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Lecture #18

Masonry Cement and Mortar

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MORTAR

binder = mortar

Masonry = mortar + masonry units

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MORTAR

definitions

differences w/ other cementitious

mixtures

classes

components

types

properties

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MORTAR

cementitious

materials

lime portland cement

sand

water

used with individual

masonry units

bonding bedding / seating

leveling

sealing irregularities

providing strength

providing aesthetic qualities

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MORTAR

weak link in masonry

construction

thin layer stronger

(compression) than thick

layer

lime added

workability

adhesive properties extensibility

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GROUT cement

fine and coarseaggregate

sand

water

high slump

no segregation

used to bond two masonry

wythes together (walls one unitthick)

filling cores and voids

binding reinforcing steel and

wythes

providing load carrying capability

ASTM C476

fine and coarse grouts fC - lessin non-absorbent molds

match with masonry fC

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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

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Differences w/ other cementitious

mixtures structural performance

PCC is structural material, resists mainly compressive

stresses

mortar, grout are binders, develop strong & durablebond 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

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Classes lime mortar

lime, sand, water

slow strength gain

calcium carbonate

formation seldom used in

permanent construction

cement/cement-lime mortar

cement, lime, sand, water

most common

masonry cement mortar proprietary ingredients

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

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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

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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

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Components aggregates

natural or manufactured gradation (ASTM C144)

Amounts Finer than Each Laboratory sieve (Square Openings),

Weight %

Fine Aggregate Coarse Aggregate

Mortar or Grout

Sieve size

GroutNatural Manufactured

Size No. 8 Size No. 89

-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 10080 to 100

50 to 85

25 to 60

10 to 30

2 to 10

10095 to 100

70 to 100

40 to 75

10 to 35

2 to 15

10095 to 100

70 to 100

40 to 75

20 to 40

10 to 25

0 to 10

100

85 to 100

10 to 300 to 10

0 to 5

100

90 to 100

20 to 555 to 30

0 to 10

0 to 5

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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

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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

Proportion by Volume (Cementitious Materials)

Masonry CementMortar Type

Portland

Cement orBlended

CementM S N

Hydrated Limeor Lime Putty

Aggregate Ratio

(Measured inDamp, Loose

Condition)

Cement-Lime M 1

S 1 Over to

N 1 Over to 1

O 1 Over 1 to 2

Masonry Cement M 1 1

M 1

S 1

S 1

N 1

O

1

Not less than

2 and notmore than 3

times the sum

of the separate

volumes ofCementitious

materials.

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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 ofmortar. (due to bulking of wet sand)

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Types (MASONWORK) Property Specificationsa

Mortar Type

Average

Compressive

Strength at 28 Days,

Min. psi (MPa)

Water Retention,

min, %

Air Content,

max, %

Aggregate Ratio

(Measured in

Damp, Loose

Condition)

Cement-Lime M 2500 (17.2) 75 12

S 1800 (12.4) 75 12N 750 (5.2) 75 14

b

O 350 (2.4) 75 14b

Masonry Cement M 2500 (17.2) 75 c

S 1800 (12.4) 75 c

N 750 (5.2) 75 c

O 350 (2.4) 75

c

Not less than 2

and not more

than 3 times the

sum of the

separate volumes

of cementitious

materials

aLaboratory prepared mortar onlyb 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%.

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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 samestructure

uneconomical

NEVER use mortar

stronger in compression

than required

shrinkage, debonding

uneconomical

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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

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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

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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

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Flow (ASTM C109) cone formed on flow table

raised & dropped 25 times in 15 seconds

flow = ratio of increase in diameter

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Bond Strength most important physical property

difficult to measure directly, simulate construction

Bond Strength

Max Bond

cement: lime

1:1 to 1:1/4Type S mortar

Suction (IRA)

Air Content

Elapsed Time

Mortar Flow

Brick Texture rough Retempering

Pressure

Movement after set

Water Retentivity

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Other Hardened Properties

durability

not significant if

properly prepared

no air-entraining

components

extensibility

max et at rupture

elongation beforecracking

lime contributes

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Other Hardened Properties compressive strength

f (cement content, w/c)

cubes (ASTM C109)

cylinders, briquettes

Proportion fc

Cement Lime Water Flow

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Other Properties

color colored aggregates - PREFERRED

colored pigment