units from a plant regularly engaged in producing precast concrete units.
Unless otherwise indicated, concrete shall be [28] [20] MPa [4,000] [3000]
psi minimum conforming to Section [03300A CAST-IN-PLACE STRUCTURAL
CONCRETE][03300N CAST-IN-PLACE CONCRETE] using 13 mm 1/2 inch to No. 4
nominal-size coarse aggregate, and minimum reinforcement shall be the
reinforcement required for handling of the units. Clearance of 19 mm 3/4
inch shall be maintained between reinforcement and faces of units. Unless
precast-concrete items have been subjected during manufacture to
saturated-steam pressure of at least 827 kPa 120 psi for at least 5 hours,
the items, after casting, shall be either damp-cured for 24 hours or
steam-cured and shall then be aged under cover for 28 days or longer.
Cast-concrete members weighing over 35 kg 80 pounds shall have built-in
loops of galvanized wire or other approved provisions for lifting and
anchoring. Units shall have beds and joints at right angles to the face,
with sharp true arises and shall be cast with drip grooves on the underside
where units overhang walls. Exposed-to-view surfaces shall be free of
surface voids, spalls, cracks, and chipped or broken edges. Precast units
exposed-to-view shall be of uniform appearance and color. Unless otherwise
specified, units shall have a smooth dense finish. Prior to use, each item
shall be wetted and inspected for crazing. Items showing evidence of
dusting, spalling, crazing, or having surfaces treated with a protective
coating will be rejected.
2.5.1
Lintels
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NOTE: Insert strength of concrete; precast lintels
usually range from 17 to 25 MPa (2500 to 3500 psi).
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Precast lintels, unless otherwise shown, shall be of a thickness equal to
the wall and reinforced with two No. 4 bars for the full length. Top of
lintels shall be labeled "TOP" or otherwise identified and each lintel
shall be clearly marked to show location in the structure. In reinforced
masonry, lintels shall conform to ACI 318M/318RM for flexural and shear
strength and shall have at least 200 mm 8 inches bearing at each end.
Concrete shall have a minimum 28 day compressive strength of [_____] MPa psi
using 13 mm 1/2 inch to No. 4 nominal-size coarse aggregate.
Reinforcement shall conform to ASTM A 615/A 615M Grade 400 MPa 60. Limit
lintel deflection due to dead plus live load to L/600 or 7 mm 0.3 inches.
Provide top and bottom bars for lintels over 900 mm 36 inches in length.
2.5.2
Sills and Copings
Sills and copings shall be cast with washes. Sills for windows having
mullions shall be cast in sections with head joints at mullions and a 6 mm
1/4 inch allowance for mortar joints. The ends of sills, except a 19 mm
3/4 inch wide margin at exposed surfaces, shall be roughened for bond.
Treads of door sills shall have rounded nosings. [Reinforce sills with not
less than two No. 15 No. 4 bars.]
2.5.3
Splash Blocks
Splash blocks shall be as detailed.
Reinforcement shall be the
manufacturer's standard.
2.5.4
Flue Linings and Thimbles
ASTM C 315, free from fractures.
Sizes and shapes shall be as indicated.
SECTION 04200
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