convert the oxides to hydroxides. LIME PUTTY: Hydrated lime in
plastic form ready for addition to mortar. LINTEL: A beam placed
over an opening in a wall. MASONRY: Brick, stone, concrete, etc.,
or masonry combinations thereof, bonded with mortar. MASONRY
CEMENT: A mill-mixed cementitious material to which sand and water
must be added. See ASTM C 91. MASONRY UNIT: Natural or manufactured
building units of burned clay, concrete, stone, glass, gypsum, etc.
Hollow Masonry Unit: One whose net cross-sectional area in any
plane parallel to the bearing surface is less than 75 percent of
the gross. Modular Masonry Unit: One whose nominal dimensions are
based on the 4 in. module. Solid Masonry Unit: One whose net
cross-sectional area in every plane parallel to the bearing surface
is 75 percent or more of the gross. MORTAR: A plastic mixture of
cementitious materials, fine aggregate and water. See ASTM
Specifications C 270, C 476 or BIA M1-72. Fat Mortar: Mortar
containing a high percentage of cementitious components. It is a
sticky mortar which adheres to a trowel. High-Bond Mortar: Mortar
which develops higher bond strengths with masonry units than
normally developed with conventional mortar. Lean Mortar: Mortar
which is deficient in cementitious components, it is usually harsh
and difficult to spread.3
NOMINAL DIMENSION: A dimension greater than a specified masonry
dimension by the thickness of a mortar joint, but not more than 1/2
in. NON-COMBUSTIBLE MATERIAL: Any material which will neither
ignite nor actively support combustion in air at a temperature of
1200 F when exposed to fire. OVERHAND WORK: Laying brick from
inside a wall by men standing on a floor or on a scaffold.
PARGETING: The process of applying a coat of cement mortar to
masonry. Often spelled and/or pronounced parging. PARTITION: An
interior wall, one story or less in height. PICK AND DIP: A method
of laying brick whereby the bricklayer simultaneously picks up a
brick with one hand and, with the other hand, enough mortar on a
trowel to lay the brick. Sometimes called the Eastern or New
England method. PIER: An isolated column of masonry. PILASTER: A
wall portion projecting from either or both wall faces and serving
as a vertical column and/or beam. PLUMB RULE: This is a combination
plumb rule and level. It is used in a horizontal position as a
level and in a vertical position as a plumb rule. They are made in
lengths of 42 and 48 in., and short lengths from 12 to 24 in.
POINTING: Troweling mortar into a joint after masonry units are
laid. PREFABRICATED BRICK MASONRY: Masonry construction fabricated
in a location other than its final inservice location in the
structure. Also known as preassembled, panelized and sectionalized
brick masonry. PRISM: A small masonry assemblage made with masonry
units and mortar. Primarily used to predict the strength of full
scale masonry members. QUEEN CLOSER: A cut brick having a nominal 2
in. horizontal face dimension. QUOIN: A projecting right angle
masonry corner. RACKING: A method entailing stepping back
successive courses of masonry. RAGGLE: A groove in a joint or
special unit to receive roofing or flashing.
RBM: Reinforced brick masonry REINFORCED MASONRY: Masonry units,
reinforcing steel, grout and/or mortar combined to act together in
resisting forces. RETURN: Any surface turned back from the face of
a principal surface. REVEAL: That portion of a jamb or recess which
is visible from the face of a wall. ROWLOCK: A brick laid on its
face edge so that the normal bedding area is visible in the wall
face. Frequently spelled rolok. SALT GLAZE: A gloss finish obtained
by thermochemical reaction between silicates of clay and vapors of
salt or chemicals. SATURATION COEFFICIENT: See C/B Ratio. SCR (Reg
U.S. Pat Off., SCPI (BIA)): Structural Clay Research (trademark Of
the Structural Clay Products Institute, BIA). "SCR acoustile" (Reg
U.S. Pat Off., SCPI (BIA) Pat. No 3,001,6O2): A sideconstruction
two-celled facing tile, having a perforated face backed with glass
wool for acoustical purposes. "SCR brick" (Reg U.S. Pat Off., SCPI
(BIA)): Brick whose nominal dimensions are 6 by 2 2/3 by 12 in.
(Reg U.S. Pat Off., SCPI (BIA)): "SCR building panel" (Reg U S. Pat
Off., SCPI (BIA) Pat. No. 3,248,836): Prefabricated, structural
ceramic panels, approximately 2 1/2 in. thick. "SCR insulated
cavity wall" (Reg U.S. Pat Off., SCPI (BIA)): Any cavity wall
containing insulation which meets rigid criteria established by the
Structural Clay Products Institute (BIA). "SCR masonry process"
(Reg. U.S. Pat Off., SCPI (BIA)): A construction aid providing
greater efficiency, better workman ship and increased production in
masonry construction. It utilizes story poles, marked lines and
adjustable scaffolding. SHALE: Clay which has been subjected to
high pressures until it has hardened. SHOVED JOINTS: Vertical
joints filled by shoving a brick against the next brick when it is
being laid in a bed of mortar. SLENDERNESS RATIO: Ratio of the
effective height of a member to its effective thickness. SLUSHED
JOINTS: Vertical joints filled, after units are laid, by throwing"
mortar in with the edge of a trowel. (Generally, not recommended.)
SOAP: A masonry unit of normal face dimensions, having a nominal 2
in. thickness.
SOFFIT: The underside of a beam, lintel or arch. SOFT-BURNED:
Clay products which have been fired at low temperature ranges,
producing relatively high absorptions and low compressive
strengths. SOLAR SCREEN: A perforated wall used as a sunshade.
SOLDIER: A stretcher set on end with face showing on the wall
surface. SPALL: A small fragment removed from the face of a masonry
unit by a blow or by action of the elements. STACK: Any structure
or part thereof which contains a flue or flues for the discharge of
gases. STORY POLE: A marked pole for measur ing masonry coursing
during construction. STRETCHER: A masonry unit laid with its
greatest dimension horizontal and its face parallel to the wall
face. STRINGING MORTAR: The procedure of spreading enough mortar on
a bed to lay several masonry units. STRUCK JOINT: Any mortar joint
which has been finished with a trowel. SUCTION: See Initial Rate of
Absorption. TEMPER: To moisten and mix clay, plaster or mortar to a
proper consistency. TIE: Any unit of material which connects
masonry to masonry or other materials. See Wall Tie. TOOLING:
Compressing and shaping the face of a mortar joint with a special
tool other than a trowel. TOOTHING: Constructing the temporary end
of a wall with the end stretcher of every alternate course
projecting. Projecting units are toothers. TRADITIONAL MASONRY:
Masonry in which design is based on empirical rules which control
minimum thickness, lateral support requirements and height without
a structural analysis. TUCK POINTING: The filling in with fresh
mortar of cut-out or defective mortar joints in masonry. VENEER: A
single wythe of masonry for facing purposes, not structurally
bonded.
VIRTUAL ECCENTRICITY: The eccentricity of a resultant axial load
required to produce axial and bending stresses equivalent to those
produced by applied axial loads and moments. It is normally found
by dividing the moment at a section by the summation of axial loads
occurring at that section. VITRIFICATION: The condition resulting
when kiln temperatures are sufficient to fuse grains and close
pores of a clay product, making the mass impervious. WALL: A
vertical member of a structure whose horizontal dimension measured
at right angles to the thickness exceeds three times its thickness.
Apron Wall: That part of a panel wall between window sill and wall
support. Area Wall: 1. The masonry surrounding or partly
surrounding an area. 2. The retaining wall around basement windows
below grade. Bearing Wall: One which supports a vertical load in
addition to its own weight. Cavity Wall: A wall built of masonry
units so arranged as to provide a continuous air space within the
wall (with or without insulating material), and in which the inner
and outer wythes of the wall are tied together with metal ties.
Composite Wall: A multiple-wythe wall in which at least one of the
wythes is dissimilar to the other wythe or wythes with respect to
type or grade of masonry unit or mortar Curtain Wall: An exterior
non-loadbearing wall not wholly supported at each story. Such walls
may be anchored to columns, spandrel beams, floors or bearing
walls, but not necessarily built between structural elements. Dwarf
Wall: A wall or partition which does not extend to the ceiling.
Enclosure Wall: An exterior non-bearing wall in skeleton frame
construction. It is anchored to columns, piers or floors, but not
necessarily built between columns or piers nor wholly supported at
each story. Exterior Wall: Any outside wall or vertical enclosure
of a building other than a party wall. Faced Wall: A composite wall
in which the masonry facing and backings are so bonded as to exert
a common reaction under load. Fire Division Wall: Any wall which
subdivides a building so as to resist the spread of fire. It is not
necessarily continuous through all stories to and above the roof.
Fire Wall: Any wall which subdivides a building to resist the
spread of fire and which extends continuously from the foundation
through the roof. Foundation Wall: That portion of a loadbearing
wall below the level of the adjacent grade, or below first floor
beams or joists.
4
Hollow Wall: A wall built of masonry units arranged to provide
an air space within the wall. The separated facing and backing are
bonded together with masonry units. Insulated Cavity Wall: See SCR
insulated cavity wall. Loadbearing Wall: A wall which supports any
vertical load in addition to its own weight. Non-Loadbearing Wall:
A wall which supports no vertical load other than its own weight.
Panel Wall: An exterior, non-loadbearing wall wholly supported at
each story. Parapet Wall: That part of any wall entirely above the
roof line. Party Wall: A wall used for joint service by adjoining
buildings. Perforated Wall: One which contains a considerable
number of relatively small openings. Often called pierced wall or
screen wall. Shear Wall: A wall which resists hori zontal forces
applied in the plane of the wall. Single Wythe Wall: A wall
containing only one masonry unit in wall thickness. Solid Masonry
Wall: A wall built of solid masonry units, laid contiguously, with
joints between units completely filled with mortar or grout.
Spandrel Wall: That part of a curtain wall above the top of a
window in one story and below the sill of the window in the story
above. Veneered Wall: A wall having a facing of masonry units or
other weather-resisting non-combustible materials securely attached
to the backing, but not so bonded as to intentionally exert common
action under load. WALL PLATE: A horizontal member anchored to a
masonry wall to which other structural elements may be attached.
Also called head plate. WALL TIE: A bonder or metal piece which
connects wythes of masonry to each other or in other materials.
WALL TIE, CAVITY: A rigid, corrosionresistant metal tie which bonds
two wythes of a cavity wall. It is usually steel, 3/16 in. in
diameter and formed in a "Z" shape or a rectangle. WALL TIE,
VENEER: A strip or piece of metal used to tie a facing veneer to
the backing. WATER RETENTIVITY: That property of a mortar which
prevents the rapid loss of water to masonry units of high suction.
It prevents bleeding or water gain when mortar is in contact with
relatively impervious units.
WATER TABLE: A projection of lower masonry on the outside of the
wall slightly above the ground. Often a damp course is placed at
the level of the water table to prevent upward penetration of
ground water. WATERPROOFING: Prevention of moisture flow through
masonry due to water pressure. WEEP HOLES: Openings placed in
mortar joints of facing material at the level of flashing, to
permit the escape of moisture. WITH INSPECTION: Masonry designed
with the higher stresses allowed under EBM. Requires the
establishing of procedures on the job to control mortar mix,
workmanship and protection of masonry materials. WITHOUT
INSPECTION: Masonry designed with the reduced stresses allowed
under EBM. WYTHE: 1. Each continuous vertical section of masonry
one unit in thickness. 2. The thickness of masonry separating flues
in a chimney. Also called withe or tier.
5
Technical Notes on Brick ConstructionBrick Industry Association
11490 Commerce Park Drive, Reston, Virginia 20191
3ADecember 1992
BRICK MASONRY MATERIAL PROPERTIESAbstract: Brick masonry has a
long history of reliable structural performance. Standards for the
structural design of masonry which are periodically updated such as
the Build ing Code Requirements for Masonry Structures (ACI
530/ASCE 5/TMS 402) and the Specifi cations for Masonry Structures
(ACI 530.1/ASCE 6/TMS 602) advance the efficiency of masonry
elements with rational design criteria. However, design of masonry
structural members begins with a thorough understanding of material
properties. This Technical Notes is an aid for the design of brick
and structural clay tile masonry structural members. Clay and shale
units, mortar, grout, steel reinforcement and assemblage material
properties are presented to simplify the design process.
Key Words: brick, grout, material properties, mortar,
reinforcement, structural clay tile.
INTRODUCTION The Masonry Standards Joint Committee (MSJC) has
developed the Building Code Requirements for Ma sonry Structures
(ACI 530/ASCE 5/TMS 402) and the Specifications for Masonry
Structures (ACI 530.1/ASCE 6/TMS 602). In this Technical Notes,
these documents will be referred to as the MSJC Code and the MSJC
Specifications, respectively. Their contents are reviewed in
Technical Notes 3. The MSJC Code and Specifications are
periodically revised by the MSJC and together provide design and
construction requirements for masonry. The MSJC Code and
Specifications apply to structural masonry assemblages of clay,
concrete or stone units. This Technical Notes is a design aid for
the MSJC Code and Specifications. It contains information on clay
and shale units, mortar, grout, steel reinforcement and assemblage
material properties. These are used in the initial stages of a
structural design or analysis to determine applied stresses and
allowable stresses. Material properties are explained to aid the
designer in selection of materials and to provide a better
understanding of the structural properties of the masonry
assemblage based on the materials selected. CONSTITUENT MATERIAL
PROPERTIES Because brick masonry is bonded into an integral mass by
mortar and grout, it is considered to be a homogeneous
construction. It is the behavior of the combination of materials
that determines the performance of the masonry as a structural
element. However, the performance of a structural masonry element
is dependent upon the properties of the constituent materials and
the interaction of the materials as an assemblage.
Therefore, it is important to first consider the properties of
the constituent materials: clay and shale units, mortar, grout and
steel reinforcement. This will be followed by a discussion of the
behavior of their combination as an assemblage. Clay and Shale
Masonry Units There are many variables in the manufacturing of clay
and shale masonry units. Primary raw materials include surface
clays, fire clays, shales or combinations of these. Units are
formed by extrusion, molding or dry-pressing and are fired in a
kiln at temperatures between 1800 oF and 2100oF (980 oC and
1150oC). These variables in manufacturing produce units with a wide
range of colors, textures, sizes and physical properties. Clay and
shale masonry units are most frequently selected as a construction
material for their aesthetics and long-term performance.
Consequently, material standards for clay and shale masonry units
contain requirements to ensure that units meet a level of
durability and visual and dimensional consistency. Clay and shale
masonry units used in structural elements of building constructions
are brick and structural clay tile. Material standards for brick
and structural clay tile include: ASTM C 216 (facing brick), ASTM C
62 (building brick), ASTM C 652 (hollow brick), ASTM C 212
(structural clay facing tile) and ASTM C 34 (structural clay
load-bearing tile). While brick and structural clay tile are both
visually appealing and durable, they are also well-suited for many
structural applications. This is primarily due to their variety of
sizes and very high compressive strength. The material properties
of brick and structural clay tile which have the most significant
effect upon structural performance of the masonry are compres-
sive strength and those properties affecting bond between the
unit and mortar, such as rate of water absorption and surface
texture. Unit Compressive Stre n g t h . The compressive strength
of brick or structural clay tile is an important material property
for structural applications. In general, increasing the compressive
strength of the unit will increase the masonry assemblage
compressive strength and elastic modulus. However, brick and
structural clay tile are frequently specified by material standard
rather than by a particular minimum unit compressive strength. ASTM
material standards for brick and structural clay tile require
minimum compressive strengths to ensure durability, which may be as
little as one-fifth the actual unit compressive strength. A recent
Brick Institute of America survey of United States brick
manufacturers resulted in a data base of unit properties [6]. A
subsequent survey of structural clay tile manufacturers was
conducted. The compressive strengths of brick and structural clay
tile evaluated in these surveys are presented in Table 1. As is
apparent, all types of brick and structural clay tile typically
exhibit compressive strengths considerably greater than the ASTM
minimum requirements. Compressive strength of brick and structural
clay tile is determined in accordance with ASTM C 67 Method of
Sampling and Testing Brick and Structural Clay Tile.TABLE 1 Brick
and Structural Clay Tile Unit Compressive StrengthsStandard Mean
Unit Deviation of Compressive Compressive Strength, Strength, psi
(MPa) psi (MPa) Extruded Molded Fire clay Raw material1 Shale
Other2 Hollow Structural clay tile3 brick3 Vertical coring
Horizontal coring 11305 (77.9) 5293 (36.5) 15346(105.8) 11258
(77.6) 9169 (63.2) 6736 (46.4) 10057 (69.3) 5119 (35.3) 4464 (30.8)
1822 (12.6) 5065 (34.9) 3487 (24.0) 3988 (27.5) 2447 (16.9) 5578
(38.5) 2067 (14.3)
Cores or frogs provide a means of mechanical interlock. The bond
strength of sanded surfaces is dependent upon the amount of sand on
the surface, the sands adherence to the unit and the absorption
rate of the unit at the time of laying. In practically all cases,
mortar bonds best to a unit whose suction at the time of laying is
less than 30 g/min/30 in. 2 (1.55 kg/min/m 2). Generally, molded
units will exhibit a higher initial rate of absorption than
extruded or dry-pressed units. Unit absorption at the time of
laying is an alterable property of brick and structural clay tile.
In accordance with the MSJC Specifications, units with initial rate
of absorption in excess of 30 g/min/30 in.2 (1.55 kg/min/m2) should
be wetted to reduce the rate of water absorption of the unit prior
to laying. In addition, suction of very absorptive units may be
accommodated by using highly water-retentive mortars. Mortar The
material properties of mortar which influence the structural
performance of masonry are compressive strength, bond strength and
elasticity. Because the compressive strength of masonry mortar is
less important than bond strength, workability and water
retentivity, the latter properties should be given principal
consideration in mortar selection. Mortar materials, properties and
selection of masonry mortars are discussed in Technical Notes 8
Series. Mortar should be selected based on the design requirements
and with due consideration of the MSJC Code and Specifications
provisions affected by the mortar selected. Laboratory testing
indicates that masonry constructed with portland cement-lime mortar
exhibit greater flexural bond strength than masonry constructed
with masonry cement mortar or air-entrained portland cement-lime
mortar of the same Type. This behavior is reflected in the MSJC
Code allowable flexural tensile stresses for unreinforced masonry,
which are based on the mortar Type and mortar materials selected.
In addition, masonry cement mortars may not be used in Seismic
Zones 3 and 4. Other MSJC Code and Specifications provisions are
the same for portland cement-lime mortars, masonry cement mortars
and air-entrained portland cement-lime mortars of the same Type.
These include the modulus of elasticity of the masonry, allowable
compressive stresses for empirical design and the Unit Strength
Method of verifying that the specified compressive strength of
masonry is supplied. Following is a general description of the
structural properties of each Type of mortar permitted by the MSJC
Code and Specifications. Type N Mortar. Type N mortar is
specifically recommended for chimneys, parapet walls and exterior
walls subject to severe exposure. It is a medium bond and
compressive strength mortar suitable for general use in exposed
masonry above grade. Type N mortar 2
Unit Type
Forming method Solid brick
1 Extruded only. 2 Made from other materials or a combination of
materials. 3 Based on gross area.
Unit Texture and Absorption. Unit texture and absorption are
properties which affect the bond strength of the masonry
assemblage. In general, mortar bonds better to roughened surfaces,
such as wire cut surfaces, than to smooth surfaces, such as die
skin surfaces.
may not be used in Seismic Zones 3 and 4. Type S Mortar. Type S
mortar is recommended for use in reinforced masonry and
unreinforced masonry where maximum flexural strength is required.
It has a high compressive strength and has a high tensile bond
strength with most brick units. Type M Mortar. Type M mortar is
specifically recommended for masonry below grade and in contact
with earth, such as foundation walls, retaining walls, sewers and
manholes. It has high compressive strength and better durability in
these environments than Type N or S mortars. For compliance with
the MSJC Specifications, mortars should conform to the requirements
of ASTM C 270 Specification for Mortar for Unit Masonry. Field
sampling of mortar for quality control should follow the procedures
given in ASTM C 780 Test Method for Preconstruction and
Construction Evaluation of Mortars for Plain and Reinforced Unit
Masonry. Test procedures for masonry mortars are covered in
Technical Notes 39 Series. Grout Grout is used in brick masonry to
fill cells of hollow units or spaces between wythes of solid unit
masonry. Grout increases the compressive, shear and flexural
strength of the masonry element and bonds steel reinforcement and
masonry together. For compliance with the MSJC Specifications,
grout which is used in brick or structural clay tile masonry should
conform to the requirements of ASTM C 476 Specification for Grout
for Masonry. Grout proportions of portland cement or blended
cement, hydrated lime or lime putty, and coarse or fine aggregate
are given in Table 2.TABLE 2 ASTM C 476 Grout Proportions by
VolumePortland Hydrated Cement Lime or or Lime Blended Putty
Cement
amount of water absorbed from grout by hollow clay units appears
to be more dependent on the initial water content of the grout than
the absorption properties of the unit [3]. Grouts with high initial
water content exhibit more shrinkage than grouts with low initial
water contents. Consequently, use of a non-shrink grout admixture
is recommended to minimize the number of flaws and shrinkage cracks
in the grout while still producing a grout slump of 8 to 11 in.
(200 to 280 mm), unless otherwise specified. The MSJC
Specifications require grout compressive strength to be at least
equal to the specified compressive strength of masonry, f , but not
less than 2,000 psi m (13.8 MPa) as determined by ASTM C 1019
Method of Sampling and Testing Grout. Test procedures for grout are
explained in more detail in Technical Notes 39 Series. In general,
the compressive strength of ASTM C 476 grout by proportions will be
greater than 2,000 psi (13.8 MPa). Prediction of the compressive
strength of grout which is proportioned in accordance with ASTM C
476 is difficult because of the many possible combinations of
materials, types of materials and construction conditions. However,
ASTM C 476 grout proportions produce a rich mix which is
recommended to complement the high compressive strength of brick
and structural clay tile.TABLE 3 Steel Reinforcement Material
Properties1Minimum Yield Strength, ksi (MPa) 40 (276) 60 (414) 50
(345) 60 (414) 40 (276) 60 (414) 60 (414) 70 (483) 75 (517) Minimum
Tensile Strength, ksi (MPa) 70 (483) 90 (620) 80 (552) 90 (620) 70
(483) 90 (620) 80 (552) 80 (552) 85 (586)
Type
ASTM Grade Specification or Type
A 615
40 60
A 616 Fine Aggregate1 Coarse Aggregate1 Bars A 617 2 1/4 to 3
times the sum of the volumes of the cementitious materials 2 1/4 to
3 times the sum of the volumes of the cementitious materials
50 60 40 60
Grout Type
A 706 None Wires A 496 1 to 2 times the sum of the volumes of
the cementitious materials1From reference [5].
60 Smooth Deformed
Fine
1
0 to 1/10
A 82
Coarse
1
0 to 1/10
1Aggregate measured by volume in a damp, loose condition.
Steel Reinforcement Steel reinforcement for masonry construction
consists of bars and wires. Reinforcing bars are used in masonry
elements such as walls, columns, pilasters and beams. Wires are
used in masonry bed joints to reinforce individual masonry wythes
or to tie multiple wythes together. Bars and wires have
approximately 3
The amount of mixing water and its migration from the grout to
the brick or structural clay tile will determine the compressive
strength of the grout and the amount of grout shrinkage. Tests
indicate that the total
the same modulus of elasticity, which is stated in the MSJC Code
as 29,000 ksi (200,000 MPa). In general, wires tend to achieve
greater ultimate strength and behave in a more brittle manner than
reinforcing bars. Common bar and wire sizes and their material
properties are given in Table 3. As stated in the MSJC
Specifications, steel reinforcement for masonry structural members
should comply with one of the material standards given in Table
4.TABLE 4 ASTM Material Standards for Steel ReinforcementSteel
Reinforcement Type Deformed bars Joint reinforcement Deformed wire
Wire fabric Anchors, ties and accessories Stainless steel ASTM
Specification A 615, A 616, A 617 or A 706 A 82 A 496 A 185 or A
497 A 36, A 366, A 185 or A 82 A 167-Type 304
ASSEMBLAGE MATERIAL PROPERTIES The properties of the constituent
materials discussed previously combine to produce the brick or
structural clay tile masonry assemblage properties. Following is a
discussion of the material properties of the masonry assemblage.
Compressive Strength Perhaps the single most important material
property in the structural design of masonry is the compressive
strength of the masonry assemblage. The specified compressive
strength of the masonry assemblage, f , is m used to determine the
allowable axial and flexural compressive stresses, shear stresses
and anchor bolt loads given in the MSJC Code. The compressive
strength of the masonry assemblage can be evaluated by the
properties of each constituent material, termed in the MSJC
Specifications the Unit Strength Method, or by testing the
properties of the entire masonry assemblage, termed the Prism
Testing Method. These methods are not to be used to establish
design values; rather, they are used by the contractor to verify
that the masonry achieves the specified compressive strength, f . m
Unit Strength Method. A benefit of verifying compliance of the
compressive strength of masonry by unit, mortar and grout
properties is the elimination of prism testing. Each of the
materials in the masonry assemblage must conform to ASTM material
standards mentioned in previous sections of this Technical Notes.
For 4
compliance with these material standards, the compressive
strength of the unit and the proportions or properties of the
mortar and grout must be evaluated. Not surprisingly, there have
been attempts by numerous researchers to accurately correlate the
assemblage compressive strength with unit, mortar and grout
compressive strengths. Testing an assemblage of three materials
produces a large scatter of compressive strengths covering all
possible combinations of materials. Therefore, estimates of the
masonry assemblage compressive strength based on unit, mortar and
grout properties are necessarily conservative. The correlations
provided in the MSJC Specifications, shown in Table 5, between unit
compressive strength, mortar type and the masonry assemblage
compressive strength represent a lower-bound to experimental data.
In addition, the MSJC Specifications Unit Strength Method does not
directly address variable grout strength, multiwythe construction
or the influence of joint reinforcement on the compressive strength
of the masonry assemblage. Consequently, compliance with the
specified compressive strength of masonry by prism testing will
always produce a more accurate and optimum use of brick or
structural clay tile masonrys compressive strength than the Unit
Strength Method. The conservative nature of Table 5 should not be
overlooked by the designer. A comparison of the predicted
assemblage compressive strength by the Unit Strength Method in the
MSJC Specifications and a data base of actual brick masonry prism
test results [1] reveals this conservatism. The average compressive
strength of prisms of solid brick units was found to be about 1.7
times the masonry compressive strength predicted by Table 5. The
average compressive strength of prisms of hollow units ungrouted
and grouted was found to be 1.9 and 1.4 times the compressive
strengths predicted by Table 5, respectively.TABLE 5 Unit Strength
Method of fm Compliance in the MSJC Specifications1Net Area Unit
Compressive Strength, psi (MPa) Type M or S mortar 2400(16.6)
4400(30.3) 6400(44.1) 8400(57.9) 10400(71.7) 12400(85.5)
14400(99.3) Type N mortar 3000 (20.7) 5500 (37.9) 8000 (55.2) 10500
(72.4) 13000 (89.7)
Net Area Assemblage Compressive Strength, psi (MPa)
1000 (6.9) 1500 (10.3) 2000 (13.8) 2500 (17.2) 3000 (20.7) 3500
(24.1) 4000 (27.6)
1 Linear interpolation is permitted.
Prism Test Method. Prism testing of brick or structural clay
tile masonry provides a number of advantages over constituent
material testing alone. The primary benefit of prism testing is a
more accurate estimation of the compressive strength of the masonry
assemblage. Another benefit of prism testing is that it provides a
method of measuring the quality of workmanship throughout the
course of a project. Low prism strengths may indicate mortar mixing
error or poor quality grout. The MSJC Specifications permit testing
of masonry prisms to show conformance with the specified
compressive strength of masonry, f . In addition, the matem rial
components must meet the appropriate standards of quality. Masonry
prisms are tested in accordance with ASTM E 447 Test Methods for
Compressive Strength of Masonry Prisms, Method B as modified by the
MSJC Specifications. At least three prisms are required by the MSJC
Specifications for each combination of materials. The average of
the three tests must exceed f . Further explanation of prism
testing procem dures is provided in Technical Notes 39B. Shear
Strength The shear strength of a masonry assemblage may be
separated into four parts: 1) the shear strength of the unit,
mortar and grout assemblage, 2) the effect of the shear
span-to-depth ratio, M/Vd, 3) the enhancement of shear strength due
to compressive stress, and 4) the contribution of shear
reinforcement in the masonry assemblage. All four phenomenon are
represented in the allowable shear stresses provided in the MSJC
Code. However, only the first and fourth items are controlled by
material properties. Items two and three vary with member size and
applied loads. The shear strength of the masonry assemblage is
directly related to the properties of the unit, mortar and grout.
Shear failure of a unit-mortar assemblage is by splitting of units,
step-cracking in mortar joints, or a combination of the two. Unit
splitting strength is increased by increasing the compressive
strength of the unit. In general, unit splitting is not a common
shear failure mode of brick or structural clay tile masonry. Unit
splitting occurs in masonry assemblages of weak units and strong
mortar and may also occur in shear walls which are heavily axially
loaded. Cracking in mortar joints is the more common shear failure
mode for brick and structural clay tile masonry assemblages. Mortar
joint failure occurs by sliding along bed joints and separation of
head joints. Mortar joint shear failure is affected by bond
strength and the frictional characteristics between the mortar and
the unit. In general, a unit-mortar combination which provides
greater bond strength will also provide greater shear strength.
Grouting the masonry assemblage will also increase shear strength
by providing a shear key between courses. The shear strength of a
masonry assemblage may be evaluated in accordance with ASTM E 519
Test 5
Method for Diagonal Tension (Shear) in Masonry Assemblages. The
contribution of unit, mortar and grout to the allowable shear
stresses stated in the MSJC Code are based on ASTM E 519 tests of
masonry assemblages. Steel reinforcement may be added to the
masonry assemblage to increase shear strength. Shear reinforcement
should be provided parallel to the direction of applied shear
force. The MSJC Code also requires a minimum amount of
reinforcement perpendicular to the shear reinforcement of one-third
the area of shear reinforcement. When shear reinforcement is
provided in accordance with the MSJC Code, allowable shear stresses
given in the MSJC Code for reinforced masonry are increased three
times for flexural members and one and one-half times for shear
walls. Flexural Tensile Strength Reinforced brick and structural
clay tile masonry is considered cracked under service loads and the
flexural tensile strength of the masonry is neglected in design.
However, cracking of an unreinforced brick or structural clay tile
masonry member constitutes failure and must be avoided. Thus,
flexural tensile strength is an important design consideration for
unreinforced masonry. Flexural tensile strength is the bond
strength of masonry in flexure. It is a function of the type of
unit, type of mortar, mortar materials, percentage of grouting of
hollow units and the direction of loading. Workmanship is also very
important for flexural tensile strength, as unfilled mortar joints
or dislodged units have no mortar-to-unit bond strength. Allowable
flexural tensile stresses stipulated in the MSJC Code for
unreinforced masonry are given in Table 6. The allowable flexural
tensile stresses for portland cement-lime mortars are based on
full-size wall tests in accordance with ASTM E 72 Method of
Conducting Strength Tests of Panels for Building Construction.
Values for masonry cement and air-entrained portland cement-lime
mortars are based on reductions obtained with comparative testing.
Flexural tensile strength may be evaluated by testing small-scale
prisms in accordance with ASTM E 518 Test Method for Flexural Bond
Strength of Masonry or ASTM C 1072 Test Method for Measurement of
Masonry Flexural Bond Strength, but these results may not directly
correlate to the allowable flexural tensile stresses in the MSJC
Code. Elastic Modulus The elastic modulus of the masonry
assemblage, in combination with the moment of inertia of the
section, determines the stiffness of a brick or structural clay
tile masonry structural element. Elastic modulus is the ratio of
applied load (stress) to corresponding deformation (strain). The
elastic modulus is roughly proportional to the compressive strength
of the masonry assemblage. Testing of brick masonry prisms
indicates that the elastic modulus of brick masonry falls
between
TABLE 6 MSJC Code Allowable Flexural Tensile Stress for
Unreinforced Masonry, psi (MPa)Mortar Type Portland cement-lime
Masonry cement and air-entrained portland cement-lime M or S N
Direction of Stress
Masonry Type Solid units
M or S
N
40 (0.28) 25 (0.17)1
30 (0.21) 19 (0.13) 58 (0.40) 60 (0.41) 38 (0.26) 60 (0.41)
24 (0.17) 15 (0.10) 41 (0.28) 48 (0.33) 30 (0.21) 48 (0.33)
15 (0.10) 9 (0.06) 26 (0.18) 30 (0.21) 19 (0.13) 30 (0.21)
Normal to bed joints
Hollow units ungrouted Hollow units fully grouted Solid
units
68 (0.47) 80 (0.55) 50 (0.34) 80 (0.55)
Parallel to bed joints
Hollow units ungrouted and partially grouted Hollow units fully
grouted
1For partially grouted masonry allowable stresses shall be
determined on the basis of linear interpolation between hollow
units which are fully grouted or ungrout-
ed and hollow units based on amount of grouting.
700 and 1200 times the masonry prism compressive strength [4].
If the Unit Strength Method is used to show compliance with the
specified compressive strength of masonry, f , an accurate
estimation of the m actual compressive strength of the masonry
assemblage may not be known. Consequently, the elastic modulus of
the masonry assemblage is determined by the mortar Type and the
unit compressive strength. See Table 7. The data in Table 1 can be
used to estimate the modulus of elasticity of the masonry
assemblage for the type of unit selected. The elastic modulus of
grout is computed as 500 times the compressive strength of the
grout in accordance with the MSJC Code. In general, the elastic
modulus of grout and the elastic moduli of brick or structural clay
tile and mortar masonry assemblages are comparable and are often
considered equal for design calculations. However, the MSJC Code
recommends that the method of transformation of areas based on
relative elastic moduli be used for computation of stresses in
grouted masonry elements. Dimensional Stability Dimensional
stability is also an important property of the masonry assemblage.
Expansion and contraction of the brick or structural clay tile
masonry may exert restraining stresses on the masonry and
surrounding elements. Material properties which affect dimensional
stability of clay and shale unit masonry are moisture expansion,
creep and thermal movements. Effects of these phenomenon may be
evaluated by the coefficients provided in the MSJC Code, which are
listed in Table 8. The coefficients in Table 8 represent average
quantities for moisture expansion and thermal move6
ments and an upper-bound value for creep. Moisture expansion and
thermal expansion and contraction are independent and may be added
directly. The magnitude of creep of clay or shale unit masonry will
depend upon the amount of load applied to the masonry element.TABLE
7 Elastic Moduli of Clay and Shale Masonry Assemblages1Assemblage
Elastic Modulus, psi (kPa) x 106 Type M mortar 3.0(20.7) 3.0(20.7)
2.8(19.3) 2.2(15.2) 1.6(11.0) 1.0 (6.9) Type S mortar 3.0(20.7)
2.9(20.0) 2.4 (16.5) 1.9(13.1) 1.4 (9.7) 0.9 (6.2) Type N mortar
2.8(19.3) 2.4(16.5) 2.0(13.8) 1.6(11.0) 1.2 (8.3) 0.8 (5.5)
Net Area Compressive Strength of Units, psi (MPa)
12000 (82.7) and > 10000 (68.9) 8000 (55.2) 6000 (41.4) 4000
(27.6) 2000 (13.8)1MSJC Code Table 5.5.1.2.
TABLE 8 MSJC Code Dimensional Stability Coefficients for Clay
and Shale Unit MasonryMaterial Property Irreversible moisture
expansion Creep Thermal expansion and contraction1
REFERENCES 1. Atkinson, R.H., Evaluation of Strength and Modulus
Tables for Grouted and Ungrouted Hollow Unit Masonry,
Atkinson-Noland and Associates, Inc., Boulder, CO, November 1990,
47 pp. 2. Building Code Requirements for Masonry Struc tures and
Commentary (ACI 530/ASCE 5/TMS 402-92) and Specifications for
Masonry Struc t u re s and C o m m e n t a ry (ACI 530.1/ASCE 6/TMS
602-92), American Concrete Institute, Detroit, MI, 1992. 3.
Kingsley, G.R., et al., The Influence of Water Content and Unit
Absorption Properties on Grout Compressive Strength and Bond
Strength in Hollow Clay Unit Masonry, Proceedings 3rd North
American Masonry Conference, The Masonry Society, Boulder, CO, June
1985, pp. 7:112. 4. P l u m m e r, H.C., Brick and Tile
Engineering, Brick Institute of America, Reston, VA, 1977, 466 pp.
5. Steel Reinforcement Properties and Availability, Report of ACI
Committee 439, Journal of the American Concrete Institute, Vol. 74,
Detroit, MI, 1977, p. 481. 6. Subasic, C.A., Borchelt, J.G., Clay
and Shale Brick Material Properties - A Statistical Report,
submitted for inclusion, Proceedings 6th North American Masonry
Conference, The Masonry Society, Boulder, CO, June 1993, 12 pp.
Coefficient 3x10-4 in./in. (3x10-4 mm/mm) 0.7x10-7 in./in./psi
(1x10-5 mm/mm/MPa) 4x10 -6 in./in./oF (1x10 -5 mm/mm/oC) 1
Conversion based on equivalent deformation at 100oF (38 oC).
SUMMARY This Technical Notes contains information about the
material properties of brick and structural clay tile masonry. This
information may be used in conjunction with the MSJC Code and
Specifications to design and analyze structural masonry elements.
Typical material properties of clay and shale masonry units,
mortar, grout, reinforcing steel and combinations of thes