placed and directed so as not to cause areas of overheating and drying of
concrete surfaces or to create fire hazards. Materials and equipment
needed for adequate curing and protection shall be available and at the
site prior to placing concrete. No fire or excessive heat, including
welding, shall be permitted near or in direct contact with the concrete at
any time. Except as otherwise permitted by paragraph Membrane Forming
Curing Compounds, moist curing shall be provided for any areas to receive
floor hardener, any paint or other applied coating, or to which other
concrete is to be bonded. Concrete containing silica fume shall be
initially cured by fog misting during finishing, followed immediately by
continuous moist curing. Except for plastic coated burlap, impervious
sheeting alone shall not be used for curing.
3.15.2
Moist Curing
Concrete to be moist-cured shall be maintained continuously wet for the
entire curing period, commencing immediately after finishing. If water or
curing materials used stain or discolor concrete surfaces which are to be
permanently exposed, the concrete surfaces shall be cleaned as approved.
When wooden forms are left in place during curing, they shall be kept wet
at all times. If steel forms are used in hot weather, nonsupporting
vertical forms shall be broken loose from the concrete soon after the
concrete hardens and curing water continually applied in this void. If the
forms are removed before the end of the curing period, curing shall be
carried out as on unformed surfaces, using suitable materials. Surfaces
shall be cured by ponding, by continuous sprinkling, by continuously
saturated burlap or cotton mats, or by continuously saturated plastic
coated burlap. Burlap and mats shall be clean and free from any
contamination and shall be completely saturated before being placed on the
concrete. The Contractor shall have an approved work system to ensure that
moist curing is continuous 24 hours per day.
3.15.3
Membrane Forming Curing Compounds
Membrane forming curing compounds shall be used only on surfaces in the
following areas, [_____]. Concrete in the following areas [may be cured
with a pigmented curing compound in lieu of moist curing.] [may be cured
with a nonpigmented curing compound containing a fugitive dye in lieu of
moist curing.] Membrane curing shall not be used on surfaces that are to
receive any subsequent treatment depending on adhesion or bonding to the
concrete, including surfaces to which a smooth finish is to be applied or
other concrete to be bonded. However, a styrene acrylate or chlorinated
rubber compound meeting ASTM C 309, Class B requirements, may be used for
surfaces which are to be painted or are to receive bituminous roofing or
waterproofing, or floors that are to receive adhesive applications of
resilient flooring. The curing compound selected shall be compatible with
any subsequent paint, roofing, waterproofing or flooring specified.
Membrane curing compound shall not be used on surfaces that are maintained
at curing temperatures with free steam. Curing compound shall be applied
to formed surfaces immediately after the forms are removed and prior to any
patching or other surface treatment except the cleaning of loose sand,
mortar, and debris from the surface. All surfaces shall be thoroughly
moistened with water. Curing compound shall be applied to slab surfaces as
soon as the bleeding water has disappeared, with the tops of joints being
temporarily sealed to prevent entry of the compound and to prevent moisture
loss during the curing period. The curing compound shall be applied in a
two-coat continuous operation by approved motorized power-spraying
equipment operating at a minimum pressure of 500 kPa 75 psi, at a uniform
coverage of not more than 10 cubic meters/L 400 square feet/gallon for each
SECTION 03300A
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