ASTM C 270 TABLE 2 Property Specification Requirements
(For laboratory prepared mortar only)
Mortar
Type
Average
Water
Air
Aggregate
Compressive
Retention
Content
Ratio
Strength
Min.
Max.
(Measured in
at 28 Days
Percent
Percent
in Damp,
Loose
Min. psi
Condition)
Approximate the f'm of the unit masonry. Mortars should be
slightly weaker than masonry units so that cracking will
occur in joints where easy to repair.
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ASTM C 270, Type [M] [N] [S]. Strength (f'm) as indicated. Test in
accordance with ASTM C 780. [Use Type [I] [II] [III] portland cement.] [Use
Type [IS] [IP] [I(PM)] blended hydraulic cement.] [Use Masonry cement.] Do
not use admixtures containing chlorides. When structural reinforcement is
incorporated, maximum air-content shall be 12 percent in cement-lime mortar
and 18 percent in masonry cement mortar.
2.8
MASONRY MORTAR
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NOTE: See ASTM C 270 for guidance in selecting
mortar types. Use Type M when masonry is in contact
with earth and high degree of compressive strength
is required.
Type S should be used for reinforced masonry and
when high degree of compressive strength or high
degree of lateral load resistance is required. Type
S mortar provides worability, weather tightness,
durability and corrosion protection, and will be
used for most work. For cavity wall construction, a
high degree of lateral load is defined as an 130
km/h (80 mph) wind.
Type N mortar generally provides improved
workability and weather tightness; it has lower
strength, durability and corrosion protection than
Type S. It should be used for all general interior
and exterior above grade masonry construction
including chimneys and parapets unless higher
compressive strength or a high degree of lateral
load resistance is required. For SOUTHNAVFACENGCOM
projects, use only Type S mortar for exterior walls
except use Type M mortar when masonry is in contact
with earth.
The proportions allowed by ASTM C 270 for
cement-lime mortars can result in properties that
are essentially of another mortar type. Mortars
proportioned for high strength can lead to debonding
between the mortar joint and the brick resulting in
reduced wall flexural capacity and increased water
penetration leading to efflorescence problems.
Therefore the proportions for cement-lime Types S
SECTION 04200
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