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SJCo Public Health Bio-Safety Level 3 Modular Laboratory Site Preparation Project
Stockton, California
CAST IN PLACE CONCRETE
B.
Deposit concrete continuously or in layers of such thickness that no concrete will be
placed on concrete which has hardened sufficiently to cause the formation of seams or
planes of weakness within the section. If a section cannot be placed continuously,
provide construction joints as specified. Deposit concrete as nearly as practicable to its
final location to avoid segregation due to rehandling or flowing,
C.
Placing Concrete in Forms:
1.
Deposit concrete in forms in horizontal layers not deeper than 24" and in a
manner to avoid inclined construction joints. Where placement consists of
several layers, place each layer while preceding layer is still plastic to avoid cold
joints.
2.
Consolidate placed concrete by mechanical vibrating equipment supplemented
by hand-spading, rodding or tamping. Use equipment and procedures for
consolidation of concrete in accordance with the recommended practices of ACI
304, to suit the type of concrete and project conditions.
3.
Do not use vibrators to transport concrete inside of forms. Insert and withdraw
vibrators vertically at uniformly spaced locations not farther than the visible
effectiveness of the machine. Place vibrators to rapidly penetrate the placed
layer of concrete and at least 6" into the preceding layer. Do not insert vibrators
into lower layers of concrete that have begun to set. At each insertion limit the
duration of vibration to the time necessary to consolidate the concrete and
complete embedment of reinforcement and other embedded items without
causing segregation of the mix.
D.
Placing Concrete Slabs:
1.
Deposit and consolidate concrete slabs in a continuous operation, within the
limits of construction joints, until the placing of a panel or section is complete.
2.
3.
4.
Consolidate concrete during placing operations so that concrete is thoroughly
worked around reinforcement and other embedded items and into corners.
Bring slab surfaces to the correct level with a straightedge and strikeoff. Use bull
floats or darbies to smooth the surface, leaving it free of humps or hollows. Do
not sprinkle water on the plastic concrete surface. Do not disturb the slab
surfaces prior to beginning finished operations.
Maintain reinforcing in the proper position during concrete placement operations
by placing concrete chairs immediately prior to pour. Hooking reinforcing in
position is not allowed.
E.
Cold Weather Placing:
1.
Protect concrete work from physical damage or reduced strength which could be
caused by frost, freezing actions, or low temperatures, in compliance with ACI
306.
2.
Do not use calcium chloride, salt and other materials containing antifreeze
agents or chemical accelerators, unless otherwise accepted in writing by the
Owner Representative.
F.
Hot Weather Placing:
1.
When hot weather conditions exist that would seriously impair the quality and
strength of concrete, place concrete in compliance with ACI 305 and as herein
specified.
2.
Cool ingredients before mixing to maintain concrete temperature at time of
placement below 90°F.
CAST IN PLACE CONCRETE
03 30 00-8