2.6
STONE ITEMS
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NOTE: The stone specified herein is for structures
requiring a limited quantity of cut stone. Where
previous experience indicates difficulty in
obtaining precast concrete trim of the specified
quality, stone may be specified as a Contractor's
option.
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Stone for trim, sills, lintels, and copings shall be limestone, sandstone,
or granite, and shall be cut to the design shown. Sandstone shall be
standard grade, buff, gray, or buff brown, with a smooth finish free from
clay pits and tool marks. Granite shall be a good commercial grade
building granite of medium or moderately coarse grain, and a light or
medium gray or light pink color, with a smooth machine finish on washes,
4-cut finish on treads, and 6-cut or equivalent machine finish on other
exposed surfaces. Limestone shall be standard buff limestone with a smooth
machine finish free from tool marks. Lintels, except when supported by a
steel member, shall be 100 mm 4 inches or more thick from face to back edge
and of the depth required to support the masonry over the opening. Stone
shall have beds and joints at right angles to the face, with sharp, true
arises. Copings and sills shall be provided with washes, and where
overhanging the walls, shall have drips cut on the underside.
2.7
MORTAR FOR STRUCTURAL MASONRY
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NOTE: The defaults for mortar and grout materials
in ASTM C 270 and ASTM C 476 are alright for general
construction. Specify Type III portland cement for
cold weather construction, Type II for moderate
sulfate resistance. The blended cements make a gray
mortar; specify portland cement mortar or masonry
cement if white or colored mortar is necessary. Use
only Type S for exterior walls and M below ground.
Do not use Type O in areas of moderate or high
seismic activity. Do not use Type N in areas of
high seismic activity.
A, added to Type designation, i.e. IIA, means
air-entrained. Use this for exterior mortar in
severe climates, but do not use for grout.
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
at 28 Days
Percent
Percent
in Damp,
Loose
Min. MPa
Condition)
Cement-lime
M
17
75
12
Not less than
S
12
75
12
2 1/4 and
N
5
75
14*
not more than
SECTION 04200
Page 24
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