Lecture #18
Masonry Cement and Mortar
1
MORTAR
• binder = mortar
• Masonry = mortar + masonry units
MORTAR
• definitions
• differences w/ other cementitious
mixtures
• classes
• components
• types
• properties
MORTAR
• cementitious
materials
– lime
– portland cement
• sand
• water
• used with individual
masonry units
–
–
–
–
–
–
bonding
bedding / seating
leveling
sealing irregularities
providing strength
providing aesthetic qualities
MORTAR
• weak link in masonry
construction
• thin layer stronger
(compression) than thick
layer
• lime added
– workability
– adhesive properties
– extensibility
GROUT
• cement
• fine and coarse
aggregate
• sand
• water
• used to bond two masonry
wythes together (walls one unit
thick)
• high slump
• no segregation
• ASTM C476
• fine and coarse grouts f’C - less
in non-absorbent molds
– filling cores and voids
– binding reinforcing steel and
wythes
– providing load carrying capability
– match with masonry f’C
Differences w/ other cementitious
mixtures
• component materials
– mortar
• cement, lime, water, fine aggregate
– grout
• cement, water, fine aggregate, small-sized coarse aggregate
– portland cement concrete
• cement, water, fine aggregate, coarse aggregate
• proportions
Differences w/ other cementitious
mixtures
• structural performance
– PCC is structural material, resists mainly compressive
stresses
– mortar, grout are binders, develop strong & durable
bond w/ masonry unit
• workability & placement methods
– PCC placed in non-absorbent forms, minimum water,
w/c ratio very important to performance
– mortar, grout placed in absorptive forms, much more
water, w/c ratio less important
8
Classes
• lime mortar
• cement/cement-lime mortar
– cement, lime, sand, water
– lime, sand, water
– most common
– slow strength gain
– calcium carbonate
formation
• masonry cement mortar
– seldom used in
– proprietary ingredients
permanent construction
– workable
– low bond strength, not
durable - most commonly
used but least desirable
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Components
• portland cement
– durability
– high early strength
– high compressive
strength
– bond strength
• sand
– filler
– strength
• lime
–
–
–
–
–
workability
water retentivity
elasticity
bond strength
extensibility
• water
– flow
– required for hydration
• admixtures
10
Components
• portland cement
– Type I - general use when special properties not
required
– Type II - when moderate sulfate resistance or moderate
heat of hydration required
– Type III - when high early strength required
– Air entrained portland cements tend to reduce bond
strengths
11
Components
• hydrated lime [Ca(OH)2]
– chalk or limestone (CaCO3) burned at 900 0C in kiln to
produce quicklime (CaO)
– water added to quicklime
– Types (ASTM C207)
•
•
•
•
N - normal, unhydrated oxides & plasticity not controlled
S - special, commonly used
NA - normal air-entraining, not recommended
SA - special air-entraining, not recommended
12
• aggregates
Components
– natural or manufactured
– gradation (ASTM C144)
Sieve size
Amounts Finer than Each Laboratory sieve (Square Openings),
Weight %
Fine Aggregate
Coarse Aggregate
Grout
½ -in (12.5-mm)
3/8-in (9.5-mm)
No. 4 (4.75-mm)
No. 8 (2.36-mm)
No. 16 (1.18-mm)
No. 30 (600-m)
No. 50 (300-m)
No. 100 (150-m)
No. 200 (75-m)
…
100
95 to 100
80 to 100
50 to 85
25 to 60
10 to 30
2 to 10
…
Mortar or Grout
Natural
Manufactured
…
…
100
95 to 100
70 to 100
40 to 75
10 to 35
2 to 15
…
…
…
100
95 to 100
70 to 100
40 to 75
20 to 40
10 to 25
0 to 10
Size No. 8
Size No. 89
100
85 to 100
10 to 30
0 to 10
0 to 5
…
…
…
…
100
90 to 100
20 to 55
5 to 30
0 to 10
0 to 5
…
…
…13
Components
• water
– clean
– potable
– free of deleterious
materials
• acids
• alkalies
• organic materials
• admixtures
– color
– workability
– reduced water
penetration
– accelerated curing
– use w/ caution
– air-entraining
– chlorides
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Types (MASONWORK)
• ASTM C270
– proportion specifications - RECOMMENDED
– property specifications
• established with laboratory testing, trial & error
– same letter designations, but
Type N (proportion) = Type N (property)
(proportion - higher compressive strength)
• Type M (paving brick)
– high strength
– general use
– below grade OR in contact w/ ground
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Types (MASONWORK)
• Type S (structural masonry, reinforced brick)
– high strength
– reinforced masonry
– areas subject to high wind
• Type N (normal, common)
– high strength
– general use
– below grade OR in contact w/ ground
16
Types (MASONWORK)
• Type O (interior)
– low strength
– non-bearing applications
– not subject to severe weathering
• Type K (restoration)
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Types (MASONWORK)
• Proportion Specifications
Mortar
Type
Cement-Lime
M
S
N
Masonry Cement
Proportion by Volume (Cementitious Materials)
Aggregate Ratio
Portland
Masonry Cement
(Measured in
Cement or
Hydrated Lime
Damp, Loose
Blended
or
Lime
Putty
M
S
N
Condition)
Cement
1
…
…
…
¼
1
…
…
…
Over ¼ to ½
1
…
…
…
Over ½ to 1 ¼
O
1
…
…
…
Over 1¼ to 2 ½
M
1
…
…
1
…
M
…
1
…
…
…
S
½
…
…
1
…
S
…
…
1
…
…
N
…
…
…
1
…
O
…
…
…
1
…
Not less than
2¼ and not
more than 3
times the sum
of the separate
volumes of
Cementitious
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materials.
Determine quantities and absolute volumes
for an N Type Mortar
• Vsand = 1.0 ft3
• Vlime= 0.5 to 1.25 Vc
• Vsand=2.25 to 3 (Vc+Vl)
• 1 ft3 of damp loose sand will yield 1 ft3 of
mortar. (due to bulking of wet sand)
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Types (MASONWORK)
• Property Specificationsa
Mortar
Type
Cement-Lime
M
S
N
O
M
S
N
O
Masonry Cement
Average
Aggregate Ratio
Water Retention, Air Content,
Compressive
(Measured in
Strength at 28 Days,
min, %
max, %
Damp, Loose
Min. psi (MPa)
Condition)
2500 (17.2)
75
12
Not less than 2¼
1800 (12.4)
75
12
and not more
750 (5.2)
75
14b
than 3½ times the
350 (2.4)
75
14b
sum of the
2500 (17.2)
75
…c
separate volumes
1800 (12.4)
75
…c
of cementitious
750 (5.2)
75
…c
materials
350 (2.4)
75
…c
Laboratory prepared mortar only
b When structural reinforcement is incorporated in cement-lime mortar,
the maximum air content shall be 12%
c When structural reinforcement is incorporated in masonry cement mortar,
the maximum air content shall be 18%.
a
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Selecting Mortar Types
• considerations
– structural
requirements
– exposure
– wall type
– workability
• no single type for all
purposes
• DO NOT change mortar
types within same
structure
– uneconomical
• NEVER use mortar
stronger in compression
than required
– shrinkage, debonding
– uneconomical
21
Laboratory vs. Field Mortar
• CANNOT COMPARE
– field mortar
• more water required (lost in evaporation or to masonry unit)
– laboratory mortar
• less water, lower initial flow
• different curing conditions
22
Properties
• plastic properties
– influence hardened
properties
–
–
–
–
workability
initial flow
flow after suction
water retentivity
• hardened properties
– determine performance
–
–
–
–
bond strength
durability
extensibilty
compressive strength
• other properties
– color
23
Workability
•
•
•
•
•
easily spread
adhere to vertical surface
difficult to measure directly
no standard test or quantitative measure
indicators include flow, water retentivity, resistance
to segregation
• affected by properties of components
24
Flow (ASTM C109)
• cone formed on flow table
• raised & dropped 25 times in 15 seconds
• flow = ratio of increase in diameter
25
Water Retentivity (ASTM C91)
• ability to resist loss of water to absorbent masonry
unit
• flow after suction (vacuum for 1 min)/ initial flow
• low retentivity will bleed moisture unless brick has
high suction (IRA)
• high retentivity will create dry surface
• low bond strength for low or high retentivity paired
with average masonry unit
26
Bond Strength
• most important physical property
• difficult to measure directly, simulate construction
Bond Strength
Suction (IRA)
Air Content 
Elapsed Time

Mortar Flow 
Brick Texture rough
Retempering
Pressure

Movement after set
Water Retentivity




Max Bond
• cement: lime





1:1 to 1:1/4
•Type S mortar
27
Bond Strength
28
Other Hardened Properties
• durability
– not significant if
properly prepared
– no air-entraining
components
• extensibility
– max et at rupture
– elongation before
cracking
– lime contributes
29
Other Hardened Properties
• compressive strength
– f (cement content, w/c)
– cubes (ASTM C109)
Cement
Lime
Water
Flow
Proportion




f’c




– cylinders, briquettes
30
Other Properties
• color
– colored aggregates - PREFERRED
– colored pigment
31